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Biomedical subjects

J H Clark

Publications and source records attributed to J H Clark.

At least 127 records · Page 7Linked to original sources
PubMed1987

Effects of feeding or infusing ammonium salts of volatile fatty acids on ruminal fermentation, plasma characteristics, and milk production of cows.

Eight rumen-fistulated Holstein cows, averaging 77 d postpartum, were used in a replicated 4 X 4 Latin square design with 28-d periods to investigate the effect of ammonium salts of isobutyrate, 2-methylbutyrate, isovalerate, and n-valerate on animal performance and their possible mechanism(s) and site(s) of action. Each cow was fed ad libitum a complete mixed diet of 55% corn silage and 45% concentrate on a dry basis that was supplemented with 1.8 kg of premix daily. Treatments were 1) control, 2) ammonium salts of volatile fatty acids in premix, 3) ammonium salts of volatile fatty acids ruminally infused, or 4) ammonium salts of volatile fatty acids abomasally infused. Mean ruminal fluid pH and concentrations of ammonia and volatile fatty acids for treatment comparisons were not different. Plasma concentrations of isobutyrate, 2-methylbutyrate, and valerate differed among treatments, but there was no significant effect on dry matter intake, milk production, milk composition, or efficiency of feed utilization. Apparent nutrient digestibility; disappearance of dry matter, cellulose, and nitrogen from polyester bags suspended in the rumen; and plasma concentrations of glucose, free fatty acids, and growth hormone also were not significantly affected by treatment.

Abomasum↗
PubMed1987

Inhibition of L-alanine uptake into bovine jejunal brush border membrane vesicles by L-amino acids.

Jejunal epithelial cells from slaughtered Holstein cows were fractionated to obtain purified brush border membranes from which membrane vesicles were prepared for use in amino acid uptake studies. Uptake of alanine was determined by incubation of vesicles with a solution containing radiolabelled alanine, isolation of vesicles and accumulated alanine by filtration, and detection of accumulated alanine by liquid scintillation counting. Uptake studies were conducted under conditions shown to provide linear rates of accumulation. Sodium-dependent active transport was determined as the difference between uptake measured in the presence and absence of sodium in the extravesicular buffer. Inhibition of alanine uptake increased with increasing extra-vesicular inhibitor concentration until a plateau value was reached. Inhibition of sodium-dependent alanine uptake by 100 mM glycine was 72%; 25 mM isoleucine, valine, or methionine completely inhibited initial alanine uptake. These results indicate the existence of at least two sodium-dependent transport systems, one capable and one incapable of accepting glycine for transport. At concentrations designed to represent expected concentrations of free amino acids in intestinal digesta, several equimolar mixtures (.2 to 5 mM) of 20 amino acids inhibited alanine uptake, suggesting that significant interaction among amino acids for uptake may be occurring under in vivo conditions.

Alanine↗
PubMed1987

Supplying the protein needs of dairy cattle from by-product feeds.

Several by-product feeds are relatively high in crude protein and exhibit relatively low ruminal degradability, which make them desirable proteinaceous feeds for dairy cows. Therefore, by-product feeds have been and will continue to be important feeds for dairy cows. Factors are discussed that affect ruminal degradability of protein in distillers grains, distillers grains with solubles, brewers grains, corn gluten feed, corn gluten meal, meat meal, meat and bone meal, blood meal, and fish meal, and the potential of these feeds to provide supplemental amino acids needed by lactating dairy cows. The importance of maximizing synthesis of microbial protein and digestion of organic matter in the rumen is emphasized in relation to total amino acid passage to the small intestine. For these feeds to be used most successfully, they must be available from a dependable source at an economical cost and should supply amino acids that complement other amino acids passing to the small intestine. Benefits that should be realized from the successful use of by-product feeds include increased milk production from feeding proteins that have greater ruminal escape potentials and a reduced cost per unit of milk produced because of decreased use of expensive supplemental protein.

Animal Feed↗
PubMed1986

Uterine type II estrogen-binding sites are not of eosinophil origin.

