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Biomedical subjects

D Sklan

Publications and source records attributed to D Sklan.

At least 145 records · Page 8Linked to original sources
PubMed1982

Vitamin E response to high dietary vitamin A in the chick.

Chicks were fed diets containing three levels of tocopherol, and control or high levels of retinyl palmitate for at least 24 days. Glutathione peroxidase activity in erythrocytes, plasma and liver was enhanced in tocopherol-depleted chicks, and in chicks fed high dietary vitamin A. Hepatic malonaldehyde production increased in high vitamin A chicks. Superoxide dismutase activity was increased in erythrocytes and livers of chicks on low tocopherol diets and depressed by high dietary vitamin A. The effects of high dietary vitamin A were at least partially attenuated by addition of tocopherol to the diet. Chicks fed high vitamin A, low vitamin E diets demonstrated a sixfold increase in clearance of labeled tocopherol from plasma. Additional dietary tocopherol partially prevented the rapid clearance of tocopherol due to vitamin A. Absorption studies with a nonabsorbed reference substance (141Ce) revealed that a greater fraction of dietary tocopherol was oxidized prior to the digesta reaching the duodenum when high vitamin A levels were present in the diet although no differences in percentage tocopherol absorption were observed. Secretion into the intestine of glucuronides of tocopherol was enhanced almost twofold by feeding high vitamin A. It is concluded that the interactions between tocopherol and vitamin A include: enhanced oxidation of dietary tocopherol prior to the intestine, increased tocopherol turnover, due, in part, to increased conjugation to glucuronides, and selective changes in enzymes involved in protection of cells against oxidative damage.

Animals↗
PubMed1982

Tocopherol absorption and metabolism in the chick and turkey.

Chickens and turkeys were fed from hatching basal diets to which tocopherol was added at levels of 10, 50 and 250 mg/kg for 28 days. During the last 4 days [3H]tocopherol and 141Ce were included in the diets. Plasma and liver tocopherol levels were correlated with dietary tocopherol in both chickens and turkeys, but concentrations were 1.5- to 4.5-fold lower in turkeys. Disappearance (absorption + catabolism) of tocopherol between feed and lower ileum was 78-90% of the ingested vitamin, and, no significant differences were found with dietary intake or between chickens and turkeys. Of the 3H-labeled material found in the duodenum, 24-40% was not extractable by organic solvents and comprised mainly tocopheryl glucuronides. The duodenal secretion of glucuronides increased with dietary tocopherol intake, and less than 30% of the secreted glucuronides were reabsorbed by the small intestine. The duodenal organic solvent-extractable 3H-contained 30-40% material that appeared to be tocopheryl quinone. This proportion increased with distance from the pylorus. Turkeys excreted 2.5- to 7-fold more glucuronides than chickens. This explains in part the lower plasma and tissue concentrations of tocopherol observed in turkeys.

Animals↗
PubMed1981

Changes in the chemical composition of oospores of Pythium aphanidermatum during bimodal germination.

The developmental mode by which oospores of Pythium aphanidermatum germinate may be controlled by the concentration of glucose present in the germination medium. When incubated in a liquid medium containing emulsified lecithin without added glucose (S + L), oospores germinated indirectly, with zoospore release occurring during the 10th to 13th h. A decrease in dry weight of the fungus took place by the 13th h of indirect germination. When 0.2 mM glucose was added to S + L, the dry weight of germlings increased and direct germination occurred without zoospore formation. Polar lipid comprised the bulk of total acylglycerides of dormant oospores. A greater decrease in total fatty acid content took place during direct germination than during indirect germination. During both developmental modes of germination, polar lipid content decreased considerably; neutral lipids, however, increased during indirect germination and decreased during direct germination. Protein content of the fungus increased in both developmental modes of germination, being initially 9.7% of the dry weight of dormant oospores. After 13 h of incubation, KOH-soluble polysaccharide decreased by 35% during direct germination and by 48% during indirect germination.

