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Biomedical subjects

K Ohyama

Publications and source records attributed to K Ohyama.

At least 145 records · Page 8Linked to original sources
PubMed1992

Cloning and nucleotide sequence of a frxC-ORF469 gene cluster of Synechocystis PCC6803: conservation with liverwort chloroplast frxC-ORF465 and nif operon.

A gene, frxC, which is unique to the chloroplast genome of the liverwort Marchantia polymorpha, has sequence similarity to nifH, the product of which is an iron protein of a nitrogenase. Although frxC is expressed to produce a protein in liverwort chloroplasts, its function is not known. Using a probe of liverwort chloroplast DNA, a 10.1-kb region containing a gene cluster consisting of open reading frames (ORF278-frxC-ORF469-ORF248) was isolated from the cyanobacterium Synechocystis PCC6803. In this region, frxC and ORF469 showed sequence similarities to liverwort chloroplast frxC (83%) and immediately downstream ORF465 (74%), respectively. Synechocystis frxC showed 31% amino acid sequence identity with nifH1 from Clostridium pasteurianum. Additionally, Synechocystis ORF469 showed a sequence similarity (19% identity) to C. pasteurianum nifK product, which is the beta subunit of a molybdenum-iron protein of a nitrogenase complex. Conservation of the gene arrangement between liverwort and Synechocystis suggests that the liverwort chloroplast frxC-ORF465 cluster may have evolved from an ancestor common to Synechocystis, and that these two genes may have been transferred to the nuclear genome in tobacco and rice during evolution.

Amino Acid Sequence↗
PubMed1991

Presence of influenza virus-reactive glycophorins other than glycophorin A in human erythrocyte membranes.

The reactivities against seven hemagglutinins including influenza A and B viruses of six sialoglycoprotein (glycophorin) fractions, M-Frs.1-3 and N-Frs.1-3, separated from human OMs and ONs erythrocyte membranes by a combination of the LIS-phenol method and gel filtration were studied. The serological results show that M-Fr.1 and N-Fr.1 were glycophorins AM and AN, respectively, the reactivities against influenza A and B viruses of both M-Fr.2 and N-Fr.2 which contained glycophorins B and C were remarkably higher than that of glycophorin A and the reactivities against influenza viruses of both M-Fr.3 and N-Fr.3 which contained glycophorins B and D were considerably lower than that of glycophorin A.

Amino Acids↗
PubMed1991

Involvement of the Chox-4 chicken homeobox genes in determination of anteroposterior axial polarity during limb development.

We have isolated and identified four chicken homeobox genes in the upstream region of the Chox-4 complex. The Chox-4g and -4f genes, at the 5' extremity of the complex, were expressed locally in the vicinity of the zone of polarizing activity (ZPA) at early stages of limb development, substantiating the involvement of the genes in anteroposterior axis determination. To confirm their function, we implanted a bead containing retinoic acid, or the ZPA itself, in the anterior margin of the limb bud, leading to formation of mirror-image duplicated digits, and observed the resultant change in gene expression. Expression of the Chox-4g and -4f genes was induced in the new digit-forming region. Those results suggest that positional information assigned by a ZPA morphogen is imprinted on cellular memory by expression of the Chox-4 genes to maintain positional signaling along the anteroposterior axis in the limb field.

Amino Acid Sequence↗
PubMed1991

Retinoic acid induces polarizing activity but is unlikely to be a morphogen in the chick limb bud.

Retinoic acid is a putative morphogen in limb formation in the chick and other vertebrates. In chick limb formation, it is thought that retinoic acid is released from the zone of polarizing activity (ZPA) and the concentration gradient of retinoic acid formed from the posterior to the anterior provides positional cues for digit formation. Implantation of a bead containing retinoic acid at the anterior margin of the limb bud induces a mirror-image symmetrical duplication of the digit pattern similar to that observed when the ZPA is grafted into the anterior margin of the host limb bud. Also, the level of endogenous retinoic acid (25 nM on average) is higher in the posterior one third of the limb bud. We found that when the bead containing either retinoic acid or an analogue but not the ZPA, was implanted in the anterior margin of the chick limb bud, expression of the retinoic acid receptor type-beta gene was induced around the bead within 4 h. These results indicate that exogenous retinoic acid is not identical with the ZPA morphogen. As the anterior tissue exposed to retinoic acid has polarizing activity, we conclude that the primary function of exogenous retinoic acid is to induce polarizing activity in the limb bud.

Amino Acid Sequence↗
PubMed1991

Radial communication between the perilymphatic scalae of the cochlea. I: Estimation by tracer perfusion.

