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L X Zhang

Publications and source records attributed to L X Zhang.

At least 19 recordsLinked to original sources
PubMed1995

Evidence for the involvement of retinoic acid receptor RAR alpha-dependent signaling pathway in the induction of tissue transglutaminase and apoptosis by retinoids.

In this study, we show that all-trans-retinoic acid (RA) is a potent inducer of tissue transglutaminase (TGase II) and apoptosis in the rat tracheobronchial epithelial cell line SPOC-1. We demonstrate that these cells express the retinoid receptors RAR alpha, RAR gamma, and RXR beta. To identify which of these receptors are involved in regulating these processes, we analyzed the effects of several receptor-selective agonists, an antagonist, and a dominant-negative RAR alpha. We show that the RAR-selective retinoid SRI-6751-84 strongly increased TGase II expression at both the protein and mRNA levels, whereas the RXR-selective retinoid SR11217 had little effect. The RAR alpha-selective retinoid Ro40-6055 was also able to induce TGase II, whereas the RAR gamma-selective retinoid CD437 was inactive. The induction of TGase II by the RAR-selective retinoid was completely inhibited by the RAR alpha-antagonist Ro41-5253. Overexpression of a truncated RAR alpha gene with dominant-negative activity also inhibited the induction of TGase II expression. The increase in TGase II is associated with an induction of apoptosis as revealed by DNA fragmentation and the generation of apoptotic cells. We demonstrate that apoptosis is affected by retinoids in a manner similar to TGase II. Our results suggest that the induction of TGase II expression and apoptosis in SPOC-1 cells are mediated through an RAR alpha-dependent signaling pathway.

Animals↗
PubMed1995

Upregulation of gap junctional communication and connexin43 gene expression by carotenoids in human dermal fibroblasts but not in human keratinocytes.

Consumption of dietary carotenoids has been statistically associated with decreased risk of cancer at several anatomic sites. In a model murine system of carcinogenesis (the 10T1/2 assay), we have previously shown that carotenoids can inhibit chemically and physically induced neoplastic transformation. This action is strongly correlated with the ability of carotenoids to increase gap-junctional communication (GJC) by induction of connexin43 (Cx43) gene expression. Here we extend these studies to human foreskin-derived dermal fibroblasts and keratinocytes. In fibroblasts, beta-carotene and canthaxanthin at concentrations between 10(-5) and 3 x 10(-6) M were found to strongly enhance GJC in a dose- and time-dependent manner. This was accompanied by an increase in the number of immunofluorescent junctional plaques recognized by an anti-Cx43 antibody and by an increase in Cx43 protein level as determined by western blot analysis. No decrease in proliferation rates was detected by [H3]thymidine labeling. Human keratinocytes grown in monolayer culture did not respond to carotenoids in terms of GJC as measured by dye transfer, immunofluorescent analysis of Cx43 distribution, or Cx43 levels as measured by western blotting. Both cell types accumulated high levels of carotenoids. Because canthaxanthin, which has no known provitamin A activity in mammals, is as active in fibroblasts as is beta-carotene, the carotenoid with the highest provitamin A activity, the induction of GJC and Cx43 expression by carotenoids in human dermal fibroblasts seems unrelated to their provitamin A status. The lack of response of keratinocytes suggests differences in regulation of Cx43 expression or in carotenoid processing.

Anticarcinogenic Agents↗
PubMed1995

Trend of initial drug resistance of tubercle bacilli isolated from new patients with pulmonary tuberculosis and its correlation with the tuberculosis programme in Beijing.

SETTING: The tuberculosis control programme of Beijing. OBJECTIVE: To observe the trend of initial drug resistance of tubercle bacilli and to try to correlate it with the Beijing tuberculosis control programme. DESIGN: Susceptibility testing of randomly collected isolates of positive sputum culture from new patients with pulmonary tuberculosis without a history of prior antituberculosis therapy, in 1962 and continuously since 1978. Collection of treatment data from the Beijing tuberculosis control programme. RESULTS: The trend of initial drug resistance in Beijing began to decline in 1978. The Beijing tuberculosis treatment programme has been very successful, resulting in rapid reduction of prevalence of smear-positive cases. CONCLUSION: It appears that the trend of initial drug resistance correlates with progress made in the implementation of the successful tuberculosis programme in Beijing. It is recommended that continuous observation of initial drug resistance be one of the indices of tuberculosis surveillance.

Antitubercular Agents↗
PubMed1994

Effects of micronutrients and antioxidants on lipid peroxidation in human plasma and in cell culture.

