Reduced mature size in progeny of swine severely restricted in protein intake during pregnancy.

The objective was to determine the effects of maternal gestation diet on mature body and organ size and composition of progeny. Female progeny of swine fed daily 1.8 kg (6,000 kcal DE) of a semipurified diet containing less than 0.5% protein (PR), 1.8 kg (6,000 kcal) of a standard maize-soybean meal-based gestation diet (C) or 0.6 kg (2,000 kcal DE) of C diet to d 70 of gestation and 1.8 kg (6,000 kcal DE) from d 71 to parturition (R) were used. They were fed ad libitum a standard maize-soybean meal-based growing diet to age 25 wk, then continued on limited feed intake to age 62 wk, then returned to ad libitum intake to age 119 wk. Body weight and ultrasonically determined subcutaneous backfat depth were recorded at 62, 79, 97, 105 and 119 wk of age and indices of body composition and organ weights were recorded on carcasses of animals killed at age 119 wk. Progeny of PR dams were permanently stunted in mature body weight and in weights of eviscerated carcass, heart, liver, kidneys, stomach and small intestine, but not in cerebrum, cerebellum weights or RNA and DNA content. It is concluded that severe protein restriction during gestation in swine resulted in permanent whole body weight stunting of progeny but that weights and total protein, RNA and DNA content of cerebrum, cerebellum and RNA and DNA concentration of longissimus muscle were unaffected.     

Somatic, endocrine and metabolic changes in controls pair-fed for six weeks to rats with dorsomedial hypothalamic nucleus lesions (DMNL rats)

One group of weanling male Sprague-Dawley rats received lesions in the dorsomedial hypothalamic nuclei (DMNL rats), whereas two additional groups of rats were sham-operated (CON). One of these CON groups was allowed to feed ad lib (CON-ADLIB) while the other CON group was pair-fed for 6 weeks to the DMNL rats (CON-PF). Despite eating the same amount of food as DMNL rats. CON-PF animals had consistently lower body weights and also utilized food energy more poorly than DMNL rats. The CON-PF group also had smaller kidneys and less percent liver protein but more epididymal fat pad percent protein than DMNL rats. Whereas plasma glucose concentrations were comparable among the three groups, insulin levels were significantly higher, and free fatty acid levels lower in CON-PF than in DMNL rats. The CON-PF group incorporated less glucose-U-C14 carbon into liver glycogen but more of the tracer into liver lipid than the DMNL group. Glucose carbon was also incorporated more avidly into epididymal fat pad lipid by CON-PF than by DMNL rats. The data not only confirm previous findings in DMNL rats but in addition show that the neurologically intact rats fed the same amount of food that is eaten spontaneously by DMNL rats show somatic and metabolic alterations that suggest that they cannot cope with this low amount of substrate. The normalcy of the DMNL rats, compared to ad lib-fed sham-operated controls, in all metabolic parameters suggests that the low food intake is indeed "normal" for this preparation and may be the reflection of an "organismic" set point.     

Effect of caloric restriction on cardiac reactivity and beta-adrenoceptor concentration

The effect of a 21-day program of caloric restriction on cardiac reactivity and beta-adrenoceptor number was investigated in male Sprague-Dawley rats. Rats on the restricted diet (Restricted) exhibited significant decreases in body weight, epididymal fat pad, and retroperitoneal fat pad weight as well as the percent of body fat represented by these adipose tissue depots when compared with rats fed ad libitum (Fed). Fed rats exhibited significantly increased total heart weight and total heart protein, but the percent cardiac protein and ratio of heart weight to body weight were similar in Fed and Restricted rats. Isolated atria from Fed and Restricted rats developed similar chronotropic and inotropic responses over a range of isoproterenol concentrations. Although total beta-adrenoceptor number (fmol/heart) was greater in Fed rats, the concentration of beta-adrenoceptors (fmol/mg protein) was remarkably similar regardless of the dietary regimen. Therefore, despite significant decreases in body weight, body fat, and heart weight, the myocardium of Restricted rats maintained the capability of responding to isoproterenol as that of Fed rats, the mechanism of which is at least partially mediated through maintenance of beta-adrenoceptor concentration.     

