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Biomedical subjects

F Wang

Publications and source records attributed to F Wang.

At least 631 records · Page 35Linked to original sources
PubMed1992

A selectable marker allows investigation of a nontransforming Epstein-Barr virus mutant.

The derivation of specifically mutated Epstein-Barr virus (EBV) recombinants is dependent on strategies to identify, enumerate, and clone infected B lymphocytes. In recent experiments, EBV recombinants containing a positive selection marker were identified and cloned in B-lymphoma (BL) cells infected and then plated under selective conditions (F. Wang, A. Marchini, and E. Kieff, J. Virol. 65:1701-1709, 1991). We now use BL cells, for the first time, as hosts for assaying and cloning otherwise isogenic EBV recombinants carrying a hygromycin phosphotransferase (HYG) gene linked to either a nontransforming deletion mutant or a transforming wild-type EBV nuclear antigen 2 (EBNA-2) gene. Both types of recombinants converted BL cells to hygromycin resistance with similar efficiency, formed episomes, and usually expressed only EBNA-1. Only the wild-type EBNA-2 HYG gene EBV recombinant transformed primary B lymphocytes. This strategy of assaying virus on BL and primary B lymphocytes makes possible the direct assessment of the transforming efficiency of an EBV recombinant. The resultant infected BL cells are also useful for the characterization of the nontransforming recombinant EBV genomes. The HYG gene insertion in the BHLF1 open reading frame eliminated BHLF1 protein expression. The insertion and resulting BHLF1 mutation did not interfere with primary B-lymphocyte infection, growth transformation, induction of lytic infection, or virus production. Thus, these experiments also indicate that neither the BHLF1 open reading frame nor the HYG gene insertion critically affects B-lymphocyte infection in vitro.

Cell Transformation, Viral↗
PubMed1992

Factors affecting movement of F-actin filaments propelled by skeletal muscle heavy meromyosin.

The measurement of fluorescent-labeled actin filament movement driven by mechanoenzymes (e.g., myosin) is an important methodology for the study of molecular motors. It is assumed that the filament velocity (Vf) is analogous to the unloaded shortening velocity (Vu) seen in muscle fibers. Methods are described to reproducibly quantitate the movement of these filaments and to select uniformly moving filaments and specify their Vf. Use of these techniques allowed comparison of Vf to literature values for Vu with regard to [ATP], [ADP], [Pi], pH, ionic strength (10-150 mM), and temperature (15-30 degrees C). Vf and Vu are quantitatively similar with respect to the effects of substrate and product concentrations and temperatures greater than 20 degrees C. However, Vf is more sensitive to decreases in pH and temperatures less than 20 degrees C than Vu. At ionic strengths of 50-150 mM, Vf and Vu exhibit similar ionic strength dependencies (decreasing with ionic strength). At ionic strengths less than 50 mM, Vf is markedly reduced. Results of experiments using adenosine 5'-O-(3-thiotriphosphate) suggest that increasing the number of weakly bound cross bridges does not seriously affect Vf. Thus, although Vf is a good analogue for Vu under certain conditions (elevated ionic strength and temperatures greater than 20 degrees C), under others it is not. The results of motility assays must be cautiously interpreted.

Actins↗
PubMed1992

Pneumocystis carinii pneumonia in patients with systemic lupus erythematosus.

At the University Hospital, Kuala Lumpur, Malaysia, nine patients with systemic lupus erythematosus (SLE) were treated for Pneumocystis carinii pneumonia (PCP) between January 1987 and December 1988. When they developed PCP all the patients' SLE disease course was active and eight of them were on prednisolone. Four of these eight patients were also receiving cyclophosphamide. Patients who were on more intensive immunosuppressive therapy were found to develop more severe PCP. All the patients except one were treated with high-dose cotrimoxazole. Four patients responded to antipneumocystis treatment and survived, while PCP was responsible for the death of the five non-survivors.

Adolescent↗
PubMed1992

Heparin-binding keratinocyte growth factor is a candidate stromal-to-epithelial-cell andromedin.

The growth of isolated epithelial and stromal cells from both androgen-dependent normal rat prostate and an androgen-responsive model rat prostate tumor is androgen-independent. When added to co-cultures of epithelial and stromal cells separated by a semipermeable membrane, androgen stimulated epithelial cell growth without an effect on stromal cell growth. Northern blot and nuclease protection analysis of mRNA revealed that stromal cells specifically expressed an androgen-sensitive secreted member of the heparin-binding fibroblast growth factor family [keratinocyte growth factor (KGF)/fibroblast growth factor-7]. KGF was mitogenic for epithelial cells, but not for stromal cells. Epithelial cells expressed specifically a splice variant of the bek receptor gene that specifically binds KGF. Expression of the bek receptor gene in stromal cells was undetectable by Northern blot and nuclease protection analyses. The results suggest that stromal cell-derived KGF has the properties of an andromedin, which mediates the indirect control of epithelial cell proliferation by androgen through a directional stromal-to-epithelial cell paracrine mechanism.

Animals↗
PubMed1992

[Effects of moxibustion on experimental gastric ulcer in rats].

