Equilibrio ácido-base durante la exposición aérea en el molusco bivalvo Perumytilus purpuratus (Lamarck, 1819) (Bivalvia: Mytilidae)

For effects of tidal rhythms, intertidal bivalves are exposed to prolonged daily emersion periods during low tide. As a response to air exposure, the mussel Perumytilus purpuratus (Lamarck, 1819) closes its valves and shifts its metabolism to anaerobic pathways by the interruption of the oxygen flux. Consequently, body fluids low their pH causing the CaCO3 disolution of the shell, which would act as a pH buffer. In this study, the role of shell CaCO3 in the regulation of internal homeostasis at different periods of aerial exposure was evaluated. We measured the variation of pH, Ca2+ and HCO3 - concentrations in the extrapallial cavity and Ca2+ concentration at the shell of P. purpuratus individuals from the low and high intertidal zones. The results show that pH increases in the extrapallial cavity fluids during the emersion period in the laboratory, followed by a decrease of the shell Ca2+. Ca2+ and HCO3 - concentrations did not show a significant variation in extrapallial fluids during the aerial exposure periods. Moreover, significant differences were found in the Ca2+ and HCO3 - concentrations at the extrapallial fluids between individuals from low and high tidal levels. However, in the majority of measured variables, in spite of acclimation period, the basal levels were different between individuals from the low and high intertidal zones, suggesting physiological differences due to genetic differences among organisms inhabiting both zonesPor efecto de los ritmos de marea, los bivalvos intermareales quedan expuestos a prolongados periodos de emersión diarios durante las mareas bajas. Bajo estas condiciones, el mitílido Perumytilus purpuratus (Lamarck, 1819) cierra sus valvas y entra en anaerobiosis por la interrupción del flujo de oxígeno. En esta situación baja el pH de los fluidos corporales provocando la disolución del CaCO3 de las valvas y que actuaría como amortiguador de pH. En este estudio se evaluaron las fluctuaciones de pH, Ca2+ y HCO3 - en los fluidos de la cavidad extrapaleal y de Ca2+ en las valvas de individuos de P. purpuratus provenientes del intermareal bajo y alto, expuestos a periodos progresivos de emersión. Los resultados indican que el pH en los fluidos de la cavidad extrapaleal aumentó durante el periodo de emersión en laboratorio, lo cual fue seguido por una disminución de la concentración de Ca2+ de las valvas. Las concentraciones de Ca2+ y HCO3 - en los fluidos extrapaleales no mostraron variación significativa durante el tiempo de exposición aérea. Además, se encontraron diferencias significativas en las concentraciones de Ca2+ y HCO3 - de los fluidos extrapaleales entre individuos del intermareal rocoso alto y bajo. No obstante lo anterior y a pesar del periodo de aclimatación, los niveles de la mayor parte de las variables medidas presentaron un valor basal diferente entre individuos del intermareal bajo y alto, lo cual sugiere diferencias fisiológicas, debido a diferencias genéticas, entre individuos de ambas zonas

The impact of a strong natural hypoxic event on the toadfish Aphos porosus in Coliumo Bay, south-central Chile

The occurrence of natural hypoxic events and coastal marine areas affected by anthropogenic hypoxia has increased over the past decades. In Coliumo Bay, a small shallow bay of the eastern South Pacific, an intense event of natural hypoxia took place in January 2008, causing the mass mortality of fish and other components of the benthic and pelagic communities. In the short term (3 months) recovery was observed in species richness as well as in total fish density. Nevertheless, in the medium term (2 years), this event produced negative effects on population size. In particular, the toadfish Aphos porosus, a dominant fish species in Coliumo Bay, showed a progressive decrease in population size since the occurrence of the hypoxic event, associated with a decrease in recruitment. We hypothesized that this reduction in population size lowered the probability of encounter of reproductive adults, decreasing the number of eggs, larvae and ultimately recruits, thus driving the population towards a low density threshold, and eventually, favoring an Allee effect condition. These results provide evidence on the causal relationship between coastal natural hypoxic events, mass mortality, life history and population dynamics. The slow recovery of the A. porosus population size suggests a process in which the population remains vulnerable to new perturbations. The observed population response is an example of the trajectory that some species may follow when faced with increasing occurrences of natural hypoxic events as predicted, for instance, by global warming scenarios.La ocurrencia de hipoxias naturales y las áreas marinas costeras afectadas por hipoxias antropogénicas se han incrementando en las últimas décadas. En Coliumo, una pequeña bahía somera del Pacífico sur-este, se registró un intenso evento de hipoxia natural en enero del 2008, provocando una mortalidad masiva de peces y otros componentes de la comunidad bentónica y pelágica. En el corto plazo (3 meses) se observó una recuperación en la riqueza y densidad total de peces, sin embargo, en el mediano plazo (2 años) este evento tuvo efectos negativos en sus tamaños poblacionales. En particular Aphos porosus, especie dominante del ensamble de peces en los fondos blandos de Bahía Coliumo, presentó una disminución progresiva en su tamaño poblacional luego del evento, asociada a una disminución en el reclutamiento. Nuestra hipótesis es que la reducción del tamaño poblacional, habría disminuido la probabilidad de encuentro de adultos reproductivos, disminuyendo huevos, larvas y finalmente los reclutas, llevando a A. porosus hacia un umbral crítico de baja densidad, favoreciendo una condición poblacional de efecto Allee. Estos resultados entregan evidencia sobre la relación de causalidad entre eventos de hipoxia natural, mortalidad masiva, historia de vida y dinámica poblacional. La lenta recuperación numérica de A. porosus sugiere un proceso en el cual la población presenta una alta vulnerabilidad a nuevas perturbaciones. Esta respuesta poblacional es un ejemplo de la trayectoria que ciertas especies pudieran seguir ante el incremento de eventos de hipoxia natural, el cual se estima podría ocurrir en un escenario de calentamiento global

