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C Fang

Publications and source records attributed to C Fang.

At least 73 records · Page 4Linked to original sources
PubMed1995

Pooling blood donor samples to reduce the cost of HIV-1 antibody testing.

Accurate, low cost testing of donated blood is a goal of the global effort to reduce the spread of the human immunodeficiency virus (HIV-1). We describe a modified enzyme immunoassay (EIA) method for detecting HIV-1 antibody (anti-HIV-1) in 15-sample pools. In this preliminary study, the modified EIA was as sensitive for detecting weakly seropositive samples, and as specific for testing HIV-1 Western blot-negative or Western blot-indeterminate results, as testing individual samples by the standard EIA. A simulation of field operations was conducted using pools of blood donor samples collected in the United States and in Shanghai, People's Republic of China. Implementation of the modified EIA method and testing 15-sample pools for anti-HIV-1 is a reliable strategy for reducing the cost of large scale testing of donated blood for anti-HIV-1 in areas of low seroprevalence.

Blood Donors↗
PubMed1995

Cell surface activation of the erythropoietin receptor by Friend spleen focus-forming virus gp55.

The leukemogenic membrane glycoprotein gp55, encoded by Friend spleen focus-forming virus (SFFV), induces erythroid cell proliferation through its interaction with the erythropoietin receptor (EPO-R). There are two forms of gp55 in SFFV-infected cells: an intracellular form (more than 95% of the total protein), which is localized within the endoplasmic reticulum (ER) membranes, and a cell surface form (about 3 to 5%). Because both forms of the viral proteins bind to EPO-R, it is not clear whether the viral protein induces mitogenesis intracellularly or at the cell surface. To address this question, we constructed an EPO-R mutant that contained a 6-amino-acid (DEKKMP) C-terminus ER retention signal. Biochemical and functional analyses with this mutant indicated that it was completely retained in the ER and not expressed at the cell surface. Further analysis showed that the mutant, like the wild-type EPO-R, interacted with SFFV gp55. However, this apparent intracellular interaction between the two proteins failed to induce growth factor-independent proliferation of Ba/F3 cells. Furthermore, spontaneous variants of the ER-retained EPO-R selected on the basis of their ability to induce cell proliferation when coexpressed with gp55 were exclusively expressed at the cell surface. Thus, our results support the hypothesis that the mitogenic activation of the EPO-R by gp55 requires the interaction of the two proteins at the cell surface.

3T3 Cells↗
PubMed1994

Human T-lymphotropic virus type II in Panamanian Guaymi Indians.

BACKGROUND: Currently, human T-lymphotropic virus type II (HTLV-II) is the most prevalent human retrovirus, detected in persons presenting to donate blood in the United States. Only scant information is available with which to counsel HTLV-II-seropositive deferred donors or other persons about the ways in which they may spread HTLV-II to others. STUDY DESIGN AND METHODS: To increase understanding of the modes of transmission of HTLV-II, a seroepidemiologic study was conducted among Panamanian Guaymi Indians, a recently identified focus of endemic HTLV-II infection. Subjects were tested for serologic evidence of infection by HTLV-II, HTLV type I, hepatitis B virus, and nine other infectious agents by enzyme immunoassays and specific confirmatory tests. RESULTS: Nine (8.3%) of 109 persons tested HTLV-II-seropositive. HTLV-II seropositivity was more likely in persons with serologic evidence of prior hepatitis B virus infection. Sexual contact with HTLV-II-seropositive partners, but neither parenteral exposure nor breast-feeding, was identified as a risk factor for HTLV-II. CONCLUSION: In Guaymi Indians, HTLV-II appears to be spread primarily through sexual transmission.

Adolescent↗
PubMed1994

Detection of human immunodeficiency virus type 1 p24 antigen and plasma RNA: relevance to indeterminate serologic tests.

