Biomedical subjects

Sheng Li

Publications and source records attributed to Sheng Li.

At least 37 records · Page 2Linked to original sources

PubMed2006

The effect of enslaving on perception of finger forces.

The primary purpose was to examine the effect of enslaving on finger force perception during isometric finger force production using an ipsilateral force-matching paradigm. Fourteen subjects were instructed to produce varying levels of reference forces [10, 20, 30, and 40% maximal voluntary contraction (MVC)] force using one finger (index, I or little, L) and to reproduce these forces using the same finger (homo-finger tasks, I/I and L/L) or a different finger (hetero-finger tasks, I/L and L/I). Forces of all fingers were recorded. During homo-finger tasks, no differences were found in force magnitude or relative level of force (expressed as a proportion of MVC). The index finger matching force magnitudes were greater than the little finger reference force magnitudes, with significantly lower levels of relative force during L/I tasks; while the little finger matching forces underestimated the index finger reference forces with significantly higher levels of relative force during I/L tasks. The difference in the matching and reference forces by the instructed finger(s), i.e., matching error, was larger in hetero-finger tasks than in homo-finger tasks, particularly at high reference force levels (30, 40% MVC). When forces of all fingers were considered, enslaving (uninstructed finger forces) significantly minimized matching errors of the total force during both I/L and L/I hetero-finger tasks, especially at high reference force levels. Our results show that there is a tendency to match the absolute magnitude of the total force during ipsilateral finger force-matching tasks. This tendency is likely related to enslaving effects. Our results provide evidence that all (instructed and uninstructed) finger forces are sensed, thus resulting in perception of the absolute magnitude of total finger force.

Adult↗

PubMed2006

Effects of changing wrist positions on finger flexor hypertonia in stroke survivors.

We sought to establish whether spastic hypertonia results from changes in intrinsic muscle properties or from altered stretch reflex properties. We hypothesized that finger flexor spastic hypertonia is primarily of neural origin, and that the dynamics of spastic muscle responses to stretch should therefore reflect the dynamics of muscle spindle receptor responses. In 12 stroke survivors, we recorded torque and electromyographic (EMG) responses of extrinsic finger flexors to constant-velocity rotation of the metacarpophalangeal (MCP) joints of the affected hand, over a range of initial muscle lengths. Stretch velocity was set to 6 degrees, 50 degrees, 150 degrees, or 300 degrees per second. Muscle length changes were imposed by changing wrist angle between 0 degree, 25 degrees, and 50 degrees of flexion. We found that reflex torque and EMG responses exhibited both velocity and length dependence, and there were significant interactions between velocity and length, replicating known characteristics of muscle spindle receptors. Our results support the hypothesis that finger flexor hypertonia is primarily of neural origin, and that it accurately reflects spindle receptor firing properties.

Adult↗

PubMed2006

Muscle engraftment of myogenic progenitor cells following intraarterial transplantation.

Cell-based therapy continues to be a promising avenue for the treatment of Duchenne muscular dystrophy (DMD), an X-linked skeletal muscle-wasting disease. Recently, we demonstrated that freshly isolated myogenic progenitors contained within the adult skeletal muscle side population (SP) can engraft into dystrophic fibers of nonirradiated mdx(5cv) mice after intravenous transplantation. Engraftment rates, however, have not been therapeutically significant, achieving at most 1% of skeletal muscle myofibers expressing protein from donor-derived nuclei. To enhance the engraftment of transplanted myogenic progenitors, an intraarterial delivery method was adapted from a previously described procedure. Cultured, lentivirus-transduced skeletal muscle SP cells, derived from mdx(5cv) mice, were transplanted into the femoral artery of noninjured mdx(5cv) mice. Based on the expression of microdystrophin or green fluorescent protein (GFP) transgenes in host muscle, sections of the recipient muscles exhibited 5%-8% of skeletal muscle fibers expressing donor-derived transgenes. Further, donor muscle SP cells, which did not express any myogenic markers prior to transplant, expressed the satellite cell transcription factor, Pax7, and the muscle-specific intermediate filament, desmin, after extravasation into host muscle. The expression of these muscle-specific markers indicates that progenitors within the side population can differentiate along the myogenic lineage after intraarterial transplantation and extravasation into host muscle. Given that femoral artery catheterization is a common, safe clinical procedure and that the transplantation of cultured adult muscle progenitor cells has proven to be safe in mice, our data may represent a step toward the improvement of cell-based therapies for DMD and other myogenic disorders.

