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Biomedical subjects

B Xu

Publications and source records attributed to B Xu.

At least 127 records · Page 7Linked to original sources
PubMed2000

Peroxynitrite attenuates hepatic ischemia-reperfusion injury.

In the present study, we examined the effects of peroxynitrite on reperfusion injury using a rat model of hepatic ischemia-reperfusion (HI/R). The left and median lobes of the liver were subjected to 30 min of ischemia, followed by 4 h of reperfusion. Groups A and B rats were sham-operated controls that received vehicle or peroxynitrite; groups C and D rats were subjected to HI/R and received peroxynitrite or vehicle, respectively. A dose of 2 micromol/kg body wt of peroxynitrite, diluted in saline (pH 9.0, 4 degrees C), was administered as a bolus through a portal vein catheter at 0, 60, and 120 min after reperfusion. Results showed that superoxide generation in the ischemic lobes of the liver and plasma alanine aminotransferase (ALT) activity of group C were decreased by 43% and 45%, respectively, compared with group D. Leukocyte accumulations in the ischemic lobes of liver and circulating leukocytes were decreased by 40% and 27%, respectively, in group C vs. D. The ratios of mRNA of P-selectin and intercellular adhesion molecule-1 (ICAM-1) to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA extracted from the ischemic lobes of the liver of group C were decreased compared with group D. There were no differences between the groups A and B in terms of plasma ALT activity, circulating leukocytes, superoxide generation, and leukocyte infiltration in the ischemic lobes of the liver. Moreover, hemodynamic parameters (i.e., mean arterial blood pressure, cardiac index, stroke index, and systemic vascular resistance) were not significantly different among groups B, C, and D. These results suggest that administration of peroxynitrite via the portal vein only has a local effect. Exogenous peroxynitrite at physiological concentrations attenuates leukocyte-endothelial interaction and reduces leukocyte infiltration. The mechanism of the reduction of leukocyte infiltration into ischemic lobes of the liver appears because of decreased expression of mRNA of P-selectin and ICAM-1. The net effect of administration of peroxynitrite may be to reduce adhesion molecule-mediated, leukocyte-dependent reperfusion injury.

Alanine Transaminase↗
PubMed2000

Expression of corticotropin-releasing hormone messenger ribonucleic acid in human pituitary corticotroph adenomas associated with proliferative potential.

Among the factors that promote the growth of human pituitary corticotroph adenomas (hPCAs), the proliferative potential of CRH secreted by hPCAs on these tumors is not well known. In this study, the CRH messenger ribonucleic acid (mRNA) transcripts were demonstrated on paraffin sections using the quantitative in situ hybridization method in 37 of 43 hPCAs, including 17 of 22 microadenomas, 15 of 15 macroadenomas, and 5 of 6 locally invasive adenomas according to Hardy's classification of pituitary adenomas. The more important findings were that CRH mRNA signal intensity in pituitary corticotroph adenoma cells was linearly correlated with Ki-67 tumor growth fractions (r = 0.802; P < 0.0001), and in macroadenoma and locally invasive adenoma cells it was significantly higher than in microadenoma cells (P = 0.035). On the other hand, CRH mRNA transcript accumulation was absent or negligible in 10 normal pituitary glands (P = 0.005). This is the first report of the frequent expression of CRH mRNA localized in human pituitary corticotroph adenoma cells. These results indicate that CRH from a local source of corticotroph adenoma cells not only has autocrine/paracrine functions in corticotroph adenomatous tissue, but also is an important factor associated with a proliferative potential of hPCAs.

Adenoma↗
PubMed2000

Obstetric complications and asthma in childhood.

Studies have shown that perinatal factors are associated with childhood asthma. The current analyses examined the association between obstetric complications and risk of asthma at the age of 7 years using a prospectively population-based birth cohort in northern Finland. Results indicated that obstetric complications were associated with a higher risk of asthma among children. Those children who were administered special procedures at birth, i.e., cesarean section, vacuum extraction, and other procedures, including use of forceps, manual auxiliary, and extraction breech, had an adjusted odds ratio (OR) for asthma of 1.38 (95% confidence interval [CI] 1.00-1.92), 1.32 (95% CI 0.80-2.19), and 2.14 (95% CI 1.06-4.33), respectively, as compared to children who were delivered normally. Children who had a lower Apgar score at the first and the fifth minute after birth also had a higher risk as compared to those who had an Apgar score of 9-10. The results encourage further evaluation of the association between obstetric complications and risk of asthma among children in other populations, and further exploration of possible mechanisms underlying the association.

Adult↗
PubMed2000

Immobilization of antibodies on ultraflat polystyrene surfaces.

