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Biomedical subjects

X Mao

Publications and source records attributed to X Mao.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Study on antifungal mechanism of alpha-pinene].

The antifungal mechanism of alpha-pinene was studied using electronic microscopy and incorporation of isotope-labelled precursor. The results demonstrated that alpha-pinene had significant roles in inhibiting and killing Candida albicans. After treatment with alpha-pinene the fungal morphology and ultrastructure showed obvious changes: their cell wall and cytoplasmic membrane ruptured; intracellular components released out and the cell residue fused to form irregular masses. In addition, the synthesis of DNA, RNA, polysaccharide of cell wall and ergosterol of cytoplasmic membrane was inhibited. It is indicated that these changes are related to antifungal mechanism of alpha-pinene.

Antifungal Agents↗
PubMed1998

Paracrine expression of a native soluble vascular endothelial growth factor receptor inhibits tumor growth, metastasis, and mortality rate.

Vascular endothelial growth factor (VEGF) is a potent and selective vascular endothelial cell mitogen and angiogenic factor. VEGF expression is elevated in a wide variety of solid tumors and is thought to support their growth by enhancing tumor neovascularization. To block VEGF-dependent angiogenesis, tumor cells were transfected with cDNA encoding the native soluble FLT-1 (sFLT-1) truncated VEGF receptor which can function both by sequestering VEGF and, in a dominant negative fashion, by forming inactive heterodimers with membrane-spanning VEGF receptors. Transient transfection of HT-1080 human fibrosarcoma cells with a gene encoding sFLT-1 significantly inhibited their implantation and growth in the lungs of nude mice following i.v. injection and their growth as nodules from cells injected s.c. High sFLT-1 expressing stably transfected HT-1080 clones grew even slower as s.c. tumors. Finally, survival was significantly prolonged in mice injected intracranially with human glioblastoma cells stably transfected with the sflt-1 gene. The ability of sFLT-1 protein to inhibit tumor growth is presumably attributable to its paracrine inhibition of tumor angiogenesis in vivo, since it did not affect tumor cell mitogenesis in vitro. These results not only support VEGF receptors as antiangiogenic targets but also demonstrate that sflt-1 gene therapy might be a feasible approach for inhibiting tumor angiogenesis and growth.

Animals↗
PubMed1998

Accelerated mRNA decay in conditional mutants of yeast mRNA capping enzyme.

Current models of mRNA decay in yeast posit that 3' deadenylation precedes enzymatic removal of the 5' cap, which then exposes the naked end to 5' exonuclease action. Here, we analyzed gene expression in Saccharomyces cerevisiae cells bearing conditional mutations of Ceg1 (capping enzyme), a 52 kDa protein that transfers GMP from GTP to the 5' end of mRNA to form the GpppN cap structure. Shift of ceg1 mutants to restrictive temperature elicited a rapid decline in the rate of protein synthesis, which correlated with a sharp reduction in the steady-state levels of multiple individual mRNAs. ceg1 mutations prevented the accumulation of SSA1 and SSA4 mRNAs that were newly synthesized at the restrictive temperature. Uncapped poly(A)+ SSA4 mRNA accumulated in cells lacking the 5' exoribonuclease Xrn1. These findings provide genetic evidence for the long-held idea that the cap guanylate is critical for mRNA stability. The deadenylation-decapping-degradation pathway appears to be short-circuited when Ceg1 is inactivated.

Exoribonucleases↗
PubMed1998

Neuroprotection by dehydroepiandrosterone-sulfate: role of an NFkappaB-like factor.

Levels of dehydroepiandrosterone (DHEA) and its sulfated derivative (DHEA-S) decline during aging and reach even lower levels in Alzheimer's disease (AD). Previously published effects of DHEA and DHEA-S on unchallenged neuronal survival led us to test them in an excitotoxicity paradigm. While DHEA-S protected hippocampal neurons against glutamate, little protection was observed with equivalent doses of DHEA itself. This differential neuroprotection was consistent with the ability of DHEA-S (but not DHEA) to elevate a kappaB-dependent transcription factor activity, a phenomenon we previously have connected with neuroprotection. Furthermore, suppression of kappaB DNA-binding by 'decoy' oligonucleotides blocked the neuroprotective activity of DHEA-S. These findings imply that age-related declines in the availability of DHEA-S could exacerbate neurotoxicity, and the data suggest that therapeutic gains may be obtained with pharmacological manipulation of kappaB-dependent transcription in neurons.

Animals↗
PubMed1998

Alleletyping of an oligodendrocyte-type-2 astrocyte lineage derive from a human glioblastoma multiforme.

