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Biomedical subjects

C Xu

Publications and source records attributed to C Xu.

At least 253 records · Page 14Linked to original sources
PubMed1996

Fluoroquinolone action in mycobacteria: similarity with effects in Escherichia coli and detection by cell lysate viscosity.

Fluoroquinolones are potent antibacterial agents that are being used as therapeutic agents for the treatment of multidrug-resistant tuberculosis. To better understand fluoroquinolone action in mycobacteria, the effects of ciprofloxacin were examined. DNA synthesis was inhibited rapidly in Mycobacterium smegmatis, DNA cleavage was readily observed by an empirical assay of cell lysate viscosity, and cell growth was blocked. These data are explained by the formation of gyrase-DNA-ciprofloxacin complexes that block replication fork movement. The bactericidal action of ciprofloxacin against M. smegmatis, Mycobacterium bovis BCG, and Escherichia coli occurred more slowly in cells with longer doubling times. The bactericidal effect against M. bovis BCG was partially blocked by pretreatment with chloramphenicol, an inhibitor of protein synthesis, and by very high concentrations of ciprofloxacin itself. Similar responses occur when E. coli is treated with ciprofloxacin. These similarities between E. coli and mycobacteria indicate that results from extensive fluoroquinolone studies with E. coli can be applied to mycobacteria. A simple viscometric assay of DNA cleavage is described. The assay is expected to be useful for screening new fluoroquinolone derivatives for increased effectiveness against clinically important bacteria.

Anti-Infective Agents↗
PubMed1996

Effects of growth factors and interleukin-1 alpha on proteoglycan and type II collagen turnover in bovine nasal and articular chondrocyte pellet cultures.

The aim of this study was to investigate the effects of insulin-like growth factor-I, transforming growth factor-beta (TGF-beta), and interluekin-1 alpha (IL-1 alpha) on the deposition and degradation of a cartilage-like matrix in high-density pellet cultures of adult bovine chondrocytes. Proteoglycan was determined by toluidine blue staining and colorimetric assay. Type II collagen was determined by immunohistochemical staining and its unwinding in situ by a recently developed immunoassay. Bovine nasal chondrocytes cultured as pellets deposited a well-organized extracellular matrix of proteoglycan and type II collagen. Insulin-like growth factor-I (2-10 ng/ml) increased the synthesis and incorporation into the matrix of both these proteins. TGF-beta (2-10 ng/ml) also increased proteoglycan synthesis. However it inhibited proteoglycan deposition, presumably through increased degradation of the molecule, as shown by increased release of aggrecan fragments into the tissue culture medium. TGF-beta had no effect on type II collagen deposition. In pellet cultures of bovine nasal or articular chondrocytes, 20 ng/ml IL-1 alpha induced a significant degradation of both proteoglycan and type II collagen. The effect on collagen clearly involved proteolytic cleavage of its triple helix because there was an increase in the proportion of unwound type II collagen in the matrix, as well as a loss of total type II collagen. In explant cultures of intact bovine articular cartilage, incubation with 50 ng/ml IL-1 alpha stimulated significant degradation of the proteoglycan but no degradation of the type II collagen. These results demonstrate that although the articular chondrocytes are capable of degrading type II collagen when isolated, they do not do so in situ, presumably because of some inherent property of the mature extracellular matrix. This study demonstrates the utility of pellet cultures when investigating chondrocyte-mediated turnover of cartilage matrix and its modulation by cytokines and growth factors.

Animals↗
PubMed1996

Ongoing mutation in MALT lymphoma immunoglobulin gene suggests that antigen stimulation plays a role in the clonal expansion.

