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Biomedical subjects

Gang Wang

Publications and source records attributed to Gang Wang.

At least 163 records · Page 9Linked to original sources
PubMed2004

[Organic agriculture and sustainable development].

Basing on the research and practice of organic agriculture at home and abroad, this paper discussed the objectives of developing green food and the principles that must be persisted in the practice in China. In the light of the arguments concerning with sustainable agriculture, we also discussed the significance of "alternative agriculture" in theory and practice. Compared with conventional high-intensity agriculture, the production approaches of organic alternatives can improve soil fertility and have fewer detrimental effects on the environment. It is unclear whether conventional agriculture can be sustained because of the shortcomings presented in this paper, and it has taken scientists approximately one century to research and practice organic farming as a representative of alternative agriculture. The development of green food in China has only gone through more than ten years, and there would be some practical and theoretical effects on the development of China's green food if we exploit an environment-friendly production pattern of organic agriculture which majors in keeping human health and maintaining sustainable agriculture.

Agriculture↗
PubMed2004

Thiocyanate elution measurement of relative affinity of phage antibodies.

Human antibodies generated by phage antibody technology have been widely used in the immunotherapy of various diseases. Among the characteristics of these therapeutic antibodies, affinity is one of the most important determinants of their biological efficacy. The binding of an antibody and its corresponding antigen could be disrupted by thiocyanate solution of different concentrations, depend upon the affinity of the antibody. This mechanism has been adopted to determine the relative affinity of monoclonal or polyclonal antibodies in routine immunological practice. Correlation between the elution method and other techniques that measure the affinity such as equilibrium dialysis and biospecific interaction analysis (BIA) has been established. Here we describe the applications of the thiocyanate elution method in the determination of the relative affinity index (RAI) of phage antibodies (Phabs). Five clone antibodies, including 3 clones of anti-keratin antibodies (AK1, AK2 and AK3) and 2 clones of anti-HBsAg antibodies (HB1 and HB2) were selected to express Phabs and Fabs, and the RAI were determined by ELISA after thiocyanate elution. A HRP-conjugated anti-M13 was used as secondary antibody for Phabs and HRP-goat-anti-human Fab was used for Fabs. The affinity ranks of the Phabs were compared with that of the Fab fragments. The results showed that all the Phabs tested were tolerant to thiocyanate treatment. The relative affinity rank of 5 Phabs coincided well with that of their corresponding Fabs. We conclude that the thiocyanate elution can be used as an easy and rapid method to measure and compare the relative affinity of Phabs.

Antibodies↗
PubMed2003

In vivo antitumor activity of interleukin 21 mediated by natural killer cells.

Immunotherapy with high-dose interleukin (IL) 2 has been shown to successfully treat tumors in animal models and cause dramatic tumor regressions in some patients with metastatic melanoma, renal cell carcinoma, and non-Hodgkin's lymphoma. However, toxicity associated with IL-2 administration has compromised its widespread use in the clinic. IL-21 is a more recently discovered cytokine produced by activated CD4(+) T cells that shares significant sequence homology to IL-2, IL-4, and IL-15. Because IL-21 and IL-2 and their receptors share significant sequence similarities and both cytokines can stimulate T and natural killer (NK) cells, we sought to study whether IL-21, like IL-2, exhibits antitumor effects in vivo. In this study, we treated established s.c. tumor in mice by systemically administering plasmid DNA encoding murine IL-21 using a hydrodynamics-based gene delivery technique. Administration of IL-21 plasmid DNA resulted in high levels of circulating IL-21 in vivo. Treatment of tumor-bearing mice with IL-21 plasmid DNA significantly inhibited the growth of B16 melanoma and MCA205 fibrosarcoma in a dose-dependent manner without significant toxicity and increased the survival rate, compared with mice treated with control plasmid DNA. In vivo depletion of either CD4(+) or CD8(+) T cells did not affect IL-21-mediated antitumor activity. However, depletion of NK cells completely abolished IL-21-induced tumor inhibition. Consistent with this, the antitumor activity of IL-21 seemed to be mediated through enhanced cytolytic activity of NK cells. Our study suggests that IL-21 has significant antitumor activity and may have therapeutic potentials as an antitumor agent in the clinic.

