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Biomedical subjects

J H Clark

Publications and source records attributed to J H Clark.

At least 19 recordsLinked to original sources
PubMed1992

An unusual case of choledochal cyst causing hepatic failure requiring orthotopic liver transplantation.

The authors describe a case of orthotopic liver transplantation (OLT) in a patient with an infantile form of choledochal cyst that progressed to severe hepatic failure. Choledochal cyst must be included in the differential diagnosis of extrahepatic biliary obstruction in infants; it represents an additional reason to consider early exploratory laparotomy, both for diagnosis and to perform definitive excision. In the event that end-stage liver disease develops, OLT should be considered.

Choledochal Cyst↗
PubMed1992

Tyrosinase-like polypeptides in the uterus and in the central nervous system of rats.

Nuclear and cytosolic fractions of rat uteri and tissues from the central nervous system contain proteins that are recognized by a polyclonal tyrosinase antibody. This antibody eliminates the cresolase activity of uterine nuclear extract when estradiol is used as substrate. Thus, it appears that tyrosinase-like proteins might be present in tissues not generally considered to chain such an enzyme.

Animals↗
PubMed1992

Tyrosinase-like activity and estradiol binding in rat uterine nuclear extracts.

Nuclear extracts from the uteri of estradiol-implanted rats contain a tyrosinase-like enzyme that has three activities: monophenolase or cresolase, diphenolase or catecholase, and estrogen binding. When [3H]estradiol was used as a substrate, 3H2O was released from the A ring in the presence of copper and ascorbic acid. The optimal concentrations of these cofactors for the cresolase activity were established. The cresolase activity was lost on attempts at further purification. Estradiol binding was observed in conjunction with the enzymatic activity and was dependent on the presence of ascorbic acid and copper. The most potent inhibitors of 3H2O release from [3H]estradiol were those with a dihydroxyphenol moiety. The reaction was also sensitive to sulfhydryl reagents. These features of the enzyme are distinctive from other oxidases capable of attacking the aromatic ring of estrogens.

Animals↗
PubMed1992

Development of an antibody that binds sulfur mustard.

An antibody that binds bis(2-chloroethyl) sulfide (sulfur mustard) was developed. The immunizing antigen was prepared from the hapten 4-(2-chloroethyl)benzoic acid covalently bound to keyhole limpet hemocyanin (KLH). The antibody was monitored by a solid phase enzyme-linked immunosorbent assay (ELISA). The test antigen consisted of a second hapten, 8-chlorocaprylic acid, covalently bound to bovine serum albumin (BSA). The test antigen was absorbed to the wells of 96-well plates. The immunizing and test antigens contain a common chloroethyl moiety. Thiodiglycol, the principal hydrolysis product of sulfur mustard, does not react with the antibody. This antibody, because of its specificity, has the potential to be a valuable tool for mustard research and forensic detection.

Animals↗
PubMed1992

Studies of the amplification of carbaryl toxicity by various oximes.

The administration of 2-pyridine aldoxime methyl chloride (2-PAM Cl) is a standard part of the regimen for treatment of human overexposure to many organophosphorus pesticides and nerve agents. However, some literature references indicate that poisoning by carbaryl (1-naphthyl N-methyl carbamate), an insecticide in everyday use, is aggravated by the administration of 2-PAM Cl. This effect has been reported in the mouse, rat, dog and man. We have found that the inhibition of both eel acetylcholinesterase (eel AChE, EC 3.1.1.7) and human serum cholinesterase (human BuChE, EC 3.1.1.8) by carbaryl was enhanced by several oximes. Based on 95% confidence limits the rank order of potentiation with eel AChE was TMB-4 = Toxogonin > HS-6 = HI-6 > 2-PAM Cl. By the same criterion, the rank order of potentiation with human BuChE was TMB-4 > Toxogonin > HS-6 = 2-PAM Cl. Carbaryl-challenged mice also reflected a potentiation since TMB-4 exacerbated the toxicity more than 2-PAM Cl. Our hypothesis is that certain oximes act as allosteric effectors of cholinesterases in carbaryl poisoning, resulting in enhanced inhibition rates and potentiation of carbaryl toxicity.

Animals↗
PubMed1992

Cholinesterase studies with (R) (+)- and (S)(-)-5-(1,3,3-trimethylindolinyl)-N-(1-phenylethyl)carbamate.

