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Biomedical subjects

K Muramatsu

Publications and source records attributed to K Muramatsu.

At least 109 records · Page 6Linked to original sources
PubMed1988

Regulation of essential fatty acid intake in the rat: self-selection of corn oil.

The present investigation was conducted to determine if rats can recognize the essential fatty acid (EFA) in the diet. Weanling rats were pre-fed a 30% hydrogenated coconut oil (30HCO) diet containing 1% cholesterol for 2 or 4 weeks to produce EFA deficiency, then allowed to choose between the fat-free (FF) diet and the 0.5, 1.0, or 2.0% corn oil diet, and between the 0.5% HCO diet and 0.5% corn oil diet. Rats pre-fed the 30HCO diet for 2 weeks selected the corn oil-containing diets for a few days at the beginning of the experiment, but the rats pre-fed for 4 weeks could not recognize the EFA-containing diet. The non pre-fed animals continued to prefer the EFA-containing diet for about 2 weeks. From these results we could demonstrate that rats have a mechanism to distinguish the EFA in their diet, but this EFA selection ability was only in the early period of the experiment, and diminished soon after.

Animals↗
PubMed1987

Lung function in prematurely delivered rabbits treated with a synthetic surfactant.

We treated prematurely delivered rabbit pups with the synthetic surfactant that has been named Exosurf. By weight, Exosurf is 61.8% dipalmitoylphosphatidylcholine, 6.8% hexadecanol, 4.6% tyloxapol, and 26.7% NaCl. This simple mixture, suspended at 15 mg lipid X ml-1 water, has appropriate in vitro characteristics for a lung surfactant substitute. As determined by static pressure volume relationships performed after 30 min ventilation, lungs treated with Exosurf accepted significantly more gas at maximal inflation (36 versus 15 ml X kg-1 body weight) and had significantly greater volumes during deflation that did saline-treated control lungs; lungs treated with natural rabbit surfactant (SAM) had significantly larger volumes at maximal inflation (65 versus 35 ml X kg-1) and during deflation than did the Exosurf-treated lungs. After 30 min of ventilation with oxygen and fixation at 10 cm H2O pressure, the ratio of air space to tissue space was determined by a point-counting technique, and mean linear intercepts were measured for air spaces. Exosurf-treated lungs were intermediate between SAM and saline-treated lungs in both measurements. With positive pressure ventilation to maintain a tidal volume of 6.5 to 7.5 ml X kg-1, total compliance was significantly greater and inspiratory pressure significantly lower in both SAM- and Exosurf-treated animals than in saline-treated control animals, although the lungs of the SAM-treated animals were more compliant than the lungs of animals treated with Exosurf. During the first minute of positive pressure ventilation, lungs treated with SAM or Exosurf expanded equally rapidly, both expanding more rapidly than the saline-treated lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Relationship between maturation of the skin and electrical skin resistance.

In 16 newborn infants (24 6-39 wk 6 days 830-3390 g) at ages between 0-70 days, the skin's electrical resistance was measured. Over 30 min we sequentially measured direct current resistance between two skin electrodes placed on the abdomen. The resistance was found to be low in very premature infants with gestation ages of 30 wk or less. It increased with both gestational age and postnatal age. In these infants, the resistance measured at 30 min during the first 4 days of life (3.4 +/- 0.3 K omega; mean +/- SD) was significantly less than that found at 20-70 days (8.8 +/- 1.2 k omega; p less than 0.001). The relationship between the infant's electrical skin resistance (y) and the gestational age (x) best fit the exponential formula: y = 7.42 X e0.24x X 10(-4) + 2.74. This formula shows that the electrical skin resistance increases exponentially during the last trimester. The measurement of electrical skin resistance is a quantitative method that can be utilized to evaluate the gestational age of infants.

Galvanic Skin Response↗
PubMed1987

Effect of dietary glycine on methionine metabolism in rats fed a high-methionine diet.

