Selectivity in plant food consumption in the lizard Liolaemus lutzae from southeastern Brazil

Selectivity in the consumption of plant matter from the natural habitat by the tropidurid lizard Liolaemus lutzae, endemic to the beach habitats of restingas of southeastern Brazil, and the differences in the qualitative properties of the plants consumed were studied in the Barra de MaricÝ restinga, Rio de Janeiro State. The diets of 180 lizards were analysed and the plant species present in the stomachs and their frequencies were recorded. Only four of the 19 species which occur on the beach (Phylloxerus portulacoides, Althernantera maritima, Ipomoea littoralis and I. pes-caprae) were consumed by the lizard and their frequencies in the stomachs differed from that of occurrence. Analysis of the composition of the leaves of the 13 most abundant plant species indicated that the plants consumed by the lizards had the highest contents of water, total nitrogen, total sugar and the lowest amount of gross fibres. Thus, it appears that L. lutzae is not a generalist herbivore, but feeds selectively on those plants in its environment that are most easily digested and assimilated. A seletividade no consumo de algumas entre as espécies vegetais ocorrentes no habitat de praia pelo lagarto tropidur¡deo Liolaemus lutzae e, as diferenças nas propriedades qualitativas presentes nas plantas consumidas em relação às demais plantas mais abundantes do habitat foram estudada na restinga da Barra de Maricá, Sudeste do Brasil. A dieta de 180 lagartos foi analisada tendo sido anotadas as espécies de plantas presentes no estômago e suas respectivas frequências. Apenas quatro entre as 19 espécies registradas na praia (Phylloxerus portulacoides, Althernantera maritima, Ipomoea littoralis and I. pes-caprae) foram consumidas por L. lutzae. As frequências destas na dieta do lagarto diferiram da frequência com que as plantas ocorrem no habitat. A análise da composição das folhas de 13 entre as espécies de plantas mais frequentes indicou que as plantas consumidas pelo lagarto possuem as mais elevadas proporçôes de água, nitrogênio total, açúcar total e a menor proporção de fibras. Aparentemente L. lutzae não é um herbivoro generalista mas seleciona no seu ambiente as plantas as quais são mais facilmente digeridas e assimiladas.     

Role of Ca2+-activated K+ channel in regulation of NaCl reabsorption in thick ascending limb of Henle's loop

1. Reabsorption of NaCl in the thick ascending limb of Henle's loop involves the integrated function of the Na+,K+,Cl- -cotransport system and a Ca2+-activated K+ channel in the luminal membrane with the Na+,K+-pump and a net Cl- conductance in the basolateral membrane. 2. Assay of K+ channel activity after reconstitution into phospholipid vesicles shows that the K+ channel is stimulated by Ca2+ in physiological concentrations and that its activity is regulated by calmodulin and phosphorylation from cAMP dependent protein kinase. 3. For purification luminal plasma membrane vesicles are isolated and solubilized in CHAPS. K+ channel protein is isolated by affinity chromatography on calmodulin columns. The purified protein has high Ca2+-activated K+ channel activity after reconstitution into vesicles. 4. The purified K+ channel consists of two proteins of 51 and 36 kDa. Phosphorylation from cAMP dependent protein kinase stimulates K+ channel activity and labels the 51 kDa band. The 36 kDa band is rapidly cleaved by trypsin and may be involved in Ca2+ stimulation. 5. Opening of the K+ channel by Ca2+ in physiological concentrations and regulation by calmodulin and phosphorylation by protein kinase may mediate kinetic and hormonal regulation of NaCl transport across the tubule cells in TAL.     

Syrticola mediterraneus n. sp., a harpacticoid copepod from the Bay of Calvi,Corsica

Syrticola mediterraneus n. sp. belonging to the family Cylindropsyllidae Sars (sensu Lang, 1948) is described from the Bay of Calvi (Corsica). The species is closely related to (?) Notopontia galapagoensis Mielke, 1982 and Syrticola flandricus Willems & Claeys, 1982. The former species is now transferred to the genus Syrticola as Syrticola galapagoensis n. comb.     

