Effect of fat pre-feeding on bile flow and composition in the rat

Studies were conducted in rats to determine if the increase in lymph triacylglycerol output on pre-feeding a 20% glyceryltrioleate diet (Mansbach, C.M., II and Arnold, A. (1986) Am. J. Physiol. 251, G263-269) was due to an increase in phosphatidylcholine output into bile. Rats who were fed chow or pre-fed the 20% fat diet were equipped with biliary and duodenal cannulas and infused with glucose-saline while bile was collected hourly. The next day a taurocholate-glyceryltrioleate infusion was given and bile collected for 5 h. Bile flow, bile acid, phosphatidylcholine and cholesterol output were greater in the chow fed group than controls during the 6 h of the glucose saline period. Outputs were low overnight. During the taurocholate-glyceryltrioleate infusion, bile flow, bile acid, phosphatidylcholine and cholesterol output were all greater in the fat pre-fed group than the chow fed controls. We conclude that fat pre-feeding profoundly influences biliary composition and flow. The 2-fold increase in biliary phosphatidylcholine output during duodenal lipid infusion offers a potential explanation for the increased delivery of triacylglycerol into the lymph in rats on a similar fat pre-feeding program.     

Effect of ambient temperature on lipid metabolism in brown fat during the perinatal period

• 1.1. Norepinephrine-induced lipolysis, cyclic AMP production and glycerokinase activity were measured, in vitro, in the brown fat of rats born and reared at either 28° or 16°C during the first 3 weeks of life.
• 2.2. During the first two postnatal days, lipolytic activity in the tissue was lower than in the foetuses at both ambient temperatures At day 10, increased values of the parameters under consideration were similarly observed in both groups.
• 3.3. However, the hormonal regulation of lipolysis seemed to be quite different from that found in adult cold-acclimated rats.
• 4.4. At day 21, the cold-induced characteristics of lipid metabolism in brown fat were observed in the 16°C exposed rats, whereas a loss of tissue stimulation occurred in the 28°C exposed ones.

     

Identification of two cell types in rat brown fat by electron microscopy]

In the Rat brown adipose tissue, the authors have observed by electron microscopy two different cellular aspects : some cells are more dark, they contain numerous glycogen granules, their mitochondrias are pressed close together and the mitochondrial matrix is darker then the cristae ; in the light cells, the mitochondrias are more sparse and moderately electron dense. The two cellular aspects are also observed on thick sections.     

Effect of growth temperature on the composition of phenols in pea roots

It was shown that, in pea (Pisum sativum L.) roots, flavans are a dominating component of the soluble phenol fraction. In plants grown at low temperature (8°C), flavan content during the early growth phase was lower than in plants grown at 22°C, but later it increased and was by 40% higher than in plants grown at 22°C. Total phenol content in the two treatments differed insignificantly. Low growth temperature decreased the content of some phenolic compounds in pea seedling roots.     

Effect of growth temperature on lipid composition of Streptococcus faecium

The effect of growth temperature on the lipid and fatty acid composition of Streptococcus faecium has been studied. No differences in the qualitative composition of S. faecium lipids were observed. In all isolated fractions (neutral lipids, glycolipids, and phospholipids plus other polar lipids), the major fatty acids were palmitic (C-16:0), palmitoleic (C-16:1), octadecenoic (C-18:1), and cyclopropane (C-19:0). Changes in the fatty acid composition of the different fractions were observed which depended on growth temperature; the most significant one was the decrease of octadecenoic acid and the increase of palmitic acid in glycolipids and polar lipids as the temperature increased. The level of cyclopropane C-19:0 was approximately eightfold lower at 8 degrees C than at the other temperatures tested (20, 30, and 45 degrees C).     

Effect of growth temperature on the fatty acid composition of Mycobacterium phlei

In Mycobacterium phlei, fatty acid unsaturation increased with decreasing temperature. The 10-hexadecenoic acid content increased as the temperature was reduced from 35°C to 26–20°C. At lower temperatures tuberculostearic acid decreased while oleic and linoleic acids increased, the latter being found in M. phlei for the first time. Concomitantly palmitic acid content decreased, and the 6- and 9-hexadecenoic acids increased slightly on reducing the temperature from 35 to 10°C. Thus, down to 26–20°C palmitic acid was mainly replaced by 10-hexadecenoic acid. From this range down to 10°C, palmitic and tuberculostearic acids were replaced by oleic and linoleic acids. Consequently, fatty acid branching decreased and mean chain length increased, as the temperature was reduced. These observations support the view that regulation of membrane fatty acid composition is part of microbial temperature adaptation, and that themechanism behind the responses might be more complex than generally believed.Abbreviations ACP acyl carrier protein - FAS I (Type I) fatty acid synthetase I - FAS II (Type II) fatty acid synthetase II - MGLP methylglucose containing lipopolysaccharide - MMP methylmannose containning polysaccharide     

Deep interscapular temperature and thermogenesis of brown fat during sleep

Deep interscapular temperature measured just below the brown fat lobes was studied in rats during sleep at two ambient temperatures (24 degrees C and 4 degrees C) before and after adaptation (9 days) to cold (4 degrees C). The results show that in the cold ambient deep interscapular temperature decreases during desynchronized sleep independently of adaptation. Such change in temperature is probably the result of the depression in sympathetic vasoconstrictor influences on heat exchangers producing blood and brown fat cooling in sequence during this stage of sleep.     

