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1996 Fluoride Abstracts. Part 1.
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J Neurochem 1996 Aug;67(2):760-6
Phospholipase D activity of rat brain neuronal nuclei.
Kanfer JN, McCartney D, Singh IN, Freysz L.
Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Phospholipase D activity of rat brain neuronal nuclei, measured with exogenous phosphatidylcholine as substrate, was characterized. The measured activity of neuronal nuclei was at least 36-fold greater than the activity in glia nuclei. The pH optimum was 6.5, and unsaturated but not saturated fatty acids stimulated the enzyme. The optimal concentration of sodium oleate for stimulation of the enzyme activity was 1.2 mM in the presence of 0.75 mM phosphatidylcholine. This phospholipase D activity was cation independent. In the absence of NaF, used as a phosphatidic acid phosphatase inhibitor, the principal product was diglyceride; whereas in the presence of NaF, the principal product was phosphatidic acid. The phospholipase D, in addition to having hydrolytic activity, was able to catalyze a transphosphatidylation reaction. Maximum phosphatidylethanol formation was seen with 0.2-0.3 M ethanol. GTPgammaS, ATPgammaS, BeF2, AIF3, phosphatidic acid, and phosphatidylethanol inhibited the neuronal nuclei phospholipase D activity. The addition of the cytosolic fraction of brain, liver, kidney, spleen, and heart to the incubation mixtures resulted in inhibition of the phospholipase D activity. Phospholipase D activity was detectable in nuclei prepared from rat kidney, spleen, heart, and liver.
PMID: 8764605 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8632163&dopt=AbstractJ Neurochem 1996 Jun;66(6):2402-9
The phosphoinositide signal transduction system is impaired in bipolar affective disorder brain.
Jope RS, Song L, Li PP, Young LT, Kish SJ, Pacheco MA, Warsh JJ.
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham 35294-0017, USA.
The function of the phosphoinositide second messenger system was assessed in occipital, temporal, and frontal cortex obtained postmortem from subjects with bipolar affective disorder and matched controls by measuring the hydrolysis of [3H]phosphatidylinositol ([3H]PI) incubated with membrane preparations and several different stimulatory agents. Phospholipase C activity, measured in the presence of 0.1 mM Ca2+ to stimulate the enzyme, was not different in bipolar and control samples. G proteins coupled to phospholipase C were concentration-dependently activated by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) and by NaF. GTP gamma S-stimulated [3H]Pl hydrolysis was markedly lower (50%) at all tested concentrations (0.3-10 microM GTP gamma S) in occipital cortical membranes from bipolar compared with control subjects. Responses to GTP gamma S in temporal and frontal cortical membranes were similar in bipolars and controls, as were responses to NaF in all three regions. Brain lithium concentrations correlated directly with GTP gamma S-stimulated [3H]Pl hydrolysis in bipolar occipital, but not temporal or frontal, cortex. Carbachol, histamine, trans-1-aminocyclopentyl-1,3-dicarboxylic acid, serotonin, and ATP each activated [3H]Pl hydrolysis above that obtained with GTP gamma S alone, and these responses were similar in bipolars and controls except for deficits in the responses to carbachol and serotonin in the occipital cortex, which were equivalent to the deficit detected with GTP gamma S alone. Thus, among the three cortical regions examined there was a selective impairment in G protein-stimulated [3H]Pl hydrolysis in occipital cortical membranes from bipolar compared with control subjects. These results directly demonstrate decreased activity of the phosphoinositide signal transduction system in specific brain regions in bipolar affective disorder.
PMID: 8632163 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8971982&dopt=AbstractProg Neurobiol 1996 Oct;50(2-3):255-73
Phosphoinositide signaling in human brain.
Pacheco MA, Jope RS.
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham 35294-0017, USA.
The phosphoinositide signal transduction system constitutes one of the primary means for intercellular communication in the central nervous system, but only recently has this system been studied in human brain. Although some investigations have studied phosphoinositide signaling in slices from biopsied human brain, due to the limited access to such material a greater number of studies have utilized membranes prepared from postmortem human brain. With membranes exposed to exogenous labeled phosphoinositides, activation of phospholipase C with calcium, with G-proteins stimulated by GTP gamma S or NaF, or with several receptor agonists, have demonstrated that all of the components of the phosphoinositide system are retained in human brain membranes and are responsive to appropriate stimuli. Investigators have begun to examine the effects of neurological (Alzheimer's disease, epilepsy, Parkinson's disease) and psychiatric (schizophrenia, major depression, bipolar affective disorder) diseases on the activity of the phosphoinositide system. Alzheimer's disease has been studied to the greatest extent and a severe deficit in phosphoinositide signaling has been identified in most studies. In addition, brain regionally selective deficits in G-protein function associated with phosphoinositide signaling have been reported in subjects with major depression or with bipolar affective disorder, and in the latter an ameliorative effect of the therapeutic drug lithium was identified. Although significant progress has been achieved in studying the phosphoinositide system in human brain, many issues remaining to be addressed are discussed in this review. With carefully controlled studies, it appears that much will be learned in the near future about the phosphoinositide signal transduction system in human brain and the effects of a variety of disorders on its function.
Publication Types:
- Review
- Review, Academic
PMID: 8971982 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8813380&dopt=AbstractBrain Res 1996 Jun 3;723(1-2):37-45
Alterations in phosphoinositide signaling and G-protein levels in depressed suicide brain.
Pacheco MA, Stockmeier C, Meltzer HY, Overholser JC, Dilley GE, Jope RS.
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham 35294-0017, USA.
The function of the phosphoinositide signal transduction system and the levels of heterotrimeric G-protein alpha-subunits were examined in postmortem prefrontal cortex regions (8/9) and region (10) from suicide victims with major depression and matched control subjects without psychiatric illness. The hydrolysis of [3H]phosphatidylinositol (PI) stimulated by phospholipase C, GTP-gamma-S, NaF, and neurotransmitter receptor agonists was measured in membrane preparations from both groups. Phospholipase C-beta activity was similar in depressed suicide and control subjects in the two regions of prefrontal cortex. In prefrontal cortex (10), but not in (8/9), the GTP-gamma-S concentration-dependent stimulation of [3H]PI hydrolysis was significantly lower (30%) in the depressed suicide group compared to the control group. Receptor-coupled, G-protein-mediated [3H]PI hydrolysis induced with carbachol, histamine, trans-1-aminocyclopentyl-1, 3-dicarboxylic acid (ACPD, a glutamatergic metabotropic receptor agonist), serotonin, or 2-methylthio-adenosine triphosphate (2mATP, a purinergic receptor agonist) in the presence of GTP-gamma-S stimulated equivalent responses in the two groups of subjects in each brain region. In prefrontal cortex (10) there was a 68% increase in the level of the 45 kDa subtype of G alpha s and in prefrontal cortex (8/9) there was a significant decrease (21%) in the level of G alpha i2 in the depressed suicide group compared to the control group. Levels of other heterotrimeric G-protein alpha-subunits (G alpha q/11, G alpha i1, and G alpha o) were not different in depressed suicide and control subjects in either brain region. Moreover, there were no differences in the levels of phospholipase C-beta or protein kinase C-alpha in the two groups of subjects in either brain region examined. These results demonstrate that in the prefrontal cortex of suicide victims with major depression compared to normal control subjects there is a region-specific alteration of G-protein-induced activation of the phosphoinositide signal transduction system and in the levels of G-protein alpha-subunits involved in cyclic AMP synthesis. These findings provide direct evidence in human brain that these two important signal transduction systems are altered in suicide subjects with major depression.
PMID: 8813380 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8627302&dopt=AbstractJ Neurochem 1996 Apr;66(4):1483-8
Differential regulation of intracellular signaling systems by sodium fluoride in rat glioma cells.
Kagaya A, Uchitomi Y, Kugaya A, Takebayashi M, Nagaoka I, Muraoka M, Yokota N, Yamawaki S.
Department of Psychiatry and Neurosciences, Hiroshima University School of Medicine, Japan.
We investigated the rapid and slow effects of NaF on intracellular signaling systems such as Ca2+ homeostasis and cyclic GMP (cGMP) generation in rat glioma C6 cells, using the Ca2+-sensitive dye fura-2 and cGMP enzyme immunoassay. We found that the following:
(a) NaF enhanced cGMP generation in a concentration-dependent manner. This enhancement was abolished by pretreatment with 100 microM BAPTA tetraacetoxymethal ester or in the presence of W-7 in a concentration-dependent manner. N G-Monomethyl-L-arginine (NMMA), a competitive inhibitor or nitric oxide synthase (NOS), also inhibited the NaF-induced generation of cGMP. These results suggest that NaF-induced cGMP generation occurs via a calcium/calmodulin- and NOS-dependent pathway.
(b) The basal intracellular Ca2+ concentration ([Ca2+]i) was transiently greater at 1 and 3 h after pretreatment with NaF. W-7 and W-13 antagonized the increase in [Ca2+]i, whereas NMMA had little effect. This suggests that the NaF-induced change in basal [Ca2+] was mediated by a calmodulin-dependent pathway but was independent of a NOS-sensitive pathway.
(c) The serotonin (5-HT)-induced intracellular mobilization of Ca2+ was reduced by pretreating the cells with NaF. The reduction in Ca2+ mobilization was antagonized by genistein, a tyrosine kinase inhibitor. W-7, W-5, and H-8 had no effect. Results suggest that NaF differentially regulated the cGMP generation. basal [Ca2+]i, and 5-HT2A receptor function in C6 glioma cells.
