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Biomedical subjects

H Yamano

Publications and source records attributed to H Yamano.

At least 37 records · Page 2Linked to original sources
PubMed1994

Cumulative risk of hepatocellular carcinoma in hepatitis C virus carriers: statistical estimations from cross-sectional data.

The probability of developing hepatocellular carcinoma (HCC) among hepatitis C virus (HCV) carriers during their life-time is unknown. This paper addresses the estimation of the cumulative risk of HCC among HCV carriers using cross-sectional data. Age-specific prevalences of HCV carriers among the general population were estimated according to 5-year age group, based on the data of 2nd-generation anti-HCV assay in blood donors resident in Osaka (33,226 males and 29,054 females). Seropositivity of anti-HCV among 422 HCC cases, and the Osaka Cancer Registry data on HCC were used in the estimations of 5-year age-specific incidence rates of HCV-linked HCC. Using these data, the cumulative risk, i.e., the probability of contracting HCC within the following 15 years in 50-year-old HCV carriers, was estimated as 28% for males and 6% for females.

Carcinoma, Hepatocellular↗
PubMed1993

Mitotic regulation of protein phosphatases by the fission yeast sds22 protein.

BACKGROUND: Cell cycle progression requires the activity of protein kinases and phosphatases at critical points in the cell cycle in all eukaryotes. We have previously reported that the dis2(+) and sds2(+) genes of fission yeast encode redundant catalytic subunits of a type 1-like protein phosphatase. The sds22(+) gene was shown to be essential for cell viability and to interact genetically with dis2(+) and sds21(+). RESULTS: Here we show by immunoprecipitation that the sds22 protein physically interacts with the dis2 and sds21 proteins, and that sds22-associated phosphatase activity has altered substrate specificity, The loss of sds22 function by a temperature sensitive mutation leads to cell cycle arrest at mid-mitosis, at which point cdc2-dependent histone Hl kinase activity is high while sds22-dependent H1 phosphatase activity is low. To examine the unusual properties of sds22 protein structure, we analyzed a collection of sds22 deletion and point mutants by a variety of functional criteria. CONCLUSION: We propose that sds22 is a regulatory subunit of the dis2/sds21 phosphatase catalytic subunits and that sds22-bound phosphatase carries a key phosphatase activity essential for the progression from metaphase to anaphase. Mutational analysis indicates that dis2/sds21 interacts with the central repetitive domain of sds22, while the C-terminal and central regions of sds22 may be involved in subcellular targeting and the N-terminus is important for stability.

Journal Article↗
PubMed1993

Negative regulation of mitosis by the fission yeast protein phosphatase ppa2.

To understand the role of the type 2A-like protein phosphatase in the cell division cycle, we investigated the mutant phenotypes obtained when the fission yeast ppa1+ and ppa2+ phosphatase genes (which encode polypeptides with approximately 80% identity to mammalian type 2A phosphatases) were either deleted or overexpressed. We also investigated the in vivo effect of okadaic acid, an inhibitor of protein serine/threonine phosphatases, on cell division. We show that ppa2+ interacts genetically with the cell cell regulators cdc25+ and wee1+, as a ppa2 deletion is lethal when combined with wee1-50 but partially suppresses the conditional lethality of cdc25-22 mutation. Evidence that ppa2+ negatively controls the entry into mitosis, possibly through the regulation of cdc2 tyrosine phosphorylation, is presented. ppa2 phosphatase is abundant in the cytoplasm, in contrast to the type 1-like phosphatase dis2, which is enriched in the nucleus. Overproduced ppa1 or ppa2 proteins accumulate in the cytoplasm near the nuclear periphery, and cells arrest in interphase. Okadaic acid-treated cells, like a ppa2 deletion, are short in length and display protein hyperphosphorylation. Cytokinesis is also inhibited, producing binucleated cells. We show that ppa2 is the genetic locus controlling okadaic acid sensitivity. The ppa2 deletion reveals the same hyperphosphorylated proteins as okadaic acid. When a strain deleted for ppa2 is treated with okadaic acid, cell size is reduced further to that of wee1-50 mutant strain or overexpressing the cdc25+ gene product, suggesting functional relationship of ppa2 with the cdc25 tyrosine phosphatase and/or the wee1 kinase in cell cycle control.

Base Sequence↗
PubMed1992

Protein phosphatases and cell division cycle control.