Transmission dynamics of HIV-1 subtype B in the Basque Country, Spain

This work was aimed to study the HIV-1 subtype B epidemics in the Basque Country, Spain. 1727 HIV-1 subtype B sequences comprising protease and reverse transcriptase (PR/RT) coding regions, sampled between 2001 and 2008, were analyzed. 156 transmission clusters were detected by means of phylogenetic analyses. Most of them comprised less than 4 individuals and, in total, they included 441 patients. Six clusters comprised 10 or more patients and were further analyzed in order to study their origin and diversification. Four clusters included men who had unprotected homosexual sex (MSM), one group was formed by intravenous drug users (IDUs), and another included both IDUs and people infected through unprotected heterosexual sex (HTs). Most of these clusters originated from the mid-1980s to the mid-1990s. Only one cluster, formed by MSM, originated after 2000. The time between infections was significantly lower in MSM groups than in those containing IDUs (P-value < 0.0001). Nucleoside RT and non-nucleoside RT inhibitor (NRTI and NNRTI)-resistance mutations to antiretroviral treatment were found in these six clusters except the most recent MSM group, but only the IDU clusters presented protease inhibitor (PI)-resistance mutations. The most prevalent mutations for each inhibitor class were PI L90M, NRTI T215D/Y/F, and NNRTI K103N, which were also among the most prevalent resistant variants in the whole dataset. In conclusion, while most infections occur as isolated introductions into the population, the number of infections found to be epidemiologically related within the Basque Country is significant. Public health control measures should be reinforced to prevent the further expansion of transmission clusters and resistant mutations occurring within them

Patrones de sensibilidad a antimicrobianos de Enterobacteriaceae causantes de infecciones intraabdominales en España: resultados del estudio SMART 2003

El estudio SMART ( Study for Monitoring Antimicrobial Resistance Trends ) es un programa mundial de vigilancia de la resistencia a los antimicrobianos de microorganismos aislados de infecciones intraabdominales. En este subanálisis se evaluó el patrón de sensibilidad de las enterobacterias recogidas en los 13 centros españoles participantes en el año 2003. Se determinaron las CMI de diferentes antimicrobianos por el método de microdilución en caldo siguiendo las recomendaciones del CLSI (antes NCCLS). Se confirmó la presencia de betalactamasas de espectro extendido (BLEE) en aquellas cepas frente a las cuales las CMI de ceftriaxona, ceftazidima y cefepima eran ¡Ý2 mg/l mediante la comparación de las CMI de cefepima con o sin ácido clavulánico (10 mg/l). Se evaluaron 981 enterobacterias de 840 pacientes. De ellas, 398 (41%) eran de adquisición comunitaria. Escherichia coli fue el aislamiento más frecuente (571 cepas; 58%), seguida por Klebsiella spp. (153 cepas; 16%), Enterobacter spp. (97 cepas; 10%) y Proteus spp. (63 cepas; 6%). Un total de 191 cepas procedentes de 176 pacientes eran productoras de betalactamasas inducibles (19%). Los carbapenémicos y la amikacina fueron los antibióticos más activos frente a las enterobacterias (sensibilidad ¡Ý99%). La resistencia a ceftazidima, ciprofloxacino y levofloxacino fue superior al 10%. Se detectaron BLEE fenotípicamente en 61 (6%) de los aislamientos, siendo más frecuentes en E. coli (61%), Klebsiella spp. (20%) y Enterobacter spp. (8%). La resistencia entre las enterobacterias aisladas de infecciones intraabdominales constituye un problema en España. Una proporción significativa de las productoras de BLEE o de betalactamasas inducibles proceden de la comunidad. Los carbapenémicos ertapenem, imipenem y meropenem, y el aminoglucósido amikacina, son muy activos in vitro frente a las enterobacterias aisladas de focos intraabdominales, incluyendo aquéllas productoras de BLEE

