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Biomedical subjects

J Bai

Publications and source records attributed to J Bai.

At least 73 records · Page 4Linked to original sources
PubMed2000

Overexpression of catalase in the mitochondrial or cytosolic compartment increases sensitivity of HepG2 cells to tumor necrosis factor-alpha-induced apoptosis.

The sensitivity of HepG2 cells overexpressing catalase in either the cytosolic or mitochondrial compartment to tumor necrosis factor-alpha (TNF-alpha) and cycloheximide was studied. Cells overexpressing catalase in the cytosol (C33 cells) and especially in mitochondria (mC5 cells) were more sensitive to TNF-alpha-induced apoptosis than were control cells (Hp cells). The activities of caspase-3 and -8 were increased by TNF-alpha, with the highest activities found in mC5 cells. Sodium azide, an inhibitor of catalase, reduced the increased sensitivity of mC5 and C33 cells to TNF-alpha to the level of toxicity found with control Hp cells. Azide also decreased the elevated caspase-3 activity of mC5 cells. A pan-caspase inhibitor prevented the TNF-alpha-induced apoptosis and toxicity produced by catalase overexpression. Addition of H(2)O(2) prevented TNF-alpha-induced apoptosis and caspase activation, an effect prevented by simultaneous addition of catalase. TNF-alpha plus cycloheximide increased ATP levels, with higher levels in C33 and mC5 cells compared with Hp cells. TNF-alpha did not produce apoptosis in mC5 cells maintained in a low energy state. TNF-alpha signaling was not altered by the overexpression of catalase, as activation of nuclear factor kappaB and AP-1 by TNF-alpha was similar in the three cell lines. These results suggest that catalase, overexpressed in the cytosolic or especially the mitochondrial compartment, potentiates TNF-alpha-induced apoptosis and activation of caspases by removal of H(2)O(2).

Adenosine Triphosphate↗
PubMed2000

Characterization of anti-CCR5 ribozyme-transduced CD34+ hematopoietic progenitor cells in vitro and in a SCID-hu mouse model in vivo.

The cellular entry of HIV is mediated by the specific interaction of viral envelope glycoproteins with the cell-surface marker CD4 and a chemokine receptor (CCR5 or CXCR4). Individuals with a 32-base-pair (bp) deletion in the CCR5 coding region, which results in a truncated peptide, show resistance to HIV-1 infection. This suggests that the downregulation of CCR5 expression on target cells may prevent HIV infection. Therefore, ribozymes that inhibit the CCR5 expression offer a novel approach for anti-HIV gene therapy. To assess the effect of an anti-CCR5 ribozyme (R5Rbz) on macrophage differentiation, CD34+ hematopoietic progenitor cells were transduced with a retroviral vector carrying RSRbz and allowed to differentiate in the presence of appropriate cytokines. R5Rbz-transduced CD34+ cells differentiated normally into mature macrophages that carried CD14 and CD4 surface markers, expressed the anti-CCR5 ribozyme, and showed significant resistance to viral infection upon challenge with the HIV-1 BaL strain. Using an in vivo thymopoiesis model, the effect of RSRbz on stem cell differentiation into thymocytes was evaluated by reconstituting SCID-hu mice thymic grafts with ribozyme-transduced CD34+ cells. FACS analysis of cell biopsies at 4 and 6 weeks postengraftment for HLA, CD4, and CD8 markers showed comparable levels of reconstitution and similar percentages of subpopulations of thymocytes between grafts receiving R5Rbz-transduced and control CD34+ cells. RT-PCR assays demonstrated the expression of the anti-CCR5 ribozyme in CD4+, CD8+, and CD4+/CD8+ thymocyte subsets derived from RSRbz-transduced CD34+ cells. These results indicate that anti-CCR5 ribozyme can be introduced into hematopoietic stem cells without adverse effects on their subsequent lineage-specific differentiation and maturation. The expression of anti-CCR5 ribozymes in HIV-1 target cells offers a novel gene therapy strategy to control HIV infection.

