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Biomedical subjects

D M Wilson

Publications and source records attributed to D M Wilson.

At least 127 records · Page 7Linked to original sources
PubMed1994

Drosophila ribosomal protein S3 contains an activity that cleaves DNA at apurinic/apyrimidinic sites.

A rat cDNA-encoding ribosomal protein S3 was used to clone the S3 homolog in Drosophila melanogaster. The Drosophila gene was in turn used to construct fusions between S3 and glutathione S-transferase that were overexpressed in Escherichia coli, purified on affinity columns, and subsequently used for antibody production and biochemical analysis. Antibody specific for S3 was originally tested to determine the subcellular location of S3 by Western (immunoblot) analysis. As expected, the S3 antigen was found associated with purified preparations of ribosomes, but notably the protein was also observed in the nucleus where it was found to be tightly associated with the nuclear matrix. This result, combined with the fact that S3 contains a nuclear localization signal and that the protein shares some homology to a yeast nuclease gene, suggested that S3 might possibly have a role in DNA metabolism. Tests were initially performed to see if S3 contained DNase activity, where it was subsequently determined that the protein specifically cleaved DNA containing an apurinic/apyrimidinic site via a beta-elimination reaction. The DNase activity was inactivated by antibody to S3, indicating that the apurinic/apyrimidinic lyase activity was associated with the Drosophila S3 protein. Taken together, these results suggest that S3 is among a growing class of multifunctional proteins with roles in transcription/translation and DNA repair.

Animals↗
PubMed1994

Transport properties of Asp-51-->Glu and Asp-120-->Glu mutants of the melibiose carrier of Escherichia coli.

Asp-51-->Glu and Asp-120-->Glu mutants of the melibiose carrier of Escherichia coli were investigated for their cation/sugar cotransport properties. The carrier containing Glu-51 showed proton/melibiose cotransport but was extremely defective in Na+ or Li+ stimulation of sugar accumulation. On the other hand, the carrier containing Glu-120 had lost the ability to couple protons with melibiose uptake while retaining considerable Na+ or Li+ cotransport with melibiose (40-fold accumulation versus 90-fold for the wild type in the presence of Na+). It is concluded that both Asp-51 and Asp-120 are important for cation recognition.

Biological Transport↗
PubMed1994

Timing and rate of sexual maturation and the onset of cigarette and alcohol use among teenage girls.

OBJECTIVE: To test the hypothesis that the patterns of pubertal progression, early vs late puberty and fast vs slow, are associated with the age at which girls start to drink alcohol and smoke cigarettes. DESIGN: The study included 1463 female students, 10.7 to 18.2 years of age, who were assessed five times during the 2.7-year study. Data regarding pubertal stage, alcohol use, and cigarette use were obtained at each assessment. These data were used to calculate two indexes of pubertal development, the age at which the midpoint of puberty was achieved and the rate of progression through puberty, and the ages when each subject first drank, first drank moderate amounts of alcohol, and first smoked. RESULTS: Girls with earlier puberty (midpoint < 12.2 years) first reported drinking any alcohol at a median age of 12.5 years, 0.7 years younger than girls whose puberty was later. Similarly, girls with earlier puberty reported drinking moderate amounts of alcohol at a median age of 13.7 years, 0.9 years younger than girls with later puberty. Girls with earlier puberty further reported first smoking cigarettes at a median age of 12.8 years, 0.6 years younger than girls with later puberty. The rate of pubertal progression was significantly associated only with the age when girls first drank moderate amounts of alcohol. CONCLUSION: Earlier puberty is associated with a younger age of onset for both drinking and smoking among adolescent girls.

Adolescent↗
PubMed1994

Pursuit of thinness and onset of eating disorder symptoms in a community sample of adolescent girls: a three-year prospective analysis.

