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Biomedical subjects

G Yang

Publications and source records attributed to G Yang.

At least 235 records · Page 13Linked to original sources
PubMed1999

[Expression of Schistosoma japonicun fatty acid binding protein gene in silkworm cells and larvae].

AIM: To express the fatty acid binding protein (Sj14FABP) gene of Schistosoma japonicun in the silkworm cells and larvae. METHODS: A 600 bp DNA fragment containing Sj14FABP gene was cloned into baculovirus transfer vector of pBacPAK His1 to construct recombinant transfer vector Sj14-pBac PAK His1. Coinfection was accomplished with this vector and Bombyx mori nuclear polyhedrosis virus (BmNPV) DNA in BmN cells. The recombinant virus of Bm-Sj14 was screened using dot-blotting. The BmN cells and silkworm larvae were infected with Bm-Sj14 to express Sj14FABF gene. Western blotting and ELISA were used to identify the antigenicity of the recombinant protein. RESULTS: Sj14FABP gene was successfully expressed in the BmN cells and silkworm larvae infected with Bm-Sj14. The product was a 18 kDa fusion protein. The yield in BmN cells was about 100 micrograms/1 x 10(6) cells and 33 micrograms/ml cell supernatant. In silkworm larvae, the product yield was 4 mg/ml haemolymph as well as 4.6 mg/g silkworm tissue. The recombinant protein could be recognized by Western blotting and ELISA using the sera from mice immunized with SWAP. CONCLUSION: Sj14FABP gene has been successfully expressed in BmNPV system and the product has high antigenicity.

Animals↗
PubMed1999

[Spectrophotometric assay of polyethyene glycol in urine using ammonium ferrothiocyanate aqueous-chloroform system].

A spectrophotometric method for the quantitative determination of polyethylene glycol-600 (PEG-600) in urine is based on partitioning a chromophore present in ammonium ferrothiocyanate reagent into an aqueous phase and a chloroform phase in the presence of PEG. The method is simple and reproducible, and can detect PEG in a concentration of 0.25 g/L. It gives a linear response over a range of 0.25-2.5 g/L. The recovery of PEG-600 in urine is 107% and relative standard deviation is less than 5%.

Chloroform↗
PubMed1998

Assembled tau filaments differ from native paired helical filaments as determined by scanning transmission electron microscopy (STEM).

Paired helical filaments (PHF) are abnormal, approximately 20-25-nm wide periodically twisted filaments, which accumulate in Alzheimer's disease (AD) brain and other neurodegenerative disorders, including corticobasal degeneration (CBD). PHF are primarily composed of highly phosphorylated tau protein. However, both phosphorylated and non-phosphorylated forms of tau are able to assemble in vitro into filaments similar in the ultrastructural appearance to PHF. In the present study, filaments were assembled in vitro from unmodified recombinant human tau and the physical mass per unit length of filaments and the mass density were determined using scanning transmission electron microscopy (STEM). Two general types of filaments were observed. One type was composed of 11.4 nm-wide, 10-75 nm long, frequently twisted and PHF-like filaments, with a mass per unit length (44 kDa/nm) approximately one third of that observed in isolated AD filaments. The other were straight filaments, approximately 6.8-nm wide and 0.2-2 microm long, which often formed parallel clusters of two or more filaments. Triple clusters were 19. 2-nm wide and had a mass per unit length (70 kDa/nm) approximately two thirds of that seen in isolated AD filaments. Despite different morphology, both twisted and straight filaments had mass densities between 0.48-0.55 kDa/nm3. These values are significantly higher than those reported for PHF found either in AD (0.40 kDa/nm3) or CBD (0.33 kDa/nm3). These results suggest that the packing of tau differs in vivo from that observed in vitro and that specific tau isoform content, elongation of tau molecules by phosphorylation or other factors may be required to reproduce pathological assembly. Therefore mass density determinations appear to be an important criterion in comparing various filaments.

Alzheimer Disease↗
PubMed1998

The brain renin-angiotensin system contributes to the hypertension in mice containing both the human renin and human angiotensinogen transgenes.

