In vitro drug resistance of salmonellae in Singapore

Strains of Salmonella typhi isolated in Singapore were susceptible to chloramphenicol (except from two imported cases) and most of them also generally susceptible to ampicillin and septrin. Drug-resistant strains of Salmonella typhimurium appeared in 1971 and caused out-breaks among young children. However, decreasing drug-resistance of S. typhimurium was recorded in recent years following a drop in the number of cases. Other Salmonella serovers were found relatively susceptible to the antibiotics tested.

Multiple myeloma with cutaneous involvement

A 49-year-old man with multiple myeloma, IgA type, contracted cutaneous plasmocytomas. No deposits of immunoglobulin were found in the cutaneous tumor by direct immunofluorescence. The case is an unusual manifestation occurring in multiple myeloma.

Retention of antimelanoma effect of polyinosinic-polycytidylic acid in neonatally thymectomized, irradiated, leukopenic mice

Polyinosinic-polycytidylic acid (PIC), a synthetic polyribonucleotide, inhibits the growth of B16 malignant melanoma in C57BL/6 mice. Since PIC has been reported to augment immune responses, we tested the hypothesis that the antitumor effect of PIC against B16 melanoma is via immune stimulation. Mice were neonatally thymectomized or neonatally thymectomized and subsequently irradiated to suppress their immune reactivity. In such animals PIC retained its ability to inhibit the growth of B16 melanoma, in the face of profound leukopenia and lymphopenia, suggesting that its antimelanoma effect is probably not mediated by augmentation of the host's immune antitumor response.

The distribution of crossovers along unreplicated lambda bacteriophage chromosomes

The distribution of crossovers along unreplicated chromosomes of bacteriophage lambda has been examined by determining the density distributions and genotypes of particles in the progenies of crosses of density-labeled by ordinary parents in the presence of genetic blocks to replication. The Red and Rec systems combined produce crossovers primarily near the ends (especially the right end) of the chromosome. Removal of the generalized lambda recombination functions by red and gam mutations results in loss of these terminal crossovers; coupled with this loss is a disappearance of the differential dependence of recombination frequencies in terminal and central intervals on DNA synthesis. Removal of the bacterial system by a recA mutation results in severe depression of crossing over among unreplicated phage, with the few recombinants produced by the lambda system occurring near the right end.