Search PubMed⌕ Search

Biomedical subjects

X Peng

Publications and source records attributed to X Peng.

At least 91 records · Page 5Linked to original sources
PubMed1999

Involvement of DNA-dependent protein kinase in UV-induced replication arrest.

Cells exposed to UV irradiation are predominantly arrested at S-phase as well as at the G(1)/S boundary while repair occurs. It is not known how UV irradiation induces S-phase arrest and yet permits DNA repair; however, UV-induced inhibition of replication is efficiently reversed by the addition of replication protein A (RPA), suggesting a role for RPA in this regulatory event. Here, we show evidence that DNA-dependent protein kinase (DNA-PK), plays a role in UV-induced replication arrest. DNA synthesis of M059K (DNA-PK catalytic subunit-positive (DNA-PKcs(+))), as measured by [(3)H]thymidine incorporation, was significantly arrested by 4 h following UV irradiation, whereas M059J (DNA-PKcs(-)) cells were much less affected. Similar results were obtained with the in vitro replication reactions where immediate replication arrest occurred in DNA-PKcs(+) cells following UV irradiation, and only a gradual decrease in replication activity was observed in DNA-PKcs(-) cells. Reversal of replication arrest was observed at 8 h following UV irradiation in DNA-PKcs(+) cells but not in DNA-PKcs(-) cells. Reversal of UV-induced replication arrest was also observed in vitro by the addition of a DNA-PK inhibitor, wortmannin, or by immunodepletion of DNA-PKcs, supporting a positive role for DNA-PK in damage-induced replication arrest. The RPA-containing fraction from UV-irradiated DNA-PKcs(+) cells poorly supported DNA replication, whereas the replication activity of the RPA-containing fraction from DNA-PKcs(-) cells was not affected by UV, suggesting that DNA-PKcs may be involved in UV-induced replication arrest through modulation of RPA activity. Together, our results strongly suggest a role for DNA-PK in S-phase (replication) arrest in response to UV irradiation.

Androstadienes↗
PubMed1999

[The significance of TT virus detection in persons with elevated alanine aminotransferase during routine medical check up and patients with liver diseases].

OBJECTIVE: To investigate the significance of the new DNA virus (TTV) infection in persons with elevated alanine aminotransferase (ALT) during routine medical check up and patients with liver diseases, and analyze its pathogenesis. METHODS: PCR was used in the detection of TTV DNA in 19 serum samples from ALT elevated persons and 41 from ALT normal persons during their routine medical check up, and 182 serum samples from patients with various kinds of liver diseases. PCR products were confirmed by RFLP. Other hepatitis viruses were simultaneously detected using routine methods. RESULTS: TTV DNA was detected in 10.53% (2/19) and 2.44% (1/41) in groups of ALT elevated and control respectively with no significant difference between their detective rates (P > 0.05). There were 9 cases with current HBV infection, 1 case with hepatitis C and 1 case with hepatitis A in group of elevated ALT. Two TTV positive cases were both superinfected with HBV. The detecting rate of TTV DNA in patients with liver diseases was 4.4%. Only one case out of 18 non A to G hepatitis showed TTV DNA in serum. CONCLUSION: There were TTV infections in Chinese population. The main cause for ALT elevation in persons during routine medical check up was HBV infection. There were TTV infections in patients with liver diseases too. However, TTV wasn't the main cause of non A to G hepatitis. Thus, the pathogenesis of TTV might be very weak.

Alanine Transaminase↗
PubMed1999

[New method for the isolation of astroglial cells and oligodendrocytes].

Based on the different properties of cellular adhesions, developmental time-courses and growth pattern of astroglial cells and oligodendrocytes, a method of isolating glial cells in vitro was developed. The observations under inverted light microscope and scan electronic microscope identified that the morphology of isolated cells were consistent with the previous description. Immunocytochemical examination showed the expressions of markers, the glial fibrillary acidic protein (GFAP) of astroglia cells and the myelin basic protein (MBP) of oligodendrocytes were consistent with the isolated cells. All parameters showed that the isolated glial cells were pure, and the new methods were easy and reliable.

Animals↗
PubMed1999

Interaction of tissue transglutaminase with nuclear transport protein importin-alpha3.

