Biomedical subjects

M Yao

Publications and source records attributed to M Yao.

At least 145 records · Page 8Linked to original sources

PubMed1996

Cleavage of insertion/deletion mismatches, flap and pseudo-Y DNA structures by deoxyinosine 3'-endonuclease from Escherichia coli.

Deoxyinosine 3'-endonuclease, an Escherichia coli repair enzyme that recognizes and cleaves DNA containing deoxyinosine and base mismatches, can cleave heteroduplexes containing a hairpin or unpaired loop. These DNA structures, referred to as insertion/deletion mismatches (IDM), are abnormal intermediate structures generated during replication of repetitive DNA sequences. In addition, the enzyme also cleaved the 5'-single-stranded tails of flap and pseudo-Y DNA structures, suggesting that deoxyinosine 3'-endonuclease is a bacterial functional homologue of human FEN1 and yeast RTH1 nucleases. These biochemical properties suggest that deoxyinosine 3'-endonuclease might be important in the repair of IDM structures generated in lagging strand during DNA replication.

DNA Repair↗

PubMed1996

hprt mutation frequency among workers exposed to 1,3-butadiene in China.

Hypoxanthine-guanine phosphoribosyl transferase (hprt) mutation frequency (M(f)) was studied in workers at a polybutadiene rubber production facility in Yanshan, China. Exposed workers included for study were active either as process analysts, who sampled butadiene production process lines and analyzed product by gas chromatography, or as process operators, who did routine process control, minor maintenance and, as needed, major repair operations. For process analysts at the polymer and dimethyl formamide (DMF) facilities, the median air levels of BD were 1.0 and 3.5 ppm, respectively. Among process operators, air levels of 1.1 ppm were found during routine activities, while the median air level during pump repair and related operations was 45 ppm (6-h time-weighted average). Overall, M(f) was similar in unexposed (mean M(f) = 20.2 x 10(-6)) and butadiene-exposed (mean M(f) = 21.6 x 10(-6)) workers (P = 0.68). M(f) decreased with cloning efficiency, increased with age, and was moderately greater in women than in men. After adjustment by multiple regression analysis for mean age, sex, and cloning efficiency, the adjusted mean M(f)(Xadj) was 13.6 x 10(-6) in unexposed and 18.0 x 10(-6) in butadiene-exposed. This 32% difference was, however, not statistically significant (P = 0.13). Butadiene exposure was associated with a modest, if any, increase in hprt M(f) in this population of Chinese workers.

Adult↗

PubMed1996

Production and crystallization of lobster muscle tropomyosin expressed in Sf9 cells.

A new form of muscle tropomyosin crystal has been obtained, by employing new strategies in protein preparation and crystallization. Non-polymerizable tropomyosin was prepared by removing 11 amino acids at the C-terminus. The truncated tropomyosin was expressed in Sf9 insect cells by use of the baculovirus-based expression system, to obtain highly homogeneous protein preparations. By routinely monitoring homogeneity by mass spectrometry, we found that the homogeneity played a key role in obtaining good crystals. The crystal quality was also dependent on isoforms; the crystals raised from a slow muscle-specific isoform diffracted to a higher resolution, compared with a fast muscle-specific counterpart. For crystallization, a high concentration of organic solvent was used as the precipitant; in the presence of 35% DMSO, tetragonal crystals were formed, which belong to space group P4(3)(1)2(1)2 with cell constants of a=b=105.6 angstrom, c=506.9 angstrom. The crystals gave rise to reflections the intensities of which were characteristically determined by the transform of alpha-helical coiled-coil. Thus in the region of 10-5.5 angstrom resolut along the c*-axis, the reflections were weak. For accurate measurement of these reflection intensities, beam-line ID2 in ESRF Grenoble was advantageous owing to the high brilliance and a low background. There the crystals diffracted to beyond 3.0 A along the c*-axis, whereas along the a*-b*-plane reflections were limited to 6.6 angstrom. Data analysis is under way on a data set from a PtCl4 derivative.

Amino Acid Sequence↗

PubMed1996

Retinoic acid promotes neural and represses mesodermal gene expression in mouse embryonic stem cells in culture.

