Aquaporins in the brain: from aqueduct to "multi-duct”

The aquaporin channel family was first considered as a family of water channels, however it is now clear that some of these channels are also permeable to small solutes such glycerol, urea and monocarboxylates. In this review, we will consider AQP4 and AQP9 expressed in the rodent brain. AQP4 is present on astrocytic end-feet in contact with brain vessels and could be involved in ionic homeostasis. However, AQP4 may also be involved in cell adhesion. AQP4 expression is highly modified in several brain disorders and it can play a key role in the cerebral edema formation. However, the exact role of AQP4 in edema formation is still debated. Recently, AQP4 has been shown to be also involved in astrocyte migration during glial scar formation. AQP9 is expressed in astrocytes and in catecholaminergic neurons. Two isoforms of AQP9 are expressed in brain cells, the shortest isoform is localized in the inner membrane of mitochondria and the longest in the cell membrane. The level of expression of AQP9 is negatively regulated by high concentrations of insulin. Taken together, these results suggest that AQP9 could be involved in brain energy metabolism. The induction of AQP9 in astrocytes is observed with time after stroke onset suggesting participation in the clearance of excess lactate in the extracellular space. These recent exciting results suggest that AQPs may not only be involved in water homeostasis in the brain but could also participate in other important physiological function

d13C tracing of dissolved inorganic carbon sources in Patagonian rivers (Argentina)

The main Patagonian rivers (Colorado, Negro, Chubut, Deseado, Coyle, Chico, Santa Cruz and Gallegos) were sampled between September 1995 and November 1998 to determine their chemical and isotopic compositions, the origins of the suspended and dissolved river loads and their inputs to the South Atlantic Ocean. This paper focuses on the dissolved inorganic carbon (DIC) transport and its υ13C isotopic signature. The υ13CDIC values vary between 12Ð8 and 1Ð8‰ and allow one to distinguish two river groups: (i) the Colorado, Negro, Chubut and Santa Cruz, which display the highest values and the lowest seasonal variations; (ii) the Deseado, Coyle, Chico and Gallegos, which show the lowest values and the highest seasonal variations. For the first group, υ13CDIC is mainly controlled by important exchanges between the river waters and atmospheric CO2, due to the presence of lakes and dams. For the second group, υ13CDIC also appears to be controlled by the oxidation of organic carbon, showing a negative relationship between υ13CDIC and the dissolved organic carbon. These biogeochemical processes interfere with the contribution of carbonate and silicate weathering to the riverine DIC and do not allow use of υ13CDIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ð 109 g. of C, i.e. a specific yield of 2Ð7 g m2 year1. The mean υ13CDIC can be estimated to 4Ð9‰, which is high compared with other rivers of the world

La photographie « documentaire » américaine : nouvelles approches

Le présent dossier vise à dessiner les contours d’un nouveau paysage historiographique et critique relatif à la grande tradition « documentaire » de la photographie américaine, qui a accompagné les épisodes majeurs de l'histoire des Etats-Unis depuis l'avènement du médium. Parmi les jalons les plus marquants de notre culture de l'image documentaire américaine, se dégagent ainsi, par exemple, les premiers reportages géo-ethnographiques des expéditions vers l'Ouest (« surveys ») visant à établi..

Percolation transition in the porous structure of latex-templated silica monoliths

International audiencePorous sol-gel silica monoliths are prepared using PMMA nanoparticles, 60 nm in diameter, as sacrificial templates. The pore-structure of the calcined pellets is investigated through nitrogen adsorption to assess the evolution of the porosity when varying the amount of porogen. The latex templated monoliths present a well defined spherical extrinsic porosity and an intrinsic microporosity due to preparation process. As a result of a careful analysis of the adsorption hysteresis, we identify a percolation threshold of the spherical porosity around 30% volume fraction. This phenomenon, similar to the percolation previously observed in latex-templated silica films, opens the way to the use of latex-templated porous silica monoliths with a tailorable and reliable pore structure

Defects in Sensory and Autonomic Ganglia and Absence of Locus Coeruleus in Mice Deficient for the Homeobox Gene Phox2a

AbstractPhox2a is a vertebrate homeodomain protein expressed in subsets of differentiating neurons. Here, we show that it is essential for proper development of the locus coeruleus, a subset of sympathetic and parasympathetic ganglia and the VIIth, IXth, and Xth cranial sensory ganglia. In the sensory ganglia, we have identified two differentiation blocks in Phox2a−/− mice. First, the transient expression of dopamine- β-hydroxylase in neuroblasts is abolished, providing evidence that Phox2a controls noradrenergic traits in vivo. Second, the expression of the GDNF receptor subunit Ret is dramatically reduced, and there is a massive increase in apoptosis of ganglion cells, which are known to depend on GDNF in vivo. Therefore, Phox2a appears to regulate conventional differentiation traits and the ability of neurons to respond to essential survival factors

