Interaction between the tRNA-Binding and C-Terminal Domains of Yeast Gcn2 Regulates Kinase Activity In Vivo

The stress-activated protein kinase Gcn2 regulates protein synthesis by phosphorylation of translation initiation factor eIF2α. Gcn2 is activated in amino acid-deprived cells by binding of uncharged tRNA to the regulatory domain related to histidyl-tRNA synthetase, but the molecular mechanism of activation is unclear. We used a genetic approach to identify a key regulatory surface in Gcn2 that is proximal to the predicted active site of the HisRS domain and likely remodeled by tRNA binding. Mutations leading to amino acid substitutions on this surface were identified that activate Gcn2 at low levels of tRNA binding (Gcd^- phenotype), while other substitutions block kinase activation (Gcn^- phenotype), in some cases without altering tRNA binding by Gcn2 in vitro. Remarkably, the Gcn^- substitutions increase affinity of the HisRS domain for the C-terminal domain (CTD), previously implicated as a kinase autoinhibitory segment, in a manner dampened by HisRS domain Gcd^- substitutions and by amino acid starvation in vivo. Moreover, tRNA specifically antagonizes HisRS/CTD association in vitro. These findings support a model wherein HisRS-CTD interaction facilitates the autoinhibitory function of the CTD in nonstarvation conditions, with tRNA binding eliciting kinase activation by weakening HisRS-CTD association with attendant disruption of the autoinhibitory KD-CTD interaction.     

Effects of the administration of cadmium and zinc on the concentration of zinc in the thymus of rats

The zinc content of thymus glands of male Wistar rats has been determined during five weeks of treatment with ZnCl₂ and CdCl₂, and compared with a group of control rats. THymus gland extracts were chromatographed on columns of Sephadex G-75 and the zinc content of the one hundred fractions obtained were determined by atomic absorption spectrophotometry. The rats treated with ZnCl₂ showed an increase in the thymus concentration of zinc bound to high and low molecular weight proteins. The rats treated with CdCl₂ showed an increase in zinc concentration, as opposed to the control group, during the first three weeks of treatment, and thereafter show a toxic effect of cadmium on the gland, with ulterior regression of the latter, and a decrease in the concentration of zinc.     

The activity of tissue enzymes in iron-deficient rat and man: an overview

The effects of iron deficiency in rat and/or man on iron-containing enzymes of different tissues is reviewed. Iron deficiency results in a decrease of skeletal muscle iron containing proteins e.g. myoglobin, cytochromes c, a + a3, and alpha-glycerophosphate oxidase. Iron deficiency produces a reduction in the activity of several respiratory enzymes in the mitochondrial fraction of cardiac muscle, particularly: NADH cytochrome c reductase, succinic cytochrome c reductase, succinic dehydrogenase and NADH ferricyanide oxidoreductase. The effects of iron deficiency on brain tissue is emphasized with respect to cytochromes, monoaminoxidase and amino acids metabolism. Host defence to infection (controversial data), decrease in body temperature, alteration of DNA synthesis, collagen and lipid metabolism, liver and gastrointestinal mucous cytochromes activity perturbations are discussed.     

Interleukin 2 production in iron-deficient children

The relationship between iron status and capacity for IL-2 production by lymphocytes was assessed in 81 children from 6 mo to 3 yr of age selected at random from a population with low socioeconomic status, undergoing free systematic examination in four children's health centers in the Paris area. Iron deficiency was defined by the existence of at least two abnormal values among the three indicators of iron status: serum ferritin level ≤12 μg/L, transferrin saturation <12%, and erythrocyte protoporphyrin concentration >3 μg/g hemoglobin. According to this definition, 53 children were classified as iron deficient and 28 as iron sufficient. No differences were observed between the iron-deficient and iron-sufficient groups in terms of the IL-2 concentration without stimulation by PHA. IL-2 production by lymphocytes stimulated with PHA, as well as the stimulation index (ratio of IL-2 concentration following stimulation by PHA to that of IL-2 concentration without stimulation by PHA) were significantly lower in iron-deficient children. The reduction in IL-2 production by activated lymphocytes observed in our study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in cell-mediated immunity.     

