No description available.

Sleep disturbances are common in patients with schizophrenia. Mice lacking the cytoskeletal-associated protein Stable Tubule Only Polypeptide (STOP) display cognitive, behavioural and neurobiological deficits that mimic those seen in schizophrenia, but there is little evidence of sleep changes in these mice. To investigate their sleep patterns, electroencephalogram (EEG) and electromyogram were recorded under a 12:12 light:dark cycle in adult male STOP-null (KO; n=7) and wild-type (WT; n=8) mice, during a 24 h baseline period, followed by 6 h of sleep deprivation, and a 24 h recovery period. In the baseline period, KO mice spent more time awake and less time in non-rapid eye movement (NREM) and REM sleep compared to WT mice. Particularly in the dark phase, KO mice had more wake and NREM sleep episodes, and shorter NREM and REM sleep episodes relative to WT mice. Following sleep deprivation, during the first 12 h of recovery (i.e. dark phase), both groups showed similar increases in NREM and REM sleep amounts and NREM EEG delta power relative to corresponding baseline periods. These findings indicate that the STOP-null mice sleep less and their sleep is more fragmented compared to WT mice. These features are consistent with the sleep abnormalities found in individuals with schizophrenia.

No description available.

Carbonaceous engine deposits tend to accumulate on most of the inner surfaces of the car engine. The presence of these deposits leads to a deteriorated efficiency of the engine and a number of adverse effects, such as higher propensity of the engine to knock. It has been proposed that selective adsorption of some of the fuel components in the porous deposits (and changing composition of the pre-combustion fuel) could be a contributing mechanism of the diminished efficiency of the engine. This, as well as other mechanisms of the deposits action, crucially depend on the porous structure of the material. Therefore, the aim of this investigation is to develop a method, which is able to accurately characterize the internal porous structure of the engine deposits and predict their adsorption properties at different conditions. This should allow us to assess whether the selective adsorption of fuel components is indeed a plausible contributing mechanism to the diminished performance of the engine. Accurate characterization of the engine deposits faces several difficulties due to their complex porous structure and chemical composition. A widely adopted approach in the characterization of activated carbons, which combines molecular simulation, specifically grand canonical Monte Carlo (GCMC) in slit pores, and experimental adsorption isotherms, is the starting point for the method suggested in this work. In this thesis, we will demonstrate that, by systematic modification of the solid-fluid interaction in the molecular simulation, we are able to correctly account for the chemical structural heterogeneity of the samples used. The new parameters of solid-fluid interaction allow us to extract representative pore size distributions and investigate the adsorption properties under different conditions of temperature and pressure, based on the obtained pore size distribution. Specifically, using the experimental data from a single ethane isotherm at 278K we accurately predict ethane adsorption at other temperatures and in different samples. Additionally, the proposed method is able to predict the adsorption of more complex hydrocarbons, i.e. n-butane and isobutane. The performance of the method is assessed by comparing the simulations results with the experimental adsorption measurements data on the engine deposits samples. Another important capability of the method is that it enables us to generate adsorption predictions of two key components commonly used to represent the combustion properties of the fuel, n-heptane and isooctane. We explore the equilibrium adsorption properties of these components based on the determined pore size distributions of the deposit samples. The results presented in the thesis highlight the importance of the adsorption in the internal porous structure of the engine deposits. The present study reinforces the value of molecular simulation combined with a limited number of experimental measurements, to accurately characterize heterogeneous carbonaceous materials and to make predictions at different conditions with sufficient precision.

miRNAs are small regulatory RNAs, which function as post-transcriptional mRNA regulators. They direct ribonucleoprotein complexes to cognate mRNA to repress them by translational inhibition and degradation. miRNAs regulate thousands of mRNAs in mammals and have been recognized as regulatory factors in most cellular and developmental processes. Dysregulation of the miRNA pathway can lead to severe defects and diseases. Interestingly, a unique situation exists in mouse oocytes, where all the miRNA pathway components are present, yet the pathway is dispensable and nonfunctional, the molecular foundation of this phenomenon and its significance still remain unclear. In spite of the pronounced effects of the miRNA pathway in gene regulation in somatic cells, study strategies of the pathway bare limitations. Current methods for studying the activity of the miRNA pathway employ corelative studies (such as NGS) or reporter assays, which have relatively low throughput and are prone to artifacts. Here, I present design and development of a new strategy for directly monitor global miRNA pathway activity and integrity in near physiological conditions in living cells, which could also be employed in vivo for studies of mouse oocytes. The strategy is based on fluorescently tagged endogenous proteins of the...

