Search PubMed⌕ Search

Biomedical subjects

K Shimura

Publications and source records attributed to K Shimura.

At least 163 records · Page 9Linked to original sources
PubMed1978

Purification and some properties of a specific nuclease which cleaves transfer RNA precursors from the posterior silk gland of Bombyx mori.

A specific endonuclease involved in the processing of tRNA precursors was isolated and partially purified from the posterior silk gland of Bombyx mori, and designated as RNase P.Bmo. This enzyme was shown to catalyze the conversion of 4.5 S precursor RNA to 4.1 S RNA by trimming the 5'-additional segment from the precursor RNA. RNase P.Bmo required divalent cations, Mg2+ or Mn2+. In the presence of these divalent cations, K+ or NH4+ activated the RNase P.Bmo reaction. Optimum pH was observed around 8.0. Ribosomal RNA's and mature tRNA from the silk gland were not cleaved by RNase P.Bmo. A 4.5 S precursor RNA fraction containing formycin, an adenosine analog, was less susceptible to RNase P.Bmo than the normal one. These results indicate that RNase P.Bmo has a high substrate specificity. An additional nuclease(s) was isolated. This activity was assumed to remove the extra 3'-segment of the 4.5 S precursor RNA.

Ammonium Chloride↗
PubMed1977

The effect of formycin on the processing of transfer RNA precursors in the posterior silk gland of Bombyx mori.

Formycin, an adenosine analog, was used in studies of RNA synthesis by silk glands of silkworms in organ culture. Formycin has been shown to inhibit preferentially the incorporation of [3H]uridine into low molecular weight RNA in the cytoplasm. When silk glands were pulse-chase labeled with [3H]uridine in the presence of formycin, the synthesis of 4.5S tRNA precursors was not affected, as determined by gel electrophoresis. However, the accumulation of mature 4S tRNA was greatly reduced in the formycin-treated system, although the precursors synthesized disappeared from the 4.5S region on chase at the same rate as in the control system. [14C]Formycin was incorporated into the 4.5S precursors but not into 4S tRNA. These findings suggest that the inhibition of tRNA synthesis by formycin is due to the existence of some degradation mechanisms of formycin-containing 4.5S precursor RNA's and the failure to process them into normal 4S tRNA.

Animals↗
PubMed1977

Gallium-67 scanning in the evaluation of therapy of malignant tumors of the head and neck.

Gallium-67 scintigraphy was performed on 25 patients with a variety of malignant tumors of the head and neck in order to evaluate the susceptibility of the tumors to irradiation and chemotherapy before treatment and to monitor the effectiveness of therapy. If certain limitations are borne in mind, gallium scanning may prove a valuable tool in planning and evaluating therapy of malignant tumors.

Adult↗
PubMed1976

Prenatal diagnosis of osteogenesis imperfecta congenita by means of fetography.

By means of fetography, prenatal diagnosis of osteogenesis imperfecta congenita was performed on two pregnant women in the 34th week of gestation with familial histories of the disease. In 1 of the 2 cases, the fetogram revealed abnormal twisting of the torso, shortening, and severe angulation deformities of the extremities with callus formation and parchmentlike skull despite clear-cut outline of the scalp. On the basis of these findings, the fetus was diagnosed as osteogenesis imperfecta congenita and subsequently confirmed. Thus, the excellent fetal resolving power of fetography permitted successful prenatal diagnosis of the disease far more easily and precisely than plain roentgenography.

Adult↗
PubMed1976

Studies on silk fibroin of Bombyx mori. I. Fractionation of fibroin prepared from the posterior silk gland.