PMID: 8627302 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8921348&dopt=AbstractFundam Appl Toxicol 1996 Oct;33(2):294-7
Sulfonyl fluorides and the promotion of diisopropyl fluorophosphate neuropathy.
Osman KA, Moretto A, Lotti M
Phenylmethanesulfonyl fluoride (PMSF) enhances the neuropathic response when given to hens after organophosphates causing delayed polyneuropathy. This study was undertaken to ascertain whether other sulfonyl fluorides promote diisopropyl fluorophosphate (DFP) neuropathy in hens and if they inhibit neuropathy target esterase (NTE), the target for organophosphate-induced delayed polyneuropathy. Among seven sulfonyl fluoride analogs of PMSF (alkyl-, and phenylsulfonyl fluorides), only n-butanesulfonyl fluoride was found to be an NTE inhibitor in vitro at a concentration (I50 = 60 microM) similar to that of PMSF, n-Butanesulfonyl fluoride (0.2 mmol.kg-1 sc to hens) caused both NTE inhibition in nervous tissues (> 80%) and promotion of neuropathy after DFP (0.003 mmol.kg-1 sc) similar to those observed after the same molar dose of PMSF. These results confirm that, so far, all known promoters of organophosphate polyneuropathy are also NTE inhibitors.
PMID: 8921348, UI: 97079637
Full report available at http://www.jbc.org/cgi/content/full/271/15/8791J Biol Chem 1996 Apr 12;271(15):8791-5
Chloride effects on Gs subunit dissociation. Fluoroaluminate binding to Gs does not cause subunit dissociation in the absence of chloride ion.
Toyoshige M, Basi NS, Rebois RV.Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, NINDS, National Institutes of Health, Bethesda, Maryland 20892-4440, USA.
The stimulatory guanine nucleotide binding protein (Gs) is heterotrimeric ( alpha beta gamma), and mediates activation of adenylyl cyclase by a ligand-receptor complex. The alpha subunit of Gs (Gsalpha) has a guanine nucleotide binding site, and activation occurs when tightly bound GDP is displaced by GTP. Together, GDP and fluoroaluminate (AlF4-) form a transition state analog of GTP that activates Gs. The work of other investigators suggests that AlF4- causes subunit dissociation when it activates Gs. We have observed that in solution AlF4- did not cause Gs subunits to dissociate unless NaCl was also present. The effect of NaCl was concentration dependent (10-200 mM). Omitting F-, Al3+, or Mg2+ prevented the NaCl-induced dissociation of Gs subunits. Na2SO4 could not substitute for NaCl in causing subunit dissociation, but KCl could, suggesting that the anion was responsible for the effect. Gs subunit reassociation occurred when the concentration of Cl- was reduced even though the concentrations of AlF4- and Mg2+ were maintained. The absence of Cl- did not prevent AlF4- binding to Gsalpha. We have concluded that AlF4-, a ligand which is capable of activating G proteins, can bind to Gs in solution without causing subunit dissociation.
PMID: 8621516 [PubMed - indexed for MEDLINE]
Full report available at http://jcs.biologists.org/cgi/reprint/109/1/209.pdfJ Cell Sci 1996 Jan;109 ( Pt 1):209-20
- The mammalian ARF-like protein 1 (Arl1) is associated with the Golgi complex.
Lowe SL, Wong SH, Hong W.
Institute of Molecular and Cell Biology, National University of Singapore.
A rat cDNA clone was isolated which encodes a protein displaying characteristics of a ras-like small GTPase. The deduced amino acid sequence shows the highest amino acid identity (79%) with the Drosophila ARF-like protein 1 (dArl1) among all the known members of the ras-like small GTPase superfamily. The encoded protein was tentatively named rat Arl1 (rArl1). Northern blotting analysis revealed that the rArl1 gene is ubiquitously expressed in rat tissues. Recombinant rArl1 fused to glutathione-S-transferase (GST) to create GST-rArl1 binds GTP-gamma-S in a dose-dependent manner. Polyclonal antibodies raised against two unique rArl1 peptides recognized a 22 kDa protein in total NRK cell lysate. Immunofluorescence microscopy of NRK cells revealed discrete perinuclear labelling that could be competed out by GST-rArl1 but not GST. Examination of 8 additional cell lines revealed a similar labelling, suggesting that the antigen recognised by the antibodies is conserved and widely-expressed. Co-localization experiments in NRK cells with antibodies to mannosidase II and a newly identified cis-Golgi protein, p28, showed that rArl1 is localized to the Golgi complex. When cells were treated with nocodazole, the Golgi complex marked by mannosidase II and p28 was fragmented into punctate structures scattered throughout the cell, in which rArl1 was colocalized. Treatment with brefeldin A (BFA) resulted in the redistribution of rArl1 and mannosidase II into the cytoplasm and endoplasmic reticulum, respectively. The kinetics of the redistribution of rArl1 in response to BFA differ from those of ARF and beta-COP, two components of non-clathrin coated vesicles.
PMID: 8834805 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8732932&dopt=AbstractAm J Ind Med 1996 May;29(5):560-8
Serum perfluorooctanoic acid and hepatic enzymes, lipoproteins, and cholesterol: a study of occupationally exposed men.
Gilliland FD, Mandel JS.
Division of Environmental and Occupational Health, School of Public Health, University of Minnesota, Minneapolis, USA.
Perfluorooctanoic acid (PFOA) produces marked hepatic effects, including hepatomegaly, focal hepatocyte necrosis, hypolipidemia, and alteration of hepatic lipid metabolism in a number of animal species. In rodents, PFOA is a peroxisome proliferator, an inducer of members of the cytochrome P450 superfamily and other enzymes involved in xenobiotic metabolism, an uncoupler of oxidative phosphorylation, and may not be a cancer promoter. Although PFOA is the major organofluorine compound found in humans, little information is available concerning human responses to PFOA exposure. This study of 115 occupationally exposed workers examined the cross-sectional associations between PFOA and hepatic enzymes, lipoproteins, and cholesterol. The findings indicate that there is no significant clinical hepatic toxicity at the PFOA levels observed in this study. PFOA may modulate the previously described hepatic responses to obesity and xenobiotics.
PMID: 8732932 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8618252&dopt=AbstractJ Toxicol Clin Toxicol 1996;34(2):183-9
Circulating testosterone levels in skeletal fluorosis patients.
Susheela AK, Jethanandani P.
Fluoride and Fluorosis Research Laboratories, All India Institute of Medical Sciences, New Delhi, India.
OBJECTIVE: The present study focuses on serum testosterone concentrations in patients with skeletal fluorosis, in order to assess the hormonal status in fluoride toxicity.
METHODS: Serum testosterones were compared for patients afflicted with skeletal fluorosis (n = 30) and healthy males consuming water containing less than 1 ppm fluoride (Control 1, n = 26) and a second category of controls (Control 2, n = 16): individuals living in the same house as the patients and consuming same water as patients but not exhibiting clinical manifestations of skeletal fluorosis.
RESULTS: Circulating serum testosterones in skeletal fluorosis patients were significantly lower than those of Control 1 at p < 0.01. Testosterone concentrations of Control 2 were also lower than those of Control 1 at p < 0.05 but were higher than those of the patient group.
CONCLUSIONS: Decreased testosterone concentrations in skeletal fluorosis patients and in males drinking the same water as the patients but with no clinical manifestations of the disease compared with those of normal, healthy males living in areas nonendemic for fluorosis suggest that fluoride toxicity may cause adverse effects in the reproductive system of males living in fluorosis endemic areas.
PMID: 8618252 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8804072&dopt=AbstractPeptides 1996;17(4):625-8
Effect of low pH treatment on opioid peptides binding to their receptors and functional coupling of G-proteins to adenylyl cyclase in the rat spinal cord.
Reddy PL, Bhargava HN.
Department of Pharmaceutics and Pharmacodynamics (M/C 865), University of Illinois at Chicago 60612, USA.
Because low pH treatment is known to alter the coupling of G-proteins to brain receptors, and little is known about such an effect in the spinal cord, the present study was undertaken to examine whether preincubation of rat spinal cord membranes at low pH (pH 4.5) alters opioid receptor binding characteristics and sodium fluoride (NaF)-stimulated adenylyl cyclase (AC) activity (as a function of G, mediated). [3H][D-Ala2,MePhe4,Gly-ol]enkephalin (DAMGO) and [3H]ethylketocyclazosine (EKC) were used to label mu- and kappa-opioid receptors, respectively. AC activity was determined using ATP as substrate and cAMP formed was quantified. Low pH treatment of membranes did not affect the mu- and kappa-opioid binding characteristics in rat spinal cord. However, the low pH treatment significantly reduced the NaF-stimulated AC activity in rat spinal cord. It is concluded that low pH treatment causes selective changes in the functional coupling of Gs-proteins to AC without affecting the opioid receptor binding characteristics in the spinal cord.
PMID: 8804072 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8815874&dopt=AbstractJ Neurosci 1996 Oct 1;16(19):5914-22
Cholinergic stimulation of AP-1 and NF kappa B transcription factors is differentially sensitive to oxidative stress in SH-SY5Y neuroblastoma: relationship to phosphoinositide hydrolysis.
Li X, Song L, Jope RS.
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham 35294-0017, USA.