Community-based prospective studies are needed to shed light on mechanisms that may influence development of eating disorders and identify variables that could serve as potential targets for prevention efforts. In this paper we examine level of weight preoccupation and other variables prospectively associated with age of onset of eating disorder symptoms over a 3-year interval in a community sample (N = 939) of young adolescent girls. 3.6% (32/887) experienced onset of symptoms over the interval. Only one factor, a measure of Weight Concerns, was significantly associated with onset (p < .001). Girls scoring in the highest quartile on the measure of Weight Concerns had the shortest survival time (12% incidence by age 14.5) and those scoring in the lowest quartile had the highest survival time (2% incidence by age 14.5; p < .001). This finding is consistent with both theoretical and clinical perspectives and represents one of the first prospective demonstrations of a linkage between weight and body shape concerns and later onset of eating disorder symptoms. An understanding of the independent variables that predispose girls to development of symptoms is a useful step towards the establishment of a rational basis for the choice of a prevention intervention target.

Adolescent↗
PubMed1994

Factors associated with eating disorder symptoms in a community sample of 6th and 7th grade girls.

Nine hundred thirty-nine 6th and 7th grade girls participated in the baseline phase of a prospective study designed to examine a set of potential risk factors for the development of eating disorders. Of the 939,839 girls (89%) completed the bulimia nervosa section of the Structured Clinical Interview for DSM-III-R disorders. One girl received the diagnosis of bulimia nervosa, another 35 were classified as a symptomatic group. Using analysis of covariance (ANCOVA), controlling for age and stage of sexual maturation, symptomatic and asymptomatic groups were compared on the following measures: Eating Disorders Inventory (EDI), BMI, triceps skinfold thickness, waist-to-hip ratio, depression symptoms (CES-D and DSRS), Restraint Scale, and a measure of family adaptability and cohesion (FACES). Symptomatic girls were more developmentally mature, significantly heavier, reported greater fear of weight gain, experienced greater dysphoria, indicated increased body dissatisfaction, and reported greater feelings of inadequacy and personal worthlessness. Their status on these dimensions may indicate potential vulnerability to eating disorders and, ultimately, suggest the choice of targets for intervention. Our future goal is to conduct the prospective analyses needed to confirm the hypothesized linkages.

Adolescent↗
PubMed1994

Expression of myc, fos, and Ha-ras in the livers of furan-treated F344 rats and B6C3F1 mice.

Furan administered by gavage for 2 yr has been reported to induce hepatocellular carcinomas in male and female B6C3F1 mice and in male but not female F344 rats. Chronic exposure studies in our laboratory using bioassay conditions showed extensive hepatocellular toxicity and sustained increases in regenerative cell proliferation after 1, 3, and 6 wk of treatment in male and female rats and male mice. Altered expression of growth-control genes associated with this hyperproliferative state may enhance the susceptibility of these genes to mutation or may provide a selective growth advantage to preneoplastic cells. Quantitative northern blot analysis of mRNA was used to examine the expression of the oncogenes myc, fos, and Ha-ras in the livers of animals treated with furan. In male rats, a single administration of 30 mg/kg furan produced necrosis and a subsequent wave of cell proliferation 48 h after treatment and induced transient peaks in the expression of myc, fos, and Ha-ras 6-24 h after treatment. In male rat liver from our cell proliferation studies, only a slight increase in myc expression was seen at the end of week 1 of treatment. However, beginning at week 3 and increasing at week 6, up to a 15-fold increase over control values was observed in the expression of myc in the treated animals. The only other notable increase in expression observed in any animals from the cell proliferation study was a threefold increase in myc at week 6 in treated female rats. The absence of an increase in Ha-ras expression in the male mouse liver suggests that the unique pattern of Ha-ras mutations previously reported in furan-induced mouse liver tumors is not due to increased mutational susceptibility related to overexpression of this gene. The lack of sustained expression of myc, fos, and Ha-ras in rapidly proliferating liver suggests that continuous expression of these genes is not necessary to maintain increased rates of cell replication. The large increase in myc expression in male but not female rats suggests an adaptive change that may be related to the sex-specific incidence of furan-induced hepatocellular carcinomas in rats.

