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Biomedical subjects

G Wang

Publications and source records attributed to G Wang.

At least 685 records · Page 38Linked to original sources
PubMed1995

Structures of the native and swollen forms of cowpea chlorotic mottle virus determined by X-ray crystallography and cryo-electron microscopy.

BACKGROUND: RNA-protein interactions stabilize many viruses and also the nucleoprotein cores of enveloped animal viruses (e.g. retroviruses). The nucleoprotein particles are frequently pleomorphic and generally unstable due to the lack of strong protein-protein interactions in their capsids. Principles governing their structures are unknown because crystals of such nucleoprotein particles that diffract to high resolution have not previously been produced. Cowpea chlorotic mottle virions (CCMV) are typical of particles stabilized by RNA-protein interactions and it has been found that crystals that diffract beyond 4.5 A resolution are difficult to grow. However, we report here the purification of CCMV with an exceptionally mild procedure and the growth of crystals that diffract X-rays to 3.2 A resolution. RESULTS: The 3.2 A X-ray structure of native CCMV, an icosahedral (T = 3) RNA plant virus, shows novel quaternary structure interactions based on interwoven carboxyterminal polypeptides that extend from canonical capsid beta-barrel subunits. Additional particle stability is provided by intercapsomere contacts between metal ion mediated carboxyl cages and by protein interactions with regions of ordered RNA. The structure of a metal-free, swollen form of the virus was determined by cryo-electron microscopy and image reconstruction. Modeling of this structure with the X-ray coordinates of the native subunits shows that the 29 A radial expansion is due to electrostatic repulsion at the carboxyl cages and is stopped short of complete disassembly by preservation of interwoven carboxyl termini and protein-RNA contacts. CONCLUSIONS: The CCMV capsid displays quaternary structural interactions that are unique compared with previously determined RNA virus structures. The loosely coupled hexamer and pentamer morphological units readily explain their versatile reassembly properties and the pH and metal ion dependent polymorphism observed in the virions. Association of capsomeres through inter-penetrating carboxy-terminal portions of the subunit polypeptides has been previously described only for the DNA tumor viruses, SV40 and polyoma.

Amino Acid Sequence↗
PubMed1995

High-level expression of prochymosin in Escherichia coli: effect of the secondary structure of the ribosome binding site.

Regulation of the expression of prochymosin cDNA in Escherichia coli at the translational level was studied by mutating the regions between the Shine-Dalgarno (SD) sequence and the initiation codon and upstream of the SD signal. Results revealed that expression plasmids with a distance of 7-10 bp from SD to ATG have the potential to be expressed at higher levels. However, an approximately 20-fold variation in expression was observed with plasmids harboring different base composition but identical distance in the spacer. Analysis of the predicted secondary structure of ribosome binding sites (RBS) indicates that the control of expression by base composition is mediated by the secondary structure of the RBS. An unfolded state of the RBS is required for high expression. Therefore, a vector for enhanced translation can be designed and constructed via prediction of the secondary structure of the proposed RBS and mutagenesis. Based on this strategy, high-level expression of prochymosin, up to 39% of the total cellular proteins, was achieved. The 9-base sequence proposed by Olins and Rangwala as a translational enhancer did not exhibit an additive effect on prochymosin expression. This is probably because the affinity of the SD sequence used in this study to 16S rRNA is strong enough that no additional element is required to facilitate the formation of the translation initiation complex.

Base Sequence↗
PubMed1995

Tetrandrine: a new ligand to block voltage-dependent Ca2+ and Ca(+)-activated K+ channels.