Tissue transglutaminase is a multifunctional enzyme which has been involved in the regulation of cell growth, differentiation, and apoptosis. Recently, nuclear localization of tTG has been reported indicating the potential of active nuclear transport. In this study we use the yeast two-hybrid assay and co-immunoprecipitation to show that tTG interacts with the nuclear transport protein importin-alpha3. Using electron microscopy we demonstrate that nuclear expression of tTG in a non-small cell lung cancer cell line is induced by retinoic acid (RA). These data suggest that importin-alpha3 could mediate active nuclear transport of tTG which may be important for the regulation of critical cellular processes.

Amino Acid Sequence↗
PubMed1999

Mechanisms of growth stimulation by suramin in non-small-cell lung cancer cell lines.

PURPOSE: Suramin, a polysulfonated naphthylurea, has been shown to be effective in the treatment of several cancers. We have reported that suramin, at dose concentrations higher than 140 microM, exerts growth-stimulatory effects in several non-small-cell lung cancer (NSCLC) cell lines. The purpose of this study was to examine the mechanisms by which suramin exerts this growth-stimulatory effect in NSCLC cells. METHODS: NCI-H596 cells were treated with agarose-immobilized suramin, directly or by addition on cell culture inserts, after which growth was determined by [3H]thymidine incorporation. PPADS, a specific purinergic receptor antagonist, was used to determine whether suramin acts via purinergic receptors. The effect of suramin on epidermal growth factor receptor (EGFR) was determined by analyzing receptor phosphorylation and dimerization. XAMR 0721, a suramin analogue containing only one of the two polysulfonated arms, was also analyzed for its effects on growth and EGFR activation. RESULTS: Agarose-immobilized suramin stimulated NCI-H596 cell growth, but only when added directly to the cells. When the suramin-conjugated beads were added to the cells on cell culture inserts, which preclude an interaction with the cell surface but allow interaction with the culture medium, there was no effect on proliferation. PPADS had no effect on the growth stimulation by suramin; however suramin treatment resulted in rapid phosphorylation and dimerization of EGFR. Treatment with XAMR 0721 did not affect growth or tyrosine phosphorylation and dimerization of EGFR. CONCLUSIONS: Suramin need not enter NCI-H596 cells to exert its growth-stimulatory effect, nor is this effect mediated by an interaction with soluble growth factors. Rather, it appears that suramin acts via an interaction with EGFR, but not with purinergic receptors.

Antineoplastic Agents↗
PubMed1999

Development of keratoacanthomas and squamous cell carcinomas in transgenic rabbits with targeted expression of EJras oncogene in epidermis.

Activated ras genes have been frequently identified in both benign and malignant human tumors, including keratoacanthoma and squamous cell carcinoma. In this study, we developed two lines of transgenic rabbits in which the expression of EJras has been specifically targeted to the rabbit epidermal keratinocytes, using the upstream regulatory region of cottontail rabbit papillomavirus. All of the F1 transgenic progenies developed multiple keratoacanthomas at about 3 days after birth. The rabbits developed an average of 20 tumors, which usually reached the size of approximately 1 cm in diameter and then spontaneously regressed in about 2 months, similar to keratoacanthoma regression in humans. In addition, up to 18% of the rabbits then developed squamous cell carcinoma at about 5 months of age. The expression of EJras was detectable in all of the keratoacanthomas and squamous cell carcinomas. These results strongly support the involvement of the ras oncogene in both the initiation and regression of keratoacanthoma, and in the development of squamous cell carcinomas. These novel transgenic rabbits, with their consistent tumorigenic phenotype at an early age, high similarity to the human lesions, and easy accessibility for examination, manipulation, biopsy, and treatment, should provide a unique model system for studying ras activation-related tumor initiation, regression, and progression, and for evaluating antitumor therapies.

Animals↗
PubMed1999

Growth factors and gene expression in cultured rat hepatocytes.

