The functional role of the alternating morphologic changes of the rat and hamster incisor ameloblasts at the stage of enamel maturation was investigated. Special attention was paid to the distribution of the intravenously injected horseradish peroxidase (HRP) throughout the ameloblastic layer.
The ameloblasts at the stage of enamel maturation were divided into two groups with respect to their distal cell borders: ruffle-ended (RA) and smooth-ended ameloblasts (SA). In the ameloblastic layer, SA were distributed as several band-like structures (SA-bands) which ran transversely or obliquely along the distal surface of the ameloblastic layer. Intravenously injected HRP permeated the intercellular spaces of SA and reached the surface of the enamel, however it did not penetrate the distal junctions of RA. Five min after the injection, HRP was incorporated into the cytoplasmic vesicles of RA, while no incorporation was shown in SA. After 1hr, however, HRP was incorporated into the incisal one-third of the ameloblasts in each SA-band. Acid phosphatase activity (p-nitrophenylphosphatase) was shown in the cytoplasmic vesicles, both in RA and SA. The most intense alkaline phosphatase activity was located on the ruffled border of RA, while no activity was detected on the unmodified apices of SA.
Contact microradiography revealed a gradual increase of the radio opacity of enamel towards the incisal direction independent of the alternating changes of overlaying RA and SA. However, the fluorescence of injected tetracycline showed intense labelling at the portions of enamel which corresponded to RA. The portions of enamel being overlayed by SA were located in between such labelled areas and showed only faint fluorescence of tetracycline.
These results suggest that, RA actively degradate, resorb and then digest the organic matrices of the enamel and also transport minerals into the enamel. It is also suggested that SA are formed from the RA which have become inactive metabolically and here the exhausted cytoplasmic organelles seem to be renewed and reactivated.

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The fine structure of a Z band abnormality which closely resembled that of nemaline body was studied using myocardial biopsies. The abnormality was found in 10 out of 103 examined patients with various cardiac muscle diseases. Ultrastructurally, they were characterized by interwoven textures of fine filaments in a form similar to the nemaline body. However, they differed in two points from the nemaline body: first, most of them were interposed between the sarcomeric arrangement as an intramyofibrillar architecture, and second, two parallel filaments with periodic bridges were demonstrated in this abnormality. In the present study, the interwoven Z band abnormalities occurred regardless of the disease's sort, the patient's age, and the hypertrophic grade in the muscle cell. Meanwhile, some degenerative changes, myofibrillar lysis and mitochondrial degeneration, were frequently detected in the cardiac muscles with the abnormalities. Pathologically, the interwoven form of the Z band abnormality seemed to indicate an unbalance of the compensative mechanism at the cell level.

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Histochemical studies have been conducted on the distribution of labeled neurons in the rat pons at the level of the locus coeruleus after HRP injections into the supraoptic nucleus. In all the fifteen cases in which the supraoptic nucleus was found to be included in the injection site, labeled neurons were detected in the locus coeruleus whereas in the other nine cases in which the injection site was outside the supraoptic nucleus, labeled neurons were not detected in the locus coeruleus. Six cases having the injection site successfully localized within the supraoptic nucleus showed definitely a few labeled multipolar neurons only in the ipsilateral locus coeruleus. These findings demonstrate the presence of an efferent projection arising from the locus coeruleus to the ipsilateral supraoptic nucleus. It is suggested that mainly multipolar neurons in both divisions of this nucleus may contribute to this projection. There remains a possibility that the locus coeruleus may project to the supraoptic nucleus on the contralateral side.

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Effects of pregnancy and lactation on the spleen and the mesenteric, iliac, axillary and popliteal lymph nodes in the mouse were morphologically examined by means of qualitative and quantitative methods.
During pregnancy the spleen weight increases to reach a peak at 15 days of pregnancy. After parturition the weight decreases gradually until 20 days postpartum when it has returned to almost normal. Both the red and white pulps increase in volume during pregnancy. After parturition, the volume of the white pulp rapidly returns to normal. The volume of the red pulp remains greater in lactating females than in control females. In non-lactating females the red pulp decreases rapidly in volume after parturition. In the spleen, plasma cells increase in number during pregnancy, and often contain Russell bodies. They are accumulated in large numbers particularly in the marginal zone and periarterial area. After parturition plasma cells decrease rapidly in number.
The weight of the mesenteric lymph node undergoes a slight but a significant increase during pregnancy, and decreases in both the lactating and non-lactating groups after parturition. During pregnancy the medulla shows an increase in volume, and the medullary cords are filled with numerous plasma cells. At 10-15 days of pregnancy, plasma cells also occur in groups in the paracortex. They decrease rapidly after parturition. During pregnancy plasma cells are also markedly increased in iliac lymph nodes, but not in axillary and popliteal lymph nodes.
The findings were discussed particularly in relation to the immune response of the peripheral lymphatic tissue in pregnancy.

