Calcium-independent cytoskeleton disassembly induced by BAPTA.

In living organisms, Ca2+ signalling is central to cell physiology. The Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) has been widely used as a probe to test the role of calcium in a large variety of cell functions. Here we show that in most cell types BAPTA has a potent actin and microtubule depolymerizing activity and that this activity is completely independent of Ca2+ chelation. Thus, the depolymerizing effect of BAPTA is shared by a derivative (D-BAPTA) showing a dramatically reduced calcium chelating activity. Because the extraordinary depolymerizing activity of BAPTA could be due to a general depletion of cell fuel molecules such as ATP, we tested the effects of BAPTA on cellular ATP levels and on mitochondrial function. We find that BAPTA depletes ATP pools and affects mitochondrial respiration in vitro as well as mitochondrial shape and distribution in cells. However, these effects are unrelated to the Ca2+ chelating properties of BAPTA and do not account for the depolymerizing effect of BAPTA on the cell cytoskeleton. We propose that D-BAPTA should be systematically introduced in calcium signalling experiments, as controls for the known and unknown calcium independent effects of BAPTA. Additionally, the concomitant depolymerizing effect of BAPTA on both tubulin and actin assemblies is intriguing and may lead to the identification of a new control mechanism for cytoskeleton assembly.     

Effects of diazepam and its metabolites on nocturnal melatonin secretion in the rat pineal and Harderian glands. A comparative in vivo and in vitro study

We investigated the effects of diazepam (DZP) and its three metabolites: nordiazepam (NZP), oxazepam (OZP), and temazepam (TZP) on pineal gland nocturnal melatonin secretion. We looked at the effects of benzodiazepines on pineal gland melatonin secretion both in vitro (using organ perifusion) and in vivo in male Wistar rats sacrificed in the middle of the dark phase. We also examined the effects of these benzodiazepines on in vivo melatonin secretion in the Harderian glands. Neither DZP (10^-5-10^-6 M) nor its metabolites (10^-4-10^-5 M) affected melatonin secretion by perifused rat pineal glands in vitro. In contrast, a 10^-4 M suprapharmacological concentration of DZP increased melatonin secretion of perifused pineal glands by 70%. In vivo, a single acute subcutaneous administration of DZP (3 mg/kg body weight) significantly affected pineal melatonin synthesis and plasma melatonin levels, while administration of the metabolites under the same conditions did not. DZP reduced pineal melatonin content (-40%), N-acetyltransferase activity (-70%), and plasma melatonin levels (-40%), but had no affects on pineal hydroxyindole-O-methyltransferase activity. Neither DZP nor its metabolites affected Harderian gland melatonin content. Our results indicate that the in vivo inhibitory effect of DZP on melatonin synthesis is not due to the metabolism of DZP. The results also show that the control of melatonin production in the Harderian glands differs from that observed in the pineal gland.     

Towards a Phylogeny for Coffea (Rubiaceae): identifying well-supported lineages based on nuclear and plastid DNA sequences

BACKGROUND AND AIMS: The phylogenetic relationships between species of Coffea and Psilanthus remain poorly understood, owing to low levels of sequence variation recovered in previous studies, coupled with relatively limited species sampling. In this study, the relationships between Coffea and Psilanthus species are assessed based on substantially increased molecular sequence data and greatly improved species sampling. METHODS: Phylogenetic relationships are assessed using parsimony, with sequence data from four plastid regions [trnL-F intron, trnL-F intergenic spacer (IGS), rpl16 intron and accD-psa1 IGS], and the internal transcribed spacer (ITS) region of nuclear rDNA (ITS 1/5.8S/ITS 2). Supported lineages in Coffea are discussed within the context of geographical correspondence, biogeography, morphology and systematics. KEY RESULTS: Several major lineages with geographical coherence, as identified in previous studies based on smaller data sets, are supported. Other lineages with either geographical or ecological correspondence are recognized for the first time. Coffea subgenus Baracoffea is shown to be monophyletic, but Coffea subgenus Coffea is paraphyletic. Sequence data do not substantiate the monophyly of either Coffea or Psilanthus. Low levels of sequence divergence do not allow detailed resolution of relationships within Coffea, most notably for species of Coffea subgenus Coffea occurring in Madagascar. The origin of C. arabica by recent hybridization between C. canephora and C. eugenioides is supported. Phylogenetic separation resulting from the presence of the Dahomey Gap is inferred based on sequence data from Coffea.     