Fission yeast has at least ten protein phosphatase genes that appear to play distinct roles in cell cycle control. Because of functional overlap, a clear lethal phenotype can be obtained only after multiple genetic alterations. Cells that have lost the protein phosphatase 1 (PP1)-like dis2/sds21 phosphatase activities prematurely enter mitosis and remain in a defective mitotic state with high H1 kinase activity and without sister chromatid disjunction. The same phenotype can be obtained in the presence of hydroxyurea. Overexpression of PP1-like phosphatase, on the other hand, delays the entry into mitosis. Cells that have lost PP2A-like ppa2 phosphatase activity also prematurely enter mitosis with a reduction in cell size. This semi-wee phenotype is enhanced in delta ppa2 mutants treated with the phosphatase inhibitor, okadaic acid. Genetic interactions between ppa2 and mitotic regulators suggest that ppa1/ppa2 phosphatase may directly or indirectly inhibit p34cdc2/cyclin kinase. Thus both PP1- and PP2A-like phosphatases in fission yeast may negatively regulate entry into mitosis. The major property of the dis2/sds21 mutant which is distinct from those of the ppa2/ppa1 mutant is its failure to inactivate the p34cdc2/cyclin complex after entry into mitosis. A novel phosphatase regulator encoded by sds22+ binds to dis2 phosphatase and controls the substrate specificity which appears to become essential in the progression from metaphase to anaphase.

Cell Division↗
PubMed1992

Gene cloning of Porphyromonas gingivalis specific antigens recognized by serum of adult periodontitis patient.

1. Porphyromonas gingivalis is believed an important pathogen of adult periodontitis. A gene library of P. gingivalis 381 was constructed in lambda phage vector L47.1. The library was probed with serum obtained from patients of severe adult periodontitis. Two clones, lambda MDBG101 and lambda MDBG103 which were expressed, 200 and 160 kDa respectively, were selected and further studied. 2. The expressed antigens in these two clones were also reacted with rabbit antiserum against whole cells, capsular fraction and cell surface fraction of P. gingivalis. 3. Genes coding protein antigens in lambda MDBG101 and lambda MDBG103 were subcloned into high-copy-number plasmid vector pACYC184 and subclones obtained were designated as MD101 and MD103. Recombinant plasmids, pMD101 and pMD103, differed in their restriction endonuclease digestion. 4. Immunodiffusion analysis showed that cloned proteins from MD101 and MD103 reacted with antiserum against P. gingivalis but did not react with antiserum against Prevotella intermedia, Prevotella loescheii and Prevotella asaccharolyticus. 5. These data suggest that P. gingivalis species-specific antigens has been successfully cloned and expressed in Escherichia coli. Since these cloned specific antigens were recognized by adult periodontitis patient sera, the recombinant antigen will be useful material for the development of serodiagnosis of P. gingivalis infection in adults periodontitis.

Adult↗
PubMed1992

Study on the interaction between soybean beta-amylase and substrate by the stopped-flow method.

The hydrolysis of substrates (maltoheptaose, maltopentaose, and maltotetraose) catalyzed by soybean beta-amylase [EC 3.2.1.2] at pH 5.4 and 25 degrees C was followed by monitoring small changes in the quenching of fluorescence due to tryptophan residues by the stopped-flow method. By analysis of whole time course, the dissociation constants, KdS, of enzyme-substrate and enzyme-product complexes were reasonably evaluated; and the difference in fluorescence intensities per mol between the enzyme-complex (ES or EP) and the free enzyme, delta F, was determined. The molecular activity, k0, was also determined by a new method of half time analysis. The KdS and k0 values are in good agreement with our kinetic data reported previously. The delta Fs of substrates were of smaller magnitude than those of products (G2 and G3), which means that the higher the binding affinity of the ligand is, the smaller the delta F value is. This indicates that at least two tryptophan residues must be located in the active site if the enzyme is rigid, or that if there is only one, the active site must undergo a structural change caused by the binding of ligand.

Hydrolysis↗
PubMed1992

Fission yeast pap1-dependent transcription is negatively regulated by an essential nuclear protein, crm1.

The fission yeast pap1+ gene encodes an AP-1-like transcription factor that contains a leucine zipper motif. We identified a target gene of pap1, the p25 gene. The 5' upstream region of the p25 gene contains an AP-1 site, and by DNase I footprint analysis, we showed that the pap1 protein binds to the AP-1 site as well as to a 14-bp palindrome sequence. p25 is overproduced when the pap1+ gene is overexpressed, whereas p25 is not produced at all in the pap1 deletion mutant. p25 was previously found to be overproduced in strains carrying cold-sensitive crm1 mutations whose gene product is essential for viability and is thought to play an important role in maintenance of a proper chromosomal architecture. Deletion and site-directed mutagenesis of sequences upstream of the p25 gene demonstrated that the AP-1 site as well as the palindrome sequence are crucial for transcriptional activation either by pap1 overproduction or by the cold-sensitive crm1 mutation; pap1+ is apparently negatively regulated by crm1+. Moreover, we found that cold-sensitive crm1 mutations are suppressed by the deletion of pap1+, further indicating a close relationship between crm1+ and pap1+. The crm1 protein is highly conserved; the budding yeast homolog, CRM1, which complements the fission yeast cold-sensitive crm1 mutation, was isolated and found to also be essential for viability. These results suggest the functional importance of chromosome structure on the regulation of gene expression through the pap1 transcription factor.

Amino Acid Sequence↗
PubMed1991

Transcriptional terminator is a positive regulatory element in the expression of the Escherichia coli crp gene.