Mouse embryonic stem cells treated with retinoic acid are induced to differentiate into neuron-like cells (Bain et al. (1995) Dev. Biol. 168, 342-357). Here we have examined the expression of a set of neural- and mesoderm-specific genes during this in vitro differentiation process. mRNAs encoding the neural genes Wnt-1, MASH1, the light and medium isoforms of neurofilaments, and the neurotransmitter-synthesizing enzyme glutamic acid decarboxylase are all strongly upregulated by retinoic acid treatment; expression of these genes occurs in a temporal pattern resembling that in the developing brain. In contrast, retinoic acid blocks the expression of the mesodermal genes Brachyury, cardiac actin, and zeta-globin. Thus, retinoic acid exerts both pro-neuronal and anti-mesodermal activities on mouse embryonic stem cells in culture.

Animals↗

PubMed1996

Von Hippel-Lindau tumour suppressor gene. Localization of expression by in situ hybridization.

Inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene is responsible not only for VHL disease, but also for sporadic renal cell carcinoma and cerebellar haemangioblastoma. The distribution of VHL gene expression in the mouse embryo was recently studied by in situ hybridization, along with human VHL in 14-week-old fetal kidney: there was widely distributed expression in the former and expression in the tubules and blastema in the latter. Adult human tissue and other fetal organs were not examined. The present paper describes an in situ hybridization study to assess the function of the VHL gene in adult human tissues and in tissues of human fetus at 28 weeks of gestation. The expression of the VHL gene was limited to the adult and fetal brain and kidney, and the adult prostate. Nerve cells in adult and fetal brain were positive, including the cerebellar Purkinje cells. In adult and fetal kidney, the proximal tubular epithelium, the putative origin of the common type of renal cell carcinoma, showed intense signal, whereas the distal nephron, glomeruli, and nephrogenic blastema showed no significant signal. The prostate showed significant signal in the basal epithelium. The adrenal, pancreas, and epidydimis showed no significant signal, in spite of the frequent occurrence at these sites of neoplastic or hamartomatous lesions in VHL disease.

Animals↗

PubMed1996

Different electrophoretic techniques produce conflicting data in the analysis of myocardial samples from dilated cardiomyopathy patients: protein levels do not necessarily reflect mRNA levels.

A variety of electrophoretic techniques were used to search for potential causes of human dilated cardiomyopathy (DCM). Northern blots were used to quantify alpha-cardiac and alpha-skeletal muscle actins, and beta-myosin heavy chain mRNAs which are the predominant expressed isoform species. We found a wide range of mRNA levels expressed in both DCM and nondiseased (ND) samples of left ventricles. However, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of the same heart samples revealed a stable and constant ratio of actin and myosin. Dystrophin deficiency might account for the DCM symptoms and so dystrophin levels of DCM and ND samples were evaluated using Western blots probed with monoclonal antibodies for the N-, C- and mid-rod portions of this protein. We found that dystrophin levels were constant in all 29 DCM and 5 ND samples suggesting that dystrophin deficiency is probably not a contributing cause. We explored the possibility that terminal failure may be due to an apoptotic-like event in the cardiomyocytes. Zymograms of DCM and ND samples revealed a significant increase in DNase I activity in the DCM group compared to the ND samples. These data raise the possibility that end-stage failure may be associated with apoptosis.

Actins↗

PubMed1996

Elevated DNase I levels in human idiopathic dilated cardiomyopathy: an indicator of apoptosis?

This is the first report to determine deoxyribonuclease I (DNase I) levels in the human myocardium and the first to demonstrate an increased DNase I level associated with end-stage heart failure due to idiopathic dilated cardiomyopathy (IDCM) compared to non-diseased heart samples. Left ventricular samples were obtained following transplantation from failing hearts of 13 patients diagnosed with IDCM and from four unused donor hearts. Using a zymogram technique, we show that the DNase I levels of the IDCM heart samples were significantly elevated (range 0.65-2.75 pg DNase I/microgram protein, mean +/- S.E. of 1.69 +/- 0.22 pg/micrograms) compared to four non-diseased, donor heart samples (range 0.12-0.35 pg/microgram protein, mean +/- S.E. of 0.22 +/- 0.05 pg/microgram). The DNase I extracted from heart tissue was characterized by: (1) a co-migration with bovine pancreatic DNase I; (2) a pH dependence consistent with DNase I; (3) a dependence of its activity on both Ca2+ and Mg2+ and an inhibition by Zn2+; and (4) an inhibition of its activity in the presence of monomeric rabbit skeletal muscle actin. The elevated DNase I levels associated with heart failure due to IDCM suggests that apoptosis may be implicated in pathophysiology of this disorder.