We have previously shown that mice transgenic for both the human renin and human angiotensinogen genes (RA+) exhibit appropriate tissue- and cell-specific expression of both transgenes, have 4-fold higher plasma angiotensin II (AII) levels, and are chronically hypertensive. However, the relative contribution of circulating and tissue-derived AII in causing hypertension in these animals is not known. We hypothesized that the brain renin-angiotensin system contributes to the elevated blood pressure in this model. To address this hypothesis, mean arterial pressure (MAP) and heart rate were measured in conscious, unrestrained mice after they were instrumented with intracerebroventricular cannulae and carotid arterial and jugular vein catheters. Intracerebroventricular administration of the selective AII type 1 (AT-1) receptor antagonist losartan (10 microgram, 1 microL) caused a significantly greater peak fall in MAP in RA+ mice than in nontransgenic RA- controls (-29+/-4 versus -4+/-2 mm Hg, P<0.01). To explore the mechanism of a central renin-angiotensin system-dependent hypertension in RA+ mice, we determined the relative depressor responses to intravenous administration of the ganglionic blocking agent hexamethonium (5 mg/kg) or an arginine vasopressin (AVP) V1 receptor antagonist (AVPX, 10 microgram/kg). Hexamethonium caused equal lowering of MAP in RA+ mice and controls (-46+/-3 versus -52+/-3, P>0.05), whereas AVPX caused a significantly greater fall in MAP in RA+ compared with RA- mice (-24+/-2 versus -6+/-1, P<0.01). Consistent with this was the observation that circulating AVP was 3-fold higher in RA+ mice than in control mice. These results suggest that increased activation of central AT-1 receptors, perhaps those located at sites involved in AVP release from the posterior pituitary gland, plays a role in the hypertension in RA+ mice. Furthermore, our finding that both human transgenes are expressed in brain regions of RA+ mice known to be involved in cardiovascular regulation raises the possibility that augmented local production of AII and increased activation of AT-1 receptors at these sites is involved.

Angiotensins↗
PubMed1998

Pathologic features of initial adenomas as predictors for metachronous adenomas of the rectum.

BACKGROUND: Colorectal cancer is the third most common cancer in the world, arising mostly from pre-existing adenomatous polyps (adenomas) of the large bowel. Patients with colorectal adenomas are at increased risk of colorectal cancer because of a high recurrence rate for adenomas. We followed a cohort of 1490 patients with rectal adenomas to determine whether recurrence might be related to pathologic characteristics of the initial adenomas. METHODS: The patients were identified in Haining County, China, from 1977 through 1978 by means of examination with a 15-cm rigid sigmoidoscope. They were followed by endoscopic examination at years 2, 4, 6, 11, and 16 after their initial polypectomy. New adenomas in the rectum were identified in 280 patients in these follow-up examinations. RESULTS: Statistically significant twofold to threefold elevated risks of metachronous (recurrent) adenomas were observed for patients who had more than two initial adenomas or whose most advanced initial adenoma was more than 1.0 cm in size, was of villous/tubulovillous type, or showed moderate to severe dysplasia. Much stronger associations were observed for advanced metachronous neoplasms, which are defined as cancers or adenomas with severe dysplasia, with multivariate adjusted relative risks (95% confidence interval) of 4.2 (1.8-9.9) for a large initial adenoma (>1.0 cm), 8.1 (4.2-15.6) for villous/tubulovillous architecture, and 14.4 (5.0-41.3) for severe dysplasia. In particular, patients who had a large (>1.0 cm) adenoma with severe dysplasia at baseline had a relative risk of 37 (7.8-174.7) of developing advanced metachronous neoplasms compared with patients who had small adenoma(s) with mild dysplasia. CONCLUSIONS: The risk of metachronous adenomas is closely related to the pathology of initial adenomas, thus allowing identification of a high-risk group of adenoma patients for close surveillance after their initial polypectomy.

Adenoma↗
PubMed1998

Extensive beta-glucuronidase activity in murine central nervous system after adenovirus-mediated gene transfer to brain.

