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Biomedical subjects

C Sun

Publications and source records attributed to C Sun.

At least 181 records · Page 10Linked to original sources
PubMed1994

The effect of postirradiation holding at 22 degrees C on the repair of sublethal, potentially lethal and potentially neoplastic transforming damage in gamma-irradiated HeLa x skin fibroblast human hybrid cells.

The effect of postirradiation holding at 22 degrees C on cell growth, progression of cells through the cell cycle, and the repair of sublethal, potentially lethal and potentially neoplastic transforming damage in gamma-irradiated HeLa x skin fibroblast human hybrid cells has been examined. Cell growth and cell cycle progression were essentially stopped at this reduced temperature. Cell survival was dramatically reduced by holding confluent cultures for 6 h at 22 degrees C, as opposed to 37 degrees C, after 7.5 Gy gamma radiation delivered at a rate of 2 Gy/min. Return of the cells to 37 degrees C for 6 h after holding at 22 degrees C did not result in increased survival. A similar effect was obtained when the cells were held at 22 degrees C between split-dose irradiation of log-phase cultures where no increase in survival was observed over a split-dose interval of 4 h. In this case a partial increase in survival was observed upon returning the cells to 37 degrees C for 3 h after holding at 22 degrees C for the first 3 h of the split-dose interval. Neoplastic transformation frequency was not enhanced by holding confluent cultures for 6 h at 22 degrees C after 7.5 Gy gamma radiation. This is consistent with previous observations that misrepair of potentially neoplastic transforming damage already occurs at 37 degrees C. The overall results are interpreted in terms of the reduced temperature favoring misrepair, rather than inhibition of repair, of sublethal, potentially lethal and potentially transforming radiation damage.

Cell Cycle↗
PubMed1993

Effects of copper coordinate complexes on the scavenging of reactive oxygen species.

Effects of a 20-membered macrocyclic bicopper complex and dioxotetramine copper complexes with linear or cyclic structure on the scavenging of ROS have been studied by ESR. The results indicated that all three copper coordinate complexes have SOD mimetic activity. The dioxotetramine copper complex with linear or cyclic structure did not have the scavenging effect on .OH produced by H2O2-Fe++ and 1O2 produced by the H2O2-NaOCl system, but the 20-membered macrocyclic bicopper complex was found to be capable of depressing the intensity of the ESR spectrum of the adduct formed from TMP and 1O2 as well as making the spectrum of DMPO-OH adduct splittings. This fact may suggest that there are interactions between the ROS and 20-membered macrocyclic ring in the SOD mimic.

Cells, Cultured↗
PubMed1993

Conformation and activity of Phaseolus coccineus var. rubronanus lectin.

The conformation of native and denatured Phaseolus coccineus var. rubronanus lectin was studied by circular dichroism (CD) and correlated to the hemagglutinating activity. The far-UV CD spectrum at 25 degrees C showed a broad, negative band around 223 nm and a positive one at 196 nm. CD data analysis of the lectin indicated a beta-sheet-rich protein. At high temperatures, the spectrum was blue-shifted with increasing magnitude; these changes correlated well with the loss of the activity. The conformation of lectin between pH 2 and 10 remained essentially unchanged. At pH 13 the CD spectrum resembled that of unordered form with a negative band near 200 nm and the activity was completely lost. The denatured lectin in 6 M guanidine hydrochloride would be renatured upon diluting the denaturant to 0.75 M; the changes in CD spectrum again correlated well with the loss of the activity. The effect of sodium dodecyl sulfate on the lectin was drastic; it sharply increased the alpha-helix at the expense of the beta-sheet and reduced the activity; the changes reached a plateau above 20 mM surfactant.

Circular Dichroism↗
PubMed1993

Conformation and activity of mannose- and N-acetylgalactosamine-specific lectins from Vicia villosa seeds.

The conformation of two Vicia villosa lectins specific for mannose and N-acetylgalactosamine, respectively, was studied by circular dichroism. Both showed a broad negative CD band around 220 nm and a positive one above 190 nm. CD data analysis indicated that they were rich in beta-sheet. However, they differed in conformational stability against extreme pH, at elevated temperature, and in guanidine hydrochloride and sodium dodecyl sulfate solutions. The unusual feature was that the conformation of N-acetylgalactosamine-specific lectin was virtually unaltered in 6 M guanidine hydrochloride and 7.5 mM surfactant.

Acetylgalactosamine↗
PubMed1993

Effects of cholesterol on the miscibility of synthetic glucosamine diesters in lipid bilayers and the entrapment of superoxide dismutase into the positively charged liposomes.