Animals↗
PubMed2000

Cavanagh and Leclerc shape-from-shadow pictures: do line versions fail because of the polarity of the regions or the contour?

Shape-from-shadow perception fails when the contour bordering a shadowed area is reduced to a black line, and the shadow area becomes white. It might be that the polarity of the shadowed and illuminated areas has to be from dark on the shadowed side to light on the illuminated side for successful perception. Or it may be that the line, which has two contours, has one too many for shape-from-shadow processing. Alternatively, the problem might be that one of the contours of the line is incorrectly polarised. To test these explanations, three shape-from-shadow figures were prepared, each depicting the same referent--an elderly person. All three figures had two correctly polarised areas. One figure had a correctly polarised contour at the border between the areas. One had two correctly polarised contours. The other had one correctly polarised contour and one incorrectly polarised contour. The referent of the figure with one incorrectly polarised contour was the one difficult to make out. The result has implications for several theories, including an account of a demonstration by Hering involving penumbra.

Adult↗
PubMed2000

Binding of the maize cytosolic Hsp70 to calmodulin, and identification of calmodulin-binding site in Hsp70.

Using a gel-overlay technique of biotinylated calmodulin (CaM), we showed that maize cytosolic Hsp70 protein could bind to CaM in the presence of 1 mM CaCl2. The purified maize cytosolic Hsp70 inhibited the activity of CaM-dependent NADK in a concentration-dependent manner. A synthetic peptide, which possesses the 21 amino acid sequence, PRALRRLRTACERAKRTLSST, at positions 261-281 in maize cytosolic Hsp70, could associate with CaM in the presence of 1 mM calcium. The synthetic peptide inhibited CaM-dependent NADK activity and PDE activity. This indicates that the 21-amino acid sequence at positions 261-281 is the CaM-binding site. The binding of CaM to Hsp70 inhibited the ATPase activity of Hsp70. The possible regulator function of Hsp70 in cell signaling events in response to heat stress is discussed.

Amino Acid Sequence↗
PubMed2000

Xanthomonas oryzae pv. oryzae avirulence genes contribute differently and specifically to pathogen aggressiveness.

Genomic copies of three Xanthomonas oryzae pv. oryzae avirulence (avr) genes, avrXa7, avrXal0, and avrxa5, and four homologous genes, aB3.5, aB3.6, aB4.3, and aB4.5, were mutagenized individually or in combination to study the roles of avr genes in one component of pathogen fitness, i.e., aggressiveness or the amount of disease X. oryzae pv. oryzae causes in susceptible rice lines. These X. oryzae pv. oryzae genes are members of the highly related Xanthomonas avrBs3 gene family. Compared to the wild-type strain, X. oryzae pv. oryzae strains with mutations in avrXa7, avrxa5, and the four homologous genes caused shorter lesions on rice line IR24, which contains no resistance genes relevant to the wild-type strain. The contribution of each gene to lesion length varied, with avrXa7 contributing the most and avrXal0 showing no measurable effect on aggressiveness. The functional, plasmidborne copies of avrXa7, aB4.5, and avrxa5 restored aggressiveness only to strains with mutations in avrXa7, aB4.5, and avrxa5, respectively. Mutations in avrXa7 were not complemented by plasmids carrying any other avr gene family members. These data indicate that some, but not all, avr family members contribute to pathogen aggressiveness and that the contributions are quantitatively different. Furthermore, despite their sequence similarity, the aggressiveness functions of these gene family members are not interchangeable. The results suggest that selection and pyramiding resistance genes can be guided by the degree of fitness penalty that is empirically determined in avr gene mutations.

Bacterial Proteins↗
PubMed2000

Profile of maternal smokers and their pregnancy outcomes in south western Sydney.