Sympathetic and adrenocorticoid influences on diet-induced thermogenesis and brown fat activity in the rat

Bilateral adrenalectomy markedly reduced body weight and energy gain and energetic efficiency of adult cafeteria-fed rats but enhanced the thermogenic response to food and stimulated brown fat activity. These changes were totally prevented by replacement of the animals with corticosterone (1 mg/rat/day). Unilateral denervation of the sympathetic nerves supplying the interscapular brown adipose tissue abolished the enhanced activity resulting from adrenalectomy and inhibited thermogenic activity in brown fat from cafeteria rats with intact adrenals, but had no effect in adrenalectomised animals treated with a high dose of corticosterone.     

Effect of carbon source on growth temperature and fatty-acid composition in Thermomonospora curvata

The growth-temperature range of the actinomycete, Thermomonospora curvata, was influenced by the nature of the soluble carbon sources used, which were derived from cellulose, pectin, starch and xylan. This thermophile had the broadest (38 to 65°C) and narrowest (42 to 59°C) temperature range during growth on cellobiose (from cellulose) and 4-deoxy-Lxxx-threo-t-hexoseulose uronic acid (from pectin), respectively. This substrate-temperature interaction was accompanied by changes in cellular fatty acids: uronic-acid-grown cells had relatively low amounts of branched chain fatty acids (particularly iso-16:0) and high amounts of monounsaturated fatty acids (particularly cis-18:1) compared with cells grown on any other substrate. Moreover, uronic-acid-grown cells could not respond to increased growth temperature by altering the ratio of branched chain fatty acids to straight chain fatty acids.F.J. Stutzenberger is with the Department of Microbiology, Clemson University, Clemson, SC 29634-1909, USA; T.C. Jenkins is with the Department of Animal, Dairy and Veterinary Sciences at the same university.     

Effect of growth temperature and media composition on the fatty acid composition of Bacillus stearothermophilus AN 002

The influence of growth temperature, media composition and cell age on the chemical composition of Bacillus stearothermophilus strain AN 002 has been determined. The total cellular protein decreased and the free amino acid content increased with growth temperature, in both exponential and stationary growth phase. The protein and free amino acid contents of cells were higher in the stationary phase than in the exponential phase, irrespective of growth temperature and media composition. The RNA content was only reduced in cells grown at 55° C. No significant variations were observed in the DNA and carbohydrate contents with respect to growth temperature and cell age. The total lipid and fatty acid compositions on the other hand varied as a function of growth temperature, cell age and media composition. Differences in the relative concentrations of even, odd and branched chain fatty acids were noticed. Novariation was observed in the antiiso and unsaturated fatty acids with respect to growth temperature. The unique variations in the fatty acid composition and total lipids at the growth temperature of 50° C and their variations in the stationary growth phase seem to be characteristic for B. stearothermophilus AN 002.     

The enzyme histochemistry of developing brown fat in the fetal rat

Summary Histochemically demonstrable enzymes, glycogen, and lipids were studied during prenatal histogenesis of brown fat in fetal rats. SDH, MDH, LDH, DPN and TPN diaphorases, - and -naphthyl esterases were demonstrable in brown fat cells on day 17 of gestation. Glycogen, lipid, G-6-PDH, cytochrome oxidase, indoxyl esterase and alkaline phosphatase were detected on day 17.5. The progressive increase in MDH, LDH, SDH, DPN diaphorase and cytochrome oxidase content paralleled increases in mitochondrial population during differentiation. MAO and esterase content increased only slightly during the prenatal period studied. Alkaline phosphatase appeared in morula stage cells. These were rare at 17.5 days, but increased in number until, at day 20, they were the predominant cells in the dorsal suprascapular brown fat lobules. Further maturation resulted in the loss of alkaline phosphatase which was present in only occasional cells at birth. Reactions for acid phosphatase, ATPase, naphthol-AS esterase, leucine aminopeptidase, -glutamyl transpeptidase, cholesterol and plasmalogens were negative in prenatal and neonatal brown fat cells.Supported in part by Grant No. 375, Nutrition Foundation, Inc.Presented in part at the annual meeting of the Histochemical Society, Atlantic City, N. J., April, 1969.     

Effect of repeated serotonin injections on temperature regulation in the rat]

The effect of repeated serotonine injections was investigated in thirty Wistar rats tested under normo-, hypo- und hyperthermic conditions. 7 mul of a 0.5% serotonine solution (5HT) were injected into the third ventricle at 1-hr intervals. Temperature responses such as oxygen consumption and rectal temperature were measured and the heat loss was calculated. Intraventricular serotonine produced cooling in all animals. The central mechanisms of heat production were inhibited and those of heat loss were activated. The serotonine responses were most pronounced in hypothermic rats and least effective in hyperthermic animals.     

Effect of noradrenaline chronic administration on brown fat phospholipids

Chronic cold exposure of rats (9 days at 5°C) induces an alteration of the fatty acid composition of phospholipids in brown adipose tissue. The alteration is due to an increase of the unsaturation degree of these lipids. The phenomenon can be reproduced by 10^–7 mole. h^–1 administration of noradrenaline for 9 days in rats kept at 25°C. Thus, phospholipid alteration in brown fat of cold exposed rats is most probably a consequence of the increase of sympathetic tone which occurs in this tissue during exposure to cold.