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Biomedical subjects

A Wang

Publications and source records attributed to A Wang.

At least 271 records · Page 15Linked to original sources
PubMed1993

Evaluation of magnetic resonance imaging in the diagnosis of osteomyelitis in diabetic foot infections.

To assess the role of magnetic resonance imaging (MRI) in diagnosing osteomyelitis in diabetic foot infections, 47 diabetic patients with clinical suspicion of osteomyelitis, nonhealing foot ulcer, or soft tissue infection of the foot were examined prospectively by MRI and plain radiographs. Pathological confirmation of diagnosis was obtained in 62 bones from 32 patients. In addition, 14 patients with pathological confirmation of diagnosis underwent technetium-99 MDP triple-phase bone and gallium-67 citrate scans. MRI was significantly more sensitive and accurate (P < .01), with equal specificity in comparison to plain radiographs and technetium and gallium scans. MRI also provided a more detailed and accurate depiction of the anatomy. At early clinical follow-up, complete resection of abnormal bone on an MRI scan correlated with clinical healing. In summary, MRI is indicated when plain radiographs are negative for osteomyelitis or when the extent and accurate depiction of the infective process will facilitate surgical planning.

Adult↗
PubMed1993

[An epidemiologic study on the etiology of primary hepatocellular carcinoma in Shaanxi].

The result of a matched case-control study on 110 cases of primary hepatocellular carcinoma (PHC) in Shaanxi is reported. It was shown that HBV was closely associated with PHC. Besides, psychosocial and genetics factors could be risk factors. Vegetables and fruits might be protective factors. Synergistic action between HBV and inheritance and foods was observed. Logistic regression analysis showed that HBV infection and negative events were possibly the risk factors, while vegetables and fruits were probably the protective factors.

Adolescent↗
PubMed1993

[Regulation of purine biosynthetic genes expression in Salmonella typhimurium. II. Isolation and characterization of Oc mutants].

Purine repressor protein, encoded by purR has shown to effect expression of purine structure genes except purB in de novo pathway in Salmonella typhimurium. However, up to date there is no direct evidence of the repressor binding to operator DNA of these genes. Report here is the isolation and characterization of purine Oc mutants in Salmonella typhimurium. purD:: MudJ (lacZ Kanr) and purG:: MudJ (lacZ Kanr) were used as starting strains Both strains were mutagenized by NTG, and derepressed mutants were selected on the MacConkey plate containing an excess of adenosine (2mmol/L). 8 independent depressed mutants were obtained from purD:: MudJ (lacZ Kanr), 9 were obtained from purG:: MudJ (lacZ Kanr). Transduction analysis and trans-acting or cis-acting test of the genes with merochromosome DNA tandem genetic duplication strains proved that 1 mutant for each group exert the constitute expression by cis-acting. This is first purine Oc mutant obtained from Salmonella typhimurium.

Gene Expression Regulation, Bacterial↗
PubMed1993

Diagnosis and treatment of iliopsoas abscess in spinal cord injury patients.

Six patients with spinal cord injury and iliopsoas abscess and other complicating conditions were evaluated with computed tomography (CT), conventional radiography, magnetic resonance imaging (MRI), and radionuclide scans. CT identified the presence of psoas abscess and revealed the depth, extent, and relationship of deep pressure ulcers to deep structures. CT-guided aspiration of the abscess cavities was performed in three patients, with placement of drainage catheters. Concurrent treatment with appropriate antibiotics, followed by staged myocutaneous flap coverage resulted successful outcomes in all patients. A high index of suspicion aids in the early diagnosis of psoas abscess in the SCI patient, as interpretations of physical examination are obscured by the lack of localizing findings. We believe that CT is the diagnostic and therapeutic modality of choice in the management of these complex conditions in the SCI patient, because of its superior ability to detect pathologic changes in the pelvic region and for decreasing the morbidity of the treatment by avoiding open surgery in these often suboptimal surgical candidates.

Adult↗
PubMed1993

The role of activated neutrophils and free radical in the pathogenesis of pulmonary hypertension.

In in situ perfused rat lungs, it was demonstrated that the perfusing pressure and permeability of pulmonary capillaries were obviously increased after activated neutrophils (PMNs) were added to the perfusate. The effect of free radicals generated by the xanthine-xanthine oxidase system on isolated rabbit pulmonary arterial ring tension was also observed, and the contractile response was found to be dose dependent: The smaller the vessel diameter, the higher the contractile response. Superoxide dismutase and catalase were able to obviously attenuate the contractile response. The response was endothelium independent, and was influenced neither by indomethacin (cyclooxygenase inhibitor) nor by nordihydroguaiaretic acid (lipoxygenase inhibitor), while removal of Ca from the bath solution or addition of the protein kinase C (PKC) inhibitor "H7" or an antiinflammatory drug (764-3, the effective component of Radix Salvia miltiorrhizae) could significantly inhibit the contractile response. The results suggest that activated PMNs may play an important role in the pathogenesis of pulmonary hypertension.

