Short-term Feeding Studies Research Articles

Evaluation of jojoba oil as a low-energy fat. 2. Intestinal transit time, stomach emptying and digestibility in short-term feeding studies in rats

The influence of jojoba oil (JO) incorporation in the diet on stomach emptying and intestinal transit time, and the digestion and absorption of JO were investigated in short-term feeding studies in rats. The animals were fed purified diets containing 18% (w/w) fat, of which half consisted of a mixture of lard and sunflower seed oil (SF) supplemented with an equivalent amount of JO. The control animals were fed a mixture of lard and SF (18%). No treatment-related differences were observed in the rate of stomach emptying or the intestinal transit time. Comparative lipid analysis of lymph, intestinal content, intestinal mucosa and faeces indicated that most of the ingested JO was degraded and absorbed. Part of the JO was present as wax ester in the lymph. Hydrolysis of JO was much slower than that of triacylglycerols and continued in the alimentary tract beyond the small intestine due to bacterial processes. JO did not influence the absorption of the conventional fat.

Physiological energetics of Japanese scallop Patinopecten yessoensis larvae

Growth and ingestion rates were determined for Japanese scallop Patinopecten yessoensis larvae reared at temperatures between 10 and 18 °C and fed concentrations of Isochrysis aff. galbana (clone T-ISO) cells between 5 and 30 cells · μl −1 to gain insight into energy balance. Veliger larvae were held in experimental chambers at densities of 0.5–100 · ml −1 to assess the influence of crowding on growth, respiratory and feeding rates. Long-term growth studies lasting 28 days indicated that growth was most rapid at highest food concentrations of 30 cells · μl −1 despite indications from short-term feeding studies that ingestion was at a maximum and independent of concentration between 15 and 30 cells · μl −1. Growth and ingestion are both reduced as the density of larvae increases. Feeding rates (6 h) remained fairly constant between densities of 1–5 larvae · ml −1 if food availability was increased proportionately. However, growth experiments lasting 28 days revealed extremely low survivorship if larvae are reared at densities of >1 2 · ml −1. Respiratory rates were higher than previously reported for bivalve larvae and reaching values of 13 nl · h −1 or 13–29 ml O 2 · g −1 [AFDW] · h −1. Oxygen consumption was reduced ≈ 35% at larval densities between 5 and 25 · ml −1 which are typical densities used when measuring metabolic rates of veliger larvae. Assimilation efficiencies between ≈ 55 and 80% were comparable to published values for mussel and oyster larvae but higher respiratory demand and comparatively slow growth rates for this species were reflected in lower growth efficiencies than those previously reported for bivalve larvae. Japanese scallop larvae apparently require a minimum food concentration of 7–15 cells · μl −1 (depending on size) to gain sufficient energy to support respiration and growth. Despite morphological similarities between species of bivalve larvae they may differ in their rates of energy acquisition and utilization.

Effects of BHA and related phenols on the forestomach of rats

To determine the pathogenesis of BHA-induced forestomach lesions, the nature and time course of the early lesions in the forestomach of Wistar rats were studied. The rats were given BHA at a dose level of 2% in a powdered diet or by oral intubation of 1 g BHA/kg body weight/day in arachis oil. The hyperplastic changes in the mucosa were visible 1 day after the second application. The localization was dependent on the mode of application. Dietary exposure yielded changes in the area of the limiting ridge; oral intubation of BHA produced lesions in the apex of the forestomach. In a subchronic 90-day feeding study in rats, no recognizable effect was observed when 0.125% BHA was incorporated into the diet as a solution in arachis oil. In reversibility studies, severe forestomach lesions observed after feeding 2% BHA for 6, 12 or 15 months regressed almost completely following withdrawal of the BHA for a period of 7 months. BHA induced similar forestomach damage in NMRI mice and Syrian golden hamsters, whereas guinea-pigs, a species having no forestomach, did not show comparable lesions. Substances with similar chemical structure were tested in short-term feeding studies ( tert-butylhydroquinone, 4-methoxyphenol, 1,4-dimethoxybenzene, hydroquinone, 3-methoxyphenol, 2-methoxyphenol, anisole, p-cresol, phenol and BHT). Only 4-methoxyphenol strongly affected the forestomach mucosa in a manner similar to that associated with BHA. The methoxy group in the para position seems to be important for the hyperplasiogenic activity.

