Biomedical subjects

Q Zhang

Publications and source records attributed to Q Zhang.

At least 163 records · Page 9Linked to original sources

PubMed2001

A non-invasive measure of changes in blood flow in the human anterior tibial muscle.

We used photoplethysmography (PPG) to monitor blood flow changes in the human anterior tibial muscle during arterial occlusion and during isometric and concentric contractions. Single-fibre laser-Doppler flowmetry (LDF) was used as a reference in 12 healthy subjects (5 men, 7 women; mean age 24 years). Post-exercise hyperaemic muscle blood flow (MBF) was measured immediately after isometric dorsiflexion of the ankle joint at maximal contraction for 1 min and full range-of-motion dorsiflexion and plantar flexion of the ankle joint for 1 min. A thigh tourniquet was applied for the evaluation of post-occlusive reactive hyperaemia. The MBF (baseline = 100%) was [mean (SD)] 150 (31)% (P = 0.003) by PPG (880 nm) and 182 (66)% (P = 0.012) by LDF. After 1 min of maximal isometric contraction, MBF increased to 150 (51)% (P = 0.003) by PPG (880 nm) and to 169 (43)% (P = 0.005) by LDF. After 1 min of maximal concentric contractions, MBF increased to 158 (59)% (P = 0.003) by PPG (880 nm) and to 170 (99)% (P = 0.008) by LDF. Skin blood flow, PPG (560 nm), did not change significantly after isometric or concentric contractions. The results indicate that reactive hyperaemia after exercise and arterial occlusion can be assessed in the human anterior tibial muscle using PPG.

Adult↗

PubMed2001

Effects of limb elevation and increased intramuscular pressure on human tibialis anterior muscle blood flow.

The effects of limb elevation and increased intramuscular pressure (IMP) on blood flow in the tibialis anterior muscle and leg neuromuscular function were studied in eight healthy subjects. Muscle blood flow (MBF) was measured by photoplethysmography using a custom-designed probe. IMP was elevated bilaterally by vein obstruction (60-65 mmHg) lasting 30 min induced by a thigh tourniquet of casted legs. Skin sensibility of the feet and the amplitude and area of the compound muscle action potentials from the extensor digitorum brevis muscle were evaluated. The subject kept one leg elevated 32 cm above heart level and the contralateral leg at heart level. All recordings were made before, during and after vein obstruction. IMP increased to 40 mmHg in the vein-obstructed casted legs. Perfusion pressure decreased from [mean (SD)] 42 (5.8) mmHg to 17 (6.4) mmHg in the elevated leg and from 65 (9.9) mmHg to 43 (8.4) mmHg in the non-elevated leg. MBF decreased by 50% in the elevated leg and by 42% in the non-elevated leg. Subjects experienced sensory dysfunction and muscular weakness in the elevated leg. In conclusion, increased IMP, induced by venous obstruction of a casted leg, reduced perfusion pressure and MBF, and resulted in a diminished amplitude and area of the compound muscle action potentials. Limb elevation above heart level combined with venous stasis of a casted leg further reduced perfusion pressure and MBF, and induced sensory dysfunction and muscular weakness.

Action Potentials↗

PubMed2001

Regulation of respiration in rotenone-treated tobacco cell suspension cultures.

Cells of Nicotiana tabacum L. suspension cultures were treated with the respiratory inhibitor rotenone, which specifically inhibits complex I activity of mitochondria. Rotenone retarded cell growth, as shown by decreases in fresh weight, dry weight and cell numbers on a suspension-volume basis. However, rates of the coupled respiration were higher in rotenone-treated compared to control cells when expressed on a fresh-weight basis. Rates of the rotenone-insensitive respiration increased substantially on both a fresh-weight and extractable-cellular-protein basis 24 h after rotenone treatment. ATP/ADP ratios were not significantly different between control and rotenone-treated cells. Our results indicated that cells of tobacco suspension cultures were able to maintain a slow rate of growth and adequate ATP/ADP ratios without the operation of complex I.

Adenosine Diphosphate↗

PubMed2001

Effect of membrane surface charge on nickel uptake by purified mung bean root protoplasts.

