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Biomedical subjects

Q Ma

Publications and source records attributed to Q Ma.

At least 109 records · Page 6Linked to original sources
PubMed1996

DNA binding by the heterodimeric Ah receptor. Relationship to dioxin-induced CYP1A1 transcription in vivo.

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin induces the microsomal enzyme cytochrome P4501A1 by increasing the transcription rate of the CYP1A1 gene. Induction requires two basic helix-loop-helix proteins, the ligand-binding aromatic hydrocarbon receptor (AhR) and its heterodimerization partner, the AhR nuclear translocator (Arnt). The AhR/Arnt heterodimer induces transcription by binding to dioxin-responsive elements (DREs) within an enhancer upstream of the CYP1A1 gene. The basic regions of AhR and Arnt are crucial for DRE binding. We have mutated these regions in order to analyze the relationship between DRE binding (determined in vitro using an electrophoretic mobility shift assay) and induction of CYP1A1 transcription (determined in vivo by genetic complementation of AhR-defective and Arnt-defective mouse hepatoma cells, using an RNase protection assay to measure mRNA accumulation). Our findings reveal the amino acids in the basic regions of AhR/Arnt that are important for both DRE binding and induction of transcription. This information provides biological background for the interpretation of structural (e.g. crystallographic) studies of the interactions between AhR/Arnt and the DRE. Our findings also indicate that the in vitro behavior of the mutants does not consistently predict their functional activity in vivo. Thus, genetic complementation constitutes an important and stringent test for analyzing the effects of mutations on AhR/Arnt function.

Amino Acid Sequence↗
PubMed1996

neurogenins, a novel family of atonal-related bHLH transcription factors, are putative mammalian neuronal determination genes that reveal progenitor cell heterogeneity in the developing CNS and PNS.

We recently identified neurogenin (ngn), a neuroD-related bHLH gene, whose Xenopus homolog functions as a neuronal determination factor and upstream activator of XneuroD (Ma et al. Cell 87: 43-52, 1996). Here we identify two additional ngn's, ngn2 and ngn3, which together define a novel subfamily of atonal-related mouse genes. Comparative analysis of ngn expression indicates that these three genes define distinct progenitor populations in the developing CNS and PNS, exhibiting nonoverlapping expression in some areas and partial overlap in others. The expression of the ngn's spatially overlaps and often temporally precedes that of neuroD, suggesting that (as in Xenopus) the ngn's and neuroD function in a cascade. Thus, as in myogenesis, different bHLH determination factors may activate a common bHLH differentiation factor in different sublineages. The ngn's therefore represent both a family of putative mammalian neuronal determination genes and useful markers of the origins of neuronal diversity.

Amino Acid Sequence↗
PubMed1996

Effect of supplemental L-arginine in a chemical-induced model of colorectal cancer.

L-Arginine inhibits the development of spontaneous, transplantable solid tumors and chemically induced mammary tumors. The aim of the present study was to investigate the effect of l-arginine on chemically induced colorectal cancer in male Wistar rats. Colorectal cancer was induced in all animals by weekly subcutaneous injections of the colonic procarcinogen 1,2-dimethylhydrazine (DMH) at a dosage of 20 mg/kg body weight. Arginine was given in a 1% solution of drinking water. Group I was the DMH control; group II, arginine for 22 weeks; group III, arginine for the first 10 weeks only. Lymphocyte function was evaluated by measuring the thymic lymphocyte proliferative response to the T cell mitogen phytohemagglutinin. The results show that tumor incidence and tumor burden (tumors/rat and tumors/tumor-bearing rat) were significantly reduced in both groups of animals receiving arginine compared to DMH controls (p < 0.05). The tumor areas and volumes were also reduced in both arginine groups (p < 0.05). Thymic lymphocyte stimulation indices were significantly increased by arginine supplementation (p < 0.05). These results would be in keeping with the reduction in colorectal tumor production due to a "nonspecific" stimulation of the host immune system by L-arginine.

1,2-Dimethylhydrazine↗
PubMed1996

Diagnosis of hepatitis C virus (HCV) infection by antigen-capturing ELISA.

