Biomedical subjects

G F Wang

Publications and source records attributed to G F Wang.

At least 19 recordsLinked to original sources

PubMed2004

Domains of phase separation in a charged colloidal dispersion driven by electrolytes.

We put forth the idea of treating coexisting phases as a composite system and express its free energy as the average of its constitutent free energies weighted by their respective volume proportions. As a result, the theoretical study of charged colloidal phase separation in the presence of electrolytes reduces to optimizing solely the entities pertaining to colloids and small ions. As concrete illustrations, we demarcated the boundaries of coexisting phases for the simplest colloidal dispersion driven by salts at moderate to high concentrations and compared the results with those obtained in the usual manner to numerically show the robust efficiency of the present theory. Also, for a charged colloidal dispersion at very low ionic strength, we crosshatched both the homogeneous one phase and coexisting phases, and used the domains of coexisting phases to interpret an anomalous "transition" of phase diagrams exhibited in dilute colloidal dispersions induced by salts on dilution.

Journal Article↗

PubMed2001

Irx4 forms an inhibitory complex with the vitamin D and retinoic X receptors to regulate cardiac chamber-specific slow MyHC3 expression.

The slow myosin heavy chain 3 gene (slow MyHC3) is restricted in its expression to the atrial chambers of the heart. Understanding its regulation provides a basis for determination of the mechanisms controlling chamber-specific gene expression in heart development. The observed chamber distribution results from repression of slow MyHC3 gene expression in the ventricles. A binding site, the vitamin D response element (VDRE), for a heterodimer of vitamin D receptor (VDR) and retinoic X receptor alpha (RXR alpha) within the slow MyHC3 promoter mediates chamber-specific expression of the gene. Irx4, an Iroquois family homeobox gene whose expression is restricted to the ventricular chambers at all stages of development, inhibits AMHC1, the chick homolog of quail slow MyHC3, gene expression within developing ventricles. Repression of the slow MyHC3 gene in ventricular cardiomyocytes by Irx4 requires the VDRE. Unlike VDR and RXR alpha, Irx4 does not bind directly to the VDRE. Instead two-hybrid and co-immunoprecipitation assays show that Irx4 interacts with the RXR alpha component of the VDR/RXR alpha heterodimer and that the amino terminus of the Irx4 protein is required for its inhibitory action. These observations indicate that the mechanism of atrial chamber-specific expression requires the formation of an inhibitory protein complex composed of VDR, RXR alpha, and Irx4 that binds at the VDRE inhibiting slow MyHC3 expression in the ventricles.

Animals↗

PubMed2001

Realistic calculation of the low- and high-density liquid phase separation in a charged colloidal dispersion.

A realistic statistical-mechanics model is applied to describe the repulsive interaction between charged colloids. The latter, in combination with the long-range van der Waals attraction simulated under excess salt environment, gives rise to a total intercolloidal particle potential showing a clear second potential minimum. Differing from the usual Derjaguin-Landau-Verwey-Overbeek (DLVO) model, the present model is valid at any finite concentration of colloids and is thus an appropriate model for investigating the low- and high-density liquid phase transition. Employing this two-body colloid-colloid potential and in conjunction with the Weeks-Chandler-Andersen [J. D. Weeks, D. Chandler, and H. C. Andersen, J. Chem. Phys. 54, 5237 (1971)] thermodynamic perturbation theory, we derive analytical expressions for the pressure, chemical potential, and related thermodynamic functions. These thermodynamic quantities were used to calculate the phase diagrams of charged colloidal dispersions in terms of the critical parameters: temperature, volume fraction, and electrolyte concentration parameter k(D). Compared with the DLVO model, we find the areas enclosed within the spinodal decomposition and also the liquid-liquid coexistence curves broader in the present model for an excess salt condition kappa=k(D)sigma(0)< or similar to 200, sigma(0) being the macroion diameter, in addition to exhibiting a shift in the critical point kappa(c) to lower values; for kappa>300, the disparities between the two models reduce. The same thermodynamic perturbation theory has been employed to study also the weak reversible coagulation whose physical origin is attributed to the presence of the second potential minimum. We examine various colloidal parameters that affect the structure of the latter and deduce from our analysis the conditions of colloidal stability. In comparison with the measured flocculation data for a binary mixture of polystyrene lattices and water, we find that our calculated results are generally reasonable, thus lending great credence to the presently used model.

