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Biomedical subjects

Z Wu

Publications and source records attributed to Z Wu.

At least 559 records · Page 31Linked to original sources
PubMed1996

Use of a modified polysaccharide gel in developing a realistic breast phantom for MRI.

A polysaccharide material, TX-151, has been used together with water, NaCl, and Al powder to create a tissue equivalent gel to make a realistic, inexpensive, conveniently moldable, temporally stable tissue equivalent MRI phantom. Various phantom compositions were studied for variations in gelling time and relaxation times. Gd-DTPA added as a T1 (and T2) modifier and aluminum powder added to decrease T2 permitted phantoms to be made with a range of relaxation times comparable to human tissues. We have used this polysaccharide gel to create breast phantoms for testing breast coils and evaluating different MRI imaging sequences available for diagnosis. The breast phantoms consisted of a layer of Crisco, a good model for adipose tissue, surrounding the TX-151 gel. Some of these phantoms were created with a silicone implant encapsulated in the gel to simulate an augmented breast. More sophisticated phantoms can easily be developed by additions of other materials to this polysaccharide gel.

Female↗
PubMed1996

The urinary bladder angiotensin system: response to infusions of angiotensin I and angiotensin-converting enzyme inhibitors.

The circulating and urinary bladder tissue concentrations of angiotensin I (ANG I) and angiotensin II [ANG-(1-8)] were examined in anesthetized Sprague-Dawley male rats given an intravenous bolus infusion of either ANG I, the angiotensin-converting enzyme (ACE) inhibitors enalaprilat or ramiprilat, or saline. The mean concentrations of ANG I and ANG-(1-8) were markedly higher in the urinary bladder tissue than in whole blood. There was a significant increase in the concentration of ANG I and ANG-(1-8), both in the urinary bladder tissue and the circulation, after the ANG I infusion. Both ACE inhibitors were associated with an increase in the concentration of whole blood ANG I; however, tissue ANG I levels were significantly increased only following ACE inhibition with ramiprilat but not with enalaprilat. Both plasma and urinary bladder tissue ANG-(1-8) levels decreased significantly following ACE inhibition, but only with ramiprilat. The elevated urinary bladder tissue levels of ANG I and ANG-(1-8) at baseline, compared with circulating levels, and the maintenance of ANG-(1-8) in bladder tissue in the face of inhibition of the circulatory renin-angiotensin system with enalaprilat support the presence of an autocrine/paracrine renin-angiotensin system in the urinary bladder. Under the current experimental conditions, ramiprilat appears to have enhanced bladder activity compared with enalaprilat.

Anesthesia↗
PubMed1996

Bacterial resistance to vancomycin: five genes and one missing hydrogen bond tell the story.

A plasmid-borne transposon encodes enzymes and regulator proteins that confer resistance of enterococcal bacteria to the antibiotic vancomycin. Purification and characterization of individual proteins encoded by this operon has helped to elucidate the molecular basis of vancomycin resistance. This new understanding provides opportunities for intervention to reverse resistance.

Anti-Bacterial Agents↗
PubMed1996

Characterization of IgG Fc receptors on CD34 antigen-expressing cell lines (KG-1 and KG-1a).

Although Fc gamma receptors (Fc gamma R) on mature blood cells have been extensively studied, there are only limited data on Fc gamma R expression in the early haematopoietic progenitor cells. In this study, we used the stem cell antigen (CD34)-expressing cell line (KG-1) and its less differentiated subline (KG-1a) as a model for the study of Fc gamma R in the early haematopoietic progenitors. Flow cytometry and immunoprecipitation studies on KG-1 and KG-1a cells with anti-Fc gamma R mAb showed that Fc gamma RII is the only Fc gamma R expressed on the cell surface. Analysis of the steady-state levels of Fc gamma R mRNA in KG-1 and KG-1a cells using a quantitative in situ hybridization assay revealed the presence of only Fc gamma RII mRNA. On further analysis Fc gamma RIIA mRNA but no Fc gamma RIIB or Fc gamma RIIC transcripts were found in these cells; Fc gamma RIIA transcripts with and without the transmembrane exon were present in approximately equal amounts. These findings are surprisingly similar to those observed previously with Fc gamma R in platelets and megakaryocytic cells but different from those found with Fc gamma R in cells of other lineages. These data suggest that the Fc gamma R transcript distribution pattern observed in the early haematopoietic progenitors (KG-1 cells) is retained in later stages of haematopoietic differentiation only in cells of megakaryocytic lineage.