BACKGROUND: Hepatitis C virus (HCV) is a major cause of non-A non-B hepatitis. Detection of circulating antibodies against HCV by enzyme-linked immunosorbent assay (ELISA) has provided the main approach for the diagnosis of HCV infection. Most ELISA kits use a mixture of core, NS3, NS4 and NS5 antigen as capture antigens and enzyme-labeled goat anti-human IgG as conjugate. OBJECTIVES: To establish an ELISA system based on the antigen-capturing principle, using a recombinant chimeric polyprotein containing four HCV antigenic components as antigen. STUDY DESIGN: HCV antigens were expressed in Escherichia coli as chimeric polyprotein either in inclusion bodies or in soluble form. Protein expressed in inclusion bodies was used as solid-phase antigen, and the antigen expressed in a soluble form was used as enzyme conjugate after being labeled with horseradish peroxidase (HRP). RESULTS: Genes coding HCV antigens were cloned and sequenced, chimeric polyproteins containing four immunodominant components (core, NS3, NS4 and NS5) were expressed in E. coli both in soluble and in inclusion body form. These two chimeric proteins retained the antigenicity of HCV antigens. Antibody-capturing ELISA using the chimeric antigens showed a sensitivity of 97% (97/100) and a specificity of 98% (97/99) using the reference panel from the National Institute for the Control of Pharmaceutic and Biological Products of China (NICPBC); the same assay showed a sensitivity of 97.9% (48/49) and a specificity of 100% (43/43) using the self-established reference panel. Antigen-capturing ELISA was set up using the antigen labeled with horseradish peroxidase as conjugate, and was shown to be as sensitive as (97.9%) and more specific than (100%) antibody-capturing ELISA using the reference panel in this work. The antigen-capturing ELISA also showed a high accordance (98.9%) with UBI HCV enzyme immunoassay (EIA) 4.0 kits (United Biomedical Inc. USA). CONCLUSION: Antigen-capturing ELISA provided a convenient, sensitive and more specific approach for the diagnosis of hepatitis C virus infection.

Journal Article↗
PubMed1996

Radioimmunoscintigraphy of gastric adenocarcinomas with 99mTc-chimeric ccM4 antibody.

Fourteen patients with gastric lesions were studied for radioimmunoscintigraphy using the 99mTc-ccM4 chimeric antibody reactive with the human tumor-associated TAG72 antigen. These include 10 gastric adenocarcinomas, 3 gastric ulcers and 1 gastric lymphoma. Each patient received an infusion of 30-40 mCi 99mTc-ccM4 antibody. Gamma camera scans were performed at 12-h postadministration. All patients underwent operation after radioimmunoscintigraphy. All surgical specimens including gastric adenocarcinomas, lymphoma and ulcers were confirmed by histopathological studies. The 99mTc-ccM4 antibody was able to detect 6 out of 10 gastric adenocarcinomas (60%) by scans. Its accuracy was even 5 out of 6 (83%) in a group of patients with well/moderately-differentiated adenocarcinomas. In addition to the primary adenocarcinomatous lesions, the 99mTc-ccM4 antibody was also able to detect metastatic lesions in liver and lymph nodes. The smallest adenocarcinomatous lesion detected by scans was about 1 x 1 x 2 cm3. All four patients with gastric ulcers or lymphoma showed negative scan results. Therefore, the chimeric ccM4 antibody may be useful in radioimmunoscintigraphy of gastric adenocarcinomas, especially the well/moderately-differentiated adenocarcinomas.

Adenocarcinoma↗
PubMed1996

Cytochromes P450 5: induction of cytochrome P4501A1: a model for analyzing mammalian gene transcription.

The induction of microsomal cytochrome P4501A1 by polycyclic aromatic hydrocarbons represents an interesting response by which mammalian cells adapt to xenobiotic exposure. Enzyme induction reflects increased transcription of the corresponding CYP1A1 gene. Analyses of the induction mechanism using genetic, biochemical, and molecular biological approaches have revealed a novel transcriptional regulatory pathway that involves ligand-dependent heterodimerization between two basic helix-loop-helix proteins (the Ah receptor and Arnt), interaction of the heterodimer with a xenobiotic-responsive enhancer, transmission of the induction signal from the enhancer to the CYP1A1 promoter, and alterations in chromatin structure. Current techniques permit examination of the induction mechanism in intact cells and analyses of the CYP1A1 gene in its native chromosomal configuration. Such experiments generate new insights into the control of mammalian transcription that are of relatively broad interest.

