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Biomedical subjects

J H Clark

Publications and source records attributed to J H Clark.

At least 145 records · Page 8Linked to original sources
PubMed1985

Changes in keratin expression during the estrogen-mediated differentiation of rat vaginal epithelium.

While vaginal cornification occurs naturally during the estrous cycle of the adult rat, it can also be artificially induced by administering exogenous hormone to ovariectomized animals. When the maturation of rat vaginal epithelium was controlled with a timed course of estradiol (E2) injections, total cell extracts from that tissue revealed that six major keratins exhibited stage-specific increases during a 48-h period of stratification and cornification. One-dimensional polyacrylamide gel electrophoresis and electrophoretic immunoblotting showed that the expression pattern involved an earlier rise of the smaller (50,000, 51,000, and 53,000 mol wt) keratins and a later rise of the larger (57,000, 58,000, and 60,000 mol wt) keratins. Polypeptide levels were quantitated by gel densitometry, and an immunodot assay was developed to specifically measure keratin expression as a function of estrogen agonist activity. By way of comparison, four other estrogenic compounds were also evaluated after their administration under a 48-h double injection protocol. Under these circumstances, diethylstilbestrol provided a more potent stimulus than E2, while estriol, enclomiphene and zuclomiphene each produced a pattern of keratin expression and intensity levels that resembled that 24-h stage of E2 treatment. Although the same keratins were expressed by these different compounds, their synthesis was selective, since they often increased 10- to 20-fold while total protein levels only doubled. Keratin levels were correlated with the various degrees of epithelial growth and differentiation observed in parallel histological studies. These results indicate that the expression of vaginal keratins provide a useful model system for the study of estrogen action.

Animals↗
PubMed1985

Nitrogen utilization and ruminal fermentation in steers fed soybean meal treated with formaldehyde.

Four rumen-fistulated steers averaging 400 kg in body weight were used in a 4 X 4 Latin square arrangement with 18-d periods to investigate the effect of treating soybean meal (SBM) with formaldehyde on nitrogen (N) utilization and ruminal fermentation. Experimental diets, on a dry matter basis, consisted of 42% corn silage, 48.5% cracked corn-mineral mixture and 9.5% SBM treated with 0, .3, .6 or .9% formaldehyde by weight. Dry matter and organic matter digestibilities were not affected by treatment. Formaldehyde treatment of SBM resulted in a linear decrease in N digestibility (P less than .005) and urinary N excretion (P less than .01) and a quadratic increase (P less than .05) in N retention. The depression in apparent N digestibility was small when SBM was treated with .3% formaldehyde. This level of formaldehyde treatment also had little effect on in vitro enzymatic hydrolysis of SBM. Ruminal ammonia-N concentrations were lower (P less than .05) in steers fed formaldehyde-treated SBM. Ruminal pH was lower (P less than .05) at 6 and 8 h postfeeding while volatile fatty acid concentrations were higher (P less than .05) at 8 and 12 h postfeeding for steers fed untreated SBM. Propionic acid (mol/100 mol) decreased linearly (P less than .05) with increasing level of formaldehyde treatment. Urea-N concentrations in plasma were decreased (P less than .001) and plasma-free essential amino acid concentrations were increased (P less than .10) by formaldehyde treatment. Ruminal disappearance of N from polyester bags containing the SBM supplements was greatly reduced (P less than .005) by formaldehyde treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1985

Achalasia and tracheal obstruction in a child.

A 13-year-old patient was referred for evaluation of pulmonary symptoms and was subsequently diagnosed to have achalasia. An esophagram revealed a dilated esophagus which obstructed the trachea at the thoracic outlet during a forced expiratory maneuver. Pulmonary function tests, obtained before and after esophagomyotomy, are presented.

Adolescent↗
PubMed1984

The agonistic and antagonistic actions of estriol.

Estriol is a short acting estrogen, and as such, displays both agonistic and antagonistic properties, when it is injected in saline solution. These are predictable attributes of any short acting agonist if one considers the basic pharmacology of receptor ligand binding interactions. That is, short acting hormones or drugs occupy receptor sites for protracted time periods and, although they stimulate responses, these are of short duration. However, when estriol is administered in continuous fashion the estrogen receptor is occupied for long periods of time and full estrogenic responses are observed, and there is no antagonism of estradiol action. The purpose of this paper is to review the work that leads to the above conclusion and to discuss our more recent work on the relationship between estrogen receptor binding and the stimulation of type II estrogen binding sites.

Animals↗
PubMed1984

Effects of chlorpromazine on the inhibition and artifactual elevation of [3H]estradiol binding to estrogen receptors in rat uterine cytosol.

