Search PubMed⌕ Search

Biomedical subjects

R L Hood

Publications and source records attributed to R L Hood.

At least 37 records · Page 2Linked to original sources
PubMed1980

Sire effect on fatty acid composition of ovine adipose tissue.

The fatty acid composition of perirenal adipose tissue from 255 purebred and crossbred sheep was examined to determine the genetic effects of sire on each of five fatty acids. The sheep, all rams, were the progeny of 30 Dorset Horn sires. The animals were grazed on pasture and slaughtered at an average age of 21 months, when their mean carcass weight was 30 kilograms. The fatty acids studied and their mean percentage compositions were: stearic, 38%; oleic, 31%; palmitic, 20%; palmitoleic, 2%, and linoleic, 2%. These amounted to over 90% by weight of the tissue sample fatty acids. In addition, numerical functions were constructed as ratios for two pairs of fatty acids, ratio 1 (palmitoleic to palmitic) and ratio 2 (oleic to stearic), for estimation of the desaturase enzyme activity in the tissue samples studied. A Softness Index, expressed as a ratio between monounsaturated and saturated acids, was also included in the analysis. Significant birth year and maternal breed effects were found for all the traits studied. This was in contrast to the regression on slaughter age, which with two exceptions was not a significant source of variation in the data. The sire effect, based on 27 degrees of freedom, was highly significant or significant for all traits except stearic or linoleic acid and ratio 2. These results are discussed with reference to utilization of genetic variation between sites in selective breeding programs to modify fatty acid composition of ovine adipose tissue.

Adipose Tissue↗
PubMed1980

A technique to study the relationship between adipose cell size and lipogenesis in a heterogeneous population of adipose cells.

A technique is described for the calculation of the incorporation of radioactive substrate into lipid in adipose cells that have been isolated and separated into groups according to their diameter from a single sample of adipose tissue containing a heterogeneous population of cells. After incorporation of radioactive substrate, a section of adipose tissue is fixed in osmium tetroxide and the fixed cells isolated and separated into specific diameter ranges using a series of nylon screens. The separated cells are weighed, decolorized with hydrogen peroxide, and the radioactivity is determined in the cells from each diameter range. With this method, true comparisons can be made between adipose cell size and lipogenic activity of isolated cells of known diameter which have been subjected to various nutritional or hormonal treatments. Results with sheep adipose tissue show that large adipose cells are considerably more active in the synthesis of lipid than small cells from the same sample of adipose tissue.

Acetates↗
PubMed1979

Effects of saponins on bile acids and plasma lipids in the rat.

1. The effects of feeding isolated saponins on plasma lipid concentrations and on concentrations of biliary and faecal bile acids and neutral sterols were studied in the rat. 2. The animals were given one of four diets, i.e. a standard low-cholesterol synthetic diet, the diet + 10 g saponins/kg, the diet + 10 g cholesterol/kg, the diet + 10 g cholesterol + 10 g saponins/kg. 3. Saponins partially reversed the hypercholesterolaemia caused by the high-cholesterol diet and increased both the rate of bile acid secretion and the faecal excretion of bile acids and neutral sterols. The proportionate contribution of the primary bile acids (particularly chenodeoxycholic) to faecal excretion was also increased by saponins. 4. The results are discussed in relation to the hypothesis that saponins act by inducing the adsorption of bile acids by dietary fibre.

Animals↗
PubMed1978

The effect of dietary monoterpenes on the cholesterol level of eggs.

Monoterpenes were included in the diets of laying hens in an attempt to inhibit the synthesis of cholesterol and hence reduce its amount in egg yolk. However, feeding five monoterpenes, phorone or 200 mg. cholesterol per day to hens did not significantly change the level of cholesterol in the egg yolk. These compounds did not cause signs of ill health in the hen or a decline in egg production.

Animals↗
PubMed1978

The effect of dietary fat supplements on cholesterol metabolism in ruminants.

The serum cholesterol on ruminant animals rises when supplemental fat is fed in a form that ensures the absorption of long-chain fatty acids. The effects of these fat supplements on cholesterol metabolism have been studied in sheep and goats. The proximal part of the small intestine was the major site of sterol synthesis in sheep. Supplementing the diet with fat significantly enhanced sterolgenesis in the small intestine both in vivo and in vitro, whereas in vitro sterolgenesis appeared to be suppressed in the liver. Increased intestinal sterolgenesis was seen with several varieties of fat, but was greatest when palm oil was fed. The reciprocal findings in the intestine and liver may reflect the increased requirement for cholesterol for the transport of triglyceride in chylomicrons and the secondary inhibiting effect of this cholesterol on sterol synthesis in the liver. Dietary fat supplementation did not alter the excretion of neutral steroids in the feces of goats but did not cause a marked reduction in the excretion of acidic steroids which may have been due to the decreased formation of sterols in the liver. In two lactating goats in which an injection of [14C] cholesterol was followed by daily intraruminal administration of labeled cholesterol, fat supplementation lowered the specific radioactivity of cholesterol in alimentary particles and in milk, being consistent with an increase in intestinally synthesized cholesterol. The hypercholesterolemia that develops in fat-fed ruminants appears to be primarily due to an increased intestinal biosynthesis of cholesterol but may also be partly due to a decreased fecal excretion of bile acids.

Acetates↗
PubMed1977

Cellularity of porcine adipose tissue: effects of growth and adiposity.

