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Biomedical subjects

M Suda

Publications and source records attributed to M Suda.

At least 199 records · Page 11Linked to original sources
PubMed1980

Effect of starvation on the circadian adrenocortical rhythm in rats.

The circadian rhythm of blood corticosterone was examined in rats whose feeding was restricted to a specific time of day. The peak of the corticosterone level was found just before feeding time regardless of whether, the rats were kept on a 12-h light, 12-h dark cycle or in constant light or were blinded. It took at least 10 days to establish the corticosterone rhythm corresponding to the feeding time, but once it had been established, it persisted for at least 2 days of stravation regardless of the lighting condition. It is concluded that the corticosterone rhythm entrained by food is endogenous.

Adrenal Cortex↗
PubMed1979

Identification of suberimidate cross-linking sites of four histone sequences in H1-depleted chromatin. Histone arrangement in nucleosome core.

The arrangement of 8 histones in the nucleosome core has been investigated by identifying the sites of 4 histone sequences cross-linked with a bifunctional amino-group reagent, dimethyl suberimidate, selected from among 4 diimidoesters of various linker lengths examined. H1-depleted calf thymus chromatin was allowed to react with 14C-labeled suberimidate at pH 8.5 and 0 degrees C. The cross-linked chromatin was then digested exhaustively with trypsin. Almost all the histone fragments were released from the chromatin with 0.25 M HCl and chromatographed on several columns and on paper. Cross-linked peptides were detected by analyzing the content of radioactive suberimidoylbislysine after acid hydrolysis. The chromatographic procedure developed here showed that the whole histone fragments contained 29 mol% of the total linked reagent as suberimidoylbisylsine. The 5 finally purified cross-linked peptides were identified from the total and N-terminal amino acids of each pair of peptides separated by two-dimensional cellulose thin layer chromatography after cutting the linker by ammonolysis. Thus, intramolecular cross-linking was found between Lys-5 and Lys-9 of H2A, and Lys-34 and Lys-85 of H2B, while intermolecular cross-linking was found between Lys-24 (or 27) of H2B and Lys-74 of H2A, Lys-85 of H2B and Lys-91 of H4, and Lys-120 of H2B and Lys-115 of H3 and/or Lys-77 of H4. Most of these lysine residues are located in the DNA-binding segments of the 4 histone sequences identified previously [Kato, Y. & Iwai, K, (1977) J. Biochem. 81, 621--630]. All the 5 or 6 cross-links can be located in a heterotypic tetramer consisting of one molecule each of H2A, H2B, H3, and H4, and a model of the histone arrangement in the tetramer is proposed. Two such tetramers may compose to the histone octamer in the nucleosome core.

Amino Acids↗
PubMed1979

Characteristics of two cell lines (TE-1 and TE-2) derived from human squamous cell carcinoma of the esophagus.

Two epithelial cell lines (TE-1 and TE-2) have been established from a well or poorly differentiated human squamous cell carcinoma of the esophagus. TE-1 has been subcultured 120 times during 2 years and 10 months, and TE-2, 50 times for almost 2 years. Cultured cells grew as isolated and piled-up colonies of epithelial cells. The average doubling time of the TE-1 cell line was 60 hr and that of TE-2, 72 hr. Distinctive marker chromosomes and a male karyotype were present in TE-1, but no marker chromosomes were seen in TE-2. Scanning electron microscopic examinations of both TE-1 and TE-2 confirmed the presence of desmosomes and interdigitated microvilli. Transmission electron micrographs of TE-1 showed the presence of abundant cell organelles, and a few organelles were found in the scanty cytoplasm of TE-2. There was a marked difference in the cell organelles between TE-1 and TE-2. Heterotransplantation of the cultured TE-1 and TE-2 cells produced tumors, the histological appearance of which was similar to that of the original ones. The carcinoembryonic antigen level of the medium in the confluent culture of TE-2 was 270 ng/10(6) cells. In the cytoplasm of TE-1 cells the number of paracrystals, which were produced by treatment with vinblastine sulfate, increased by the addition of cholera toxin to the medium.

