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L S Wright

Publications and source records attributed to L S Wright.

At least 19 recordsLinked to original sources
PubMed2001

Increased glutamate, GABA and glutamine in lateral geniculate nucleus but not in medial geniculate nucleus caused by visual attention to novelty.

This study is concerned with cortico-thalamic neural mechanisms underlying attentional phenomena. Previous results from this laboratory demonstrated that the visual sector of the GABAergic thalamic reticular nucleus is selectively c-fos activated in rats that are naturally paying attention to features of a novel-complex environment, and that this activation is dependent on top-down glutamatergic inputs from the primary visual cortex. By contrast, the acoustic sector of the thalamic reticular nucleus is not activated despite noise generated by exploration and c-fos activation of brainstem acoustic centers (e.g. dorsal cochlear nucleus, inferior colliculus). A prediction of these results is that the levels of the neurotransmitters glutamate and GABA, and the glutamate-related amino acid glutamine, will be increased in the lateral geniculate nucleus (LGN), but not in the medial geniculate nucleus (MGN) of rats that explore a novel-complex environment in comparison to levels of these amino acids in control rats. By means of neurochemical analysis of these amino acids (HPLC) the results of this study confirmed this prediction. The results are consistent with the previously proposed 'focal attention' hypothesis postulating that a focus of attention in the primary visual cortex generates top-down center-surround facilitatory-inhibitory effects on geniculocortical transmission via corticoreticulogeniculate pathways. The results also supports the notion that a main function of corticothalamic pathways to relay thalamic nuclei is attention-dependent modulation of thalamocortical transmission.

Animals↗
PubMed1999

Proteomic analysis of simulated occupational jet fuel exposure in the lung.

We analyzed protein expression in the cytosolic fraction prepared from whole lung tissue in male Swiss-Webster mice exposed 1 h/day for seven days to aerosolized JP-8 jet fuel at concentrations of 1000 and 2500 mg/m3, simulating military occupational exposure. Lung cytosol samples were solubilized and separated via large scale, high resolution two-dimensional electrophoresis (2-DE) and gel patterns scanned, digitized and processed for statistical analysis. Significant quantitative and qualitative changes in tissue cytosol proteins resulted from jet fuel exposure. Several of the altered proteins were identified by peptide mass fingerprinting, confirmed by sequence tag analysis, and related to impaired protein synthetic machinery, toxic/metabolic stress and detoxification systems, ultrastructural damage, and functional responses to CO2 handling, acid-base homeostasis and fluid secretion. These results demonstrate a significant but comparatively moderate JP-8 effect on protein expression and corroborate previous morphological and biochemical evidence. Further molecular marker development and mechanistic inferences from these observations await proteomic analysis of whole tissue homogenates and other cell compartment, i.e., mitochondria, microsomes, and nuclei of lung and other targets.

Animals↗
PubMed1999

Maturation of cochlear glutathione-S-transferases correlates with the end of the sensitive period for ototoxicity.

The developing mammalian cochlea is especially sensitive to chemical toxins. In rats, the period of increased sensitivity falls roughly between postnatal days (P) 8 and 28. One unexplored hypothesis for this 'sensitive period' is that young cochleas may have immature complements of detoxification enzymes. Glutathione-S-transferases (GSTs) are a family of detoxification enzymes which catalyze the conjugation of many xenobiotics to glutathione. Using high performance liquid chromatography (HPLC), we measured the concentrations of soluble GST isoforms in cochleas of developing Fischer 344 rats. At P1, the concentration of isoform rGSTP1 was 9 pmol/mg protein. That of the remaining isoforms studied was low, <2 pmol/mg protein, and, except for rGSTA3, remained so throughout the period of study. At P2, immunolabelling visualized rGSTP1 in the stria vascularis, Reissner's membrane, spiral limbus and organ of Corti. From P1 to P28, rGSTP1 increased to 15 pmol/mg protein and was detected additionally in satellite cells of the spiral ganglion and in the spiral ligament. From P7 to P28, rGSTA3 increased 8-fold (3-24 pmol/mg protein), became the predominant isoform in the adult organ and localized to pillar cells, the limbus and the spiral ligament. In the vestibule, rGSTP1 predominated, although rGSTA3 increased slightly over time. These observations suggest that biochemical immaturity in detoxification enzymes in the cochlea may contribute to the increased sensitivity to ototoxins during development and that differences in detoxification enzymes between cells in the cochlea and between inner ear organs may underlie differences in susceptibility to ototoxins.

