The adenohypophysis of the threespine stickleback, Gasterosteus aculeatus, was studied light-microscopically to determine and estimate the cell types and their function. For these purposes, the adult specimens obtained during the period from migration to spawning were examined. Further, the juveniles caught in the spawning bed were subjected artificially to sea water.
The rostral pars distalis (RPD) consists mainly of two types of cells: dorsally shifted lead hematoxylin (PbH)-positive cells bordering the neurohypophysis correspond to corticotrophs, and antero-ventrally shifted acidophil cells are identified as prolactin cells. The latter undergo marked hypertrophy and active state just at the time of entering the river (February), while no detectable change was seen in the former throughout anadromous migration. The role of prolactin on the osmoregulation in freshwater environment is thus suggested.
The proximal pars distalis (PPD) consists mainly of two cell types: the basophil cells in round shape are regarded as the gonadotrophs and the acidophil cells in ellipsoid shape are considered to be somatotrophs. The size of the gonadotrophs reaches the maximum at the time of spawning. A few AF-positive cells of elongate shape occur in the dorsal region and are identified as thyrotrophs.
In the pars intermedia (PI), two types of cells are discernible: PAS-positive and PAS-negative cells. The latter attained their maximal size in the earliest time of anadromous migration.

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Human liver specimens obtained by needle biopsy were extensively osmicated by the revised tannin-osmium method of MURAKAMI (1974) and cracked in air after critical point drying, to be observed in the scanning electron microscope.
The fracture tended to occur along the membranous elements and exposed beautifully fractured faces of the hepatic cell.
The nucleus of the hepatic cell was spherical. The nuclear pores were demonstrated as small pits 0.1μ in diameter and their total occurrence in one nucleus was estimated to be 2, 100. In the spongy framework resembling the endoplasmic reticulum, oval-shaped mitochondria and multivesicular tufts of the Golgi complex were observed. The nucleolus of the hepatic cell nucleus was noticed as a highlighted mass in the cloudy nucleoplasm.

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The postnatal development and sequence of eruption of mandibular cheek teeth of rabbits were studied by histological methods. Hemi-mandibles were dissected and sectioned in longitudinal sections of 7μ and stained with hematoxylin-eosin and Masson's trichrome. The presence of two mandibular deciduous molars which are replaced by corresponding premolars and of three mandibular permanent monofisary molars was confirmed.
Eruption of deciduous molars of the mandible begins at 4 days after birth and of the mandibular permanent molars at 9 days, while that of mandibular premolars occurs at 23 days, replacing the mandibular deciduous molars which have exfoliated. At 32 days all the mandibular permanent cheek-teeth are erupted.
At birth the mandibular deciduous molars are completely developed and at 4 days their root resorption is initiated. At the first day P₃ is in the bell stage and the P₄ has begun dentinogenesis. In M₁ and M₂ amelogenesis is observed.

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The claustrum of the cat is basically composed of 4 classes of neuron. Class I is a rather small neuron (<10μ in diameter) and is provided with rather few cytoplasmic organelles, while Class IV, large (25-30μ), neuron possesses an abundance of them. Class II, medium-sized (15-20μ), neuron and fusiform Class III neuron (about 15×25μ) exhibit an intermediate form of the former two classes. Perikaryal and proximal dendritic surface of Class IV neurons are covered with many boutons, while neurons of the other three classes have few of such terminals on their perikaryal surface. The dendritic profiles of rather reduced diameter bear a few axonal terminals.
Five types of terminals are recognized: (1) Type A terminal, small in profile, with uniform sized round vesicles (about 300A in diameter) making asymmetrical synapses; (2) Type B terminal of small size, containing round vesicles of various diameters (300-400Å) and forming asymmetrical synaptic contacts; (3) Type C, also small in profile, being filled with pleomorphic vesicles and making symmetrical synapses; (4) Type D large terminal with numerous pleomorphic vesicles, many mitochondria and a number of glycogen-like granules, forming symmetrical synapses; and (5) Type E terminal containing numerous granular vesicles (800-1, 000Å). The Type C and some of Type A terminals usually synapse upon the cell bodies and proximal dendrites, while most of Type A, B, D and E make synapse upon medium to small dendritic profiles and spines.
The problem whether or not the cytoarchitecture of the claustrum at the light microscope level is identifiable at the ultrastructural level as well, and the possible origin of various types of terminals above described, were discussed briefly.

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Bone marrow sinuses of young rats were examined under the scanning (SEM) and transmission electron microscopes (TEM).
Marrow sinus wall was composed of three layers: an inner or luminal endothelium, an outer or adventitial cell layer, and a basal lamina in between. The luminal surface of the endothelial cells was quite smooth and showed some fenestrations, which could be divided into two types according to their size. One was represented by larger fenestrations (1-3μm in diameter) which were presumed to be formed transiently at the site of blood cell migration, while the other by small pores (0.1μm) grouped into a cribriform area. The adventitial cells showed a discontinuous layer in the TEM. Under the SEM, the discontinuity corresponded to the spaces formed between the cytoplasmic attenuations of the cells.
Blood cell migration from the extravascular hemopoietic tissue into the sinus lumen was numerously observed. The migration occurred not through an intercellular gap, but through the larger intracellular fenestration of the endothelial lining mentioned above.
A number of megakaryocytes were identified by their bulky cytoplasm in the parenchyme. Figures suggesting the sequence of platelet liberation from this cell could be demonstrated. First, the megakaryocyte extended its peripheral cytoplasmic processes into the sinus through endothelial fenestrations. The processes, being conspicuously extended, became periodically constricted. Finally, platelets were believed to be produced by separation at the constricted portions and liberated to circulation.
The occurrence of a few endothelial fenestrations apparently unassociated with blood cell migration may possibly be ascribed to detachment of a blood cells due to vascular perfusion. The functional significance of the adventitial cell was discussed in association with blood cell migration.

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Rats were 1) fed raw soybeans for 30 days, 2) given trypsin inhibitor as drinking water for 7 days, or 3) repeatedly injected with cholecystokinin-pancreozymin (CCK-PZ) for 7 days. After all these treatments the pancreas of the animals was markedly enlarged. Microscopic examination revealed, besides hypertrophy of acinar cells, increased mitotic figures in the acinar, centro-acinar, intercalated portion and excretory duct cells. The islets of Langerhans were found conspicuously enlarged due to mitotic proliferation of B cells. The endogenous CCK-PZ released by the intraluminal trypsin inhibitor and the exogenous CCK-PZ given by injections thus exerts not only secretagogous, but also trophic effects upon the endocrine and exocrine pancreas. The exocrine pancreas likely is affected also by the increased release of insulin from the B cells stimulated by CCK-PZ.

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