Journal Article↗

PubMed2001

Chromosomal DNA from a variety of bacterial species is present in synovial tissue from patients with various forms of arthritis.

OBJECTIVE: We and others have reported the presence of Chlamydia and other bacterial species in joint specimens from patients with reactive arthritis (ReA). The present study was conducted to investigate whether bacteria other than those specified by diagnostic criteria for ReA could be identified in synovial fluid (SF) or tissue from patients with various arthritides, and whether the presence of such organisms corresponds to particular clinical characteristics in any patient set or subset. METHODS: DNA in synovial biopsy samples and SF obtained from 237 patients with various arthritides, including ReA, rheumatoid arthritis, and undifferentiated oligoarthritis, was assayed by polymerase chain reaction (PCR) using "panbacterial" primers; we chose only samples known to be PCR negative for Chlamydia, Borrelia, and Mycoplasma species. PCR products were cloned, and cloned amplicons from each sample were sequenced; DNA sequences were compared against all others in GenBank for identification of bacterial species involved. RESULTS: Ten percent of patient samples were PCR positive in panbacterial screening assays. Bacterial species identified belonged to the genera Neisseria, Acinetobacter, Moraxella, Salmonella, Pseudomonas, and others. Thirty-five percent of PCR-positive patients showed the presence of DNA from more than a single bacterial species in synovium; overall, however, we could identify no clear relationship between specific single or multiple bacterial species in the synovium and any general clinical characteristics of any individual or group of patients. CONCLUSION: This analysis provides the first systematic attempt to relate bacterial nucleic acids in the synovium to clinical characteristics, joint findings, and outcomes. Many patients with arthritis have bacterial DNA in the joint, and, in some cases, DNA from more than a single species is present. However, except for 1 case of a control patient with staphylococcal septic arthritis, it is not clear from the present study whether the synovial presence of such organisms is related to disease pathogenesis or evolution in any or all cases.

Acinetobacter↗

PubMed2001

Chlamydial nucleic acids in synovium in osteoarthritis: what are the implications?

OBJECTIVE: To study whether there is evidence of bacterial DNA in some osteoarthritic (OA) joint tissues, and the clinical implications of finding bacterial DNA in this relatively noninflammatory disease. METHODS: Polymerase chain reaction (PCR) was used to detect DNA of Chlamydia trachomatis, Chlamydia pneumoniae, and other bacteria using panbacterial primers in synovial membranes and other articular tissues of 32 consecutive patients undergoing surgery for hip and knee OA. Patients were interviewed and examined postoperatively. Operative reports were reviewed and followup examinations were accomplished on all patients. RESULTS: Nine of 32 patients with OA (28.1%) had evidence for bacterial DNA in joint tissues with at least one set of primers for Chlamydia: 7 for C. trachomatis (21.9%), 2 for C. pneumoniae (6.2%). Five of 32 (15.6%) patients had postoperative complications; 3 of these were in patients who showed amplified DNA of C. trachomatis in joints and one in a patient in whom we detected Escherichia coli. CONCLUSION: C. trachomatis and C. pneumoniae nucleic acids can be present in joints in some cases of apparently classical OA. Whether chlamydial or other difficult to culture bacterial presence is associated with complications is suggested, but remains to be determined. Simple presence of C. trachomatis by PCR does not define a clinical syndrome or disease course.

Aged↗

PubMed2001

[Expression of the gE gene of pseudorabies virus in insect cells].