Oxidative stress appears to contribute to neuronal dysfunction in a number of neurodegenerative conditions, notably including Alzheimer's disease, in which cholinergic receptor-linked signal transduction activity is severely impaired. To test whether oxidative stress could contribute to deficits in cholinergic signaling, responses to carbachol were measured in human neuroblastoma SH-SY5Y cells exposed to H2O2. DNA binding activities of two transcription factors that are respondent to oxidative conditions, AP-1 and NF kappa B, were measured in nuclear extracts. H2O2 and carbachol individually induced dose- and time-dependent increases in AP-1 and NF kappa B. In contrast, when given together, H2O2 concentration dependently (30-300 microM) inhibited the increase after carbachol in AP-1. Carbachol's stimulation of NF kappa B was not inhibited except with a high concentration (300 microM) of H2O2, which was associated with impaired activation of protein kinase C. Lower concentrations of H2O2 (30-300 microM) inhibited carbachol-induced [3H]phosphoinositide hydrolysis, and this inhibition correlated (r = 0.95) with the inhibition of carbachol-induced AP-1. Activation [3H]phosphoinositide hydrolysis by the calcium ionophore ionomycin was unaffected by H2O2, indicating that phospholipase C and phosphoinositides were impervious to this treatment. In contrast, activation with NaF of G-proteins coupled to phospholipase C was concentration dependently inhibited by H2O2, indicating impaired G-protein function. These effects of H2O2 are similar to signaling impairments reported in Alzheimer's disease brain, which involve deficits in receptor- and G-protein-stimulated phosphoinositide hydrolysis, but not phospholipase C activity. Thus, these findings indicate that oxidative stress may contribute to impaired phosphoinositide signaling in neurological disorders in which oxidative stress occurs, and that oxidative stress can differentially influence transcription factors activated by cholinergic stimulation.
PMID: 8815874 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8736579&dopt=AbstractBrain Res Bull 1996;40(3):183-6
Inositol phosphate formation in mice prenatally exposed to drugs: relation to muscarinic receptors and postreceptor effects.
Abu-Roumi M, Newman ME, Yanai J.
Melvin A. and Eleanor Ross Laboratory for Studies in Neural Birth Defects, Department of Anatomy and Embryology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Mice were exposed to phenobarbital or heroin [diacetylmorphine (DAM)] prenatally by feeding the mother phenobarbital on gestation day 9-18; DAM was injected into the mother on gestation days 9-18. At the age of 50 days, mice exposed to phenobarbital or DAM prenatally were examined for long-term biochemical changes in the postsynaptic septohippocampal system as measured by alterations in formation of the second messenger inositol phosphate (i.p.). A significant increase in i.p. formation in response to carbachol was found after prenatal exposure to DAM. An increase in i.p. formation in response to 20 mM KCl alone or in the additional presence of 10 mM carbachol or 1mM physostigmine was found after prenatal exposure to phenobarbital or DAM. In addition, a significant increase in IP formation in response to sodium fluoride was found after prenatal exposure to phenobarbital or DAM. It is suggested that an increase in G-protein activation and in the second messenger formation accompanies the early drug-induced upregulation of the muscarinic receptors found in our previous studies.
PMID: 8736579 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8731456&dopt=AbstractBiol Psychiatry 1996 Apr 15;39(8):697-702
Platelet phosphoinositide signaling system: an overstimulated pathway in depression.
Karege F, Bovier P, Rudolph W, Gaillard JM.
University of Geneva Institutes of Psychiatry, Division of Neuropsychiatry, Chene-Bourg (Geneva), Switzerland.
In order to test a possible depression-associated defect in signal transduction, platelet alpha 2-adrenergic-mediated phosphoinositide (PI) hydrolysis was measured, both in drug-free major depressed patients and in control healthy subjects. Results that express phospholipase C activity have shown significant increase in the metabolites of epinephrine-stimulated tritiated phosphatidyl-4,5-biphosphate (3H-PIP2) with respect to basal activity (saline-stimulated). Thrombin (2 units) and 10 mM sodium fluoride (NaF) also induced an increase in 3H-PIP2 metabolites. These increases were potentiated in drug-free depressed patients both in epinephrine-and thrombin-stimulated platelets. In contrast, sodium fluoride, which directly stimulates G protein without receptor interaction, did not differentiate between patients and controls with respect to PI hydrolysis. This result suggests a possible depression-associated defect in heterologous receptor-G protein interaction.
Publication Types: Clinical TrialPMID: 8731456 [PubMed - indexed for MEDLINE]
Fluoride 1996; 29(2):63-71Investigations of soft tissue functions in fluorotic individuals of north Gujarat
Michael M, Barot VV, Chinoy NJ
Reproductive Toxicology and Endocrinology Unit, Department of Zoology, School of Sciences, Gujarat University, Ahmedabad, India
Summary: The present study was undertaken to investigate the various health problems caused by water-borne fluroide in endemic villages of Mehsana and Banaskantha districts of Gujarat. The study revealed high levels of fluoride in serum samples of the villagers. Mottling of teeth and skeletal complications were common. Intake of fluoride caused a decrease in haemoglobin content and in the serum protein levels. Serum cholesterol levels were normal. Circulating levels of testosterone were decreased, but not significantly enough to indicate an effect on reproductive functions. The enhanced levels of serum transaminases, which are markers for liver function, indicated structural and functional changes in liver due to fluoride intake. Changes in the serum calcium, sodium and potassium levels revealed electrolyte imbalance in the fluorotic individuals. While levels of thyroid stimulating hormone (TSH) and triodothyronine (T3) did not vary, a significant increase in the thyroxine (T4) levels suggested alteration in thyroid function. Thus the study revealed some harmful effects of fluoride in the soft tissue functions of the endemic population.
Fluoride 1996; 29(2):72-76Fluoride inhibition of [2-14C]Thymidine incorporation into DNA in mung bean seedlings
Narita A (a), Nakamura Y (a), Shigematsu (a), Yu MH (b)
(a) Institute of Whole Body Metabolism, Chiba, Japan
(b) Center for Environmental Sciences, Western Washington University, Bellingham, WashingtonSummary: The effect of sodium fluoride (NaF) on the incorporation of [2-14C]thymidine into DNA in germinating mung bean (Vigna radiata cv Uthong-1) seedlings was studied. One-day-old mung bean seedlings were treated with water (control) or 1.0 mM NaF containing [2-14C]thymidine for 24 h and the thymidine incorporation into various parts of the radicle was examined. Silver grains shown by the autoradiograph of the F-exposed radicle were markedly decreased compared with those of the control. Fission rates (%) exhibited by various parts of the experimental radicles were much lower than those of the control. The results indicted that NaF suppressed DNA synthesis in mung bean seedlings.
Fluoride 1996; 29(4):190-192Effect of a High Fluoride Water Supply on Children's Intelligence
Zhao LB, Liang GH, Zhang DN, Wu XR Lu-Liang
Public Health Bureau, Shanxi 033000, China.
In Shanxi Province, China, children living in the endemic fluoride village of Sima (water supply F = 4.12 mg/L) located near Xiaoyi City had average IQ (97.69) significantly lower (p < 0.02) than children living to the north in the nonendemic village of Xinghua (F = 0.91 mg/L; average IQ = 105.21). These differences were not associated with gender, but the IQ scores were directly related to educational level of the parents.
Fluoride 1996; 29(4):217-226Ameliorative role of amino acids on fluorde-induced alterations in uterine carbohydrate metabolism in mice
NJ Chinoy * and D Patel
* Director, School of Sciences and Head, Zoology Department, Gujarat University, Ahmedabad, India
Summary: The effects on female mice of sodium fluoride (NaF) administration, at a dose of 5 mg/kg body weight for varied durations (7, 15, 30, 45 and 60 days), were investigated in order to evaluate time-related changes in uterine carbohydrate metabolism. The therapeutic effects of simultaneous glycine and/or glutamine administration along with NaF, for 45 and 60 days, were also investigated. The results revealed that the NaF was effective from the 45th day of treatment, and was much more effective after 60 days. A significant decline in body weight and uterine weight was observed. Accumulation of glycogen in the uterus with a concomitant decrease in blood glucose could be correlated with inhibition of phosphorylase activity affecting uterine carbohydrate metabolism. The serum catecholamine concentrations were significantly enhanced, possibly due to stress induced by administration of fluoride. The elevated catecholamine levels may be one of the causative factors affecting carbohydrate metabolism, and would influence the hypothalamus gonadal axis. Decreased levels of protein in serum and uterus indicated altered uterine metabolsm in the presence of fluoride. Administration of the amino acids glycine and gluthamine, individually and in combination, along with NaF, helped to maintain the status quo of all parameters compared with controls. The results demonstrate that the amino acids glycine and glutamine have an ameliorative effect on NaF-treated animals. Hence it is suggested that a protein rich diet could mitigate the fluoride-induced health hazards in endemic areas the world over.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8954949&dopt=AbstractBiochem Biophys Res Commun 1996 Dec 13;229(2):630-4
Evidence for G-protein-dependent and G-protein-independent activation of phospholipase D in lymphocytes.
Cao YZ, Reddy PV, Sordillo LM, Hildenbrandt GR, Reddy CC.
Environmental Resources Research Institute, Pennsylvania State University, University Park 16802, USA.
