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1994 Fluoride Abstracts. Part 1.
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Brain Res 1994 Nov 21;664(1-2):94-100
Fluorocitrate and fluoroacetate effects on astrocyte metabolism in vitro.
Swanson RA, Graham SH.
Department of Neurology, University of California, San Francisco.
The Krebs cycle inhibitor fluorocitrate (FC) and its precursor fluoroacetate (FA) are taken up in brain preferentially by glia. These compounds are used experimentally to inhibit glial metabolism in situ. The actions of these agents have been attributed to both the disruption of carbon flux through the Krebs cycle and to impairment of ATP production. We used primary astrocyte cultures to evaluate these two possible modes of action. Astrocyte ATP levels exhibited little or no reduction during incubation with 0.5 mM FC or 25 mM FA. Correspondingly, FC and FA caused less than 30% reductions in glutamate uptake (P > 0.05), an important energy-dependent astrocyte function. Carbon flux through the Krebs cycle was assessed by measuring astrocyte glutamine production in the absence of exogenous glutamate or aspartate. Under these conditions, glutamine production was reduced 65 +/- 5% by 0.5 mM FC and 61 +/- 3% by 25 mM FA (P < 0.01). In contrast, FC and FA had no effect on glutamine production when 50 microM glutamate was provided in the media. These findings suggest that the metabolic effects of FC and FA on astrocytes in vivo result from impairment of carbon flux through the Krebs cycle, and not from impairment of oxidative ATP production.
PMID: 7895052 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7833696&dopt=AbstractBrain Res Cogn Brain Res 1994 Sep;2(2):93-102
Astrocytes implicated in the energizing of intermediate memory processes in neonate chicks.
O'Dowd BS, Gibbs ME, Sedman GL, Ng KT.
La Trobe University, Bundoora, Vic., Australia.
Day-old chicks trained in a single trial passive avoidance task develop three sequentially dependent stages of discrimination memory. The second intermediate stage is made up of two phases: the initial A phase being susceptible to inhibition of oxidative metabolism in the tricarboxcylic acid (TCA) system with 2,4-dinitrophenol (DNP), and a second DNP-insensitive B phase. The studies reported in this paper found that doses of the metabolic toxins fluoroacetate (0.2 mM) and fluorocitrate (0.1 mM) previously reported to disrupt the astrocytic TCA cycle only, also disrupt the A (but not the B) phase of intermediate memory, suggesting an interaction between the astrocytic and neuronal oxidative systems may be required to meet the metabolic demands of this earlier phase. The B phase, on the other hand, was not expressed in the presence of the glycolytic inhibitor iodoacetate (1 mM), suggesting that glycolysis (known to be more efficient in astrocytes) and glycogenolysis (which may be exclusive to astrocytes) may support this second phase of intermediate memory. In this regard, the rise in forebrain noradrenaline levels previously reported to occur before the appearance of the B phase is particularly relevant. Given that noradrenaline has been shown to be capable of enhancing glycogenolysis in astrocyte-enriched cell cultures, it is conceivable that noradrenaline exerts an effect on memory by stimulating the glycolytic system in astrocytes, thereby providing energy or metabolites (e.g. pyruvate) needed to sustain the cellular processes operating during the B phase of intermediate memory.
PMID: 7833696 [PubMed - indexed for MEDLINE]
Fluoride 1994; 27(3):155-159Effect of long-term administration of fluoride on levels of protein, free amino acids and RNA in rabbit brain
Shashi A (1), Singh JP (1), Thapar SP (2)
(1) Department of Zoology, Punjabi University, Patiala 14702, India
(2) Department of Anatomy, Dayanand Medical Collee and Hospital, Ludhiana, IndiaSummary: Biochemical alterations in the brain produced during experimental fluorosis were studied. Albino rabbits of both sexes were administered sodium fluoride solutions in the concentrations of 5, 10, 20, and 50 mg/kg body wt/day by subcutaneous injection for 100 days. The control rabbits were given 1 cc distilled water/kg body weight/day for the same length of time. In fluoride treated rabbits the brain showed significant decline (P <0.001) in soluble, basic total protein and free amino acid levels. RNA content rapidly decreased (P <0.001) in the brains of experimental animals compared to the controls. However, in male animals treated with 5 and 10 mg fluoride no statistically significant differences in RNA content of brain were observed. The depletion of proteins produced degenerative changes in purkinje clles of the cerebellar cortex. These changes in the brain lead to paralysis of limbs in fluoridated animals.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8056997&dopt=AbstractInt Clin Psychopharmacol 1994 Summer;9(2):79-82
Psychopharmacology of fluoride: a review.
Spittle B.
Department of Psychological Medicine, University of Otago Medical School, Dunedin, New Zealand.
Although the blood-brain barrier is relatively impermeable to fluoride, it does not pose an absolute barrier and fluoride has the ability to enter the brain. The literature was examined to assess the quality of the evidence for cerebral impairment occurring due to exposure to fluoride from therapeutic or environmental sources. Several surveys of persons chronically exposed to industrial fluoride pollution reported symptoms related to impaired central nervous system functioning with impaired cognition and memory. Examination of individual case reports showed the evidence for aetiological relationships between symptoms and fluoride exposure to be of variable quality. The evidence was seen as being suggestive of a relationship rather than being definitive. The difficulties with concentration and memory described in relation to exposure to fluoride did not occur in isolation but were accompanied by other symptoms of which general malaise and fatigue were central. Possible mechanisms whereby fluoride could affect brain function include influencing calcium currents, altering enzyme configuration by forming strong hydrogen bonds with amide groups, inhibiting cortical adenylyl cyclase activity and increasing phosphoinositide hydrolysis.
Publication Types:
- Review
- Review, Tutorial
PMID: 8056997 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7842887&dopt=AbstractZhonghua Yu Fang Yi Xue Za Zhi 1994 Sep;28(5):264-6
[Effects of sodium fluoride on the activity of Ca2+Mg(2+)-ATPase in synaptic membrane in rat brain]
[Article in Chinese]
Zhao XL, Gao WH, Zhao ZL.
Department of Environment Health Ningxia Medical College, Yinchuan.