Animals↗
PubMed1978

Postnatal development of circadian rhythms in disaccharidase activities in rat small intestine.

The circadian rhythms in the activities of maltase and lactase of the small intestine were examined at various stages of postnatal development in rats. When the rats were fed ad libitum, no circadian change in the enzyme activities was found during the suckling period or the weaning period. However, several days after the time of weaning, the enzymes showed the same circadian changes as in adult rats with higher activities at night. After weaning, when the rats were fed only during the daytime, the phase of the enzyme rhythm shifted about half a day, and the highest activity was observed around feeding time. However, during the suckling period, no circadian rhythm in the enzyme acvities was found, even when the rats were allowed to feed only during a restricted time of the day.

Aging↗
PubMed1978

Parallel between circadian rhythms of intestinal disaccharidases and foot intake of rats under constant lighting conditions.

The relationship between the circadian rhythmic changes in the disaccharidase activities of the small intestine and the circadian feeding pattern was investigated in rats kept in the dark or in the light continuously for 4 weeks. Rats kept continuously in the light and fed ad libitum showed no rhythmic change in food intake or disaccharidase activities, but when they were only fed during a restricted time of day, their disaccharidase activities showed rhythmic changes with higher activities around the feeding time. In contrast, rats kept continuously in the dark and fed ad libitum showed circadian variations in food intake and disaccharidase activities essentially similar to rats kept under the normal light-dark lighting schedule. These findings show that the rhythm of disaccharidase activities is synchronized with the feeding rhythm, not with the lighting rhythm.

Animals↗
PubMed1978

Circadian rhythm and dietary response of disaccharidase activities in isolated rat jejunum.

Studies were made on the effects of intraluminal factors on the circadian rhythm and the adaptive change to diet of maltase and sucrase activities in rat small intestine. Rats given carbohydrate-free diet for 1 week showed lower specific activities of these enzymes than rats on the latter diet. Segments of jejunum, isolated as blind sacs with normal blood and nerve supplies, showed the same circadian rhythm as unligatured jejunum, but their enzyme activities were not increased by administration of carbohydrate-rich diet for 1 week. Thus it was concluded that the adaptive changes of disaccharidase activities caused by change in diet depend primarily on the presence of carbohydrate in the intestinal lumen, whereas the circadian rhythmic changes do not.

Animals↗
PubMed1977

A specific method for the determination of threonine in rat blood plasma using aldehyde dehydrogenase.

A simple and sensitive method for the determination of threonine in rat blood plasma using aldehyde dehydrogenase after oxidation with periodate was developed. By the present method, threonine could be completely discriminated from serine and determined at the nanomole level. The amount of threonine in rat blood plasma obtained by the present method coincided well with the value determined on an amino acid analyzer.

Aldehyde Oxidoreductases↗
PubMed1976

Circadian rhythms in disaccharidases of rat small intestine and its relation to food intake.

The activities of maltase and sucrase of the small intestine were low at night and high in the daytime in rats which had been fed from 09.00 h to 15.00 h for 2 weeks. A remarkable rise of enzyme activities was observed at 08.00 h, 1 h before the start of feeding. The rhythmic changes in disaccharidase activities continued for at least 2 days after starvation, but completely disappeared after 5 days of starvation. It was suggested that the disaccharidase rhythms are not a direct consequence of food intake, but that anticipation of food intake acts as a trigger for initiation of the disaccharidase rhythms.

Circadian Rhythm↗
PubMed1976

Circadian rhythms of digestive enzymes in the small intestine of the rat. II. Effects of fasting and refeeding.