Indirect antigenic stimulation by H. pylori-specific T cells is implicated in the development of low-grade gastric lymphoma of mucosa-associated lymphoid tissue (MALT), however, the role of direct antigen stimulation is unknown. To study the role of direct antigen stimulation in MALT lymphomagenesis and its relationship with the pathogenesis of distinct pathological lesions, which represent different stages of the tumour progression, we cloned and sequenced the rearranged immunoglobulin (Ig) heavy chain gene in three low-grade (two from the lung, one from the stomach) and one high-grade (from the stomach) cases. In the low-grade gastric case, we studied the Ig sequence in primary as well as its disseminated and recurrent tumours. In the high-grade gastric case, we analysed the Ig sequence in tumour cell populations microdissected from the residual diffuse low-grade lesions, diffuse high-grade areas from follicles colonized by high-grade blasts. Compared with the published germline sequences, the heavy chain variable (VH) genes of three MALT lymphomas, in which the putative germline was identified, contained frequent somatic mutations, showing a much higher ratio of replacement/silent mutations in the complementarity determining regions (CDRs) than the framework regions (FRs). Ongoing mutation as indicated by intraclonal variation of the Ig sequence clearly existed in low-grade tumour including its dissemination and recurrence, but was not evident in high-grade tumour cell populations including those microdissected from independent colonized follicles. In addition, the germlines of VH genes used by the three MALT lymphomas are frequently found in autoreactive antibodies. Our results suggest that MALT lymphoma derives from postgerminal centre memory B cells, possibly autoreactive B cell clones, and that direct antigen stimulation may play an important role in the clonal expansion of low-grade MALT lymphoma.

Animals↗
PubMed1996

Modeling of the pH dependence of the binding of WIN 35,428 to the dopamine transporter in rat striatal membranes: is the bioactive form positively charged or neutral?

Cocaine and its phenyltropane analogs, including 2beta-carbomethoxy-3beta-(4-fluorophenyl) tropane can exist in either the cationic or the neutral form, with the proportion of each form determined by the pKA and ambient pH. It is unknown which form is the active form for binding to the dopamine transporter. Our study examines the following models for the pH dependency of [3H]2beta-carbomethoxy-3beta-(4-fluorophenyl) tropane binding to the dopamine transporter in rat striatal membranes: 1) pH does not affect the binding affinity of the ligand for the dopamine transporter, and the observed binding is a function only of the concentration of the active form; and 2) pH affects the binding affinity of the ligand for the transporter, and changes in this affinity as well as in the concentration of the active form of the ligand in the medium contribute to the observed binding changes upon varying pH. For each model, predictions are formulated for the case that either the cation, neutral base, or both are the active form, and these predictions are compared with the experimental data obtained over a pH range of 6 to 9.5. Observations for 2beta-carbomethoxy-3beta-(4-fluorophenyl) tropane, which can be both in the cationic and neutral form, are compared with those for cocaine methiodide, which is permanently cationic, and benzocaine, which is permanently neutral. Consonant with all data is a simple model in which the cationic and neutral form have similar binding activity and binding changes as a function of pH are caused by changes at the level of the transporter rather than the ligand.

Animals↗
PubMed1996

[Analysis of 106,272 cases of postterm pregnancy in China].

106272 cases of postterm pregnancy in 945 hospitals in China during the period from Oct. 1986 to Sept. 1987 were surveyed, the overall incidence rate was 85.48/1000. Provincially, the highest two rates were 127.36/1000 and 120.92/1000 in Jilin and Shandong provinces respectively, and the lowest two rates 53.98/1000 and 61.38/1000 in Xizang and Qinghai provinces respectively. The perinatal mortality was 27.90/1000 (corrected 12.49/1000). The incidence of macrosomia (89.50/1000) in postterm pregnancy was twice as much as that in term delivery. Postterm pregnancy was more frequent in pregnant women of 20-34 years old,and of 42 weeks' gestation. The incidence malformations in postterm pregnancy was 154.13 per ten thousand, in which the frequency of malformations associated with low birth weight was three times that associated with macrosomia.

Adult↗
PubMed1996

[Epidemiology of gastroschisis in China].

