Biomedical subjects

J L York

Publications and source records attributed to J L York.

At least 19 recordsLinked to original sources

PubMed2001

Oxidative stress and reactive nitrogen species generation during renal ischemia.

Previous evidence suggests that both oxygen radicals and nitric oxide (NO) are important mediators of injury during renal ischemia-reperfusion (I-R) injury. However, the generation of reactive nitrogen species (RNS) has not been evaluated in this model at early time points. The purpose of these studies was to examine the development of oxidant stress and the formation of RNS during I-R injury. Male Sprague-Dawley rats were anesthetized and subjected to 40 min of bilateral renal ischemia followed by 0, 3, or 6 h of reperfusion. Control animals received a sham operation. Plasma urea nitrogen and creatinine levels were monitored as markers of renal injury. Glutathione (GSH) oxidation and 4-hydroxynonenal (4-HNE)-protein adducts were used as markers of oxidant stress. 3-Nitrotyrosine (3-NT) was used as a biomarker of RNS formation. Significant increases in plasma creatinine concentrations and urea nitrogen levels were found following both 3 and 6 h of reperfusion. Increases in GSH oxidation, 4-HNE-protein adduct levels, and 3-NT levels were observed following 40 min of ischemia with no reperfusion. Since these results suggested RNS generation during the 40 min of ischemia, a time course of RNS generation following 0, 5, 10, 20, and 40 min of ischemia was evaluated. Significant increases in 3-NT generation was detected as early as 10 min of ischemia and rose to values nearly 10-fold higher than Control at 40 min of ischemia. No additional increase was observed following reperfusion. The data clearly demonstrate that oxidative stress and RNS generation occur in the kidney during ischemia.

Aldehydes↗

PubMed2000

Carboxyl residues in the active site of human phenol sulfotransferase (SULT1A1).

The carboxyl-specific amino acid modification reagent, Woodward's reagent K (WK), was utilized to characterize carboxyl residues (Asp and Glu) in the active site of human phenol sulfotransferase (SULT1A1). SULT1A1 was purified using the pMAL-c2 expression system in E. coli. WK inactivated SULT1A1 activity in a time- and concentration-dependent manner. The inactivation followed first-order kinetics relative to both SULT1A1 and WK. Both phenolic substrates and adenosine 3'-phosphate 5'-phosphosulfate (PAPS) protected against the inactivation, which suggests the carboxyl residue modification causing the inactivation took place within the active site of the enzyme. With partially inactivated SULT1A1, both V(max) and K(m) changed for PAPS, while for phenolic substrates, V(max) decreased and K(m) did not change significantly. A computer model of the three-dimensional structure of SULT1A1 was constructed based on the mouse estrogen sulfotransferase (mSULT1E1) X-ray crystal structure. According to the model, Glu83, Asp134, Glu246, and Asp263 are the residues likely responsible for the inactivation of SULT1A1 by WK. According to these results, five SULT1A1 mutants, E83A, D134A, E246A, D263A, and E151A, were generated (E151A as control mutant). Specific activity determination of the mutants demonstrated that E83A and D134A lost almost 100% of the catalytic activity. E246A and D263A also decreased SULT1A1 activity, while E151A did not change SULT1A1 catalytic activity significantly. This work demonstrates that carboxyl residues are present in the active site and are important for SULT1A1 catalytic activity. Glu83 and E134 are essential amino acids for SULT1A1 catalytic activity.

Amino Acid Sequence↗

PubMed1999

Acute and chronic alcohol-cocaine interactions in rats.

The widespread combined use of alcohol and cocaine across the United States underscores the importance of understanding how the actions of those two agents interact upon important physiological regulatory processes. In an experiment exploring acute ethanol-cocaine interactions, 16 rats were given 2.0 g/kg (IP) doses of ethanol at time zero. Two hours later, half of the rats were given cocaine (20 mg/kg, IP), while the other half were given injections of saline. The group given cocaine displayed a prolongation of the hypothermia condition induced by ethanol injection. In a chronic experiment, three groups of rats (n = 6-8) were exposed for an 11-day period to daily IP injections of 10 mg/kg cocaine, 20 mg/kg of cocaine, or saline. On day 12 these groups did not differ in their response to loss of the righting reflex induced by a 3.0 g/kg dose of ethanol. However, recovery from ethanol hypothermia was more rapid in the rats exposed to chronic cocaine. In summary, these initial studies provide evidence for exacerbation of the acute hypothermic effects of ethanol when a cocaine challenge is given 2 h after ethanol. In contrast, ethanol hypothermia was observed to be reduced when tested on day 12 after an 11-day chronic regimen of cocaine. Other dosage regimens and response measures need to be tested to understand the full scope of acute and chronic cocaine-ethanol interactions and the possible health consequences.