Animals↗
PubMed2003

Combinatorial synthesis of a small-molecule library based on the vinyl sulfone scaffold.

[reaction: see text] A 30-member library of small molecules based on the vinyl sulfone scaffold was prepared on rink amide resin, using solid phase-based reactions such as oxidation and Horner-Wadsworth-Emmons reaction. The library was designed such that three points of diversity were readily introduced in the library to accommodate the S(1)', S(1), and S(2) binding pockets of different cysteine proteases, making the strategy suitable for high-throughput generation of potential cysteine protease inhibitors.

Journal Article↗
PubMed2003

Cyclin dependent kinase inhibitor p27(Kip1) is upregulated by hypoxia via an ARNT dependent pathway.

Expression of cyclin dependent kinase (Cdk) inhibitor p27(Kip1), which blocks cell cycle progression from G(1) to S phase, can be regulated via multiple mechanisms including transcription, protein degradation, and translation. Recently, it was shown that p27(Kip1) plays an important role in the cellular response to hypoxia. However, the mechanisms involved in the hypoxia-induced regulation of p27(Kip1) expression are still not clear. In this study, we compare the expression of p27(Kip1) in two related murine hepatoma cell lines, Hepa-1 and c4. Hepa-1 produces functional aryl hydrocarbon receptor nuclear translocator (ARNT). c4 cells are derived from Hepa-1, but are ARNT deficient. Interestingly, we observed cell line-dependent effects of hypoxia on the expression of p27(Kip1). The level of p27(Kip1) protein in Hepa-1 cells is enhanced by hypoxia, but is reduced by hypoxia in c4 cells. Further investigation demonstrated that hypoxia-induced, ARNT-mediated, transactivation of the p27(Kip1) gene in Hepa-1 cells is responsible for the increase in p27(Kip1) protein. Once c4 cells were stably transfected with the wild type ARNT gene, a hypoxia-induced increase in p27(Kip1) mRNA was observed and reduction of p27(Kip1) protein caused by hypoxia was blocked. Hence, our data indicate that ARNT is involved in transcriptional upregulation of the p27(Kip1) gene under hypoxic conditions.

Animals↗
PubMed2003

[Bombesin-mediated non-cholinergic late slow excitatory postsynaptic potentials in guinea pig inferior mesenteric ganglion in vitro].

