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Biomedical subjects

W Xie

Publications and source records attributed to W Xie.

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

Symmetry discrimination in patients with retinitis pigmentosa.

To investigate the relative sensory and perceptual contributions to central visual function of patients with retinitis pigmentosa (RP), we tested symmetry discrimination using block patterns with varying types of symmetric organization. Eleven control subjects with normal vision and 11 patients with RP with 20/30 visual acuity or better, viewed patterns presented for 255 msec. The patterns differed in the type of symmetric organization and the subjects were required to identify the type. The control subjects performed significantly better (89.2%) than the patients (74.5%). Four hypotheses to account for these findings were tested and the results were as follows, (1) A reduction in pattern luminance did not change symmetry discrimination performance in the control subjects. (2) Large reductions in pattern contrast did not alter symmetry discrimination in the control subjects. (3) Reductions in stimulus duration, likewise, did not produce similar error patterns in the control subjects as those observed in the patients with RP. (4) Alterations in spatial sampling density did not completely account for the patients' deficits. None of the retinally based explanations alone was sufficient to account for our findings. Additionally, we suggest that alterations of sensory input may affect the perceptual encoding of the relationship among pattern elements.

Adult↗
PubMed1995

Effect of spatial sampling on grating resolution and letter identification.

The purpose of the study was to determine whether spatial sampling has equivalent effects on visual performance for grating and letter stimuli, two optotypes that are frequently used in the clinical assessment of visual function. Test targets consisted of five-bar square-wave gratings, spatial D6 (sixth derivative of a Gaussian) patterns, or individual Sloan letters, presented for 255 ms in the center of an adapting field. Spatial sampling was introduced by replacing random regions of the targets with occluding elements that had the same luminance as the adapting field, so that only random samples of the test target were visible on each trial. The occluding elements consisted of 4 x 4, 8 x 8, or 16 x 16 pixel arrays (subtending 0.67, 1.33, and 2.67 arcmin, respectively), and the percentage of the test target that remained unoccluded ranged from 3% to 100%. Visual acuity and contrast sensitivity for the spatially sampled targets were measured in two visually normal subjects. Results were compared with the predicted effect of the reduction in effective contrast that was introduced by the sampling paradigm. For grating stimuli the effect of spatial sampling was equivalent to the reduction in effective stimulus contrast produced by the sampling, regardless of occluding-element size. For letter stimuli the reduction in effective stimulus contrast predicted most, but not all, of the loss of visual acuity and contrast sensitivity for sampled targets, and the deficit in performance increased when larger occluding elements were used.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Inhibition of T lymphocyte activation by a novel p56lck tyrosine kinase inhibitor.

A new p56lck tyrosine kinase inhibitor WIN 61651 [1,4-dihydro-7-(4-methyl-1-piperizinyl)-1-(4-(4-methyl-1-piperi zinyl))phenyl- 4-oxo-3-quinolinecarboxamide) is described. WIN 61651, which is competitive with ATP, demonstrates selectivity for the lymphoid restricted tyrosine kinase p56lck over serine/threonine kinases, such as protein kinase C and protein kinase A, and over some other tyrosine kinases, including erbB2, epidermal growth factor receptor, and insulin receptor; however, it is equipotent for inhibition of p56lck and the platelet derived growth factor receptor tyrosine kinases. WIN 61651 inhibits p56lck activity in cell-free assays, tyrosine kinase activity in a T lymphocytic cell line, and T cell activation, as measured by IL-2 production by purified CD4 positive peripheral blood T lymphocytes and the mixed lymphocyte reaction. WIN 61651 constitutes a new tool for studies on the role for tyrosine kinases in lymphocyte function.

Antibodies↗
PubMed1995

[Preliminary studies on protective effects of selenium on human fetal hepatocyte in vitro injured by lipid peroxidation].

A selenium protection model of human fetal hepatocyte in vitro injured by lipid peroxidation was established. It was found that survival rate and secretion of albumin of the injured cells decreased, and release of alanine transaminase (ALT) and its activities in the cells increased, as compared with those in controls, with a very significant difference. Under electronic microscope, ultrastructure of the injured cells appeared obscure, their membrane and membranous organella swelling, or membranous structure breaking. Injuries mentioned above in cells pre-treated with selenium were obviously decreased and activities of glutathione peroxidase increased. But protective effects of selenium supplement were weaker. It suggested that preventive supplement with selenium could reduce injury to human hepatocyte caused by lipid peroxidation.

Cell Survival↗
PubMed1995

[Diagnosis and treatment of primary ureteral carcinoma--a report of 12 cases].

