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M Yao

Publications and source records attributed to M Yao.

At least 163 records · Page 9Linked to original sources
PubMed1995

Neuronal differentiation of P19 embryonal carcinoma cells in defined media.

The P19 embryonal carcinoma cell line is a useful model system for analyzing the factors that regulate neuronal differentiation. In order to analyze the extrinsic factors that are involved in differentiation, it is necessary to carry out experiments in fully defined media. Here we have investigated the neuronal differentiation of P19 cells in two defined media. Cells that are propagated and induced with retinoic acid in standard serum-containing medium are capable of differentiating into neuron-like cells in N2 medium. Dividing fibroblast-like cells also appeared in these cultures. After about 10 days in culture in N2 medium, the great majority of neuron-like cells died. On the other hand, culturing induced cells in N2 medium for 5 days and then switching to a defined medium consisting of Neurobasal medium plus B27 supplement allowed the neuron-like cells to survive for prolonged periods of time. This defined medium thus provides a suitable system for analyzing extrinsic factors that affect the survival and differentiation of P19 neurons. P19 cells induced with retinoic acid and plated in N2 were exposed to bFGF and EGF, which are known to be mitogens for neuronal precursor cells. Both growth factors were mitogenic for a subpopulation of the induced cells. In separate experiments, cells cultured in N2 in the presence of RA were induced to differentiate into neuron-like cells.

Animals↗
PubMed1995

Mechanism of bioactivation and covalent binding of 2,4,6-trinitrotoluene.

Studies were undertaken to investigate the mechanism of bioactivation and covalent binding of TNT. Incubation of [14C]TNT with rat liver microsomes in the presence of an NADPH generating system resulted in metabolism and covalent binding to microsomal proteins. Time-dependence studies showed that TNT was rapidly reduced to yield 4-hydroxylamino-2,6-dinitrotoluene (4HA), 4-amino-2,6-dinitrotoluene (4A) and 2-amino-4,6-dinitrotoluene (2A) as intermediates which were further metabolized to form 2,4-diamino-6-nitrotoluene (2,4DA) and 2,6-diamino-4-nitrotoluene (2,6DA). In contrast to the rapid disappearance of TNT, formation of covalent protein adducts increased with time, suggesting that the reactive intermediate was likely to be formed not directly from TNT but from proximal intermediates such as 4HA. The hypothesis that 4HA was more readily converted to the reactive intermediate than TNT was further supported by the increased levels of covalent adduct formation when [14C]4HA was incubated directly with liver microsomes. Covalent binding of TNT and 4HA was dependent on oxygen concentration. Higher levels of covalent adducts were formed when TNT was incubated aerobically (up to 50% oxygen concentration) than under anaerobic conditions. Covalent binding of [14C]4HA also increased with increasing oxygen concentrations. These results suggest that the reactive intermediate is likely to be an oxidized metabolite of 4HA, e.g. 4-nitroso-2,6-dinitrotoluene. Compounds containing a free sulfhydryl group (cysteine, N-acetylcysteine, GSH or 3,4-dichlorobenzenethiol) decreased the amount of covalent binding to various degrees, suggesting the involvement of the sulfhydryl group in adduct formation with TNT following bioactivation. Metabolic activation of TNT by liver microsomes required NADPH but not NADH as the cofactor. Incubation of [14C]TNT with purified rat liver NADPH cytochrome P450 reductase under either aerobic or anaerobic conditions yielded exclusively 4HA. In contrast, 2A and 4A were formed following incubation of TNT with the reconstituted system containing cytochrome P450, NADPH cytochrome P450, reductase and dilauroyl phosphatidylcholine. These observations suggest that the initial reduction of the nitro group can be catalyzed by NADPH cytochrome P450 reductase alone but cytochrome P450 is needed in the reduction of the hydroxylamine to the amine.

Animals↗
PubMed1995

How valid are denaturant-induced unfolding free energy measurements? Level of conformance to common assumptions over an extended range of ribonuclease A stability.