Actins↗

PubMed1996

A case of chromophobe renal cell carcinoma associated with low chromosome number and microsatellite instability.

Cytogenetic study in a case of a human chromophobe renal cell carcinoma revealed a hypodiploid chromosome number of 36 with loss of chromosomes 1, 2, 5, 6, 10, 13, 15, 17, 21, and X. The tumor DNA showed microsatellite instability in dinucleotide repeat microsatellite markers. This is the fourth case that has been fully karyotyped and showed a low chromosome number in a chromophobe renal cell carcinoma. Our data in the present study are consistent with those in the literature. It is suggested that human chromophobe renal cell carcinoma may possibly be characterized by tumor cells with low chromosome number or microsatellite instability.

Adult↗

PubMed1996

A comparison of methotrexate versus laparoscopic surgery for the treatment of ectopic pregnancy: a cost analysis.

This study was a cost analysis of direct medical costs of the methotrexate management versus laparoscopic surgery in the treatment of ectopic pregnancy. A total of 40 patients treated from January 1991 to October 1994 with methotrexate were compared with another 40 patients treated at the same hospital by laparoscopy from April 1986 to June 1994. Medical records for all these patients were received and hospital databases were used to retrieve information on cost. Treatment cost included the primary treatment, hospitalization and outpatient follow-up necessitated by treatment, complications and secondary treatment in cases of treatment failure. The cost related to diagnosis was excluded. The direct medical costs for methotrexate and laparoscopy groups were based on success rates of 72.5 and 95% respectively. The total cost of methotrexate treatment was Canadian $35,180 compared with Canadian $73,440 for the laparoscopic treatment. The mean +/- SD cost per patient was Canadian $880 +/- 160 in the methotrexate group compared with Canadian $1,840 +/- 150 in the laparoscopic group (P < 0.001). The mean +/- SE cost per patient with methotrexate success was Canadian $330 +/- 67 compared with Canadian $2,330 +/- 220 per patient with methotrexate failure (P = 0.001). A complete assessment of methotrexate treatment, including cost-benefit and cost-effectiveness, is warranted.

Chorionic Gonadotropin↗

PubMed1996

Molecular genetic diagnosis of von Hippel-Lindau disease: analysis of five Japanese families.

We analyzed deoxyribonucleic acids from blood samples of five Japanese von Hippel-Lindau (VHL) disease families (three familial cases, two new mutations) for the presence of VHL gene mutations by single-strand conformational polymorphism analysis and direct sequencing. Four of the five families showed germ line mutations in VHL gene, comprising 2 missense mutations, 1 deletion, and 1 splice-site mutation. Two families had VHL gene mutations at exon 1; 1 family at exon 3; and 1 family at the splice-site adjacent to exon 3. Presymptomatic patients were accurately diagnosed by these methods. However, one family did not show a VHL gene mutation in the germ line but showed a somatic mutation at exon 2 in the hemangioblastoma tissue. The consequence of the somatic mutation was a microdeletion leading to a frameshift mutation. Our study is the first report of VHL gene analyses of Japanese VHL disease families, and suggests that not only germ line mutation, but also somatic mutation can lead to development of a tumor associated with the VHL disease.

Base Sequence↗

PubMed1996

New telomere formation coupled with site-specific chromosome breakage in Tetrahymena thermophila.

Programmed chromosome breakage occurs in many ciliated protozoa and is accompanied by efficient new telomere formation. In this study, we have investigated the relationship between programmed chromosome breakage and telomere formation in Tetrahymena thermophila. Using specially constructed DNA clones containing the breakage signal Cbs in transformation studies, we have determined the locations of telomere addition around the breakage sites. They occur at variable positions, over 90% of which are within a small region (less than 30 bp) starting 4 bp from Cbs. This distribution is independent of the nucleotide sequence in the region or of the orientation of Cbs. In five of six cases determined, these sites occur at or before a T, and in the remaining case, the site occurs at or before a G. When sequences devoid of G or T are placed in this region, telomere addition still occurs within the region to maintain a similar distance relationship with Cbs. This efficient and healing process appears to be associated specifically with Cbs-directed breakage, since it does not occur when DNA ends are generated by restriction enzyme digestion. These results suggest a strong mechanistic link between chromosome breakage and telomere formation.

