The effects of reduced dietary intake upon the body and organ weights, and some clinical chemistry and haematological variates of the young Wistar rat

Two groups, one of each sex, of 5-week-old Wistar rats were fed ab lib for 5 weeks with a commercial diet (LAD 2). Four other groups of each sex, were given the same diet daily; each male received 21, 19, 17 or 15 g and each female 17, 16, 15 or 13 g. In a second experiment, in addition to the groups fed ad lib, each day for 5 weeks males were given 30 ('daily ad lib' group), 23, 22 or 21 g and females 25 ('daily ad lib' group), 19, 18 or 17 g. Rats, particularly males, fed ad lib showed differences, e.g. in body weight, with rats fed 'daily ad lib' even though food consumption was similar. Rats fed reduced amounts of diet had smaller livers, increased haemoglobin concentration, erythrocyte count, haematocrit, and plasma chloride. These rats excreted an increased volume of more alkaline urine of lower specific gravity with more precipitated triple phosphate than rats fed ad lib. In the comparisons of the modestly reduced food intake groups with the ad lib groups the significant decreases found in plasma protein, urea and alkaline phosphatase activity probably arose mainly from differences in post-prandial intervals. In groups where the reduction in food intake was greater, the decreases observed were not wholly dependent upon the post-prandial interval.     

Ethanol administration in the drinking fluid to pregnant rats as a model for the fetal alcohol syndrome

Addition of ethanol (ET) to the drinking fluid of pregnant rats has been questioned as an experimental model for the fetal alcohol syndrome (FAS). This model, however, closely simulates human alcohol intake, and in this study we used a modified version of previous protocols to overcome their major defects. A group of female rats was given 10% ET in drinking fluid for one week, 15% for the second week, 20% for the third, and 25% for the fourth, at the end of which they were mated with non-treated males and given 25% ET throughout gestation. Three groups of non-ET treated sex and age-matched rats were studied in parallel: (1) normal controls receiving solid diet ad lib, (2) paired fed rats, and (3) rats fed ad lib the solid diet mixed with 50% fiber. In the ET group, food intake decreased as ET consumption augmented, the ET calories comprising over 30% of the total energy intake during pregnancy. Total energy intake was similar for ET group and normal controls, and was higher than in paired fed animals or those on 50% fiber diet. Body weight gain in ET rats was similar to those on 50% fiber diet, lower than in normal controls and higher than in paired fed animals. At the 21st day of gestation, rats on ET had plasma ethanol levels of 147 +/- 18 mg/dl and higher plasma osmolality than in the other groups studied. In ET rats, fetal body weight was lower than in either normal controls or rats on 50% fiber diet, and fetal body length was shorter than in any other group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of undernutrition on transit time and body weight of rats.

Rats given 50% and 25% of their ad lib food intake were taken as undernourished, while those on ad lib intake served as controls. Water was given ad lib for all rats. Body weight of all rats was measured daily. It showed decrease in undernourished groups but not to the extent expected from calorie intake. Fifty tiny (1-2 mm) orange coloured plastic markers mixed with food were given to all rats, at 11.00 p.m., and were collected from faeces at regular intervals of 1 h each till 80% of markers were obtained. Period (hrs) for collection of 80% markers was taken as total transit time. It showed increase with increased undernutrition (ad lib 38.9 +/- 2.1 hrs, 50% cal 68.2 +/- 5.3 hrs, 25% cal 105.00 +/- 3.3 hrs). Delayed transit time in the undernourished by prolonging contact period between food and absorptive surface of intestine probably caused increase in absorption of nutrients and thus counteracted against the loss in body weight of underfed rats.     

Two years feeding toxicity study of tamarind seed polysaccharide in rats (author's transl)

Tamarind seed polysaccharide (Glyloid) was incorporated at the level of 4, 8, 12% in a standard commercial diet and fed ad lib. to male and female rats for 2 years. No significant changes were noted in the behavior, mortality, body weight, food intake, biochemical analysis of urine and blood, hematological test, organ weight and histopathological findings of rats receiving Glyloid. In all groups containing control group, spontaneous diseases with aging, such as myocardial change, nephropathy, mammary tumor (in female), pituitary tumor etc., were seen. These diseases played important role as the cause of death of the dead rats.     