BACKGROUND: Most enzyme immunoassay-reactive specimens producing indeterminate Western blot results belong to individuals who are not infected with human immunodeficiency virus type 1 (HIV-1). However, a small percentage may correspond to early seroconversion or advanced disease, at which stage partial reactivity on Western blot may be observed. STUDY DESIGN AND METHODS: To determine the utility of HIV-1 p24 antigen and cell-free RNA detection for the resolution of Western blot-indeterminate serologic results, several types of enzyme immunoassay-positive, sero-indeterminate specimens were analyzed. Samples were obtained from infected individuals at the time of seroconversion (n = 20), from patients with AIDS (n = 2), as specimens from clinical samples obtained for diagnostic testing (n = 57), from blood donors producing persistent indeterminate results (n = 47), and from random blood donors (n = 72). RESULTS: HIV-1 p24 antigen was detected in 10 of 20 specimens collected from 9 of 12 individuals who seroconverted and in 2 of 2 AIDS patients. HIV-1 plasma RNA was positive in 22 of 22 samples from those 14 individuals. All of 57 diagnostic specimens and 47 samples obtained from persistently indeterminate donors were negative for HIV-1 p24 antigen and plasma HIV-1 RNA. One of 72 blood donor specimens was positive for HIV-1 plasma RNA and had borderline reactivity for p24 antigen. CONCLUSION: The detection of plasma RNA appears to be sensitive and specific; negative test results may be used to identify false-positive serologic reactions. The detection of p24 antigen and plasma RNA can also be used to confirm HIV-1 infection in persons with indeterminate serologic results associated with early seroconversion or late-stage disease.

Blotting, Western↗
PubMed1994

CYP3A gene expression in human gut epithelium.

CYP3A4, a major Phase I xenobiotic metabolizing enzyme present in liver, is also present in human small bowel epithelium where it appears to catalyse significant 'first pass' metabolism of some drugs. To determine whether CYP3A4 or the related enzymes CYP3A3, CYP3A5, and CYP3A7 are present in other regions of the digestive tract, we used CYP3A-specific antibodies to examine histological sections and epithelial microsomes obtained from a human organ donor. CYP3A-related proteins were detected in epithelia throughout the digestive tract and in gastric parietal cells, in pericentral hepatocytes, and in ductular cells of the pancreas. Immunoblot analysis suggested that the major CYP3A protein present in liver, jejunum, colon, and pancreas was CYP3A4 or CYP3A3, whereas CYP3A5 was the major protein present in stomach. Both CYP3A4 and CYP3A5 mRNA were detectable in all regions of the digestive tract using the polymerase chain reaction (PCR); however, only CYP3A4 could be detected by Northern blot analysis. CYP3A7 mRNA was consistently detected only in the liver by PCR and CYP3A3 mRNA was not detected in any of the tissues. We conclude that CYP3A4 and CYP3A5 are present throughout the human digestive tract and that differences in the expression of these enzymes may account for inter-organ differences in the metabolism of CYP3A substrates.

Adult↗
PubMed1994

Enzyme immunoassay using native envelope glycoprotein (gp160) for detection of human immunodeficiency virus type 1 antibodies.

An enzyme immunoassay using the purified native gp160 for the detection of human immunodeficiency virus type 1 (HIV-1) antibody was developed. This assay was determined to be highly specific, since (i) 157 serum samples that were confirmed negative by Western blot (immunoblot) (WB) were negative, (ii) 41 serum samples from populations with medical conditions that might cause nonspecific assay reactivity were all negative, and (iii) all 15 serum samples that showed false-positive reactions in one or more commercial HIV-1 screening tests were negative. The assay gave 100% specificity with a randomly selected and unlinked panel of 1,000 serum samples from healthy blood donors. The sensitivity of the assay was assessed by testing 238 samples confirmed as HIV-1 antibody positive by a standardized WB assay. All 238 serum samples (100%) were reactive in the native gp160 assay. In a dilution panel of 14 weakly WB-positive serum samples, 7 samples reacted two-to fivefold more strongly in the gp160 assay than in a virus lysate-based assay; the remaining 7 samples gave comparable reactivities in the two tests. The reactivities of 13 of these 14 serum samples in the gp160 assay were higher than in a commercial enzyme immunoassay that uses a recombinant envelope protein as the antigen. The native gp160 assay was more sensitive to identify seroconversion. In a well-characterized panel of sequential blood samples from a seroconverter, the new assay detected antibodies at least one sample ahead of the other commercial assays tested.

