Effect of fasting and insulin on the glucagon-induced orthophosphate incorporation to the isolated perfused rat liver.

Isolated perfused fed rat livers spontaneously liberated glucose and orthophosphate to the medium; 24-hr fasted rat livers did not exhibit these phenomena. In perfused fed rat livers, glucagon (2 mug) increased glucose output and promoted orthophosphate incorporation. In perfused fed rat livers, insulin (250 or 500 mU) inhibited the spontaneous liberation of glucose and orthophosphate. Comparable doses of insulin significantly reduced the glucagon (2 mug)-induced increase in glucose output from perfused fed rat liver, but did not affect orthophosphate uptake by the organ.     

Determination of intermediary metabolites in yeast. Critical examination of the effect of sampling conditions and recommendations for obtaining true levels

Summary The effect of sampling conditions on the levels of adenine nucleotides, pyridine nucleotides, glycolytic intermediates and related metabolites in yeast has been studied. A systematic examination of the conditions for harvesting has shown that it can be best accomplished by rapid filtration. Delays in the handling for removal of the medium, as is usual in the process of obtaining a number of data reported in the literature, lead to important changes in some of the metabolites examined. It is also shown that when a washing is imperative it can be carried out with a methanol-water mixture (50/50, v/v) cooled at –40° without loss of intracellular concentrations of non-readily diffusible metabolites.On the basis of this experience the outline of a generally applicable procedure is presented.     

Alcohol:NAD oxidoreductase in brain of rats from a colony fed dilute ethanol for many generations.

—Alcohol:NAD oxidoreductase (EC 1.1.1.1) was studied in brain cortex, hypothalamus, cerebellum and midbrain of adult and immature rats, and in the whole encephalon of neonatal rats. The rats used in this study were (i) from a colony which has been given 12% (v/v) aqueous ethanol as the only fluid for 54 generations (‘E.F.’ rats); (ii) rats removed from this colony after the forty-eighth generation and thereafter fed water instead of the alcohol solution (‘E.F./H₂O’ rats); and (iii) normal rats. Enzyme activity in the 20,000 g supernatant of tissue homogenates was measured by the method of Raskin and Sokoloff. Activity was found to be highest in neonatal rat brain and to decrease as the age increased. Activity in the hypothalamus of adult E.F. rats was significantly higher than that found in the same region of adult E.F./H₂O rats. Immature rat cerebellum alcohol:NAD oxidoreductase activity was higher both in ‘E.F.’ and ‘E.F./H₂O’ suggesting a possible genetic change be involved in this CNS region. It may be concluded that, with the exception of neonatal rats, ethanol consumption induces an increase in rat CNS alcohol :NAD oxidoreductase activity.     

Ecology,morphology and physiology of Chroothece richteriana (Rhodophyta,Stylonematophyceae) in the highly calcareous Río Chícamo,south-east Spain

The ecology of Chroothece was studied in the highly calcareous Río Chícamo, south-east Spain, in order to explain its success there, but rarity elsewhere. The river, which originates mainly from an underground aquifer, has water with high conductivity, sulphate and nitrate but low phosphate concentrations, the latter mainly organic. Chroothece occurs in mats and in lobed colonies reaching 4 cm in the broadest dimension. The colony surface consists of one layer of cells, each of which is attached to a stalk, which dichotomizes when the cell divides; stalks often extend to the colony base. The central region of many mat cells and almost all colony cells has a yellow to orange-brown colour, associated with the numerous lipid droplets densely covering the surface of the pyrenoid and arms of the star-shaped chloroplast. Field material and laboratory isolates indicate that stalk formation occurs under moderate P limitation and both stalks and cell sheath show high phosphatase activities. This also occurred in a culture collection strain maintained for 30 years in a very P-rich medium, but then transferred to a moderately P-limiting medium (c. 0.9 mg l^?1). We suggest that colony formation is initiated by aggregation of motile cells following P pulses in the water. Comparisons are made with Rivularia, a competitor in this nitrate-rich river, in spite of being a N₂-fixer. One difference is that Chroothece cells lie at the periphery of the colonies and are therefore exposed to maximum sunlight, whereas Rivularia trichomes grow inside colonies with photoprotection by scytonemin. However, the ability to withstand heavy grazing pressure may be an especially important factor favouring Rivularia here.     

Reconfiguration of a Multi-oscillator Network by Light in the Drosophila Circadian Clock

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Individual variability in tree allometry determines light resource allocation in forest ecosystems: a hierarchical Bayesian approach

Tree species differences in crown size and shape are often highlighted as key characteristics determining light interception strategies and successional dynamics. The phenotypic plasticity of species in response to light and space availability suggests that intraspecific variability can have potential consequences on light interception and community dynamics. Species crown size varies depending on site characteristics and other factors at the individual level which differ from competition for light and space. These factors, such as individual genetic characteristics, past disturbances or environmental micro-site effects, combine with competition-related phenotypic plasticity to determine the individual variability in crown size. Site and individual variability are typically ignored when considering crown size and light interception by trees, and residual variability is relegated to a residual error term, which is then ignored when studying ecological processes. In the present study, we structured and quantified variability at the species, site, and individual levels for three frequently used tree allometric relations using fixed and random effects in a hierarchical Bayesian framework. We focused on two species: Abies alba (silver fir) and Picea abies (Norway spruce) in nine forest stands of the western Alps. We demonstrated that species had different allometric relations from site to site and that individual variability accounted for a large part of the variation in allometric relations. Using a spatially explicit radiation transmission model on real stands, we showed that individual variability in tree allometry had a substantial impact on light resource allocation in the forest. Individual variability in tree allometry modulates species’ light-intercepting ability. It generates heterogeneous light conditions under the canopy, with high light micro-habitats that may promote the regeneration of light-demanding species and slow down successional dynamics.     

Lipid content and apoptosis of in vitro-produced bovine embryos as determinants of susceptibility to vitrification

The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition—Control; after 60 h—PES Day 2.5 of embryo culture; and after 96 h—PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification (Control: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts (Control: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification.