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Sheng Li

Publications and source records attributed to Sheng Li.

82 records · Page 5Linked to original sources
PubMed2002

Effects of age and gender on finger coordination in MVC and submaximal force-matching tasks.

The objective of the study is to examine the effects of age and gender on finger coordination. Twelve young (24 +/- 8 yr; 6 men and 6 women) and 12 elderly (75 +/- 5 yr; 6 men and 6 women) subjects performed single-finger maximal contraction [maximal voluntary contraction (MVC)], four-finger MVC, and four-finger ramp force production tasks by pressing on individual force transducers. A drop in the force of individual fingers during four-finger MVC tasks compared with single-finger MVC tasks (force deficit) was larger, whereas unintended force production by other fingers during single-finger MVC tasks (enslaving) was smaller, in elderly than in young subjects and in women than in men. Force deficit was smaller and enslaving was larger in subjects with higher peak force. During the ramp task, the difference between the variance of total force and the sum of variances of individual forces showed a logarithmic relation to the level of total force, across all subject groups. These findings suggest that indexes of finger coordination scale with force-generating capabilities across gender and age groups.

Adult↗
PubMed2002

Relations between surface EMG of extrinsic flexors and individual finger forces support the notion of muscle compartments.

The goal of this experiment was to investigate the relationship between individual fingertip forces and the surface EMG of multi-digit muscles. The surface EMG of the hand extrinsic flexors (flexor digitorum profundis and superficialis) was recorded in eight subjects during multi-digit force production tasks. In one session, subjects pressed with all four fingers (IMRL, I = index, M = middle, R = ring, and L = little finger) with the total force ranging from 10% and 90% of their maximum force (MVC). Results showed a close linear relationship between an integrated EMG index and force. In another session, subjects produced constant total force of either 10% or 30% of their IMRL MVC, with different finger combinations such that the degree of involvement of each finger was manipulated (15 finger combinations were tested). The EMG level of the flexors depended greatly on the finger combination (P < 0.001). Multi-variable regression made it possible to describe the flexor EMG as a linear function of individual fingertip forces. These results suggest that: (1) hand extrinsic flexors muscles are arranged in functional compartments serving individual fingers, and (2) each compartment has a force/EMG relationship that is close to being linear.

Adult↗
PubMed2002

Central mechanisms of finger interaction during one- and two-hand force production at distal and proximal phalanges.

In this study we used changes in the relative involvement of different muscle groups during force production at the distal (DT) and proximal (PR) phalanges to test and modify a hypothesis on the central organization of multi-finger control for tasks involving non-homologous elements in the two hands. Ten subjects produced maximal force with different finger combinations. Two symmetrical (PR/PR and DT/DT) and two asymmetrical (PR/DT and DT/PR) combinations of force application sites in the two hands were used. During one-hand tasks, higher forces were produced at the PR site. In multi-finger tasks, total peak force was smaller than the sum of peak forces in single-finger tasks by the involved fingers (force deficit). Force production by some fingers of a hand was accompanied by involuntary force production by other fingers (enslaving). Force deficit and enslaving were both higher at the PR site. Two-hand tasks were accompanied by an additional drop in the force of individual fingers, i.e., bilateral deficit (BD). When symmetrical sites of force production were used in the two hands, BD was lower for symmetrical finger groups than for asymmetrical groups. During tests at asymmetrical sites, BD was higher and did not depend on symmetry of involved finger groups. We conclude that within-a-hand force deficit and enslaving are likely to be of a central, neural origin. An earlier introduced hypothesis has been expanded assuming that excitatory projections to contralateral finger representations exist only for homologous elements (sub-synergies) of a multi-finger force production synergy, while only inhibitory projections connect non-homologous elements.

Adult↗
PubMed2002

Viral vectors for gene transfer of micro-, mini-, or full-length dystrophin.

Gene therapy for Duchenne muscular dystrophy will require methods to deliver gene constructs encoding functional versions of dystrophin to the vast majority of a patient's musculature. Obstacles to achieving these goals include identifying which forms of dystrophin would be effective in a clinical setting and developing gene delivery shuttles capable of carrying and expressing dystrophin cassettes without toxic or adverse immunologic consequences. We review here recent work from our laboratory to identify sequences within dystrophin that are required to prevent development of dystrophic changes in muscle or which might be able to correct pre-existing damage. We also describe work aimed at developing viral shuttle vectors able to carry and express these dystrophin cassettes at high levels and in a muscle-specific fashion. While great challenges remain in developing methods for systemic gene delivery, we show that a variety of viral vectors are able to carry and express therapeutic levels of dystrophin when delivered directly to mouse skeletal muscle.

Adenoviridae↗
PubMed2002

The eukaryotic two-component histidine kinase Sln1p regulates OCH1 via the transcription factor, Skn7p.