Animals↗

PubMed2006

Influences of ventilation on maximal isometric force of the finger flexors.

Force production may be influenced by the phase of ventilation during which force is exerted. To examine the potential influences of ventilation on variability in maximal force measurements, we recorded peak isometric forces of the finger flexors during normal breathing, forced inspiration, forced expiration, and the Valsalva maneuver in 14 healthy adult subjects. The peak force increased significantly from forced inspiration to forced expiration (about 10%). Both forced expiration and inspiration resulted in increases in the flexor/extensor cocontraction ratio, whereas the Valsalva maneuver had no significant effects on maximal force or cocontraction ratio. Thus, this study clearly demonstrates the effects of ventilation on maximal finger force-generating capability. Ventilation needs to be controlled for accurate assessments of maximal force.

Adult↗

PubMed2006

The effect of three-dimensional glottal geometry on intraglottal quasi-steady flow distributions and their relationship with phonation.

Vocal fold geometry plays an important role in human phonation. The intraglottal quasi-steady pressure and velocity distributions depend upon the shape, size, and diameter of the glottis. This study reports the effects of the variation of glottal shapes on intraglottal pressures and velocities using a Plexiglas model with a glottis having nine symmetric glottal angles (uniform, as well as convergent and divergent 5 degrees, 10 degrees, 20 degrees and 40 degrees), while the minimal glottal diameter was held constant at 0.06 cm. The empirical data were supported by penalty finite element computational results. The results suggest that larger convergent glottal angles correspond to increased pressures and decreased velocities in the glottis upstream of the minimum glottal location, with a reversal of this pattern at the minimal glottal diameter location. The pressure dip near the glottal entrance for divergent glottal angles was greatest for the 10 degrees divergence angle condition, and was sequentially less for 5 degrees, 20 degrees, and 40 degrees. Flow resistance was greater for a convergent angle than a divergent angle of the same value, and least for the 10 degrees divergent condition. Pressure recovery in the glottis suggested that the optimal glottal diffuser angle was near 10 degrees. Results suggest that the glottal geometry has a critical relationship with phonation (especially for vocal efficiency), and therefore important significance to understanding artistic voice and clinical voice management.

Glottis↗

PubMed2006

Analysis of velopharyngeal morphology in adults with velopharyngeal incompetence after surgery of a cleft palate.

This study analyzed the relationship of velopharyngeal morphology and velopharyngeal function among 13 adults with velopharyngeal incompetence (VPI), 14 adults with velopharyngeal competence (VPC) after primary surgical treatment of cleft palate, and 20 noncleft adults. The measurements included velar length, pharyngeal depth, pharyngeal height, and the need ratio of pharyngeal depth to velar length. In addition, the cranial base, cervical vertebrae, posterior nasal spine, and also the position of the posterior pharyngeal wall (PPW) in the pharyngeal triangle were analyzed. All data were subjected to the Student t test of statistical significance. The results showed that the VPI group had normal pharyngeal depth and a significantly shorter velar length, resulting in a greater depth/length ratio than those of the VPC group and normal control subjects. The position of PPW in the pharyngeal triangle was located significantly more superior in the VPI group compared with the VPC group and normal control subjects. Measurements of the anteroposterior and the vertical dimensions in the regions of the cranial base and cervical vertebrae revealed no significant difference among the 3 groups. According to this study, the velopharyngeal morphology of adults with VPI is characterized by a shorter palate, greater need ratio, slightly counterclockwise-rotated pharyngeal triangle, and superiorly positioned PPW.

Adolescent↗

PubMed2006

Clinical and epidemiologic studies of nonsyndromic cleft lip and palate in china: analysis of 4268 cases.

The aim of our study was to review clinical and epidemiologic characteristic of the nonsyndromic cleft lip and cleft palate over a period of 10 years at West China Stomatological Hospital, Sichuan University. Four thousand two hundred sixty-eight nonsyndromic cleft lip and cleft palate cases were retrospectively analyzed according to the following variables: general information, cleft type, maternal age, familial history, as well as associated malformations, et al. In these cases, 1075 of which were cleft lip, 1985 were cleft lip with cleft palate; 1208 were isolated cleft palate. There were more men than women in the cleft lip and cleft lip with cleft palate group, while there were more women than men in the isolated cleft palate group. There were significantly more unilateral cleft lip cases than cleft lip on both sides; the cases of cleft lip on the left side were more than that of cleft lip on the right side. The cases with inherited history accounted for 6.68% of all the cases. Most infection cases occurred among the deleterious factors and the complications experienced during the first 3 months after the pregnancy. In all of the 14 twin cases, only 1 of the babies was affected. There were totally 152 cases with other associated malformations. Patients with cleft lip born in November to January were less than those born in the other three quarters of the year. Patients of A blood group composed a higher proportion than the control group. Our data may provide references for appropriate resource use, cleft lip and cleft palate prevention programs, and counseling programs with China-specific data.