Review of investigations of dichloromethane metabolism and subchronic oral toxicity as the basis for the design of chronic oral studies in rats and mice

In preparation for the design and performance of chronic toxicity and carcinogenicity studies in rats and mice on dichloromethane (methylene chloride; DCM), biochemical, mutagenicity, short-term, metabolic and subchronic feeding studies were carried out. These studies established that it was feasible to present DCM to rodents at adequate levels in drinking-water. Saturation of metabolic pathways was demonstrated in both rats and mice at oral doses of approximately 100 mg/kg. The lowest toxic effect levels after 90 days of treatment were found to be approximately 190 and 580 mg/kg for rats and mice, respectively. Dose, vehicle and the exposure regimen were found to affect DCM challenge to target tissues and its metabolism to CO and CO 2.

A short-term feeding study with deoxynivalenol (vomitoxin) using rats

Groups of 25 male and 25 female Sprague-Dawley rats were fed diets containing 0, 0.25, 0.5, or 1.0 mg of deoxynivalenol (DON)/kg body wt for approximately 9 weeks. Each animal's body weight and feed consumption were measured weekly. Upon termination of the study, each animal's body, heart, liver, spleen, thymus, and kidneys were weighed. A hematological assessment and a 16-parameter serum evaluation were conducted and 8 animals from each group were randomly selected to receive tritiated thymidine iv to assess mitotic activity in the esophagus, jejunum, and spleen. A statistically significant, dose-related decrease in body weight gain was observed for all treated females, but only the males dosed at 1.0 mg/kg were found to have a treatment-related weight gain suppression. The reduced body weight was attributed to a reduced feed consumption. Reductions that were observed in absolute organ weights, were not apparent after adjusting for body weight suppression. No dose-related hematological findings were found. Serum chemistry changes included increased concentrations of chloride and decreased concentrations of CO 2 and albumin, but only in the females. No histopathological lesions were attributed to DON treatment, but significant decreases in thymidine labeling occurred in the spleens and jejunums from the males dosed at 1.0 mg/kg.

The USDA trypsin inhibitor study. I. Background, objectives, and procedural details

Short-term feeding studies have shown that raw soy flour and purified trypsin inhibitors (TI) cause pancreatic hypertrophy and hyperplasia in certain monogastric animals. Prolonged exposure to high levels of TI in raw soy ultimately leads to pancreatic nodular hyperplasia and acinar cell adenoma in rats exposed to low levels of pancreatic carcinogens. Such change has been observed even in the absence of any exposure to known carcinogens. These results emphasized the need for chronic (2 yr) feeding trials which would clearly reveal dose response relationships of alterations in pancreatic pathology to dietary TI and possible interactions with dietary protein and fat. Here we report on the objectives and designs of the first phase of the USDA TI Study, including composition of diets, preparation, and analyses of test substances. To provide the requisite TI and protein levels, raw and heated defatted soy flours, soy protein isolates, and lactic casein were used. The interrelationship of dietary level of TI (93–1270 mg/100 g diet) and that of protein (10%, 20%, and 30%) to pancreatic function and pathology will be reported in the following three papers. Both serial and chronic sacrifice regimes, respectively, were employed with 26 diets and 40 weaning male Wistar rats per dietary group.

Nitrate Reduction by Roots of Soybean (Glycine max [L.] Merr.) Seedlings

Studies were conducted with 9 to 12 day-old soybean (Glycine max [L.] Merr. cv. Williams) seedlings to determine the contribution of roots to whole plant NO(3) (-) reduction. Using an in vivo -NO(3) (-) nitrate reductase (NR) assay (no exogenous NO(3) (-) added to incubation medium) developed for roots, the roots accounted for approximately 30% of whole plant nitrate reductase activity (NRA) of plants grown on 15 mm NO(3) (-).Nitrogen analyses of xylem exudate showed that 53 to 66% of the total-N was as reduced-N, depending on the time of day of exudate collection. These observations supported enzyme data that suggested roots were contributing significantly to whole plant NO(3) (-) reduction. In short-term feeding studies using (15)N-NO(3) (-) significant and increasing atom percent (15)N excess was found in the reduced-N fraction of xylem exudate at 1.5 and 3 hours after feeding, respectively, which verified that roots were capable of reducing NO(3) (-).Estimated reduced-N accumulation by plants based on in vivo -NO(3) (-) NR assays of all plant parts substantially over-estimated actual reduced-N accumulation by the plants. Thus, the in vivo NR assay cannot be used to accurately estimate reduced-N accumulation but still serves as a useful assay for relative differences in treatment conditions.

