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Biomedical subjects

W Xie

Publications and source records attributed to W Xie.

At least 181 records · Page 10Linked to original sources
PubMed1993

Prostaglandin G/H synthase isoenzyme 2 expression in fibroblasts: regulation by dexamethasone, mitogens, and oncogenes.

Mitogens increase prostaglandin synthesis in fibroblasts. In the present studies, transcriptional activation of the prostaglandin G/H synthase isoenzyme 2 (PGHS-2) gene is shown to be responsible for this induction. Transcription of the PGHS-2 gene maximally increased within 15 min of stimulation, and elevated cellular PGHS-2 mRNA, protein, and prostaglandin synthase activity were detected shortly thereafter. Pulse-chase experiments showed induced isoenzyme 2 is short lived, with a half-life of 22 min in chicken embryo fibroblasts. Neoplastic transformation of fibroblasts by a variety of oncogenes induced either or both PGHS-1 and PGHS-2 mRNAs in immortalized murine NIH3T3 cells. Some preference of oncogenes such as v-src to induce PGHS-2 mRNA has been previously observed. However, in this study exceptions in which v-src did not induce PGHS-2 mRNA were noted. Analysis of independent cell lines transformed by v-fes showed this oncogene induced both PGHS-1 and PGHS-2. Dexamethasone, a synthetic glucocorticoid, selectively decreased both basal and induced levels of PGHS-2 mRNA. Simultaneous addition of the steroid with mitogen reduced mitogen-induced PGHS-2 mRNA levels by 80%. However, nuclear run-on experiments failed to detect any decrease in PGHS-2 mRNA transcription. This suggested dexamethasone rapidly caused PGHS-2 mRNA destabilization. Cycloheximide blocked PGHS-2 mRNA decrease. A fibroblast cell line, RS2, was identified that contained only isoenzyme 2 and possessed PGHS activity that was more highly mitogen-inducible than in any other cell line yet described. Mitogen-inducible activity in RS2 cells was inhibited by aspirin, indicating that PGHS-2, like PGHS-1, can be inactivated by this drug.

3T3 Cells↗
PubMed1993

The effect of contrast polarity on letter identification.

To determine the effect of contrast polarity on the spatial characteristics of letter identification, we measured contrast sensitivity for individual Sloan letters that were presented either as luminance increments or luminance decrements relative to a continuously presented adapting field. The temporal mode of presentation consisted of either a rapid onset with a Gaussian offset, or the reverse. When contrast was specified in terms of Rayleigh (Michelson) units, the contrast sensitivity function for letters of positive contrast extended to smaller letter sizes than the function for letters of negative contrast. However, when contrast was defined in Weber terms, letter contrast sensitivity functions were identical for letters of positive and negative contrast, indicating that letter identification was equivalent for luminance increments and decrements that had equal absolute magnitude. Onset-offset characteristics had no differential effect on letter contrast sensitivity by either contrast definition. These findings provide a basis for predicting the effect of contrast polarity on tasks that involve letter identification.

Adaptation, Ocular↗
PubMed1993

[Anti-implantation action of nylestriol and its effect on uterine cytosol estrogen and progesterone receptor in rabbits].

The anti-implantation action of nylestriol in rabbit was studied. The changes of uterine cytosol estrogen and progesterone receptor (ER and PR) were analysed with the dextran-coated charcoal method. Plasma progesterone level of early pregnant rabbits was measured by radioimmunoassay. The results showed that oral nylestriol could obviously prevent the early pregnancy of rabbit by anti-implantation of blastocyst. The content of ER decreased in the nylestriol group (P < 0.01). The content of PR in nylestriol group was lower than that of the control group (P < 0.05). No significant difference of plasma progesterone level was noted between the control and treatment groups. These results suggest that there is close relationship between the anti-implantation effect of nylestriol and the decreased content of cytosol ER and PR during the pre-implantation period.

Animals↗
PubMed1993

[Effect of Schistosoma japonicum infection on liver drug-metabolizing enzymes of mice].

