Mesenteric Fat Depots Research Articles

17β-Estradiol inhibits 11β-hydroxysteroid dehydrogenase type 1 activity in rodent adipocytes

17Beta-estradiol (E(2)) serves as an anti-obesity steroid; however, the mechanism underlying this effect has not been fully clarified. The effect of E(2) on adipocytes opposes that of glucocorticoids, which potentiate adipogenesis and anabolic lipid metabolism. The key to the intracellular activation of glucocorticoid in adipocytes is 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which catalyses the production of active glucocorticoids (cortisol in humans and corticosterone in rodents) from inactive 11-keto steroids (cortisone in humans and 11-dehydrocorticosterone in rodents). Using differentiated 3T3-L1 adipocytes, we showed that E(2) inhibited 11beta-HSD1 activity. Estrogen receptor (ER) antagonists, ICI-182 780 and tamoxifen, failed to reverse this inhibition. A significant inhibitory effect of E(2) on 11beta-HSD1 activity was observed within 5-10 min. Furthermore, acetylation or alpha-epimerization of 17-hydroxy group of E(2) attenuated the inhibitory effect on 11beta-HSD1. These results indicate that the inhibition of 11beta-HSD1 by E(2) depends on neither an ER-dependent route, transcriptional pathway nor non-specific fashion. Hexose-6-phosphate dehydrogenase, which provides the cofactor NADPH for full activation of 11beta-HSD1, was unaffected by E(2). A kinetic study revealed that E(2) acted as a non-competitive inhibitor of 11beta-HSD1. The inhibitory effect of E(2) on 11beta-HSD1 was reproduced in adipocytes isolated from rat mesenteric fat depots. This is the first demonstration that E(2) inhibits 11beta-HSD1, thereby providing a novel insight into the anti-obesity mechanism of estrogen.

Máxima Fase estável de lactato em ratos obesos de ambos os gêneros

A incidência de obesidade vem crescendo entre a população mundial, levando a inúmeras complicaçõe,s como risco de doenças crônico-degenerativas. Por outro lado, o exercício físico tem sido empregado isoladamente ou em associação a dieta, no tratamento dessa doença. Assim, pesquisas envolvendo exercício são imprescindíveis para evolução no tratamento e controle da obesidade. O objetivo deste estudo foi identificar a intensidade de exercício equivalente à transição metabólica aeróbio-anaeróbia em ratos Wistar obesos de ambos os gêneros, por tratamento com glutamato monossódico (MSG), utilizando o protocolo de máxima fase estável de lactato (MFEL). Para isso, foram testados 40 ratos adultos subdivididos em quatro grupos com 10 animais cada um: controle machos, controle fêmeas, obeso machos e obeso fêmeas. Depois de adequada adaptação (três semanas) ao exercício em meio líquido (31 ± 1ºC) os animais foram submetidos a teste de natação (25 min) suportando sobrecargas contínua e aleatória correspondentes a 4,5 - 5,0 - 5,5 - 6,0 e 6,5% do peso corporal (PC), com intervalo de 72 horas entre elas. Os animais dos grupos obesos tiveram aumentos no peso do tecido adiposo subcutâneo, mesentérico e retroperitonial em relação aos grupos controle. O índice de Lee foi maior nos animais obesos em comparação com os controles. Foi possível identificar a MFEL a 6,0% do PC nos dois grupos obesos. Para o grupo controle fêmea, a MFEL esteve por volta de 5,0% do PC enquanto que nos controle macho a 4,5% do PC. Desse modo pode-se concluir que a obesidade induzida por MSG interfere na cinética de lactato durante o exercício em ambos os sexos, alterando a intensidade de esforço referente à transição metabólica.

Genetic mapping for aggressive behavior using B6-MSM consomic mouse strains

The goal of this study was to determine the adiposity of a range of rat strains, including a panel of consomics, to estimate heritability. To that end, we assessed the body fat distribution and organ weights of groups of adult male rats from 3 outbred strains, 11 inbred strains and 22 consomic strains. We measured the weights of the gonadal, retroperitoneal, mesenteric, femoral, subscapular and pericardial white fat depots, the subscapular brown fat depot, the kidneys, liver, heart, spleen, and brain. Strains were compared for the measured weight of each of these adipose depots and organs, and also for these weights adjusted statistically for body size. All individual adipose depot and organ weights were highly heritable, in most cases h2 > 0.50. The fourteen inbred and outbred rat strains were not very different in body length but there was a three-fold difference in body weight, and up to a twenty-fold difference in the weight of some adipose depots. Comparison of the FHH-Chr nBN consomic strains with the FHH host strain revealed 98 quantitative trait loci (QTLs) for body composition and organ weight, with the introgressed chromosome reducing weight or adiposity in most cases. These results can be used to guide the choice of appropriate rat strains for future studies of the genetic architecture of obesity and body size.

