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Biomedical subjects

H Yokogoshi

Publications and source records attributed to H Yokogoshi.

15 recordsLinked to original sources
PubMed1992

Changes in vitamin A status following prolonged immobilization (simulated weightlessness).

A study was conducted to investigate the effects of a simulated weightlessness induced by chronic immobilization on vitamin A status. To simulate the stress condition of weightlessness, rats were suspended for 10 days in a special jacket to which metal chains were attached. Animals received a commercial stock diet. Control rats were pair-fed in reference to the suspended rats. As compared with the control, prolonged immobilization resulted in a decrease in body weight gain and an increase in adrenal weight occurred. In the suspended rats, serum concentrations of retinol and retinol-binding protein (RBP) declined. Hepatic retinyl palmitate content increased, and the hepatic retinol level was decreased. The prolonged immobilization led to significantly reduced retinyl palmitate levels in the testis and lung as well as lowered testicular retinol levels. The results suggest that the stress state induced by prolonged immobilization caused accumulation of hepatic retinyl palmitate, decreasing the serum retinol concentration and retinyl ester content in the extrahepatic tissues.

Adrenal Glands↗
PubMed1992

The quality and quantity of dietary protein affect brain protein synthesis in rats.

The influence of the amino acid supply in diets with different quality and quantity of protein on the rate of protein synthesis in the brain was investigated. Amino acid concentrations in serum and brain altered in accordance with the amino acid levels of the diets, with the exception of some amino acids such as aspartic acid, glutamic acid, glycine and threonine. When rats were fed various levels of dietary casein (0, 5 and 20%), the aggregation of ribosomes increased and the fractional rate of protein synthesis tended to increase with the increase in dietary protein. When rats were fed a 20% casein diet, greater aggregation of brain ribosomes and protein synthesis rate were observed compared with those in rats fed 20% wheat gluten or gelatin diets. The RNA activity was related to the degree of the aggregation of brain ribosomes and the fractional rate of protein synthesis.

Amino Acids↗
PubMed1992

Effect of exercise on tissue protein synthesis in rats.

The effect of exercise on the protein metabolism in skeletal muscles (gastrocnemius and soleus), liver and small intestine was investigated in rats. Treadmill treatment for 7 d resulted in atrophy of the liver and small intestine, which was associated with a reduction in protein content. The rates of protein synthesis in the liver and small intestine were significantly suppressed in rats subjected to exercise. The change in protein synthesis in the visceral organs was mediated by the change in RNA activity (protein synthesis per unit RNA) but not by the change in RNA concentration. The tissue weight and the rate of protein synthesis in the gastrocnemius and soleus muscles were not affected by exercise. The results suggest that these changes in protein synthesis in the liver and small intestine may explain, at least partly, the atrophy of these organs which was observed after 7 d of exercise.

Animals↗
PubMed1991

Changes in hepatic metabolism through simulated weightlessness: decrease of glycogen and increase of lipids following prolonged immobilization in the rat.

The effect of simulated weightlessness on hepatic metabolisms of carbohydrates and lipids was investigated in rats that were chronically immobilized by means of a suspension harness. During the 10-day period of the suspension, the animals showed a substantial decrease in the hepatic glycogen content, whereas the content of hepatic total lipids was markedly elevated. Similar results were obtained when the "suspended" animals were provided with a regular amount of nutrients by a force-feeding procedure. In the suspended animals, hepatic parenchymal cells were filled with large fat droplets, and hepatic triglyceride contents were elevated. The prolonged immobilization led to a slight, but significant, increase in glucose-6-phosphatase activity in the liver, suggesting that an increased glycogen breakdown might have occurred in the suspended animals. However, it was unlikely that the increased amount of glucose produced by the glycogen breakdown was utilized as a substrate for the lipogenesis in the liver, because hepatic lipogenic enzyme activities were unaffected by the suspension. The results suggest that the hepatic lipids accumulate in animals exposed to a prolonged immobilization state, presumably due to a decreased lipolysis and/or a suppressed lipoprotein mobilization from the liver into the blood stream.

