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Biomedical subjects

Wei Chen

Publications and source records attributed to Wei Chen.

At least 181 records · Page 10Linked to original sources
PubMed2006

[Research advances in thermotolerance regulation of cool-season turfgrass].

Among abiotic stresses, high temperature is one of the important ecological factors limiting the growth and development of cool-season turfgrass in the transitional and warm climatic regions, especially during hot summer, which leads to the decline of turf quality, loss of chlorophyll, metamorphism of protein, decrease of photosynthetic activities, and even, cell death. Therefore, how to overcome the difficulty for cool-season turfgrass in spending hot summer successfully, especially in the transitional and warm climatic regions, is a serious problem. Based on the statement of regulation principle in thermotolerance, the research advances in thermotolerance regulation of cool-season turfgrass were reported, including the advances in morphological, ecological, physiological, and biochemical characters in thermotolerance, and the advances in thermotolerance regulation by proper management and regulation measurements such as lowing the soil temperature, application of growth regulators and fertilization, proper clipping, and irrigation.

Adaptation, Physiological↗
PubMed2006

[Cause and treatment of trachea cannula exodus after executed tracheotomy].

OBJECTIVE: To explore the reason and correct management of trachea cannula exodus in the patient who had been executed tracheotomy, and reduce the occurrence of trachea cannula exodus and its complication. METHOD: To analysis retrospectively 23 cases of trachea cannula exodus after executed tracheotomy in patients who had been obstructed in upper respiratory. RESULT: In 23 cases of trachea cannula exodus, 21 cases were rescued succeeded, 1 case death, 1 case became plant man. CONCLUSION: Occurrence of trachea cannula exodus after executed tracheotomy was correlated with operative procedure, postoperative care and suitable selection of tracheal cannula. Quick-witted ability of doctor and correct management is a key that rescued succeeded.

Adolescent↗
PubMed2006

[Coexpression of Schwann cell marker GFAP and myoepithelial cell marker alpha-SMA in salivary adenoid cystic carcinoma].

OBJECTIVE: To observe the expression of Schwann cell marker GFAP and myoepithelial cell marker alpha-SMA in salivary adenoid cystic carcinoma (ACC), and to evaluate the relationship of GFAP, alpha-SMA and perineural invasion in ACC. METHODS: Immunohistochemical SABC method, double-label immunofluorescence and CLSM were used to detect the expression of GFAP and alpha-SMA proteins in salivary ACC tissue samples. RESULTS: In salivary ACC tissue samples, both GFAP and alpha-SMA proteins were positive, which were coexpressed in cytoplasm of the same onco-myoepithelial cells. CONCLUSIONS: There may be Schwann cell differentiation in onco-myoepithelial cell of salivary ACC, and it may be the pathological base of perineural invasion in salivary ACC.

Actins↗
PubMed2006

[Studies on in vitro culture of adventitious root in Salvia miltiorrhiza].

OBJECTIVE: To study the culture of adventitious root of Salvia miltiorrhiza in vitro systemically. METHOD: Effects of sucrose concentrations, medium pH, inoculum size and plant growth regulators on adventitious root growth and secondary metabolites production in S. miltiorrhiza were investigated. RESULT: With the increase of initial sucrose concentration, adventitious root growth rates increased and tanshinone II A content decreased, while content of protocatechuic aldehyde showed a broken line change and its highest production was obtained under 30 g x L(-1) sucrose in the medium. As for the effect of medium pH, medium pH of 6.5, 5.5 (or 6.0) and 5.8 was favorable for adventitious root growth, tanshinone II A and protocatechuic aldehyde synthesis respectively. Furthermore, adventitious root growth, rate was greatly increased when inoculum size was 2.5%. MS medium added with 0.5 mg x L(-1) KT was much favorable for tanshinone II A and protocatechuic aldehyde accumulation. CONCLUSION: Parameters including sucrose concentrations, medium pH, inoculum size and plant growth regulators have distinct effects on the in vitro culture of adventitious root growth and secondary metabolites synthesis of S. miltiorrhiza.

