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Biomedical subjects

Y Mishima

Publications and source records attributed to Y Mishima.

At least 325 records · Page 18Linked to original sources
PubMed1981

In vitro transcription of a cloned mouse ribosomal RNA gene.

An in vitro transcription system which utilizes cloned mouse ribosomal RNA gene (rDNA) fragments and a mouse cell extract has been developed. RNA polymerases I is apparently responsible for this transcription as evidenced by the complete resistance to a high concentration (200 micrograms/ml) of alpha-amanitin. Run-off products obtained with three different truncated rDNA fragments indicated that RNA was transcribed from a unique site of rDNA. The S1 nuclease protection mapping of the in vitro product and of in vivo 45S RNA confirmed this site, indicating that, in this in vitro system, transcription of rDNA started from the same site as in vivo. This site is located at several hundred nucleotides upstream from the putative initiation site reported by us (1) and by others (2). Some sequence homology surrounding this region was noted among mouse, Xenopus laevis and Drosophila melanogaster. The data also suggest that some processing of the primary transcript occurs in this in vitro system.

Animals↗
PubMed1981

Organization of ribosomal RNA gene repeats of the mouse.

The organization of the ribosomal RNA (rRNA) genes of the mouse was determined by Southern blot hybridization using cloned rDNA fragments as probes, which could encompass the entire spacer region between two rRNA gene regions. The rRNA genes are organized into tandem repeats of nearly uniform length of about 44 kb. The heterogeneity detected in the nontranscribed spacer appears to be caused by its sequence rather than its length difference. At least three kinds of repetitive sequences are present in the non-transcribed spacer region; two of them are located 13 kb upstream from the 5'-end of 18S RNA gene and the other located 1 to 4 kb downstream from the 3'-end of 28S RNA gene.

Animals↗
PubMed1981

Isolation and biochemical characterization of tyrosinase-rich GERL and coated vesicle in melanin synthesizing cells.

The site of condensation and activation of tyrosinase prior to melanosome melanogenesis has been investigated using subcellular fractionation and enzymic analysis of so-called Golgi apparatus of melanoma cells. Two different functional units have been found in the so-called Golgi fraction, the tyrosinase-rich GERL-coated vesicle unit and the TPPase-rich Golgi unit. The tyrosinase-rich unit consists of a tubular structure with a cisternal portion corresponding to the three-dimensional structural characteristics of GERL, and spheroid vesicles, corresponding to the currently accepted criteria for coated vesicles. This fact suggests, in agreement with electron microscopic observations, that the GERL-coated vesicle unit is a specialized portion of smooth endoplasmic reticulum having the function of activating and condensing the tyrosinase synthesized by ribosomes.

Animals↗
PubMed1981

Biochemical characterization of tyrosinase inhibitors using tyrosinase binding affinity chromatography.

Purification of tyrosinase inhibitors of hamster melanomas was carried out using tyrosinase binding affinity column chromatography. This method enables the isolation of tyrosinase inhibitors with a 124-fold purification index as compared to that of crude preparation after dialysation. The purified inhibitors consist of a mixture of 5000-6000 and a 310 molecular weight fraction. They also show characteristics of polypeptides which contain glycine, glutamic acid, serine, proline and alanine as main amino acids.

Amino Acids↗
PubMed1981

Cumulative effect of surfactants on cutaneous horny layers: lysosomal activity of human keratin layers in vivo.

Anionic surfactants have various degrees of membrane labilizing action on isolated lysosome in vitro. This action has been found to correlate with the degrees of skin roughness induced by the surfactants using the circulation method applied to the forearm of human subjects. It has been shown that the acid phosphatase activity in the human horny layer decreases during the in vivo application of the surfactants by the circulation method. The magnitude of the decrease in acid phosphatase activity has been found to correlate to the degree of skin roughness and to in vitro lysosome labilization induced by the surfactants.

Acid Phosphatase↗
PubMed1981

Outer root sheath keratinization in anagen and catagen of the mammalian hair follicle. A seventh distinct type of keratinization in the hair follicle: trichilemmal keratinization.

Trichilemmal keratinization, first described in Maurer in 1895 and rediscovered by Holmes (1968) and Pinkus (1968) converts the stratified epithelium of the outer root sheath into anuclear keratin without an intervening keratohyalin layer. It is a distinct seventh type of keratinization in the hair follicle, not derived from the hair matrix. It occurs wherever outer root sheath is not apposed to inner root sheath, in anagen in the zone of sloughing just below the opening of the sebaceous duct, in catagen in the trichilemmal sac surrounding the lower end of the dying hair shaft where it forms the club of the telogen hair. Electron microscopic study of the thick hairs of dogs (but not the tiny hairs of rodents) reveals intricate infoldings of non-keratinized and keratinized cells. It also shows unique ladder-like membrane coating granules in anagen, which are strongly acid phosphatase-positive and are suggested to be the source of enzyme involved with disintegration of the inner root sheath.

Acid Phosphatase↗
PubMed1980

The nucleotide sequence of the putative transcription initiation site of a cloned ribosomal RNA gene of the mouse.