La tempête de verglas : une occasion d’étudier les effets du stress prénatal chez l’enfant et la mère

Depuis plusieurs années, des études ont démontré que les événements stressants pendant la grossesse affectent le niveau de développement neurologique, de même que le fonctionnement cognitif et psychologique ultérieurs de l'enfant. Par exemple, Mednick (1997) a examiné l'impact d'un important séisme survenu en Chine sur le développement intellectuel et psychologique d'enfants à naître. Vingt-trois ans plus tard, des différences significatives dans le fonctionnement intellectuel, la dépression et la taille de certaines régions du cerveau ont été constatées chez ce groupe en comparaison aux enfants du groupe témoin. Des événements de moindre envergure, tels un divorce ou la perte d'emploi durant la grossesse, peuvent également augmenter l'incidence des complications obstétricales et avoir un impact sur le fonctionnement neurologique du bébé, son poids à la naissance et la circonférence de sa tête. Le décès du père ou l'exposition à un désastre naturel durant la grossesse ont été associés à la dépression, à la schizophrénie et à la criminalité à l'âge adulte. Divers effets adverses reliés aux événements stressants ont aussi été notés chez les primates. L'ensemble de ces études suggèrent que le second trimestre de la grossesse constitue une période critique pendant laquelle les événements stressants peuvent affecter le développement du foetus. Des contraintes méthodologiques nuisent actuellement à la recherche sur le stress prénatal maternel. Les études sur des animaux offrent d'excellents contrôles des environnements prénatal et postnatal. Cependant, les résultats de ces études sont difficilement applicables à l'humain à cause de la présence chez ce dernier, de nombreux facteurs de risque ou de protection absents chez les animaux. De plus, on ne peut assigner les stresseurs de façon aléatoire, dans les études sur les effets des événements de vie pendant la grossesse humaine. En effet, les traits de personnalité de la mère peuvent être transmis certes génétiquement mais également au niveau du développement. Par ailleurs, les enfants d'une mère avec de telles difficultés de personnalité sont exposés à plus d'événements de vie prénatale. D'autre part, la majorité des études sur l'humain ont une variance restreinte car il faut un très vaste échantillon de femmes enceintes pour garantir un nombre suffisant de sujets ayant vécu des événements de vie majeurs. Finalement, les études rétrospectives démontrant un lien entre un risque élevé de schizophrénie ou de dépression et des événements prénataux n'incluent pas de mesures prises sur le champ de la gravité objective ou de la manifestation biologique du stress. Nous présentons ici une revue de littérature portant sur le stress prénatal suivie d'une discussion sur comment la tempête de verglas de 1998 pourrait être utilisée pour faire la lumière sur des questions telles que les mécanismes par lesquels le stress prénatal exerce une influence sur la santé mentale du foetus.Over the last several years, studies have shown that stressful experiences during the pregnancy can predict levels of neurological development, as well as cognitive and psychological functioning, during childhood and adulthood. For example, Mednick (1997) has been studying the effects of a major earthquake in China on the psychological and intellectual development of the unborn child. Twenty-three years after the quake, significant differences have been found between the earthquake group and a control group born one year later in terms of intellectual functioning, depression, and the size of certain brain regions. Less severe events, such as a divorce or job loss during the pregnancy, may also increase the risk of obstetric complications and may have an effect on the baby's neurological well being, weight and head circumference at birth. Death of the baby's father during the pregnancy and natural disasters have both been associated with increased rates of depression, schizophrenia and criminality in adulthood. Several of these same effects have been found in studies of prenatal stress in non-human primates. Many of these studies suggest that the second trimester of pregnancy is a particularly critical period during which stressful events may compromise development of the fetus. Methodological constraints limit research on prenatal maternal stress. Animal studies are able to control for pre- and postnatal environments. However, animal studies have limited generalizability to humans for whom numerous risk and protective factors are in operation. Studies of human pregnancies cannot randomly assign subjects to stress conditions. Maternal personality and temperament may be associated with characteristics of a woman's child not only through genetic transmission of personality, but possibly also through differential exposure to difficult life conditions which may, in part, be self-imposed. In addition, studies of prenatal life events in humans have severely restricted variance; very large samples of women must be screened to identify even small numbers of women who have experienced major life events during the pregnancy. Finally, follow-back studies which show an association between prenatal events and later rates of mental illness, do not include timely evaluations of actual rates of exposure to the event, nor the pregnant woman's subjective or biological reactions to the event. In this paper, we present a review of the literature on prenatal maternal stress followed by a discussion of how the January 1998 Québec ice storm could be used to study the mechanisms by which prenatal stress may influence mental health outcomes in the unborn child.Desde hace varios años, estudios han demostrado que los hechos estresantes durante el embarazo afectan el grado de desarrollo neurológico, como posteriormente el funcionamiento cognoscitivo y psicológico del niño. Por ejemplo, Mednick (1997) examinó el impacto de un terremoto importante occurrido en China en el desarrollo intelectual y psicológico del futuro niño. Veintitres años después, diferencias significativas fueron constatadas en en funcionamiento intelectual, la depresión y la dimensión de ciertas regiones del cerebro en este grupo, comparativamente a un grupo testigo. Hechos de menor envergadura como el divorcio o la pérdida del empleo durante el embarazo pueden igualmente aumentar la incidencia de las complicaciones obstétricas y tener un impacto en el funcionamiento neurológico del bebé, su peso en el nacimiento y la circunferencia de la cabeza. La muerte del padre o la exposición a un desastre natural durante el embarazo han sido asociados a la depresión, la esquizofrenia y la criminalidad en la edad adulta. Diversos efectos adversos ligados a hechos estresantes también han sido notados en los primates. El conjunto de estos estudios sugieren que el segundo trimestre del embarazo constituye un período crítico durante el cual los eventos estresantes pueden afectar el desarrollo del feto. Impedimentos metodológicos afectan actualmente la investigación sobre el estrés perinatal materno. Los estudios con animales ofrecen excelentes controles del medio perinatal y postnatal. Sin embargo los resultados de estos estudios dificilmente son aplicables al ser humano a causa de la presencia de numerosos factores de riesgo o de protección, ausentes en los animales. Además, en los estudios sobre los efectos de los eventos de vida durante el embarazo no se puede asignar estresores de forma aleatoria. En efecto, los rasgos de personalidad de la madre pueden ser transmitidos genéticamante, pero también en el curso del desarrollo. Entre otras, los niños de una madre con determinadas dificultades de personalidad están expuestos a más hechos perinatales de vida. Por otra parte, la mayoría de los estudios sobre el humano varían poco puesto que se necesita un amplio muestreo de mujeres embarazadas que garantice un número suficiente de sujetos que hayan vivido eventos de vida mayores. Para terminar, los estudios retrospectivos demuestran una relación entre el alto riesgo de esquizofrenia o de depresión y los hechos perinatales no incluyen la toma rápida de medidas sobre la gravedad objetiva o sobre la manifestación biológica del estres. Nosotros presentamos aquí una revista de la literatura que aborda el estres perinatal, seguida de una discusión sobre cómo la tempestad de hielo de 1998 podría se utilizada para aclarar sobre interrogantes tales los mecanismos por los cuales el estres perinatal ejerce una influencia en la salud mental de feto