BACKGROUND: Functional antibody surfaces were prepared on ultraflat polystyrene surfaces by physical adsorption, and the uniform distribution of monoclonal antibodies against hepatitis B surface antigen (anti-HBs) on such surfaces and the presence of dense hepatitis B surface antigen (HBsAg) particles captured by immobilized antibodies were identified. METHODS: A model polystyrene film was spin-coated directly onto a silicon wafer surface. Atomic force microscopy was used to directly monitor the immobilization of anti-HBs antibodies and their specific molecular interaction with HBsAg. Enzyme immunoassay was also used to characterize functional antibody surfaces. RESULTS: A mean roughness of 2 A for areas of 25 microm(2) was produced. We found a uniform distribution of anti-HBs antibodies on ultraflat polystyrene surfaces and the presence of dense HBsAg particles bound to such anti-HBs surfaces after incubation with HBsAg. CONCLUSIONS: This study confirmed the potential of preparing dense, homogeneous, highly specific, and highly stable antibody surfaces by immobilizing antibodies on polystyrene surfaces with controlled roughness. It is expected that such biofunctional surfaces could be of interest for the development of new solid-phase immunoassay techniques and biosensor techniques.

Adsorption↗
PubMed2000

[Multiplication of the shrimp baculovirus HHNBV with primary cell cultures from lymphoid organ of Penaeus chinensis].

The hypodermal and hematopoietic necrosis baculovirus HHNBV has been confirmed to be the causative agent for the explosive epidermic disease of farmed shrimp Penaeus chinensis since 1993. The virus was isolated and multiplied successfully in the primary cell cultures from the lymphoid organ of the shrimp. A cell monolayer was formed in three days in the medium MPS and could be maintained for 1-3 months as the medium replaced every 4-5 days. The cytopathic effect occurred in 5 days after inoculation of the tissue extract from the diseased shrimp. The transmission electron microscopy showed many rod-shaped virions of HHNBV in the nuclei of infected cells.

Animals↗
PubMed2000

No-scalpel vasectomy outside China.

Since 1985, the no-scalpel vasectomy technique has been widely used outside China. The prevalence of this technique has helped to increase the acceptability of male sterilization in many parts of the world. More than 5000 physicians in twenty-five developing countries have been trained in the no-scalpel vasectomy technique. In the United States in 1995, nearly one third of vasectomies employed the no-scalpel technique, and in the whole Northern American region, a total of 1100 doctors have been made familiar with the technique. Doctors believe that there are several advantages of the no-scalpel technique, including no incision, no stitches, faster procedure, faster recovery, less chance of bleeding, less discomfort and high efficacy. The key steps of the technique include fixation of the vas and infiltration anaesthesia of the spermatic cord, as well as grasping, delivering and isolating the vas. No-scalpel technique provides a good approach to expose the vas, in conjunction with which, different vas-end occlusion methods may be used.

Africa↗
PubMed2000

Different mechanisms mediate beta adrenoceptor stimulated vasorelaxation of coronary and femoral arteries.

AIM: To determine whether different mechanisms mediate vasorelaxation of swine coronary and femoral arteries induced by beta adrenoceptor stimulation. METHODS: The organ-bath was used to observe the tension changes in rings of coronary and femoral arteries to different concentrations of isoprenaline (ISO) after endothelium removal, nitric-oxide synthase (NOS) inhibition by L-NMMA and beta 1 and/or beta 2 adrenoceptor antagonization. RESULTS: Endothelium removal, NOS inhibition, beta 2 adrenoceptor antagonization did not change the vasorelaxation induced by ISO in coronary artery, however, abolished the vasorelaxation in femoral artery. beta 1 Adrenoceptor antagonization did not change the tension of femoral artery, but abolished the ISO induced vasorelaxation of coronary artery. CONCLUSIONS: Vasorelaxing effect of ISO in swine coronary artery is mediated through beta 1 adrenoceptor and not through L-arginine/nitric oxide pathway, however, in femoral artery, it is mediated through beta 2 adrenoceptor and L-arginine/nitric oxide pathway.

Adrenergic beta-Antagonists↗
PubMed2000

Differentiation-inducing action of 10-hydroxycamptothecin on human hepatoma Hep G2 cells.

AIM: To study the mechanism of differentiation-inducing action of 10-hydroxycamptothecin (HCPT) on human hepatoma Hep G2 cells. METHODS: The proliferating cell nuclear antigen (PCNA) expression was studied by immunocytochemical staining method. The cell cycle distribution and the wild-type protein p53 expression were measured by flow cytometry. Telomerase activity was assayed with telomeric repeat amplification protocol (TRAP). RESULTS: After treatment with HCPT at differentiation-inducing concentrations 5-20 micrograms.L-1 for 6 d, Hep G2 cells were mainly arrested at G2/M phase and the PCNA expression rate was lower than that of control cells. When Hep G2 cells grew in a medium containing HCPT 5 micrograms.L-1 for 6 d, the p53 expression level markedly increased in comparison with the control cells. The telomerase activity did not change in Hep G2 cells treated with HCPT 5-20 micrograms.L-1 for 8 d. CONCLUSION: The differentiation-inducing effect of HCPT on Hep G2 cells is related with the cell cycle arrest at G2/M phase, down-regulation of PCNA and up-regulation of wild-type protein p53.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Effects of diltiazem on down-regulation of lymphocyte beta-adrenoceptors in patients with chronic congestive heart failure.

