Biomedical subjects

X Tian

Publications and source records attributed to X Tian.

At least 73 records · Page 4Linked to original sources

PubMed1999

Characterization of two novel haloalkaliphilic archaea Natronorubrum bangense gen. nov., sp. nov. and Natronorubrum tibetense gen. nov., sp. nov.

Two haloalkaliphilic archaea were isolated from a soda lake in Tibet. The two strains, designated A33T and GA33T, were Gram-negative, pleomorphic, flat, non-motile and strictly aerobic. Growth required at least 12% NaCl. Growth was between pH 8.0 and pH 11 with an optimum at pH 9.0-9.5. Cells were chemo-organotrophic. Polar lipids were C20-C25 derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate. The nucleotide sequences of the 16S rRNA genes from the two strains were obtained by the analysis of the cloned rDNAs. On 16S rRNA phylogenetic trees, the two strains formed a monophyletic cluster. They differed from their closet neighbours, Halobacterium trapanicum and Natrialba asiatica, in polar lipid composition, as well as physiological and phenotypic characteristics. DNA-DNA hybridization indicated that the two strains belonged to different species of the same genus. The results indicated that the strains A33T and GA33T should be classified in a new genus Natronorubrum gen. nov. as Natronorubrum bangense sp. nov. (strain A33T) and Natronorubrum tibetense sp. nov. (strain GA33T).

Archaea↗

PubMed1999

Myofibroblast proliferation, fibrosis, and defective pancreatic repair induced by cyclosporin in rats.

BACKGROUND: Full recovery is always achieved after caerulein induced pancreatitis. Cyclosporin stimulates transforming growth factor beta (TGF-beta) and may interfere with pancreatic regeneration. AIM: To investigate the effects of cyclosporin after caerulein induced pancreatitis or after caerulein injury. METHODS: Protocol A: rats received cyclosporin daily (20 mg/kg) and caerulein pancreatitis was induced on days 2 and 8. Protocol B: six courses of caerulein pancreatitis were induced at weekly intervals. Cyclosporin was administered on induction and the day before. Rats recovered for two weeks before being killed. Control groups received saline, cyclosporin, or caerulein alone. RESULTS: Protocol A: plasma TGF-beta1 and tissue collagenase rose after pancreatitis but decreased towards baseline values on day 15, matching a low collagen content. Morphology disclosed minimal inflammatory infiltration and some interstitial cells immunoreactive for smooth muscle alpha-actin (SMA). TGF-beta1 increased, and remained high in cyclosporin treated groups (cyclosporin alone and cyclosporin plus caerulein). Rats treated with cyclosporin and caerulein showed severe pancreatic weight reduction, abundant inflammatory infiltrates, increased SMA immunoreactive interstitial cells, high collagen content, and delayed collagenase response. No SMA immunoreactive cells were detected in normal rats. Cyclosporin alone also increased SMA immunoreactive cells, despite the absence of inflammatory infiltration and fairly conserved pancreatic structure. Protocol B: the combined pulse treatment induced appreciable collagen deposition and resulted in a smaller pancreas than controls. Morphological examination showed atrophy, fibrosis, fibroblast proliferation, and mononuclear infiltrates. CONCLUSION: Cyclosporin greatly distorts pancreatic repair, transforming caerulein induced pancreatitis into a fibrotic chronic-like disease. The mechanism involves TGF-beta, myofibroblasts, and defective collagenase activation.

Actins↗

PubMed1999

Importance of glucose-6-phosphate dehydrogenase activity in cell death.

The intracellular redox potential plays an important role in cell survival. The principal intracellular reductant NADPH is mainly produced by the pentose phosphate pathway by glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme, and by 6-phosphogluconate dehydrogenase. Considering the importance of NADPH, we hypothesized that G6PDH plays a critical role in cell death. Our results show that 1) G6PDH inhibitors potentiated H2O2-induced cell death; 2) overexpression of G6PDH increased resistance to H2O2-induced cell death; 3) serum deprivation, a stimulator of cell death, was associated with decreased G6PDH activity and resulted in elevated reactive oxygen species (ROS); 4) additions of substrates for G6PDH to serum-deprived cells almost completely abrogated the serum deprivation-induced rise in ROS; 5) consequences of G6PDH inhibition included a significant increase in apoptosis, loss of protein thiols, and degradation of G6PDH; and 6) G6PDH inhibition caused changes in mitogen-activated protein kinase phosphorylation that were similar to the changes seen with H2O2. We conclude that G6PDH plays a critical role in cell death by affecting the redox potential.

