The effect of feeding regimen on apparent and true ileal nitrogen digestibility for rats fed diets containing different sources of protein

A standard protocol is required for carrying out routine ileal nitrogen (N) digestibility rat bioassays. The aim of this study was to determine the effects of feeding regimen on ileal N digestibility in rats fed diets containing different protein sources and chromic oxide as an indigestible marker. The experimental design was seven diets (protein‐free (PF), enzyme‐hydrolysed casein (EHC), lactalbumin (LAC), wheat gluten (GLU), fish fillets (FIS), soy protein isolate (SOY), zein) by three feeding regimens (frequent, meal, ad libitum) with 10 rats per diet. In frequent feeding, food was provided for eight 10 min periods between 09:00 and 16:00; in meal feeding, food was provided for one 3 h period at 09:00; in ad libitum feeding, food was available at all times. Rats were fed for 8 days, killed and digesta were collected from the terminal 20 cm of the ileum. The diets and freeze‐dried digesta were then analysed for N and chromium (Cr). There were statistically significant effects of feeding regimen on ileal digesta weight, ileal N/Cr ratio and apparent (AND) and true (PF TND, EHC TND) N digestibility. Mean N digestibilities, averaged over four dietary treatments (LAC, GLU, FIS, SOY), for the frequent, meal and ad libitum feeding regimens respectively were: AND, 88.8, 90.4, 85.8; PF TND, 94.9, 96.4, 97.0; EHC TND, 92.7, 94.0, 95.6. Although the N digestibilities were higher for rats on meal feeding compared with frequent feeding, the only statistically significant differences were for the lactalbumin treatment, and these were small in absolute terms. This study demonstrated that meal feeding was suitable and frequent feeding was unnecessary for most protein sources tested, and that ad libitum feeding was not ideal because of the smaller and more variable quantities of digesta collected and the more variable ileal N/Cr ratios. © 2002 Society of Chemical Industry     

The effect of 2,4-dichlorophenol on enzyme activities and other parameters in parenchymatous organs of rats]

After repeated administration of 2,4-dichlorophenol the aminopeptidases AAP and LAP, and the alkaline phosphatase in various organs were influenced. The treatment causes stimulatory or inhibitory activities. Also with histological and histochemical methods damages could be detected.     

Experimental effect of the quality of various diets on blood vessel walls

In experiments on rats it was shown that the rations containing casein (18 and 5% calorific value) and fatty component completely substituted for butter (30 and 50% calorific value), in the presence of hypersholesterolemia, hyper-beta-lipoproteinemia and hypo-alpha-lipoproteinemia, induced changes in the elasticity of the aorta, coronary and intrarenal arteries. Swelling, separation, disappearance of elasticity and tinctorial properties of elastic fibers of tunica media vasorum and internal elastic membrane were observed in the animals given the above rations during 1-6 months. In the coronary and intrarenal arteries these changes were attended by vacuolization and destruction of the medial smooth muscle cells. The vascular alterations were most early and drastically manifest in the animals that received the ration with 5% protein and 50% butter. No vascular changes were noted in the animals given sunflower oil in similar amounts and during the same period as butter, with 18% protein in the ration. Such action of sunflower oil was not pronounced when the ration contained 5% protein, large amount of cholesterol (1% of the ration mass) or trans-isomers of unsaturated fatty acids.     

Influence of methandrostenolone on some aspects of protein metabolism in rats in the context of various protein rations]

Wistar male-rats receiving by mouth dianobol for 10 days and 9 months and fed on rations with different proportions of protein were investigated. Dianobol is shown to produce under definite conditions changes in the intensity of the protein synthesis in the muscle tissue and liver of the test animals and also to raise the activity of tryptophan-peroxidase and of alanine-amintransferase, the protein level in the ration being here of substantial importance. With its long-term administration to rats dianobol displays an androgenic effect on the gonads and the supernumerally genitals without exercising any stimulating action on the weight gain.     

Cellular and humoral immunity of volunteers consuming diets with various protein levels

Eight male volunteers were examined for the functions of T and B lymphocytes (blast transformation reaction, leukocyte migration inhibition test, lymphocyte cytotoxicity, suppressor activity, measurement of IgG, IgM, IgA, IgD and IgE in blood serum, and concentration of natural staphylococcal antibodies) in the background of varying protein supply of the body. Reduction of the protein quota (5 to 9 g/day according to nitrogen) in the diet led to inhibition of the activity of immunocompetent cells.     