Abietanes↗
PubMed2006

[Obtaining new germplast of Brassica napus with high oleic acid content by RNA interference and marker-free transformation of Fad2 gene].

A seed-specific Fad2 gene expression cassette, which is free-marker gene and with sense and antisense structure, was constructed by using the promoter and terminator of rape seed storage protein cruciferin gene. Transgenic rape plants without selection marker genes were obtained by Agrobacterium-mediated transformation. The oleic acid content of transgenic plant seeds is 83.9%, which is nearly the same as that of Brassica napus with double Fad2 mutation (85%). The result of RT-PCR analysis shows that the raising of oleic acid content may be due to the degradation of Fad2 mRNA induced by co-transformation of sense-antisense Fad2 gene. These transgenic plants with high oleic acid trait grew normally and without the disadvantageous agronomic traits such as weak cold resistance, tardy development, death of buds and low rate of seed setting caused by Fad2 inactivation in mutant Brassica napus plants. This work would serve as a good base for breeding of more lines with high oleic acid content.

Brassica napus↗
PubMed2006

[Characterization of hydrogen peroxide production by a novel oral streptococci, S. oligofermentans isolated from human oral cavity].

High level of hydrogen peroxide was produced by S . oligofermentans, a novel oral streptococcus isolated from human oral cavity previously in our laboratory. To characterize the hydrogen peroxide production by S. oligofermentans, hydrogen peroxide yields at different growth phases and from different substrates were assayed. The results turned out that hydrogen peroxide production started at the beginning of logarithmic phase, and reached the maximal yield at the early stationary phase. Peptone and yeast extract could be the main substrates for hydrogen peroxide production. Moreover, lactate, as a fermentative product of glucose, can be another substrate for hydrogen peroxide production. Furthermore three oxidases activities possibly associated with H2O2 production were assayed, and both activities of lactate oxidase and NADH oxidase were detected under aerobic condition, while pyruvate oxidase activity was not detected in the permeabilized cells of S. oligofermentans, implying that S. oligofermentans could mainly rely on the two enzymes activities for H2O2 production.

Humans↗
PubMed2006

[Responses of Shenyang urban tree phrenology to climate warming].

By using statistic and linear regression methods, this paper studied the last 40 years responses of Shenyang urban tree phenology to climate warming. The results showed that there was a significant correlation between the duration of tree dormancy and the mean air temperature in winter. Appropriate cold condition was beneficial to bud break, and a significant negative correlation was observed between the outset of sprouting and the mean air temperature in winter and early spring. Leaf expansion started 15 days after sprouting, which was mainly affected by the mean air temperature in spring but had no correlation with the temperature in winter. The air temperature within 20-80 days and especially 20-40 days before flowering had a significant effect on the outset of flowering, i. e. , an increasing temperature in spring could advance the outset of flowering. Both sprouting and leaf expansion were negatively correlated with cold index (CI) , but no significant correlation was observed between the outset of flowering and CI. An increase of mean annual air temperature by 1 degree C would advance the outset of sprouting by 9 days, leaf expansion by 10 days, and outset of flowering by 5 days.

China↗
PubMed2006

[A novel method of amplifying the heavy-chain variable regions from immunoglobulin cDNAs].