Animals↗
PubMed1998

Effects of lead on rat kidney and liver: GST expression and oxidative stress.

The effect of acute exposure to lead acetate on the expression of glutathione S-transferase (GST) subunits and the levels of reduced and oxidized glutathione (GSH) and malondialdehyde (MDA) in rat kidney and liver was determined. The purpose of this study was to determine if GSH depletion and/or oxidative stress were responsible for changes in the expression of some or all GSTs that followed lead exposure. In kidney, all GST subunits increased following injection of lead. The level of kidney GSH was not changed at either 0.5 or 1 h after lead exposure, but increased 3, 6, 12 and 24 h after a single injection of lead. MDA levels (a marker of lipid peroxidation) did not change in kidney following lead injection. Immunohistochemical markers of oxidative stress and nitric oxide production were also unchanged by lead administration. Therefore. we conclude that the increases in GST levels in kidney following lead exposure were not dependent on oxidative stress. In liver, lead injection caused GSH depletion (61% of control 12 h after lead treatment) and increased MDA production (2.5-fold increase 6 h after lead exposure), while GSTA1, GSTA2, GSTM1 and GSTM2 did not increase. Analysis of the effects of lead on GST mRNA and GST cellular localization were performed by Northern blot and immunohistochemical techniques. Immunoperoxidase light microscopy and immunogold electron microscopy revealed that the increase in kidney GSTM1 and GSTP1 occurred in nuclei, cytoplasm and microvilli of proximal tubules. Northern blot analysis of GSTA2 and GSTP1 mRNAs showed that their increase following lead exposure was inhibited by actinomycin D, suggesting transcriptional induction. This study demonstrates that acute lead exposure causes dramatic changes in the subcellular distribution and expression of rat kidney GSTs, and that these changes are not a result of oxidative stress.

Animals↗
PubMed1998

Glutathione S-transferases: two-dimensional electrophoretic protein markers of lead exposure.

Glutathione S-transferases (GST) are a family of detoxification isoenzymes that catalyze the conjugation of xenobiotics and their metabolites with reduced glutathione. Lead exposure in rats is known to induce GST isoenzymes in the liver and kidney. These changes in expression have potential use as biomarkers of lead exposure. Because two-dimensional electrophoresis (2-DE) enables one to analyze both protein abundance changes and chemical changes in protein structure, 2-DE was used to determine the effect of in vivo lead exposure on GST isoform expression in rat kidney cytosols. Male Sprague-Dawley rats were exposed to inorganic lead, and proteins were separated by conventional ISO-DALT and NEPHGE-DALT techniques and blotted for immunological identification. Lead exposure caused detectable inductions in both GSTP1 and GSTM1 and quantifiable charge modification in GSTP1. These preliminary data confirm the utility of 2-D electrophoretic GST analysis as indicative of lead exposure and toxicity and support its use for further elaboration of lead's effects on renal protein expression.

Animals↗
PubMed1998

Differential expression of cytosolic proteins in the rat kidney cortex and medulla: preliminary proteomics.

The rodent kidney is a target of many xenobiotics and is typified by regionally specific structure and function. This renders distinct regions of the kidney differentially susceptible to toxic exposure and effect. To characterize these differences at the proteome level, protein patterns from male rat kidney cortex and medulla cytosols were examined by two-dimensional electrophoresis (2-DE) and image analysis and prominent proteins identified immunologically or by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and electrospray/ionization-tandem mass spectrometry (ESI-MS/MS) sequence tag identification. An average of 727 protein spots were resolved and matched to the cortex cytosol reference pattern, and 716 in the medulla. Of this total, 127 proteins were found to differ in abundance (86 higher in cortex; 41 higher in medulla) (P < 0.001). Of those proteins that were detectable in both cortex and medulla, the abundance of 97 differed significantly while 30 proteins were found to be unique to one region or the other (26 in cortex, 4 in medulla). Twenty protein spots were identified and their regional differences are discussed. These results both confirm and expand our understanding of the molecular heterogeneity characterizing structurally and functionally distinct regions of the kidney and serve as a useful foundation for future nephrotoxicologic studies.

Alpha-Globulins↗
PubMed1998

Effects of lead on glutathione S-transferase expression in rat kidney: a dose-response study.

