Inhibition of TnA translocation by TnA.

Plasmids already containing TnA showed decreased susceptibility to the translocation of a further TnA unit when compared with related plasmids that did not contain TnA. The translocation immunity imposed by TnA is exerted only on the plasmid of which it is part. It is suggested that this desensitization by a translocation unit is a general phenomenon that reduces the mutational effects of translocation.     

Persistence and spread of a chloramphenicol resistance-mediating plasmid in antigenic types of Escherichia coli, pathogenic for piglets

All chloramphenicol-resistant Escherichia coli strains isolated from piglets in the State veterinary Serum Laboratory, Copenhagen, in 1974-1975 harbored plasmids of IncFII group with largely the same resistance markers. Two strains from 1978 carried plasmids with similar characters. Restriction enzyme analysis of DNA from these plasmids with restriction endonucleases EcoRI, BglII, and PstI shows that the Cm plasmids are extremely closely related; but the patterns obtained (particularly from PstI digests) enable the classification of the plasmids into groups. These bear a strong relation to time and place of isolation so that plasmids isolated on the same farm belong to the same group even when their host strains are of different antigenic types. It is concluded that these plasmids have evolved from a single plasmid.     

Oxytocin-induced parturition in copper-deficient guinea pigs.

Dietary copper-deficient guinea pig dams (0.8 microgram Cu/g diet) were administered oxytocin to induce delivery of pups, whereas dietary copper-sufficient guinea pig dams (5.8 micrograms Cu/g diet) had uneventful deliveries with 79% surviving pups. The copper-deficient dams carried the fully-formed fetuses to term but did not go into labor unless 0.5 to 6.2 U oxytocin was administered (i.m.). Birth of live pups from copper-deficient dams increased from 28% overall, to 50% if oxytocin was administered in a timely manner. Many pups died of internal hemorrhages probably the result of defective connective tissue crosslinks requiring copper as a co-factor for lysyl oxidase activity. Dietary copper deficiency may be a factor in depressed parturition in the copper-deficient guinea pig dam that responds to administration of exogenous oxytocin for delivery of pups.     

Low concentrations of dimethyl sulphoxide accelerate conjugation and incorporation of glycine and glucosamine intetrahymena

Summary Dimethyl sulphoxide at relatively low comentrations, 0.01 to 1 mM, enhanced the conjugation and cell-to-cell adhesion of complementary strains of matingTetrahymena thermophila. The time required to form stable conjugates was reduced by dimethyl sulphoxide. This chemical stimulated the uptake of glycine and glucosamine from the suspending media. Incorporation of 2-¹⁴C-glycine and 6-³H-D-glucosamine into protein and glycoprotein was enhanced in whole cells, surface membrane and cilia. Incorporation of glucosamine into the microsomal fraction was increased in the dimethyl sulphoxidetreated cells while there was little change in glycine incorporation. There were no detectable changes in glycine and glucosamine incorporation into the nuclear fractions isolated from conjugatingTetrahymena exposed to dimethyl sulphoxide.     

Esterase 6 of Drosophila melanogaster: Kinetics of transfer to females,decay in females and male recovery

Esterase 6 (E.C. 3.1.1.1) is an enzyme in the reproductive system of Drosophila melanogaster and is transferred from males to females at mating. This enzyme is conveyed during the first 3 min of a copulation lasting approximately 20 min and remains active in the female reproductive tract for 1–2 hr after mating. Males require 24–48 hr to recover premating levels of esterase 6 activity. These results suggest that the effect of esterase 6 on the rate of sperm loss in females, which extends to 4 days after mating, is indirect since activity in the female falls rapidly after insemination. It is suggested that esterase 6 may also be a part of a pheromone system which influences female reproductive behaviour.     

Control of Cell Elongation in Nitella by Endogenous Cell Wall pH Gradients: MULTIAXIAL EXTENSIBILITY AND GROWTH STUDIES

The multiaxial stress of turgor pressure was stimulated in vitro by inflating isolated Nitella cell walls with mercury. The initial in vitro extension at pH 6.5, 5 atmospheres pressure, returned the wall approximately to the in vivo stressed length, and did not induce any additional extension during a 15-minute period. Upon release of pressure, a plastic deformation was observed which did not correlate with cell growth rates until the final stages of cell maturation. Since wall plasticity does not correlate with growth rate, a metabolic factor(s) is implicated. Walls at all stages of development exhibited a primary yield stress between 0 and 2 atmospheres, while rapidly growing cells (1-3% per hour) exhibited a secondary yield stress of 4 to 5 atmospheres. The creep rate and plastic deformation of young walls were markedly enhanced by acid buffers (10 millimolar, pH ≤ 5.3).