No description available.

L’un des domaines clés de la recherche en neurosciences modernes consiste à comprendre les interactions complexes entre le stress et la génétique qui conduisent à la manifestation de troubles tels que la dépression, l’anxiété et le dysfonctionnement cognitif. Des preuves de plus en plus nombreuses suggèrent que le système glutamatergique peut être une cible thérapeutique pertinente pour de tels troubles. Le glutamate est le neurotransmetteur utilisé par la grande majorité des synapses excitatrices dans le cerveau. Et les sous-types des récepteurs métabotropique au glutamate (mGluR1 – mGluR8) agissent avant tout comme d’importants régulateurs postsynaptiques de la neurotransmission dans le système nerveux central (SNC), en fournissant un mécanisme par lequel les réponses synaptiques rapides à travers des canaux cationiques dépendants du glutamate peuvent être affinées. Ainsi, les récepteurs mGluR participent à une grande variété de fonctions du système nerveux central. Au sein dela famille des récepteurs métabotropiques au glutamate, le récepteur présynaptique mGluR7 montre la conservation évolutive la plus élevée et on pense qu'il agit comme un régulateur de la libération de neurotransmetteurs. Le récepteur mGluR7 est également le plus largement distribué des récepteurs présynaptiques mGluR, présent sur une large gamme de synapses démontrées comme critiques à la fois dans le fonctionnement normal du système nerveux central, mais également dans une large gamme de troubles psychiatriques et neurologiques. De plus, un nombre croissant de preuves expérimentales suggèrent que le récepteur mGluR7 est non seulement un acteur clé dans l’élaboration de réponses synaptiques au niveau des synapses glutamatergiques, mais qu’il est également un régulateur clé de la transmission GABAergique inhibitrice. Le développement d’outils pharmacologiques et génétiques sélectifs a permis le démantèlement de la fonction du récepteur mGluR7 dans une multitude de processus physiologiques et comportementaux. Ainsi les souris knock-out ont mis en évidence un rôle du récepteur mGluR7 dans l’anxiété, le conditionnement de la peur, l’aversion, l’apprentissage et la mémoire spatiale. De plus, ces souris dépourvues du récepteur métabrotrope mGluR7 démontrent une sensibilité accrue aux crises épileptiques suggérant un rôle unique de ce récepteur dans la régulation de l’excitabilité neuronale. De même, une altération de la plasticité synaptique à court terme dans les souris transgéniques dépourvues du récepteur métabotrope au glutamate mGluR7 démontre que l’absence de récepteurs mGluR7 engendre des altérations de la plasticité synaptique à court terme dans l’hippocampe. En outre, la découverte et la caractérisation récente du premier antagoniste allostérique agissant sur le domaine VFTD de l’extrémité N-terminale du récepteur mGluR7 potentialise définitivement les observations effectuées sur les souris mGluR7 knock-out quant à la fonction de ce récepteur dans l’anxiété et la dépression. Ensemble, ces données suggèrent que le récepteur mGluR7 est un important régulateur de la fonction glutamatergique, de la peur, de l’aversion et de la cognition et donc ce récepteur représente une cible thérapeutique innovante pour les troubles liés au stress à l’interface de la cognition et de l’anxiété. / Metabotropic glutamate receptors (mGluRs) consist of eight different subtypes and exert their effects on second messengers and ion channels via G-proteins. The function of individual mGluR subtypes in the CNS, however, largely remains to be clarified. To study the role of mGluR7 receptors, we used homologous recombination to generate mice lacking this metabotropic receptor subtype (mGluR7). Immunohistochemical and immunoelectron-microscopic analyses showed that mGluR7 is highly expressed in amygdala and preferentially localized at the presynaptic axon terminals of glutamatergic neurons, suggesting strongly that mGluR7 is involved in neural processes subserving amygdala-dependent averse responses. To examine amygdala-dependent behavior, we examined first the fear response of freezing after electric shock in wild-type and mGluR7 (mGluR7-/-) knockout littermates. Wild-type mice displayed freezing immediately after footshock. In comparison, mGluR7 knockout mice showed significantly reduced levels in both immediate postshock and delayed freezing responses. However, the knockout mice exhibited no abnormalities in pain sensitivity and locomotor activity. Secondly, we performed conditioned taste aversion (CTA) experiments. In wild-type mice, the administration of saccharin followed by intraperitoneal injection of the malaise-inducing agent LiCl resulted in an association between saccharin and LiCl. This association caused strong CTA toward saccharin. In contrast, mGluR7 knockout mice failed to associate between the taste and the negative reinforcer in CTA experiments. Again, the knockout mice showed no abnormalities in taste preference and in the sensitivity to LiCl toxicity. These results indicated that mGluR7 deficiency causes an impairment of two distinct amygdala-dependent behavioral paradigms. Because the amygdale function is essential for these two distinct behavioral paradigms, our results suggest that mGluR7 is critical in amygdale function. The amygdale is a brain region that is known to be critical for the manifestation of anxiolysis and antidepressant action and glutamatergic neurotransmission has been strongly implicated in the pathophysiology of affective disorders. To this end we analyzed the behavioral profiles of mGluR7-/- mice in animal models of depression and anxiety. mGluR7-/- mice were compared to wildtype littermates and showed substantially less behavioural immobility in both the forced swim test and the tail suspension test. Both behavioural paradigms are widely used to predict antidepressant-like activity. Further, mGluR7-/- mice displayed anxiolytic activity in four different behavioural tests namely the light-dark box, the elevated plus maze, the staircase test, and the stress-induced hyperthermia test, while their cognitive performance was normal in the passive avoidance paradigm. [...]