In this paper, the effect of Schistosoma japonicum infection on liver drug-metabolizing enzymes of mice was studied. The prolongation of hypnosis duration of sodium pentobarbital in vivo and the inhibition of liver aniline hydroxylase (AH), aminopyrine N-demethylase (APD) as well as cytochrome P-450 (Cyt P-450) in vitro were observed in mice infected with 20, 40 and 60 cercariae of S. japonicum after 6 weeks. Meanwhile, with 30 cercariae infection, no significant inhibition of the activity of AH, APD and Cyt P-450 was observed in mice 4 weeks after infection, but significant inhibition of these enzymes was shown by 8 weeks. As compared with control, the activity of AH, APD and Cyt P-450 decreased to 32.6%, 13.7% and 7.7% at 8 weeks. The results indicate that infection of S. japonicum can inhibit the liver drug-metabolizing capacity of mice, and the degree of inhibition depends on the infectivity and the duration of infection.

Aminopyrine N-Demethylase↗
PubMed1992

Analysis of the rat ribosomal DNA promoter: characterization of linker-scanning mutants and of the binding of UBF.

To investigate the mechanism of transcription of the rat ribosomal DNA (rDNA) promoter, a series of 23 linker-scanning mutants were constructed and assayed in transfected CHO cells and with cell-free extracts. With minor variation, the results of the in vitro and in vivo assays paralleled one another. For example, these assays demonstrated that the mutagenesis of bases from -133 to -124, and those from -106 to -101 of the rDNA promoter significantly inhibited transcription both in vivo and in vitro. Both of these sites lie within the upstream promoter element (UPE) of the rDNA promoter. Several constructs, in particular one that mutated the bases between -49 and -45, were better promoters in vivo than the wild-type promoter. DNAse footprinting experiments with purified UBF, an RNA polymerase I transcription factor, demonstrated the importance of the bases between -106 and -101 for the binding of that factor, providing a positive correlation between the transcription experiments and the binding of UBF to the rDNA promoter.

Animals↗
PubMed1992

Analysis of the phosphorylation, DNA-binding and dimerization properties of the RNA polymerase I transcription factors UBF1 and UBF2.

The phosphorylation, DNA-binding and dimerization properties of both forms of the RNA polymerase I transcription factor UBF were studied and compared. Tryptic peptide maps of in vivo 32P-labeled UBF contained four phospho-peptides. Two of these peptides are predicted to derive from the serine-rich, carboxyl-terminal of UBF. This region contains nine consensus phosphorylation sites for casein kinase II, and is one of the regions phosphorylated in vitro by casein kinase II. Analysis of the DNA-binding properties of recombinant forms of UBF1 and UBF2 by Southwestern blots revealed: (1) a role for the NH2-terminal 102 amino acid domain of UBF1/UBF2 in DNA-binding; (2) the importance of the bases from -106 to -101 of the rat ribosomal DNA promoter for the binding of UBF; and (3) functional differences between UBF1 and UBF2. Glutaraldehyde cross-linking and overlay assays using recombinant forms of UBF1 and UBF2 demonstrated that the molecules can form both homodimers and heterodimers. These assays also demonstrated that the NH2-terminal 102 amino acids of UBF plays a significant role in dimerization and that other domains contribute to dimerization. The dimerization properties of recombinant forms of UBF1 and UBF2 were different, suggesting that the HMG box 2 of UBF1, which is partially deleted in UBF2, also contributes to UBF dimerization.

Animals↗
PubMed1992

Stimulation of thymidine kinase activity in baculovirus infected cells is not due to a virus-coded enzyme.

A polyhedrin-positive recombinant autographa californica nuclear polyhedrosis virus (AcNPV) carrying a herpes simplex virus thymidine kinase gene under the control of the SynXIV promoter, a fusion of synthetic and linker-modified polyhedrin promoters, has been constructed. When this recombinant baculovirus was used to infect a variant of Spodoptera frugiperda cells deficient in thymidine kinase (TK-), a high level of TK activity was detected. These results, in conjunction with the demonstration that AcNPV could replicate in TK- S. frugiperda cells and no TK activity was found throughout infection, imply that the wild type virus-stimulated TK activity observed in S. frugiperda (TK+) cells is not contributed by a virus-coded enzyme.