Approximately one kilobase pairs surrounding and upstream the transcription initiation site of a cloned ribosomal DNA (rDNA) of the mouse were sequenced. The putative transcription initiation site was determined by two independent methods: one nuclease S1 protection and the other reverse transcriptase elongation mapping using isolated 45S ribosomal RNA precursor (45S RNA) and appropriate restriction fragments of rDNA. Both methods gave an identical result; 45S RNA had a structure starting from ACTCTTAG---. Characteristically, mouse rDNA had many T clusters (greater than or equal to 5) upstream the initiation site, the longest being 21 consecutive T's. A pentadecanucleotide, TGCCTCCCGAGTGCA, appeared twice within 260 nucleotides upstream the putative initiation site. No such characteristic sequences were found downstream this site. Little similarity was found in the upstream of the transcription initiation site between the mouse, Xenopus laevis and Saccharomyces cerevisiae rDNA.

Animals↗
PubMed1980

Cloning and determination of a putative promoter region of a mouse ribosomal deoxyribonucleic acid fragment.

An endonuclease EcoRI digest of mouse DNA was subjected to molecular cloning, after partial purification with respect to the ribosomal RNA sequence, using lambda gtWES x lambda B with an in vitro packaging technique. Twelve positive clones were obtained from approximately 2 X 10(4) plaques. One of the clones transferred to the plasmid pBR322 (PMrEL-1) was about 14.9 kb long, hybridizing only with 18S rRNA but not with 28S rRNA. Hybridization of restriction fragments and electron microscopic studies of the R-loop confirmed that this fragment carried about half of the 18S rRNA sequences at one end, suggesting that it contained the initiation site for the 45S preribosomal RNA (pre-rRNA). S1-nuclease protection mapping with hybrids between restriction fragments of the cloned DNA and the 45S pre-rRNA indicated that at least major transcription of the 45S RNA started at a site approximately 4.0 kb upstream from the 5' end of the 18S rRNA. This was confirmed by electron microscopic observations of these hybrids.

Animals↗
PubMed1980

Enhancement by thyroid hormone of free and bound RNA polymerase IB activities in rat liver nucleoli.

After having defined reliable assay conditions for free and template-bound RNA polymerase I activities, we examined in detail the effect of thyroid hormone in vivo on nucleolar RNA polymerase I in rat liver. The enzyme activity decreased markedly in the hypothyroid state produced by either thyroidectomy, hypophysectomy or by administration of propylthiouracil (PTU). One large dose (25 microgram/100 g body weight) of T3 given intraperitoneally caused a rapid recovery of the enzyme activity within 24 h either in the presence or absence of the pituitary. The enzyme activity of both free and chromatin-bound enzyme changed in parallel throughout. A similar recovery was noted after daily subcutaneous injections of a physiological dose (1 microgram/100 g body weight) of T3 for about 3 weeks. Analyses of subfractions of the enzyme indicated that only IB-type enzyme (the enzyme fraction containing the whole set of subunits) changed in response to thyroid hormone action, also irrespective of the presence or absence of the pituitary. The possibility that thyroid hormone is a major physiological regulator of the synthesis of RNA polymerase I in rat liver is discussed.

Animals↗
PubMed1980

Apocrine acrosyringeal complex in the human skin.

The acrosyringium of human apocrine sweat apparatus has been studied by light and electron microscopy using horizontal continuous serial sections. The apocrine acrosyringium is composed of 3 structurally different portions, a highly keratinizing upper portion, an incompletely keratinizing midportion, and a least keratinizing lower portion. Throughout these 3 portions, there are 2 distinctly different but closely inter-related cellular units, namely (I) a keratinization process lacking membrane-coating granules but containing keratohyalin droplets occurring in its inner cell layer, and (II) a keratinization process rich in membrane-coating granules and containing keratohyalin granules occurring in its outer surrounding concentric cell layers. In contrast to the inner cell layer, the outer cell layer does not belong to the duct proper but rather should be considered as the periacrosyringeal complex layer which is specially differentiated to envelop the intra-epithelial duct. This apocrine acrosyringeal complex in the hair follicle seems to be essentially similar to that of the eccrine apparatus in the epidermis.

Adolescent↗
PubMed1980

Isolation and characterization of tyrosinase inhibitors and their differential action on melanogenic subcellular compartments in amelanotic and melanomas.

Further purification of highly active tyrosinase inhibitors by DEAE-Sephadex column chromatography has revealed that the mode of action of the inhibitors from melanomas with different melanogenic status is organelle specific. The inhibitor from amelanotic melanoma has a relatively strong suppressive effect on the tyrosinases in GERL and coated vesicle containing fractions. On the other hand, the inhibitor from melanotic melanoma has no substantial effect on these tyrosinases, although melanosomal tyrosinase is inhibited by both. The present evidence suggests that the defect of melanization in amelanotic melanoma in vivo is related to the tyrosinase inhibition of the smooth membrane system including GERL and coated vesicle by the highly active inhibitor characteristic of amelanotic melanoma.

Animals↗