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Biomedical subjects

S Mizuno

Publications and source records attributed to S Mizuno.

At least 649 records · Page 36Linked to original sources
PubMed1976

In situ hybridization of "nick-translated" 3H-ribosomal DNA to chromosomes from salamanders.

A technique is described for preparation of 3H-labelled DNA by nick-translation employing deoxyribonuclease I and DNA polymerase I. The labelled DNA can be obtained in high yield with specific activities of 10(6) cpm/mug or more. Ribosomal DNA, isolated from ovaries of young Xenopus laevis, and whole DNA from Plethodon cinereus were labelled in this way. The rDNA was used for in situ hybridization to meiotic chromosomes from P. cinereus, P. vehiculum and P. dunni. Autoradiographs of in situ hybrids were exposed for 5 to 10 days, by which time nucleolus organizer regions on the chromosomes of all 3 species were clearly and specifically labelled. In all cases, labelling was confined to a short region near the middle of the short arm of both halves of a medium length bivalent. It is concluded that nick-translation is a useful and altogether efficient method of labelling nucleic acids for subsequent use in experiments involving in situ hybridizations.

Animals↗
PubMed1976

The pathogenesis of Perthes' disease.

It has been shown that in the puppy, two infarcts separated by an interval of four weeks produce a disorder of long duration which results in flattening and broadening of the femoral head and which reproduces the radiological changes seen in Perthes' disease in man. The histological appearances produced by two infarcts are characteristic. In this study the histological appearance of fifty-seven femoral head biopsy specimens in Perthes' disease in man have been studied. In 51 per cent of hips histopathological changes characteristic of double infarction were present, and there were grounds for postulating that double infarction might eventually occur in all cases. The findings support the concept that the deformation of the femoral head and the chronicity of Perthes' disease in man may be due at least as much or even more to repeated episodes of infarction and the ensuing abnormalities of growth as to mechanical factors related to weight-bearing.

Adolescent↗
PubMed1976

Inhibition of the initial dipeptide synthesis of globin chains by the antibiotic enomycin in the reticulocyte lysate.

During inhibition of protein synthesis by the antibiotic enomycin at less than 5nm in the reticulocyte lysate system, polyribosomes disaggregated and the 80S ribosomes accumulated. At these concentrations little inhibition of chain elongation and release from the ribosomes was demonstrated. Enomycin caused an increase in the amount of 80S initiation complex as well as the 40S ribosomal subunit-Met-tRNA complex. The former complex could react with puromycin under the inhibiting conditions. Val-tRNA binding to the 80S ribosomes was not decreased by the antibiotic. However pactamycin-induced accumulation of the initial dipeptide (fMet-Val) was inhibited when the system was preincubated with enomycin and and fMet-tRnaf. Thus the preferential inhibition of the initial phase of protein synthesis by enomycin is made evident by its inhibition of the initial dipeptide synthesis.

Antibiotics, Antineoplastic↗
PubMed1975

Temperature sensitivity of protein synthesis initiation in the reticulocyte lysate system. Reduced formation of the 40 S ribosomal subunit - Met-tRNAf complex at an elevated temperature.

Analysis of protein synthesis in the rabbit reticulocyte lysate system revealed the existence of a temperature-sensitive step in chain initiation which became irreversibly inactivated in the incubation at 42 degrees C. This inactivation of initiation was accompanied by a marked reduction in formation of the 40 S ribosomal subunit - Met-tRNAf complex. Decreased protein synthesis and a decrease in formation of the 40 S complex were also evident in unfortified lysates which had been prewarmed at 42 degrees C prior to protein synthesis. Hemin did not protect such lysates. The addition of supernatant fraction of a fresh lysate did not promote recovery of the reduced protein synthesis by such prewarmed lysates. Moreover, the addition of supernatant fraction prewarmed at 42 degrees C in the presence of added hemin caused little inhibition of protein synthesis by fresh lysate. The results indicate that the supernatant fraction is not involved in the inactivation.

Animals↗
PubMed1975

Stepwise reduction of cytochromes b-562, b-566 and b-558 in rat liver mitochondria.

