Regulator of G-Protein Signaling 18 Controls Both Platelet Generation and Function

RGS18 is a myeloerythroid lineage-specific regulator of G-protein signaling, highly expressed in megakaryocytes (MKs) and platelets. In the present study, we describe the first generation of a RGS18 knockout mouse model (RGS18-/-). Interesting phenotypic differences between RGS18-/- and wild-type (WT) mice were identified, and show that RGS18 plays a significant role in both platelet generation and function. RGS18 deficiency produced a gain of function phenotype in platelets. In resting platelets, the level of CD62P expression was increased in RGS18-/- mice. This increase correlated with a higher level of plasmatic serotonin concentration. RGS18-/- platelets displayed a higher sensitivity to activation in vitro. RGS18 deficiency markedly increased thrombus formation in vivo. In addition, RGS18-/- mice presented a mild thrombocytopenia, accompanied with a marked deficit in MK number in the bone marrow. Analysis of MK maturation in vitro and in vivo revealed a defective megakaryopoiesis in RGS18-/- mice, with a lower bone marrow content of only the most committed MK precursors. Finally, RGS18 deficiency was correlated to a defect of platelet recovery in vivo under acute conditions of thrombocytopenia. Thus, we highlight a role for RGS18 in platelet generation and function, and provide additional insights into the physiology of RGS18.     

Hybridation entre Saga campbelli Kaltenbach 1965 et Saga hellenica Kaltenbach 1967 (Orthoptera: Tettigoniidae)

Dans le cadre de ses recherches sur le genre Saga, le G.E.E.M. enregistre en mai 2009 la naissance en élevage, d’un male et d’une femelle issus du croisement d’une femelle de Saga campbelli Kaltenbach 1965 avec un mâle de Saga hellenica Kaltenbach 1967. L’analyse cytogénétique de la femelle hybride confirme son origine hybride et qu’une seule translocation robertsonienne sépare les caryotypes de S. hellenica de S. campbelli. L’habitus du mâle montre une affinité plus forte avec S. hellenica qu’avec S. campbelli.     

Palynologie des variants androgénétiques de Nicotiana plumbaginifolia (Solanaceae)

L'examen des grains de pollen de variants androgénétiques de Nicotiana plumbaginifolia a permis d'aborder une nouvelle approche de la variabilité des plantes cultivées in vitro. En plus de la morphométrie et de la MEB, techniques classiquement utilisées en palynologie, la mise en oeuvre de la spectrométrie X à sélection d'énergie et de la microfluorométrie de la sporopollénine, a permis de mettre en évidence des différences intraspécifiques très importantes pouvant aider à la compréhension de l'installation de la variation somaclonale.

Pollen grains of androgenetic variants of Nicotiana plumbaginifolia were studied using classical methods in palynology (morphometry, SEM) and by energy dispersive X-ray spectrometry or microfluorometry of sporopollenin can allow a new advance in variability studies in conjunction with in vitro plant production. It is also more interesting to study possible relationships between palynological parameters and ploidy level.     

Marine plastics in LCA: current status and MarILCA’s contributions

The International Journal of Life Cycle Assessment -     

Development under the control of insulin of lipogenic enzymes,lipoprotein lipase,isoproterenol and glucagon sensitivity in differentiating rat preadipocytes in primary culture

In preadipose cellular fractions (I, II and III) isolated by density gradient centrifugation from the inguinal tissue of young rats, we followed the activity of fatty acid synthetase, ATP citrate lyase and lipoprotein lipase during differentiation in culture. 1.5 nM insulin when added at confluence markedly induced the activity of ATP citrate lyase and fatty acid synthetase in the cells derived from the lighter fractions (I and II). The magnitude of this response was 25–50-fold the initial value 15 days after plating. In the cells of the heaviest fraction (III) both enzymes exhibited low activity which was slightly stimulated by the presence of insulin, VLDL and heparin. In contrast, the activity of lipoprotein lipase appeared before confluence in cells from all three fractions and peaked at day 6 after plating. This early emergence was independent of the addition of insulin to the medium. However, insulin slightly enhanced the peak activity in post-confluent cells. The development of cAMP production in response to isoproterenol (100 μM) and to glucagon (0.3 μM) was determined in the cells of fraction II in the same culture conditions. The responsiveness to isoproterenol was present very early in these cells and rose rapidly during the exponential growth phase, reaching a peak value at day 8 after plating. In contrast, the development of glucagon sensitivity occurred only during late differentiation. The stimulatory effect of glucagon was enhanced when VLDL and heparin were added with insulin to the medium.     