The effects of fasting were examined on the rhythmic changes in the activities of maltase [EC 3.2.1.20] and leucine aminopeptidase [EC 3.4.11.1] in the small intestine of rats which has been kept under scheduled feeding conditions. Irrespective of whether the rats had been kept on a daytime or nighttime feeding schedule, the rhythms of maltase and leucine aminopeptidase persisted when the animals were starved. However, the amplitude of the leucine aminopeptidase rhythm began to decrease from the first day of fasting, while that of maltase did not. Conspicuous rhythms persisted for at least 2 days during fasting, but they gradually became vague and disappeared after 5 days. When rats were refed after fasting, the leucine aminopeptidase activity increased within a few hours, but the maltose activity did not. It is suggested that the rhythms of the digestive enzymes in the small intestine of rats are not a direct consequence of food intake, but are triggered off by the anticipatory mechanism which operates when rats expect to be fed. The rhythmic change of leucine aminopeptidase seemed to be intensified by food intake.

Animals↗
PubMed1975

Dietary and hormonal regulation of serine synthesis in the rat.

The importance of the so-called phosphorylated pathway for the synthesis of serine in rat liver was confirmed by studies on in vitro serine synthesis and also by the existence of a correlation between the serine-synthesizing activity of liver extracts and the activities of the enzymes involved in the pathway under various dietary conditions. Serine-synthesizing activity was found to be distributed in various rat tissues such as kidney, brain, testis, spleen, pancreas, and fat pad. However, only in the liver was the synthesis regulated by dietary protein. In the liver, the three enzymes of the phosphorylated pathway were found to be repressed by high-protein diets or by starvation and induced by low-protein diets. The dietary induction of the enzymes required the presence of insulin and was suppressed by glucocorticoids. A suggestion is made that the effects of diet or hormones may be mediated by changes in the hepatic pool of essential amino acids.

Animals↗
PubMed1975

Circadian rhythms in digestive enzymes in the small intestine of rats. I. Patterns of the rhythms in various regions of the small intestine.

The activities of the digestive enzymes, maltase [EC 3.2.1.20], sucrase [EC 3.2.1.26], trehalase [EC 3.2.1.28], Leucine aminopeptidase [EC 3.4.11.1], and alkaline phosphatase [EC 3.1.3.1] were measured in various regions of the small intestine of rats. The activities of all these enzymes were much higher in the jejunum than in the ileum, and in the distal regions of the ileum no sucrase, trehalase or alkaline phosphatase activity was detected. In the jejunum, the activities of all the enzymes tested exhibited clear circadian variations with the highest activity at 0000-0400 h and the lowest at 1200 h when the rats were fed ad libitum. In the ileum, maltase and sucrase also exhibited circadian variations, but the amplitude of the rhythm was smaller than that in the jejenum. Trehalase and alkaline phosphatase did not show any circadian variation in the ileum. Leucine aminopeptidase showed a circadian variation in the ileum with the same amplitude as in the jejunum. The phase of the circadian variations shifted about half a day when the rats were fed in the daytime, but the amplitude of the rhythm did not change.

Alkaline Phosphatase↗
PubMed1975

Effect of diet on enzymes of the brush border of the small intestine and kidney of rats.

The effect of diets containing various amounts of casein and starch on enzymes bound to the brush border of the small intestine and kidney of rats were investigated with the following results. 1) Diets with low starch and high casein contents resulted in higher specific activity of leucineaminopeptidase in the small intestine than diets with high starch and low casein contents. Diets with high starch and low casein contents increased the specific activity of maltase. 2) Rat small intestine contains at least two isoenzymes of leucineaminopeptidase: one bound to the brush border and the other not bound to it but recoverable in the soluble fraction. Only the former was influenced by the diet. 3) The maximum velocity (Vmax) of leucineaminopeptidase bound to the brush border was twice as much in rats on a high casein diet as in those on a low casein diet, but the Michaelis constant (Km) was approximately the same in both groups of rats. 4) Leucineaminopeptidase and maltase activities in the kidney were not influenced by diet.

Animals↗