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Biomedical subjects

H Yoshikawa

Publications and source records attributed to H Yoshikawa.

At least 19 recordsLinked to original sources
PubMed1979

Effect of novobiocin on initiation of DNA replication in Bacillus subtilis.

The initiation of DNA replication of small replicons in vitro involves conformational changes in the whole DNA molecule or in the region near to the replication origin. One striking finding has been the role of DNA gyrase (that is, the necessity for supercoiled structure) in the initial stage of ColE1 replication in vitro. However, little is known about the effect of gyrase on the initiation of replication of bacterial chromosomes in vivo. We have constructed a map of cleavage sites of restriction enzymes at the region of the origin of replication of the Bacillus subtilis chromosome (accompanying paper). This has now enabled us to examine the effect of novobiocin, a selective inhibitor of DNA gyrase, on the replication of the specific chromosomal segments near the origin and to seek a possible role for the gyrase in the initiation of chromosomal replication. We have found that only a limited segment of the chromosome at the origin region was replicated in the presence of novobiocin. This effect allowed us to locate the site of the origin of replication to within a DNA fragment of molecular weight 3.4 x 10(6).

Bacillus subtilis↗
PubMed1979

A simplified assay method of superoxide dismutase activity for clinical use.

A simple and inexpensive assay method of superoxide dismutase (SOD) activity of various biological materials has been developed. SOD activity can easily be measured by reading the medium's intense absorbance directly, and many samples can be treated in a short time using a reaction stopper which acts for a long time. Reproducibility of the assay method was excellent for the sample from an individual estimated at two different times (a week to a month) and the coefficient of variance was 5.1%. The mean and standard deviation of SOD activities of 45 blood samples from normal Japanese males 32.9 +/- 10.5 microgram per ml of blood; estimated using bovine SOD standard. The SOD activity of the fluid from lavaged lungs was 15.7 +/- 1.8 microgram/ml, and that of lung tissue homogenates from rats was 2.85 +/- 0.66 microgram/mg of protein.

Adult↗
PubMed1979

Suppression of tuberculin reactivity during natural rubella. Observations with 54 patients.

Fifty-four patients with previously positive tuberculin reactions were followed for tuberculin sensitivity, between the incubation period of natural rubella and the 40th day after the onset of rash. In many instances, tuberculin sensitivity was partially or completely depressed beginning in the incubation period and extending for up to 4 weeks after rash onset. Two of 3 cases of subclinical rubella infection also showed this phenomenon. The highest incidence of negative reactions was 83% in the first 3 days after rash onset. A few subjects had a larger skin reaction to tuberculin than the baseline reading during the 2 to 5 weeks after rash onset.

Adolescent↗
PubMed1979

[Accumulation of cadmium in organs of mice by a long-term injection of cadmium and interactions of cadmium with copper, manganese and zinc already present in the animals (author's transl)].

It is well known that the greater part of the administered cadmium is accumulated in liver and kidneys. But, in considering the toxicity of cadmium, it is important to make clear the time pattern of cadmium accumulation not only in liver and kidneys but in the other organs. Male mice were injected subcutaneously 1 mg/kg of cadmium daily for 25 weeks except one day in every week. Five mice at a time were killed in the suitable time during this experiment, and Cd, Cu, Mn, and Zn concentrations in several organs were determined by atomic absorption spectrophotometry. Cadmium content in liver and kidneys increased remarkably during the first 30 days, and it is scarcely increased after that period. Cadmium content in other organs, that is, heart, lungs, spleen, testes and femurs, increased slowly during the first 20 days, and this content increased hardly after that. The results show further that: Cd administered at the early stage accumulated mainly in liver an in kidneys. As Cd concentration in liver and kidneys arrives at saturation, Cd content in other orbans increased remarkably. And, after 30th day, Cd content in all the organs increased little in spite of the continuous injection of Cd. Concentrations of Cu, Mn, and Zn in the organs of mice injected with Cd were as follows: Cu concentration increased significantly in heart, liver, and kidneys, Zn concentration increased in heart, lungs, liver, and kidneys, whereas Mn concentration decreased remarkably in kidneys. Cadmium content in the organs of mice injected with Zn (0.5 mg/kg) or Mn (0.5 mg/kg) together with Cd (1 mg/kg) showed a tendency to increase remarkably compared with single injection of Cd.

Animals↗
PubMed1979

Herbicidins C and E, two new necleoside antibiotics.

Streptomyces saganonensis No. 4075 used for production of herbicidins A and B has also produced other two antibiotics, herbicidins C and E in submerged culture. Isolation of the antibiotics was performed by adsorption on resinous adsorbent followed by elution with aqueous MeOH and completed by silica-gel chromatography. Physico-chemical characteriation revealed that herbicidins C and E are new nucleoside antibiotics having an adenine moiety in their structures. Herbicidins C and E indicated inhibitory activity against germination of chinese cabbage at 12.5 micrograms/ml and 25 micrograms/ml, respectively, and Anacystis nidulans, a blue green algae, at 100 approximately 200 micrograms/ml.

Anti-Bacterial Agents↗
PubMed1979

Herbicidins F and G, two new nucleoside antibiotics.

A mutant of Streptomyces saganonensis No. 4075, obtained with N-methyl-N'-nitro-N-nitrosoguanidine treatment, produced herbicidins F and G without herbicidins A and B. Isolation of the antibiotics was performed by adsorption on resinous adsorbent followed by elution with aqueous MeOH. Herbicidin F was obtained as colorless needles after extraction of the eluate using methylene dichloride. Purification of herbicidin G was completed with silica-gel chromatography to give a crystalline powder. physico-chemical characterization revealed that herbicidins F and G were new nucleoside antibiotics having an adenine moiety in their structures. There was no inhibition activity at 100 micrograms/ml of herbicidins F and G against all of bacteria and yeast tested. Herbicidin F, as well as herbicidin G, are inhibitory activity against some of fungi such as Tricophyton rubrum (MIC; 6.25 micrograms/ml), T. asteroides (6.25 micrograms/ml), T. mentagrophytes (6.25 approximately 12.5 micrograms/ml), Botrytis cinerea (12.5 micrograms/ml), Blastomyces brasiliensis (12.5 approximately 25 micrograms/ml).

Animals↗
PubMed1978

An explanation for the high incidence of congenital rubella syndrome in Ryukyu.

An exceptionally high incidence of congenital rubella syndrome (CRS) has been noted in Ryukan children who were infants in utero during an extensive rubella epidemic in the Ryukyu Islands in 1964 through the spring of 1965. In 1965, the Congenital Rubella Study Group of Kyushu University registered in the Ryukyus 408 cases of CRS and an incidence of 20 cases of CRS per 1000 births. The nearby Amami Islands, on the other hand, had a low incidence of CRS. Seroepidemiologic studies indicated a high prevalence of antibodies in the Ryukyus but a low prevalence in the Amamis. Since CRS is uncommon throughout Japan, some investigators have hypothesized that Japanese strains of the virus are avirulent and that a virulent American strain caused the epidemic in the Ryukyus. However, retrospective seroepidemiologic studies reported here indicate that the high incidence of CRS in the Ryukyus was more probably due to low seropositivity and a resultant high attack rate of rubella among pregnant women, rather than to a hypothetical virulent teratogenic strain of rubella virus. Conversely, the data suggest that the low incidence of CRS in Japan may reflect the infrequency of rubella nonimmunes in women of childbearing age.

Antibodies, Viral↗