Fiducial-less alignment of cryo-sections

Cryo-electron tomography of vitreous sections is currently the most promising technique for visualizing arbitrary regions of eukaryotic cells or tissue at molecular resolution. Despite significant progress in the sample preparation techniques over the past few years, the three dimensional reconstruction using electron tomography is not as simple as in plunge frozen samples for various reasons, but mainly due to the effects of irradiation on the sections and the resulting poor alignment. Here, we present a new algorithm, which can provide a useful three-dimensional marker model after investigation of hundreds to thousands of observations calculated using local cross-correlation throughout the tilt series. The observations are chosen according to their coherence to a particular model and assigned to virtual markers. Through this type of measurement a merit figure can be calculated, precisely estimating the quality of the reconstruction. The merit figures of this alignment method are comparable to those obtained with plunge frozen samples using fiducial gold markers. An additional advantage of the algorithm is the implicit detection of areas in the sections that behave as rigid bodies and can thus be properly reconstructed.     

Mutational analysis of the Escherichia coli DEAD box protein CsdA

The Escherichia coli cold shock protein CsdA is a member of the DEAD box family of ATP-dependent RNA helicases, which share a core of nine conserved motifs. The DEAD (Asp-Glu-Ala-Asp) motif for which this family is named has been demonstrated to be essential for ATP hydrolysis. We show here that CsdA exhibits in vitro ATPase and helicase activities in the presence of short RNA duplexes with either 3' or 5' extensions at 15 degrees C. In contrast to wild-type CsdA, a DQAD variant of CsdA (Glu-157-->Gln) had no detectible helicase or ATPase activity at 15 degrees C in vitro. A plasmid encoding the DQAD variant was also unable to suppress the impaired growth of the csdA null mutant at 15 degrees C. Plasmid-encoded CsdADelta444, which lacks most of the carboxy-terminal extension, enhanced the growth of a csdA null mutant at 25 degrees C but not at 15 degrees C; this truncated protein also has limited in vitro activity at 15 degrees C. These results support the physiological function of CsdA as a DEAD box ATP-dependent RNA helicase at low temperature.     

Divergence in symbiotic interactions between same genotypic PCR–RFLP Frankia strains and different Casuarinaceae species under natural conditions

The symbiotic interactions between Frankia strains and their associated plants from the Casuarinaceae under controlled conditions are well documented but little is known about these interactions under natural conditions. We explored the symbiotic interactions between eight genotypically characterized Frankia strains and five Casuarinaceae species in long-term field trials. Characterization of strains was performed using the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) for the nifD – nifK intergenic transcribed spacer (ITS) and 16S–23S ITS. Assessments of the symbiotic interactions were based on nodulation patterns using nodule dry weight and viability, and on actual N₂ fixation using the δ¹⁵N method. The PCR–RFLP patterns showed that the analyzed strains belonged to the same genotypic group (CeD group), regardless of the host species and environment of origin. The nodule viability index is introduced as a new tool to measure the viability of perennial nodules and to predict their effectiveness. The host Casuarinaceae species was a key factor influencing both the actual N₂-fixing activity of the associated Frankia strain and the viability of nodules within a location. This is the first study providing information on the symbiotic interactions between genotypically characterized Frankia strains and actinorhizal plants under natural conditions. The results revealed a way to improve a long-term management of the Casuarinaceae symbiosis.     

Nocturnal expression of phosphorylated-ERK1/2 in gastrin-releasing peptide neurons of the rat suprachiasmatic nucleus

Extracellular regulated kinase (ERK) signalling is believed to play roles in various aspects of circadian clock mechanisms. In this study, we show in rat that the nuclear versus cytoplasmic intracellular distribution of the phosphorylated forms of ERK1/2 (P-ERK1/2) in the central clock, namely the suprachiasmatic nucleus (SCN), is proportionally constant across the light/dark cycle while the spatial distribution and neurochemical phenotype of cells expressing these activated forms are time-regulated according to a daily rhythm and light-regulated. P-ERK1/2 was exclusively found in neuronal elements. At daytime, it was detected throughout the dorsoventral extent of the SCN, partly within neurons synthesizing either arginine-vasopressin or vasoactive intestinal peptide (VIP). At night time, it was segregated in the ventrolateral aspect of the nucleus, within a cluster of cells 45% of which were gastrin-releasing peptide (GRP) neurons with or without co-localization with VIP. After a light pulse at night, expression of P-ERK1/2 increased in GRP neurons but also appeared in a population of neurons that stained for VIP only. These data show that the GRP neurons are closely associated with ERK1/2 activation at night and point to the importance of ERK1/2 signalling not only in intra-SCN transmission of photic information but also in maintenance of neuronal rhythms in the SCN.