Biomedical subjects

D Sklan

Publications and source records attributed to D Sklan.

At least 73 records · Page 4Linked to original sources

PubMed1997

The response of broiler chickens and turkey poults to steam-pelleted diets supplemented with fat or carbohydrates.

The responses of growth and feed efficiency to pelleted feed was investigated in 4- to 7-wk-old broiler chickens, and in 8- to 12- and 16- to 20-wk-old turkeys. In all cases, the growth and feed efficiency responses were linear within the ranges of dietary energy tested. When energy was added by carbohydrate supplementation, weight gain and feed efficiency responses were parallel for both mash and pellets, but due to the growth response to pellets, the elevation was higher for pellets than for mash. When energy was added by fat, the growth response to pellets also resulted in an increase in function elevation but the slope of the response was lower than in mash feeding, possibly due to a decline in pellet quality as dietary fat increased. Grinding of pellets completely abolished the growth and feed efficiency responses observed when the physical form was preserved. In chickens, comparisons of ground pellets to mash suggested some decline in nutritional quality due to the process of pelleting when either carbohydrates or fat were increased in the diets. In both chickens and turkeys, the feeding of pelleted diets resulted in an increase in abdominal fat.

Animal Feed↗

PubMed1997

Vitamin A repletion in thoroughbred mares with retinyl palmitate or beta-carotene.

Forty-five Thoroughbred mares used in an 8-mo depletion study were kept for an additional 20 mo on the same three forage diets (15 mares each): 2-yr-old orchardgrass hay and vitamin A-free concentrate on a drylot (HC); pasture, orchardgrass/alfalfa hay, and vitamin A-free concentrate (PHC); or pasture and orchardgrass/alfalfa hay only (PH). Each diet group was divided into three subgroups, and mares (n = 5) in each group were given either retinyl palmitate (A) at twice the NRC (1989) recommended daily intake, the equivalent amount of vitamin A in the form of water-dispersible beta-carotene (B), or the vehicle (C). Vitamin A status was monitored with serum retinol and a relative dose response (RDR) test every 60 d. In the C subgroups, retinol concentration was 18.65 +/- .84 micrograms/dL (mean +/- SE) and the RDR was 16.26 +/- 1.72% over the 20 mo. Retinol and RDR fluctuated seasonally regardless of supplementation. Vitamin A status, based on serum retinol (P = .001) and RDR (P < .001) values, was lower in the HC than in the PH and PHC. Vitamin A status, based on retinol (P = .05) and RDR (P = .013) values, was improved by retinyl palmitate supplementation in all diet groups, but not by water-dispersible beta-carotene supplementation. Supplementation of the HC mares with vitamin A matched the serum retinol, but not the RDR, of the two pasture, control subgroups. Thus, replete vitamin A status in previously depleted mares was barely obtained by supplementation with twice the currently recommended daily intake of vitamin A.

Animals↗

PubMed1997

Effect of calcium soaps of fatty acids and administration of somatotropin in early lactation on productive and reproductive performance of high producing dairy cows.

This study examined the mechanisms by which calcium soaps of fatty acids and bovine somatotropin (bST) affect production and reproduction of high producing cows. Calcium soaps of fatty acids were fed at 2.2% dry matter, and 500 mg of Zn-sometribove (Monsanto Inc., St Louis, MO) were injected subcutaneously every 14 d from 10 to 150 d in milk (DIM). Production of fat-corrected milk was increased by 3.5 kg/d when calcium soaps of fatty acids were fed, by 6.1 kg/d when bST was administered, and by 7.4 kg/d when calcium soaps of fatty acids were fed and bST was administered. Body weight was similar for cows on all treatments until 85 DIM after which cows that were treated with bST had lower body weights. Body condition scores decreased more for cows treated with bST and began increasing later and more slowly. Treatment with bST resulted in more cows that experienced first ovulation after 30 DIM, and more cows on the control treatment exhibited first estrus before 35 DIM. Days open were greater when bST was administered. After the first artificial insemination, conception rates were similar for cows on the control treatment and for cows fed calcium soaps of fatty acids; conception rates after the first artificial insemination were low for all cows treated with bST. Pregnancy rates at 120 and 150 DIM were decreased by bST. Number of DIM to first ovulation, number of DIM to first estrus, and days open were negatively correlated with glucose and cholesterol concentrations in plasma. Production of fat-corrected milk was correlated with days open and with concentrations of triglycerides in plasma, nonesterified fatty acids, and cholesterol. Increased production had different effects on reproduction when induced by calcium soaps of fatty acids or bST treatment. Some of the adverse effects of bST treatments were alleviated by calcium soaps of fatty acids.

