Nest size and hatchling sex ratio in chinstrap penguins

Variation in the sex ratio at hatching in the chinstrap penguin Pygoscelis antarctica was investigated, using molecular sexing to test predictions of sex allocation theory. The sex ratio was slightly male-biased (0.54) but did not differ significantly from parity. The proportion of males increased with nest size, an estimator of parental quality in chinstrap penguins. High-quality parents were able to produce and rear a higher proportion of male offspring, the more costly sex in this slightly sexually dimorphic species. Our results may be in agreement with Trivers and Willards (1973) argument on biases in the offspring sex ratio being contingent on parental condition or quality.     

Alcohol exposure alters the expression pattern of neural cell adhesion molecules during brain development

Neural cell adhesion molecules (NCAMs) play critical roles during development of the nervous system. The aim of this study is to investigate the possible effect of ethanol exposure on the pattern of expression and sialylation of NCAM isoforms during postnatal rat brain development because alterations in NCAM content and distribution have been associated with defects in cell migration, synapse formation, and memory consolidation, and deficits in these processes have been observed after in utero alcohol exposure. The expression of NCAM isoforms in the developing cerebral cortex of pups from control and alcohol-fed mothers was assessed by western blotting, ribonuclease protection assay, and immunocytochemistry. The highly sialylated form of NCAM [polysialic acid (PSA)-NCAM] is mainly expressed during the neonatal period and then is down-regulated in parallel with the appearance of NCAM 180 and NCAM 140. Ethanol exposure increases PSA-NCAM levels during the neonatal period, delays the loss of PSA-NCAM, decreases the amount of NCAM 180 and NCAM 140 isoforms, and reduces sialyltransferase activity during postnatal brain development. Neuraminidase treatment of ethanol-exposed neonatal brains leads to more intense band degradation products, suggesting a higher content of NCAM polypeptides carrying PSA in these samples. However, NCAM mRNA levels are not changed by ethanol. Immunocytochemical analysis demonstrates that ethanol triggers an increase in PSA-NCAM immunolabeling in the cytoplasm of astroglial cells, accompanied by a decrease in immunogold particles over the plasma membrane. These findings indicate that ethanol exposure during brain development alters the pattern of NCAM expression and suggest that modification of NCAM could affect neuronal-glial interactions that might contribute to the brain defects observed after in utero alcohol exposure.     

Worldwide Occurrence of Integrative Conjugative Element Encoding Multidrug Resistance Determinants in Epidemic Vibrio cholerae O1

In the last decades, there has been an increase of cholera epidemics caused by multidrug resistant strains. Particularly, the integrative and conjugative element (ICE) seems to play a major role in the emergence of multidrug resistant Vibrio cholerae. This study fully characterized, by whole genome sequencing, new ICEs carried by multidrug resistant V. cholerae O1 strains from Nigeria (2010) (ICEVchNig1) and Nepal (1994) (ICEVchNep1). The gene content and gene order of these two ICEs are the same, and identical to ICEVchInd5, ICEVchBan5 and ICEVchHai1 previously identified in multidrug resistant V. cholerae O1. This ICE is characterized by dfrA1, sul2, strAB and floR antimicrobial resistance genes, and by unique gene content in HS4 and HS5 ICE regions. Screening for ICEs, in publicly available V. cholerae genomes, revealed the occurrence and widespread distribution of this ICE among V. cholerae O1. Metagenomic analysis found segments of this ICE in marine environments far from the direct influence of the cholera epidemic. Therefore, this study revealed the epidemiology of a spatio-temporal prevalent ICE in V. cholerae O1. Its occurrence and dispersion in V. cholerae O1 strains from different continents throughout more than two decades can be indicative of its role in the fitness of the current pandemic lineage.     

The importance of fine-scale breeding site selection patterns under a landscape-sharing approach for wolf conservation