Human tissue lipids: occurrence of fatty acid isomers from dietary hydrogenated oils.

Hydrogenation of vegetable oils produces fatty acids with unusual structures having trans double bonds and double bonds in new positions of the acyl chain. This study was designed to determine which of these fatty acid isomers are incorporated or accumulated in humans during long-term dietary consumption of hydrogenated fats. The double bond position and configuration of the octadecenoate fraction of total lipids extracted from human heart, brain, liver, aorta, and adipose tissue were determined. The level of trans octadecenoate in the tissues as determined by both direct gas-liquid chromatography (GLC) and by GLC after silver nitrate thin-layer chromatography ranged between 0.4 and 5.0%, with an average of 2.7%. Tissues were found to contain trans-octadecenoic isomers having double bonds between the 6 and 15 positions, whereas cis double bonds were found to occur between the 6 and 14 positions. The distribution of double bonds in adipose tissue correlated very closely with the composition of dietary hydrogenated fat. Thus, essentially all of the unusual octadecenoic fatty acid isomers that are produced during vegetable oil hydrogenation are incorporated into human tissue. However, in contrast to results of short-term (1-6 months) feeding studies of animals, our results suggest that long-term (20-60 years) consumption of hydrogenated fats by humans does not lead to substantial preferential accumulation of positional isomers in human tissue total lipids.

Effect of Histidine Intake on Plasma and Urine Histidine Levels, Nitrogen Balance and N7-Methylhistidine Excretion in Normal and Chronically Uremic Men

This study assessed whether changes in plasma histidine or nitrogen balance could indicate the dietary histidine requirement in short-term feeding studies. Five normal and two chronically uremic men were fed diets varying in histidine content in a metabolic research unit. Subjects received amino acid diets for 71 ± 12 (sd) days during which time the histidine intake was varied between 60 and 2,800 mg/day at 8.0 ± 0.5 day intervals. The results indicated that both postabsorptive plasma histidine and urinary histidine correlated with the dietary histidine intake. However, in individual patients the response curve of plasma histidine to the dietary histidine intake did not demonstrate a consistent breakpoint which could be used to indicate the dietary histidine requirement. Rather, the histidine intake above which the plasma levels increased rapidly seemed to be influenced by the previous dietary histidine. Urinary histidine excretion also correlated with plasma histidine. N7-methylhistidine was increased in plasma and reduced in urine of the uremic patients as compared to normal subjects. Nitrogen balances were less positive with histidine intakes of 2 mg/kg/day or lower. These data support the finding that histidine is an essential amino acid in normal and chronically uremic man. However, clinical and metabolic studies of greater duration may be necessary to determine the daily histidine requirement.histidine essential amino acids nitrogen balance 3-methylhistidine

The influence of dietary minerals and fat on the absorption of lead

The nutritional factors influencing the absorption of lead from the gut have been studied using both intact animals and ligated gut loop preparation. Short-term feeding studies have been made in groups of six animals using diets of constant lead content (0.075 %) but in which the nutritional components were varied sequentially. Dietary lead was labelled with 203Pb. Absorption was determined in the carcass and individual organs by means of a small-animal whole-body counter. The results showed that absorption was enhanced to twenty-times control value by diets deficient in minerals and seven-fold by diets of high fat content. Conversely, high mineral diets have been shown to result in a two-fold reduction in lead absorption. The interaction of lead with individual dietary components has been further studied under controlled conditions using ligated gut loop preparations. Using this technique the relative roles of luminal interaction and tissue response for lead absorption have been explored and the kinetics of lead absorption determined.

Effect of sodium 2-methyl-4-chlorophenoxyacetate on spermatogenesis in the rat.

The substance 2-methyl-4-chlorophenoxyacetic acid (MCPA) is a widely used herbicide. Chlorophenoxyacetic acids or their derivatives and some impurities have teratogenic and embryotoxic properties in several animals (Courtney & Moore, 1971; Yasuda & Maeda, 1972), but little is known about the effects of MCPA or other chlorophenoxyacetic acids on the structure and function of male reproductive organs. In a short-term feeding study MCPA increased the relative weight of rat testes, but did not induce obvious histological alterations in the testes or other organs (Verschuuren, Kroes & den Tonkelaar, 1975). Because 2,4-dichlorophenoxyacetic acid and MCPA cause reduced fertility in rats (Schiller, 1964), we studied the effects of short-term administration of the sodium salt of MCPA on the composition of the seminiferous epithelium and spermatogenesis in the rat.