Glutathione S-transferases (GST, EC 2.5.1.18) are a family of phase II detoxification enzymes involved in the conjugation of glutathione to a highly diverse group of compounds. The purpose of this study was to evaluate the dose-response effects of lead acetate administration on the expression of rat kidney GST. Sprague-Dawley rats were injected with doses of lead acetate ranging from 0.11 to 114 mg/kg (0.3 to 300 mumol/kg) for three consecutive days and sacrificed 24 h later. Kidney GST activity, GST isoform HPLC profiles, blood lead analysis, and electron microscopy were performed. A dose of 1.1 mg/kg lead acetate resulted in a blood lead level of 26 micrograms/dl and produced a significant increase in GST activity which continued to increase with dose up to 38 mg/kg. Morphological changes were detected at 3.8 mg/kg and increasing severity of cellular damage paralleled dose, blood lead levels, and changes in body weight. Individual GST isoforms exhibited different thresholds and maxima; rGSTP1 and rGSTM1 had thresholds of 1.1 and 3.8 mg/kg, respectively, very similar rates of increase with dose, and a maximum yield that was 450% above control at a dose of 38 mg/kg for both enzymes. rGSTA1 and rGSTA3 showed similar thresholds (1.1 mg/kg) and maximal fold increase (275%) but varied in the relative response to each dose. These results indicate that renal GST increases occur at lead levels which are environmentally significant, that these changes precede cellular damage, and suggest that GST may serve as a tissue biomarker of lead exposure.

Animals↗
PubMed1997

Effects of triethyl lead administration on the expression of glutathione S-transferase isoenzymes and quinone reductase in rat kidney and liver.

The effects of triethyl lead chloride (TEL) on the expression of two detoxication enzyme families, glutathione S-transferases (GSTs) and NAD(P)H:quinone oxidoreductase (QR) were determined in rat liver and kidney. Fischer 344 rats were given one intraperitoneal (i.p.) injection of TEL. GST activity, GST isoenzyme levels, mRNA levels of alpha class GST isoenzymes Ya1, Ya2, and Yc1 and activity of QR were determined. Treatment of rats with TEL caused a significant increase in GST activity in kidney. In kidney, the levels of all GST subunits were significantly elevated; the largest increase was a 3.2-fold increase in GST Yb1. The levels of GST Ya1, Ya2, and Yc1 mRNA also increased after injection of TEL. In liver, TEL injection resulted in decreased GST activity and lower levels of hepatic GSTs Yb2, Yb3, Ya1, and Ya2. The largest decrease was a 40% reduction of GST Ya1. In contrast, the level of liver GST Yc1 increased from day 4 through day 14 after injection of 10 mg/kg TEL and Yp was increased 1.4-fold 4 days after injection of 12 mg/kg TEL. The levels of liver mRNAs coding for alpha class GSTs Ya1, Ya2, and Yc1 were reduced 12 h after injection of TEL. The mRNA levels of GST Ya1 and Ya2 returned to basal level while Yc1 message increased to a level higher than controls 24 h after TEL injection. The increase in Yc1 protein between days 4 and 14 is consistent with the increase in the corresponding mRNA. The activity of QR was elevated 1.5-fold in kidney and 2.7-fold in liver 14 days after the injection of TEL. This report demonstrates that administration of organic lead significantly affects GST expression and QR activity in a tissue-specific and isoenzyme-specific manner. These results indicate that GST expression and QR activity are not co-regulated.

Animals↗
PubMed1997

Increased levels of glutathione S transferases and appearance of novel alpha class isoenzymes in kidneys of mice exposed to mercuric chloride. I. Biochemical and immunohistochemical studies.

Glutathione S transferases (GST) are a family of enzymes that detoxify electrophilic xenobiotics. This enzyme family was examined in kidneys of mice exposed to mercuric chloride, a known nephrotoxin, because GST have been shown to protect cells against toxicant-induced damage and may serve as biomarkers for toxicant exposure. The purpose of this study was to determine the effect of mercuric chloride on GST activity, isoenzyme levels, and cellular localization in the kidney of Swiss Webster mice. The cellular localizations of alpha, mu, and pi class GST in the kidneys of control and mercuric chloride treated mice were studied immunohistochemically. The GST isoenzyme levels were measured by high-performance liquid chromatography. The mice treated with mercuric chloride had (1) increased amounts of GSTA1/A2 protein in kidney homogenates as compared with controls when analyzed by chromatography and electrophoresis; (2) two new isoforms of the alpha isoenzyme in kidney as demonstrated by Western blot, polyacrylamide gel electrophoresis, and high-performance liquid chromatography, and (3) increased reactivity between antibodies, against GSTA1/A2 or GSTM1 isoenzymes, and cells in the proximal and distal renal tubules as shown by immunohistochemical techniques. The authors conclude that the GSTA1/A2 may protect those cells in the proximal and distal tubules of the renal cortex from toxicant effects of mercuric chloride. This would be one general mechanism for cell protection against a wide variety of toxicants including heavy metals and halogenated aromatics.