Previously we reported that tumor-promoting phorbol esters stimulate phospholipase D (PLD) independent of protein kinase C (PKC) activation in bovine lymph node lymphocytes. (Cao et al., Biochem. Biophys. Res. Commun. 171, 955-962, 1990; 217, 908-915, 1995). In the present study, we examined the effects of prostagladins (PGs), E2, F2 alpha, D2, and H2 on PLD activity as measured by conversion of [1-14C] arachidonic acid-labeled phospholipids into phosphatidylethanol (PEt) in bovine lymph node lymphocytes. Prostaglandins stimulated the formation of PEt at an optimal concentration of 10 microM with relative stimulatory effect on the order of PGE2 > PGF2 alpha > PGH2 > PGD2. The PGE2-stimulated formation of PEt was dose-dependent in the range of 0.1 to 10 microM and was not inhibited by PKC inhibitors staurosporine and K252a. When both PGE2 and 12-0-tetradecanoylphorbol-13-acetate (TPA) were included, their effect on the PLD activation was additive. Furthermore, NaF, a G-protein activator, stimulated the PEt formation. Interestingly, the stimulatory effects of PGE2 and NaF were not additive; however, the formation of PEt by NaF and TPA was additive. These results suggest that similar to TPA, PGs increase PLD activity independent of PKC and the stimulation by PGs and TPA in lymphocytes may involve both G-protein-dependent and G-protein-independent signaling pathways.
PMID: 8954949 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8637511&dopt=AbstractMutat Res 1996 May;368(1):7-13
Clastogenic activity of sodium fluoride to rat vertebral body-derived cells in culture.
Mihashi M, Tsutsui T.
Department of Pharmacology, School of Dentistry at Tokyo, Nippon Dental University, Japan.
The US National Toxicology Program has shown equivocal evidence of carcinogenic activity of sodium fluoride (NaF) in male F344/N rats based on the occurrence of five osteosarcomas in treated animals. In the study the osteosarcomas developed mainly in the rat vertebrae. To provide a possible mechanistic basis for the observed tumors, the genotoxic effects of NaF on the possible target organ of NaF carcinogenesis were examined. Rat vertebral body-derived (RVBd) cells were established from trabecular bone of vertebral bodies of a male F344/N rat 6 weeks of age and treated with NaF. RVBd cells in secondary culture exhibited a high level of alkaline phosphatase (ALP) activity when the cells at confluence were assayed by ALP staining. When the histochemical examination was performed on RVBd cell colonies, most of the colonies were stained positively for ALP. Confluent RVBd cells were responsive to 10(-8) M 1 alpha.25-dihydroxyvitamin D3 with a 7.7-fold increase in osteocalcin production over base line values. The von Kossa staining demonstrated that in the presence of 2 mM beta-glycerophosphate, RVBd cells that were allowed to grow past confluence for approximately 2 months formed mineralized nodules. When RVBd cells in tertiary culture were treated with NaF at 0.5-2.0 mM for 24-72 h, the growth and/or survival of the treated cells was reduced in a dose-dependent manner. Significant increases in the frequencies of chromosome aberrations were induced in a dose- and treatment time-dependent fashion when NaF was administered to RVBd cells at 0.5 and 1.0 mM for 24 and 48 h. The results indicate that NaF is genotoxic to rat vertebrae, providing a possible mechanism for the vertebrae, as a target organ of NaF carcinogenesis.
PMID: 8637511 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8940250&dopt=AbstractExp Cell Res 1996 Nov 25;229(1):69-76
Heterotrimeric G-proteins are implicated in the regulation of apoptosis in pancreatic beta-cells.
Loweth AC, Williams GT, Scarpello JH, Morgan NG.
Cellular Pharmacology Group, Department of Biological Sciences, Keele University, Staffordshire, United Kingdom.
Recent studies have provided evidence that apoptosis of pancreatic beta-cells is important in the early etiology of both type I and type II diabetes mellitus. The mechanisms responsible for induction of apoptosis are unknown, but we present evidence that the signal transduction pathway controlling the process in pancreatic beta-cells is regulated by G-proteins. We have employed the global G-protein activator fluoride and show that this agent induces apoptosis in clonal RINm5F pancreatic beta-cells and also in the cells of normal rat islets of Langerhans. The process is time and concentration dependent and may reflect the formation of AIF4- since it was inhibited by the aluminum chelator deferoxamine. Induction of apoptosis by fluoride was confirmed by acridine orange staining of cell nuclei, by electron-microscopic examination of chromatin condensation, and by oligonucleosomal degradation of DNA. The involvement of G-proteins was confirmed by culture of beta-cells in the presence of pertussis toxin (PTX) prior to exposure to fluoride. PTX did not affect the extent of cell death under control conditions but it consistently, and markedly, enhanced the response to fluoride. The results demonstrate that apoptosis can be induced in pancreatic beta-cells by sustained activation of a G-protein-dependent signaling pathway(s) and they further suggest that a pertussis toxin-sensitive G-protein is involved in attenuation of the response. Treatment of RINm5F pancreatic beta-cells with dibutyrylcAMP resulted in a dose-dependent, saturable increase in cell death, suggesting that a sustained rise in intracellular cAMP may form part of the effector system controlling apoptosis.
PMID: 8940250 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8890832&dopt=AbstractJ Am Coll Cardiol 1996 Nov 1;28(5):1314-22
Myocardial sympathetic denervation prevents chamber-specific alteration of beta-adrenergic transmembrane signaling in rabbits with heart failure.
Anzai T, Yoshikawa T, Baba A, Nishimura H, Shiraki H, Nagami K, Suzuki M, Wainai Y, Ogawa S.
Department of Medicine, Keio University School of Medicine, Tokyo, Japan.
OBJECTIVES: The purpose of this study was to assess the effect of myocardial sympathetic denervation on the chamber-specific alteration of beta-adrenergic signaling in left ventricular failure in rabbits.
BACKGROUND: Local abnormalities in sympathetic nerve terminals, including the neuronal reuptake of norepinephrine, are thought to be responsible for the chamber-specific regulation of beta-adrenergic signaling in heart failure.
METHODS: Sixteen rabbits were given 6-hydroxydopamine, 25 mg/kg body weight intravenously on days 1 and 2 and 50 mg/kg intravenously on days 7 and 8. Another 16 rabbits received vehicle. Aortic regurgitation was induced in eight of the 6-hydroxydopamine-treated and eight of the vehicle-treated rabbits on day 14. Another eight of the 6-hydroxydopamine-treated and eight of the vehicle-treated rabbits underwent a sham operation. The hearts were excised for biochemical analysis on day 21.
RESULTS: Hemodynamic characteristics on day 21 showed left ventricular failure in both the aortic regurgitation groups. The plasma norepinephrine concentration on day 21 was higher in both the aortic regurgitation groups than in the sham groups. The beta-adrenoceptor densities and isoproterenol plus 5'-guanylylimidodiphosphate-, 5'-guanylylimidodiphosphate- and sodium fluoride-stimulated adenylyl cyclase activities were decreased only in the failing left ventricle of the vehicle-pretreated aortic regurgitation group, but in both ventricles of the 6-hydroxydopamine-pretreated aortic regurgitation group. The basal and forskolin-stimulated adenylyl cyclase activities were similar in both the aortic regurgitation groups and in the sham groups.
CONCLUSIONS: Sympathetic denervation prevented chamber-specific alterations in beta-adrenergic signaling in acute left ventricular failure. Local loss of sympathetic nerve endings, and especially the defective neuronal norepinephrine reuptake, are likely to be responsible for the chamber-specific alteration of the beta-adrenoceptor-G protein-adenylyl cyclase system in heart failure in rabbits.
PMID: 8890832 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8915773&dopt=AbstractJ Bone Miner Res 1996 Nov;11(11):1655-65
Role of protein kinase C alpha, Arf, and cytoplasmic calcium transients in phospholipase D activation by sodium fluoride in osteoblast-like cells.
Bourgoin SG, Harbour D, Poubelle PE.
Centre de Recherche en Rhumatologie et Immunologie, C.H.U.L., Ste-Foy, Quebec, Canada.
The effect of fluoride on phospholipase D (PLD) activation was studied using in vitro culture of Saos-2, MG-63 osteosarcoma cells, and normal osteoblast-like cells derived from human bone explants. Millimolar concentrations of NaF induced a significant accumulation of phosphatidylethanol (PEt) in Saos-2 cells but not in MG-63 and normal osteoblast-like cells. PLD activation was evident at 15 mM and concentration-dependent up to 50 mM. This stimulation was inhibited by deferoxamine, a chelator of Al3+, suggesting that PLD activation involves fluoride-sensitive G proteins. A good correlation was found between the levels of intracellular free Ca2+ and the activation of PLD. The time courses of the two responses were nearly identical. The ability of NaF to induce both responses was largely dependent on the presence of extracellular calcium. The calcium ionophore A23187 reproduced the effect of NaF, and this effect was antagonized by EGTA, suggesting that PLD activation was, at least in part, a calcium-regulated event. Phorbol 12-myristate 13-acetate (PMA) also stimulated PLD activity in human bone cells. Protein kinase C alpha (PKC alpha) and epsilon were expressed in Saos-2 cells. Acute pretreatment of cells with PMA reduced concomitantly the amounts of PKC alpha, but not of PKC epsilon, and the subsequent activation of PLD elicited by PKC activators. The PLD response to NaF was not attenuated but rather enhanced by down-regulation of PKC alpha. Therefore, PKC-alpha-induced PLD activation is unlikely to mediate the effect of NaF. Moreover, PMA and NaF showed a supraadditive effect on PLD activation in Saos-2 cells. This stimulation, in contrast to NaF alone, was not reduced by EGTA. Hence, mobilization of calcium by NaF cannot account for the enhanced PLD activation in response to PMA stimulation. Membrane Arf and RhoA contents were assessed by Western immunoblot analyses. Membranes derived from NaF-stimulated Saos-2 cells contained more Arf and RhoA when compared with membranes derived from control or PMA-stimulated cells. Translocation of the small GTPases was calcium-independent. We conclude that PLD activation by NaF in Saos-2 cells includes a fluoride-sensitive G protein, increases in the levels of intracellular calcium, and Arf/RhoA redistribution to membranes. The results also indicate that the NaF-induced Arf/RhoA translocation exerts in concert with PMA-activated PKC alpha a synergistic effect on the activation of PLD in Saos-2 cells.
