Mutagens in the feces of 3 South-African populations at different levels of risk for colon cancer.

The incidence of mutagens in the feces of 3 South-African populations at different risk levels for colon cancer has been determined. Lyophilized fecal samples were extracted with ether and the mutagenicity of the extracts determined using the Salmonella/mammalian microsome mutagenicity test. 19% of the samples from urban white South-Africans, a population at a high risk for colon cancer, were mutagenic using Salmonella typhimurium strain TA100. This incidence was significantly greater (p less than 0.001) than the incidence of mutagen excretion in the low-risk populations of urban blacks (2%) and rural blacks (0%). This pattern was also obtained using Salmonella typhimurium strain TA98. The incidence of mutagen excretion for urban whites was 10%, as compared to 5% and 2% for urban and rural blacks, respectively.     

Durvilldiol and durvillonol: Structure and occurrence

The triterpenoids durvilldiol and durvillonol, isolated in earlier studies from the lichen Pseudocyphellaria berberina, syn. P. durvillei, are identified as stictane-3β,22α-diol and 22α-hydroxystictan-3-one respectively.     

Transport of 5-hydroxytryptamine by dense granules from porcine platelets

A method is described for the isolation of a homogeneous preparation of dense granules from procine platelets. The purified dense granule fraction contained approximately 400 nmol of 5-hydroxytryptamine/mg of protein and appeared to be homogeneous when examined by electron microscopy. Isolated dense granules transport exogenously added 5-hydroxytryptamine via two mechanisms: 1) a carrier-mediated process predominating at low substrate concentrations and 2) a diffusion-controlled process predominating at high substrate concentrations. Temperature studies revealed an apparent energy of activation of 14.9 kcal/mol for the carrier-mediated transport. Kinetic data yielded a Km of 3.3 micron and a Vmax of 0.79 nmol/min/mg of protein for the mediated transport process. Steady state uptake was sensitive to changes in medium osmotic pressure and a decline in uptake below 300 mosM was correlated with release of endogenous 5-hydroxytryptamine. The transport was inhibited by a number of structural analogs of 5-hydroxytryptamine. These results demonstrate the existence of a carrier-mediated transport system for 5-hydroxytryptamine in the membranes of the platelet dense granules.     

Expression of alpha-lactalbumin, alpha-S1-casein, and lactoferrin genes is heterogeneous in sheep and cattle mammary tissue.

We used 35S-labeled cRNA probes to localize the sites of alpha-lactalbumin, alpha-S1-casein, and lactoferrin mRNA synthesis in sheep and forcibly weaned cattle mammary tissue. Expression of alpha-lactalbumin was absent in three of four "virgin" glands studied, present in some alveoli of "pregnant" glands but not in others, despite a similar histological appearance. In the early lactating gland, expression was high in those alveoli with few fat globules in their cells and lumen and was absent in alveoli with abundant fat globules. These observations suggest either that alpha-lactalbumin gene expression is linked to the long-term secretory activity of cells and falls once cells are resting or regressing, or that there are cyclical variations in expression, or that in the lactating gland some groups of epithelial cells are synthesizing alpha-lactalbumin and some are synthesizing fat. Expression patterns of alpha-S1-casein were similar to those of alpha-lactalbumin. Lactoferrin, in contrast, was expressed almost exclusively in the "fatty alveoli" of both species. Our results show that dramatic variations in milk gene expression can occur throughout the mammary gland of sheep and cattle and that at no stage of pregnancy, lactation, or involution can the gland be considered metabolically homogeneous.     

Effects of growth temperature on transport and membrane viscosity in Streptococcus faecalis

A shift in the growth temperature of Streptococcus faecalis from 37 to 10°C resulted in an 18% increase in the proportion of unsaturated fatty acids. Electron spin resonance spectra of spin-labeled membranes and extracted phospholipids indicated viscosity changes consistent with the alterations in fatty acid composition. Growth temperature had no significant effect on the active transport of leucine and alanine; uptake rates assayed at 10 or 35°C were essentially the same in cells grown at either 10 or 37°C. The relative rapidity of amino acid transport, which presumably contributes to the ability of S. faecalis to thrive in cold environments, is evidently unrelated to adaptive changes in the viscosity of membrane lipids.Abbreviations doxyl 4-4-dimethyloxazolidine-N-oxyl - proxyl 2,2-disubstituted 5,5-dimethylpyrrolidine-N-oxyl     

Depsidone constituents from the quintaria group of Nephroma species

A new lichen depsidone was isolated, in the form of its triacetate derivative from the acetylated extracts of Nephroma antarcticum and has been demonstrated to be hypoconstictic acid-triacetate. Two related depsidones, hypostictic acid hyposalazinic acid, were isolated from N. australe.     

Some redox properties of myohemerythrin from retractor muscle of Themiste zostericola

Distinct semimetmyohemerythrin species are produced by one-electron oxidation of deoxymyohemerythrin and one-electron reduction of metmyohemerythrin. The former, (semimetmyo)o, changes (greater than or equal to 90%) to the latter, (semimetmyo)R, with k = 1.0 x 10(-2) s-1, delta H = 15.1 kcal mol-1 and delta S = -17 eu. Oxidation of (semimetmyo)o by Fe(CN)6(3)- rapidly produces an unstable metmyohemerythrin form which converts to the final metmyohemerythrin with k = 4.6 x 10(-3) s-1, delta H = 16.8 kcal mol-1, and delta S = -13 eu. The two met forms react at the same rate with N3-, but the unstable form reacts very rapidly with S2O4(2-) in contrast to stable metmyohemerythrin. (Semimetmyo)R or a mixture of metmyohemerythrin and deoxymyohemerythrin equilibrate very slowly to a mixture containing all three species. The rate constants for disproportionation and comproportionation are 0.89 M-1 s-1 and 9.4 M-1 s-1, respectively. EPR spectra near liquid He temperatures and optical absorption spectra have been used to characterize and measure the rates at 25 degrees C, pH 8.2, and I = 0.15 M. The comparative behavior of octameric and monomeric protein is discussed.     

Specimen housing unit for cinemicrographic studies in the vertical plane.

The destructive action of chlorine on the pathogenic Naegleria fowleri and Acanthamoeba culbertsoni, the nonpathogenic N. gruberi, and an avirulent Acanthamoeba isolate was investigated. N fowleri is somewhat more sensitive to chlorine than N. gruberi, whereas the two Acanthamoeba strains are very resistant. This study yields information needed for the destruction of amoebic cysts in drinking water and swimming pools. It also gives some explanation for the occurence of Acanthamoeba strains in these waters.