Methyl-D-glucosamine-3,6-dilauroyl, dimyristoyl, dipalmitoyl or distearoyl esters were synthesized as positively charged lipids. They were incorporated into phosphatidylcholine liposomal membranes and the entrapment of superoxide dismutase (SOD) into the liposomes was attempted. The efficiency of the SOD-entrapment into the positively charged multilamellar vesicles (MLVs), comprising egg yolk phosphatidylcholine and synthetic glucosamine diesters, was enhanced by the addition of cholesterol to the membranes. A differential scanning calorimetric study showed that the miscibility (solubility) of glucosamine diesters in phosphatidylcholine-bilayers increased on the addition of cholesterol to the membranes. Cholesterol assisted in the mixing of phosphatidylcholines with positively charged glucosamine diesters and increased the positive charges on the liposomal membranes. This was confirmed by incremental increases in the zeta-potential of liposomal membranes with an increase in the cholesterol content. Entrapment of SOD thus became more efficient due to the enhanced electrostatic attraction between the positively charged membranes and the negatively charged SOD, and/or the electrostatic repulsive interactions between positively charged membranes; the latter interactions induced a thickening of the water layer in MLVs.

Cholesterol↗
PubMed1993

Total gastrectomy via thoracotomy for cancer of the cardia or fundus of the stomach (report of 90 cases).

From 1978 through 1990, 90 total gastrectomies with esophagojejunostomy via thoracotomy were performed for the treatment of cancer of the cardia or fundus of the stomach in our hospital. Eighty-five patients were in TNM-stage III and five in stage IV. The 30-day postresectional mortality was 1.1%, and the 5-year survival rate was 13.8%. 14CO2 breathing test and clinical evaluation of 34 postoperative patients (not included in the 90 patients) showed that total gastrectomy may decrease the incidence of positive residual cancer along the incision lines, and may help to avoid small stomach syndrome. There was no statistical difference in postoperative fat absorption between patients treated by ordinary proximal subtotal gastrectomy and those receiving total gastrectomy via thoracotomy.

Adult↗
PubMed1993

Election spin resonance studies of free radical formation and oxygen consumption of lens epithelium during ultraviolet exposure.

A long life election spin resonance (ESR) signal at g = 2.0006 was observed in the normal lens epithelium and cortical fibers. During ultraviolet (UV) exposure, a new ESR signal at g = 2.0060 was found in the lens epithelium. But this specific signal was not detected in the lens cortical fibers. This suggested that lens epithelial cells were more susceptible to the free radical formation which was induced by UV light. By means of ESR spin probe oximetry, the oxygen uptake of lens epithelial cells was measured. The more the oxygen uptake, the higher the K value was. The K value of the oxygen consumption of epithelial cell linearly correlated with time of consumption (20-60 min) and increased as a function of UV exposure time (1-5 min). The oxygen consumption rate of lens epithelial cell was approximately 1.38 x 10(6) and increased to 7.1 x 10(6) O2 molecules per cell per sec. The oxygen consumption rate increased more than 5 times. These results indicates that UV light can accelerate the respiratory function of lens epithelial cells. The necessity of excess oxygen of lens epithelial cells may play a role in the cataract formation induced by UV light.

Animals↗
PubMed1993

Misdiagnosis of lung cancer in patients under age 40--a clinical analysis of 47 cases.

Diagnosis of lung cancer in 47 patients aged younger than 40 years was delayed as a result of misdiagnosis, accounting for 70.1% of all cases of lung cancer in those aged less than 40 years treated in PUMC Hospital in the same period. Pulmonary tuberculosis and tuberculous pleurisy were diagnosed in 26 cases (55.3%). Pulmonary inflammation was suspected in 24 cases (51.1%). The delay in diagnosis was one to three months in 28 cases and longer than 3 months in 19 cases. Twenty-eight (59.6%) of the 47 patients underwent surgery, including exploratory thoracotomy (21.4%) and pneumonectomy (40.9%). The five-year survival rates in the resectable group and in the non-surgical group were 31.6% and 5.3%, respectively. We recommend that accessory examinations should be performed wherever possible in younger patients with suggestive pulmonary nodules in order to collect sufficient evidence to confirm or rule out the diagnosis of lung cancer and thereby reduce the rate of misdiagnosis in such younger people.

Adenocarcinoma↗
PubMed1993

The effects of hybridoma growth factor in conditioned media upon the growth, cloning, and antibody production of heterohybridoma cell lines.