Animals↗
PubMed1992

Transforming growth factor beta differentially regulates expression of integrin subunits in guinea pig airway epithelial cells.

The integrin family is composed of a large number of heterodimers, each one mediating distinct interactions with extracellular matrix and/or cell surface ligands. The expression of integrins appears to be tightly regulated in vivo, but the mechanisms by which cells control the formation and surface expression of specific pairs of subunits have not been well characterized. Two integrin subunits, the alpha subunit alpha v, and the beta subunit beta 1, could pose special problems in regulation because of their capacity to associate with multiple partners. In the present study, we have examined the effects of the cytokine transforming growth factor beta 1 (TGF-beta 1) on the expression of alpha v- and beta 1-containing integrins in primary cultures of guinea pig airway epithelial cells, e.g. cells that we have previously found to express multiple potential partners for both alpha v and beta 1. TGF-beta 1 increased the surface expression of both alpha v- and beta 1-containing heterodimers after periods of stimulation from 24 to 72 h. These increases in surface expression were associated with significant increases in the concentrations of mRNA encoding each of the partners of alpha v and beta 1, but with only minimal increases in mRNA encoding alpha v and beta 1 themselves. Airway epithelial cells metabolically labeled with [35S]methionine during stimulation with TGF-beta 1 demonstrated only a minimal increase in the synthesis of new alpha v protein at a time when synthesis of alpha v's beta subunit partners and surface expression of alpha v-containing heterodimers were dramatically increased. These data suggest that, at least in some cells, promiscuous integrin subunits (both alpha and beta) may normally be synthesized in excess. Thus, the surface expression of specific integrin heterodimers can be regulated primarily through regulation of the synthesis of the specific partners of these subunits.

Animals↗
PubMed1992

Increased apolipoprotein E and c-fms gene expression without elevated interleukin 1 or 6 mRNA levels indicates selective activation of macrophage functions in advanced human atheroma.

Cells found within atherosclerotic lesions can produce in culture protein mediators that may participate in atherogenesis. To test whether human atheromata actually contain transcripts for certain of these genes, we compared levels of mRNAs in carotid or coronary atheromata and in nonatherosclerotic human vessels by polymerase chain reaction (PCR) amplification of cDNAs reverse-transcribed from RNA. We measured PCR products (generated during exponential amplification) by incorporation of 32P-labeled primers. Levels of interleukin 1 alpha, 1 beta, or 6 mRNAs in plaques and controls did not differ. Compared to uninvolved vessels, plaques did contain higher levels of mRNA encoding platelet-derived growth factor A chain (42 +/- 24 vs. 12 +/- 10 fmol of product; mean +/- SD; n = 8 and 8, respectively; P = 0.007) and B chain (41 +/- 36 vs. 4 +/- 3 fmol of product, n = 14 and 6, respectively; P = 0.024). Atherosclerotic lesions consistently had much higher levels of apolipoprotein E (apoE) mRNA than did control vessels (131 +/- 71 vs. 5 +/- 3 fmol of product; n = 12 and 10, respectively; P less than 0.001). Direct RNA blot analyses confirmed elevated levels of apoE mRNA in plaque extracts. To test whether mononuclear phagocytes might be a source of the apoE mRNA, we studied a selective marker for cells of the monocytic lineage, the c-fms protooncogene, which encodes the receptor for macrophage colony-stimulating factor. Plaques also contained elevated levels of c-fms mRNA (30 +/- 17 vs. 5 +/- 3 fmol of product; n = 10 and 7, respectively; P = 0.002). Immunohistochemical colocalization demonstrated apoE protein in association with macrophages in plaques, whereas nonatherosclerotic vessels showed no immunoreactive apoE. ApoE produced locally in atheroma might modulate the functions of lesional T cells or promote "reverse cholesterol transport" by associating with high density lipoprotein particles, thus targeting them for peripheral uptake. Macrophages within the advanced human atheroma appear to exhibit a selective program of activation as they express high levels of apoE, whereas overall levels of interleukin 1 or 6 mRNAs in plaques are not elevated.

Apolipoproteins E↗
PubMed1992

Effects of prostaglandin E2 on ganglionic transmission in the guinea pig trachea.