A limited number of carbamates have been found useful for treatment of cholinergic symptoms with pyridostigmine and physostigmine being the main focus. In recent years 5-(1,3,3-trimethylindolinyl)N,N-dimethylcarbamate (I) has received considerable attention in the Chinese literature for a similar role. We report on the first synthesis of stereoisomers of an analog of (I). The isomers prepared were (R)(+)-5-(1,3,3-trimethylindolinyl)-N-(1-phenylethyl)carbamate (II) and (S)(-)-5-(1,3,3-trimethylindolinyl)-N-(1-phenylethyl)carbamate (III). The pKa value for each isomer was 6.8. Eel acetylcholinesterase inhibition studies were carried out at 25.0 degrees C over the pH range of 6.0 to 9.0. They reflect the first pH profiles using enantiomorphs of a cholinesterase inhibitor. The inhibition potencies for (II) and (III) over the range examined were similar. At pH 7.60 the ki for II = 7.38 x 10(3) M-1 min-1 (SD = 398) and for (III) the ki = 6.67 x 10(3) M-1 min-1 (SD = 355). In accord with the findings of Wilson and Bergmann20 on physostigmine our results indicate that the protonated form of (II) and (III) is the more potent inhibitor.

Acetylcholinesterase↗
PubMed1992

Supplementation of dairy cow diets with calcium salts of long-chain fatty acids and nicotinic acid in early lactation.

Forty multiparous Holstein cows were assigned to one of four treatments 15 d postpartum according to milk yield during wk 2 postpartum to examine the effects of supplementing niacin, Ca salts of long-chain fatty acids, and their interaction. Treatments were control, niacin (12 g/d), Ca salts of long-chain fatty acids (3% of dietary DM), or a combination of niacin and Ca salts. On d 99 postpartum, all cows were fed the control treatment for 2 wk to evaluate residual effects. Milk and FCM yields, blood plasma NEFA and beta-hydroxybutyrate concentrations, and apparent total tract hemicellulose digestibility were increased; milk protein percentage, milk SNF percentage, and blood plasma glucose concentrations were reduced by treatments containing the Ca soaps. Niacin supplementation increased milk protein content and yield but reduced blood plasma beta-hydroxybutyrate concentration. During the residual period, in which all cows received the control treatment, milk yield and plasma NEFA concentration remained elevated, milk protein and SNF contents remained depressed, and milk fat content was reduced for cows previously supplemented with Ca salts of long-chain fatty acids. Methionine and phenylalanine uptakes by the mammary gland were enhanced by niacin supplementation. Results indicated that dairy cattle in early lactation yielded more milk when their diets were supplemented with Ca salts of long-chain fatty acids and that niacin supplementation increased milk protein content and yield.

3-Hydroxybutyric Acid↗
PubMed1992

Infusion of long-chain fatty acids varying in saturation and chain length into the abomasum of lactating dairy cows.

Free long-chain fatty acids were infused into the abomasum of lactating dairy cows to determine postruminal effects on feed intake, production and composition of milk, nutrient digestibilities, and metabolites in blood. Four Holstein cows averaging 120 DIM and fitted with ruminal cannulas were used in a 4 x 4 Latin square design with 14-d periods. Treatments were abomasal infusions of 1) control, 168 g/d of meat solubles (carrier for fatty acids), 2) control plus 450 g/d of mostly saturated fatty acids (C16:C18 = .75), 3) control plus 450 g/d of a mixture of saturated and unsaturated fatty acids (C16:C18 = .40), and 4) control plus 450 g/d of mostly unsaturated fatty acids (C16:C18 = .11). Production of milk and milk components, DMI, and intake of digestible energy decreased linearly as unsaturation and chain length of infused fatty acids increased. Percentages of fat, CP, and SNF in milk and total tract apparent digestibilities of DM, OM, ADF, NDF, energy, and fatty acids were not affected significantly by treatments. Infusing fatty acids decreased proportions and yields of short- and medium-chain fatty acids and increased proportions and yields of unsaturated C18 fatty acids in milk fat. Increasing unsaturation and chain length of infused fatty acids linearly decreased proportion and yield of palmitic acid but increased proportions and yields of polyunsaturated C18 fatty acids in milk fat. Infusing fatty acids increased concentrations of NEFA and cholesterol in blood plasma. The profile of fatty acids reaching the intestine may be an important determinant of responses to supplemental fats fed to lactating dairy cows.

