T cells are derived from progenitor thymocytes, of which only a minority receive the appropriate TCR signal, undergo positive selection and mature. Owing to the very short lifespan of thymocytes, the prerequisite for ...T cells are derived from progenitor thymocytes, of which only a minority receive the appropriate TCR signal, undergo positive selection and mature. Owing to the very short lifespan of thymocytes, the prerequisite for posi- tive selection is survival. TCR signal-induced Bcl-2 expression is believed to play a dominant role in the survival of positively selecting thymocytes, but how Bcl-2 is directly regulated is unknown. Here we report that the immediate early gene （IEG） c-Fos can stimulate the expression of Bcl-2, depending on a specific AP-l-binding site in the Bcl-2 promoter. In c-Fos transgenic （Fos-Tg） mice, c-Fos binds to this site and promotes the expression of Bcl-2. As a result, Fos-Tg thymocytes exhibited enhanced survival, and more mature single-positive （SP） thymocytes were generated, even on a unique TCR background. The TCR repertoire remained normal in Fos-Tg mice. Our results identified c-Fos as the mediator of the stimulatory effect of TCR signaling on Bcl-2 expression. Therefore, c-Fos, as an IEG, because of its early response ability, can quickly rescue the survival of short-lived thymocytes during positive selection. Our results provide novel insight into the mechanism regulating the survival of positively selecting thymocytes.展开更多
BACKGROUND： Both animal experiments and clinical studies have shown that basic fibroblast growth factor （bFGF） and danshen （Salvia miltiorrhiza） can exhibit protective effects on ischemia-reperfusion cerebral inj...BACKGROUND： Both animal experiments and clinical studies have shown that basic fibroblast growth factor （bFGF） and danshen （Salvia miltiorrhiza） can exhibit protective effects on ischemia-reperfusion cerebral injury. OBJECTIVE： To test whether bFGF and danshen can protect cerebral injury induced by exposure to repeated, high, positive acceleration （＋Gz） in an animal model and to analyze the possible mechanisms. DESIGN, TIME AND SETTING： Randomized controlled animal study. The experiment was performed at the Research Center for Molecular Biology, Air-force General Hospital of Chinese PLA from April to August 2000. MATERIALS： A total of 20 clean grade, healthy, Sprague Dawley rats of both genders, weighing （200 ± 15） g, were provided by our experimental animal center. Rats were randomly divided into 5 groups： the control group, ＋Gz exposure group, bFGF group, danshen group, and saline group, with 4 animals per group. bFGF （Beijing Bailuyuan Biotechnology Co. Ltd.） and danshen solution （Shanghai Zhongxi Pharmaceutical Co. Ltd.） were used. METHODS： All rats were fixed on a rotary arm of a centrifugal apparatus （2 m in radius） with their heads oriented towards the center of the apparatus. Except for rats in the control group, the value of ＋Gz exposure was ＋14 Gz with an acceleration rate of 1.5 G/s. The peak force lasted for 45 seconds. ＋Gz exposure was performed three times with intervals of 30 minutes. Rats in the control group received the same ＋Gz procedure, but the G value was ＋1 Gz. Rats in bFGF group and danshen group were intraperitoneally injected with 100 μg/kg bFGF or 15 g/kg danshen solution, respectively, at 30 minutes prior to centrifugation and immediately after centrifugation. Rats in saline group were injected with the same volume of saline. Six hours after exposure, rats were decapitated. One hemisphere was preserved in liquid nitrogen for RNA extraction and the other was processed for apoptosis detection. MAIN OUTCOME MEASURES： mRNA levels of bcl-2 and p53 were measured by semi-quantitative reverse-transcription polymerase chain reaction. Apoptotic cell death was detected by terminal deoxynuleotidyl transferase-mediated dUTP nick end labeling. RESULTS： Changes in mRNA expression of bcl-2 and p53 and apoptotic cells were observed in rat brain six hours after repeated ＋Gz exposures, bFGF and danshen were able block the changes of bcl-2 and p53 expression and inhibit apoptotic cell death. CONCLUSION： The data suggest that apoptosis and changes in bcl-2 and p53 expression in the rat brain can be induced by repeated ＋Gz exposures. Apoptosis is, therefore, one of the molecular mechanisms of brain damage induced by repeated ＋Gz exposures, bFGF and danshen were of the equal potency in preventing brain injury induced by repeated ＋Gz exposures.展开更多
To evaluate the apoptosis positivity, the expression of Bcl-2, bax proteinsin 30 patients with squamous cell cervix carcinoma before and after radiotherapy. Methods: By usingimmuno-histochemical and TDT-dUTP nick end ...To evaluate the apoptosis positivity, the expression of Bcl-2, bax proteinsin 30 patients with squamous cell cervix carcinoma before and after radiotherapy. Methods: By usingimmuno-histochemical and TDT-dUTP nick end labelling techniques, 30 cases of squamous cell cervicalcarcinoma were analyzed. Results: The apoptosis positivity before and after irradiation was 76.7%and 100% respectively, with the difference being significant (P 【 0.05); The positive rates of Bcl-2protein before and after irradiation were 73.3% and 46.7% respectively, with the difference beingsignificant (P 【 0.05); The positive rates of bax protein before and after irradiation were 86% and100% respectively, with the difference being significant (P 【 0.05). Conclusion: bax and Bcl-2protein play an important role in apoptosis induced by fractionated radiation therapy. Apoptosisinduced by irradiation is contributed to upregulation of bax protein or downregulation of Bcl-2protein.展开更多
文摘T cells are derived from progenitor thymocytes, of which only a minority receive the appropriate TCR signal, undergo positive selection and mature. Owing to the very short lifespan of thymocytes, the prerequisite for posi- tive selection is survival. TCR signal-induced Bcl-2 expression is believed to play a dominant role in the survival of positively selecting thymocytes, but how Bcl-2 is directly regulated is unknown. Here we report that the immediate early gene （IEG） c-Fos can stimulate the expression of Bcl-2, depending on a specific AP-l-binding site in the Bcl-2 promoter. In c-Fos transgenic （Fos-Tg） mice, c-Fos binds to this site and promotes the expression of Bcl-2. As a result, Fos-Tg thymocytes exhibited enhanced survival, and more mature single-positive （SP） thymocytes were generated, even on a unique TCR background. The TCR repertoire remained normal in Fos-Tg mice. Our results identified c-Fos as the mediator of the stimulatory effect of TCR signaling on Bcl-2 expression. Therefore, c-Fos, as an IEG, because of its early response ability, can quickly rescue the survival of short-lived thymocytes during positive selection. Our results provide novel insight into the mechanism regulating the survival of positively selecting thymocytes.