AIM: To determine whether diltiazem could reverse down-regulation of lymphocyte beta-adrenoceptor (beta-AR) in patients with chronic congestive heart failure (CHF). METHODS: Before and after the treatment with diltiazem in CHF patients, lymphocyte beta-AR density was measured with [3H]dihydroalprenolol radioligand binding assay, levels of free cytosolic calcium ([Ca2+]i) in platelets were estimated with fluorescent indicator Fura 2-AM, plasma norepinephrine (NE) levels were measured with 125I-radioimmunoassay. RESULTS: Lymphocyte beta-AR density was lower and [Ca2+]i in platelets was significantly higher in CHF patients than those in control. Plasma NE levels were higher in CHF patients than those in control. Diltiazem therapy reduced [Ca2+]i in platelets and increased lymphocyte beta-AR density in CHF patients without significant change of plasma NE concentration. CONCLUSIONS: Diltiazem partly reversed down-regulation of lymphocyte beta-AR density in CHF patients, and this effect was not related to the level of plasma NE, and might be attributed to intracellular [Ca2+]i decrease.

Blood Platelets↗
PubMed2000

Antiangiogenic effect of alpha-anordrin in vitro and in vivo.

AIM: To study the antiangiogenic effect of alpha-anordrin (alpha-Ano), a partial antagonist of estrogen receptor. METHODS: The in vivo inhibitory effect of alpha-Ano on angiogenesis was determined by microvascular density (MVD) in tumors and the chicken chorioallantoic membrane (CAM) model. The in vitro effects of alpha-Ano on proliferation, migration, and attachment of human umbilical vein endothelial cells (HUVEC) were assessed by trypan blue exclusion, wound-induced two-dimensional migration model, and their ability to adhere to type I collagen, respectively. The possible involvement of nitric oxide (NO) in alpha-Ano antiangiogenic effect was determined by measuring NO content using fluorescent assay. RESULTS: alpha-Ano significantly inhibited the MVD in Lewis lung carcinoma model and this effect was correlated with its inhibition of the tumor growth. alpha-Ano also showed an inhibitory effect on the angiogenesis of CAM with the inhibitory rate of 53% and such action of alpha-Ano could not be blocked by simultaneous administration of 17 beta-estrodiol, a typical agonist of estrogen receptor. In vitro studies showed that alpha-ANO obviously suppressed the proliferation and migration of HUVEC, but had no obvious effect on the attachment of HUVEC to the type I collagen. Moreover, alpha-Ano significantly reduced the level of NO released by HUVEC in a dose- and time-dependent manner. CONCLUSION: alpha-Ano possesses an antiangiogenic effect, and this effect is mediated, at least in part, by reducing the NO content and subsequently inhibiting the proliferation and migration of endothelial cells.

Angiogenesis Inhibitors↗
PubMed2000

[Epidemiological aspects of the genotype of hepatitis C virus].

OBJECTIVE: To research the epidemiological characteristics of genotype of hepatitis C virus. METHODS: 107 HCV isolates from 7 cities in southern, northern and northeast of China were analyzed using PCR and second generation line probe assay (INNO-LiPA). RESULTS: The analysis of HCV genotypes showed that: 1. HCV l b was the common genotype (83 17%), however the frequency of genotype l b in northeast (72.22%) was lower than northern (87.65%, P <0.01), and the frequency of the genotype 2 was in low level (6.86%). The rate of coinfection with l b and other genotype was 10.29%. 2. The rate of infection with genotype l b in female patients was higher (93.61%) than that in male (75.0%) showing statistical significance (P <0.01). 3. In three age groups (< 30, 30 - 49 and > 50 years old) the rates of infection with genotype l b were 77.77%, 83.92% and 90.90%, respectively. 4. The detection rates of genotype l b in patients with infection period > 10 years and <10 years were 100% and 80.43% respectively (P <0.01). CONCLUSIONS: There are some relationship between HCV genotype and HCV geographic distribution, sex, age and infection period of patients.

Adolescent↗
PubMed2000

Differentiation of human hepatoma Hep G2 cells induced by 10-hydroxycamptothecin.

