The contribution of endogenous and exogenous effects to radiation-induced damage in the bacterial spore

Radical scavengers such as polyethylene glycol 400 and 4000 and bovine albumin have been used to define the contribution of exogenous and endogenous effects to the gamma-radiation-induced damage in aqueous buffered suspensions of Bacillus pumilus spores. The results indicate that this damage in the bacterial spore is predominantly endogenous both in the presence of 1 atmosphere of oxygen, and in anoxia.     

Evaluation of dibromonitrosobenzene sulfonate as a spin trap in biological systems

In the present study dibromonitrosobenzene sulfonate (DBNBS) was examined for its suitability for spin trapping for ESR detection of superoxide radicals in biological systems. This nitroso spin trap recently has been reported to yield very persistent spin adducts with O2. as well as with various carbon-centered radicals. In the present work the possible toxicity of DBNBS, the partitioning of its spin adducts into cells, and the stability of the adducts and the parent compound inside cells were studied. No significant toxicity was found. In cellular systems, however, DBNBS did not produce detectable adducts with O2.; it also did not detectably trap superoxide generated in the xanthine/xanthine oxidase system. Both DBNBS and a DBNBS adduct performed extracellularly and then added to cell suspensions were rapidly metabolized by cells. Intracellular spin adducts were not detected under any condition. Evidently, in spite of its promising features, DBNBS will not be useful for spin trapping radicals in cellular systems or for detecting superoxide radicals in any biological system.     

Identification of nitroxide radioprotectors.

The nitroxide Tempol, a stable free radical, has recently been shown to protect mammalian cells against several forms of oxidative stress including radiation-induced cytotoxicity. To extend this observation, six additional water-soluble nitroxides with different structural features were evaluated for potential radioprotective properties using Chinese hamster V79 cells and clonogenic assays. Nitroxides (10 mM) were added 10 min prior to radiation exposure and full radiation dose-response curves were determined. In addition to Tempol, five of the six nitroxides afforded in vitro radioprotection. The best protectors were found to be the positively charged nitroxides, Tempamine and 3-aminomethyl-PROXYL, with protection factors of 2.3 and 2.4, respectively, compared with Tempol, which had a protection factor of 1.3. 3-Carboxy-PROXYL, a negatively charged nitroxide, provided minimal protection. DNA binding characteristics as studied by nonequilibrium dialysis of DNA with each of the nitroxides demonstrated that Tempamine and 3-amino-methyl-PROXYL bound more strongly to DNA than did Tempol. Since DNA is assumed to be the target of radiation-induced cytotoxicity, differences in protection may be explained by variabilities in affinity of the protector for the target. This study establishes nitroxides as a general class of new nonthiol radioprotectors and suggests other parameters that may be exploited to find even better nitroxide-induced radioprotection.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Dynamics of pH-induced spectral changes in bacteriorhodopsin.

The kinetics of the spectral shift induced in bacteriorhodopsin by low pH are investigated by using the rapid-mixing, stopped-flow technique. The generation of the acid form of the chromophore (A605) occurs in two distinct steps: a fast process (t1/2I = 21 +/- 4 ms) is followed by a much slower reaction (t1/2II = 6 +/- 2 s). The observations are interpreted in terms of neutralization of an acid group in the neighborhood of the retinyl chromophore, the double-staged kinetics being attributed to cooperative effects between chromophores. The method may serve as a tool for studying the kinetics of proton migration across the purple membrane.     

Biodiversity of 52 chicken populations assessed by microsatellite typing of DNA pools

In a project on the biodiversity of chickens funded by the European Commission (EC), eight laboratories collaborated to assess the genetic variation within and between 52 populations from a wide range of chicken types. Twenty-two di-nucleotide microsatellite markers were used to genotype DNA pools of 50 birds from each population. The polymorphism measures for the average, the least polymorphic population (inbred C line) and the most polymorphic population (Gallus gallus spadiceus) were, respectively, as follows: number of alleles per locus, per population: 3.5, 1.3 and 5.2; average gene diversity across markers: 0.47, 0.05 and 0.64; and proportion of polymorphic markers: 0.91, 0.25 and 1.0. These were in good agreement with the breeding history of the populations. For instance, unselected populations were found to be more polymorphic than selected breeds such as layers. Thus DNA pools are effective in the preliminary assessment of genetic variation of populations and markers. Mean genetic distance indicates the extent to which a given population shares its genetic diversity with that of the whole tested gene pool and is a useful criterion for conservation of diversity. The distribution of population-specific (private) alleles and the amount of genetic variation shared among populations supports the hypothesis that the red jungle fowl is the main progenitor of the domesticated chicken.