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Biomedical subjects

D S Kronfeld

Publications and source records attributed to D S Kronfeld.

At least 91 records · Page 5Linked to original sources
PubMed1985

Measurement of portal and hepatic blood flows using a modified method for surgical placement of catheters in the major splanchnic vessels of sheep.

A modified catheterization and para-aminohippurate dye dilution technique was used to measure portal and hepatic blood flows in sheep. Blood flows (mean +/- 1SD) for 7 healthy sheep were 1.54 +/- 0.71 L/min and 1.98 +/- 0.75 L/min for portal and hepatic flows, respectively. Blood flow measurement was facilitated when dye injection rates produced blood para-aminohippurate acid concentrations greater than 15 mg/L. Uniform mixing of dye with blood was confirmed in 1 sheep with 2 portal vein catheters. Surgery to place the catheters was facilitated by using a ventral para-costal approach. Blood gas analysis was useful in confirming the placement of the catheters. Useful catheter life in this experiment was 41 days, which was longer than in previous reports. Treating the catheters with an organo-silane preparation, protecting the catheters against dislodgement, and use of a belly bandage to minimize damage to the external parts of the catheter may have prolonged catheter life in this experiment.

Animals↗
PubMed1984

Effects of dipyrone on endotoxin-induced fever, central nervous depression and hypoglycaemia in sheep.

Sixteen sheep were divided into four groups and were given saline, Escherichia coli endotoxin at 35 micrograms/kg0.75, dipyrone at 88 mg/kg0.75, or endotoxin and dipyrone intravenously. Plasma glucose concentrations, rectal temperature and depression of central nervous function were assessed at hourly intervals for 10 h and again at 24 h. Dipyrone had no effect on normal sheep but in sheep given endotoxin, it blocked the febrile response and partially blocked the depression effect upon the central nervous system without affecting the hypoglycaemic response.

Aminopyrine↗
PubMed1984

Hepatic and extrahepatic lactate metabolism in sheep: effects of lactate loading and pH.

Hepatic lactate metabolism was studied in five sheep receiving infusions of either lactic acid or sodium lactate using an arteriovenous difference technique. Hepatic uptake of lactate was a saturable process with second order (Michaelis-Menten) kinetics. Although lactic acid infusion decreased blood pH, hepatic saturation of lactate uptake occurred before changes in pH could influence hepatic lactate metabolism. The Vmax for hepatic lactate metabolism is 5.72 mmol X kg-0.75 X h-1 and the Km 3.06 mmol/l. These findings have therapeutic relevance. In acidosis, the hepatic response to therapeutic administration of sodium lactate during fluid therapy will be variable. If plasma lactate is low, lactated fluids may increase hepatic uptake and produce an alkalizing effect. If plasma lactate is already high, hepatic lactate metabolism is nearly saturated, and additional lactate will not produce a hepatic alkalizing response. Extrahepatic tissues switch from lactate production to lactate utilization under conditions of lactate loading. They remove more lactate than liver at high plasma lactate concentrations. Muscle may be important in lactate removal in certain types of exercise.

Animals↗
PubMed1984

Calcium homeostasis in cows, with special reference to parturient hypocalcemia.

Calcium homeostasis is described in terms of controlled, disturbing, and controlling signals. Plasma calcium concentration [( Ca]p) and bone calcium mass (Mb) are the two main controlled signals. Disturbing signals include calcium intake (Vi) and clearance of plasma calcium to feces ( Clf ), bone (Clo+), placenta (Clp), and milk ( Clm ). Clo+ is a disturbing signal for [Ca]p and a controlling signal for Mb. Homeostasis is maintained by input control. Fractional renal calcium reabsorption (alpha r) decreases when calcium entry into plasma is excessive, but usually calcium entry rate (VT) responds effectively to small changes in [Ca]p associated with changes in disturbing signals. With increases in Vi, both fractional calcium absorption (alpha d) and fraction of bone calcium removed (lambda b) decrease to maintain VT at an appropriate level. As Clo+ declines with advancing age, [Ca]p rises slightly but VT decreases: a 1% change in [Ca]p would lead to a 13% change in VT. In heavily lactating cows, this response of VT may be enhanced. Parturient hypocalcemia may be the result of delayed negative feedback responses of lambda b (1 wk) and alpha d (1 day). Positive feedback between [Ca]p and gut motility may lead to transient suppression of VT during hypocalcemia, despite high plasma parathyroid hormone and 1,25-dihydroxyvitamin D3 concentrations. Parturient paresis is an example of a disordered accelerative response in a complex control system amenable to a variety of physiologically rational management procedures.