1. Addition of KCN to aerobic, rotenone-inhibited rat liver mitochondria with out addition of substrate caused reduction of cytochromes b-562 (having an alpha-band at 562 nm at room temperature), c + c1, and a + a3. The effect of KCN on cytochrome b-562 was reversed by pentachlorophenol, though the effect of KCN on cytochromes c+c1 and a+a3 was not reversed by this uncoupler.2. Addition of ATP to aerobic, rat liver mitochondria inhibited with 500 muM KCN under conditions were cytochromes b-562, c+c1 and a+a3 were reduced, caused reduction of cytochrome b-566. The absorbance spectrum of cytochrome b-566 had an alpha-band at 565.5 nm, a beta-band at 538 nm and a gamma-band at 431 nm, but no shoulder around 558 nm at room temperature. 3. Addition of succinate to rotenone-KCN-inhibited and ATP-treated rat liver mitochondria under conditions where cytochromes b-566, b-562, c+c1 and a+a3 were already fully reduced, caused reduction of cytochrome b-558 (having an alpha-band at 558 nm, a beta-band at 527 nm and a gamma-band at 426 nm at room temperature) after exhaustion of molecular oxygen in the reaction medium, without any contribution from a long-wavelength species (cytochrome b-566). 4. It was concluded that the 558-nm band is not a short-wavelength shoulder of cytochrome b-566, but is due to a different species from cytochrome b-566.

Adenosine Triphosphate↗
PubMed1975

Mechanism of inhbition of protein systhesis initiation by diacetoxyscirpenol and fusarenon X in the reticulocyte lysate system.

The mechanism of inhibition of peptide chain initiation by diacetoxyscirpenol and fusarenon X, (trichotecene mycotoxins), was studied in the reticulocyte lysate protein-synthesizing system. The mycotoxins did not inhibit formation of the complex between Met-tRNA-f and the 40S ribosomal subunit nor the initiation codon AUG-promoted combination of the complex with 60S ribosomal subunit. Formyl-methionyl-valine accumulated when the system was incubated with the mycotoxins and fMet-tRNA-f. This suggests that the inhibition occurs after the formation of the first peptide bond.

Animals↗
PubMed1975

In situ hybridization of ribosomal DNA labelled with 125iodine to metaphase and lampbrush chromosomes from newts.

Methods are described for in situ hybridization of ribosomal DNA from Xenopus laevis, labelled in vitro with 125iodine, to mitotic and lampbrush chromosomes from Triturus cristatus carnifex. The hybridization reaction was carried out in a mixture containing 50% formamide, 4 X SSC, 0.1 M KI, at 37 degrees C, or in 2 X SSC, 0.1 M KI at 65 degrees C. Autoradiographs of mitotic metaphases from 2 males showed labelling over the middle of the short arm of one chromosome IX in each metaphase. In some cases, a region near the end of a longer chromosome was also labelled. In a lampbrush preparations, labelling was confined to a region identified as about 53 units, near the middle of the short arm of both halves of bivalent IX. The usefulness of the technique and the significance of the labelling of only 1 of the 2 chromosomes IX in mitotic preparations are discussed.

Animals↗
PubMed1975

Cross-resistant relationships among the aminoglucoside antibiotics in Mycobacterium tuberculosis.

Phenotypes of isolates of Mycobacterium tuberculosis H37RV showing resistance to the aminoglucoside antibiotics streptomycin, viomycin, kanamycin, capreomycin, tuberactinomycin N, lividomycin and paromomycin could be grouped into the following types: (I) resistant only to different levels of streptomycins; (2) resistant only to a low level of kanamycin; (3) triply resistant, to low levels of viomycin, tuberactinomycin N and capreomycin; (4) triply resistant, to a low level of kanamycin and high levels of lividomycin and paromomycin; (5) quadruply resistant, to a low level of capreomycin and high levels of kanamycin, lividomycin and paromomycin; (6) hextuply resistant, to high levels of viomycin, tuberactinomycin N, capreomycin, kanamycin, lividomycin, and paromomycin. Three modificatied types of the latter were also observed. Appearance rates of the six types were estimated as 10(-6) to 10(-9), 10(-6), 10(-6) to 10(-7), 10(-8), 10(-8), and 10(-8) to 10(-9), respectively, in a total viable population of the parent strain. Mutations to all phenotypes were considered to be produced by single mutations. According to cross-resistance relationships, aminoglucoside antibiotics were classified into three groups: (I) streptomycin; (II) viomycin, tuberactinomycin N and capreomycin; (III) kanamycin, lividomycin and paromomycin. No cross-resistance relationship between streptomycin and other antibiotics was observed. Resistances to viomycin, tuberactinomycin N and capreomycin occurred by single mutation to type 3. Resistances to kanamycin, lividomycin and paromomycin occurred by single mutations to types 4 and 5. Low resistance to capreomycin was produced by mutation to type 5. Therefore capreomycin was considered to be an intermediate between the second and third groups. These two groups had a close relationship, as resistance to all six agents in these groups could be produced by a single mutation to type 6 (and its modified types).

Antibiotics, Antitubercular↗