Animals↗
PubMed1996

Calmodulin N-methyltransferase. Kinetics, mechanism, and inhibitors.

The present study was undertaken to determine kinetic and inhibition parameters and the mechanism of S-adenosyl-L-methionine:calmodulin-L-lysine N6-methyltransferase (EC 2.1.1.60, CLNMT), an enzyme for which calmodulin is a substrate. Partially purified CLNMT isolated from rat testes had a Vmax of 540 pmol/min/mg and Km values for mushroom demethylcalmodulin and S-adenosyl-L-methionine of 230 nM and 2.0 microM, respectively. Kinetic analysis indicated a complex Bi Bi sequential kinetic mechanism for CLNMT where S-adenosyl-L-methionine binds initially and is followed by demethylcalmodulin binding. When the effects of 20 different compounds that are either inhibitors of calmodulin-specific or methylation-specific functions were examined, CLNMT displayed a pattern of inhibition which differs from that seen with calmodulin-activated enzymes. The product of calmodulin methylation, fully trimethylated calmodulin, and nonmethylatable VU-3 calmodulin acted as competitive inhibitors of CLNMT, with Ki values of 310 and 400 nM, respectively. Of the 13 compounds tested, which are inhibitors of calmodulin-dependent cyclic nucleotide phosphodiesterase, only the calmodulin-binding domain from Ca2+/calmodulin-dependent kinase II, melittin, and calmidazolium were effective inhibitors of CLNMT and each exhibited a complex pattern of inhibition with Kis values of 21, 50, and 65 nM, respectively. The only potent methylation-specific inhibitor was S-adenosyl-L-homocysteine, which also displayed a complex pattern of inhibition.

Animals↗
PubMed1993

Concomitant preparative isolation of calmodulin and heat shock protein (hsp90) from bovine testes.

We have described a convenient procedure for isolating large amounts of both calmodulin and the 90-kDa heat shock protein (hsp90) from bovine testes. These two proteins coeluted from phenyl-Sepharose during calcium-dependent hydrophobic interaction chromatography. The hsp90 was separated from calmodulin by gel filtration, purified by reverse-phase HPLC or lectin affinity chromatography, and identified by N-terminal amino acid sequence and immunoblotting with hsp90-specific monoclonal antibody. The N-terminus of bovine hsp90 shared 93% amino acid identity with the murine alpha-isoform of hsp90. A third major testes protein of 97 kDa was also isolated with this protocol and was found to be homologous to the 94-kDa glucose-regulated protein.

Amino Acid Sequence↗
PubMed1993

Protein methylation in cerebellar synaptosomes.

Synaptosomes from five regions of adult rat brain were isolated, analyzed for methyl acceptor proteins, and probed for methyltransferases by photoaffinity labeling. Methylated proteins of 17 and 35 kDa were observed in all regions, but cerebellar synaptosomes were enriched in a 21-26-kDa family of methyl acceptor proteins and contained a unique major methylated protein of 52 kDa and a protein of 50 kDa, which was methylated only in the presence of EGTA. When cerebellar and liver subcellular fractions were compared, the cytosolic fractions of each tissue contained methylated proteins of 17 and 35 kDa; liver membrane fractions contained few methylated proteins, whereas cerebellar microsomes had robust methylation of the 21-26-kDa group. Differential centrifugation of lysed cerebellar synaptosomes localized the 17- and 35-kDa methyl acceptor proteins to the synaptoplasm, the 21-26-kDa family to the synaptic membranes, and the 52-kDa to synaptic vesicles. The 21-26-kDa family was identified as GTP-binding proteins by [alpha-32P]GTP overlay assay; these proteins contained a putative methylated carboxyl cysteine, based on the presence of volatile methyl esters and the inhibition of methylation by acetylfarnesylcysteine. The 52-kDa methylated protein also contained volatile methyl esters, but did not bind [alpha-32P]GTP. When synaptosomes were screened for putative methyltransferases by S-adenosyl-L-[methyl-3H]methionine photoaffinity labeling, a protein of 24 kDa was detected only in cerebellum, and this labeled protein was localized to synaptic membranes.