Adult↗

PubMed2006

Possible association between response inhibition and a variant in the brain-expressed tryptophan hydroxylase-2 gene.

UNLABELLED: The ability to inhibit a response is an important component of normal behavioral control and is an aspect of psychopathology when diminished. Converging evidence implicates the serotonergic neurotransmitter system in response inhibition circuitry. OBJECTIVES: The present study examined potential associations between serotonergic genetic markers and response inhibition as indexed by Stop Task performance. METHODS: College-age participants (N=199) completed self-report questionnaires, the computerized Stop Task, and donated buccal cells for genetic analyses. Statistics were analyzed by ANOVA. RESULTS: Stop Signal reaction time was not associated with allelic variation at a monoamine oxidase A promoter length polymorphism or a serotonin 1B terminal autoreceptor polymorphism (G861C). An intronic genetic marker of the neuronal tryptophan hydroxylase-2 (the rate-limiting enzyme for serotonin biosynthesis) gene, however, was associated with the Stop Signal reaction time. Individuals homozygous for the T variant at an intron-8 polymorphism had the longest Stop Signal reaction time (i.e. greater impulsivity, P=0.01), and this effect was stronger in males (P=0.01) than in females (P=0.10). CONCLUSIONS: A genotype at an intron-8 tryptophan hydroxylase-2 polymorphism was associated with response inhibition as indexed by the Stop Task. These results, if replicated, would implicate dorsal raphe serotonin neurons in response inhibition. It may be that individuals with the T/T genotype may have reduced tryptophan hydroxylase-2 function and correspondingly lower central serotonin levels; however, further investigation of the reported association is required.

Adult↗

PubMed2006

The effect of glottal angle on intraglottal pressure.

Intraglottal pressure distributions depend upon glottal shape, size, and diameter. This study reports the effects of varying glottal angle on intraglottal and transglottal pressures using a three-dimensional Plexiglas model with a glottis having nine symmetric glottal angles and a constant minimal glottal diameter of 0.06 cm. The empirical data were supported by computational results using FLUENT. The results suggested that (1) the greater the convergent glottal angle, the greater outward driving forces (higher intraglottal pressures) on the vocal folds; (2) flow resistance was greatest for the uniform glottis, and least for the 10 degrees divergent glottis; (3) the greatest negative pressure in the glottis and therefore the greatest pressure recovery for diverging glottal shapes occurred for an angle of 10 degrees; (4) the smaller the convergent angle, the greater the flow resistance; (5) FLUENT was highly accurate in predicting the empirical pressures of this model; (6) flow separation locations (given by FLUENT) for the divergent glottis moved upstream for larger flows and larger glottal angles. The results suggest that phonatory efficiency related to aerodynamics may be enhanced with vocal fold oscillations that include large convergent angles during glottal opening and small (5 degrees - 10 degrees) divergent angles during glottal closing.

Glottis↗

PubMed2006

Numerical study of the effects of inferior and superior vocal fold surface angles on vocal fold pressure distributions.

Vocal fold geometry plays an important role in human phonation. A wide range of inferior and superior vocal fold surface angles has been shown to be present during phonation [Nanayakkara, Master's thesis, Bowling Green State University, Bowling Green, OH (2005)]. This study explored how these angles affect pressure distributions on the vocal folds, and thus how they may affect phonation. The computational code FLUENT was used to obtain pressure distributions for laminar, incompressible flow. Eighteen inferior vocal fold surface angles and nineteen superior vocal fold surface angles were selected for three specific glottal angles, uniform 0 degrees, convergent 10 degrees, and divergent 10 degrees. Minimal glottal diameter (0.01 cm), transglottal pressure (8 cm H2O), and glottal entrance radius (0.15 cm) were held constant, and the glottal exit radius was constant for each glottal angle. Results suggest that the vocal fold surface pressures are independent of the inferior and superior vocal fold surface angles realistic for human phonation. These results suggest that, in contrast to the important effects of glottal entrance and exit radii, minimal diameter, and angle on intraglottal pressures, the inferior and superior vocal fold surface angles (excluding possible interactive effects with the false vocal folds) do not have an influence on the intraglottal pressures.