BACKGROUND/AIM: The aim of this study was to evaluate the effect of replication on function variables in cultured hepatocytes. METHODS: Isolated rat hepatocytes were cultured in HCM medium and plated on collagen-coated dishes at cell densities from 0.2 x 10(5) (subconfluent) to 1.0 x 10(5) x cm(-2) (confluent) with and without addition of hepatocyte growth factor, epidermal growth factor and insulin-like growth factor-I. The synthesis rate was measured for DNA, albumin, urea, and glucose together with mRNA levels (Northern blots) for albumin, urea cycle enzymes, and acute phase and "house-keeping" proteins. RESULTS: In subconfluent culture the synthesis of DNA and urea was higher (118% and 112%, respectively), and of albumin and glucose lower (40% and 67%, respectively) than in confluent culture. The mRNA levels of carbamoylphosphate synthase, argininosuccinate synthetase, argininosuccinate lyase, arginase, a2-macroglobulin, beta-fibrinogen, and albumin were lower (23%, 58%, 77%, 33%, 12%, 50%, and 51%, respectively) in subconfluent culture compared with confluent culture. Relatively increased levels were found for beta-actin (109%) and alpha-tubulin (136%). In subconfluent culture hepatocyte growth factor increased the DNA synthesis rate 6-fold, epidermal growth factor 3-fold, and insulin-like growth factor-I 2-fold; that of albumin, urea and glucose was not increased significantly. In confluent culture the effect of growth factors on synthesis rates was not significant, and the growth factors had little influence on mRNA levels. CONCLUSIONS: Hepatocytes produce urea at the same rate in subconfluent as in confluent culture in spite of a lower mRNA level of urea cycle enzymes. Hepatocyte growth factor and epidermal growth factor increase DNA synthesis markedly in subconfluent culture only, without significantly changing the ratio between subconfluent and confluent culture of other variables. This suggests that active replication is not an important cause of the relatively low liver-specific function of hepatocytes in subconfluent culture.

Actins↗
PubMed1999

Chinese traditional medicine and abnormal sex ratio at birth in China.

A study of the abnormal sex ratio at birth in China reveals that it is not an entirely new phenomenon that emerged since the 1980s, but is simply more visible at present. Deliberate intervention to determine the sex of children has existed in the past few decades, at least in certain groups. Apart from modern medical methods, traditional Chinese medical practice is shown to be highly accurate in identifying the sex of a fetus. This may lead to sex-selective abortion and an abnormal sex ratio at birth. The possible causes of the abnormal sex ratio at birth include not only the real imbalance due to the disturbance of social factors, but also a spurious one attributable to the undercounting of female births. The real magnitude of the imbalance has been exaggerated by statistical error. The phenomenon is a complicated one reflecting the comprehensive socioeconomic setting. Among these factors, the stage of the fertility transition is one of the most decisive.

Child↗
PubMed1999

NBPA: a cerebral ischaemic protective agent.

1. NBPA is a derivative of 3-n-butylpathalide isolated from Apium granolens Linn. 2. At concentrations ranging from 6 x 10(-6) to 10(-6) mol/L, NBPA inhibited the L-type calcium current in guinea-pig myocardial cells and cultured human neuroblastoma cells. 3. At 10(-6) mol/L, NBPA markedly inhibited calcium-dependent and -independent release of glutamate from synaptosomes. 4. The [31P] nuclear magnetic resonance spectrum has shown that pretreatment with NBPA at 15 mg/kg, i.p., improved energy metabolism. 5. In situ hybridization has shown that 10 and 20 mg/kg, i.p., NBPA prior to cerebral artery occlusion can accelerate the expression of heat shock protein 70 mRNA and inhibit c-fos mRNA expression. 6. It has been shown that NBPA decreases the nitric oxide content and bc nitric oxide synthase (NOS) activity in the global cerebral ischaemia-reperfusion model in rats. In addition, it has been shown that NBPA significantly inhibits the expression of inducible NOS protein.

Animals↗
PubMed1999

Characterization of the meta-cleavage compound hydrolase gene involved in degradation of the lignin-related biphenyl structure by Sphingomonas paucimobilis SYK-6.

Sphingomonas paucimobilis SYK-6 has the ability to transform a lignin-related biphenyl compound, 2,2'-dihydroxy-3,3'-dimethoxy-5, 5'-dicarboxybiphenyl (DDVA), to 5-carboxyvanillic acid (5CVA) via 2, 2',3-trihydroxy-3'-methoxy-5,5'-dicarboxybiphenyl (OH-DDVA). In the 4.9-kb HindIII fragment containing the OH-DDVA meta-cleavage dioxygenase gene (ligZ), we found a novel hydrolase gene (ligY) responsible for the conversion of the meta-cleavage compound of OH-DDVA to 5CVA. Incorporation of 18O from H218O into 5CVA indicated there was a hydrolytic conversion of the OH-DDVA meta-cleavage compound to 5CVA. LigY exhibited hydrolase activity only toward the meta-cleavage compound of OH-DDVA, suggesting its restricted substrate specificity.