3T3 Cells↗

PubMed1999

Studies on renin-2 gene in transgenic rats.

OBJECTIVE: To determine the function of, in vivo, renin and its role in the pathogenesis of hypertension. METHODS: A renin-2 gene restriction map was constructed by endonuclease digestion and Southern blotting hybridization. Transgenic rats were produced via microinjection method. RESULTS: The 24 kb fragments containing mouse full-length ren-2 and its flanking sequence were cleaved by single enzymes (EcoR I, Kpn I and BamH I) and combined enzymes (EcoR I/Kpn I, Kpn I/BamH I and BamH I/EcoR I), respectively. The digests were electrophoresed in 0.8% agarose plates and transferred onto NC membranes. Radioactive 735 bp and 1400 bp probes obtained from half and full-length renin-1 cDNA were used in southern blotting hybridization. According to the electrophoresis and hybridization patterns, a ren-2 restriction map was constructed. 1603 fertilized rat ova after injection with purified 24 kb renin-2 gene were implanted into the oviducts of 81 pseudopregnant recipients in about 20 ova per female rat. 306 progenies were obtained from 50 foster mothers (average of pregnancies was 56.6%). 248 survived pups were identified by PCR analysis and Southern hybridization, and eight positive rats were found to be the transgenic rats (founder, F). All of them carried long fragments (24 kb) of renin-2 gene with normal blood pressure. Preliminary breeding and screening were carried out in the founder. Total survival pups (17.8%) and overall efficiencies (1%) were harvested as the same as those reported in the literatures. A systemic observation and the problems occurred during production of transgenic rats were also described besides the technique procedure used in this study. CONCLUSIONS: Mapping of full-length murine ren-2 can be used in investigation of the structure and function of the gene. The results denoted that the ren-2 transgenic rats were successfully established in this study and the technique used in the production of transgenic rats was proved to be valid in leading to wide-spread application of transgenic technique to many other related researches.

Animals↗

PubMed1999

Urinary cross-linked N-telopeptides of type I collagen and bone metabolic diseases.

OBJECTIVE: To evaluate the type I collagen cross-linked N-telopeptide (NTx) levels in human urine as an indicator of bone resorption rate in different ages, sex and in bone metabolic diseases. METHODS: Urinary NTx was determined by immunoassay in 591 Beijing healthy subjects aged from 0 to 86 years and 379 patients with bone metabolic diseases. RESULTS: The levels of urinary NTx were significantly higher in children than in adults (P < 0.001) and higher in boys than in girls (P < 0.01) and increased 1.4-2.2 times in postmenopausal females than in men and premenopausal women. Urine NTx had a positive linear correlation with urine HOP/Cr (r = 0.778, P < 0.01) and Ca/Cr ratio (r = 0.320, P < 0.01), and a negative linear correlation with age (r = -0.523, P < 0.01) and lumbar spine BMD (r = -0.426, P < 0.01). The levels of urine NTx increased for 3.6 times in pregnancy, 1.5 times in osteoporosis, 1.9 times in fragility fracture, 3.6 times in chronic renal failure, 2.1 times in rickets and 7.2 times in multiple myeloma compared to age matched controls. CONCLUSIONS: NTx in urine is a specific and sensitive indicator of bone resorption and is able to distinguish normal premenopause from late osteoporotic patients. NTx could be used as diagnostic information about metabolic bone diseases, and to monitor antiresorptive therapy.

Adolescent↗

PubMed1999

Relationship between serum antisperm antibodies and anticardiolipin antibodies and clinical pregnancy outcome in an in vitro fertilization and embryo transfer program.

OBJECTIVE: To study the influence of maternal immunological factors on clinical pregnancy outcome in an in vitro fertilization and embryo transfer (IVF-ET) program. METHODS: One hundred and fifty IVF-ET treatment cycles from November 1995 to November 1996 were studied. The indication for IVF-ET treatment was bilateral blocked tubes. Serum antisperm antibodies and anticardiolipin antibodies were measured using enzyme-linked immunosorbent assay (ELISA). Cleavage rate and successful pregnancy rate in relation to antibody status of infertile women after IVF-ET treatment were assessed. RESULTS: Lower cleavage rate (64.2% +/- 32.1%) was found in 44 cycles of antisperm antibody seropositive women, compared with 84.8% +/- 18.7% in 106 cycles of seronegative women (P < 0.05). The clinical pregnancy rate was 31.8% in antisperm antibody-positive cycles and 20.8% in negative cycles (P > 0.05). The abortion rates of the two groups were similar (P > 0.05). Lower pregnancy rate (9.5%) was found in 21 cycles of serum anticardiolipin antibody-positive group, compared with 26.3% in 129 cycles of seronegative women (P < 0.05). Of patients with bio-chemical pregnancy and no pregnancy, 20.0% and 16.2%, respectively, had seropositive anticardiolipin antibody, compared with 5.6% of patients with clinical pregnancy (P < 0.05). CONCLUSION: Serum immunological factors may play a part in clinical pregnancy outcome in IVF-ET.