Animals↗
PubMed1996

A tandem duplication within the fibrillin 1 gene is associated with the mouse tight skin mutation.

Mice carrying the Tight skin (Tsk) mutation have thickened skin and visceral fibrosis resulting from an accumulation of extracellular matrix molecules. These and other connective tissue abnormalities have made Tskl + mice models for scleroderma, hereditary emphysema, and myocardial hypertrophy. Previously we localized Tsk to mouse chromosome 2 in a region syntenic with human chromosome 15. The microfibrillar glycoprotein gene, fibrillin 1 (FBN1), on human chromosome 15q, provided a candidate for the Tsk mutation. We now demonstrate that the Tsk chromosome harbors a 30- to 40-kb genomic duplication within the Fbn1 gene that results in a larger than normal in-frame Fbn1 transcript. These findings provide hypotheses to explain some of the phenotypic characteristics of Tskl + mice and the lethality of Tsk/Tsk embryos.

Amino Acid Sequence↗
PubMed1996

Dioxin-induced CYP1A1 transcription in vivo: the aromatic hydrocarbon receptor mediates transactivation, enhancer-promoter communication, and changes in chromatin structure.

We have analyzed the dioxin-inducible transcriptional control mechanism for the mouse CYP1A1 gene in its native chromosomal context. Our genetic and biochemical studies indicate that a C-terminal segment of the aromatic hydrocarbon receptor (AhR) contains latent transactivation capability and communicates the induction signal from enhancer to promoter. Thus, transactivation and enhancer-promoter communication may be congruent functions of AhR. Both functions require heterodimerization between AhR and the AhR nuclear translocator (Arnt). Our findings also indicate that heterodimerization activates AhR's latent transactivation function and silences that of Arnt. Furthermore, removal of Arnt's transactivation domain does not affect dioxin-induced CYP1A1 transcription in vivo. In addition, our studies demonstrate that dioxin-induced changes in chromatin structure occur by different mechanisms at the CYP1A1 enhancer and promoter and that events at an enhancer can be experimentally dissociated from events at the cognate promoter during mechanistic analyses of mammalian transcription in vivo.

Animals↗
PubMed1996

The aromatic hydrocarbon receptor modulates the Hepa 1c1c7 cell cycle and differentiated state independently of dioxin.

The aromatic hydrocarbon receptor (AhR) has been defined and characterized according to its ability to mediate biological responses to exogenous ligands, such as the synthetic environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The natural ligand(s) for AhR is unknown, and we know relatively little about AhR function in the absence of TCDD. Here, we have exploited the availability of AhR-defective (AhR-D) mouse hepatoma (Hepa 1c1c7) cells to analyze AhR's effects under conditions in which TCDD is not present. Our results reveal that AhR-D cells exhibit a different morphology, decreased albumin synthesis, and a prolonged doubling time compared with wild-type cells. Introduction of AhR cDNA into AhR-D cells by stable transfection alters these characteristics such that the cells resemble wild-type cells. Conversely, introduction of antisense AhR cDNA into wild-type cells changes their phenotype such that they resemble AhR-D cells. Fluorescence microscopy reveals that AhR-D cells do not exhibit an increased rate of death. Flow cytometric and biochemical analyses imply that the slowed growth rate of AhR-D cells reflects prolongation of G1. Our findings reveal a potential link between AhR and the G1 phase of the Hepa 1c1c7 cell cycle. These effects of AhR occur in the absence of TCDD. We speculate that they represent responses to an endogenous AhR ligand in Hepa 1c1c7 cells.

Animals↗
PubMed1996

In situ amplification of DNA fragments specific for human Y chromosome in cellular nuclei by PCR.

