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Biomedical subjects

M Yoshino

Publications and source records attributed to M Yoshino.

At least 19 recordsLinked to original sources
PubMed1992

Enalapril reduces the enhanced 1,2-diacylglycerol content and RNA synthesis in spontaneously hypertensive rat hearts before established hypertension.

There is evidence that cardiac hypertrophy in spontaneously hypertensive rats (SHR) occurs before the development of hypertension. 1,2-Diacylglycerol, which is thought to be a second messenger activating protein kinase C, is also produced in excess in SHR hearts at 4 weeks of age, before established hypertension. We determined myocardial 1,2-diacylglycerol content in SHR with and without prazosin and enalapril from 3 to 4 weeks of age. Hearts from untreated SHR had greater RNA and DNA synthesis and greater relative weights at 4 weeks of age than those from Wistar-Kyoto (WKY) rats. There was no difference in triglyceride content or phospholipid species between WKY rats and untreated SHR, except for a higher cholesterol content in SHR. Treatment of SHR with enalapril, but not prazosin, lowered not only 1,2-diacylglycerol content but also RNA synthesis to the levels of WKY rats. Moreover, fatty acids involved in 1,2-diacylglycerol were altered by enalapril despite the lack of a difference between WKY rats and untreated SHR. Prazosin did not have any effect on 1,2-diacylglycerol fatty acid composition. Enalapril may decrease cardiac hypertrophy in SHR by lowering myocardial 1,2-diacylglycerol production.

Animals↗
PubMed1992

Aluminum: a pH-dependent inhibitor of NADP-isocitrate dehydrogenase from porcine heart.

Aluminum showed a pH-dependent inhibitory effect on NADP-isocitrate dehydrogenase from porcine heart. Aluminum ions (Al3+) acted as a partial competitive inhibitor of the enzyme with respect to the substrate threo-Ds-isocitrate and inhibited the enzyme non-competitively with respect to NADP at pH 6.85. Fractional velocity plot analysis showed the Ki of the enzyme for aluminum ions to be 0.88 microM. When pH was elevated to 8.0, aluminum ions, which occur as a form of the Al(OH)4- anion, acted as partial uncompetitive and non-competitive inhibitors of the enzyme with respect to the substrates isocitrate and NADP, respectively. The Kí of the enzyme was determined to be 5.64 microM at pH 8.0 by fractional velocity plot analysis. The inhibition of NADP-isocitrate dehydrogenase by two forms of aluminum ions may explain aluminum toxicity in various tissues and organs.

Aluminum↗
PubMed1992

Inhibition by aluminum ion of NAD- and NADP-dependent isocitrate dehydrogenases from yeast.

1. NADP-dependent isocitrate dehydrogenase from yeast was potently inhibited by aluminum ion competitively with respect to the substrate isocitrate, and noncompetitively with the other substrate NADP. Ki value was determined to be 0.43 microM. 2. Aluminum ion acted as only a weak allosteric inhibitor of yeast NAD-dependent isocitrate dehydrogenase toward isocitrate, and as a noncompetitive inhibitor toward NAD. 3. Inhibition by aluminum ion of NADP- and NAD-isocitrate dehydrogenases can reduce the aerobic energy production in yeast, and may contribute to the biological toxicity of aluminum in ecosystems and human life.

Allosteric Regulation↗
PubMed1992

Stabilization of the adenylate energy charge in erythrocytes of rats and humans at high altitude hypoxia.

1. Stabilization of adenylate energy charge and control of adenylate pool were analysed in the erythrocytes of the rat and the human exposed to highly hypoxic conditions. 2. Red cell energy charge was decreased in the rats exposed to a simulated altitude of 5000-8000 m, and then recovered to the normal value with the depletion of adenylate pool. 3. The energy charge and the adenylate pool size of the human erythrocytes did not show any change under highly hypoxic conditions. 4. Anaerobic incubation of rat erythrocytes caused a marked decrease in the energy charge, and its recovery was accompanied by the depletion of total adenylates. 5. The energy charge and total adenylates of human red cells did not change under the anaerobic incubation of erythrocytes. 6. These results suggest that the energy charge of rat erythrocytes can be controlled by depletion of the adenylate pool, but the adenylate degradation is not responsible for the stabilization of the energy charge in human erythrocytes.