OBJECTIVE: To study the clinical and epidemiologic characteristics of perinates with gastroschisis (GA) in China. METHODS: The birth defects monitoring program was undertaken in 945 hospitals from 29 provinces, cities and autonomous regions of China. Data about perinates including intrauterine death and stillbirth from 28 weeks of gestation to a period of 7 days after birth was collected through the medical records between October 1986 and September 1987. RESULTS: A total of 194 cases with GA was found in 1243284 perinates monitored. The incidence of GA in China varied from 0.4 to 3.4 with a mean of 1.6 per 10,000. The highest prevalence was in Shandong province (3.4/10,000) which was significantly higher than the average (P < 0.01). The prevalence of GA perinates with low birth weight was higher than that with normal birth weight (1.6 vs 0.6 per 10,000, P < 0.01), as well as that in the rural area higher than in the urban area (2.5 vs 1.1 per 10,000, P < 0.01). 70.6% of the cases with GA were accompanied with other major defects. The overall perinatal mortality rate (PMR) of GA was 91.8%. PMR of GA with other birth defects (95.6%) was significantly higher than that of GA only (82.5%, P < 0.01). Only 15% of GA were diagnosed before birth. CONCLUSIONS: GA was a serious malformation. Cases with GA had high PMR and low detection rates in prenatal diagnosis, and most often accompanied with multiple defects.

Abdominal Muscles↗
PubMed1996

[Accelerated streptokinase dose regimens for coronary thrombolysis].

Forty patients entering our hospital up to 12 hours (5.1 +/- 2.8 hours) after the onset of definite acute myocardial infarction were treated with accelerated streptokinase dose regimens (1.5 million U/30 min) intravenously. The reperfusion rate of infarct-related arteries determined by clinical evidence of reperfusion was 77.5% (31/40). There was significant difference in reperfusion rates: 89.3% (25/28) among patients within 6 hours versus 50% (6/12) among patients within 6-12 hours after the onset of chest pain. Five cases (12.5%) experienced mild bleeding complications. One patient had chill. Three patients (7.5%) had hypotension (BP < or = 10.7/6.67 kPa, 1 kPa = 7.5 mmHg). The 5 week mortality was 2.5% (1/40). In conclusion, intravenous accelerated streptokinase dose regimen for coronary thrombolysis seems to improve reperfusion rate markedly without increasing adverse events such as allergic reactions, severe bleeding and hypotension.

Adult↗
PubMed1996

[Study of heterogeneity in DNA ploidy and its clinical-pathological significance in esophageal squamous cell carcinoma].

In order to investigate the intratumoral DNA ploid heterogeneity in esophageal squamous cell carcinoma and its significance, nuclear DNA ploidy of 80 cases of squamous cell carcinoma of the esophagus were determined for multiple samples obtained from the same tumor, using a flow cytometry (FCM) technique. The results showed that: (1) DNA indeces ranged from 7.7-1.74, and the incidence of DNA aneuploidy was 88.8% (71/80) in this series; (2) of 80 cases, (47.5% 38 cases) showed intratumoral heterogeneity in DNA ploidy (3) the heterogeneity in DNA ploidy was related to the extent of wall penetration by tumor, the incidnce of lymph node metastasis and patient's prognosis, not to histological grades and size of tumor. The results from this study indicated that DNA ploidy heterogeneity may be a exact indicator in reflecting the biological characteristics of tumor and patient's prognosis than DNA aneuploidy from single site sampling.

Adult↗
PubMed1996

A comparative study of intravenous accelerated streptokinase dose regimen with conventional dose regimen for coronary thrombolysis.