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This report deals with the ultrastructural changes observed in neurons of the posterior root ganglion of slow loris (Nycticebus coucang) following administration of tricresylphosphate (TCP) 0.2ml/kg body weight for 10 days. The observed changes involved the rough and smooth endoplasmic reticulum profiles, neurofilaments, Golgi complex as well as lipofuscin pigment. Nissl substance was markedly dispersed to the periphery of the neuron. Membranous profiles of the smooth endoplasmic reticulum were lost. Neurofilaments were markedly increased and manifested neurofibrillary tangles or else were scattered over the cytoplasm. Golgi complexes were dilated and there was a marked increase in lipofuscin.
These observations suggest that TCP produces degenerative changes in the organelles of sensory neurons similar to those seen at the height of chromatolysis produced by mechanical interference in the dorsal root ganglia and other neurons.

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A method combining glyoxylic acid perfusion with potassium permanganate postfixation revealed a moderate number of characteristic axon terminals including noradrenaline storage granules in the rat thoracic segmental lateral horn (Th₁, Th₃, Th₆, Th₉, Th₁₂). The region showed two kinds of cells: the one (principal cell) was characterized by a remarkably indented nucleus, many mitochondria and long endoplasmic reticulum, and the other by markedly developed short endoplasmic reticulum to increase its cytoplasmic density.
The axon terminals observed on lateral horn cells could be roughly divided into four types depending upon the shape and size of the synaptic vesicles included and their contents: type I contained many small and a few large granular vesicles. Type II mainly had many large vesicles with diffuse contents and hardly noticeable cores or granules; type III included only small spherical vesicles without any granules; the rare type IV had flattened vesicles with small and large granular vesicles. Type I, type II and type III contacted not only the soma and dendrites of the principal cells but also each other, forming a so-called “cluster, ” which suggested an axo-axonic contact. No difference could be observed between each level of the thoracic lateral horn (Th₁, Th₃, Th₆, Th₉, Th₁₂) in terms of noradrenaline granules and synaptic organization. Occasionally, the contacts of a certain process were observed which resembled a dendrite, including short endoplasmic reticulum, lysosomal dense bodies and large and small vesicles with a dendrite of the principal cell.
These findings corresponded to the present data of innervation of abundant amine fibers descending through the dorsal half of the lateral funiculus to accumulate around lateral horn cells by the histofluorescent method.

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The taste buds in tortoises (Clemmys japonica and Geoclemys reevesii), lizards (Takydromus tachydromoides) and snakes (Elaphe quadrivirgata) were examined by both ultrastructural and histochemical methods.
The taste buds consisted of at least three types of cells: the type I, II and III cells. The type I cells were characterized by the presence of secretory dense granules containing polysaccharides which were demonstrated by periodic acid-chromic acid-silver methenamine technique. The type II cells contained numerous tubular, vesicular and lamellated structures. The type III cells were characterized by dense cored vesicles and afferent synaptic contacts. Besides these cells, basally located cells which resembled the basal cells of other lower vertebrates were sometimes found in the tortoises.
After administration of L-DOPA following nialamide, some taste bud cells of the tortoises, Clemmys japonica, showed weak yellowish green fluorescence by monoamine fluorescence histochemistry and the dense-cored vesicles in the type III cells increased in number. Acetylcholine esterase activity was not observed in tortoise taste buds.
It is suggested that the three types of cells which compose the taste buds of the reptiles may correspond to the three types of cells in mammalian, and the type III cells represent the gustatory cells which are able to potentially produce biogenic monoamines.
From these results, the taste buds of the reptiles may hold an intermediate position between those of mammals and amphibia or fishes.

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