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The amount of metabolic fecal amino acids (MFAA) in dependence on the amino acid intake was determined for graded maize rations with 15N-labelled rats and the quota of labelled endogenous amino acids in faeces was calculated according to the isotope dilution method. The excretion of amino acids and MFAA in faeces are described as functions of the amino acid intake for 17 amino acids and regressively calculated. For all 17 amino acids investigated, there was a more or less steep increase of MFAA according to an increasing amino acid intake. In contrast to MFAA in N-free feeding, MFAA in feeding with pure maize (16.5% crude protein) increase to the 2- to 4.5-fold value. The thesis of the constancy of the excretion of MFAA can consequently be no longer maintained. The true digestibility according to the conventional method is, on an average of all amino acids, 7.3 units below the one ascertained according to the 15N-isotope method. For the limiting amino acids lysine and threonine the difference is biggest (23 resp. 17 units). Tryptophane as first limiting amino acid could not be determined. The true digestibility of nearly all amino acids ascertained for maize according to the isotope method is above 90%. For the limiting amino acids the expenditure resp. the loss of endogenous amino acids is biggest.

Growing rats received either a protein-free experimental diet or a diet containing 15% crude protein (whole egg). The crude fibre content of the diet was adjusted to 5%, 10%, or 20% by adding various proportions of what straw meal. Following a preliminary 7-day period of feeding the animals received L-14C-Leucine administered by stomach tube or by subcutaneous injection. In a 72-hour post-experimental period analyses were made to investigate the urinary and faecal excretion of radioactivity. About 50% of the amount of radioactivity excreted with the feaces were of endogenic origin. In general, higher percentages of straw meal in the diet produced higher levels of faecal 14C excretion. It was only in the animals placed on the whole egg diet that the TCA soluble portion of radioactivity was found to rise with the increasing straw content of the diet. The experimental results substantiate the assumption that native crude fibre influences the process of intestinal sloughing and, additionally, it is capable of abosrbing or adsorbing amino acids, peptides or protein, due to its spatial configuration. Similarly, it affects the digestion and resorption of proteins.

Rats were used in 7 trials each comprising 9 animals (197 total metabolism trials carried out at an environmental temperature of 30 degree). The animals received casein, casein+methionine, wheat gluten, wheat gluten+lysine as protein sources and were investigated for their nitrogen and energy turnover. The rations fed contained between 10% and 27% protein. Supplementation of the natural proteins with synthetic amino acids positively influenced the growth rate and the rate of N retention. The feeding of wheat gluten as sole protein source induced an absolute depression of the food and energy intake. The rates of tetention of protein and fat energy per animal/day showed opposing trends, in dependence upon the protein levels in the rations. It was found in the trials with casein that the proteins yielded 25%, or 18% of the total energy retention if the rats received low protein rations while the percentage of protein energy retention increased to 49-53%, if the rations contained high protein levels. The rats utilized between 67% and 84% of the metabolizable energy for the turnover of body energy. A negative correlation was found between the levels of energy utilization and protein intake. The energy demends for protein retention were calculated (mean of all trials) to be 1.67 kcal of metabolizable energy while those for fat retention amounted to 1.15 kcal. The energy demands for protein retention were not found to be dependent on the type of protein source used. The maintenance requirements of the rats were 102 kcal of metabolizable energy per kg LM0,75.

Albino rats received after nine days of adaptation to a fish meal diet in comparison with a gelatin diet 14C-U-Leucine and 15N-L-leucine via a pellet made from the specific diet after food deprivation for 15 h. Thereafter, the experimental animals consumed the non-labelled experimental diet ad libitum. Five times after the pellet intake, 30 min, and 1, 2, 4 and 6 h after injection of the labelled food, four experimental rats were sacrificed. The contents of the digestive tract and tissue samples were examined for 14C and 15N. We detected to following percentages of 14C-intake or the intake of 15N-excess (15N') in the TCA-soluble fraction of the gastric contents: [Formula: see text] We found in the TCA-soluble fraction of digesta of small intestine the following percentage of intake: [Formula see text] Where these values regarded as non-absorbed leucine, the 14C values obtained up to four hour period of experiment would be too high. Presumably, they are in the case of both diets simulated by other 14C-metabolites which originate from the leucine catabolism and reach the intestinal lumen. Amino acids labelled with 15N should be preferred in studies on the absorption of amino acids because, in case of catabolism, the 15N-aminogroup is excreted mainly in the form of urea via urine.

