The roles of Groucho/Tle in left-right asymmetry and Kupffer's vesicle organogenesis

The heart is the first organ to form and function in the vertebrate embryo. Furthermore, differences between the left and right sides of the embryo become first detectable during cardiac development. We observed strong cardiac laterality phenotypes in medaka embryos by manipulating Groucho protein activity. The phenotypes produced by misexpressing Tle4 and the dominant-negative Aes reveal a general effect of these corepressor proteins on left-right (LR) development. With the help of an inducible expression system, we were able to define temporally different phases for these effects. In an early phase during gastrulation, Groucho proteins regulate Brachyury expression in the dorsal forerunner cells, which later gives rise to the Kupffer's vesicle (KV). The interference of endogenous Groucho proteins by misexpression of Aes leads to KVs of reduced size, whereas overexpression of Tle4 results in enlarged KVs. The expression level of the cilia marker Lrd was also affected both positively and negatively from these treatments. In the late phase during somitogenesis, Groucho proteins regulate the asymmetric activities of Nodal and Lefty genes. Altering canonical Wnt signaling produced similar results in late embryos, however, this did not affect KV morphogenesis or Lrd expression in early embryos. Therefore, changes in Kupffer's vesicle morphogenesis and the laterality of visceral organs following alterations in Groucho corepressor levels demonstrate two distinct phases in which Groucho proteins help establish LR asymmetry in medaka fish.     

Genetic differentiation and history of populations of the Italian treefrog Hyla intermedia: lack of concordance between mitochondrial and nuclear markers

The genetic differentiation among 33 populations of the Italian treefrog, Hyla intermedia (Anura: Hylidae), was investigated using both biparentally (23 allozyme loci) and maternally (partial mitochondrial cytochrome b gene) inherited markers. Two main population groups were evidenced by both markers, located north and south of the northern Apennines. However, the pattern of differentiation between these two groups was much less pronounced at allozymes than at mtDNA, leading to gene flow estimates that were 25 times lower at mitochondrial than at nuclear level. Also, the mtDNA divergence between the two groups was particularly marked for two cospecific lineages of anuran amphibians (the P-distance being on average 9.04%), while their average genetic distance at allozymes was comparatively low (D _NEI = 0.07). This contrasting pattern of nuclear versus mitochondrial genetic variation is discussed in the context of: (1) marker specific selection, (2) secondary contact and sex-biased gene flow and (3) ancestral polymorphism and colonization from north to south. Finally we emphasize how, for population genetic studies, the use of multiple markers having distinct evolutionary properties can help unravel the existence of more complex evolutionary histories.     

Food intake regulates oleoylethanolamide formation and degradation in the proximal small intestine

Oleoylethanolamide (OEA) is a lipid mediator that inhibits food intake by activating the nuclear receptor peroxisome proliferator-activated receptor-alpha. In the rodent small intestine OEA levels decrease during food deprivation and increase upon refeeding, suggesting that endogenous OEA may participate in the regulation of satiety. Here we show that feeding stimulates OEA mobilization in the mucosal layer of rat duodenum and jejunum but not in the serosal layer from the same intestinal segments in other sections of the gastrointestinal tract (stomach, ileum, colon) or in a broad series of internal organs and tissues (e.g. liver, brain, heart, plasma). Feeding also increases the levels of other unsaturated fatty acid ethanolamides (FAEs) (e.g. linoleoylethanolamide) without affecting those of saturated FAEs (e.g. palmitoylethanolamide). Feeding-induced OEA mobilization is accompanied by enhanced accumulation of OEA-generating N-acylphosphatidylethanolamines (NAPEs) increased activity and expression of the OEA-synthesizing enzyme NAPE-phospholipase D, and decreased activity and expression of the OEAdegrading enzyme fatty acid amide hydrolase. Immunostaining studies revealed that NAPE-phospholipase D and fatty acid amide hydrolase are expressed in intestinal enterocytes and lamina propria cells. Collectively, these results indicate that nutrient availability controls OEA mobilization in the mucosa of the proximal intestine through a concerted regulation of OEA biosynthesis and degradation.     

Acute beta-adrenergic overload produces myocyte damage through calcium leakage from the ryanodine receptor 2 but spares cardiac stem cells

A hyperadrenergic state is a seminal aspect of chronic heart failure. Also, "Takotsubo stress cardiomyopathy," is associated with increased plasma catecholamine levels. The mechanisms of myocyte damage secondary to excess catecholamine exposure as well as the consequence of this neurohumoral burst on cardiac stem cells (CSCs) are unknown. Cardiomyocytes and CSCs were exposed to high doses of isoproterenol (ISO), in vivo and in vitro. Male Wistar rats received a single injection of ISO (5 mg kg-1) and were sacrificed 1, 3, and 6 days later. In comparison with controls, LV function was impaired in rats 1 day after ISO and started to improve at 3 days. The fraction of dead myocytes peaked 1 day after ISO and decreased thereafter. ISO administration resulted in significant ryanodine receptor 2 (RyR2) hyperphosphorylation and RyR2-calstabin dissociation. JTV519, a RyR2 stabilizer, prevented the ISO-induced death of adult myocytes in vitro. In contrast, CSCs were resistant to the acute neurohumoral overload. Indeed, CSCs expressed a decreased and inverted complement of beta1/beta2-adrenoreceptors and absence of RyR2, which may explain their survival to ISO insult. Thus, a single injection of ISO causes diffuse myocyte death through Ca2+ leakage secondary to the acutely dysfunctional RyR2. CSCs are resistant to the noxious effects of an acute hyperadrenergic state and through their activation participate in the response to the ISO-induced myocardial injury. The latter could contribute to the ability of the myocardium to rapidly recover from acute hyperadrenergic damage.     