The degree to which radial exchange between scala tympani (ST) and scala vestibuli (SV) can occur has not previously been quantified. We have measured the amount of cross-communication in the third turn of the guinea pig cochlea using an ionic tracer, trimethylphenylammonium (TMPA). TMPA was perfused through one scala while TMPA concentrations were measured simultaneously in the perfused and non-perfused scalae. On the basis of the time course of TMPA increase recorded in the non-perfused scala, we were able to calculate rate constants for cross-leak and clearance. Cross-leak in the third turn occurred remarkably rapidly with a rate constant from ST to SV of 0.049 min-1 and from SV to ST of 0.031 min-1. These correspond to transfer half times of 14.2 and 22.4 min respectively. This result demonstrates that ST and SV in the third turn cannot be regarded as independent compartments.

Animals↗
PubMed1991

Radial communication between the perilymphatic scalae of the cochlea. II: Estimation by bolus injection of tracer into the sealed cochlea.

Radial communication between ST and SV was measured in the sealed cochlea by monitoring the dispersal of an ionic tracer, trimethylphenylammonium (TMPA) injected in the form of a minute bolus. Tracer movements were recorded by a pair of ion-selective electrodes sealed into the injected and non-injected scalae close to the injection site. Measurements were made in the basal or third turn of the guinea pig cochlea. In the third turn, radial communication occurred rapidly with a ST half time from ST to SV of 25 min and from SV to ST of 26 min. In the basal turn the communication was markedly slower, with a ST half time from ST to SV of 170 min and from SV to ST of 240 min. However, the difference between the basal and third turns can be shown to arise almost totally from differences in cross-sectional area of the perilymphatic scalae. When normalized with respect to scala cross-section, the process of tracer movement across the spiral ligament is similar in the basal and third turns. These results demonstrate that radial communication between scala tympani and scala vestibuli is an important route which must be considered in studies involving perilymph.

Animals↗
PubMed1991

Spontaneous otoacoustic emissions in the guinea pig.

Measurement of spontaneous otoacoustic emission (SOAE) in a large number of animals was conducted in the guinea pig. A remarkably high incidence of SOAE (51 ears out of 248 ears; 20.6%) was observed in the animals that were raised under unexceptional conditions. The frequencies of SOAE were distributed between 0.7 kHz and 2.3 kHz (average: 1.16 kHz). The emission signals disappeared with hypoxia and with furosemide injection, and recovered after certain periods with some frequency fluctuations. Their electrical correlates that behaved in exactly the same manner as SOAE were clearly distinguished by FFT analysis of the AC potential from the cochlear surface. The signals could be divided into 4 types: (1) emission with pure and stable frequency spectrum and steady level, (2) emission with stable frequency and fluctuating level, (3) emission alternating between two closely situated frequency points, (4) emission having an irregular, wide spectrum band. Light microscopy revealed no abnormalities in the organ of Corti that have been widely accepted to be SOAE-related, i.e., patchy lesions of the organ of Corti and/or irregularities in hair cell arrangement. This suggests that the spontaneous oscillation within the guinea pig cochlea can be generated by some minor, functional, and probably reversible disturbances of the active cochlear transduction mechanism, without major structural derangement of the organ of Corti.

Acoustics↗
PubMed1991

Mechanisms of stimulation of collagen synthesis during chick embryonic skin development.

To study how collagen synthesis is regulated in developing chick embryonic skin, hydroxyproline synthesis, incorporation of proline, and translational activity and content of collagen mRNA in 12-, 15-, and 18-day skins were determined and compared with each other. Hydroxyproline synthesis in the 18-day skins was markedly increased over that in the 12-day skins, whereas proline incorporation was moderately increased. The increase in collagen synthesis from day 15 to 18 was accompanied by increases in both the translational activity and the content of type I procollagen mRNA, with a selective increase in the lower-molecular-weight species of pro alpha 1 (I) collagen mRNA. In contrast, the stimulation of collagen synthesis from day 12 to day 15 did not parallel the levels of type I procollagen mRNA. These results suggest that the stimulation of collagen synthesis is regulated by collagen mRNA levels only in the later stage of development (from day 15 to day 18). Both the collagen synthesis and type I procollagen mRNA levels in the fibroblasts isolated on each corresponding day were constant. The difference in collagen synthesis under two different culture conditions suggests that cell-matrix interaction and/or some serum factors, including several growth factors, are essential for the marked stimulation of collagen synthesis observed in 12- to 18-day skin.

Actins↗
PubMed1991

Secretion of a unique collagen by spontaneously transformed murine keratinocytes (PAM cells) in vitro.