The effects of low-dose gamma-irradiation on the wholesomeness of mangoes (Mangifera indica) as determined by short-term feeding studies using rats.

1. A control diet and diets containing 150 g non-irradiated or 150 g irradiated mangopulp/kg were given to female rats from day 15 of the gestation period until weaning in trials 1 and 2, and from 40 d before mating until 28 d post weaning in trial 3. 2. Food intake and dry-matter digestibility were similar with all diets. 3. There were no significant differences between animals given the different dietary regimens in the daily body-weight changes of weanling males, pups, nursing females or females during the immediate postlactation period. 4. No differences in haematological or blood chemistry values were found which could be attributed to the ingestion of irradiated mangoes. There was no evidence for the presence of any toxic substances in the irradiated-mango-pulp diet. 5. Gross pathological observations revealed no aberrations which could be related to the ingestion of irradiated mangoes. 6. It may be concluded that the wholesomeness of mangoes was not affected by gamma-irradiation at a dose of 75 krd.

Rapeseed meal. IV. Continuous water extraction and short-term feeding studies in rats with the detoxified product.

AbstractA continuous two‐hour water extraction procedure is proposed instead of the former 14‐hour method to remove the thioglucosides from rapeseed presscake meal (RSM). This new procedure produced a complete removal of isothiocyanates (ITC) and a reduction of 97% in oxazolidinethiones (VTO). Net protein utilisation (n.p.u.) increased from 40 to 69% and protein efficiency ratio (p.e.r.) from 0.8 to 1.94. The detoxified material showed a satisfactory growth‐promoting capacity for the rat at the level of 10% dietary protein. It did not cause hypertrophy of the thyroid, as compared to the untreated meal, but it produced histopathological damage of variable intensity to this gland. It also caused a slight increase in the size of the liver although the histology of this organ does not show signs of damage. The importance of the minimal residual VTO content in the washed rapeseed meal upon the effect of thyroid histology is discussed and the presence of substances other than VTO and ITC which could be responsible for such adverse effects is postulated.

Acute (rat and mouse) and short-term (rat) toxicitystudies on dialkyl 79 adipate

Acute toxicity studies in rats and mice and a short-term feeding study in rats have been carried out on dialkyl 79 adipate. Diarrhoea was the only effect seen in mice after administration of single doses of up to 20 g/kg intraperitoneally to rats and mice and orally to rats. The oral LD50 in mice was between 8 and 12 g/kg.In the short-term study, rats were fed for 98 days on dietary levels of 0·0 (control), 0· 125, 0·25, 0·5 or 1·0%. No effects on growth, food consumption, haematological indices, results of urine analyses, serum chemistry, organ weights or histopathology were found at dietary levels of 0·125 or 0·25 %. Weight gain was slightly lower in females at the 1·0 % level and this was associated with a reduced food intake. An increase in relative kidney weight was found in both sexes at the 1· 0 % level and in females at the 0· 5 % level. In the blood, the haemoglobin concentration was reduced at the 1·0%level.The results have been compared with those of the corresponding phthalate ester. The no-effectlevel was approximately 125 mg/kg/day.

