On the description of Tisochrysis lutea gen. nov. sp. nov. and Isochrysis nuda sp. nov. in the Isochrysidales, and the transfer of Dicrateria to the Prymnesiales (Haptophyta)

The Isochrysidaceae is a family of non-calcifying organisms within the haptophyte order Isochrysidales. Isochrysis galbana, a species widely used as a food source in aquaculture, is the best-known representative of this family that contains three genera but only six described species. We sequenced partial nuclear small subunit (SSU) and large subunit rDNA and mitochondrial cytochrome oxidase 1 genes of 34 isochrysidacean culture strains (including authentic strains when available) and compared molecular phylogenetic inferences with cytological and ultrastructural observations. The isochrysidaceaen culture strain Isochrysis affinis galbana (Tahiti isolate), widely used in aquaculture and commonly known as T-Iso, is clearly genetically distinct from Isochrysis galbana, despite seemingly being morphologically identical. A strain with a similar ultrastructure to that of Isochrysis galbana except for the lack of body scales had sequences that were more similar to but still distinct from those of Isochrysis galbana. Dicrateria inornata, a species that lacks body scales, is classified within the Isochrysidaceae, but the SSU rDNA sequence of the authentic strain of this species matches that of Imantonia rotunda within another haptophye order, the Prymnesiales. D. inornata and Imantonia rotunda have similar ultrastructure except for the respective absence/presence of scales. These results lead us to propose the erection of one new genus (Tisochrysis gen. nov.) and two new species (Tisochrysis lutea sp. nov. and Isochrysis nuda sp. nov.). D. inornata is reclassified within the Prymnesiales, and Imantonia rotunda is transferred to this genus (Dicrateria rotunda comb. nov.).     

TEP/IRM hybride en neuro-imagerie

The hybrid Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) is a newly available imaging modality combining the molecular and metabolic PET information with the morphological and functional data provided by MRI. Integrated PET/MRI tomographs were conceived in analogy to the current PET/Computed Tomography (PET/CT) technology, with specific properties linked to the intrinsic differences of MRI and CT imaging. In the field of neuro-imaging, in particular, MRI provides a larger panel of information, as compared with CT, and is already systematically fused and used as a support for PET images for diagnostic and research purposes. We summarize here our current experience with the first integrated PET/MRI tomograph installed in Switzerland, concerning specifically three clinical applications: brain tumors characterization, the diagnosis of neurodegenerative dementias and the presurgical evaluation of pharmaco-resistant epilepsy. With this sequential tomograph, we could combine the full range of diagnostic MR sequences (including diffusion tensor imaging, tractography, spectroscopy, functional MR) with PET imaging of brain glucose metabolism (by ¹⁸F-Fluorodeoxyglucose–FDG) and of amino acid transport (by ¹⁸F-Fluoroethyltyrosine–FET). We also summarize the main results obtained in neuro-imaging by the different groups working with these new hybrid tomographs. These data show that PET/MRI, acquired in a single imaging session, may represent the modality of choice for neuro-imaging.     

The complex history of the olive tree: from Late Quaternary diversification of Mediterranean lineages to primary domestication in the northern Levant

The location and timing of domestication of the olive tree, a key crop in Early Mediterranean societies, remain hotly debated. Here, we unravel the history of wild olives (oleasters), and then infer the primary origins of the domesticated olive. Phylogeography and Bayesian molecular dating analyses based on plastid genome profiling of 1263 oleasters and 534 cultivated genotypes reveal three main lineages of pre-Quaternary origin. Regional hotspots of plastid diversity, species distribution modelling and macrofossils support the existence of three long-term refugia; namely the Near East (including Cyprus), the Aegean area and the Strait of Gibraltar. These ancestral wild gene pools have provided the essential foundations for cultivated olive breeding. Comparison of the geographical pattern of plastid diversity between wild and cultivated olives indicates the cradle of first domestication in the northern Levant followed by dispersals across the Mediterranean basin in parallel with the expansion of civilizations and human exchanges in this part of the world.     

