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Biomedical subjects

M Furuya

Publications and source records attributed to M Furuya.

At least 127 records · Page 7Linked to original sources
PubMed1989

[Cellular thermosensitivity].

(1) modes of expression of thermosensitivity and theoretical interpretation of thermal dose, (2) differential thermosensitivities between strains of cells and the possible correlation to heat shock proteins and their syntheses, (3) cell phase responses to hyperthermia, (4) low hyperthermia and the induction of thermotolerance, (5) comparative thermosensitivities at the temperatures between below and above 42.5 degrees C -43 degrees C, (6) Arrhenius plot and mean cellular lethal heating periods, (7) step-up heating and the thermotolerance induction, (8) step-down heating and the thermoenhancement, (9) fractionated high hyperthermia and the thermotolerance induction and (10) modification of thermosensitivity by chemical substance including anticancer drugs; are compactly reviewed mainly on cell level.

Cell Cycle↗
PubMed1989

46,XY pure gonadal dysgenesis with gonadoblastoma.

A case of gonadoblastoma on one side in streak gonads in a phenotypic female with chromosomal 46,XY pattern is described. The histopathological resemblance between gonadoblastoma and sex cord tumor with annular tubules is discussed. The high serum testosterone level, being unrelated to the administration of human chorionic gonadotropin is valuable for the diagnosis of gonadoblastoma in an individual with dysgenetic gonads. Gonadoblastoma is frequently very small in size and is located in ectopic regions, so that laparotomy with biopsy has been stressed. The hormonal supplement for a postgonadectomized girl is also discussed.

Adolescent↗
PubMed1988

Stimulation of guanylate cyclase activity by irreversible binding of atrial natriuretic peptide to its receptor.

We examined receptor binding profiles of atrial natriuretic peptide (ANP) in rat tissue using 125I-labeled alpha-rat ANP [( 125I]alpha-rANP). Specific [125I]alpha-rANP binding to its receptor was reversible following addition of unlabeled free alpha-rANP, but it became increasingly irreversible with time during incubation. Irreversible binding of alpha-rANP was observed both at 0 degrees and 25 degrees in homogenates of adrenal capsules and lungs, crude membranes of renal glomeruli, partially purified membranes of lung, solubilized membrane preparations from renal glomeruli, and intact renal glomeruli. Irreversible binding increased in a time- and temperature-dependent manner. HPLC analysis demonstrated that the irreversibly bound radioactivity, which was extracted by 1 N CH3COOH from both intact renal glomeruli and from partially purified membranes, was associated with intact [125I]alpha-rANP. Irreversibly bound alpha-rANP increased cGMP concentrations by activating guanylate cyclase activity. These findings suggest that the appearance of irreversible binding of alpha-rANP to its receptor is independent of its internalization, and may be involved in message transduction and subsequent biological responses.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Purification of myxamoebal fragmin, and switching of myxamoebal fragmin to plasmodial fragmin during differentiation of Physarum polycephalum.

We have isolated and purified an activity from amoebae of Physarum polycephalum that reduces the flow birefringence of a solution of F-actin in a Ca2+-dependent manner. The purified activity from 100 g of amoebae consisted of 1 mg of a 40,000 mol. wt protein. DNase I-affinity chromatography demonstrated that the protein binds to Physarum actin in a Ca2+-dependent manner, and the binding is not reversed by excess EGTA. Viscometric measurement indicated that the protein (i) accelerates polymerization of G-actin, and (ii) severs F-actin, in a Ca2+-dependent manner. Thus, the protein appeared functionally similar to the fragmin previously isolated from Physarum plasmodia (plasmodial fragmin). However, the two proteins had slightly different mobilities on urea-SDS-PAGE, and antibodies raised against the two proteins scarcely cross-reacted with each other. Hence, we conclude that the two proteins are closely related to but are different from each other, and we have named the novel protein 'myxamoebal fragmin'. Immunoblot analysis indicated that myxamoebal and plasmodial fragmins are specifically present in amoebae and plasmodia, respectively. Results of immunofluorescence staining suggest that the synthesis of plasmodial fragmin is switched on coordinately with the synthesis of the heavy chain of plasmodial myosin and other plasmodium-specific contractile proteins during the apogamic differentiation of amoebae to plasmodia.

Actins↗
PubMed1988

Protective effect of alpha-human atrial natriuretic polypeptide (alpha-hANP) on chemical-induced pulmonary edema.

