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Biomedical subjects

M Takata

Publications and source records attributed to M Takata.

357 records · Page 20Linked to original sources
PubMed1966

Blockage of sodium conductance increase in lobster giant axon by tarichatoxin (tetrodotoxin).

Tarichatoxin, isolated from California newt eggs, has been found to selectively block the increase of sodium conductance associated with excitation in lobster giant axons at nanomolar concentrations. This resulted from a reduction in the amplitude of the conductance increase rather than a change in its temporal characteristics. The normal potassium conductance increase with depolarization is not altered. A high concentration of calcium applied concomitantly with the toxin significantly improves the reversibility of the sodium blocking. This toxin has recently been identified as chemically identical with tetrodotoxin from the puffer fish. Toxins from the two sources are equally effective and are shown to have an action which is distinctly different from that of procaine.

Animals↗
PubMed1966

Ionic conductance changes in lobster axon membrane when lanthanum is substituted for calcium.

The trivalent rare earth lanthanum was substituted for calcium in the sea water bathing the exterior of an "artificial node" of a lobster axon in a sucrose gap. It caused a progressive rise in threshold, and a decrease in the height of the action potential as well as in its rates of rise and fall. Prolonged application produced an excitation block. Voltage-clamp studies of the ionic currents showed that the time courses of the ionic conductance changes for both sodium and potassium were increased. Concurrently, the potentials at which the conductance increases occurred were shifted to more positive inside values for the La+++ sea water. These effects resemble changes resulting from a high external calcium concentration. Over and above this, La+++ also causes a marked reduction in the maximum amount of conductance increase following a depolarizing potential step. Membrane action potentials similar to those observed experimentally in the La+++ solution have been computed with appropriate parameter changes in the Hodgkin-Huxley equations.

Action Potentials↗
PubMedDate not supplied

Interaction of zinc with cadmium and copper on ossification of embryonic chick bone in tissue culture.

Histological changes are shown of ossification induced by a simultaneous exposure to zinc and cadmium or to zinc and copper using embryonic chick femur in a culture system. Cadmium caused an atrophic change of the osseous tissue in the absence of zinc but caused an osteomalacic change with a partial degenerative change in the presence of zinc after a 6-day culture. Copper caused an atrophic change in the absence or presence of zinc. These observations were partly supported by the fact that the diaphysial calcium content was significantly decreased by zinc alone, and the decrease was unaffected by cadmium or copper. Zinc significantly decreased cadmium accumulation but not copper accumulation in the diaphysis. Thus, in spite of the inhibitory effect on calcification, zinc prevented a decrease in bone matrix formation caused by cadmium but not that by copper. Exposure of chick femur culture to zinc and cadmium induced changes consistent with osteomalacia, i.e., decreased mineralization of bone, with or without suppression of matrix formation. Exposure to zinc and copper, however, induced changes consistent with osteoporosis, i.e., decreased mineralization and matrix formation.

Animals↗
PubMedDate not supplied

Multi-layer amniotic membrane graft for pterygium in a patient with xeroderma pigmentosum.

BACKGROUND: Xeroderma pigmentosum (XP) is a rare, autosomal recessive, premalignant condition of the skin, and is reported to be associated with ocular surface disorders such as conjunctival malignancy and pterygium. Herein, we report a case of successful management of pterygium with multi-layer amniotic membrane graft (AMG) in a young XP patient. CASE: An 11-year-old Japanese girl, who had been diagnosed as having XP, was referred to us for treatment of her bilateral pterygium. Surgical intervention was attempted for a temporal, presumably fast-growing pterygium in her left eye. Multi-layer amniotic membrane grafting was performed. OBSERVATIONS: The surgery-induced pain and irritation disappeared within a day. The limbal conjunctival autograft survived on the AMG and re-epithelialization over the AMG was completed in 2 weeks. Best corrected visual acuity improved from 20/32 to 20/16 one month postoperatively. During the 1-year follow-up period, no recurrence was noted. CONCLUSIONS: The present case exemplifies that AMG as an adjunct to primary pterygium resection is effective even in a young patient with XP. In addition, multi-layer AMG, which we first demonstrated in this report, seems to be useful for protecting bare sclera and extraocular muscles from mechanical injury.

Amnion↗
PubMedDate not supplied

Role of bradykinin potentiation in the antihypertensive effect of captopril in conscious rabbits with two-kidney, one-clip hypertension.

The role of bradykinin potentiation in the antihypertensive effect of captopril was assessed in conscious rabbits with two-kidney, one-clip hypertension. On the 35th day after clipping the renal artery, a bolus injection of bradykinin 0.2 microgram/kg was repeated at 15-min intervals three times before and for 180 min after the administration of captopril 0.5 mg/kg. The magnitude and duration of captopril-induced hypotension were more marked in hypertensive rabbits than in controls. The bradykinin-induced hypotension was markedly enhanced by captopril. However, the bradykinin potentiation by captopril was not correlated with its vasodepressive effect. On the other hand, a close relationship (r = 0.825, p less than 0.001) was observed between plasma renin activity and the maximum reduction in blood pressure induced by captopril. The experiment performed after sodium depletion for 7 days revealed that the bradykinin potentiating effect of captopril was not affected by sodium depletion. Therefore, it is concluded that the vasodepression by captopril does not necessarily depend on its bradykinin potentiating action and the latter is not influenced by the renin-angiotensin system or fluid volume depletion.

Animals↗
PubMedDate not supplied

Fetal hydrocephalus secondary to intraventricular hemorrhage diagnosed by ultrasonography and in utero fast magnetic resonance imaging. A case report.

Although fetal hydrocephalus is commonly detected by prenatal ultrasonographic examination, posthemorrhagic hydrocephalus has rarely been observed in the fetus. We report a case of hydrocephalus secondary to intraventricular hemorrhage (IVH) diagnosed by in utero magnetic resonance imaging (MRI) at 37 + 1 weeks of gestation. Ultrasonography revealed enlargement of the bilateral ventricles and an irregular mass measuring 20 x 12 x 10 mm in the right lateral ventricle. T1-weighted images with two-dimensional fast low-angle shot (2D-FLASH) and T2-weighted images with half-Fourier single-shot turbo spin echo (HASTE) demonstrated that an old hemorrhagic clot existed in the right lateral ventricle of the fetus. Hydrocephalus secondary to IVH was confirmed by postnatal MRI and ventriculoscopy. Fast MRI is especially useful for prenatal diagnosis of fetal brain abnormalities because it minimizes the artifact of fetal movement.

Adult↗
PubMedDate not supplied

Induction of anti-tumor immunity by mouse tumor cells transfected with mouse interleukin-12 gene.

Interleukin-12 (IL-12) is a heterodimeric cytokine. In order to transduce both cDNAs for p35 and p40 of IL-12 in the tumor cells, a polycistronic retroviral vector was constructed by inserting the internal ribosome entry site gene of encephalomyocarditis virus between two cDNAs. On the other hand, two cDNAs were sequentially transfected in the tumor cells. Both polycistronic gene transfectants and double transfectants produced biologically active mouse IL-12. IL-12-expressing tumor cells were all rejected in syngeneic mice, and induced cytotoxic T lymphocyte activity. The capacity to induce anti-tumor memory may depend on the amount of IL-12 produced by the transfectants, because the relatively higher IL-12 producer tumor cell line induced the anti-tumor memory in the rejected mice, but the lower producer did not.

Animals↗