The yeast "two-component" osmotic stress phosphorelay consists of the histidine kinase, Sln1p, the phosphorelay intermediate, Ypd1p and two response regulators, Ssk1p and Skn7p, whose activities are regulated by phosphorylation of a conserved aspartyl residue in the receiver domain. Dephospho-Ssk1p leads to activation of the hyper-osmotic response (HOG) pathway, whereas phospho-Skn7p presumably leads to activation of hypo-osmotic response genes. The multifunctional Skn7 protein is important in oxidative as well as osmotic stress; however, the Skn7p receiver domain aspartate that is the phosphoacceptor in the SLN1 pathway is dispensable for oxidative stress. Like many well-characterized bacterial response regulators, Skn7p is a transcription factor. In this report we investigate the role of Skn7p in osmotic response gene activation. Our studies reveal that the Skn7p HSF-like DNA binding domain interacts with a cis-acting element identified upstream of OCH1 that is distinct from the previously defined HSE-like Skn7p binding site. Our data support a model in which Skn7p receiver domain phosphorylation affects transcriptional activation rather than DNA binding to this class of DNA binding site.

Aspartic Acid↗
PubMed2002

Antisocial alcoholism and serotonin-related polymorphisms: association tests.

Central serotonin dysfunction appears to be related to a subtype of alcoholism with antisocial impulsive features (type II; antisocial alcoholism). The serotonergic deficit may be associated with greater impulsivity, which in turn facilitates both alcohol dependence and antisocial behavior. The present study tested association of antisocial impulsive alcoholism with candidate genes related to serotonergic neurotransmission, using families. Eight markers were assayed using polymerase chain reaction: tryptophan hydroxylase (intron 7), the serotonin transporter SLC6A4 (VNTR 9/12), HTTLPR, the three serotonin receptor types HTR1B (G861C), HTR2A (T102C) and HTR2C (Cys23Ser), monoamine oxidase A (T1460C), and (CA)(n). Eligible probands had early age of onset of alcoholism, child conduct disorder, and two or more symptoms of adult Antisocial Personality Disorder. This sample included 35 probands, their parents, and some siblings (n = 116). Association tests were conducted using the Haplotype Relative Risk method for antisocial alcoholism diagnosis and the George-Elston regression method (the S.A.G.E. program ASSOC) for quantitative antisocial alcoholism severity. Haplotype Relative Risk analyses were not significant at the 0.05 level for any of the markers. Trends suggestive for future research occurred for tryptophan hydroxylase and HTR2A. Quantitative ASSOC analyses showed significant marker effects (P < 0.05) for both monoamine oxidase A markers, which were in linkage disequilibrium. Antisocial alcoholism symptom severity was higher with monoamine oxidase A C homozygotes or hemizygotes, indicating that low monoamine oxidase activity may be important. Future studies are needed to examine joint and interactive effects of serotonin-related markers.

Adult↗
PubMed2002

Purification and characterization of a novel chitinase from Bacillus brevis.

An extracellular chitinase secreted by Bacillus brevis was purified to homogeneity by a combination of ammonium sulfate precipitation, Phenyl-Sepharose hydrophobic-interaction chromatography and DEAE anion-exchange chromatography. On SDS-polyacrylamide gel electrophoresis analysis, the purified enzyme showed a mass of 85 kD even in the presence of beta mercaptoethanol, but shifted to 48 kD when heated in boiling water or treated with 8 mol/L urea at 50 degrees for 10 min. The depolymerization of subunits was accompanied with the loss of chitinase activity, and removing denaturing factors by dialysis could restore the dimer structure and enzymatic activity. The enzyme had an isoelectric point of 5.5 and an optimal temperature of 60 degrees, and was most active at pH 8.0. The enzymatic activity was stable at pH 6-10, and inhibited by Ag(+). Ten N-terminal amino acids were determined to be AVSNSKIIGY, demonstrating that the purified enzyme was a novel one. The hydrolysis pattern of the purified enzyme indicated that the chitinase was an endochitinase. The extraordinary thermo-stability and high resistance to proteolysis provide the enzyme with a good prospect to be used as a new tool for biocontrol.

Bacillus↗
PubMed2002

[Endovascular thrombolysis and stent angioplasty for obliteration in cerebral venous sinuses].

OBJECTIVE: To summarize the experience of treating the obliteration of the cerebral venous sinus in 17 patients by using direct thrombolysis and stent angioplasty. METHODS: All 17 patients with thrombosis and stenosis of the venous sinus were confirmed by digital subtraction angiography. Of these 3 patients had thrombosis in a single sinus and 14 had thrombosis in multiple sinuses. The circulating time was prolonged for over 13 seconds. The micro-catheter was preserved in the sinus for 5 days, followed by infusion of urokinase 1.5 million units and oral warfarin 3-5 mg each day. Stent angioplasty was done for 4 patients with obvious stenosis of the venous sinus detected by DSA after thrombosis. RESULTS: After contact thrombosis and stent angioplasty in sinuses of the 17 patients, remarkable recanalization of obliterated sinuses was achieved. After treatment, intracranial hypertension pressure (ICP) returned to normal in 7 patients, and 8 thrombosis relapsed in different degree after 7 days. Anticoagulation was prescribed. Only 2 patients showed the ICP above 280 mm H(2)O. No obvious relapse was found in 15 patients during the follow-up for 3-60 months. CONCLUSION: Our results demonstrated that successive thrombolysis and stent angioplasty for occlusion and thrombosis of the venous sinus are effective in promoting drainage of cerebral venous blood and rapidly decreasing ICP.

Administration, Oral↗