Effects of food deprivation on caffeine consumption in male and female rats

The effect of food deprivation on caffeine consumption was investigated in male and female rats utilizing two-bottle preference tests. During ad lib food and water access, proportional consumption of six increasingly concentrated caffeine solutions (0.01-0.125%) steadily declined as concentration increased with no sex differences. Across concentrations, females tended to ingest more mg/kg caffeine than males. Food deprivation increased both proportional and mg/kg caffeine consumption in both sexes. When returned to ad lib food, proportional, but not mg/kg, caffeine consumption returned to pre-deprivation levels. Consumption of a quinine solution (0.02%), comparable to the caffeine in two-bottle preference, declined somewhat during food deprivation. These results indicate that caffeine preference and mg/kg consumption are increased by food deprivation and that this effect does not result from increased preference for bitter tastes per se. Rather, the results suggest that increased caffeine intake during food deprivation is due to a specific interaction between reduced body weight and the drug. The results also suggest that the deprivation effect is somewhat weaker in females than males, perhaps due to sex differences in reactivity to caffeine.     

Sweet taste preference in women smokers: Comparison with nonsmokers and effects of menstrual phase and nicotine abstinence

Cigarette smokers weigh less than comparably aged nonsmokers, and many gain weight following cessation. Though some evidence suggests that nicotine reduces food intake, with a selective effect on sweet-tasting foods, the issue remains unresolved. In the current study, 64 women (20 smokers, 26 never-smokers, and 18 ex-smokers) were tested for sweet taste preference; 9 of these smokers were studied under conditions of both ad lib smoking and overnight abstinence, in three hormonally verified menstrual phases. 1) Although no overall differences were detected in taste preference among the three groups, significantly more smokers than nonsmokers preferred the higher sucrose concentrations. 2) No significant differences due to menstrual phase were observed. 3) Although preference ratings did not differ significantly between overnight abstinence and ad lib smoking, a subset of smokers who preferred higher sucrose concentrations rated their preference for the solutions significantly higher during the ad lib smoking sessions. Our findings suggest that smoking and nonsmoking women differ with respect to taste preference and that, at least in a subset of female smokers, preference is affected by nicotine abstinence/acute dosing.     

Behavioural changes on diet selection and serotonin (5-HT) turnover in rats under pizotifen treatment.

The effects of pizotifen on protein and carbohydrate self-selection in rats over a seven-day period, and on 5-HT turnover was studied. Four groups of male Wistar rats were individually caged and ad lib fed with a standard (SD) and (50%) carbohydrate-enriched diet (CED), sweet (diet group I) or not (diet group II). Food intake was measured daily 4 hr after IP injection of pizotifen (2.5 mg/kg) or vehicle. 5-HT and 5-HIAA in the hypothalamus (Hy), striatum (St) and hippocampus (Hi) were assayed on the 8th day of the experiment. Pizotifen increased the consumption of SD. The absolute intake of CED remained totally and daily unchanged, while the percentage proportion was reduced. Total food intake was increased by the drug which seemed to affect the proportion rather than the absolute amounts of carbohydrate and protein consumed. This effect was independent of the carbohydrate taste. There was a decrease of 5-HT levels in the Hi, while 5-HIAA/5-HT ratio was increased in the Hy and in the Hi of animals that consumed sweet carbohydrate. The above data suggest a role of pizotifen on 5-HT central metabolism and diet selection and support the view that changes of 5-HT metabolism in the Hy and Hi are responsible for protein selection and the regulation of SD/CED ratio, but they cannot explain drug's effect on total food intake.     