OBJECTIVE: The prevalence of maternal smoking remains high in New South Wales. In order to better understand the profile of maternal smokers, a study has been conducted to examine the social and demographic characteristics and pregnancy outcomes of women who smoked during their pregnancy in south western Sydney. METHODS: Women and babies of a retrospective cohort of 7,191 singleton births between March 1996 and December 1998, at Liverpool Hospital were analyzed. RESULTS: The prevalence of maternal smoking for the study population was 18.8%. The study found that the sociodemographic factors, such as marital status, ethnic origin, English speaking background, working status during pregnancy, and private health insurance status were independent risk factors for maternal smoking, but maternal age was not. Women who smoked during their pregnancy had higher rates of abruptio placenta, threatened premature labour, and premature labour. The adverse neonatal outcomes due to maternal smoking were low birth weight and increased neonatal morbidity. Smoking appears to have a protective effect on pregnancy induced hypertension. CONCLUSION: The findings of this study suggests that future smoking cessation programs should pay more attention to addressing sociodemographic and cultural factors that influence the behaviour of maternal smokers.

Adolescent↗
PubMed2000

Incidence of tuberculosis among a cohort of tuberculin-positive refugees in Australia: reappraising the estimates of risk.

Estimates of the lifetime risk of tuberculosis have varied widely and may not be applicable in all current settings. The aim of this study was to measure the incidence of reactivation of latent tuberculosis in a cohort of 15,489 predominantly Southeast Asian refugees aged 12 yr and over who arrived in Sydney, Australia during the period 1984 to 1994 and who had a clear chest X-ray on arrival. Tuberculin skin test (TST) reaction size and the presence of a BCG scar were recorded at entry. Incident cases of tuberculosis, occurring before June 1998, were identified by record linkage analysis with confirmatory review of case notes. There were 122 cases of tuberculosis over an average 10.3 yr of follow-up (crude annual incidence, 76.2/100,000). There was a linear increase in risk with increasing TST reaction size above 10 mm. The risk, and the relation of risk to TST reaction size, were unrelated to BCG scar status. Among those whose initial TST reaction was >/= 15 mm, the annual incidence rate in the first 3 yr was 213 (95% CI, 150 to 300) per 100,000 person-years and in the subsequent 10 yr the rate averaged 122 (95% CI, 90 to 165) per 100,000 person-years. The observed rates are similar to those estimated in the general population of the United States in the 1950s and 1960s. Further data on the prognosis of tuberculosis and the effects of isoniazid preventive therapy in Southeast Asian migrants to Western countries are required to inform policy and practice for the prevention of tuberculosis in this population.

Adolescent↗
PubMed2000

Expression of thioredoxin and glutaredoxin, redox-regulating proteins, in pancreatic cancer.

Pancreatic cancer (pancreatic ductal carcinoma) is one of the most malignant solid tumors with poor prognosis. There is accumulating evidence that cellular reduction/oxidation (redox) status is deeply involved in the growth promotion and drug resistance of cancer cells. We therefore investigated the expression of redox-regulating proteins, such as thioredoxin (TRX) and glutaredoxin (GRX) in surgically resected pancreatic tissues and cis-diamminedichloroplatinum (CDDP)-resistant cells. Plasma levels of TRX were also measured in subjects with pancreatic diseases. Pancreatic ductal carcinoma tissues were immunohistochemically more positive for TRX (24/32 cases) and GRX (29/32 cases) than pancreatic cystadenocarcinoma or normal pancreas tissues. Plasma levels of TRX (mean +/- SD) measured by ELISA were significantly higher in patients with pancreatic ductal carcinoma (54.8 +/- 37.6 ng/ml, n = 60) than in healthy controls (24.4 +/- 12.9 ng/ml, n = 81). CDDP-resistant subclones of HeLa cells, HeLa-CP5 cells, had higher expression of TRX (1.5 fold) and GRX (1.6 fold) compared with parental HeLa cells by immunoblotting. These results indicate the possible association of TRX and GRX with malignant potential of pancreatic ductal carcinoma.

Adult↗
PubMed2000

A telemedicine management model based on message-trigger service.