The amplification of variable regions (Fv) of immunoglobulins has become a crucial technique for studying antigen-antibody interactions and cloning the monoclonal antibodies (mAbs). But this work becomes a major challenge in cloning antibody genes either from hybridoma cell lines or B cells. Isolation of the immunoglobulin heavy-chain variable regions (VH) from two mouse hybridoma cell lines based on conventional protocols using both the specific consensus primers and the commercial primer set of VH regions, was unsuccessful. This prompted us to design our own primers for VH regions of immunoglobulins. A novel algorithms and reverse polymerase chain reaction (PCR) protocol--3' RACE and 5' RACE were established in order to recognize the VH genes. The most conserved region in the end of framework region (FR1) of the VH cDNA region was identified with the program and a degenerated primer were designed in the most conserved region followed by 3' RACE and 5' RACE. The new protocol rescued the failed PCR amplifications. Thereby, a improvement in the degenerate primers designing programs and a notable increase in amplification specificity were achieved. This approach can be useful in primer design and amplification of VH and light-chain variable regions (VL) gene libraries or cloning of the unknown genes in the large gene families and extend to other species or members of the immunoglobulin superfamily.

Algorithms↗
PubMed2005

The E7 proteins of low- and high-risk human papillomaviruses share the ability to target the pRB family member p130 for degradation.

High-risk human papillomaviruses (HPVs) (e.g., HPV-16) cause anogenital and head and neck cancers, and low-risk HPVs (e.g., HPV-6) cause benign hyperproliferative disease. The E7 protein of HPV-16 binds all retinoblastoma tumor suppressor protein (pRB) family members with higher affinity than HPV-6E7. The HPV-16 E7 protein has been reported to target pRB family members for degradation and to immortalize cells. Here we tested the hypothesis that the low-risk E7 protein has an intrinsic ability to decrease expression of pRB family members. First, we introduced a high-affinity pRB-binding site into HPV-6 E7 (6E7G22D) and showed that, in human foreskin keratinocytes, HPV-6 E7G22D decreased the level of pRB protein but not pRB mRNA. Second, we analyzed the ability of wild-type HPV-6 E7 to destabilize the other pRB family members, p107 and p130. HPV-6 E7, like HPV-16 E7, decreased the level of p130 protein. This decrease was inhibited by MG132, a proteasome inhibitor. Binding of HPV-6 E7 to p130 was necessary but not sufficient to decrease the level of p130. Furthermore, the destabilization of p130 correlated with a decrease in the expression of involucrin, a differentiation marker. We suggest that the shared activity of HPV-16 E7 and HPV-6 E7 to destabilize p130 and decrease or delay differentiation may be related to the role of E7 in the HPV life cycle. The added ability of HPV-16 E7 to regulate pRB and p107 may be related to oncogenic activity.

Amino Acid Sequence↗
PubMed2005

Supramembrane potential-induced electroconformational changes in sodium channel proteins: a potential mechanism involved in electric injury.

Effects of imposed large supraphysiological transmembrane potential (TP) pulses on channel proteins, particularly on the voltage-gated Na channels, were investigated. Voltage clamp techniques were used to deliver both shock and stimulation pulses, and to monitor changes in the channel functions. Our experimental results indicated that more than one 4 ms duration TP shock of -450 mV resulted in electroconformational denature of voltage-gated Na channels. This resulted in functional reductions in muscle cells' excitability. We quantified the TP shock-induced decrease in the Na channel currents, compared the pre- and post-shocked Na channel currents' voltage dependency, and studied the reversibility of the electroconformationally denatured ion channel proteins. These observations are particularly relevant to the problem of explaining the neuromuscular damage following high voltage electrical shock injuries despite no evidence of a thermal injury component.

Animals↗
PubMed2005

A dynamic fMRI study of illusory double-flash effect on human visual cortex.

