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Biomedical subjects

Y Chang

Publications and source records attributed to Y Chang.

At least 343 records · Page 19Linked to original sources
PubMed1980

Radiation therapy of nasopharyngeal carcinoma.

Carcinoma of the nasopharynx is one of the most frequent malignant tumors in the southern parts of China. A total of 3 263 cases treated with irradiation in the course of the thirty years since the Liberation have been analysed retrospectively. The 5-year survival rate has risen from 27.7 per cent for cases treated during 1955 to 1960 to 54 per cent for those treated in 1973. The technique of irradiation is described, emphasizing the importance of suitable techniques for the treatment of the cervical lymph nodes. The value of elective irradiation of cervical regions not involved clinically is elucidated. Finally, the causes of failure of treatment are discussed.

Cobalt Radioisotopes↗
PubMed1979

Comparative study of different iron compounds in inhibition of sphaerotilus growth.

The effectiveness of iron compounds on growth inhibition of Sphaerotilus species was compared. In this study, two strains of Sphaerotilus were tested with different iron concentrations in a synthetic sewage (S-medium) as formulated by Lackey and Wattie (Sewage Works J. 12:669-684, 1940). For both strains, >80% inhibition of the maximum respiration rate was obtained by the following levels of soluble iron concentrations at pH 6.0: iron citrate, 20 mg/liter as Fe; iron cysteine, 5 mg/liter as Fe; and ferrous sulfate, 10 mg/liter as Fe. At a pH of 6.7 with iron citrate (20 mg/liter as Fe), inhibition of both strains was in excess of 50%. Insoluble iron compounds, such as iron hydroxides and ferrous carbonate, were found to be much less effective than the soluble iron compounds as inhibitors of these two strains. Aged iron hydroxide (500 mg/liter as Fe) produced a 70% inhibition in the maximum respiration rate while fresh iron hydroxide (52 mg/liter as Fe) and ferrous carbonate (500 mg/liter as Fe) produced a 20% inhibition. Chemical analyses of the iron-inhibited Sphaerotilus strains showed a close relationship between the inhibition of the organism's growth and the amount of iron sorbed by the organism.

Journal Article↗
PubMed1978

Light-scattering studies on bile acid salts I: Pattern of self-association of sodium cholate, sodium glycocholate, and sodium taurocholate in aqueous electrolyte solutions.

The pattern of association of the trihydroxy bile salts in aqueous electrolyte solutions was investigated utilizing the light-scattering technique. The turbidity of the bile salts sodium cholate, sodium taurocholate, and sodium glycocholate was determined over the concentration range of 0-25 mg/ml at 25 degrees. For sodium cholate, the concentration of the supporting electrolyte was varied from 0.15 to 0.5 M. For all bile salts in 0.15 M electrolyte, the turbidity was determined in sodium fluoride, sodium chloride, sodium bromide, and sodium iodide. Comparison of the light-scattering data with amonomer-micellar model showed that qualitative agreement was obtained; however, quantitative agreement could not be achieved. Further examination of the data showed that the light-scattering results were in good agreement with a model that includes dimers, trimers, and a higher aggregate containing approximately eight monomeric units.

Chemical Phenomena↗
PubMed1978

Solubilization of napthalene by sodium cholate and pattern of self-association of sodium cholate in 0.15 M sodium chloride.

Naphthalene solubility was determined in aqueous 0.15 M NaCl containing sodium cholate in the 0-0.05 M concentration range at 25 +/- 0.1 degrees. Sodium cholate tends to self-associate in aqueous solutions. Most often, the association pattern has been described in terms of a monomer-micellar model in which it is assumed that no association occurs below the critical micelle concentration. By comparison of the experimental solubilization curve with curves calculated on the basis of the monomer-micellar model, it was shown that this model is inappropriate for the self-association pattern of sodium cholate. The solubility data were consistent with a model that assumes that sodium cholate associates to form dimers, trimers, and higher aggregates with an average aggregation number of 7.63. Model calculations suggest that naphthalene is solubilized by dimers and higher aggregates. Solubilization of naphthalene by trimers appears to be negligible.

Cholic Acids↗
PubMed1978

Light-scattering studies on bile acid salts II: pattern of self-association of sodium deoxycholate, sodium taurodeoxycholate, and sodium glycodeoxycholate in aqueous electrolyte solutions.

The pattern of self-association of the bile salts sodium deoxycholate, sodium glycodeoxycholate, and sodium taurodeoxycholate was investigated in aqueous electrolyte solutions by the light-scattering technique. The turbidity of the bile salt solutions was obtained over the concentration range of 0-20 mg/ml at 25 degrees. These data were analyzed according to a monomer-micellar equilibrium model and a stepwise association model. Comparison of the light-scattering data with these models suggests that the monomer-micellar model may be inappropriate. Analysis of the data according to the stepwise association model suggests that the dihydroxy bile salts associate to form dimers, trimers, and tetramers in addition to a larger aggregate which varies in size depending on the degree of conjugation of the bile salt.