Abstract Collagen molecules consist of three polypeptide chains that are coiled around each other to form a triple-helical structure. The formation of stable collagen triple helices requires the hydroxylation of proline residues catalyzed by collagen prolyl 4-hydroxylases (C-P4H). Vertebrate C-P4H is an ER-resident enzyme that consists of two catalytically active α subunits and two β subunits. Production of recombinant human collagen and gelatin could have numerous medical and industrial applications, but most recombinant systems lack the C-P4H activity. The yeast Pichia pastoris has been successfully engineered to produce stable human collagens and gelatins by co-expression of the collagen polypeptide chains with the two C-P4H subunits. This study examined the effect of deletion of the C-propeptide, or its replacement by a trimerizing foldon domain, on the assembly of type I and III collagen triple helices in P. pastoris. It was observed that the absence of the C-propeptide leads to inefficient collagen chain assembly whereas the replacement of C-propeptide with a foldon domain increased the assembly up to 3-fold. Moreover, the co-expression of α1(I) and α2(I) chains fused with foldon yielded heterotrimeric type I collagen molecules with a typical chain ratio of 2:1. As the foldon domain contains no information for collagen chain recognition, the present data indicate that the chain assembly is defined not only by the C-propeptides but also by other determinants present in the α chains. Another aspect studied here was the expression and secretion of gelatin fragments of varying size and conformation in P. pastoris. It was discovered that gelatin fragment size affects its secretion as the 90 kDa fragment was less efficiently secreted than the 45 kDa fragment. Secretion was also dependent on the fragment conformation as induction of the triple helix formation by either C-propeptide or foldon led to the accumulation of the fragments inside the yeast cells despite the presence of an efficient secretory signal. C-P4H was long assumed to exist as one type only but the cloning of several C-P4H α subunits raised questions concerning the specific roles of the C-P4H isoenzymes. The generation of mice lacking the type I C-P4H, which is regarded as the major C-P4H isoenzyme, indicated that this isoenzyme is essential for the embryonic development of the mouse. The embryos lacking type I C-P4H died at an early stage of their development due to the disruption of basement membranes. It was found that the basement membranes of the homozygous null embryos lacked type IV collagen whereas the fibrillar collagens were synthesized, although with altered morphology. The data reported here also demonstrate that the other C-P4H isoenzymes cannot compensate for the lack of type I isoenzyme.