Twelve cases with primary ureteral carcinoma are reported with a review of literatures. Urography was the main method of diagnosis, and retrograde uretero-pyelography was more helpful. Cystoscopy was mandatory before operation. CT was useful for diagnosis and staging. If needed, ureteroscopy could be used to increase diagnostic accuracy. The traditional total nephroureterectomy with a cuff excision of the urinary bladder was the first and basic choice of treatment. Regular cystoscopy, excretory urography and adjuvant intravesical therapy should be carried out after operation.

Aged↗
PubMed1995

[Studies on the deltamethrin-medicated bath of domestic dogs for interrupting visceral leishmaniasis transmission].

In a previous paper, it was reported that deltamethrin-medicated bath of domestic dogs had a strong killing effect against Ph. chinensis, and could also inhibit its blood sucking ability or cause its death shortly after blood sucking. The effect could last for 30 days to 114 days, and mostly for 2 months in the local area. Based on our previous study, three villages (Yongle, Yongfeng, Anle) and a town (Chengguan) were selected from the mountainous region with high incidence of visceral leishmaniasis in Nanping County, northern Sichuan for carrying out an extensive experiment of medicated bathing of domestic dogs, where there were 13 new infected cases in the year of 1991 before the experiment. During the sandfly season in 1992, two rounds of medicated bathing of dogs were conducted, the drug concentration used was 50 ppm. From September 1992 to August 1993, the number of new infected cases was 11 in the above mentioned three villages and a town. Another two rounds of medicated bathing of dogs had been conducted during the sandfly season in 1993. The results show that there was no new infection from September 1993 to October 1994 in the three villages and a town, indicating that through two years' consecutive extensive medicated bathing of dogs in the endemic areas, canine visceral leishmaniasis transmission had been significantly interrupted. The authors consider that in the mountainous region of southern Gansu and northern Sichuan where it has been difficult to treat dogs, it might be more practical to use deltamethrin bathing of dogs for interrupting the transmission of canine visceral leishmaniasis.

Animals↗
PubMed1994

Transforming growth factor beta 1 augments mitogen-induced prostaglandin synthesis and expression of the TIS10/prostaglandin synthase 2 gene both in Swiss 3T3 cells and in murine embryo fibroblasts.

Transforming growth factor-beta (TGF-beta), a potent cytokine, modulates a wide variety of biological responses. Among its actions, TGF-beta can augment prostaglandin synthesis in several cell types. Although TGF-beta alone has no effect on prostaglandin production in Swiss 3T3 cells, we find that TGF-beta augments the ability of tetradecanoyl phorbol acetate (TPA) or serum to stimulate PGE2 production. The TIS10 gene is a primary response gene encoding a second form of prostaglandin synthase (PGS), the rate-limiting enzyme in the biosynthesis of prostaglandins, thromboxanes, and prostacyclins from arachidonic acid. TIS10/PGS-2 expression is induced by mitogens in Swiss 3T3 cells. TGF-beta also augments mitogen-induced synthesis and accumulation of TIS10/PGS-2 protein and induction of TIS10/PGS-2 message in Swiss 3T3 cells. In contrast, TGF-beta has little or no effect on the level of PGS-1 (EC1.14.99.1) message, either alone or in concert with TPA or serum. TGF-beta concentrations in the range of 0.01-0.10 ng/ml (0.4-4.0 pM) maximally enhance mitogen induction of TIS10/PGS-2 message. TPA-induced accumulation of unspliced TIS10/PGS-2 transcript is augmented by TGF-beta, suggesting that this cytokine exerts its effect on expression of the TIS10/PGS-2 gene by transcriptional regulation. TGF-beta also augments TPA-induced prostaglandin production, TIS10/PGS-2 antigen accumulation, and TIS10/PGS-2 message induction in primary cultures of mouse embryo fibroblasts. Dexamethasone attenuates TGF-beta enhancement of all these mitogen-induced responses: PGE2 accumulation, appearance of TIS10/PGS-2 protein and message, and accumulation of TIS10/PGS-2 unprocessed transcript.

3T3 Cells↗
PubMed1994

TGF-beta 1 inhibits both endotoxin-induced prostaglandin synthesis and expression of the TIS10/prostaglandin synthase 2 gene in murine macrophages.