Animals↗

PubMed1999

Clinical significance of alcohol intake parameters at initiation of drinking.

A considerable effort is now being focused upon the identification in young adulthood of predictive variables that can be used to detect individuals at risk for developing future alcohol problems. One goal is that such individuals may be targeted for early intervention efforts aimed at preventing the development of serious alcohol-related problems. Another goal is to extend the understanding of the etiology of alcoholism by identifying physiological and behavioral mechanisms underlying the addictive process. Reviewed below are efforts focused upon the importance and predictive value of the response to early exposures to ethanol, including alcohol intake variables at onset of drinking.

Adolescent↗

PubMed1999

Muscle performance in detoxified alcoholics.

OBJECTIVE: Although numerous reports have described alcohol muscle dysfunction (myopathy) in histochemical and morphological terms, a description of the relative impact of alcoholism on the functional capabilities (strength, power) of the various muscle groups of the arms and legs has not been reported. METHOD: The strength of flexor and extensor muscles of the elbow, knee and ankle was evaluated in a group of healthy detoxified white, alcoholic men (N = 83) and lifestyle control subjects (N = 61) using a computer-operated isokinetic dynamometer. RESULTS: The muscle mass (muscle-plus-bone cross-sectional area) did not differ significantly in alcoholics and controls for any of the limbs studied. Tests of isokinetic torque, work and power revealed small deficits (3-8%) in alcoholics in muscle groups involved in elbow flexion/extension, knee extension and ankle dorsiflexion. Tests of isometric torque in the knee extensors at different degrees of muscle stretch revealed approximately 4-6% lower torque in alcoholics at four different muscle lengths. The force-velocity (isoinertia knee extension) measures indicated slightly slower speeds of contraction (3.9-6.6%) in alcoholics under varying load conditions. CONCLUSIONS: The small magnitude of the muscle performance deficit in this group of alcoholics was less than expected and is probably related to (1) the elimination of subjects with other medical comorbidities or polydrug abuse, (2) the comparison with a control group of somewhat similar lifestyle and (3) the long (35-day) detoxification period elapsing before testing.

Adult↗

PubMed1998

The drinking day as a unit of exposure in the epidemiology of alcohol-related medical disorders.

Tissue or organ system damage resulting from alcohol ingestion typically requires several years of heavy drinking to reach clinical significance. Based upon earlier empirical findings and theorizing, we hypothesized that the lifetime number of exposures (drinking days) may be of significance in understanding the relationship between chronic alcohol consumption and organ system perturbations in alcoholic populations. To test this hypothesis, detailed lifetime alcohol consumption histories from a racially mixed cohort of detoxified alcoholics (n = 253) and nonalcoholics (n = 61) were examined to determine the lifetime total number of drinking days. Linear regressions corrected for lifetime total dose and pertinent confounding variables yielded statistically significant correlations of moderate size of the number of lifetime alcohol drinking days with diastolic blood pressure and quadriceps muscle strength. The findings were considered to provide evidence that an alcohol exposure (drinking day), independent of dose, is a biologically significant event in the genesis of tissue toxicities in the cohorts studied.

Adult↗

PubMed1998

Reduction of MTT by glutathione S-transferase.

The reduction of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to a blue formazan product is widely used for assaying cell survival and proliferation. The reduction reaction is catalyzed by dehydrogenases localized in the mitochondria of viable cells. As part of an analysis of the ability of glutathione S-transferase (GST) enzymes to protect cells from electrophilic compounds, we found extremely high background levels of the formazan product produced by cells that overexpressed the mouse GST P1-1 enzyme. Further analysis with purified GST enzymes confirmed the ability of these enzymes to reduce MTT in vitro. These data suggest that cytotoxicity assays using MTT should be interpreted with caution, especially when studying the effects of compounds that can influence GST expression.

Animals↗

PubMed1997

Mosquito hexamerins: characterization during larval development.