For large carnivores persisting in human-dominated landscapes, conservation planning is often hindered by the large spatial requirements of these species, availability of protected areas, and human land uses. Protected areas are usually too small to support viable populations, and scattered across a human land-use matrix. Therefore, large carnivore conservation should be planned at large spatial scales under a land-sharing approach (allowing the coexistence between large carnivores and people in the same landscape), which means increasing the focus on the human-dominated matrix. Most of the critical factors determining large carnivore persistence (i.e., those related to food availability and vulnerability to humans) interact synergistically in space and time during the breeding season. Here, using as a case study a wolf population in NW Iberia, we studied fine-scale breeding site selection patterns (1 and 9 km²) in relation to human pressure, and the availability of food and refuge. The selection of wolf breeding sites in this human-dominated landscape was not determined by potential availability of prey biomass in the immediate vicinity (1 km²). However, wolves selected breeding sites with high availability of refuge (concealing vegetation), and low human accessibility and activity levels. Paved roads showed the highest proportion of independent contribution to explaining breeding site selection patterns (negative influence), being followed by refuge availability (positive influence) and the remoteness of breeding sites in relation to the surrounding spatial context (positive influence). Refuge availability, even at very small spatial scales taking into account the spatial requirements of wolves, may compensate for moderate levels of human activities in the vicinity of breeding sites. The strength of breeding selection patterns varied along a hierarchical process at different spatial scales. Under a landscape-sharing approach, integrating key processes observed in the human-dominated matrix, such as breeding site selection patterns, into landscape planning is of paramount importance for carnivore conservation. By temporally restricting human use on breeding sites and small portions of surrounding lands (~ 1 km²), and by maintaining several small refuge areas interspersed within the human-dominated matrix, we could favor wolf persistence without reducing land availability for other uses, improving the conditions for coexistence between wolves and humans.     

The efficiency of the red alga Mastocarpus stellatus for remediation of cadmium pollution

This work reports the results of the study for cadmium binding by the dead red macroalga Mastocarpus stellatus. Kinetics sorption experiments demonstrated the high rate of metal biosorption: the system attained over 50% of the total biomass cadmium uptake within 2 min of contact and over 90% in the first 9 min. The kinetic data were successfully described by a pseudo-second order model with rate constants ranging from 1.06 to 10 gmmol(-1)min(-1), as a function of initial metal concentration and temperature. The equilibrium binding was accurately represented in terms of Langmuir and Langmuir-Freundlich models. The sorption isotherms at constant pH showed uptake values as 0.49 mmol g(-1) (at pH 2.4), 0.56 mmol g(-1) (at pH 4) and 0.59 mmol g(-1) (at pH 6), while the affinity constant values were between 0.6 and 5 mmol(-1) L (Langmuir fit). The acid-base properties of the alga were also studied, obtaining the total number of acid groups, 2.5 mmol g(-1), and their apparent pK value, 1.56, using the Katchalsky model. Desorption studies were conducted employing different HNO(3) concentrations and desorption times.     

Hif1 is a component of yeast histone acetyltransferase B, a complex mainly localized in the nucleus

Hat1 is the catalytic subunit of the only type B histone acetyltransferase known (HAT-B). The enzyme specifically acetylates lysine 12, and to a lesser extent lysine 5, of free, non-chromatin-bound histone H4. The complex is usually isolated with cytosolic fractions and is thought to be involved in chromatin assembly. The Saccharomyces cerevisiae HAT-B complex also contains Hat2, a protein stimulating Hat1 catalytic activity. We have now identified by two-hybrid experiments Hif1 as both a Hat1- and a histone H4-interacting protein. These interactions were dependent on HAT2, indicating a mediating role for Hat2. Biochemical fractionation and co-immunoprecipitation assays demonstrated that Hif1 is a component of a yeast heterotrimeric HAT-B complex, in which Hat2 bridges Hat1 and Hif1 proteins. In contrast to Hat2, this novel subunit does not appear to regulate Hat1 enzymatic activity. Nevertheless, similarly to Hat1, Hif1 influences telomeric silencing. In a localization analysis by immunofluorescence microscopy on yeast strains expressing tagged versions of Hat1, Hat2, and Hif1, we have found that all three HAT-B proteins are mainly localized in the nucleus. Thus, we propose that the distinction between A- and B-type enzymes should henceforth be based on their capacity to acetylate histones bound to nucleosomes and not on their location within the cell. Finally, by Western blotting assays, we have not detected differences in the in vivo acetylation of H4 lysine 12 (acK12H4) between wild-type and hat1Delta, hat2Delta, or hif1Delta mutant strains, suggesting that the level of HAT-B-dependent acK12H4 may be very low under normal growth conditions.     