Animals↗
PubMed1994

Protein kinase C mediates the calcium-induced activation of rat colonic particulate guanylate cyclase.

Calcium can influence the cGMP/guanylate cyclase system in many tissues, including rat colon. The mechanisms involved in this phenomenon, however, are unclear. To further elucidate the mechanisms involved in the Ca(2+)-induced activation of rat colonic particulate guanylate cyclase, isolated colonocytes were incubated with Ca2+ or other agents, and crude membrane prepared and analyzed for particulate guanylate cyclase activity. Alternatively, the test agents were directly added to the guanylate cyclase reaction mixture containing isolated membranes. The results of these studies demonstrated: (i) extracellular Ca2+ (1 and 2 mM) increased basal particulate guanylate cyclase activity; (ii) increases in intracellular Ca2+ induced by 10 microM thapsigargin activated this enzyme; (iii) preincubation of the cells with 50 nM staurosporine, a broad-spectrum inhibitor of protein kinases, including protein kinase C (PKC), or 5 microM U73122, a specific inhibitor of phosphoinositide-phospholipase C-dependent processes, blocked the Ca(2+)-induced increase in particulate guanylate cyclase activity; (iv) incubation of cells with 1 microM 12-O-tetradecanoyl phorbol 13-acetate (TPA), an activator of PKC, stimulated guanylate cyclase; (v) no additivity in stimulation of this enzyme was observed when cells were concomitantly incubated with 1 microM TPA and 2 mM extracellular Ca2+; (vi) incubation of membranes with 250 nM TPA, in the presence of 0.2 mM Ca2+, 6 mM Mg2+, and 1 mM ATP, activated guanylate cyclase; and (vii) incubation of membranes with purified rat brain PKC further augmented this stimulation. These results indicate that Ca2+ activates rat colonic particulate guanylate cyclase, at least in part, via a PKC-dependent mechanism.

Alkaloids↗
PubMed1994

Renal ammonia in autosomal dominant polycystic kidney disease.

Recent studies have suggested that defective medullary trapping of ammonia underlies the acidosis associated with renal failure and sets in motion maladaptive compensatory mechanisms that contribute to the progression of renal disease. Since a renal concentrating defect is an early functional abnormality in autosomal dominant polycystic kidney disease (ADPKD), defective medullary trapping and urinary excretion of ammonia may also occur early and have important pathophysiological consequences. The urinary pH and excretions of ammonia, titratable acid, and bicarbonate, were measured during a 24-hour baseline period and following the administration of ammonium chloride (100 mg/kg body wt) in ADPKD patients with normal glomerular filtration rate and in age- and gender-matched healthy control subjects. The distal nephron hydrogen ion secretory capacity was assessed during a bicarbonate infusion. Ammonia, sodium, pH, C3dg, and C5b-9 were measured in cyst fluid samples. The excretion rates of ammonia during the 24-hour baseline period and following the administration of ammonium chloride were significantly lower, and the relationship of ammonia excretion to urinary pH was significantly shifted downward in ADPKD. No difference in the increment of urinary pCO2 (delta pCO2) or the peripheral blood-urine pCO2 gradient (U-B pCO2) between ADPKD patients and control subjects was detected during a sodium bicarbonate infusion. Calculated concentrations of free-base ammonia in cyst fluid samples exceeded those calculated from reported concentrations of ammonia in renal venous blood of normal subjects. C3dg and C5b-9 were detected in some cyst fluids. The urinary excretion of ammonia is reduced in ADPKD patients with normal glomerular filtration rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1994

Acute ethanol exposure suppresses the repair of O6-methylguanine DNA lesions in castrated adult male rats.