Amino Acid Sequence↗
PubMed1999

Protection of rabbits from viral challenge by gene gun-based intracutaneous vaccination with a combination of cottontail rabbit papillomavirus E1, E2, E6, and E7 genes.

In this study, cottontail rabbit papillomavirus infection of domestic rabbits was used as an animal model to develop papillomavirus early gene-based vaccines. Groups of rabbits were intracutaneously vaccinated with single papillomavirus early genes E1, E2, E6, and E7 or with a combination of these four genes. Only a fraction of rabbits were protected from subsequent viral challenge when vaccinated with the E1 or E6 gene. Viral tumor growth in those rabbits vaccinated with the E1 or E2 gene was suppressed compared to that in controls. In contrast, seven of nine rabbits vaccinated with the combination of the E1, E2, E6, and E7 genes were completely protected against viral challenge. These data indicated that intracutaneous genetic vaccination with the combination of the E1, E2, E6, and E7 genes can be an effective strategy for immunoprophylaxis of papillomavirus infection.

Animals↗
PubMed1999

[Study on telomerase inhibition by ribozyme targeted to telomerase RNA component].

OBJECTIVE: To evaluate the possibility of using ribozyme technology for telomerase inhibition and cancer therapy. METHODS: A hammer head ribozyme (telomerase ribozyme, teloRZ) directed against the RNA component of human telomerase (hTR) was designed and synthesized to serve as a telomerase inhibitor. An in vitro transcription plasmid and a eukaryotic expression plasmid containing teloRZ gene were constructed. In vitro cleavage reaction was carried out by mixing the ribozyme RNA with DIG-labeled-hTR in different reaction conditions. Cleavage bands were detected by digoxin chemilumines- cent assay. The eukaryotic expression plasmid was inducted into HeLa cells by lipofectamine; the telomerase activities and bio-characteristics of HeLa cells were detected continuously. RESULTS: teloRZ showed a specific cleavage activity against the telomerase RNA component used as template. The in vitro cleavage ratio reached about 60%. The telomerase activities of cells expressing teloRZ dropped to eight times; the doubling times became longer and apoptosis ratios became higher with increasing population doublings (PDS); at 19-20 PDS 95% cells showed apoptosis. CONCLUSION: These findings support the potential use of this ribozyme against immortalized cancer cells.

Apoptosis↗
PubMed1999

[Changes and significance of natural killer cell, IL-2, IL-6 and TNF alpha of heroin addicts after detoxification].

In order to find out the activity of NKC and production of IL-2 in the peripheral blood mononuclear cells and the level of IL-6 and TNF alpha in the peripheral blood serum, we investigated 51 herion addicts who were in the course of detoxification. MTT colorimetric assay and ELISA assay methods were adopted. The results showed that, in the herion addicts, NK activity was 30.11 +/- 5.2%, IL-2 activity was 8.06 +/- 1.66 IU/ml, IL-6 level was 61.17 +/- 12.07 pg/ml, and TNF alpha level was 91.83 +/- 19.19 pg/ml, whereas in the healthy controls, the results were 44.89 +/- 4.75%, 15.91 +/- 3.83 IU/ml, 22.18 +/- 9.31 pg/ml and 30.55 +/- 11.94 pg/ml respectively. When the herion addicts were subjected to detoxication, their NKC and IL-2 activities, IL-6 and TNF alpha levels gradually restored to normal, and were correlated with the time of their detoxification (NKC: r = 0.626, P < 0.001; IL-2: r = 0.684, P < 0.001; IL-6: r = -0.791, P < 0.001; TNF alpha: r = -0.703, P < 0.001).

Adult↗
PubMed1999

[Effects of nitric oxide on platelet function in burned rats].

OBJECTIVE: To investigate the effects of nitric oxide (NO) on rat platelet function after burn injury. METHODS: Wistar rats with 30% TBSA full thickness burns were used as model, indices of platelet functions including platelet aggregation rate in first minute (PAR-1), maximal platelet aggregation rate (PAR-m), platelet dissipation rate (PDR) and platelet adhesion rate (PAR) were determined in four groups, namely burn control (B), NO donor (sin-1), NO synthesis inhibitor (L-NAME) and the normal control (C). RESULTS: The PAR-1, PAR-m and PAR were significantly increased and the PDR was decreased remarkably after burn injury. In sin-1 group the PAR-1, PAR-m and PAR were obviously lower and the PDR was higher than that of B group (P < 0.05-0.01). In L-NAME group the PAR-1 was higher and the PDR was lower as compared with B group, but the PAR-m and PAR showed no significant differences between two groups. CONCLUSIONS: The ability of platelet adhesion and aggregation induced by activated platelet are increased after burn injury. NO can partially reduce the degree of platelet activation and inhibit platelet aggregation. Moreover, it may dissipate aggregated platelets.