América Latina y el mundo : exploraciones en torno a identidades, discursos y genealogías

América Latina y el Mundo reúne una selección de artículos elaborados a partir de un grupo de ponencias expuestas en las IV Jornadas de Estudiantes de Postgrado en Humanidades, Artes y Ciencias Sociales, realizadas entre el 13 y el 15 de enero del 2003 en la Facultad de Filosofía y Humanidades de la Universidad de Chile. En los artículos reunidos en este volumen se puede reconocer una actitud crítica frente a la hegemonía de los modelos metropolitanos, aunada a esfuerzos destinados a rescatar las actividades, historias y saberes invisibilizados o bien tergiversados por las retóricas y prácticas dominantes en los proyectos modernizadores. Dentro de estas posturas críticas es posible distinguir tres principales líneas temáticas, tales como la reflexión en torno a las identidades, la discusión sobre los modelos de representación y la necesidad de establecer líneas genealógicas que han sido ignoradas por la historiografía tradicional

Germline biallelic Mcm8 variants are associated with early-onset Lynch-like syndrome

Lynch syndrome is the most common cause of hereditary colorectal cancer (CRC), and it is characterized by DNA mismatch repair (MMR) deficiency. The term Lynch-like syndrome (LLS) is used for patients with MMR-deficient tumors and neither germline mutation in MLH1, MSH2, MSH6, PMS2, or EPCAM nor MLH1 somatic methylation. Biallelic somatic inactivation or cryptic germline MMR variants undetected during genetic testing have been proposed to be involved. Sixteen patients with early-onset LLS CRC were selected for germline and tumor whole-exome sequencing. Two potentially pathogenic germline MCM8 variants were detected in a male patient with LLS with fertility problems. A knockout cellular model for MCM8 was generated by CRISPR/Cas9 and detected genetic variants were produced by mutagenesis. DNA damage, microsatellite instability, and mutational signatures were monitored. DNA damage was evident for MCM8KO cells and the analyzed genetic variants. Microsatellite instability and mutational signatures in MCM8KO cells were compatible with the involvement of MCM8 in MMR. Replication in an independent familial cancer cohort detected additional carriers. Unexplained MMR-deficient CRC cases, even showing somatic biallelic MMR inactivation, may be caused by underlying germline defects in genes different than MMR genes. We suggest MCM8 as a gene involved in CRC germline predisposition with a recessive pattern of inheritance

HIV-1 viral load and CD4 cell count in untreated children with vertically acquired asymptomatic or mild disease. Paediatric European Network for Treatment of AIDS (PENTA).

BACKGROUND: Plasma HIV-1 RNA levels are high in vertically infected infants. Information in older children is limited, particularly in those who have not received antiretroviral therapy. OBJECTIVES: To describe the relationships between HIV-1 RNA, age and CD4 cell count in untreated vertically infected children. DESIGN: HIV-1 RNA was measured in 70 children [median age, 3.5 years (range, 0.4-11.9 years); median CD4 cell count, 881 x 10(6)/l (interquartile range, 576-1347 x 10(6) cells/l)] enrolled in a randomized placebo-controlled trial comparing immediate with deferred zidovudine in asymptomatic or mildly symptomatic vertically infected children (PENTA-1 trial). Short-term variability was assessed by comparing HIV-1 RNA at -2 and 0 weeks (prior to randomization). The relationship between age and HIV-1 RNA, and CD4 cell count was analysed using data from all children prior to randomization and sequential samples from 35 remaining on placebo for up to 105 weeks, by fitting mixed linear models. RESULTS: The within-individual SD in viral load was 0.26 log10 copies/ml. The median plasma HIV-1 RNA at enrollment was 4.61 log10 (range, 2.3-6.56 log10 copies/ml), significantly higher in children aged 2 years (4.51 log10 copies/ml; P < 0.0001). Mean HIV-1 RNA fell by 0.38 log10 copies/ml per year up to 2 years of age, by 0.21 log10 copies/ml per year from 2 to 4 years of age, and by 0.03 log10 copies/ml per year from 4 to 6 years of age reaching a nadir of 4.25 log10 copies/ml at 6 years. Mean log10 CD4 cell count declined steadily with age and was not significantly correlated with HIV-1 RNA, although there was some evidence that the rate of log10 CD4 cell decline was negatively correlated with the initial rate of HIV-1 RNA decline. No mutations associated with resistance to zidovudine were observed. CONCLUSIONS: Age is a key factor in the interpretation of both viral load and CD4 cell count in vertically infected childre