Lymphocyte surface components. I. Stimulation of enzyme-treated rabbit lymphocytes by non-specific mitogens

Rabbit lymphocytes from various locations were treated briefly with proteases and the rate of incorporation of thymidine following stimulation by `non-specific' stimulants (Staphylococcus filtrate, SF, and Phaseolus vulgaris phytohaemagglutinin, PHA) measured. The proteases themselves, especially at concentrations exceeding 0·005%, sometimes caused cells to incorporate more thymidine than untreated cells. Stimulation with SF or PHA was much greater when lymphocytes were first treated with protease at low concentrations (when enzyme alone failed to stimulate). This effect was shown particularly by lymphocytes from gut-associated lymphoid organs. Peripheral blood lymphocytes, while unaffected by proteases at a concentration of 0·005%, incorporated increased amounts of thymidine after treatment with proteases at higher concentrations: pronase is especially potent. Further evidence is presented, distinguishing between the cytoagglutinating and mitogenic characters of PHA.

Studies on the metabolism of nuclear basic proteins after radiation in vitro

Exposure of isolated rabbit lymphocytes to 1000 R γ-radiation results in an increased rate of incorporation of amino acids-14C into cellular proteins during the first hour after irradiation. Fractionation of the proteins showed that the synthesis of basic proteins extracted from the nucleus was most affected. Two factors contributed to this apparent stimulation of protein synthesis by irradiation: (a) a transient increase in the amount of amino acid-14C available for protein synthesis in the cell; and (b) an increase in concentration of sodium ions in the cell. It is suggested that much of the observed increase in amino acid incorporation after irradiation of the lymphocytes is caused by radiation-induced changes in cell permeability.

Intestinal and cloacal lymphoepithelial glands in the Australian echidna: a possible homologue of the bursa of Fabricius

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Protruding chromosome arms in histological sections of tumours with large marker chromosomes

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