Animals↗

PubMed1997

The effect of retinol and retinoic acids on lipoxygenase activity.

Lipoxygenase catalyzes the dioxygenation of polyenoic fatty acids such as linoleate and arachidonate. The aim of the present study was to examine the effect of retinol, all-trans-retinoic acid and 13-cis-retinoic acid on the activity of lipoxygenase-1 and lipoxygenase-2 towards linoleic acid. Lipoxygenase activity toward linoleic acid was followed by determining changes in absorption at 234 nm. All retinoids inhibited lipoxygenase-1 and lipoxygenase-2 activity. Lipoxygenase-2 activity towards linoleic acid was rapid at pH 6.5; all-trans-retinol (10 microM) caused a 50% inhibition in reaction rate. All-trans-retinol was oxidized in parallel with diene production by lipoxygenase-2. Lipoxygenase-2 activity on linoleic acid was competitively inhibited by all-trans-retinol and all-trans-retinoic acid; 13-cis-retinoic acid exhibited mixed type inhibition. Activity of lipoxygenase-1 towards linoleic acid at pH 9.0 was also inhibited by retinoic acids by 32-73%. All-trans-retinoic acid and 13-cis-retinoic acid inhibited lipoxygenase-1 activity competitively, whereas all-trans-retinol inhibited lipoxygenase-1 activity in a mixed manner. These findings suggest that retinoids may bind to the active site of the enzyme or simultaneously act as an antioxidant.

Binding Sites↗

PubMed1997

In vitro and in vivo effects of beta-carotene on rat epidermal lipoxygenases.

The in vitro and in vivo interaction between beta-carotene (BC) and lipoxygenase (LOX) was studied in rat skin. Significant in vitro inhibitory effects of BC on epidermal LOX activity were observed with both linoleic acid or arachidonic acid as substrate. Lineweaver-Burk plots for the inhibition of epidermal purified LOX indicated mixed competitive/non-competitive inhibition. In vivo effects of BC were examined in an ultraviolet A (UVA) irradiation model. Following UVA irradiation (200 Kjoule/m2) significant increases in LOX activity and malondialdehyde (MDA) values were found, whereas catalase activity was significantly decreased. Topical pretreatment of skin with BC prevented increases in LOX activity and MDA values 4 hr post-irradiation. Catalase activity was not affected by BC treatment. BC was more effective at preventing UVA induced lipid peroxidation at low then at high concentrations. Our present results indicate the protective potential of BC on in vivo UVA induced skin damage by reduction of non-enzymatic and enzymatic lipid peroxidation.

Animals↗

PubMed1996

Development of the small intestine in heavy and light strain chicks before and after hatching.

1. Intestinal development was examined in Arbor Acres and Lohmann chicks from one week before hatching until one week after. Changes in morphology and concentrations of DNA, RNA and protein in the duodenal tissue were determined. 2. Villus height and perimeter increased 9 to 11 fold from day 14 of incubation until 7 d after hatching. Arbor Acres chicks had values which were consistently higher than Lohmann chicks. 3. DNA concentration of duodenal tissue increased with age in parallel to the increase in the number of enterocytes per villus. In the pre-hatch period tissue activity as indicated by RNA/DNA, and ribosomal capacity as shown by the RNA/protein ratios, were high for both strains; values for Arbor Acres embryos and chicks were greater than for Lohmann. 4. DNA concentrations, RNA/DNA, RNA/protein and protein/DNA ratios correlate with morphological measurements and can be used as additional criteria for evaluating development in chick intestine. 5. In the last week of incubation and immediately after hatching, intestinal growth appears to arise mainly from cellular hyperplasia and not from cellular hypertrophy. Intestinal development patterns were similar for both strains but growth was more rapid in Arbor Acres chicks.

Aging↗

PubMed1996

Routes of yolk utilisation in the newly-hatched chick.