In order to develop a simple and safe test for the detection of vaccinated as well as wild type Pseudorabies virus (PRV) infected pigs, the modified gE gene of PRV Ea strain, obtained by cutting the 5' UTR using PCR and DNA recombinant technique, was inserted into baculovirus expression vector pFastBac 1, resulting the trans-position plamid pFE1.75. After homologous recombination, recombinant baculovirus rvBacE1.75 was gained and high level expression of glycoprotein E (gE) was observed after the infection of rvBacE1.75 to Tn-5B1-4 cells. The expression product was 80-88 kD and was specific to antisera against PRV Ea strain by Western-blotting. Purified recombinant proteins were used as an antigen in Latex Agglutination Test(gE-LAT) and the test was specific, sensitive, safe and simple.

Animals↗

PubMed2000

Comparison of inactivation and unfolding of methanol dehydrogenase during denaturation in guanidine hydrochloride and urea.

The activity and the conformational changes of methanol dehydrogenase (MDH), a quinoprotein containing pyrrolo-quinoline quinone as its prosthetic group, have been studied during denaturation in guanidine hydrochloride (GdnHCl) and urea. The unfolding of MDH was followed using the steady-state and time resolved fluorescence methods. Increasing the denaturant concentration in the denatured system significantly enhanced the inactivation and unfolding of MDH. The enzyme was completely inactivated at 1 M GdnHCl or 6 M urea. The fluorescence emission maximum of the native enzyme was at 332 nm. With increasing denaturant concentrations, the fluorescence emission maximum red-shifted in magnitude to a maximum value (355 nm) at 5 M GdnHCl or 8 M urea. Comparison of inactivation and conformational changes during denaturation showed that in general accord with the suggestion made previously by Tsou, the active sites of MDH are situated in a region more flexible than the molecule as a whole.

Alcohol Oxidoreductases↗

PubMed2000

Transferrin-bound and transferrin free iron uptake by cultured rat astrocytes.

Previously we had demonstrated the presence of transferrin receptor (TfR) on the plasma membrane of cultured rat cortical astrocytes. In this study, we investigated the roles of TfR in transferrin-bound iron (Tf-Fe) as well as transferrin-free iron (Fe II) uptake by the cells. The cultured rat astrocytes were incubated with 1 microM of double-labelled transferrin (125I-Tf-59Fe) in serum- free DMEM F12 medium or 59Fe II in isotonic sucrose solution at 37 degrees C or 4 degrees C for varying times. The cellular Tf-Fe, Tf and Fe II uptake was analyzed by measuring the intracellular radioactivity with gamma counter. The result showed that Tf-Fe uptake kept increasing in a linear manner at least in the first 30-min. In contrast to Tf-Fe uptake, the internalization of Tf into the cells was rapid initially but then slowed to a plateau level after 10 min. of incubation. The addition of either NH4Cl or CH3NH2, the blockers of Tf-Fe uptake via inhibiting iron release from Tf within endosomes, decreased the cellular Tf-Fe uptake but had no significant effect on Tf uptake. Pre-treated cells with trypsin inhibited significantly the cellular uptake of Tf-Fe as well as Tf. These findings suggested that Tf-Fe transport across the membrane of astrocytes is mediated by Tf-TfR endocytosis. The results of transferrin-free iron uptake indicated that the cultured rat cortical astrocytes had the capacity to acquire Fe II. The highest uptake of Fe II occurred at pH 6.5. The Fe II uptake was time and temperature dependent, iron concentration saturable, inhibited by several divalent metal ions, such as Co2+, Zn2+, Mn2+ and Ni2+ and not significantly affected by phenylarsine oxide treatment. These characteristics of Fe II uptake by the cultured astrocytes suggested that Fe II uptake is not mediated by TfR and implied that a carrier-mediated iron transport system might be present on the membrane of the cultured cells.

Animals↗

PubMed2000

[Interleukin-2 stimulates the proliferation of cultured RC-4B/C pituitary adenoma cell line].