We have conducted alleletyping of two novel cell lines derived from glioblastoma multiforme, which appear to have arisen from different glial lineages, by using 76 fluorescently labeled oligonucleotide primers amplifying microsatellite loci covering the entire human genome. One cell line, Hu-O-2A/Gb1, expresses antigens and metabolic profiles characteristic of the oligodendrocyte-type-2 astrocyte (0-2A) lineage of the rat central nervous system. This cell line generated, in vitro, cells with characteristics of 0-2A progenitor cells, oligodendrocytes and astrocytes. The second cell line, IN1434, is derived from an astrocyte or a precursor cell restricted to astrocytic differentiation. Hu-O-2A/Gbl cells show allelic losses of loci on chromosomes 2, 5, 6, 7, 8, 9, 10, 11, 13, 15, 16, 17, 20 and 21. IN1434 cells are likely to have allelic losses of loci on chromosomes 1, 3, 8 and 10, although no control DNA is available for this cell line. These results, for the first time, provide a detailed information of the molecular genetic defects occurring in Hu-O-2A/Gb1 and IN1434.

Alleles↗
PubMed1998

Quantitative proton magnetic resonance spectroscopy of childhood adrenoleukodystrophy.

Cerebral metabolic disturbances in patients with childhood adrenoleukodystrophy (ALD) were assessed by quantitative localized proton MRS. Patient monitoring by follow-up MRS studies served to identify putative markers for disease onset and progression. Whereas normal-appearing white matter of neurologically asymptomatic patients is characterized by slightly elevated concentrations of choline-containing compounds (Cho), an increase of both Cho and myo-inositol (Ins) seems to indicate the onset of demyelination. Markedly elevated concentrations of Cho, Ins, and glutamine in affected white matter reflect active demyelination and glial proliferation. A simultaneous reduction of the concentrations of N-acetylaspartate and glutamate is consistent with neuronal damage or loss. The observation of elevated lactate is in line with inflammation and/or macrophage infiltration. The more severe metabolic disturbances in cerebral ALD correspond to progressive demyelination, neuroaxonal loss and gliosis leading to clinical deterioration and eventually death. The detection of MRS abnormalities before the onset of neurological symptoms may help in the selection of patients for bone marrow transplantation (BMT). Stabilization and partial reversal of metabolic abnormalities is demonstrated in a patient after BMT.

Adolescent↗
PubMed1998

Chinese geneticists' views of ethical issues in genetic testing and screening: evidence for eugenics in China.

To identify Chinese geneticists' views of ethical issues in genetic testing and screening, a national survey was conducted. Of 402 Chinese geneticists asked to participate, 255 (63%) returned by mail anonymous questionnaires. The majority of respondents thought that genetic testing should be offered in the workplace for alpha-antitrypsin deficiency (95%) and the predisposition of executives to heart disease, cancer, and diabetes (94%); that genetic testing should be included in preemployment physical examinations (86%); that governments should require premarital carrier tests (86%), newborn screening for sickle cell (77%), and Duchenne muscular dystrophy (71%); and that children should be tested for genes for late-onset disorders such as Huntington disease (85%), susceptibility to cancers (85%), familial hypercholesterolemia (84%), alcoholism (69%), and Alzheimer disease (61%). Most believed that partners should know each other's genetic status before marriage (92%), that carriers of the same defective gene should not mate with each other (91%), and that women should have a prenatal diagnosis if medically indicated (91%). The majority said that in China decisions about family planning were shared by the couple (82%). More than half had views that, in China, there were no laws to prohibit disability discrimination (64%), particularly to protect people with adult polycystic kidney disease (57%), cystic fibrosis (56%), or genetic predisposition to other diseases (50%). To some extent, these results might provide a basis for a discussion of eugenics in China, particularly about China's Maternal and Infant Health Care Law (1994).

Adult↗
PubMed1998

[Laboratory diagnosis of Chlamydia trachomatis and Ureaplasma urealyticum of chronic prostatitis].

Prostatic fluid taken from 1038 cases of chronic prostatitis were detected by fluorescent monoclonal antibody technique and isolating cultural method for Chlamydia Trachomatis (CT) and Ureaplasma Urealyticum (UU). The control group consisted of 80 cases. CT and UU were not found in control group. The positive rates of CT and UU infection were 28.4% and 33.0% respectively in the tested group whose cases were abacterial prostatitis. The results suggested that CT and UU are pathogens causing chronic abacterial prostatitis.

Adult↗
PubMed1998

[Nucleotide sequence analysis of an antibiotic biosynthesis gene of Streptomyces globisporus].

Antitumor antibiotic C-1027 produced by Streptomyces globisporus has very high biological activity both in vivo and in vitro. Research works showed that one of biosynthesis gene of C-1027 is in the F2 DNA fragment. The plasmid pUC18 was used as vector to subclone the F2 DNA fragment. The nucleotide sequence analysis for F2 DNA fragment was carried out. Results showed that there is an open reading frame encoding for 122 amino acids. According to EMBO and GeneBanks data, this sequence may be a new one.

Amino Acid Sequence↗
PubMed1998

[Microscopic identification of Herba Dianthi grown in Shandong].

