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Biomedical subjects

C Cheng

Publications and source records attributed to C Cheng.

At least 199 records · Page 11Linked to original sources
PubMed1983

Characterization of certain minor monodispersed bands found on serum protein electrophoresis as C-reactive protein.

A monodispersed band is a dense, homogeneous band on serum protein electrophoresis (SPE), indicating the presence of a discrete protein. Minor monodispersed bands in the gamma region on SPE usually indicate minor monoclonal immunoglobulins that can be characterized by immunofixation. Occasionally, these minor monodispersed bands cannot be shown to be immunoglobulins. This report illustrates that elevated levels of C-reactive protein (CRP) may be detectable as an "M-spike" on SPE; therefore, if immunofixation is performed, anti-CRP could be included in the panel of antisera used to characterize the minor monodispersed band. The detection of CRP as an "M-spike" in the gamma region is, however, dependent upon the absence of a chelating agent in the SPE support medium. When EDTA is present, the electrophoretic mobility of CRP is altered to a beta mobility.

Blood Protein Electrophoresis↗
PubMed1980

Calcium regulation of growth and differentiation of mouse epidermal cells in culture.

Modification of the ionic calcium concentration in the culture medium markedly alters the pattern of proliferation and differentiation in cultured mouse epidermal cells. When medium calcium is lowered to 0.05--0.1 mM, keratinocytes proliferate rapidly with a high growth fraction and do not stratify, but continue to synthesize keratin. The cells grow as a monolayer for several months and can be subcultured and cloned in low Ca++ medium. Ultrastructural examination of cells cultured under low Ca++ conditions reveals widened intercellular spaces, abundant microvilli and perinuclear organization of tonofilaments and cellular organelles. Desmosomes are absent. Epidermal cells growing as a monolayer in low Ca++ can be induced to terminally differentiate by adding calcium to the level normally found in the culture medium (1.2 mM). Cell-to-cell contact occurs rapidly and desmosomes form within 2 hr. The cells stratify by 1--2 days and terminally differentiate with cell sloughing by 3--4 days. After Ca++ addition, DNA synthesis decreases with a lag of 5--10 hr and is totally inhibited within 34 hr. In contrast, RNA and protein synthesis continue at 40--50% of the low Ca++ level at day 3, a time when many cells are detaching from the culture dish. Keratin synthesis is unaffected by the Ca++ switch.

Animals↗
PubMed1980

Iridium- 191 angiocardiography for the detection and quantitation of left-to-right shunting.

An osmium- 191 leads to iridium- 191 generator that can deliver multiple doses of Ir- 191m for first-pass radionuclide angiography has been developed. Iridium- 191m has a physical half-life of 4.96 sec and decays with emission of 65-keV and 129-keV photons in 58 and 30% abundance, respectively. Using a gamma camera, Ir- 191m radionuclide angiography was carried out, in dogs and ten patients, for the detection and quantitation of left-to-right shunting. In a one-year-old patients, 25 mCi of Ir- 191m results in a whole-body radiation absorbed dose of 35 mrad. Multiple Ir- 191m angiograms can be performed, seconds to minutes apart, without interference from background. The 15.4-day half-life of Os- 191 permits transportation of the generator to centers far from the production facility. With the low radiation dose, high information density, and the ability to repeat studies with Ir- 191m, clinical use of radionuclide angiography should be expanded.

Adolescent↗
PubMed1980

A new osmium-191 leads to iridium-191m generator.

A new osmium-191 leads to iridium-191m generator suitable for first-pass radionuclide angiocardiography has been developed. This generator system allows repeated elutions of 4.96-sec iridium-191m from its 15.4-day Os- 191 parent. The Os-191 is loaded on an anion-exchange column (AGMP-1) and Ir- 191m eluted with 0.9% NaCl at pH 1. Each elution (0.6 to 1 ml) of the generator yields about 7 to 10% Ir-191m and gives 0.003-0.008% of Os-191 breakthrough. Toxicity studies of the generator eluate carried out in animals support the safety of using iridium-191m in humans. The long shelf-life of the generator (approximately equal to 2 wk) will allow medical centers to use Ir- 191m for routine clinical diagnosis. Iridium-191m obtained by this method should find additional useful applications in nuclear medicine.

Animals↗
PubMed1979

Staphylococci-induced human platelet injury mediated by protein A and immunoglobulin G Fc fragment receptor.