PMID: 8915773 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8915775&dopt=AbstractJ Bone Miner Res 1996 Nov;11(11):1676-87
Characteristics of NaF-induced differentiation of HL-60 cells.
Kawase T, Oguro A, Orikasa M, Burns DM.
Department of Pharmacology, Niigata University School of Dentistry, Japan.
Sodium fluoride (NaF) is known to stimulate osteoblastic bone formation, but little attention has been given to the possibility that NaF also affects bone resorption and the differentiation of osteoclastic progenitor cells. When human promyelocytic HL-60 cells were treated with NaF (0.5 mM, 0-4 days), cell proliferation was inhibited, and the addition of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (10nM, 0-4 days) augmented this antiproliferative effect. NaF increased cellular reduction of nitroblue tetrazolium (NBT), and this effect was strongly augmented by 1,25(OH)2D3. In addition, NaF produced marked changes in cellular morphology, increased cellular adhesion to plastic, reduced the nuclear/cytoplasmic ratio, and increased cellular expression of chloroacetate esterase, but failed to alter cellular nonspecific esterase activity. Furthermore, NaF increased expression of CD11b and CD66b, and this stimulation was enhanced by adding 1,25(OH)2D3. The sum of these changes in classical promyelocytic cellular indices suggest: (1) that NaF stimulates the early stages of HL-60 differentiation toward a granulocyte-like cell and
(2) that 1,25(OH)2D3 promotes these actions of NaF.
Additional experiments aimed at further understanding the NaF-induced conversion of HL-60 cells identified further changes. NaF also increased cellular production of prostaglandin E2 (PGE2) and nitric oxide (NO) and induced expression of inducible nitric oxide synthase (iNOS); 1,25(OH)2D3 once again augmented these NaF-induced effects. Similarly, NaF stimulated the production of interleukin 1 alpha (IL-1 alpha), IL-6, and tumor necrosis factor-alpha, and 1,25(OH)2D3 again strongly enhanced these effects. Indomethacin completely blocked stimulation of NBT reduction, NO production, and iNOS expression induced by NaF plus 1,25(OH)2D3; adding exogenous PGE2 (0.1-10 ng/ml) to these indomethacin-blocked cultures dose-dependently restored NO production. These additional findings together with the observed slow onset (24-48 h) of NaF and 1,25(OH)2D3 interaction strongly suggest that 1,25(OH)2D3 acts as a cofactor with NaF primarily through interaction with an endogenous NaF-induced cyclo-oxygenase product(s), quite possibly PGE2 itself. Such a mechanism for NaF and 1,25(OH)2D3 interaction would be strongly analogous to the interaction we have recently demonstrated between 1,25(OH)2D3 and PGE1 on the differentiation of HL-60 cells.
PMID: 8915775 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8770696&dopt=AbstractJ Bone Miner Res 1996 Jan;11(1):46-55
Aluminum potentiates the effect of fluoride on tyrosine phosphorylation and osteoblast replication in vitro and bone mass in vivo.
Caverzasio J, Imai T, Ammann P, Burgener D, Bonjour JP.
Department of Medicine, University Hospital of Geneva, Switzerland.
Osteosclerosis in workers exposed to fluoride (F) and aluminum (Al) (industrial fluorosis) led to the use of F as a treatment to increase bone mass in osteoporosis patients. Because the influence of traces of Al on the effects of F on bone formation is heretofore unknown, we have investigated this issue both in vitro and in vivo. We have found that minute amounts of Al (< or = 10(-5) M) potentiate the effects of F in vitro such that osteoblast proliferation increased by 15 +/- 2.7% at 50 microM (p < 0.001) and by 117.6 +/- 5.1% at 750 microM (p < 0.001), concentrations of F with no mitogenic effect alone. F + Al time-dependently modulated a growth factor signaling pathway(s) associated with enhanced tyrosine phosphorylation (TyrP) of several proteins (p90 [2.9x], p77 [4.9x], p68 [9.6x], and mitogen activated protein kinases [3x]). TyrP was only slightly or not at all changed by F and Al alone, respectively. The effects of F + Al on TyrP and cell proliferation were markedly reduced by 100 microM tyrphostin-51, a tyrosine kinase inhibitor. Protein kinase A (PKA) and protein kinase C (PKC) pathways were not involved in this response. In vivo, F + Al administered for 8 months, at doses that had no effect when the minerals were administered individually, significantly enhanced proximal tibia bone mineral density (BMD) by 6.3 +/- 1% compared with initial values and by 2-fold compared with control ovariectomized rats (p < 0.0001). These effects are consistent with a crucial role of Al in osteosclerosis observed in industrial fluorosis. The results suggest that the combination of F + Al modulates a growth factor-dependent TyrP pathway enhancing mitogen-activated protein kinase and osteoblastic proliferation and bone mass.
PMID: 8770696 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9167048&dopt=AbstractCent Eur J Public Health 1996;4 Suppl:6-10
The use of isolated lung cells in in vitro pulmonary toxicology: studies of DNA damage, apoptosis and alteration of gene expression.
Schwarze PE, Johnsen NM, Samuelsen JT, Thrane EV, Lund K, Lag M, Refsnes M, Kongerud J, Becher R, Boe J, Holme JA, Wiger R.
Department of Environmental Medicine, National Institute of Public Health, Oslo, Norway.
Isolated lung cells constitute a valuable system for studying mechanisms involved in chemically induced toxicity in the lung. Different lung cells isolated from various species may be studied. Bronchiolar Clara and alveolar type 2 cells produce important lung-specific proteins, hold a major role in the metabolism of xenobiotics and serve as progenitor cells for other lung cell types. They are possible target cells in lung carcinogenesis. Alveolar macrophages play an important role in lung defence and in inflammatory responses. In the present study we have characterised chemically induced DNA damage, apoptosis, changes in cell cycle progression, transformation and alterations in gene expression in these specific lung cells isolated from rat, rabbit and human. Major differences between the cell types and the various species in the induction of DNA damage by chemicals were found, as measured by the 32P-postlabelling and alkaline filter elution techniques. Benzo(a)pyrene and hydrogen fluoride were found to induce apoptosis in the isolated cells as measured by microscopical analysis and flow cytometry. The function of various important tissue- or cell type specific proteins (CYP 2B1, Clara cell protein) and/or cellular signal transduction pathways constitute important targets that may be affected by exposure to toxic compounds. Using immunological and molecular techniques the differential expression of specific proteins/RNAs and their activity can be studied. Among other proteins, c/ebp is involved in the regulation of transcription at the end of signal pathways. The protein is differentially expressed in rat lung cells and thus could be suitable for studying differential toxic effects in various lung cells. In humans, bronchoalveolar lavage (BAL) fluid from human volunteers can be readily obtained and examined after exposure to different chemical compounds. An increase in the percentage of CD3-positive cells (T-lymphocytes) was found after exposure to hydrogen fluoride. The number of certain cell types and cytokines may be used to estimate the degree of inflammatory reaction. In conclusion, the use of in vitro data including the use of specific, primary human lung cell types may contribute considerably to the quality of risk assessment, together with in vivo data from animals and man.
PMID: 9167048 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8895884&dopt=AbstractNeuroscience 1996 Oct;74(4):1175-85
Bidirectional regulation of neuronal potassium currents by the G-protein activator aluminum fluoride as a function of intracellular calcium concentration.
Matzel LD, Rogers RF, Talk AC.
Department of Psychology, Rutgers University, New Brunswick, NJ 08903, USA.
Hydrolysis-resistant activation of G-proteins by extracellular perfusion of fluoride ions was examined in Type B cells isolated from the cerebral ganglion of the marine mollusc Hermissenda. Under single-electrode voltage-clamp, modulation by aluminum fluoride ions of several classes of outward K+ currents as well as an inward Ca2+ current was observed. Following injection of the Ca2+ chelator EGTA, aluminum fluoride ions selectively increased a slow, voltage-dependent K+ current (IK) within 5 min of application, while in the absence of EGTA, aluminum fluoride ions induced a small, transient reduction of IK. Neither the magnitude nor steady-state inactivation of a fast, voltage-dependent K+ current (IA), nor a slow, Ca2+-dependent K+ current (IK-Ca), were affected by aluminum fluoride ions. In contrast, when perfusion of aluminum fluoride ions was accompanied by a repetitive depolarization and a concomitant increase in intracellular Ca2+, both IA and the combined late currents (IK and IK-Ca) were markedly reduced, a reduction which was not observed following depolarization alone or if the pairing of aluminum fluoride ions and depolarization was preceded by an injection of EGTA. The reduction of membrane conductance by the pairing of aluminum fluoride ions with depolarization could not be accounted for by an increased Ca2+ conductance, as aluminum fluoride ions produced only a small decrease in the voltage-dependent Ca2+ current. In total, these results indicate that regulatory G-proteins may bidirectionally modulate neuronal K+ currents, the direction of which is dependent on intracellular Ca2+ concentration. Such a dual regulatory mechanism may contribute to the modulation of membrane excitability observed when presynaptic activity is paired with postsynaptic depolarization, and thus may contribute to some forms of activity-dependent plasticity involving metabatropic receptors.