Fatty Acids↗
PubMed1981

Retinol esterification in lamb kidney.

Retinol esterification was demonstrated in vivo and in vitro in lamb kidney. Retinol labeled with hydrogen-3 injected into the renal artery of lambs appeared in the labeled retinyl ester fraction in the renal vein. Degree of tracer incorporation into retinyl esters increased with vitamin A intake. In homogenates, activity was concentrated in microsomes and enhanced fourfold by addition of adenosine 5'-triphosphate and coenzyme A to the incubation mixture. These findings suggest that the esterification is a function of fatty acyl coenzyme A:retinol acyl transferase. Renal esterification may play a role in retinol homeostasis.

Animals↗
PubMed1980

Glucose absorption and starch digestion in the intestine of the chicken.

Starch digestion and glucose absorption were determined in vivo along the chick's (Gallus domesticus) intestine, using 91Y and 51Cr-EDTA as unabsorbed reference substances. About 65% of the ingested starch was digested up to the end of the duodenum, 85% up to the end of the jejunum and about 97% at the terminal ileum. A fraction of about 97% of the glucose, ingested or released from ingested starch, was absorbed. The duodenum was the major site of glucose absorption which continued at a decreased rate down the small intestine. Glucose absorption increased linearily with luminal concentration with no indication of saturation. The apparent permeability for glucose was similar for the jejunum and ileum.

Animals↗
PubMed1980

Protein digestion and absorption in young chicks and turkeys.

The site of digestion and absorption of protein was examined in chicks fed soybean meal and casein and in turkeys fed soybean meal, using 91YCl3 as a non-absorbed reference substance. In soy-fed chicks, peptides with molecular weight (MW) between 8,000 to 15,000 accumulated in the proximal small intestine, and low MW peptides accumulated distally. A similar pattern was observed in soy-fed turkeys, although with events occurring proximally to those in the chick. In casein-fed chicks, a gradual reduction in the peptide MW was observed with increasing distance from the pylorus. The rates of formation and absorption of peptides with MW below 500 were similar throughout the small intestine in soy-fed chicks; whereas, the rate of their formation exceeded absorption rate in casein-fed chicks. Net secretion of nitrogen into the duodenum was observed in soybean-fed chicks, no net secretion in casein-fed chicks and 50% absorption in soybean-fed turkeys with net secretion in the gizzard. From the sequence of digestive and absorptive events, apparently solubilization and breakdown of intermediate peptides are rate-limiting in protein absorption from soybean meal diets. But when casein is fed, the rate of uptake of low MW peptides appears to be limiting.

Animals↗
PubMed1980

Intestinal uptake of fatty acids complexed to proteins in the chick intestine.

Intestinal mucosal uptake of protein complexed-fatty acids was studied in ligated duodenal loops in the chick. Increasing the concentration of an albumin oleic acid-complex resulted in a linear increase in uptake of oleic acid. Varying the albumin-to-oleic-acid ratio with constant albumin concentration resulted in depressed oleic acid uptake when the ratio was below 1:3. Uptake of oleic acid complexed to albumin was increased by some 60% on addition of taurocholic acid above its critical micellar concentration. In the absence of albumin, oleic acid uptake was some 60% high from a micellar solution. Uptake of lauric acid from aqueous solution was linear with concentration until its maximum solubility was reached, whereas uptake from albumin complexes at varying lauric acid concentrations was not linear with increasing concentration. Stearic acid exhibited lowest uptake and linoleic and linolenic acid highest uptake both when complexed to albumin or from micellar solution, although albumin-complexed fatty acids were transported at about half the rate of micellar fatty acids. We concluded that some proportion of fatty acids complexed to lipophilic proteins can be absorbed in the intestine in the absence of bile acids. When oleic acid was complexed to casein, bovine serum albumin or beta-lactoglobulin at protein:oleic acid ratio of 1:10 serosal transport was 40 to 50% of mucosal uptake.

Animals↗
PubMed1980

Digestion and absorption of casein at different dietary levels in the chick: effect on fatty acid and bile acid absorption.