We report here the first examination of hexamerins expressed during mosquito larval development. Haemolymph proteins from fourth-instar larvae of six species representing the two major subfamilies of mosquitoes were characterized by immunoblotting using antisera to calliphorin, the major hexamerin of the blowfly. Calliphora vicina, or to LSP1 or LSP2, the two distinct hexamerins of Drosophila melanogaster. In each mosquito species the antisera demonstrated the presence of multiple abundant hexamerin polypeptides of 66-85 kDa in molecular weight. According to the subunit composition of native proteins, the larval hexamerins from both Aedes aegypti and Anopheles gambiae form heterohexamers. Furthermore, the two major Aedes hexamerin subunits (AaHex1 and AaHex2) are neither rich in aromatic amino acids nor methionine. cDNA clones encoding AaHex1 and AaHex2 were isolated and used to show that hexamerin mRNA is uniquely expressed in fourth-instar larvae of both A. aegypti and A. gambiae and disappears rapidly at the onset of pupal development.

Aedes↗

PubMed1997

Association between blood pressure and lifetime drinking patterns in moderate drinkers.

OBJECTIVE: To compare the relationship between blood pressure and recent vs lifetime alcohol intake measures in a nonalcoholic cohort using measures that normalized alcohol intake in terms of the volume of distribution for ethanol (total body water) for each subject. METHOD: Correlations between blood pressure and alcohol intake measures were determined in a cohort of 84 (48 male) normotensive moderate drinkers, using multiple linear regressions to correct for the influence of potentially confounding variables. RESULTS: Significant correlations were observed between systolic pressure and measures of both recent and lifetime alcohol consumption in men. Diastolic pressure was found to be significantly associated only with the duration of lifetime drinking, and only in women. Measures of lifetime total dose were not significantly correlated with either systolic or diastolic pressure. Alcohol intake expressed in terms of the number of "drinks" per drinking day was as highly associated with blood pressure (systolic) in men as were measures that normalized alcohol intake in terms of the body water content of each subject. A measure of the mean number of drinks consumed on drinking occasions over the drinking career produced the highest correlations with systolic pressure. CONCLUSIONS: Measures of both recent and lifetime alcohol intake may be relevant to the understanding of alcohol-blood pressure relationships.

Adult↗

PubMed1996

Role of parasympathetic (vagal) cardiac control in elevated heart rates of smokers.

Smokers may develop chronic increases in cardiac rate and alterations in cardiovascular control. If the increased mean heart rate (HR) in cigarette smokers is due in part to a deficit in vagal cardiac rate control, this should be reflected in a decreased amplitude of respiratory sinus arrhythmia (RSA). To test this hypothesis we studied 36 smokers and 36 non-smokers, matched for age, race, gender and blood pressure. All subjects were studied in the supine and seated positions. Mean heart rate was determined from the ECG during 30 s of quiet breathing; RSA was determined for 10 consecutive deep (>50% vital capacity) slow (5-7/min) breaths. Mean HRs in smokers were significantly higher than in non-smokers, but the increases in mean HRs evoked by a shift from the supine to seated position were lower in smokers than in non-smokers, suggesting that chronic tobacco use may alter the relative contributions of sympathetic and parasympathetic control of cardiac rate. Because neither the RSAs nor the position-dependent increase in RSA were different between smokers and non-smokers, we conclude that the elevated mean HRs in smokers were not the result of decreased respiratory or vasomotor modulation of vagal cardiac control, but instead were the result primarily of sympathetic stimulation.

Journal Article↗

PubMed1996

Residual pressor effects of chronic alcohol in detoxified alcoholics.

Although research in population studies has indicated that recent alcohol intake is positively correlated with blood pressure, there is a need to study the relationship of blood pressure to measures of lifetime alcohol intake in alcoholics. To this end, we assessed systolic and diastolic pressures and lifetime alcohol intake through structured interviews with 253 normotensive recovering alcoholics. Blood pressures were first corrected with multiple linear regression for the influence of confounding or modifying variables and then were regressed against alcohol consumption measures. Systolic pressure was significantly correlated (positively) with only a few measures of recent alcohol intake, and the correlations were not high (r2 = .05 to .11, P < .05). Diastolic pressure was found to be highly and positively correlated with the duration of the drinking career, but more so in blacks than in whites. The total lifetime dose of alcohol was found to be positively correlated with diastolic but not systolic pressure, but only in black male alcoholics. The steeper slope of the regression of blood pressure versus lifetime total alcohol or duration of the drinking career in black alcoholics suggests greater cardiovascular susceptibility to alcohol toxicity as lifetime doses increase and as the drinking career lengthens.

Adolescent↗

PubMed1996

Expressed Peromyscus maniculatus (Pema) MHC class I genes: evolutionary implications and the identification of a gene encoding a Qa1-like antigen.