Effects of food restriction on testis and accessory sex glands in maturing rats

Reduced food consumption and associated lower body weights may occur in subacute toxicity studies. The short-term effects of food restriction (FR) on body and reproductive organ weights, hormones, and testis histology were assessed in Sprague-Dawley rats fed 20% to 36% less (21 g feed/day) than rats fed ad libitum (AL) starting at six, eight, ten, or twelve weeks of age for two or six weeks. Body weight and relative seminal vesicle, ventral prostate, and/or epididymis weights were reduced in rats FR for two or six weeks. Degeneration of stage VII pachytene spermatocytes was seen in rats FR for six weeks when initiated at eight, ten, and twelve weeks of age. Plasma testosterone concentrations were lower in rats FR at ages six to eight weeks, eight to ten weeks, six to twelve weeks, and eight to fourteen weeks. Luteinizing hormone was not statistically different in FR rats compared with AL counterparts. Therefore, duration of lower food intake had a greater impact on spermatogenesis, whereas a younger initial age of lower food intake was more influential on testosterone levels. These interactions are important in the interpretation of subacute toxicology studies employing FR or when test articles lower food consumption relative to AL-fed rats.     

Effects of recombinant chicken growth hormone in randombred meat-type chickens

Recombinant chicken growth hormone (rcGH) was administered subcutaneously twice daily to male and female Athens-Canadian randombred meat-type chickens between 2 and 14 days posthatch. Treatment groups consisted of non-injected controls, saline-injected controls, and those injected with either 50 or 250 micrograms/kg rcGH per injection. Body weight, body weight gain, feed consumption, and feed efficiency were determined. Body weight or body weight gain was not significantly affected by rcGH through 28 d. Feed consumption and efficiency were not significantly affected by treatment through 21 d. It was concluded that rcGH failed to demonstrate any significant growth-promoting effects in young, slow-growing randombred chickens.     

Effect of maternal feed restriction on blood pressure in the adult guinea pig

Small size at birth has been associated with increased blood pressure in adult men and women. In rats, isocaloric protein restriction reduces fetal growth and increases systolic blood pressure in adult offspring. Balanced maternal undernutrition in the rat also increases adult blood pressure, but not consistently. The aim of this study was to determine the effect of moderate balanced maternal undernutrition (85% of ad libitum intake from 4 weeks before, and throughout pregnancy) on blood pressure of adult offspring in the guinea pig, a species that is relatively mature at birth. Blood pressure was measured in chronically catheterised offspring of ad libitum fed or feed-restricted mothers, at 3 months of age (young adult). Maternal feed restriction reduced birth weight (-17%) and increased systolic blood pressure (+9%, P < 0.03) in young adult male offspring. In offspring of ad libitum fed and feed-restricted mothers, combined data showed that systolic blood pressure and mean arterial pressure correlated negatively with head width at birth (P = 0.02 and P = 0.04, respectively, n = 28). Systolic blood pressure also correlated negatively with birth weight and the ratio birth weight/birth length, but only in offspring of ad libitum fed mothers (P = 0.04 and P = 0.03, respectively, n = 22). The effect of maternal feed restriction on systolic blood pressure in male offspring was not significant when adjusted for these measures of size at birth. Thus, moderate balanced undernutrition in the guinea pig increases systolic blood pressure in young adult male offspring; however, these effects may be mediated, at least in part, through effects on fetal growth.     

Growth analysis in two lines of rats and their reciprocal F1 crosses under two nutritional environments. Heterosis for body weight and maturing rate

The heterotic effects for body weight during the early postweaning period and on the von Bertalanffy growth equation parameters in relation with the growth pattern as a whole were investigated in rats with caloric restriction (20%) and in controls with ad libitum feeding. Body weight at fixed ages, weight-age curves, asymptotic weight, mature size and maturing curves were evaluated in a cross between two highly inbred lines of rats. Growth curve parameters were combined in a single value by the multivariate method of principal components in order to characterize the particular growth pattern of each group. Positive and significant heterotic effects for body weight were observed suggesting the presence of non-additive genetic variation for this trait. Additivity was an important source in asymptotic size. An heterotic response was observed in mature rate showing a dominant deviation towards high values of this character. Caloric restriction diminished body weight, but asymptotic size was not modified. Maturity was affected along the period studied. Hybrids reached an intermediate asymptotic weight in relation to parental lines exhibiting greater maturity in the prepuberal period. It is suggested that in livestock production crossbreeding will be profitable if additivity for asymptotic weight and dominance deviation for maturing rate could be combined in the F1 hybrid. Maternal breed should be lighter and mature more rapidly than the paternal one if maintenance costs of the breeding stock and growing potentiality of the crossbred progeny are considered.     