Methodical aspects are discussed concerning an analysis of time series which result from experimental investigations of metabolic parameters in rats. Especially there are 2 questions. Should the measured temporal variations of the metabolic parameters be recorded model-free by empirical regression or by functional expression? Before treatment, a time-period was designed in which the rats could become a stable group. Should be chosen a steady description of the temporal parameter changes for the whole time-period of the experiment or should they be described separately for the periods of acclimating and of treatment? Especially due to the discrete time points of measurements, the 1st approach also allows the description of possible jumps in the parameter changing at the begin of the treatment. As consequence of the 2nd mode of description always a jump results. Further parametric and non-parametric statistical procedures are used for analysis of the time series and for comparisons of the time courses. In detail following statistical problems are discussed: Homogeneity of dispersion along a single-measurements course or along a mean value course, equality resp. parallelism of 2 courses, and local or global level differences between 2 courses. Finally it is pointed out that besides the characterization of the mean temporal variations of a parameter also the description of correlation between 2 parameters by empirical regression curve may give information on the mechanisms which give rise to the observed phenomena.

The purpose of this paper was to show whether the activity of the zinc-dependent enzyme alkaline ribonuclease in zinc-sensitive tissues allows conclusions to be drawn on the Zn supply status. For this 27 weaned male Sprague-Dawley rats were divided into three groups of 9 animals each. A Zn deficiency group, which was given a diet with a Zn content of 3 ppm ad libitum, was compared to a pair-fed and an ad libitum control group with a Zn content in the diet of 60 ppm each. After 22 trial days the animals were killed, and the zinc and protein contents as well as the activity of the alkaline ribonuclease in the serum, testicles, femur, urine, liver, and kidneys were determined. Although the Zn concentration in the serum, testicles, femur, and kidneys of the deficiency animals were significantly reduced, the alkaline ribonuclease showed an increased activity only in the kidneys, in the testicles the activity was reduced, and in the serum, femur, urine and liver it remained unchanged. The protein concentration in serum and femur was reduced because of Zn deficiency, whereas the decrease in testicles, liver and kidneys must be attributed to the reduced feed intake. The influence of the dietary Zn deficiency on the activity of the alkaline ribonuclease was therefore more the result of an altered feed intake and growth rate than a direct effect of zinc on the enzymatic system. Therefore the determination of the activity of the alkaline ribonuclease can be excluded as a parameter for the diagnosis of Zn supply and Zn deficiency.

Male rats received in 8 groups of 10 animals each for a period of 7 days 7 synthetic diets and one semisynthetic diet on maintenance requirement level. A L-amino acid mixture corresponding to the pattern of egg protein without glutamic acid was the protein source of the synthetic diets. Glutamic acid was supplemented successively from 0 to 58 mol-% of the total amino acid content. The crude protein source of diet 8 was whole egg powder. On the 8th day of experiment 5 animals per group were labelled by intragastric infusion (i.g.) with 14C-U-glutamic acid. During the following 24 hours the excretion of CO2 and 14CO2 was measured. Throughout the experimental feeding body weight was relative constant, however, when the synthetic diets were fed it was necessary to increase the daily amount of energy from 460 to 480 kJ/kg0,67. The relative 14CO2-excretion within 24 hours was 68-75% of the dose. However, the main part of the amount of radioactivity excreted during 24 hours was found after 4 to 6 hours already. Exponential functions calculated from the data of cumulative 14CO2-excretion suggest the existence of a fast process of 14CO2-formation directly from 14C-glutamic acid, reaching a plateau within 2 hours and a slow process of oxidation of intermediates of glutamic acid metabolism, causing a continued 14CO2-formation even after 24 hours. The oxidation of 14C-glutamic acid to CO2 decreased 2 to 14 hours after i.g. labelling if the glutamic acid content of the diet increased. The same was found for the specific radioactivity of 14CO2. A storage of intermediates of glutamic acid before degradation was assumed.

In 4 experiments with 3 times 3 male Wistar rats each, which received rations with different protein contents (10; 25 and 40% crude protein in the dry matter), in the growth range between approximately 65 and 180 g live weight and with an environmental temperature of 30 degrees C, a total of 226 measurings of the total metabolism were carried out on the energy level maintenance, partly also with the insertion of a fasting day. The most important results were: On the energy level maintenance with the simultaneous catabolisation of body fat there was considerable protein energy retention, which amounted to between 30 and 40% of the retention achieved in the growth periods. The energy maintenance requirement can be determined with good reproducibility (standard mean deviation: +/-6%). The average energy requirement directly measured at the feeding level maintenance of 437 kJ metabolizable energy (ME)/kg live weight 0,75.d (n=224) differs insignificantly from the average value obtained by means of multiple regression analysis from experiment periods with feeding for growth 423 kJ ME/kg live weight 0,75.d (n=437). Consequently it is not necessary to differentiate between energy requirement for maintenance and energy requirement connected correlatively with the live weight (metabolic weight of the body) under conditions of growth. Energy maintenance requirement proved to be insignificantly dependent on the amount of protein in the feed. The relative values of protein quotas of 10, 25 and 40% in the feed were 100, 101 and 103%; the expected values (derived from the efficiency of ATP synthesis in the oxidation of carbohydrates and protein) amount of 100, 104 and 109%. The problem of the thermogenous effect of protein, which is also of great importance to human nutrition urgently requires further experimental investigation. For growing rats the best adaptation of the energy maintenance over the investigated period of development is achieved if the 2/3 potence of the live weight is chosen as the expression of the metabolic body weight. With high probability this can also be transferred to the characterisation of protein metabolisation.