Absorption↗
PubMed1984

Rumen fermentation in vitro as influenced by long chain fatty acids.

Responses of rumen microbes to fatty acids were evaluated by production of total volatile fatty acid and ratio of acetate to propionate. Fermentations were under carbon dioxide for 20 h in 50-ml Erlenmeyer flasks in a Dubnoff metabolic shaking incubator. Flasks contained 20 ml medium, 1 ml reducing solution, 750 mg substrate (450 mg hay plus 300 mg grain), and varying amounts of long-chain fatty acids supplied as free acids, as calcium salts, or as triglycerides. They were inoculated with 5 ml rumen fluid obtained from a cow fed 3.6 kg grass hay, 2.3 kg grain, and .2 kg tallow daily. Volatile fatty acid production was decreased by long-chain fatty acids that contained less than 18 carbon atoms and by unsaturated long-chain fatty acids with 18 carbon atoms. Lauric acid decreased volatile fatty acid production by 69% and induced unusual acetate/propionate ratio (40:1). Stearic acid, however, did not affect volatile fatty acid production or acetate/propionate ratio. Within two series of long chain fatty acids (myristic, palmitic, stearic, arachidic; stearic, oleic, linolenic), melting point accounted for 93 to 95% of the variation of volatile fatty acid production and acetate/propionate. As calcium salts, long chain fatty acids caused small changes of fermentation. Our data support the proposition that hard fats and calcium salts of long-chain fatty acids do not interfere with ruminal fermentation.

Acetates↗
PubMed1983

Retinol homeostasis in lambs given low and high intakes of vitamin A.

Four groups of lambs were fed on a low-carotene basal diet. One group received no supplemental vitamin A (mildly deficient). Remaining groups were supplemented daily with vitamin A acetate equivalent to 100 (control) 9000 (mildly intoxicated) and 18000 (severely intoxicated) microgram retinol/kg body-weight. After 16 weeks lambs received a bolus of [15-3H]retinol intravenously; blood, urine and faeces were sampled for 48 h. Plasma retinol was complexed to a protein of 20000 molecular weight (MW), which in turn was complexed to a protein of 65000 MW; these proteins correspond respectively to retinol-binding protein and prealbumin. Plasma retinol concentration reached plateau values in intoxicated lambs, but plasma retinyl ester concentrations increased rapidly when liver contents of both retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded 30 micrograms. Labelled compounds, more polar than retinol, were found in plasma; their concentration increased tenfold in intoxicated lambs within 48 h. Plasma retinol transport rates were 0.1, 10.5 and 11.8 times control values, and clearance rates were 0.3, 14.1 and 14.3 times control values in mildly-deficient, and mildly- or severely-intoxicated lambs respectively. Turnover of retinol increased rapidly when liver contents of retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded approximately 30 micrograms. Plasma clearance of retinyl esters was unchanged with intake. Faecal excretion of tracer increased linearly with plasma retinol clearance. Our findings identify several variables that appear to be involved in retinol homeostasis, including plasma retinol clearance and excretion.

Animals↗
PubMed1983

Transfer of vitamin A from intestine to plasma in lambs fed low and high intakes of vitamin A.

Three groups of lambs were fed a low carotene diet supplemented with vitamin A proprionate equivalent to 0, 100 or 12,000 micrograms retinol per kilogram per day via rumen cannulae. These groups were mildly deficient, normal (control) and intoxicated, respectively. After 17 weeks, abomasal cannulae were implanted, [15-3H]retinol was injected into the abomasum, and jugular blood was sampled for 48 hours. After 7 days, the tracer was injected into a jugular vein, and blood was sampled for 48 hours. Rates of retinol and retinyl ester transport and retinol clearance from plasma reflected intake (P less than 0.05); clearance of retinyl esters was unaffected. Mean efficiencies of total vitamin A (retinol and retinyl ester) transfer from digestive tract to plasma were 86, 60 and 60%, whereas those of retinol were 91, 58 and 14% (P less than 0.05) for mildly deficient, control and intoxicated lambs, respectively. Thus lower transfer efficiencies were associated with higher transport rates of plasma retinol and retinyl ester and with increased clearance of retinol but not retinyl ester from plasma. These results suggest that vitamin A transfer from intestine to plasma is sensitive to vitamin A intake, and that retinol is the primary form of vitamin A affected.

