Biomedical subjects

D Sklan

Publications and source records attributed to D Sklan.

At least 19 recordsLinked to original sources

PubMed1998

Antioxidant capacity is correlated with steroidogenic status of the corpus luteum during the bovine estrous cycle.

The reactions of steroid hormone biosynthesis are accompanied by formation of oxygen radicals. We determined the levels of some antioxidants and antioxidative enzymes at different developmental stages of bovine corpora lutea to examine their correlation with steroidogenic status. Plasma progesterone concentrations of estrous cycle synchronized cows increased until day 16, and then decreased rapidly during luteal regression. The levels of steroidogenic cytochrome P450scc and adrenodoxin paralleled the changes in plasma progesterone. Among the antioxidative enzymes examined, the SOD and catalase activities showed patterns most similar to plasma progesterone. Catalase and SOD activities increased 6-8 fold from day 6 to 16 of the estrous cycle and then decreased during the luteal regression. Ascorbate and beta-carotene showed low but significant correlation with P450scc and plasma progesterone levels. The profiles of two lipophilic antioxidants in corpora lutea were very different. beta-carotene concentration increased by approximately 6 fold from day 6 to 16, and decreased in regressive tissue. alpha-tocopherol showed a 3 fold increase between days 6 and 9 followed by a rapid decrease. Thus, at the peak of steroidogenesis at mid-luteal phase alpha-tocopherol levels decreased, but beta-carotene levels increased. The correlation between the levels of some antioxidant enzymes and compounds with progesterone levels indicates that antioxidative mechanisms are activated to cope with steroidogenesis dependent oxyradical formation in the bovine corpus luteum.

Adrenodoxin↗

PubMed1998

Cell proliferation in chicken intestinal epithelium occurs both in the crypt and along the villus.

The location of cell proliferation and differentiation in chicken small intestinal epithelium was examined using immunostaining, measurement of DNA synthesis and brush-border enzyme activities. Chicken enterocytes were removed sequentially from the villus using a modification of the Weiser (1973) method. Alkaline phosphatase activity was relatively constant along the villus tip-crypt axis but decreased in the crypt fractions, whereas sucrase and maltase activities showed higher activity in the upper half of the villus and lower activity in the lower half of the villus and in the crypt. Immunostaining of proliferating cell nuclear antigen indicated the presence of proliferating cells both in the crypt and along the villus, including some activity in the upper portion; the crypt region exhibited a significantly higher number of proliferating cells. Labelled thymidine incorporation into cell fractions after 2 h incubation exhibited a similar pattern of proliferation, with the most active region observed in the crypt and proliferation activity decreasing along the villus. However, some activity was found in the upper half of the villus. After 17 h incubation, cells from the middle region of the villi showed greater proliferation ability than the 2 h incubation. These results indicate that, unlike mammals, chicken enterocyte proliferation is not localized only in the crypt region, and that the site of enterocyte differentiation is not precisely localized.

Animals↗

PubMed1998

Yolk utilisation in the newly hatched poult.

1. Routes of yolk utilisation and some aspects of intestinal digestion and absorption were determined in the hatching poult and compared to the chick. 2. Transfer from yolk to blood was observed pre-hatch and up to 72 h post-hatch. From hatch the transport pattern was similar to the chick. 3. Transport from the yolk sac into the intestine via the yolk stalk was observed up to 120 h after hatch. Secretion was initially to the proximal ileum and reflux occurred, transporting contents to the proximal small intestine and gizzard. Antiperistaltic movements increased after hatch and secretion continued for longer post-hatch than in the chick. 4. In situ uptake of glucose per unit of duodenum did not change with age, whereas uptake of methionine and oleic acid decreased with age. In contrast, in the chick glucose and methionine uptake capacity increased slightly between hatch and 7 d. 5. The lipid class distribution of intestinal contents resembled that of yolk close to hatch, however, some lipolysis was observed in the duodenum. With age the proportion of free fatty acids increased rapidly, first in the duodenum then in the ileum and finally in the caecum. Yolk in the distal small intestine close to hatch did not appear to be utilised.

Aging↗

PubMed1998

Posthatch development of mucosal function in the broiler small intestine.

Changes in small intestinal morphology, in the indices of cellular development, and in the activities of some mucosal enzymes were examined in broilers from hatch through 14 d. In addition the effects of holding birds without access to feed for 36 h and of deutectomy were examined. Development of the intestine was rapid from 2 d after hatch although rates of development were different in duodenum, jejunum, and ileum. Villus volume in the duodenum reached a plateau after 7 d although it continued to increase in the jejunum and ileum. Enterocyte density changed little with age. Indices of tissue activity, ribosomal capacity, and cell size decreased with age but at differing rates at the three intestinal sites. Sucrase-maltase activity was low in the duodenum and highest in jejunum and ileum and increased in the jejunum to a maximum 2 d after hatch, then decreased. Delayed access to feed after hatch depressed mucosal development for several days, with the duodenum generally reaching control values earlier than the jejunum. Morphological changes following delayed access to feed included some clumping of microvilli on Day 1 after hatching and abnormal crypt structure between Days 7 and 9. Deutectomy resulted in initial decreased intestinal growth, but this was compensated for by 6 to 8 d in the duodenum, after which development was parallel to that of normal chicks. It appears that nutrient supply from yolk is less crucial for mucosal development then withholding feed for 36 h, which delays normal intestinal development.