Using single primer pairs Y3 and Y4 in situ polymerase chain reaction (in situ PCR) was successfully performed on the specimen slides of peripheral leukocytes. By both of the direct digoxiginin-11-dUTP incorporation into PCR products with in situ PCR (direct in situ PCR) and in situ PCR followed by detection of in situ hybridization (indirect in situ PCR), DNA fragments specific for human Y chromosome were obviously amplified in cellular nuclei of specimens on the slides. The results were verified by Southern analysis. The methodology of in situ PCR and its application were discussed.

Cell Nucleus↗
PubMed1996

[An experimental study on BMP gene expression in vivo].

The authors inserted the full length BMP-1 cDNA into Xbal-treated pRc/RSV plasmid via ligation, resulting in construction of pRc/RSV/BMP-1 eukaryotic expression vector. The validity of the reconstructed vector was confirmed by the restriction map. Then more reconstructed plasmids were extracted. According to the general principle of gene therapy, 100 micrograms of pRc/RSV/BMP-1 plasmid was transferred into a Balb/c mouse quadriceps by implantation under anaesthesia respectively. After 3 weeks, the BMP gene expression was detected in the mouse muscles by histoimmunochemistry.

Animals↗
PubMed1995

Roles of histidine-194, aspartate-163, and a glycine-rich sequence of NAD(P)H:quinone oxidoreductase in the interaction with nicotinamide coenzymes.

NAD(P)H:(quinone-acceptor) oxidoreductase (NQOR, EC 1.6.99.2), an enzyme catalyzing the obligatory two electron reduction of quinones, can utilize both NADH and NADPH as electron donors at similar efficiencies. Based on site-directed mutagenesis studies, we previously suggested that the glycine-rich region of rat liver NQOR is important for the binding of NAD(P)H (Ma et al., J. Biol. Chem. 267, 22298-22304, 1992). However, the mode of interactions between the active site and NADH or NADPH is not clearly known. In this study, we conducted site-directed mutagenesis experiments and identified H194 and D163 of NQOR as key residues affecting the Km of NADPH. Steady-state kinetic analysis for the reduction of dichloroindophenol (DCIP) showed that Km(NADPH) values of purified mutant proteins H194D, H194A, and D163V were 288-, 14-, and 96-fold higher, respectively, than that of NQOR; but the Km(NADH) values were only slightly higher. The kcat(NADPH) values were almost the same as that of NQOR in the reduction of DCIP at the respective pH optima which were affected by the mutations. The kcat(NADH) values of these mutant enzymes were 30 to 60% that of NQOR. In the reduction of menadione, the mutations also caused much larger increases in km(NADPH) than Km(NADH). The results suggest that H194 and D163 are important for the interaction with the 2'-phosphate group of NADPH. NAD(P)H analogues, N-methyldihydronicotinamide and dihydronicotinamide mononucleotide, can also serve as electron donors for NQOR, but the Km values were 4.5- and 495-fold higher, respectively, than that with NADH. Mutations at H194 and D163 and at the glycine-rich region of NQOR, which increased Km(NADH) and Km(NADPH), did not substantially affect the Km values of these two analogues. This result is consistent with the suggested roles of these amino acid residues in the interaction with nicotinamide coenzymes. Based on these results, a model of the NAD(P)H binding site is proposed showing the interaction of the pyrophosphate group with the glycine-rich region and the interaction of 2'-phosphate group with H194 and D163.

Animals↗
PubMed1995

Transcriptional activation by the mouse Ah receptor. Interplay between multiple stimulatory and inhibitory functions.

The aromatic hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates cellular responses to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We cloned AhR cDNA from C57BL/6 mouse liver and verified by transfection that it encodes a functional protein. Analyses of deletion mutants indicate that the carboxyl half of AhR contains several types of transactivation domain, which function independently of domains that mediate TCDD recognition, DNA binding, and heterodimerization with the Ah receptor nuclear translocator (Arnt) protein. The transactivation domains function independently of each other, display different levels of activity, and act synergistically when linked. In addition, AhR contains an 82-amino acid domain that inhibits transactivation. The inhibitory domain displays specificity, in that it blocks the transactivating functions of AhR and Arnt, but not that of the herpes simplex protein VP16. The inhibitory activity depends upon the cell type in which AhR is expressed, implying that a cell-specific protein mediates the effect.

