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Biomedical subjects

M Ohkuma

Publications and source records attributed to M Ohkuma.

105 records · Page 6Linked to original sources
PubMed1976

Kuhnt intermediary tissue as a barrier between the optic nerve and retina.

Utilizing adult albino rats and lanthanum nitrate as a tracer, electron microscopic studies were done to provide additional information on the blood-optic nerve barrier. Following injection into the cervical artery, lanthanum was observed to fill the intercellular space of the optic nerve parenchyma. Diffusion from the prelaminar optic nerve into the juxta-optic nerve retina was, however, prevented by the Kuhnt tissue at the level of the rod and cone layer. In this region, tight junctions were found between the glial cells of the Kuhnt intermediary tissue and were continuous from the tight junctions of the retinal pigment epithelial cells to the junctions (zonulae adhaerentes) of the outer limiting membrane. From the level of the outer limiting membrane to the inner limiting membrane there was no diffusion of lanthanum into the adjacent retina despite the absence of tight junctions, and the lanthanum which had diffused from the choroid was never observed in the area of the inner limiting membrane of the optic nerve head. It is in this region that the functional barrier may exist.

Animals↗
PubMed1976

Freeze-fracture replica of the rat cornea.

The fine structures of the rat cornea, with special reference to their intercellular junctions, were studied using the freeze-fracture technique. At the corneal epithelium, gap junctions could be observed between the adjacent cells. At the stroma, crater-shaped depressions (between 300 and 500 A diameter) with pipe-like appearing structures connecting the lamellae were found. Intercellular junctions existing between the endothelial cells at the area near the anterior chamber are postulated to be the fascia (macula) occludens.

Animals↗
PubMed1976

Differentiation of host-mediated antitumor agents from mitotic posons by the antitumor foot-pad reaction in Ehrlich carcinoma-ddY mouse system.

The effect of antitumor agents (lentinan, PS-K, Mitomycin-C, 6-mercaptopurine, etc.) on the antitumor delayed hypersensitivity reaction (DHR) measured by the foot-pad test was compared with their effect on tumor growth in ddY mice with Ehrlich tumor. These agents all inhibited growth of Ehrlich carcinoma. Lentianan and PS-K enhanced the antitumor DHR, but Mitomycin-C and 6-mercaptopurine did not. By plotting the effect of agents on the anti-tumor DHR against these effects on tumor weight, host-mediated antitumor agents could be differentiated from mitotic poisons. Attempts to distinguish these two types of agents by the same method using a syngeneic tumor system were unsuccessful.

Animals↗
PubMed1975

Histochemical and electron microscopic studies of the human cutaneous lymphatic capillary.

The light microscopic characteristics of the normal cutaneous lymphatic capillary of man are the presence of elastic fibers around the vessel and a sudden change in contour of the lumen as observed on serial sections. Both are useful characteristics for differentiating the lymphatic from the blood capillary. Electron microscopic investigation is necessary to identify definitely vessels as lymphatic capillaries by demonstrating the absent or scanty basal lamina of the endothelial cell.

Adult↗
PubMedDate not supplied

Molluscum contagiosum treated with iodine solution and salicylic acid plaster.

Twenty cases of molluscum have been evaluated for the clinical effectiveness of 10% PVP-iodine solution and 50% salicylic acid plaster therapy. The treatment works well, and the shorter duration of treatment necessary for healing is statistically significant as compared with the duration of treatment for controls who lacked either one of the applications. Although the working mechanism for the effectiveness is not known, the treatment is characterized as a less expensive and less painful procedure. All patients were completely healed after a mean treatment of 26 days; there were no adverse effects. This therapy is recommended for the office patient, young children, diabetic patients, and those with multiple lesions.

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PubMedDate not supplied

Phylogenetic identification of the symbiotic hypermastigote Trichonympha agilis in the hindgut of the termite Reticulitermes speratus based on small-subunit rRNA sequence.

The phylogeny of a symbiotic hypermastigote Trichonympha agilis (class Parabasalia; order Hypermastigida) in the hindgut of the lower termite Reticulitermes speratus was examined by a strategy that does not rely on cultivation. From mixed-population DNA obtained from the termite gut, small subunit (16S-like) ribosomal RNA sequences were directly amplified by the polymerase chain reaction method using primers specific for eukaryotes. Comparative sequence analysis of the clones revealed two kinds of sequences, one from the termite itself and the other from a symbiotic protist. A fluorescent-labeled oligonucleotide probe for the latter sequence was designed and used in whole-cell hybridization experiments to provide direct visual evidence that the sequence originated from a larger hypermastigote in the termite hindgut, Trichonympha agilis. According to the phylogenetic trees constructed, the hypermastigote represented one of the deepest branches of eukaryotes. The hypermastigote along with members of the order Trichomonadida formed a monophyletic lineage, indicating that this hypermastigote and trichomonads shared a recent common ancestry.

Animals↗
PubMedDate not supplied

Phylogenetic identification of hypermastigotes, Pseudotrichonympha, Spirotrichonympha, Holomastigotoides, and parabasalian symbionts in the hindgut of termites.

The phylogenetic diversity of parabasalian flagellates was examined based on the sequences of small subunit ribosomal RNA genes amplified directly from the mixed population of flagellates in the hindgut of lower termites. In total, 33 representative sequences of parabasalids were recovered from eight termite species. Fluorescent-labeled oligonucleotide probes specific for certain sequences were designed and used for the in situ identification of parabasalian species by whole-cell hybridization. The hypermastigotes, Pseudotrichonympha grassii, Spirotrichonympha leidyi, and Holomastigotoides mirabile in the hindgut of Coptotermes formosanus, and Spirotrichonympha sp. and Trichonympha spp. in Hodotermopsis sjoestedti were identified. In the phylogenetic tree constructed, the sequences from the termites were dispersed within the groups of known members of parabasalids, reflecting the presence of diverse parabasalids in the hindgut of termites. There were three paraphyletic lineages of hypermastigotes represented by Pseudotrichonympha, Trichonympha, and Spirotrichonympha, in agreement with the morphology-based taxonomic groups. The analysis of the tree-root suggested that the Pseudotrichonympha group is the most probable ancient lineage of parabasalids and that the Trichonympha group is the secondly deep-branching lineage. The Spirotrichonympha group and the Trichomonadida may have emerged later.

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