It has been established that alpha-hANP, the newly discovered peptide extracted from human cardiac atria, has potent natriuretic and hypotensive actions. Our present investigation is the first to demonstrate that alpha-hANP is capable of protecting against pulmonary edema caused by various chemicals, using isolated perfused guinea pig lung system. Lungs were perfused via pulmonary artery with Krebs-Ringer bicarbonate buffer at 5.0 ml/min, and wet weight of lungs and perfusion pressure of pulmonary artery (Pa) were monitored. Bolus injection of Triton-X or CHAPS into cannulated pulmonary artery produced edema as indicated by a massive increase in wet weight and a slight increase in Pa. Constant infusion of alpha-hANP through pulmonary artery at 200 ng/ml was effective in causing decrease in wet weight of lung. Perfusion of lung with paraquat or PGF2 alpha, and repeated bolus injection of arachidonic acid or PGE2 caused elevation in both wet weight of lung and Pa. The treatment with alpha-hANP similar to that described above also protected against edema caused by paraquat or arachidonic acid. Bolus administration of epinephrine induced a slight increase in wet weight and Pa, and alpha-hANP was effective in decreasing the elevated lung wet weight and Pa of lungs. Infusion or bolus administration of alpha-hANP into control lungs increased cGMP level in outflow perfusate as well as in lung tissue significantly. In lungs with edema which were induced by Triton-X or paraquat, there was a slight increase in cGMP level in Triton-X treated and no increase in paraquat treated lung tissues. In either cases, was there any increase in cGMP level in perfusate. The specific binding study of [125I]alpha-hANP revealed that the lack of increase in cGMP was not due to a loss of receptor in Triton-X or paraquat treated lungs. Thus our study demonstrated that alpha-hANP had a direct anti-edematic action(s) in lung which was not secondary to the systemic natriuretic and/or hypotensive action(s).

Animals↗
PubMed1987

Effects of the Timing of Flashes of Light during the Course of Cellular Rotation on Phototactic Orientation of Individual Cells of Cryptomonas.

The swimming movement of Cryptomonas sp. cells generates a helical path, as a result of rotations with an average period of 500 milliseconds. When a flash of light at 570 nanometers for 20 microseconds was applied unidirectionally at intervals of 500 milliseconds, only a fixed side of each rotating cell was repeatedly exposed to the flashes of light. The relationship between the irradiated side of a cell and the phototactic orientation of the cell, rotating with a period of 475 to 525 milliseconds, was determined by infrared videomicrography. Only when the ventral sides of the cells were exposed to the flashes of light did their courses shift predominantly toward the light source. This result suggests that light is efficiently detected by the ventral side of these organisms.

Journal Article↗
PubMed1987

Wavelength Effect on the Action of a N-Phenylimide S-23142 and a Diphenylether Acifluorfen-Ethyl in Cotyledons of Cucumber (Cucumis sativus L.) Seedlings.

Specific wavelengths of light required for expression of phytotoxic activity of S-23142 (N-[4-chloro-2-fluoro-5-propargyloxy]phenyl-3,4,5,6-tetra- hydrophthalimide) and acifluorfen-ethyl (ethyl-5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitro benzoic acid) were determined in cotyledons of cucumber seedlings using the Okazaki Large Spectrograph. Leakage of amino acids from the cotyledons was measured as an indication of the phytotoxic activity. The wavelength effects showed common major peaks of activity at 550 and 650 nanometers and a minor peak at 450 nanometers for both herbicides, indicating a common primary photoreaction. Concomitant application of DCMU (3-[3,4-dichlorophenyl]-1,1-dimethylurea) with S-23142 had little influence on the effective wavelengths for S-23142 activity. Light of 450 and 650 nanometers was relatively less effective in achlorophyllous tissue grown in far red light than in green tissue. These results strongly suggest that the phytotoxic action of S-23142 and diphenylethers involves multiple photoreactions and that one of the photoreceptor pigments may be chlorophyll or its related pigment, although photosynthesis is not involved.

Journal Article↗
PubMed1987

Alpha-human atrial natriuretic peptide (alpha-hANP) prevents pulmonary edema induced by arachidonic acid treatment in isolated perfused lung from guinea pig.