A telemedicine system model, based on a message-trigger service, is described. This model distributes system applications on multiple computers and establishes a communication platform to exchange messages among all applications. By broadcasting event messages, an application is able to trigger a set of local and remote services. At the same time, a protocol for message exchange is proposed to fulfill cooperation of applications. To validate the model, a teleconsultation system is designed. The results indicate that the model has good compatibility and that the characteristics are easy to implement.

Computer Communication Networks↗
PubMed2000

Simulation evaluation of cardiac assist devices.

During past decades, various cardiac assist devices were invented. These cardiac assist devices can be classified into two categories: parallel connected or sequentially connected to the natural heart. In the past, more attention was paid to the assistance of the device provided to the failing heart and most research was conducted towards that goal. While less attention was paid to the "dose" of the assistance for rehabilitation of the natural heart. In our study, the hemodynamic effects of parallel as well as sequential cardiac assist devices are investigated in terms of the working load to the natural heart, and the oxygen supply and consumption of the natural heart. Preliminary results show that the sequential assistance could reduce the working load of the natural heart as well as increase the coronary flow. The results also indicate that the control scheme of the cardiac assist device has effect on the oxygen supply and consumption of the natural heart. There is optimal "dose" of assistance for the rehabilitation of the natural heart.

Computer Simulation↗
PubMed2000

[The advance of research for technique of fusing physiological information].

With the increase of human life's pace and people's psychological burden, the spectrum of morbidities changed, and the dynamic disease which is caused by the maladjustment between heart and body becomes the main menace to human being. Through fusing various physiological information, dynamic disease can be diagnosed effectively. The paper discussed the principle of analyzing physiological system's dynamic property and evaluating dynamically human body's health level. It emphasized on introducing the progress of foreign research, and analyzed briefly the problems needed to be dealt with and the future resrarch direction of this field.

Arrhythmia, Sinus↗
PubMed2000

Operative laparoscopy versus laparotomy for the management of ectopic pregnancy.

OBJECTIVE: To compare the surgical managements for ectopic pregnancy. METHODS: In a retrospective analysis, we examined the trend of surgical procedures and the results of different management in 149 patients. RESULTS: The change from laparotomy to laparoscopic treatment was significant. The success rates of salpingostomy and salpingectomy under laparoscopy or laparotomy were 100%. No serious complications occurred. The operation time and length of hospital stay for laparoscopic salpingostomy were shorter than those for laparotomy with salpingostomy. CONCLUSION: Laparoscopic salpingostomy and laparoscopic salpingectomy are better than laparotomy in the treatment of ectopic pregnancy.

Adult↗
PubMed2000

[Relationship between serum insulin, C-peptide in hypertension and syndrome differentiation-typing in TCM].

OBJECTIVE: To study the relationship between insulin-resistance (IR), hyperinsulinemia and TCM Syndrome Differentiation-typing. METHODS: The serum insulin, C-peptide level of the four Syndrome-types of hypertension (30 cases each type) and the control group (30 cases) were determined. RESULTS: The serum insulin level in hypertension patients were significantly higher than that of control group, and there were obvious difference among the four types of Syndrome. The following order was: The abundant phlegm-dampness type > exuberant Liver-Fire type > both Yin-Yang deficiency type > Yin deficiency and Yang-Excess type > control type. CONCLUSIONS: The Excess Syndrome was severe and deficiency Syndrome was mild in hyperinsulinemia. The pattern of change was in accordance with etiology and pathogenesis of TCM. It has the guiding significance to the clinical practice and research of TCM and integrated TCM-WM.

Aged↗
PubMed2000

[Effects of silk hydrates on the blood glucose metabolism in rats with experimental diabetes].

Male Wistar rats were divided into two groups by random. One group was injected with streptozotocin(STZ) 30 mg/kg BW via tail vein. Three weeks later, the rats were fed on diet of high fat, high sucrose and high calorie for another 8 weeks. There were 38 rats with impaired glucose tolerance and insulin level higher or equal to the control group selected as the diabetic model group. Another 36 rats not injected with STZ and fed on normal diet were selected as controls. The two groups were divided into two subgroups and fed with normal diet for another 4 weeks. The four subgroups were normal control group, normal +SH group, diabetes control group and diabetes +SH group. The rats in normal +SH group and diabetes +SH group were tube feeding every day with silk hydrate (SH) 1.0 g/kg BW for 4 weeks. The results showed that in the diabetes +SH group, the glucose tolerance, blood lipid and the predictive index of coronary heart disease were significantly improved, but no effect on their blood insulin level. There was no change in the normal +SH group. The results suggested that SH could modulate the metabolism of blood glucose and partly improve the disorder of the serum lipid of diabetic rats.