This study was designed to determine whether moxibustion at "Shenjue" plays a role in protecting gastric mucosa in rats. The areas and histological changes of gastric ulcer were examined. The results were as follows: 1. Moxibustion pretreatment within 3 weeks significantly prevented the formation of gastric ulcer. 2. As gastric ulcer had formed, moxibustion couldn't shorten the period of recovery of gastric ulcer. The results suggested that moxibustion pretreatment at "Shenjue" had a protective effect on gastric mucosa. After the experimental ulcer had formed, however, the moxibustion had little protective effect on it.

Acetates↗
PubMed1992

[Immuno-ricin A chain specific for gastric cancer: internalization and its significance].

Biotinylated ricin A chain (RTA) was introduced to antigastric cancer monoclonal antibody MGb2 with chemical conjugating technique to form an immuno-ricin A chain conjugate (I-RTA) specific for gastric cancer. Its internalization in human gastric cancer cell line SGC-7901 was followed by double dynamic EM labelling procedure using streptavidin-gold and sheep anti-mouse IgG-gold probes. The effects of verapamil on I-RTA internalization routings were also observed. The results demonstrated that the main entry modality of I-RTA was non-coated microinvagination, followed by coated pits and interioration of microvilli. The internalized I-RTA was found to be quickly transported to multivesicular bodies and finally to lysosomes, where it was degraded, whilst in the non-membranous structures I-RTA was only occasionally encountered. Ultrastructurally, verapamil displayed its effects by making the internalized I-RTA stay longer in tubulovesicular structures and be delivered in a less amount and more slowly into lysosomes. Furthermore, I-RTA was increased in the non-membranous structures, and the in vitro killing effect was significantly enhanced. The present data revealed the basic cell biology process of I-RTA-cell interaction, which will provide not only an important clue to improving I-RTA targeting therapy efficiency, but also a new way for further screening targeting potentiators.

Animals↗
PubMed1992

[A clinical analysis of atrial-ventricular sequential pacing].

Forty one patients were implanted DDD pacemakers (3 cases DDDR) from August, 1983 to July, 1990. 32 males and 9 females. The mean age was 62.3 years (range 32 to 91). 19 patients had coronary artery disease. The indication for pacing was II degrees-III degrees AV block in 16 patients and sick sinus syndrome in 25 patients. During follow-up period there were 2 patients had displacement, 4 patients had undersensing, 3 patients had pacemaker-mediated tachycardia and 3 patients had crosstalk. That was corrected through external programmer. The experience of this operation was discussed.

Adult↗
PubMed1992

Magnetic resonance imaging of osteomyelitis.

Early diagnosis and detection of osteomyelitis and differentiation of soft-tissue infection from bone involvement is a difficult clinical and imaging problem. Magnetic resonance imaging has proven to be as sensitive as bone scintigraphy in the early detection of osteomyelitis, and, with its superior spatial resolution, MR is often more specific than planar scintigraphy in differentiating bone from soft-tissue infection and separating arthritis, cellulitis, and soft-tissue abscess from osteomyelitis. In several comparative studies, MR has been more advantageous in detecting the presence and determining the extent of osteomyelitis over scintigraphy, CT scan, and conventional radiography. MRI may facilitate differentiation of acute from chronic osteomyelitis and may help to detect foci of active infection in the presence of chronic inflammation or posttraumatic lesions. MRI has a large role in evaluating the presence and extent of spondylitis and epidural abscess and certain distribution features may help recognize tuberculous spondylitis. Gadolinium-enhanced MR could be helpful in delineating the meninges and demonstrating the border and extent of epidural abscesses.

Abscess↗
PubMed1991

Structural analyses of proteins electroblotted from native polyacrylamide gels onto polyvinyldiene difluoride membranes. A method for determining the stoichiometry of protein-protein interaction in solution.

The usefulness of a native gel electroblotting technique in the study of protein-protein interactions was demonstrated by the determination of the stoichiometry of the interaction between interleukin-2 (IL-2) and the alpha subunit of IL-2 receptor (IL-2R alpha) in solution. Complexes formed between the recombinant forms of the two proteins in solution were separated from the noncomplexed protein molecules by electrophoresis in a native polyacrylamide gel and the protein bands were electroblotted quantitatively onto polyvinyldiene difluoride membranes for further structural analysis. The data obtained from sequence and amino acid analyses of the blotted proteins provided direct evidence that IL-2 binds to IL-2R alpha in a 1:1 ratio. This methodology should be applicable to the study of other structure/function aspects of protein-protein interactions in solution.

Amino Acid Sequence↗
PubMed1991

A ring of uncharged polar amino acids as a component of channel constriction in the nicotinic acetylcholine receptor.

