Biomedical subjects

Sheng Li

Publications and source records attributed to Sheng Li.

At least 73 records · Page 4Linked to original sources

PubMed2004

Nicotinic acetylcholine receptor alpha7 subunit mediates migration of vascular smooth muscle cells toward nicotine.

GbaSM-4 cells, vascular smooth muscle cells (VSMCs) derived from brain basilar arteries, were shown to migrate toward d-nicotine by augmenting the actin cytoskeleton in their cell bodies and lamellipodia, and expression of nicotinic acetylcholine receptor (alpha7-nAChR) was detected in GbaSM-4 cells. Their chemotaxis was antagonized by an alpha7-nAChR antagonist of methyllycaconitine. It was also antagonized by inhibiting myosin light chain (MLC) kinase and by down-regulating MLC kinase. However, the changes in MLC phosphorylation were not associated with the nicotine treatment, suggesting the involvement of non-kinase activity of MLC kinase as reviewed by Gao et al. (IUBMB Life. 2001;51:337). This plot may work to induce arteriosclerosis during cigarette smoking.

Aconitine↗

PubMed2004

[The influence to maxillary growth by exposed bone wound in hard palate of rat].

OBJECTIVE: To confirm if denuded bone on lateral aspects of the hard palate of surgical repairs of the cleft palate is the main reason of causing disturbance of facial growth and to investigate the mechanism. METHODS: 48 SD rats were employed in the study. Among them 40 animals were divided into normal control and experimental group randomly. Normal control was not operated. Hard palate mucoperiosteum on the left side in experimental group were excised. Left hard palate mucoperiosteum in another 8 female three-week-old SD rats were excised with same method and were sacrificed at 2nd, 5th, 8th, and 12th day, respectively. The 8 rats were used for histological research. RESULTS: The width of all left sides hard palates in experimental group was significantly narrower than right side, and demonstrated statistical difference. Chronic osteomyelitis on the denuded hard palate was observed. CONCLUSION: The denuded bone wound might be a principal factor for the following maxillary growth deformity in cleft palate patients who received palatoplasty in childhood. The mechanism of causing the deformity might be wound and scar contraction, decreased blood flow and nutrition plus chronic osteomyelitis.

Animals↗

PubMed2004

[The expression of CXCR4 on acute leukemia cells and its implication for extramedullary infiltration].

OBJECTIVE: To study the expression of CXCR4 in acute leukemic cells and its clinical significance. METHOD: Bone marrow samples from 73 acute leukemia patients and leukemic cell lines were investigated by flow cytometry (FCM), the expression of SDF-1 in human marrow stromal cells and meninges were studied by using reverse transcription polymerase chain reaction (RT-PCR). Adhesion, migration and invasion of U937, NB4 and K562 cells were studied in vitro. RESULTS: The expression rates of CXCR4 in ALL and AML patients was 65.6% and 17.1%, respectively. And it was 0.2%, 41.0% and 52.0% in K562, U937 and NB4 cells, respectively. The extramedullary infiltration rates were 61.9% and 18.2% for CXCR4 positive and negative groups of ALL, respectively (P < 0.05); while in AML, the number of peripheral white blood cells in CXCR4 positive group was lower than that in CXCR4 negative group (P < 0.05). SDF-1alpha could enhance the adhesion, migration and invasion capacity of leukemic cells in vitro. CONCLUSION: Overexpression of CXCR4 in AL cells might be the molecular mechanism of extramedullary infiltration in leukemia.

Acute Disease↗

PubMed2004

[Determination of trace germanium in coal by spectrophotometry with 2,4-dichlorophenylfluorone].

A method for the determination of germanium in coal samples by spectrophotometry has been developed. The color reaction of germanium with 2,4-dichlorophenylfluorone (2,4-DCIPF) in the presence of cetyltrimethylammonium bromide (CTMAB) has been studied. The results show that Ge(IV) reacts on 2,4-DCIPF and CTMAB to form a multicomponent complex in a 1.8-2.5 mol x L(-1) H2SO4 medium. The complex has the maximum absorption wavelength at 516 nm and its apparent molar absorptivity epsilon is 1.38 x 10(5) L x mol(-1) x cm(-1). Beer's law is obeyed in the range of 0-12.5 microg x (25 mL)(-1) for Ge(IV). The recovery of standard addition is 103%-106% and the relative standard deviation (RSD) is 1.1%-1.7%. This method has been applied to the determination of Ge(IV) in coal samples with satisfactory results.

