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G YASUZUMI

Publications and source records attributed to G YASUZUMI.

At least 19 recordsLinked to original sources
PubMed1962

Electron microscopy and x-ray scanning microanalysis of needle biopsy material from human liver.

A study has been made of the fine structure of hepatic parenchymal cells of human biopsy material in a case of pancreatic tumor with obstructive jaundice. Dense particles about 60 A in diameter have been found in the cytoplasm, which are considered to be ferritin molecules by electron microscopy. They are encountered throughout the cytoplasmic matrix and are often aggregated in electron-transparent areas, most of which are enclosed by an apparently single-layered membrane. Identification of the elemental iron has been pursued by the application of the x-ray scanning microanalyser which reveals a quantitative value within 1.0 per cent of the pure iron sample. The use of x-ray scanning microanalysis enables one to obtain accurate data from extremely small and precisely defined volumes of biological specimens.

Biopsy↗
PubMed1960

Spermatogenesis in animals as revealed by electron microscopy. VII. Spermatid differentiation in the crab, Eriocheir japonicus.

Testes of Eriocheir japonicus were fixed in buffered (pH 7.2) 1 per cent osmium tetroxide and thin sections of the methacrylate-embedded tissue were studied with the electron microscope. Spermatozoa from the vasa deferentia and spermatids from the testes were examined in smear preparations and sections. The most useful stainings proved to be the Feulgen, Unna-Pappenheim, and PAS reactions. The present paper covers one of the late stages of spermatogenesis. At the late stage of differentiation of the spermatid, the nucleus shows a concave disc-like contour in longitudinal sections and the karyoplasm is finely alveolar in appearance. A vesicle with a fibrillar or granular content appears situated between the cytoplasm and the nucleus. In an advanced spermatid, a large vacuole develops between the nucleus and this vesicle. As development of the spermatid proceeds, the cytoplasm is sloughed off. Thus, the advanced spermatid consists of an ovoid vesicle surrounded by a flattened nuclear disc. The former corresponds to the "capsule" or the "head," and the latter to the "pseudopodia." Concurrently with the sloughing off of the cytoplasm, a lamellar structure appears at the periphery of the head. It is composed of thin plates imbricated like the leaves of an onion. Each plate consists of triple layers, two dense layers separated by a lighter space. Each layer measures about 7 mmicro in diameter. At the distal pole of the head, a depression develops into a tubule which reaches the proximal pole of this structure. The lumen of the tubule is occupied by a dense substance part of which arises from the limiting membrane of the vacuole. The dense material begins to fill the tubule from the distal towards the proximal end. It finds its way till the middle of the tubule, leaving its proximal half unfiled. Thus, the proximal portion of the mature sperm head has a straight tubule whlich opens on its surface. The latter is covered by a dense membrane about 60 mmicro in width. Cytochemical analysis reveals that the pseudopodia contain DNA, and the head a carbohydrate component as well as PNA. The classical concept that the head becomes the male pronucleus after fertilization can no longer be accepted on the basis of the cytochemical analysis. The present study came to no definite conclusions concerning the functional significance of the head.

Animals↗
PubMed1960

Spermatogenesis in animals as revealed by electron microscopy. VIII. Relation between the nutritive cells and the developing spermatids in a pond snail, Cipangopaludina malleata Reeve.

This paper deals with spermatogenesis in Cipangopaludina malleata Reeve, with special regard to the relation between the nutritive cells and the developing spermatids. The nutritive cell gives rise to numerous, slender or broad, elongate pseudopodia which extend from its surface toward the seminiferous lumen. They are characteristically provided with rows of circular, oval, and elongate profiles identical in form and position with the profiles of the endoplasmic reticulum. As the elongate pseudopodia increase in number, they become more slender and more closely packed until they coalesce into a continuous sheet circumferentially disposed around the nucleus and the full length of the middle piece of the typical spermatid. Thus the mantle of the typical spermatozoon of the pond snail is formed by a thin fold of the cytoplasm of the nutritive cells. This wrapping appears to contain 16 to 18 elements of the smooth surfaced endoplasmic reticulum, which run parallel and helically (50 to 100 mmicro apart). It is suggested that these constitute a conductor system for nutritional supply from the nutritive cells to the developing typical spermatids. The mantle is assumed to be a transient structure which disappears when the sperms are detached. The atypical spermatids develop while lodged in deep indentations of the surface of the nutritive cells.

Animals↗