Indirect ultraviolet-reactivation of phage lambda

When an F(-) recipient Escherichia coli K12 bacterium receives Hfr or F-lac(+) DNA from an ultraviolet-irradiated donor, its capacity to promote DNA repair and mutagenesis of ultraviolet-damaged phage lambda is substantially increased. We call this phenomenon indirect ultraviolet-reactivation, since its features are essentially the same as those of ultraviolet-reactivation; this repair process occurs in pyrimidine dimer excision-deficient strains and produces clear plaque mutations of the restored phage. Moreover, this process is similar to indirect ultraviolet-induction of prophage lambda, since it is promoted by conjugation. However, contrarily to indirect induction, it is produced by Hfr donors and occurs in recipients restricting the incoming ultraviolet-damaged donor DNA. The occurrence of indirect ultraviolet-reactivation provides evidence for the existence in E. coli of an inducible error-prone mechanism for the repair of DNA.

Increased growth hormone in partial and total lipoatrophy

Since some clinical and metabolic features of lipoatrophy suggest increased human growth hormone (HGH) activity, we studied HGH responses in five patients with partial or total lipoatrophy. Two patients with total lipoatrophy had elevated basal levels of HGH of 80 and 25 ng. per milliliter, while two with partial lipoatrophy had abnormally high levels after arginine stimulation. The elevated levels seemed to correlate with the clinical activity of the disease. In one of the patients there was a slowing of the growth rate and a moderate weight gain after long-term chlorpromazine therapy decreased HGH levels; a comparison of the immunoreactive HGH in her serum with that from a normal patient by serial dilution technics suggested that the two were immunologically identical, and chromatographic mobilities were also identical. Oral glucose suppressed elevated HGH in all of the patients. These studies suggest that HGH levels are elevated intermittently in lipoatrophic patients and that the increase may contribute to some features of the disease.