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Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 1,225 records · Page 68Linked to original sources
PubMed1985

Fructose 1,6-bisphosphate-dependent L-lactate dehydrogenase from Thermus aquaticus YT-1, an extreme thermophile: activation by citrate and modification reagents and comparison with Thermus caldophilus GK24 L-lactate dehydrogenase.

Heat-stable fructose 1,6-bisphosphate-dependent L-lactate dehydrogenase [EC 1.1.1.27] was purified from an extremely thermophilic bacterium, Thermus aquaticus YT-1. The amino acid composition and NH2-terminal 34 amino acid sequence of the enzyme were determined. Its NH2-terminal sequence shows high homology with those of Thermus caldophilus GK24 (82% identity) and some other bacterial L-lactate dehydrogenases (44-53% identity), indicating the close phylogenic relationship of the two Thermus species. At the same time, the two Thermus L-lactate dehydrogenases were found not to be identical not only chemically but also kinetically and immunologically. Citrate activated the T. aquaticus enzyme in the weak acidic pH region, while fructose 1,6-bisphosphate did in both acidic and neutral pH regions. The maximum activity obtained with citrate at pH 5.0 was about 2.5 times higher than that in the presence of fructose 1,6-bisphosphate at pH 6.7. The enzymes modified with 2,3-butanedione, acetic anhydride and diethyl pyrocarbonate in the presence of both NADH and oxamate were desensitized to fructose 1,6-bisphosphate, and the modified enzymes were active even in the absence of fructose 1,6-bisphosphate. All of the modified enzymes examined were still activated by citrate similarly to the native enzyme. These results suggest that the mechanism of activation by citrate is different from that by fructose 1,6-bisphosphate, and that the citrate-binding site is different from the fructose 1,6-bisphosphate-binding site.

Amino Acids↗
PubMed1985

Ouabain-resistant cells cultured in a synthetic medium.

Several strains of kidney and liver cells cultured in a synthetic medium were found to be resistant to ouabain. These cell strains were characterized because this resistance may serve as a good marker in genetic studies on somatic cells in chemically defined conditions in the absence of Na+ related growth factors and hormones. The phenotype was stable in the absence of selection for at least two years, and the original strains before adaptation to the synthetic medium were found to have ouabain sensitivity equal to the corresponding cells in the synthetic medium. The resting membrane potential, Na+,K+-ATPase activity, and growth rate of the resistant cells were similar to those of ouabain-sensitive cells. The resistance of the cells was not affected by serum or antibodies against some cytoskeletal proteins and the sensitivity of the Na+,K+-ATPase was not restored by partial purification of the membranes. Western blotting of the Na+,K+-ATPase of the ouabain-resistant cells showed that the molecular weights of its two subunits and its immunoreactivity were similar to those of the enzyme from the ouabain-sensitive strain. Thus the ouabain resistance is caused not by ouabain-like hormone produced by the cells or change in the cytoskeletal system, but by a mutation resulting in expression of an ouabain-resistant ATPase gene.

Animals↗
PubMed1985

Large scale isolation and some properties of AGY-specific serine tRNA from bovine heart mitochondria.

A method was developed for large scale isolation of AGY-specific serine tRNA (tRNASerAGY) from bovine heart mitochondria. By this method, 5 A260 units of tRNASerAGY were recovered from 6.3 kg of bovine hearts. The nucleotide sequence was identical to that reported previously. tRNASerAGY showed abnormal melting profiles, as was predicted from its unique primary sequence. Its secondary and/or tertiary structure was analyzed by nuclease digestion method. It was suggested that three extra base pairs could occur in the anticodon stem region, with one adenosine residue protruding. The T loop was quite sensitive to nuclease S1, suggesting that the T loop doesn't interact with other regions. This finding is consistent with the model proposed by Sundaralingam (1980). tRNASerAGY was aminoacylated in vitro with only mitochondrial enzyme but not with the enzymes from E. coli and yeast. The aminoacylation rate of tRNASerAGY with mitochondrial enzyme was much faster than that of cytosolic tRNASerUCN, perhaps reflecting differences due to the presence and absence of the D arm of the tRNAs.

Animals↗
PubMed1985

Relationship between sleep efficiency and urinary excretion of catecholamines in bed-rested humans.

The relationship between urinary excretion of catecholamines during sleep and sleep disturbance was examined in four healthy subjects who were confined to bed for approximately 1 week under an entrained condition. Polysomnographic recordings were made throughout the period of continuous bed rest. Free epinephrine and norepinephrine excretion were measured. Sleep efficiency, i.e., percentage of total sleep time over an allotted sleep period, was an indicator of sleep disturbance. All subjects showed a negative correlation between sleep efficiency and epinephrine excretion (average correlation coefficient -0.79, p less than 0.004). Norepinephrine excretion correlated negatively with sleep efficiency in only one subject, and the group average correlation coefficient of -0.28 was not significant. Circadian variations were observed in sleep efficiency and catecholamine excretion. Although epinephrine excretion was influenced by psychophysiological stress arising from the experimental conditions of forced bed rest, the correlation between sleep efficiency and epinephrine excretion remained stable and negative. The urinary excretion of epinephrine could be an effective indicator of sleep disturbance.

Adult↗
PubMed1985

Chronobiological comparison of sleep-wake rhythm between chronic schizophrenia and normal control.

Few studies on schizophrenia with respect to the circadian alteration of the sleep-wake rhythm have been reported. We made a comparative study of the sleep-wake rhythm between chronic inpatient schizophrenics with a relatively bed-prone daily life and normal subjects under the conditions of absolute bed-rest to elucidate the chronobiological features of schizophrenia. The sleep-wake rhythm of the schizophrenics differed from that of the normals in two points: A significant difference was observed in the decrease of Stage 4 during their nocturnal sleep compared with the normal subjects, becoming conspicuous with the increasing lapse of time during sleep. The distribution and amount of their REM sleep in the morning were markedly low and the latency of their REM sleep was also prolonged. These facts suggested that the smooth slide of the sleep-wake rhythm was somewhat disturbed in the schizophrenics and that they were, therefore, in a state of hyperarousal despite their bed-prone life.

