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G YASUZUMI

Publications and source records attributed to G YASUZUMI.

At least 37 records · Page 2Linked to original sources
PubMed1958

Spermatogenesis in animals as revealed by electron microscopy. VI. Researches on the spermatozoon-dimorphism in a pond snail, Cipango-paludina malleata.

This paper reports an electron microscope study of typical and atypical spermatogenesis in the pond snail, Cipangopaludina malteata. In the typical spermatid the nucleus undergoes profound changes as development proceeds, affecting both its form and internal fine structure. A large number of roughly parallel, dense filaments, arranged along the long axis of the nucleus, fuse with each other to form in the end the homogeneous helical body characteristic of the head of the adult spermatozoa. The nebenkern is apparently mitochondrial in nature and, in its early development, is similar to that of insects except that it appears as a double structure from the beginning. As differentiation proceeds, the mitochondria lose their membranes, and the residual, now denuded cristae, reorganize to give a parallel radial arrangement. In the last stages of development, the nebenkern derivations become applied to the sheath of the middle piece in a compact helical fashion. In the development of the atypical spermatozoa, the nucleus fails to differentiate and simply shrinks in volume until only a remnant, devoid of DNA, is left. The cytoplasm shows numerous vesicles containing small Feulgen-positive bodies, 80 to 130 mmicro in diameter. These vesicles plus contents increase in number as spermatogenesis proceeds. The "head" structure of the atypical spermatozoa consists of a bundle (7 to 17) of tail flagella, each with a centriole at its anterior end. The end-piece of the atypical form appears brush-like and is made up of the free ends of the several flagella.

Animals↗
PubMed1957

Spermatogenesis in animals as revealed by electron microscopy. II. Submicroscopic structure of developing spermatid nuclei of grasshopper.

The submicroscopic structure of the maturing spermatid nucleus of the grasshopper, Gelastorrhinus bicoler de Haan, has been studied in thin tissue sections by electron microscopy. In the early spermatid the nucleus appears dense with no clearly resolvable fine structure. In the advanced spermatid with a conical-shaped nucleus, the karyoplasm begins to show a fibrillar structure. At subsequent stages, the elongated spermatid nucleus displays in cross-sections a hexagonal honeycomb pattern and in longitudinal sections an array of parallel lines, 70 A in diameter and spaced 100 to 220 A apart. As differentiation of the spermatid proceeds further, the space between the lines becomes narrower and narrower until it can no longer be resolved.

Animals↗