Objective The biological characteristics and action mechanisms underlying the excellent performance of skeletal muscles were studied through experiments to provide a scientific basis for the development of flexible actuators with performance comparable to that of skeletal muscles.Methods A frog skeletal muscle sample was contracted by applying electrical stimulation,and then tensile load was applied to it to analyze the relationship between the driving properties(such as contraction length and output force)of skeletal muscle and its structure from three aspects:skeletal muscle dimensions,tendon,and epimysium.Results The contraction lengths of these skeletal muscle samples were approximately 28.92％and 20％under unloaded conditions and under 50％of their maximum output force,respectively.When the load on the skeletal muscles did not exceed 20％of their maximum output force,they also exhibited the property of rapid reduction(approximately 1.25 s).The active tendon increased contraction by approximately 19.68％compared with the inactive tendon,and the integrity of the epimysium protected the force transfer efficiency of skeletal muscles.Conclusions By simulating the structural and biomechanical properties of skeletal muscles,flexible actuators can achieve better driving performance,thus greatly promoting the development of bionic robots.

Objective The biological characteristics and action mechanisms underlying the excellent performance of skeletal muscles were studied through experiments to provide a scientific basis for the development of flexible actuators with performance comparable to that of skeletal muscles.Methods A frog skeletal muscle sample was contracted by applying electrical stimulation,and then tensile load was applied to it to analyze the relationship between the driving properties(such as contraction length and output force)of skeletal muscle and its structure from three aspects:skeletal muscle dimensions,tendon,and epimysium.Results The contraction lengths of these skeletal muscle samples were approximately 28.92％and 20％under unloaded conditions and under 50％of their maximum output force,respectively.When the load on the skeletal muscles did not exceed 20％of their maximum output force,they also exhibited the property of rapid reduction(approximately 1.25 s).The active tendon increased contraction by approximately 19.68％compared with the inactive tendon,and the integrity of the epimysium protected the force transfer efficiency of skeletal muscles.Conclusions By simulating the structural and biomechanical properties of skeletal muscles,flexible actuators can achieve better driving performance,thus greatly promoting the development of bionic robots.

Tetracycline (TC) natural products possess a variety of remarkable bioactivities and diverse structures. They are an important and fertile source for developing novel drugs. As one of the most successful drug families, TC antibiotics have been in clinical use for over seven decades, and continue to make an important contribution to human health nowadays. To date, studies on TC natural products and their biosynthesis have revealed numerous novel biochemical mechanisms and regulatory elements, which facilitates the rational metabolic engineering studies for generating novel bioactive TC analogs and inspires the development of new synthetic biology tools. In this review, we provide a comprehensive overview on the discovery, biosynthesis, and engineering of the existing TC natural products. These analyses will be of great value for the discovery, design and development of novel TC drugs in the future.
Humans ; Biological Products/metabolism* ; Anti-Bacterial Agents ; Metabolic Engineering ; Synthetic Biology ; Tetracycline

Alzheimer's disease (AD) is a chronic central neurodegenerative disease. The pathological features of AD are the extracellular deposition of senile plaques formed by amyloid-β oligomers (AβOs) and the intracellular accumulation of neurofibrillary tangles formed by hyperphosphorylated tau protein. In this paper, an in vitro pathological model of AD based on neuronal network chip and its real-time dynamic analysis were presented. The hippocampal neuronal network was cultured on the microelectrode array (MEA) chip and induced by AβOs as an AD model in vitro to simultaneously record two firing patterns from the interneurons and pyramidal neurons. The spatial firing patterns mapping and cross-correlation between channels were performed to validate the degeneration of neuronal network connectivity. This biosensor enabled the detection of the AβOs toxicity responses, and the identification of connectivity and interactions between neuronal networks, which can be a novel technique in the research of AD pathological model in vitro.
Alzheimer Disease ; Amyloid beta-Peptides ; Humans ; Neurofibrillary Tangles ; tau Proteins

Alzheimer's disease (AD) is a chronic central neurodegenerative disease. The pathological features of AD are the extracellular deposition of senile plaques formed by amyloid-β oligomers (AβOs) and the intracellular accumulation of neurofibrillary tangles formed by hyperphosphorylated tau protein. In this paper, an in vitro pathological model of AD based on neuronal network chip and its real-time dynamic analysis were presented. The hippocampal neuronal network was cultured on the microelectrode array (MEA) chip and induced by AβOs as an AD model to simultaneously record two firing patterns from the interneurons and pyramidal neurons. The spatial firing patterns mapping and cross-correlation between channels were performed to validate the degeneration of neuronal network connectivity. This biosensor enabled the detection of the AβOs toxicity responses, and the identification of connectivity and interactions between neuronal networks, which can be a novel technique in the research of AD pathological model .
Alzheimer Disease ; Amyloid beta-Peptides ; Humans ; Neurofibrillary Tangles ; tau Proteins