A spontaneously transformed murine keratinocyte cell line (PAM cell) was found to secrete two nondisulfide-linked collagenous polypeptides with apparent molecular weight (MW) 190-kd and 120-kd. Pulse-chase experiments indicated that the 190-kd polypeptide was secreted into the culture medium in 2 h and processed to the 120-kd collagen component within 4 h. This process was inhibited by EDTA. The 120-kd polypeptide was sensitive to pepsin, and a 50-kd fragment was produced by a mild pepsin treatment at 4 degrees C. A cyanogen bromide peptide map of the 120-kd polypeptide was distinct from that of types I, II, III, IV, and V collagens. These properties indicate similarities to the type VIII-related collagen produced by human astrocytoma cells. The secretion of the collagen rapidly reached a maximum level on the first day of culture and subsequently declined with cell proliferation. An accelerated processing to the 120-kd polypeptide was observed under culture conditions of high cell density. Similar collagens were also found to be produced by normal human keratinocytes. These results indicate that the 120-kd polypeptide is a potentially functional protein that may participate in the formation of the extracellular matrix of keratinocytes.

Animals↗
PubMed1991

Effect of cyproterone acetate on active and inactive renin secretion in patients with precocious puberty and genetic short stature.

To evaluate the effect of cyproterone acetate (CA) on the renin-angiotensin-aldosterone axis, we measured the plasma active, inactive and total renin concentrations (PARC, PIRC and PTRC) during and after CA treatment in patients with precocious puberty and genetic short stature. CA was administered at a daily dose of 150-170 mg/m2 in all subjects. PARC and PTRC were measured by immunoradiometric assays. During CA treatment, PARC, PIRC, PTRC and the PARC/PTRC ratio were significantly decreased. The plasma renin activity, measured by enzymatic assay, and the plasma aldosterone concentration were also decreased. After CA discontinuation, all of these were increased immediately along normal ranges. PARC closely correlated with plasma renin activity. These results suggest that CA produces mineralocorticoid action and suppresses the production and activation of renin.

Androgen Antagonists↗
PubMed1991

Gene encoding a putative zinc finger protein in Synechocystis PCC6803.

A 5.5-kb HindIII fragment of Synechocystis PCC6803 containing a liverwort (ORF316) homolog encoding a putative zinc finger protein was cloned. Nucleotide sequence analysis showed that the homology of the amino acid sequence deduced from the ORF326 of Synechocystis PCC6803 with the counterparts of a liverwort and tobacco was 50% and 46%, respectively. Synechocystis ORF326 also showed 38% homology with the dedB gene in Escherichia coli. The gene organization of the region in these species of organisms was quite different. This suggests that the Synechocystis ORF326 and liverwort ORF316 genes may be related to a common regulatory gene, but not photosynthetic gene characteristic to chloroplasts.

Amino Acid Sequence↗
PubMed1991

[Immunomodulatory effects of interferons on target human gliosarcoma cells in the tumor-specific CTL- and LAK-mediated cytolysis].

We compared the regulatory effects of interferon (IFN)-beta and IFN-gamma on the susceptibility of a human gliosarcoma line GI-1 to the attack of autologous cloned tumor-specific cytotoxic T-lymphocytes (CTL) and lymphokine-activated killer (LAK) cells. Preincubation of GI-1 cells with IFN-gamma caused augmented susceptibility to the cytotoxic attack of two autologous CTL clones, whereas IFN-beta exhibited no such marked effect. On the other hand, preincubation with either IFN-beta or IFN-gamma made the GI-1 cells resistant to the attack of autologous LAK cells. Both IFNs augmented the surface expression of HLA class-I molecules on GI-1 cells. A monoclonal anti-HLA class-I antibody blocked the cytolysis by one CTL clone, but not by the other one. These results suggest that IFN-gamma exerts some different effect (s) from that of IFN-beta on the target GI-1 cells in their susceptibility to the CTL-mediated cytolysis, and that recognition mechanisms of target cells by the CTL are different from those by LAK cells. This draws our attention to IFN administration in adoptive immunotherapy against brain tumors using CTLs and LAK cells.

Brain Neoplasms↗
PubMed1990

Expression of hepatocyte growth factor gene in endothelial and Kupffer cells of damaged rat livers, as revealed by in situ hybridization.

Hepatocyte growth factor (HGF) has been demonstrated to be synthesized and secreted by non-parenchymal liver cells for liver regeneration after hepatic injury. We performed in situ hybridization to identify HGF-producing cell types in rat liver hepatitis induced by administrating carbon tetrachloride as a hepatotoxin. We found that transcripts of the HGF gene are localized in the Kupffer and endothelial cells in normal livers and increased remarkably in the Kupffer cells of the damaged livers. Thus, HGF is concluded to be synthesized in the Kupffer and endothelial cells to repair the liver tissue in paracrine fashion. No significant increase in the transcripts of the HGF gene was observed in livers after partial hepatectomy, indicating that a mechanism on liver regeneration after the hepatectomy differs from that on liver repairs. Since the HGF gene expression was also found in lung and kidney, HGF may be a ubiquitous factor for tissue repairs.