Short-term feeding study of sodium ferrocyanide in rats

Short-term feeding study of sodium ferrocyanide in rats

Studies on Brown FK. V. short-term feeding studies in the rat and pig

Brown FK was administered to rats at dietary levels of 0.0 (control), 0.001, 0.01, 0.1 and 1.0% for up to 21 wk and to miniature pigs in daily doses of 0, 100, 250 and 500 mg/kg for 24 wk. No effect was observed in either species with respect to growth rate, food consumption, organ weights or liver and kidney function. Apart from the observations described below, no histopathological changes were seen in any organs of the rats or pigs and no significant haematological abnormality was noted in either species. In rats, lipofuscin deposits were observed in the heart, skeletal muscle, kidney tubules, liver parenchymal cells and Kupffer cells at the 1.0% dietary level, in females at 13 wk and in both sexes at 21 wk. At this dietary level, one male showed myocardial changes similar in every respect to those seen following repeated daily administration of Brown FK by stomach tube and reported in paper III of this series (Grasso, Gaunt, Hall, Golberg & Batstone, Fd Cosmet. Toxicol. 1968, 6, 1). After 150 days' treatment, lipofuscin deposits were seen in renal tubular cells also at the 0.01 and 0.1% dietary levels. Deposition of lipofuscin was the principal change observed in pigs. It affected mainly the liver, in which it was observed in both males and females at all dosage levels of Brown FK and was accompanied by increased lysosomal enzyme activity, more marked at the higher dose levels. Lipofuscin was seen also in the heart in males, and here it was associated with an increased acid-phosphatase activity. It was not detectable in the heart in females. Lipofuscin was also present in the kidneys of both sexes, at the highest dose level in females and at all levels in males.

Short-term feeding study of the emulsifier Homodan MO in pigs

Groups of four female pigs were fed the emulsifier Homodan MO for 98 days at dietary levels of 0, 0·4, 2 and 10%. No significant effect was exercised on growth rate, food consumption, blood picture, liver and kidney function or organ weights and pathology, at any of the dietary levels administered.

Short-term feeding study of lauric diethanolamide in rats

A short-term feeding study has been carried out on lauric diethanolamide (LDE) in the rat. Dietary levels of 0.0 (control), 0.1, 0.5, 1.0 and 2.0% for 90 days evoked no adverse effect on the appearance or condition of the animals. Growth retardation was associated with diminished food intake, at and above the 0.5% level. Food refusal was demonstrably due to an effect of the test material on palatability of the diet. Terminal haematological examination revealed a reduction in the haemoglobin level, haematocrit and red cell count at the 1 and 2% levels in females but less pronounced effects were seen in males. Serum levels of glutamic-oxaloacetic transaminase were elevated at dietary levels of 0.5% and above in females but only at 0.5% in males. No untoward effect was observed in the renal function tests. The principal organ weight changes were: increases in the relative kidney weight in all test groups except at 0.1% in females and at 0.1 and 0.5% in males; and increases in the relative liver weight in females on the two highest levels. The types and incidence of histological lesions were comparable in control and test groups. A no-effect level was established of 0.1% LDE in the diet of rats for 90 days, a level equivalent to 50 mg/kg/day.

Acute (mouse and rat) and short-term (rat) toxicity studies on Carmoisine

Acute toxicity studies in rats and mice and a short-term feeding study in rats have been carried out on Carmoisine. The acute intraperitoneal LD 50 was approximately 1 g/kg in mice and rats. Orally, doses up to 8 g/kg in mice and 10 g/kg in rats were tolerated without lethal effect. Feeding of Carmoisine to rats at dietary levels of 0·0 (control), 0·05, 0·1, 0·5 and 1·0% for 90 days evoked no adverse effect on general health, growth or food consumption and no departure from normality was seen in the haematological studies and in the liver and kidney function tests. The principal organ weight finding was an elevated relative kidney weight at 1% in females. The types and incidence of histological changes were comparable in control and test groups. A no-effect level of 0·5% Carmoisine was established in the diet of rats for 90 days, a level equivalent to 250 mg/kg/day.

Acute (mouse and rat) and short-term (rat) toxicity studies on Ponceau 4R

Acute toxicity studies in rats and mice and a short-term feeding study in rats have been carried out on Ponceau 4R. The acute intraperitoneal LD 50s in male and female rats were 0·6 and 2·6 g/kg respectively. Corresponding values in mice were 1·9 and 1·6 g/kg. The oral LD 50 exceeded 8 g/kg in both species. Feeding of Ponceau 4R to rats at dietary levels of 0·0 (control), 0·5, 1·0 and 2·0% for 90 days evoked no adverse effect on the appearance or condition of the animals. Growth and food consumption were unaffected by treatment. Haematological indices and levels of serum glutamic-oxaloacetic and glutamic-pyruvic transaminases showed no change at levels up to 1% but at the 2% level, especially in females, a slightly depressed red cell count was associated with decreases in haemoglobin concentration and haematocrit value. Serum transaminase activity was also elevated at the highest level. No departure from normality was revealed in the renal function tests and organ weight measurements. The types and incidence of histological lesions were comparable in control and test groups. A no-effect level of 1% Ponceau 4R was established in the diet of rats for 90 days, a level equivalent to 500 mg/kg/day.