Mechanical Design with Experimental Verification of a Lightweight Exoskeleton Chair

In this study,a human-chair model was developed as the basis for a wearable-chair design.Aprototype chair,HUST-EC,based on the model was fabricated and evaluate...     

Effect of dietary fiber on the lipid metabolism and immune function of aged Sprague-Dawley rats

Eight-month-old Sprague-Dawley rats were fed on diets containing dietary fiber at the 5% level for 3 weeks to examine the effect on the lipid metabolism and immune function. Among cellulose, guar gum, partially hydrolyzed guar gum (PHGG), glucomannan and highly methoxylated pectin, guar gum induced a significant decrease in the food intake and weight gain, as well as a significant increase in the liver weight. In addition, the epidydimal adipose tissue weight of the rats fed on PHGG was significantly higher than that of the rats fed on cellulose. There was no significant effect on the serum lipid levels, but the serum IgG level of the rats fed on guar gum was significantly lower than that of the rats fed on cellulose. The IgA and IgG productivity in mesenteric lymph node (MLN) lymphocytes was significantly higher in the rats fed on guar gum, glucomannan and pectin than in those fed on cellulose, while the effect on Ig productivity in spleen lymphocytes was not as marked. In addition, only guar gum induced a significant increase of IgM productivity in MLN lymphocytes when compared to the cellulose group. These results suggest that enhancement of the immune function by dietary fiber is mainly expressed in the gut immune system.     

Conformational changes and inactivation of rabbit muscle creatine kinase in dimethyl sulfoxide solutions.

The effects of dimethyl sulfoxide (DMSO) on creatine kinase (CK) conformation and enzymatic activity were studied by measuring activity changes, aggregation, and fluorescence spectra. The results showed that at low concentrations (< 65% v/v), DMSO had little effect on CK activity and structure. However, higher concentrations of DMSO led to CK inactivation, partial unfolding, and exposure of hydrophobic surfaces and thiol groups. DMSO caused aggregation during CK denaturation. A 75% DMSO concentration induced the most significant aggregation of CK. The CK inactivation and unfolding kinetics were single phase. The unfolding of CK was an irreversible process in the DMSO solutions. The results suggest that to a certain extent, an enzyme can maintain catalytic activity and conformation in water-organic mixture environments. Higher concentrations of DMSO affected the enzyme structure but not its active site. Inactivation occurred along with noticeable conformational change during CK denaturation. The inactivation and unfolding of CK in DMSO solutions differed from other denaturants such as guanidine, urea, and sodium dodecyl sulfate. The exposure of hydrophobic surfaces was a primary reason for the protein aggregation.     

Prostaglandin H2 (PGH2) accelerates formation of amyloid beta1-42 oligomers

Epidemiologic evidence implicates cyclooxygenase activity in the pathogenesis of Alzheimer's disease, in which amyloid plaques have been found to contain increased levels of dimers and higher multimers of the amyloid beta peptide. The product of the oxygenation of arachidonic acid by the cyclooxygenases, prostaglandin H2 (PGH2), rearranges non-enzymatically to several prostaglandins, including the highly reactive gamma-keto aldehydes, levuglandins E2 and D2. We demonstrate that PGH2 markedly accelerates the formation of dimers and higher oligomers of amyloid beta1-42. This is associated with the formation of levuglandin adducts of the peptide. These findings provide the molecular basis for a hypothesis linking cyclooxygenase activity to the formation of oligomers of amyloid beta.     

Effect of 1,10-phenanthroline on bacterial conjugation in Escherichia coli K-12: inhibition of maturation from preliminary mates into effective mates.

The addition of 1 mM orthophenanthroline (OP) into a mating mixture drastically reduced the production of recombinants. Examination of the effect of OP on each step of conjugation showed that the effect on the following steps could not account for the up to 500-fold reduction of recombinant formation: (i) preliminary mate formation and (ii) deoxyribonucleic acid transfer and integration. Taking these results and additional experiments together, we conclude that OP inhibits the maturation of preliminary mates into effective mates. Kinetic experiments showed that there were two phases in the maturation of preliminary (OP-sensitive) mates into effective (OP-resistant) mates. The half-time (the time required to reach 50% OP-resistant mates) was 2.5 min for the first phase and 4 min for the second phase, with an overall half-time of 7.5 min. In contrast, only 3 min was required to reach 50% Zn2+-resistant mates. The difference in half-time suggests that there is an intermediate step involved to form an effective mate from a preliminary mate.     

Disulfide bonds stabilize JC virus capsid-like structure by protecting calcium ions from chelation

To investigate the role of disulfide bonds in the capsid structure, a recombinant JC virus-like particle (VLP) was used. The major capsid protein, VP1, of the JC virus was expressed in yeast cells. The yeast-expressed VP1 was self-assembled into a VLP. Disulfide bonds were found in the VLP which caused dimeric and trimeric VP1 linkages as demonstrated by non-reducing SDS–PAGE. The VLP remained intact when disulfide bonds were reduced by dithiothreitol. The VLP without disulfide bonds could be disassembled into capsomeres by EGTA alone, but those with disulfide bonds could not be disassembled by EGTA. Capsomeres were reassembled into VLPs in the presence of calcium ions. Capsomeres formed irregular aggregations instead of VLPs when treated with diamide to reconstitute the disulfide bonds. These results indicate that disulfide bonds play an important role in maintaining the integrity of the JC VLP by protecting calcium ions from chelation.     