Alcohol has clearly been associated with an increase of cancers in numerous tissue, including the respiratory tract, colon, rectum, liver, but especially the esophagus, larynx, pharynx, and mouth. Alcohol alone has not been shown to be a mutagen until it is converted to acetaldehyde and, therefore, alcohol presumably acts as a cocarcinogen. Previous data has shown that alcohol concentrations of 2% or greater inhibits DNA repair, and in light of the widespread consumption of alcoholic beverages with alcohol contents ranging from 4 to 5% (beer and wine coolers) to 50% (whiskey), interest in determining the mechanism(s) responsible for alcohol-induced carcinogenesis has heightened. Although previous studies, in intact rats, have investigated the effects of chronic alcohol exposure on some aspects of DNA repair, we have begun to address the effects of acute or "binge" alcohol exposure on mammalian DNA repair. Toward this end, we report the inhibition of O6-methylguanine-DNA methyltransferase (MGMT) by a single intraperitoneal injection of 30% ethanol in adult male castrated rats. This inhibition lasted for at least 24 hr. We also observed a dose-response effect of ethanol on MGMT activity, again only in the castrated rats. The finding of ethanol's effect on MGMT activity in castrated and not intact rats implies a hormonal component of MGMT DNA repair response, which has only been alluded to in past research.

Animals↗
PubMed1994

Renal cystic disease and ammoniagenesis in Han:SPRD rats.

Cyst formation in conditions associated with increased renal ammoniagenesis (hypokalemia, distal renal tubular acidosis, renal mass reduction) and experimental links between increased ammoniagenesis and interstitial inflammation have suggested a role for ammonia in the pathogenesis of polycystic kidney disease (PKD). To explore this hypothesis, Han:SPRD rats, a PKD model that affects male more severely than female animals, have been used. Heterozygous cystic (Cy/+) and homozygous normal (+/+) male and female offspring of Cy/+ rats were divided at 3 wk of age into control groups drinking water and experimental groups drinking 300 mM NH4Cl, 300 mM KHCO3, 200 mM KHCO3, 200 mM KCl, 200 mM NaHCO3, or 200 mM NaCl. At 2 months of age, the rats were kept fasting from 8:00 p.m. to 8:00 a.m. in metabolic cages and urine samples were collected under mineral oil. The rats were then weighed and anesthetized for the collection of blood and kidneys. The administration of 300 mM NH4Cl, and to a lesser extent that of 200 mM NaCl, was accompanied by an increase in the urinary excretion of ammonia and aggravation of the renal cystic disease. On the other hand, the administration of 300 mM KHCO3, 200 mM KHCO3, or 200 mM NaHCO3 lowered the urinary excretion of ammonia and markedly reduced the severity of the cystic disease and interstitial inflammation. The administration of 300 mM KHCO3, and to a lesser extent that of 200 mM KHCO3, resulted in the precipitation of calcium phosphate in the medullary collecting ducts.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1993

M3 muscarinic receptors on rat colonocytes are coupled to particulate guanylate cyclase activation.

The ability of muscarinic receptor antagonists to compete with (-)-[3H]quinuclidinyl benzilate ([3H]QNB) binding was compared with their ability to block carbachol-mediated stimulation of particulate guanylate cyclase activity in rat colonocytes. The binding of [3H]QNB to membranes was inhibited by antagonists with the following rank order of potencies (inhibitory constants, nM): atropine (2.5) approximately 4-diphenylacetoxy-N-methylpiperidine iodide (4-DAMP) [4.6] >> pirenzepine (121) > methoctramine (385). 4-DAMP (IC50 = approximately 10 nM) was also more potent in blocking carbachol-induced stimulation of guanylate cyclase activity than either pirenzepine (IC50 = approximately 700 nM) or methoctramine (IC50 = approximately 1500 nM).

Animals↗
PubMed1993

Effects of estrogen on growth hormone following clonidine stimulation.