The aim of the present study was to investigate whether interleukin-2 (IL-2) is involved in the proliferation control of the cultured RC-4B/C cell, which is a derived pituitary adenoma cell line of the rat. The level of cell proliferation was estimated by assessing (3)H-thymidine ((3)H-TdR) incorporation rate. IL-2 (10 1000 U/ml) significantly stimulated (3)H-TdR incorporation into the cell line in a dose-dependent manner. Specific PTK inhibitor tyrphostin (1 micromol/L) suppressed RC-4B/C cell proliferation and blocked the effect of IL-2 on RC-4B/C cells. After the PKA signaling pathway was inhibited by specific PKA inhibitor H-9 (1 micromol/L), the proliferation rate of RC-4B/C cells increased significantly. H-9 also enhanced the stimulation of IL-2 on RC-4B/C cell growth. Anti-estrogen tamoxifen (1 micromol/L) had no significant effect on the action of IL-2 on the proliferation of RC-4B/C cells. In conclusion, it is suggested that IL-2 modulates the proliferation of the cultured RC-4B/C pituitary adenoma cell line, and the action is closely related with the PTK and PKA signaling pathway.

Adenoma↗

PubMed2000

[The detection of Epstein-Barr virus in middle ear effusion of secretory otitis media].

OBJECTIVE: To study the involvement of Epstein-Barr Virus (EBV) in the pathogenesis of secretory otitis media (SOM). METHOD: Epstein-Barr Virus (EBV) in blood serum, oral gargle and middle ear effusion was detected by polymerase chain reaction (PCR) method in 34 patients with secretory otitis media and 20 normal subjects. RESULT: The detection rate of EBV in serum and oral gargle in the SOM group was remarkably higher than that in normal control group (P < 0.01). EBV positive rate of middle ear effusion was higher than that of serum group in SOM individuals. CONCLUSION: EBV plays a role in the pathogenesis of secretory otitis media (SOM).

Adolescent↗

PubMed1999

Frequency of apolipoprotein E (APOE) allele types in patients with Chlamydia-associated arthritis and other arthritides.

Genetic background is important in determining whether certain infecting bacteria disseminate to the joint and cause arthritis. We assessed whether APOE genotype is associated with the presence of DNA from Chlamydia or other bacteria in synovial tissues of patients with various arthritides. Nucleic acids from synovial tissues of 135 patients were screened by PCR for DNA from Chlamydia trachomatis, C. pneumoniae and other bacteria (pan-bacteria). APOE genotype was determined by a PCR-based method for all patients in each of four resulting groups comprised of about 35 individuals each, positive for C. trachomatis only, C. pneumoniae only, other bacteria, or no bacteria. RT-PCR was used to assess synovial APOE expression. The latter assays confirmed that APOE mRNA is present in synovial tissue. Determination of APOE genotype showed that patients PCR-negative in all assays, and those positive in the C. trachomatis - and pan-bacteria- (excluding Chlamydia) directed assays, had distributions of the APOE epsilon2, epsilon3 and epsilon4 alleles mirroring those of the general population (i.e. about 8%, 79% and 13%, respectively). In contrast, 68% of patients with C. pneumoniae DNA in synovium possessed a copy of the epsilon4 allele. These results indicate that no association exists between APOE genotype and synovial presence of C. trachomatis or other bacteria. However, individuals bearing at least one copy of the APOE epsilon4 allele may be at increased risk for synovial infection by C. pneumoniae.

Alleles↗

PubMed1999

A retinoic acid-inducible transgenic marker of sino-atrial development in the mouse heart.