Chlorpromazine acts to inhibit the specific binding of estradiol in rat uterine cytosol in vitro at concentrations between 0.1 and 0.75 mM. However, at higher concentrations (1.0-2.0 mM) it causes an apparent increase in binding that is due to free labeled estradiol in the assay buffer which is not adsorbed by the charcoal-dextran. This artifactual elevation can lead to misinterpretations of drug-induced potentiation of receptor sites.

Animals↗
PubMed1984

Spontaneous bacterial peritonitis.

Spontaneous bacterial peritonitis should be considered in the evaluation of any patient with acute abdominal complaints, especially in the presence of preexistent ascites. Paracentesis is indicated in all suspected cases of spontaneous peritonitis in order to obtain necessary studies, including microbial cultures. Broad-spectrum antibiotic coverage has become necessary because of the increasing incidence of gram-negative isolates. Ascitic pH and lactate may provide accurate information in the evaluation of spontaneous peritonitis, although increased clinical awareness remains the key to proper diagnosis.

Adult↗
PubMed1984

Estrogen stimulates the transient association of calmodulin and myosin light chain kinase with the chicken liver nuclear matrix.

Previous work has demonstrated that estrogen administration to immature chickens results in a rapid but transient increase in nuclear estrogen receptor content, a large portion of which is associated with the nuclear matrix. The present studies were undertaken to determine whether estrogen produced a more generalized change in the protein composition of the nuclear matrix. High-resolution two-dimensional gel analysis of the matrix revealed a very complex protein pattern, but several major qualitative differences were observed after estrogen treatment. To simplify the number of proteins evaluated, we examined the effects of estrogen on a subset of matrix proteins, namely, calmodulin and its binding proteins. Calmodulin was measured by radioimmunoassay and the binding proteins were detected by interaction of 125I-calmodulin with matrix proteins distributed on one-dimensional polyacrylamide gels. Calmodulin and two specific Ca2+-dependent calmodulin-binding proteins were found to be associated with matrix preparations. The two binding proteins exhibited apparent Mr of 200,000 and 130,000. The Mr 130,000 protein was identified as myosin light chain kinase on the basis of enzymatic activity and immunoreactivity with a specific antibody to this enzyme. Estrogen treatment of immature chickens did not alter the hepatic content of calmodulin. However, the steroid did result in an enrichment of the proportion of calmodulin and its two binding proteins associated with the nuclear matrix within 4 h after injection. The time course of these changes paralleled those previously documented for estrogen receptor. Taken together, these data are compatible with a role for calmodulin and myosin light chain kinase in the response of chicken liver cells to steroid hormones.

Animals↗
PubMed1984

Effect of rumen-protected methionine on plasma free amino acids and production by dairy cows.

The effectiveness of an encapsulated rumen-protected methionine compound (RPMet) for delivering methionine postruminally and its effect on plasma amino acid concentrations, milk production and milk composition were evaluated. Thirty multiparous Holstein cows in early lactation were randomly assigned to five levels of RPMet. RPMet was supplied at 0, 550, 1100, 1650 or 3300 mg/kg of concentrate resulting in an intake of 0, 6.9, 12.9, 19.6 or 40.2 g of supplemental DL-methionine/day for each cow. The basal diet was alfalfa-bromegrass hay and a 15.8% crude protein corn- and soybean meal-based concentrate mixture. The experiment was divided into pretreatment and treatment periods, each consisting of 21 days. Feed intake and milk production were measured daily, milk composition weekly and plasma amino acid concentrations twice daily on days 17 and 20 of the pretreatment period and on days 4, 10 and 21 of the treatment period. RPMet was effective in delivering methionine postruminally, which increased concentrations of methionine in plasma. Dry matter intake, milk production, milk composition and body weight were not significantly affected by RPMet.

Amino Acids↗
PubMed1984

Effect of exogenous corticosteroid therapy on growth in children with HBsAg-negative chronic aggressive hepatitis.

The effect of exogenous corticosteroid therapy on growth was studied in 12 patients with HBsAg-negative chronic aggressive hepatitis. All patients were less than 13 years of age at diagnosis and were free of cirrhosis. The patients' growth records were retrospectively reviewed for incremental growth changes while they were receiving daily prednisone and alternate-day prednisone, as well as for 1 year after the cessation of therapy. These values were compared with age-matched growth velocities in normal children. Daily steroid therapy was associated with a reduction in growth velocity (p less than 0.01). There was an acceleration in growth velocity during the period of alternate-day therapy, compared with predicted values (p less than 0.03), which persisted during the 1st year after therapy was discontinued (p less than 0.02). Nine of 12 patients crossed growth percentiles during steroid therapy. We have confirmed that daily steroid administration is associated with a reduction in linear growth, while alternate-day therapy has an apparent positive effect on growth, presumably through control of the underlying disease. The mechanism of this supranormal growth rate is unclear.