Interleukin 6 (IL-6)/hybridoma growth factor (HGF) has been shown to be the requirement for growth of murine hybridomas in vivo or in vitro. In this paper, two kinds of conditioned media (CM) from the culture supernatants of a human fibroblast cell line CRL1506 and a cloned Epstein-Barr virus (EBV) transformed human lymphoblastoid cell line (LCL) N23 were found to have IL-6 activity by strongly promoting the growth, antibody secretion (increase of one- to three-fold), and cloning efficiencies of heterohybridomas secreting human monoclonal anti-hemorrhagic fever with renal syndrome virus antibodies and LCL. Since these CM contained no detectable IL-2, and IL-4 had no effects on the growth of the cell lines, IL-6 was considered to be the main active component of the CM responsible for promoting hybridoma growth. This effect was further confirmed by IL-6-dependent cell line 7TD1 bioassay (IL-6 activity in the CM ranging from 1,000 to 10,000 units/ml). Moreover, we successfully established four EBV-transformed lymphoblastoid cell lines at single-cell level by adding an equal volume of CRL1506-CM to 10% FCS-RPMI1640 in limiting dilution. Finally, it is worth noting that the sensitivity of the heterohybridomas to the two kinds of CM was not the same and was not consistent with that of their parental myeloma cell lines. Thus, it suggests that the CM might contain more than one factor, and the choice of proper conditioned media should be very useful for human monoclonal antibody production.

Animals↗
PubMed1992

Lack of differential G2 chromosomal radiosensitivity between non-tumorigenic and tumorigenic human hybrid cells (HeLa x skin fibroblasts).

Previous studies have shown, that for log phase cultures, tumorigenic segregants of HeLa x skin fibroblast human hybrid cells are slightly more radiosensitive in terms of cell killing than their nontumorigenic parents (Redpath et al. 1985, Colman et al. 1988). Other studies have shown that these same tumorigenic segregants exhibit a markedly enhanced G2 chromosomal radiosensitivity (Sanford et al. 1986) thus offering a possible explanation for the cell killing data. The present study set out to examine the G2-phase radiosensitivity of these cells in terms of cell killing with the expectation that an enhanced sensitivity in the tumorigenic cells would be seen. No enhanced sensitivity was observed. The G2 chromosomal radiosensitivity was then examined and no differential was seen between the non-tumorigenic and tumorigenic cells. This lack of confirmation of previously reported studies may be due to some technical differences in the experimental protocols.

Cell Line, Transformed↗
PubMed1992

A simplified and rapid staining method for the HeLa x skin fibroblast human hybrid cell neoplastic transformation assay.

A simplified and rapid screening method for detecting radiation-induced neoplastically transformed foci in the HeLa x skin fibroblast human hybrid cell assay system has been developed. The method is based on the recent identification of the tumor-associated antigen in this system as intestinal alkaline phosphatase (IAP), and on the recent commercial development of a stable alkaline phosphatase chromogenic substrate solution, Western blue (WB). Cleavage of the substrate results in the production of a blue insoluble precipitate. It is shown that WB can be used on both viable and paraformaldehyde-fixed cells. Fixation does not noticeably reduce the IAP enzymatic activity. A direct comparison with the current method of immunoperoxidase (IMPO) staining indicates that the WB method is not only easier, but appears to be more sensitive in picking up weakly positive foci with a resulting higher (factor of 2.5) induced transformation frequency for 7 Gy of 137Cs gamma radiation. Whereas the IMPO staining procedure is time-consuming and requires access to large amounts of expensive IAP-specific BD6 monoclonal antibody and peroxidase-labeled secondary antibody, the WB staining procedure is rapid and utilizes an inexpensive and readily available reagent. It should now allow this assay system to enter general use.

Alkaline Phosphatase↗
PubMed1992

The effect of multi-glycosides of Tripterygium wilfordii Hook f. (GTW) on the survival time of cardiac allografts in rats.

Heterotopic heart transplantation was carried out in rats and the influence of multi-glycosides of Tripterygium wilfordii Hook f. (GTW) and a subtherapeutic dose of cyclosporine A (CsA) on the mean survival time (MST) of the cardiac allografts was investigated. The results showed that the MSTs of cardiac allografts in both the GTW and CsA-treated groups were significantly prolonged (P < 0.01 vs control). The rate of allograft rejection in the drug-treated groups was much lower than that in the control group.

Abdomen↗
PubMed1992

[Morphology and delta-endotoxin proteins of Bacillus thuringiensis from soils and their toxicities to insects].

94 strains of Bacillus thuringiensis were isolated from soils in southwest and northwest of China. The morphology of cells, spores and parasporal crystals of these strains was investigated under transmission and scanning electro-microscope. Proteins of delta-endotoxins from all strains were analysed by rapid SDS-PAGE. 9 species of insects in Lepidoptera, Coleoptera and Diptera were tested for assay of delta-endotoxins. Some kinds of parasporal crystals were quite different in form and in composition of protein from those reported before. Most of strains were nontoxic to all of 9 species used in bio-assay. Some strains were very effective in species of Coleoptera or Noctuidae.

Animals↗
PubMed1991

Another discontinuous epitope on glycoprotein gp120 that is important in human immunodeficiency virus type 1 neutralization is identified by a monoclonal antibody.