Proteolytic conversion of hepatitis B virus e antigen precursor to end product occurs in a postendoplasmic reticulum compartment.

At least two proteolytic events are involved in the biogenesis of hepatitis B virus e antigen. The first proteolytic event removes the signal peptide and results in the translocation of the precursor protein, P22, into the lumen of the endoplasmic reticulum (ER). The second proteolytic event removes the carboxy-terminal arginine-rich sequence of P22 and converts it to the 16-kDa hepatitis B virus e antigen end product. In contrast to the first proteolytic event, the second proteolytic event is suppressed by brefeldin A, a chemical that inhibits the transport of protein from the ER to the Golgi apparatus. In subcellular fractionation experiments, P22 was detected in both the ER and the Golgi fractions, but P16 was detected only in the Golgi fraction. On the basis of these results, we conclude that the conversion of P22 to P16 occurs ina post-ER compartment, mostly likely the Golgi apparatus.     

EDHF contributes to strain-related differences in pulmonary arterial relaxation in rats

Pulmonary arteries from the Madison (M) strain relax more in response to acetylcholine (ACh) than those from the Hilltop (H) strain of Sprague-Dawley rats. We hypothesized that differences in endothelial nitric oxide (NO) synthase (eNOS) expression and function, metabolism of ACh by cholinesterases, release of prostacyclin, or endothelium-derived hyperpolarizing factor(s) (EDHF) from the endothelium would explain the differences in the relaxation response to ACh in isolated pulmonary arteries. eNOS mRNA and protein levels as well as the NO-dependent relaxation responses to thapsigargin in phenylephrine (10(-6) M)-precontracted pulmonary arteries from the M and H strains were identical. The greater relaxation response to ACh in M compared with H rats was also observed with carbachol, a cholinesterase-resistant analog of ACh, a response that was not modified by pretreatment with meclofenamate (10(-5) M). N(omega)-nitro-L-arginine (10(-4) M) completely abolished carbachol-induced relaxation in H rat pulmonary arteries but not in M rat pulmonary arteries. Precontraction with KCl (20 mM) blunted the relaxation response to carbachol in M rat pulmonary arteries and eliminated differences between the M and H rat pulmonary arteries. NO-independent relaxation present in the M rat pulmonary arteries was significantly reduced by 17-octadecynoic acid (2 microM) and was completely abolished by charybdotoxin plus apamin (100 nM each). These findings suggest that EDHF, but not NO, contributes to the strain-related differences in pulmonary artery reactivity. Also, EDHF may be a metabolite of cytochrome P-450 that activates Ca(2+)-dependent K(+) channels.     

Quantification of puerarin in plasma by on-line solid-phase extraction column switching liquid chromatography-tandem mass spectrometry and its applications to a pharmacokinetic study

A highly precise, automatic and rapid method for quantification of puerarin in canine and human plasma using an on-line solid-phase extraction (SPE) column switching procedure combined with liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS) was developed. The eluent of SPE column consisted of acetonitrile/methanol/0.1% formic acid (25/25/50) at a flow rate of 0.2mLmin(-1). Puerarin was analyzed by a linear ion trap mass spectrometer, LTQ-MS, operating in the negative ion and selective reaction monitoring (SRM) acquisition mode. Method validation results demonstrated that the linear calibration curve covered a wide range of 0.39-400.00ngmL(-1), the correlation coefficients (r(2)) were above 0.999. The lower limit of detection (LLOD) with the signal-to-noise (S/N) ratio higher than 12 was 0.39ngmL(-1). The intra- and inter-batch precisions were less than 7.61% and 6.42%, respectively. The accuracy was well within the accept limit. The on-line SPE column switching HPLC-MS system was applied to pharmacokinetic (PK) study of puerarin after a single orally dose in beagles. And the optimum conditions were successfully utilized to quantify puerarin in human plasma, which indicated the feasibility and the reliability of this method for application in preclinical and clinical PK studies of isoflavone drugs.     

Photosynthetic characteristics of C4 trait in chlorina mutant of rice (Oryza sativa L.)

Biao 810S is a chlorina mutant of the thermosensitive genic male sterile (TGMS) rice. We compared photosynthetic characteristics of these two lines. The contents of chlorophylls and carotenoids in Biao 810S were approximately half of those in 810S. However, the net photosynthetic rate (P _N) of Biao 810S was higher than that of 810S under high irradiance or low concentration of carbon dioxide, and the photon quantum efficiency was higher than that of 810S. The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase in Biao 810S was only 69.80 % of that in 810S, but the activities of phosphoenolpyruvate carboxylase and NADP-malic enzyme were 79.50 and 69.06 % higher than those of 810S, respectively, suggesting that the efficiency of photon energy utilization in Biao 810S was enhanced by reduction of thermal dissipation and increase of electron transfer rate to generate sufficient assimilation power for the dark reactions. Consequently, the increased activities of C₄ photosynthetic enzymes lead to more effective fixation of CO₂ and the synergistic effect of light and dark reactions contributed to the higher P _N of Biao 810S.