OBJECTIVE: To study the differentiation-inducing effect of hydroxycamptothecin (HCPT) on hepatoma Hep G2 cells. METHODS: 3-[4, 5-dimethylthial-2-yl]-3, 5-diphenyl-tetrazolinium bromide (MTT) colorimetric method was used for determining HepG2 cells viability. Alphafetoprotein (AFP) and albumin (ALB) levels were determined with Elisa Kits. RESULTS: The AFP secretion of HCPT-treated cells was reduced by 44.0%-49.2% while the ALB level was increased markedly. CONCLUSION: Hydroxycamptothecin can induce human hepatoma Hep G2 cells to differentiation.

Antineoplastic Agents, Phytogenic↗
PubMed2000

[Low-molecular-weight heparin for preventing deep-vein thrombosis after total joint arthroplasty].

OBJECTIVE: To evaluate the efficacy and safety of low-molecular-weight heparin (LMWH) in preventing deep-vein thrombosis (DVT) after total hip and knee replacement (THR, TKR). METHODS: From November 1997 to March 1999, we performed total joint replacement for 47 control patients (34 knees, 28 hips) and for 31 patients (19 knees, 17 hips) who had been given low-molecular-weight heparin for preventing deep-vein thrombosis. All patients received venography of the operated limbs after operation. RESULTS: DVT occurred in 19.4% of the LMWH patients (26.3% in TKR, 11.8% in THR) and the reduction was significant (P < 0.05) compared to the control group (48.4%, 55.9%, 39.3% respectively). The incidence of proximal DVT was also reduced significantly (P < 0.05) from 19.4% of the control group to 2.8% of the LMWH group. CONCLUSION: Low-molecular-weight heparin can significantly reduce the incidence of deep-vein thrombosis after total joint replacement.

Arthroplasty, Replacement, Hip↗
PubMed2000

[The effective dielectric function of porous SiO2 glass].

In this paper, we discussed the effective dielectric function of porous SiO2 glass with pore size 7.5 nm. We briefly discussed different formulae proposed by different theoretical models of porous systems, and compared the relationship of effective dielectric functions changing with different porosity of porous SiO2 of each formula. Through comparing the experimental spectra and the theoretical spectra of each formula, we found the equation ln epsilon e = theta 1 ln epsilon 1 + theta 2 + theta 2 ln epsilon 2 best indicates the effective dielectric function of porous SiO2. This work is helpful in selecting special absorption materials.

English Abstract↗
PubMed2000

[Open operation of the vertical condylar fracture].

OBJECTIVE: This article is mentioned to study the incidence, diagnosis, management of the vertical condylar fractures. METHODS: 11 patients, 14 cases of the vertical condylar fractures, were treated in our department between June 1997 and August 1998. All the patients were diagnosed through history, physical examination, radiographs, computed tomography scan and three-dimensional reconstruction of a computed tomography scan, treated with various surgical approaches. RESULTS: All the patients had got satisfactory postoperative result in the aspects of occlusion, degree of opening, joint noise, pain in the area of temporomandibular joint, deviation in mandibular motion and healing of the incision. CONCLUSION: Enough attention should be paid to the vertical condylar fractures. The key to a successful open operation is the correct diagnosis, the accurate reduction and the stable fixation.

English Abstract↗
PubMed1999

The chitinase PfCHT1 from the human malaria parasite Plasmodium falciparum lacks proenzyme and chitin-binding domains and displays unique substrate preferences.

Within hours after the ingestion of a blood meal, the mosquito midgut epithelium synthesizes a chitinous sac, the peritrophic matrix. Plasmodium ookinetes traverse the peritrophic matrix while escaping the mosquito midgut. Chitinases (EC 3.2.1.14) are critical for parasite invasion of the midgut: the presence of the chitinase inhibitor, allosamidin, in an infectious blood meal prevents oocyst development. A chitinase gene, PgCHT1, recently has been identified in the avian malaria parasite P. gallinaceum. We used the sequence of PgCHT1 to identify a P. falciparum chitinase gene, PfCHT1, in the P. falciparum genome database. PfCHT1 differs from PgCHT1 in that the P. falciparum gene lacks proenzyme and chitin-binding domains. PfCHT1 was expressed as an active recombinant enzyme in Escherichia coli. PfCHT1 shares with PgCHT1 a substrate preference unique to Plasmodium chitinases: the enzymes cleave tri- and tetramers of GlcNAc from penta- and hexameric oligomers and are unable to cleave smaller native chitin oligosaccharides. The pH activity profile of PfCHT1 and its IC(50) (40 nM) to allosamidin are distinct from endochitinase activities secreted by P. gallinaceum ookinetes. Homology modeling predicts that PgCHT1 has a novel pocket in the catalytic active site that PfCHT1 lacks, which may explain the differential sensitivity of PfCHT1 and PgCHT1 to allosamidin. PfCHT1 may be the ortholog of a second, as yet unidentified, chitinase gene of P. gallinaceum. These results may allow us to develop novel strategies of blocking human malaria transmission based on interfering with P. falciparum chitinase.

Acetylglucosamine↗