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Biomedical subjects

S H Yu

Publications and source records attributed to S H Yu.

At least 73 records · Page 4Linked to original sources
PubMed1984

Pulmonary surfactant.

The mammalian lung is stabilized by a specialized material, the pulmonary surfactant, which acts by reversibly reducing the surface tension at the air-liquid interface of the lung during breathing. Pulmonary surfactant contains approximately 90% lipid and 10% proteins. Dipalmitoyl phosphatidylcholine, the major lipid component, appears to be primarily responsible for the ability to reduce surface tension to near 0 dyn/cm (1 dyn = 10 microN). The other components of pulmonary surfactant promote the adsorption and spreading of this disaturated lecithin at the air-liquid interface. Surfactant activity can be accessed by physical and biological assays. Apparent discrepancies between the results obtained with the Wilhelmy plate surface balance and the pulsating bubble surfactometer have led to the suggestion that separate "protein-facilitated" (catalytic type) and "protein-mediated" (chemical type) processes may be involved in adsorption and (or) spreading at the different surfactant concentrations used with these two techniques. Artificial surfactants, which mimic the essential properties of the natural product with the pulsating bubble surfactometer, can be produced with synthetic lipids. Treatment of prematurely delivered infants suffering from the neonatal respiratory distress syndrome with lipid extracts of pulmonary surfactant leads to a marked improvement in gaseous exchange.

Animals↗
PubMed1982

Characterization of high- and low-metastatic clones derived from a methylcholanthrene-induced murine fibrosarcoma.

A methylcholanthrene-induced fibrosarcoma (3AM) and several of its clones were evaluated for pulmonary metastasis, growth rate, and chromosome composition. Heterogeneity was observed in the three parameters, and no correlation was found between growth rate and metastatic potential. Furthermore, three clones (10, 34, and 27) were identified with distinctive, high or low, metastatic potential and marker chromosomes. The marker chromosomes characteristic for each clone were identified in the early passages of the parental 3AM line, indicating the preexistence of the different cell types in the original neoplasm. The three clones were then characterized as to tendency to adhere to vascular endothelium, immunogenicity, and antigenic specificity. Clone 10, with two large metacentric markers (T2, 4 and T10, 15) and the highest metastatic potential (221 foci/lung), expressed the highest endothelial attachment and immunogenicity. Clone 27 was characterized with an extremely low rate of metastasis (nine foci/lung) and a T2, 7 large acrocentric marker, while clone 34 was characterized with a moderate rate of metastasis (107.5 foci/lung) and a T4, 16 acrocentric marker. Antigenically, clone 10 cross-reacted with clones 34 and 27 and 3AM, while clones 27 and 34 cross-reacted with clone 10 and 3AM but not with each other, suggesting that, within the original tumor, there were common tumor antigens shared by some cells but no universal antigen shared by all cells.

Animals↗
PubMed1979

A rapid method for the purification of supercoiled PM2 DNA by affinity chromatography on H1 histone covalently coupled to agarose.

A simple and rapid method is described for the purification of supercoiled PM2 DNA by affinity chromatography on columns of H1 histone covalently coupled to agarose. The method does not require the use of intercalating agents or ultracentrifugation procedures. Under the conditions most appropriate for purification, elution is carried out in a single step with buffered 0.7 M NaCl after the sample has been loaded onto the column in buffered 0.2 M NaCl. The DNA eluted at the higher salt concentration consists of supercoiled closed circular DNA at greater than 90% purity independently of the ratio of supercoiled to nicked circular DNA in the input mixture.

Bacteriophages↗
PubMed1978

Chromatography of different forms of DNA on immobilized histone columns.

Histones 1, 2A, 2B, 3, 4, and 5 from chicken erythrocytes have each been covalently immobilized on agarose beads and tested for their ability to bind DNA. Both calf thymus DNA and PM-2 viral DNA (form II, a nicked circle) bind to columns of immobilized histone at low ionic strength and can be eluted with 0.2--0.8 M NaC1, depending on the histone column. The strength of DNA binding by histone columns is in the order H5 greater than H1 greater than greater than H2B approximately H3 greater than H4 approximately H2A. About 70% of a heat-denatured calf thymus DNA sample and 100% of a supercoiled (form I) PM-2 DNA sample bind very tightly to histone columns and are released only by strong protein denaturants.

Animals↗