Hideki Takahama

Fine structure of the spermatophores and their ejaculated forms, sperm reservoirs, of the Japanese common squid, Todarodes pacificus

Spermatophores in a squid, Todarodes pacificus, were observed by light and electron microscopy and were further analyzed by X‐ray microanalysis (XMA) of frozen thin sections. Each spermatophore consists of a sperm mass, a cement body, an ejaculatory apparatus, and some fluid materials, all of which are covered by an outer tunic. The outer tunic consists of about 20 membranous layers, each containing straight, parallel microgrooves. Each layers microgroove pattern is roughly in an orthogonal arrangement with respect to the next layers pattern. The sperm mass, which is the only cellular component, consists of a sperm rope which is coiled more than 500 times. Most of the spermatozoa in the rope are arranged regularly and are enveloped in materials which are well‐stained by Alcian blue. The cement body is located between the sperm mass and ejaculatory apparatus and has a hard outer shell with an arrowhead‐like structure, presumably for penetration into the tissue of the female. Calcium and phosphorus are present in the shell of the cement body, which also has an affinity for alizarin red. The ejaculatory apparatus consists of two tubes, designated as the inner tunic and the inner membrane.

Cytochemical studies of hydrogen peroxide production in the tadpole tail ofRana japonica during metamorphic climax

SummaryThe degeneration of tadpole tail tissue was investigated cytochemically by localizing the sites of hydrogen peroxide production. A cerium perhydroxide precipitation method was used. No reaction product was found in resting macrophages and intact muscle fibres during premetamorphosis. In the metamorphosis phase, extensive cerium precipitates were visualized on the outer surface of the plasma membrane of phagocytotic macrophages, fibroblasts, neutrophils, epidermal cells, muscle fibres, notochordal cells, nerve cells and capillary endothelial cells. The reaction products were localized on those parts of the plasma membranes of the macrophages that were in contact with those of adjoining cells. When catalase were added, the amount of deposits decreased. α-Tocopherol and indomethacin, but not dexamethasone, significantly inhibited the formation of the reaction products. These findings are taken to indicate that active oxygen is produced on the plasma membrane of activated macrophages and may play a role in the degeneration of the tail tissue.

Electron-microscopical study of the operculum in anuran tadpole after extirpation of the right forelimb during metamorphosis.

SummaryThe process of histolysis and fenestration of the skin of the prospective opercular perforation region of Rana japonica after extirpation of the right forelimb was observed during metamorphosis by transmission and scanning electron microscopy.Epidermal cells of the belly of the tadpole, including the operculum, are extremely similar in their ultrastructure. Epidermal cells of the prospective opercular perforation region during metamorphosis become thin and vacuolated especially around the nucleus perhaps by autolysis, associated with lysosomal activity. The histolysis and formation of the perforation of the operculum occurs in the complete absence of forelimb. Macrophages containing phagosomes and lymphocytes or other blood cells are almost always found in the intercellular epidermis. Necrotic epidermal cells progressively separate by cleft formation and slough off without cornification.

Satellite cells in the tail muscles of the urodelan larvae during development.

SummaryThe incidence and ultrastructure of satellite cells in the tail muscles of urodelan larvae were examined during development during which the number of satellite cells is gradually reduced. They are found more frequently in red than in the white fibres in all four stages examined (stage 53, 64, 66+ and juvenile). As development proceeds, intercellular space between satellite cell and muscle fibre is in general gradually extended and is mostly filled with basal lamina. Small muscle cells, satellite fibres, which are situated under the basal lamina of the parent fibre, are morphologically similar to satellite cells but contain a small amount of myofibrils. Three types of satellite fibres are distinguishable on the basis of differences in K2-EDTA-treated ATPase activity, width of Z line, and parent fibre type. Neuromuscular junctions are visible in satellite fibres.

Identification of Cells by Backscattered Electron Imaging of Silver Stained Bulk Tissues in Scanning Electron Microscopy

Anuran tadpole tail muscle was stained en bloc by a modified light microscope silver stain for light microscopy and freeze-fractured in liquid nitrogen after partial dehydration with ethanol. The fractured specimens were observed in both secondary electron and backscattered electron modes in a scanning electron microscope. Since the cell nuclei specifically stained with silver provided high contrast against the unstained background due to atomic number contrast of backscattered electron image, various cells were easily identified by a comparison of secondary electron images and compositional images of backscattered electron signals.

Changes in the satellite cells of the anuran tadpole tail muscles during metamorphosis

SummaryThe incidence and the ultrastructure of the satellite cells associated with red and white muscle fibres of the anuran (Rana japonica) tadpole tail were examined in three stages (hindlimb-bud, prometamorphic, and climax) during metamorphosis. In these three stages the satellite cells are found more frequently in the red fibres than in the white fibres. As metamorphosis proceeds, the incidence of the satellite cells decreases in both red and white fibres. The satellite cells in the hindlimb-bud stage have abundant cytoplasm rich in organells. Cisternae of rough endoplasmic reticulum are often dilated. The intercellular space between the satellite cell and the muscle fibre is narrow and relatively constant (15–25 nm). Some satellite cells appear to be in the process of fusion with the muscle fibre. Cytoplasmic volume and organellar content are gradually reduced during metamorphosis. In the prometamorphic and climax stages, the intercellular space is in general gradually extended. It often exceeds 0.5 μm, and usually contains the basal lamina and fibrous materials. Some satellite cells have cytoplasmic processes that project into the interstitial space through a gap in the basal lamina.