Effects of sodium fluoride on Ca2+Mg(2+)-ATPase activity of synaptic membrane in rat brain were studied with in vitro or in vivo methods. Concentrations of sodium fluoride of 0.3, 1.6, 8.0, 20.0 and 40.0 mmol/L can significantly inhibit the activity of the enzyme with proportions of 6.6%, 18.0%, 41.0%, 55.5% and 63.1%, respectively, and with a half inhibitory concentration of 14.8 mmol/L reflecting an obvious dose-effect and time effect relationship. Analysis of enzyme substrate kinetics showed the effect that sodium fluoride had was a non competitive inhibition. Activity of Ca2+Mg(2+)-ATPase on synaptic membrane in female rat brain showed a decreasing tendency after feeding with water fluorinated with 5, 15 and 50 mg/L of fluoride during their gestation and lactation for 50 days, and that in their newborn offsprings with 5 and 50 mg/L of fluoride was inhibited by 11.3 and 32.1%, respectively.
PMID: 7842887 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8263518&dopt=AbstractJ Neurochem 1994 Jan;62(1):180-6
Agonist-induced, GTP-dependent phosphoinositide hydrolysis in postmortem human brain membranes.
Jope RS, Song L, Powers R.
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham 35294-0017.
Membranes prepared from postmortem human brain were used to measure the activities of three components of the phosphoinositide second messenger system. [3H]Phosphatidylinositol ([3H]PI) hydrolysis was stimulated by directly activating phospholipase C with calcium, by activating guanine nucleotide-binding proteins (G proteins) with guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) or with AIF4, and by receptors activated with several agonists (in the presence of GTP gamma S), including (in order of increasing magnitudes of responses) carbachol, pilocarpine, histamine, trans-1-aminocyclopentyl-1,3-dicarboxylic acid (a selective excitatory amino acid metabotropic receptor agonist), serotonin, and ATP. Gq/11 was identified as the G protein most likely to mediate [3H]PI hydrolysis in human brain membranes based on the findings that this process was not impaired by pretreatment with pertussis toxin and it was inhibited by antibodies specific for the alpha-subunit of Gq/11 but not by antibodies for G0 or Gi1. The effects of postmortem delay on [3H]PI hydrolysis were examined by studying tissues obtained 6-21 h postmortem. A slight increase in basal [3H]PI hydrolysis was associated with increased postmortem time, suggesting a slow loss of the normal inhibitory control of phospholipase C. GTP gamma S-stimulated [3H]PI hydrolysis was unaffected by postmortem times within this range, but carbachol-induced [3H]PI hydrolysis tended to decrease with increasing postmortem times. These results demonstrate that the entire phosphoinositide complex remains functional and experimentally detectable in postmortem human brain membranes. This method provides a means to study the function, regulation, effects of diseases, and responses to drugs of the phosphoinositide system in human brain.
PMID: 8263518 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7914511&dopt=AbstractGlia 1994 Apr;10(4):237-43
Synaptic transmission in the hippocampus: critical role for glial cells.
Keyser DO, Pellmar TC.
Physiology Department, Armed Forces Radiobiology Research Institute, Bethesda, Maryland 20889-5603.
The importance of glial cells in controlling the neuronal microenvironment has been increasingly recognized. We now demonstrate that glial cells play an integral role in hippocampal synaptic transmission by using the glial-specific metabolic blocker fluoroacetate (FAC) to selectively inhibit glial cell function. FAC inhibits evoked intracellular postsynaptic potentials (PSPs; IC50 = 39 microM) as well as population PSPs (IC50 = 65 microM) in field CA1 of the guinea pig hippocampal slice. Spontaneous synaptic transmission is concurrently decreased. These effects are time and dose dependent. ATP concentrations in glial but not neuronal elements are also significantly reduced with FAC treatment. Simultaneous application of the metabolic substrate isocitrate with FAC prevents both the reduction in glial ATP concentrations and the decrease in evoked PSPs. Given that isocitrate is selectively taken up by glia, these data further support a glial specific metabolic action of FAC. Additionally, FAC has no postsynaptic effects as peak responses to iontophoretically applied glutamate are unchanged. However, the decay of both iontophoretic and evoked PSPs are prolonged following FAC treatment suggesting inhibition of glutamate uptake may contribute to the FAC-induced depression of synaptic potentials. These results show, for the first time, that glial cells are critical for maintenance of synaptic transmission and suggest a role for glial cells in the modulation of synaptic efficacy.
PMID: 7914511 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8048055&dopt=AbstractToxicol Appl Pharmacol 1994 Jul;127(1):64-75
Glucocorticoids enhance intracellular signaling via adenylate cyclase at three distinct loci in the fetus: a mechanism for heterologous teratogenic sensitization?
Slotkin TA, Lau C, McCook EC, Lappi SE, Seidler FJ.
Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710.
Although high doses of glucocorticoids are teratogenic, endogenous hormones are necessary for development. Because of the central role of cAMP to control cell differentiation, we examined the dose dependence, tissue selectivity, and critical periods involved in glucocorticoid regulation of fetal intracellular signaling mediated by adenylate cyclase. Pregnant rats were given dexamethasone at doses spanning the threshold for therapeutic effects (0.05, 0.2, and 0.8 mg/kg) on either Gestational Days 11, 12, and 13 or Days 17, 18, and 19. Development of adenylate cyclase was evaluated in cell membrane preparations using basal activity in the absence or presence of GTP, maximal G-protein activation by fluoride, and maximal catalytic subunit stimulation by forskolin-Mn2+. Even at the lowest dose, dexamethasone on gestational days 11 through 13 enhanced fetal adenylate cyclase activity by accelerating development of both the G-protein component and the catalytic subunit. As a result, supersensitivity of the response to beta-adrenergic receptor stimulation by isoproterenol was also produced, even though development of beta-adrenergic receptors was unaffected. Treatment with dexamethasone later in gestation similarly fostered development of both G-protein and catalytic subunit components, with selectivity for liver and heart as opposed to brain. Again, heterologous sensitization to isoproterenol stimulation was demonstrable; in addition, late gestational treatment elevated yet a third signal transduction locus, the beta-adrenergic receptor binding site. These effects are likely contributors to glucocorticoid teratogenesis (high doses) or to more subtle disruption of cell development (low doses); because adenylate cyclase is at the convergence of multiple neuronal, hormonal, and environmental inputs, glucocorticoids may sensitize the cell to heterologous stimuli, lowering the threshold for teratogenesis by other agents.
PMID: 8048055 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7528715&dopt=AbstractHua Xi Yi Ke Da Xue Xue Bao 1994 Jun;25(2):188-91
[Effect of excessive fluoride intake on mental work capacity of children and a preliminary study of its mechanism]
[Article in Chinese]
Li Y, Li X, Wei S.