Pancreatic contamination of mesenteric adipose tissue samples can be avoided by adjusted dissection procedures

Mesenteric adipose tissue, located in the mesenterium of the intestines, is believed to play a central role in the development of obesity-related diseases. We have found that mesenteric fat samples harvested from rodents are frequently of poor quality, exhibiting partly degraded RNA. To investigate the background for this observation, we screened adipose tissue samples from two independent studies on rodents for markers of different tissues and cell types. We found that mesenteric adipose tissue samples of low quality are "contaminated" by pancreatic tissue. To locate the affected area, we dissected the mesenteric fat depots from 14 mice and measured abundance of pancreas-specific gene expression and amylase activity. As expected, we observed that the proximal section of the mesenterium, located near the pancreas, expressed pancreatic markers, whereas the distal sections did not. Approximately one-third of the mesenteric adipose tissue depots contained pancreatic tissue. Because the boundary between pancreas and mesenteric fat cannot be easily distinguished during dissection, we conclude that investigators should routinely exclude the proximal section of the mesenteric adipose tissue depot to avoid pancreatic contamination.

Metabolic Characteristics of Wistar Rats Submitted to High Fructose Ingestion by Different Protocols

PURPOSE: Although the fructose-fed rat model exhibits many signals of the metabolic syndrome, the alterations observed are quite divergent among the studies. In search of an adequate animal model for the study of the effects of exercise on the development of the metabolic syndrome, the present study was designed to analyze metabolic characteristics of Wistar rats submitted to high fructose ingestion by different protocols. METHODS: In the first, two groups of adult rats (90 days old) were studied: a Control group (C 1; n = 6) received regular rodent chow and a Fructose group (F1; n= 6) was fed regular rodent chow and fructose was administered as a 10% solution in drinking water. In the second, also two groups of adult rats (90 days old) were evaluated: a Control group (C2; n = 6) was fed a balanced diet (AIN93) and a fructose group (F2; n= 6) was fed a purified 60% fructose diet. In the third, two groups of young rats (28 days old) were analyzed: a Control group (C3; n = 6) was fed the balanced AIN93 diet and a fructose diet group (F3; n= 6) was fed the 60 % fructose diet. The animals were evaluated with respect to: glucose tolerance (area under serum glucose concentrations during oral glucose tolerance test), peripheral insulin sensivity (serum glucose disappearance rates during subcutaneous insulin tolerance test), serum triglycerides concentration and mesenteric fat depot weight. C3 and F3 rats were also evaluated with respect to the aerobic capacity (maximal lactate steady state determination during swimming) RESULTS: Glucose tolerance was lower in the fructose groups F2 (10%) and F3 (10.4%) whereas serum triglycerides were higher (F2=99%, F3=60.2%) than in the respective controls (t- student P< 0.05). Insulin sensivity in F2 decreased (35.6%) and mesenteric fat depot weight increased (56.6%) in relation to C2. High fructose intake (F3) did not alter the aerobic capacity of the animals. CONCLUSIONS: In conclusion, high fructose intake is more effective in producing signals of metabolic syndrome in adult (90 days old) than in young (28 days old) Wistar rats. Also diet seems to be a more effective route for fructose administration than drinking water. Supported by Fapesp: process 07/54098-0; Capes and CNPq

Postnatal Testosterone Exposure Results in Insulin Resistance, Enlarged Mesenteric Adipocytes, and an Atherogenic Lipid Profile in Adult Female Rats: Comparisons with Estradiol and Dihydrotestosterone

Postnatal events contribute to features of the metabolic syndrome in adulthood. In this study, postnatally administered testosterone reduced insulin sensitivity and increased the mesenteric fat depot, the size of mesenteric adipocytes, serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides, and the atherogenic index in adult female rats. To assess the involvement of estrogen and androgen receptors in these programming effects, we compared testosterone-exposed rats to rats exposed to estradiol or dihydrotestosterone (DHT). Estradiol-treated rats had lower insulin sensitivity than testosterone-treated rats and, like those rats, had enlarged mesenteric adipocytes and increased triglyceride levels. DHT also reduced insulin sensitivity but did not mimic the other metabolic effects of testosterone. All treated rats were probably anovulatory, but only those treated with testosterone had reduced testosterone levels. This study confirms our previous finding that postnatal administration of testosterone reduces insulin sensitivity in adult female rats and shows that this effect is accompanied by unfavorable changes in mesenteric fat tissue and in serum lipid levels. The findings in the estradiol and DHT groups suggest that estrogen receptors exert stronger metabolic programming effects than androgen receptors. Thus, insults such as sex hormone exposure in early life may have long-lasting effects, thereby creating a predisposition to disturbances in insulin sensitivity, adipose tissue, and lipid profile in adulthood.