1. This study was conducted to study the routes by which yolk is utilised in the chick during the initial posthatch phase. 2. Transfer from yolk to blood was examined by injecting, in the form of labelled compounds, oleic acid, triolein, inulin and dextran into the yolk; movement from yolk to blood was observed up to 72 h posthatch. 3. Transport of these molecules from blood to yolk was also observed by injecting them into the circulation and determining label in yolk. The yolk sac membrane was permcable in both directions for all labelled materials tested. 4. In the newly-hatched chick, blue dextran injected into the yolk sac could be seen moving in pulses into the intestine at irregular intervals. Transport of labelled materials from the yolk sac into the intestine was observed up to 72 h after hatching, and marker was found in the proximal small intestine and gizzard. The yolk stalk provided a pathway for transport to the intestine until lymphoid cells began to accumulate, with passage becoming partially occluded at 72 h posthatch. 5. Yolk utilisation was more rapid in fed than in fasted birds suggesting that the transport of yolk through the intestine could be increased by the greater intestinal activity found in fed chicks.

Animals↗

PubMed1996

Uptake capacity in vitro for glucose and methionine and in situ for oleic acid in the proximal small intestine of posthatch chicks.

The uptake capacity of the duodenum and jejunum was determined in vitro for glucose and methionine using 14C-inulin as an unabsorbed reference substance in posthatch chicks. Fatty acid uptake in situ was also determined in the duodenum. Methionine uptake capacity increased in both duodenum and jejunum between hatch and 7 d and was constant between 7 and 14 d. Calculation of apparent Michaelis constant (Kt) for both substrates indicated little change with age and thus the amount of carrier in the intestine may be increasing. Uptake capacity of the duodenum for glucose increased between hatch and 7 d of age but no changes were found between 7 and 14 d. In the jejunum, uptake capacity was constant from hatch to 14 d of age. In situ uptake of oleic acid in the duodenum did not change between hatch and 14 d of age. These results suggest that intestinal uptake capacity changes little after 7 d of age, and thus feed intake may be the major factor controlling nutrient uptake in chicks.

Aging↗

PubMed1996

Intestinal uptake and metabolism of fatty acids in the chick.

Uptake and metabolism of fatty acids in the duodenal mucosa of the chick was studied. In vitro incubations of a mucosal homogenate with 14C-oleic acid indicated that together with glycerides, water-soluble 14C compounds and 14CO2 were formed; the latter comprised approximately one quarter of metabolites formed. Studies in chickens introducing 14C-oleic acid into the duodenum and determining appearance of label in the cannulated pancreaticoduodenal vein and brachial artery indicated that similar processes occur in vivo, with both labeled glycerides and water-soluble compounds appearing in the blood. Quantitatively, metabolism of 14C-oleic acid to nonlipid compounds amounted to some 15% of the dose after 60 min. These findings suggest that a considerable portion of ingested fatty acids are metabolized before transport to the circulation.

Animals↗

PubMed1995

Differences in cord serum retinol concentrations by ethnic origin in the Negev (southern Israel).

Subclinical vitamin A deficiency is related to increased morbidity and mortality in infants and children. Previous studies indicate that the traditional diet of Moslem Bedouins, an important ethnic group in Southern Israel, is low in vitamin A content. Cord serum retinol (vitamin A) concentration was measured by HPLC in samples from 251 apparently healthy (birth weight > 2500 g, gestational age > 37 weeks) neonates with no abnormal perinatal events, 138 Jews and 113 Bedouins. Retinol < 15 micrograms/dl was measured in a total of 14% of infants: in 7% of Jewish and 26% of Bedouin newborns (P < 0.001). However, mean cord serum retinol was only slightly lower in Bedouins than in Jews (30 +/- 26 vs. 37 +/- 27 micrograms/dl mean +/- S.D., n.s.). Cord serum retinol was not related to socioeconomic indices. Cord serum retinol < 15 micrograms/dl was measured in 25% and in 12% of infants with birth weight less than and equal or greater than 3000 g, respectively (P = 0.01), and in 28% and 13% of infants with gestational age 37-38 weeks and 39-41 weeks, respectively (P = 0.03). Low cord serum retinol was found to be prevalent in Southern Israel, particularly in Bedouin infants. In the population of healthy neonates studied, very low cord serum retinol concentrations were found more frequently in infants born with a lower weight and/or after a shorter gestation.

Arabs↗

PubMed1995

Lipoxygenase activity in rat dermis and epidermis: partial purification and characterization.