Animals↗
PubMed1982

Placental transport of retinol in sheep.

Six ewes in the last trimester of pregnancy were maintained on adequate intakes of vitamin A. Indwelling catheters were implanted surgically in fetal jugular veins and carotid arteries. Three ewes and three fatal lambs received intravenous [15-3H] retinol 19 days prior to parturition, followed by sequential sampling of maternal and fetal blood. Fetal plasma retinol was found to be complexed with retinol-binding protein and another protein other than prealbumin, with a total molecular weight of 30,000 to 35,000. Transfer of labeled retinol from ewe to fetus peaked at 24 hours after maternal injection. Calculation of plasma retinol transport rate from the areas under the radioactivity-time curves showed that transport in the fetus averaged 5% of that in the ewe. Approximately 250 microgram of retinol was transferred daily from ewes to fetal lambs and 50 microgram/day carried back to mothers. The study suggested that the carrier system of retinol in blood may not be the same in the fetal lamb as in adults, and demonstrated that retinol transfer is appreciable from fetus to ewe.

Animals↗
PubMed1982

Effects of fiber on digestibility and transit time in dogs.

This study examines effects of variations in fiber content on nutrient assimilation, fecal output, and gastrointestinal transit time in the dog. Four normal Beagles were fed four diets in a randomized block design. The basal diet was a canned, balanced, meat-based dog food (Alpo Trio) to which added 3, 6, and 9% by weight of alpha cellulose (Solka Flok). Food intake and fecal outputs were recorded for 5-day periods. Samples of diets and fecal collections were analyzed for dry matter, nitrogen, fat, carbohydrate and ash; digestibilities were calculated. Transit times were measured by a radiographic marker technique. Fecal weight and water increased linearly; digestibility of dry matter decreased from 90 to 70% and ash from 43 to 32% with added fiber. Responses of protein, carbohydrate and fat were less pronounced but were regular; regressions of their digestibilities on added fiber were significant. Regression estimate of true digestibility for alpha-cellulose was 6%. Intestinal transit time decreased from a mean of 37.4 to 28.7 hours with added fiber. Decreased intestinal time would contribute to depression of fry matter digestibility. Increased fecal water output probably also reflected retention by fiber.

Animals↗
PubMed1982

Parathyrin and calcium homeostasis in the fetus.

The response of plasma parathyrin (PT) in cattle fetuses to changes in plasma calcium was investigated in utero. Resting plasma calcium levels for 4 fetuses averaged 3.1 mg/dl higher than for their mothers. Fetal PT levels (0.67 ng/ml) were half those of the mother (1.40 ng/ml). Hypocalcemia induced by EDTA infusion evoked a rise in plasma PT in 2 or 3 fetuses. The relationship between plasma PT and calcium levels in these fetuses was curvilinear, PT rising from about 0.7 ng/ml at 13 mg calcium/dl to a plateau of about 1.6 ng/ml below 10 mg calcium/dl. This contrasted with one of the mothers in which PT rose above 3 ng/ml when plasma calcium fell from 9 to 7 mg/dl. During infusion of EDTA to mother or fetus there were no changes in plasma calcium or PT levels in the respective fetus or mother.

Animals↗
PubMed1982

Nutritional status of dairy cows indicated by analysis of blood.

A study of 395 cows in 21 herds tested the suitability of applying the normal distribution to 23 blood variables in setting reference ranges and the potential of multiple regression equations for predicting energy and nutrient intakes, milk and fat production, and reproductive variables from blood measurements. After adjustment for herd and lactational group within herd, deviations from the normal distribution were significant for nine blood variables: glucose, cholesterol, glycerol, triglyceride, acetoacetate, urea, uric acid, creatinine, and chloride. Multiple regressions were calculated for group-averages of ration variables on group-medians of blood variables, and for production and reproductive variables on blood variables in individual cows. Coefficients of determination were .06 to .14 for milk production and reproductive variables and .55 to .79 for ration variables. Best serum predictors of ration variables were glutamic-oxaloacetic and glutamicpyruvic transaminases and cholesterol, phosphorus, triglyceride, and globulin. These results suggest that the normal distribution should not be assumed for blood variables: instead it should be tested. Multiple regressions on blood variables may be useful in predicting energy and nutrient intakes, and regression analysis may help in selection of blood measurements for inclusion in profiles.

