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Biomedical subjects

M Shimada

Publications and source records attributed to M Shimada.

At least 739 records · Page 41Linked to original sources
PubMed1988

Cooperative interactions of myosin two heads in muscle force generation.

To investigate the possibility of cooperative interactions between the two myosin heads in muscle contraction, Ca2+-activated force development, K+-EDTA- and Mg2+-ATPase activities, muscle fiber stiffness, and the velocity of unloaded shortening were measured on partially p-PDM treated glycerinated muscle fibers, which contained a mixture of myosin molecules with zero, one and two of their heads inactivated. It was found that the magnitude of the Ca2+-activated isometric force development was proportional to the square of both K+-EDTA- and Mg2+-ATPase activities and also to the square of muscle fiber stiffness. If the two myosin heads in the glycerinated fibers are assumed to react independently with p-PDM, the above results strongly suggest that (i) each myosin molecule in the thick filaments can generate force only when its two heads do not react with p-PDM, (ii) muscle fiber stiffness is determined by the total number of native heads, and (iii) there is no cooperative interaction between the two myosin heads in catalyzing ATP hydrolysis.

Adenosine Triphosphatases↗
PubMed1988

[Lymphography].

Explore the source record for details and available documents.

Humans↗
PubMed1988

Degenerative changes in lymphatic endothelium of jirds infected with Brugia pahangi.

The quantitative changes of cytoplasmic vesicles and vacuoles in lymphatic endothelial cells of the mongolian jirds associated with Brugia pahangi infections were observed by transmission electron microscopy. The present study revealed a decrease in the proportion of cytoplasm occupied by vesicles and in the number of cytoplasmic vesicles in endothelial cells from lymphatic vessels harboring B. pahangi at 3, 4, and 10 mo after infection (3.55, 3.36, and 2.55 vesicles/micron 2, respectively) when compared with cells from uninfected control vessels (7.03 vesicles/micron 2). On the contrary, there was an increase in the area of vacuoles in endothelial cells of jirds at 3, 4, and 10 mo postinfection. The mean +/- SD diameter of vesicles in cells from lymphatic vessels at 10 mo after infection was significantly smaller (78.6 +/- 5.6 nm) compared to vesicles in uninfected vessels (87.5 +/- 9.7 nm).

Animals↗
PubMed1987

Regiospecific oxygenations during ring cleavage of a secondary metabolite, 3,4-dimethoxybenzyl alcohol catalyzed by lignin peroxidase.

Enzymatic oxidation of veratryl alcohol yielded a new ring cleavage product (delta-lactone) in addition to the two known gamma-lactone products. The experiment with 18O-enriched water and dioxygen clearly showed that one oxygen atom each from water and dioxygen is specifically incorporated into the cleavage product at the original C3 or C4 position of 3,4-dimethoxybenzyl alcohol. A new type of reaction mechanism proposed for the ring cleavage of this compound is rationally explained in good accord with the one-electron transfer mechanism.

Benzyl Alcohols↗
PubMed1987

Effects of the mass screening of neuroblastoma in Sapporo City.

One hundred sixty-seven cases of neuroblastoma in the Registry of Childhood Malignancies in Hokkaido Prefecture from 1969 to 1984 were studied, using the age at diagnosis, the clinical stage at diagnosis, and the survival rate to assess the influence of the mass screening of neuroblastoma performed in Sapporo City since 1981. In Sapporo City, the capital of Hokkaido Prefecture, the condition of the three parameters improved significantly after the institution of mass screening (e.g., the 48-month survival rate improved--from 21.3% to 87.5%). In Hokkaido Prefecture (Sapporo City excluded), however, where the mass screening had not yet been performed, no significant change was observed in any of the three parameters (48-month survival rate changed only from 21.1% to 28.1%). Consequently, the improvement in Sapporo City was thought to be attributable to the effects of the mass screening.

Age Factors↗
PubMed1987

Suppression of levels of phenobarbital-inducible rat liver cytochrome P-450 by pituitary hormone.

The effect of pituitary factor on the constitutive and inducible levels of hepatic phenobarbital (PB)-inducible major cytochrome P-450, P-450b and P-450e, in male and female rat livers was studied by immunoblot analyses. Although only trace amounts (approximately 4 pmol/mg protein) of P-450b and P-450e were detected in untreated adult rats, hypophysectomy increased the contents of P-450b and P-450e 58- and 14-fold, respectively, in male rats and 118- and 30-fold, respectively, in female rats. The increases were also observed in treatment with dexamethasone, which suppressed the pituitary function. Treatment with PB increased more effectively the hepatic contents of P-450b and P-450e, but their contents were still 4-fold higher in the male than the female. Treatment of hypophysectomized female rats with PB increased the contents of P-450b and P-450e 4-fold higher than the contents in PB-treated nonhypophysectomized female rats. Consequently, the sex-related difference in their contents was reduced less than 1.4-fold in the hypophysectomized rats treated with PB. Similar results were also obtained from the quantitation of microsomal O-pentylresorufin O-depentylation and testosterone 16 beta-hydroxylation. Either intermittent injection or continuous infusion of human growth hormone, but not of ovine prolactin, into hypophysectomized male and female rats decreased the contents of both cytochromes. These results indicate that growth hormone acts as a repressive factor for the constitutive and inducible levels of P-450b and P-450e in a manner different from the regulation of P-450-male and P-450-female.

Aging↗
PubMed1987

The fibers which leave the Probst's longitudinal bundle seen in the brain of an acallosal mouse: a study with the horseradish peroxidase technique.