Adrenal Glands↗
PubMed1991

Effect of amino acid supplementation to a low-protein diet on brain neurotransmitters and memory-learning ability of rats.

The supplementation of methionine and threonine to a 10% soy protein isolate diet caused sharp decreases in the concentrations of brain tryptophan, serotonin and 5HIAA (5-hydroxyindole acetic acid) (e.g., in the hypothalamus, hippocampus, amygdala, locus coeruleus and brain stem). The serum tryptophan ratio (i.e., the ratio of the serum concentration of tryptophan to the sum of the concentrations of other large neutral amino acids, such as tyrosine, phenylalanine, leucine, isoleucine, valine and methionine) significantly decreased. The changes in catecholamines were small on the supplementation of amino acids to the soy protein diet. In the brightness-discrimination learning test, the number of total responses (R+, correct; R-, incorrect) of rats fed the amino acid-supplemented diet increased as compared with that of rats fed the nonsupplemented diet. The correct response ratio in the primary learning test did not change, but in the reverse learning test, the response ratio of rats fed the amino acid-supplemented diet increased. Therefore, it may be considered that the learning ability is correlated with the nutritional state.

Amino Acids↗
PubMed1991

Triiodothyronine administration affects urea synthesis in rats.

The purpose of the present study was to elucidate the mechanism by which thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investigated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid inhibitor) and treated with triiodothyronine (T3). Compared with that of normal or control rats, the plasma level of T3 was significantly lower in rats fed a diet containing PTU only and elevated in rats given PTU + T3. Urinary excretion of urea and the liver content of ornithine in rats given PTU + T3 were significantly lower than in rats given PTU only. The liver level of ornithine was closely correlated to the excretion of urea in the present study. Fractional rates of protein synthesis in liver, kidney and small intestine were lower in the hypothyroid group. However, most free amino acid concentrations, except ornithine in liver and plasma and the activity of hepatic argininosuccinate synthetase (EC 6.3.4.5) of hypothyroid rats, were significantly reduced as compared with those of control or hyperthyroid rats. The results indicate that the increased hepatic ornithine content in the hypothyroid rats may be one of the regulatory factors causing changes in urea synthesis.

Administration, Oral↗
PubMed1991

Effect of suspension hypokinesia/hypodynamia on tissue protein turnover in rats.

The effect of suspension hypokinesia/hypodynamia on the protein metabolism in skeletal muscles (gastrocnemius and soleus) and visceral organs (liver and small intestine) was investigated in the rat. Suspension for 10 days resulted in atrophy of the visceral organs as well as the skeletal muscles, which was associated with decreases in the amounts of visceral and muscle protein. There was marked breakdown of muscle protein, which was reflected by increases in the urinary excretion of N7-methylhistidine and cathepsin D activity. Measurement of protein synthesis by the L-[4-3H]phenylalanine method revealed that the synthesis in the gastrocnemius, but not in the soleus, muscle was suppressed on suspension for 10 days. Thus, both the increased catabolism and decreased synthesis of protein in the muscles may be causally related to the muscle atrophy occurring in suspension. In the visceral organs, on the other hand, the protein synthesis was found to increase in hypokinetic rats. Moreover, the concentration of visceral protein was also increased, despite the decreased amount of muscle protein. These changes in protein metabolism in the liver and small intestine may explain, at least partly, the slightly positive nitrogen balance which was observed after long-term weightlessness.

Animals↗
PubMed1991

Effects of various dietary protein contents on vitamin A status of rats exposed to prolonged immobilization through suspension.

