THE EFFECT OF GROWTH ILLUMINATION ON THE PIGMENTATION OF A MARINE DINOFLAGELLATE12

Amphidinium klebsii cultures grown under different light intensities exhibited similar chlorophyll a content per cell. Among the accessory pigments, chlorophyll c concentration decreased slightly in cells exposed to increasing light intensities up to 0.129 ly/min. The concentration of the 2 major xanthophylls present in A. klebsii cells–peridinin and diadinoxanthin–however, varied according to the light background of the cells. Some biochemical pathways in the formation of peridinin in dinoflagellates are discussed.     

2-Deoxy-D-galactose metabolism in ascites hepatoma cells results in phosphate trapping and glycolysis inhibition.

The metabolism of 2-deoxy-D-galactose has been studied in AS-30D rat ascites hepatoma cells in suspension. Using 2-deoxy-D-(1-14C)galactose and an alkaline ethanol deproteinization procedure, the quantitatively identified metabolites included 2-deoxy-D-galactose 1-phosphate comprising 99.3%, and UDP-2-deoxy-D-galactose and UDP-2-deoxy-D-glucose, together amounting to 0.4% of the total metabolites. After incubation for 5 h in the presence of 2-deoxy-D-galactose (1 mmo1/1), the content of 2-deoxy-D-galactose 1-phosphate reached 35 mmo1x(kg cells)-1. The rate of phosphorylation of 2-deoxy-D-galactose was rapid during the first 30 min and decreased to approximately 20% of this rate during the subsequent hours. The rapid trapping of Pi in the form of 2-deoxy-D-galactose 1-phosphate resulted in a depression of free intracellular Pi in spite of a concomitant increase in net 32Pi uptake from the medium and a decrease of ATP and other 5'-nucleotides. The rates of glucose utilization and lactate production were depressed by more than 80% in the presence of 2-deoxy-D-galactose (1 mmo1/1). Interruption of Pi trapping by removal of 2-deoxy-D-galactose from the medium reversed the depressions of Pi and ATP and resulted in a rapid but incomplete relief of glycolysis inhibition. Crossover analysis of glycolytic intermediates indicated an inhibition at the 6-phosphofructokinase step. The depression of glucose utilization may be mediated by the increased level of glucose 6-phosphate, a potent inhibitor of hexokinase. An additional inhibitory effect of a metabolite of 2-deoxy-D-galactose at the 6-phosphofructokinase step was indicated by crossover analysis after reversal of Pi and ATP depressions in the presence of a high intracellular content of 2-deoxy-D-glactose 1-phosphate. The quantitative analysis of the metabolites of 2-deoxy-D-galactose demonstrated the predominance of the monophosphate and the negligible formation of UPD derivatives of this sugar analog in AS-30D hepatoma cells. This provides a system for the investigation of a galactose analog as a phosphate-trapping agent in the virtual absence of uridylate trapping.     

Hydrocarbons obtained by pyrolysis of some precambrian rocks of minnesota

Drill core samples of 42 Precambrian sedimentary, igneous, and metamorphic rocks were analyzed by heating under partial vacuum at 100°C and at 400°C to release hydrocarbons and other volatile products.The core samples yielded methane in amounts ranging from traces to 3 microliters per gram, but averaged much less. By way of comparison, samples of Middle Devonian Marcellus black shale, from Pennsylvania, yielded methane in amounts up to 7ul/g.Other straight chain hydrocarbons up to C₁₁ were found in the volatile products, especially those obtained at 400°C, and benzene was a common product, also mainly in the 400°C experiments. Carbon dioxide and nitrogen appear to form a large part of the nonhydrocarbon volatiles in at least some of the samples.Spectral data indicate that the straight chain pyrolysis products of the Precambrian rocks are mainly alkenes, whereas those of the Devonian rocks, referred to above, are a mixture of alkanes and alkenes. Alkanes were however, obtained from several algae-bearing Middle Precambrian argillites. Available evidence indicates, although not conclusively, that the alkenes were contained in the rock rather than being produced from alkanes during pyrolysis.The writers believe that surface contamination in most of the drill cores was minimal owing to the low permeability of the rocks studied, and that contamination by drilling was also minimal.There is a reasonable possibility that the volatiles, if not formed from kerogen residues by the pyrolysis experiments, are in part juvenile igneous gases or are substances that were distilled out of the deeperlying rocks during intervals of folding and metamorphism, and subsequently accumulated at higher levels.     

Field studies on the population dynamics of Biomphalaria glabrata, intermediate host of Schistosoma mansoni on the West Indian Island of St. Lucia

Growth curves, calculated for field populations of B. glabrata, were not materially affected by habitat, altitude or season. A mean growth curve was therefore used to estimate the age-frequency distribution of snails in successive field samples. These data permitted the construction of ecological life tables and the estimation of r, the intrinsic rate of natural increase (or decrease) of the different populations. The calculated values of r were inserted in a simple model of unlimited population growth but the resultant curves poorly represented the observed data. A model for unlimited growth was more satisfactory for pond and marsh populations but, apparently, immigration made it less satisfactory for stream and banana drain populations. Nevertheless, r may still be of value in predicting repopulation rates in certain habitats after a mollusciciding which does not kill the entire snail population.