Adult↗

PubMed1999

Modulation of in vivo granuloma formation related to regulation of in vitro IFN-gamma and IL-4 expressions in experimental schistosomiasis japonica.

OBJECTIVE: To find out relationship between the in vitro schistosome egg antigen (SEA) stimulated IFN-gamma and IL-4 mRNA expressions and the in vivo SEA elicited granulomatous responses, the transcriptions of IFN-gamma and IL-4 gene were investigated in the spleen of BALB/c mice infected with Schistosoma japonicum (S. japonicum). METHODS: Spleens were removed at 0, 3, 5, 8, and 10 and 12 weeks after infection and the spleen cells were incubated in the presence of SEA. The extracted RNA was analyzed for IFN-gamma and IL-4 mRNA by reverse transcription PCR (RT-PCR). Newly-formed liver granulomas were measured. RESULTS: The study revealed that no detectable IFN-gamma and IL-4 mRNA RT-PCR products were found in SEA treated spleen cells from uninfected, or 3-week infected mice, whereas IL-4 mRNA was found to be expressed in 5- and 8-week infected mice, and an appreciable enhanced expression of IL-4 mRNA was observed in SEA stimulated spleen cells at 8-week infection than at 5-week infections. However, SEA could not induce IFN-gamma and IL-4 mRNA transcription in 10- and 12-week infected mice, indicating the modulated expression of IFN-gamma and IL-4 mRNA. CONCLUSION: The significant changes of IL-4 mRNA expression in SEA stimulated spleen cells during S. japonicum infection were coincident with SEA elicited granuloma formation and modulation in vivo.

Animals↗

PubMed1999

[Preparation of monoclonal antibodies to human vascular endothelial growth factor(VEGF121) and identification of its expression on gastric carcinoma cell line MGC803].

OBJECTIVE: To further elucidate the source of VEGF in solid tumors. METHODS: Traditional hybridoma technology was used to prepare VEGF monoclonal antibodies (McAb); it's activity was measured by 3H-TdR incorporation on human umbilical vein endothelial cells (HUVEC). VEGF gene was amplified by PCR with cDNA as template from MGC803 cell lines. The PCR products were cloned into fusion protein prokaryotic expression vector PGEX2T which expressed in E. coli XL-1 blue. Western blot analysis was used to identify expression of VEGF. RESULTS: The McAbs could specifically bind to VEGF in ELISA. One of the McAbs(5C5) could neutralize the mitogenic activity of VEGF121 on HUVEC in a dose-dependent manner. The VEGF gene fragment obtained from RT-PCR cloned to PGEX2T vector expressed a protein product which reacted specifically with McAb 5C5. CONCLUSION: Gastric carcinoma is shown to express VEGF. It may be a major source of VEGF in human solid tumor. Monoclonal antibody against VEGF may be of value in the treatment of cancer.

Animals↗

PubMed1999

[Endoscopic treatment of sphenoidal and ethmoidal mucoceles].

OBJECTIVE: To evaluate endoscopic surgery for sphenoidal and ethmoidal mucoceles. METHOD: Seventeen patients diagnosed as having paranasal sinus mucoceles underwent attempted endoscopic marsupialization between 1989 and 1995. Ten of the mucoceles were in the sphenoid sinus, seven in the ethmoid sinus. Postoperative endoscopic follow-up period varied from 3 to 9 years. RESULT: All the sphenoidal and ethmoidal mucoceles were satisfactorily approached endoscopically. Postoperative endoscopic examination manifested all the operating cavity was satisfactorily marsupialized. The symptoms were improved or relieved in 15 patients. None of the patients undergoing endoscopic surgery had significant complications. CONCLUSION: Our results show that endoscopic surgery seems to be a safe, valuable way for management of sphenoidal and ethmoidal mucoceles.

Adult↗

PubMed1999

Expression of Plasmodium falciparum-infected erythrocyte membrane protein from cerebral malaria patients.