The aim of this study is to test the patency rate and safety of the accelerated streptokinase dose regimen for coronary thrombolysis compared with the conventional one. One hundred and four patients entering three hospitals up to 12 hours after the onset of definite acute myocardial infarction were randomizely treated with intravenous accelerated streptokinase dose regimen (1.5 million units/30 min) (group A, 47 cases) and conventional dose regimen (1.5 million units/60 min) (group B, 57 casese). The reperfusion rate of infarct-related arteries determined by clinical evidence of reperfusion was 76.6% (36/47) in group A VS 61.4% (35/57) in group B. There was significant difference in reperfusion rates among patients within 6 hours after the onset of chest pain: 87.9% (29/33) in group A VS 67.4 (29/43) in group B (P < 0.05). The incidence of mild bleeding, allergic reaction, hypotension was 12.8% (6/47), 4.3% (2/47), 12.8 (6/47) respectively in group A vs 21.1 (12/57), 3.5 (2/57), 17.5% (10/57) respectively in group B. Compared to conventional dose regimen, intravenous accelerated streptokinase dose regimen for coronary thrombolysis seems to improve reperfusion rate markedly without increasing adverse events such as bleeding, allergic reaction and hypotension. It suggests that accelerated streptokinase therapy deserves more extensive investigation.

Aged↗
PubMed1996

[Transfer of thymidine kinase gene of herpes simplex virus mediated by retrovirus vector into ovarian cancer cells].

OBJECTIVE: To search for the application of the retrovirus vector (RV)/herpes simplex virus type I thymidine kinase gene (HSV-tk)/ganciclovior (GCV) gene therapeutic system in the treatment of ovarian cancer. METHODS: Two kinds of vector-producing cells (VPC) which can produce retrovirus vectors constructed to contain neoR gene and two kinds of HSV-tk genes (marked as "HSV-tka" and "HSV-tkc) were employed to transfer those genes into ovarian cancer AO, 3AO cell lines. And the response of those anti-G418 clones to GCV therapy was observed. RESULTS: In the transduction to AO cells, the vector titer of the VPC/HSV-tkc culture was 9.3 x 100,000 cfu/ml, and there were 263 anti-G418 clones in the 25 cm2 cell culture flask in which 1:1,000 diluted VPC/HSV-tkc culture was added, and 235 clones in a similar flask in which 1:10 diluted VPC/HSV-tka culture was added. Further more, all of the HSV-tkc positive clones exposed to 10 micrograms/ml GCV could be eliminated, and 96% of those clones died in 5 days after GCV was used. CONCLUSIONS: The application of the RV/HSV-tk/GCV system is very promising in the gene therapy of ovarian cancer.

Antiviral Agents↗
PubMed1996

[Clinical diagnostic problems of the female coronary heart disease evaluated by coronary artery angiography].

The clinical data of 100 female cases with suspected coronary heart disease (CHD) undergoing coronary artery angiography (CAA) were analysed. CHD was defined as an estimated diameter stenosis of 75% and more in the main coronary arteries or coronary stenosis of 50%-75% with evidence of cardiac ischemia. Forty-eight case were confirmed as having CHD by CAA. The remaining 52 cases were confirmed as non-CHD and served as the control group, including 49 cases with normal coronary arteries and 3 cases with stenosis of less than 50% in the right coronary artery or left anterior descending artery. The risk factors of CHD and clinical characteristics of chest pain were compared for the two groups. The data demonstrated that menopause was a special risk factor for females and the incidence of CHD was increasing with aging after menopause. However, the clinical characteristics of chest pain in female CHD were usually atypical. When chest pain, whether clinically typical or atypical, were present after menopause and accompanied by evident risk factors, the probability of CHD would be high. If there was only chest pain without any risk factor after menopause, the diagnosis of CHD would be less likely.

Adult↗
PubMed1996

[A study on the effect of emodin on smooth muscle cell proliferation].

By using smooth muscle cell (SMC) culture in vitro and H3-TdR incorporation technique, we tested the effect of Emodin on SMC proliferation in three groups: (1) Normal rabbit iliac artery, (2) atherosclerotic rabbit iliac artery, (3) atherosclerotic rabbit iliac artery after PTA. These data indicated: Emodin has antiproliferative effect on SMC, which is dose dependent; it blocks the transition of SMC cycle from G0 to S. In PTA group it exerts a more significant proliferative effect than in the normal one. This is a the first report of Emodin's effect on SMC proliferation, it implies that the drug may be used clinically to prevent restenosis after PTCA.

