The effects of estrogen and progesterone on the spleen of gonadectomized male mice were studied by means of quantitative methods.
Estrogen caused an increase in the weight of the spleen. The splenic pulps, red and white, were significantly enlarged, and particularly the red pulp was found to be markedly increased in volume. In the red pulp of the control, erythroid cells were most numerous in the various hemopoietic cell lines. Estrogen caused a further increase of erythroid cells, and erythroblasts underwent a two-fold increase in number. By stereological analysis using electron microscopy, erythroblasts could be classified into three categories in nuclear and cell sizes: small, medium and large. Large and medium erythroblasts were three to four times as numerous in the estrogen-treated group as in the control.
The white pulp did not show any histological changes following estrogen injection, and progesterone exerted almost no influence upon the splenic pulps.

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Corrosion casts of the blood vessels in the oral mucosa of Rana esculenta were examined by the scanning electron microscope. Special attention was paid to the palatine capillaries characterized by numerous blind diverticula. Microanatomy and topography of these peculiar vessels suggests their involvement in gas exchange. The diverticula of the capillaries visible in the casts in form of nodules of various shape and size were examined in detail.

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The organ of Corti in human fetuses aged 5 and 7 months, respectively, was observed with the scanning and transmission electron microscope (SEM and TEM).
By SEM observation, bulbous cytoplasmic structures protruding from the apical surface of the outer and inner hair cells were observed as was the case in SEM reports by others. By TEM observation, it was revealed that these structures are cytoplasmic projections from the so-called cuticular notch which, in adults, houses the basal body and is a site for synthesis of auditory stereocilia and a single kinocilium.
The stria vascularis was examined only in the 5 month specimen. The cytoplasm of the differentiating marginal cells is characterized by the presence of thick walled tubular membranes. The observation suggests that this tubular system may represent “a particular site” for secretion of some ions into the endolymph in the fetal condition.

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The immunohistochemical method was used to study lens formation in a new dominant mouse strain with a small eye and lens cataract (gene symbol Cs). Antisera to pure alpha- and gamma-crystallins were used.
In the homozygotes, the eyes have cataractous lenses about half the size of normal lenses. In the heterozygotes, the eyes show opacities of the lens but the lens itself is normal in size.
The mouse strain has two genes in the same autosome which cause the phenogenetical characteristics of small eyes and cataracts. One reflects the defect of the gammacrystallin synthesis in the secondary lens fibers in the equatorial zone. This is a recessive gene and it may cause the small lens. The other gene is responsible for the swollen, granular and misshaped fiber cells. This is a dominant gene like that in the Fraser's cataract and it may cause the cataract lens.

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The current investigation was undertaken to study whether mammalian prolactin can induce mitotic activity in the anterior pituitary gland in chicks. It was found that intramuscular injections of ovine prolactin (1.5 i. u., 5 i. u. and 10 i. u. each daily per bird for 10 days) significantly increased mitotic frequency in the adenohypophysis of juvenile cockerels. It is suggested that ovine prolactin has a mitogenic action on the adenohypophysis of the male chicks and that the reaction may be dose-dependent.

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Unusual tubular inclusions in the mitochondrial matrix of human hepatocytes were found in 7 out of 15 cases with cholelithiasis. These inclusions were composed of tubular structures which were about 50nm in diameter and varying in number. The wall of the individual tubules appeared to consist of about 10 tubular subunits with a diameter of about 5nm. Although some relationship between occurrence of these tubular inclusions and production of gallstones might be suggested, their origin and functional significance are unknown.

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Goblet cells in the jejunal epithelium of adult and suckling rats were studied with transmission electron microscope. The use of triple fixation, i.e., osmium-aldehyde-osmium has some advantages in the preservation of mucous substances and some cell organelles. Cytochemical demonstration of polysaccharide and glycoprotein by methenamine silver as well as detection of TPPase and acid phosphatase (AcPase) were performed. Accumulation of secretory substances and combination with sugar moieties occurred in the internal sacs of Golgi lamellae, where TPPase activity was recognized. No rigid lamella usually positive to AcPase was found in goblet cells, though it was easily found in the columnar absorptive cells. AcPase was positive in some small immature mucus droplets as well as lysosomes.
As the differentiation of goblet cells advances, mucus droplets come into contact and fuse to each other. As a result of the close contact of two adjacent membranes of mucus droplets, a pentalaminar structure is first formed. Then the central dense lamina disappears and the membrane becomes trilaminar. Disappearance of one of the apposed unit membranes, leaving another unit membrane, may take place. Finally the single unit membrane left between the adjacent droplets is also ruptured and complete fusion occurs.
The mechanism of extrusion of mucous substance is complicated. Some mucus droplets located at the most superficial area may be released by the mechanism of exocytosis. More frequently, however, deeply located droplets fuse to each other and a huge vacuole is made in the apical cytoplasm. The substance filling the vacuole contains debris of cytoplasmic matrix and droplet membranes along with mucous secretory substance. These substances derived from different sources are expelled into the lumen at the same time. This may be classified into the apocrine mechanism, because a part of the cytoplasm and membranes are lost. The typical apocrine secretion, i. e., pinching off of cytoplasmic projection containing mucus droplets, was also found in the goblet cells. Thus, two or three different mechanisms of secretion discharge may possibly occur simultaneously in goblet cells.

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The Tomes' processes of ameloblasts in the kitten were examined with both transmission and scanning electron microscopes and their three-dimensional structure demonstrated. In general, Tomes' process can be envisaged as the upper part of a diagonally cut column. It was established that the flat crescent face of the process which is slanted cervically, is the secretory surface (S-face) and the curved crescent surface which is cuspally directed, is the nonsecretory surface (N-face). The cervical border of the S-face is confluent with the free apical surfaces of cervically adjacent ameloblasts. Only the S-face and the adjoining small part of the next ameloblasts produce enamel and arrange crystallites into prisms as evidenced by the perpendicular orientation of crystallites to the S-face of Tomes' process and the free ameloblast surface. Crystallite arrangement within prisms and prism arrangement within enamel are determined by the three-dimensional morphology of the Tomes' processes. The processes are schematically represented and their relationship to other ultrastructural features as seen in sections is discussed.

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