4-Aminopyridine↗

PubMed2003

Matrix analyses of interaction among fingers in static force production tasks.

The fingers on a hand show interactions in force production tasks. The interfinger connection matrices (IFMs) quantify these interactions (Li et al. 2002; Zatsiorsky et al. 2002b; Danion et al. 2003). The goal of the present study was to explore the differences in the IFMs of individual subjects and, in particular, to establish a procedure that may be used in the future for diagnostic purposes. Subjects ( n=20) pressed downward maximally with ten different combinations of the four fingers, index (I), middle (M), ring (R), and little (L): I, M, R, L, IM, MR, RL, IMR, MRL, and IMRL. Voluntary activation of a subset of the four fingers was accompanied by an involuntary force production by fingers that were not intentionally activated (enslaving). Interfinger connection matrices were computed for each subject by the artificial neural network. The similarities/dissimilarities (proximities) between the individual matrices were determined. This procedure was performed twice: (a) for nonnormalized IFMs whose elements represented the amount of force (in newtons) exerted by a finger i in response to a unit command to a finger j; and (b) for normalized IFMs, after dividing the elements of each IFM by the total force produced by the four fingers acting together (the elements of the matrix are in percents). The 20x20 matrix of the proximities was subjected to multidimensional scaling (MDS) to reduce the number of dimensions and identify the major ones. To interpret the meaning of the computed dimensions, they were regressed on a set of finger force parameters described in the text. For the nonnormalized IFMs an interpretable dimension was the strength of the subjects. For the normalized IFMs two dimensions were interpreted: (a) the location of the point of resultant force application along the mediolateral axis that is defined by the pattern of force sharing among the fingers and (b) the total contribution of the enslaved forces into the total finger force. We speculate that the similarity of typical everyday tasks across the population promotes the similarity of the IMFs reflecting optimal hand functioning over these tasks.

Adult↗

PubMed2003

Dendrimer disassembly by benzyl ether depolymerization.

The disassembly of dendritic structures was realized by a cascade cleavage reaction triggered by an initially stimulated group in the dendrimer periphery. A depolymerizable backbone was engineered into prototypical dendritic structures. Evidence for the completion of the disassembly process is provided by the absorbance peak of the p-nitrophenoxide ion that was intentionally installed at the focal point of the dendrons. Observation of the UV spectra during the disassembly process supports a stepwise cascade cleavage proceeding from the periphery into the core.

Delayed-Action Preparations↗

PubMed2003

Association of APOE gene with schizophrenia in Chinese: a possible risk factor in times of malnutrition.

Five hundred and seventy nine Chinese patients with schizophrenia who met DSMIV criteria for the disorder were genotyped for alleles epsilon 2,3,4 of apolipoprotein E (APOE) gene. All were recruited from inpatients and outpatients attending a large mental health centre in Shanghai. Results were compared to APOE data on 1528 controls drawn from the same area. Major differences in APOE genotype ratios and allele frequencies were observed between the patients and controls. The patients with schizophrenia had highly significantly (p<0.0001) increased epsilon 4/-genotypes and allele frequencies, and decreased epsilon 3/3 genotypes and epsilon 3 allele frequencies compared to controls. The effect was independent of sex and/or age of onset of illness, but strongly influenced by date of birth. Significant differences were restricted to individuals with schizophrenia born either before 1949 or during the period 1958-1967. Both were times of severe food shortages and malnutrition. We suggest that APOE may operate as an additional risk factor for schizophrenia in individuals subjected to fetal and/or early postnatal malnutrition.

Adult↗

PubMed2003

Finger interaction during multi-finger tasks involving finger addition and removal.