We made an investigation in 157 children, aged 12-13, born and grew up in a coal burning pattern endemic fluorosis area and an experiment on excessive fluoride intake in rat. The results showed:
(1) Excessive fluoride intake since early childhood would reduce mental work capacity (MWC) and hair zinc content:
(2) The effect on zinc metabolism was a mechanism of influence on MWC by excessive fluoride intake;
(3) Excessive fluoride intake decreased 5-hydroxy indole acetic acid and increased norepinephrine in rat brain; whether this is also a mechanism of the influence on MWC awaits confirmation.
PMID: 7528715 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7907938&dopt=Abstract
Brain Res 1994 Jan 7;633(1-2):72-6Prolonged enhancement of synaptic transmission in area CA1 of rat hippocampal slices induced by NaF/AlCl3 does not require NMDA receptor activation but is suppressed by inhibitors of phosphoinositide-mediated signalling pathways.
Breakwell NA, Publicover SJ.
School of Biological Sciences, University of Birmingham, Edgbaston, UK.
The processes underlying the action of AlF4- (10 mM NaF/10 microM AlCl3) in inducing long-lasting enhancement of synaptic transmission in area CA1 of rat hippocampal slices have been investigated. Exposure of hippocampal slices to AlF4- for 10 min caused population EPSP slope to rise by approximately 50% within 60 min of washing off the NaF/AlCl3 saline. This effect was not inhibited either by APV (50 microM), or by temporary interruption of the delivery of test stimuli during and for up to 20 min after application of the AlF4- -containing medium. However, pretreatment of preparations with either thapsigargin (1 microM) or staurosporine (1 microM), or omission of Ca2+ from the AlF4- -containing saline (no addition of EGTA) prevented the potentiating action of NaF/AlCl3. We conclude that the potentiating effect of AlF4- is via a G-protein linked to phosphoinositide turnover, and that both arms of this signalling pathway are necessary for potentiation to occur. Ca2+ influx is also a requirement, but does not occur through the NMDA receptor.
PMID: 7907938 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8067979&dopt=AbstractBehav Neural Biol 1994 May;61(3):233-41
Chronic aluminum fluoride administration. I. Behavioral observations.
Varner JA, Horvath WJ, Huie CW, Naslund HR, Isaacson RL.
Department of Psychology, Binghamton University, New York 13902-6000.
This study examined the behavioral effects of chronic ingestion of various monofluoroaluminum complexes (AlF3) in drinking water. Forty young adult male Long-Evans rats were divided into four groups of 10 rats each. The groups received different concentrations of AlF3 in the drinking water from three sample solutions having a total Al concentration of 0.5, 5.0, and 50 ppm, respectively, or double-distilled deionized water on an ad lib. basis for 45 weeks. General decline of bodily appearance was observed in the lowest concentration AlF3 group, and animals in this group succumbed in greater numbers during the course of the study than those in any other group. Examinations of performance in an open field, an analysis of walking patterns, and a balance beam test did not find any difficulties indicative of motor disorder. Indeed, on the initial trial on the balance beam, the AlF3-treated animals exhibited superior performance. No group differences were found in behavior assessed by spontaneous alternation or by a modified Morris water maze test. When retested in the Morris maze after a low dose of scopolamine (0.4 mg/kg), the control animals took longer to reach the platform while the AlF3-treated rats were not affected. In an olfactory preference test, the AlF3-treated animals failed to show preferences exhibited by the controls, indicating a possible olfactory impairment. The level of Al in the brains of the AlF3-exposed rats, as determined by direct current plasma analysis, was almost double that of the control animals. There was a similar trend for the Al content found in the kidneys.
PMID: 8067979 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7837981&dopt=AbstractMutagenesis 1994 Sep;9(5):467-71
Cytogenetic studies of sodium fluoride in mice.
Zeiger E, Gulati DK, Kaur P, Mohamed AH, Revazova J, Deaton TG.
National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
The cytogenetic effects of sodium fluoride (NaF) were measured in mice following administration in the drinking water for 6 weeks. Bone fluoride levels were determined and showed a dose-related incorporation of fluoride. Micronuclei were measured in peripheral blood erythrocytes following 1 and 6 weeks of NaF administration. Bone marrow cell preparations were examined for the presence of chromosome aberrations following 6 weeks of treatment; metaphase and anaphase cells were examined. Anaphase cells were scored in three independent laboratories, two of which also scored metaphase cells from the same slides. No increases in micronuclei were seen in peripheral erythrocytes at either time point, and no increases in chromosome aberrations were seen in bone marrow cells when metaphase or anaphase cells were examined. A concurrent positive control, cyclophosphamide, produced significant increases in peripheral blood cell micronuclei and in chromosome aberrations in bone marrow cells in metaphase. No increases in aberrations were seen in the same cyclophosphamide-treated mice when anaphase cells were examined.
PMID: 7837981 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8032126&dopt=AbstractReprod Toxicol 1994 Mar-Apr;8(2):155-9
In vitro fluoride toxicity in human spermatozoa.
Chinoy NJ, Narayana MV.
Department of Zoology, School of Sciences, Gujarat University, Ahmedabad, India.
Effects of sodium fluoride (NaF) on washed, ejaculated human spermatozoa at doses of 25, 50, and 250 mM were investigated in vitro at intervals of 5, 10, and 20 min. Sodium fluoride (NaF) did not affect the extracellular pH of sperm, except that a slight acidification was caused by the 250 mM dose only. The treatment caused a significant enhancement in acid phosphatase (ACPase) and hyaluronidase activities after 5 and 10 min. However, the decrease in the lysosomal enzyme activity after 20 min treatment could have been due to the gradual increase in fluoride accumulation by spermatozoa leading to membrane damage. Silver nitrate staining of sperm revealed elongated heads, deflagellation, and loss of the acrosome together with coiling of the tail. Sperm glutathione levels also showed a time-dependent decrease with complete depletion after 20 min indicating rapid glutathione oxidation in detoxification of the NaF. The altered lysosomal enzyme activity and glutathione levels together with morphologic anomalies resulted in a significant decline in sperm motility with an effective dose of 250 mM.
PMID: 8032126 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7889087&dopt=AbstractInt J Fertil Menopausal Stud 1994 Nov-Dec;39(6):337-46
Reversible effects of sodium fluoride ingestion on spermatozoa of the rat.
Narayana MV, Chinoy NJ.
Reproductive Endocrinology & Toxicology Unit, School of Sciences, Gujarat University, Ahmedabad, India.