Binomial Distribution↗

PubMed2006

Intracellular signal transduction for migration and actin remodeling in vascular smooth muscle cells after sphingosylphosphorylcholine stimulation.

Molecular mechanisms underlying migration of vascular smooth muscle cells (VSMCs) toward sphingosylphosphorylcholine (SPC) were analyzed in light of the hypothesis that remodeling of the actin cytoskeleton should be involved. After SPC stimulation, mitogen-activated protein kinases (MAPKs), including p38 MAPK (p38) and p42/44 MAPK (p42/44), were found to be phosphorylated. Migration of cells toward SPC was reduced in the presence of SB-203580, an inhibitor of p38, but not PD-98059, an inhibitor of p42/44. Pertussis toxin (PTX), a Gi protein inhibitor, induced an inhibitory effect on p38 phosphorylation and VSMC migration. Myosin light chain (MLC) phosphorylation occurred after SPC stimulation with or without pretreatment with SB-203580 or PTX. The MLC kinase inhibitor ML-7 and the Rho kinase inhibitor Y-27632 inhibited MLC phosphorylation but only partially inhibited SPC-directed migration. Complete inhibition was achieved with the addition of SB-203580. After SPC stimulation, the actin cytoskeleton formed thick bundles of actin filaments around the periphery of cells, and the cells were surrounded by elongated filopodia, i.e., magunapodia. The peripheral actin bundles consisted of alpha- and beta-actin, but magunapodia consisted exclusively of beta-actin. Such a remodeling of actin was reversed by addition of SB-203580 and PTX, but not ML-7 or Y-27632. Taken together, our biochemical and morphological data confirmed the regulation of actin remodeling and suggest that VSMCs migrate toward SPC, not only by an MLC phosphorylation-dependent pathway, but also by an MLC phosphorylation-independent pathway.

Actins↗

PubMed2006

[Separation and culture of mouse embryonic palatal mesenchymal cells in vitro].

OBJECTIVE: To modify the operation of dissecting embryonic palatal shelves and purify the mouse embryonic palatal mesenchymal (EPM) cells in primary culture. METHODS: The embryonic palatal shelves were dissected using a surgical microscope by modified operation. Then the embryonic palatal shelves were incubated with Dispase and the isolated EPM cells were cultured. Immunofluorescence technique was used to identify the characteristics of cells. RESULTS: Embryonic palatal shelves could be dissected accurately and easily with a modified operation. The purified EPM cells contained scarcely epithelial cells. EPM cells were anti-HNK-1, S-100, vimentin positive and anti-CK negative. CONCLUSION: A modified method for dissecting embryonic palatal shelves and purifying the EPM cells of primary culture was established.

Animals↗

PubMed2006

[Individual repair technique of microform cleft lip: state of art].

OBJECTIVE: To explore an technique to repair the microform cleft lip (MCL). METHODS: The individual method was used to repair the MCL, a contrastive research was carried to analyzed the result. RESULTS: It was found that the form of the cupid's bow was good, and the configure of the upper lip was reconstructed. The deficit of the orbicularis muscle was overcame and the function was satisfying by this procedure. Symmetry was recovered. CONCLUSIONS: Individual technique is an available method to repair the microform cleft lip. Furthermore, this technique is also promising to repair the other kinds of cleft lip.

Cleft Lip↗

PubMed2005

Molecular determinants for interaction of SHEP1 with Cas localize to a highly solvent-protected region in the complex.

Protein-protein interactions between SHEP and Cas proteins influence cellular signaling through tyrosine kinases, as well as integrin-mediated signaling, and may be linked to antiestrogen resistance. Data from past studies suggests that association between SHEP and Cas proteins is critical for these cellular effects. In this study, the interacting domains of each protein were co-expressed in bacteria and a soluble stable complex was purified. Deuterium exchange mass spectrometry was used to define regions that are buried when SHEP1 is in complex with Cas. The results reveal four segments in SHEP1 that are highly protected, including a region (residues 619-640) that contains a key residue, tyrosine 635, required for association with Cas. This region is predominately hydrophilic, yet remains protected from solvent in the complex.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Loss of heterozygosity analyzed by single nucleotide polymorphism array in cancer.