Where and why? Bees,snail shells and climate: Distribution of Rhodanthidium (Hymenoptera: Megachilidae) in the Iberian Peninsula

Species distribution patterns are widely studied through species distribution models (SDMs), focusing mostly on climatic variables. Joint species distribution models (JSDMs) allow inferring if other factors (biotic interactions, shared phylogenetic history or other unmeasured variables) can also have an influence on species distribution. We identified current distributional areas and optimal suitability areas of three species of the solitary snail‐shell bee Rhodanthidium (Hymenoptera: Megachilidae), and their host gastropod species in the Iberian Peninsula. We undertook SDMs using Maxent software, based on presence points and climatic variables. We also undertook JSDMs for the bees and the snails to infer if co‐occurrence could be a result of biotic interactions. We found that the three bee species: (1) use at least five different species of Mediterranean snails; (2) use empty shells not only for nesting but also for sheltering when there is adverse weather and during the night; (3) have their most suitable areas in the eastern and southern Iberian Peninsula, mostly on limestone areas; and (4) have their optimal range under Mediterranean climatic values for the studied variables. There is positive co‐occurrence of Rhodanthidium with the gastropod species, especially with the snail Sphincterochila candidissima. The contribution of the environmental component to the co‐occurrence is less than that of the residual component in those cases, suggesting that: (i) the use of biotic resources (between Rhodanthidium and the gastropod species); (ii) shared phylogenetic history (between R. septemdentatum and R. sticticum); or (iii) unmeasured variables are largely responsible for co‐occurrence.     

miR‐181a negatively modulates synaptic plasticity in hippocampal cultures and its inhibition rescues memory deficits in a mouse model of Alzheimer’s disease

MicroRNAs play a pivotal role in rapid, dynamic, and spatiotemporal modulation of synaptic functions. Among them, recent emerging evidence highlights that microRNA‐181a (miR‐181a) is particularly abundant in hippocampal neurons and controls the expression of key plasticity‐related proteins at synapses. We have previously demonstrated that miR‐181a was upregulated in the hippocampus of a mouse model of Alzheimer's disease (AD) and correlated with reduced levels of plasticity‐related proteins. Here, we further investigated the underlying mechanisms by which miR‐181a negatively modulated synaptic plasticity and memory. In primary hippocampal cultures, we found that an activity‐dependent upregulation of the microRNA‐regulating protein, translin, correlated with reduction of miR‐181a upon chemical long‐term potentiation (cLTP), which induced upregulation of GluA2, a predicted target for miR‐181a, and other plasticity‐related proteins. Additionally, Aβ treatment inhibited cLTP‐dependent induction of translin and subsequent reduction of miR‐181a, and cotreatment with miR‐181a antagomir effectively reversed the effects elicited by Aβ but did not rescue translin levels, suggesting that the activity‐dependent upregulation of translin was upstream of miR‐181a. In mice, a learning episode markedly decreased miR‐181a in the hippocampus and raised the protein levels of GluA2. Lastly, we observed that inhibition of miR‐181a alleviated memory deficits and increased GluA2 and GluA1 levels, without restoring translin, in the 3xTg‐AD model. Taken together, our results indicate that miR‐181a is a major negative regulator of the cellular events that underlie synaptic plasticity and memory through AMPA receptors, and importantly, Aβ disrupts this process by suppressing translin and leads to synaptic dysfunction and memory impairments in AD.     

Metabolism, Intake, and Digestibility of Lambs Supplemented with Organic Chromium

The aim of the present study was to evaluate the metabolism of organic chromium and its effect on digestibility and intake of lambs. Four 4-month-old male lambs, each weighing 28 kg, were used. The animals were kept in metabolic cages for a period of 20 days (15 days of adaptation and 5 days of experimentation), in two experimental phases, with inverted treatments. Organic chromium was administered by intraruminal infusion of 1 mg of chromium-rich yeast (Saccharomyces cerevisiae) throughout the adaptive and experimental period. The dry material rates of the diet and feces of the animals were evaluated to estimate consumption, digestibility, and fecal production. During the experimental period, blood, feces, and urine were collected every 24 h to determine chromium levels. There was no significant difference in the excretion of chromium in the urine, and no mineral remnants were detected in the blood. Excretion was generally fecal. There was greater excretion of chromium in the feces of lambs in the treated group on day 0 and day 3, compared with the control group. The use of organic chromium promoted an increase in the consumption of dry material in the treated animals only at day 0 (P?<?0.05). The production of fecal dry matter was greater among the treated lambs than among the animals of the control group on day 1, day 2, day 3, and day 4 (P?<?0.05). The results obtained showed that organic chromium associated with live yeasts is not absorbed by the body and do not affect the intake time in the dose used.     