1. Fractionation of fibroin prepared from the posterior silk glands of Bombyx mori was carried out. After carboxymethylation of the fibroin, it was fractionated by ammonium sulfate precipitation, Sephadex G-200 gel filtration and DEAE-cellulose column chromatography. 2. The fibroin was composed of at least two protein groups of large molecular size and three or four components of small molecular size, and, in addition, a mixture of proteins ranging in size from about 25,000 to more than 100,000 daltons with almost the same amino acid compositions. 3. The latter proteins contained about 48% glycine, 32% alanine, 11% serine, 4.5% tyrosine, 2% valine, and other minor amino acids. The sum of these main five amino acids accounts for more than 97% of the total amino acid residues of the proteins. 4. The present results indicate major heterogeneity in the molecular size of posterior silk gland fibroin, and, in addition, suggest the possibility of repeating sequences with relatively simple amino acid compositions in major peptide chains of fibroin.

Amino Acids↗
PubMed1976

The biosynthesis of transfer RNA in insects. II. Isolation of transfer RNA precursors from the posterior silk gland of Bombyx mori.

The occurrence of precursors to tRNA in the post-polysomal fraction of the posterior silk gland of Bombyx mori was demonstrated by pulse-chase labeling and DNA-RNA hybridization competition experiments. These precursors had molecular sizes ranging from 4S to 5S on polyacrylamide gel electrophoresis. Analysis of the incorporation of the methyl group from [methyl-14C]methionine revealed that a radioactive peak on polyacrylamide gel appeared in the 4.5S region during brief labeling. This suggested that some methylation occurred at the 4.5S precursor step.

Bombyx↗
PubMed1975

Clinical evaluation of 67Ga-citrate scanning in the oral region.

Gallium-67-citrate was administered to thirty-nine patients who had a variety of benign, malignant, and inflammatory lesions of the oral region. The gallium-67 scintigram was noted to be valuable in the diagnosis of maxillary carcinoma, parotid carcinoma, and malignant lymphoma. Clinically, it is possible to differentiate malignant tumors from benign ones with the aid of 67Ga scanning. It is difficult, however, to differentiate malignant tumors from inflammatory lesions. At present, it is difficult to defect the small malignant lesion by means of a 67Ga scintigram.

Adolescent↗
PubMed1975

Fractionation, isolation and characterization of nonhistone chromosomal protein from calf thymus.

1) A method is described for the separation and fractionation of nonhistone chromosomal proteins from salt-urea dissociated calf thymus chromatin. After precipitating DNA in the dissociated chromatin solution with LaCl3, the chromosomal proteins in the supernatant were fractionated by SP-Sephadex C-25 column chromatography using a combination of NaCl stepwise and linear gradient elutions. Much care was taken to prevent proteolytic degradation of the chromosomal proteins during the preparation. 2) Among the protein fractions separated by this chromatography, twenty subfractions were found to be homogeneous on SDS-polyacrylamide gel electrophoresis. These purified proteins account for about 18% of the whole chromosomal protein. Eleven subfractions of these purified nonhistone proteins had ratios of acidic to basic amino acids above 1.0 and the nine remaining subfractions had ratios below 1.0, corresponding to nonhistone proteins of basic character. 3) The molecular weights of the purified nonhistone proteins ranged from 7,400 to 19,000.

Amino Acids↗
PubMed1975

The biosynthesis of transfer RNA in insects. I. Increase of amino acid acceptor activity of specific tRNA's utilized for silk protein biosynthesis in the silk gland of Bombyx mori.

1) To detect the quantitative changes of amino acid acceptor activity of tRNA's from the posterior and middle silk glands of Bombyx mori at various ages, a relatively simple and rapid method was established using a mixture of radioactive amino acids in Chlorella hydrolysate. 2) The acceptor activities of silk gland tRNA for 15 amino acids tested seemed to be almost on the same level at the end of the 4th moult stage. During the 5th instar, however, characteristic increases were observed in glycine, alanine, and serine acceptor activities in both silk glands. 3) In the posterior silk gland, which produces fibroin, the acceptor activities for glycine and alanine increased more than that for serine. In the middle silk gland, which produces sericine, the acceptor activity for serine increased more than those for glycine and alanine. 4) In the light of observations on the increase of corresponding aminoacyl-tRNA synthetase activities in the silk glands, a functional adaptation of tRNA synthesis in the tissue is discussed.

Alanine-tRNA Ligase↗