Plasmids were constructed that contain deletions in the stem region of the presumed rho-independent terminator of the cloned crp gene of Escherichia coli. The level of cyclic AMP binding activity and the amount of CRP in cells harboring the deletion plasmids were found to be significantly lower than those in cells harboring the wild-type crp plasmid. Quantitative S1 assays indicated that the steady-state levels of crp mRNA were markedly reduced in cells harboring the deletion plasmids. Evidence was also presented to show that the crp mRNAs produced from deletion plasmids are less stable than that from the intact crp gene. In vitro transcription assays revealed that the putative crp terminator is indeed a rho-independent terminator. Using the galK expression system and Northern blot analysis we showed that the crp terminator is functional in vivo. Moreover it was shown that the deletion mutations in the stem region of the crp terminator cause a significant readthrough. We conclude that the 3'-flanking sequence of the crp gene acts to stabilize its own mRNA as well as to terminate transcription.

Base Sequence↗
PubMed1991

Protein phosphatases in cell division: how vital are they?

In contrast to the wealth of information on cellular function of protein kinases, many of which are known to be the products of proto-oncogenes, little is known about how protein dephosphorylation is involved in growth control of normal and malignant cells. In the present study, roles of protein phosphatases in cell division cycle control were examined by molecular genetic approaches using a lower eukaryote, the fission yeast Schizosaccharomyces pombe. Nine protein phosphatase genes have been so far identified and characterized in this organism. Each of two (dis2+, sds21+, and ppa1+, ppa2+) gene products is highly similar to mammalian type 1 and 2A ser/thr phosphatases, respectively. The ppx1+ product is an intermediate of type 1 and 2A, while the ppb1+ product is similar to Ca(2+)-dependent type 2B. At least two protein tyrosine phosphatase genes (pyp1+ and pyp2+) exist. The cdc25 protein is now established to be a tyrosine phosphatase that activates cdc2 kinase. Some of these phosphatase genes are interrelated but have distinct, essential functions in cell cycle control. Missense mutations, deletions or high dosage expression of these phosphatase genes affect entry into and exit from mitosis, mitotic chromosome disjunction, cell size and cell shape. They seem to interact with the main regulators of mitosis, cdc2, cdc13/cyclin, cdc25 and weel, or with mitotic structural components, such as condensed chromosomes or the spindle apparatus. We show that the product of an essential gene, sds22+, is an important, positive factor in controlling the expression and modulating the activity of dis2 phosphatase.

Amino Acid Sequence↗
PubMed1990

Effects of maternal caffeine with zinc intake during gestation and lactation on bone development in newborn rats.

On day 9 of gestation, pregnant dams were randomly divided into 3 groups. Dams of group 1 were fed a 20% protein diet as a control. Dams of group 2 were fed a 20% protein diet supplemented with caffeine. Dams of group 3 were fed a 20% protein diet supplemented with caffeine and zinc. The amount of caffeine added to the maternal diet was 2 mg/100 g body weight; the amount of zinc was 0.6 g/kg of diet. At birth, pups were mixed within each group, and 8 randomly selected pups from each group were assigned to each dam of the respective group and were continuously fed the same diet. On day 15, the pups were killed and cranial bones, mandibles and femurs removed. The bones were measured, and the mineral content of the mandibles and femurs was determined. Although there were no differences in the dimensions of the cranial bones among the groups, the measurements and mineral content of the mandibles and femurs were consistently affected by the caffeine in the diet. On the other hand, supplementation of the caffeine-added diets with zinc led to greatly improved bone development, reaching values up to or beyond control levels. Thus zinc supplementation of a caffeine diet given to the dams during gestation and lactation can favourably influence the otherwise impaired bone development of their offspring.

Animals↗
PubMed1990

[Study for improvement of oral health among the elderly. Present status of dental care service at elderly homes].

Since the dental environment at a living place could potentially become a factor causing a need for dental care, all 33 elderly homes (27 of which responded to the survey) in Tokyo were investigated for the purpose of identifying the present status of dental care service and the problems existing at these homes. The following are the obtained conclusions. 1. The rate of homes with dental care facilities is as low as 19.2%, and cooperation by dental care institutions, including house calls, is ensured only at the low rate of 11.1%. As a result, usually patients visit the dental institutions. 2. The involvement of the dental staff, including part-time, was 44.4%, less than half of the homes surveyed. The homes wishing to employ or receive service from dental staff accounted for 76.9%. The homes also expected them to be engaged in the activities of overall oral hygiene, including not only dental treatment, but also participation in the planning of oral hygienic management. However, 23.1% of the respondents did not wish to employ any dental staff or receive any such service. 3. Specific programs for the guidance and management of oral hygiene were not observed. Homes that conducted dental examination periodically and those that carried out activities related to oral hygiene during Dental Health Week were also lacking. In addition, the homes which had assigned personnel responsibility for oral hygiene represented only 12.0%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