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Biomedical subjects

Y Obara

Publications and source records attributed to Y Obara.

At least 127 records · Page 7Linked to original sources
PubMed1980

Simplified purification and biophysicochemical characteristics of Kanagawa phenomenon-associated hemolysin of Vibrio parahaemolyticus.

Kanagawa phenomenon-associated hemolysin (K-hemolysin) was purified by Sephadex gel and ion-exchange column chromatography, after the culture supernatant had been adsorbed on and eluted from diethylaminoethyl-Sepharose CL-6B, and acid precipitated. K-hemolysin was a heat-stable and trypsin-susceptible protein with an apparent molecular weight of 44,000, the subunit of which was 22,000. The isoelectric point was 4.9. The minimum hemolytic dose was 0.1 mug/ml. The fifty percent lethal dose by intravenous injection was 1.4 mug. Electron microscopy of the small intestine of suckling mice orally challenged with the highest dose (50 mug) not only showed disappearance of epithelial cell microvilli, but also structural disturbances of the endoplasmic reticulum and mitochondrial swelling. One blueing dose representing permeability factor activity was 0.3 mug, and positive reaction in the rabbit ileal loop appeared at above 125 mug. Besides these data in experimental models, we discovered the appearance of an antibody in patients which neutralizes K-hemolysin during the course of the disease. This finding reinforces our view that K-hemolysin plays a most significant role in the pathogenesis of this enteric human disease.

Amino Acids↗
PubMed1980

Effect of tiopronin on senile cataracts. A double-blind clinical study.

The therapeutic effect of tiopronin on incipient senile cataracts was evaluated in 150 cases (275 eyes) by a double-blind study using nonactive placebo. A more favorable tendency to visual acuity was noted in the tiopronin than in the placebo group. The slit-lamp microscopic findings showed a statistically significant difference between the tiopronin and the placebo groups. Integrated judgement revealed tiopronin to be significantly effective as compared with the placebo. A side effect of fever with systemic eruption was observed in 1 case in the tiopronin group but disappeared completely when administration of the drug was discontinued.

Age Factors↗
PubMed1980

Measuring thyroxine and thyrotropin simultaneously in a dried blood sample on filter paper, to screen for neonatal hypothyroidism.

We have developed a highly sensitive radioimmunoassay of thyroxine and thyrotropin for mass screening for neonatal hypothyroidism. This assay involves a single disc (3 mm diameter) of dried blood on filter paper. The minimum detectable concentrations are 15 pg/tube (10 microgram/L) for thyroxine and 15 nano-int. units/tube (10 milli-int. units/L) for thyrotropin; intra- and interassay CV's are less than 15% in both assays. The high sensitivity of this method is due to use of labeled thyroxine with high specific activity (3 kCi/g) and of an anti-thyrotropin serum with high affinity (Keq = 7.8 x 10(11) L/mol). With this method, 11337 newborns were screened; a follow-up study revealed that only newborns with both high thyrotropin and low thyroxine concentrations had permanent hypothyroidism. We conclude that this method is sensitive, simple, and reliable and that the recall rate with this method is much lower than that of tests for measuring thyroxine or thyrotropin alone.

Blood Specimen Collection↗
PubMed1979

Intraruminal injection of urea and changes in secretion of parotid saliva in sheep.

1. Sheep were injected with varying doses of urea into the rumen and changes in the amount of saliva secreted from one parotid gland were studied. When the dose of urea was 0.1-0.2 g/kg, the secretion underwent no change. When the dose was 0.3 g/kg, the secretion was inhibited. When the dose was 0.4 or 0.5 g/kg, there was a marked inhibition in the secretion. 2. There was a close relationship between the ammonia level of the jugular blood and the inhibition of salivary secretion. When the ammonia level exceeded approximately 0.28 mmol/l, the secretion was inhibited abruptly. 3. Salivary secretion and rumen movement were inhibited when the blood ammonia level exceeded 0.28 mmol/l, after injection of ammonium acetate into the jugular vein. 4. Based on the results mentioned previously, the mechanism of inhibition on the secretion of parotid saliva is discussed in relation to the domestic ruminant in which urea had been injected into the rumen.

Ammonia↗
PubMed1979

Preservation of Neisseria gonorrhoeae by the gelatin-disc method.

Studies of Neisseria gonorrhoeae are difficult to perform because of the organism's poor survival in vitro. To solve this problem we tried to preserve the organism by a gelatin-disc method. The rate of survival and changes of variations in some biochemical properties of eight strains of N. gonorrhoeae were followed for three years. These studies proved that preservation was satisfactory with only a 1/10 reduction of the living cells. Another trial showed that the organism survived for over six months after being frozen at -20 degrees C. The colonial types, agglutination against red cells from rabbit and guinea pig, and antibiotic susceptibility to penicillin, chloramphenicol, tetracycline, kanamycin, and streptomycin did not change after three years' preservation.

Anti-Bacterial Agents↗
PubMed1975

Detection by means of cell fusion of macromolecular synthesis involved in the reconstruction of the nuclear envelope in mitosis.