Activated macrophages produce substantial quantities of paracrine mediators, including cytokines, nitric oxide, and prostaglandins. Transforming growth factor beta 1 (TGF-beta) is a potent modulator of immune function. TGF-beta inhibits the cytotoxic activity of endotoxin/lipopolysaccharide (LPS)-activated macrophage cell lines and primary macrophage cultures, reducing their expression of cytokines and nitric oxide. In this report we demonstrate that TGF-beta also attenuates the LPS-induced synthesis and secretion of prostaglandin E2 in murine RAW 264.7 macrophage cells. Macrophage activation also induces accumulation of the recently described ligand-responsive prostaglandin synthase (PGS) TIS10/PGS-2. While TGF-beta alone has no effect on expression from the TIS10/PGS-2 gene, this cytokine inhibits LPS-induced TIS10/PGS-2 protein accumulation and synthesis, as well as LPS-induced TIS10/PGS-2 message accumulation in RAW 264.7 cells. TGF-beta concentrations in the range of 0.1-1.0 ng/ml (4-40 pM) maximally inhibit LPS-induced TIS10/PGS-2 message accumulation. In contrast, neither LPS nor TGF-beta has any effect on the level of PGS-1 (EC 1.14.99.1) message. TGF-beta also attenuates LPS-induced accumulation of unspliced TIS10/PGS-2 transcripts in RAW 264.7 cells, suggesting that this cytokine exerts its effects on TIS10/PGS-2 expression at the transcriptional level. TGF-beta inhibits the LPS-induced accumulation of TIS10/PGS-2 protein and message in cultured murine peritoneal macrophages, as well as in macrophage cell lines.

Animals↗
PubMed1994

Production of trichothecene mycotoxins by Fusarium graminearum and Fusarium culmorum on barley and wheat.

Wheat cultivars (Stoa, MN87150, SuMai-3, YMI-6, Wheaton) and barley cultivars (Robust, Excel, Chevron, M69) were inoculated in the field with isolates of Fusarium graminearum and F. culmorum. The disease (Fusarium head blight) kernels were analyzed for deoxynivalenol (DON), 15-acetyldeoxynivalenol (15-ADON) and nivalenol (NIV). F. culmorum produced all three trichothecenes on all cultivars tested whereas F. graminearum only produced DON and 15-ADON. There was no well defined correlation between DON production in the host and resistance although the data tended to favor SuMai-3 as having definitive resistance to both F. graminearum and F. culmorum.

Animal Feed↗
PubMed1994

v-src induction of the TIS10/PGS2 prostaglandin synthase gene is mediated by an ATF/CRE transcription response element.

We recently reported the cloning of a mitogen-inducible prostaglandin synthase gene, TIS10/PGS2. In addition to growth factors and tumor promoters, the v-src oncogene induces TIS10/PGS2 expression in 3T3 cells. Deletion analysis, using luciferase reporters, identifies a region between -80 and -40 nucleotides 5' of the TIS10/PGS2 transcription start site that mediates pp60v-src induction in 3T3 cells. This region contains the sequence CGTCACGTG, which includes overlapping ATF/CRE (CGTCA) and E-box (CACGTG) sequences. Gel shift-oligonucleotide competition experiments with nuclear extracts from cells stably transfected with a temperature-sensitive v-src gene demonstrate that the CGTCACGTG sequence can bind proteins at both the ATF/CRE and E-box sequences. Dominant-negative CREB and Myc proteins that bind DNA, but do not transactivate, block v-src induction of a luciferase reporter driven by the first 80 nucleotides of the TIS10/PGS2 promoter. Mutational analysis distinguishes which TIS10/PGS2 cis-acting element mediates pp60v-src induction. E-box mutation has no effect on the fold induction in response to pp60v-src. In contrast, ATF/CRE mutation attenuates the pp60v-src response. Antibody supershift and methylation interference experiments demonstrate that CREB and at least one other ATF transcription factor in these extracts bind to the TIS10/PGS2 ATF/CRE element. Expression of a dominant-negative ras gene also blocks TIS10/PGS2 induction by v-src. Our data suggest that Ras mediates pp60v-src activation of an ATF transcription factor, leading to induced TIS10/PGS2 expression via the ATF/CRE element of the TIS10/PGS2 promoter. This is the first description of v-src activation of gene expression via an ATF/CRE element.

3T3 Cells↗
PubMed1994

Spatial-frequency characteristics of letter identification.