Amino Acid Sequence↗

PubMed1996

Clinical and hematological characteristics of hepatosplenic T gamma/delta lymphoma with isochromosome for long arm of chromosome 7.

Hepatosplenic T gamma/delta lymphoma is a rare entity of peripheral T cell lymphoma. Three of 386 patients with non-Hodgkin's lymphoma in our institute were found to have this subtype of lymphoma. All had chromosomal abnormalities of isochromosome 7q and trisomy 8. The clinical and hematological features of these three patients are reported. All were males with ages ranging from 23 to 29 years. Initial presentation comprised purpura and variable degree of hepatosplenomegaly. None had superficial lymphadenopathy. Hematologically, they showed pictures resembling immune related thrombocytopenia and/or hemolytic anemia. Examination of the bone marrows revealed hypercellularity with increased number of megakaryocytes and erythroid cells and various degrees of abnormal lymphoid cell infiltration. The histopathologic section of the spleen from one patient who underwent splenectomy revealed abnormal cell infiltration in the sinusoids of the red pulp. Lymphoma cells showed T gamma/delta lymphoid immunophenotype (CD3+ CD2+ CD4- CD8-, TCR delta-1+, and beta F1-). The platelet counts were elevated transiently after initial treatment with corticosteroids, but the condition soon deteriorated. All died of refractory lymphoma five to nine months after diagnosis. Review of the literature, showed that only four other cases have been reported until now and although no cytogenetic data were available for these patients, they had very similar clinical pictures as those in this series. It is suggested that hepatosplenic T gamma/delta lymphoma represents a rare, but distinct, clinicopathological and cytogenetic entity.

Adolescent↗

PubMed1996

[Recurrent and up-grading bladder cancer in a young female: a case report].

We report a case of superficial bladder cancer in a young female, with grade-up tumor after frequent recurrences. A 29-year-old woman complained of gross hematuria on April 25, 1991. Cystoscopic examination revealed a papillary pedunculated tumor and transurethral resection of bladder tumor (TUR-BT) was performed. Pathological examination showed transitional cell carcinoma (TCC) pT1 grade 1. In spite of prophylactic therapy, such as intravesical instillation of anticancer drugs and radiochemohyperthermia, she suffered frequent recurrences. At the 6th recurrence, the tumor deteriorated to grade 3 on September 2, 1992. Total cystectomy was done on February 15, 1993 because of uncontrollable bleeding from bladder cancer. Convalescence was uneventful, and no evidence of recurrence was present 2.8 years postoperatively.

Adult↗

PubMed1996

Induction therapy of newly diagnosed acute nonlymphocytic leukemia with idarubicin and cytosine arabinoside--the Taiwan experience.

From October 1993 to December 1994, 26 patients with newly diagnosed and untreated acute nonlymphocytic leukemia (ANLL) received induction chemotherapy with the 3 + 7 regimen, i.e., idarubicin (IDA) 12 mg/m2/d for 3 days any cytosine arabinoside (Ara-C) 100 mg/m2/d for 7 days. Complete remission (CR) was achieved in 80.8% of the whole group and in 66.7% (two of three) of the elderly subgroup (age > or = 60 years). Seventeen patients achieved a CR after only one course, whereas four needed two courses. Toxicity was tolerable. All of the patients experienced myelosuppression, and infection episodes were noted in all except one patients. Other toxicities included vomiting (62%, mostly mild to moderate, grade I/II), diarrhea (46%, mostly grade I), mucositis (65%, mostly grade I), and alopecia (100%). None presented with liver dysfunction or cardiotoxicity. Of the 21 complete responders, one refused further consolidation, 20 received either two additional courses of IDA/Ara-C or high-dose Ara-C as consolidation, and one died of infectious complications during consolidation. As of May 1995, nine had relapsed, and 11 (55%) continued in CR for 6 to 21 months (median, 14.5). All four patients who needed two courses of IDA/ Ara-C to achieve remission had relapsed, with either high-dose Ara-C or allogeneic bone marrow transplantation (BMT) as postremission therapy. We suggest that induction failure with one course of IDA/Ara-C is a poor prognostic factor in ANLL.

