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Biomedical subjects

J Swanson

Publications and source records attributed to J Swanson.

At least 181 records · Page 10Linked to original sources
PubMed1969

Electron microscopic studies on streptococci. I. M antigen.

The presence of M antigens on group A streptococci is associated with hairlike fimbriae that cover the surface of the streptococcal cell wall and are demonstrable by electron microscopy. These fimbriae also may be associated with R antigen. Like M protein, the surface fimbriae are destroyed by trypsin treatment and reappear when "trypsinized" streptococci are reincubated in fresh, trypsin-free broth. Ferritin-conjugated, type-specific antibodies localize on homologous M+ cells in a pattern suggestive of several M antigenic sites along the length of individual surface fimbria. The M-associated fimbriae remain on the residual cell wall after removal of the bulk of group-specific polysaccharide through nitrous acid extraction. This suggests attachment of the fimbriae to the mucopeptide and minor polysaccharide components remaining in the nitrous acid-extracted wall. The pattern of localization of ferritin-conjugated antibodies on homologous streptococci before and after trypsin exposure and upon reincubation of the trypsinized cells in fresh medium suggests the following hypothesis: M antigen is secreted by the cell, is partially excreted through the otherwise intact cell wall, and is bound by the wall so that M protein occupies a peripheral, exposed position on the surfaces of the streptococcal cell wall.

Antigens↗
PubMed1969

The serum bactericidal system: ultrastructural changes in Neisseria meningitidis exposed to normal rat serum.

Exposure of meningococci to the bactericidal system of normal rat serum initiates a series of ultrastructural changes that accompany death of the organism. These morphological alterations consist of complement-dependent holes in the cell wall outer membrane, edema of the periplasmic space and cytoplasm, and accumulation of fibrillar material in and on the cell wall. Dissolution of the dense line and rupture of the cytoplasmic membrane also occur in meningococci exposed to normal rate serum. These latter two changes, however, are not seen in meningococci that are killed by bentonite-absorbed (lysozyme-deficient) serum, nor are they invariably present when other serum-susceptible organisms (N. catarrhalis and Herellea sp.) are treated with normal rat serum. The pattern of development of edema in serum-treated meningococci suggests that the cell wall outer membrane, mucopeptide layer, and cytoplasmic membrane act synergistically to maintain osmotic equilibrium of the bacterium. Death of the bacterium seems related to alteration of permeability following injury to the outer membrane. Holes are demonstrable, by negative straining, in the outer membrane of the meningococcal cell wall after exposure to the bactericidal effects of rat serum. The lesions are 110 A average greatest diameter and depend on the presence of antibody and complement for their formation. In addition, 82 A diameter holes are present in the walls of normal, untreated meningococci. The relation of complement-dependent holes to the smaller, naturally occurring holes is not known.

Animals↗
PubMed1969

Electron microscopic studies on opaque colony variants of group A streptococci.

Opaque colony variants of two strains of group A streptococci have been compared with blue colonies of the same strains by electron microscopy. In opaque colonies, the cocci are joined into elongated chains by exaggerated intercellular septa that often occupy the major portion of each cell's circumference. The thickness and lamination of cell walls in opaque colony variants are identical to those aspects of cell walls in blue colony forms. The similarity in cell wall architecture is found between opaque and blue forms whether or not M protein (and M associated surface fimbriae) is present. Extensive, direct contact between the nucleoid and the cytoplasmic membrane beneath intercellular septa is seen in opaque colony variants. The relationship of this marked nucleoid-cytoplasmic membrane association to the unusual chain forms in the opaque colony variants is unclear.

Cell Membrane↗