Increased adiposity on normal diet, but decreased susceptibility to diet-induced obesity in mu-opioid receptor-deficient mice

The mu-opioid receptor encoded by the Oprm1 gene plays a crucial role in the mediation of food reward and drug-induced positive reinforcement, but its genetic deletion has been shown to provide food intake-independent, partial protection from diet-induced obesity. We hypothesized that mu-opioid receptor-deficient mice would show an even greater, intake-dependent, resistance to high-fat diet-induced obesity if the diet comprises a sweet component. We generated an F2 population by crossing the heterozygous offspring of homozygous female Oprm1(-/-) mice (on a mixed C57BL/6 and BALB/c genetic background) with male inbred C57BL/6 mice. Groups of genotyped wild-type (WT) and homozygous mutant (KO) males and females were fed either control chow or a high caloric palatable diet consisting of sweet, liquid chocolate-flavored Ensure together with a solid high-fat diet. Food intake, body weight, and body composition was measured over a period of 16 weeks. Unexpectedly, male, and to a lesser extent female, KO mice fed chow for the entire period showed progressively increased body weight and adiposity while eating significantly more chow. In contrast, when exposed to the sweet plus high-fat diet, male, and to a lesser extent female, KO mice gained significantly less body weight and fat mass compared to WT mice when using chow fed counterparts for reference values. Male KO mice consumed 33% less of the sweet liquid diet but increased intake of high-fat pellets, so that total calorie intake was not different from WT animals. These results demonstrate a dissociation of the role of mu-opioid receptors in the control of adiposity for different diets and sex. On a bland diet, normal receptor function appears to confer a slightly catabolic predisposition, but on a highly palatable diet, it confers an anabolic metabolic profile, favoring fat accretion. Because of the complexity of mu-opioid gene regulation and tissue distribution, more selective and targeted approaches will be necessary to fully understand the underlying mechanisms.     

HPLC-purified human satietin does not produce conditioned taste aversion in rats

Human satietin is thought to be an endogenous glycoprotein that can suppress food intake and body weight. However, it was also found to be aversive when rats infused intracerebroventricularly (ICV) with human satietin were subjected to a two-bottle taste aversion test. More recently, the human satietin previously thought homogenous was separated by HPLC into two Peaks, denoted as A and B. In the present study, male Sprague-Dawley rats were fitted with chronic third ventricle cannulas and presented with fluid for 1 h/day, while food was given ad lib. After training, the rats were ICV infused with either artificial cerebrospinal fluid, Peak A or Peak B of human satietin. Peak B significantly reduced short-term and 24-h food intake, whereas their fluid intake was nonsignificantly attenuated. Peak A had no affect on either food or fluid intake on the day it was administered. When the rats were given the two-bottle taste aversion test neither compound was found to be aversive. These data suggest that Peak B may contain satietin(s) which could be a candidate for an endogenous satiety agent.     

The effect of chronic underfeeding on organ weights of rats How to interpret organ weight changes in cases of marked growth retardation in toxicity tests?

Growing male rats were kept on a restricted feed intake. After 13 weeks they reached a final body weight of 250 g in comparison with 366 g of their ad lib. fed controls.The relative weights of the heart, kidneys, spleen, pituitary and prostate/ seminal vesicle were not altered by underfeeding. The relative weights of the brain, adrenals and testes were increased by 30 to 40% in the feed-restricted groups, the thyroid by about 20%. The relative weight of the liver was decreased by about 30%.When growth is markedly reduced in a toxicity experiment alterations of this kind in the organ weight: body weight ratios have to be expected as a physiological response of the organism to decreased feed intake. They must be differentiated from organ weight changes resulting from primary toxic influences of the drug tested.     