A recent report by Lyttle et al. (Lyttle, C. R., Medlock, R. L., and Sheehan, D. M. (1984) J. Biol. Chem. 259, 2697-2700) suggested that nuclear type II sites in the rat uterus are of eosinophil origin and may represent [3H]estradiol binding to eosinophil peroxidase. To further evaluate this hypothesis we examined the response of nuclear type II sites to estrogen under conditions where eosinophils are not present. Results of our experiments show that physiological levels of estradiol-17 beta (10 nM for 72 h) will stimulate nuclear type II sites in highly purified cultures (21-25 days; 4 passages) of rat uterine stromal and myometrial cells. The magnitude of the response of type II sites to estradiol in these stromal (4-fold) and myometrial (80-fold) cell cultures was essentially identical to that observed in the uterine cell types following in vivo estrogen treatment. Since these highly purified cultures of uterine cells were prepared from the uterus of a 21-day ovariectomized rat which is devoid of eosinophils, we conclude that estradiol stimulation of nuclear type II sites is a direct intracellular response to estrogen which occurs independent of eosinophil accumulation. Furthermore, we have found that type II sites in the rat uterus are not peroxidase. This was demonstrated by experiments which show type II sites are present in the 39,000 X g supernatant fraction of uterine cytosol, whereas peroxidase activity is quantitatively recovered in the crude mitochondrial (39,000 X g) pellet. Likewise, the small amount of peroxidase activity (approximately 10%) in the total homogenate which contaminates our nuclear pellet preparations was extracted (98-100%) with 0.5 M CaCl2. Type II estrogen-binding sites (95-100%) remained associated with the nuclear pellet fraction after peroxidase extraction. Therefore, stimulation of cytosol and nuclear type II sites by estrogen in the rat uterus is a direct intracellular response to the hormone unrelated to eosinophil accumulation and/or peroxidase activity.

Animals↗
PubMed1986

An endogenous ligand for type II binding sites in normal and neoplastic tissues.

The rat uterus contains two classes of specific nuclear estrogen binding sites which may be involved in estrogen action. Type I sites represent the classic estrogen receptor (Kd 1 nM) and type II sites (Kd 10-20 nM) are stimulated in the nucleus by estrogen under conditions which cause uterine hyperplasia. Dilution of uterine nuclear fractions from estrogen treated rats prior to quantitation of estrogen binding sites by [3H]-estradiol exchange results in an increase (3-4 fold) in the measurable quantities of the type II site. Estimates of type I sites are not affected by dilution. These increases in type II sites following nuclear dilution occur independently of protein concentration and result from the dilution of a specific endogenous inhibitor of [3H]-estradiol binding to these sites. The inhibitor activity is present in cytosol preparations from rat uterus, spleen, diaphragm, skeletal muscle and serum. Preliminary characterization of the inhibitor activity by Sephadex G-25 chromatography shows two distinct peaks which are similar in molecular weight (300). These components (alpha and beta) can be separated on LH-20 chromatography since the beta-peak component is preferentially retained on this lipophilic resin. Partial purification of the LH-20-beta inhibitor component by high performance liquid chromatography and gas-liquid chromatography-mass spectrometric analysis suggest the putative inhibitor activity is not steroidal in nature and consists of two very similar phenanthrene-like molecules (molecular weights 302 and 304). Analysis of cytosol preparations on LH-20 chromatography shows that non-neoplastic tissues (uterus, liver, lactating mammary gland) contain both alpha and beta inhibitor components whereas estrogen-induced rat mammary tumors contain very low to non-measurable quantities of the beta-peak inhibitor activity.

Animals↗
PubMed1986

Subcellular localization of triphenylethylene antiestrogen binding sites (TABS) in rat liver.

The subcellular distribution of triphenylethylene anti-estrogen binding sites (TABS) was examined in the rat liver. Nuclear, mitochondrial and microsomal fractions were prepared by differential centrifugation, extracted with 0.5 M KCl and bound [3H]tamoxifen was determined by the dextran coated charcoal method. The relative concentration of TABS in each fractions were: nuclear 30.2; mitochondrial, 14.8 and microsomal, 10.2 pmol/g tissues. No TABS were detected in the high speed cytosol. The dissociation constants of nuclear and mitochondrial TABS were similar (1-2 nM); however, a higher number was obtained for microsomal TABS (5-6 mM). The ability of other triphenylethylene drugs to compete for [3H]tamoxifen binding to TABS was similar to tamoxifen for mitochondrial and microsomal sites. In contrast, nafoxidine was a more potent inhibitory for nuclear TABS. Exposure of high salt nuclear extracts to charcoal prior to assay did not reveal any evidence for an endogenous ligand of high affinity. We conclude that TABS are present in nuclear, mitochondrial and microsomal fractions of rat liver and that the nuclear fraction contains the highest concentration of these sites.