Antigens, CD34↗
PubMed1996

Risk factors for initiation of drug use among young males in southwest China.

To identify risk factors for drug use among young males in southwest China a cross-sectional survey and a non-concurrent cohort study were conducted. Demographic, behavioral and drug-use information was collected from young males aged 18-29 years. The non-concurrent cohort included the period 1 January 1991 to 1 August 1994. A total of 1548 subjects were interviewed. The cumulative incidence increased between 1991 and 1993. Multivariate analysis identified the following significant risk factors for drug use: being divorced/widowed/separated, having been encouraged by friends/others to try drugs, smoking cigarettes, belonging to the Jingpo ethnic group, and having a family member who used drugs in 1991. More than 6 years of education was a protective factor for drug use. Drug use in the community was associated with having been encouraged by friends or others to try drugs (71%), to smoking cigarettes (50%), and to belonging to the Jingpo group (24%). The results are consistent with community based prevention approaches which should be studied carefully because of the unique cultural and epidemiological situation in China.

Adolescent↗
PubMed1996

Risk factors for intravenous drug use and sharing equipment among young male drug users in Longchuan County, south-west China.

OBJECTIVES: To identify the risk factors for intravenous drug use and sharing of equipment in Longchuan County in south-west China. METHODS: Demographic information and sexual and drug-use-related behavior between 1 January 1991 and 1 August 1994 were collected retrospectively from a cohort of young male drug users aged 18-29 years in 82 villages. RESULTS: A total of 433 drug users were identified. The cumulative incidence of intravenous drug use was 40.0% during the 3.7-year study period. The annual incidence increased from 10% in 1991 to over 30% in 1994. Risk factors for intravenous drug use among drug users, according to the multivariate model, included having had premarital/extramarital sex [odds ratio (OR), 1.5; 95% confidence interval (CI), 1.01-2.3], having a family member who used drugs in 1991 (OR, 1.8; 95% CI, 1.1-2.9), and currently not married (OR, 1.6; 95% CI, 0.98-2.7). Being Buddhist protected against intravenous drug use (OR, 0.4; 95% CI, 0.2-0.9). The population attributable fraction was 30% for not being currently married, 17% for having had premarital/extramarital sex and 14% for having a family member who used drugs. The risk factor for sharing of equipment was being of Jingpo ethnicity (OR, 5.8; 95% CI, 2.5-13.8). The average incidence of sharing equipment was 19.6% per year. The population attributable fraction for sharing equipment was 58.5% for being Jingpo. CONCLUSIONS: The incidence of intravenous drug use and sharing equipment is increasing. Therefore, it is urgent that vigorous, effective intervention programs be initiated in southern Yunnan. Unmarried, sexually promiscuous Jingpo drug users with a family history of drug use should be especially targeted. Given the problems of transport and communication in this remote area of China, intervention programs which use existing social, governmental and community networks should be implemented.

Adolescent↗
PubMed1996

Rapid nitric oxide- and prostaglandin-dependent release of calcitonin gene-related peptide (CGRP) triggered by endotoxin in rat mesenteric arterial bed.