Animals↗
PubMed2000

[Mechanism of silk hydrates on modulating the blood glucose metabolism in rats with experimental diabetes].

Thirty eight adult male Wistar rats injected with streptozotocin(STZ) 30 mg/kg BW via tail vein and fed on a diet of high fat, high sucrose and high calorie for 3 weeks and then for another 8 weeks were successfully established as the diabetes model(type II diabetes mellitus). The effects of feeding silk hydrates(SH) for 12 weeks on the activities of insulin receptors and postreceptors were observed. The results showed that: 1) SH greatly improved the glucose tolerance of diabetic rats, but no effect on the secretion of insulin in rats with or without diabetes; 2) Only the low-affinity constant of insulin binding rates(K2) in skeletal muscle cell membranes of diabetic rats fed with SH were obviously increased, the high-affinity binding constant and the number of receptors were not changed; 3) the uptake of glucose in skeletal muscle of diabetic rats fed on SH was significantly increased. 4) SH partly improved the metabolism of serum lipids. The results indicated that SH could modulate the metabolism of blood glucose mainly through the mechanism on the activity of insulin postreceptor.

Animals↗
PubMed2000

[The effect of integrin-like proteins on pollen germiantion and tube growth of Nicotiana tabacum].

The effects of antiserum against human VnR integrin and integrin antagonist GRGDSP peptides on Nicotiana tabacum pollen germination and tube growth both in in vitro and in semi-vivo conditions were studied. No obvious inhibitory effects on pollen germination and tube growth in vitro were observed when anti-VnR serum or GRGDSP peptides was added to BK culture medium, but the enhancement of pollen germination and tube growth in vitro promoted by calmodulin was depressed by adding anti-VnR serum or GRGDSP peptides to BK culture medium. In addition to that, pollen germination and tube growth on stigma, as well as tube growth in styles were also inhibited at some extent by treating stigma and microinjecting GRGDSP peptides or anti-VnR serum into styles. The role of integrin-like proteins in regulation of pollen germination and tube growth in situ was discussed.

Humans↗
PubMed1999

Overexpression of catalase in cytosolic or mitochondrial compartment protects HepG2 cells against oxidative injury.

HepG2 cells were transfected with vectors containing human catalase cDNA and catalase cDNA with a mitochondrial leader sequence to allow comparison of the effectiveness of catalase overexpressed in the cytosolic or mitochondrial compartments to protect against oxidant-induced injury. Overexpression of catalase in cytosol and in mitochondria was confirmed by Western blot, and activity measurement and stable cell lines were established. The intracellular level of H(2)O(2) induced by exogenously added H(2)O(2) or antimycin A was lower in C33 cell lines overexpressing catalase in the cytosol and mC5 cell lines overexpressing catalase in the mitochondria as compared with Hp cell lines transfected with empty vector. Cell death caused by H(2)O(2), antimycin A, and menadione was considerably suppressed in both the mC5 and C33 cell lines. C33 and mC5 cells were also more resistant to apoptosis induced by H(2)O(2) and to the loss of mitochondrial membrane potential induced by H(2)O(2) and antimycin A. In view of the comparable protection by catalase overexpressed in the cytosol versus the mitochondria, catalase produced in both cellular compartments might act as a sink to decompose H(2)O(2) and move diffusable H(2)O(2) down its concentration gradient. The present study suggests that catalase in cytosol and catalase in mitochondria are capable of protecting HepG2 cells against cytotoxicity or apoptosis induced by oxidative stress.

Antimycin A↗