PMID: 8895884 [PubMed - indexed for MEDLINE]
NOTE: AG Gilman, co-author of this report, shared the 1994 Nobel Prize for the discovery of "G-proteins and the role of these proteins in signal transduction in cells."Full report available free at http://www.jbc.org/cgi/content/full/271/44/27209
J Biol Chem 1996 Nov 1;271(44):27209-12
The GTPase-activating protein RGS4 stabilizes the transition state for nucleotide hydrolysis.
Berman DM, Kozasa T, Gilman AG.
Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
RGS proteins constitute a newly appreciated group of negative regulators of G protein signaling. Discovered by genetic screens in yeast, worms, and other organisms, two mammalian RGS proteins, RGS4 and GAIP, act as GTPase-activating proteins for members of the Gi family of G protein alpha subunits. We have purified recombinant RGS4 to homogeneity and demonstrate that it acts catalytically to stimulate GTP hydrolysis by Gi proteins. Furthermore, RGS4 stabilizes the transition state for GTP hydrolysis, as evidenced by its high affinity for the GDP-AlF4--bound forms of Goalpha and Gialpha and its relatively low affinity for the GTPgammaS- and GDP-bound forms of these proteins. Consequently, RGS4 is most likely not a downstream effector for activated Galpha subunits. All members of the Gi subfamily of proteins tested are substrates for RGS4 (including Gtalpha and Gzalpha); the protein has lower affinity for Gqalpha, and it does not stimulate the GTPase activity of Gsalpha or G12alpha.
PMID: 8910288 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8938585&dopt=AbstractJ Mol Endocrinol 1996 Oct;17(2):101-7
Production of [3H]choline-labelled metabolites from endogenously 3H-labelled phosphatidylcholine in mouse pancreatic islets.
Capito K, Hansen SE, Thams P.
Department of Medical Biochemistry and Genetics, Panum Institute, University of Copenhagen, Denmark.
The involvement of phosphatidylcholine (PC) hydrolysis in the regulation of insulin secretion was studied in mouse pancreatic islets prelabelled with [3H]choline. Phospholipase C (PLC) and phospholipase D (PLD) activities were demonstrated and also that of an enzyme that removes both fatty acids from PC and thus catalyses the production of [3H]glycerophosphorylcholine (GroPCho). After 2 min of incubation with 20 mM glucose a 35% increase in the content of [3H]GroPCho was observed in prelabelled islets, whereas the amount of [3H]lysoPC, [3H]phosphorylcholine (PCho) and [3H]choline was unaffected. After 30 min of incubation with 20 mM glucose, 0.2 mM tolbutamide, 40 mM KC1, 10 mM succinic acid monomethyl ester (SME) or 10 mM NaF, a 25-50% increase in [3H]GroPCho was observed. In the presence of 100 microM diazoxide or 35 microM RHC 80267 the glucose activation was attenuated. PLC was stimulated slightly by tolbutamide and 100 microM isoprenaline (isoproterenol), whereas SME decreased the amount of [3H]PCho by 10%. [3H]Choline content was increased by 25-40% in the presence of 0.16 microM 12-O-tetradecanoylphorbol 13-acetate (TPA), 10 mM NaF or 100 microM carbachol. This effect of fluoride was potentiated in the presence of 20 mM glucose. It is concluded that metabolism of PC to GroPCho may be involved in the regulation of glucose-stimulated insulin secretion, and that PLD may participate in insulin secretion evoked by TPA, carbachol and fluoride.
PMID: 8938585 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8772164&dopt=AbstractCell Tissue Res 1996 Sep;285(3):501-7
Secretagogue-induced apocrine secretion in the Harderian gland of the rat.
Gesase AP, Satoh Y, Ono K.
Department of Anatomy, Asahikawa Medical College, Asahikawa 078, Japan.
Harderian glands of male albino rats were stimulated with secretagogues and examined by transmission and scanning electron microscopy for the purpose of studying the apocrine secretory mechanism. Rats in the control group were perfused with standard HEPES-buffered Ringer's solution. Their glandular endpieces showed wide lumina that contained few secretory materials; spontaneous exocytosis was sometimes observed. However, there were no features suggestive of an apocrine secretory mechanism or myoepithelial cell contractions. After stimulation with NaF+AlCl3 or carbachol in HEPES-buffered Ringer's solution, the rats shed "bloody tears" and the glandular lumina were jammed with apical protrusions, cytoplasmic material and secretory products. The basal surface of the glandular cells showed bulging caused by myoepithelial cell contraction. Perfusion with HEPES-buffered Ringer's solution containing papaverine inhibited secretagogue-induced myoepithelial cell contraction but not the enhanced secretory activities of the glandular cells. The present results demonstrate that the Harderian gland of the rat can release secretory material not only by exocytosis, but also by an apocrine mechanism under stimulating conditions, and that myoepithelial cell contraction may not be involved in causing apical protrusion in the glandular cells.
PMID: 8772164 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8765098&dopt=AbstractBiochim Biophys Acta 1996 Aug 14;1283(1):80-8
Modulation of the skeletal muscle ryanodine receptor by endogenous phosphorylation of 160/150-kDa proteins of the sarcoplasmic reticulum.
Orr I, Shoshan-Barmatz V.
Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
This paper demonstrates and characterizes the inhibition of ryanodine binding caused by the phosphorylation of the 160/150-kDa proteins in skeletal muscle sarcoplasmic reticulum (SR). Inhibition of ryanodine binding was obtained by preincubation of SR membranes with ATP + NaF . The inhibition was characterized by the following findings:
(a) If ATP was replaced by AdoPP[NH]P, inhibition of ryanodine binding activity was not observed.
(b) The inhibitory effect of preincubation with ATP + NaF, like the phosphorylation of 150/160-kDa proteins, was Ca2+ dependent.
(c) Inhibition of ryanodine binding, as the protein phosphorylation, was not observed if NaF (> 30 mM) was replaced with okadaic acid.
(d) The optimal pH for the inhibition and the phosphorylation was about 7.0.
(e) Both the phosphorylation of the 160/150-kDa proteins and inhibition of ryanodine binding were prevented by dichlorobenzimidazole riboside and hemin, inhibitors of casein kinase II. (f) Dephosphorylation of the 160/150-kDa proteins prevented the inhibition of ryanodine binding.
(g) The presence of NP-40 during the phosphorylation prevented both the 160/150-kDa phosphorylation and the inhibition of ryanodine binding.
Furthermore, a linear relationship was obtained between the degree of ryanodine binding inhibition and the level of phosphorylation of the 160/150-kDa proteins, as controlled by ATP or NaF concentrations. The binding affinity for Ca2+ of the ryanodine receptor (RyR) was modified by phosphorylation of the 160/150-kDa proteins, decreasing by up to 100-fold. The phosphorylation of the SR membranes resulted in an elimination of ryanodine binding sites with slight effect on the ryanodine binding affinity. These results suggest the modulation of the properties of the RyR by phosphorylation/dephosphorylation of the 160/150-kDa proteins. The identification of the phosphorylated 160/150-kDa proteins, their kinase, and the structural interactions between them and the RyR are presented in the accompanying paper.
PMID: 8765098 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8739246&dopt=AbstractMol Cell Biochem 1996 Apr 12-26;157(1-2):191-6
Beta-adrenoceptor mediated signal transduction in congestive heart failure in cardiomyopathic (UM-X7.1) hamsters.
Kaura D, Takeda N, Sethi R, Wang X, Nagano M, Dhalla NS.
Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
In view of the lack of information regarding the status of beta-adrenoceptor mediated signal transduction mechanisms at severe stages of congestive heart failure, the status of beta-adrenoceptors, G-proteins and adenylyl cyclase activities was examined in 220-275 day old cardiomyopathic hamster hearts. Although no changes in the Kd values for beta 1- and beta 2-adrenoceptors were seen, the number of beta 1-adrenoceptors, unlike that of beta 2-adrenoceptors, was markedly decreased in cardiac membranes from failing hearts. The activation of adenylyl cyclase in the failing hearts by different concentrations of isoproterenol was also attenuated in comparison to the control preparations. The basal adenylyl cyclase activity in cardiac membranes from the failing hearts was not altered; however, the stimulated enzyme activities, when measured in the presence of forskolin, NaF or Gpp(NH)p were depressed significantly. The functional activity of Gs-proteins (measured by cholera toxin stimulation of adenylyl cyclase) was depressed whereas that of Gi-proteins (measured by pertussis toxin stimulation of adenylyl cyclase) was increased in the failing hearts. Not only were the Gs- and Gi-protein contents (measured by immunoblotting) increased, the bioactivities of these proteins as determined by ADP-ribosylations in the presence of cholera toxin and pertussis toxin, respectively, were also higher in failing hearts in comparison to the control values. Northern blot analysis revealed that the signals for Gs- and Gi-protein mRNAs were augmented at this stage of heart failure. These results indicate that the loss of adrenergic support at severe stages of congestive heart failure in cardiomyopathic hamsters may involve a reduction in the number of beta 1-adrenoceptors, and an increase in Gi-protein contents as well as bioactivities in addition to an uncoupling of Gs-proteins from the catalytic site of adenylyl cyclase in cardiac membrane.