A thermodynamic cycle is used to explore a host of assumptions, conditions, and criteria which must be met for evaluation of authentic unfolding free energy changes. The thermodynamic cycle involves measurement of the unfolding free energy change (delta GzeroN-U) for RNase A at a reference pH, along with determination of the titration free energy changes for the native and unfolded species over an extended pH range. From these free energy changes, delta GzeroN-U at any pH in the range can be predicted and compared with delta GzeroN-U determined by use of the linear extrapolation method (LEM). Good agreement is found between predicted and determined free energy changes covering a broad range of protein stability changes (5 kcal/mol), pH (pH from 3 to 8.5), and lengths of linear extrapolation (C1/2 values from 2.4 to 7.7 M urea). The agreement between predicted and LEM-determined delta GzeroN-U values demonstrates (1) that delta GzeroN-U determined by the LEM is a function of state; i.e., it has the properties of additivity and independence of pathway required of an authentic free energy quantity; (2) the ability to obtain delta GzeroN-U values which are in agreement with the free energy change predicted by the cycle is independent of the length of linear extrapolation; and (3) the two-state assumption holds over an extensive pH range. The fact that the pH titration curve of unfolded RNase A in 6 M GdnHCl could be used in accurately predicting urea-induced delta GzeroN-U values shows that the unfolded ensemble in 6 M GdnHCl is thermodynamically identical to urea-unfolded RNase A as far as the pH dependence of protein stability is concerned. Urea-induced and GdnHCl-induced RNase A delta GzeroN-U values at pH 3 were found not to agree with one another, but this appears to be due to the inability to control the salt effect of GdnHCl on the native state of RNase A. These results provide strong evidence that the LEM applied to urea-induced unfolding of RNase A results in reliable free energy changes that meet a number of essential criteria for authentic thermodynamic quantities. The titration method is important in its own right in providing a means for evaluating the pH dependence of two-state protein unfolding free energy changes which does not require analysis of denaturant-induced unfolding transitions.

Enzyme Stability↗
PubMed1995

Germline mutations in the von Hippel-Lindau disease tumor suppressor gene: correlations with phenotype.

von Hippel-Lindau disease (VHL) is an inherited neoplastic disease characterized by a predisposition to develop retinal angiomas, central nervous system hemangioblastomas, renal cell carcinomas, pancreatic cysts, and pheochromocytomas. The VHL gene was recently isolated by positional cloning. The cDNA encodes 852 nucleotides in 3 exons. The VHL gene is unrelated to any known gene families. We identified germline mutations in 85/114 (75%) of VHL families. Clinical heterogeneity is a well-known feature of VHL. VHL families were classified into 2 types based on the presence or absence of pheochromocytoma. The types of mutations responsible for VHL without pheochromocytoma (VHL type 1) differed from those responsible for VHL with pheochromocytoma (VHL type 2). Fifty-six % of the mutations responsible for VHL type 1 were microdeletions/insertions, nonsense mutations, or deletions; 96% of the mutations responsible for VHL type 2 were missense mutations. Specific mutations in codon 238 accounted for 43% of the mutations responsible for VHL type 2. The mutations identified in these families will be useful in presymptomatic diagnosis. The identification of mutations associated with phenotypes contributes to the understanding of fundamental genetic mechanisms of VHL disease.

Adrenal Gland Neoplasms↗
PubMed1995

Embryonic stem cells express neuronal properties in vitro.

Mouse embryonic stem (ES) cells cultured as aggregates and exposed to retinoic acid are induced to express multiple phenotypes normally associated with neurons. A large percentage of treated aggregates produce a rich neuritic outgrowth. Dissociating the induced aggregates with trypsin and plating the cells as a monolayer results in cultures in which a sizable percentage of the cells have a neuronal appearance. These neuron-like cells express class III beta-tubulin and the neurofilament M subunit. Induced cultures express transcripts for neural-associated genes including the neurofilament L subunit, glutamate receptor subunits, the transcription factor Brn-3, and GFAP. Levels of neurofilament L and GAD67 and GAD65 transcripts rise dramatically upon induction. Physiological studies show that the neuron-like cells generate action potentials and express TTX-sensitive sodium channels, as well as voltage-gated potassium channels and calcium channels. We conclude that a complex system of neuronal gene expression can be activated in cultured ES cells. This system should be favorable for investigating some of the mechanisms that regulate neuronal differentiation.

Animals↗
PubMed1995

Polymorphisms in the human DNA polymerase beta gene.

Recently, evidence has accumulated that mutations in DNA repair genes might be associated with certain steps in carcinogenesis. The DNA polymerase beta gene is one of the DNA repair genes, and mutations in it have been detected in 83% of human colorectal cancers. To assess the involvement of polymerase beta gene mutations in the development of human prostate cancers, we performed sequence analyses of human DNA samples. Unexpectedly, we found six regions that were polymorphic. This information should be taken into consideration at the time of sequence analysis of the DNA polymerase beta gene.

