The distribution and fine structure of the granulated vesicles in the central nervous system of rodents (rats, guinea pigs and rabbits) have been investigated by means of electron microscopy. Some properties of these vesicles were studied by the administration of certain drugs, radioautography and cytochemistry at the fine structural levels.
1. Granulated vesicles were most numerous in the nuclei hypothalamicus anterior, paraventricularis and ventro-medialis and less numerous in the subependymal layer of the third or fourth ventricles and the nuclei hypothalamicus lateralis and posterior. A moderate number of granulated vesicles were demonstrated in the preoptic areas, the central gray matter of the midbrain, the nucleus interpeduncularis, the mamillary body, formatio reticularis (midbrain and pons), locus caeruleus, nucleus habenulae, nucleus dorsalis nervi vagi, area postrema and supraoptic crest.
2. The midbrain and pontine reticular formation showed many axo-somatic synapses, and some presynaptic bags of granulated vesicles were seen mixed with synaptic vesicles. In the perikaryon of the nerve cells of the formatio reticularis, area postrema and nucleus hypothalamicus posterior, mature and various immature types of granulated vesicles were concentrated around the Golgi apparatus and in the neighbourhood of the multivesicular bodies.
3. The membrane (80Å) of granulated vesicles showed a trilaminar structure and the dense core inside consisted of electron-opaque subunits of about 40Å in diameter and sometimes showed clear globular structures.
4. Intraperitoneal injection of reserpine (10mg/kg) caused the majority of granulated vesicles in the madial hypothalamus to evaculate their core or their core to decrease in electron density and to lose catecholamine. An injection of Win 18501-2 resulted in a decrease in the content of noradrenalin and a parallel decrease in the number of granulated vesicles in the hypothalamus. The dopamine content did not show any relation with the morphological alteration of granulated vesicles in animals injected with Win 18501-2.
5. The distribution of acetylcholine-esterase activity was studied by electron microscopy by the method of KARNOVSKY. In the neuropil of the nucleus caudatus and in the mossy fiber endings of the cerebellum, activity was demonstrated on the plasma membranes of the preterminal axons, presynaptic terminals and dendritic branches. The locus caeruleus, nucleus dorsalis nervi vagi and medial hypothalamus also showed activity on the plasma membrane of the axon terminals which contained both granulated and synaptic vesicles.
6. At various times after intraperitoneal administration of H³-DOPA to the rat pretreated with catron, the brain was fixed as described in methods 1 (normal distribution of the granulated vesicles) and the ultrathin sections were coated with Sakura NA-Hl by the wire-loop or pushing method. Electron microscopic autoradiography of the nuclei hypothalamicus anterior and ventro-medialis showed that two-thirds or three-quarters of the total silver grains were located on the neuropils. In the neuropils about 70% of the silver grains were localized on the synaptic endings and dendrites. There was a tendency for the number of silver grains on the presynaptic terminals containing granulated vesicles to increase with time after the administration of H³-DOPA.

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1. This paper is a preliminary report on the eosinophilic vesicles found in the head epidermis of Blepsias cirrhosus.
2. Such vesicles occurred also in the following three species: Cottus nozawae, Hemitripterus villosus and Myoxocephalus sp. Accordingly, the vesicles seemed to be not a morbid structure, but a wide-spread one among the fishes belonging to the family Cottidae.
3. They were roundish oval or pear shaped, and of variable sizes, and their tips occasionally opened to external. They were generally prominent in the species supplied with few mucous cells.
4. The contents of the vesicles looked light yellow or colorless, and were stained more easily with acid dyes, especially with eosin, than with the basic ones. They exhibited considerable variations in staining intensity and color tone according to whether they consisted of gross granules or fine ones.
5. The chemistry and the function of these vesicles need further investigation.