Metacercariae of centrocestus formosanus (Nishigori, 1924) (Trematoda) in freshwater Fishes in México and their transmission by the Thiarid Snail Melanoides tuberculata

We report for the first time Centrocestus formosanus (Nishigori, 1924) Price, 1932 (Trematoda: Heterophyidae) metacercariae parasitizing natural populations of Xiphophorus hellen (Poeciliidae) and Gobiomorus dormitor (Gobiidae) in Mexico. Adult forms confirming the specific identity were recovered from experimental infections of domestic chicks and laboratory mice. The first intermediate host of this parasite is Melanoides tuberculata, its role in transmission of the infection was assessed by experiments with aquarium Guppies and Cercariae shed from naturally infected snails. Both, the snail and the trematode were introduced in the American continent.     

HIGH HYDROSTATIC PRESSURE INDUCES SYNTHESIS OF HEAT‐SHOCK PROTEINS AND TREHALOSE‐6‐PHOSPHATE SYNTHASE IN Anastrepha ludens LARVAE

The Mexican fruit fly (Anastrepha ludens) is responsible for losses of up to 25% of crops such as mango and citrus fruits in Central America and México. The larval life cycle of A. ludens comprises three stages with a duration ranging from 3 to 8 days. Because of the damage caused by A. ludens, several methods of control have been studied and implemented. High hydrostatic pressures (HHP) are currently applied to foods and it is now proposed to be employed to inactivate eggs and larvae of A. ludens. Originally HHP was designed to inactivate microorganisms, since it exerts marked effects on cell morphology, and can affect enzymatic reactions and genetic mechanisms of microbial cells, with no major changes altering the sensory or nutritional quality of the foodstuff. In this study, A. ludens in two larval stages (5‐ and 8‐day‐old) were subjected to HHP treatments. The biochemical response of the larvae of A. ludens was dependent on their stage of development. The third larval stage (L3) developed a better protection mechanism based on the synthesis of stress proteins or heat‐shock proteins (HSPs) and the enzyme trehalose‐6‐phosphate synthase, which are linked and possibly act together to achieve greater survivability to stress caused by hydrostatic pressure.     

Elements of the Polycomb Repressor SU(Z)12 Needed for Histone H3-K27 Methylation,the Interface with E(Z), and In Vivo Function

Polycomb repressive complex 2 (PRC2) is an essential chromatin-modifying enzyme that implements gene silencing. PRC2 methylates histone H3 on lysine-27 and is conserved from plants to flies to humans. In Drosophila melanogaster, PRC2 contains four core subunits: E(Z), SU(Z)12, ESC, and NURF55. E(Z) bears a SET domain that houses the enzyme active site. However, PRC2 activity depends upon critical inputs from SU(Z)12 and ESC. The stimulatory mechanisms are not understood. We present here functional dissection of the SU(Z)12 subunit. SU(Z)12 contains two highly conserved domains: an ∼140-amino-acid VEFS domain and a Cys₂-His₂ zinc finger (ZnF). Analysis of recombinant PRC2 bearing VEFS domain alterations, including some modeled after leukemia mutations, identifies distinct elements needed for SU(Z)12 assembly with E(Z) and stimulation of histone methyltransferase. The results define an extensive VEFS subdomain that organizes the SU(Z)12-E(Z) interface. Although the SU(Z)12 ZnF is not needed for methyltransferase in vitro, genetic rescue assays show that the ZnF is required in vivo. Chromatin immunoprecipitations reveal that this ZnF facilitates PRC2 binding to a genomic target. This study defines functionally critical SU(Z)12 elements, including key determinants of SU(Z)12-E(Z) communication. Together with recent findings, this illuminates PRC2 modulation by conserved inputs from its noncatalytic subunits.