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Biomedical subjects

R C Williams

Publications and source records attributed to R C Williams.

At least 595 records · Page 33Linked to original sources
PubMed1969

Entry and release of poliovirus as observed by electron microscopy of cultured cells.

Cells of differing culture types were inoculated with poliovirus at 37 C, sampled at intervals during the replicative cycle, and examined in thin sections by electron microscopy. The earliest samples, taken at 2 and 5 min postinoculation, showed virus particles adjacent to the exterior of the plasma membrane and others that had apparently penetrated it directly; later samples showed fewer such particles or none. Particles lying in the peripheral cytoplasm frequently appeared swollen and distorted in shape. No sign of virus entry by a pinocytotic process was found at any time. At 3 hr, and subsequently during the replication cycle, particles of progeny virus appeared in the cytoplasm. They were found free in the cytoplasmic matrix, aligned along the elements of filamentous complexes, and enclosed within vesicles. Some of the vesicles were found to be open to the extracellular space, indicating a likely mechanism of virus release.

Amnion↗
PubMed1969

Two distinct groups of immunoglobulin A(IgA) revealed by peptic digestion.

Serum IgA M-components, secretory IgA separated from colostrum, and IgA from serum of patients with cirrhosis of the liver were digested with pepsin at pH 4.1. The IgA M-components segregated into two groups on the basis of their relative rates of peptic digestion. Serum and colostral IgA were digested at a total rate intermediate to that of the two groups of IgA myeloma proteins. It appeared, however, that colostral IgA may have been initially more resistant to peptic digestion than serum IgA. The variability in the rate of peptic digestion was not related to electrophoretic mobility, light-chain type, or IgA subclass. Experimental conditions related to enzyme to substrate ratio or to the pH of the reaction mixture did not appear to explain the differences found.These findings indicate that (a) two groups of IgA proteins can be distinguished on the basis of susceptibility to proteolysis with pepsin, and (b) secretory piece confers, at most, only a minor increase in stability to the IgA molecule against the digestive action of pepsin.

Chemical Phenomena↗