Adenosine Diphosphate↗
PubMed1992

Bone marrow imaging using STIR at 0.5 and 1.5 T.

We retrospectively examined MR images in 82 patients to evaluate the usefulness of short inversion time inversion recovery (STIR) in bone marrow imaging at 0.5 and 1.5 T. The study included 56 patients at 1.5 T and 26 patients at 0.5 T with a variety of pathologic bone marrow lesions (principally oncological), and compared the contrast and image quality of STIR imaging with spin-echo short repetition time/echo time (TR/TE), long TR/TE, and gradient-echo sequences. The pulse sequences were adjusted for optimal image quality, contrast, and fat nulling. STIR appears especially useful for the evaluation of red marrow (e.g., spine), where contrast between normal and infiltrated marrow is greater than with either gradient-echo or T1-weighted images. STIR is also extremely sensitive for evaluation of osteomyelitis, including soft tissue extent. In more peripheral (yellow) marrow, T1-weighted images are usually as sensitive as STIR. Limitations of STIR include artifacts, in particular motion artifact that at high field strength necessitates motion compensation. At 0.5 T, however, motion compensation is usually not necessary. Also, because of extreme sensitivity to water content, STIR may overstate the margins of a marrow lesion. With these limitations in mind, STIR is a very effective pulse sequence at both 0.5 and 1.5 T for evaluation of marrow abnormalities.

Adolescent↗
PubMed1992

The amplified long genomic sequence (ALGS) located in the centromeric regions of mouse chromosomes.

We reported previously that the haploid genome of standard strains of laboratory mice contains approximately 70 copies of an amplified long genomic sequence, designated ALGS, that includes a retroposon of the gene for elongation factor 2 (MER). The length of each repeating unit is more than 60 kb, and the sequence of the unit is highly conserved among the repeats. In the present study, Southern blot analysis of the genomes of wild rodents demonstrated that the ALGS is present in all subspecies of Mus musculus and is abundant in M. spicilegus, whereas it is absent in M. spretus as well as in Rattus and other closely related genera. This result indicates that the amplification occurred after the species differentiation with the genus Mus and at least prior to the differentiation of subspecies of M. musculus. To locate chromosomal positions of the ALGS, in situ hybridization was carried out with laboratory strains and wild mice. It appears that the ALGS is located in the centromeric regions of most chromosomes in laboratory mice, M. musculus and M. spicilegus, whereas no positive signals were observed with M. spretus, in accordance with the results from the Southern blotting analysis.

Animals↗
PubMed1992

Changes in ventricular 1,2-diacylglycerol content in rats following monocrotaline treatment.

OBJECTIVE: 1,2-Diacylglycerol may initiate cardiac hypertrophy, probably by activating protein kinase C. To test this hypothesis we determined the 1,2-diacylglycerol content of hypertrophied tissue. METHODS: Rats were treated with monocrotaline and developed severe right ventricular hypertrophy followed by congestive heart failure. 1,2-Diacylglycerol content and fatty acid composition, DNA concentrations, and RNA concentrations in the right ventricle from monocrotaline treated rats were compared with values obtained from the left side or from control rats. RESULTS: During the first week, the right ventricle showed no significant change in 1,2-diacylglycerol content and a small increase in RNA concentration. However, the 1,2-diacylglycerol content was significantly increased by 55% at two weeks after monocrotaline injection, when DNA and RNA synthesis was also enhanced to its highest level when compared with control rats (37% and 18%, respectively). At four weeks after monocrotaline injection, conversely, the 1,2-diacylglycerol content was decreased by 25% in the right ventricle from monocrotaline treated rats, most of which had pleural and peritoneal effusions indicating congestive heart failure, although RNA synthesis was sustained at a high level. The fatty acid composition of 1,2-diacylglycerol did not differ significantly between the right and left ventricles or control rat ventricles. CONCLUSIONS: These results suggest that 1,2-diacylglycerol accumulation is associated with development of hypertrophy in monocrotaline treated rats. In contrast, at a stage of congestive heart failure 1,2-diacylglycerol production decreased, suggesting that intracellular transduction mechanisms may be attenuated.