The investigation was carried out to clarify the effects of various dietary protein contents on vitamin A status of rats exposed to prolonged immobilization through suspension. A rat wearing a special jacket to which metal chains were attached, was suspended for 10 days as an analogy of simulated weightlessness. Five groups of suspended rats were fed on the diets containing various amounts of casein (5, 10, 20, 40 and 60, w/w%), while control group received the 20% casein diet. Through suspending animals, a decrease in body weight gain and increase in adrenal weights occurred. Serum albumin concentration of the suspended rats fed on the 10, 20, 40 and 60% diets were the same as that of the control rats. The suspended rats showed lowered serum retinol concentrations and elevated hepatic retinyl palmitate contents without noticeable differences between the diets. The hepatic retinol levels were not clearly affected. In the suspended rats, testicular levels of retinyl palmitate and retinol significantly decreased as compared with the control. These parameters' alterations did not relate to serum albumin concentration and were independent of dietary protein levels. The results suggest that stress state may cause suppression of releasing hepatic vitamin A, resulting in a lowered serum retinol concentration, being independent of nutritional status of protein.

Adrenal Glands↗
PubMed1986

Selection of dietary protein and carbohydrate by rats: changes with maturation.

Weaning (21-day-old; 40-50 g) male rats given simultaneous access to two foods, containing 18% casein and 15 or 70% carbohydrate (dextrin), tended to consume only 29-35% as much protein as carbohydrate (i.e., protein/carbohydrate ratios were 0.29-0.35). With maturation, when animals weighed 100 g or more, about half continued this pattern of nutrient choice, but the others abruptly began to consume considerably larger proportions of protein, exhibiting protein/carbohydrate ratios as high as 0.80-1.00. Each adult animal's protein/carbohydrate ratio tended to vary only slightly (s.e. = 3% of means). Adult protein/carbohydrate ratios were not correlated with fasting brain 5-HT or 5-HIAA levels. These marked differences among rats in eating behavior would not be observed when--as is usually the case--animals are given access to only one diet.

Age Factors↗
PubMed1978

Studies on carbamoylphosphate synthetase in livers of rats fed a protein free diet supplemented with methionine and threonine and injected with N-acetylglutamic acid.

Supplementation of methionine and threonine to a protein free diet reduces urinary nitrogen excretion in rats, and it has been assumed that N-acetylglutamic acid may have a regulatory role in urea synthesis. The present paper reports the effect of supplementation of methionine and threonine on the levels of N-acetylglutamic acid and of carbamoylphosphate synthetase (EC 2.7.2.5) in liver. In spite of a significant decrease in urinary urea when methionine and threonine were supplemented to the protein free diet, the activity of carbamoylphosphate synthetase was not reduced. On the other hand, following injection of glutamic acid, N-acetylglutamic acid or N-acetylglutamine, the excretion of urinary urea of rats fed the protein free diet supplemented with methionine and threonine was significantly reduced whereas the level of carbamoylphosphate synthetase was the same in each group. Furthermore, the concentrations of N-acetylglutamic acid in liver of rats fed the protein free diet or the protein free diet supplemented with methionine and threonine were the same. Therefore, these results indicated that, when methionine and threonine were supplemented to the protein free diet, the changes in the levels of N-acetylglutamic acid and of carbamoylphosphate synthetase in liver does not contribute to the reduced body weight loss and urinary nitrogen excretion.

Ammonia↗
PubMed1977

Effect of supplementation of methionine and threonine to a protein free diet on urinary excretion of nitrogen and tissue free amino acids in rats.

It was previously reported that methionine and threonine supplementation to a protein free diet had a greater nitrogen sparing effect than methionine supplementation along. The reduced urinary nitrogen excretion by methionine and threonine is due to the reduced excretion of urea. In the present study, the changes in tissue level of free amino acids and ammonia were investigated. Ornithine is one of the urea cycle inter-mediates and may play an important role for urea formation, therefore the liver concentration of ornithine was also determined. The contents of ammonia in plasma were the same in these two groups and the ammonia content in liver of rats fed the control diet was smaller than that of rats fed the protein free diet supplemented with methionine and threonine. The contents of some amino acids in tissues were significantly reduced. The concentrations of aspartic acid, glutamic acid, alanine and serine in plasma and liver of rats fed the protein free diet supplemented with methionine and threonine were, particularly, significantly reduced as compared with those of rats fed the protein free diet. In addition to the decrease of free amino acids which are considered to be nonspecific nitrogen carriers from the peripheral tissues, the concentration of ornithine in liver was also significantly reduced. The results suggest that the decreased migration of free amino acids from peripheral tissues to the decreased level of liver ornithine would efficiently reduce the urea formation in rats fed the protein free diet supplemented with methionine and threonine.