The effects of ingestion of sodium fluoride (NaF), 10 mg/kg body weight for 50 days, on the structure and metabolism of sperm of albino rats (Rattus norvegicus), were investigated. In different groups of rats, the reversible effects upon withdrawal of NaF treatment and by administering some therapeutic agents, viz., ascorbic acid and calcium alone and in combination with NaF (50 and 70 days), on sperm structure and metabolism were also studied. The results revealed that the sperm acrosomal hyaluronidase and acrosin were reduced after 50 days of NaF treatment. Sperm stained with acidic alcoholic silver nitrate revealed acrosomal damage and deflagellation, which might be causative factors for the reduced activity of the enzymes. These alterations also resulted in a decline in sperm motility. The cauda epididymal sperm count was decreased, perhaps because of spermatogenic arrest. Thus, the low sperm motility and count ultimately contributed toward reduction in fertility by NaF treatment. However, withdrawal of NaF treatment for 70 days produced incomplete recovery, while administration of ascorbic acid and calcium, individually and in combination, brought about significant recovery of fluoride-induced effects. Thus, the effects of fluoride on sperm structure and metabolism of rats are transient and reversible.
PMID: 7889087 [PubMed - indexed for MEDLINE]
Fluoride 1994; 27(1):7-12Effect of fluoride on rat testicular steroidogenesis
MV Narayana and NJ Chinoy
Zoology Department, School of Sciences, Gujarat University, Ahmedabad 380 009, Gujarat, India
Summary: In view of reports of infertility among human populations in fluorosis prevailing regions, we investigated the effect of fluoride ingestion on testicular steroidogenesis in rats. Sodium fluoride (NaF) was administered to the rats orally at a daily dose of 10 mg/kg bodyweight for 50 days. The treatment did not cause significant change in testicular cholesterol levels, indicating that metabolism was not altered and that there was no hypo/hypercholesterolemic effect. In addition, activities of the intermediary enzymes in adrongenesis, viz, 3B- and 17B-hydroxysteriod dehydrogenase were only modestly decreased by NaF ingestion. Subsequently, the determination of circulating androgen levels was similar in NaF-treated rats showed a downward trend compared to those of the control group, suggesting alteration in testosterone concentratio. The histomorphometric studies revealed significant change in the Leydig cell diameter in correlation with the androgen levels. These results indicate that fluoride does interfere with steroidogenesis in short-term low-dose exposures in rats.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7920753&dopt=AbstractInt J Fertil Menopausal Stud 1994 May-Jun;39(3):164-71
Ultrastructural studies of spermiogenesis in rabbit exposed to chronic fluoride toxicity.
Kumar A, Susheela AK.
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India.
OBJECTIVE--To address the role of fluoride in causing defects to spermatids and epididymal spermatozoa.
METHODS--Male rabbits were treated with 10 mg NaF/kg body weight daily for 18 months and maintained under identical laboratory conditions along with the control rabbits not given NaF. Testis and epididymis (caput) were investigated for ultrastructural details of spermatids and spermatozoa.
RESULTS--A wide variety of structural defects were observed in the flagellum, the acrosome, and the nucleus of the spermatids and epididymal spermatozoa of fluoride-treated rabbits. Abnormalities included absence of outer microtubules, complete absence of axonemes, structural and numeric aberrations of outer dense fibers, breakdown of the fibrous sheath, and structural defects in the mitochondria of the middle piece of the flagellum. Detachment and peeling off of the acrosome from the flat surfaces of the nucleus were also observed.
CONCLUSION--The abnormalities observed render the sperm nonfunctional and ineffective, and thus there is a possible role of fluoride in causing infertility.
PMID: 7920753 [PubMed - indexed for MEDLINE]
Fluoride 1994; 27(2):76-80Preliminary observations on alterations in rabbit ovary DNA and RNA content in experimental fluorosis
A Shashi
Department of Zoology, Punjabi University, Patiala 147002, India
Summary: Forty-eight albino rabbits were administered fluorde as sodium fluoride subcutaneously in daily doses of 5, 10, 20, and 50 mg/kg body weight for three and a half months. Twelve controls received 1 cc distilled water/kg body weight/day for the same period. Ovaries from the control and fluoridated animals were analysed for DNA and RNA content. The experimental animals showed significant depletion (P < 0.001) of ovarian DNA and RNA compared to the controls. The data indicate that fluoride inhibits nucleic acid synthesis in the ovary. The findings also suggest that fluoride acts directly on DNA to produce structural changes in ovarian tissue which were subsequently confirmed by histopathological examination of control and treated animals. Further studies are desirable to define the possible role of fluoride in causing deleterious effects on reproduction such as delayed oestrus, repeated failure to conceive, and lowered viability detected earlier in experimental animals.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8195239&dopt=AbstractJ Biol Chem 1994 Jun 3;269(22):15846-52
Thrombin-mediated phosphoinositide hydrolysis in Chinese hamster ovary cells overexpressing phospholipase C-delta 1.
Banno Y, Okano Y, Nozawa Y.
Department of Biochemistry, Gifu University School of Medicine, Japan.
The regulatory mechanism(s) of a phosphoinositide-specific phospholipase C, PLC-delta 1, was investigated using a clone of stably overexpressed PLC-delta 1 (PLC delta 30 cells) in Chinese hamster ovary cells. Thrombin stimulation of PLC delta 30 cells exhibited 6.5-fold increase in total inositol phosphates (InsP), which was significantly higher than that in the vector-transfected (V1) cells (2.0-fold). AIF-4 increased InsP accumulation in both V1 and PLC delta 30 cells, and pertussis toxin partially blocked InsP accumulation in thrombin-stimulated PLC delta 30 cells. Guanosine thiotriphosphate (GTP gamma S) markedly potentiated thrombin-stimulated InsP generation in permeabilized PLC delta 30 cells compared with V1 cells, suggesting possible involvement of a G-protein (s) in the activation of PLC-delta 1. In PLC delta 30 cells, ionomycin-induced significant InsP generation and thrombin-stimulated InsP generation were completely inhibited by addition of EGTA. Furthermore, the stimulatory effects of thrombin plus GTP gamma S in PLC delta 30 cells were more sensitive to change in free calcium concentration than in V1 cells. Suppression by 12-O-tetradecanoylphorbol 13-acetate of thrombin-stimulated InsP accumulation was not affected by increasing Ca2+ concentration. These results indicate that thrombin-induced PLC-delta 1 activation is regulated via both G-protein(s) and calcium.
PMID: 8195239 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8110024&dopt=AbstractArch Environ Contam Toxicol 1994 Jan;26(1):60-3
The genotoxic and cytotoxic activities of inorganic fluoride in cultured rat bone marrow cells.