Animals↗
PubMed1992

Wilson's disease treatment by triethylene tetramine dihydrochloride (trientine, 2HCl): long-term observations.

Wilson's disease is an autosomal recessive disorder characterized by an accumulation of a toxic amount of copper in the body. Triethylene tetramine dihydrochloride (trientine, 2HCl) is a new chelating agent that may be effective in the removal of excess copper but long-term efficacy has not yet been investigated. Here we report the use of trientine over more than 8 years in 2 patients with Wilson's disease who could not tolerate D-penicillamine. We found no significant side effect, except a decreased serum iron concentration without clinical symptoms of anemia. In annual examinations at a steady state, the serum copper levels remained below 20 micrograms/100 ml. The 24-hour urinary copper excretion was less than that found using D-penicillamine, while the basal copper excretion, after 5 days abstinence from trientine, was maintained below 100 micrograms/day. Both hepatic and neurological manifestations except bulbar symptoms were recovered without any initial deterioration.

Adolescent↗
PubMed1992

Blocking action of terodiline on calcium channels in single smooth muscle cells of the guinea pig urinary bladder.

The blocking action of terodiline, a nonspecific organic Ca++ antagonist, on smooth muscle Ca++ channels of the guinea pig urinary bladder was investigated. Inward Ca++ currents were recorded from smooth muscle cells isolated from the urinary bladder using the whole-cell patch-clamp technique. In the absence of terodiline, a use-dependent reduction in the amplitude of inward Ca++ current was observed at a stimulus frequency of 0.2 Hz. When terodiline (1-10 microM) was applied, the use-dependent reduction was accelerated markedly, depending on the stimulus frequency. The blocking action of terodiline was also dose-dependent; the Kd value as measured at the end of 20 times repetitive stimulation at 0.2 Hz was 1.7 microM. In addition to such a use-dependent block, terodiline produced a hyperpolarizing shift in the steady-state inactivation curve. The results suggest that terodiline preferentially binds to the Ca++ channel in the open state and also in the inactivated state.

Action Potentials↗
PubMed1991

Retrospective survey of urea cycle disorders: Part 2. Neurological outcome in forty-nine Japanese patients with urea cycle enzymopathies.

We analyzed neurological data, including DQ or IQ, EEG, and CT scan, in 49 patients with urea cycle enzymopathies, all of whom were included in a retrospective survey from 1978-1988 in Japan. We classified 3 groups depending on age-at-onset: group 1 (0-28 days, N = 11), group 2 (29 days-5 years, N = 31), and group 3 (greater than 5 years, N = 7). The least DQ or IQ score and the highest CT score, representing the most severe brain damage was found in group 1, and the highest DQ or IQ and the least CT score was found in group 3. Intermediate scores of both parameters were found in group 2. There was a negative correlation between these 2 parameters (r = -0.82, P less than 0.01). Abnormal EEG during the attack-free period was predominantly observed in patients with CT abnormalities compared to those with a normal CT scan (P less than 0.01). Approximately 40% of the patients, mostly in groups 2 and 3 (92.8%) had normal findings in all 3 parameters. Thus, the magnitude of developmental abnormalities is clearly related to the degree of brain damage and to the age-at-onset of these diseases.

Brain↗
PubMed1991

Activation by spermine of citrate synthase from porcine heart.

Spermine activated citrate synthase from porcine heart by decreasing the Km value for the substrate oxaloacetate without affecting the maximal velocity. Spermine markedly increased the maximal velocity of the saturation function with respect to acetyl-CoA as the substrate under conditions of intracellular concentrations of oxaloacetate, but the enzyme was not activated by spermine under conditions of higher concentrations of oxaloacetate. The concentration of spermine required for 50% activation of the enzyme was about 50 microM. Spermidine showed only a little activation, while putrescine caused no activation. Spermine, which contributes to an activation of Ca2(+)-sensitive dehydrogenases of the citric acid cycle by enhancing Ca2+ uptake into mitochondria, can activate citrate synthase directly, and is responsible for the stimulation of oxidative metabolism in mitochondria.