Base Sequence↗
PubMed1995

Detection of dural involvement by magnetic resonance imaging in adult patients with acute leukemias--preliminary experience.

Retrospectively, the dura in 18 adult patients with acute leukemia were evaluated by gadolinium-enhanced T1-weighted magnetic resonance imaging (MRI). Abnormal dural enhancements were detected in three of four patients with positive cerebrospinal fluid (CSF) cytology, in one of five with suspicious central nervous system (CNS) disease, and in two of nine asymptomatic patients. Computed tomography failed to demonstrate any dural abnormality in these six patients. The abnormal dural enhancement was found in either (a) the brain and the spine, (b) the thoracolumbar spine, or (c) the area adjacent to the parenchymal lesions. Three of the patients were in hematological remission stage; disappearance of the abnormal dural enhancement was observed 1-2 months after radiotherapy and high-dose systemic chemotherapy. The results suggest that MRI is a sensitive and noninvasive imaging modality and superior to CT in detecting dural disease in leukemic patients.

Adolescent↗
PubMed1995

Monitoring human risk and exposure to trinitrotoluene (TNT) using haemoglobin adducts as biomarkers.

Two studies were carried out in a trinitrotoluene (TNT) plant using TNT haemoglobin (TNT-Hb) adduct as a biomarker to study dose-adduct and adduct-response relationships. In the first study, TNT-Hb adduct levels were determined in 117 TNT-exposed workers in different working sites with different exposure conditions. External exposure was calculated from the inhaled air concentration plus skin contamination. TNT-Hb adduct levels in blood were significantly correlated with their external exposure to TNT. Two methods, HPLC-UV and CI-ELISA, were developed for measuring TNT-Hb adduct: good correlations (r = 0.77 and 0.86) were found between these 2 methods. In the second study, TNT cataract was used as an indicator of health effects. The prevalence of cataract and the degree of lenticular damage increased with the increase of blood TNT-Hb level.

Cataract↗
PubMed1995

Renal oncocytoma containing "chromophobe" cells.

We report a rare case of renal oncocytoma containing occasional "chromophobe" cells. This case suggests an intimate relationship between oncocytoma and "chromophobe" renal cell carcinoma.

Adenoma, Oxyphilic↗
PubMed1995

Alangionosides G-M: glycosides of megastigmane derivatives from the leaves of Alangium premnifolium.

Phytochemical investigation of the 1-BuOH-soluble fraction of the MeOH extract of Alangium premnifolium resulted in the isolation of ten megastigmane glycosides, of which, two, (6R,9R)-3-oxo-alpha-ionol apiofuranosylglucopyranoside and roseoside with (6S,9R)-blumeol A as an aglycone were known. The structures of the eight new compounds were determined by spectroscopic methods.

Cyclohexanes↗
PubMed1995

[Molecular genetic analysis of a family with von Hippel-Lindau disease].

We analyzed germline mutations of the von Hippel-Lindau (VHL) gene located at chromosome 3p25 in a family of VHL disease by using single strand conformational polymorphism (SSCP) and Southern blot analyses. In 10 individuals including 2 patients with multiple renal cell carcinomas, multiple pancreatic cysts and cerebellar hemangioblastoma, there are no positive results in SSCP analysis. However, in 2 patients and one kindred, same abnormal band was observed in Southern blot analysis. Moreover, in this one kindred of 17 years old girl, multiple pancreatic cysts were found by computerized tomography (CT). These results shows the alteration in the VHL gene is a major rearrangement but not a small mutation and this alteration caused VHL disease in this family. Furthermore, presymptomatic diagnosis by direct mutation analysis seems to be very useful for early detection of this disease.

Adolescent↗
PubMed1995

[Prognostic factors for metastatic renal cell cancer].