Khalil AM, Da'dara AA.
Department of Biological Sciences, Yarmouk University, Irbid, Jordan.
The effects of sodium and potassium fluoride (NaF and KF) at concentrations ranging from 10(-7) to 10(-2) M for 12, 24, or 36 h on cultured rat bone marrow cells have been studied with respect to cytotoxicity and induction of sister-chromatid exchanges (SCE). At the three exposure times, cell survival progressively decreased with increasing concentrations. Treatment with 10(-2) M fluoride resulted in a statistically significant death (62-65%) of cells. Similarly, no dividing cells were encountered at concentrations of 10(-3) M and 10(-2) M, and significant reductions in mitotic index (MI) were calculated at 10(-4) M. In contrast, cell kinetics, expressed as cell proliferation index (CPI), revealed no significant inhibitory effect of fluoride on cell proliferation. Furthermore, the mean SCE score reached a maximum (7.64 SCE/cell) in the 24-h-treated cultures. This value was not significantly different from that observed in sodium chloride (NaCl) at 10(-2) M (5.42 SCE/cell) and distilled water (4.86 SCE/cell) controls. In comparison, mitomycin-C (MMC, positive control) at 5 x 10(-8) M caused an average of 22.13 SCE/cell. These results indicated an inhibition of cell division and death of cells with high doses of fluoride with no effect on SCE frequencies.
PMID: 8110024 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7858459&dopt=AbstractJ Formos Med Assoc 1994 Aug;93(8):721-3
Acute confusion induced by a high-dose infusion of 5-fluorouracil and folinic acid.
Yeh KH, Cheng AL.
Department of Oncology, National Taiwan University Hospital, Taipei, R.O.C.
A 61-year-old man was treated with combination chemotherapy incorporating cisplatinum, etoposide, high-dose 5-fluorouracil (2,250 mg/m2/24 hours) and folinic acid for an inoperable gastric adenocarcinoma. He developed acute neurologic symptoms of mental confusion, disorientation and irritability, and then lapsed into a deep coma, lasting for approximately 40 hours during the first dose (day 2) of 5-fluorouracil and folinic acid infusion. This complication reappeared on day 25 during the second dose of 5-fluorouracil and folinic acid, which were then the only drugs given. Because folinic acid was unlikely to be associated with this condition, neurotoxicity due to high-dose 5-fluorouracil was highly suspected. The pathogenesis of 5-fluorouracil neurotoxicity may be due to a Krebs cycle blockade by fluoroacetate and fluorocitrate, thiamine deficiency, or dihydrouracil dehydrogenase deficiency. High-dose 5-fluorouracil/folinic acid infusion therapy has recently become a popular regimen for various cancers. It is necessary that both oncologists and neurologists be fully aware of this unusual complication.
PMID: 7858459 [PubMed - indexed for MEDLINE]
Fluoride 1994; 27(4):215-219Sister chromatid exchanges: a study in fluorotic individuals of North Gujarat
Sheth FJ, Multani AS, Chinoy NJ
Division of Human Genetics, Department of Zoology, University School of Sciences, Gujarat University, Ahmedabad, India. Correspondence to Professor Chinoy.
Summary: The purpose of this preliminary investigation was to compare the genotoxic effect of fluoride in human individuals directly exposed to high concentations of drinking water fluroide (1.95 to 2.2 ppm) with those in individuals exposed to concentrations (0.6 to 1.0 ppm) within the WHO permissible limit. Sister chromatid exchanges (SCE) and cell cycle proliferative index were studied in whole-blood cultures of fluorotc individuals and compared with normal controls of age-matched groups. The results suggest that the SCE rate in persons exposed to fluoride in the endemic (1.95-2.2 ppm) areas of North Gujarat is significantly higher than that of those living in Ahmedabad (0.6-1.0 ppm). There is no significant difference in the cell cycle proliferative index. Further investigations are needed to confirm the findings.
Fluoride 1994; 27(1):25-33Teratogenic effects of fluoride on chick embryo
S Krupanidhi and TM Dhanarajan
Department of Biosciences, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam, Andhra Pradesh, India
Summary:
1) The teratogenic effects of sodium fluoride on the ankle joint and toe bones of white leghorn chick embryos are reported.
2) Due to endochondrial osteofluorosis, the excessive growth of trabeculae in the epiphyses of distal tibiotarsus and proximal tarsometatarsus obliterated the ankle synovial joint space.
3) An increase occurred in the volume of bones, such as tibiotarsus, tarsometatarsus and phalanx.
4) Toe bones, namely phalanx and their articular surfaces with fibrocartilage containing spherical chondrocytes, were observed in control embryos. In fluoride-treated embryos, the distal and proximal regions of the phalanx grew enormously and irregularly, leaving little space for articulation.
5) Blackening and falling of feathers occurred in the fluoride-treated chick embryos.
Fluoride 1994; 27(2):67-75Beneficial effects of ascorbic acid and calcium on reproductive functions of sodium fluoride-treated prepubertal male rats
Chinoy NJ, Reddy VVPC, Michael M
Department of Zoology, School of Sciences, Gujarat University, Ahmedabad 388 009, India
Summary: The therapeutic effects of ascorbic acid and calcium (Ca2+) supplementation on reproductive functions of fluoride-treated (10 mg/kg body weight) male rats were investigated. Sodium fluoride treatement resulted in a decrease in almost all parameters studied except concentration of testicular cholesterol, which implies that androgen synthesis might not be affected by NaF treatment. Succinate dehydrogenase activity decreased in testis suggesting that its oxidative metabolism was altered by NaF treatment. Adenosine triposphatase activity, protein, and sialic acid levels in caput and cauda epididymides also showed a decrease. All these changes resulted in a significant decrease in sperm motility and thereby fertility rate. Glycogen concentrations in vas deferens were altered, probably due to impaired metabolic turnover. The fructose levels in vas deferens and seminal vesicle as well as the acid phosphatase activity in ventral prostate were also decreased significantly by NaF treatment.
On the other hand, simultaneous treatment of NaF along with ascorbic acid or calcium resulted in recovery in all the affected parameters studied. The recovery was more significant after treatment with ascorbic acid than with calcium. Therefore, ascorbic acid and calcium may be useful for amelioration of fluoride toxicity in endemic areas.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8082815&dopt=AbstractDev Comp Immunol 1994 Mar-Apr;18(2):137-46
Role of protein phosphatases in the regulation of nonspecific cytotoxic cell activity.