We studied the effects of prostaglandin E2 (PGE2) on the contractile responses of in vitro guinea pig tracheal preparations with intact vagal innervation. The preparation was stimulated either through the vagal nerves (NS) or with an electrical field (EFS) and trachealis response was assessed from the pressure change inside the tracheal tube. Ganglionic blockade by hexamethonium inhibited responses to NS but did not affect EFS while both responses to NS and EFS were abolished by atropine or tetrodotoxin. This indicates that responses to both stimulation modalities were mediated by cholinergic nerves but that NS involved a ganglionic relay whereas EFS did not. Within the frequency range of 0.1-20 Hz, there was a gradual increase in the pressure generated by the trachealis muscle with increasing frequency of stimulation. The frequency-response relationship was similar for NS and EFS. Thus, the ganglion does not appear to play an important filtering or amplifying role under those conditions. PGE2 (1-50 mM) produced a concentration-dependent inhibition of NS and EFS without affecting responses to exogenous acetylcholine (ACh). This suggests that the main action of PGE2 is to reduce ACh release from post-ganglionic nerve terminals. PGE2 inhibited EFS to a larger extent than NS; we postulate a possible excitatory effect of PGE2 on neurotransmission in the airway ganglia.

Animals↗
PubMed1992

Modifying effects of fungal and herb metabolites on azoxymethane-induced intestinal carcinogenesis in rats.

Modifying effects of a fungal product, flavoglaucin, and four plant-derived chemicals, shikonin, gingerol, oleanolic acid and paeoniflorin, on intestinal carcinogenesis were examined in a rat model using azoxymethane (AOM). A total of 280 male F344 rats, 6 weeks old, were divided into 12 groups. Group 1 (30 rats) was given two subcutaneous injections of 15 mg/kg of AOM at the start of the experiment. Groups 2 (30 rats), 3 (20 rats), 4 (20 rats), 5 (30 rats) and 6 (30 rats) received a test chemical (flavoglaucin, shikonin, gingerol, oleanolic acid or paeoniflorin, respectively) in the diet at a concentration of 0.02% for 3 weeks, during which time AOM was applied, and then kept on basal diet until the end of experiment (one year). Groups 7-11 (each 20 rats) were given a test chemical corresponding to Groups 2-6, respectively. Group 12 (20 rats) served as a control. The incidence and average number of intestinal tumors in Group 2 (47%, 0.57 +/- 0.68) were significantly less than in Group 1 (74%, 1.07 +/- 0.87) (P < 0.05, respectively). Multiplicity of intestinal neoplasms of Group 3 (0.55 +/- 0.60) or 4 (0.47 +/- 0.51) was also significantly smaller than that of Group 1 (P < 0.05 and P < 0.01, respectively). These results suggest that flavoglaucin, shikonin and gingerol might be promising chemopreventive agents for intestinal neoplasia.

Animals↗
PubMed1992

Conserved charge of glomerular and mesangial cell proteoglycans: possible role of amino acid-derived sulphate.

Sulphation of proteoglycans was studied in isolated glomeruli and cultured rat mesangial cells. Both preparations produced heparan, dermatan, and chondroitin sulphates, recoverable both from the tissue layers and the conditioned media. The proportion of heparan sulphate made by mesangial cells was independent of the age of the culture, but declined in later passage. These preparations differed from several other nontransformed cell types studied to date in that the degree of proteoglycan sulphation was independent of the concentration of inorganic sulphate provided. Even when no exogenous sulphate was added, sulphation-dependent charge density of newly synthesized proteoglycans was conserved. Both isolated glomeruli and cultured mesangial cells produced proteoglycans with 35S-labelled sulphate esters when [35S]methionine was provided as the sole source of labelled sulphate. Conversion of methionine to cysteine and subsequent oxidation of organic sulphate via the sulphinyl pyruvate pathway is the only mechanism known in eukaryotic cells that can account for this observation. We conclude that facile oxidation of sulphur-containing amino acids can contribute to sulphation of glomerular proteoglycans and may serve to sustain the charge density of these multifunctional molecules when the supply of inorganic sulphate is otherwise compromised.

Amino Acids↗
PubMed1992

[Regulation of purine biosynthesis. I. Isolation of add:: MudJ (lacZ, Kanr) insertions and genetic mapping].

Report here is the isolation of adenosine deaminase deficient mutants and genetic mapping. Engineering transposon MudJ (lacZ, Kanr) was used for mutagenesis and six add:: MudJ were obtained among 20,000 Kanr transductants. Adenosine deaminase activity of these mutants were assayed and all are negative. Cotransduction analysis of add::MudJ indicated that add is 70% linked to pmi(31') and 37% linked to zxx1900::Tn10d-tet insertion which is 10% linked to purR(30'). Three points cross showed that add is located between pmi and Tn10d-tet insertion. Therefore the gene order is purR-zxx1900::Tn10d-tet-add-pmi.

Adenosine Deaminase↗
PubMed1992

[Isolation of vitamin B2 auxotroph and preliminary genetic mapping in Salmonella typhimurium].