The influence of membrane surface charge on cation uptake was investigated in protoplasts prepared from roots of mung bean (Vigna radiata L.). Confocal laser scanning microscopy showed that a fluorescent trivalent cation accumulated to very high concentrations at the surface of the protoplasts when they were incubated in medium containing low concentrations of Ca or other cations, but that this accumulation could be completely reversed by suppression of membrane surface negativity by high cation concentrations. Influx of 63Ni was strongly reduced by a range of divalent cations. Increasing the Ca concentration in the medium from 25 microM to 10 mM inhibited 63Ni influx by more than 85%. 63Ni influx was also inhibited by 85% by reducing the pH from 7 to 4. Computation of the activity of Ni at the membrane surface under the various treatment conditions showed that Ni uptake was closely correlated with its activity at the membrane surface but not with its concentration in the bulk medium. It was concluded that the effects on Ni uptake of addition of monovalent, divalent and trivalent cations, and of variations in pH are all consistent with the proposition that the activity of Ni at the membrane surface is the major determinant of the rate of Ni influx into mung bean protoplasts. It is proposed that the surface charge on the plasma membrane will influence the membrane transport of most charged molecules into cells.

Aluminum↗

PubMed2001

Identification of an 85-kb DNA fragment containing pms1, a locus for photoperiod-sensitive genic male sterility in rice.

Photoperiod-sensitive genic male-sterile rice has a number of desirable characteristics for hybrid rice production. Previous studies identified pms1, located on chromosome 7, as a major locus for photoperiod-sensitive genic male sterility. The objective of this study was to localize the pms1 locus to a specific DNA fragment by genetic and physical mapping. Using 240 highly sterile individuals and a random sample of 599 individuals from an F2 population of over 5000 individuals from a cross between Minghui 63 and 32001S, we localized the pms1 locus by molecular marker analysis to a genetic interval of about 4 cM, 0.25 cM from RG477 on one side and 3.8 cM from R1807 on the other side. A contig map composed of seven BAC clones spanning approximate 500 kb in length was constructed for the pms1 region by screening a BAC library of Minghui 63 DNA using RFLP markers and chromosomal walking. Analysis of recombination events in the pms1 region among the highly sterile individuals reduced the length of the contig map to three BAC clones. Sequencing of one BAC clone, 2109, identified two SSR markers located 85 kb apart in the clone that flanked the pms1 locus on both sides, as indicated by the distribution of recombination events. We thus concluded that the pms1 locus was located on the fragment bounded by the two SSR markers.

Chromosome Mapping↗

PubMed2001

Effects of homocysteine on murine splenic B lymphocyte proliferation and its signal transduction mechanism.

OBJECTIVE: Elevated plasma homocysteine (Hcy) levels have been defined as an increased risk of atherosclerosis. However, the mechanisms that Hcy induces the development of atherosclerosis are not fully understood. Therefore, effect of Hcy on B lymphocyte proliferation and its cellular mechanism were examined in normal and hyperhomocysteinemia ApoE-knockout mice. METHODS: Mouse B lymphocytes were incubated with Hcy, related compounds and/or antioxidants and/or inhibitors of PKC, p38 MAPK, NF-kappaB in the presence or absence of lipopolysaccharide. DNA synthesis, production of reactive oxygen species was measured. RESULTS: Hcy (0.1-3.0 mM) and other compounds with thiol (-SH), such as cysteine and glutathione significantly increased resting and lipopolysaccharide-induced B lymphocyte proliferation. ApoE-knockout mice with hypercysteinemia (plasma Hcy levels were 20.3+/-2.9 vs. 2.6+/-0.6 microM in control, P<0.05) had a significant promotion of B cell proliferation in response to lipopolysaccharide. Hcy also increased intracellular reactive oxygen species production. Radical scavengers reduced Hcy-induced B lymphocyte proliferation. The promotion of Hcy was significantly inhibited by inhibitors of PKC (calphostin C and RO-31-8220), p38 MAPK (SB 202190 and PD 169316) and NF-kappaB (pyrrolidine dithiocarbamate). CONCLUSIONS: The reactive oxygen species generated by thiol (-SH) auto-oxidation of Hcy are essential, and PKC, p38 MAPK and NF-kappaB are involved in the Hcy-induced B lymphocyte proliferation. Hyperhomocysteinemia may increase B lymphocyte susceptibility to inflammatory progression of atherosclerotic lesions.

Analysis of Variance↗

PubMed2001

Taraxastane-type triterpenoids from Saussurea petrovii.

Two taraxastane triterpenoids, i.e. taraxast-20-ene-3beta,30-diol (1) and 20alpha,21alpha-epoxy-taraxastane-3beta,22alpha-diol (2), as well as four known triterpenes taraxast-20(30)ene-3beta,21alpha-diol (3), taraxast-20(30)-ene-3beta-ol (4), taraxast-20-ene-3beta-ol (5) and taraxastane-3beta,20alpha-diol (6) were isolated from the Chinese medicinal plant Saussurea petrovii. Their structures were elucidated by spectroscopic methods. These compounds, especially 1 and 2, exhibit significant antitumor and antibacterial activity.