Extensive pharmacological investigations on tetrandrine, one of the traditional medicinal alkaloids, are reviewed. Tetrandrine has been used clinically in China for centuries in the treatment of many diseases. A recent series of studies has revealed major mechanisms underlying its multiple pharmacological and therapeutic actions. One of the most interesting discoveries is that tetrandrine is a new kind blocker of the voltage-activated, L-type Ca2+ channel in a variety of excitable cells, such as cardiac, GH3 anterior pituitary and neuroblastoma cells, as well as in rat neurohypophysial nerve terminals. Although tetrandrine does not belong to any of the three classical Ca2+ channel blocker groups, electrophysiological and radioligand binding studies show that tetrandrine is an L-type Ca2+ channel blocker with its binding site located at the benzothiazepine receptor on the alpha 1-subunit of the channel. In addition, tetrandrine is a blocker of the voltage-dependent T-type Ca2+ channel. It is clear that tetrandrine's actions in the treatment of cardiovascular diseases, including hypertension and supraventricular arrhythmia, are due primarily to its blocking of voltage-activated L-type and T-type Ca2+ channels. Furthermore, this alkaloid is a potent blocker of the Ca(2+)-activated K+ (K(Ca)) channels of neurohypophysial nerve terminals. The blocking kinetics of tetrandrine on the K(Ca) channel is quite different from that of typical K(Ca) channel blockers such as tetraethylammonium and Ba2+. Although the clinical role of tetrandrine as a blocker of the K(Ca) channels is unclear, it is a promising ligand for the study of K(Ca) channel function.

Alkaloids↗
PubMed1995

Difference of lifestyle advice between traditional Chinese medical doctors (TCMDs) and Western-style medical doctors (WSMDs) in People's Republic of China.

The role of physicians in providing lifestyle advice is very important in disease prevention and health promotion. This study was designed to examine (a) the difference of lifestyle advice provided for general practice patients between traditional Chinese medical doctors (TCMDs) and Western-style medical doctors (WSMDs), (b) the difference of lifestyle advice provided for cardiovascular disease (CVD) patients between the TCMDs and WSMDs, (c) the difference of lifestyle advice provided for general practice and CVD patients by the TCMDs, and (d) the difference of lifestyle advice provided for general practice and CVD patients by the WSMDs. One thousand four-hundred and thirty general practice patient records and 640 CVD patient records from a Western-style medical hospital, and 1620 general practice records and 830 CVD patient records from a traditional Chinese medical hospital were selected for comparison. Results indicated that TCMDs were more likely to provide nutrition, exercise, and stress management for their patients than WSMDs. On the other hand, WSMDs were more likely to provide smoking and alcohol consumption for their patients than the TCMDs. In addition, both TCMDs and WSMDs were more likely to provide all categories of lifestyle advice for their CVD patients than their general practice patients.

China↗
PubMed1995

Temporal bone volumetric image deblurring in spiral computed tomography scanning.

RATIONALE AND OBJECTIVES: We developed a method for volumetric image deblurring in spiral (helical) computed tomography (CT) scanning with a three-dimensional (3D) Gaussian point spread function (PSF) to improve the quality of temporal bone spiral CT images for assessing the position of cochlear implants electrodes. METHODS: A patient was scanned after cochlear implantation, and the temporal bone was reconstructed into a volume with 128 voxels per dimension, 0.1 mm per voxel side, and x 10 gray-scale expansion. The 3D PSF in spiral CT imaging was assumed to be Gaussian separable transversely and longitudinally. Standard deviations of the PSF were derived and subjectively adjusted. The image was then deconvolved using Wiener filtering and maximum-likelihood deconvolution methods. Image quality was assessed both visually and quantitatively using cross-sectional area at half of the maximum (CAHM) of the implanted array as the figure of merit. RESULTS: Substantial image deblurring was achieved via deconvolution. Subjectively, anatomic structures were more clearly shown. Deconvolution reduced the CAHM by approximately one third, on average. Three-dimensional deconvolution had better image quality than two-dimensional deconvolution. The maximum-likelihood method produced superior image quality but took longer to process relative to Wiener filtering. CONCLUSION: Volumetric image deblurring is practical with a Gaussian PSF. The maximum-likelihood method is preferred if time permits. Deconvolution facilitates the study of fine details of the temporal bone and cochlear implant.

Adult↗
PubMed1995

Alkylating agents induce UVM, a recA-independent inducible mutagenic phenomenon in Escherichia coli.