PMID: 8739246 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8825685&dopt=AbstractArch Toxicol 1996;70(3-4):249-51
Apoptotic cell death following exposure to fluoride in rat alveolar macrophages.
Hirano S, Ando M.
Regional Environment Division, National Institute for Environmental Studies, Ibaraki, Japan.
Since inhaled fluoride is implicated in the acute respiratory failure, cytotoxic effects of fluoride on alveolar macrophages, primary target cells of inhaled toxicants, were investigated. The LC50 of sodium fluoride was estimated to be 0.41 mM, while 1 mM sodium chloride, bromide and iodide had virtually no effects on the viability of alveolar macrophages. Photomicroscopic observation revealed that nuclei of the fluoride-exposed alveolar macrophages were fragmented. The ladder formation was observed when DNA isolated from fluoride-exposed alveolar macrophages was electrophoresed in agarose gel. These results suggest that cytotoxicity of fluoride is associated with apoptosis in rat alveolar macrophages.
PMID: 8825685 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8882385&dopt=AbstractCell Biol Toxicol 1996 Feb;12(1):11-7
Evaluation of mutagenic and cytotoxic effects of sodium fluoride on mammalian cells influenced by an acid environment.
Slamenova D, Ruppova K, Gabelova A, Wsolova L.
Cancer Research Institute of Slovak Academy of Sciences, Bratislava, Slovak Republic.
The mutagenic activity of sodium fluoride at reduced pH was studied in the V79/HGPRT system. Statistical analysis of the results of mutagenicity testing suggests that, despite its high toxicity, sodium fluoride has no mutagenic effects at reduced pH on hamster V79 cells. Short-term treatment of cells with sodium fluoride at reduced pH inhibits growth activity of cells as well as synthesis of pulse-labeled nascent DNA and cumulative RNA synthesis and proteosynthesis. From the results of this study we suggest that an acid environment which supports formation of hydrogen fluoride increases toxic but not mutagenic potencies of sodium fluoride.
PMID: 8882385 [PubMed - indexed for MEDLINE]
- http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8818202&dopt=Abstract
Arch Physiol Biochem 1996;104(2):180-4
Sodium fluoride inhibits the antisecretory effect of peptide YY and its analog in rabbit jejunum.
Eto B, Boisset M, Desjeux JF.
Unite de Recherche sur les Fonctions Intestinales, le Metabolisme et la Nutrition, Hopital Saint-Lazare, Paris, France.
The antisecretory peptide YY (PYY) inhibits jejunal secretion through and inhibitory protein (Gi), whereas sodium fluoride (NaF) is a potent activator of G-proteins. This work was conducted to characterize the role of NaF in the antisecretory effect of PYY. For this purpose, electrogenic chloride secretion was assessed by measuring the in vitro variations in short-circuit current (delta Isc) due to alterations in ionic transport, using Ussing chambers Results:
1) NaF induced a transient increase in Isc at concentrations exceeding 5 mM.
2) 2 mM NaF inhibited the antisecretory effect of 0.1 microM PYY and of its analog P915.
3) stimulation of secretion by forskolin and dbcAMP was halved in the presence of 2 mM NaF.
4) Inhibition of protein kinase C by 0.1 mM bisindolylmaleimide caused a sustained increase in Isc in the presence of 5 mM NaF.
In conclusion, these results confirm that PYY inhibits electrogenic chloride secretion and show that NaF stimulates it, and suggest that NaF reduces PYY-induced inhibition via a G-dependent and a G-independent functional pathway.
PMID: 8818202 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8769995&dopt=AbstractAm J Physiol 1996 Aug;271(2 Pt 1):C555-62
Dual regulation of PLA2 and PGI2 production by G proteins in bovine aortic endothelial cells.
Rosenstock M, Danon A, Rimon G.
Department of Clinical Pharmacology, Corob Center for Health Sciences, Ben-Gurion University, Beer-Sheva, Israel.
NaF, a nonselective activator of heterotrimeric guanine nucleotide-binding proteins (G proteins), increased the release of arachidonic acid (AA) and prostacyclin (PGI2) production in bovine aortic endothelial cells (BAEC) at low concentrations (40-60 mM). On the other hand, higher concentrations (100 mM) inhibited phospholipase A2 (PLA2) compared with the basal activity. Intracellular Ca2+ levels did not rise after treatment with stimulatory concentrations of NaF, and, moreover, neither neomycin nor Ca(2+)-free medium affected the biphasic pattern of PGI2 synthesis in response to NaF. CGP-43187, an inhibitor of the 14-kDa secretory PLA2, did not affect NaF-induced AA release. However, AACOCF3, a specific inhibitor of the cytosolic 85-kDa PLA2 (cPLA2), abrogated AA release and PGI2 production in response to 60 mM NaF. A biphasic pattern of PGI2 production was also obtained with the guanosine 5'-triphosphate analogues guanosine 5'-O-(3-thiotriphosphate) and guanylylimidodiphosphate in permeabilized BAEC. Pretreatment of the cells with guanosine 5'-O-(2-thiodiphosphate) suppressed the inhibition and the stimulation of AA release induced by guanylylimidodiphosphate. In addition, phenylisopropyl adenosine inhibited the release of AA and PGI2, whereas ATP and bradykinin increased PGI2. Pertussis toxin not only inhibited ATP- and bradykinin-stimulated PGI2 release, it also reversed the inhibitory effect of phenylisopropyl adenosine, resulting in a significant stimulation. These findings strongly suggest that, in BAEC, cPLA2 is coupled with more than one G protein that are involved in inhibition and stimulation of cPLA2 activity.
PMID: 8769995 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8754735&dopt=AbstractEndocrinology 1996 Aug;137(8):3170-6
Increased cyclic adenosine 3',5'-monophosphate inhibits G protein-coupled activation of phospholipase C in rat FRTL-5 thyroid cells.
Laglia G, Zeiger MA, Leipricht A, Caturegli P, Levine MA, Kohn LD, Saji M.
Section on Cell Regulation, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Thyroid cell growth and function are regulated by several hormones and growth factors that bind to cell surface receptors coupled via G proteins, Gs and Gq, to stimulation of adenylyl cyclase and phospholipase C (PLC), respectively. We created a permanently transfected FRTL-5 cell line (TG8) in which the thyroglobulin gene promoter directs expression of the cholera toxin (CT) A1 subunit (CTA1). CTA1 catalyzes ADP ribosylation of Gs alpha, which results in persistent activation of Gs alpha. Activated Gs alpha causes constitutive stimulation of adenylyl cyclase and increases levels of intracellular cAMP. Because G protein-coupled signaling pathways exhibit cross-talk, we compared TG8 cells to FRTL-5 cells transfected with the neomycin resistance gene (TG4) to determine whether constitutive stimulation of adenylyl cyclase influences the PLC pathway. PLC activity was assessed by measuring levels of total inositol phosphates (IPs) in TG4 and TG8 cells that had been preincubated with myo-[3H]inositol for 2 days. Baseline values of [3H]IP production were similar for the two cell lines. Incubation of TG4 control cells with 10(-8) M TSH, 300 microM ATP, and 100 microM norepinephrine for 60 min stimulated 2.5-, 8.1-, and 3.4-fold increases, respectively, in [3H]IP production over the control value. By contrast, there was no [3H]IP response to any of these ligands in TG8 cells. TG8 cells exhibit a decrease in [35S]adenosine 5'-(gamma-thio)triphosphate binding to their cell surface compared to TG4 control cells counterparts, but no decrease in [125I]TSH binding. Treatment of TG4 cells with 100 ng/ml CT, 50 microM forskolin, or 1 mM 8-bromo-cAMP for 2 days reproduced the loss of ligand-stimulated [3H]IP synthesis present in TG8 cells. Although levels of immunoreactive Gq alpha and Gq alpha 11 were normal in TG8 cells, sodium fluoride-induced [3H]IP production was also inhibited. Levels of immunoreactive PLC beta 3, the dominant subtype of PLC beta in FRTL-5 cells, were not altered in TG8 cells or by CT treatment of TG4 cells. These data indicate that elevated levels of cAMP can inhibit the activity of G protein-coupled PLC. Further study of this model will elucidate our understanding of the exact mechanism responsible for this interaction.
PMID: 8754735 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8706742&dopt=AbstractEur J Biochem 1996 Jul 15;239(2):369-75
In vitro activation of the NADPH oxidase by fluoride. Possible involvement of a factor activating GTP hydrolysis on Rac (Rac-GAP).
Wolfl J, Dagher MC, Fuchs A, Geiszt M, Ligeti E.
Department of Physiology, Semmelweis Medical University, Budapest, Hungary.