Long-term dietary restriction influences plasma ghrelin and GOAT mRNA level in rats

The objective of this study was to examine the effect of chronic dietary restriction on the physical characteristics of the intestine and gut-derived satiety hormone production. Male Wistar rats (8 weeks) were randomized to ad libitum (AL) or 35% dietary restriction (DR) for 5 months. At the end of the study, physical measurements were made on the intestine and satiety hormone secretion and mRNA expression determined. A comparison group of young, growing AL rats (5 weeks) was also examined. The adult DR rats gained less weight over 5 months and had lower fat mass than adult AL rats (p < 0.05). The weight of the small intestine as a percentage of total body weight was greater in adult DR compared to adult AL but lower than young AL rats. Compared to AL, DR down-regulated proglucagon and cholecystokinin mRNA in the duodenum and ghrelin mRNA in the stomach of adult rats but was not different from young AL. Ghrelin-O-acyltransferase (GOAT) mRNA in the stomach was up-regulated 21-fold in adult AL rats compared to young AL and 14-fold compared to adult DR rats. Total and des-acyl ghrelin was approximately 50% higher in adult DR and young AL rats compared to adult AL. Plasma leptin and insulin were lower in adult DR and young AL rats compared to adult AL. Our findings suggest that long-term energy deficits continue to drive up ghrelin levels which may have profound implications for practical implementation of DR as an anti-aging or anti-obesity strategy in humans.     

The effects of ad libitum feeding and marked dietary restriction on spontaneous skeletal muscle pathology in Sprague-Dawley rats

The effects of ad libitum (AL) feeding and marked dietary restriction (DR) on spontaneous age-related skeletal muscle changes in male Sprague-Dawley (SD) rats were evaluated at 1 and 2 years. SD rats were fed Certified UAR A04C Rodent Chow ad libitum (AL), or DR at 50% of AL for (106 weeks). Body weights and organ weights were measured at the 1-year interim and 2-year final necropsies. In addition to the routine histopathologic examination, determination of 5 stereologic parameters was done in the vastus lateralis muscle after histochemistry of ATPase activity at 1 and 2 years. Body and skeletal muscle weights were proportional to the food intake. In AL-fed rats, muscle weights decreased between 1 and 2 years, in correlation with decreased type 2 myofiber numbers. In this group, fibrovascular index markedly increased with aging and muscle degeneration occurred at 2 years. In DR rats, there were no significant changes in muscle weights between 1 and 2 years. No histopathological changes were observed and the fibrovascular index was unchanged. These results demonstrated a protective effect of DR on the age-related skeletal muscle pathology in SD rats.     

Effects of early feed restriction in broilers. I. Growth performance and carcass composition

The effect of severe nutrient restriction at an early age was investigated in male and female broilers. At day 5 (females) or day 6 (males) post-hatching, chicks on limited intake were provided only enough feed (starter diet) to meet daily maintenance energy requirements only. Restriction was carried out for either 6 or 12 days, after which refeeding was on an ad libitum basis. Ad libitum fed controls were included. Minimal weight gain was noted during the period of restriction. Two weeks following refeeding, weight gains in the treated chicks exceeded that of controls. Final body weights (8 weeks) of 6-day-restricted chicks was slightly greater than controls, whereas 12-day-restricted chicks were significantly lower. Limiting nutrient intake at an early age resulted in better feed efficiency accompanied by less carcass fat and smaller abdominal fat pads. A similar, though not as dramatic effect was observed in female broilers. Results of early feed restriction on broiler growth patterns suggest that significant improvements in feed efficiency can be attained along with a reduction in total body fat.     

Effect of experimental feeding of Codiaeum variegatum leaves on growth, hematology, gonadal, and extra-gonadal sperm reserves of adult albino rats