Short-term effects of unilateral lesion of the primary motor cortex (M1) on ipsilesional hand dexterity in adult macaque monkeys

Although the arrangement of the corticospinal projection in primates is consistent with a more prominent role of the ipsilateral motor cortex on proximal muscles, rather than on distal muscles involved in manual dexterity, the role played by the primary motor cortex on the control of manual dexterity for the ipsilateral hand remains a matter a debate, either in the normal function or after a lesion. We, therefore, tested the impact of permanent unilateral motor cortex lesion on the manual dexterity of the ipsilateral hand in 11 macaque monkeys, within a time window of 60days post-lesion. For comparison, unilateral reversible pharmacological inactivation of the motor cortex was produced in an additional monkey. Manual dexterity was assessed quantitatively based on three motor parameters derived from two reach and grasp manual tasks. In contrast to the expected dramatic, complete deficit of manual dexterity of the contralesional hand that persists for several weeks, the impact on the manual dexterity of the ipsilesional hand was generally moderate (but statistically significant) and, when present, lasted less than 20days. Out of the 11 monkeys, only 3 showed a deficit of the ipsilesional hand for 2 of the 3 motor parameters, and 4 animals had a deficit for only one motor parameter. Four monkeys did not show any deficit. The reversible inactivation experiment yielded results consistent with the permanent lesion data. In conclusion, the primary motor cortex exerts a modest role on ipsilateral manual dexterity, most likely in the form of indirect hand postural contro