The field high-amplitude SX Phe variable BL Cam: results from a multisite photometric campaign. II. Evidence of a binary - possibly triple - system

Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M_{\sun}) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M_{\sun}), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary.Comment: 7 pages, 5 figures, accepted for publication in A&

Vol. 3, Núm. 1 (2005)

Se realizaron cuatros cruceros oceanográficos durante primavera, verano, otoño e invierno de 2002. El grupo fitoplanctónico dominante fue el de las diatomeas durante otoño, invierno y primavera llegando a un 75%, mientras que en verano dominaron los dinoflagelados con un 70%. Coscinodiscus granii Gough mostró una marcada relación con el rango de temperaturas entre 22 y 25°C en los transectos oceánicos y costeros. El patrón de circulación mostró tendencia general hacia el sur con una variabilidad estacional que se reflejó en la presencia de giros con transporte neto hacia mar abierto durante invierno y verano, mientras que en primavera y otoño fue hacia continente, las mayores velocidades se alcanzaron en primavera al sur de la zona de estudio, llegando a ser de 0.6 m seg-1. La concentración de nutrientes mostró una relación puntual con descargas continentales, su comportamiento estuvo más bien influenciado por los mecanismos de fertilización de la dinámica de circulación de la zona de estudio, alcanzando las máximas concentraciones cerca de la termoclina, que en promedio se situó a una profundidad de 35 metros a lo largo del periodo anual

Efecto de la comunidad bacteriana en el crecimiento, pigmentos y toxinas paralizantes en el dinoflagelado Gymnodinium catenatum (Graham)

Gymnodinium catenatum, un dinoflagelado productor de toxinas paralizantes, es una de las especies de dinoflagelados más estudiadas, sin embargo, poco se conoce sobre sus interacciones con bacterias. En este estudio se determinó el efecto de un consorcio bacteriano en cepas de G. catenatum. Se emplearon 4 cepas de G. catenatum aisladas de Bahía de Santiago, Colima; Lázaro Cárdenas, Michoacán; Bahía Concepción y Bahía de La Paz, Baja California Sur. De la cepa originaria de la costa de Colima se aisló un consorcio bacteriano compuesto de 3 bacterias empleando placas de agar con medio GSe. Se incubaron a una salinidad de 34, a 24 °C y en un ciclo de 12:12 h L:O. Gymnodinum catenatum se cultivó en medio GSe líquido en las mismas condiciones que las bacterias. La interacción entre los microorganismos se evaluó inoculando el consorcio bacteriano en las cepas de G. catenatum. Se determinó la abundancia máxima, las tasas de crecimiento, la longitud de cadenas y el perfil de pigmentos y toxinas paralizantes en G. catenatum en presencia y ausencia del consorcio bacteriano. En presencia de las bacterias no se observó la misma respuesta en el crecimiento de las cepas de G. catenatum, ni en el perfil y contenido de toxinas, pero sí se observó un incremento significativo en el número de células en cadena. También se notaron cambios en la morfología de G. catenatum. Además, en presencia del consorcio bacteriano, en la mayoría de las cepas incrementó el contenido de pigmentos accesorios. Los resultados sugieren que el consorcio bacteriano pudiera ser un agente estresante para G. catenatum proporcionando nuevas perspectivas de interacción entre las bacterias y G. catenatum

Rabphilin-3A as a novel target to reverse α-synuclein-induced synaptic loss in Parkinson's disease

Toxic aggregates of α-synuclein (αsyn) are considered key drivers of Parkinson's disease (PD) pathology. In early PD, αsyn induces synaptic dysfunction also modulating the glutamatergic neurotransmission. However, a more detailed understanding of the molecular mechanisms underlying αsyn-triggered synaptic failure is required to design novel therapeutic interventions. Here, we described the role of Rabphilin-3A (Rph3A) as novel target to counteract αsyn-induced synaptic loss in PD. Rph3A is a synaptic protein interacting with αsyn and involved in stabilizing dendritic spines and in promoting the synaptic retention of NMDA-type glutamate receptors. We found that in vivo intrastriatal injection of αsyn-preformed fibrils in mice induces the early loss of striatal synapses associated with decreased synaptic levels of Rph3A and impaired Rph3A/NMDA receptors interaction. Modulating Rph3A striatal expression or interfering with the Rph3A/αsyn complex with a small molecule prevented dendritic spine loss and rescued associated early motor defects in αsyn-injected mice. Notably, the same experimental approaches prevented αsyn-induced synaptic loss in vitro in primary hippocampal neurons. Overall, these findings indicate that approaches aimed at restoring Rph3A synaptic functions can slow down the early synaptic detrimental effects of αsyn aggregates in PD

Remote memories are enhanced by COMT activity through dysregulation of the endocannabinoid system in the prefrontal cortex

The prefrontal cortex (PFC) is a crucial hub for the flexible modulation of recent memories (executive functions) as well as for the stable organization of remote memories. Dopamine in the PFC is implicated in both these processes and genetic variants affecting its neurotransmission might control the unique balance between cognitive stability and flexibility present in each individual. Functional genetic variants in the catechol-O-methyltransferase (COMT) gene result in a different catabolism of dopamine in the PFC. However, despite the established role played by COMT genetic variation in executive functions, its impact on remote memory formation and recall is still poorly explored. Here we report that transgenic mice overexpressing the human COMT-Val gene (COMT-Val-tg) present exaggerated remote memories (450 days) while having unaltered recent memories (<24 h). COMT selectively and reversibly modulated the recall of remote memories as silencing COMT Val overexpression starting from 30 days after the initial aversive conditioning normalized remote memories. COMT genetic overactivity produced a selective overdrive of the endocannabinoid system within the PFC, but not in the striatum and hippocampus, which was associated with enhanced remote memories. Indeed, acute pharmacological blockade of CB1 receptors was sufficient to rescue the altered remote memory recall in COMT-Val-tg mice and increased PFC dopamine levels. These results demonstrate that COMT genetic variations modulate the retrieval of remote memories through the dysregulation of the endocannabinoid system in the PFC

The field high-amplitude SX Phe variable BL Cam: Results from a multisite photometric campaign: II. Evidence of a binary - Possibly triple - System

Context.Short-period high-amplitude pulsating stars of Population I (d Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. Aims.We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. Methods.An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. Results. In addition to a positive (161 ± 3) × 10-9 yr-1 secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short-(144.2 d) and long-term (~3400 d) variations, both incompatible with a scenario of stellar evolution. Conclusions. Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M?) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star (=0.03 M?), orbiting in ~3400 d at a distance of 4.5 AU from the primary. © ESO, 2010