Noninstructive DNA damage in Escherichia coli induces SOS functions hypothesized to be required for mutagenesis and translesion DNA synthesis at noncoding DNA lesions. We have recently demonstrated that in E. coli cells incapable of SOS induction, prior UV-irradiation nevertheless strongly enhances mutagenesis at a noninstructive lesion borne on M13 DNA. Here, we address the question whether this effect, named UVM for UV modulation of mutagenesis, can be induced by other DNA damaging agents. Exponentially growing delta recA cells were pretreated with alkylating agents before transfection with M13 single-stranded DNA bearing a site-specific ethenocytosine residue. Effect of cell pretreatment on survival of the transfected DNA was determined as transfection efficiency. Mutagenesis at the ethenocytosine site in pretreated or untreated cells was analyzed by multiplex DNA sequencing, a phenotype-independent technology. Our data show that 1-methyl-3-nitro-1-nitrosoguanidine, N-nitroso-N-methylurea and dimethylsulfate, but not methyl iodide, are potent inducers of UVM. Because alkylating agents induce the adaptive response to defend against DNA alkylation, we asked if the genes constituting the adaptive response are required for UVM. Our data show that MNNG induction of UVM is independent of ada, alkA and alkB genes and define UVM as an inducible mutagenic phenomenon distinct from the E. coli adaptive and SOS responses.

Alkylating Agents↗
PubMed1995

Functional platelet-derived growth factor-beta (PDGF-beta) receptor expressed on early B-lineage precursor cells.

Growth and maturation of B lymphocytes from stem cells require a series of complex processes that are dependent at least in part on growth factors. Uncontrolled expression of receptors from these early growth factors may contribute to a leukaemogenesis of such early B cell progenitors. We show here that early pre-pre-B cells, but not mature B cells, express the PDGF receptor-beta (PDGFR-beta). These receptors contain a protein tyrosine kinase domain which is activated upon ligation with PDGF in pre-pre-B cells. Further, pre-pre-B leukaemia cells seem to express more PDGFR-beta compared with their normal counterparts, suggesting a role for these receptors in growth promotion of leukaemia cells.

B-Lymphocytes↗
PubMed1995

Targeted mutagenesis in mammalian cells mediated by intracellular triple helix formation.

As an alternative to standard gene transfer techniques for genetic manipulation, we have investigated the use of triple helix-forming oligonucleotides to target mutations to selected genes within mammalian cells. By treating monkey COS cells with oligonucleotides linked to psoralen, we have generated targeted mutations in a simian virus 40 (SV40) vector contained within the cells via intracellular triple helix formation. Oligonucleotide entry into the cells and sequence-specific triplex formation within the SV40 DNA deliver the psoralen to the targeted site. Photoactivation of the psoralen by long-wavelength UV light yields adducts and thereby mutations at that site. We engineered into the SV40 vector novel supF mutation reporter genes containing modified polypurine sites amenable to triplex formation. By comparing the abilities of a series of oligonucleotides to target these new sites, we show that targeted mutagenesis in vivo depends on the strength and specificity of the third-strand binding. Oligonucleotides with weak target site binding affinity or with only partial target site homology were ineffective at inducing mutations in the SV40 vectors within the COS cells. We also show that the targeted mutagenesis is dependent on the oligonucleotide concentration and is influenced by the timing of the oligonucleotide treatment and of the UV irradiation of the cells. Frequencies of intracellular targeted mutagenesis in the range of 1 to 2% were observed, depending upon the conditions of the experiment. DNA sequence analysis revealed that most of the mutations were T.A-to-A.T transversions precisely at the targeted psoralen intercalation site. Several deletions encompassing that site were also seen. The ability to target mutations to selected sites within mammalian cells by using modified triplex-forming oligonucleotides may provide a new research tool and may eventually lead to therapeutic applications.

Animals↗
PubMed1995

Technical optimization of spiral CT for depiction of renal artery stenosis: in vitro analysis.