Objective To observe the effect of sevoflurane preconditioning on serum GDF-15,TNF-α, cTnI expression during perioperative period in patients in congenital heart diseases(CHD)with pulmonary artery hypertension(PAH),and to investigate the mechanism of myocardial protection. Methods Forty adult patients of CHD with PAH who received open-heart surgery under extracorporeal circulation were randomly divided into two groups(n=20):sevoflurane preconditioning group(Group S)and the control group(Group C). In the group S, 1MAC sevoflurane was inhaled for 20 min from beginning of operation ,and followed with oxygen elution for 10 min,in twice;only inhaling pure oxygen in the Group C. The artery blood samples were collected for measurements of serum GDF-15,TNF-α,cTnI immediately before anesthesia induction(T0),at 2 h(T1),12 h(T2),24 h (T3)after aorta declamping and 7 d(T4)after operation. The restoration of spontaneous heart beat ,reperfusion arrhythmia scores,preoperative and postoperative pulmonary artery systolic pressure were recorded. Results Com-pared with preoperative pumonary artery systolic pressure(PASP),it became low in the two groups at 7 days after operation(P<0.05);compared with the group C,the rate of restoration of spontaneous heart beat was promoted, and reperfusion arrhythmia scores were decreased in the group S(P<0.05);compared with the group C,GDF-15 were increased,TNF-α,cTnI were decreased in the group S at T1～3(P < 0.05);Compared with T0,GDF-15, TNF-α,cTnI were increased in the two groups at T1～3,GDF-15 in the two groups were decreased at T4(P <0.05). Conclusion Sevoflurane preconditioning may reduce inflammatory reaction during perioperative period in patients of CHD with PAH by promoting the expression of GDF-15,inhibiting the expression of TNF-α and then improve myocardial ischemia-reperfusion injury.

Penicillin expandase, also known as deacetoxycephalosporin C synthase (DAOCS), is an essential enzyme involved in cephalosporin C biosynthesis. To evaluate the catalytic behaviors of penicillin expandase under high penicillin G concentration and to identify mutants suitable for industrial applications, the specific activities of wild-type DAOCS and several mutants with increased activities toward penicillin G were determined by HPLC under high penicillin G concentrations. Their specific activity profiles were compared with theoretical predictions by different catalytic dynamics models. We evaluated the specific activities of wild-type DAOCS and previous reported high-activity mutants H4, H5, H6 and H7 at concentrations ranging from 5.6 to 500 mmol/L penicillin G. The specific activities of wild-type DAOCS and mutant H4 increased as penicillin G concentration increased, but decreased when concentrations of substrate go above 200 mmol/L. Other mutants H5, H6 and H7 showed more complex behaviors under high concentration of penicillin G. Among all tested enzymes, mutant H6 showed the highest activity when concentration of penicillin G is above 100 mmol/L. Our results revealed that the substrate inhibition to wild-type DAOCS' by penicillin G is noncompetitive. Other DAOCS mutants showed more complex trends in their specific activities at high concentration of penicillin G (>100 mmol/L), indicating more complex substrate inhibition mechanism might exist. The substrate inhibition and activity of DAOCS mutants at high penicillin G concentration provide important insight to help select proper mutants for industrial application.
Catalysis ; Intramolecular Transferases ; genetics ; Mutation ; Penicillin G ; pharmacology ; Penicillin-Binding Proteins ; genetics ; Streptomyces ; enzymology ; genetics

JadH is a bifunctional hydoxylase/dehydrase involved in jadomycin biosynthesis; it catalyzes a post-PKS modification reaction to convert 2,3-dehydro-UWM6 to dehydrorabelomycin. To identify the key residues involved in substrate-binding and catalysis, structural modeling and multiple sequence alignments of JadH homologs were performed to predict nine residues at the proximity of substrate. Site-directed mutagenesis of the corresponding residues and in vitro evaluation of the activities of the mutant enzymes, indicate these mutations severely reduced JadH activity. Our results indicate these residues are specifically involved in substrate-binding or catalysis in JadH.
Amino Acid Sequence ; Catalysis ; Hydro-Lyases ; genetics ; metabolism ; Isoquinolines ; metabolism ; Mixed Function Oxygenases ; genetics ; metabolism ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Mutant Proteins ; metabolism ; Naphthoquinones ; metabolism ; Streptomyces ; metabolism ; Substrate Specificity

Objective To study the therapeutic of anastomotic leakage in post-esophagogastrectomy. Meth-ods There were 18 cases of anastomotic leakage in 127 cases with cancer of the thoracic esophagus who underwent esophagectomy were retrospectively studied. There were ten cases had anastomotic leakage of 67 cases of esophagogas-trectomy from 1995 to 2001 (first phase),the intestines nutrition sustain treatment taked rice water,fish soup and broth, there were eight cases had anastomotic leakage of 60 cases of esophagogastrectomy from 2002 to 2007 (second phase) ,the intestines nutrition sustain treatment taked supportan,fresubin. Results There were six cases death of 10 cases of anastomotic leakage at first phase, and there was any not death in the second phase. Conclusion When anastomotic leakage of esophagogastreetomy,it can elevate the cure rate with early diagncsis and treatment and intes-tines nutrition sustain treatment choose by supportan or fresubin.