Functional MRI (fMRI) combined with the paired-stimuli paradigms (referred as dynamic fMRI) was used to study the "illusory double-flash" effect on brain activity in the human visual cortex. Three experiments were designed. The first two experiments aimed to examine the cross-modal neural interaction between the visual and auditory sensory systems caused by the illusory double-flash effect using combined auditory (beep sound) and visual (light flash) stimuli. The fMRI signal in the visual cortex was significantly increased in response to the illusory double flashes compared to the physical single flash when the inter-stimuli delay between the auditory and visual stimuli was 25 ms. This increase disappeared when the delay was prolonged to approximately 300 ms. These results reveal that the illusory double-flash effect can significantly affect the brain activity in the visual cortex, and the degree of this effect is dynamically sensitive to the inter-stimuli delay. The third experiment was to address the spatial differentiation of brain activation in the visual cortex in response to the illusory double-flash stimulation. It was found that the illusory double-flash effect in the human visual cortex is much stronger in the periphery than the fovea. This finding suggests that the periphery may be involved in high-level brain processing beyond the retinotopic visual perception. The behavioral measures conducted in this study indicate an excellent correlation between the fMRI results and behavioral performance. Finally, this work demonstrates a unique merit of fMRI for providing both temporal and spatial information regarding cross-modal neural interaction between different sensory systems.

Acoustic Stimulation↗
PubMed2005

Characterization and manipulation of the electroosmotic flow in porous anodic alumina membranes.

Porous anodic alumina membranes (PAAMs) have uniform and high-density nanopores, and the dimension and interval of the pores can be easily controlled by varying the anodization conditions. The application of PAAMs could widely impact the cost and efficiency of the liquid-based nanoscale separations. We report here the property of electroosmotic flow in PAAMs, which plays a significant role in the mass transport across these membranes that have charged pore surfaces. By controlling the solution pH and the magnitude and sign of the applied current, the mass transport through these nanoporous membranes can be spatially and temporally manipulated. The effects of electrosurface properties and electrolyte ionic strength on electroosmotic flow were studied. The anion incorporation and adsorption cause the variation of the electrosurface properties of PAAMs, which in turn influence the rate and direction of the mass transport. As compared to the membrane with fixed surface charge, this diversity makes it possible for the PAAMs to be used in various conditions.

Journal Article↗
PubMed2005

The trigonal bipyramidal MN3M species: a new kind of aromatic complex containing a multiple-fold aromatic N3 subunit.

A new kind of aromatic trigonal bipyramidal MN3M (M=Be, B, Mg, Al, and Ca) species, with all real frequencies, is obtained at the MP2/6-311+G(3d) level. The nucleus-independent chemical shift values are -102.16 ppm for the N3 (3-) ring, and -74.09, -79.39, -65.06, -74.44, and -62.33 ppm (at the geometrical center of the trigonal bipyramid) for BeN3Be, BN3B, MgN3Mg, AlN3Al, and CaN3Ca, respectively. Molecular orbital analysis indicates that the regular triangular N3 (3-) ring and each MN3M species have three aromatic six-electron systems (pi, sigma(p), and sigma(s)) and exhibit threefold aromaticity. The CaN3Ca species has a very low vertical ionization energy of 3.64 eV at the CCSD(T)/6-311+G(3d) level, which is even lower than the ionization energy (3.9 eV) of the Cs atom. Therefore, CaN3Ca can be considered as a new superalkali species. A further study on the CaN3CaCl molecule confirms the superalkali characteristics of CaN3Ca. Two interesting phenomena are explored in the MN3M species: the delocalized electron cloud of the N3 subunit is elongated by two M cations, and the electron clouds of two M cations are distended by the N3 (3-) ring.

Journal Article↗
PubMed2005

Dysregulation of the Hedgehog pathway in human hepatocarcinogenesis.