Angioplasty, Balloon↗
PubMed1996

[Analysis of 822 infants with limb reduction defect in China].

This work is aimed at the basic condition of infants with limb reduction defect (LRD) in China. 822 cases of LRD occurring among 1,243,284 live and stillbirths of 28 or more gestation weeks in China from Oct. 1986 to Sept. 1987 were analysed. The overall prevalence of LRD was 6.6 per 10,000 ranging from 14.4 per 10,000 to 3.6 per 10,000. No sex difference was observed. The prevalence of LRD in infants with low birthweight was significantly higher than that in infants with normal birthweight (P < 0.001). Also the prevalence of LRD in rural area was higher than that in urban area (P < 0.001). Four-limb involvement was most common. The cases with only upper limb involvement (278/451, 61.6%) were significantly more prevalent than those with only lower limb involvement (173/451, 38.4%, P < 0.001), but no difference was found between the left LRD and right LRD (P > 0.05), nor was a significant difference noted between single LRD and multiple LRD. 75.8% of the infants with LRD had defects in other systems.

Abnormalities, Multiple↗
PubMed1996

[An estimate of recurrence risk for neural tube defects in China].

A retrospective survey was made for estimating the recurrence risk of neural tube defects (NTD) in 233 hospitals of China during the period from July 1990 to June 1993. A total of 2159 women who born a baby with NTD in this pregnancy were investigated. Among them, 674 had one or more previous births (total in 889 births) before this pregnancy. Of the 889 children, 61 had NTD. Thus the overall estimate recurrence risk of NTD is 6.86%. The estimate recurrence risk of NTD is correlated with the prevalence. The estimate recurrence risks are 3.70%, 4.50% and 8.32% in the low-, average and high-prevalence areas respectively. There is a high recurrence risk for the same defect (anencephaly of spina bifida or encephalocele) of the index case.

Anencephaly↗
PubMed1996

[The detection of the antibodies of human cytomegalovirus in the sera of patients with coronary heart disease].

To explore the relationship between human cytomegalovirus infection and atherosclerosis, we assayed the antibodies of human cytomegalovirus in the sera of 106 patients with coronary heart disease and 80 healthy people by indirect ELISA technique. The results showed that the positive rate of antibodies of HCMV IgG, HCMV IgM and HCMV IgA (95.3%, 12.3%, 13.2% respectively) is significantly higher than that in healthy people (85.0%, 2.5%, 3.8% respectively). Our findings indicated that HCMV infection is related to coronary heart disease. We consider that HCMV may be an etiological factor for human atherosclerosis. The periodical activation of latent HCMV may play a role in atherogenesis.

Adult↗
PubMed1996

Inhibitory effect of tetrahydropalmatine on calcium current in isolated cardiomyocyte of guinea pig.

AIM: To study the effect of tetrahydropalmatine (THP) on calcium channels in ventricular single cells of guinea pig heart. METHODS: Patch-clamp technique (whole cell recording) was used to observe calcium current in ventricular myocytes. RESULTS: THP decreased ICa in ventricular myocytes with a dose and frequency-dependent manner. THP (0.1, 1, and 10 mumol.L-1) decreased ICa from 1.15 +/- 0.22, 0.91 +/- 0.18, and 1.60 +/- 0.42 nA (control) to 0.9 +/- 0.21 (P < 0.01), 0.56 +/- 0.21 (P < 0.01), and 0.83 +/- 0.21 nA (P < 0.05), respectively, number of cells is five in each group (n = 5), and the rates of the depression of ICa were 22%, 38%, and 48%, respectively. The effect was easily reduced by washing the cell with the Tyrode's solution. The current-voltage relation curve showed that the potential producing peak value of ICa was 0 mV at which THP had the most markedly inhibited action on ICa. When the stimulating frequency was changed, ICa varied in a frequency-dependent manner 5 min after THP was given, and the inhibition of THP was stronger at 2 Hz than that at 0.1 Hz. CONCLUSION: THP possessed a Ca2+ channel blocking effect.

Action Potentials↗