1. Our objective was to determine whether endotoxin (ETX) could directly trigger the release of calcitonin gene-related peptide (CGRP) from perivascular sensory nerves in the isolated mesenteric arterial bed (MAB) of the rat and to determine whether nitric oxide (NO) and prostaglandins (PGs) are involved. 2. ETX caused time- and concentration-dependent release of CGRP, and as much as a 17 fold increase in CGRP levels in the perfusate at 10-15 min after the administration of ETX (50 micrograms ml-1). 3. CGRP-like immunoreactivity in the perfusate was shown to co-elute with synthetic rat CGRP by reverse-phase h.p.l.c. 4. Pretreatment of MAB with capsaicin or ruthenium red inhibited ETX-induced CGRP release by 90% and 71%, respectively. ETX-evoked CGRP release was decreased by 84% during Ca2(+)-free perfusion. 5. The release of CGRP evoked by ETX was enhanced by L-arginine by 43% and inhibited by N omega-nitro-L-arginine (L-NOARG) and methylene blue by 37% and 38%, respectively. L-Arginine reversed the effect of L-NOARG. 6. Indomethacin and ibuprofen also inhibited the ETX-induced CGRP release by 34% and 44%, respectively. No additive inhibition could be found when L-NOARG and indomethacin were concomitantly incubated. 7. The data suggest that ETX triggers the release of CGRP from capsaicin-sensitive sensory nerves innervating blood vessels. The ETX-induced CGRP release is dependent on extracellular Ca2+ influx and involves a ruthenium red-sensitive mechanism. Both NO and PGs appear to be involved in the ETX-induced release of CGRP in the rat mesenteric arterial bed.

Animals↗
PubMed1996

Induction of peroxisome proliferator-activated receptor gamma during the conversion of 3T3 fibroblasts into adipocytes is mediated by C/EBPbeta, C/EBPdelta, and glucocorticoids.

The differentiation of 3T3 preadipocytes into adipocytes is accompanied by a transient induction of C/EBPbeta and C/EBPdelta expression in response to treatment of the cells with methylisobutylxanthine (MIX) and dexamethasone (DEX), respectively. In this report, we demonstrate that peroxisome proliferator-activated receptor gamma (PPARgamma) expression in 3T3-L1 preadipocytes is induced by MIX and DEX, suggesting that C/EBPbeta and C/EBPdelta may be involved in this process. Using a tetracycline-responsive expression system, we have recently shown that the conditional ectopic expression of C/EBPbeta in NIH 3T3 fibroblasts (beta2 cells) in the presence of DEX activates the synthesis of peroxisome PPARgamma mRNA. Subsequent exposure of these cells to PPAR activators stimulates their conversion into adipocytes; however, neither the expression of C/EBPbeta nor exposure to DEX alone is capable of inducing PPARgamma expression in the beta2 cell line. We find that unlike the case for 3T3 preadipocytes, C/EBPdelta is not induced by DEX in these 3T3 fibroblasts and therefore is not relaying the effect of this glucocorticoid to the PPARgamma gene. To define the role of glucocorticoids in regulating PPARgamma expression and the possible involvement of C/EBPdelta, we have established an additional set of NIH 3T3 cell lines expressing either C/EBPdelta alone (delta23 cells) or C/EBPdelta and C/EBPbeta together (beta/delta39 cells), using the tetracycline-responsive system. Culture of these cells in tetracycline-deficient medium containing DEX, MIX, insulin, and fetal bovine serum shows that the beta/delta39 cells express PPARgamma and aP2 mRNAs at levels that are almost equivalent to those observed in fully differentiated 3T3-L1 adipocytes. These levels are approximately threefold higher than their levels of expression in the beta2 cells. Despite the fact that these beta/delta39 cells produce abundant amounts of C/EBPbeta and C/EBPdelta (in the absence of tetracycline), they still require glucocorticoids to attain maximum expression of PPARgamma mRNA. Furthermore, the induction of PPARgamma mRNA by exposure of these cells to DEX occurs in the absence of ongoing protein synthesis. The delta23 cells, on the other hand, are not capable of activating PPARgamma gene expression when exposed to the same adipogenic inducers. Finally, attenuation of ectopic C/EBPbeta production at various stages during the differentiation process results in a concomitant inhibition of PPARgamma and the adipogenic program. These data strongly suggest that the induction of PPARgamma gene expression in multipotential mesenchymal stem cells (NIH 3T3 fibroblasts) is dependent on elevated levels of C/EBPbeta throughout the differentiation process, as well as an initial exposure to glucocorticoids. C/EBPdelta may function by synergizing with C/EBPbeta to enhance the level of PPARgamma expression.

3T3 Cells↗
PubMed1996

Immunofunctional assay of human growth hormone (hGH) in serum: a possible consensus for quantitative hGH measurement.