Segregation of infectious pancreatic necrosis resistance QTL in the early life cycle of Atlantic Salmon (Salmo salar)

In a previous study, three significant quantitative trait loci (QTL) associated with resistance to Infectious Pancreatic Necrosis (IPN) disease were identified by analysing challenge data from one sub-population of Landcatch Atlantic salmon (Salmo salar) smolt. While these QTL were shown to affect the resistance in seawater, their effect in freshwater was unknown. This study investigates the effect of these QTL on IPN resistance in salmon fry in freshwater. Twenty families with intermediate levels of IPN mortality were analysed from a freshwater challenge trial undertaken on a different sup-population of LNS salmon to that studied previously. Only the QTL from linkage group 21 (LG21) appeared to have a significant and large effect on resistance in freshwater; the same QTL was found to have the largest effect in seawater in the previous study. Variance component analysis showed a high heritability for the QTL: 0.45 ± 0.07 on the liability scale and 0.25 ± 0.05 on the observed scale. In a family where both parents were segregating for the QTL, there was a 0% vs. 100% mortality in homozygous offspring for resistant and susceptible QTL alleles. The finding that the same QTL has major effect in both freshwater and seawater has important practical implications, as this will allow the improvement of resistance in both phases through marker assisted selection by targeting this QTL. Moreover, the segregation of the LG21 QTL in a different sub-population gives further evidence of its association with IPN-resistance.     

The mutagenicity of 5-azacytidine and other inhibitors of replicative DNA synthesis in the L5178Y mouse lymphoma cell

The mutagenic potential of the cytidine analog, 5-azacytidine (Aza Cyd), was tested at the thymidine kinase (TK) gene locus of L5178Y mouse lymphoma cells. 3-h exposure to as little as 20 ng/ml Aza Cyd yielded a substantial increase in TK-deficient L5178Y cells as measured by drug-induced resistance to trifluorothymidine (TFTres) 48 h later. This mutagenic effect was diminished up to 75% when Aza Cyd was tested in the presence of either enzymatically active or heat-denatured 9000 X g supernatant prepared from rat liver homogenate. The mutagenicity of Aza Cyd was also decreased in the presence of 1-5 X 10(-3) M thymidine and eliminated in the presence of greater than 1 X 10(-5) M cytidine. Two L5178Y TK-deficient cell lines had no selective survival advantage compared to TK-competent L5178Y cell stock when plated in soft-agar medium that contained Aza Cyd. Four other specific inhibitors of scheduled DNA synthesis in mammalian cells, deoxyadenosine, aphidicolin, 1-beta-D-arabinofuranosylcytosine, and hydroxyurea were also L5178Y/TK mutagens. These data along with other published results suggest that chemicals known to disrupt nucleotide biosynthesis, alter deoxyribonucleotide pools, or directly inhibit DNA polymerase can cause stable, heritable increases in TFT resistance through mechanisms dependent upon altered replicative DNA synthesis, yet not necessarily dependent upon DNA incorporation or the binding of these mutagenic agents to nuclear DNA.     

The effect of temperature on the kinetics of ethanol production by a thermotolerant strain of Kluveromyces marxianus

Summary The batch fermentation kinetics of a novel thermotolerant strain of the yeast Kluveromyces marxianus were evaluated between 30°C and 48°C. The most significant effects of elevated temperature were reductions in overall biomass and ethanol yields. Decreases in the concentration of ethanol attained, and the presence of unutilized substrate suggested increased ethanol inhibition at the higher temperatures studied.     

On the relationship between rate of ATP synthesis and H+ electrochemical gradient in rat-liver mitochondria

The relationship between rate of ATP synthesis, JATP, and value of the proton electrochemical gradient, delta mu H, has been analyzed in intact mitochondria. Onset of phosphorylation causes a depression of delta mu H of 1.5 kJ/mol. There is a close parallelism between inhibition of JATP and restoration of delta mu H to its state-4 value during titrations with oligomycin or atractyloside. Titrations with ionophores display the following features: (a) delta mu H can be depressed by 3-4 kJ/mol by valinomycin + K+ without affecting the rate of ATP synthesis; (b) uncouplers abolish JATP completely while depressing delta mu H by 3 kJ/mol; (c) complete abolition of ATP synthesis by inhibitors of electron transport is accompanied by a depression of delta mu H of only 1 kJ/mol. The results indicate that: (a) there is a close functional relationship between redox and ATPase H+ pumps, whereby inhibition of electron transfer is accompanied by simultaneous inhibition of the ATPase H+ pumps; and (b) uncoupling of oxidative phosphorylation is not due to depression of delta mu H per se. The consistence of the present data with either a chemiosmotic model where delta mu H is the sole and obligatory intermediate for energy coupling, or models where there is a direct transfer of energy between the two pumps is discussed.