Animal Nutritional Physiological Phenomena↗
PubMed1982

Major metabolic determinants of milk volume, mammary efficiency, and spontaneous ketosis in dairy cows.

Mammary uptakes of glucose and long-chain fatty acids are proposed to be the major metabolic determinants of milk volume production and mammary efficiency, respectively. Moreover, the ratio of glucogenic to lipogenic nutrients in the diet is proposed to be the major determinant of spontaneous ketosis. Experimental evidence and clinical observations are adduced in support of these three interrelated propositions. Their heuristic value would be demonstrable in tests of formulations of high-fat rations and administrations of articles, such as growth hormone preparations, intended to promote maximal production and efficiency with least risk of ketosis.

Acidosis↗
PubMed1981

Vitamin A nutrition of the equine: growth, serum biochemistry and hematology.

Four diets were fed to pony fillies for 40 weeks. One group received a basal diet low in carotene, designated mildly deficient. Other groups were fed basal diet plus vitamin A propionate equivalent to 12 (control), 1,200 (mildly intoxicated) or 12,000 (severely intoxicated) microgram retinol/kg body weight/day. The mildly deficient group exhibited impairment of growth and hematopoiesis with decreased serum concentrations of iron, albumin and cholesterol prior to depletion of liver vitamin A. Growth was depressed in mildly intoxicated and severely intoxicated fillies. The latter became debilitated and died in less than 40 weeks with reduced serum concentrations of iron, albumin and cholesterol. Significant associations were calculated between dietary vitamin A and vitamin A concentrations in plasma, liver and kidney, and between plasma vitamin A and liver and kidney vitamin A. Plasma retinyl ester increased logarithmically with plasma total vitamin A and linearly with kidney vitamin A. The data suggest that increases in retinyl ester due to excessive dietary vitamin A occur prior to appearance of clinical signs and perhaps reflect kidney vitamin A levels. Calculated estimates of optimal vitamin A intake fo maximal growth averaged 1.4 times the current National Research Council recommendation, for liver secreted serum constituents 5.4 times and for red blood cell criteria 10 times. Thus the recommended intake of 12 microgram/kg for weanling horses appears less than optimal. The data suggest hematologic criteria and serum biochemistries may be more sensitive indicators of vitamin A nutriture than growth.

Animals↗
PubMed1980

Veterinary services to the Pennsylvania sheep industry.

Questionnaires on ovine management and disease were distributed to sheep producers and large animal veterinarians in Pennsylvania. Returns indicated economic analysis of veterinary services to eastern farm flocks to be of primary importance. Although most producers were reluctant to request veterinary services because of cost, the average expenditure for veterinary services was reasonable ($143 per flock per year). Producers appeared to have little awareness of expected benefits from veterinary services. It was concluded that coordination of veterinary services and producer management should increase production and economic returns. Determination of cost/benefit ratios for individual and flock veterinary care would allow for formulation of sound flock health programs and would demonstrate effectiveness of such programs to producers and veterinarians.

Animal Nutritional Physiological Phenomena↗
PubMed1980

Metabolic effects of feeding protected tallow to dairy cows.

Twelve Holstein cows were matched into pairs after 7 days lactation. Each was fed 1 kg of grain concentrate per 3 kg milk and corn silage free choice. At 2 wk, one cow from each pair was maintained on this diet and the other was fed a protected tallow product mixed with the grain concentrate, 1 to 2, providing 25% of metabolizable energy as fat. For 14 wk, milk fat production was 12.4% higher and efficiency of utilization of metabolizable energy for lactation was 8.0 to 13.6% higher in tallow-fed cows. These had higher concentrations of glucose in plasma and cholesterol in serum and lower concentrations of acetoacetate and betahydroxybutyrate in plasma. At 16 wk, cows were fed in two groups, the concentrate to milk ratio was 1:4 and silage intake 41 kg/day. Digestible protein was reduced from 118 g/kg dry matter to only 80 g/kg. Milk production declined rapidly, so that duration of lactation averaged only 163 days in both groups. Protected tallow conferred metabolic advantages during the first 16 wk of lactation. Its influence on the duration of lactation requires further study in cows fed adequate protein.

Animals↗