Abomasum↗
PubMed1992

Effects of feeding lactating dairy cows diets containing whole soybeans and tallow.

Four multiparous Holstein cows averaging 133 d postpartum and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design to investigate the effects of feeding diets containing whole soybeans and tallow. Treatments were 1) control, no added fat; 2) control and 10% whole raw soybeans; 3) control, 10% whole raw soybeans, and 2.5% tallow; and 4) control, 10% whole raw soybeans, and 4.0% tallow. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (45:5:50, DM basis). Intakes of DM and production of milk, milk CP, milk SNF, and 4% FCM were not affected by feeding supplemental fat. Production of milk fat and weight percentages and yields of long-chain fatty acids in milk fat were increased, whereas weight percentages and yields of short- and medium-chain fatty acids were decreased by feeding supplemental fat. Digestibilities of DM, OM, energy, cellulose, and fatty acids were decreased slightly when fat was added to the diet, but utilization of energy and N for production of milk was not altered. Supplemental fats increased concentrations of NEFA and cholesterol in plasma. These data indicate that relatively large amounts of unprotected fat can be added to the diet of lactating dairy cows without deleterious effects on milk composition, ruminal fermentation, or nutrient digestibilities.

Animal Feed↗
PubMed1992

Microbial protein synthesis and flows of nitrogen fractions to the duodenum of dairy cows.

Attempts have been made to increase nutrient availability for milk production by increasing feed intake, optimizing ruminal fermentation, and supplementing nutrients to the diet that will escape ruminal degradation. Energy and N are the nutritional factors that most often limit microbial growth and milk production. Ruminal fermentation and flow of microbial and dietary protein to the small intestine are affected by feed intake and by the amount and source of energy and protein in the diet. Feeding protein and carbohydrate that are not degraded in the rumen increases the quantity of dietary protein that passes to the small intestine but may decrease the quantity of microbial protein that is synthesized in the rumen. This often results in only small differences in the total NAN that passes to the small intestine. Because microbial protein supplies a large quantity of total AA that passes to the small intestine, differences in passage of individual AA often are only slight. Additional research with cows consuming large amounts of feed are needed to identify combinations of feed ingredients that synchronize availabilities of energy and N for optimizing ruminal digestion, microbial protein synthesis, nutrient flow to the small intestine, and milk production and composition.

Amino Acids↗
PubMed1992

Effects of feeding diets containing calcium salts of long-chain fatty acids to lactating dairy cows.

Four cows were utilized in a 4 x 4 Latin square design to investigate the effects of feeding Ca salts of long-chain fatty acids. Treatments were control diet with 1) no added fat, 2) 3% Ca salts of long-chain fatty acids, 3) 6% Ca salts of long-chain fatty acids, and 4) 9% Ca salts of long-chain fatty acids. Cows were fed chopped alfalfa hay, alfalfa haylage, corn silage, and concentrate (15:22:13:50) on a DM basis. Dry matter intake, energy intake, and ruminal fermentation were not altered greatly until Ca salts of long-chain fatty acids constituted 9% of DMI. Digestibilities of DM, OM, ADF, NDF, and hemicellulose were not affected by treatment. Digestibilities of cellulose, soluble residue, total C18 fatty acids, and total fatty acids followed quadratic patterns. Absorption of N was increased linearly when fat was fed, but digestibility of Ca was decreased linearly. Milk production, CP, and SNF were not altered greatly by inclusion of 3 or 6% Ca salts of long-chain fatty acids in the diet, but inclusion of 9% Ca salts of long-chain fatty acids decreased their production. Calcium salts of long-chain fatty acids increased milk fat percentage and production of fat and FCM when fed as 3 or 6% of the dietary DM but decreased yields of milk fat and FCM when fed as 9%. Calcium salts of fatty acids can be fed to provide up to 6% of the dietary DM without deleterious effects on ruminal fermentation and digestibilities of most nutrients.

Animal Feed↗
PubMed1992

Effects of feeding lactating dairy cows diets containing extruded soybeans and calcium salts of long-chain fatty acids.