Varying plant protein sources in the diet of sea bass Dicentrarchus labrax differently affects lipid metabolism and deposition

The liver activity of lipogenic enzymes, the lipid content in various tissues, and plasma lipid levels of major, were measured in sea bass (D. labrax) fed over 96 days either a, fish meal-based control diet or preparations where 70% of fish meal protein was replaced by wheat gluten singly or in combination with pea or soybean meals. Relative to the controls, sea bass fed the wheat gluten-based diet resulted in stimulated lipogenesis in liver and increased lipid deposition in muscle. The opposite occurred when a substantial amount of soybean meal was included in the diet. Mesenteric fat depots were apparently insensitive to major changes in dietary protein source in fish showing similar intakes of digestible protein, energy and lipid. These results confirm that varying plant protein source in the diet differently affects lipid metabolism and deposition in sea bass.

Effect of chicken egg yolk antibody against adipose tissue plasma membranes on carcass composition and lipogenic hormones and enzymes in pigs

Abstract Chicken egg yolk antibody against pig adipose tissue plasma membranes (AIgY) was raised and used in the present experiment to evaluate the effect of dietary AIgY supplementation on pig growth and carcass composition. 160 crossbred (Duroc–Jersey × Landrace·Meishan) pigs, with initial live body weight of 27.5 ± 2.4 kg, were treated with AIgY or non-immunized control egg yolk powder (NIgY) at the inclusion level of 75 mg/kg diet. Following a 104-day trial, the pigs were slaughtered for analyzing the carcass and meat quality traits. The perirenal, mesenteric and subcutaneous fat depots were weighed and the diameter of adipocytes from different fat depots was measured with histological methods. Serum concentrations of insulin and leptin as well as the activities of malic enzyme (ME) and lipoprotein lipase (LPL) in adipose tissue were measured. Dietary supplementation of AIgY enhanced average daily gain and feed efficiency by 13.03% (P

Identification of depot-specific human fat cell progenitors through distinct expression profiles and developmental gene patterns

Anatomically separate fat depots differ in size, function, and contribution to pathological states, such as the metabolic syndrome. We isolated preadipocytes from different human fat depots to determine whether the basis for this variation is partly attributable to differences in inherent properties of fat cell progenitors. We found that genome-wide expression profiles of primary preadipocytes cultured in parallel from abdominal subcutaneous, mesenteric, and omental fat depots were distinct. Interestingly, visceral fat was not homogeneous. Preadipocytes from one of the two main visceral depots, mesenteric fat, had an expression profile closer to that of subcutaneous than omental preadipocytes, the other main visceral depot. Expression of genes that regulate early development, including homeotic genes, differed extensively among undifferentiated preadipocytes isolated from different fat depots. These profiles were confirmed by real-time PCR analysis of preadipocytes from additional lean and obese male and female subjects. We made preadipocyte strains from single abdominal subcutaneous and omental preadipocytes by expressing telomerase. Depot-specific developmental gene expression profiles persisted for 40 population doublings in these strains. Thus, human fat cell progenitors from different regions are effectively distinct, consistent with different fat depots being separate mini-organs.

Time course of changes inin vitrolipolysis of intra-abdominal fat depots in relation to high-fat diet-induced hepatic steatosis in rats

