Near ultraviolet light inactivation of dihydroxyacid dehydratase in Escherichia coli

The effects of near ultraviolet (NUV) light on a NUV chromophore-containing oxidant-sensitive enzyme, dihydroxyacid dehydratase (DHAD), were measured in seven strains of Escherichia coli. The strains differed in production of the oxidant-defense enzymes, superoxide dismutases (Fe-SOD and Mn-SOD), and catalases HPI and HPII. With the stress of aerobic growth but without NUV exposure, the strains lacking either Fe or Mn SOD or both SODs had 57%, 25%, and 12%, respectively, of the DHAD-specific activity of the parent (K12) strain. Under the same conditions, the catalase strains that were wild type, overproducing, and deficient had comparable DHAD-specific activities. When aerobic cultures were exposed for 30 min to NUV with a fluence of 216 J/m²/s at 310–400 nm, the percentage decreases in DHAD-specific activities were similar (ranging from 75% to 89%) in strains with none, either, or both SODs missing, and in the catalase-overproducing strain. However, the decreases were only 58% and 52% in the strain with catalase missing and in its parent, respectively. The NUV-induced loss of DHAD enzyme activity was not accompanied by any detectable loss of the DHAD protein as measured by polyclonal antibody to DHAD.     

Cloning and restriction fragment length polymorphism analysis of a cDNA for swine PIT-1, a gene controlling growth hormone expression*

A partial swine cDNA which encodes the functional domain of PIT-1 was isolated by the polymerse chain reaction (PCR). The swine PIT-1 cDNA clone is 95% identical at the protein level to the rat Pit-1 gene. Thus, Pit-l's known function in control of rat growth hormone and prolactin expression is likely to be conserved in swine. This swine cDNA clone was used to investigate genetic variability at PIT-1 in several American and Chinese breeds. Polymorphic BamIII fragments were found in pure-bred Meishan animals (n= 13), but only monomorphic fragments in five American breeds (n= 36).     

Shallow water rissoiform gastropods from Tristan da Cunha, South Atlantic Ocean, with records of species from Gough Island

Shallow water rissoiform gastropods collected by the Norwegian Scientific Expedition (1937-1938) to Tristan da Cunha are described. The fauna consists of Powellisefia cf. philomelae (Watson) (Rissoidae), three new species of Eatoniella, E. trochiformisa, E. lineuta , and E. tristanensis (Eatoniellidae). two new species of Onoba, O. crassicordara and O. tristanensis (Rissoidae) and Rissoella cf. irma (Bartsch) (Rissoellidae). A small collection from Cough Island is also described, containing three species referred to Onoha , one of which is described as new. O. merelinoides , and a species of Eutoniella. The biogeographie relationships of the fauna are briefly discussed.     

Alterations in the hepatic enzymes following experimental lead poisoning

An investigation on the influence of lead toxicity on some of the hepatic enzymes was studied in rats both after a shorter interval of 15 d and after longer intervals of 60 and 90 d. Three different doses of lead as 5, 10, and 50 mg/kg body wt were administered orally on every alternate day. Whereas significant inhibition of succinic dehydrogenase was seen following lead poisoning, the activity acid and alkaline phosphatase increased with lead intoxication. The histoarchitecture of the liver was grossly intact. Liver accumulated less lead compared to kidney at 60 and 90 d.     

Isolation of nitrogen deregulated mutants of erythromycin biosynthesis

Summary Ammonium represses erythromycin synthesis bySaccharopolyspora erythraea and insensitive mutants to this effect were isolated. Six mutants were selected and one of them produces 50% more antibiotic than the wild type in 100 mM NH₄Cl as nitrogen source. Glutamine synthetase and alanine dehydrogenase levels in the mutants were determined and no differences with wild type strain were observed.