The medicinal materials of four species and two varieties of Herba Dianthi grown in Shandong were identified. The result shows that they are identified easily and accurately according to the outer properties, and they are apparently divided into the Shizhu group, the Qumai group and the Dianthus shandongensis on the basis of their morphological and structural characteristics of the stem and leaf, but they have not obvious distinction among the species of every group.

Dianthus↗
PubMed1998

[Ultra-morphological study on the surface of the stem and leaf of the original plant of herba Dianthi in Shandong].

Ultra-morphology of 4 spieces and 2 varities of the original plant of Herba Dianthi grown in Shandong was identified with SEM. The result showed that they were aparently divided into the Shizhu group and the Qumai group, and the Dianthus shandongensis was between the two groups, on the basis of the cutin-grain type of the epidermis of the stem and leaf as well as the surface of the guard cell of the stoma.

Caryophyllaceae↗
PubMed1997

The LIM-domain binding protein Ldb1 and its partner LMO2 act as negative regulators of erythroid differentiation.

The nuclear LIM domain protein LMO2, a T cell oncoprotein, is essential for embryonic erythropoiesis. LIM-only proteins are presumed to act primarily through protein-protein interactions. We, and others, have identified a widely expressed protein, Ldb1, whose C-terminal 76-residues are sufficient to mediate interaction with LMO2. In murine erythroleukemia cells, the endogenous Lbd1 and LMO2 proteins exist in a stable complex, whose binding affinity appears greater than that between LMO2 and the bHLH transcription factor SCL. However, Ldb1, LMO2, and SCL/E12 can assemble as a multiprotein complex on a consensus SCL binding site. Like LMO2, the Ldb1 gene is expressed in fetal liver and erythroid cell lines. Forced expression of Ldb1 in G1ER proerythroblast cells inhibited cellular maturation, a finding compatible with the decrease in Ldb1 gene expression that normally occurs during erythroid differentiation. Overexpression of the LMO2 gene also inhibited erythroid differentiation. Our studies demonstrate a function for Ldb1 in hemopoietic cells and suggest that one role of the Ldb1/LMO2 complex is to maintain erythroid precursors in an immature state.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Mutations of O6-methylguanine-DNA methyltransferase gene in esophageal cancer tissues from Northern China.

Epidemiologic studies have implicated the involvement of environmental factors in the etiology of esophageal cancer (EC). Our previous data have indicated that EC patients and their blood relatives show genomic instability and are deficient in repair of DNA damage induced by N-nitroso-compounds and related genotoxic agents. Thus, exposure to high levels of N-alkylnitrosamines, which are known animal carcinogens and which induce alkyl adducts in DNA, may be causally linked to EC. Among the alkyl adducts, O6-alkylguanine was shown to be the critical one related to carcinogenic lesions; its repair varies widely in a tissue-specific fashion. O6-methylguanine-DNA methyltransferase (MGMT) is responsible for its repair. Hence, inactivating mutations in this protein would impair the efficiency of the repair process. To screen for possible mutations in the MGMT polypeptide in EC patients, we analyzed a highly conserved region of the MGMT gene in 40 EC tissues and lymphocytes of 6 high-risk EC family members from high EC areas of Northern China by polymerase chain reaction single-strand conformation polymorphism and by direct sequencing of PCR products. Ten base substitutions (point mutations) within 8 codons of 7 EC samples were identified. However, no germline mutation was found in the high EC families studied so far. Concurrent study in 30 pairs of fresh EC tissues and their adjacent normal mucosa by Southern blot and Western blot analyses showed deletion of the MGMT gene in 2 samples. Thus, the high frequency of mutations (7/40) and deletions (2/30) of the MGMT gene may be partially responsible for the overall high mutation rate observed in EC tissues.

Base Sequence↗
PubMed1997

China's genetic services providers' attitudes towards several ethical issues: a cross-cultural survey.

Attitudes towards ethical, legal and social issues in genetic research and practice were investigated in 402 genetic services providers from 30 provinces and autonomous regions in China. This was done using a Chinese version of an international survey questionnaire on ethics and genetics that has been circulated in 37 nations. In all, 255 study participants completed questionnaires (63%). The majority of the respondents (89%) reported that they agreed with the current Chinese laws and regulations on termination of pregnancy for genetic abnormalities and non-medical indications, on the basis of considerations of population control and family planning. More than half the respondents opposed sex selection by prenatal diagnosis in the absence of an X-linked disorder. However, most of them (86%) would prefer directive counseling. More than half would agree to disclose genetic information to relatives at risk, and would permit third parties such as law enforcement agencies, spouse/partner, blood relatives, employers involving public safety, life and health insurers to access stored DNA without consent. The majority (73%-98%) also thought that DNA fingerprinting should be required for prisoners convicted of or charged with crimes, members of armed forces and all newborns. Although these are only the first part of the results of our international survey, they provide an initial basis for international discussion on ethics and genetics in China.

Attitude of Health Personnel↗