The effect of bombesin (BOM) on non-cholinergic excitatory synaptic transmission of the guinea pig inferior mesenteric ganglion (IMG) was investigated by intracellular recording. Repetitive stimulation of the colon nerves (1 ms, 25 Hz, 4 s) elicited a burst of action potentials, which was followed by a long-lasting depolarization in 74.3% (52/70) of the IMG neurons. The depolarization was not blocked by nicotinic (d-tubocurarine, 100 micromol/L) and muscarinic (atropine, 1 micromol/L) antagonists, but was eliminated in a low Ca(2+)/high Mg(2+) Krebs solution, indicating that the depolarization was due to the release of non-cholinergic transmitters. Superfusing the ganglia with BOM (10 micromol/L, 1 min) induced a slow depolarization in 66.5% (109/164) neurons tested. The BOM response was not appreciably changed in low Ca(2+)/high Mg(2+) Krebs solution (n=6, P>0.05), suggesting that BOM depolarized the neurons by acting directly on the postsynaptic membrane rather than via a release of other endogenous depolarizing substances. In a total of 102 cells that exhibited late slow excitatory postsynaptic potential (ls-EPSP), superfusion of the ganglia with BOM produced a membrane depolarization in 82 neurons (80%), while the remaining 20 cells (20%) exhibited no response to BOM. In 18 neurons with ls-EPSP, 4 (22%) neurons were sensitive to both BOM and SP; 6 (33%) and 5 (28%) neurons were only sensitive to BOM and SP, respectively. The remaining 3 (17%) neurons were insensitive to both BOM and SP. Membrane resistance (Rm) had no apparent change in 47.3%, 59.5 % of the neurons tested during the ls-EPSP (n=55) and BOM depolarization (n=84), respectively, but had a marked decrease in 38.2%, 27.4%, and a marked increase in the remaining 14.5%, 13.1% of the neurons. However, when the Rm change accompanying ls-EPSP was compared with that accompanying BOM depolarization (n=20) in the same neuron, the changes in Rm were always parallel. Moreover, ls-EPSP (n=6) and BOM depolarization (n=8) were all augmented by conditioning hyperpolarization. The extrapolated values of the reversal potentials of ls-EPSP and BOM depolarization were 46.0+/-8.0 and 50.0+/-7.0 mV (n=8, P>0.05), respectively. In 14 BOM-sensitive neurons, a ls-EPSP was elicited by repetitive colon nerve stimulation. Superfusion of BOM (10 micromol/L) in these cells initially caused a large depolarization and then membrane potential gradually subsided to resting level in the continuous presence of BOM. Stimulation of the presynaptic nerves at this time failed to elicit a detecable ls-EPSP in 2 neurons and induced a much smaller one in 10 cells, while the ls-EPSP in the remaining 2 neurons was not appreciably affected. On the other hand, prolonged superfusion of BOM had no effect on the amplitude and duration of ls-EPSP in 6 BOM-insensititive neurons studied (P>0.05). The amplitude and duration of SP-induced depolarization were not altered by prolonged superfusion of BOM (n=4, P>0.05) Superfusion of tyr(4) D-phe(12) bombesin (1 micromol/L, 10 15 min), a BOM receptor antagonist, did not cause any noticeable changes in passive membrane properties nor block nicotinic f-EPSPs, but markedly suppressed (n=5) or completely abolished (n=11) BOM depolarization in all 16 neurons tested Similarly, tyr(4) D-phe(12) bombesin partially or completely antagonized the ls-EPSP in 9 out of a total of BOM sensitive neurons (n=11). The ls-EPSP elicited in the remaining two neurons was insignificantly affected by this drug. However, following 10 20 min of wash with Krebs solution the ls-EPSP was reversed. In contrast, superfusion of the ganglia with tyr(4) D-phe(12) bombesin did not change the amplitude and duration (P>0.05) of ls-EPSP in 10 BOM-insensitive cells. Similarly, the amplitude and duration of SP-induced depolarization were not appreciably affected by tyr(4) D-phe(12) bombesin (n=6, P>0.05). In conclusion, our results indicate that BOM may be another transmitter mediating the ls-EPSP in the guinea pig IMG and that there is no cross-desensitization of BOM receptors and SP receptors.

Action Potentials↗
PubMed2003

Representation of cardinal contour overlaps less with representation of nearby angles in cat visual cortex.

Extensive attempts have been made to explain the neurobiological basis of the greater sensitivity of the visual system to vertically or horizontally oriented information than to information presented at oblique angles. However, investigators have largely ignored the overlap of the representation of a given angle with the representation of nearby angles. Recordings based on intrinsic optical signals were obtained in area 17 from 12 adult cats during the presentation of contours in various orientations. A method investigating both amplitude and statistical significance of changes was proposed to evaluate the orientation tuning properties for cell populations in the central area retinotopically corresponding to 0-15 degrees of visual field. Cardinal orientations were found to activate significantly greater areas in the exposed cortical area than the areas activated by oblique orientations. Areas activated by cardinal or oblique contours and those separated from them by 10 degrees were compared. A significantly lower degree of overlap was seen between areas activated by presentation of cardinal contours and areas activated by neighboring orientations compared with those for oblique orientations which overlapped more extensively with neighboring orientations. In addition, areas activated only by cardinal contours were significantly larger than areas activated only by oblique contours. These results demonstrated in cell population level that more cells prefer horizontal or vertical orientations, and these cells are tuned more sharply than oblique selective cells.

Animals↗
PubMed2003

Angiotensin II attenuates functional hyperemia in the mouse somatosensory cortex.