Evans DL, Jaso-Friedmann L.
Department of Medical Microbiology, College of Veterinary Medicine, University of Georgia, Athens 30602.
In vitro and in vivo experiments were conducted to determine the effects of the protein phosphatase (PPase) inhibitors sodium fluoride (fluoride), sodium orthovanadate (vanadate), and lithium chloride on nonspecific cytotoxic cell (NCC) lysis of target cells. Both vanadate and fluoride stimulated NCC activity. Lithium chloride had no effects. Optimum enhancement for "normal" NCC was at low effector:target cell ratios and at least 30 min treatment was required to achieve maximum activation effects. Fluoride, but not vanadate activation effects were largely reversible. Vanadate, 2.5-10 mM, produced a 5-10-fold increase in cytotoxicity at 25:1 E:T, whereas less than twofold increases were produced by these concentrations at 100:1. NCC activity from "stressed" fish that had essentially no cytotoxic activity were also activated by vanadate. In vitro preincubation of NCC with 10-20 mM fluoride or 2.5-10 mM vanadate produced up to a 20-fold increase in stressed cytotoxicity. Combined treatments with 2.5 mM vanadate and 20 mM fluoride produced even greater responses. In vivo responses to vanadate were also determined. Treatment of catfish by immersion in 50 microM vanadate produced significant increases in cytotoxicity by 24-48 h posttreatment. Activation of cytotoxicity was not accompanied by increases in percentage of NCC (small lymphocyte content) or in total cell numbers in anterior kidney tissue. These studies indicated that levels of NCC activity are partially regulated by control of dephosphorylation of membrane proteins. Inability of NCC from stressed fish to lyse IM-9 target cells was reversed (probably) by disruption of an equilibrium between kinase and phosphatase activities. Normal NCC were "superactivated" only under conditions were they were in limiting numbers. These data show that phosphatases must be considered as active participants in regulation of signal transduction processes.
PMID: 8082815 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7881870&dopt=AbstractRes Commun Mol Pathol Pharmacol 1994 Nov;86(2):216-26
Exocytosis in neutrophils induced by thapsigargin and other inhibitors of calcium ATP-ase.
Elferink JG.
Department of Medical Biochemistry, University of Leiden, The Netherlands.
Inhibitors of the Ca(2+)-ATPase of intracellular calcium stores, such as thapsigargin, cyclopiazonic acid and 2,5-di-(t-butyl)-1,4-benzohydro-quinone, causes exocytosis in rabbit peritoneal neutrophils. In the absence of extracellular Ca2+ no exocytosis takes place. Fluoride, a non-specific inhibitor of Ca(2+)-ATPase, also causes exocytosis. It is known that all agents tested cause both a release of calcium from intracellular stores as well as an influx of extracellular calcium. The results indicate that induction of exocytosis is not due to a release of calcium from intracellular stores, but to the influx of extracellular calcium. Thapsigargin-induced exocytosis is not inhibited by L-type channel antagonists like verapamil, but is strongly inhibited by lanthanum ions, suggesting that the calcium required for induction of exocytosis is not entering via L-type channels, but via La(3+)-sensitive calcium channels.
PMID: 7881870 [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.pnas.org/cgi/reprint/91/21/9828.pdf
Proc Natl Acad Sci U S A 1994 Oct 11;91(21):9828-31
Mechanism of GTP hydrolysis by G-protein alpha subunits.
Kleuss C, Raw AS, Lee E, Sprang SR, Gilman AG.
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235.
Hydrolysis of GTP by a variety of guanine nucleotide-binding proteins is a crucial step for regulation of these biological switches. Mutations that impair the GTPase activity of certain heterotrimeric signal-transducing G proteins or of p21ras cause tumors in man. A conserved glutamic residue in the alpha subunit of G proteins has been hypothesized to serve as a general base, thereby activating a water molecule for nucleophilic attack on GTP. The results of mutagenesis of this residue (Glu-207) in Gi alpha 1 refute this hypothesis. Based on the structure of the complex of Gi alpha 1 with GDP, Mg2+, and AlF-4, which appears to resemble the transition state for GTP hydrolysis, we believe that Gln-204 of Gi alpha 1, rather than Glu-207, supports catalysis of GTP hydrolysis by stabilization of the transition state.
PMID: 7937899 [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."Science 1994 Sep 2;265(5177):1405-12
Structures of active conformations of Gi alpha 1 and the mechanism of GTP hydrolysis.
Coleman DE, Berghuis AM, Lee E, Linder ME, Gilman AG, Sprang SR.
Howard Hughes Medical Institute, Dallas, TX.
Mechanisms of guanosine triphosphate (GTP) hydrolysis by members of the G protein alpha subunit-p21ras superfamily of guanosine triphosphatases have been studied extensively but have not been well understood. High-resolution x-ray structures of the GTP gamma S and GDP.AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues. Glutamine204 (Gln61 in p21ras) stabilizes and orients the hydrolytic water in the trigonal-bipyramidal transition state. Arginine 178 stabilizes the negative charge at the equatorial oxygen atoms of the pentacoordinate phosphate intermediate. Conserved only in the G alpha family, this residue may account for the higher hydrolytic rate of G alpha proteins relative to those of the p21ras family members. The fold of Gi alpha 1 differs from that of the homologous Gt alpha subunit in the conformation of a helix-loop sequence located in the alpha-helical domain that is characteristic of these proteins; this site may participate in effector binding. The amino-terminal 33 residues are disordered in GTP gamma S-Gi alpha 1, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.
PMID: 8073283 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7961906&dopt=Abstract
J Biol Chem 1994 Nov 25;269(47):29339-42
Requirement for intramolecular domain interaction in activation of G protein alpha subunit by aluminum fluoride and GDP but not by GTP gamma S.
Codina J, Birnbaumer L.
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
An ion-counterion interaction between the lysine of the NKXD motif in the GTPase domain and an aspartate in the inserted helical domain of alpha subunits of heterotrimeric G proteins, Lys-278 and Asp-158, respectively, of Gs alpha is shown to be essential for activation by AlF4- and partially so for interaction with beta gamma dimers and activation by GTP and receptor. However, this domain interaction is not required for activation by the non-hydrolyzable analog guanosine 5'-3-O-(thio)triphosphate. Proximity of the helical domain to the GTPase domain is thus involved in the fundamental inactive-->active transition of the protein in a way that further distinguishes alpha subunits of heterotrimeric G proteins from ras and ras-like GTPases that lack helical domains and are neither activated by AlF4- nor combine with beta gamma dimers.