Animals↗
PubMed1995

The yeast homologue YTIS11, of the mammalian TIS11 gene family is a non-essential, glucose repressible gene.

The murine TIS11 primary response gene is rapidly and transiently induced in response to many extracellular signals. A CX8CX5CX3H sequence is present twice in the TIS11 protein, in two additional murine proteins, TIS11B and TIS11D, that share regions of strong sequence conservation with TIS11, and in a Drosophila homologue (DTIS11). Although immunolocalization of TIS11 protein to the nucleus and zinc binding have lead to the speculation that the TIS11 family proteins are transcription factors, no function for these proteins has yet been clearly determined. We have now identified a TIS11 homologue, YTIS11, from Saccharomyces cerevisiae. The Ytis11p protein conserves both the two putative zinc finger CX8CX5CX3H sequences and the spacing between them, as well as additional amino acids in this region. The amino terminal 169 amino acid portion of Ytis11p protein, which contains a large number of acidic amino acids, can serve as a transactivator when fused to the Gal4 DNA-binding domain. Expression of the YTIS11 gene is not induced in response to DNA damaging agents, heat shock, sporulation conditions, or mating factor. However, YTIS11 expression is subjected to rapid glucose repression. Disruption of the YTIS11 gene in the M12B strain of Saccharomyces cerevisiae does not effect viability, growth in rich or synthetic medium, mating, or spore formation. However, YTIS11 gene disruption causes an alteration in metabolism that is reflected by a pH color change when cells are grown on YP plates supplemented with 2% glucose. Overexpression of murine TIS11 or TIS11B proteins dramatically attenuates the growth of both ytis11 and wild-type yeast.

Amino Acid Sequence↗
PubMed1995

The measurement and application of TSH-IRMA levels among different age groups in areas with iodine deficiency disorders.

Using immunoradiometric TSH assay (TSH-IRMA) to measure whole blood TSH levels spotted onto filter paper, we compared TSH levels among different age groups (neonates, < 1 yr infants, schoolchildren aged 7 to 14 yrs, adults, pregnant women and reproductive-age women) in Guiyang, where iodine deficiency has long been a problem. The results showed: 1) The percentage of subjects with TSH levels equal to or greater than 5 mIU/L in the neonate group was 38.9% while the percentages in the other groups were 0-3.3% (P < 0.01); 2) The TSH levels of the neonates were inversely related to the urinary iodine values of their mothers (pregnant women). (r = -0.5, P < 0.01); 3) 97.6% of the inhabitants in Guiyang ingested salt with less than 20 mg/kg iodine. The results indicate that iodine deficiency remains a problem in Guiyang. Neonates are the only ideal population for monitoring iodine deficiency.

Adolescent↗
PubMed1995

[The course of malaria control and present status in Zhejiang Province].

Through forty years' sustained efforts in the prevention and treatment of malaria in Zhejiang Province, the malaria incidence dropped from 76.650/000 in the Fifties to 0.910/000 in the Eighties. Three malaria epidemics emerged in 1954, 1962 and 1973, respectively, among them the epidemic in 1962 was the most serious one with 0.88 million cases reported and an incidence of 3300/000. The annual incidence of the overall counties/cities was below 10/000 after 1988. Only 172 malaria cases were found in 1992, the incidence being 0.040/000. No indigenous malaria case was found in 38 counties in 1992, accounting to 43.7% of the total malaria endemic counties. The number of imported malara cases was 3,829, amounting to 89.2% of the total number of cases. Through the spot-check of the Ministry of Public Health in 1993, it was confirmed that the criteria of basic elimination of malaria in the province was attained.

Animals↗
PubMed1995

[Effects of three kinds of decoction on histopathology of gastric mucosa, gastric pH and the content of bile acid in experimental chronic gastritis in rats].

Experimental chronic gastritis (ECG) models were established in rats by inserting a spring into pyloric canal as well as feeding sodium deoxycholate. An experiment was undertaken to observe the therapeutic effects of three formulas of traditional Chinese medicine "Shipitong", "Ganpingyangwei" and "Weile". The experimental results show that all of the three decoctions can reduce gastric pH and bile acid of the ECG rats and make gastric mucosal histomorphology of these rats change markedly.

Animals↗