The purpose of the present study was to determine the time course of changes in in vitro lipolysis and in perilipin content (Western blot) in the mesenteric and/or the retroperitoneal fat depots in relation to the development of hepatic steatosis in high-fat diet-fed rats. Female Sprague-Dawley rats were submitted to a high-fat diet (HF diet; 42 % as kJ) or a standard diet (SD diet) for 1, 2, 3 or 8 weeks. Fat accretion in the mesenteric and retroperitoneal tissues was higher (P<0.01) in HF diet-fed than in SD diet-fed rats as soon as 1 week after the beginning of the diet. Liver triacylglycerol concentrations were significantly (P<0.01) higher in HF diet-fed than in SD diet-fed rats throughout the experiment, the highest values being reached at week 2 of the diet. Basal and stimulated lipolysis (10(-4) to 10(-7) M-isoproterienol) in the mesenteric and retroperitoneal fat depots was not changed during the first 3 weeks, regardless of the diet. Lipolysis in the mesenteric adipose tissue in the basal and stimulated states was, however, higher (P<0.01) in HF diet-fed than in SD diet-fed rats after 8 weeks of the diets. There were no significant (P>0.05) effects of diet and time on perilipin content of mesenteric tissue. In spite of a rapid fat accretion, the present results do not provide any evidence of a rapid (3 weeks) increase in in vitro lipolysis in intra-abdominal fat depots upon the undertaking of an HF diet at a time where liver lipid infiltration is the most significant.

Induction of colitis causes inflammatory responses in fat depots: Evidence for substance P pathways in human mesenteric preadipocytes

Intracolonic administration of trinitrobenzene sulfonic acid in mice causes inflammation in the colon that is accompanied by increased expression of proinflammatory cytokines and of the substance P (SP), neurokinin 1 receptor (NK-1R) in the proximal mesenteric fat depot. We also investigated whether human mesenteric preadipocytes contain NK-1R and examined the functional consequences of exposure of these cells to SP as it relates to proinflammatory signaling. We found that human mesenteric preadipocytes express NK-1R both at the mRNA and protein levels. Exposure of human mesenteric preadipocytes to SP increased NK-1R mRNA and protein expression by 3-fold, and stimulated IL-8 mRNA expression and protein secretion. This effect was abolished when these cells were pretreated with the specific NK-1R antagonist CJ 012,255. Moreover, human mesenteric preadipocytes transfected with a luciferase promoter/reporter system containing the IL-8 promoter with a mutated NF-kappaB site lost their ability to respond to SP, indicating that SP-induced IL-8 expression is NF-kappaB-dependent. This report indicates that human mesenteric preadipocytes contain functional SP receptors that are linked to proinflammatory pathways, and that SP can directly increase NK-1R expression. We speculate that mesenteric fat depots may participate in intestinal inflammatory responses via SP-NK-1R-related pathways, as well as other systemic responses to the presence of an ongoing inflammation of the colon.

Lipogenic activity in goats ( Blancaceltibérica) with different body condition scores

The aim was to study the variation in the amount of adipose tissue, size and number of adipocytes and lipogenic enzyme activities in does with different body condition scores (BCS). These parameters were studied in the omental (OM), mesenteric (MES), perirenal (PR), subcutaneous (SC) and intermuscular (IM) fat depots of 22 adult, non-pregnant and non-lactating Blanca celtibérica does, with a BCS ranging from 1.5 to 4.5 (scale 0–5). SC adipose tissue showed the highest deposition-mobilization phase (highest fat relative to the variation per BCS unit of 74%), followed by OM (65%), PR (63%), MES (48%) and IM (46%) adipose depots. Adipocyte size varied with the amount of fat ( P < 0.001), while the SC depot was the only depot that showed a positive correlation between adipocyte number and BCS ( r 2 = 0.20; P < 0.05). The activities of glycerol 3-phosphate dehydrogenase (G3PDH) and fatty acid synthetase (FAS) enzymes were not generally affected by BCS, due to the fact that animals were on a maintenance diet prior to slaughter. The findings obtained in this work indicate that the processes of storage and mobilization of fat reserves in adult goats are principally due to variation in the size of the adipocyte cells. Therefore, the use of BCS could be a good method for predicting nutritional status in goats.

The effect of a silage additive and level of concentrate supplementation on silage intake, animal performance and carcass characteristics of finishing beef cattle