Animals↗
PubMed1986

Purine excretion during tumor lysis in children with acute lymphocytic leukemia receiving allopurinol: relationship to acute renal failure.

We measured serial urine levels of hypoxanthine, xanthine, and uric acid in 19 children with acute lymphocytic leukemia (ALL) receiving allopurinol therapy during tumor lysis; four of these children developed acute renal failure. The urinary excretion of uric acid rose moderately from 447 +/- 251 micrograms/dl glomerular filtrate before chemotherapy to 778 +/- 463 micrograms/dl glomerular filtrate during tumor lysis (P less than 0.05) whereas the urinary excretion of hypoxanthine (17.9 +/- 15 to 292 +/- 213 micrograms/dl glomerular filtrate) and xanthine (74 +/- 62 to 1091 +/- 1085 micrograms/dl glomerular filtrate) rose dramatically (P less than 0.001). The urinary excretion of uric acid, hypoxanthine, and xanthine per deciliter of filtrate was significantly higher (P less than 0.001) in those who developed acute renal failure than in those who did not, but the highest urine concentration of these purine metabolites did not differ in the two groups. In all 19 children, the highest urine concentration of uric acid and hypoxanthine during tumor lysis did not exceed the solubility limit of each in an alkaline urine specimen. In contrast, the peak urine concentration of xanthine exceeded its solubility limit in an alkaline urine specimen in 16 of 19 children. The urine sediment during the period of tumor lysis was examined by diffuse reflectance infrared spectroscopy; precipitated xanthine was found in sediment from eight of the 19 children, was significantly (P less than 0.001) associated with a urine xanthine level greater than 350 mg/dL, and occurred with equal frequency in those who did or did not develop acute renal failure. We conclude that urinary excretion of hypoxanthine and xanthine increases dramatically whereas uric acid excretion rises moderately in children undergoing tumor lysis while receiving allopurinol, that acute renal failure occurs in children with a higher purine load per deciliter of glomerular filtrate, but that factors other than tubular precipitation of purine metabolites are likely to be involved in the pathogenesis of renal failure during tumor lysis.

Acute Kidney Injury↗
PubMed1986

Dietary fructose in the management of intractable diarrhea of infancy.

Carbohydrate digestion/absorption was evaluated in 11 infants with intractable diarrhea while they were receiving a carbohydrate-free soy-isolate formula. Seven patients were fed within 48 h of admission. Enteral feedings were initiated in the remainder after they had gained 1 kg while receiving parenteral nutrition. All feedings were initially administered by continuous nasogastric infusion. Nine patients were initially fed formula with polymeric glucose; two received fructose as the carbohydrate source, based on a documented history of polymeric glucose intolerance. Five of the nine developed watery, acidic stools while receiving polymeric glucose. All were switched to fructose, which resulted in improvement in stool pH and consistency. Glucose tolerance was normal 1 month after discharge in all seven fructose-requiring infants. Three of six infants have shown a persistent inability to hydrolyze sucrose. Several putative mechanisms of polymeric glucose intolerance are discussed, as well as the apparent association with primary sucrase-isomaltase deficiency in three of the patients. Fructose is an effective alternative carbohydrate source in infants unable to tolerate polymeric glucose, and early initiation of fructose may obviate the need for total parenteral nutrition and prolonged bowel rest.

Diarrhea, Infantile↗
PubMed1986

Preparation of brush border membrane vesicles from fresh and frozen bovine intestine for nutrient uptake studies.

Purified brush border membranes were obtained from homogenized jejunal epithelial cells of cattle by divalent cation aggregation of nonbrush border membranes and differential centrifugation. Membrane marker enzyme assays determined effectiveness of the fractionation procedure. Compared with cellular homogenate, maltase and sodium+-potassium+-adenosine triphosphatase specific activities in the membrane fraction isolated from the interface of discontinuous (35 and 45% wt/wt) sucrose gradients increased 14.5- and 1.9-fold whereas enzyme recoveries averaged 20.2 and 2.4%. These data indicate significant enrichment in brush border membranes with minimal basolateral membrane contamination. Vesicles formed from this membrane fraction had a predominately (93%) luminal side out orientation. After incubating vesicles with radiolabeled substrates, vesicles and accumulated substrates were separated from the incubation buffer by filtration and substrate uptake quantified by liquid scintillation counting. Observed uptake was the result of substrate accumulation within an osmotically active intravesicular space and was not due to nonspecific binding of the substrate to vesicular membranes. Vesicles exhibited sodium-dependent and independent substrate uptake pathways and were able to discriminate between substrate stereoisomers for uptake. Major differences were not detected between results obtained with vesicles prepared from fresh or frozen intestines. These vesicles can be utilized to investigate nutrient uptake by the bovine small intestine.