To define the domains in the envelope glycoprotein important for antibody neutralization of the human immunodeficiency virus type 1 (HIV-1), monoclonal antibodies (mAbs) were generated by immunizing mice with purified glycoprotein gp120 of the IIIB isolate. One mAb, G3-4, reacted with the gp120 of homologous (IIIB) and heterologous (RF) isolates. In addition, mAb G3-4 efficiently neutralized both IIIB and RF viruses in vitro, as well as four of nine primary HIV-1 isolates. In competition immunoassays, mAb G3-4 and soluble CD4 were found to inhibit one another in binding to gp120. However, no competition was seen between mAb G3-4 and mAbs directed to the third variable region or the fourth conserved region of gp120. In particular, mAb G3-4 did not compete with our human mAb 15e, which identifies a discontinuous epitope on gp120 involved in group-specific neutralization of HIV-1 and in gp120-CD4 binding. Epitope-mapping studies on mAb G3-4 with synthetic or unglycosylated recombinant peptides were negative, suggesting that its epitope may be discontinuous. Indeed, this hypothesis was confirmed by showing the loss of mAb G3-4 serologic reactivity when gp120 was first denatured. We conclude that the site recognized by mAb G3-4 represents another discontinuous epitope on gp120 important for neutralization of HIV-1.

Animals↗
PubMed1991

Transfectomas expressing both secreted and membrane-bound forms of chimeric IgE with anti-viral specificity.

Because of the lack of a cell line expressing on surface and secreting human IgE of known Ag specificity, the construction of a transfectoma line possessing such properties would be useful for studying the roles of surface IgE and the effects of anti-IgE antibodies on IgE-producing B cells. Toward this goal, the human genomic DNA segment encompassing the two exons encoding the membrane anchor peptide of epsilon-chain and their flanking regions was sequenced. Hybrid epsilon and kappa genomic DNA comprising the C regions of human epsilon- and kappa-chains and the H and L chain V regions of the murine mAb BAT123, which reacts with the gp120 envelope protein of HIV-1, were constructed. Mammalian expression vectors containing these fusion genes were used to transfect murine myeloma Sp2/0 cells, and transfectants stably expressing on surface and secreting into culture medium chimeric IgE were obtained. The chimeric IgE showed identical Ag-binding properties as the murine mAb BAT123. Acting in concert with the specific peptide Ag polyvalently coupled to a protein carrier, the chimeric antibody could induce histamine release from human blood basophils. These results demonstrate the potential utility of the transfectoma cells and the chimeric IgE in studying the roles of membrane-bound IgE and effects of anti-IgE antibodies on IgE-producing B cells.

Amino Acid Sequence↗
PubMed1991

Monitoring of cyclosporine concentrations by using dry blood-spot samples.

We modified the Incstar Cyclo Trac SP kit to enable its use with dry blood-spots on filter paper. The recovery ranged from 92 to 106%. Dilution studies have shown excellent linearity and parallelism throughout the range of the assay. Precision is demonstrated by within-assay CV's of 6.6 and 4.3% at 96 and 342 micrograms/L respectively and between-assay CV's of 9.1 and 7.0% at 138 and 506 micrograms/L respectively. A comparison study (n = 209) with whole blood assay gave a correlation coefficient of 0.97, a slope of 1.04, and an intercept of 13.2. Whole blood and dry blood-spot cyclosporine assays on heart, kidney, liver, and lung transplants were also compared.

Cyclosporins↗
PubMed1991

Lack of immunity to hepatitis B virus among the expatriates residing in southern Taiwan.

Taiwan is an endemic area for hepatitis B virus (HBV) infection. There are more than 3-million carriers on this island. Chronic HBV infections may result in liver cirrhosis and hepatocellular carcinoma, which are common in Taiwan. However little information is available concerning the immunity and the susceptibility to HBV among the expatriate-population (non-permanent residents from foreign countries) in Taiwan. Thus controversies exist on the indications for HBV vaccination among the foreign visitors and expatriates. This study evaluated the serological status of those who attended the Kaohsiung Adventist Clinic between May 1986 and August 1989. Hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) were determined by ELISA. A total of 152 expatriates (85M, 67F, aged 5 to 64 years, duration of residence in Taiwan: 2 weeks to 11 years) without previous HBV vaccination, were tested. HBsAg and anti-HBs were not detected in 125 (82%). Anti-HBs was found in 22 (15%). There was no correlation between the duration of residence and anti-HBs positivity. However, there was an increased prevalence of anti-HBs with increasing age after 30. For those expatriates who were anti-HBs positive, 64% had a history of sexual contact with a partner from an endemic area of HBV. HBsAg was detected in 5 (3%). Three were symptomatic with abnormal liver function tests. Four had a history of sexual exposure. Their children were not antigenemic. It is concluded that most (greater than 82%) of the expatriates residing in southern Taiwan have no immunity to HBV and sexual contact is a major route (70%) of transmission.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