Neoplastic progression is generally characterized by the accumulation of multiple genetic alterations including loss of tumor suppression gene function. Loss of heterozygosity (LOH) has been used to identify genomic regions that harbor tumor suppressor genes and to characterize different tumor types, pathological stages and progression. LOH pattern has been detected by allelotyping using restriction fragment length polymorphism, and later by simple sequence length polymorphisms (SSLPs or microsatellite) for 10 years. This paper reviews the detection of LOH by recently developed single nucleotide polymorphism (SNP) arrays (all analyzed by Affymetrix array); furthermore, its advantage and disadvantage were analyzed in several kinds of cancer.

Genes, Tumor Suppressor↗

PubMed2005

Structural determinants for the binding of anthrax lethal factor to oligomeric protective antigen.

Anthrax lethal toxin assembles at the surface of mammalian cells when the lethal factor (LF) binds via its amino-terminal domain, LF(N), to oligomeric forms of activated protective antigen (PA). LF x PA complexes are then trafficked to acidified endosomes, where PA forms heptameric pores in the bounding membrane and LF translocates through these pores to the cytosol. We used enhanced peptide amide hydrogen/deuterium exchange mass spectrometry and directed mutagenesis to define the surface on LF(N) that interacts with PA. A continuous surface encompassing one face of LF(N) became protected from deuterium exchange when LF(N) was bound to a PA dimer. Directed mutational analysis demonstrated that residues within this surface on LF(N) interact with Lys-197 on two PA subunits simultaneously, thereby showing that LF(N) spans the PA subunit:subunit interface and explaining why heptameric PA binds a maximum of three LF(N) molecules. Our results elucidate the structural basis for anthrax lethal toxin assembly and may be useful in developing drugs to block toxin action.

Antigens, Bacterial↗

PubMed2005

Comparing two evolutionary mechanisms of modern tRNAs.

All modern tRNA gene families have a high similarity in their primary structure, and share the same cloverleaf secondary structure and an inverted L tertiary structure, which provide the clues for the study of their origin and evolution. There are two important mechanisms of the tRNA sequences evolution. One is point mutation, another is complementary duplication method. Both of them are supported by some specific examples. To find out the superior one of the two mechanisms or find out the most suitable mechanism for modern tRNAs evolution, we constructed two types of networks, parallel and antiparallel networks, based on the two mechanisms respectively, and then compared the degree distribution and clustering coefficient of networks constructed by the tRNA sequences of the single anticodon group, single isoaccepting group, and the whole tRNAs group of the two types of networks. The result of the comparison seems consistent with the idea that modern tRNA sequences evolved primarily by the mechanism of complementary method, and point mutation is an important and indispensable auxiliary mechanism during the evolutionary event.

Base Pairing↗

PubMed2005

Bright cyclic light accelerates photoreceptor cell degeneration in tubby mice.

Photoreceptor cell death is an irreversible, pathologic event in many blinding retinal diseases including retinitis pigmentosa, age-related macular disease, and retinal detachment. Light exposure can exacerbate a variety of human retinal diseases by increasing the rate of photoreceptor cell death. In the present study, we characterize the kinetics of photoreceptor cell death in Tubby (homozygous tub/tub, which have inherited, progressive retinal degeneration) mice born and raised in a bright cyclic light environment. Our data show that raising tub/tub mice in a bright cyclic light environment induces rapid loss of photoreceptors. This effect can be slowed, but not prevented, by raising animals in constant darkness, which suggests the involvement of phototransduction in the accelerated death of photoreceptors in this animal. We further demonstrated that the activities of cytosolic cytochrome c and caspases-3 and -9 were significantly increased in the retinas of tub/tub mice. Raising animals in darkness significantly reduced the increased activities of caspases-3 and -9, as well as cytosolic cytochrome c. We also observed that rhodopsin, a phototransduction protein, is not restricted to the rod outer segment, but is distributed throughout the rod cell, including the inner segments, cell bodies, and synapses. In addition, the light-dependent translocation and compartmentalization of arrestin and transducin are affected by the tubby mutation. Our results support the interpretation that problems in protein trafficking in the photoreceptors of the tub/tub mouse may contribute to retinal degeneration.

Adaptor Proteins, Signal Transducing↗