Animals↗
PubMed1986

Effects of ruminal exposure on the amino acid profile of heated and formaldehyde-treated soybean meal.

Rumen cannulated Holstein steers, fed corn silage and a corn-soybean grain mixture twice a day, were used to compare the effectiveness of heat and formaldehyde treatments in preserving the amino acid profile of soybean meal exposed to ruminal fermentation for 12 h. Formaldehyde treatments were 0, .3, .6, and .9 g/100 g soybean meal. Defatted soybean flakes treated at 250, 250, 215, and 180 degrees C for 30, 20, 20, and 25 min, respectively, and unheated soybean meal comprised the heat treatments. The in situ polyester bag technique was used to obtain estimates of ruminal degradation of the treated and untreated soybean meals and to obtain undegraded residues from the soybean meals following 12 h of rumen exposure. Diaminopimelic acid was used to assess the extent of bacterial contamination. Significant amounts of apparent diaminopimelic acid were detected in unexposed samples (2.0 to 7.6% of soybean nitrogen) and in residues (4.8 to 12.7% of residue nitrogen). Significant differences in amino acid contents were detected between untreated and heat-treated soybean meals and their respective residues. Formaldehyde treatment was effective in preserving the original amino acid profile of soybean meal.

Amino Acids↗
PubMed1986

Effects of intake and postruminal casein infusion on performance and concentrations of hormones in plasma of lactating cows.

Four Holstein cows were utilized in a Latin square design with a factorial arrangement of treatments to examine the interaction between effects of dry matter intake (107 vs. 78% of energy requirements) and postruminal infusions (water vs. 395 g/d casein) on lactational performance, utilization of nitrogen and energy, and plasma concentrations of hormones. Yields of milk and milk protein were decreased by feed restriction and increased by casein infusion with no treatment interactions. Restricting feed intake decreased total nitrogen intake by 143 g/d and resulted in smaller quantities of fecal, absorbed, urinary, milk, and retained nitrogen compared with cows fed ad libitum. Casein infusion increased total nitrogen intake (55 g/d), absorbed nitrogen (54 g/d), urinary nitrogen excretion (28 g/d), and milk nitrogen (13 g/d). Casein by dry matter intake interactions were not significant for nitrogen utilization. Restricting feed intake increased plasma growth hormone and decreased concentrations of insulin and triiodothyronine. Glucagon, prolactin, and thyroxine were not affected by intake. Casein infusion did not affect growth hormone, insulin, prolactin, triiodothyronine, or thyroxine. Increased milk and milk protein yields obtained with casein infusion were apparently not mediated through changes in circulating concentrations of these hormones; however, plasma glucagon was increased by casein infusions.

Animals↗
PubMed1986

Celiac artery aneurysmectomy with pancreatectomy.

A case of symptomatic celiac artery aneurysm with pancreatic involvement treated by excision, 85% pancreatectomy, and direct reanastomosis of the common hepatic artery with restoration of arterial continuity is reported. This is the first reported case, of which we are aware, in which celiac artery aneurysm resection also required partial pancreatectomy. Pancreatic involvement by celiac artery aneurysm is discussed. The rationale for early diagnosis and recommended treatment is presented.

Aneurysm↗
PubMed1985

Vitamin E sufficiency in children with cholestasis: a comparison between erythrocyte peroxide hemolysis and serum alpha-tocopherol.

Vitamin E sufficiency was assessed in 19 children with chronic cholestasis by determining both erythrocyte peroxide hemolysis (EPH) and serum alpha-tocopherol (alpha-T) levels. Eight had normal alpha-T (1.19 +/- 0.67 mg/dl; normal greater than 0.5). The mean EPH in this group was 13.1 +/- 14.3% (normal less than 20%). The remaining 11 patients had low alpha-T levels (0.25 +/- 0.15 mg/dl) and elevated EPH (83.9 +/- 17.1%). Children found to be vitamin E deficient received either oral alpha-T (50-100 IU/kg per day) or parenteral alpha-tocopherol acetate in sesame oil every 2-4 wk (200-300 mg). This permitted serial monitoring of EPH and alpha-T. We found that normalization of the EPH was uniformly accompanied by normalization of the alpha-T level. However, normal alpha-T levels occurred with elevated EPH (between 20% and 80%) on 11 occasions. EPH greater than 80% correctly identified vitamin E deficiency in all cases. Hence, EPH is a satisfactory screening test of vitamin E sufficiently. When the EPH is less than 20%, the patient is vitamin E sufficient. Conversely, when the EPH is greater than 80%, the patient is vitamin E deficient. Serum alpha-T measurements are needed to determine vitamin E sufficiency when the EPH is greater than 20% and less than 80%.

