Elizabeth B. Jackson

Studies on Scrub Typhus. II. Preparation of Formalinized Vaccines from Tissues of Infected Mice and Rats.

Summary Formalinized vaccines prepared from lungs or spleens of white mice, cotton rats, and white rats infected with R. orientalis are capable of protecting mice against infection with scrub typhus. White rats are the animals of choice for the preparation of vaccines by the method described.

Serological relationship of trachoma, psittacosis and lymphogranuloma venereum viruses.

Summary Sera from patients with trachoma, psittacosis and lymphogranuloma venereum were tested in the complement fixation test with both “purified” elementary body antigens and boiled phenolized group antigens made with each of the 3 viruses. Group antigen prepared with trachoma virus reacted similarly to group antigens made with psittacosis and lymphogranuloma venereum viruses. The trachoma elementary body antigen reacted only with sera from trachoma patients. Psittacosis and lymphogranuloma venereum elementary body antigens failed to react with trachoma serum but did react about equally with sera from both psittacosis and lymphogranuloma venereum patients. It is concluded that trachoma virus contains the group antigen of the P-LV group and in addition a specific antigen which permits its serologic differentiation from the agents of psittacosis and lymphogranuloma venereum.

A toxic substance associated with the Gilliam strain of R. orientalis.

Conclusion Yolk sacs of embryonated eggs infected with the Gilliam strain of R. orientalis contain a specific toxin lethal for mice. The toxic substance is readily neutralized by Gilliam antiserum, but antisera against 8 other strains of R. orientalis contain only small amounts of antitoxin or none.

Growth Inhibitor in Liver Tissue

Liver has been known for a long time to contain substances which inhibit growth and migration of cells from explants. Walton 1 observed that extracts of liver had an inhibiting effect on tissue cultures, in contrast to all other tissue extracts tried. Lynch 2 and Lewis 3 noticed that no cells migrate from cultures of chick embryo liver after the sixteenth day, and it has been suggested that the inhibitor in liver may be responsible for this effect. Despite the great amount of work that has been done on extracts and substances which increase growth of tissues in vitro or make possible their prolonged cultivation, relatively little attention has been paid to inhibitors. The following is a report of investigations made in this laboratory on the inhibiting power of liver extract. We have used, in general, first explants of embryonic and sarcomatous tissues, grown by the usual coverslip or Carrel flask techniques in solid plasma media. In order to get a quantitative measure of inhibition, we have compared the average radial growth in a test solution at a given time with that in a control medium consisting of plasma and Tyrodes solution, using tissues explanted at the same time from the same embryonic organ. Of course, Parker 4 has shown that the growth rates of fibroblasts from different parts of the same organ may vary; we have found, however, that by using series of 5 or more explants a growth index can be obtained which does not vary more than 10 or 15% from series to series, or from day to day in the same series.