Age‐dependent alterations of the NMDA receptor developmental profile and adult behavior in postnatally ketamine‐treated mice

Ketamine is a NMDA receptor (NMDAR) antagonist used in pediatric anesthesia. Given the role of glutamatergic signaling during brain maturation, we studied the effects of a single ketamine injection (40 mg/kg s.c) in mouse neonates depending on postnatal age at injection (P2, P5, or P10) on cortical NMDAR subunits expression and association with Membrane‐Associated Guanylate Kinases PSD95 and SAP102. The effects of ketamine injection at P2, P5, or P10 on motor activity were compared in adulthood. Ketamine increased GluN2A and GluN2B mRNA levels in P2‐treated mice without change in proteins, while it decreased GluN2B protein in P10‐treated mice without change in mRNA. Ketamine reduced GluN2A mRNA and protein levels in P5‐treated mice without change in GluN2B and GluN1. Ketamine affected the GluN2A/PSD95 association regardless of the age at injection, while GluN2B/PSD95 association was enhanced only in P5‐treated mice. Microdissection of ketamine‐treated mouse cortex showed a decrease in GluN2A mRNA level in superficial layers (I–IV) and an increase in all subunit expressions in deep layers (V–VI) in P5‐ and P10‐treated mice, respectively. Our data suggest that ketamine impairs cortical NMDAR subunit developmental profile and delays the synaptic targeting of GluN2A‐enriched NMDAR. Ketamine injection at P2 or P10 resulted in hyperlocomotion in adult male mice in an open field, without change in females. Voluntary running‐wheel exercise showed age‐ and sex‐dependent alterations of the mouse activity, especially during the dark phase. Overall, a single neonatal ketamine exposure led to short‐term NMDAR cortical developmental profile impairments and long‐term motor activity alterations persisting in adulthood. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 75: 315–333, 2015     

cAMP-Signalling Regulates Gametocyte-Infected Erythrocyte Deformability Required for Malaria Parasite Transmission

Blocking Plasmodium falciparum transmission to mosquitoes has been designated a strategic objective in the global agenda of malaria elimination. Transmission is ensured by gametocyte-infected erythrocytes (GIE) that sequester in the bone marrow and at maturation are released into peripheral blood from where they are taken up during a mosquito blood meal. Release into the blood circulation is accompanied by an increase in GIE deformability that allows them to pass through the spleen. Here, we used a microsphere matrix to mimic splenic filtration and investigated the role of cAMP-signalling in regulating GIE deformability. We demonstrated that mature GIE deformability is dependent on reduced cAMP-signalling and on increased phosphodiesterase expression in stage V gametocytes, and that parasite cAMP-dependent kinase activity contributes to the stiffness of immature gametocytes. Importantly, pharmacological agents that raise cAMP levels in transmissible stage V gametocytes render them less deformable and hence less likely to circulate through the spleen. Therefore, phosphodiesterase inhibitors that raise cAMP levels in P. falciparum infected erythrocytes, such as sildenafil, represent new candidate drugs to block transmission of malaria parasites.     

Spatial genetic structure in Beta vulgaris subsp. maritima and Beta macrocarpa reveals the effect of contrasting mating system,influence of marine currents,and footprints of postglacial recolonization routes

Understanding the factors that contribute to population genetic divergence across a species' range is a long‐standing goal in evolutionary biology and ecological genetics. We examined the relative importance of historical and ecological features in shaping the present‐day spatial patterns of genetic structure in two related plant species, Beta vulgaris subsp. maritima and Beta macrocarpa. Using nuclear and mitochondrial markers, we surveyed 93 populations from Brittany (France) to Morocco – the southern limit of their species' range distribution. Whereas B. macrocarpa showed a genotypic structure and a high level of genetic differentiation indicative of selfing, the population genetic structure of B. vulgaris subsp. maritima was consistent with an outcrossing mating system. We further showed (1) a strong geographic clustering in coastal B. vulgaris subsp. maritima populations that highlighted the influence of marine currents in shaping different lineages and (2) a peculiar genetic structure of inland B. vulgaris subsp. maritima populations that could indicate the admixture of distinct evolutionary lineages and recent expansions associated with anthropogenic disturbances. Spatial patterns of nuclear diversity and differentiation also supported a stepwise recolonization of Europe from Atlantic‐Mediterranean refugia after the last glacial period, with leading‐edge expansions. However, cytoplasmic diversity was not impacted by postglacial recolonization: stochastic long‐distance seed dispersal mediated by major oceanic currents may mitigate the common patterns of reduced cytoplasmic diversity observed for edge populations. Overall, the patterns we documented here challenge the general view of reduced genetic diversity at the edge of a species' range distribution and provide clues for understanding how life‐history and major geographic features interact to shape the distribution of genetic diversity.     

Metallothionein and brain inflammation

Since the seminal discoveries of Bert Vallee regarding zinc and metallothioneins (MTs) more than 50 years ago, thousands of studies have been published concerning this fascinating story. One of the most active areas of research is the involvement of these proteins in the inflammatory response in general, and in neuroinflammation in particular. We describe the general aspects of the inflammatory response, highlighting the essential role of the major cytokine interleukin-6, and review briefly the expression and function of MTs in the central nervous system in the context of neuroinflammation. Particular attention is paid to the Tg2576 Alzheimer disease mouse model and the preliminary results obtained in mice into which human Zn₇MT-2A was injected, which suggest a reversal of the behavioral deficits while enhancing amyloid plaque load and gliosis.