Mucopolysaccharidosis type VII (MPS VII), caused by beta-glucuronidase deficiency, is a classic lysosomal storage disease. In the central nervous system (CNS), there is widespread pathology with distention of vacuoles in neurons and glia. An approach to therapy for MPS VII would require extensive delivery of enzyme to the CNS and subsequent uptake by the affected cells. In this study we show that intrastriatal injection of recombinant adenovirus encoding beta-glucuronidase (Ad betagluc) to MPS VII or wild-type mice results in focal, intense beta-glucuronidase mRNA expression near the injection site. Further, histochemical staining for enzyme activity showed that beta-glucuronidase activity extended well beyond transduced cells. Activity was detected throughout the ipsilateral striatum as well as in the corpus callosum, ventricles, and bilateral neocortex. Similarly, after injection into the right lateral ventricle or cisterna magna, enzyme activity was present in the ependymal cells of the ventricles, in the subarachnoid spaces, and also in the underlying cortex (150-500 microm from ependyma). The distribution of enzyme was most extensive 21 days after gene transfer to normal mouse brain, with more than 50% of the hemisphere positive for beta-glucuronidase activity. Eighty-four days after adenovirus injection a substantial level of enzyme expression remained (>40% of hemisphere positive for beta-glucuronidase activity). Histological sections from striatum of beta-glucuronidase-deficient mice injected with Ad betagluc showed a marked reduction in the number of distended vacuoles in both neurons and glia, as compared with uninjected striatum. Importantly, correction was noted in both hemispheres. Our finding that a relatively small number of transduced cells produce enzyme that reaches a large proportion of the CNS has favorable implications in developing direct gene transfer therapies for lysosomal storage disorders.

Adenoviridae↗
PubMed1998

A catalytic antibody against cocaine prevents cocaine's reinforcing and toxic effects in rats.

Cocaine addiction and overdose have long defied specific treatment. To provide a new approach, the high-activity catalytic antibody mAb 15A10 was elicited using a transition-state analog for the hydrolysis of cocaine to nontoxic, nonaddictive products. In a model of cocaine overdose, mAb 15A10 protected rats from cocaine-induced seizures and sudden death in a dose-dependent fashion; a noncatalytic anticocaine antibody did not reduce toxicity. Consistent with accelerated catalysis, the hydrolysis product ecgonine methyl ester was increased >10-fold in plasma of rats receiving mAb 15A10 and lethal amounts of cocaine. In a model of cocaine addiction, mAb 15A10 blocked completely the reinforcing effect of cocaine in rats. mAb 15A10 blocked cocaine specifically and did not affect behavior maintained by milk or by the dopamine reuptake inhibitor bupropion. This artificial cocaine esterase is a rationally designed cocaine antagonist and a catalytic antibody with potential for medicinal use.

Animals↗
PubMed1998

Dietary habits and stomach cancer in Shanghai, China.

Stomach cancer remains the second leading cancer in incidence in Shanghai, China, despite its decline over the past 2 decades. To clarify risk factors for this common malignancy, we conducted a population-based case-control study in Shanghai, China. Included in the study were 1,124 stomach cancer patients (age 20-69) newly diagnosed in 1988-1989 and 1,451 controls randomly selected among Shanghai residents. Usual adult dietary intake was assessed using a comprehensive food frequency questionnaire. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models. Risks of stomach cancer were inversely associated with high consumption of several food groups, including fresh vegetables and fruits, poultry, eggs, plant oil, and some nutrients, such as protein, fat, fiber and antioxidant vitamins. By contrast, risks increased with increasing consumption of dietary carbohydrates, with odds ratios (ORs) of 1.5 (95% confidence interval [CI] 1.1-2.1) and 1.9 (95% CI 1.3-2.9) in the highest quartile of intake among men (p for trend=0.02) and women (p=0.0007), respectively. Similar increases in risk were associated with frequent intake of noodles and bread in both men (p=0.07) and women (p=0.05) after further adjustment for fiber consumption. In addition, elevated risks were associated with frequent consumption of preserved, salty or fried foods, and hot soup/porridge, and with irregular meals, speed eating and binge eating. No major differences in risk were seen according to subsite (cardia vs. non-cardia). Our findings add to the evidence that diet plays a major role in stomach cancer risk and suggest the need for further evaluation of risks associated with carbohydrates and starchy foods as well as the mechanisms involved.