Affinity Labels↗
PubMed1991

A calmodulin endoproteinase from mitochondrial membranes.

A proteinase specific for calmodulin has been identified in a crude rat kidney Triton-extracted or sonicated mitochondrial fraction and solubilized by EGTA extraction of these membranes. Mitochondrial fractions from other tissues had less activity, with relative activities: kidney = spleen greater than testes greater than liver, and no detectable activity in either brain or skeletal muscle. This enzyme is active in the presence of EGTA, but not in the presence of calcium, and cleaves calmodulin into three major peptide fragments with Mr 6000, 9000 and 10,000. N-methylated and non-methylated calmodulins were both cleaved by calmodulin proteinase and while troponin was a poor substrate, it was cleaved in the presence of either calcium or EGTA. No other EF hand calcium-binding proteins or other major mitochondrial proteins were cleaved by this enzyme. The peptides resulting from calmodulin proteinase action were isolated by reverse-phase high performance liquid chromatography (HPLC) and sequenced. Sequence analysis indicated that calmodulin proteinase cleaves calmodulin at Lys-75. The effects of proteinase inhibitors indicate that calmodulin proteinase is a trypsin-like enzyme belonging to the serine endopeptidase family of enzymes.

Amino Acid Sequence↗
PubMed1991

Correlates of drinking and drug use by higher education faculty and staff: implications for prevention.

The prevalence and frequency of drug and alcohol abuse among higher education faculty and staff is not known. Higher education is a cultural environment which, on the one hand, is stressful and, on the other, permits a high degree of autonomy. This relationship of stress and autonomy is predicted to produce drug and alcohol abuse. Information is gathered by anonymous, self-report questionnaires, on the frequency and prevalence of faculty and staff drug and alcohol use at a regional university. Responses show alcohol and drug use within the last year and month among four higher education occupational groups: faculty, administrators, clerical staff, and physical plant/custodial staff. While stress was found to be weakly correlated with some drug use in the last month, depression was consistently correlated with drug use and moderately correlated with suicidal thoughts and tendencies, as well as job dissatisfaction. Drug and alcohol abuse is a factor in behavioral problems that affect faculty/staff and can be addressed through Employee Assistance Programs.

Administrative Personnel↗
PubMed1990

Coagulopathy and warfarin-associated breast necrosis in a patient with a primary brain tumor.

Although the association of coagulopathy and neoplastic disease is well documented, there have been few reports of patients with primary central nervous system tumors who exhibited hypercoagulable states. We report the case of a 58-year-old woman with a recurrent falcine meningioma and repeated episodes of venous thrombosis who developed warfarin-associated breast necrosis on the fifth day of coumadin therapy. Laboratory evaluation at that time demonstrated an elevated prothrombin time and normal activated partial thromboplastin time. Of the 24 cases of warfarin-associated massive necrosis of the breast described in the literature, only one other case was associated with a neoplasm, a resected craniopharyngioma.

Blood Coagulation Disorders↗
PubMed1990

The relationship of alcohol, tobacco, marijuana, and other illegal drug use to delinquency among Mexican-American, black, and white adolescent males.

This study examined the relationship between drug use and delinquent behavior among 348 high school males (154 whites, 172 Mexican-Americans, and 22 blacks) and 89 adjudicated delinquent males confined to a maximum-security facility for violent and repeat offenders (37 whites, 25 Mexican-Americans, and 27 blacks). Data were collected in the spring of 1986 using self-administered questionnaires. Analyses were performed separately for each racial subgroup. Simple correlations revealed that self-reported alcohol, tobacco, marijuana, and other illegal drug use were all significantly related to both minor and violent delinquency for all three racial groups. Multiple regression analysis revealed that the use of these substances accounted for 40% to 47% of the variance in minor delinquency and for 59% of the variance in violent delinquency among blacks, 53% of the variance in violent delinquency among Mexican-Americans, and 34% of the variance in violent delinquency among whites. The best predictors of violent delinquency were the frequent use of illegal drugs other than marijuana and use of tobacco, in that order, among Mexican-Americans; the frequent use of other illegal drugs, marijuana, and tobacco, in that order, for whites; and the frequent use of illegal drugs, followed by marijuana, for blacks.

Adolescent↗