Plant Virus Cell-to-Cell Movement Is Not Dependent on the Transmembrane Disposition of Its Movement Protein

The cell-to-cell transport of plant viruses depends on one or more virus-encoded movement proteins (MPs). Some MPs are integral membrane proteins that interact with the membrane of the endoplasmic reticulum, but a detailed understanding of the interaction between MPs and biological membranes has been lacking. The cell-to-cell movement of the Prunus necrotic ringspot virus (PNRSV) is facilitated by a single MP of the 30K superfamily. Here, using a myriad of biochemical and biophysical approaches, we show that the PNRSV MP contains only one hydrophobic region (HR) that interacts with the membrane interface, as opposed to being a transmembrane protein. We also show that a proline residue located in the middle of the HR constrains the structural conformation of this region at the membrane interface, and its replacement precludes virus movement.Plant viruses encode movement proteins (MPs) that mediate the intra- and intercellular spread of the viral genome via plasmodesmata, membranous channels that traverse the walls of plant cells and enable intercellular transport and communication. There is a range of diversity in the number and type of viral proteins required for viral movement (21). Research on tobacco mosaic virus (TMV) has played a leading role in understanding MP activity (2). The genome of TMV encodes a single 30-kDa multidomain protein, the namesake of the 30K superfamily (7). Viral RNA is associated with the membrane of the endoplasmic reticulum (ER) and microtubules in the presence of this MP (23, 30).A large number of plant viruses have 30K MPs, which share common abilities, including binding nucleic acids, localizing and increasing the size exclusion limit of plasmodesmata, and interacting with the ER membrane. A topological model has been proposed in which the TMV MP has two putative transmembrane (TM) helices, both the N and C termini oriented toward the cytoplasm, and a short loop exposed in the ER lumen (4). There is less experimental information for other 30K MPs, but they are likely to have some membrane interaction.Direct experimental evidence of the integration of MPs into the membrane has been obtained only for small hydrophobic MPs that do not belong to the 30K superfamily. There are two TM segments in the p9 protein of carnation mottle virus (41), whereas the p6 protein of beet yellow virus (29) and the p7B protein of melon necrotic spot virus (22) have a single TM segment. In viruses with genomes that include three partially overlapping open reading frames, termed the triple-gene block (TGB), all three TGB proteins are required for movement where the two smaller proteins, TGBp2 and TGBp3, are also TM proteins (24). Furthermore, cross-linking experiments with carnation mottle virus p9 protein demonstrated that its membrane insertion occurs cotranslationally in a signal recognition particle-dependent manner and throughout the cellular membrane integration components, the translocon (33, 34).Prunus necrotic ringspot virus (PNRSV) is a tripartite, positive-strand RNA virus in the genus Ilarvirus of the family Bromoviridae. RNAs 1 and 2 encode the polymerase proteins P1 and P2, respectively. RNA 3 is translated into a single 30K-type MP. The coat protein is translated from a subgenomic RNA 4 produced during virus replication.The present study tackled the association of the PNRSV MP with biological membranes. The in vitro translation of model integral membrane protein constructs in the presence of microsomal membranes demonstrated that the hydrophobic region (HR) of the PNRSV MP did not span the membranes. Different biochemical and biophysical experiments suggested that the protein is tightly associated with, but does not traverse, the membrane, leaving both its N- and C-terminal hydrophilic regions facing the cytosol. Finally, a mutational analysis of the HR revealed that both the helicity and hydrophobicity of the region are essential for viral cell-to-cell movement.     

Chronic exposure to ammonia induces isoform-selective alterations in the intracellular distribution and NMDA receptor-mediated translocation of protein kinase C in cerebellar neurons in culture

Hyperammonemia is responsible for most neurological alterations in patients with hepatic encephalopathy by mechanisms that remain unclear. Hyperammonemia alters phosphorylation of neuronal protein kinase C (PKC) substrates and impairs NMDA receptor-associated signal transduction. The aim of this work was to analyse the effects of hyperammonemia on the amount and intracellular distribution of PKC isoforms and on translocation of each isoform induced by NMDA receptor activation in cerebellar neurons. Chronic hyperammonemia alters differentially the intracellular distribution of PKC isoforms. The amount of all isoforms (except PKC zeta) was reduced (17-50%) in the particulate fraction. The contents of alpha, beta1, and epsilon isoforms decreased similarly in cytosol (65-78%) and membranes (66-83%), whereas gamma, delta, and theta; isoforms increased in cytosol but decreased in membranes, and zeta isoform increased in membranes and decreased in cytosol. Chronic hyperammonemia also affects differentially NMDA-induced translocation of PKC isoforms. NMDA-induced translocation of PKC alpha and beta is prevented by ammonia, whereas PKC gamma, delta, epsilon, or theta; translocation is not affected. Inhibition of phospholipase C did not affect PKC alpha translocation but reduced significantly PKC gamma translocation, indicating that NMDA-induced translocation of PKC alpha is mediated by Ca2+, whereas PKC gamma translocation is mediated by diacylglycerol. Chronic hyperammonemia reduces Ca+2-mediated but not diacylglycerol-mediated translocation of PKC isoforms induced by NMDA.