Licht- und elektronenmikroskopische Studien an kernhaltigen Erythrocyten

Zusammenfassung Das Cytoplasma der kernhaltigen Erythrocyten enthält einige Mitochondrien von rundlicher oder irregulärer Form in Nähe der Kernmembran. Das endoplasmatische Reticulum erscheint spärlich in Form kleiner Bläschen. Der nicht stark entwickelte Golgiapparat besitzt die Form rundlicher Vakuolen. Das Plasmalemm erscheint als doppelte osmiophile Membran von 90–100 Å Dicke.Der Kern ist aus unregelmäßig geformten, amorphen Körperchen und netzartig angeordneten Mikrofibrillen einer Dicke von etwa 100 Å zusammengesetzt; erstere sind als das Heterochromatin aufzufassen, letztere als die euchromatischen Elemente.Zum Schlüsse möchte ich Herrn Dr. S. Ueyama, Dr. S. Higashizawa und cand. med. H. Yamamoto für Hilfe bei dieser Arbeit meinen herzlichsten Dank aussprechen.     

Spermatogenesis in Animals as Revealed by Electron Microscopy : VI. Researches on the Spermatozoon-Dimorphism in a Pond Snail, Cipangopaludina 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 mµ 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.     

Spermatogenesis in animals as revealed by electron microscopy

Summary The fine structure of the developing middle piece of the silkworm spermatid was studied in the electron microscope.The formation of Nebenkern and its metamorphosis are characteristic, for a given species of animal, and different from those of other species.Microtubules, with a wall approximately 50 Å thick and a lumen 110 Å in diameter, have been found in the developing middle piece; these are in close relationship with the differentiation of the axial tail filaments and of the Nebenkern derivatives.When the middle piece has reached a certain degree of maturity, a peripheral cytoplasmic layer of the middle piece is separated by the outer membrane of the endoplasmic reticulum, and later sloughed off from its trunk. The naked middle piece is subsequently covered by a mantle provided with 12–18 projections which develop descending from the proximal head part of the late spermatid.The clear band developing along the surface of the middle piece is a characteristic, complex structure which seems to represent an apparatus for pinocytosis or exosmosis.This study was supported by Grant GM-8327-04 from the United States Public Health Service.     

Striated microfilament bundles attaching to the plasma membrane of cytoplasmic bridges connecting spermatogenic cells in the black snail, Semisulcospira libertina (Mollusca, Mesogastropoda)

Striated microfilament bundles attaching to the plasma membrane of cytoplasmic bridges between spermatogenic cells are described in the black snail, Semisulcospira libertina. The bundles were occasionally observed in bridges connecting spermatogonia, spermatocytes and typical spermatids. Relations between bundles and centrioles could not be detected. The bundle had electron dense cross bands with a periodicity of approximately 200 nm, and attached to the membrane with almost right angle at the cross linker level. Phalloidin cytochemistry revealed that the bundle contained F-actin. In a case, a bundle connected two cytoplasmic bridges.     

Spermatogenesis in animals as revealed by electron microscopy

Summary The development of nuclei and cytoplasmic microtubules was studied in the maturing spermatids of the grasshopper, Acrida lata, fixed with glutaraldehyde-potassium bichromate-osmium tetroxide and embedded in epoxy Epon-resin. Utilization of microkaryosomes for the formation of paracrystalline nucleoprotein is suggested by the fact that they are no longer visible in the advanced spermatid nuclei showing the paracrystalline structure. The cytoplasmic microtubules approximately 220 Å in diameter develop in close association with a linear material similar in density to the nuclear envelope. Only a single layer of the double-layered nuclear envelope is visible during the development of microtubules. Although cytoplasmic microtubules are assumed to have several physiological functions, such apparatus seem to be related to the polymerization of nucleoproteins as well, since the depolymerization of nucleoproteins occurs simultaneously along with the disappearance of cytoplasmic microtubules.     

Electron microscope researches on the ultrastructure of nucleoli in animal tissues

Summary On the basis of electron microscopy of nucleoli in various physiological stages of similar and different cells, it is assumed that the nucleolonemata appear for the first time in the pre-mitotic stage and subsequently the nucleolus-associated body makes its appearance.The nucleolonema is composed of helically coiled filaments 50 Å in diameter.The nucleolus-associated body comprises tightly packed filaments about 15–30 Å thick which are helically coiled.     

Spermatogenesis in animals as revealed by electron microscopy

Summary Testes of Bombyx mori Linné were fixed in buffered (pH 8.2) 1% OsO₄ or 3 % KMnO₄ and thin sections of the tissue, embedded in methacrylate or epoxy Epon resin, were studied under the electron or light microscope.At the late stage of differentiation of the spermatid, the nucleus shows an elongated conical contour, being composed of fine fibrillar elements. These fibrillar elements fixed in OsO₄ measure 100 to 130 Å in diameter, while those fixed with KMnO₄ are approximately 70 Å in diameter.It has been found for the first time in the spermiogenesis of the silkworm that two bands and a tubular structure develop in close proximity to one another and attached to the plasma membrane of the spermatid. The two bands fixed in OsO₄ are electron dense, but in the material fixed with KMnO₄, one of them, situated within the cell body, is as dense as that fixed in OsO₄, while the other, outside the cell body, is much less dense. These apparently novel apparatuses develop from the caudal nuclear region along the elongating spermatid, but the dense band intertwines with the acrosome in the apical region of the nucleus along the major axis of spermatid, while the tubular structure and the clear band reach far into the nutritive cell where the dense band and acre-some are not visible.A possible relationship between the tubular structure and the nutritive cell has been discussed.This study was supported by Grant GM-8327-03 from the United States Public Health Service.     

Spermatogenesis in animals as revealed by electron microscopy

Summary The fine structure of the spermatids in late stages of the differentiation, which appeared in the testis of early pupa of the silkworm Bombyx mori Linné, was studied in the electron imcroscope, being fixed in buffered (pH 8.2) 2.5% osmium tetroxide or 3% potassium permanganate.The clear band differentiates into elaborated elements consisting of an array of at least 12 membranes which run loosely winding along the major axis of the spermatid. The elaborated clear band, i. e., clear band derivatives, may be an apparatus to facilitate the activity of spermatozoa, since they are present along the full length of the remarkably elongated premature spermatozoa.It has been revealed that the clear band derivatives possess a highly ordered, fine structure which is seen to be of a paracrystalline nature. The periodic pattern has first occurred along the long axis of the clear band derivatives. After such structure is decomposed into an apparently homogeneous material, a characteristic periodic pattern occurs again crossed the major axis of the clear band derivatives, the significance of such ultrastructural changes remaining obscure.The tubular structure appears through the head part of the developing spermatids, revealing even in an apical region where the nucleus is not visible, and it appears enlarged at the base of the nucleus, but no more visible in the tail piece. In the stages when the clear band becomes progressively specialized, the tubular structure appears attached to the nucleus, although it situated at the peripheral part of the cell in a more early stage of the differentiation. The tubule is incompletely separated into two layers by a dense septum projected from the tubular wall, suggesting that such structure provides the tubule with a relatively large interior surface for metabolic reactions.This study was supported by Grant GM-8327-04 from the United States Public Health Service.