Adult↗
PubMed1985

Studies on the in vivo and in vitro distribution of apolipoprotein A-IV in human plasma and lymph.

To investigate the unique distribution in plasma of apolipoprotein A-IV (apo A-IV) we have determined, in a series of in vitro and in vivo studies, the redistribution among lipoproteins of 125I-apo A-IV. Free 125I-apo A-IV associated predominantly with high density lipoprotein (HDL) (72 +/- 3.5%) in incubations with plasma, and with triglyceride-rich lipoproteins (TRL) (65 +/- 3.0%) in incubations with lymph, rather than with the lipoprotein-deficient fraction (LDF) where greater than 90% of apo A-IV resides. Incubations with 125I-apo A-IV (incorporated within HDL or TRL) also resulted in similar redistributions of label. Specific radioactivities of apo A-IV in HDL and in TRL were of a similar order and 15-fold higher than those in LDF. However, when 125I-apo A-IV in LDF was incubated with plasma, 57 +/- 2.6% of label remained in the LDF, though the specific radioactivity of apo A-IV in HDL was 15-fold higher than in LDF. Thus, apo A-IV apparently exchanges freely between TRL, HDL, and a part of apo A-IV in LDF, but most of apo A-IV in LDF is refractive to free exchange or transfer. In vivo experiments carried out in five subjects, in which 125I-apo A-IV was injected within TRL, HDL, or LDF, were consistent with the in vitro data in showing rapid exchange of label among plasma apo A-IV containing fractions with much higher specific radioactivities in HDL than in LDF (10-30-fold). However, the small fraction of apo A-IV in LDF that did become labeled was removed from plasma in a biexponential fashion and at the same rate as from HDL. Thus, only a small fraction of the bulk of apo A-IV in plasma LDF exchanges freely with apo A-IV in TRL and HDL, suggesting that apo A-IV in LDF exists in at least two pools. This is consistent with our previous findings that apo A-IV in plasma is present in two distinct complexes with lipids and other peptides.

Apolipoproteins A↗
PubMed1985

Cytochalasin D inhibits the progression from the Go to S phase at the mid-prereplicative stage in GC-7 cells stimulated with serum.

When the growth of serum-arrested GC-7 cells, a clone from African green monkey kidney, was induced by the addition of 10% calf serum, they began to enter S phase after 15-16 h. When stimulated cells were cultured in the presence of 0.6 micrograms/ml of cytochalasin D, the entrance into S phase was inhibited. Treatment of cells with cytochalasin D during the period earlier than 8 h or later than 11 h after the serum stimulation showed no or little inhibitory effect on the entrance of cells into S phase. Inhibition of the entrance into S phase was observed only when stimulated cells were treated with cytochalasin D during the periods including 9-10 h after stimulation. A rapid increase in protein synthesis occurred 9-12 h after the serum stimulation and was inhibited in the presence of cytochalasin D. These and other results suggested that in the course of the prereplicative process from Go through S phase only the stage around 9-10 h after the start of the cell cycle was sensitive to cytochalasin D and that the block of the cycle was correlated with the inhibition of protein synthesis at this stage.

Animals↗
PubMed1985

Comparative study of the work load between one-man buses and two-man buses.

The differences in physiological and safety conditions of one-man buses and two-man buses were examined from the view point of occupational fatigue. This survey consisted of a work load study which included a time study, study of subsidiary behavior, auditory task, memory test, Galvanic Skin Response (GSR) and physiological function tests and a self-administered questionnaire which involved items concerning safety and subjective fatigue complaints. The visual and postural restrictions in the one-man bus were greater than in the two-man bus. The mental capacity of the one-man bus drivers was found to be less. Greater mental fatigue and stress were observed in the one-man bus. More subjective fatigue complaints were observed in the one-man bus. More cases of near accidents were observed in the one-man bus. From these results it was concluded that the one-man bus caused bus drivers a greater mental and physical work load.

Accidents, Traffic↗
PubMed1985

Bipolar diathermy forceps with automatic irrigation. Technical note.

A method for providing a saline drip during bipolar diathermy is described. Stainless steel tubing is incorporated in both blades of standard bipolar forceps and connected to the irrigating line. Irrigation is started when the forceps are closed and is stopped when they are open.

Diathermy↗
PubMed1985

Control of phenotypic expression of cultured B16 melanoma cells by plant glycosides.

The effects of two plant glycosides, ginsenosides Rh1 and Rh2, on the growth and differentiation of mouse melanoma (B16) cells in culture were studied. These plant glycosides have a dammarane skeleton resembling a steroid skeleton as an aglycone. Ginsenoside Rh2 inhibits the growth of B16 melanoma cells, causes morphological alterations, and stimulates melanogenesis at high cellular density. When ginsenoside Rh2 was removed after 2 or 6 days of treatment, the growth rate recovered slightly but not completely, during the period of observation (4 days after removal). On the other hand, ginsenoside Rh1 does not inhibit the growth of melanoma cells even at concentrations over 100 microM but stimulates the expression of the melanotic phenotype. Ginsenosides Rh1 and Rh2, possessing a glucose molecule at C-6 and C-3, respectively, have very similar chemical structures, but their effects on B16 melanoma cells differ remarkably. While it appears that the degree of differentiation is inversely related to cell growth, the present observations suggest that the differentiation and growth capacity of this B16 melanoma subline are independent phenotypic expressions.

Animals↗