Lipoxygenase (LOX) activity in epidermis and dermis was distributed among microsomal and cytosolic fractions. The main products of polyunsaturated fatty acid metabolism were 12-hydroperoxy-cis-5,8,14, trans-10-eicosatetraenoic acid (12-HPETE), 15-hydroperoxy-cis-5,8,11, trans-13-eicosatetraenoic acid (15-HPETE) and 13-hydroxy-cis-9, trans-11-octadecadienoic acid (13-HOD). Enzyme activities were isolated from rat dermis and epidermis by ammonium sulphate precipitation, hydrophobic chromatography and gel filtration. In the dermis, activity was found at a molecular mass of 68 kDa, a pI of 4.6 and a Km of 50 microM. This activity was inhibited by known LOX inhibitors. The main reaction products indicated that this was 15-LOX. In the epidermis, activity was found in a fraction with a molecular mass of 68 kDa, a pI of 4.6 and a Km of 80 microM. Activity was inhibited by known LOX inhibitors whereas the reaction products indicated that this was 12-LOX. LOX activity in rat skin may involve one enzyme with dual regional specificities or may comprise two different enzymes.

Animals↗

PubMed1995

Electron leakage from the adrenal cortex mitochondrial P450scc and P450c11 systems: NADPH and steroid dependence.

In the present study we examined the coupling of NADPH oxidation to substrate hydroxylation and the effects of steroids on this process in reconstituted P450scc and P450c11 systems. To determine the relative rates of substrate hydroxylation vs electron leakage we assayed both the steroid product and H2O2 in the same sample. For both P450 systems the rates of steroid product and superoxide formation increased as NADPH concentration was increased. However, P450c11 was found to be more leaky. The leakage from the P450scc system was not affected by pregnenolone, the product of cholesterol side chain cleavage. In contrast, corticosterone, the product of P450c11, increased the rate of futile NADPH oxidation by the P450c11 system. We also tested a series of steroids to analyze the stereospecificity of their effects. Relative to the control without steroid, both C-19 and C-21 steroids with 11 alpha-hydroxy groups (11 alpha-OH-testosterone and 11 alpha-OH-cortisol) decreased leakage, and those with 11 beta-OH groups (11 beta-OH-testosterone and cortisol) stimulated both NADPH oxidation and electron leakage as measured by H2O2 formation. The results revealed a correlation between the effects previously observed in living cells and in our reconstituted systems. These findings provide further evidence that mitochondrial P450 systems indeed function as a significant source of oxygen radicals in steroidogenic cells.

Adrenal Cortex↗

PubMed1995

Retinoid metabolism in human leucocytes.

Leucocytes from subjects from 0 to 80 years old were separated into mononuclear and granulocyte fractions and the retinoids and retinoid-binding fractions were examined. Both leucocyte fractions were found to contain retinol, retinoic acid and an additional retinoid; retinoic acid comprised 40% of retinoids in some samples. The protein fractions containing retinoids included a 200 kDa protein and several 14-18 kDa proteins. Plasma concentrations of retinol changed little with increasing age. In contrast, leucocyte concentrations of retinoids and retinoid-binding proteins increased quadratically with age. However, in granulocytes from young children retinoids were almost undetectable.

Adolescent↗

PubMed1995

The effect of varying dietary concentrations of vitamin A on immune response in the turkey.

1. The effect of dietary vitamin A on antibody production and T-cell proliferative response was determined in poults from 21 to 41 d old. Poults were fed on soyabean meal-sorghum-based diets with concentrations of supplemented vitamin A from 0 to 13.2 micrograms/g retinol equivalents from hatching and were immunised with Newcastle disease virus (NDV) and turkey pox vaccines. T-cell proliferation response to concanavlin A was determined in vitro at 31 d old. Antibodies to NDV and turkey pox in serum were determined at 10 and 20 d after inoculation. 2. Poults receiving the diet with no added dietary vitamin A died by 22 d and had very low concentrations of plasma and liver vitamin A. 3. Increasing dietary concentrations of vitamin A enhanced the proliferative response until the diet contained 6.0 micrograms/g, above which the response began to decrease. The antibody titres to NDV and turkey pox increased as dietary vitamin A increased, with maximal values found 10 d after inoculation with 6.0 micrograms/g. At 20 d after inoculation low antibody titres were found with low vitamin A intake. 4. These data suggest that maximal immune responses in the poult may be achieved at dietary intakes of vitamin A at or higher than those recommended by NRC (1984, 1994).