Abstract Fatty acids are one of the most essential categories of biological lipids and their synthesis and degradation are vital for all organisms. Severely compromised phenotypes of yeast mutants and human patients, which have defective components in their degradative or synthetic processes for fatty acid metabolism, have highlighted the importance of these processes for overall metabolism. Most fatty acids are degraded by β-oxidation, which occurs in mitochondria and peroxisomes in mammals, whereas synthesis is catalyzed by cytosolic multifunctional peptides, although a synthesis system involving individual enzymes in mitochondria has been also proposed. In this study a novel mitochondrial 2-enoyl thioester reductase Etr1p from the yeast Candida tropicalis, its homolog Mrf1p from Saccharomyces cerevisiae, and their mammalian ortholog were identified and characterized. Observations indicating that mitochondrial localization as well as enzymatic activity is needed to complement the respiratory-deficient phenotype of the mrf1Δ strain from S. cerevisiae suggests that Etr1p and Mrf1p might act as a part of the mitochondrial fatty acid synthesis machinery, the proper function of which is essential for respiration and the maintenance of mitochondrial morphology in yeast. The mammalian enzyme, denoted Nrbf-1p, showed similar localization, enzymatic activity, and ability to rescue the growth of the mrf1Δ strain suggesting that mammals are also likely to possess the ability and required machinery for mitochondrial fatty acid synthesis. This study further included the characterization of another mitochondrial thioester reductase, 2,4-dienoyl-CoA reductase, which acts as an auxiliary enzyme in the β-oxidation of unsaturated fatty acids. The function of this gene was analyzed by creating a knock-out mouse model. While unstressed mice deficient in 2,4-dienoyl-CoA reductase were asymptomatic, metabolically challenged mice showed symptoms including hypoglycemia, hepatic steatosis, accumulation of acylcarnitines, and severe intolerance to acute cold exposure. Although the oxidation of saturated fatty acids proceeds normally, the phenotype was in many ways similar to mouse models of the disrupted classical β-oxidation pathway, except that an altered ketogenic response was not observed. This mouse model shows that a proper oxidative metabolism for unsaturated fatty acids is important for balanced fatty acid and energy metabolism.

Of the thousands of dividing progenitor cells (PCs) generated daily in the adult brain only a very small proportion survive to become mature neurons through the process of neurogenesis. Identification of the mechanisms that regulate cell death associated with neurogenesis would aid in harnessing the potential therapeutic value of PCs. Apoptosis, or programmed cell death, is suggested to regulate death of PCs in the adult brain as overexpression of B-cell lymphoma 2 (Bcl-2), an anti-apoptotic protein, enhances the survival of new neurons. To directly assess if Bcl-2 is a regulator of apoptosis in PCs, this study examined the outcome of removal of Bcl-2 from the developing PCs in the adult mouse brain. Retroviral mediated gene transfer of Cre into adult floxed Bcl-2 mice eliminated Bcl-2 from developing PCs and resulted in the complete absence of new neurons at 30 days post viral injection. Similarly, Bcl-2 removal through the use of nestin-induced conditional knockout mice resulted in reduced number of mature neurons. The function of Bcl-2 in the PCs was also dependent on Bcl-2-associated X (BAX) protein, as demonstrated by an increase in new neurons formed following viral-mediated removal of Bcl-2 in BAX knockout mice. Together these findings demonstrate that Bcl-2 is an essential regulator of neurogenesis in the adult hippocampus.