The purpose of this study was to investigate changes in finger forces and their interactions in one-hand multi-finger force production tasks involving finger addition and removal. Eight male subjects were instructed to produce maximal (MVC) forces with explicitly instructed ('master') fingers. After reaching maximal force with a set of master fingers, the subjects added/removed one master finger while continuing to produce the MVC with the new group of master fingers. The non-instructed ('slave') fingers also produced forces (enslaving). Finger addition/removal led to changes in the forces of individual master fingers expected from earlier studies of maximal force production by different finger groups acting synchronously. A significant increase in the forces of remaining master fingers was observed after finger removal and a close-to-significant drop in the forces of previously recruited master fingers was observed after finger addition. These effects were larger when subjects started the task with a smaller number of explicitly involved fingers. The enslaving effects increased after finger addition while they did not change after finger removal. Forces produced by the same group of master fingers acting in different tasks showed no history-dependent effects. However, significant effects of history were seen in enslaving. These observations speak against hypotheses of more independent behaviour of effectors during their asynchronous involvement. They show that finger interaction may show effects of the history of finger involvement in a task.

Adult↗

PubMed2003

Regulation of protein tyrosine phosphatase 1B in intact cells by S-nitrosothiols.

Protein tyrosine phosphatases (PTPases) contain an active site cysteine which when oxidized leads to loss of phosphatase activity and accumulation of phosphoproteins. For example, oxidants produced following EGF stimulation inhibit PTP1B and enhance EGF receptor phosphorylation. Because NO-derived species also modify reactive thiols, we postulated that NO would reversibly inhibit PTP1B. In our studies we exposed A431 or Jurkat cells to NO donors and measured PTP1B activity or used 3-maleimidylpropionylbiocytin (MPB) to measure thiol redox status. Nitrosothiols led to a rapid inhibition of PTP1B through a mechanism that was greatly enhanced by addition of cysteine to the medium. Analysis of thiol oxidation status using immunoprecipitated PTP1B showed modification consistent with loss of activity. Both enzyme inhibition and modification were reversible in intact cells or after addition of DTT to cell lysates. While DTT reversed oxidation, ascorbate did not, suggesting that formation of a mixed disulfide (possibly glutathionylation) rather than S-nitrosylation accounts for PTP1B inhibition. Importantly, PTP1B inhibition by nitrosothiols led to EGF receptor phosphorylation even in the absence of exogenously added EGF. These findings suggest an important role for NO in modulating signaling pathways since inhibition of PTPases could potentially enhance or prolong activity of phosphoproteins.

Cell Line↗

PubMed2003

Pathogenesis of clinical signs in recessive ataxia with saccadic intrusions.

We describe a family of Slovenian descent with progressive ataxia, corticospinal signs, axonal sensorimotor neuropathy, and disruption of visual fixation by saccadic intrusions. Chromosome mapping indicated a mutation on 1p36, and this recessive disorder has been designated spinocerebellar ataxia with saccadic intrusions. Affected patients showed overshooting horizontal saccades, macrosaccadic oscillations, and increased velocity of larger saccades; other eye movements were normal. Slowed conduction in axons that are selectively vulnerable to the molecular defect could explain both the sensorimotor neuropathy and the saccadic disorder, which would be caused by delayed feedback control because of slow conduction in cerebellar parallel fibers.

Adult↗

PubMed2003

A mode hypothesis for finger interaction during multi-finger force-production tasks.

Finger forces are known to change involuntarily during multi-finger force-production tasks, even when a finger's involvement in a task is not consciously changed (the enslaving effect). Furthermore, during maximal force-production (MVC) tests, the force produced by a given finger in a multi-finger task is smaller than the force generated by this finger in its single-finger MVC test (the force-deficit effect). A set of hypothetical control variables - modes - is introduced. Modes can be estimated based on individual finger forces during single-finger MVC tests. We show that a simple formal model based on modes with only one free parameter accounts for finger forces during a variety of multi-finger MVC tests. The free parameter accounts for the force-deficit effect, and its value depends only on the number of explicitly involved fingers. This approach offers a simple framework for the analysis of finger interaction during multi-finger actions.

Biomechanical Phenomena↗

PubMed2003

3-hydroxy-3-methylglutaryl-coenzyme A reductase in the lobster mandibular organ: regulation by the eyestalk.

