ABSTRACT
Objective To investigate the effect of different duration skeletal muscle denervation on acetylcholine receptor activity in rats.Methods Fourteen Balb/c mice weighing 18-22 g were used in this study.The denervation model was established by excising sciatic nerve.Two rats were chosen before(T0 ) and at days 1,4,7,14,21 and 28 after excising sciatic nerve (T1～6),and flexor digitorum brevis of the hindfoot was acutely isolated Skeletal muscle cells were isolated ( five cells in each rat),the acetylcholine currents were recorded using whole-cell patch-clamo technique.Extracellular fluid containing 30 μmol/L acetylcholine was first applied to skeletal muscle cells for 10 s,acetylcholine currents (11)were recorded,then the ceils were washed out using extracellularfluid.Skeletal muscle cells were balanced using extracellular fluid containing 0,0.1,1,10,30,100,1000,3000,or 10 000 nmol/L atracurium for 3 min respectively,then perfused using extracellular fluid containing 30 μmol/L acetylcholine and differents concentrations of atracurium mentioned above for 10 s respectively,and acetylcholine currents were recorded,then the cells were washed out,and 30 μmol/L acetylcholine was perfused again and currents(I2 ) were recorded.The mean value of I1 and I2 was taken as control current,and inhibitory percentage of control current was calculated,and the inhibition concentrations for the half-maximal response (IC50) of atracurium were determined by nonlinear regression analysis.Results Compared with T0,IC50 significantly increased at T1～6 ( P ＜ 0.05).IC50 was increased gradually at T1～3 ( P ＜ 0.05).Compared with T3,IC50 was decreased at T4～6 ( P ＜ 0.05).IC50 was decreased gradually at T4～6 ( P ＜ 0.05 ).Conclusion Skeletal muscle denervation can inhibite acetylcholine receptor activity,which is relate to the denervation time.
ABSTRACT
This study investigated the effect of cadmium on the telomerase activity, the expression of TERT, c-myc and p53 and the apoptosis of rat hepatocytes. The rats were administrated 5, 10 and 20 μmol/kg cadmium chloride intraperitoneally and sacrificed 48 h after the initial treatment. The telomerase activity of the rat hepatocytes was measured by the telomeric repeat amplification protocol (TRAP), and apoptosis was detected by flow cytometry. The mRNA expressions of TERT, c-myc and p53 were measured by reverse transcription-polymerase chain reaction (RT-PCR). C-myc and P53 proteins were determined by immunochemistry. The results showed that cadmium chloride increased the hepatocellular telomerase activity in a dose-dependant manner and induced the apoptosis of hepatocytes significantly. The value of relative coefficient between the telomerase activity and the apoptosis rate was 0.9398. RT-PCR revealed that specific bands corresponding to the TERT mRNA, c-myc mRNA, and p53 mRNA were displayed at 185, 342 and 538 bp respectively. Cadmium chloride could substantially increase the mRNA expressions of TERT, c-myc and p53 in rat hepatocytes, as compared with control. Moreover, cadmium chloride at the doses of 5, 10 and 20 μmol/kg could increase the content of P53 protein in rat hepatocytes obviously, but only that at the doses of 10 and 20 μmol/kg substantially promoted the c-myc protein level in rat hepatocytes. Our study herein suggested that cadmium may contribute to the carcinogenesis by activating telomerase, and overexpressing the mRNAs of TERT, c-myc and p53, and causing apoptosis of normal cells.
Subject(s)
Animals , Male , Rats , Apoptosis , Cadmium , Toxicity , Hepatocytes , Metabolism , Pathology , Proto-Oncogene Proteins c-myc , Genetics , Metabolism , RNA, Messenger , Genetics , Metabolism , Rats, Sprague-Dawley , Telomerase , Genetics , Metabolism , Tumor Suppressor Protein p53 , Genetics , MetabolismABSTRACT
This study investigated the effect of cadmium on the telomerase activity, the expression of TERT, c-myc and p53 and the apoptosis of rat hepatocytes. The rats were administrated 5, 10 and 20 μmol/kg cadmium chloride intraperitoneally and sacrificed 48 h after the initial treatment. The telomerase activity of the rat hepatocytes was measured by the telomeric repeat amplification protocol (TRAP), and apoptosis was detected by flow cytometry. The mRNA expressions of TERT, c-myc and p53 were measured by reverse transcription-polymerase chain reaction (RT-PCR). C-myc and P53 proteins were determined by immunochemistry. The results showed that cadmium chloride increased the hepatocellular telomerase activity in a dose-dependant manner and induced the apoptosis of hepatocytes significantly. The value of relative coefficient between the telomerase activity and the apoptosis rate was 0.9398. RT-PCR revealed that specific bands corresponding to the TERT mRNA, c-myc mRNA, and p53 mRNA were displayed at 185, 342 and 538 bp respectively. Cadmium chloride could substantially increase the mRNA expressions of TERT, c-myc and p53 in rat hepatocytes, as compared with control. Moreover, cadmium chloride at the doses of 5, 10 and 20 μmol/kg could increase the content of P53 protein in rat hepatocytes obviously, but only that at the doses of 10 and 20 μmol/kg substantially promoted the c-myc protein level in rat hepatocytes. Our study herein suggested that cadmium may contribute to the carcinogenesis by activating telomerase, and overexpressing the mRNAs of TERT, c-myc and p53, and causing apoptosis of normal cells.
ABSTRACT
The purpose of this study was to examine whether repetitive muscle tasks in low weight load might influence the fatigue of forearm muscles, and to identify ergonomic risk factors of forearm muscle fatigue in these tasks. Sixteen healthy male volunteers performed eight wrist extensions in different frequency, weight and angle loads while being instructed to keep a dominant upper limb posture as constant as possible. Surface electromyograph (sEMG) was recorded from right extensors digitorium (ED), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) during the task performance. Our results showed that mean power frequency (MPF) and median frequency (MF) values of ED, FCR and FCU were significantly lower (P＜0.05) at high frequency load level than at low load level. However, MPF and MF values of ED were significantly lower (P＜0.01) in higher load groups of frequency, angle and weight than in lower load groups. These results indicated that the fatigue of muscles varied in the same task, and the number-one risk factor of ECU, ED and FCR was angle load.
ABSTRACT
The purpose of this study was to examine whether repetitive muscle tasks in low weight load might influence the fatigue of forearm muscles, and to identify ergonomic risk factors of forearm muscle fatigue in these tasks. Sixteen healthy male volunteers performed eight wrist extensions in different frequency, weight and angle loads while being instructed to keep a dominant upper limb posture as constant as possible. Surface electromyograph (sEMG) was recorded from right extensors digitorium (ED), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) during the task performance. Our results showed that mean power frequency (MPF) and median frequency (MF) values of ED, FCR and FCU were significantly lower (P<0.05) at high frequency load level than at low load level. However, MPF and MF values of ED were significantly lower (P<0.01) in higher load groups of frequency, angle and weight than in lower load groups. These results indicated that the fatigue of muscles varied in the same task, and the number-one risk factor of ECU, ED and FCR was angle load.