PMID: 7961906 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7898487&dopt=AbstractMol Cell Biochem 1994 Nov 23;140(2):163-70
Alterations in G-proteins in congestive heart failure in cardiomyopathic (UM-X7.1) hamsters.
Sethi R, Bector N, Takeda N, Nagano M, Jasmin G, Dhalla NS.
Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
In order to explain the attenuated sympathetic support during the development of heart failure, the status of beta-adrenergic mechanisms in the failing myocardium was assessed by employing cardiomyopathic hamsters (155-170 days old) at moderate degree of congestive heart failure. The norepinephrine turnover rate was increased but the norepinephrine content was decreased in cardiomyopathic hearts. The number and the affinity of beta receptors in the sarcolemmal preparations were not changed in these hearts at moderate stage of congestive heart failure. While the basal adenylyl cyclase activity was not altered in sarcolemma, the stimulation of enzyme activity by NaF, forskolin, Gpp(NH)p or epinephrine was depressed in hearts from these cardiomyopathic hamsters. Since G-proteins are involved in modifying the adenylyl cyclase activity, the functional and bioactivities as well as contents of both Gs and Gi proteins were determined in the cardiomyopathic heart sarcolemma. The functional stimulation of adenylyl cyclase by cholera toxin, which activates Gs proteins, was markedly depressed whereas that by Pertussis toxin, which inhibits Gi proteins, was markedly augmented in cardiomyopathic hearts. The cholera toxin and pertussis toxin catalyzed ADP-ribosylation was increased by 37 and 126%, respectively; this indicated increased bioactivities of both Gs and Gi proteins in experimental preparations. The immunoblot analysis suggested 74 and 124% increase in Gs and Gi contents in failing hearts, respectively. These results suggest that depressed adenylyl cyclase activation in cardiomyopathic hamsters may not only be due to increased content and bioactivity of Gi proteins but the functional uncoupling of Gs proteins from the adenylyl cyclase enzyme may also be involved at this stage of heart failure.
PMID: 7898487 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7992312&dopt=AbstractToxicol Appl Pharmacol 1994 Dec;129(2):223-34
Beta-adrenergic receptor overexpression in the fetal rat: distribution, receptor subtypes, and coupling to adenylate cyclase activity via G-proteins.
Slotkin TA, Lau C, Seidler FJ.
Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710.
Biogenic amines are hypothesized to play a role in the control of cell differentiation. We assessed the development of beta-adrenergic receptors and their linkage to adenylate cyclase activity in order to determine whether catecholaminergic cell signaling can take place early in development. On Gestational Day 12, beta-receptors were present in rat embryo in concentrations comparable to those in mature adrenergic target tissues; the concentrations climbed fivefold by Gestational Day 18. beta-Receptor expression was higher in liver than in heart and brain, as identified both by binding to isolated membrane preparations and by receptor autoradiography; nevertheless, receptor distribution was quite widespread, with labeling visible throughout the fetus. Receptor subtype selectivities (beta 2 in liver, beta 1 in heart, predominantly beta 2 in whole fetus) were already in place in early development, but receptor coupling to adenylate cyclase via G-proteins showed substantial developmental changes. Agonist-induced displacement of radioligand binding showed little or no GTP sensitivity on Gestational Day 12, suggesting relatively poor receptor linkage to Gs. In contrast, by Day 18, GTP produced a large shift in the agonist displacement curve. Receptor stimulation of adenylate cyclase by isoproterenol also showed a developmental spike by Gestational Day 18; the pattern for isoproterenol stimulation was distinct from the ontogeny of adenylate cyclase itself and from stimulation by forskolin-Mn2+ (which bypasses the need for receptors or G-proteins) or by fluoride (which activates G-proteins nonselectively). Thus, beta-receptors are highly expressed during fetal development and the receptors are readily capable of modulating intracellular cAMP production. Fetal catecholamines, which are produced and released by the adrenal medulla, extraadrenal chromaffin tissue, and cells that transiently express adrenergic phenotype, can thus have a direct impact on the differentiation of a wide variety of cells.
PMID: 7992312 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7703916&dopt=AbstractBiochem Mol Biol Int 1994 Nov;34(5):993-1001
Adenovirus infection of myocardial cells induces an enhanced sensitivity to beta-adrenergic agonists by increasing the concentration of the stimulatory G-protein.
Novotny J, Gustafson B, Kvapil P, Ransnas LA.
Wallenberg Laboratory for Cardiovascular Research, Gothenburg University, Sweden.
Neonatal rat cardiocytes were infected with a recombinant adenovirus type 5 containing the SV40 early promoter-Gsa fusion gene in order to evaluate the presumed role of the stimulatory G-protein (Gs) in hypertrophy of myocardial cells. In vitro infection of myocardial cells with the recombinant adenovirus induced a 79-fold increase in Gs alpha mRNA and a 5-fold increase in Gs alpha protein, which was accompanied by a pronounced cell hypertrophy but not cell proliferation. Interestingly, adenovirus-infected cells displayed features of cell hypertrophy, an increase in sodium fluoride-stimulatible membrane-bound activity of adenylyl cyclase, and an enhanced beta-adrenergic sensitivity irrespective of the presence or absence of the SV40 early promoter-Gs alpha fusion gene in the virus. While the recombinant adenovirus induced a 5-fold versus 3-fold increase for plain adenovirus in cellular Gs alpha, membrane-bound Gs alpha was increased about 2-fold in both instances, which can explain similar increase in the G-protein-modulated adenylyl cyclase activity determined in membranes derived from myocardial cells infected with both types of the virus. It is concluded that adenovirus infection per se can lead to overexpression of Gs alpha and myocardial hypertrophy and thus may be of importance in the pathogenesis of virus-induced cardiomyopathy.
PMID: 7703916 [PubMed - indexed for MEDLINE]
Full report available at http://www.pnas.org/cgi/reprint/91/14/6274.pdfProc Natl Acad Sci U S A 1994 Jul 5;91(14):6274-8
- Regulation of phospholipase A2 in human leukemia cell lines: its implication for intracellular signaling.
Tsujishita Y, Asaoka Y, Nishizuka Y.
Department of Biochemistry, Kobe University School of Medicine, Japan.