To investigate the spatial-frequency components that govern letter identification we compared contrast thresholds for three types of visual stimulus (1) standard Sloan letters, (2) Sloan letters that were spatially bandpass filtered by cosine log filters, and (3) D6 patterns (sixth spatial derivatives of Gaussians). Stimuli were presented on a gray-scale display screen of a Macintosh computer-based testing system at temporal frequencies primarily of 2 and 16 Hz. Contrast thresholds were measured in two subjects with normal visual acuity with use of forced-choice staircases. Contrast sensitivity functions for standard Sloan letters and D6 patterns were comparable at a temporal frequency of 16 Hz but differed systematically at a temporal frequency of 2 Hz. The measurement of contrast sensitivity for cosine log filtered letters presented at a temporal frequency of 2 Hz indicated that the object spatial frequency of maximum sensitivity shifted to lower frequencies as letter size decreased, whereas the retinal spatial frequency of maximum sensitivity remained relatively constant. When letters were spatially bandpass filtered at a peak object spatial frequency of 2.5 cycles/letter, then contrast sensitivity functions for letter identification were equivalent to those for D6 patterns at both temporal frequencies. These results suggest that spatially filtered letters may provide a more appropriate test of visual function than do standard letter optotypes.

Adult↗
PubMed1994

[Anti-implantation action of nylestriol and its effect on endometrium in rabbits].

The anti-implantation action of nylestriol in rabbits was studied. Using the method of arresting mitosis by injection of colchicine, we detected the mitosis frequency of endometrial cells. The activities of carbonic anhydrase (CAH), A1P and PAS reaction were observed under light microscope combined with the histochemical method and microscopic autoexposure control device. The results were as follows: 1. Giving nylestriol orally to rabbits on day 1 of pregnancy produced an obvious anti-implantation effect; 2. The number of mitosis cells in glandular epithelium and stroma of the endometrium in the treatment group was less than that in the control group (P < 0.05); and 3. Compared with the control group, the activities of CAH and A1P, and glycogen content in the endometrium decreased significantly in the treatment group (P < 0.05). The result suggests that nylestriol may prevent the implantation of blastocyst by disturbing decidulization of the endometrium.

Alkaline Phosphatase↗
PubMed1993

Coordinated decreases in rRNA gene transcription factors and rRNA synthesis during muscle cell differentiation.

rRNA synthesis decreases significantly during the differentiation of rat L6 myoblasts to myotubes. Nuclear run-on assays demonstrated that the decrease was attributable to decreased rates of rRNA gene transcription. Immunoblot analysis indicated a marked reduction in amounts of the RNA polymerase I transcription factors UBF1 and UBF2 (upstream binding factors 1 and 2, respectively). The levels of these factors dropped in parallel with the down-shift in rRNA gene transcription. The amount of UBF does not fall due to a general decrease in cellular protein, as myosin heavy-chain protein accumulates markedly during this same time. RNA blots of total RNA isolated from myoblasts and differentiating myotubes showed a decrease in the mRNA for UBF, at the same time the mRNA for myogenin was accumulating. The down-shift in UBF mRNA levels preceded the decrease in the protein levels for UBF. There have been reports that the acute response of the rRNA gene transcription system to physiological signals in many systems involves an RNA polymerase I-associated factor. However, our results imply that the regulation of rRNA gene DNA transcription in response to physiological processes, such as differentiation, may involve multiple regulatory pathways.

Adenosine Triphosphate↗
PubMed1993

Structural determination and promoter analysis of the chicken mitogen-inducible prostaglandin G/H synthase gene and genetic mapping of the murine homolog.

We have previously reported the isolation and characterization of a new form (PGHS-2) of prostaglandin G/H synthase (PGHS, cyclooxygenase) from chicken embryo fibroblasts. To further study the regulation and structure of the gene, we have cloned the entire chicken PGHS-2 (previously termed miPGHSch) gene with its 5'-flanking region from a chicken genomic library. A genomic Southern blot showed the existence of a single PGHS-2 gene. The size of the gene was estimated at 8.9 kb through DNA sequencing and polymerase chain reaction analysis. The PGHS-2 gene was found to contain 10 exons, giving it a structure similar to that of the human PGHS-1 and murine PGHS-2 genes. The transcription start site was determined by primer extension, and the nucleotide sequence of 1.6 kb of the 5'-flanking region immediately upstream of the transcription start site was determined. The promoter sequence contained a TATA box and a variety of enhancer elements, including a serum response element, an AP-1, an NF-kappa B, and several SP-1 and AP-2 sites. Chloramphenicol acetyltransferase (CAT) assays showed that the first 158 nucleotides of the promoter efficiently drove transcription of the CAT reporter gene in serum-stimulated cells. Dexamethasone, a potent inhibitor of prostaglandin synthesis, had no effect on CAT activity, although this drug is known to markedly decrease PGHS-2 mRNA in vivo. This suggests that dexamethasone may inhibit PGHS-2 mRNA expression at the post-transcriptional level. Analysis of hamster/mouse somatic cell hybrids with radiolabeled cDNA probes demonstrated that PGHS-1 mapped to chromosome 2 and PGHS-2 mapped to chromosome 1 of the mouse genome.

3T3 Cells↗