Aging↗

PubMed1998

The effect of dietary protein level on the lysine and arginine requirements of growing chickens.

Comparisons were made of the growth and carcass fat responses to dietary lysine and of the lysine requirements of 1-wk-old broiler chickens receiving diets containing either 18, 20, 23 or 25% protein. Similar comparisons were made of the responses elicited by dietary arginine in diets containing 18 or 23% dietary protein. The responses to lysine supplementation and the lysine requirements of chicks receiving 23 or 25% protein diets were similar. In comparing the 18 or 20% to the 23% protein diet, the initial responses of growth and feed efficiency to dietary lysine were augmented, but the maximal weight gain diminished as dietary protein decreased, leading to a decrease in the lysine requirements. The amounts of extractable carcass fat or abdominal fat pad increased as dietary protein was lowered and, in general, were reduced either by lysine or arginine supplementation. Percentage of pectoral muscle increased slightly with dietary arginine and protein supplementation. The results suggest that when total dietary amino acid level is reduced, the requirements for the individual amino acid decrease due to growth retardation resulting from single or multiple amino acid deficiencies. Single amino acid supplementation of low protein diet is more effective in improving the amino acid balance than supplementation of high protein diets, resulting in a further decrease in the requirements.

Animal Nutritional Physiological Phenomena↗

PubMed1998

Humoral immune response impairment following excess vitamin E nutrition in the chick and turkey.

The effect of high dietary intakes of vitamin E on antibody production was investigated in chicks and turkeys. Chicks were fed four diets with 0, 10, 30, and 150 mg/kg added vitamin E and turkeys were fed three diets with 0, 50, and 150 mg/kg added vitamin E. Antibodies produced in response to naturally occurring Escherichia coli and to Newcastle disease virus and turkey pox vaccines were determined. In chicks, antibody production in response to E. coli and Newcastle disease was affected by vitamin E nutrition: significantly higher responses were measured in chicks that received 0 and 10 mg/kg added vitamin E, whereas in chicks receiving 30 and 150 mg/kg, antibody production was significantly lower. In turkeys, concentrations of circulating antibodies to Newcastle disease virus and to turkey pox were also influenced by dietary vitamin E: antibody titers to Newcastle disease and turkey pox vaccines were highest in groups receiving 0 mg/kg added vitamin E, whereas titer in groups receiving 150 mg/kg were significantly lower. Responses of groups receiving 50 mg/kg added vitamin E were slightly lower than groups receiving 0 mg/kg, though not significantly so in most cases. These results indicate that humoral immune responses are directly effected by vitamin E, and that excessive vitamin E intake has a detrimental effect on antibody production in chickens and turkeys.

Animal Nutritional Physiological Phenomena↗

PubMed1998

Dietary polyunsaturated fatty acids decrease anti-dsDNA and anti-cardiolipin antibodies production in idiotype induced mouse model of systemic lupus erythematosus.

OBJECTIVE: To examine the effect of diets with different polyunsaturated fatty acid contents, including linseed oil which contains 70% omega-3 fatty acids, on autoantibody production in idiotype induced mouse model of systemic lupus erythematosus (SLE). METHODS: Five different fats were fed to mice with induced SLE and antibody titers to anti-DNA and anti-cardiolipin were determined and histological examination of kidneys were carried out. RESULTS: SLE mice fed linseed oil showed lower titers of antibodies to DNA and to cardiolipin and less severe kidney damage than mice fed other diets, including fish oil. CONCLUSION: Use of linseed oil may attenuate the severity of SLE and this diet may be recommended for other auto-immune diseases as well.

Animals↗

PubMed1998

Calculation of fecal kinetics in horses fed hay or hay and concentrate.