Adult↗
PubMed1998

Reduced lysyl oxidase messenger RNA levels in experimental and human prostate cancer.

To identify genes associated with prostate cancer progression, we developed a strategy involving the use of differential display PCR and a panel of genetically matched primary tumor- and metastasis-derived mouse prostate cancer cell lines. We analyzed sequences that were differentially stimulated by transforming growth factor-beta1 in primary tumor-versus metastasis-derived cell lines, based on our previous studies indicating that acquisition of differential responses to this growth factor could result in phenotypic traits that facilitate tumor metastasis from specific cell clones within the primary tumor. Using this system, we isolated and sequenced a cDNA fragment that encoded mouse lysyl oxidase (LO) and was induced by transforming growth factor-beta1 in primary tumor but not in metastasis-derived cells. Northern blotting analysis revealed increased LO expression in a panel of primary tumor cell lines but significantly reduced or nondetectable expression in their matched metastatic counterparts. Further in situ hybridization analysis revealed LO expression in normal mouse prostate epithelium but, in most cases, progressive loss of expression in primary prostate cancer and associated metastatic lesions. Importantly, in situ hybridization studies of normal human prostate and prostate malignancies revealed a similar loss of expression during progression to metastasis. The progressive loss of LO expression during prostate cancer progression provides information that may increase our understanding of the mechanisms that underlie this disease. In addition, LO may provide a useful molecular marker and/or establish a novel therapeutic target for prostate cancer.

Animals↗
PubMed1998

Oxygen toxicity and iron accumulation in the lungs of mice lacking heme oxygenase-2.

Heme oxygenase (HO) activity leads to accumulation of the antioxidant bilirubin, and degradation of the prooxidant heme. Moderate overexpression of the inducible form, HO-1, is associated with protection against oxidative injury. However, the role of HO-2 in oxidative stress has not been explored. We evaluated survival, indices of oxidative injury, and lung and HO expression in HO-2 null mutant mice exposed to > 95% O2 compared with wild-type controls. Similar basal levels of major lung antioxidants were observed, except that the knockouts had a twofold increase in total glutathione content. Despite increased HO-1 expression from HO-1 induction, knockout animals were sensitized to hyperoxia-induced oxidative injury and mortality, and also had significantly increased markers of oxidative injury before hyperoxic exposure. Furthermore, during hyperoxia, lung hemoproteins and iron content were significantly increased without increased ferritin, suggesting accumulation of available redox-active iron. These results demonstrate that the absence of HO-2 is associated with induction of HO-1 and increased oxygen toxicity in vivo, apparently due to accumulation of lung iron. These results suggest that HO-2 functions to augment the turnover of lung iron during oxidative stress, and that this function does not appear to be compensated for by induction of HO-1 in the knockouts.

Animals↗
PubMed1998

Assessment of the biologic markers p53, Ki-67, and apoptotic index as predictive indicators of prostate carcinoma recurrence after surgery.

BACKGROUND: This study was designed to evaluate the potential of the molecular and cellular markers p53, Ki-67, and apoptotic index (AI) as adjuncts to the commonly available variables of tumor grade, clinical stage, and serum prostate specific antigen to predict prostate carcinoma recurrence after radical prostatectomy. METHODS: Representative punch biopsy specimens of prostate carcinoma from whole mount paraffin blocks were evaluated from 47 men who underwent radical prostatectomy. Two groups were defined: those without evidence of prostate carcinoma recurrence after 5 years of follow-up (N = 30) and those with carcinoma recurrence (N = 17). Gleason grade, clustered p53 immunostaining, Ki-67 immunostaining, and AI were determined by standard techniques. RESULTS: All variables tested were associated with disease recurrence by univariate analysis: AI (P = 0.005), clustered p53 immunostaining (P = 0.0070), and Ki-67 immunostaining (P = 0.0390). Using multivariate analyses that included each biomarker with routinely available features, only AI (P = 0.0234) and clustered p53 immunostaining (P = 0.0389) added independent prognostic information (Ki-67 immunostaining, P = 0.1285). In the final logistic regression model that included standard variables with AI and p53, only AI reached statistical significance (P = 0.0332). CONCLUSIONS: The continued assessment of additional biomarkers for prostate carcinoma recurrence is important to identify better those patients who may be candidates for early adjuvant therapy and also to further our understanding of the neoplastic potential of a particular malignancy.