Plasma levels of triglycerides, retinol, cholesterol, lipid-phase antioxidants (alpha-, gamma-tocopherols, beta-carotene, alpha-carotene, lycopene, beta-cryptoxanthin and lutein/zeaxanthin), and thiobarbituric acid-reactive substances (TBA-RS), as an indicator of lipid peroxidation, were repeatedly determined in nine individuals over a 3-month period. Levels of TBA-RS were positively correlated with plasma triglycerides and gamma-tocopherol, and negatively correlated with plasma carotenoids. These results were consistent with in vitro cell culture studies which showed increased TBA-RS for cells supplemented with linolenic acid and decreased levels when treated with beta-carotene. We conclude that TBA-RS measurements in plasma accurately reflect the level of peroxidizable substrate as modified by the presence of a variety of dietary antioxidants, particularly carotenoids. Although the inter- and intra-individual variabilities for TBA-RS are comparable with the micronutrients and antioxidants measured in this study, high interassay variability and the strong association with the more commonly measured plasma triglycerides suggest the TBA-RS assay to be of limited use in epidemiologic studies. However, this assay does appear to be useful in cell culture studies where experimental conditions can be better controlled. Low ratios of inter- to intra-individual variability in some of the plasma micronutrient and lipid-phase antioxidants measured suggest that multiple samples may be required to characterize individuals in studies evaluating the relation between these plasma constituents and disease incidence.

Animals↗
PubMed1994

[Effects of microiontophoretically applied GABA and 5-HT on the electric activities of neurons in nucleus parafascicularis of thalamus in rats].

The effects of GABA and 5-HT on the electric activities of neurons of nucleus parafascicularis thalami (Pf) were observed in anesthetized rats with multimicropipete and iontophoresis and technique. It was found that: (1) Pain discharges of the Pf neurons were inhibited by microiontophoretically applied (MIA) GABA, an effect that could be reversed by MIA picrotoxin. Picrotoxin alone could enhance the pain discharges. The results indicate that GABA may be an inhibitory neurotransmitter responsible for the electric activities of Pf neurons. (2) MIA 5-HT has both excitatory and inhibitory effects on the pain discharge of Pf neurons, while only the former could be blocked by MIA cyproheptadine. It was suggested that 5-HT may participate in the modulation of the electric activities of the Pf neurons with different subtypes of receptors.

Animals↗
PubMed1994

[Diagnosis of falciparum malaria by polymerase chain reaction].

Polymerase Chain Reaction (PCR) method using a pair of Plasmodium falciparum-specific oligonucleotides as primers was used to detect malaria patient blood samples collected from Yunnan endemic malarious area. The results showed that a DNA fragment of 492 bp was amplified in all 53 microscopically diagnosed P. falciparum samples, but negative in 8 P. vivax samples and 12 normal blood samples. This method seems to have high sensitivity and high specificity.

Animals↗
PubMed1993

Purification and characterization of a DNA-binding heterodimer of 52 and 100 kDa from HeLa cells.

In studies of protein binding to the upstream region of the human proliferation-associated antigen p120 gene, a heterodimer of 52 and 100 kDa proteins was purified from HeLa cells. A 1:1 ratio of p52 and p100 was constant throughout the purification. The heterodimer was localized to cell nuclei, as shown by immunofluorescence. The pI values of the p52 and p100 were 7.8 and 8.6 respectively. The peptide sequences obtained for p52 (QSNKTFNLEKQNHTPRKKHQ and PLRGKQLRVRFAAHSASLTVR) and for p100 (PGGPKPGGGPGLSTPGGHPKPPHRGGGEPPRGRQ and GPGPGQSGPKPPIPPPPPHQQ) were not found in the computer databanks. One p52 peptide sequence, PLRGKQLRVRFA, shows considerable sequence similarity to a conserved motif in topoisomerase II of multiple species. The p52/100 heterodimer bound to different DNA probes. The binding was competed by poly(dI-dC), sonicated salmon sperm DNA, and circular or linearized plasmid DNA. The optimal DNA binding for the heterodimer was at pH 7-9 with low salt. The DNA-binding subunit of the heterodimer was the p100 polypeptide, as shown by u.v.-cross-linking assays and Southwestern blots.

Amino Acid Sequence↗
PubMed1993

Predigestion of soybean proteins with immobilized trypsin for infant formula.

Soybean protein isolates of low soybean trypsin inhibitor (STI) residue were prepared by acidic precipitation of soybean flour water extracts (0.8-1.2%) at pH 5.0, followed by acidic washing at this pH and affinity adsorption of residual STI with immobilized trypsin on polystyrene anion-exchange resin GM 201. After heat treatment, soybean protein isolates were subjected to controlled hydrolysis with the immobilized trypsin. Then, the predigested soybean protein was prepared. The predigested soybean protein was free of STI activity, and its solubility at acidic pH range was greatly increased. Sedimentation test showed that it formed a much finer clot at pH 4.5 than that of untreated soybean protein. The pepsin digestibility index at pH 4.0 and chymotrypsin digestibility index at pH 8.0 were obviously improved. These results suggested that the predigested soybean protein prepared by this method may be used in infant formulas.