The mandibular organ (MO) of the lobster, Homarus americanus, produces the isoprenoid methyl farnesoate (MF), a compound related to insect juvenile hormone (JH). To better understand the synthesis and regulation of MF, we studied 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase (HMGR), the rate-limiting enzyme in isoprenoid biosynthesis. Lobster HMGR had a Km of 11.4 microM for HMG-CoA, a Km of 14.8 microM for NADPH, and was at least 2000-fold more selective for this cofactor than for NADH. Lovastatin and mevalonic acid inhibited HMGR, with KI values of 1.3 nM and 25.3 microM, respectively, whereas MF, farnesoic acid, cholesterol, 20-hydroxyecdysone, and progesterone had no effect. Approximately 75% of the HMGR activity in lobster MO was soluble. Similar levels of HMGR activity were observed in all regions of the MO. Eyestalk removal increased MF synthesis and the activity of farnesoic acid O-methyltransferase (FAOMeT, the final step in MF synthesis) in the MO by 10.7- and 5.7-fold, respectively, and caused a 3.1-fold increase of HMGR activity. Injection of the eyestalk ablated lobsters with an extract of two sinus glands (SG), a neuroendocrine organ in the eyestalk, decreased MF synthesis, FAOMeT activity and HMGR activity to 3, 8, and 20%, respectively, of the levels observed in saline-treated animals. The regulation of crustacean HMGR by the SG suggests that the lobster MO is a useful model system for investigating the cellular regulation of HMGR activity.

Animals↗

PubMed2003

Juvenile hormone synthesis, metabolism, and resulting haemolymph titre in Heliothis virescens larvae parasitized by Toxoneuron nigriceps.

Last instar larvae of the tobacco budworm, Heliothis virescens F., fail to pupate and have little 20-hydroxyecdysone when parasitized by Toxoneuron nigriceps (Viereck). In this paper, we extend these observations to juvenile hormone (JH) to determine if parasitism by this wasp affects other endocrine systems. To this end, we compared the production of JH by corpora cardiaca-corpora allata complexes (CC-CA), the metabolism of JH by haemolymph enzymes, and the haemolymph titre of JH in parasitized and non-parasitized control larvae of H. virescens during the last larval instar. CC-CA from parasitized and control larvae had similar peaks of JH synthesis on day 1 of the fifth instar, with JH II accounting for more than 90% of total JH in both groups. On subsequent days, JH synthesis dropped to undetectable levels more quickly in non-parasitized controls than in parasitized larvae. JH metabolism by haemolymph of parasitized and control animals increased from low levels on day 1 of the fifth instar to high levels on days 2 and 3 of the instar. JH metabolism was significantly higher in control larvae than in parasitized larvae. After day 3, JH metabolism decreased in both groups, but was significantly higher in parasitized larvae. The major metabolite of JH in both groups was JH acid, though traces of JH diol and JH acid diol were also detected. The haemolymph titre of JH in both groups peaked on day 1 of the fifth instar and, similar to the synthesis of JH by CC-CA, decreased more rapidly in control larvae. As a result, non-parasitized animals had significantly lower JH titres on day 2. The higher JH titres observed in parasitized larvae during the early fifth instar may contribute to their developmental arrest. The possible role of these JH alterations in the host developmental and metabolic redirection is discussed and a more comprehensive physiological model accounting for host-parasitoid interactions is proposed.

Animals↗

PubMed2003

Finger interactions studied with transcranial magnetic stimulation during multi-finger force production tasks.

OBJECTIVE: We used transcranial magnetic stimulation (TMS) to investigate interactions among neuromuscular complexes involved in force production by individual fingers of a hand during single- and multi-finger tasks. METHODS: Subjects were asked to press with the fingertips at various levels of force using different finger combinations. TMS was applied over the M1 cortical hand area during constant force production. TMS-induced increments in fingertip forces were analyzed, as well as motor evoked potentials (MEPs) in flexor digitorum superficialis. RESULTS: Both MEP size and individual force increments had inverted U-shaped dependences on the background force (peak responses were seen at about 50% of the maximal force). Similar relationships were obtained when subjects were asked to produce different forces with the same finger combination or the same total force with different finger combinations. The relationships were similar when the force was produced by explicitly instructed fingers or by other fingers of the hand. Effects of TMS on the force of a finger showed a strong dependence on the background force produced by this finger and minimal or no dependence on forces produced by other fingers of the hand. CONCLUSIONS: Overall, TMS applied over M1 revealed little interaction among fingers. This supports the notion of digit-specific compartments in multi-digit extrinsic muscles of the hand and suggests that these compartments possess a high degree of physiological independence.

Adult↗

PubMed2003

The effects of stroke and age on finger interaction in multi-finger force production tasks.