Aged↗
PubMed1998

Neutralizing antibodies against HIV determined by amplification of viral long terminal repeat sequences from cells infected in vitro by nonneutralized virions.

Based on the earliest intracellular synthesis of nascent HIV-1 long terminal repeat (LTR) fragments, we have established a heminested polymerase chain reaction (HNPCR) amplification of the 5' LTR sequences (LTR-HNPCR) for molecular assay of virus-neutralizing antibodies (VNAb). We incubated HIV antibodies with virus isolates for an hour, followed by addition of lymphoid cells (H9 or peripheral blood mononuclear cells [PBMC]) and further incubation for an hour. After washing the cells three times for thorough removal of free virions and antibodies, LTR-HNPCR consistently revealed HIV DNA in H9 cells after 15 minutes, in PBMC after 4 hours, and corresponding virion expression after 7 days in culture. Replication-competent HIV detected by LTR-HNPCR following overnight culture of infected PBMC for 16 to 18 hours was comparable with tissue culture infectivity measured by p24 antigen expression at 7 days. After establishing a molecular assay for in vitro HIV neutralization by HIV Ig, a panel of five HIV isolates tested with 6 monoclonal antibodies and HIV Ig revealed that LTR-HNPCR was comparable with other VNAb assays. These preliminary data indicate that the molecular assay for HIV neutralization has a clear-cut end point, is specific, reliable, and more rapid than other VNAb assays. Therefore, it offers potential utility in evaluating immune response to candidate vaccines.

Cell Line↗
PubMed1998

Quantitative immunohistochemical analysis of insulin-like growth factor binding protein-3 in human prostatic adenocarcinoma: a prognostic study.

PURPOSE: We sought to characterize and quantitate the expression of IGFBP-3 in adenocarcinoma of the prostate and to test whether it correlated with tumor differentiation determined by Gleason grade. We also investigated the potential of using IGFBP-3 as a prognostic indicator of clinically localized prostate cancer. MATERIALS AND METHODS: Initially we evaluated the expression of IGFBP-3 in six normal and twenty neoplastic prostates using standard immunohistochemical techniques (study 1). We then obtained radical prostatectomy specimens from twenty-four patients with a preoperative diagnosis of clinically localized prostate adenocarcinoma and five year follow up information, and nine normal prostates from organ donors or from patients undergoing cystoprostatectomy (study 2). All specimens were immunostained with a polyclonal anti-human IGFBP-3 antibody. A single pathologist reviewed all sections and assigned a Gleason grade to each cancer focus. Using computer-assisted video image analysis, we quantified the intensity of IGFBP-3 immunostaining of each cancer focus and of normal controls. RESULTS: Normal prostatic epithelium showed intense cytoplasmic IGFBP-3 staining. The stromal compartment showed less intense staining, although there were occasional areas with strong immunoreactivity. The cellular distribution of IGFBP-3 staining in prostatic adenocarcinoma was comparable to normal tissue; however, the intensity of detectable staining in neoplastic epithelial cells was significantly decreased. Two foci of prostatic intraepithelial neoplasia (PIN) demonstrated IGFBP-3 immunoreactivity decreased in comparison to normal epithelium, but greater than prostatic adenocarcinoma. Histologically normal epithelium surrounding cancer foci also showed decreased immunostaining for IGFBP-3 compared with normal prostate. The marked decrease in immunostaining intensity of IGFBP-3 in prostate adenocarcinoma was not associated with Gleason grade or with clinical outcome. CONCLUSION: Malignant transformation of prostatic epithelium was associated with a significant decrease in the amount of immunoreactive IGFBP-3 (p <0.0001); however, this parameter did not correlate with Gleason grade of the tumor or with patient outcome. The decrease in immunostaining intensity of IGFBP-3 in all Gleason grades and in PIN suggests that lower expression of IGFBP-3 is an early event in prostatic carcinogenesis. The finding that decreased IGFBP-3 immunostaining did not correlate with clinical outcome suggests that this parameter is not a therapy-guiding prognostic indicator for clinically localized prostate cancer.

