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951.
952.
For an increasing fraction of proteins whose structures are being studied, sequence homology to known structures permits building of low resolution structural models. It is demonstrated that dipolar couplings, measured in a liquid crystalline medium, not only can validate such structural models, but also refine them. Here, experimental 1H-15N, 1H-13C, and 13C-13C dipolar couplings are shown to decrease the backbone rmsd between various homology models of calmodulin (CaM) and its crystal structure. Starting from a model of the Ca2+-saturated C-terminal domain of CaM, built from the structure of Ca2+-free recoverin on the basis of remote sequence homology, dipolar couplings are used to decrease the rmsd between the model and the crystal structure from 5.0 to 1.25 Å. A better starting model, built from the crystal structure of Ca2+-saturated parvalbumin, decreases in rmsd from 1.25 to 0.93 Å. Similarly, starting from the structure of the Ca2+-ligated CaM N-terminal domain, experimental dipolar couplings measured for the Ca2+-free form decrease the backbone rmsd relative to the refined solution structure of apo-CaM from 4.2 to 1.0 Å. 相似文献
953.
Ho HY Cheng ML Lu FJ Chou YH Stern A Liang CM Chiu DT 《Free radical biology & medicine》2000,29(2):156-169
Glucose-6-phosphate dehydrogenase (G6PD) is involved in the generation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) and the maintenance of the cellular redox balance. The biological effects of G6PD deficiency in nucleated cells were studied using G6PD-deficient human foreskin fibroblasts (HFF). In contrast to that of normal HFF, the doubling time of G6PD-deficient cells increased readily from population doubling level (PDL) 15 to 63. This was accompanied by a significant increase in the percentage of G(1) cells. The slow-down in growth preceded an early entry of these cells into a nondividing state reminiscent of cellular senescence. These cells exhibited a significant increase in level of senescence-associated beta-galactosidase (SA-beta-gal) staining. The importance of G6PD activity in cell growth was corroborated by the finding that ectopic expression of active G6PD in the deficient cells prevented their growth retardation and early onset of senescence. Mechanistically, the enhanced fluorescence in dichlorofluorescin (H(2)DCF)-stained G6PD-deficient cells suggests the possible involvement of reactive oxygen species in senescence. Taken together, our results show that G6PD deficiency predisposes human fibroblasts to retarded growth and accelerated cellular senescence. Moreover, G6PD-deficient HFF provides a useful model system for delineating the effects of redox alterations on cellular processes. 相似文献
954.
955.
Study of the viral infections and cytokines associated with recurrent aphthous ulceration 总被引:3,自引:0,他引:3
Lin SS Chou MY Ho CC Kao CT Tsai CH Wang L Yang CC 《Microbes and infection / Institut Pasteur》2005,7(4):635-644
Mouth ulcers are one of the most common oral complaints. However, the association between oral ulceration and viruses and cytokines is uncertain. We detected the presence of human papilloma virus (HPV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus (HSV)-1, HSV-2 and human herpesvirus (HHV)-8 DNA in oral tissues by polymerase chain reaction (PCR) and Southern hybridization techniques, and quantified the serum levels of cytokines including interleukin (IL)-2, IL-4, granulocyte-macrophage colony-stimulating factor (GM-CSF), soluble Fas (sFas) and the Fas ligand (FasL) by enzyme-linked immunosorbent assay (ELISA) for 67 recurrent aphthous ulcer (RAU) patients and 72 normal individuals. Seven patient specimens were excluded from the study due to the negative PCR results for the beta-globin used as the internal control. Among the 32 (53.3%) virus-positive results from 60 patients' samples, 8 (13.3%) HPV, 4 (6.7%) HSV-1, 11 (18.3%) CMV, 9 (15.0%) EBV, and 16 (26.7%) HHV-8 samples proved to be positive. No HSV-2-positive samples were found. The percentage of single-virus infection (56.3%) was significantly greater than that of double-virus co-infection (31.3%) and the percentage of double-virus co-infection was significantly greater than the percentage of triple-virus co-infection (12.5%) (P < 0.05). In the 72 normal oral-tissue specimens, no viral DNA was detected. The mean serum cytokine level for patients was significantly (P < 0.05) greater than for controls for most of the separate age groups. The mean serum cytokine concentrations for the patient group demonstrated a diffuse pattern covering a wide range of serum concentrations, a very different result from the compact serum concentration pattern and lower mean serum cytokine concentrations revealed by the normal group. Overall association between viruses and recurrent aphthous ulceration is HHV-8 > CMV > EBV > HPV > HSV-1, regarding the frequency of prevalence (P < 0.05). 相似文献
956.