文摘BACKGROUND： Both animal experiments and clinical studies have shown that basic fibroblast growth factor （bFGF） and danshen （Salvia miltiorrhiza） can exhibit protective effects on ischemia-reperfusion cerebral injury. OBJECTIVE： To test whether bFGF and danshen can protect cerebral injury induced by exposure to repeated, high, positive acceleration （＋Gz） in an animal model and to analyze the possible mechanisms. DESIGN, TIME AND SETTING： Randomized controlled animal study. The experiment was performed at the Research Center for Molecular Biology, Air-force General Hospital of Chinese PLA from April to August 2000. MATERIALS： A total of 20 clean grade, healthy, Sprague Dawley rats of both genders, weighing （200 ± 15） g, were provided by our experimental animal center. Rats were randomly divided into 5 groups： the control group, ＋Gz exposure group, bFGF group, danshen group, and saline group, with 4 animals per group. bFGF （Beijing Bailuyuan Biotechnology Co. Ltd.） and danshen solution （Shanghai Zhongxi Pharmaceutical Co. Ltd.） were used. METHODS： All rats were fixed on a rotary arm of a centrifugal apparatus （2 m in radius） with their heads oriented towards the center of the apparatus. Except for rats in the control group, the value of ＋Gz exposure was ＋14 Gz with an acceleration rate of 1.5 G/s. The peak force lasted for 45 seconds. ＋Gz exposure was performed three times with intervals of 30 minutes. Rats in the control group received the same ＋Gz procedure, but the G value was ＋1 Gz. Rats in bFGF group and danshen group were intraperitoneally injected with 100 μg/kg bFGF or 15 g/kg danshen solution, respectively, at 30 minutes prior to centrifugation and immediately after centrifugation. Rats in saline group were injected with the same volume of saline. Six hours after exposure, rats were decapitated. One hemisphere was preserved in liquid nitrogen for RNA extraction and the other was processed for apoptosis detection. MAIN OUTCOME MEASURES： mRNA levels of bcl-2 and p53 were measured by semi-quantitative reverse-transcription polymerase chain reaction. Apoptotic cell death was detected by terminal deoxynuleotidyl transferase-mediated dUTP nick end labeling. RESULTS： Changes in mRNA expression of bcl-2 and p53 and apoptotic cells were observed in rat brain six hours after repeated ＋Gz exposures, bFGF and danshen were able block the changes of bcl-2 and p53 expression and inhibit apoptotic cell death. CONCLUSION： The data suggest that apoptosis and changes in bcl-2 and p53 expression in the rat brain can be induced by repeated ＋Gz exposures. Apoptosis is, therefore, one of the molecular mechanisms of brain damage induced by repeated ＋Gz exposures, bFGF and danshen were of the equal potency in preventing brain injury induced by repeated ＋Gz exposures.
文摘To evaluate the apoptosis positivity, the expression of Bcl-2, bax proteinsin 30 patients with squamous cell cervix carcinoma before and after radiotherapy. Methods: By usingimmuno-histochemical and TDT-dUTP nick end labelling techniques, 30 cases of squamous cell cervicalcarcinoma were analyzed. Results: The apoptosis positivity before and after irradiation was 76.7%and 100% respectively, with the difference being significant (P 【 0.05); The positive rates of Bcl-2protein before and after irradiation were 73.3% and 46.7% respectively, with the difference beingsignificant (P 【 0.05); The positive rates of bax protein before and after irradiation were 86% and100% respectively, with the difference being significant (P 【 0.05). Conclusion: bax and Bcl-2protein play an important role in apoptosis induced by fractionated radiation therapy. Apoptosisinduced by irradiation is contributed to upregulation of bax protein or downregulation of Bcl-2protein.