Analysis of Variance↗

PubMed1995

Response of three class-IV major histocompatibility complex haplotypes to Eimeria acervulina in meat-type chickens.

1. The importance of MHC genes and background genes in controlling disease resistance, including resistance to avian coccidiosis, has not been clarified in meat-type chickens. 2. The role of class IV MHC genes in resistance to Eimeria acervulina was assessed in F2 progeny of a cross between 2 meat-type lines, selected divergently for immune response to Escherichia coli. 3. Disease susceptibility was assessed by lesion score, body weight, packed cell volume and carotene absorption. 4. Chickens with the "K" class IV MHC haplotype had lower lesion scores than chickens with "F" and "A" haplotypes. 5. Plasma carotene concentrations were higher in chickens with "K" haplotype and lower in chickens with "F" and "A" haplotypes whereas body weight and packed cell volume were less sensitive measures of Eimeria infection. 6. Eimeria acervulina resistance appears to be associated with MHC class IV genes; information about MHC haplotypes may be useful in selecting for increased resistance of meat-type chickens to coccidiosis.

Animals↗

PubMed1995

Seasonal vitamin A depletion in grazing horses is assessed better by the relative dose response test than by serum retinol concentration.

Vitamin A influences growth and reproduction in horses. A retinol dose response (RDR) test for retinol has been shown to be better than serum retinol concentration for assessing vitamin A status in other species, so we have compared these two methods in the horse. Forty-five Thoroughbred broodmares were assigned randomly to three groups fed pasture and hay (PH), pasture, hay and vitamin A-free concentrate (PHC), or hay and concentrate (HC) in early summer (May 1991). Mares in pasture groups produced 23 foals (March through June) that had access to their dam's diets and were also studied. In the mares, significant vitamin A depletion developed in 2 mo in the nonpasture group (HC) and in 8 mo in the two pasture groups (PH and PHC) according to the RDR test, and in all three groups at 8 mo as shown by a decrease in serum retinol concentration. In the weanlings (PH and PHC only), no differences between groups were found for serum retinol, but the RDR was significantly higher in the PH group, which had suffered a respiratory infection, than in the PHC group. These findings indicated that vitamin A depletion was detected more readily by the RDR test than by serum retinol concentration, that consumption of pasture delayed depletion in the late fall, and that infection was associated with lower vitamin A status.

Analysis of Variance↗

PubMed1995

Digestion and absorption in the young chick.

Digestion, enzyme secretion and intestinal rate of passage were determined in broiler chicks from hatch until 21 d using 141Ce as a nonabsorbed reference substance. Body weight and feed intake increased more rapidly after 10 d posthatch, and, in parallel, time of passage of feed through the intestines decreased by approximately 33%. Net duodenal secretion of amylase, trypsin, and lipase was low at 4 d and increased 100-, 50-, and 20-fold, respectively, by 21 d. Enzyme activity decreased distally in the small intestine. This change was greater with age. The contribution of the ileum to fatty acid absorption decreased after 7 d. Small intestine digestion of nitrogen increased from 78% at 4 d to 92% at 21 d, whereas fatty acid and starch digestion ranged from 82 to 89% in this period. It appears that digestibilities of starch and lipids are not limiting factors in the growth of young chicks.

Age Factors↗

PubMed1995

Effect of dietary fatty acids on antibody production and fatty acid composition of lymphoid organs in broiler chicks.

This study examined the effect of increasing amounts of dietary polyunsaturated fatty acids on antibody production in vivo and fatty acid composition of plasma and lymphoid tissues in the broiler. Chicks were fed four diets containing 12% added fat made up of different proportions of palm oil and soybean oil and immunized against bovine serum albumin at 14 to 16 d of age. Blood samples were taken every 4 to 5 d for 30 d; then the chicks were killed and liver, spleen, thymus, bursa of Fabricius, and bone marrow were sampled. Fatty acid composition in serum and tissues reflected the composition of the diets, although amounts of saturated fatty acids were tissue-specific. Arachidonic acid concentration was not changed by dietary fatty acid content. Antibody production developed more rapidly, reached a higher level, and was more persistent in the chicks fed lower levels of linoleic acid. A quadratic relationship was found between tissue linoleic acid or total polyunsaturated fatty acid concentrations and antibody production at 11 and 14 d after challenge. No correlation was found with arachidonic acid. It is concluded that dietary fatty acid composition can influence immune response in broilers.

Animals↗