OBJECTIVE: To test the usefulness of estrogen priming to enhance the growth hormone (GH) response following stimulation with clonidine hydrochloride in short children. DESIGN: Randomized and patient series. SETTING: Pediatric endocrine clinic in a referral center. SUBJECTS: Seventy-three children (63% male) between 1.8 and 15.4 years of age (mean age, 8.8 years) with growth problems who underwent clonidine GH stimulation tests were randomly assigned to receive either estrogen pretreatment or no pretreatment. An additional 49 subjects, seen before or after the randomized study and who did not receive conjugated estrogen, are also described. SELECTION PROCEDURE: Consecutive sample. INTERVENTION: Estrogen pretreatment consisted of 2.5 mg of conjugated estrogen (Premarin) to be taken the evening before and the morning of the clonidine GH stimulation test. Growth hormone concentrations were determined before and 60 and 90 minutes after the subjects received oral clonidine hydrochloride (5 micrograms/kg) by a laboratory blinded to the subject's estrogen status. Growth hormone concentrations greater than 10 micrograms/L were considered normal. RESULTS: Eight of the 73 subjects failed both clonidine and arginine-insulin GH stimulation tests. We analyzed the GH data from the 65 GH-sufficient subjects to determine the effect of estrogen pretreatment on the specificity of the clonidine GH stimulation test. There were no statistically significant differences in the mean GH concentrations between the two groups at any time point during the test. CONCLUSIONS: Our data demonstrate that estrogen priming does not improve the diagnostic yield of clonidine GH stimulation tests.

Administration, Oral↗
PubMed1993

An attempt to modify unhealthful eating attitudes and weight regulation practices of young adolescent girls.

This is the first long-term, controlled study evaluating the effectiveness of a prevention curriculum designed to modify the eating attitudes and unhealthful weight regulation practices of young adolescent girls. Nine hundred sixty-seven sixth and seventh-grade girls were randomized to experimental healthy weight regulation curriculum or no-treatment control classes. A prevention intervention was developed around three principal components: (1) Instruction on the harmful effects of unhealthful weight regulation; (2) promotion of healthful weight regulation through the practice of sound nutrition and dietary principles and regular aerobic physical activity; (3) development of coping skills for resisting the diverse sociocultural influences that appear linked to the current popular obsessions with thinness and dieting. The intervention failed to achieve the hoped-for impact. We did observe a significant increase in knowledge among girls receiving the intervention and among high-risk students only, there was a small albeit statistically significant effect on body mass index. These findings question the wisdom of providing a curriculum directed at all young adolescents, most of whom are not at risk to develop an eating disorder. Rather than targeting the entire population, a healthy weight curriculum designed to modify the eating attitudes and unhealthful weight regulation practices of young adolescent girls might better focus on "at risk" students.

Adolescent↗
PubMed1993

Toxicity evaluations of L-cysteine and Procysteine, a cysteine prodrug, given once intravenously to neonatal rats.

Decreased enzymatic production of cysteine in premature and newborn infants may limit the synthesis of glutathione. Unfortunately, cysteine supplementation is limited by associated toxicity and product instability. Procysteine (L-2-oxothiazolidine-4-carboxylate) is a prodrug of cysteine that is inert until metabolized to cysteine intracellularly, thus stimulating glutathione synthesis. The potential toxicities of cysteine and Procysteine were compared in two studies with neonatal rats (10 per group; 3 +/- 1 days of age) after a single intravenous administration. In one study, acute high dosage survivorship was compared for approximately equimolar cysteine dosages of L-cysteine and Procysteine. Mortality at 7 days after single intravenous dosages of L-cysteine at 1.52 or 1.14 g/kg or Procysteine at 1.80 or 1.35 g/kg was 80, 50, 10 and 0%, respectively. Clinical pathology parameters and body and organ weights were compared in a second study, following a moderate dosage of Procysteine or equimolar or lower dosages of L-cysteine. No differences were observed in clinical pathology parameters nor body or organ weights at 14 days following single intravenous dosages of L-cysteine at 369, 185 or 37 mg/kg or Procysteine at 450 mg/kg. Also, Procysteine solutions were considerably more stable than L-cysteine solutions (months vs. hours, respectively). These studies indicated that cysteine supplementation in infants may be enhanced by Procysteine administration.

Animals↗