To study the specification of inflow structures in the heart we generated transgenic animals harboring the human alkaline phosphatase (HAP) gene driven by the proximal 840 bp of a quail SMyHC3 promoter. In transgenic mice, the SMyHC3-HAP reporter was expressed in posterior heart precursors at 8.25 dpc, in sinus venosa and in the atrium at 8.5 and 9.0 dpc, and in the atria from 10.5 dpc onwards. SMyHC3-HAP transgene expression overlapped synthesis and endogenous response to retinoic acid (RA) in the heart, as determined by antibodies directed against a key RA synthetic enzyme and by staining of RAREhsplacZ transgenic animals. A single pulse of all-trans RA administered to pregnant mice at 7.5, but not after 8.5, dpc induced cardiac dismorphology, ranging from complete absence of outflow tract and ventricles to hearts with reduced ventricles expressing both SMyHC3-HAP and ventricular markers. Blockade of RA synthesis with disulfiram inhibited RA-induced transcription and produced hearts lacking the atrial chamber. This study defines a novel marker for atrial-restricted transcription in the developing mouse heart. It also suggests that atrial-specific gene expression is controlled by localized synthesis of RA, and that exclusion of RA from ventricular precursors is essential for correct specification of the ventricles.

Alkaline Phosphatase↗

PubMed1999

Anisodamine as an effective drug to treat snakebites.

Anisodamine is a natural alkaloid drug isolated from the plant Anisodus tanguticus growing in western China. The chemical structure and pharmacological action are just like the cholinergic receptor blocking agents atropine or scopolamine. The specific characteristic of the drug is being able to relieve the dangerous situation of microcirculatory failure, especially in case of DIC or renal failure. The prognosis of the patients will be quite good. Another characteristic of the drug is that no serious toxic reaction occurs even in successive doses given intravenously up to 500 mg a day. This is about fifty times greater than a common dose of 10 mg. Since we begin with the drug as a routine medication for the symptomatic treatment of renal failure, DIC bleeding, and microcirculatory failure, we should say that the specific antivenin and anisodamine are two treasure drugs for snakebites.

Animals↗

PubMed1998

Enhanced radioimmunotherapeutic efficacy of a monoclonal antibody cocktail against SMMC-7721 human hepatocellular carcinoma.

The improved tumoricidal effect of the radioantibody mixture ("cocktail") has been reported recently for the treatment of colon tumor. In the present study, we demonstrated the enhanced radioimmunotherapeutic efficacy of a monoclonal antibody (MAb) cocktail against human hepatocellular carcinoma. Therapeutic efficacy was determined by measuring the change in tumor size over a period, determining the percentage of growth inhibition of each treatment at various times after radioantibody therapy. Radioimmunotherapy of SMMC-7721 human hepatoma xenografts in athymic nude mice with combination of 131I-labeled Hepama-1 and 131I-labeled 9403 mouse MAbs was more effective than using either Hepeam-1 or 9403 MAb alone The MAb cocktail could target a greater number of hepatoma cells and increase the magnitude of hepatoma cell uptake of radioantibodies. The in vitro results explain the enhanced effect of the MAb cocktail in in vivo model system.

Animals↗

PubMed1998

A positive GATA element and a negative vitamin D receptor-like element control atrial chamber-specific expression of a slow myosin heavy-chain gene during cardiac morphogenesis.

We have used the slow myosin heavy chain (MyHC) 3 gene to study the molecular mechanisms that control atrial chamber-specific gene expression. Initially, slow MyHC 3 is uniformly expressed throughout the tubular heart of the quail embryo. As cardiac development proceeds, an anterior-posterior gradient of slow MyHC 3 expression develops, culminating in atrial chamber-restricted expression of this gene following chamberization. Two cis elements within the slow MyHC 3 gene promoter, a GATA-binding motif and a vitamin D receptor (VDR)-like binding motif, control chamber-specific expression. The GATA element of the slow MyHC 3 is sufficient for expression of a heterologous reporter gene in both atrial and ventricular cardiomyocytes, and expression of GATA-4, but not Nkx2-5 or myocyte enhancer factor 2C, activates reporter gene expression in fibroblasts. Equivalent levels of GATA-binding activity were found in extracts of atrial and ventricular cardiomyocytes from embryonic chamberized hearts. These observations suggest that GATA factors positively regulate slow MyHC 3 gene expression throughout the tubular heart and subsequently in the atria. In contrast, an inhibitory activity, operating through the VDR-like element, increased in ventricular cardiomyocytes during the transition of the heart from a tubular to a chambered structure. Overexpression of the VDR, acting via the VDR-like element, duplicates the inhibitory activity in ventricular but not in atrial cardiomyocytes. These data suggest that atrial chamber-specific expression of the slow MyHC 3 gene is achieved through the VDR-like inhibitory element in ventricular cardiomyocytes at the time distinct atrial and ventricular chambers form.