Animals↗

PubMed2001

Modulation of cell interactions with extracellular matrix by lysophosphatidic acid and sphingosine 1-phosphate.

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (SPP) are lipid mediators released upon platelet activation. The concentration of LPA in serum is estimated at 1-10 microM whereas the concentration in plasma is considerably less. The SPP concentration in serum is 0.5 microM, approximately two-fold higher than the plasma concentration. The lipids are present during tissue injury and promote cellular processes involved in wound repair. LPA and SPP have multiple effects on cells, many of which are pertinent to wound healing and require that the cells interact in some fashion with components of the extracellular matrix. This review focuses on modulation of cell adhesion, cell migration, collagen gel contraction, and fibronectin matrix assembly by LPA and SPP.

Cell Adhesion↗

PubMed2001

Influence of seaward boundary condition on contaminant transport in unconfined coastal aquifers.

Contaminant transport in coastal aquifers is complicated partly due to the conditions at the seaward boundary including seawater intrusion and tidal variations of sea level. Their inclusion in modelling this system will be computationally expensive. Therefore, it will be instructive to investigate the consequence of simplifying the seaward boundary condition by neglecting the seawater density and tidal variations in numerical predictions of contaminant transport in this zone. This paper presents a comparison of numerical predictions for a simplified seaward boundary condition with experimental results for a corresponding realistic one including a saltwater interface and tidal variations. Different densities for contaminants are considered. The comparison suggests that the neglect of the seawater intrusion and tidal variations does not affect noticeably the overall migration rate of the plume before it reaches the saltwater interface. However, numerical prediction shows that a more dense contaminant travels further seaward and part of the solute mass exits under the sea if the seawater density is not included. This is not consistent with the experimental result, which shows that the contaminant travels upwards to the shoreline along the saltwater interface. Neglect of seawater density, therefore, will result in an underestimation of the exit rate of solute mass around the coastline and fictitious migration paths under the seabed. For a less dense contaminant, neglect of seawater density has little effect on numerical prediction of migration paths.

Coloring Agents↗

PubMed2001

Motor unit recruitment in the trapezius muscle with special reference to coarse arm movements.

Chronic shoulder pain is common in a variety of occupations. The "Cinderella hypothesis" suggests that the pain originates from damaged type I muscle fibres driven into degenerative processes as a result of too long activation and too short recovery time. The main purpose of this study was to investigate if the same motor units are active during all phases of coarse arm movements. Eight healthy volunteers participated in the study. Intramuscular electromyographic signals were picked up with a four-lead fine wire electrode, during a unilateral straight arm movement. The movement started with either (part 1) an abduction or a flexion, then (2) a movement in the horizontal plane from the sagittal to the frontal plane or vice versa, and finally (3) an adduction or an extension to the start position. The movement cycle was performed in three different speeds, slow, medium, and high, with one, two or five cycles per 20 s, respectively. On an average, the motor unit action potentials (MUAPs) of 6 motor units (range, 1-15) were identified per trail. In total 94% of the MUAP trains that were identified showed firings in all 3 parts of the movements. The findings support the Cinderella hypothesis, although there is a need to further investigate the temporal pattern of long-term motor unit activity.

Action Potentials↗

PubMed2001

Structural characterization of the complex of the Rev response element RNA with a selected peptide.

INTRODUCTION: The RSG-1.2 peptide was selected for specific binding to the Rev response element RNA, as the natural Rev peptide does. The RSG-1.2 sequence has features incompatible with the helical structure of the bound Rev peptide, indicating that it must bind in a different conformation. RESULTS: The binding of the RSG-1.2 peptide to the Rev response element RNA was characterized using multinuclear, multidimensional NMR. The RSG-1.2 peptide is shown to bind with the N-terminal segment of the peptide along the major groove in an extended conformation and turn preceding a C-terminal helical segment, which crosses the RNA groove in the region widened by the presence of purine-purine base pairs. These features make the details of the bound state rather different than that of the Rev peptide which targets the same RNA sequence binding as a single helix along the groove axis. CONCLUSIONS: These studies further demonstrate the versatility of arginine-rich peptides in recognition of specific RNA elements and the lack of conserved structural features in the bound state.

Arginine↗

PubMed2001

Enhanced CD4+ T cell proliferation and Th2 cytokine production in DR6-deficient mice.