Permeabilized human leukemia HL-60 and U-937 cells suspended in an acidic or alkaline medium release various unsaturated fatty acids, most abundantly oleic and arachidonic acids. Concomitant production of lysophospholipids suggests that phospholipases A2 play a major role in this fatty acid release reaction. The fatty acid release at acidic conditions depends on the intracellular Ca2+ concentrations at the 10(-8)-10(-7) M range and is enhanced by membrane-permeant diacylglycerols, although this enhancement seems independent of protein kinase C activation. On the other hand, the fatty acid release at alkaline conditions is potentiated by vanadate, and this potentiation is counteracted by genistein, suggesting a role of tyrosine phosphorylation in this release reaction. GTP[gamma S], an activator of G proteins, greatly enhances the fatty acid release. Aluminum fluoride, another activator of heterotrimeric G proteins, also greatly potentiates this release reaction. Phorbol ester increases the fatty acid release at alkaline conditions, to some extent, whereas it counteracts the vanadate-induced potentiation of fatty acid release. The results imply that several phospholipases A2 are coupled to receptors for their activation, thereby functioning in the transmembrane control of cellular events.
PMID: 8022772 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8138152&dopt=AbstractGenetics 1994 Jan;136(1):145-54
Isolation, characterization and epistasis of fluoride-resistant mutants of Caenorhabditis elegans.
Katsura I, Kondo K, Amano T, Ishihara T, Kawakami M.
DNA Research Center, National Institute of Genetics, Mishima, Japan.
We have isolated 13 fluoride-resistant mutants of the nematode Caenorhabditis elegans. All the mutations are recessive and mapped to five genes. Mutants in three of the genes (class 1 genes: flr-1 X, flr-3 IV, and flr-4 X) are resistant to 400 micrograms/ml NaF. Furthermore, they grow twice as slowly as and have smaller brood size than wild-type worms even in the absence of fluoride ion. In contrast, mutants in the other two genes (class 2 genes: flr-2 V and flr-5 V) are only partially resistant to 400 micrograms/ml NaF, and they have almost normal growth rates and brood sizes in the absence of fluoride ion. Studies on the phenotypes of double mutants showed that class 2 mutations are epistatic to class 1 mutations concerning growth rate and brood size but hypostatic with respect to fluoride resistance. We propose two models that can explain the epistasis. Since fluoride ion depletes calcium ion, inhibits some protein phosphatases and activates trimeric G-proteins, studies on these mutants may lead to discovery of a new signal transduction system that controls the growth of C. elegans.
PMID: 8138152 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7515622&dopt=AbstractBiochem Pharmacol 1994 May 18;47(10):1813-20
Effect of signal transduction pathways on the action of thapsigargin on rat mast cells. Crosstalks between cellular signalling and cytosolic pH.
Alfonso A, Botana MA, Vieytes MR, Louzao MC, Botana LM.
Departamento de Farmacologia, Facultad de Veterinaria, Lugo, Spain.
Thapsigargin elicits histamine release on rat mast cells, and this effect is increased if cells are pretreated with thapsigargin before the addition of external calcium. Okadaic acid does not modify the response of mast cells to thapsigargin, while sodium fluoride or the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) increases several fold the sensitivity of cells to thapsigargin. On the other hand, pertussis and cholera toxins inhibit the response to thapsigargin. Thapsigargin increases the activity of the Na(+)-H+ exchanger, this effect being blocked by fluoride and not modified by TPA. The metals cadmium and lanthanum completely block the effect of TPA or thapsigargin on the Na(+)-H+ exchanger. The influx of 45Ca in rat mast cells is not modified by thapsigargin, but if cells are treated with thapsigargin before the addition of calcium, the influx is markedly increased in the first 2 min before returning to normal. Our results indicate that exocytosis is modulated by crosstalks between intracellular calcium, cytosolic pH and external calcium.
PMID: 7515622 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7877135&dopt=AbstractJ Recept Res 1994 Dec;14(6-8):357-79
Characterization of mammalian Gs-alpha proteins expressed in yeast.
Stadel JM, Ecker DJ, Powers DA, Marsh J, Hoyle K, Gross M, Minnich MD, Butt TR, Crooke ST.
Department of Molecular Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406.
The guanine nucleotide regulatory protein, GS, mediates transmembrane signaling by coupling membrane receptors to the stimulation of adenylyl cyclase activity. The full length coding sequences for the M(r) = 42-45,000, short form (S), and M(r) = 46-52,000, long form (L), of the alpha-subunits of rat GS were placed in yeast expression vectors under the regulatory control of the copper-inducible CUP1 promoter and transformed into Saccharomyces cerevisiae. In the presence of 100 microM CuSO4, the transformed yeast expressed GS-alpha mRNAs and proteins. In reconstitution experiments, rat GS-alpha(S and L), solubilized from yeast membranes with 1% cholate, conferred NaF-, (-)isoproterenol-, and guanine nucleotide-dependent sensitivity to adenylyl cyclase catalytic units in S49 lymphoma cyc- cell membranes, which are devoid of endogenous GS-alpha. GS-alpha (S) demonstrated twice the activity of GS-alpha(L) in reconstitution assays of fluoride-stimulated adenylyl cyclase activity. Comparison of GS-alpha (S) expressed in yeast with GS purified from rabbit liver or human erythrocytes showed that the crude recombinant protein was fully competent in reconstituting NaF-stimulated adenylyl cyclase activity, but was only 2-5% as potent as purified GS. Addition of bovine brain beta gamma subunits during reconstitution enhanced all parameters of adenylyl cyclase activity for GS-alpha(S and L) obtained from yeast. In contrast, transducin beta gamma only enhanced agonist-stimulated adenylyl cyclase activity for GS-alpha (S and L) following reconstitution. These results demonstrate that the expression of functional mammalian GS-alpha subunits in yeast may be useful for their biochemical characterization.
PMID: 7877135 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7944352&dopt=AbstractAppl Biochem Biotechnol 1994 Aug;48(2):57-9
Degradation and disposal of some enzyme inhibitors. Scientific note.
Lunn G, Sansone EB.
Program Resources, Inc./DynCorp, Environmental Control and Research Program, NCI-Frederick Cancer Research and Development Center, MD 21702-1201.
Five enzyme inhibitors (phenylmethylsulfonyl fluoride, 4-amidinophenylmethanesulfonyl fluoride, 4-(2-aminoethyl)benzenesulfonyl fluoride, N alpha-p-tosyl-L-lysine chloromethyl ketone, and N-tosyl-L-phenylalanine chloromethyl ketone) in buffer, DMSO, or stock solutions were completely degraded by adding 1M NaOH and the final reaction mixtures were not mutagenic. The stability of these compounds decreased as the pH increased.
PMID: 7944352 [PubMed - indexed for MEDLINE]
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