Using the cultured Chinese hamster cell line Don, G1 or S or a mixture of late-S/G2 cells were prepared by release from metaphase arrest. Metaphase (M) cells were also obtained by mitotic arrest of log-phase cultures with Colcemid and held in metaphase; such M cells remained untreated with any other compound and were termed standard M cells. When interphase (I) cells were fused at pH 8.0 and 37 degrees C with standard cells in the presence of Colcemid by means of UV-inactivated Sendai virus, binucleate interphase-metaphase (I-M) cells were obtained. In a given I-M cell there occurred within 30 min after fusion either prophasing of the I nucleus or formation of a nuclear envelope (NE) around the chromosomes. About 20% of early G1 cells, 35% of cells at the G1/S boundary, 50% of S cells, and 70% of late S/G2 cells could induce NE formation. If, before fusion, cycloheximide (CHE), an inhibitor of protein synthesis, was present during release from M arrest, the cells entered G1 but not S. About 20% of such early G1 cells, like the untreated early G1 cells, had the capacity to induce NE formation during subsequent fusion. If the cells were blocked in S with 5 mM thymidine (TdR), At least 80% of these cells could induce NE formation during subsequent fusion, but in the presence of both TdR and CHE only 35% could do so. It appeared, therefore, that protein synthesis in interphase was required for NE formation. Experiments with actinomycin D indicated that RNA synthesis was also necessary for acquisition of NE-inducing capacity. About 35% of G1 cells from confluent monolayers had the NE-inducing capacity, but prolonged exposure to CHE reduced their number to 8% . Removal of CHE restored the ability while the cells still remained in G1. This result indicated that continuing protein synthesis in the G1 cell was needed for NE formation subsequent to fusion. The fact that macromolecular synthesis must occur in the I cell before fusion if NE formation was to occur in the fused I-M cell lends further support to evidence adduced earlier that this phenomenon is a normal mitotic event. Prophasing of the I nucleus in I-M cells did not appear to be dependent on macromolecular synthesis in the I cell; earlier results from this laboratory showed, however, that protein synthesis in the prior G2 period of the M cell of the I-M pair was required for prophasing.

Animals↗
PubMed1974

Prophasing of interphase nuclei and induction of nuclear envelopes around metaphase chromosomes in HeLa and Chinese hamster homo- and heterokaryons.

Fusing human HeLa metaphase cells with HeLa interphase cells resulted within 30 min in either of two phenomena in the resultant binucleate cell: either prophasing of the interphase nucleus or formation of a normal-appearing nuclear envelope around the metaphase chromosomes. The frequency of either occurrence was strongly dependent on environmental pH. At pH's of 6.6-8.0, prophasing predominated; at pH 8.5 nuclear envelope formation predominated. Additionally, the frequencies of the two events in multinucleate cells depended on the metaphase/interphase ratio. When the ratio was 0.33 nuclear envelope formation predominated; when it was 2.0 prophasing predominated. In their general features, the results with fused HeLa cells resembled those reported earlier with fused Chinese hamster Don cells. However, the results provided an indication that between pH 6.6 and 8.0 the HeLa metaphase cells possessed a much greater capacity than the Don metaphase cells to induce prophasing. Fusion of Don metaphase cells with HeLa interphase cells or of Don interphase cells with HeLa metaphase cells at pH 8.0 resulted in nuclear envelope formation or prophasing in each kind of heterokaryon. As in the homokaryons, the frequencies of the two events in the heterokaryons depended on the metaphase/interphase ratio. The statistics of prophasing and nuclear envelope formation in the homo- and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.

Cell Division↗
PubMed1973

Contrast between the environmental pH dependencies of prophasing and nuclear membrane formation in interphase-metaphase cells.

In Chinese hamster Don cells, fusion of an interphase cell with a metaphase cell resulted either in prophasing of the interphase nucleus, including loss of the nuclear envelope (NE), or in the formation of a double membrane around the metaphase chromosomes. Only one of these phenomena occurred in a given interphase-metaphase (I-M) binucleate cell. At pH 7.4, there was about an equal probability that either event could occur amongst the population of I-M cells. The effect of pH changes in the medium containing the fused cells was examined. At pH 6.6, prophasing was the predominant event; at pH 8.0, membrane formation predominated. It was found that the rate of progression of a mononucleate cell from G(2) to metaphase was appreciably faster at pH 6.6 than at pH 8.0. Conversely, the progression from metaphase to G(1) was faster at pH 8.0 than at pH 6.6. These results with the mononucleate cells strengthen the hypothesis that structural changes in I-M cells are reflections of normal mitotic phenomena. Additional evidence for this hypothesis was produced by electron microscope examination after direct fixation in chrom-osmium. The double membrane around the chromosomes of the I-M cell was indistinguishable from the normal NE. The results obtained by varying the pH of the medium containing the fused cells provide an indication that disruption or formation of the NE of Don cells depends on the balance reached between disruptive and formative processes.

Animals↗