We examined various prognostic factors of metastatic renal cell carcinoma. Patients who had metastasis at nephrectomy (A group, 38 cases) and those who had metastasis as recurrent tumors after nephrectomy (B group, 38 cases) entered in this study. Five-year survival rate of total cases after confirmation of metastatic foci was 15% and there was no statistical significant difference between A and B groups. Several pathological factors were related to poorer prognosis and included large diameters of original tumors, positive lymph nodes, higher grade tumors and non-clear cell type tumors. Patients who have a solitary lung metastasis showed better prognosis compared to those with multiple lung metastases or metastases of other organs. Two factors related to treatment were shown to contribute to better prognosis. These were the response to interferon alfa (IFN alpha) and the possibility of total resection of visible metastatic tumors. Patients who belong to A group were shown to achieve markedly better therapeutic benefit from IFN alpha or IFN alpha plus anticancer drugs. Five-year survival rate for the responders was 40%, as compared to less than 5% for the non-responders. Ten-year survival rate for patients with metastasis who had undergone complete resection of visible tumor was 50%, and the for patients belonging to B group Showed 80%. We concluded that these prognostic factors should be considered to decide how to select patients with metastatic renal cell cancer.

Adult↗
PubMed1995

[Clinical investigation of grade-up superficial bladder cancer].

Between January 1977 and December 1993, 249 patients with grade 1 or grade 2 superficial bladder cancer were initially treated at Yokohama City University Hospital. Eighty-six patients (33%) had recurrent tumors after initial resection, and sixteen recurrent cases were so-called grade-up tumors that is, grade 3 originating from grade 1 or grade 2 tumor. The morphology of the grade-up tumors mostly showed non-papillary and invasive type. Positivity for urinary cytology of grade-up tumors was 88%. The five-year survival rate of the patients with grade-up tumors was 85% after initial resection of grade-up patients and 48% after treatment of grade-up tumors. The five-year survival rate of the patients with grade-up tumors who were treated by total cystectomy was 72%, whereas that in the patients who were treated by bladder preservation therapy showed a 13% five-year survival rate and all of the six patients died of cancer during the six-year follow-up period. These findings suggest that patients who have grade up tumors should be treated by radical treatment with radical cystectomy.

Adult↗
PubMed1995

[Results of mutation analyses of von Hippel-Lindau disease gene in Japanese patients: comparison with results in United States and United Kingdom].

Recently the gene responsible for the von Hippel-Lindau (VHL) disease was identified as a tumor suppressor gene. Our ongoing studies on the mutation of the VHL gene in Japanese 28 VHL families with single strand conformational analyses of DNA and Southern blot analyses revealed 6 cases of insertion or deletion, 1 cases of splice site mutation and 9 cases of missense mutation, and 3 possible intragenic deletions. Our analytical findings are essentially similar to those observed in the western countries. The VHL families associated with pheochromocytoma had the same mutational hot spot as those in the western countries. Molecular analyses of the VHL gene in the Japanese VHL disease substantially improved the understanding of this disease and its inheritance character.

Blotting, Southern↗
PubMed1995

Effects of mebendazole, albendazole and praziquantel on alanine aminotransferase and aspartate aminotransferase of Echinococcus granulosus cyst wall harbored in mice.

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) of Echinococcus granulosus cyst wall harbored in mice for 10-12 months was measured. The activities of the 2 enzymes were 3,430 +/- 1,370-4,160 +/- 1,790 and 1,560 +/- 840-2,890 +/- 1,470, respectively. When infected mice were treated ig with mebendazole (Meb) 25 mg.kg-1.d-1 for 7-14 d, or 50 mg.kg-1.d-1 for 7 d, the ALT activities of cyst walls of both collapsed and full cysts were inhibited significantly with average inhibition rates of about 50%. Another benzimidazole derivative, albendazole (Alb), also inhibited ALT activity of the cyst wall with an inhibition rate of 40.7%, but this was not the case in the treatment with praziquantel 500 mg.kg-1.d-1 of the infected mice for 14 d. When the infected mice were treated ig with the above mentioned drugs at the same regimens, no apparent effect on AST activities of the cyst wall was seen except for the group treated ig with Meb at a higher daily dose, the inhibition rates being 26% (collapsed cyst) and 43.9% (full cyst). The significance of the results has been discussed briefly.

Alanine Transaminase↗
PubMed1995

Retinoblastoma gene mutation in primary human renal cell carcinoma.

We searched for possible mutations in the E2F-binding region of retinoblastoma gene in primary human renal cell carcinomas, using polymerase chain reaction and single-strand conformational polymorphism analysis of RNA. Retinoblastoma gene mutation was detected in 1 of 21 cases (5%). DNA sequencing of the polymerase chain reaction product verified that this case had a 6-base deletion at the beginning of exon 8. Our findings suggest that mutation of the retinoblastoma gene is involved in only a subgroup of sporadic human renal cell carcinomas.

Base Sequence↗