The possible mechanism of activation of the NADPH oxidase by fluoride was investigated in the cell-free system. It is shown that the stimulatory effect of fluoride is inhibited by guanosine 5'-O-(2-thiodiphosphate) (GDP[S]) and potentiated by GTP. The effect of fluoride is not additive with GTP[S]. Fluoride activation requires the presence of Mg2+ in millimolar concentration but is independent of Al3+. The activating effect of fluoride is preserved in solubilized membrane extract after removal of the majority of heterotrimeric GTP-binding proteins by immunoadsorption. Fluoride has no direct action either on the nucleotide exchange of GTP hydrolysis of the isolated Rac protein. In contrast, fluoride effectively inhibits Rac-GTPase activity enhanced by a membrane component. In this way, fluoride could prolong the prevalence of Rac in the GTP-bound state and, as a consequence, activate NADPH oxidase. The possibility of the involvement of a membrane-bound Rac GTPase-activating protein activity in the physiological regulation of the enzyme is raised.
PMID: 8706742 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8712682&dopt=AbstractAnticancer Res 1996 Jul-Aug;16(4A):1643-50
Modulation of calcium signalling and proliferation in monoblastoid U-937 cells.
Ridefelt P, Larsson R, Nygren P, Larsson E, Nilsson K.
Department of Surgery, Uppsala University, Sweden.
The effects of TPA (12-0-tetradecanoylphorbol-13-acetate) and G-protein modulators on the concentration of cytoplasmic Ca2+ ([Ca2+]i), cytoplasmic pH and cell growth were investigated in monoblastoid U-937 cells. The G-protein activator NaF causes a dose-dependent increase of [Ca2+]i, that is partially sensitive to inhibition by pertussis toxin. The [Ca2+]i rise appears to come mainly from extracellular sources, and the Ca2+ influx is mediated by channels insensitive to the Ca2+ blocker verapamil. The Ca2+ ionophore ionomycin causes a biphasic rise of [Ca2+]i, reaching steady state levels slightly higher than those attained with NaF. TPA per se has no effect on [Ca2+]i, but potently reverses the NaF or ionomycin induced [Ca2+]i rise. Also, TPA partially counteracted the acidification induced by NaF. Both NaF and ionomycin per se had no effect on cell growth but partially counteracted TPA induced growth inhibition. Interferon-gamma and tumor necrosis factor-alpha did not affect [Ca2+]i by themselves but lowered the [Ca2+]i of NaF stimulated cells. The cytokines had no effect on cytoplasmic pH. This study indicates that elevations of [Ca2+]i in themselves does not trigger proliferation, but alterations of [Ca2+]i modulates the regulation of U937-cell growth.
PMID: 8712682 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8733583&dopt=AbstractBr J Pharmacol 1996 May;118(1):115-22
Enhanced contractile responses of arteries from streptozotocin diabetic rats to sodium fluoride.
Weber LP, Chow WL, Abebe W, MacLeod KM.
Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
1. Previous studies from this laboratory have demonstrated that alpha 1-adrenoceptor-mediated increases in tension and phosphoinositide metabolism are enhanced in the aorta and mesenteric arteries from diabetic rats. The purpose of the present investigation was to determine whether contractile responses to sodium fluoride (NaF), which directly stimulates GTP-binding proteins (G-proteins), are also enhanced in diabetic arteries.
2. NaF (1-20 mM) in the presence of 10 microM aluminium chloride produced slowly developing, concentration-dependent contractions in mesenteric arteries from three month streptozotocin-diabetic (60 mg kg-1, i.v.) male Wistar rats and age-matched control rats. The maximum contractile response but not the sensitivity to NaF was significantly greater in mesenteric arteries from diabetic than from control rats, as was the response to noradrenaline (NA). Maximum contractile responses of aorta and caudal artery from diabetic rats to NaF were also significantly enhanced.
3. Removal of the endothelium and denervation with 6-hydroxydopamine did not significantly alter the maximum contractile response of mesenteric arteries from either control or diabetic rats to NaF. Similarly, NaF had no effect on cyclic AMP levels in aorta, and no difference in cyclic AMP levels, either basally or in the presence of NaF, was detected between control and diabetic rat aorta.
4. Contractile responses of mesenteric arteries from both control and diabetic rats to NaF were diminished in calcium-free Krebs solution, but the NaF response remained significantly elevated in mesenteric arteries from diabetic rats compared to control.
5. Ryanodine (30 microM) which depletes intracellular calcium stores, nifedipine (3 microM) which blocks dihydropyridine-sensitive calcium channels and calphostin C (0.5 microM) which selectively inhibits protein kinase C, all significantly inhibited maximum contractile responses of mesenteric arteries from control and diabetic rats to NaF. There were no significant differences between control and diabetic arteries in the relative magnitude of the inhibition produce by the three antagonist.
6. These data suggest that there may be increased activation of the same signalling processes that mediate NA-stimulated vasoconstriction, perhaps contraction-associated G-proteins or the effectors coupled to these G-proteins, in response to NaF in mesenteric arteries from diabetic rats. This may also be responsible for the enhanced contractile responses of these arteries to alpha 1-adrenoceptor stimulation.
PMID: 8733583 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8665403&dopt=AbstractComp Biochem Physiol C Pharmacol Toxicol Endocrinol 1996 Jan;113(1):81-4
Photoperiodic elevation of testicular zinc protects seminiferous tubules against fluoride toxicity in the bank vole (Clethrionomys glareolus).
Krasowska A, Wlostowski T.
Institute of Biology, Bialystok Branch of Warsaw University, Poland.
Recent work has shown that a high fluoride (F) intake in rodents leads to histopathologic changes in the germinal epithelium of testes and to zinc deficiency in the testis and several other organs. The purpose of the present study was to determine whether an elecvation of testicular zinc concentration during fluoride exposure could protect the testes of bank vole from damage. The elevation of testicular zinc was achieved by exposing the bank voles to a long photoperiod (16 hr light/8 hr dark). The zinc concentration in the testes of bank voles kept under the long photoperiod was 38% higher than that in animals exposed to a moderate photoperiod (12 hr light/12 hr dark). Fluoride exposure (200 micrograms F/ml drinking water) during 4 months decreased additionally (p < 0.05) zinc concentration in the testes of bank voles kept under the moderate photoperiod. The same animals also exhibited histopathologic changes in the germinal epithelium. By contrast, these disturbances were not observed in animals maintained in the long photoperiod. This experiment suggests that an increase in testicular zinc due to a long photoperiod prevents seminiferous tubules from a damage induced by fluoride in bank voles. The protective effects of zinc (or a long photoperiod) did not appear to be related to a decrease in testicular fluoride accumulation or lipid peroxidation.
PMID: 8665403 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8606623&dopt=AbstractLife Sci 1996;58(2):145-53
Inhibition of muscarinic stimulated phosphoinositide hydrolysis in the rat parotid gland by cAMP.
Gerstin EH Jr, Ehlert FJ.
Department of Pharmacology, College of Medicine, University of California, Irvine, 92717 USA.
The ability of agents that increase or mimic cAMP to affect muscarinic receptor mediated phosphoinositide hydrolysis was investigated in the rat parotid gland. Forskolin (10 microM) and isoproterenol (10 microM) elevated cAMP in the parotid gland by 2-fold and 7-fold, respectively, and these agents also inhibited oxotremorine-M (3 microM) mediated phosphoinositide hydrolysis by 14% and 26%, respectively. Forskolin (1, 4.3, 18, and 75 microM) increased cAMP accumulation and inhibited PIP2 hydrolysis in a concentration-dependent manner. Forskolin (75 micrometers) shifted the concentration-response curve for the full agonist oxotremorine-M rightward by 4.2-fold. Pre-treatment with the phosphodiesterase inhibitor isobutylmethylxanthine (1 mM) reduced the maximum effect of oxotremorine-M by 31%. The inhibitory effect of isoproterenol and forskolin on muscarinic receptor-mediated phosphoinositide hydrolysis was unaffected by the removal of extracellular Ca2+. Moreover, isoproterenol and forskolin dampened sodium fluoride and oxotremorine-M mediated phosphoinositide hydrolysis to the same extent suggesting that the inhibitory effect of cAMP is downstream from the muscarinic receptor.
PMID: 8606623 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8696079&dopt=Abstract
- Biometals 1996 Jul;9(3):277-83
Impact of aluminium, fluoride and fluoroaluminate complex on ATPase activity of Nostoc linckia and Chlorella vulgaris.
Husaini Y, Rai LC, Mallick N.
Department of Botany, Banaras Hindu University, Varanasi, India.
This study demonstrates a pH-dependent inhibition of Mg(2+)- and Ca(2+)-ATPase activities of Nostoc linckia and Chlorella vulgaris exposed to AlCl3, AlF3, NaF and AlCl3+NaF together. AlF3 and the combination of AlCl3+NaF were more inhibitory to both the enzymes as compared with AlCl3 and NaF. Toxicity of the test compounds increased with increasing acidity. Interaction of AlCl3+NaF was additive on N. linckia and C. vulgaris, respectively, at pH 7.5 and 6.8, and synergistic at pH 6.0 and 4.5. In the presence of 60 and 100 microM PO4(3-) an increased NaF concentration (in the AlCl3+NaF combination) was required to produce the same degree of inhibition in ATP synthesis and ATPase activity. Toxicity of fluoroaluminate was reduced in the presence of EDTA and citrate. Except for beryllium to some extent, combinations of cadmium, cobalt, iron, manganese, tin and zinc with fluoride were not as effective as aluminium in inhibiting the ATPase activity. The presence of a 100 kDa protein band in SDS-PAGE of both control as well as AlCl3+NaF-treated samples suggested that AlF4- inhibits the ATPase activity by acting as a functional barrier without affecting the structure of the enzyme.
PMID: 8696079 [PubMed - indexed for MEDLINE]
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