Amino Acids↗
PubMed1976

Some factors affecting the nitrogen sparing action of methionine and threonine in rats fed a protein free diet.

It was previously reported that methionine and threonine supplementation of a protein free diet had a greater nitrogen sparing action than methionine supplementation alone. Investigated in this study were (1) effects of depletion of labile body protein on the nitrogen sparing action of methionine and threonine supplementation of a protein free diet, (2) the effects of graded levels of methionine and threonine on urinary nitrogen excretion, (3) the effect of supplementation of other amino acids to the protein free diet plus methionine and threonine on the urinary excretion of nitrogen and (4) sex differences in the nitrogen sparing action of methionine and threonine supplementation of a protein free diet. After 10 days of feeding a protein free diet to deplete the body labile proteins, nitrogen excretion in urine of female rats was significantly reduced within the first 2 days of feeding a protein free diet supplemented with methionine and threonine. After 7 days of feeding a protein free diet supplemented with methionine and threonine, nitrogen excretion was reduced when even as little as 0.0188% of each amino acid was added. The supplementation of all essential amino acids to the protein free diet did not reduce the urinary excretion of nitrogen further than the supplementation of methionine and threonine, but improved the nitrogen balance slightly. The excretion of urinary nitrogen by female rats fed the protein free diet supplemented with small amounts (0.0188%) of methionine and threonine was significantly reduced after 7 to 14 days of feeding. In males, small amounts of methionine and threonine had no significant effect at either 7 or 14 days.

Amino Acids↗
PubMed1975

Comparison between the metabolic effects of tryptophan and histidine deficiencies in the rat.

Rats fed a tryptophan-free diet for 2 days showed less weight loss but more nitrogen loss than those fed a histidine-free diet. The metabolic nature of the body weight loss and of urinary nitrogen loss in rats fed the tryptophan-free diet was investigated in comparison with those fed the histidine-free diet. More body water was retained in rats fed the tryptophan-free diet than in those fed the histidine-free diet. This suggests that the lesser weight loss associated with tryptophan deficiency than with histidine deficiency may be due to the greater water content in rats fed the tryptophan-free diet. The tryptophan contents of the muscle, plasma, and liver decreased rapidly in rats fed the tryptophan-free diet, whereas the histidine contents of these tissues did not decrease as much as in rats fed the histidine-free diet. The conversion of radioactivity of (U-14-C)phenylalanine into respiratory CO-2 and liver and muscle proteins of rats fed the tryptophan- and histidine-free diets were compared. The relative recovery ratio of 14-C into respiratory CO-2 was found to be higher in tryptophan deficiency than in histidine deficiency, and the recovery ratio in muscle was lower in tryptophan deficiency than in histidine deficiency. These results suggest that the greater nitrogen loss seen in tryptophan deficiency than in histidine deficiency may be due to reduced synthesis of muscle protein, presumably due to the low free-tryptophan content in muscle resulting from the tryptophan-free diet.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

Preparation of peptide mixture with high Fischer ratio from protein hydrolysate by adsorption on activated carbon.

A peptide mixture with a high Fischer ratio (a molar ratio of Val + Leu + Ile to Phe + Tyr) was prepared by the adsorptive separation of a casein hydrolysate by activated carbon. The effects of the pH and ethanol content of the hydrolysate on the Fischer ratio and on the yield of the resulting peptide mixture were examined. A peptide mixture with the Fischer ratio of 31.6 was obtained at pH 2.5 without the addition of ethanol. The Fischer ratio was close to the ratio of the infusion solution of free amino acids that is now used for patients with liver diseases.

Adsorption↗