We have found that DR6, a member of the TNF receptor family, is highly expressed in resting T cells and downregulated in activated T cells. DR6-targeted mutant mice were generated and showed normal development. However, DR6(-/-) CD4(+) T cells hyperproliferated in response to TCR-mediated stimulation and protein antigen challenge. Activated DR6(-/-) CD4(+) T cells exhibited upregulated CD25 expression and enhanced proliferation in response to exogenous IL-2 stimulation. In addition, increased CD28 and reduced CTLA-4 expression were observed in these cells. Enhanced Th2 cytokine production by activated DR6(-/-) CD4(+) T cells was associated with the increased transcription factor NF-ATc in nuclei. DR6, therefore, functions as a regulatory receptor for mediating CD4(+) T cell activation and maintaining proper immune responses.

Abatacept↗

PubMed2001

Vibrational spectra and normal coordinate analysis of a weak ligand complex, Co(p-DMABA)2Cl2 x 2H2O.

The complex Co(p-DMABA)2Cl2 x 2H2O (p-dimethylaminobenzaldehyde, p-DMABA) was prepared from the solid-state reaction of a weak ligand p-DMABA and CoCl2 x 6H2O at lower heating temperature (60 degrees C). It is very difficult to obtain the title complex using solution reaction method, less than isolating single crystals. In order to determine the crystal structure of the title compound, we have to rely on the X-ray powder diffraction data. That is, the crystal structure can be solved directly from powder data, which crucial step is to constitute the structure model. Indirect spectroscopic methods, such as infrared and Raman spectroscopes, and further vibrational assignments made with the aid of normal coordinate calculations by using a modified Urey-Bradley force field, were analyzed to proposed molecular structure. One hundred and fifty-seven internal coordinates were established and 129 theoretical vibrational frequencies were calculated. An appropriate set of internal coordinates and force constants in the course of calculation were introduced, so that the calculated vibration frequencies are good agreement with the observed values. The average difference and the maximum deviation between theoretic and experimental frequencies are 2.44 and 8.0 cm(-1), respectively. Thus the normal coordinate analysis is a powerful tool to the molecular structure. Other structural and spectral properties are also discussed in this paper. The purpose of the present paper is to obtain a good structural model. This model was used as starting model for crystal structure determination from powder X-ray diffraction (XRD) data.

Crystallization↗

PubMed2001

Silyl ether-coupled poly(epsilon-caprolactone)s with stepwise hydrolytic degradation profiles.

Silyl ether-coupled poly(epsilon-caprolactone)s (PCLs) with stepwise degradation profiles were synthesized via the cross-dehydrocoupling polymerizations between 1,4-bis(dimethylsilyl)benzene (BDSB) and telechelic, diol-terminated PCL macromonomers. With the presence of 10 wt % palladium on activated carbon as the catalyst, the condensations between BDSB and diol-terminated PCL macromonomers having molecular weights of 1200, 2010, and 5500 g/mol were performed in toluene at 100 degrees C under argon. Hydrogen was eliminated as the condensate upon the formation of silyl ether bonds linking the PCL blocks, yielding within 24 h, silyl ether-coupled PCLs of molecular mass 7590, 29,900, and 29,500 g/mol, respectively. The characterization of each polymer included (1)H NMR, (13)C NMR, and (29)Si NMR spectroscopies, size exclusion chromatography (SEC), and differential scanning calorimetry. The hydrolytic degradation properties of the polymers in solution were studied, and the molecular weight reductions over time were monitored by SEC. The silyl ether linkages of the polymers underwent hydrolysis in the presence of mineral acids, whereas the PCL segments released from the cleavage of the labile silyl ether coupling unit did not undergo detectable molecular weight reduction over 15 days. In the presence of acetic acid, the silyl ether functionalities were cleaved with a half-life of 3 days; however, the PCL chain required reaction with trifluoroacetic acid to give a number-average molecular weight loss half-life of 4 days. The silyl ether-coupled PCLs underwent degradation in a gradient fashion, therefore, by a protocol that involved the addition of acetic acid for cleavage of the silyl ether functionalities, followed by further addition of trifluoroacetic acid to bring the hydrolysis of the silyl ether functionalities to completion and to trigger the degradation of PCL segments.

Biodegradation, Environmental↗

PubMed2001

Nanostructured materials designed for cell binding and transduction.