Adult↗

PubMed1996

[Consideration of therapeutic choice for grade 3 superficial bladder cancer].

Between January, 1977 and December, 1994, 90 patients with grade 3 (G3) superficial bladder cancer were treated at Yokohama City University Hospital, Yokohama Municipal Hospital and Kanagawa Cancer Center. These patients were clinically observed. The prognostic factors of the patients with G3 superficial bladder tumors were age and growth pattern of tumors. Patients older than 67 showed significantly poor survival compared with younger patients (p < 0.01). Patients with non-papillary sessile tumors showed significantly poor survival compared with the other groups (p < 0.05). The five-year survival rate of the patients with G3 superficial tumors who were treated by total cystectomy was 75%, whereas all the patients who were treated by bladder preservation therapy died within 4 years, the difference being significant (p < 0.05). Eleven patients with G3 superficial bladder tumors died of cancer, and most of these patients had multiple and non-papillary sessile tumors. These findings suggest that the patients with G3 superficial tumors, which are non-papillary sessile tumors, should be treated by radical cystectomy.

Adult↗

PubMed1996

[Unilateral and synchronous occurrence of renal cell carcinoma and ureteral tumor: a case report].

An 81-year-old woman was admitted to our hospital with left flank pain. Excretory urography revealed left hydronephrosis. Abdominal computed tomography (CT) revealed a large heterogenous tumor in the upper pole and marked hydronephrosis and hydroureter in the lower portion of the left kidney. Left total nephroureterectomy was performed under the diagnosis of renal pelvic and ureter tumor. The pathological diagnosis was of renal cell carcinoma (spindle type, grade 3) in the kidney and transitional cell carcinoma (grade 2) in the ureter. Postoperative chemotherapy was not given. Convalescence was uneventful and fifteen months after the operation she is alive with no recurrence or metastasis.

Aged↗

PubMed1996

[Prevention from secondary nerve root adhesion: an experimental study].

In the study, 27 dogs were divided into three groups: A, B and C. Then all of the dogs had their lumbar intervertebral disks removed. Into the wounded cavity of group A, 1 ml of dimethicone was dropped and gelatin sponge was applied on the surface of the nerve root of group B. Group C was served as the control. The dogs were killed and the operation area was removed respectively 2 weeks, 4 weeks, and 12 weeks after the operation for macroscopical observation, nerve root motility measurement and histological examination. The result of the experiment proved that dimethicone was fairly effective in the prevention from secondary nerve root adhesion. While gelatin sponge in the process of its absorption induced the formation of quite a few scar tissues, thus aggrevating nerve root adhesion.

Animals↗

PubMed1995

Interaction of deoxyinosine 3'-endonuclease from Escherichia coli with DNA containing deoxyinosine.

By using a band mobility shift assay, deoxyinosine 3'-endonuclease, an Escherichia coli enzyme which recognizes deoxyinosine, AP site, urea residue, and base mismatches in DNA, was shown to bind tightly to deoxyinosine-containing oligonucleotide duplexes. Two distinct protein-DNA complexes were observed, the faster migrating complex (complex I, Kd = 4 x 10(-9) M) contained one molecule of deoxyinosine 3'-endonuclease, while the slower migrating complex (complex II, Kd = 4 x 10(-7) M) contained two molecules of the protein bound to every molecule of duplex DNA. The endonucleolytic activity of deoxyinosine 3'-endonuclease paralleled the formation of the complex I. Interestingly, deoxyinosine 3'-endonuclease exhibited similar affinities for both the substrate and the nicked duplex product and thus remained bound to the DNA after the cleavage reaction. The formation of a stable complex required the presence of a duplex structure 5' to the deoxyinosine residue. DNase I footprinting revealed that deoxyinosine 3'-endonuclease protected 4-5 nucleotides 5' to the deoxyinosine, and when complex II was formed, at least 13 nucleotides 3' to deoxyinosine were protected. Based on these results, a model is proposed for the interaction of deoxyinosine 3'-endonuclease with DNA containing deoxyinosine.

Base Sequence↗