Twenty-four male adult albino rats, weighing between 130 and 239 g, were randomly divided into four groups of six rats per group (A to D). The rats were fed either normal pelleted commercial feed containing 14.5% crude protein alone (group A) or feed supplemented with pulverized dry leaves of Codiaeum variegatum (garden croton) at the levels of 0.25% (B), 0.5% (C), and 1.0% (D). All four groups of rats were fed for 12 weeks, during which period clean water was provided ad libitum. Every 2 weeks, body weights of individual rats were taken and blood collected for hematology (packed cell volume (PCV), total and differential leukocyte counts). Hemoglobin concentration was determined at 4-week intervals. At the end of the 12-week study period, all rats were sacrificed; testes and epididymes of individual rats were weighed separately to calculate the organosomatic index for both organs. Thereafter, testicular and epididymal sperm counts were performed. Supplementing rat feed with C. variegatum leaves in treated groups (B, C, and D) resulted in reduced weight gain such that by the 12th week of study, the mean body weight of group D rats was significantly lower than that of the unsupplemented control (group A) rats. The testicular and epididymal organosomatic index for the different treatment groups were not significantly (P?>?0. 05) different from the mean values for group A rats. The hematological evaluation of the rats showed that supplementation at any of the level used did not significantly (P?>?0. 05) alter the mean PCV values. The mean total leukocyte and the mean absolute neutrophil counts (by the fourth week) for the treated groups were significantly (P?<?0. 05) higher than the corresponding values for the control groups. Likewise, the mean hemoglobin concentration for the treated groups was only slightly lower than the mean values for the control group for the greater part of the study period. The mean testicular sperm counts for the treated rat groups were generally lower in a dose-dependent manner, but was not significantly different (P?>?0.05) from the mean values for the control group. On the other hand, the mean epididymal sperm counts for the treated rat groups were significantly (P?<?0. 05) lower than the mean values for the control in a dose-dependent pattern. This study has shown that feeding male rats in particular and probably other animals in general on the leaves of garden croton at a level as low as 0.25% level of supplementation has the tendency to stimulate the immune function of animals but could severely reduce the testicular and epididymal sperm reserve counts, thereby reducing the reproductive efficiency of male animals. These results recommend further studies in respect to the immunostimulating and spermatotoxic properties of the leaves of this plant.     

Effects of oxytocin on the IGF-axis and some gastrointestinal hormones in ad libitum fed and food-restricted female rats.

The aims of this study were to investigate if administration of oxytocin to ad libitum fed and food-restricted female rats affects weight gain, body fatness, the IGF-axis, and some vagally mediated gastrointestinal hormones, such as gastrin, cholecystokinin (CCK) and somatostatin. Ad libitum fed and food-restricted (receiving 70% of the food intake of the ad libitum fed group) female rats were injected subcutaneously, once a day, for 10 days, with saline (control) or oxytocin (1 mg kg-1 bodyweight). The animals were killed 5 days after the last injection. Oxytocin-treated food-restricted females had more body fat and lower plasma levels of IGF-I, IGFBP-1 and IGFBP-3 compared with saline-treated counterparts. Oxytocin-treated ad libitum fed rats also had lower plasma levels of IGFBP-1 but contained less body fat, compared with saline-treated counterparts. There was no effect of oxytocin treatment on body weight or weight gain in either of the feeding groups. Except for gastrin, which was lower, there was no effect of oxytocin on the gastrointestinal hormones studied. The results indicate that oxytocin treatment influences fat deposition and the IGF-axis in female rats, but that the results are dependent on the nutritional status of the animal.     

Effects of intermittent feeding upon body weight and lifespan in inbred mice: interaction of genotype and age

Beginning at either 1.5, 6 or 10 months of age, male mice from the A/J and C57BL/6J strains and their F1 hybrid, B6AF1/J were fed a diet (4.2 kcal/g) either ad libitum every day or in a restricted fashion by ad libitum feeding every other day. Relative to estimates for ad libitum controls, the body weights of the intermittently-fed restricted C57BL/6J and hybrid mice were reduced and mean and maximum life span were incremented when the every-other-day regimen was initiated at 1.5 or 6 months of age. When every-other-day feeding was introduced at 10 months of age, again both these genotypes lost body weight relative to controls; however, mean life span was not significantly affected although maximum life span was increased. Among A/J mice, intermittent feeding did not reduce body weight relative to ad libitum controls when introduced at 1.5 or 10 months of age; however, this treatment did increase mean and maximum life span when begun at 1.5 months, while it decreased mean and maximum life span when begun at 10 months. When restricted feeding was introduced to this genotype at 6 months of age, body weight reduction compared to control values was apparent at some ages, but the treatment had no significant effects on mean or maximum life span. These results illustrate that the effects of particular regimens of dietary restriction on body weight and life span are greatly dependent upon the genotype and age of initiation. Moreover, when examining the relationship of body weight to life span both between and within the various groups, it was clear that the complexity of this relationship made it difficult to predict that lower body weight would induce life span increment.     