We investigated whether angiotensin II (ANG II), a peptide that plays a central role in the genesis of hypertension, alters the coupling between synaptic activity and cerebral blood flow (CBF), a critical homeostatic mechanism that assures adequate cerebral perfusion to active brain regions. The somatosensory cortex was activated by stroking the facial whiskers in anesthetized C57BL/6J mice while local CBF was recorded by laser-Doppler flowmetry. Intravenous ANG II infusion (0.25 mug.kg-1.min-1) increased mean arterial pressure (MAP) from 82 +/- 2 to 102 +/- 3 mmHg (P < 0.05) without affecting resting CBF (P > 0.05). ANG II attenuated the CBF increase produced by whisker stimulation by 65% (P < 0.05) but did not affect the response to hypercapnia or to neocortical application of the nitric oxide donor S-nitroso-N-acetyl penicillamine (P > 0.05). The effect of ANG II on functional hyperemia persisted if the elevation in MAP was offset by controlled hemorrhage or prevented by topical application of the peptide to the activated cortex. ANG II did not reduce the amplitude of the P1 wave of the field potentials evoked by whisker stimulation (P > 0.05). Infusion of phenylephrine increased MAP (P > 0.05 from ANG II) but did not alter the functional hyperemic response (P > 0.05). The data suggest that ANG II alters the coupling between CBF and neural activity. The mechanisms of the effect are not related to the elevation in MAP and/or to inhibition of the synaptic activity evoked by whisker stimulation. The imbalance between CBF and neural activity induced by ANG II may alter the homeostasis of the neuronal microenvironment and contribute to brain dysfunction during ANG II-induced hypertension.

Angiotensin II↗
PubMed2003

PEG-catalytic water splitting in the interface of a bipolar membrane.

This paper investigates the effect of polyethylene glycol (PEG) on the water dissociation of bipolar membranes. To do this, bipolar membranes were prepared by immersing anion exchange membranes in different-concentration solutions of different-molecular-weight PEGs and then casting the solutions of sulfonated polyphenylene oxide (SPPO) on the anion exchange membranes. All the bipolar membranes with PEG in the interface are evaluated by current-voltage curves. The experimental results prove that PEG has excellent catalytic function for water dissociation. Furthermore, this function is enhanced by both PEG amount (PEG concentration) and PEG molecular weight in the interface of a bipolar membrane.

Journal Article↗
PubMed2003

Aminoglycoside complexation with a DNA.RNA hybrid duplex: the thermodynamics of recognition and inhibition of RNA processing enzymes.

Spectroscopic and calorimetric techniques were employed to characterize and contrast the binding of the aminoglycoside paromomycin to three octamer nucleic acid duplexes of identical sequence but different strand composition (a DNA.RNA hybrid duplex and the corresponding DNA.DNA and RNA.RNA duplexes). In addition, the impact of paromomycin binding on both RNase H- and RNase A-mediated cleavage of the RNA strand in the DNA.RNA duplex was also determined. Our results reveal the following significant features: (i) Paromomycin binding enhances the thermal stabilities of the RNA.RNA and DNA.RNA duplexes to similar extents, with this thermal enhancement being substantially greater in magnitude than that of the DNA.DNA duplex. (ii) Paromomycin binding to the DNA.RNA hybrid duplex induces CD changes consistent with a shift from an A-like to a more canonical A-conformation. (iii) Paromomycin binding to all three octamer duplexes is linked to the uptake of a similar number of protons, with the magnitude of this number being dependent on pH. (iv) The affinity of paromomycin for the three host duplexes follows the hierarchy, RNA.RNA > DNA.RNA >> DNA.DNA. (v) The observed affinity of paromomycin for the RNA.RNA and DNA.RNA duplexes decreases with increasing pH. (vi) The binding of paromomycin to the DNA.RNA hybrid duplex inhibits both RNase H- and RNase A-mediated cleavage of the RNA strand. We discuss the implications of our combined results with regard to the specific targeting of DNA.RNA hybrid duplex domains and potential antiretroviral applications.

Calorimetry↗
PubMed2003

Solid-phase synthesis of peptide vinyl sulfones as potential inhibitors and activity-based probes of cysteine proteases.

Peptide vinyl sulfones were prepared from 2-chlorotrityl resin-bound phenolic amino vinyl sulfones in high yield and purity. This method enables the convenient synthesis of peptide vinyl sulfones having different amino acids at the P(1) position. It also allows efficient synthesis of vinyl sulfone-containing, activity-based probes of cysteine proteases used in a proteomic experiment.