The surface-functionalization of shell cross-linked (SCK) nanoparticles with the oligomeric peptide sequence YGRKKRRQRRR, the protein transduction domain (PTD) from the human immunodeficiency virus TAT protein, is described, and the cell binding interactions these nanobioconjugates exhibit are demonstrated. A convergent synthetic strategy was employed, whereby the SCK nanoparticles and the PTD were prepared independently and then coupled together during immobilization of the PTD component on a solid support. The SCK nanoparticles were prepared by the micellization of amphiphilic block copolymers of poly(epsilon-caprolactone-b-acrylic acid), followed by amidation-based cross-linking of the acrylic acid residues located within the micellar corona. The PTD sequence was constructed upon a solid support, from C-terminus to N-terminus, followed by extension with four glycine residues, leaving the amino chain end for subsequent coupling with remaining acrylic acid functionalities present on the surface of the SCK. Finally, cleavage from the solid support was performed, which also facilitated deprotection of the peptide side chain functionalities as well as hydrolysis of the poly(epsilon-caprolactone) segments composing the SCK core domain, to yield PTD-derivatized nanocage structures (PTD-nanocage). Covalent labeling of the SCK precursor with fluorescein-5-thiosemicarbazide provided fluorescently tagged PTD-nanocage nanobioconjugates to allow for their detection by fluorescence microscopy. The fluorescent PTD-nanocage bioconjugates were found to interact with CHO cells and HeLa cells, whereas the analogous structure lacking the PTD component did not. CHO cells bound with fluorescent PTD-nanocage bioconjugates were analyzed using flow cytometry and fluorescence activated cell sorting (FACS). Fluorescence confocal microscopy of isolated bioconjugate-bound CHO cells indicated that the bioconjugated nanoparticles were primarily located near the cell periphery; however, transduction of the nanoparticle into the cells also occurred.

Animals↗

PubMed2001

Antisweet saponins from Gymnema sylvestre.

Three new oleanane-type triterpene glycosides (1-3), along with the sodium salt of alternoside II (4), were isolated from an ethanol extract of the leaves of Gymnema sylvestre. The structures of these new saponins were identified as 21 beta-O-benzoylsitakisogenin 3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucuronopyranoside (1), the potassium salt of longispinogenin 3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucuronopyranoside (2), and the potassium salt of 29-hydroxylongispinogenin 3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucuronopyranoside (3). The aglycon of 3, gymnemagenol (3a), was characterized as 3 beta,16 beta,28, 29-tetrahydroxyolean-12-ene. Structure elucidation was accomplished by interpretation of NMR (DQF-COSY, HMQC, and HMBC) results, FABMS, and hydrolysis. Saponin 1 and the sodium salt of alternoside II (4) exhibited antisweet activity.

Adult↗

PubMed2001

Isolation and structure determination of novamethymycin, a new bioactive metabolite of the methymycin biosynthetic pathway in Streptomyces venezuelae.

Novamethymycin (9), a novel macrolide antibiotic, was isolated from Streptomyces venezuelae, the producer of methymycin (4) and neomethymycin (5). Spectroscopic analysis of 9 indicated that it is highly related to 4 and 5 but contains hydroxy groups at both C-10 and C-12 on the macrolactone ring. Bioconversion studies using the PikC cytochrome P450 hydroxylase demonstrated that 4 is converted to 9, further broadening the remarkable substrate flexibility of this enzyme.

Anti-Bacterial Agents↗

PubMed2001

Sex identification by male-specific growth hormone pseudogene (GH-psi) in Oncorhynchus masou complex and a related hybrid.

It is often difficult to identify sexes of many fish species by conventional cytological method because of the lack of heteromorphic sex chromosomes. Isolation of sex-specific molecular markers is thus important for sexing and for understanding sex chromosome evolution in these species. We have identified genetic sexes by PCR-based male-specificity of a growth hormone pseudogene (GH-psi) in masu and Biwa salmon, two subspecies of the Oncorhynchus masou complex, and their hybrid Honmasu. PCRs with primers designed from sequences of chinook salmon GH genes amplified GH-I and GH-II fragments in both sexes, but a third GH-psi fragment was detected in predominant proportion of males and very few phenotypic females. The consistency of phenotypic sex with genetic sex identified by GH-psi for masu salmon, Biwa salmon and Honmasu was 93.1, 96.7 and 94%, respectively. The remaining individuals showed inconsistency or deviation from sex-specificity: a few phenotypic males lacked the GH-psi, whereas a few phenotypic females possessed the GH-psi. Sequence of the putative GH-psi fragment from such females was identical to that from genetic males, and shared about 95% homology with the corresponding GH-psi fragment from chinook salmon. This result confirmed that these females were really GH-psi-bearing individuals. PCR analyses with primers designed from masu salmon GH-psi gave identical results, indicating that the absence of GH-psi in a few males was not resulted from primer mismatching. These GH-psi-bearing females and GH-psi-absent males were more likely to originate from spontaneous sex reversion than from crossing-over between GH-psi and the sex determination gene/region.

Animals↗