Specific heat output (SHO) of visceral organs/tissues: the hypothesis and first estimations

It was hypothesized that each organ/tissue has a characteristic specific heat output (SHO; kcal/d.g). Heat output (HO; kcal/d) is defined as the product of the SHO and the weight, g, of the organ/tissue. FHP (fasting heat production) is defined as the sum of HO values of all tissues of fasted animals. FHP and organ weight were perturbed by variations of food intake of 48 young swine before FHP and weights of 36 organ/tissue variables were measured. Cluster analysis was used to group the variables and simplify the analyses and indicated that small intestine, kidneys, liver and pancreas were principal sources of FHP. Regression estimates indicated that the SHO of pancreas and kidneys was high (1.1 to 1.9), that of small intestine, liver and colon was intermediate (.21 to .26), and that of stomach and lungs was low (.11 to .14). All other viscera tissues were assumed to have SHO near that for nonviscera, estimated at .0165 kcal/d.g. Mean values of FHP and empty body weight were 1856 kcal/d and 46,651 g respectively; thus the mean SHO value of all tissues was about .04 kcal/d.g. The SHO values of stomach, intestine, colon, pancreas, kidneys, liver and lungs were in the range 3- to 50-fold greater than SHO of the whole body and in the range 7- to 120-fold greater than the estimated SHO of the nonviscera. These findings indicate that the small intestine, liver and kidneys account for about 60% of HO from viscera or about 30% of total FHP.     

Diabesity: a polygenic model of dietary-induced obesity from ad libitum overfeeding of Sprague-Dawley rats and its modulation by moderate and marked dietary restriction

This study compared the effects of ad libitum (AL) overfeeding and moderate or marked dietary restriction (DR) on the pathogenesis of a metabolic syndrome of diabesity comprised of age-related degenerative diseases and obesity in a outbred stock of Sprague-Dawley (SD) rats [Crl:CD (SD) IGS BR]. SD rats were fed Purina Certified Rodent Diet AL (group 1), DR at 72-79% of AL (group 2), DR at 68-72% of AL (group 3) or DR at 47-48% of AL (group 4) for 106 weeks. Interim necropsies were performed at 13, 26, and 53 weeks, after a 7-day 5-bromo-2-deoxyuridine (BrdU)-filled minipump implantation. Body weights, organ weights, carcass analysis, in-life data including estrous cyclicity, and histopathology were determined. At 6-7 weeks of age SD rats had 6% body fat. AL-feeding resulted in hypertriglyceridemia, hypercholesterolemia, and dietary-induced obesity (DIO) by study week 14, with 25% body fat that progressed to 36-42% body fat by 106 weeks. As early as 14 weeks, key biomarkers developed for spontaneous nephropathy, cardiomyopathy, and degenerative changes in multiple organ systems. Early endocrine disruption was indicated by changes in metabolic and endocrine profiles and the early development and progression of lesions in the pituitary, pancreatic islets, adrenals, thyroids, parathyroids, liver, kidneys, and other tissues. Reproductive senescence was seen by 9 months with declines in estrous cyclicity and pathological changes in the reproductive organs of both sexes fed AL or moderate DR, but not marked DR. The diabesity syndrome in AL-fed, DIO SD rats was readily modulated or prevented by moderate to marked DR. Moderate DR of balanced diets resulted in a better toxicology model by significantly improving survival, controlling adult body weight and obesity, reducing the onset, severity, and morbidity of age-related renal, endocrine, metabolic, and cardiac diseases. Moderate DR feeding reduces study-to-study variability, increases treatment exposure time, and increases the ability to distinguish true treatment effects from spontaneous aging. The structural and metabolic differences between the phenotypes of DIO and DR SD rats indicated changes of polygenic expression over time in this outbred stock. AL-overfeeding of SD rats produces a needed model of DIO and diabesity that needs further study of its patterns of polygenic expression and phenotype.     

The gross morphology of skeletal disease in adult male breeding turkeys

The incidence of skeletal disease has been studied in two groups of male turkeys which were reared and kept as breeding birds. One group was fed ad libitum throughout life whereas the other was reared under dietary restriction to give body weights between 50% and 80% of the ad libitum values, depending on age. Losses during rearing were higher in ad libitum fed birds with lameness the major single cause. The majority of birds were killed at 55 weeks of age. It was noted that before death, more than half of the ad libitum birds were lame and the remainder showed gait abnormalities. By contrast, gait and posture was judged to be normal in many of the birds kept under feed restriction and none was lame. Post mortem dissections revealed a much higher incidence of skeletal disease in birds fed ad libitum. Although these observations suggest that feed restriction may alleviate skeletal disease in male breeding turkeys, it is suggested that such a strategy is of no long term benefit in parent breeding stock.     

