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Biomedical subjects

Y Mikami

Publications and source records attributed to Y Mikami.

At least 307 records · Page 17Linked to original sources
PubMed1980

Some chemotherapeutic properties of two new antitumor antibiotics, saframycins A and C.

The antitumor activity of saframycin was examined against four different experimental tumor systems in mice. Saframycin A and C inhibited the growth of L1210 cells in suspension culture completely at concentrations of 0.02 microgram/ml and 1.0 microgram/ml, respectively. The LD50's of saframycin A for ddY mice were 4.9 mg/kg (ip) and 3.3 mg/kg (iv), respectively. In C3H/He mice, the LD50's were 10.5 mg/kg (ip) and 9.7 mg/kg (iv), respectively. Saframycin A was highly active against Ehrlich ascites carcinoma and P388 leukemia, and moderately active against L1210 leukemia and B16 melanoma. The antitumor activity of saframycin A was 50 to 100 times greater than that of saframycin C. The survivors cured of Ehrlich ascites carcinoma by treatment with saframycin A developed a resistance to rechallenge with the same tumor. On the other hand, when carbazilquinone and adriamycin were used as reference drugs, the cured mice in these cases did not resist rechallenge with the same tumor. When saframycin A (5 mg/kg) was administered intraperitoneally into mice, the blood concentration of saframycin A was 4.6 microgram/ml after 30 min, and 2.8 microgram/ml after 1 hr, and the total recovery within 3 hr from the urine was 30%. Saframycin A was found to be distributed widely, though to different extents, in various organs when injected intraperitoneally into mice.

Animals↗
PubMed1977

Morphological changes in yeasts as a result of the action of 5-fluorocytosine.

The mode of action of 5-fluorocytosine on Candida albicans and Saccharomyces cerevisiae was studied with special reference to morphology and ultrastructure. Shortly after contact of yeast cells with 10 mug of 5-fluorocytosine per ml, marked enlargement of the cells occurred. The initial increase in cell size was almost the same with both yeast strains. As incubation proceeded, further increase in cell volume continued with C. albicans, whereas no further change in cell volume was observed with S. cerevisiae. An electron microscope examination of C. albicans cells after exposure to the drug revealed characteristic changes, consisting of an enlarged nucleus and a thin cell wall. The morphological changes were exactly comparable to those reported with inhibitors of deoxyribonucleic acid synthesis in mammalian cells and some bacteria.

Candida albicans↗
PubMed1977

Phagocytosis of Candida albicans by rabbit alveolar macrophages and guinea pig neutrophils.

Studies of host-parasite relationships at the cellular level, using Candida albicans and rabbit alveolar macrophages or guinea pig neutrophils are presented. Guinea pig neutrophils killed the intracellular candida cells presumed by myeloperoxidase-halide-hydrogen peroxide system. In contrast, rabbit alveolar macrophages did not kill the intracellular candida cells although their phagocytic rate was almost comparable to that of neutrophils. Phagocytizing macrophages were eventually destroyed by the intracellular proliferation of candida cells and formation of germ tubes and pseudomycelia. No significant improvement of candidacidal activity was observed with macrophages from normal and immunized rabbits in immune serum. The mode of phagocytosis by macrophages and neutrophils were also studied under the scanning electron microscope.

Animals↗
PubMed1977

[Agenesis of internal carotid artery associated with aneurysm of anterior communicating artery (author's transl)].

A case of agenesis of the left internal carotid artery with an aneurysm of the anterior communicating artery was reported in detail. The patient was a 48-year-old man who had an episode of subarachnoid hemorrhage about 10 years ago. This time left heminumbness and motor weakness of the left lower extremity occured and he was brought our hospital. Right common carotid angiography, left retrograde brachial serial angiography and aortography demonstrated an agenesis of the left internal carotid artery, an aneurysm of the anterior communicating artery, tortuous megadolic hobasilar artery and anomalies on the circle of Willis such as absence of supra optic portion of the right anterior cerebral artery, and large left posterior communicating artery. We confirmed latter findings by operation. After successful neck clipping of the aneurysm, his clinical findings were remarkably improved.