Animals↗
PubMed1990

Biosynthesis, glycosylation and intracellular processing of the neuroglandular antigen, a human melanoma-associated antigen.

Neuroglandular antigen (NGA) was identified as a human melanoma-associated antigen by a panel of murine monoclonal antibodies of both IgG2a (LS62, LS76, LS159) and IgG1 (LS113, LS140, LS152) subclasses, developed in this laboratory (L. Sikora, A. Pinto, D. Demetrick, W. Dixon, S. Urbanski, and L. M. Jerry, Int. J. Cancer, 39: 138-145, 1987). Monoclonal antibody LS62 was used to immunoprecipitate NGA from radiolabeled cultured melanoma cells, and it behaved as a heterogeneous glycoprotein "smear" on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis (Mr 29,000-70,000). Radioactive pulse-chase time course experiments using human melanoma cells cultured in the presence or absence of inhibitors of protein glycosylation showed that the antigen consisted of a core protein with a molecular weight of 22,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This molecule was modified by the addition of at least three N-linked oligosaccharide side chains (as revealed by limited N-glycanase digestion) to give a precursor form with a molecular weight of approximately 34,000. Subsequent processing steps yielded a heterogeneous family of glycoproteins with varying amounts of covalently attached carbohydrate. Much of this heterogeneity in both molecular weight and pI (as revealed by two-dimensional electrophoresis) could be removed by treatment of the antigen with neuraminidase, suggesting heavy sialylation of the glycoprotein. NGA could be detected on the surface of melanoma cells by fluorescence-activated cell sorter analysis, surface radioiodination, and, as previously shown, immunoperoxidase staining. However, there was a larger intracellular pool of the molecule and the antigen was rapidly released into the culture supernatant. The function of NGA remains unknown but its elevated expression in transformed melanocytes have prompted this characterization to understand its biochemical nature and relation to other melanoma-associated antigens.

Antibodies, Monoclonal↗
PubMed1990

A factor from damaged rat kidney stimulates collagen biosynthesis by mesangial cells.

Rats were administered CCl4, a well-defined nephrotoxin, for 20 weeks to produce glomerular sclerosis. Tubular degeneration and necrosis with interstitial fibrosis was clearly evident by histological examination. Kidneys were homogenized in phosphate-buffered saline and a collagen synthesis-stimulating factor was isolated by Sephadex G-50 gel filtration. The 5 kDa component stimulated both type I and type IV procollagen synthesis by mesangial cells and type I procollagen synthesis by rat skin fibroblasts. In each cell type, 2-6-fold increases in procollagen protein production or cell proliferation was noted. The steady-state levels of mRNA encoding for procollagen alpha 1(I) and procollagen alpha 1(IV) chains in mesangial cells were determined by by hybridization to their corresponding cDNA clones. The type I procollagen mRNA was elevated 1.4-fold compared to a 1.6-fold increase in mRNA encoding for type IV procollagen. The similar properties and chemical characteristics of this fibrogenic factor with a factor from fibrotic liver suggests they are the same and that a common endogenous collagen synthesis stimulator may be present in fibrosing organs, thus providing a driving force for collagen over-production.

Animals↗
PubMed1990

Biochemical characterization of glycoprotein components in human ovarian cyst fluids by lectins.

1. Perchloric acid-soluble glycoprotein fractions (PASFs) were separated, in yields of 180-610 mg per 100 ml of cyst fluid, from the cyst fluids of human ovarian cystadenomas (OCAs) in benign and borderline and ovarian clear cell carcinoma (OCC) in malignant, and then identified as glycoproteins with 19.1-69.5% carbohydrate by their chemical composition analyses. 2. These PASFs reacted with anti-A, -B, -Lea and/or -Leb sera, but did not react with anti-H, -M and -N sera. All of the PASFs reacted with Ricinus communis lectin (RCA-I). Among these PASFs, PASFs from the cyst fluids of OCA in benign did not react with Arachis hypogaea anti-T lectin (PNA) and both of the anti-N lectins of Vicia graminea (VGA) and Vicia unijuga (VUA), and PASFs from OCA in borderline reacted with only PNA and PASFs from OCC in malignant reacted with the three lectins, PNA, VGA and VUA. However, none of PASFs from human normal sera and various normal organ tissues reacted with any of RCA, PNA, VGA and VUA. 3. The above-mentioned results seem to show that the examination of glycoproteins of ovarian cyst fluids by the combined use of RCA-I, PNA and VGA (or VUA) permits biochemical diagnosis of the canceration degree of ovarian cystomas.

Adenocarcinoma↗