AIDS Serodiagnosis↗
PubMed1993

Modeling of the last stage of production phase of oxytetracycline fermentation processes.

In an attempt to disclose the reason why, during the last stage of FBOFP (fed-batch oxytetracycline fermentation processes) its specific production rate in general decreases notably, the authors started with the modeling of the process based on operation data, and thus reached the conclusion that this is due to too low residual nitrogen in the substrate. This inference is quite unacceptable to the current practice of the process operations. It was finally realized that the trouble lies in that our old measurement method of residual nitrogen is misleading. Upon using improved measuring method, it was found that while the total residual nitrogen is plentiful, the available nitrogen notably decreases with time, and thus confirmed the authors' conclusions. Experiments on industrial fermentators showed that the product can be increased by 1%, and the titer reaches 3200 micrograms/ml.

Fermentation↗
PubMed1992

Identification of rifampin-inducible P450IIIA4 (CYP3A4) in human small bowel enterocytes.

Enzymes within the P450IIIA (CYP3A) subfamily appear to account for significant "first pass" metabolism of some drugs in the intestine. To identify which of the known P450IIIA genes are expressed in intestine, enterocyte RNA was hybridized on Northern blots with synthetic oligonucleotides complementary to hypervariable regions of hepatic P450IIIA4, P450IIIA5, and P450IIIA7 cDNAs. Hybridization was detected only with the P450IIIA4-specific oligonucleotide. The identity of the hybridizing mRNA was confirmed to be P450IIIA4 by direct sequencing of a DNA fragment amplified from enterocyte cDNA by the polymerase chain reaction. To determine if enterocyte P450IIIA4 is inducible, biopsies of small bowel mucosa were obtained from five volunteers before and after they received 7d of treatment with rifampin, a known inducer of P450IIIA4 in liver. Rifampin treatment resulted in a five- or eightfold mean increase (P < 0.05) in the biopsy concentration of P450IIIA4 mRNA when normalized for content of sucrase isomaltase or intestinal fatty acid binding protein mRNAs, respectively. Rifampin also induced P450IIIA immunoreactive protein in enterocytes in each of the subjects, as judged by immunohistochemistry, and resulted in a 10-fold increase in P450IIIA4-specific catalytic activity (erythromycin N-demethylation) in the one patient studied. Our identification of inducible P450IIIA4 in enterocytes may in part account for drug interactions characteristic of P450IIIA4 substrates and suggests a strategy for controlling entry into the body of a major class of xenobiotics.

Adult↗
PubMed1991

Characterization of a novel receptor in toad retina with dual specificity for insulin and insulin-like growth factor I.

The biochemical properties of insulin receptors from toad retinal membranes were examined in an effort to gain insight into the role this receptor plays in the retina. Competition binding assays revealed that toad retinal membranes contained binding sites that displayed an equal affinity for insulin and insulin-like growth factor I (IGF-I). Affinity labeling of toad retinal membrane proteins with 125I-insulin resulted in the specific labeling of insulin receptor alpha-subunits of approximately 105 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of partially reduced (alpha beta-heterodimer) receptors affinity-labeled with 125I-insulin indicated the presence of a disulfide-linked beta-subunit of approximately 95 kDa. Endoglycosidase F digestion of the affinity-labeled alpha-subunits increased their mobility by reducing their apparent mass to approximately 83 kDa. This receptor was not detected by immunoblot analysis with a site-specific antipeptide antibody directed against residues 657-670 of the carboxy terminal of the human insulin receptor alpha-subunit, whereas this antibody did label insulin receptor alpha-subunits from pig, cow, rabbit, and chick retinas. In in vitro autophosphorylation assays insulin stimulated the tyrosine phosphorylation of toad retina insulin receptor beta-subunits. These data indicate that toad retinal insulin receptors have a heterotetrameric structure whose alpha-subunits are smaller than other previously reported neuronal insulin receptors. They further suggest that a single receptor may account for both the insulin and IGF-I binding activities associated with toad retinal membranes.