AIM: To provide theoretical evidence for studying the molecular pathogenesis of human cerebral malaria. METHODS: The expressions of Plasmodium falciparum erythrocyte membrane protein 1(PfEMP1) on the surface of parasitized erythrocyte (PE) specimens from 19 cases of cerebral malaria patients in Yunnan Province were quantitatively analyzed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) technique. 43 patients of falciparum malaria, 9 patients of vivax malaria and 6 healthy controls were also investigated. RESULTS: The expressions of higher molecular mass (Mr) 260-320 kDa forms of PfEMP1 were found on PE from cerebral malaria patients. By contrast, the expression of PfEMP1 and P. vivax erythrocyte membrane protein (PvEMP1) on PE from falciparum malaria patients and vivax malaria patients had a PfEMP1 with Mr 240 kDa and a PvEMP1 with Mr 180 kDa band, respectively. Healthy controls expressed an EMP of Mr 140 kDa. CONCLUSION: The binding of 260-320 kDa PfEMP1 proteins expressed on PE from cerebral malaria patients to diverse receptor molecules on the endothelial cell(EC) of the cerebral microvessels such as CD36, thrombospondin (TSP), intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), endothelial leukocyte adhesion molecule 1(ELAM-1) and chondroitin sulfate A (CSA) might be the molecular basis for the pathogenesis of cerebral malaria.

Adolescent↗

PubMed1999

[Establishment of a rabbit model of Acanthamoeba keratitis].

AIM: To establish an animal model of Acanthamoeba keratitis. METHODS: Six New Zealand white rabbits were each injected intrastromally with Acanthamoeba suspension 3 days after subconjunctival injection with dexamethasone. RESULTS: All of the 6 rabbits developed keratitis. Acanthamoeba protozoa were identified by the methods of corneal scraping with 10% potassium hydroxide wet mount examined under microscope, corneal protozoa culture and pathological section examination. CONCLUSION: A rabbit model of Acanthamoeba keratitis was established.

Acanthamoeba Keratitis↗

PubMed1999

[Isolated sphenoid sinus disease].

OBJECTIVE: The purpose of this study is to review isolated sphenoid sinus disease, to establish correct diagnosis and to treat it effectively in the future. METHOD: 26 patients underwent endoscopic surgery, in which 20 sphenoid sinus mucocoeles were removed and 6 sphenoid sinuses were explored. 3 sphenoid sinus mucocoeles were removed by external approach, 1 patient underwent skull base surgery and decompression of optic nerve. RESULT: 24 patients were free from disease postoperatively within 0.5-4 years follow-up, 2 patients underwent re-operation because of recurrence, 1 patient was undergoing radiotherapy, 3 patients could not contact. CONCLUSION: This study shows that CT not only makes contribution to establish correct diagnosis but also plays an important role in surgery of isolated sphenoid sinus disease. Endoscopic surgery is valuable in treatment for benign disease of sphenoid sinus.

Adolescent↗

PubMed1999

[Transmission grating spectrograph for soft X-ray spectrum measurements with a pre-optics].

A novel diffraction spectroscopic instrument consisting of a large area transmission grating and a grazing-incidence pre-optics comprising of a toroidal mirror, a slit and a cylindrical mirror has been implemented. A nearly perfect stigmatism and a medium spectral resolution are due to the separation of the focusing and dispersing function. The experimental results show that it is possible to construct large area transmission grating spectrograph with high collecting efficiency and good spatial resolution.

English Abstract↗

PubMed1998

Importance of glucose-6-phosphate dehydrogenase activity for cell growth.

The intracellular redox potential, which is determined by the level of oxidants and reductants, has been shown to play an important role in the regulation of cell growth. The principal intracellular reductant is NADPH, which is mainly produced by the pentose phosphate pathway through the actions of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway, and by 6-phosphogluconate dehydrogenase. Previous research has suggested that an increase in G6PD activity is important for cell growth. In this article, we suggest that G6PD activity plays a critical role in cell growth by providing NADPH for redox regulation. The results show the following: 1) inhibition of G6PD activity abrogated growth factor stimulation of [3H]thymidine incorporation in all cell lines tested; 2) overexpression of G6PD stimulated cell growth, as measured by an increase in [3H]thymidine incorporations as compared with cells transfected with vector alone; 3) inhibition of G6PD caused cells to be more susceptible to the growth inhibitory effects of H2O2; 4) inhibition of G6PD led to a 30-40% decrease in the NADPH/NADP ratio; and 5) inhibition of G6PD inhibited cell anchorage and significantly decreased the growth-related stimulation of tyrosine phosphorylation.