Body Height↗
PubMed1984

The effect of low dose continuous exposure to estradiol on the estrogen receptor (type I) and nuclear type II sites.

These studies were done to evaluate the temporal relationships between cytoplasmic and nuclear estrogen receptors (type I sites), nuclear type II estrogen binding sites, and uterotropic response (true uterine growth; DNA content) after low dose estrogen administration to adult-ovariectomized rats by beeswax pellet implant. Administration of low dose (2.5 micrograms estradiol-17 beta/pellet) estrogen pellets resulted in a slight accumulation of nuclear type I sites (approximately 1700 sites per cell above ovariectomized controls) and a 2-fold stimulation of nuclear type II estrogen binding sites (approximately 5,000 sites per cell) at short times (1-24 h) after estrogen treatment. By 96 h, nuclear levels of type I sites were not different from control even though nuclear type II sites remained elevated and uterotropic response was maintained. Similar temporal responses were observed after treatment with a higher dose estradiol (20 micrograms/pellet) except that early response (1-24 h) to the hormone was accompanied by a more pronounced accumulation (approximately 3,000 sites per cell above control) of type I sites in the nucleus. By 96 h after the administration of the 20-micrograms estradiol pellet, nuclear type I sites declined to control, however nuclear type II sites continued to increase (approximately 30,000 sites per cell) and maximum uterotropic response was observed. Comparison of the results obtained with these two dose levels of estradiol suggested that at early times (1-24 h) after treatment only a very small quantity (approximately 1,700 sites per cell) of nuclear type I sites is required for uterine growth. Likewise, although nuclear type II sites can be maximally stimulated (approximately 30,000 sites per cell) by higher doses of estrogen (20 micrograms) only 5,000 sites per cell may be necessary for maximal response. Surprisingly, uterine growth was sustained by very low to non-measurable quantities of type I sites in the nucleus (96 h). Regardless of the initial numbers of type I sites translocated to the nucleus (approximately 1,700 sites per cell, 2.5 micrograms estradiol; approximately 3,000 sites per cell, 20 micrograms estradiol), at early times (1-24 h), these levels decline to control approximately 96 h after treatment. These results are not due to a decreased rate of estrogen release from the beeswax pellet implant and the data suggest a down-regulation of nuclear type I sites is a normal response to the hormone under these experimental conditions, even though maximum uterine growth is maintained.

Animals↗
PubMed1984

Estrogen modulation of nuclear matrix-associated steroid hormone binding.

Estrogen regulation of the intranuclear distribution of estrogen-binding proteins has been examined in the chicken liver. Administration of estrogen [diethylstilbestrol (DES)] resulted in a rapid, dose-dependent increase in two types of estrogen-binding sites associated with the nuclear matrix. Type I appeared to be the estrogen receptor (ER; Kd for estradiol = 2.0 nM), whereas type II was equivalent to binding sites previously defined in rat uterine nuclei (Kd = 15 nM). The association of nuclear ER and type II sites with the nuclear matrix followed a time course corresponding to the maximal accumulation of nuclear ER in the liver. A 2-fold enrichment (per U protein) of nuclear ER in the matrix was obtained at a dose of 20 micrograms DES/0.2 kg compared to control values. Further enrichment was observed with higher doses of DES (200 and 2000 micrograms). The antiestrogens tamoxifen (tamoxifen-citrate) and zuclomiphine 2-[p-(chloro-1,2-diphenyl-vinyl)phenoxyl]citrate) were potent inhibitors (greater than or equal to 50%) of the estrogen-stimulated association of both ER and type II sites with the matrix. However, they did not increase total nuclear or matrix ER concentrations when administered alone. These data demonstrate that the association of ER with liver nuclear matrix is estrogen dependent and suggest that the biological effects of estrogen at the nuclear level may be mediated by this association.

Animals↗
PubMed1984

Concurrent validity of WISC-R factor scores for educable mentally handicapped children.

The present study investigated the concurrent validity of the WISC-R Verbal Comprehension, Perceptual Organization, and Freedom from Distractibility factor scores relative to the Reading, Spelling, and Arithmetic subtest standard scores obtained on the Wide Range Achievement Test. The sample of 46 students were identified as educable mentally handicapped in a public school setting. The results of separate bivariate analyses indicated that the WISC-R factor scores are not significantly correlated with achievement as measured by this achievement test. Implications of these results and directions for future research are discussed.

Achievement↗
PubMed1984

Orotate in milk and urine of dairy cows with a partial deficiency of uridine monophosphate synthase.