Confirmation of the diagnosis of GH deficiency in adults and children involves provocative testing for human (h) GH. Different commercially available immunoassays yield largely discrepant results in the measurement of GH levels in human serum. These discrepancies result in doubtful relevance of cut-off levels proposed for GH provocative testing. We have developed an immunofunctional assay method that allows quantitation of only those GH forms in circulation that possess both binding sites of the hormone for its receptor and thus can initiate a biological signal in target cells. An anti-hGH monoclonal antibody recognizing binding site 2 of hGH is immobilized and used to capture hGH from the serum sample. Biotin-labeled recombinant GH-binding protein in a second incubation step forms a complex with those hGH molecular isoforms that have both binding sites for the receptor. The signal is detected after a short third incubation step with labeled streptavidin. The assay is sensitive (detection range, 0.1-100 micrograms/L) and has average inter- and intraassay precisions of 10.3% and 7.3% respectively. Endogenous GH-binding protein does not interfere with the hGH result; placental lactogen slows no detectable cross-reaction in this immunofunctional assay. The degree of immunofunctionally active hGH forms in serum samples, calculated by comparison of immunofunctional assay and RIA results, varied between 52-93%. We propose this immunofunctional assay for GH measurement as a new reference method for hGH quantitation in serum. The immunofunction assay translates only hGH forms into an assay signal that are capable of dimerizing GH receptors and, thus, of initiating a biological effect in target cells.

Antibodies, Monoclonal↗
PubMed1996

The effect of protein binding on the deep tissue penetration and efflux of dermally applied salicylic acid, lidocaine and diazepam in the perfused rat hindlimb.

Doses of radiolabeled water, salicylic acid, lidocaine and diazepam were applied in 2 ml of phosphate buffer saline to the exposed dermis on the thigh of a perfused rat hindlimb. Hindlimbs were perfused with Krebs-Heinseleit buffer at 37 degrees C containing 4% albumin or 2.5% dextran 40 at a constant rate of 4 ml/min. Clearance of solutes from dermal sites was monitored by frequent sampling at the dermal site and of the outflowing perfusate. In addition, the concentration of solutes in the various tissues below the treated and contralateral sites were determined at the end of a perfusion after dissection, solubilization and scintillation counting of the individual tissues. Estimates of the absorption rate constant from the dermis and the elimination rate constant from the perfused limb were made by the simultaneous fitting of absorption and efflux data with a one-compartmental pharmacokinetic model. Diazepam was cleared fastest through the dermis, followed by water, salicylic acid and lidocaine. The efflux of diazepam and salicylic acid from the hindlimb was significantly enhanced by the presence of albumin in the perfusate relative to no albumin (P < .05), whereas the efflux of water and lidocaine were unaffected by changes in albumin content. Analysis of individual tissues at the end of the perfusion showed that water had the highest relative tissue concentrations with diazepam the least, high concentrations appearing to partition into and remain associated with the dermis. The presence of albumin in the perfusate significantly increased the concentration of diazepam found in contralateral skin samples (P < .05) and showed the same trend for salicylic acid and lidocaine. These findings show that protein binding significantly affects the deep tissue penetration and distribution of dermally applied solutes and that this effect is more prominent for highly protein-bound solutes.

Administration, Cutaneous↗
PubMed1996

Characterization of Fc gamma receptors on human megakaryocytes.

Megakaryocyte and platelet Fc gamma receptors (FcR) are of importance in the pathophysiology of immune complex-mediated thrombocytopenias such as heparin-induced thrombocytopenia. In this study, Fc gamma R proteins and mRNAs in normal human megakaryocytes were examined. Fc gamma R proteins were studied with immunocytochemical staining, dual colour flow cytometry and immunoprecipitation using monoclonal antibodies against Fc gamma R I, Fc gamma R II and Fc gamma R III. Fc gamma R mRNAs were measured with biotinylated cDNA of oligonucleotide probes using a novel quantitative in situ hybridization technique. Using these techniques, Fc gamma R II protein and mRNA, but not Fc gamma R I and Fc gamma R III proteins and transcripts were detected in megakaryocytes. Further, transcript analysis showed that megakaryocytes contain only the transcript of Fc gamma R IIA gene but no transcripts of Fc gamma R IIB nor Fc gamma R IIC genes; Fc gamma R IIA transcripts with and without the transmembrane (TM) exon are present in approximately equal proportions. In contrast, neutrophils and macrophages also contain Fc gamma R IIA transcript but Fc gamma R IIA transcript with the TM exon predominates suggesting cell lineage-specific Fc gamma R IIA expression. Fc gamma R IIA transcript lacking the TM exon predicts the presence of a potential soluble form of Fc gamma R in platelets and megakaryocytes which may have a physiological role as it can compete with the membrane-bound Fc gamma R IIA for binding of IgG-containing immune complexes and thus protect these cells from excessive binding and injurious effects of immune complexes.