To gain insight into the evolution of rodent major histocompatibility complex (MHC) class I genes and identify important (conserved) nonclassical class I (class I b) gene products and residues in these proteins, six Peromyscus maniculatus MHC (Pema) class I cDNA clones were isolated and sequenced. Five Pema class I cDNAs appeared most similar to mouse and rat classical class I (class I a) genes. One exhibited highest similarity to an H2 class I b gene, H2-T23 (encoding the Qa1 antigen). Phylogenetic trees constructed with Pema, RT1, and H2 class I sequences suggested that the lineages of some rodent class I b genes (e. g., T23 and T24) originated prior to Mus and Peromyscus speciation [>50 million years (My) ago]. Sequences of four Qa1-like proteins from three species permitted the identification of ten Qa1-specific amino acids. On the basis of molecular modeling, three residues showed the potential to interact with T-cell receptors and three residues (all corresponding to polymorphic positions among H2 class I a proteins) were predicted to influence antigen binding. The recognition of mouse Qa1 proteins by a subset of T-cells in influenced by a locus, Qdm, which encodes the H2-D leader peptide. One of the Pema class I cDNA clones classified as H2-K, D/L-like (class I a) is predicted to encode an identical peptide, implying that an antigen binding protein (Qa1) and the antigen to which it binds (the product of Qdm) has been conserved for over 50 My.

Amino Acid Sequence↗

PubMed1996

Differential expression of glutathione S-transferase isoforms in compartments of the testis and segments of the epididymis of the rat.

Specific cell types of the mammalian testes demonstrate varying susceptibility to toxic insult by chemical agents. The mammalian testis is divided into two major compartments: seminiferous tubules, the site of spermatogenesis, and interstitium, which contains the Leydig cells. Glutathione S-transferase (GST) expression was examined in isolated compartments of the rat testis and in segments of the epididymis. Western blot analysis revealed the presence of GST class alpha, mu, and pi bands in each of the isolated compartments of the testis, and HPLC analysis of monomeric isoforms provided evidence for differential expression of multiple GST isoforms in testicular compartments. All major isoforms (e.g., forms 1, 2, 3, 4, 6, 7, 8, 9, and 11) were detected in the cytosol of whole testis. Isoform subunit 4 was the major form in the tubule, whereas isoform subunit 11 is the dominant form in the Leydig cells. Isoform subunits 3, 4, and 6 were enriched in the tubules as compared to interstitial or Leydig cells. The preferential action of reproductive toxicants at specific stages of aging may be due to an age-dependent expression of the activating or detoxifying enzymes in the reproductive tract. Therefore, the age-dependent expression of testicular GST isoforms was also examined. Expression of isoform subunits 2 and 4 displayed an age dependence, with the largest increase in these subunits occurring between ages 4 and 15 weeks. Isoform expression did not correlate with serum testosterone levels. HPLC analysis of the GST isoforms in the longitudinal segments of the epididymis and vas deferens revealed differential expression within these segments. Total GST protein and catalytic activity was highest in the caput epididymis and progressively decreased toward the vas deferens. Isoform subunit 2 was the major form expressed in the epididymis. The results of this study indicate that the GSTs are differentially expressed in testicular compartments and epididymal segments, and that this may contribute to susceptibility of different cell types to xenobiotic damage.

Animals↗

PubMed1995

Depression of an inhibitory reflex, the masseteric silent period, in recovering alcoholics.

Because inhibitory deficits may contribute to motor incoordination of alcoholics, we proposed that the duration of the masseteric silent period (SP), an inhibitory reflex, might be shorter in alcoholics (ALs) than in nonalcoholics (NAs). To test this hypothesis, we measured the SP in a racially mixed group of 12 ALs and 12 NAs matched for age (31-49 years) and sex. All subjects were normotensive, had full dentition, and reported no major medical problems. Sensory and motor conduction velocities of the anterior tibialis, ulnar, and medial nerves were measured for each subject, and were not different in ALs and NAs. Jaw jerk and SP were evoked by tapping the chin manually with a rubber hammer containing a circuit to trigger the oscilloscope display of the masseter EMGs. Averaged mean latencies and durations of the SPs were not significantly different between the right and left masseters. SP latencies were significantly (0.7 msec) shorter in ALs than NAs (p < 0.01). The mean SP duration for ALs (13.9 +/- 1.6 msec) was also significantly shorter than that of the NAs (24.4 +/- 2.4 msec; p < 0.001). Results support the hypothesis that chronic alcoholism may interfere with inhibitory mechanisms in the CNS.