Amino Acids↗
PubMed2003

Difference in the representation of cardinal and oblique contours in cat visual cortex.

Optical imaging based on intrinsic signals was used to analyze the structure of orientation column in area 18 of cat visual cortex. Recordings were obtained in 12 adult cats during presentation of contours in various orientations. In order to quantitatively evaluate the size of the response area, a method combining both information on the amplitude of the changes and the statistical significance of the changes was proposed. The results showed that the proportion of the cortical area activated reached a peak during the presentation of horizontal or vertical contours, whereas the areas activated by oblique contours were relatively smaller. Cardinal contours (0 degrees and 90 degrees ) activated 50.63 +/- 1.88% (mean +/- SE) of the cortical area in the recording site, whereas oblique contours (45 degrees and 135 degrees ) activated only 45.25 +/- 2.02% of the area. This difference in area was statistically significant (t = 2.38, d.f. = 11, and P < 0.05). The results demonstrated a difference in the representations of the cardinal and oblique contours in area 18 of the cat visual cortex.

Animals↗
PubMed2003

Proteome analysis of Saccharomyces cerevisiae under metal stress by two-dimensional differential gel electrophoresis.

The defense mechanism by which cells combat metal stress remains poorly understood. By utilizing a newly developed technique - the differential gel electrophoresis (DIGE) - we evaluated the biological alterations of metal stress on Saccharomyces cerevisiae at its translational level. By simultaneously comparing the differential expression profiles of thousands of proteins as results of 15 different metal treatments, we were able to closely examine the response of a large number of proteins within the yeast proteome towards individual metals, as well as the response of the same proteins towards different metals. This, to our knowledge, is the first case which demonstrates the potential of DIGE as a high-throughput tool for large-scale proteome analysis. From our studies, where yeast cells were exhaustively treated with exogenous metals, 20-30% of all proteins detected showed statistically significant changes. According to different effects (up-/downregulation) of protein expression levels observed, we were able to tentatively divide the 15 metals into three groups. By mass spectrometric analysis, more than 50 protein spots were positively identified, both quantitatively and qualitatively. One of the proteins was identified to be Cu/Zn superoxide dismutase (SOD1), and its expression levels as a result of 15 different metal treatments was further examined in greater details. Significant changes in SOD1 expression were observed throughout all 15 DIGE gels.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2003

Effects of mycophenolate mofetil on renal interstitial fibrosis after Unilateral ureteral obstruction in rats.

To investigate the effects of mycophenolate mofetil (MMF) on the process of renal interstitial fibrosis, unilateral ureteral obstruction (UUO) model was established in rats. Twenty Sprague-Dawley rats underwent UUO and received vehicle (n = 10) or MMF (20 mg.kg-1.d-1, by daily gastric gavage, n = 10) during a period of 5 days following surgery, and the additional 10 rats were served as sham-operated group. The rats were killed 5 days after surgery. Immunohistochemistry was performed on renal tissue for proliferating cell nuclear antigen (PCNA), alpha-smooth muscle actin (alpha-SMA) and type I and III collagen (col I, col III). Histological studies were also done by MASSON staining. Five days after surgery, proliferating cells in tubules, interstitium as well as interstitial myofibroblast (MyoF) infiltration and interstitial col I, col III deposition were all significantly reduced by MMF treatment. MMF also alleviated the histological changes of UUO rats. These results suggested that the reduction of interstitial MyoF infiltration may be an important event by which MMF prevents renal injury caused by UUO and MMF could be used to limit the progression of renal fibrosis.

Animals↗
PubMed2003

Expression of TGF-beta in region of bone defect repaired by collagen/nano-beta-tricalcium phosphate composite artificial bone.