OBJECTIVE: The main purpose of this study was to investigate changes in finger interaction after stroke with strongly unilateral motor effects. Effects of age on finger interaction were also analyzed. METHODS: Sixteen stroke subjects and 16 control subjects produced maximal voluntary contractions with different finger combinations by one hand and by two hands simultaneously. Individual finger forces were measured. In multi-finger tasks, force deficit (FD) was quantified as the difference between the peak finger forces in single-finger tasks and in multi-finger tasks, while enslaving (ENSL) was quantified as forces produced by fingers that were not required to produce force. RESULTS: In stroke subjects, the peak forces produced by the fingers of the impaired hand (IH) were about 36% less than those produced by the unimpaired hand. Stroke resulted in higher ENSL and decreased FD in the IH, particularly when the index and middle fingers produced force together, while aging led to higher FD and no change in ENSL. Two-hand tasks were accompanied by an additional drop in the force of individual fingers, i.e. bilateral deficit (BD). No changes in BD were observed with age or after stroke. CONCLUSIONS: We conclude that IH function in persons after stroke is accompanied not only by a general loss of finger force but also by changes in indices of multi-finger interaction. The contrast between the significantly changed indices of one-hand multi-finger interaction and unchanged BD implies that cortical neurons mediating interhemispheric inhibition are relatively spared in unilateral stroke. SIGNIFICANCE: The study shows that stroke leads to changes not only in finger force but also in finger interaction. The conclusion on relatively spared interhemispheric projections is potentially important for therapy of hand function in stroke survivors.

Adult↗

PubMed2003

[The expression and clinical implication of gelatinase A in acute leukemic cells].

OBJECTIVE: To study the expression of gelatinase A (MMP2) in acute leukemic cells and its clinical implication. METHODS: The bone marrow samples from 46 acute leukemia patients were investigated by reverse transcription polymerase chain reaction (RT-PCR) and Gelatin Zymography method. Matrigel invasion assay was studied on U937, NB4, K562 and SHI1 cells in vitro. RESULTS: The expression of MMP2 was positive in 24 of 46 patients with AL (52.2%). In MMP2 positive and negative groups of AL, the extramedullary infiltration rates were 50.0% and 18.2% (P < 0.05), whilst the percentage of blast cell in peripheral white blood cells were (77.21 +/- 13.9)% and (62.95 +/- 17.2)% (P < 0.01), respectively. The positive expression of TIMP2 and MT1-MMP in 46 AL patients were 27 (58.7%) and 33 (71.7)%. The matrigel invasion assay suggested that MMP2 is involved in migration of leukemic cell through extracellular matrix (Matrigel). CONCLUSION: The active form of MMP2 might be essential to the egress of leukemic cells from bone marrow into peripheral blood, followed by an extramedullary infiltration.

Acute Disease↗

PubMed2002

Coupling phenomena during asynchronous submaximal two-hand, multi-finger force production tasks in humans.

We studied asynchronous two-hand multi-finger force production at submaximal levels. Subjects produced constant levels of force with one hand (F(REF)), and started ramp force production with the other hand (F(RAMP)) 3 s later. The zero-maximal force-zero ramp lasted 10 s. Visual feedback was provided only for F(REF) during the first 3 s and only for F(RAMP) during the rest of the trial. The initiation of F(RAMP) induced a transient overshoot by F(RAMP) and a drop in F(REF); both scaled with F(REF). Later into the trial, F(REF) dropped slowly, while F(RAMP) undershot maximal force by about 15%. Two regimes of bimanual interaction are hypothesized, 'strong interaction' when an effector is added to a one-hand task, and 'weak interaction' during two-hand force production.

Adult↗

PubMed2002

Localization of electromagnetic waves in a two-dimensional random medium.

Motivated by previous investigations on the radiative effects of the electric dipoles embedded in structured cavities, localization of electromagnetic waves in two dimensions is studied ab initio for a system consisting of many randomly distributed two-dimensional dipoles. A set of self-consistent equations, incorporating all orders of multiple scattering of the electromagnetic waves, is derived from first principles and then solved numerically for the total electromagnetic field. The results show that spatially localized electromagnetic waves are possible in such a simple but realistic disordered system. When localization occurs, a coherent behavior appears and is revealed as a unique property differentiating localization from either the residual absorption or the attenuation effects.

Journal Article↗