Adipose tissue, from two depots in pigs of three breeding groups with different propensities to fatten, was characterized in terms of weight of the adipose tissue organ, adipose cell number, and mean cell volume as determined by electronic counting of adipose cells fixed with osmium tetroxide. Perirenal and extramuscular adipose tissue growth was accompanied by progressive adipose cell enlargement along with an increase in cell number. By approximately 18-20 weeks of life, adipose tissue growth in both lean Hampshire x Yorkshire and fat Minnesota 3 x 1 pigs occurred exclusively by cellular hypertrophy. By 24 weeks of life (37 kg), hyperplasia was complete in Hormel Miniature pigs, which contained about one-third as many extramuscular adipose cells as the conventional pigs. Adiposity in the pig was due to cellular hypertrophy rather than cellular hyperplasia, since during growth, the leaner conventional pigs (30.6% extramuscular fat) contained more adipose cells than the fatter pigs (46.6% extramuscular fat). The number of adipose cells per animal or per adipose organ was directly related to the true body size (weight of fat-free carcass) of the animal. Fat Minnesota 3 x 1 pigs had fewer adipose cells than lean Hampshire x Yorkshire pigs at an equivalent live weight due to the smaller true body size of these animals. In young animals (28 and 54 kg), growth rate was positively correlated with adipose cell number. However, growth rate was unrelated to the total number of cells in the more mature animals (83 and 109 kg). Therefore a slow, normal growth rate may delay but not alter the final cell number.

Adipose Tissue↗
PubMed1976

Fatty liver and kidney syndrome in chicks. I. Effect of biotin in diet.

Fatty liver and kidney syndrome, a disorder of young chicks, was studied under laboratory conditions. Affected chicks had enlarged livers (hepatomegaly), an increased content of lipid in the liver, and an increased level of palmitoleic acid in the liver lipids. The disorder was observed mainly in chicks from young parent flocks, and was associated either with commerical diets which were subsequently found to be low in biotin, or with specially formulated low-biotin diets. A third factor, imposition of stress, was required to initiate the disorder. There was evidence of increased lipogenesis causing an increase of triacylglycerols in the liver lipids and an increased production of saturated fatty acids, particularly palmitic acid. Increased levels of palmitoleic acid resulted from an increased desaturation of palmitic acid. Under stress, affected chicks had low blood glucose levels, suggesting that gluconeogenesis was impaired. Since biotin-dependent enzymes are involved in both gluconeogenesis and lipogenesis, it would appear that the relevant enzymes respond differently to a deficiency of biotin.

Animals↗
PubMed1976

Fatty liver and kidney syndrome in chicks. II. Biochemical role of biotin.

The role of biotin-dependent enzymes in the fatty liver and kidney syndrome of young chicks was studied. Under conditions of a marginal deficiency of dietary biotin, the level of biotin in the liver has differing effects on the activities of two biotin-dependent enzymes, pyruvate carboxylase and acetyl-CoA carboxylase. The activity of acetyl-CoA carboxylase is increased, but when the dietary deficiency of biotin produces biotin levels which are below 0-8 mug/g of liver, the activity of pyruvate carboxylase may be insufficient to completely metabolize pyruvate via gluconeogenesis. There is an increase in liver size and in the activities of enzymes involved in alternate pathways for the removal of pyruvate. Blood lactate accumulates and there is increased synthesis of fatty acids, and an accumulation of palmitoleic acid; these steps are accomplished by increased activities of at least the following enzymes: acetyl-CoA carboxylase, malate dehydrogenase (decarboxylating) (NADP+) and the desaturase enzyme. When the biotin level is below 0-35 mug/g of liver and the chick is subjected to a stress, physiological defence mechanisms of the chick may be inadequate to maintain homeostasis and they finally collapse, resulting in accumulation of triacylglycerol in the liver and blood; the chick is unable to maintain blood glucose levels and death occurs, often only a few hours after the imposition of the stress.

Acetyl-CoA Carboxylase↗
PubMed1976

Gas-liquid chromatography of ethyl ester artifacts formed during the preparation of fatty acid methyl esters.

Ethanol is typically used as a stabilizer in chloroform. Failure to remove this ethanol from the chloroform used in the extraction of lipids leads subsequently to the formation of ethyl ester artifacts during the preparation of methyl esters by a commonly employed transesterification procedure. Depending on the conditions and phases used during gas-liquid chromatography, the ethyl esters may be resolved from the corresponding methyl esters. The resulting chromatograms contain extraneous peaks and may be incorrectly identified.

Chemical Phenomena↗
PubMed1973

Cellularity of bovine adipose tissue.

Subcutaneous and perirenal adipose tissue from bovine animals that had different fat deposition patterns were characterized in terms of the weight of the adipose tissue organ and adipose cell number and mean cell size as determined by electronic counting of osmium-fixed adipose cells. Similar parameters were also measured in the interfascicular adipose tissue dissected from four muscles. Adipose tissue from animals of the leaner Holstein breed contained smaller cells than the respective tissues from the fatter Hereford x Angus animals. The small subcutaneous deposit in the Holstein animals was due to a small number of adipose cells that were small in size. During growth of the bovine animal, an increase in adipose tissue mass was accompanied by cellular hypertrophy and hyperplasia. However, by 14 months of life hyperplasia was complete in all but the interfascicular adipose tissue. In the 14-month-old Hereford x Angus steers, interfascicular adipose tissue had an appreciable number of small cells and a bimodal distribution for cell diameter. The results of this study suggest that interfascicular adipose tissue is a late developing depot and that hyperplasia is still an active process in this depot at 14 months of life, whereas hyperplasia appears to be nearly complete in the subcutaneous and perirenal depots of bovine animals by about 8 months of life or shortly thereafter. Correlation coefficients indicated that intramuscular lipid content was positively related to the number of interfascicular adipose cells per 100 g of muscle in four different muscles. However, average cell diameter and volume were significantly correlated to intramuscular lipid content in only one of the four muscles studied.

Adipose Tissue↗