The alleviation mechanism of methionine toxicity by dietary glycine was investigated in weanling rats fed a high-methionine diet. When rats were fed a 10% casein diet containing 2% methionine, the activities of methionine adenosyltransferase, cystathionine beta-synthase, and cystathionine gamma-lyase, which participate in the methionine metabolism in the transsulfuration pathway, were significantly enhanced. But the addition of 2% glycine to the high methionine diet did not cause further increase in these enzyme activities; the activities of methionine adenosyltransferase and cystathionine beta-synthase were rather decreased while cystathionine gamma-lyase activity was not altered. Methionine transaminase activity was essentially insensitive to the dietary addition of methionine and glycine. In rats fed a high methionine diet, the hepatic methionine level was significantly increased with a concomitant decrease in the levels of glycine, serine, and threonine. The addition of glycine to the high methionine diet effectively suppressed the enhancement of the hepatic methionine level and almost completely restored the glycine level, but it only partially restored the serine level and further decreased the threonine level. From these results, it is suggested that the alleviating effect of dietary glycine on methionine toxicity is primarily elicited by the restoration of the hepatic glycine level rather than by an increase in hepatic enzyme activity.

Amino Acids↗
PubMed1987

Self-selection of histidine and arginine intake and the requirements for these amino acids in growing rats.

The regulation of histidine and arginine intake in rats was investigated using the self-selection feeding method. The usefulness of the self-selection feeding technique for the determination of amino acid requirements is also discussed. When weanling rats were offered a choice of two diets differing only in histidine or arginine content for 2 weeks, they chose diets to support maximal growth, with the exception of some groups that did not grow to the maximum level. Histidine and arginine intake of the self-selecting rats ranged from 0.25% to 2.22% and from 0.43% to 2.43% of the diets ingested. These results demonstrate clearly that rats have the ability to consume a minimum amount that satisfies histidine and arginine needs for maximal growth. Previous and the present results suggest that the self-selection feeding method is a useful technique for the determination of amino acid requirements in growing rats.

Animals↗
PubMed1987

Comparative effects of choline chloride and phosphatidylcholine on plasma and liver lipid levels in rats fed a choline-deficient high cholesterol diet.

The effects of dietary choline chloride and phosphatidylcholine (PC) on plasma and liver lipid levels were investigated with rats fed a choline-deficient high cholesterol diet. The plasma cholesterol level significantly increased as the dietary level of choline chloride was increased. The addition of PC to the choline-free diet also resulted in an increase in the plasma cholesterol level, but the magnitude of the increase was significantly lower than that by choline chloride. There was no difference, on the other hand, in the effect of choline chloride and PC on the plasma triglyceride level. The contents of cholesterol and triglyceride in the liver markedly decreased in rats fed a diet containing PC at a high level. The fecal excretion of neutral sterol significantly increased by the addition of PC at a high level, but not at a low level. The results indicate that the plasma cholesterol level, but not triglyceride, is differentially influenced by dietary choline chloride and PC, and that PC has both hyper- and antihypercholesterolemic effects when compared with a choline-free diet and a diet supplemented with choline chloride, respectively.

Animals↗
PubMed1986

Relationship between amino acid composition of diet and plasma cholesterol level in growing rats fed a high cholesterol diet.

The effects of dietary sulfur-containing amino acids and glycine on plasma cholesterol level were studied in rats fed amino acid mixture diets containing cholesterol. The relationship between the amino acid composition of dietary proteins and plasma cholesterol levels was also investigated in rats fed diets containing various kinds of protein such as casein, egg albumin, pork protein, fish protein, corn gluten, wheat gluten and soy protein. Feeding the amino acid mixture corresponding to casein led to an approximately two-fold level of plasma total cholesterol as compared with feeding the amino acid mixture corresponding to wheat gluten. It was possible to reduce the plasma cholesterol of rats fed the amino acid mixture of the casein type by increasing the proportion of cystine in the total sulfur amino acids. Inversely, the deprivation of cystine resulted in an enhancement of the plasma cholesterol of rats fed the gluten type amino acid mixture. Glycine had a tendency to resist increases in the plasma cholesterol level. A significant negative correlation was noted between plasma cholesterol levels and the content of cystine in intact dietary proteins. The results suggest that the differential effect of dietary proteins on plasma cholesterol level is mainly associated with sulfur-containing amino acids included in the protein, regardless of whether it is of animal or plant origin.

Amino Acids↗
PubMed1986

Effects of methionine and related compounds on plasma cholesterol level in rats fed a high cholesterol diet.

The comparative effects of methionine and its structurally and metabolically related compounds on plasma cholesterol level were investigated with rats fed a high cholesterol diet. The plasma cholesterol level was significantly enhanced by the dietary addition of methyl compounds such as L-methionine, D-methionine, choline and betaine. On the other hand, the intermediary metabolites of methionine such as homocystine, cysteine and 3-methylthiopropionate reduced plasma cholesterol. S-Methyl-L-cysteine and dimethylglycine had no significant effect. The plasma cholesterol-elevating effects of methionine, betaine and histidine were all prevented, more or less, by the concurrent addition of glycine to the diet, suggesting the existence of a common mechanism for their effects. The results support a possibility that the plasma cholesterol-elevating efficacy of methionine is attributable to its methyl group.