Animals↗
PubMed1992

The effect of tolbutamide on burn hypermetabolism.

The effect of tolbutamide on improving burn hypermetabolism was studied prospectively in 31 burn adults with total body surface area burned > 40 per cent and 18 burned rabbits immediately after burn injury to postburn day 10. The results showed that burn hypermetabolism could be reduced using tolbutamide, which may be the result of the correction of relative insulin insufficiency, tissue insulin resistance and improving glucose utilization.

Adult↗
PubMed1992

Production of the Mycotoxin Fumonisin B(1) by Alternaria alternata f. sp. lycopersici.

The mycotoxin fumonisin B(1), originally described as being produced by Fusarium moniliforme, was detected in liquid cultures of Alternaria alternata f. sp. lycopersici, a host-specific pathogen of tomato plants. The metabolite was detected by high-pressure liquid chromatography and mass spectrometry. Its identity was confirmed by fast atom bombardment and ion spray mass spectrometry, as well as parent-daughter tandem mass spectrometry. In three separate experiments, the concentrations found ranged between 5 and 140 ppm (mug/ml).

Journal Article↗
PubMed1992

Occurrence of fumonisin in forage grass in new zealand.

Fumonisin B(1) (FB(1)) was isolated from samples of forage grass originating in paddocks associated with an idiopathic disease of Canadian wapiti and wapiti-red deer hybrids characterized by "ill thrift" and liver dysfunction. Four of 40 samples contained 1, 3, 6, and 9 ppm (micrograms per gram) of FB(1) and 4, 0.5, 2, and 0.5 ppm, respectively, of the methyl ester of FB(1). Analyses were done by ion spray mass spectrometry and confirmed by both fast atom bombardment (solids probe) and mass spectral analysis by electron impact ionization of the trifluoroacetate derivative of the base hydrolyzed product (pentolamine) of FB(1). This article contains the first report of the presence of fumonisin B(1) in grass.

Journal Article↗
PubMed1992

[Study on toxicology of a new anthelmintic "85012"].

"85012", a new anthelmintic containing amidine synthesized in our laboratory, was experimentally effective against Nippostrongylus braziliensis and Ancylostoma caninum. In acute and subacute toxicity test, it was proved lowly toxic. There was no evidence that the drug induced any damages to main organs and tissues of animals. In order to evaluate its potential mutagenicity and teratogenicity, micronucleus test, bone marrow metaphase analysis, CHL cells chromosomal aberration assay, spermatic aberration test as well as teratogenicity test were performed. No mutagenic and teratogenic effects were observed.

Amidines↗
PubMed1990

Isolation and Structural Identification of a New Metabolite of Fusarium equiseti.

A fluorescent compound was isolated and purified from rice cultures of Fusarium equiseti (Alaska 2-2). Mass spectrometry and nuclear magnetic resonance data indicated that its structure is 2,2-dimethyl-5-amino-6-(3'-hydroxyl-4'-methoxyl-butyryl)-4-chromone. It is an analog of the mycotoxin fusarochromanone, in which the amino group on C-3' is replaced by a hydroxyl group and the hydroxyl group on C-4' is replaced by a methoxyl group.

Journal Article↗
PubMed1989

Variation in Deoxynivalenol, 15-Acetyldeoxynivalenol, 3-Acetyldeoxynivalenol, and Zearalenone Production by Fusarium graminearum Isolates.

Of 88 isolates of Fusarium graminearum collected from soil or cereals in the United States, 49 produced 15-acetyldeoxynivalenol (15-ADON) as the major isomer; one produced 3-acetyldeoxynivalenol (3-ADON). A total of 26 isolates collected from cereals or soil in Australia, New Zealand, Norway, China, and Poland were used for comparison. Of these, 15 produced 3-ADON as the major isomer and 2 produced 15-ADON.

Journal Article↗
PubMed1989

[Morphological observation on 6th-week development of human kidneys and gonads].