In a complex investigation were evidenced 12 selected enzymes (oxidoreductases and hydrolases) in the pancreas of normoglycemic sand rats (Psammomys obesus). The sand rat developed a spontaneous diabetic metabolism by holding in the vivarium. The material based of animal groups that were fooded ad libitum or after defined dietetic regimes. The topochemical pattern of enzymes in the Langerhans' islets and exocrine acini can be compared between the sand rat groups and with the good investigated model of the Wistar rat. Because enzymhistochemical investigations of the sand rat pancreas absented, were the results compared with the rare specific observations of other animals and the man and the changed metabolic level were discussed under the especially food situation and in diabetes mellitus.

Methodical recommendations are suggested--predominantly for laboratory and small animals (rats and young chickens)--for the determination of parameters of the protein metabolism of the whole body after single doses of a mixture of 15N labelled amino acids by means of the determination of the temporal course of cumulative 15N excretion in urine and the assessment of the tracer kinetic data in a compartment model. These recommendations are to make it possible to carry out purposefully such experiments under comparable conditions. The advantages of this method are: the non-invasive character of the method; the possibility of repeating the experiment with the same animal; the adaptability to other methods of investigation (e.g. measuring energy metabolism); the relatively low expenditure of labour and requirement of test animals; the relatively good reproducibility of the method. Thus this method is a good supplement to the flooding and permanent infusion methods and should be used wherever the determination of parameters of the protein metabolism of the total body is sufficient.

The influence of different segments of the small intestine on the absorption of vitamin B6 from the mucosal to the serosal solution was studied with varying concentrations of pyridoxine . HCl (PN . HCl) of mucosal solution in 18 male and female rats, each weighing 150 to 160 g. The absorption was measured by the in vitro method with everted sacs, which were prepared of the duodenum (DA 1) and six additional segments (DA 2-7) of a length of 12 cm. The everted sacs were incubated at vitamin B6 concentrations of 0, 0.1, 0.5, 1, 2, 4 microgram PN . HCl per ml mucosal solution. Furthermore the dry matter and protein content of the intestinal wall was analyzed of 44 rats of either sex. Dry matter and protein content of the whole intestine of female rats were 3 per cent higher than of males. On the average of the male and female rats the protein content of the intestinal wall decreased from the proximal to the distal segments of the jejunum significantly by about 6 per cent, whereas dry matter content increased slightly. The ability to absorb vitamin B6 was significantly different between the intestinal segments, parallel in male and female rats. On the average of all concentrations the vitamin B6 uptake into the intestinal all and the vitamin B6 flux into the serosal solution was diminished by 30 and 50 per cent, respectively, from DA 1 to DA 7. A sexuell difference concerning absorbability of vitamin B6 did not appear. Between the concentration of PN . HCl of the mucosal solution and the absorption of vitamin B6 existed a highly positive correlation.

40 rats with a body weight of 100 g received 7 semisynthetic diets with different contents of glutamic acid and one diet contained whole egg. A L-amino acid mixture corresponding to the pattern of egg protein was the protein source of the semisynthetic diets. Glutamic acid was supplemented successively from 0 to 58 mol-% of the total amino acid content. On the 8th day of experimental feeding the animals were labelled by subcutaneous injection of 14C-U-L-glutamic acid. Subsequently the CO2- and the 14CO2-excretion were measured for 24 hours. In this period 64 to 68% of the injected radioactivity were recovered as 14CO2. The curve pattern of 14CO2-excretion indicates two different processes of 14CO2-formation. One characterizing the direct degradation of glutamic acid to CO2 with a high rate constant and a second one with a lower rate constant characterizing the 14CO2-formation via metabolites of glutamic acid. 77% of the total 14CO2-excretion in 24 hours resulted from the direct oxidation of glutamic acid and 23% from the oxidation of intermediates. When 14CO2-formation was measured 10 to 24 hours after injection of 14C-glutamic acid a positive correlation to the content of glutamic acid in the diet was observed. The intestinal tissue contribute considerably to the catabolization of glutamic acid, however, there seems to exist an upper limit for this capacity.