Effect of schedule feeding on water intake and urine output in rats

Water intake of schedule feeding rats was correlated to food intake through variations in calorie content of food. On intake time restriction (3 h) schedule, it was positively correlated while on amount restriction schedule (25% and 15% food) correlation was negative. Water-to-food ratio (W/F) of 3 hFW rats was decreased whereas W/F of 25% and 15% food animals, it was increased as compared to ad lib W/F. On calorically rich (3.2 cal/gr) diet 3 hFW rats food intake (7.8 +/- 0.6 gr) and water intake (4.7 +/- 0.3 ml) remained unaltered, while ad lib rats food intake (14.7 +/- 0.9) was decreased and water intake (16.2 +/- 1.1) increased as compared to their intake on calorically poor (2.8 cal/gr) diet. Urine percent over water intake (u/w x 100) was inversely related to food intake of rats (on ad lib food, 13.8%; on 25% food 29.1% on 15% food 31.8%) excepting for urine percent of 3 hFW rats which was (7.6%) disproportionately decreased.     

The association of serum leptin with the reduction of food intake and body weight during electroacupuncture in rats

Previous studies indicate that acupuncture or electroacupuncture (EA) treatment reduces body weight and food intake in rats by increasing the level of anoretic peptides and decreasing that of orexigenic peptides in the hypothalamus. Considering a well-established role of leptin as a major regulator for feeding behavior in the hypothalamus, we hypothesized that EA might exert its effect via increasing serum leptin levels. In this study, we tested our hypothesis by evaluating the effects of EA on food intake and body weight, as well as on serum leptin levels in rats. Rats were randomly divided into 3 groups: AL (fed ad libitum with no treatments), Holder (fed ad libitum with daily holder restraint) and EA (fed ad libitum with daily holder restraint and 100 Hz EA stimulation) groups. During the four-week experimental period, daily food intake and body weight were measured. At the end of the experiment, levels of serum leptin and corticosterone, and plasma epinephrine (Epi) and norepinephrine (NE) were determined. Here we demonstrate that EA treatment indeed led to reduction of food intake and body weight, and to an increase of serum leptin levels. The level of Epi, NE, and corticosterone increased in the Holder group, but such increase in the level of aforementioned stress hormones was not observed in the EA group. Overall, our results suggest that EA treatment reduces food intake and body weight in rats possibly through increasing leptin levels, and that this effect of EA is not due to the stress caused by the daily holder restraint.     

Testicular effects of cyclohexylamine hydrochloride in the rat

Testicular effects of cyclohexylamine hydrochloride (CHA) were investigated in Wistar and Sprague-Dawley rats. Groups of 25 rats were fed diets containing 6000, 2000 and 600 ppm CHA for 90 days and in addition ad lib., pair-fed and paired-weight control groups were used to assess the role of reduced food intake in the development of testicular lesions.Rats fed diets containing 6000 and 2000 ppm CHA showed significant decreases in food consumption, body weight and body weight gain. However, significant increases in the incidence of testicular lesions were found only in those animals fed 6000 ppm CHA. Absence of a similar incidence of lesions in either the paired-weight of pair-fed control groups indicated that inanition was not primarily responsible for the development of the lesions. The toxicological significance of these findings is discussed.     

Lung collagen and elastin after ozone exposure in vitamin B-6-deficient rats

The effects of vitamin B-6 deficiency and ozone exposure on selected features of connective tissue metabolism in lung were investigated in groups of weanling male rats fed one of three diets: B-6-supplemented, fed ad lib; B-6-deficient, fed ad lib; or B-6-supplemented, restricted to the food intake of deficient rats for 5 weeks. Also, perinatal rat pups were studied that were nursed from dams fed one of the 3 diets from parturition to day 15 of lactation. During the final week of each experiment, half of the rats in each of the groups were exposed to 0.64 ppm of ozone (23.5 h per day). The collagen and elastin content, collagen synthesis rate, total protein synthesis rate, and lysyloxidase activity of lungs were measured. Perinatal pups rendered vitamin B-6-deficient were particularly sensitive to ozone exposure (65% died as compared to fewer than 5% of the ad lib or food-restricted controls). When L-proline incorporation into collagen and total protein was investigated using lung minces, food restriction and B-6-deficiency resulted in about one-half the incorporation normally observed. Total lung lysyl oxidase activity was also decreased in B-6-deficient and food-restricted rats compared to B-6-supplemented rats fed ad lib. Exposure to ozone resulted in increased lysyl oxidase activity and collagen synthesis in lungs from B-6-supplemented rats, but such responses were not observed in B-6-deficient or food-restricted (FR) rats exposed to ozone.     

