Magnetic resonance imaging and electromyography as indexes of muscle function.

Electromyography (EMG) is commonly used to determine the electrical activity of skeletal muscle during contraction. To date, independent verification of the relationship between muscle use and EMG has not been provided. It has recently been shown that relaxation- (e.g., T2) weighted magnetic resonance images (MRI) of skeletal muscle demonstrate exercise-induced contrast enhancement that is graded with exercise intensity. This study was conducted to test the hypothesis that exercise-induced magnetic resonance (MR) contrast shifts would relate to EMG amplitude if both measures reflect muscle use during exercise. Both MRI and EMG data were collected for separate eccentric (ECC) and concentric (CON) exercise of increasing intensity to take advantage of the fact that the rate of increase and amplitude of EMG activity are markedly greater for CON muscle actions. Seven subjects 30 +/- 2 (SE) yr old performed five sets of 10 CON or ECC arm curls with each of four resistances representing 40, 60, 80, and 100% of their 10 repetition maximum for CON curls. There was 1.5 min between sets and 30 min between bouts (5 sets of 10 actions at each relative resistance). Multiple echo, transaxial T2-weighted MR images (1.5 T, TR/TE 2,000/30) were collected from a 7-cm region in the middle of the arm before exercise and immediately after each bout. Surface EMG signals were collected from both heads of the biceps brachii and the long head of the triceps brachii muscles. CON and ECC actions resulted in increased integrated EMG (IEMG) and T2 values that were strongly related (r = 0.99, P < 0.05) with relative resistance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lipase catalyzed reactions of aliphatic and arylaliphatic carbonic acid esters

Symmetrical dialkyl carbonates and dibenzyl carbonates reacted with various nucleophiles in the presence of Candida antarctica lipase B in organic solvents. For example, reaction of dibutyl and dibenzyl carbonate with an alcohol gave a mixture of the mono- and disubstituted products. Aminolysis, however, afforded only the carbamates, without subsequent reaction to the ureum derivatives. The reaction rates were rather low compared with carboxylic esters; the reactivity increased in the order dimethyl相似文献   

The interaction of nucleotides and yeast hexokinase

The kinetics of ethenoadenosine triphosphate (?ATP) as the phosphate donor in the phosphoryl transfer reaction of hexokinase were examined to obtain the K_m′s, V's, and K_α's for the nucleotide and sugar. Dissociation constants for eATP and ?ADP with hexokinase were obtained from fluorometric measurements and compared with similar constants obtained kinetically. Other selected nucleoside triphosphates were used as phosphate donors in the hexokinase reaction and their kinetic constants were obtained. Reactions were also performed using two nucleotides simultaneously as phosphorylating substrates for the hexokinase reaction in an attempt to find the individual dissociation constants, K_m′s and K_i′s. These were compared with the K_m′s obtained from using the nucleotides separately in the hexokinase reaction. From these kinetic and fluorescence binding studies, evidence is presented supporting the postulate that the K_m′s are primarily dissociation constants in a random bi-bi mechanism. Analysis of the K_m values provides additional evidence to support the importance of the amino group in position 6 on the purine ring as a hydrogen-bond acceptor during binding. It was found that ?CTP was a much better hexokinase substrate than CTP. These observations suggest that the V for this reaction is highly dependent upon the size of the nucleotide.     

The effectiveness of constructed wetland for treatment of woodwaste leachate

Percolation of rainfall through woodwaste piles leaches natural chemicals from the wood residuals that can have adverse impacts on the environment. A study was conducted on a woodwaste storage site, adjacent to the Lower Fraser River, near Mission, BC, Canada. The objective of this research was to evaluate the effectiveness of constructed wetland for treatment of this woodwaste leachate. The leachate was characterized by high oxygen demand, tannin and lignin, and volatile fatty acids (VFAs), but low pH and nutrients. Diluted leachate passed through six pilot-scale wetland cells, four planted with cattail (Typha latifolia) and two unplanted controls, with a hydraulic retention time of 7 days and an average depth of 40 cm. Nutrient addition and pH adjustments were made to improve contaminant removal. Reductions in contaminants were consistently achieved, with average removals for BOD, COD, VFAs and tannin and lignin of 60, 50, 69 and 42%, respectively. Climatic conditions had an impact on the performance of the constructed wetland. Further operation of the system will help to elucidate the seasonal fluctuations. Aging of the constructed wetland system increased the treatment performance.     

A 15N nuclear magnetic resonance study of the biosynthesis of quinoxaline antibiotics

Uniformly ¹⁵N-labelled triostin A and echinomycin have been prepared by growing the producing organisms on enriched media and their ¹⁵N nuclear magnetic resonance spectra partially assigned by a combination of nuclear Overhauser effect and scalar coupling constant measurements. Selective feeding experiments using unlabelled L-tryptophan-supplemented media have shown that N-1 and N-4 of the quinoxaline rings have their origins in the indole and amino groups of tryptophan, respectively.     

Enumeration of potentially pathogenic bacteria from sewage sludges.

To ascertain the health risks that may be posed by the land application of sewage sludges, a scheme was devised to determine the types and numbers of pathogenic and potentially pathogenic bacteria present in sludges. A processing treatment was adapted to sludge to give a homogenate which yielded the greatest numbers of viable bacteria. Conventional methods were successful in enumerating Klebsiella, Staphylococcus, gram-negative enteric bacteria, and commonly used indicator organisms. Modifications of conventional methods improved the enumeration of Salmonella, Mycobacterium sp., fluorescent Pseudomonas sp., and Clostridium perfringens. However, Shigella methodology yielded only one isolate. Utilizing the proposed scheme, the population densities of these organisms were estimated in three domestic wastewater sludges. In light of these results, the potential impact of land application of sewage sludges is discussed.