The development of kidney and gonad of 3-6th-week human embryos were studied. Their positions at different developing stages were measured in terms of the sequence of neural ganglion according to Felix's method. The 9.5 mm embryo: Pronephrons are seen as 2 epithelial blind tubules on the right side and 1 on the left at the 6th cervical ganglion level. The lateral tubule on the right side and the left one are pronephric ducts, whereas the medial one on the right side is the pronephric tubule. The cranial ends of mesonephrons on both sides level at the 1st thoracic ganglia and run caudally to the 11th thoracic ganglia, their total number amount to 62. The mesonephric ducts on both sides firstly appear opposite to the 1st thoracic ganglia and open caudally into the cloaca. The metanephrons, the ureteric buds are unbranched yet and the metanephric mesoderm appears as clusters of cells on both sides. The gonads are indifferent. The 11 mm embryo: Pronephrons degenerated. The cranial ends of mesonephric tubules locate at the 3rd thoracic ganglia level on both sides and extend caudally to the level of the 11th ganglion in the right side and 12th in the left, their total number amounts to 65. Mesonephric ducts appear opposite to the 4th thoracic ganglia on both sides, running caudally, and open into the cloaca. Metanephrons, the ureteric buds give off 1st grade branches on both sides and metanephric mesoderm remain as clusters of cells. The gonads are indifferent. The 12 mm embryo: Pronephrons degenerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonads↗
PubMed1989

[Anti-implantation effect and morphological changes of corpus luteum and endometrium in rat by estriol].

The anti-implantation effect of estriol on rats was studied by enzyme histochemical methods. The activities of 3beta-hydroxy-steroid dehydrogenase (3beta-HSD), AcP in corpus luteum, A1P in endometrium of treatment groups were compared with those of control groups. In order to know the effect of estriol on endometrium during preparing for blastocyst implanting, we counted the number of mitosis cell in endometrium of 4th day pregnant rat under microscope. Serum progesterone level of early pregnant rats was measured by radioimmunoassay the results were as follows: 1. Estriol administrated postcoitally could prevent the early pregnancy of rats by the way of anti-implantation of blastocyst; 2. Activity of ovarian corpus luteal 3beta-HSD was depressed, whereas activity of AcP increased in the treatment group; 3. The number of mitotic cell in endometrial stroma was: in the treatment group 0.2 +/- 0.2, in the control group 45.7 +/- 16.2 (P less than 0.001); A1P reaction of endometrial stroma was negative in the treatment group, whereas it was positive in the control group; and 4. The serum progesterone level was: in the treatment group 17.4 +/- 12.6, in the control group 39.3 +/- 11.1 ng/ml (P less than 0.01). The results suggest that estriol can disturb the biosynthesis of progesterone of corpus luteum and reduce the serum progesterone level. Mitosis and decidulization of stroma cell can be disturbed owing to the low serum progesterone level, so the blastocyst cannot be implanted successfully.

Animals↗
PubMedDate not supplied

Drug inhibition and cellular regulation of prostaglandin G/H synthase isoenzyme 2.

Prostaglandin G/H synthase isoenzyme 2 (PGHS-2) was identified as an immediate-early gene product induced by Rous sarcoma virus, serum, phorbol ester and a wide variety of other mitogens. Induction of PGHS-2 occurs through an increase in PGHS-2 gene transcription. Dexamethasone inhibits both the basal and induced levels of PGHS-2 mRNA. In contrast, PGHS-1 gene transcription rate, mRNA, and protein levels are unaffected by mitogens and dexamethasone. Post-transcriptional down-regulation of PGHS-2 mRNA plays a significant role in causing dexamethasone's effect. Specific cell systems have been identified which allow selective analysis of PGHS-1 and PGHS-2 at the nucleic acid and protein levels. These cell systems indicate that PGHS-1 and PGHS-2 may have different sensitivities to non-steroidal anti-inflammatory drugs. Furthermore, inhibition of PGHS activity correlates well with suppression of the transformed phenotype in an in vitro cell model.

Animals↗