Saat M Tochihara Y Hashiguchi N Sirisinghe RG Fujita M Chou CM 《Journal of PHYSIOLOGICAL ANTHROPOLOGY and Applied Human Science》2005,24(4):267-275
The effect of low-intensity exercise in the heat on thermoregulation and certain biochemical changes in temperate and tropical subjects under poorly and well-hydrated states was examined. Two VO2max matched groups of subjects consisting of 8 Japanese (JS) and 8 Malaysians (MS) participated in this study under two conditions: poorly-hydrated (no water was given) and well-hydrated (3 mL x Kg(-1) body weight of water was provided at onset of exercise, and the 15th, 35th and 55th min of exercise). The experimental room in both countries was adjusted to a constant level (Ta: 31.6+/-0.03 degrees C, rh: 72.3+/-0.13%). Subjects spent an initial 10 min rest, 60 min of cycling at 40% VO2max and then 40 min recovery in the experimental room. Rectal temperatures (Tre) skin temperatures (Tsk), heart rate (HR), heat-activated sweat glands density (HASG), local sweat rate (M sw-back) and percent dehydration were recorded during the test. Blood samples were analysed for plasma glucose and lactate levels.The extent of dehydration was significantly higher in the combined groups of JS (1.43+/-0.08%) compared to MS (1.15+/-0.05%). During exercise M sw-back was significantly higher in JS compared to MS in the well-hydrated condition. The HASG was significantly more in JS compared to MS at rest and recovery. Tre was higher in MS during the test. Tsk was significantly higher starting at the 5th min of exercise until the end of the recovery period in MS compared to JS.In conclusion, tropical natives have lower M sw-back associated with higher Tsk and Tre during the rest, exercise and recovery periods. However, temperate natives have higher M sw-back and lower Tsk and Tre during experiments in a hot environment. This phenomenon occurs in both poorly-hydrated and well-hydrated states with low intensity exercise. The differences in M sw-back, Tsk and Tre are probably due to a setting of the core temperature at a higher level and enhancement of dry heat loss, which occurred during passive heat exposure. 相似文献
957.
Glycogen overload by postexercise insulin administration abolished the exercise-induced increase in GLUT4 protein 总被引:2,自引:0,他引:2
Chou CH Tsai YL Hou CW Lee HH Chang WH Lin TW Hsu TH Huang YJ Kuo CH 《Journal of biomedical science》2005,12(6):991-998
Summary To elucidate the role of muscle glycogen storage on regulation of GLUT4 protein expression and whole-body glucose tolerance,
muscle glycogen level was manipulated by exercise and insulin administration. Sixty Sprague-Dawley rats were evenly separated
into three groups: control (CON), immediately after exercise (EX0), and 16 h after exercise (EX16). Rats from each group were
further divided into two groups: saline- and insulin-injected. The 2-day exercise protocol consisted of 2 bouts of 3-h swimming
with 45-min rest for each day, which effectively depleted glycogen in both red gastrocnemius (RG) and plantaris muscles. EX0
rats were sacrificed immediately after the last bout of exercise on second day. CON and EX16 rats were intubated with 1 g/kg
glucose solution following exercise and recovery for 16 h before muscle tissue collection. Insulin (0.5 μU/kg) or saline was
injected daily at the time when glucose was intubated. Insulin injection elevated muscle glycogen levels substantially in
both muscles above saline-injected group at CON and EX16. With previous day insulin injection, EX0 preserved greater amount
of postexercise glycogen above their saline-injected control. In the saline-injected rats, EX16 significantly increased GLUT4
protein level above CON, concurrent with muscle glycogen supercompensation. Insulin injection for EX16 rats significantly
enhanced muscle glycogen level above their saline-injected control, but the increases in muscle GLUT4 protein and whole-body
glucose tolerance were attenuated. In conclusion, the new finding of the study was that glycogen overload by postexercise
insulin administration significantly abolished the exercise-induced increases in GLUT4 protein and glucose tolerance. 相似文献
958.
Sheu TW Chou CW Tsai SF Liang PC 《Computer methods in biomechanics and biomedical engineering》2005,8(4):229-240
Increase of temperature above 50 approximately 60 degrees C for few minutes by the emitted radio-frequency (RF) energy has been shown to be able to denaturate the intracellular proteins and destruct membranes of tumor cells. To improve the efficacy of this thermal therapy, it is important to investigate factors that may affect the RF heating characteristics for the hepatocellular carcinoma and metastatic liver tumors. In order to make sure the applied RF energy is adequate to ablate the target tumor, a 3D thermoelectric analysis for the system consisting of liver, liver arteries and 4 mm diameter tumor is conducted. The effect of blood perfusion is addressed in this study. 相似文献
959.
960.