Effect of diets with different caloric levels on blood protein turnover

The content of albumin, fibrinogen, the summary fraction of IgG + transferrin and summary serum proteins in the blood plasma, their turnover constant and half-life were investigated in 122 Wistar male rats that during a month received rations with reduced calorific value at the expense of carbohydrates or due to gradual diminution of protein, fat and carbohydrates in the ration. It has been shown that the permissible level of the ration calorific value reduction depends not only on the energy deficiency level, but also on the ration components at the expense of which the reduction is achieved. The reduction of the animals' nutrition calorific value influences the general development of growing rats and the blood protein turnover rate, the specific action on the mechanisms of the blood protein half-life regulation being of a greater importance than the energy deficiency.     

Behavior of certain parameters of lipid and energy metabolism. 5. Effects of high-fat and low-fat diets on certain biochemical parameters in rat livers before and after change of diet]

Typical metabolic patterns are detectable in the livers of growing rats after feeding diets with high (25%) or low (2%) fat contents. In view of the elucidation of problems related to the regulation of the metabolic processes, it is of interest to know in what way these metabolic patterns change after short-time change from the one diet to the other and if there are hierarchies. Within 2 days after change of diet, the enzymes glucose-6-phosphate dehydrogenase, NAD-malate dehydrogenase, lactate dehydrogenase, citrate synthase and fatty acid synthase were affected, only the 3'.5'-c AMP-splitting phosphodieterase showed no change. The metabolites lactate and pyruvate also changed, inversely to lactate dehydrogenase activity, the lactate-pyruvate ratio remaining almost constant. Acetyl CoA also responded in a characteristic manner. The single parameters were differently affected by the kind of the change of diet (from high-fat to low-fat diet or inversely). For example, glucose-6-phosphate dehydrogenase responded very rapidly to the change from the high-fat to the low-fat diet, malate dehydrogenase behaved inversely, and citrate synthase responded to both changes. Consequently, the regulatory processes after change of diet start from different sides. It is thinkable that this behaviour is related to the different roles of the determined parameters in fat and energy metabolism.     

The vitamin E allowance of rats on different combinations of sunflower and soybean oils in their diets

Soybean oil and its combinations with sunflower oil, as 1:1 and 1:3, were used in the rations intended for rats. As it is evidenced by the data on the content of tocopherol in the tissues, malonic dialdehide in the liver, diene conjugates in the liver and red blood cells, and red blood cell resistance, the fatty products used in the rations sufficiently provided the animals with antioxidants. The role of tocopherol isomers and phosphatides, as synergists of antioxidants in varying combinations of soybean and sunflower oils, formed for simultaneous intake of linoleic and linolenic acids with the ration, has been analyzed.     

Protein fractions and total proteins in serum of rats on high fat diets]

This paper deals with the behaviour of serum protein fractions in rats fed 22 resp. 52 weeks a 50% or 3% fat diet using Millipore electrophoresis. The total serum protein concentration was also estimated. In rats on the high-fat diet the albumin fraction significantly dropped, while elevated levels of alpha 1- and gamma-globulin fraction were found. Serum protein content was slightly elevated in rats fed the diet 22 weeks, but this elevation was only significant after 52 weeks feeding. Within the same diet group there were no significant differences observed.     

Influence of qualitatively different diets on the reproductive capacity and function of the adrenal cortex in rats with experimental toxic hepatitis]

The effect of a diet rich in protein and the group B vitamins on the function of the ovaries and adrenal cortex, as well as on the reproductive capacity of animals with experimental affection of the liver produced by administration of carbon tetrachloride was studied on 115 mongrel albino female-rats. A high-standard semisynthetic diet devised at the Institute of nutrition of the AMS of the USSR and three isocaloric experimental diets calorifically enriched by 20, 50 and 100 per cent and containing a double amount of the group B vitamins were used in tests. The protein and vitamins enrichment of the diet, although failing to normalize the estrual cycle, neveretheless contributed to a significant reduction of the embryos' death in pregnant animals, the restoration of the reproductive capacity of the rats being directly proportional to the degree of the protein enrichment of the diet. The use of experimental diets helped normalize the adrenal cortex function in pregnant rats with toxic hepatitis, this manifesting itself in the falling amount of corticosterone in the blood serum outflowing from the suprarenals down to the control level.