The site of digestion and absorption of protein was determined in chicks fed diets containing 10, 30 and 45% casein as the protein source, 3% added oil with 91Y Cl3 added as a non-absorbed reference substance. Digestion of protein to low molecular weight (MW) peptides and amino acids was rapid in all diets with major absorption occurring between duodenum and lower jejunum. Increasing the dietary casein resulted in increases in low MW peptide levels in the duodenum. This increase was disproportionate with intake when 45% casein was fed, suggesting that absorptive capacity of the duodenum was exceeded. Overall nitrogen absorption was similar in all treatments reflecting the increased participation of the ileum in nitrogen absorption when high dietary casein levels were fed. Fatty acid and bile acid absorption was depressed when 45% casein was fed, mainly due to inhibition of absorption in the ileum, presumably by binding to undigested protein.

Animals↗
PubMed1980

Colchicine inhibition of retinol-binding protein secretion by rat liver.

Studies were conducted to explore the effects of colchicine on the secretion and metabolism of retinol-binding protein (RBP) by the liver. In the vitamin A-deficient rat, the rate of secretion of RBP from the liver into the serum is greatly reduced, and RBP accumulates in the liver. Injection of retinol (dispersed in a 20% Tween 40 solution) into deficient rats stimulated a rapid secretion of RBP from the liver into the serum. Colchicine treatment markedly inhibited the retinol-stimulated secretion of RBP from the liver into the serum. The effect of colchicine was most pronounced during the early period after retinol injection, particularly during the first 30 to 60 minutes. Ninety minutes after retinol injection, the serum RBP level of colchicine treated rats was only 36% as great as that of the control rats. In parallel experiments, a quantitatively similar inhibition of very low density lipoprotein (VLDL) secretion by colchicine was observed in the retinol-deficient rats. In contrast, colchicine did not affect the overall rate of hepatic protein synthesis, as estimated from the incorporation of [(3)H]leucine into total liver and serum protein; the secretion of newly synthesized protein was, however, inhibited. When rats were treated with colchicine and then injected with retinol, the level of RBP in a Golgi-rich fraction obtained from the liver homogenate increased markedly as compared to the level of prealbumin. The inhibition of RBP secretion by colchicine suggests that the microtubules play a role in RBP secretion. By analogy to studies on VLDL and albumin, these data provide presumptive evidence that the Golgi apparatus and secretory vesicles are involved in RBP secretion.-Smith, J. E., D. D. Deen, Jr., D. Sklan, and D. S. Goodman. Colchicine inhibition of retinol-binding protein secretion by rat liver.

Animals↗
PubMed1979

Cholesterol metabolism in the liver and intestine of the chick: effect of dietary cholesterol, taurocholic acid and cholestyramine.

The effect of feeding cholesterol, taurocholic acid, or cholestyramine to chicks on cholesterogenesis from [1-14C] acetate in liver and intestine was determined in vitro using tissue slices, and in vivo by i.v. injection of [14C] acetate. The conversion of cholesterol to bile acids in liver in vivo was measured in the same treatments after i.v. injection of [3H] cholesterol. Hepatic cholesterogenesis in vitro and in vivo was depressed by dietary cholesterol and taurocholate and enhanced by cholestyramine. Intestinal cholesterogenesis in vivo was depressed only by taurocholate whereas ileal cholesterogenesis in vitro was reduced by dietary cholesterol. Conversion of cholesterol to bile acids was enhanced by dietary cholesterol and cholestyramine and depressed by taurocholate. Hepatic cholesterol metabolism in the chick appears to be regulated by mechanisms similar to those reported for other species.

Acetates↗
PubMed1979

Digestion and absorption of lipids in chicks fed triglycerides or free fatty acids: synthesis of monoglycerides in the intestine.

