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Biomedical subjects

A Wada

Publications and source records attributed to A Wada.

At least 523 records · Page 29Linked to original sources
PubMed1977

Kinetics of the polymerization reaction of tobacco mosaic virus protein: transient-saturation type polymerization reaction.

The kinetics of the endothermic polymerization reaction of tobacco mosaic virus protein in the mild acid region was studied by means of temperature-jump (rising time of 6 sec)-turbidimetry, electron microscopy, and computer simulation. The time course profile of the turbidity increase changed from a normal one to an anomalous one as the size of the temperature-jump was made greater. The anomalous type polymerization profile, which we named the "transient-saturation" type, could be characterized by a rapid increase of turbidity and its transient saturation, and a slow increase to the final level. At a higher concentration of the protein, this transient-saturation effect was more marked, whereas the slow turbidity in the second phase occurred with a higher rate. This transient-saturation type polymerization profile was observed also in a pH-induced polymerization reaction. It was not observed in the case of the N-bromosuccinimide modified tobacco mosaic virus protein under a similar environmental change. By an electron microscopic study and computer simulation, it was revealed that in the first phase, a large number of short polymers were formed, and the concentration of the polymerizing units was rapidly reduced to the equilibrium value, and the polymerization reaction stopped transiently. In the second phase, polymer-polymer associations took place slowly and longer polymers were formed. The revlevance of the present study to the polymerization reaction of actin, myosin, and to a transient-overshoot type polymerization are discussed.

Bromosuccinimide↗
PubMed1976

The alpha-helix as an electric macro-dipole.

A polypeptide chain is found to form an electric macro-dipole in solution when it is folded to take the alpha-helical conformation. This is due to the polar peptide residues, all of which are oriented to have their moment in the axial direction in its regular helical conformation. This remarkable electric nature of the alpha-helix has extensively been examined for nearly twenty years, and the study is still in a state of development. The dielectric behavior of a solution consisting of the macrodipole is one major concern of the study, and the other is to probe with this unique property into the regular conformation and helix-coil transition of polypeptides. Historical and topical, but not comprehensive, surveys have been given here for both of these dielectric aspects of the alpha-helix.

Alanine↗
PubMed1975

Fine structures in denaturation curves of bacteriophage lambda DNA. Their relation to the intramolecular heterogeneity in base compositon.

Precise recording of polyphasic optical melting curves was carried out for three kinds of bacteriophage lambda DNA differing in length (lambdac1857s7, lambdacIb2 and lambdacIb2b5). Each of denaturation steps in melting profiles was characterized by two parameters, the melting temperature and the relative size. Any difference in fine structures in melting profiles was not recognized between the intact lambdacI857s7DNA and the DNA fragmented into halves. The change in fine structures in melting profiles caused by the deletions of the b2 and b5 region agreed qualitatively well with the prediction based on the physical and the genetical maps of phage lambda chromosome. The combined results indicate that, first, the well-known linear relationship between melting temperature and G+C content may apply also to each of denaturation steps in polyphasic melting curves due to heterogeneity of nucleotide distribution in a single DNA species, and, second, the effect of molecular ends on melting fine structures can be neglected at moderate salt concentration (0.01 M less than or equal to Na+ less than or equal to 0.2 M) for such a high molecular weight DNA. The heterogeneous distribution of nucleotides was derived for lambdaDNA and for its b2 and b5 regions.

Base Sequence↗
PubMed1975

Diffuse submucosal cysts and carcinoma of the stomach.

Gastric submucosal cysts, carcinomas, and atypical hyperplasia have been observed in the superficial mucosa of 12 stomachs. It is thought that gastritis may give rise to these heterotopic glands, that the development of heterotopic cysts in the submucosa may make the surface mucosa prone to erosion, and that repeated erosion and regeneration may cause carcinoma or atypical hyperplasia.

Adult↗
PubMed1975

Argyrophil cell carcinomas (apudomas) of the uterine cervix. Light and electron microscopic observations of 5 cases.

Of a series of 97 invasive carcinomas of the cervix, 5 were found to have argyrophil tumor cells, and 3 of these 5 tumors were studied by electron microscopy. The ages of the 5 patients ranged from 36 to 49 years, with a mean age of 42.4 years. The morphologic features of these five tumors were well consistent with those described on a variety of endocrine polypeptide neoplasms such as thyroid medullary carcinomas, carcinoids, pancreatic islet-cell tumors, and oat cell carcinomas of the lung. Microscopically, the 5 tumors were characterized by the formation of solid-sheets, ribbons, streams, and rosettes. They were characterized electron microscopically by the presence of neurosecretory-type granules, the abundance of intracytoplasmic microfilaments, the absence of tonofibrils, and the paucity of desmosomal attachments. On the basis of the microscopic, electron microscopic and cytochemical characteristics, it is suggested that the tumors are a specific type of cervical carcinoma derived from the argyrophil cells, normally found among the linings of the endocervical glands and the cervical squamous epithelium. We believe these 5 tumors should be regarded as an endocrine tumor, another member of apudomas.

Adult↗
PubMed1975

Morphological and biochemical studies on the heart of the cardiomyopathic Syrian hamster.

Histological and ultrastructural observations of embryonic hearts and cultured cells from hamsters with inherited cardiomyopathy (BIO 14.6 line) showed a significant delay in maturation of the sarcomeric units in comparison with those of unrelated healthy control hamsters. Phase-contrast microscopic observation of the cultured cardiomyocytes revealed more rapid diminution of beating frequencies in the diseased hamsters than in the controls. Negatively stained ultrastructure and yield of the actomyosin extracted both from the cardiomyopathic and the control hamsters showed no fundamental differences. Disc electrophoresis of the erythrocyte ghosts revealed, at least, a quantitative difference in one of the composing proteins between these two groups.

Actomyosin↗
PubMed1975

Trauma as an essential factor in atherogenesis-ultimate proof.

Intimal foam-cell plaques developed within three weeks on the shoulders of cuts through aortic rings within diffusion chambers implanted subcutaneously into rabbits fed cholesterol. Since hemodynamic and thrombogenic factors were excluded the development of cholesterol-atherosclerosis and the localization of the plaques were the result of an interplay of three factors: trauma, a cholesterol-rich plasma insudate, and a susceptible aortic intima.

Animals↗