Adolescent↗
PubMed1985

Confirmation of serum salicylate levels in Reye's syndrome: a comparison between the Natelson colorimetric method and high performance liquid chromatography.

Serum was obtained from 11 patients with Reye's syndrome at admission and analyzed for the presence of salicylates by the Natelson colorimetric technique and high performance liquid chromatography. Salicylate levels obtained by the Natelson method had a mean of 6.00 mg/dl +/- 4.58; the mean HPLC salicylic acid level was 5.09 mg/dl +/- 5.14. The correlation coefficient was 0.985 with a linear regression line y = 0.8788x + 1.527. No other salicylate metabolites nor interfering substances were identified. Once the accuracy of the Natelson method was confirmed, the charts of 82 patients were reviewed for admission salicylate levels. The overall mean was 8.63 mg/dl (survivors, 8.45 mg/dl +/- 8.56; fatalities, 9.28 mg/dl +/- 5.34). There was no correlation found between admission salicylate level and peak ammonia level, another important index of disease severity.

Ammonia↗
PubMed1985

Hemorrhagic complications of Henoch-Schönlein syndrome.

Two patients are described with atypical manifestations of Henoch-Schönlein syndrome. One patient suffered severe intracranial hemorrhage and a subsequent massive gastric hemorrhage. The other patient developed an asymptomatic serosanguinous pleural effusion. Both had evidence of profound hypoprothrombinemia at the time of admission. Aggressive management of any coagulopathy accompanying Henoch-Schönlein syndrome is cardinal in order to prevent life-threatening complications such as gastrointestinal, intracranial, and pulmonary hemorrhage.

Cerebral Hemorrhage↗
PubMed1985

Nephrolithiasis in childhood inflammatory bowel disease.

Six children with inflammatory bowel disease and nephrolithiasis are reported. Their mean age at the passage of the first stone was 12.5 years and the mean duration of active inflammatory bowel disease was 34.5 months. Four had ulcerative colitis and two had Crohn's disease. In three patients, the onset of stone disease was associated with a flare in the bowel disease. Stone passage in four patients was accompanied by an increase in abdominal pain; three experienced gross hematuria. Stones from four of the patients were composed primarily of calcium phosphate; stones from the remaining patients contained uric acid and/or calcium oxalate. The pathogenesis of nephrolithiasis as it relates to inflammatory bowel disease is considered and an approach to therapy offered.

Adolescent↗
PubMed1985

Identification and analysis of keratin polypeptides from isolated rat vaginal epithelium.

Under the influence of estradiol, the vaginal epithelium undergoes a process of growth and differentiation known as cornification. To analyze the biosynthetic changes that underlie this phenomenon in rats, it was necessary to first isolate the vaginal epithelium from hormonally stimulated animals. This was accomplished by two different methods: enzymatic digestion with a trypsin/pancreatin solution, which produced a disaggregated population of cells from the living epithelial layers; or disruption of basement membrane adhesion with a chaotropic salt solution (2 M NaSCN), which produced intact, full thickness tissue sheets. Extended extraction of the cells and sheets with an alkaline urea buffer followed by analysis of these extracts on denaturing polyacrylamide gels revealed that both preparations contained six major polypeptides in the mol wt range of 50,000-60,000 daltons. Differential solubilization indicated that these proteins are keratin subunits, and amino acid analysis confirmed this for the 53,000-dalton polypeptide (53K) purified from preparative sodium dodecyl sulfate gels. On two-dimensional gel electrophoresis, 53K produced a group of three acidic spots (alpha, beta, and gamma), with isoelectric points of 4.6, 5.5, and 5.4, respectively. Partial peptide maps revealed that these spots are isoelectric variants of the same protein. Immunization of rabbits with 53K produced a keratin antiserum that was primarily directed against the immunogen and cross-reacted weakly with a 50,000- and a 57,000-dalton band. This work demonstrated the feasibility of obtaining well defined molecular probes from a hormone-responsive epithelial system.

Amino Acids↗