Carotid Artery, Internal↗
PubMed1976

Isolation and characterization of satellite antibiotics, mimosamycin and chlorocarcins from Streptomyces lavendulae, streptothricin source.

Under novel conditions of culture, Streptomyces lavendulae No. 314 was found to produce new antibiotics, chlorocarcins and mimosamycin in addition to streptothricin. The antibiotics are extracted from culture filtrate with organic solvents and further purified by silica gel chromatography. Chlorocarcins A, B and C are closely related basic antibiotics which are active against gram-positive bacteria, EHRLICH carcinoma and L 1210 leukemia of mice. Mimosamycin is a neutral antibiotic which is mainly active against mycobacteria. Production, isolation and physicochemical properties of the antibiotics are described.

Animals↗
PubMed1976

Identification of producer and biological activities of new antibiotics, mimosamycin and chlorocarcins.

A strain of Streptomyces, No. 314 identified as a Streptomyces lavendulae produced under a novel condition of culture, four new antibiotics, mimosamycin and chlorocarcins A, B, and C. Among the components of chlorocarcin complex, chlorocarcin A was found to be most biologically active. This antibiotic inhibited the growth of Staphylococcus aureus FDA 209P and Corynebacterium diphtheriae at the concentrations of 0.1 and 0.003 mcg/ml, respectively. Chlorocarcin A also exhibited antitumor activity on EHRLICH carcinoma, ascitic and solid forms, and mouse leukemia L1210. Mimosamycin proved to be mainly active on Mycobacterium tuberculosis and inactive on the experimental murine tumors.

Animals↗
PubMed1972

Chromogenicity of Streptomyces.

A simplified technique to detect polyphenol oxidase and melanin formation by Streptomyces culture filtrates was developed. The procedure involves the direct assay of pigment formation by the culture filtrate with 3-(3,4-dihydroxyphenyl)-L-alanine (L-dopa) as a substrate. Among cultures of the International Streptomyces Project, 34 failed to produce a diffusible dark brown pigment on peptone-yeast extract-iron-agar and synthetic tyrosine-agar and gave a negative reaction to the melanin formation test. Sixteen cultures produced a diffusible dark brown pigment on both peptone-yeast extract-iron-agar and synthetic tyrosine-agar and gave positive reactions to the test with either L-tyrosine or L-dopa as substrate. Twenty-one cultures produced a diffusible dark brown pigment on peptone-yeast extract-iron-agar, but failed to do so on synthetic tyrosine-agar. Most of these cultures gave a positive reaction to the test when L-dopa was used as the substrate. The correlation between chromogenicity on complex organic media and melanin formation was more clearly established with L-dopa as substrate than with synthetic tyrosine-agar in the present test. The melanin formation test by the present technique, instead of chromogenicity on complex organic media, is recommended as a key feature for the classification of Streptomyces.

Agar↗
PubMed1972

Chromogenesis mirabilis in Streptomyces griseus.

A number of chromogenic Streptomyces, producing diffusible melanoid pigment on complex organic media, fail to form melanin pigment on conventionally used synthetic tyrosine agar. By means of our new melanin formation test, almost all the chromogenic streptomyces can now be detected in chemically defined medium. In contrast to ordinary chromogenic streptomyces, two streptomyces species of the International Streptomyces Project, S. griseus ISP 5236 and S. ornatus ISP 5307, produce melanin pigment only on synthetic tyrosine agar, without showing chromogenicity on complex organic media. From the results obtained with S. griseus ISP 5236 and S. phaeochromogenes ISP 5073, it was revealed that melanin formation by Streptomyces, in general, is inhibited by L-cysteine present in organic nitrogen sources incorporated into natural media. Most chromogenic species of streptomyces produce a higher level of tyrosinase and rapidly utilize L-cysteine in the culture media which result in the manifestation of good chromogenicity on natural media. Peculiarity of chromogenicity of S. griseus and S. ornatus might be due to the lower ability to produce tyrosinase and to utilize L-cysteine in the culture medium.

Agar↗