3T3 Cells↗

PubMed1998

Response time of myocardial oxygen consumption to cardiac work jumps at 28 degrees C varies with exogenous carbon substrate.

In isolated rabbit heart perfused with hemoglobin-free Tyrode's solution at 28 degrees C the response time of myocardial oxidative phosphorylation to steps in heart rate, which is about 8 s, is decreased by about 2.5 s when lactate of pyruvate are given as exogenous carbon substrate. A hypothesis that may explain the decrease in response times is that glycolytic buffering in compartments near the energy consuming ATPases delays the transport of the energetic signal between sites of ATP consumption and the mitochondria. Pyruvate inhibits this glycolytic buffering, which would explain the faster response time. Whatever the mechanism may be, the type of exogenous substrate available to the heart has a major effect on the speed of response of oxidative phosphorylation to quick changes in cardiac workload.

Animals↗

PubMed1998

Superoxide dismutase-dependent, catalase-sensitive peroxides in human endothelial cells infected by Rickettsia rickettsii.

The generation and intracellular accumulation of reactive oxygen species have been shown to be associated with the infection of human umbilical vein endothelial cells (HUVEC) by Rickettsia rickettsii. In response to the oxidant superoxide, the activity of the enzyme superoxide dismutase (SOD) increases following infection by this obligate intracellular bacterium. Other oxidants which are capable of oxidizing the fluorescent probe 2',7'-dichlorofluorescin (DCFH) also accumulate intracellularly within infected cells. In the study reported here, we show that (i) an inhibitor of SOD, diethyldithiocarbamic acid, reduces the observed rise in SOD activity in infected cells by 40 to 60% and at the same time reduces the degree of intracellular oxidation of DCFH; (ii) catalase-sensitive peroxides can be detected in supernatants of R. rickettsii-infected cells shortly after rickettsial exposure; and (iii) fluorescence-activated cell sorter analysis demonstrates significant intracellular oxidant activity in infected cells within 5 h after exposure to R. rickettsii. The results of these experiments indicate that hydrogen peroxide is a major oxidant associated with infection of HUVEC by R. rickettsii and that intracellular oxidant activity sensitive to SOD inhibition is detectable early and prior to significant rickettsial multiplication and much earlier than the ultrastructural manifestations of cell injury seen by electron microscopy.

Catalase↗

PubMed1998

Preparation and blood compatibility of new silica-chitosan hybrid biomaterials.

The development of new materials containing both organic and inorganic structures is of great interest with respect to achievement of obtaining the special properties, and the solgel process has provided new opportunities for making such materials. In this paper, new silica-chitosan hybrid biomaterials were produced by this technique, using biopolymer chitosan and its heparin-like derivative as the organic species to be incorporated into the silicon alkoxide (TEOS) based network. All the samples made were in form of thin, flexible films with optical clarity. Microphase separated structure was observed in the hybrid surface, with hydrophobic SiO2 and hydrophilic chitosan interleaved. These hybrid materials displayed good blood compatibility in comparison with their single component systems.

Biocompatible Materials↗

PubMed1998

HLA-DRB1 genes in 5 rheumatic disease multi-case families.

OBJECTIVE: To detect HLA-DRB1 (DR1-10) alleles in 5 families with multi-case rheumatic diseases, and to study the possible influence of DRB1 genes in the pathogenesis of rheumatic diseases. METHODS: Sequence-Specific Primer PCR (PCR-SSP) method was used to examine HLA-DRB1 alleles. Totally 36 members of 5 families and 166 healthy people were involved in this study. The results were assessed by Chi-square test. RESULTS: The HLA-DRB1 allele frequency in the patients and their relatives was similar. No significant difference was found. But DR4 allele frequency in the patients (90.9%) and their relatives (68%) was much higher than that in normal controls (16.8%) and the difference was statistically significant (P < 0.0001). In family 4, two RA patients have different DRB1 alleles, while in family 5, two patients have the same DRB1 alleles, one developed SLE and the other developed RA. CONCLUSIONS: DR4 is closely related to rheumatoid arthritis. The nelatives of RA patients may be at greater risk to develop RA than individuals without family history. Some patients had the same DRB1 allele but developed different rheumatic diseases. This suggested that there might be some common pathways in genetic predisposing of rheumatic diseases. On the other hand, only a few patients with the same DRB1 allele developed rheumatic diseases during their life, so other factors besides DRB1 gene might also be involved in the pathogenesis of rheumatic diseases.

Adolescent↗