14 organs and tissues of the rat were tested for inhibitors of the respiratory chain. Electron transfer particles (ETP) from beef heart mitochondria served as test object. The respiratory measurements were carried out in the presence of serum albumin to avoid the reversible inhibition by fatty acids. Inhibition of the NADH oxidase system was observed with testicle, ovary, placenta, amnion, mammary gland, sceletal muscle, skin, liver, kidney, spleen, lungs and brain; the succinate oxidase system was inhibited by preparations from testicle, placenta, amnion, mammary gland, sceletal muscle and skin. Moreover, a self-inhibition of the succinate oxidase activity of the homogenates was observed with brain, liver and placenta. The respiration of the homogenates was inhibited by the respiratory inhibitor RF from rabbit reticulocytes in any case tested. With some objects besides inhibitions also stimulatory effects on the respiration of ETP appeared (vesicular gland, sceletal muscle, spleen, lungs). The inhibitory activities of the rat organs and tissues disappeared in most cases by heat treatment (10 min, 60 degrees C). A part of the inhibitors was sensitive against storage as well as freezing and thawing. They might be lipids (e.g. slow irreversible inhibition by fatty acids not relieved by serum albumin) or inhibitory proteins like RF and enzymes (proteinases and phospholipases). A protein nature is likely for the NADH oxidase inhibitors from liver, kidney, lungs, brain, sceletal muscle and placenta as well as for the succinate oxidase inhibitor from testicle. The results presented suggest the universal distribution and action of endogenous respiratory inhibitors. Presumably they occur in all mitochondria-containing cells. Their primary biological importance may be the triggering of the degradation of mitochondria. High inhibitory activities are present in cells with a high rate of renewal of the mitochondria and furthermore in maturation, differentiation and involution processes which are accompanied by a decline of the number of mitochondria.

Trials with graded Cu supplementation were carried out to establish the minimum and optimum Cu demands of pregnant, lactating and non-pregnants rats. The rats were investigated for the rate of live weight gains of the dams and young rats, for the number of stillbirths and, in particular, for the Cu status in the liver, body and blood serum of the animals and for coeruloplasmin activity. All Cu values obtained from the organs investigated had reached a saturation level at 8 mug Cu/g diet with the exception of the values for body Cu found in the dams that were killed on the day of delivery. The same results were obtained, for the above criteria, with lactating rats. So, it may be concluded that pregnant and lactating rats receive an optimum supply of Cu when they are fed a starch + casein diet containing 8 ppm Cu. For non-pregnant female rats, the limits that might be regarded as adequate were even below the 8 ppm level of dietary Cu. The saturation level for Cu was also found to be dependent, in regard of the criteria investigated, on the physiological state of the animals. It was found that, on the day of parturition, the level of Cu concentration and coeruloplasmin activity in the serum of the dams and the Cu content in the liver of the new-born rats were the best indicators for the state of Cu supply to the dams. However, after a sucking period of 17 days, the level of total Cu content in the dams was found to respond very sensitively to changes in the Cu supply.

48 male rats (body weight 80-100 g) were fed with 2 diets different in the glutamic acid content (diet I 2.42 and diet II 6.24% glutamic acid in the dry matter). The mixture of the other synthetic L-amino acids was adapted to the egg protein pattern corresponding 10% crude protein in the diet. Each diet was fed either on 73% or 98 to 104% of the energy maintenance requirement. After 7 days of experimental feeding 14C-U-L-glutamic acid was given to each group by intragastric infusion (i.g.), intraperitoneal (i.p.) or subcutaneous injection (s.c.), respectively, followed by a measurement of the CO2-and 14CO2-excretion during two subsequent periods of 3 hours. The CO2-excretion was lower in animals with restricted energy intake especially during the first 3 hour-period, which was started 2 hours after feed intake. The relative 14CO2-excretion (percent of the dose) was neither significantly influenced by the level of energy intake nor by the amount of dietary glutamic acid. The highest degradation rates of 14C-glutamic acid to 14CO2 were measured after i.g. application (more than 50%), followed by the i.p. injection (nearly 50%) and the lowest values were observed after s.c. injection (about 40%). These differences were only evident during the first CO2-absorption period. Furthermore the s.c. injection caused a lower specific radioactivity of CO2 compared with the data after i.g. and i.p. application. The results suggest the high metabolic activity of the intestinal tissue for glutamic acid.