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The electron microscopic observation of pancreatic islets of normal and alloxan treated hypoglycemic rabbits yielded the following results.
1. The elaboration of secretory granules by both A cells and B cells involves the activity of the rough endoplasmic reticulum and Golgi apparatus.
2. The secretory granule of the A cell is released by emiocytosis.
3. As to the release mechanism of the B granule, in addition to emiocytosis reported by several authors, the possibility of a diacrine type of secretion might be considered, especially under pathological conditions. It is suggested that alloxan might alter the limiting membrane of the B granules and the B cell plasma membrane to allow, by a pathological diacrine mechanism, the release of a large amount of insulin which causes the severe hypoglycemia after administration of this substance. In the experimental animal, the capillary endothelium becomes irregular in shape with numerous cytoplasmic processes and shows increase in the number of small vesicles suggesting the pinocytosis.
4. The alloxan treated B cell containing empty granular sacs and relatively denser cytoplasmic matrix stains with aldehyde-thionine or aldehyde-fuchsin. It is obscure which causes this positive reaction, the empty sac or the hormonal substance diffused in the cytoplasmic matrix.
5. The alloxan may alter not only the limiting membrane of the secretory granule but also the nucleus and cyto-organelles of the B cell, and thus disturb the formation of new secretory granules. Then the animal might become hyperglycemic because of the destruction of the B cell.
6. The numerous cytoplasmic filaments found especially in the B cell seem to arise from free ribosomes or attached ribosomes of the outer nuclear membrane.

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Using in vivo local labeling method, cell proliferation and differentiatiation in the human epidermis covering the mammary gland of 41 and 42 year old women were studied by means of ³H-thymidine autoradiography.
1. Stratum germinativum or G-zone of the human epidermis in which cells are proliferating corresponds to epibasal and basal layers, but not the basal layer alone. Proliferating cells are predominantly located in the epibasal layer.
2. Melanin containing cell in the basal layer is a kind of minor-differentiated cell and proliferates at much slower rate than the non-pigmented basal cell.
3. Generation time of the genertive cell is estimated at 4 days and the maximum length of DNA synthesis, at 10 hours. Many differentiating cells stay in the epibasal layer and they amount to 50% of the total cells in the layer. Their transit time in the layer is estimated at an average of 4 days.
4. The unequal division or (G, M) division is not a mechanism to maintain the steady state, nor do any types of mitosis play a decisive role in the regulation of cell differentiation. Mitoses yield two equivalent daughter cells which are in the same state as the mother cell.
5. Cell differentiation in the human epidermis seems to be determined by the rule of probability in an individual daughter cell during t₁ or G₁ period, as has been confirmed in various other cell systems.

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A structure similar in morphology to the synaptic ribbon was found in the inner segment of the lamprey retina.

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Sodium localization in the plasma membrane of the intestinal absorptive epithelial cell was demonstrated by using potassium pyroantimonate and electron microscopy.
Sodium precipitates were found exclusively on the plasma membrane and were most numerous at the apical free surface of the cell.
Sodium precipitates were found on the cytoplasmic side of the plasma membrane including the inner leaflet of the unit membrane.
The functional significance of the finding was discussed.

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The M. levator pinnae pectoralis of Carassius auratus appeared red and the M. levator pinnae lateralis abdominis pale to the naked eye. The fine structure of both these muscles were observed to correlate with the recent electrophysiological findings gained in the same material.
The average diameter of both fibres was 36.0μ for the red fibres and 49.4μ for the white ones.
The fibre type of both these muscles can be clearly identified by the examination of transverse sections. In the red fibres, the mitochondrial accumulation beneath the sarcolemma and rich deposits of glycogen were seen. The peripheral myofibrils of both tissues appeared in ribbon-like forms in a radial direction but almost all inner fibrils were polygonal in the red fibres.
Regarding the arrangement of the myofilaments, no differences between the red and white fibres were observed. The Z, I, A, H and M bands were found to be well delineated. The Z lines were disposed to form a regular zigzag configuration and at the M lines well defined cross-bridges between the thick myofilaments were seen. The triads were located at the Z line level and the sarcoplasmic reticulum was well developed. In short, the internal structure of these two kinds of muscle was similar to that of the fast fibres of the frog.
On the other hand, the innervation of both these muscles resembled that of the slow fibres of the frog; they showed the diffuse innervation. The nerve endings of both muscle fibres were so-called“en grappe”type. In the red fibres, densely grouped terminals in some areas of the fibre surface were found. The types of innervation might be classified as multi-focal diffuse innervation in the red fibre and mono-focal diffuse innervation in the white. These differences were confirmed by electrophysiological findings.
The electrophysiological properties of the red fibres showed a tendency to be similar to the slow fibres of the frog and the white fibres to the fast fibres of the frog. However, the morphological differences between the fast and slow fibres in the frog could not be recognized in the muscles of this fish.

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