The distribution and function of transforming growth factor-beta (TGF-beta) in the region of bone defect repaired by collagen/nano-beta-tricalcium phosphate composite artificial bone (Co/N-TCP) and the ability of Co/N-TCP recruiting osteoblasts to precipitate the repair of bone defect were investigated. Twenty-four domestic rabbits were operated on bilateral cranial bone to create an experimental bone defect of 8.0 mm in diameter through the whole bone. On the left, Co/N-TCP was implanted as experimental group, but on the right, Co/TCP was implanted as control group. At 2nd, 4th, 8th, 12th week after operation, all animals were sacrificed and the implanted materials with surrounding bone were taken out. Immunohistochemical staining was performed for TGF-beta assay by avidin-biotin complex method (SABC). Simultaneously, TGF-beta was quantitatively analyzed by HPIAS-1000 imaging analysis system. The immunohistochemical staining for TGF-beta revealed that osteoblasts and immature osteocytes highly expressed TGF-beta. Diffused TGF-beta positive staining particles appeared in the mesenchymal and fibrous-tissue. There was no significant difference in the TGF-beta positive staining between two groups in the medial region to original osseous beds at different time points (P > 0.05). However, in distal original osseous bed of the defected region, the positive expression of TGF-beta in the Co/N-TCP group was significantly stronger than in the control group (P < 0.05 or 0.01). The Co/N-TCP has good bioactivities and ability of stimulating and conducting TGF-beta to aggregate and precipitate the healing of bone defect.

Animals↗
PubMed2003

Amperometric hydrogen peroxide biosensor with sol-gel/chitosan network-like film as immobilization matrix.

A new type of sol-gel/organic hybrid composite material based on the cross-linking of natural polymer chitosan with (3-aoryloxypropyl) dimethoxymethylsilane was developed for the fabrication of an amperometric H(2)O(2) biosensor. The composite film was used to immobilize horseradish peroxidase (HRP) on a gold disk electrode. The properties of sol-gel/chitosan and sol-gel/chitosan-HRP films have been carefully characterized by atomic force microscopy and Fourier transform infrared. By using fluorescent label, a protein density on sol-gel/chitosan has been calculated to be 3.14 x 10(12) moleculescm(-2). With the aid of catechol mediator, the biosensor had a fast response of less than 2 s with linear range of 5.0 x 10(-9)-1.0 x 10(-7) mol l(-1) and a detection limit of 2 x 10(-9) mol l(-1). Its current response shows a typical Michaelis-Menten mechanism. The apparent Michaelis-Menten constant K(M)(app) is found to be 1.30 micromol l(-1). The activation energy for enzymatic reaction is calculated to be 8.22 kJ mol(-1). The biosensor retained approximately 75% of its original activity after about 60 days of storage in a phosphate buffer at 4 degrees C.

Biosensing Techniques↗
PubMed2003

Isoflurane and propofol inhibit voltage-gated sodium channels in isolated rat neurohypophysial nerve terminals.

Mounting electrophysiological evidence indicates that certain general anesthetics, volatile anesthetics in particular, depress excitatory synaptic transmission by presynaptic mechanisms. We studied the effects of representative general anesthetics on voltage-gated Na+ currents (INa) in nerve terminals isolated from rat neurohypophysis using patch-clamp electrophysiological analysis. Both isoflurane and propofol inhibited INa in a dose-dependent and reversible manner. At holding potentials of -70 or -90 mV, isoflurane inhibited peak INa with IC50 values of 0.45 and 0.56 mM, and propofol inhibited peak INa with IC50 values of 4.1 and 6.0 microM, respectively. Isoflurane (0.8 mM) did not significantly alter the V1/2 of activation; propofol caused a small positive shift. Isoflurane (0.8 mM) or propofol (5 microM) produced a negative shift in the voltage dependence of inactivation. Recovery of INa from inactivation was slower from a holding potential of -70 mV than from -90 mV; isoflurane and propofol further delayed recovery from inactivation. In conclusion, the volatile anesthetic isoflurane and the intravenous anesthetic propofol inhibit voltage-gated Na+ currents in isolated neurohypophysial nerve terminals in a concentration- and voltage-dependent manner. Marked effects on the voltage dependence and kinetics of inactivation and minimal effects on activation support preferential anesthetic interactions with the fast inactivated state of the Na+ channel. These results are consistent with direct inhibition of oxytocin and vasopressin release from the neurohypophysis by isoflurane and propofol. Inhibition of voltage-gated Na+ channels may contribute to the presynaptic effects of general anesthetics on nerve terminal excitability and neurotransmitter release.

Anesthetics, Inhalation↗