Bloodstream infections with staphylococci are accompanied by thromboembolic complications. We have studied the mechanism of the interaction of staphylococci with human blood platelets. Staphylococci that possess protein A, a bacterial receptor for the Fc fragment of immunoglobulin G (IgG), caused aggregation of human platelets in whole plasma accompanied by release of [(3)H]serotonin. These reactions were time and concentration dependent, requiring two or more staphylococci per platelet to give maximal response within 5 min. The interaction between staphylococci and platelets required the presence of cell wall-bound protein A and of IgG with an intact Fc fragment. It did not require an intact complement system. Cell wall-bound protein A (solid phase) was capable of aggregating human platelets in whole plasma. In contrast, free, solubilized protein A (fluid phase) did not cause measurable aggregation, and release of [(3)H]serotonin was reduced. An excess of free, solubilized protein A blocked aggregation of human platelets induced by staphylococci in whole plasma. The role of the Fc fragment of IgG in the staphylococci-human platelet interaction was demonstrated by an experiment in which free, isolated Fc fragment blocked aggregation of platelets in whole plasma induced by staphylococci. Furthermore, binding of (125)I-protein A to human platelets was demonstrated in the presence of complete IgG with intact Fc fragment but not in the presence of the F(ab)(2) fragment. Binding of the protein A-IgG complex to the human platelet Fc receptor was paralleled by the release of [(3)H]serotonin. These results represent a novel example of the interaction of two phylogenetically different Fc receptors, one on prokaryotic staphylococci and the other on human platelets. Their common ligand, IgG, is amplified by one Fc receptor (protein A) to react with another Fc receptor present on human platelets, which results in membrane-mediated aggregation and release reaction occurring in whole plasma. This mechanism can be of significance in the pathomechanism of thromboembolic complications at the site(s) of intravascular staphylococcal infection.

Binding Sites↗
PubMed1978

GLC determination of caffeine in plasma using alkali flame detection.

A rapid, specific, and sensitive GLC assay for caffeine in plasma was developed utilizing alkali flame-ionization detection. The procedure involves the addition of mepivacaine as an internal standard, alkalinization of the sample, and extraction with chloroform. Peak height ratio measurements produced linear standard curves in the 0.25-10.0-microgram/ml range. Absolute sensitivity from a 1.0-ml plasma sample was 0.1 microgram/ml. The relative standard deviation of a 2.0-microgram/ml pooled plasma standard run repeatedly over several months was 5.2%. The method is applicable to time-concentration studies in human and animal plasma following typical oral doses of caffeine.

Animals↗
PubMed1977

Membrane changes in human platelets induced by lipopolysaccharide endotoxin.

The unexplained occurrence of thrombocytopenia in cases of Gramnegative sepsis in man led us, in the light of animal experiments indicating the blood platelet as the target cell for endotoxin, to examine the effect of Salmonella enteritidis lipopolysaccharide B on human platelets. Human platelets were separated from a coat of plasma proteins by Sepharose 2B filtration or by a combined procedure of albumin gradient and Sepharose 2B filtration. The action of endotoxin on human platelets resulted in membrane changes manifested by dose-dependent release of [3H]serotonin and adenine nucleotides. Cytoplasmic marker, lactic dehydrogenase, and lysosomal marker, beta glucuronidase, were retained indicating that the release reaction was selective. Release of [3H]serotonin was specific for endotoxin since other particulates, zymosan and erythrocyte stroma, were without effect. Endotoxin, added to gel-filtered human platelets, induced a significant evolution of platelet factor 3 procoagulant activity. Preincubation of endotoxin with a membrane-rich homogenate of human platelets inhibited its labilizing effect on human platelets thus suggesting an interaction between endotoxin and the platelet membrane itself. Other plausible factors in this interaction [fibrinogen, adenine nucleotides, thrombin, sialic acid residues, and IgG] were eliminated on the basis of a series of control experiments. From the negligible effect of aspirin and indomethacin, we may infer that the interaction of endotoxin with platelets does not depend on the platelet prostaglandin synthesis pathway. The direct interaction of endotoxin with the human platelet membrane comprises a new mechanism which may help to clarify the pathogenesis of vascular and haemostatic disorders accompanying bloodstream infections due to Gram-negative bacteria.

Blood Platelets↗
PubMed1976

Follow-up study of oral contraceptive acceptors in Howrah District in India.

In the Howrah District in India, three clinics--one in each of the urban, slum, and rural areas of the city--were initiated by the Humanity Association of Howrah in November of 1968 to supply oral contraceptives (OCs) to women from 15 to 45 years of age. The project was discontinued in September, 1972. Of the 1700 patients still active when the project ended, 1527 were contacted for the follow-up survey. Findings indicate that most women in this district were satisfied with OCs and would continue to use them if they were available. In corroboration of this, it was found that 43% of the women had used OC'S obtained from other sources after the project was discontinued. While 35.5% of the women who used no contraceptive method after project ended reported becoming pregnant or suspected that they were pregnant at the time of the interview, only 4.2% of those who reported using some form of contraception reported pregnancy or suspected pregnancy. The demographic impact of the project will be evaluated on the basis of data to be obtained in a subsequent survey of the same communities.

Abortion, Induced↗