Animals↗
PubMed1991

Retrospective survey of urea cycle disorders: Part 1. Clinical and laboratory observations of thirty-two Japanese male patients with ornithine transcarbamylase deficiency.

In a retrospective survey done from 1978-1988 in Japan, 32 male patients with ornithine transcarbamylase (OTC) deficiency were identified. We classified a neonatal and 2 late-onset groups, depending on clinical manifestations and the age at onset; group 1 (0-28 days; N = 10), group 2 (29 days-5 years; N = 13), and group 3 (greater than 5 years; N = 9). Compared to findings in the group 2 patients, there was a higher rate of mortality and a higher incidence of mental retardation in association with a great decrease in enzyme activity in group 1. In group 3, the mortality rate and enzyme activities were similar to those in group 1. However, patients in this group were asymptomatic prior to the first episode. Enzyme activities were measured mostly in autopsy samples. The serum citrulline levels (enzyme product) were highest in this group. Thus, the mutant enzymes were apparently labile with greater activities in vivo than in vitro. Treatments, including a protein-restricted diet, arginine supplementation, and sodium benzoate administration, resulted in a favorable prognosis for survivors with partial enzyme deficiency. We wish to emphasize that the incidence of late onset of this disease is higher than heretofore considered.

Child, Preschool↗
PubMed1991

Acclimatization to hypoxia modulates the tryptophan 2,3-dioxygenase activity in rats exposed to simulated high altitude.

1. Exposure of rats to an 8000 m altitude increased the hepatic tryptophan 2,3-dioxygenase (EC 1.13.1.12) activity. 2. Acclimatization to hypoxia by a repeated exposure to an altitude of 5000 m induced a marked decrease in liver tryptophan dioxygenase activity after the rats were subjected to an 8000 m altitude, but a pre-exposure to 4000 m altitude showed no effect on the enzyme activity. 3. Plasma tryptophan was rapidly decreased by exposure to 8000 m altitude to the same extent in the acclimatized and non-acclimatized rats. 4. Plasma tryptophan may be utilized as the substrate for tryptophan dioxygenase in liver of the non-acclimatized rats under highly hypoxic conditions; however, acclimatized rats can reserve tryptophan as the substrate for the alternative metabolism other than the degradation pathway in liver.

Acclimatization↗
PubMed1991

Microscopical study on estimation of time since death in skeletal remains.

For the purpose of estimating time since death in skeletal remains, postmortem changes in human compact bones were examined by microradiography and electron microscopy. The UV-fluorescence of the peripheral zone of compact bone was also examined by microscopic spectrophotometry. Microradiographic examination revealed no morphological changes in bones left in the open air for long periods, except one of 15 years since death. In bones left in the soil, vacuoles of 5-10 microns diameter, which contained a honeycomb-like structure formed by small vacuoles of 0.5-1 microns diameter, were found in the peripheral zone of the substantia compacta approximately 5 years since death, and in bones of 6 years or more, this change extended to the mid-zone. In bones left in the sea for 4-5 years, vacuoles of 5-10 microns diameter were observed in the outer peripheral zone of the substantia compacta. The relative intensity of UV-fluorescence in bones dwindled with time since death and the correlation coefficient was considerably high.

Bone and Bones↗
PubMed1991

A nationwide survey on transient hyperammonemia in newborn infants in Japan: prognosis of life and neurological outcome.

A nationwide survey of transient hyperammonemia in newborns was carried out in Japan. A total of 18 patients, consisting of 12 male and 6 female infants, were reported from 11 facilities. These neonates exhibited hyperammonemia with plasma ammonia levels in the range from 124 to 6256 micrograms/dl. Four newborn infants of the 18 died in the neonatal period, and an additional one died in the early infancy. Among the 13 infants who were alive at the time of this survey, 6 had neurological sequelae, including mental retardation, spastic quadriplegia and epilepsy. The multivariate analysis revealed that the Apgar score at 1 minute, peak plasma ammonia concentration, birth weight and sex were significant factors affecting the prognosis of life.

Ammonia↗