PURPOSE: To determine empirically the effect of scan parameters and postprocessing techniques on depiction accuracy of renal artery stenosis with spiral computed tomographic angiography. MATERIALS AND METHODS: Critical (85%) and noncritical (45%) stenoses in the coronal plane were modeled in vitro and scanned with 12 combinations of collimation (1, 2, or 3 mm), table increment (pitch = 1-2),2 and reconstruction interval (0.5 or 1.0 mm). Five test images were generated for each spiral scanning technique: multiplanar reformation (MPR), maximum-intensity projections (MIPs: coronal MIP [MIPcor], coronal MIP targeted to phantom vessel and surrounding fat [target MIPcor]), transaxial imaging, and transaxial MIP. RESULTS: With 3-mm collimation, critical stenosis was overestimated to the point of occlusion on MIPcor images and underestimated on MPR and target MIPcor images. A 0.5-mm reconstruction interval was marginally beneficial for 1- and 2-mm collimation, but noise was prohibitive with 1-mm collimation. CONCLUSION: Critical renal artery stenosis is best depicted with 2-mm collimation, 2-4-mm table increment, and 1-mm reconstruction interval.

Humans↗
PubMed1995

[The studies on the effect of proliferative response of peripheral blood lymphocyte of healthy persons by preparations of M. vaccea].

This paper present that preparations of M. vaccea, which included suspensions of live bacilli, irradiation-killed bacilli and high temperature killed bacilli, for the effect on lymphocyte proliferative response of peripheral blood in healthy persons were compared by 3H-TdR incorporation method. CPM of control was 448 +/- 131, CPM adding suspensions of live M. vaccea, irradiation-killed bacilli and high temperature killed bacilli were 1037 +/- 194, 2299 +/- 140, 1819 +/- 528, 994 +/- 186, respectively. Stimulative index of all four preparations were more than 2.0, specially suspensions of live and irradiation killed M. vaccea is more effective than BCG and high temperature killed M. vaccea, which were 5.13, 4.06, respectively. In another experiment, suspensions of live, irradiation-killed and high temperature killed M. vaccea plus rIL-2 were found more effective than rIL-2 alone. CPM of them were 9544 +/- 1727, 8530 +/- 714, 8230 +/- 1035, and 3721 +/- 1336, respectively, but BCG was 6904 +/- 1218. The results show that preparations of M. vaccea tested have distinctly promotive effect for proliferative response of lymphocyte in vitro. The addition of rIL-2 to suspendions of live M. vaccea, irradiation killed and high temperature killed M. vaccea cooperatively increased the effects of proliferative response mentioned above.

BCG Vaccine↗
PubMed1995

[Epidemiological studies on endemic fluorosis and arsenism in Xinjiang].

Epidemiological and clinical studies on the water of 102 wells containing high-level fluoride and arsenic and a population of 50,760 drinking the water in Kuitun Area, Xinjiang were conducted. Results indicated fluoride and arsenic contents in the well water were associated with geochemical environment, and drinking the water containing high-level fluoride and arsenic for a long-term was the cause of fluorosis and arsenism. Also, diagnostic criteria and major clinical manifestations for fluorosis and arsenism were put forward in the paper. Relationship between fluoride and arsenic contents in the well water and prevalence of fluorosis and arsenism in local residents was analyzed. It suggested fluorosis and arsenism was a systematic disorder and further studies on its potential hazard were merited.

Adolescent↗
PubMed1995

[Lugol's solution in endoscopic diagnosis of early esophageal cancer].

About 1500 high-risk subjects of esophageal cancer were found during screening by balloon cytology and all of them were examined endoscopically. Among them, 120 were considered as having early esophageal cancer and precancerous lesions. During the examination, Lugol's solution staining was used and guiding biopsy was taken. 98 subjects with unstained lesions were found, and biopsy showed early esophageal cancer in 60 (61.2%) and moderate and severe dysplasia in 38 (38.8%). It is usually extremely difficult to detect and localize the very early esophageal mucosal and submucosal carcinoma. But endoscopic examination and using Lugol's solution staining with multiple spots biopsy from unstained area are of great assistance. Minute malignant lesions may not be overlooked.

Adult↗
PubMed1995

[Molluscicidal activity of seed of Camellia sinensis].

This paper is a preliminary report on the molluscicidal activity of seed of Camellia sinensis (L) O. Kuntze (SCS). Its LD50 and LD90 were 10 and 16 micrograms/ml, respectively. We found also SCS inhibited oxygen consumption 65% and glycogen content of Oncomelania snail by 80%. The activity of hatching eggs to juvenile snails was inhibited by this seed at 8-16 micrograms/ml. Juvenile snails may also be killed by this molluscicide.

Animals↗