Anastrozole quantification in human plasma by high-performance liquid chromatography coupled to photospray tandem mass spectrometry applied to pharmacokinetic studies

A rapid, sensitive and specific method for quantifying the aromatase inhibitor (anastrozole) in human plasma using dexchlorpheniramine as the internal standard (I.S.) is described herein. The analyte and the I.S. were extracted from 200 microl of human plasma by liquid-liquid extraction using a mixture of diethyl ether:dichloromethane (70:30, v/v) solution. Extracts were removed and dried in the organic phase then reconstituted with 200 microl of acetonitrile:water (50:50; v/v). The extracts were analyzed by high performance liquid chromatography coupled with photospray tandem mass spectrometry (HPLC-MS-MS). Chromatography was performed isocratically on a Genesis, C18 4 microm analytical column (100 mm x 2.1mm i.d.). The method had a chromatographic run time of 2.5 min and a linear calibration curve ranging from 0.05-10 ng ml(-1). The limit of quantification (LOQ) was 0.05 ng ml(-1). This HPLC-MS-MS procedure was used to assess pharmacokinetic studies.     

Expression of marker genes during early ear development in medaka

Induction of the otic placode involves a number of regulatory interactions. Early studies revealed that the induction of this program is initiated by instructive signals from the mesendoderm as well as from the adjacent hindbrain. Further investigations on the molecular level identified in zebrafish Fgf3, Fgf8, Foxi1, Pax8, Dlx3b and Dlx4b genes as key players during the induction phase. Thereafter an increasing number of genes participates in the regulatory interactions finally resulting in a highly structured sensory organ. Based on data from zebrafish we selected medaka genes with presumptive functions during early ear development for an expression analysis. In addition we isolated Foxi1 and Dlx3b gene fragments from embryonic cDNA. Altogether we screened the spatio-temporal distribution of more than 20 representative marker genes for otic development in medaka embryos, with special emphasis on the early phases. Whereas the spatial distribution of these genes is largely conserved between medaka and zebrafish, our comparative analysis revealed several differences, in particular for the timing of expression.     

Inundation,Hydrodynamics and Vegetation Influence Carbon Dioxide Concentrations in Amazon Floodplain Lakes

Ecosystems - Extensive floodplains and numerous lakes in the Amazon basin are well suited to examine the role of floodable lands within the context of the sources and processing of carbon within...     

Meta-analysis Reveals Different Competition Effects on Tree Growth Resistance and Resilience to Drought

Ecosystems - Drought will increasingly threaten forest ecosystems worldwide. Understanding how competition influences tree growth response to drought is essential for forest management aiming at...     

Warming and water deficit impact leaf photosynthesis and decrease forage quality and digestibility of a C4 tropical grass

Global warming is predicted to cause more intense extreme events such as heat waves, flooding and severe droughts, producing significant effects on agriculture. In tropics, climate change will severely impact livestock production affecting water availability, forage quality and food for cattle. We investigated the isolated and combined effects of soil water deficit (wS) and + 2°C increase in canopy temperature (eT) on leaf gas exchange, chlorophyll fluorescence, carbohydrate content, forage quality and in vitro dry matter digestibility (IVDMD) of a field‐grown C4 tropical forage grass Panicum maximum Jacq. using a temperature‐free air‐controlled enhancement (T‐FACE) system. The wS and eT treatments showed no effects on photosystem II photochemistry. However, wS under ambient temperature decreased net photosynthesis rate (A), stomatal conductance (g_s) and maximum rate of carboxylation of Rubisco (V_cmax), leading to a reduced starch content in leaves. A 16% reduction in leaf dry mass (LDM) and reduction in forage quality by increasing fibers, reducing crude protein (CP) and decreasing the IVDMD was also observed by effect of wS. Warming under adequate soil moisture (eT) significantly increased LDM by 25% but reduced the forage quality, increasing the lignin content and reducing starch, CP and digestibility. The combined wSeT treatment reduced A, g_s, V_cmax and the forage quality. When compared to control, the lignin content in leaves increased by 43, 28 and 17% in wS, eT and wSeT, respectively, causing a significant reduction in IVDMD. We concluded that despite physiological mechanisms to acclimate to warming, both warming and water deficit will impair the quality and digestibility of C4 tropical pastures.