Pancreatic and intestinal growth-promoting effect of truncal vagotomy in the rat

The effect of chronic subdiaphragmatic truncal vagotomy was investigated on body weight gain, food intake pattern, and also on intestinal and pancreatic growth, in adult rats. Two sham-operated groups, the one fed ad libitum, the other pair-fed with the vagotomized rats, served as controls. Body weight of vagotomized rats decreased in the first 5 postoperative days, due to hypophagia. Then, body weight increased as food intake reached the presurgery level. The rats were killed after 34 days of vagotomy. A moderate pancreatic and intestinal hypertrophy was observed in the vagotomized rats, while the tissue weight of and the DNA and protein contents in the colon and the oxyntic and antral areas of the stomach did not change compared to controls. The mechanism of the intestinal and pancreatic hypertrophy is unknown; several humoral and nervous factors may be involved in it.     

Effects of preweaning and postweaning feed restriction on the development of polygenic obese mice

Polygenic obese (M16) and control (ICR) mice were raised in litters of 8 (N8) or preweaning restricted in litters of 14 (N14). Mice were fed either ad libitum or postweaning restricted by automatic feeders from 4 to 10 weeks of age. All mice were fed ad libitum from 10 to 16 weeks. Preweaning restriction (N14) resulted in mice at 4 weeks with smaller body weights, fat percent, subcutaneous fat depot and adipocyte diameter than N8 mice. Most of the effects of preweaning restriction were overcome by 10 weeks. Obese mice, at 10 and 16 weeks, were heavier and had higher fat percent and larger fat depots with more and larger adipocytes than control mice. Postweaning restriction resulted in mice at 10 weeks with smaller body weight but greater fat percent, especially in the control line. Postweaning restriction of obese mice resulted in a higher percent of fat at 16 weeks. The change in eating pattern, stress or other factors associated with postweaning restriction, as imposed in this study, resulted in an altered metabolism that distributed a greater proportion of energy to fat storage than in the ad libitum fed mice. Ultimate body size and adipose tissue characteristics were determined primarily by genotype, whereas most effects of nutritional restriction were temporary.     

全反式维甲酸对生长发育期大鼠实质器官的损伤

目的 探讨体内过量全反式维甲酸（ATRA）对生长发育期SD大鼠的脑、心、肺、肝、肾和脾的影响。方法 以48只3周雄性SD大鼠为实验对象,随机分为对照组和3个实验组,ATRA剂量分别为40、60、80 mg/(kg·d),每组12只,进行连续10 d ATRA灌胃处理,记录SD大鼠每日体重,于灌胃第10天解剖称量各器官的重量以及计算脏器指数,然后对各器官进行HE染色。结果 ATRA灌胃后,与对照组比较,40 mg/(kg·d) ATRA组肾指数升高,体重变化差异无统计学意义;60 mg/(kg·d) ATRA组体重降低,心、肾指数升高,脾脏重量降低;80 mg/(kg·d)ATRA组体重明显降低,脑、心、肾指数升高,脑、脾重量降低;HE染色显示,与对照组比较,ATRA处理组的肺泡壁增厚,肾小管上皮细胞有空泡样改变,脾脏红髓出现较多巨噬细胞,而大脑、肝脏、心肌无明显组织学变化。结论 体内过量全反式维甲酸能够对生长发育期SD大鼠的肺、肾和脾有一定的损伤作用。     

Effect of dietary restriction and aging on polyploidy in rat liver

Liver polyploidy levels were compared as a function of age and diet in male Fischer 344 rats between 1 and 24 months of age. Dietary restriction was imposed on one group by reducing their food intake to 60% of ad libitum food intake. Histological sections of the livers of animals at each age and diet were examined. Diploid, tetraploid and octaploid nuclei were observed, and their size and frequency established. There were no differences in the diameter or volume of these size classes as a function of age or diet. An age-related decline in the percentage of diploid nuclei, coupled with an increase in the percentage of tetraploid and octaploid nuclei was observed in both groups. The major difference between the two groups was that the adult level of liver polyploidy was attained more slowly in the animals on dietary restriction as compared to the ad libitum fed controls. Polyploid cell formation in the liver is under the control of growth hormone, thyroid hormone and thymus, all of which might be influenced by dietary restriction.