Four multiparous Holstein cows averaging 36 DIM and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design to investigate the effects of feeding extruded whole soybeans and Ca salts of long-chain fatty acids. Treatments were diets containing 1) no added fat, 2) 16% extruded whole soybeans, 3) 16% extruded whole soybeans and 3% Ca salts of long-chain fatty acids, and 4) 16% extruded whole soybeans and 6% Ca salts of long-chain fatty acids. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (35:15:50, DM basis). Intakes of DM and energy and production of milk, 4% FCM, fat, CP, and SNF were decreased by feeding extruded whole soybeans and 6% Ca salts of long-chain fatty acids, but differences were small among the other treatments. The weight percentages and yields of C18:0, C18:1, and C18:2 in milk were increased, and most shorter chain fatty acids were decreased, by feeding supplemental fat. Digestibilities of DM, OM, ADF, soluble residue, total C18 fatty acids, and total fatty acids were decreased, but digestibility of hemicellulose was increased by feeding supplemental fat. The largest decrease in digestibilities of most dietary constituents and in energy and N utilization occurred when 16% extruded whole soybeans plus 6% Ca salts of long-chain fatty acids were fed to the cows. Calcium salts of long-chain fatty acids can supply up to 3% of the dietary DM in diets containing 16% extruded whole soybeans without having deleterious effects on most variables measured in this experiment.

Animal Feed↗
PubMed1991

Risk factors for carriage of meningococcus in the Los Angeles County men's jail system.

Ten cases of meningococcal meningitis in the Los Angeles County men's jail system in 1986 were the first known reported cases in this population. New cases have continued into 1990. Nineteen of 21 symptomatic cases identified by serogroup from the men's jail occurring through 1988 had serogroup C. The prevalence of meningococcal carriage and potential risk factors were studied in 1988 among 150 men booked to enter the jail, 350 inmates being released, and 100 jail staff. The prevalence of meningococcal carriage among releases, bookings, and staff were 25.4%, 18.7%, and 5.0%, respectively. Among releases, imprisonment longer than a threshold of 28 days increased carriage of serogroup C 10.0 times (95% confidence interval (CI) 4.6-21.6). Among bookings, household crowding increased serogroup C carriage 8.2 times (95% CI 1.5-45.3). Direct and passive smoking at home increased carriage of any serogroup 5.2 (95% CI 1.2-47.5) and 2.5 (95% CI 1.1-5.8) times, respectively. Feasible potential interventions include banning smoking in the jail and immunization with quadrivalent meningococcal vaccine of booked men sentenced for one month or more.

Carrier State↗
PubMed1991

High level expression of biologically active estrogen receptor in Saccharomyces cerevisiae.

Biochemical over-expression of the human estrogen receptor was achieved using a Saccharomyces cerevisiae expression system. The receptor was produced as a novel ubiquitin fusion protein. This fusion protein is short lived in the cell and is processed to produce unfused receptor shortly after folding. Conventional high copy expression plasmids produced receptor to about 0.04% of the total soluble protein. By incorporating a defective leu2 allele into these vectors, an additional 5-fold increase in receptor production was obtained. The recombinant receptor was undergraded, soluble and biologically active. Conventional methods of disrupting cells using glass beads had a detrimental effect on the ability of the receptor to bind hormone. Enzymatic digestion of the cell wall followed by hypotonic shock liberates the receptor that quantitatively binds estrogen.

Alleles↗
PubMed1991

Effects of urea and sodium bicarbonate supplementation of a high-fiber diet on nutrient digestion and ruminal characteristics of defaunated sheep.