Marker methods are needed for estimating fecal output by grazing animals in studies of nutrition and environmental impact. In addition, estimates of prefecal mass and turnover time are relevant to exercise performance and certain digestive disorders. As a first step in developing marker methods for field use, a chromic oxide model of fecal kinetics was developed and tested in the context of a digestion balance experiment with stall-fed horses. The model consists of removal of feces at a constant rate from a single compartment, the prefecal mass. Four horses were fed hay, and another four were fed hay and concentrate. Balance-marker experiments were conducted for 10 d, following 7 d of adaptation. A dose of chromic oxide mixed in chopped hay and molasses was administered from a nose bag at 0700 daily for 10 d. Dry matter and Cr were measured in feeds and feces. Fecal Cr concentration (C, mg/kg DM) varied during the day, so data from total daily collections were used for model development. These fecal Cr data (Ct) at time t (days) were fitted to a single exponential, with one rate constant (k), rising to an asymptote (Ca): Ct = Ca - Ca x e(-kt). Superior fits were obtained when a delay (d) was introduced between the pulse oral dose and the entry of marker into the prefecal pool: Ct = Ca - Ca x e(-k(t-d)). Using pooled data, delays of 2.7 and 2.0 h gave best fits (highest estimates of R2) for pooled data from horses fed hay or hay plus concentrate, respectively. The model generated estimates of 3.4 and 3.8 kg/d of DM for fecal outputs (dose/Ca) of horses fed hay or hay and concentrate, respectively. The rate constants yielded turnover times (1/k) of 33 and 18 h, and prefecal masses [(dose/Ca)/k] of 4.6 and 2.9 kg of DM for hay or hay and concentrate groups, respectively. Using data from individual horses, mean estimates for each diet were similar to corresponding values for the pooled data. In balance experiments, feces collected were 3.7 and 4.4 kg/d, and Cr recoveries were 108 and 115% dose for the hay and hay plus concentrate diets, respectively. Marker estimates (M) were correlated with total collection estimates (T) of fecal output [M = T(.890 +/- .045); r = .70, P = .041]. Adjusting for recovery improved the regression coefficient to 1.009 +/- .028 (r = .87, P = .002). The findings suggest that if Cr doses are more frequent than daily and if Cr inputs other than dose can be eliminated this method should give accurate and precise estimates of fecal output.

Animal Feed↗

PubMed1997

Effect of vitamin A on the oxidative stability of broiler meat during storage: lack of interactions with vitamin E.

1. An experiment was carried out with male broiler chicks to evaluate the combined effect of two concentrations of vitamin A (1.032 and 10.32 mg retinyl acetate/kg diet) and two concentrations of vitamin E (0 and 150 mg alpha-tocopheryl acetate/kg diet) on the oxidative stability of the drumstick meat of broiler chickens. The experimental diets were fed from 1 to 42 d of age. The oxidative stability, evaluated by thiobarbituric acid reactive substances (TBARS) values, was determined after 125 d of storage at -18 degrees C. 2. TBARS values were very low and not significantly affected by dietary vitamins A and E or their combinations. However, the TBARS values in the meat of birds fed on the vitamin E-free diets, but not on the vitamin E-supplemented diets, were markedly increased after using an accelerated test of oxidation of the meat lipids by incubation. This resulted in a significant (P<0.001) difference from vitamin E supplementation. Vitamin A, alone or in combination with vitamin E, did not affect TBARS values found after incubation. 3. It is concluded that vitamin A at the concentrations used had no effect on the oxidative stability of the meat, in contrast to the protective effect of vitamin E, and that there is no interaction between the effect of these two vitamins on meat stability.

Animal Feed↗

PubMed1997

Effect of dietary fatty acids on humoral immune response of turkeys.

1. This study examined the effect of increasing amounts of dietary polyunsaturated fatty acids on the fatty acid composition in serum and antibody production following a standard vaccination programme in growing turkeys. Turkey poults were fed on 5 diets containing 75g/kg added fat made up of different proportions of palm and soyabean oils, and were vaccinated against Newcastle disease, infectious bronchitis and necrotic enteritis according to a standard vaccination programme. Blood samples were taken before and one week after each vaccination. 2. Fatty acid composition in serum reflected the composition of the diets although arachidonic acid concentration was not changed by dietary fatty acid content. Growth, erythrocyte and leukocyte parameters were not affected by the respective diets. 3. Specific antibody production was related quadratically to serum linoleic and total n-6 polyunsaturated fatty acid concentrations. No correlation was found with linolenic or arachidonic acids. 4. It is concluded that dietary fatty acid composition can augment the specific anti-vaccine immune response in turkey poults.

Animal Feed↗

PubMed1997

The response of broiler chickens and turkey poults to dietary energy supplied either by fat or carbohydrates.

The efficacy of fat and carbohydrates as energy sources was compared in 1- to 4- and 4- to 7-wk-old broiler chickens and in 16- to 19-wk-old turkeys. An increase in dietary energy by carbohydrate was made by a graded replacement of wheat bran by wheat. Energy was increased by fat through a graded replacement of soybean hulls with refined soybean oil. In the experiments with broiler chickens, the feed efficiency responses to added energy were observed within the entire range of dietary energy tested, with no significant differences between the responses to carbohydrate and fat as energy supplements. The growth response to energy from either source appeared to be characterized by diminishing returns in the chicken. In the 16- to 19-wk-old turkeys, the growth and feed efficiency responses were linear within the range from 2,650 to 3,250 kcal/kg. In chickens and in turkeys, the growth and feed efficiency responses to energy supplied by fat were indistinguishable from those of carbohydrates. In chickens, the fractions of abdominal fat and pectoral muscle were not affected significantly by the energy density and source.

Adipose Tissue↗

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↗