Chemical Precipitation↗
PubMed1993

Effect of CCK-8 on audiogenic epileptic seizure in P77PMC rats.

P77PMC rat is a breed of rat with congenital audiogenic seizure(AS). AS attacks were suppressed by cholecystokinin octapeptide (CCK-8) injected intraperitoneally (i.p.) at a dose of 50 micrograms/kg, but not at 25 micrograms/kg. Radioimmunoassay study showed that the CCK-8 immunoreactivity (IR) in the cerebrocortex and hippocampus is much lower in P77PMC rats than that of Wistar rats. The results suggest that a low cerebral content of CCK-8 may account for the high susceptibility of audiogenic seizure in P77PMC rats.

Acoustic Stimulation↗
PubMed1993

Inhibitors of endogenous nitrogen oxide formation block the promotion of neoplastic transformation in C3H 10T1/2 fibroblasts.

The endogenous production of nitric oxide (NO) and its role in the neoplastic transformation of C3H 10T1/2 mouse fibroblasts were investigated. NO production, as indicated by NO2- in the culture medium, was increased in cells initiated with 3-methylcholanthrene or stimulated with the combination of interferon-gamma (IFN gamma, 10 ng/ml) plus bacterial lipopolysaccharide (LPS, 1 micrograms/ml). NO2- was detectable within 24-48 h of IFN gamma/LPS treatment and accumulated to micromolar concentrations within 4 days. NO production was inhibited in a dose-dependent manner by analogs of L-arginine in which the terminal guanidino nitrogen is blocked, consistent with NO production by the oxidative deamination of L-arginine by nitric oxide synthase (NOS). IFN gamma/LPS-stimulated cells expressed a 4.4 kb mRNA which hybridized to a probe for the mouse macrophage-inducible NOS. Expression of the rat cerebellar constitutive NOS was not detected in these cells. Arginine analogs added to the culture medium during the post-confluence promotional stages of the C3H 10T1/2 transformation assay blocked the formation of transformed foci in a dose-dependent manner comparable to their inhibition of NO production. These data demonstrate that C3H 10T1/2 mouse fibroblasts are a useful model for the study of the effects of endogenous NO production in carcinogenesis and suggest that NO plays a significant role in the promotional phase of neoplastic transformation of these cells.

Amino Acid Oxidoreductases↗
PubMed1993

[Fluidity of red blood cell membrane from mouse infected with Malaria parasite].

The fluidity of membrane lipid regions of Plasmodium berghei- or Plasmodium yoelii-infected red blood cells has been determined by the fluorescence polarization technique using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. The results showed that the fluidity of Plasmodium (berghei or yoelii)-infected red blood cell membranes was increased significantly as compared with that of normal controls judging from the degree of polarization and the microviscosity. Its mechanism was discussed briefly.

Animals↗
PubMed1993

[Further report on application of DNA probe in diagnosis of vivax malaria infection].

Southern blotting with a labeled and linearized pUC 19 DNA containing a specific fragment of 0.24 kb DNA of Plasmodium vivax asexual blood stages (kindly offered by Dr. C. Kidson) was used for further identification of blood samples showing positive reaction by dot-blot hybridization. The results showed that those with positive reaction from patients with P. vivax, with P. falciparum or with fever but with negative microscopic findings were also positive by Southern blotting. It was confirmed that some of those positive with P. falciparum were likely to infect P. vivax at the same time. So did a part of those with fever but negative in the blood films (Figs. 1,2).

Animals↗
PubMed1993

[Effect of Japanese Ganoderma Lucidum on production of interleukin-2 from murine splenocytes].

The purpose of this study was to determine the effect of Ganoderma lucidum (GL) planted in Japan on the production of Interleukin-2 (IL-2) from murine splenocytes. It was observed that hydrocortisone (HC) 0.025-1 microgram /ml could significantly antagonize the inhibitory activity of HC and CSA to increase the production of IL-2 in vitro, P < 0.01. When the splenocytes pretreated with GL alone or in combination with HC, it was shown that pretreatment alone had no significant effect on IL-2 production, but preincubating splenocytes with HC and GL resulted in a significant increase of IL-2 production when compared with that of HC group, P < 0.01. In vivo, GL 300 mg/kg could increase the production of IL-2 when oral taken GL alone or in combination of HC.

Animals↗