The channel pore of the nicotinic acetylcholine receptor (AChR) has been investigated by analysing single-channel conductances of systematically mutated Torpedo receptors expressed in Xenopus oocytes. The mutations mainly alter the size and polarity of uncharged polar amino acid residues of the acetylcholine receptor subunits positioned between the cytoplasmic ring and the extracellular ring. From the results obtained, we conclude that a ring of uncharged polar residues comprising threonine 244 of the alpha-subunit (alpha T244), beta S250, gamma T253 and delta S258 (referred to as the central ring) and the anionic intermediate ring, which are adjacent to each other in the assumed alpha-helical configuration of the M2-containing transmembrane segment, together form a narrow channel constriction of short length, located close to the cytoplasmic side of the membrane. Our results also suggest that individual subunits, particularly the gamma-subunit, are asymmetrically positioned at the channel constriction.

Amino Acid Sequence↗
PubMed1991

Induction of bcl-2 expression by Epstein-Barr virus latent membrane protein 1 protects infected B cells from programmed cell death.

Epstein-Barr virus (EBV) not only induces growth transformation in human B lymphocytes, but has more recently been shown to enhance B cell survival under suboptimal conditions where growth is inhibited; both effects are mediated through the coordinate action of eight virus-coded latent proteins. The effect upon cell survival is best recognized in EBV-positive Burkitt's lymphoma cell lines where activation of full virus latent gene expression protects the cells from programmed cell death (apoptosis). Here we show by DNA transfection into human B cells that protection from apoptosis is conferred through expression of a single EBV latent protein, the latent membrane protein LMP 1. Furthermore, we demonstrate that LMP 1 mediates this effect by up-regulating expression of the cellular oncogene bcl-2. The interplay between EBV infection and expression of this cellular oncogene has important implications for virus persistence and for the pathogenesis of virus-associated malignant disease.

Antigens, Viral↗
PubMed1991

The DNA intercalator, ethidium bromide, alters the pattern of DNAse I hypersensitive sites of the beta A-globin gene in chicken erythrocytes.

We have analysed the effects of a DNA intercalator, ethidium bromide (EB), on chromatin structure in nuclei from both chicken mature erythrocytes (RBC) and reticulocytes (Ret). A differential release of nuclear proteins was obtained from both types of nuclei exposed to EB. Among these proteins, a species of 45 kDa is the major component. Furthermore, in the 10 mM EB-treated nuclei, the pattern of DNAse I hypersensitive sites (DHS) around the chicken beta A-globin gene were significantly altered, i.e., the original set was replaced by a new set of DHS. We have discussed the implications of our observations, in the light of current concepts of functional aspects of the conformational heterogeneity of DNA in both protein-DNA interactions and chromatin structure, as well as the effects of DNA intercalators on DNA conformation.

Animals↗
PubMed1991

Rings of anionic amino acids as structural determinants of ion selectivity in the acetylcholine receptor channel.

To gain an insight into the molecular basis of the weak but significant selectivity among alkali metal cations of the nicotinic acetylcholine receptor (AChR) channel, we have determined single-channel conductance and permeability ratios for alkali metal cations on specifically mutated Torpedo californica AChR channels expressed in Xenopus oocytes. The mutations involved charged and polar side chains in the three anionic rings (extracellular, intermediate and cytoplasmic ring) which have previously been found to determine the rate of K+ transport through the AChR channel. The results obtained reveal that mutations in the intermediate ring exert much stronger effects on ion selectivity than do mutations in the extracellular and the cytoplasmic ring. The experimental results, together with simulations of the channel's energy profile, suggest that the amino acid residues forming the intermediate ring come into close contact with permeating cations and possibly represent part of the physical correlate of the postulated selectivity filter in the AChR channel.

Amino Acid Sequence↗
PubMed1991

Macrophages express functional receptors for calcitonin-gene-related peptide.

The present study was designed to investigate whether non-activated macrophages express calcitonin (CT) or calcitonin-gene-related peptide (CGRP) receptors. To this end, we first analyzed whether CT and CGRP induce a cAMP accumulation in macrophages. Macrophages were treated for 2 min with increasing concentrations of either CT or CGRP in the presence or absence of IBMX. A dose-dependent cAMP accumulation was measured in response to CGRP with a half-maximal effect attained with 1 nM CGRP. CT failed at all doses to induce an accumulation of cAMP. The effects of CT and CGRP on the activation of the Na-H exchanger were next assessed by spectrofluorometry by using the pH-sensitive dye 2,7 biscarboxyethyl-5(6)-carboxyfluorescein (BCECF). Steady-state pHi of macrophages in a 7.4, HCO3-free solution (HEPES-buffered) was 7.04 +/- 0.08 (n = 22). pHi recovery following an NH4+/NH3 acid load was inhibited by the removal of Na+ or by the addition of the amiloride analog EIPA; therefore recovery is dependent on Na-H exchange activity. CT had no effect on steady-state pHi but CGRP increased pHi in a dose-dependent fashion (10(-12) to 10(-6) M). The pHi change induced by CGRP was due to the stimulation of the Na-H exchanger as CGRP enhanced the rate of recovery (dpHi/dt) from an acid load from 45.3 to 77.2 microMs-1 (n = 8, P less than 0.002) and was completely blocked by EIPA. These data indicate that CGRP both enhances the activity of the Na-H exchanger and increases intracellular cAMP, thus demonstrating that macrophages express functional CGRP receptors.

1-Methyl-3-isobutylxanthine↗