Hedgehog (Hh) pathway activation promotes tumors in several endodermally derived tissues, but its role in the pathogenesis of hepatocellular carcinoma (HCC) is unknown. Although normal hepatocytes lack Hh signaling, activation of the Hh pathway in endodermal progenitors is required for liver development. Thus, we hypothesized that hepatocarcinogenesis may involve regulation of Hh signaling. This pathway is activated when Hh ligand binds to its receptor, Patched (PTC). In an unoccupied state, PTC normally functions as a tumor suppressor that inhibits Smoothened (SMO), a proto-oncoprotein, from activating downstream components and transcription of target genes. Here we show that in HCCs, overexpression of the Smo proto-oncogene, as well as an increase in the stoichiometric ratio of Smo to Ptc mRNA levels, correlated with tumor size, a prognostic indicator in HCC biology. In one tumor we identified a novel Smo mutation in an evolutionarily conserved residue. We also demonstrated that HCC cell lines (HepG2 and Hep3B) expressed Hh pathway components and activated Hh transcriptional targets. In Hep3B cells, cyclopamine, an inhibitor of wild-type SMO, had no effect, but KAAD-cyclopamine, a blocker of oncogenic SMO, inhibited Hh signaling activity by 50%, decreased expression of the hepatocarcinogenic oncogene, c-myc, by 8-fold, and inhibited the growth rate of Hep3B cells by 94%. These data support our hypothesis that Hh signaling is dysregulated in human hepatocarcinogenesis. We demonstrate that overexpression and/or tumorigenic activation of the Smo proto-oncogene mediates c-myc overexpression which plays a critical role in hepatocarcinogenesis and suggests that Smo is a prognostic factor in HCC tumorigenesis.

Animals↗
PubMed2005

Exogenous acid fibroblast growth factor inhibits ischemia-reperfusion-induced damage in intestinal epithelium via regulating P53 and P21WAF-1 expression.

AIM: To detect the effect of acid fibroblast growth factor (aFGF) on P53 and P21WAF-1 expression in rat intestine after ischemia-reperfusion (I-R) injury in order to explore the protective mechanisms of aFGF. METHODS: Male rats were randomly divided into four groups, namely intestinal ischemia-reperfusion group (R), aFGF treatment group (A), intestinal ischemia group (I), and sham-operated control group (C). In group I, the animals were killed after 45 min of superior mesenteric artery (SMA) occlusion. In groups R and A, the rats sustained for 45 min of SMA occlusion and were treated with normal saline (0.15 mL) and aFGF (20 mug/kg, 0.15 mL), then sustained at various times for up to 48 h after reperfusion. In group C, SMA was separated, but without occlusion. Apoptosis in intestinal villi was determined with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling technique (TUNEL). Intestinal tissue samples were taken not only for RT-PCR to detect P53 and P21WAF-1 gene expression, but also for immunohistochemical analysis to detect P53 and P21WAF-1 protein expression and distribution. RESULTS: In histopathological study, ameliorated intestinal structures were observed at 2, 6, and 12 h after reperfusion in A group compared to R group. The apoptotic rates were (41.17+/-3.49)%, (42.83+/-5.23)%, and (53.33+/-6.92)% at 2, 6, and 12 h after reperfusion, respectively in A group, which were apparently lower than those in R group at their matched time points (50.67+/-6.95)%, (54.17+/-7.86)%, and (64.33+/-6.47)%, respectively, (P<0.05)). The protein contents of P53 and P21WAF-1 were both significantly decreased in A group compared to R group (P<0.05) at 2-12 h after reperfusion, while the mRNA levels of P53 and P21WAF-1 in A group were obviously lower than those in R group at 6-12 h after reperfusion (P<0.05). CONCLUSION: P53 and P21WAF-1 protein accumulations are associated with intestinal barrier injury induced by I-R insult, while intravenous aFGF can alleviate apoptosis of rat intestinal cells by inhibiting P53 and P21WAF-1 protein expression.

Animals↗
PubMed2005

Long-ranged attraction between charged polystyrene spheres at aqueous interfaces.

We report an optical and atomic force microscopic study of interactions between charged polystyrene spheres at a water-air interface. Optical observations of bonded particle clusters and formation of circular chainlike structures at the interface demonstrate that the interaction potential is of dipole origin. Atomic force microscope phase images show patchy domains on the colloidal surface, indicating that the surface charge distribution is not uniform as is commonly believed. Such surface heterogeneity introduces in-plane dipoles, leading to an attraction at short interparticle distances.

Colloids↗