On the reporting and review requirements of ISO 14044

The International Journal of Life Cycle Assessment -     

In silico and empirical evaluation of twelve metabarcoding primer sets for insectivorous diet analyses

During the most recent decade, environmental DNA metabarcoding approaches have been both developed and improved to minimize the biological and technical biases in these protocols. However, challenges remain, notably those relating to primer design. In the current study, we comprehensively assessed the performance of ten COI and two 16S primer pairs for eDNA metabarcoding, including novel and previously published primers. We used a combined approach of in silico, in vivo‐mock community (33 arthropod taxa from 16 orders), and guano‐based analyses to identify primer sets that would maximize arthropod detection and taxonomic identification, successfully identify the predator (bat) species, and minimize the time and financial costs of the experiment. We focused on two insectivorous bat species that live together in mixed colonies: the greater horseshoe bat (Rhinolophus ferrumequinum) and Geoffroy's bat (Myotis emarginatus). We found that primer degeneracy is the main factor that influences arthropod detection in silico and mock community analyses, while amplicon length is critical for the detection of arthropods from degraded DNA samples. Our guano‐based results highlight the importance of detecting and identifying both predator and prey, as guano samples can be contaminated by other insectivorous species. Moreover, we demonstrate that amplifying bat DNA does not reduce the primers' capacity to detect arthropods. We therefore recommend the simultaneous identification of predator and prey. Finally, our results suggest that up to one‐third of prey occurrences may be unreliable and are probably not of primary interest in diet studies, which may decrease the relevance of combining several primer sets instead of using a single efficient one. In conclusion, this study provides a pragmatic framework for eDNA primer selection with respect to scientific and methodological constraints.     

D1- and D2-like receptors differentially mediate the effects of dopaminergic transmission on cost–benefit evaluation and motivation in monkeys

It has been widely accepted that dopamine (DA) plays a major role in motivation, yet the specific contribution of DA signaling at D₁-like receptor (D₁R) and D₂-like receptor (D₂R) to cost–benefit trade-off remains unclear. Here, by combining pharmacological manipulation of DA receptors (DARs) and positron emission tomography (PET) imaging, we assessed the relationship between the degree of D₁R/D₂R blockade and changes in benefit- and cost-based motivation for goal-directed behavior of macaque monkeys. We found that the degree of blockade of either D₁R or D₂R was associated with a reduction of the positive impact of reward amount and increasing delay discounting. Workload discounting was selectively increased by D₂R antagonism. In addition, blocking both D₁R and D₂R had a synergistic effect on delay discounting but an antagonist effect on workload discounting. These results provide fundamental insight into the distinct mechanisms of DA action in the regulation of the benefit- and cost-based motivation, which have important implications for motivational alterations in both neurological and psychiatric disorders.

Using quantitatively controlled pharmacological manipulations, this study teases apart the role of D1- and D2-like dopamine receptors in motivation and goal-directed behavior in monkeys, revealing complementary roles of two dopamine receptor subtypes in the computation of the cost/benefit trade-off to guide action.     

Microtubule target for new antileishmanial drugs based on ethyl 3-haloacetamidobenzoates

A new family of antimicrotubule drugs named (3-haloacetamidobenzoyl) ureas and ethyl 3-haloacetamidobenzoates were found to be cytotoxic to the Leishmania parasite protozoa. While the benzoylureas were shown to strongly inhibit in vitro mammalian brain microtubule assembly, the ethyl ester derivatives were characterized as very poor inhibitors of this process. Ethyl 3-chloroacetamidobenzoate, MF29, was found to be the most efficient drug on the promastigote stage of three Leishmania species (IC₅₀: 0.3–1.8 μM). MF29 maintained its activity against the clinical relevant intracellular stage of L. mexicana with IC₅₀ value of 0.33 μM. It was the only compound that exhibits a high activity on all the Leishmania species tested. This compound appeared to alter parasite microtubule organisation as demonstrated by using antibodies directed against microtubule components and more precisely the class of microtubule decorated by the MAP2-like protein. It is interesting to notice that this MAP2-like protein was identified for the first time in a Leishmania parasite