Animals↗

PubMed1997

[Effect of interleukin-2 on the proliferation of cultured rat anterior pituitary cells].

The present study was to investigate whether IL-2 is involved in the proliferation control of anterior pituitary (AP) cells. Primary culture of AP cells was obtained from either male or female Sprague-Dawley rats. The effects of IL-2 were assessed by 3H-thymidine incorporation rate. It was found that: (1) IL-2 (10-500 U/ml) significantly stimulated 3H-TdR incorporation into AP cells of female pregnant as well as none-pregnant rats, but inhibited 3H-TdR incorporation in the male rats. (2) The stimulatory effect of IL-2 was reversed in overiectomized rats, but could be restored when the overiectomized rats were treated with estradiol benzoate (5 micrograms/d per rat). (3) When the male rats were orchiectomized for 2 weeks, the inhibitory effects of IL-2 did not occur. The above data indicated that the proliferative effect of IL-2 on AP is a joint action of sex steroids hormones.

Animals↗

PubMed1996

Atrial chamber-specific expression of the slow myosin heavy chain 3 gene in the embryonic heart.

The quail slow myosin heavy chain 3 (slow MyHC 3) gene is expressed in the developing heart and in slow muscles of the developing limb. It is first expressed in the pulsatile cardiac tube in the embryo, and as the heart chamberizes its expression becomes restricted to the atria. To identify regulatory elements responsible for atrial-specific expression, the 5' upstream region of slow MyHC 3 gene was investigated. An atrial regulatory domain (ARD1) between -840 and -680 acts as an atrial cell-specific enhancer in primary cardiocyte cultures. ARD1 also specifies atrial-specific expression in vivo when the ARD1/heterologous promoter was introduced into developing chick embryos by a replication-competent retroviral vector. ARD1 is the first atrial cell-specific enhancer to be identified. Fine deletion and mutation analysis within ARD1 defined a 40-base pair vitamin D3 receptor-like element that controls atrial cell-specific expression of the slow MyHC 3 gene by inhibiting its expression in ventricular cardiocytes.

Animals↗

PubMed1996

Isolation and characterization of an avian slow myosin heavy chain gene expressed during embryonic skeletal muscle fiber formation.

We have isolated and begun characterization of the quail slow myosin heavy chain (MyHC) 3 gene, the first reported avian slow MyHC gene. Expression of slow MyHC 3 in skeletal muscle is restricted to the embryonic period of development, when the fiber pattern of future fast and slow muscle is established. In embryonic hindlimb development, slow MyHC 3 gene expression coincides with slow muscle fiber formation as distinguished by slow MyHC-specific antibody staining. In addition to expression in embryonic appendicular muscle, slow MyHC 3 is expressed continuously in the atria. Transfection of slow MyHC 3 promoter-reporter constructs into embryonic myoblasts that form slow MyHC-expressing fibers identified two regions regulating expression of this gene in skeletal muscle. The proximal promoter, containing potential muscle-specific regulatory motifs, permits expression of a reporter gene in embryonic slow muscle fibers, while a distal element, located greater than 2600 base pairs upstream, further enhances expression 3-fold. The slow muscle fiber-restricted expression of slow MyHC 3 during embryonic development, and expression of slow MyHC 3 promoter-reporter constructs in embryonic muscle fibers in vitro, makes this gene a useful marker to study the mechanism establishing the slow fiber lineage in the embryo.

Amino Acid Sequence↗