Cows with a partial deficiency of uridine monophosphate synthase have elevated orotate in their milk and urine. Variability of orotate was assessed in two such cows monitored biweekly for two complete lactations. Concentrations of milk and urinary orotate showed extensive variation during lactation, but coefficients of variation were similar for deficient and normal cows. Orotate averaged 500 micrograms/ml milk for deficient cows (versus a normal of 80 micrograms/ml), and a threshold of 200 micrograms/ml distinguished normal from deficient cows. Deficient cows had low milk orotate upon initiation of lactation and exhibited a latency of 1 to 7 wk to attain that threshold. The deficiency also resulted in a lactation-induced orotic aciduria. Orotate averaged 32.2 micrograms/ml urine for deficient cows (versus a normal of 7.3 micrograms/ml), and a threshold of 15 micrograms/ml urine differentiated the animals. Latency was 3 to 18 wk for deficient cows to exceed that threshold. Total orotate output and orotate concentration were elevated in milk and urine of lactating cows deficient for uridine monophosphate synthase. The output of orotate was predominantly in milk rather than urine for both deficient and normal cows. Additionally, orotate was elevated in blood of deficient cows when they were lactating.

Animals↗
PubMed1984

Milk production and nitrogen utilization by dairy cows infused postruminally with sodium caseinate, soybean meal, or cottonseed meal.

Four Holstein cows with fistulated rumens were in a 4 X 4 Latin square design for us to determine effects of administering different sources of protein postruminally on milk production, milk composition, and efficiency of nitrogen utilization. Treatments consisted of postruminal infusion of 1) water, 2) sodium caseinate, 3) soybean meal, or 4) cottonseed meal. Milk yield (kg/day) and milk protein production (g/day) for the four treatments were: 1) 30.6, 1043; 2) 32.7, 1146; 3) 32.1, 1102; and 4) 31.1, 1087. Synthesis of milk protein increased during postruminal infusions of protein as indicated by the increased casein nitrogen fraction in milk. All protein infusions improved efficiency of use of absorbed nitrogen for synthesis of milk protein. Milk fat percentage and daily production of milk fat were not affected by treatments.

Abomasum↗
PubMed1984

Effect of ruminal ammonia-nitrogen concentration on protein degradation in situ.

Two experiments were conducted to determine the effect of ruminal ammonia-nitrogen concentration on rate of ruminal protein degradation. In Experiment 1, four Holstein steers were fed a basal diet of corn grain and corn silage at hourly intervals. Continuous intraruminal infusions of solutions containing sodium bicarbonate and either sodium chloride or ammonium chloride resulted in ruminal ammonia-nitrogen concentrations that averaged 4.8 and 17.3 mg/dl. Ruminal fluid pH, fluid volume, and turnover rate of fluid and molar percentage of acetate, propionate, and butyrate were similar across treatments, reflecting steady state conditions. Rates of nitrogen and dry matter disappearance from polyester bags containing soybean protein supplements with 10.2 or 50.1% soluble nitrogen were not affected by increase of ruminal ammonia-nitrogen concentrations from 4.8 to 17.3 mg/dl. In Experiment 2, Holstein steers were fed twice daily a basal diet of urea-supplemented corn grain and corn silage. Polyester bags containing soybean protein supplements were placed in the rumen at -4, 0, or 4 h with reference to feeding and incubated from 1 to 12 h. Peak ruminal ammonia-nitrogen concentrations occurred during different periods of incubation for each treatment. Ruminal ammonia-nitrogen concentrations ranged from 3 mg/dl at 6 h postfeeding to 46 mg/dl at 1 h postfeeding. Nitrogen and dry matter disappearance rates during 0 to 1 and 1 to 12 h of incubation did not differ among treatments.

Ammonia↗
PubMed1984

An endogenous inhibitor of [3H]estradiol binding to nuclear type II estrogen binding sites in normal and malignant tissues.

Previous studies from our laboratory have demonstrated that nonneoplastic tissues, such as rat uterus, contain an endogenous inhibitor of [3H]estradiol binding to nuclear type II sites. Since the stimulation of nuclear type II estrogen binding sites in the rat uterus is highly correlated with the stimulation of uterine growth and DNA synthesis, we have suggested that this inhibitor may be an endogenous ligand for the type II site which may antagonize estrogenic response. The present studies demonstrate that normal mouse mammary gland cytosol contains very high levels of this inhibitor activity, whereas cytosol from mouse mammary tumors and human breast cancer contains very low quantities of this inhibitor. These results are consistent with the observations that rapidly proliferating neoplastic tissue contains very high quantities of nuclear type II sites and that this may be directly related to lower levels of this endogenous inhibitor in these tissues.

Animals↗