An experiment was carried out to examine silage fermentation, effluent production and aerobic stability in unwilted grass silage, which was either ensiled without additive or with a commercially available blend of ammonium hexamethanoate, ammonium hexapropionate and octanoic acid (6 l t−1, Maxgrass, BP Chemicals Ltd., Northwich, UK) and to determine alternative approaches to obtaining the same performance in finishing beef cattle. Seventy-two Limousin × Friesian and Charolais × Friesian steers (mean initial live weight 424 kg s.d. 28·3) were blocked into groups of nine according to live weight and previous performance and offered silage, either with or without the additive, and supplemented with 0, 1·5, 3·0 or 4·5 kg d−1 of a concentrate with a crude protein content of 150 g kg−1 DM or allocated to a pre-experimental slaughter group to enable calculation of daily carcass gain. Daily silage intakes were recorded for 112 days. At the end of the experiment, all cattle were slaughtered and daily carcass gain, omental, mesenteric, perinephric and retroperitoneal fat depots [kidney-knob and channel fat (KKCF)], fatness, conformation, subcutaneous fat depth over M. longissimus dorsi muscle and carcass fat, protein and bone contents were assessed. Across all levels of supplementation, cattle offered the silage with the additive showed significantly (P < 0·001) higher daily DM intakes than those offered the silage without additive. Cattle offered the silage with the additive but unsupplemented had significantly (P < 0·001) higher daily carcass gains than those offered the silage without additive and unsupplemented. The response in carcass gain was 76 and 35 g kg−1 additional concentrate for the silages with and without the additive respectively.

Distribution of angiotensin II receptors in rat and human adipocytes.

Angiotensin II (AII) receptor binding assays were performed in rat adipocytes from three separate anatomic depots. Fat cells were isolated by collagenase digestion, and plasma membranes were prepared from the epididymal, mesenteric, and retroperitoneal fat depots of male Sprague-Dawley rats at 100 days of age. Binding of 125I-labeled [Sar1,Ile8]AII was rapid, saturable, and specific in membranes from all depots, identifying a receptor with a similar affinity of approximately 1 nM. Site-associated differences in receptor number were observed, with epididymal and mesenteric fat cell membranes exhibiting significantly more receptors than retroperitoneal fat cells when binding was expressed per unit of membrane protein. When corrected for cell volume, the number of receptors per cell ranked epididymal > retroperitoneal > mesenteric. Inhibitory constants for the peptide agonists AII and AIII and the peptide antagonist [Sar1,Ala8]AII indicated similar affinities in all three depots. Because the receptor has been classified pharmacologically into two subtypes, the AT1 selective antagonist losartan, and the AT2 selective antagonist PD 123,319 were used to classify the adipocyte receptor, indicating an AT1 subtype with an affinity for losartan in the mesenteric and retroperitoneal adipocytes that was significantly greater than the epididymal. Similar studies were performed in adipocyte membranes obtained from human omental and subcutaneous adipose tissue, revealing the presence of an AII receptor in both depots with an affinity of approximately 10 nM for losartan. These data indicate site-specific differences in AII receptor number in fat cell membranes from rats and the existence of human adipocyte AII receptors, suggesting that the adipocyte is significant for the peripheral metabolism of components of the renin-angiotensin system.

Regional changes in adipose tissue blood flow and metabolism in rats after a meal.

Adipose tissue blood flow was measured in five depots, and plasma concentrations of glucose, insulin, and triglyceride were measured at 0, 15, 30, and 45 min after the start of a meal in unanesthetized, freely moving rats. In addition, adipose tissue lipoprotein lipase activity was measured in four depots before and 45 min after the start of a meal. Plasma glucose was significantly elevated only at the 15-min time point, and while plasma triglyceride increased these changes did not reach significance. Plasma insulin was significantly elevated at all time points after a meal. Feeding resulted in a consistent decrease of adipose tissue blood flow expressed per gram wet weight of tissue. This decrease was maximal at 30 min after the start of feeding. The decrease in adipose tissue blood flow averaged 45% at 45 min after the start of feeding for the five depots evaluated. Lipoprotein lipase activity significantly increased in the retroperitoneal and mesenteric fat depots at 45 min after the meal start, but did not change in the epididymal or dorsal subcutaneous fat depots. These results suggest that a decrease in adipose tissue blood flow is a normal result of a meal in the rat. The regional specificity of changes in adipose tissue lipoprotein lipase activity supports the concept of regional specificity of function for adipose tissue and suggests that the mesenteric and retroperitoneal depots are particularly important for the storage of triglycerides immediately after a meal.

Metabolism of adipose tissue in intraabdominal depots of nonobese men and women

Adipocyte size, lipoprotein lipase (LPL) activity, and the lipolytic response to noradrenaline and isoproterenol were studied in three intraabdominal depots (mesenteric, omental, retroperitoneal), as well as in subcutaneous abdominal adipose tissue, in nonobese groups of middle-aged men and in premenopausal and postmenopausal women. Subcutaneous adipocytes were larger than intraabdominal adipocytes in all groups. The men had large adipocytes in all intraabdominal depots as compared with the women. The premenopausal women seemed to have low LPL activity in intraabdominal depots. Two types of response to catecholamine-stimulated lipolysis were observed: a similar response from mesenteric and omental (portal) fat depots and from retroperitoneal and subcutaneous abdominal (nonportal) fat depots. Young women had higher lipolysis in nonportal than in portal adipose tissues. In the men the reverse characteristics were found. These dissimilarities seem to be based on differences in β-adrenergic responsiveness. Postmenopausal women showed no differences between depots. The differences in lipolytic responsiveness between these groups might be caused by sex steroid hormones.