The congenital absence of the corpus callosum, a brain anomaly frequently noted in humans, has been recently found to occur in some mice of the ddN strain in our laboratory. In the brains of these mice, the Probst's longitudinal bundle is always present on both cerebral hemispheres and gives rise to some aberrant fibers toward the midline. In this research, the neuroanatomical features of these fibers were studied by iontophoretical injections of horseradish peroxidase (HRP) into the neocortex of acallosal mouse brains. The results revealed that the fibers which leave the Probst's longitudinal bundle are, at least, of 3 kinds: namely, the fibers that run out from the anterior portion of the bundle and take a U-turn ipsilaterally without crossing the midline through the septal tissue to go back again into the longitudinal bundle at the level where they have left it; the commissural fibers that leave the bundle from its middle portion and cross through a tiny bridge of tissue associated with the ventral hippocampal commissure to the opposite hemisphere; and the fibers that arise from the posterior portion of the bundle and accumulate as an anomalous fascicle below the cingulum. The observation that no labeled fibers were seen within the anterior commissure in the present HRP materials suggests that the axons from neocortex which are prevented from crossing the midline in mice with congenital absence of the corpus callosum cannot find an alternative pathway via the anterior commissure.

Agenesis of Corpus Callosum↗
PubMed1987

Erythrocyte-oxidized glutathione transport in pyrimidine 5'-nucleotidase deficiency.

The oxidized form of glutathione transport was studied in human erythrocytes in pyrimidine 5'-nucleotidase (P5N) deficiency, a disorder in which the amounts of CTP and UTP in the erythrocytes are elevated. The inhibition of ATP-requiring oxidized glutathione (GSSG) transport by CTP and UTP is believed to play a role in elevating the levels of the reduced form of glutathione (GSH) in the erythrocytes of patients with P5N deficiency. The current investigation was undertaken to determine if GSSG transport actually decreases in the erythrocytes of such patients. Erythrocytes from a 17-year-old patient and a 13-year-old patient with P5N deficiency hemolytic anemia and from ten normal subjects were used as materials for the experiment. Erythrocytes, which had been previously incubated with [3H]glycine, were incubated at 37 degrees C, and the rate of [3H]GSSG transported by the cells was estimated. The velocity of GSSG transport out of the erythrocytes was quite low in the patients, 3.17-3.65 nmol GSSG/ml erythrocytes/hr at 37 degrees C in one case, and 3.30 nmol GSSG/ml erythrocytes/hr in the other case, vs that in the normal controls (6.00 +/- 0.80 nmol GSSG/ml erythrocytes/hr; mean +/- SD). The activity of gamma-glutamylcysteine synthetase and glutathione synthetase did not decrease in the patients. Decreased transport activity of GSSG in addition to a normal synthesis rate for GSH may explain the increased concentration of erythrocyte GSH in P5N deficiency.

5'-Nucleotidase↗
PubMed1987

Golgi study on brain of macular mutant mouse as a model of Menkes kinky hair disease.

This study was undertaken to elucidate, using the Golgi method, the neuropathological change in the brain of the macular mutant mouse, whose hemizygote (Ml/y) is considered to be a model of Menkes kinky hair disease (MKHD). The hemizygote mice gradually lost weight after 10 days of age and died with emaciation and seizure around day 15. The normal littermate (+/y) was well developed. In the cerebrum, the arborization of pyramidal neurons in the layer V of the Ml/y was the same as that in the +/y on day 10. However, development of arborization in the Ml/y was delayed in comparison with that in the +/y on days 12 and 14. Purkinje cells with several somal sprouts were observed in the cerebellum in both the Ml/y and +/y on day 7. The somal sprouts in the +/y had regressed gradually by day 12, while they were still in the anterior and middle lobes of the Ml/y on day 14. Additionally, the trunks of Ml/y stem dendrites became thicker and a cactus formation was recognized on the branching portion of the dendrites on day 14. Arborization of these abnormal Purkinje cells was distinctly poor compared with that in the +/y. These results suggest that the growth of the neurons is delayed in the Ml/y and simultaneously their cytoskeletal developments are disturbed, especially in the Purkinje cells. There is a close similarity in many respects to the neuropathological change in MKHD.

Animals↗
PubMed1987

Clinico-pathological study on macular mutant mouse.

The macular mutant mouse was clinically and pathologically examined. The hemizygotes began to show white fur color and curly whiskers around postnatal day 3, then seizures and ataxia around day 8, while the normal littermates did not. The hemizygotes also increased weight gradually from birth to day 9, but then showed weight loss and died around day 15 with severe emaciation. These clinical features resembled those in Menkes kinky hair disease. There were no pathological changes in the cerebral cortex in the hemizygotes on day 7. On day 10, two to three clear vacuoles began to appear in a few neurons in the cerebrum. These neurons with vacuoles increased gradually in number and degenerative neurons were also observed by day 14. Ultrastructurally, they corresponded to giant abnormal mitochondria with an electron-lucent matrix and short peripherally located cristae. Other abnormal mitochondria, which were characterized by an electron-dense matrix with tubular or vesicular cristae, were also observed in the cerebral cortical neurons.

Age Factors↗
PubMed1987

Light and electron microscopic study on cerebellar cortex of macular mutant mouse as a model of Menkes kinky hair disease.

The macular mouse is a mutant mouse, the hemizygotes of which show clinical and biochemical abnormalities similar to those in Menkes kinky hair disease (MKHD) in humans. The cerebellar cortex of this mutant suckling mouse was examined by light and electron microscopy. In hemizygotes, the Purkinje cells showed a delay in the maturation of dendrites and somatic spines. Somal sprouts, abnormal mitochondria, and filamentous cytoplasmic inclusions were observed on these cells on day 13. Axonal swellings, containing abnormal mitochondrias were also seen in the inner granular layer. These findings correspond with those of MKHD in humans and those of the brindled mouse, another model mouse of MKHD.

Animals↗