Range of the antigenic specificity of peptidoglycan in Staphylococcus aureus compared to other representatives of the Staphylococcus genus

In investigations based on the use of a highly sensitive test system permitting the detection of normal human antibodies to S. aureus peptidoglycan, the antigenic relationships between the peptidoglycans of S. aureus and other representatives of the genus Staphylococcus have been studied. Among other staphylococcal species, S. simulans, S. xylosus, S. hyicus, S. cohnii, S. hyicus s. s. chromogenes have been found to possess peptidoglycans most closely related to S. aureus peptidoglycans, while S. warneri and S. epidermidis peptidoglycans have proved to be least closely related to it.     

Antigen-specific T helper clones in a nonresponder strain require augmentation for expression of helper activity. Evidence for a possible antigen presentation defect in B cells

Hen egg-white lysozyme (HEL)-specific Thy-1+, Lyt-1+2- T cell lines and clones were derived from the nonresponder C57BL/6 strain. Although the antigen-specific proliferative response of these T cells in the presence of syngeneic irradiated spleen cells as a source of antigen-presenting cells (APC) was normal, the same cells were incapable of stimulating B cells to secrete antibody in vitro. This deficiency could, however, be corrected by the addition of an excess of normal T cells or a supernatant from concanavalin A-stimulated rat spleen cells. Alternatively, the use of highly cross-reactive ring-necked pheasant lysozyme in the cultures allowed expression of efficient help, ruling out any inherent deficiency in the T cells. The antibody response was specific and required MHC compatibility between the T lines and responding B cells. By using (H-2b X H-2d)F1 B cells and another H-2d-restricted HEL-specific T line, it was shown that only the H-2b-restricted T-B collaboration required exogenous factors, and the H-2d-restricted collaboration did not. Because both proliferative and helper responses are dependent upon MHC-restricted antigen presentation by macrophage-APC and B cells, respectively, these results suggest that the defect in the nonresponder H-2b-restricted T-B collaborative pathway may relate to the inability of B cells to adequately process and present HEL to clonal T cells.     

Propagation of Zea mays L. by Shoot Tip Culture: A Feasibility Study

A procedure for the stimulation of axillary bud developmentfrom young shoots of maize, their subculture to root-inducingmedia and transfer as rooted plants to soil is described. Axillarybud development was enhanced by the addition of kinetin andauxin to the culture medium. Root initiation on explanted axillarybuds, while successful with some cultivars, was variable. Anumber of mature plants with normal tassels and ears were producedfrom the lowermost buds of an original stem explant. Buds fromhigher positions on the explant exhibited different potentialitieswith some, those normally from cob producing nodes, producingshort-stalked plants with terminal female influorescences. Agradient of bud potentiality along the stem appears to be establishedextremely early after each is initiated. Zea mays., corn, maize, shoot tip culture, clone, vegetative propagation