Chemical Phenomena↗
PubMed1978

Atomic absorption spectrophotometry of free circulating platinum species in plasma derived from cis-dichlorodiammineplatinum(II).

We describe a method of analysis for free circulating platinum species derived from cis-dichlorodiammineplatinum(II) in blood plasma. Protein-bound and free platinum species were separated from each other by centrifugal ultrafiltration. Platinum in the ultrafiltrate was converted to a cationic complex by reaction with ethylenediamine, and the product was collected on paper impregnated with cation-exchange resin, where it could be stored indefinitely without loss. The platinum was eluted from the disk with 5 mol/liter hydrochloric acid, and an aliquot of this solution was then analyzed by flameless atomic absorption spectrophotometry. The overall analytical recovery of platinum was 80 +/- 2%. The minimum quantity of cis-dichlorodiammineplatinum detectable was 35 microgram/liter of plasma at the 99% confidence level. Detector response was linearly related to drug concentration in the range from 80 microgram to 290 mg of Pt per liter of plasma. Reaction variables were made optimal, so as to yield maximum sensitivity and reproducibility (+/- 2%) consistent with minimal sample transfers and manipulations.

Cisplatin↗
PubMed1967

Detoxification of Salmonella typhimurium lipopolysaccharide by ionizing radiation.

The efficiency of ionizing radiation in detoxifying the lethal determinant(s) of the lipopolysaccharide (LPS) of Salmonella typhimurium, S. enteritidis, and Escherichia coli in aqueous solution and associated with heat-killed S. typhimurium cells in suspension decreased with doses above 1 Mrad. The 50% end point of inactivation was more than 7.0 Mrad for heat-killed salmonellae and 4.8, 4.5, and 1.0 Mrad for the LPS of S. typhimurium, S. enteritidis, and E. coli, respectively. After exposure to 20 Mrad, S. typhimurium LPS retained a small portion of its lethal properties although the ld(50) was much greater than 9.5 mg per 20-g mouse. However, at -184 C, no inactivation of the lethal determinant(s) occurred after exposure to as much as 20 Mrad. This demonstrated the significance of the indirect effect and the mobility and formation of free radicals. At 22 C, the optical density at 400 mmu increased and the pH decreased with increasing radiation dose, but no qualitative changes were observed in the infrared spectrum. No change was observed in the pyrogenicity of S. typhimurium LPS; a slight decrease in antigenicity was revealed when 6 days, but not when 1 day, elapsed between vaccination and challenge in the mouse protection test. The results were interpreted as evidence of the existence of two or more lethal and antigenic determinants. The differential effect of radiation on these properties and on the pyrogenic component(s) probably are indicative of separate functional sites for lethal, antigenic, and pyrogenic activities.

Animals↗
PubMedDate not supplied

Intramuscular administration of expression plasmids encoding interferon-gamma receptor/IgG1 or IL-4/IgG1 chimeric proteins protects from autoimmunity.

BACKGROUND: Interferon gamma (IFNgamma) is an inflammatory cytokine that promotes autoimmune insulitis and diabetes in NOD mice, while interleukin-4 (IL-4) is protective. We constructed plasmids encoding either an IFNgamma receptor/IgG1 (IFNgammaR/IgG1) chimeric protein which inhibits IFNgamma, or an IL-4/IgG1 chimeric protein with IL-4 activity, for therapeutic gene transfer into NOD mice. METHODS: Murine IFNgammaR/IgG1 and IL-4/IgG1 cDNA segments were cloned into the VICAL VR1255 expression plasmid. Naked plasmid DNA was injected i.m. into young NOD mice, which were then observed for development of insulitis and diabetes. RESULTS: After transient transfection of COS-7 cells, IFNgammaR/IgG1 and IL-4/IgG1 fusion proteins are secreted in vitro as disulfide-linked homodimers, with the expected biological activity. Intramuscular injection of these vectors results in the production of the respective fusion proteins locally in muscle. In serum, the IFNgammaR/IgG1 protein is present at >200 ng/ml over 130 days after the last of five DNA injections, but IL-4/IgG1 is undetectable in our assays (<10 pg/ml) at all time points. Both vectors protect NOD mice from autoimmune insulitis and diabetes, but the IL-4/IgG1 vector is more effective. Neutralization of IFNgamma with IFNgammaR/IgG1 was most protective when treatment was begun early (3 weeks of age). CONCLUSION: Gene therapy by i.m. injection of these plasmids protects NOD mice from autoimmunity, and the IL-4/IgG1 vector is more effective despite low circulating protein levels. These chimeric proteins consist of nonimmunogenic self elements and are suitable for long-term therapy of autoimmune disorders.

Animals↗