Five sheep (average BW 48 kg) with ruminal, duodenal, and ileal cannulas were fed 63% roughage: 37% concentrate diets (CP = 14.5%) in a 5 x 5 Latin square design to study effects of urea and sodium bicarbonate supplementation on nutrient digestion and ruminal characteristics of defaunated sheep. Diets were fed twice daily (DMI = 1,076 g/d). Defaunation was accomplished with 25-ml doses of alkanate 3SL3/sheep daily for 3 d. Control sheep were faunated (Treatment 1) and fed soybean meal as the major N supplement. Remaining sheep were maintained defaunated and fed either the same diet as Treatment 1 (Treatment 2), Treatment 1 with urea replacing 30% of the soybean meal N (Treatment 3), or Treatment 1 with 2% sodium bicarbonate in the diet (Treatment 4). Treatment 5 was a combination of Treatments 3 and 4. Compared with the faunated control, defaunation decreased (P less than .05) total tract DM, OM, NDF, ADF, and CP digestibilities (71.5 vs 69.4, 73.8 vs 71.7, 64.6 vs 61.4, 58.7 vs 55.8, and 74.2 vs 70.6%, respectively) and average (2 to 12 h postfeeding) ruminal fluid ammonia (23.5 vs 13.7 mg/dl) and isobutyrate (.9 vs .7 mM) concentrations. However, defaunation increased (P less than .05) linoleic and linolenic acid flows (.58 vs .45 g C18:2/d; .17 vs .14 g C18:3/d) to and disappearance (.50 vs .39 g C18:2/d; .14 vs .11 g C18:3/d) from the small intestine. Urea supplementation increased (P less than .05) total tract DM (70.2 vs 68.6%) and OM (72.3 vs 71.0%) digestibilities of defaunated sheep but lowered (P less than .05) ruminal fluid isobutyrate concentration (.6 vs .8 mM). Sodium bicarbonate supplementation increased (P less than .05) ruminal fluid pH (6.4 vs 6.2), isobutyrate concentration (.75 vs .60 mM), total tract ADF digestibility (57.6 vs 54.2%), and ruminal NDF (41.6 vs 28.5%), ADF (36.6 vs 22.8%), and CP (-5.5 vs -26.8%) digestibilities in defaunated sheep. Dietary supplementation of urea or sodium bicarbonate increased nutrient digestion by defaunated sheep.

Absorption↗
PubMed1991

Effects of feeding alkaline hydrogen peroxide-treated wheat straw-based diets on intake, digestion, ruminal fermentation, and production responses by mid-lactation dairy cows.

The objective of this experiment was to determine the effects of feeding different levels of alkaline hydrogen peroxide-treated wheat straw (AHP-WS) in the diet on feed intake, nutrient digestion, ruminal fermentation, and production responses in mid-lactation dairy cows. Eight Holstein cows, averaging 147 d postpartum, were used in two replications of a 4 x 4 Latin square design. Complete mixed diets consisted of 70% forage and 30% concentrate (DM basis) with various levels of AHP-WS, alfalfa haylage, and corn silage as forage sources. Treatments contained 0 (control), 20.0, 40.1, or 60.0% AHP-WS in the diet. A quadratic effect (P = .08) of AHP-WS level on DMI was noted, with values of 2.16, 22.3, 20.8, and 18.9 kg/d for the control, 20.0, 40.1, and 60.0% AHP-WS treatments, respectively. Apparent digestibilities of DM, OM, CP, and ADF were not affected (P greater than .10) by replacing haylage and corn silage with increasing amounts of AHP-WS in the diet, but there was a linear increase (P = .03) in NDF digestibility (44% for control vs 59% for the 60.0% AHP-WS diet) and a parallel decrease (P less than .05) in cell content digestibility (82 vs 70% for these two diets). Yields of milk and 4% fat-corrected milk (FCM) were decreased (quadratic; P = .0001) as the level of AHP-WS increased in the diet. The addition of AHP-WS to the diet decreased the milk fat percentage from 3.72 to 3.60% (quadratic; P = .05) and decreased milk protein percentage from 3.27 to 3.13% (linear; P = .0001). Cows fed the higher levels of AHP-WS had linear increases (P = .0001) in ruminal concentrations of total VFA (128.0 mM for control vs 136.0 mM for the 60.0% AHP-WS treatment) and molar proportion of acetate, resulting in a quadratic effect (P less than .0001) on the acetate:propionate ratio. These data indicate that feeding the 40.1 and 60.0% AHP-WS diets lowered digestible DM and OM intakes, which resulted in reduced 4% FCM yield as nutrient intakes were decreased compared with cows fed the 20.0% AHP-WS diet or the control diet containing alfalfa haylage and corn silage. Although substituting AHP-WS for haylage and corn silage increased NDF digestibility and tended to increase digestible NDF intake, milk production was depressed because digestible DMI decreased.

Animal Feed↗