Animals↗
PubMed1986

Effect of green tea catechins on plasma cholesterol level in cholesterol-fed rats.

Effects of tea catechins (tannins) on lipid metabolism were studied in male weanling rats fed a 25% casein diet containing 15% lard and 1% cholesterol for 28 days. Crude tea catechins prepared from green tea powder were supplemented at a 1% and 2% of the lard-cholesterol diet. The addition of 2% tea catechins slightly depressed growth but at the 1% level was without effect. Tea catechins decreased plasma total cholesterol, cholesterol ester, total cholesterol--HDL-cholesterol (VIDL-+LDL-cholesterol) and atherogenic index (VLDL-+LDL-cholesterol/HDL-cholesterol). Hematocrit and plasma glucose were not altered by the addition of tea catechins. The liver weight, liver total lipids and cholesterol concentrations in rats fed the lard-cholesterol diet increased more than in the control rats, but the addition of tea catechins to the lard-cholesterol diet decreased those parameters. Tea catechin supplementation increased fecal excretion of total lipids and cholesterol. The results demonstrate that tea catechins exert a hypocholesterolemic effect in cholesterol-fed rats.

Animals↗
PubMed1986

Effect of individual amino acids on plasma cholesterol level in rats fed a high cholesterol diet.

The effect of individual amino acids added to a cholesterol containing casein diet on the plasma cholesterol level of rats was systematically investigated with objective of confirming the possibility that specific amino acids are responsible for the regulation of plasma cholesterol level by dietary proteins. Half the amino acids tested were effective to some degree in influencing the plasma cholesterol level when amino acids were added singly to the diet at a 5% level. However, only sulfur containing amino acids had significant effects when added to the diet at a 1% level; Met enhanced and Cys reduced the plasma cholesterol level. In addition, the results of an experiment with amino acid mixture diets with different Met, Cys, and/or Gly contents indicated the importance of sulfur amino acids and also of Gly in plasma cholesterol regulation. The results obtained here support the notion that the plasma cholesterol level of rats can be influenced by specific amino acids or amino acid compositions of dietary proteins, at least under the experimental conditions used.

Amino Acids↗
PubMed1985

Disassembly from both ends of thick filaments in rabbit skeletal muscle fibers. An optical diffraction study.

We show in this paper that the change of the internal structure of a sarcomere in a rabbit glycerinated psoas muscle fiber can be examined by analyzing the intensity change of the first- and the second-order optical diffraction lines. A unit-cell (sarcomere)-structure model has been applied to the estimation of the length of thick filaments in a muscle fiber while they undergo dissociation. The optical factors, except for the unit-cell-structure factor, hardly changed during the dissociation of the filaments. Our results show that thick filaments dissociate from both ends on increasing the KCl concentration in the presence of 10 mM pyrophosphate and 5 mM MgCl2. Micromolar concentrations of Ca2+ suppressed to some extent the dissociation of thick filaments. The disassembly of thick filaments occurred at higher KCl concentrations in the absence of pyrophosphate. There was a correlation between the stability of the thick filament structure and cross-bridge formation, which was induced either by the addition of micromolar concentrations of Ca2+ in the presence of Mg-pyrophosphate or by removal of Mg-pyrophosphate.

Animals↗
PubMed1984

Skin gas tensions and resistances measured by mass spectrometry in adults.

We used a dual-sampling chamber 2.5 cm in diameter, controlled by an Apple II microcomputer, to measure gas tensions in the skin of adults by mass spectrometry. The tensions of O2, CO2, N2, and water vapor and the resistances to the flows of gases through the skin were calculated from the voltages for the different gases passing through two separate membranes of different permeability. We compared the skin O2 and CO2 tensions with arterial values in 13 patients with lung disease during a standardized exercise test. The skin values followed changes in the arterial values. The regression line relating skin to arterial O2 tension had a slope of 1.05 and that for CO2 a slope of 1.51. We conclude that mass spectrometry is capable of providing measurements of gas tension from the heated skin that are similar to those found using electrochemical methods in adults.

Carbon Dioxide↗