Protective effect of alpha-human atrial natriuretic peptide (alpha-hANP) on pulmonary edema was investigated using an isolated perfused lung model. Infusion of alpha-hANP (1.7 to 22 ng/ml or 0.56 to 7.3 nM) prevented the edema induced in isolated lung from guinea pig by repeated treatment of 50 micrograms of arachidonic acid at 30 min intervals via the pulmonary artery. The antiedematic action of alpha-hANP was considered to be receptor mediated because the effective concentration was close to the Kd value of the binding of the ANP receptors in the lung homogenate.

Animals↗
PubMed1987

[An electron microscopic study of malignant giant cell tumor of bone].

Three cases of malignant giant cell tumors were studied by light microscope and electron microscope. Light microscopic observation revealed three different types of tumor cells, namely, malignant stromal cells, fibrosarcomatous cell and osteosarcomatous cells. Electron microscopic observation revealed that fibrosarcomatous cells had ultrastructure similar to that of malignant stromal cells. Both types of cells showed nuclear pseudo-inclusions (NPI), and well developed organellae related to matrix synthesis in the cytoplasm. Polysaccharide staining of the same cells revealed positive products in the cytoplasm. Osteosarcomatous cells showed irregular nuclei which contained NPI and well developed r-ER. The cells were located in the non-calcified matrix which consisted of collagen fibers. No alkaline phosphatase activity was observed in this area. These facts suggest that: (1) malignant stromal cells and fibrosarcomatous cells synthesize collagenous stroma as normal fibroblasts do, and (2) osteosarcomatous cells are devoid of the ability to promote matrix calcification.

Adult↗
PubMed1986

Effects of low temperature and calcium on microfilament structure in flagellates of Physarum polycephalum.

Microfilament structures of the ridge and the backbone in Physarum flagellates disintegrated selectively within a few minutes upon cooling by ice-water. The elongated cells concurrently rounded up to spherical or irregular and amoeboid shape. When such rounded cells were warmed to 25 degrees C, the microfilament structures were reconstructed within 1 min and cells subsequently returned to an elongated shape. Disruption of microfilaments by cytochalasin A also caused the rounding up of cells, indicating that the rounding up resulted from disintegration of microfilament structures. This transformation induced by the cold treatment was retarded by preincubation of the cells with EGTA for 15 min, but addition of EGTA immediately before the onset of the cold treatment was less effective. The effect of EGTA was cancelled by simultaneous addition of excess Ca2+. Addition of procaine also inhibited the transformation induced by the cold treatment, while caffeine inhibited the recovery of the elongated shape when returned to 25 degrees C. Furthermore, addition of A23187 at 25 degrees C in the presence of Ca2+ mimicked the effect of the cold treatment. Thus, intracellular release of Ca2+ was suggested to be involved in the transformation induced by the cold treatment. Lability of the microfilament structures at a high concentration of Ca2+ was directly proved using Triton-permeabilized cells. Therefore we concluded that low temperature disrupts microfilament structures that are necessary for the maintenance of the elongated cell shape by inducing intracellular Ca2+ release. However, microfilament structures in Physarum amoeba cells were affected neither by the cold treatment nor by high Ca2+ concentration.

Actin Cytoskeleton↗
PubMed1986

Localization of binding sites for alpha-rat atrial natriuretic polypeptide in rat kidney.

To determine the intrarenal localization of receptors for atrial natriuretic polypeptide (ANP) in the rat, we performed autoradiography and binding assay by using 125I-labeled alpha-rat ANP (alpha-rANP). Autoradiography at the slice and microscopic level in the kidney and binding assay in isolated glomeruli demonstrated that receptors in the renal cortex were distributed mainly in glomeruli. Although dense silver grains were distributed diffusely both in inner medulla and outer stripe of outer medulla, a marked displacement of the grains was observed only in the inner medulla. Autoradiography at the microscopic level also showed that silver grains were distributed in the renal artery, renal pelvis, and inner medullary collecting tubule (IMCT) prepared by the microdissection method, but not in the arcuate artery, interlobular artery, and afferent or efferent arterioles. Specific binding was demonstrated in the isolated glomeruli and the preparation was rich in fragments of IMCT. Apparent binding affinity (Kd) and receptor density (R) for 125I-labeled alpha-rANP in isolated glomeruli and IMCT were Kd = 3.2 and 21 X 10(-9) M, and R = 320 and 420 fmol/mg protein, respectively. These observations suggest that alpha-rANP has a physiological action on glomeruli and possibly on the inner medullary collecting tubules in addition to the renal artery.

Animals↗