Adenocarcinoma↗
PubMed1998

Hepatitis G and C viruses respond to interferon-alpha with different virologic kinetics.

The aim of this work was to specify the time course of response to interferon (IFN) of hepatitis G virus (HGV) and hepatitis C virus (HCV) in coinfected individuals. A group of 33 patients, undergoing 12 months of IFN therapy for chronic hepatitis C, was screened for the presence of both HGV and HCV RNAs to select seven coinfected patients. Spontaneous recovery from HGV infection was excluded through the detection of antibodies to the envelope-2 protein of HGV and HCV isolates were genotyped. Within three months of treatment, we found that HGV RNA was transiently cleared in 6/7 patients, but the rate of long-term favorable response was very low (1/7). In addition, considering the same individuals separately, it was shown that HGV and HCV responded to IFN with different kinetics in 5/7 patients. Taken together, these results underscore the importance of the virological basis of the resistance to IFN treatment.

Antiviral Agents↗
PubMed1998

Suppression of caveolin expression induces androgen sensitivity in metastatic androgen-insensitive mouse prostate cancer cells.

Although prostate cancer cells are often initially sensitive to androgen ablation, they eventually lose this response and continue to survive, grow and spread in the absence of androgenic steroids. The mechanism(s) that underlie resistance to androgen ablation therapy remain mostly unknown. We have demonstrated that elevated caveolin protein levels are associated with human prostate cancer progression in pathological specimens. Here we show that suppression of caveolin expression by a stably transfected antisense caveolin-1 cDNA vector converted androgen-insensitive metastatic mouse prostate cancer cells to an androgen-sensitive phenotype. Orthotopically grown tumors and low-density cell cultures derived from antisense caveolin clones had increased apoptosis in the absence of androgenic steroids, whereas similarly grown tumors and cells from vector (control) clones and parental cells were not sensitive to androgens. Studies using a representative antisense caveolin clone showed that selection for androgen resistance in vivo correlated with increased caveolin levels, and that adenovirus-mediated caveolin expression blocked androgen sensitivity. Our results identify a new candidate gene for hormone-resistant prostate cancer in man and indicate that androgen insensitivity can be an inherent property of metastatic prostate cancer.

Androgens↗
PubMed1998

Lack of influence of hepatitis G virus infection on alcohol-related hepatic lesions.

BACKGROUND: The purposes of this study were to analyse the prevalence and histologic impact of hepatitis G virus (HGV), a newly discovered virus, in alcoholic patients, a population known to be at risk for viral hepatitis. METHODS: One hundred and thirty-nine consecutive alcoholics admitted to our liver unit (106 men and 33 women; mean age, 47.1 +/- 10.9 years) were included in the study. All patients had consumed more than 60 g of ethanol per day for at least 1 year. One hundred healthy blood donors constituted a control group. Antibodies to HGV E2 protein and HGV-RNA testing by reverse transcription-polymerase chain reaction (RT-PCR) with primers derived from the NS5 coding region were performed in all serum samples. RESULTS: A significantly higher seroprevalence of anti-E2 antibodies was observed in alcoholic patients than in healthy blood donors (41 (29.5%) versus 8 (8%); P < 0.0001). Moreover, the prevalence of HGV-RNA was significantly higher in alcoholic patients (13 (9.3%) versus 1 (1%); P = 0.01). HGV-RNA and anti-HGV antibodies were never detected simultaneously. HGV viraemia was not associated with an increased risk of cirrhosis or hepatocarcinoma in alcoholic subjects. CONCLUSIONS: Our study reports a high prevalence of HGV in alcoholic patients. HGV infection does not modify or aggravate the course of alcoholic liver disease.

Case-Control Studies↗