Mechanism for the 'anti-lipolytic' action of vasopressin in the starved rat.

The marked decrease in blood non-esterified fatty acids and ketone bodies after vasopressin infusion into starved rats [Rofe & Williamson (1983) Biochem. J. 212, 231-239] was investigated. Vasopressin did not inhibit lipolysis in isolated rat adipocytes. The metabolic effects in vivo were still present after pretreatment of rats with indomethacin, indicating that the effect is not secondary to the release of prostaglandins. Vasopressin significantly decreased blood flow through the retroperitoneal, epididymal and mesenteric fat depots, by 80%, 76% and 46% respectively. The specific haemodynamic effect of vasopressin on adipose tissue is considered to be the primary cause of the major metabolic changes seen in the starved rat.

Relationship between cell size, plasma cholesterol and rat adipocyte cholesterol storage

Plasma cholesterol and cholesterol storage/10 6 adipocytes were determined in the epididymal, perirenal, subcutaneous, and mesenteric fat depots of the fasted male rat. Adipocyte cholesterol increased exponentially as functions of mean cell diameter, body weight, and cell size (μg triacylglycerol/cell) in all depots examined, whereas plasma cholesterol was best described as a parabolic function of body weight. In all but the mesenteric depot, expression of storage as a ratio of cellular cholesterol:triacylglycerol was also described as a parabolic function of body weight, resulting in curves parallel to the cholesterolbody weight relationship. It is suggested that (1) adipose tissue cholesterol storage is most rapid after adipocyte number becomes fixed, (2) the level of cholesterol in the plasma may be a major determinant of fat cell cholesterol storage, especially in subcutaneous cells from adult animals in which cell size is constant but cholesterol storage continues to increase, and (3) the effect of plasma cholesterol is less pronounced in mesenteric adipocytes.

Influence of body weight, age, diet and sex on fat depots in rats.

AbstractWeanling male and female littermate Osborne Mendel rats were randomly separated into two groups. The control group was fed a grain ration. The second group was fed a high fat ration which ultimately produced obesity. Male and female rats were killed at weaning (body weight, 50–60 gm). Thereafter rats from both diet groups were killed after an initial weight gain of about 100 gm and subsequent gains of about 150 gm. The inguinal, forelimb (axillary), interscapular perirenal, genital, xiphoid, and mesenteric and omental fat depots were removed, weighed, and weights recorded. Fat depots usually increased in weight more rapidly than overall body weight. This was typical of younger rats from both diet groups, but more pronounced in rats fed the high fat ration. The perirenal depots increased in weight more rapidly than body weight throughout the 450+ days of the study. In both sexes and diet groups, from weaning through sexual maturity, the weight of the genital fat depots increased proportionately more rapidly than body weight. Thereafter, the weight gain more nearly paralleled the body weight gain. In both diet groups, with the exception of the interscapular depot, the subcutaneous depots increased rapidly in weight during the first 100 days of life. The weight gain of these depots maintained a close relationship to body weight gain after 100 days of age. The interscapular depot in obese females increased at a very rapid rate as the animals approached 900 gm of body weight.

Effects of castration and of progesterone implantation on muscle composition in the ferret.

SUMMARY Longissimus dorsi muscles from intact and castrated male ferrets were investigated at the time of maximum body weight in winter, and muscles from control and progesterone-treated animals in summer. The animals had free access to food throughout. The seasonal decrease in body weight was accompanied by decreased fat concentration in the muscle and by reduction of the subcutaneous and mesenteric fat depots. Implantation of progesterone pellets increased the body and muscle weights of intact males (but not of castrated animals) and also increased intramuscular fat. It may have reversed the seasonal pattern of changes in that the fat in the muscle became more unsaturated. The water content of the muscle decreased only reciprocally in relation to the increased fat content. Progesterone had no obvious effect on the composition of muscle in castrated ferrets. In summer the castrated animals had more intramuscular fat than the intact males at this time; moreover, despite the higher concentration, its degree of unsaturation was greater.