Digestion and absorption of lipids were determined in 3-week-old chicks fed diets containing triglycerides, free fatty acids, or free fatty acids with added glycerol. The 91YCl3 was present as a non-absorbed reference substance. Overall absorption of total fatty acids was highest in triglyceride-fed chicks and lowest in chicks receiving fatty acids. Net secretion of endogenous fatty acids from biliary phospholipids was observed in the duodenum of triglyceride fed chicks, whereas in the other treatments net absorption was observed at this site. Fractionation of the intestinal lipids by thin layer chromatography showed that triglycerides were almost completely hydrolyzed in the duodenum. Monoglycerides were present at high levels in the duodenum of triglyceride fed chicks and at lower levels in chicks receiving free fatty acids and glycerol and at trace levels in free fatty acid-fed chicks. Total micellar fatty acids were lowest in the duodenum of free fatty acid-fed chicks. In vitro incubation of pancreatic homogenate with oleic acid, glycerol, phosphatidyl choline, and taurocholate revealed synthesis of monoglycerides. The poorer fat absorption observed on feeding acidulated soapstock instead of triglycerides is partially explained by less efficient micellarization when free fatty acids are fed.

Animals↗
PubMed1978

Hydrolysis of biliary phospholipids in the upper small intestine of the chick.

Chick endogenous phospholipids were doubly labeled by an intravenous injection of [32P] phosphate and [1-14C] oleic acid, and the free fatty acid and phospholipid fraction of gall bladder bile and in contents of upper small intestine were analyzed 4 days later. There was evidence of hydrolysis of biliary phosphatidylcholine to lysophosphatidylcholine in the duodenum and jejunum, but this did not account for the pronounced increase in the 14C radioactivity of the free fatty acids relative to the 32P phospholipid radioactivity between bile and upper intestinal segments. It is suggested that phosphatidylcholine is largely absorbed in the duodenum of the chick while the remainder is progressively hydrolyzed and absorbed.

Animals↗
PubMed1978

Retrograde movement of digesta in the duodenum of the chick: extent, frequency, and nutritional implications.

Movement of digesta from the duodenum to the gizzard of chicks was assessed by injection of 99mTc-diethyl-triamino-pentaacetic acid via an indwelling cannula in the hepatic bile duct. The change in location of isotope with time was followed with a Gamma Camera. About 40% of the injected isotope refluxed to the gizzard within 2 minutes of injection. Clearance of the isotope from the gizzard had a T1/2 of some 20 minutes. Some possible implications of retrograde movement of digesta were examined. Cholesterol, bile salts and pancreatic enzymes were found in the gizzard at 10% to 20% of duodenal concentrations. The proteolysis and lipolysis in the gizzard and duodenum were determined in chicks fed a duet containing 91Y as a non-absorbed reference substance. Thirty percent of the feed triglycerides were found hydrolysed in the gizzard as compared to 50% to 60% in the duodenum. Proteins were 30% to 50% trichloroacetic acid soluble in the gizzard reaching almost 70% in the duodenum. A small net secretion of both fatty acids and protein was observed in the gizzard, probably due to reflux of endogenous secretions from the duodenum. The nutritional significance of these results is discussed.

Animal Nutritional Physiological Phenomena↗
PubMed1978

Prostaglandin F2alpha human blood during labor.

Plasma prostaglandin F2alpha (PGF2alpha) concentrations were determined by radioimmunoassay in serial samples during labor and the early postpartum period. PGF2alpha was also measured during and between contractions every 20 to 30 seconds. The highest levels of PGF2alpha were found during expulsion of the fetus and placenta with an additional rise half an hour after delivery and a decrease 2 hours after delivery to the levels of first stage of labor. PGF2alpha values from cord blood were higher than in maternal peripheral blood in labor. The maximum PGF2alpha concentration occurred between 100 to 120 seconds after the peak uterine contraction and between 40 and 60 seconds prior to peak of the next contraction. The possible explanation is that PGF2alpha initiates uterine contractions and plays a role in the maintenance of labor, in the expulsion of the fetus and the placenta, and in the involution after delivery.

Female↗