Animals↗
PubMed1991

Preventing transfusion-transmitted infections: issues related to migrating populations and increasing world travel.

Blood donations by emigrants or other travelers from distant lands require special attention for the prevention of transfusion-transmitted infections. The human immunodeficiency virus, type 1 (HIV-1) is only one of several bloodborne viruses that may be introduced into non-epidemic areas by transfusion and spread further by sexual intercourse, needles shared by drug users or mother-child transmission. Although transfusion-transmitted parasites, such as Trypanosoma cruzi, do not spread further in non-endemic areas in the absence of specific vectors, such unlikely infections may cause serious disease before a diagnosis is made. The challenges posed by transfusion-transmitted infections in a shrinking world require specific preventive strategies and enhanced clinical awareness for timely diagnosis and treatment.

Blood Donors↗
PubMed1989

[Immunochemical identification and localization of cytochrome P-45OHS; isozyme in human gastric mucosa and gastric carcinoma].

Monoclonal antibody to rat liver cytochrome P-450 j isozyme, an activating enzyme specific to nitrosamine metabolism, was used in combination with immunoblotting, densitometer scanning of SDS-PAGE gels, and immunohistochemical staining, there was a trace of P-450 isozyme (Mr. 51. 5 kd) in human gastric mucosa with or without cancer. It was similar to P-450 j in molecular weight, catalysis and immunochemistry. We named it P-450 HSj isozyme. Both in 25 gastric cancer patients and 17 non-cancer patients, the concentrations (%) of P-450 HSj in the mucosa of the lesser curvature were higher than those of the greater curvature (P less than 0.01). This might be one of the important reasons why gastric carcinoma caused by nitrosamines is most common in the lesser curvature. The P-450 HSj was localized in the cytoplasm of some epithelial cells, especially in the glands with hyperplastic and intestinal metaplastic changes adjacent to carcinoma. It was also found in some normal glands and in tumor cells of highly differentiated adenocarcinoma, but not in tumor cells of lowly differentiated adenocarcinoma.

Adenocarcinoma↗
PubMed1987

A test for human cytomegalovirus-specific immunoglobulins using a modification of a commercial test kit.

A technique (Ig-EIA) for the detection of CMV-specific IgG, IgM and IgA in human blood is described. Ig-EIA utilizes alkaline phosphatase-labeled goat anti-human IgG, IgM and IgA as a detection probe and CMV antigen-coated solid phase from commercial kits. Ig-EIA is compared to indirect fluorescent assay (IFA) and indirect hemagglutination (IHA) for sensitivity and specificity. On sequential samples of blood from a set of patients, Ig-EIA clearly demonstrated seroconversion in CMV-specific IgG and IgM. A test of 332 blood donors by Ig-EIA showed 177 (53%) had CMV-specific IgG and 17 (5%) had CMV IgM. Only two of the 17 donors with CMV IgM were nonreactive for CMV-IgG. The potential of CMV-IgM as an indicator of CMV infectivity is discussed.

Adult↗
PubMed1983

Failure of topical prostaglandin inhibitors to improve wound healing following deep partial-thickness burns.

The present study was designed to determine the efficacy of topical inhibitors of prostaglandins on wound healing. Two uniform deep partial-thickness burns were inflicted on mirror-image areas of guinea pig backs by an aluminum template heated to 75 degrees C and applied for 10 seconds. Indomethacin was tested extensively in a wide range of concentrations in groups of six or more animals each. The healing rates measured at 21 days postburn showed that topical indomethacin at each concentration tested was not effective for improving wound healing. In fact, the treated sites were consistently worse than the control sites. Moreover, the drug adversely affected the healing process proportional to the concentration and was associated with death, which was related to perforations of the GI tract. Also, the India ink filling in the dermal microcirculation was no better in the experimental wounds than in the controls. The evaluations for hair growth were definitely in favor of the controls. The other tested inhibitors, ibuprofen, flurbiprofen, tolmetin, zomepirac, piroxicam, and dipyridamole, also failed to show any benefit.

Administration, Topical↗