Adult↗

PubMed1995

Drinking patterns and health status in smoking and nonsmoking alcoholics.

Alcoholics who smoked also reported that they drank more frequently and consumed more alcohol on drinking occasions than alcoholics who did not smoke, a practice that resulted in a substantially greater lifetime alcohol consumption in the smokers. Smoking alcoholics also consumed more cigarettes and reported more smoking-related physical symptoms than social drinkers who smoked. The heart rates (HRs) of smoking and nonsmoking alcoholics were similar and both exceeded the HRs for the smoking social drinkers by approximately 13 beats/min (bpm) in males and by approximately 7 bpm in females. Surprisingly, correlations between HR and lifetime alcohol consumption were higher and slopes were steeper in controls than in alcoholics. HRs in a subset of the male alcoholics fell only approximately 3 bpm after 24 weeks of abstinence, but changed no further over an additional 24-week period. Taken together, the findings suggest that HRs may have been higher in this group of alcoholics before the onset of alcohol abuse and that alcohol intake contributed only slightly to the high HR.

Adult↗

PubMed1995

Progression of alcohol consumption across the drinking career in alcoholics and social drinkers.

OBJECTIVE: To document and compare the changes in alcohol intake over the drinking career in alcoholic (n = 273) and social (n = 152) drinkers and to relate the changes to age and to the prevalence of morning drinking. METHOD: Lifetime alcohol intake was assessed in face-to-face interviews by asking subjects to report drinking patterns during different "phases" of their drinking careers, beginning with the onset of regular drinking and continuing up to the present. RESULTS: Alcohol consumption began at higher quantities and higher frequencies in alcoholics (prealcoholics) and rapidly escalated within a few years to values well out of the range of moderation. The alcohol intake of social drinkers at the beginning phase was only about 70% that of alcoholics. In contrast to alcoholics, the alcohol intake of social drinkers remained relatively constant across subsequent drinking phases at about three to four drinks per drinking occasion, with only a slight increase in the frequency of drinking over sequential drinking phases. The relationship of total alcohol consumption to age in alcoholics was described best by a curvilinear function, with alcohol consumption peaking near age 40. CONCLUSIONS: Gender differences in consumption were decreased with adjustment for body water content. The higher initial alcohol intakes in alcoholics may reflect a lower sensitivity to the intoxicating effects of alcohol, or, alternatively, a greater ability of alcoholics to develop tolerance. The high prevalence of morning drinking in alcoholics compared to social drinkers reinforces the usefulness of morning drinking as a diagnostic tool, particularly for female alcoholism.

Adult↗

PubMed1994

Influence of age on the development of rapid tolerance to ethanol.

Fischer-344 rats of three different ages (4, 13, and 25 months) were tested to determine the extent and duration of rapid tolerance to ethanol-induced hypothermia and hypnosis. There were no significant differences among groups with regard to maximal ethanol hypothermia (3.0-3.5 g/kg ethanol), nor did any of the groups display a significant change (rapid tolerance) in the maximal hypothermic response when tested with a second identical challenge 48 h later. Rapid tolerance to ethanol hypnosis was observed across groups at 48 h, utilizing two different dosing schemes. No tolerance was observed if 14 days were allowed to elapse between the initial and the test challenge. Young rats were observed to develop a greater degree of rapid tolerance than did middle-aged or old rats, using hypnosis as a measure.

Aging↗

PubMed1994

Age effects on chronic tolerance to ethanol hypnosis and hypothermia.

Male Fischer 344 rats of three different ages (young, 4 months; middle, 13 months; and old, 25 months) were tested for their hypnotic and hypothermic response to a 3.5 g/kg dose of ethanol on day 1 and after an 8-day exposure to 4.0 g/kg of ethanol administered via intragastric intubation. All three age groups displayed, to a similar extent, an increased rate of blood ethanol disappearance (metabolic tolerance) on day 10 and day 16, as compared to day 1. Both young and middle-age rats demonstrated tolerance to ethanol hypothermia, but older rats did not. The same test dose of ethanol (3.5 g/kg, IP) administered on day 16, after a 5-day interval with no ethanol, produced a hypnosis response similar to that observed on day 1 (no tolerance), but the response to ethanol hypothermia was still significantly reduced over the day 1 and day 10 value in young and middle-age rats, suggesting a persistence and intensification of tolerance to hypothermia over the 5-day rest interval. However, tolerance to ethanol hypothermia was not observed in old rats. Thus, the effects of age on the development of chronic functional tolerance were complex and depended upon the test measure used.

Aging↗