Base Sequence↗
PubMed1996

Inhibitory effects of isoproterenol on PAF-induced endothelial cell permeability and morphological changes.

Using a model to study vascular permeability under hydrostatically perfused bovine pulmonary artery endothelial cell (EC) monolayers and a software to automatically analyse cell morphological parameters in a computer image workstation, the effects of isoproterenol (IPN) on platelet-activating factor (PAF)-induced changes in EC monolayer permeability and cell morphological parameters were studied. Albumin has the fortifying effect on endothelial barrier function. After treatment of EC monolayer with 10(-8) mol/L PAF, trans-monolayer permeability increased, cell surface area decreased, and intercellular space enlarged. As pretreatment with 10(-4) mol/L IPN, PAF-induced EC permeability increment and morphological changes were blocked. The results suggest that EC contraction and intercellular gap expansion are important mechanisms for PAF-induced high vascular permeability. IPN inhibits the effects of PAF via stabilization of EC morphology and prevention of intercellular gap formation.

Adrenergic beta-Agonists↗
PubMed1996

[Expression of PCNA and protooncogenes during experimental hepatocarcinogenesis in rats].

The expression of PCNA and the protooncogenes of ras family (N-ras, H-ras and Ki-ras) in hepatocarcinoma cells and the proliferating liver cells in precancerous, hyperplastic nodules during experimental hepatocarcinogenesis, induced by diethylnitrosamine in rat liver was observed immunohistochemically and by in situ hybridization. The results indicated that there was a positive expression of PCNA in both the carcinomas cells and precancerous liver cells. The amount of PCNA-positive cells exhibited a negative correlation with the amount of infiltrating mast cells surrounding carcinoma cell nests and the hyperplastic, precancerous nodules. These results basically coincided with that of the separate observation of the expression of protooncogenes in the same study.

Animals↗
PubMed1996

Long-term oral administration of L-arginine enhances endothelium-dependent vasorelaxation and inhibits neointimal thickening after endothelial denudation in rats.

OBJECTIVE: To further prove the hypothesis that local decrease of nitric oxide (NO) synthesis and/or its activity might be critically important in the disturbance of vascular homeostasis after vascular injuries. METHODS: Intimal thickening model induced by air-drying denudation of rat right common carotid artery was performed to evaluate the effects of long-term oral administration of L-arginine on neointimal thickening and acetylcholine-induced endothelium-dependent vasorelaxation (EDR) by histomorphometric and functional studies. RESULTS: Reductions in EDR function persisted and simultaneously developed prominent neointimal thickening by 14 days after denudation. Long-term oral supplementation of L-arginine (1 g/kg/day) significantly enhanced EDR from 43.5% +/- 12.35% to 68.8% +/- 9.0% (n = 10, P < 0.001) and reduced neointimal thickening from 62.45 microns +/- 11.26 microns to 21.45 microns +/- 6.34 microns (n = 10, P < 0.001) as compared with each control animals. CONCLUSIONS: This study shows that oral administration of L-arginine significantly inhibits neointimal thickening and preserves NO-mediated EDR in experimental endothelial denudation, suggesting an important role for L-arginine, NO pathway in the regulation of vascular homeostasis after endothelial injury which might be salutary in prevention restenosis after coronary angioplasty.

Administration, Oral↗
PubMed1996

[The repair of heel defect].

A total of 12 lateral leg complex flaps with gastrocnemius muscle, lateral cutaneous nerve of calf, cortex of fibula have been applied successfully to repair the heel defects. The walking and weight carrying function of feet were recovered. The author think that repair of heel defect might base on the anatomical, physiological function of heel to choose the appropriate complex flap.

Adolescent↗