Animals↗
PubMed1999

[Isolation and sequencing of a novel form of cytochrome p-450 4F family from human liver].

OBJECTIVE: To isolate and sequence a novel gene of cytochrome p-450 4F family. METHODS: A cDNA was isolated by touchdown PCR from a cDNA library of human fetal liver using specific primers. The DNA sequencing was done by an auto-sequence machine through forward and reverse directions. The expression of cDNA encoded protein was tested in yeast cells. RESULTS: Sequencing of the full length cDNA revealed a sequence of 1,980 nucleotides coding for a protein of 520 amino acids with a molecular weight of 59,700 Da. The cDNA-deduced amino acid sequence showed 92% homology to that of human polymorphonuclear leukocytes (PMN) LTB4-hydroxylase (CYP4F3) and 91% homology to that of human liver LTB4 hydroxylase (CYP4F2). The expression of protein in the yeast cells showed a fusion protein with a molecular weight of about 86,000 Da and 60,000 Da after a proteolytic removal of the GST affinity tag. It was confirmed by RT-PCR that the gene was expressed in the adult liver. CONCLUSION: Our results clearly show a novel form of cytochrome p-450 4F in human liver.

Amino Acid Sequence↗
PubMed1999

[Expression of multidrug resistance-associated protein in human non-small cell lung cancer].

OBJECTIVE: To investigate the expression of the multidrug resistance-associated protein(MRP) gene and MRP in human non-small-cell lung cancer tissues and to determine whether such expression was related to cell type, differentiation, tumour size, lymph node metastasis and prognosis. METHODS: 92 paraffin-embeded lung tumor samples (43 squamous cell carcinoma, 49 adenocarcinoma) and 16 fresh non-small-cell lung cancer samples were examined by using immunohistochemistry method and the reverse transcription-polymerase chain reaction (RT-PCR) technology respectively. RESULTS: The expression of MRP mRNA and MRP were detectable in 31% (5-16) and 54% (50/92) of non-small-cell lung cancer specimens respectively. Eighteen(42%) squamous cell carcinoma specimens and thirty-two(65%) adenocarcinoma specimens showed positive immunostaining for MRP(P < 0.05). The expression of MRP was not related to tumour size, lymph node metastasis and cell differentiation significantly(P > 0.05). The five-year survival rate after operation of patients with MRP-positive tumours and MRP-negative tumours were 16% (8/50), 52% (22/42) respectively. Patients with MRP-positive tumours had shorter survival time than the MRP-negative patients significantly(P < 0.01). CONCLUSIONS: Adenocarcinoma had higher MRP expression than squamous carcinoma significantly, positive MRP immunostaining appears to be an independent indicator of poor prognosis in NSCLC.

Adult↗
PubMed1999

[Expression of multidrug resistance-associated protein (MRP) and lung resistance protein (LRP) in human rectal carcinomas and its clinical significance].

OBJECTIVE: To investigate the expression and clinical significance of multidrug resistance-associated protein(MRP) and lung resistance protein(LRP) in rectal carcinoma. METHODS: Fiftyseven paraffin embeded primary rectal carcinoma specimens were examined by immunohistochemical staining. RESULTS: Of the 57 tumour specimens examined, 28(49.1%) and 24(42.1%) were positively immunostaned for MRP and LRP, respectively. Co-expression of the two proteins was observed in 10(17.5%) specimens. Positive immunostaning of either of the two proteins was not correlated with cell differentiation and Dukes stage (P > 0.05). Patients with MRP-positive tumours had shorter survival than MRP-negative patients (P < 0.05). No such correlation was found for LRP expression, nor was found between MRP and LRP expression. CONCLUSION: Positive MRP expression in rectal carcinoma appears to be an independant factor of prognostic significance. To examine its expression may help guide rational comprehensive therapy of rectal carcinoma.

Adult↗