Relation between dopaminergic control of pituitary lactotroph function and deceleration of age-related changes in serum prolactin of diet-restricted rats

Pituitary lactotroph function has been examined in diet-restricted (6 hr/day) male and female rats and compared with that in animals fed ad lib. After 12 months the age-related increase in serum prolactin concentration was significantly attenuated in diet-restricted female rats. Similar effects were not observed in male rats. Isolated superfused anterior pituitary glands removed from rats on both feeding regimens at 12 or 18 months and challenged with dopamine in vitro (5 microM) did not show differential prolactin secretion. No significant differences were observed in serum prolactin secretion in vivo after administration of bromocriptine (3 mg/kg body weight, sc) or haloperidol (1.75 mg/kg body weight, ip). These results do not support an altered dopamine receptor function in the anterior pituitary lactotrophs. In contrast, central dopamine receptor function in rats 12 months of age was altered by dietary restriction, since the frequency of cataleptic responses to haloperidol injection (2 mg/kg body weight, ip) was significantly depressed in the test animals.     

Long-term in vivo carcinogenicity study of phenytoin (5,5-diphenylhydantoin) in F344 rats

The carcinogenicity of phenytoin was studied in F344/DuCrj rats. Phenytoin was mixed with powdered basal diet at levels of 0 (control), 0.025 or 0.05% and groups of 50 male and 50 female rats were administered these doses ad lib. for 2 yr. Survival of the treated male and female rats was similar to that of the corresponding controls. There was a dose-related decrease in mean body weight of treated female rats, but body weights of treated male rats were similar to those of controls. A variety of tumours developed in all groups including the control group, but all of the neoplasms that were observed were histologically similar to known spontaneous tumours in this strain of rats and no statistically significant increase in the incidence of any particular tumour type was evident in the treated groups of either sex. Nor was there any evidence of accelerated tumour induction in any phenytoin-treated group. Thus, it is concluded that under the conditions used in this experiment phenytoin had no carcinogenic potential in F344 rats.     

Hypothalamic norepinephrine synthesis rate in overfed, underfed and fasted mice

Hypothalamic norepinephrine (NE) synthesis rate during acute (1-day and 3-day) and chronic (11-day) overfeeding (14 kcal/day) and underfeeding (7 kcal/day) and 24 hr food deprivation was determined in four-week-old female mice. Mice were fed ad lib quantity or 51% of ad lib in a meal-feeding paradigm, a 60% fat diet providing constant protein intake across groups. NE synthesis rate, during the thermic effect of a meal, was calculated from the rate of NE accumulation after monoamine oxidase inhibition by pargyline and clorgyline. Acute and chronic underfeeding versus overfeeding had no effect on NE synthesis rate in the hypothalamus or in the rest of brain, or chronically in hypothalamic nuclei. In mice deprived of food for 24 hr, NE synthesis rate in the paraventricular nucleus only was five-fold higher than in fed mice. Thus, NE synthesis rate within the hypothalamus appears to be more related to short-term food intake regulation than to the thermic effect of eating or body fat content.     

Subchronic toxicity study of Caramel Colour II in F344 rats.