The first independent vitamin B2 auxotrophs of Salmonella typhimurium were obtained by using selective medium containing extraordinarily high concentration of B2 (300 micrograms/ml) after mutagenesis. Transduction analysis showed that 21 B2 auxotrophs could be divided into four groups, which were unlinked to each other. It means that at least 4 structural genes were involved in B2 biosynthetic pathway. Preliminary genetic mapping indicated that 2 genes located in 7'-22' and other 2 located in 22'-34' and 61.5'-69' region on the genetic map of S. typhimurium respectively.

Chromosome Mapping↗
PubMed1991

Polarized regulation of fibronectin secretion and alternative splicing by transforming growth factor.

Fibronectin is a multifunctional protein that is synthesized in several different forms that result from alternative splicing of mRNA. Although expression of splicing variants appears to be both developmentally regulated and tissue-specific, the functional significance of these isoforms is largely unknown. We found that cultured airway epithelial cells vectorially secrete two distinct species of fibronectin, one which contains the alternatively spliced EIIIA region (EIIIA+) and one in which the EIIIA segment is spliced out (EIIIA-). Fibronectin containing the EIIIA region is preferentially secreted apically. Although both apical and basal stimulation with transforming growth factor beta 1 increased fibronectin synthesis, the secretory response differed depending on which surface was being stimulated. Apical secretion of fibronectin and expression of EIIIA+ fibronectin mRNA increased only after apical stimulation. These data demonstrate a novel mechanism for the polarized regulation of targeted secretion and alternative splicing of fibronectin and suggest that the EIIIA segment may act as a targeting signal for the vectorial secretion of fibronectin.

Amino Acid Sequence↗
PubMed1991

High-resolution NMR studies of chimeric DNA-RNA-DNA duplexes, heteronomous base pairing, and continuous base stacking at junctions.

Two symmetrical DNA-RNA-DNA duplex chimeras, d(CGCG)r(AAUU)d(CGCG) (designated rAAUU) and d(CGCG)r(UAUA)d(CGCG) (designated rUAUA), and a nonsymmetrical chimeric duplex, d(CGTT)r(AUAA)d(TGCG)/d(CGCA)r(UUAU)d(A ACG) (designated rAUAA), as well as their pure DNA analogues, containing dU instead of T, have been synthesized by solid-phase phosphoramidite methods and studied by high-resolution NMR techniques. The 1D imino proton NOE spectra of these d-r-d chimeras indicate normal Watson-Crick hydrogen bonding and base stacking at the junction region. Preliminary qualitative NOESY, COSY, and chemical shift data suggest that the internal RNA segment contains C3'-endo (A-type) sugar conformations except for the first RNA residues (position 5 and 17) following the 3' end of the DNA block, which, unlike the other six ribonucleotides, exhibit detectable H1'-H2' J coupling. The nucleosides of the two flanking DNA segments appear to adopt a fairly normal C2'-endo B-DNA conformation except at the junction with the RNA blocks (residues 4 and 16), where the last DNA residue appears to adopt an intermediate sugar conformation. The DNA-RNA junction residues exhibit quite different COSY, chemical shift, and NOE behavior, but these effects do not appear to propagate into the DNA or RNA segments. The circular dichroism spectra of these d-r-d chimeras also display a mixture of characteristic A-type and B-type absorption bands. The data indicate that A-type and B-type conformations can coexist in a single short continuous nucleic acid duplex, but our results differ somewhat from previous theoretical model studies.

Base Sequence↗
PubMed1991

The mec-3 gene contains cis-acting elements mediating positive and negative regulation in cells produced by asymmetric cell division in Caenorhabditis elegans.

The homeo box-containing genes mec-3 and unc-86 are necessary to specify the fate of a defined set of mechanoreceptors in Caenorhabditis elegans. Previous experiments have shown that mec-3 expression can be divided into two phases: initial synthesis mediated in part by unc-86, and continued synthesis that requires mec-3 itself. We now identify sequences that have been conserved during Caenorhabditis evolution and are necessary for establishment, maintenance, and repression of mec-3 expression. Upstream of the start codon for the mec-3-coding sequence are four segments (regions I-IV) of 71, 29, 28, and 24 bp, which are almost identical between C. elegans and Caenorhabditis vulgarensis. Region I is the only conserved sequence that effects establishment of mec-3 synthesis. Maintenance of mec-3 expression is mediated primarily by region II. Repression appears to be controlled by several segments: Mutation of region III, region IV, and parts of region I in a mec-3-lacZ fusion results in beta-galactosidase expression in some non-mec-3-expressing sisters of mec-3-positive cells. These results indicate that the mec-3 5' region contains target sequences that mediate a genetic switch between alternative fates expressed by sister cells in a stereotyped cell lineage.

Amino Acid Sequence↗