Caramel Colour II is a distinct type of colourant with a pronounced reddish hue. It is made with sulphite reactants but without ammonia. The red colour and a high alcohol solubility provide functional characteristics that are important in foods or beverages containing natural flavour extractives. Caramel Colour II is widely used in ice creams and liqueurs; however, it represents less than 1% of total caramel colour manufacture. The toxicity of Caramel Colour II was evaluated in a 13-wk study in Fischer-344 (F344) rats. The test material was mixed with demineralized water and the solutions were given to the animals ad lib. in the drinking fluid. The concentrations of caramel colour in the drinking fluid were adjusted periodically to achieve the desired caramel colour intake/kg body weight/day. Groups of 20 rats/sex were given Caramel Colour II at levels of 0, 4, 8, 12 or 16 g/kg for at least 13 wk. There were no deaths in any of the groups fed Caramel Colour II. All rats fed caramel colour had soft faeces. All treated groups also had lower fluid consumption that was attributed to poor palatability of the high concentrations of caramel colour that were fed. A number of changes observed (reduced food consumption in all treatment groups except males given 4 g/kg; significantly lower body weights for males given 12 g/kg or more and for females given 8 g/kg or more; lower urine volume and higher specific gravity) were attributed to the reduced water intake and not considered to be toxicologically significant. There were no consistent treatment-related alterations in haematology or blood chemistry variables, and random changes noted were not associated with macroscopic or microscopic pathological alterations. There were no toxicologically important pathological findings. Based on this study, Caramel Colour II was not toxic in F344 rats treated for 13 wk. The highest dose level tested in this study (16 g/kg) was considered to be the no-observed-adverse-effect level.     

Body weight regulation in rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin

Rats treated with a sublethal dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 15 μg/kg) exhibited reduced feed intake and loss of body weight for the first 3 weeks after treatment. During the next 10 weeks, TCDD-treated rats maintained their body weight at a lower nearly constant percentage of that of control rats fed ad libitum. At no time did rats treated with TCDD exhibit hyperphagia which would have returned their weight to a normal level. Control rats pair-fed to TCDD-treated rats for more than 7 weeks displayed compensatory hyperphagia when permitted to feed ad libitum and their weight recovered to a near-normal level. The lower level of body weight in TCDD-treated animals was apparently due to a reduction in the regulation level or “set-point” for body weight. The following findings in TCDD-treated and control rats fed ad libitum supported this idea. First, when the reduced weight of the TCDD group was challenged by changes in the caloric density or palatability of the diet, TCDD-treated rats exhibited adjustments in feed intake and body weight that were essentially identical to those of control rats. Second, when body weight was manipulated by feeding a high-calorie diet or by restricting feed intake, both TCDD-treated and control rats quickly returned to weight levels from which they had been displaced. Third, carcass analyses conducted 7 weeks after treatment revealed that TCDD-treated rats had lower absolute amounts of body fat, protein, and water. However, when these constituents were expressed as percentages of total body weight no remarkable differences from the control were observed. Fourth, when TCDD-treated rats were induced to overeat and restore body weight to the same levei as control rats fed ad libitum, TCDD-treated animals did not reassume a normal body composition but became obese. Obesity was also observed when control rats were induced to overeat. Thus, TCDD-treated rats regulate their body weight in the same fashion as control rats but at a weight regulation level or set-point that is markedly reduced.     

Antioxidant and lipid peroxidation activities in rats fed with Aspergillus carbonarius carotenoid

Effect of feeding partially saturated canthaxanthin (PSC), purified from Aspergillus carbonarius mutant, was studied using four groups of female albino rats (n = 6) for 4 weeks. While the control group received basal diet ad libitum, Groups I, II and III were fed with basal diet containing 50, 100 and 250 ppm PSC, respectively. PSC feeding did not cause any significant changes in food intake and there was no gain in body weight either. PSC included in the diet significantly decreased cholesterol in blood. There was 44.75% and 60.54% decrease in LDL-cholesterol in rats fed with 50 and 100 ppm carotenoid. Hepatic ascorbic acid content increased by 44.59% in rats fed with 50 ppm PSC. Dietary PSC at 250 ppm lowered lipid peroxides by 19.49%. Activities of antioxidant enzymes, glutathione transferase and catalase were significantly higher in serum and liver of PSC fed rats compared to the controls. The results suggested that PSC feeding can induce hypocholesterolmic and antioxidant properties in rats.