Satellitome comparison of two oedipodine grasshoppers highlights the contingent nature of satellite DNA evolution.

BACKGROUND: The full catalog of satellite DNA (satDNA) within a same genome constitutes the satellitome. The Library Hypothesis predicts that satDNA in relative species reflects that in their common ancestor, but the evolutionary mechanisms and pathways of satDNA evolution have never been analyzed for full satellitomes. We compare here the satellitomes of two Oedipodine grasshoppers (Locusta migratoria and Oedaleus decorus) which shared their most recent common ancestor about 22.8 Ma ago. RESULTS: We found that about one third of their satDNA families (near 60 in every species) showed sequence homology and were grouped into 12 orthologous superfamilies. The turnover rate of consensus sequences was extremely variable among the 20 orthologous family pairs analyzed in both species. The satDNAs shared by both species showed poor association with sequence signatures and motives frequently argued as functional, except for short inverted repeats allowing short dyad symmetries and non-B DNA conformations. Orthologous satDNAs frequently showed different FISH patterns at both intra- and interspecific levels. We defined indices of homogenization and degeneration and quantified the level of incomplete library sorting between species. CONCLUSIONS: Our analyses revealed that satDNA degenerates through point mutation and homogenizes through partial turnovers caused by massive tandem duplications (the so-called satDNA amplification). Remarkably, satDNA amplification increases homogenization, at intragenomic level, and diversification between species, thus constituting the basis for concerted evolution. We suggest a model of satDNA evolution by means of recursive cycles of amplification and degeneration, leading to mostly contingent evolutionary pathways where concerted evolution emerges promptly after lineages split.

Long-term persistence of supernumerary B chromosomes in multiple species of Astyanax fish.

BACKGROUND: Eukaryote genomes frequently harbor supernumerary B chromosomes in addition to the "standard" A chromosome set. B chromosomes are thought to arise as byproducts of genome rearrangements and have mostly been considered intraspecific oddities. However, their evolutionary transcendence beyond species level has remained untested. RESULTS: Here we reveal that the large metacentric B chromosomes reported in several fish species of the genus Astyanax arose in a common ancestor at least 4 million years ago. We generated transcriptomes of A. scabripinnis and A. paranae 0B and 1B individuals and used these assemblies as a reference for mapping all gDNA and RNA libraries to quantify coverage differences between B-lacking and B-carrying genomes. We show that the B chromosomes of A. scabripinnis and A. paranae share 19 protein-coding genes, of which 14 and 11 were also present in the B chromosomes of A. bockmanni and A. fasciatus, respectively. Our search for B-specific single-nucleotide polymorphisms (SNPs) identified the presence of B-derived transcripts in B-carrying ovaries, 80% of which belonged to nobox, a gene involved in oogenesis regulation. Importantly, the B chromosome nobox paralog is expressed > 30× more than the A chromosome paralog. This indicates that the normal regulation of this gene is altered in B-carrying females, which could potentially facilitate B inheritance at higher rates than Mendelian law prediction. CONCLUSIONS: Taken together, our results demonstrate the long-term survival of B chromosomes despite their lack of regular pairing and segregation during meiosis and that they can endure episodes of population divergence leading to species formation.

Gene expression changes elicited by a parasitic B chromosome in the grasshopper Eyprepocnemis plorans are consistent with its phenotypic effects.

Parasitism evokes adaptive physiological changes in the host, many of which take place through gene expression changes. This response can be more or less local, depending on the organ or tissue affected by the parasite, or else systemic when the parasite affects the entire host body. The most extreme of the latter cases is intragenomic parasitism, where the parasite is present in all host nuclei as any other genomic element. Here, we show the molecular crosstalk between a parasitic chromosome (also named B chromosome) and the host genome, manifested through gene expression changes. The transcriptome analysis of 0B and 1B females of the grasshopper Eyprepocnemis plorans, validated by a microarray experiment performed on four B-lacking and five B-carrying females, revealed changes in gene expression for 188 unigenes being consistent in both experiments. Once discarded B-derived transcripts, there were 46 differentially expressed genes (30 up- and 16 downregulated) related with the adaptation of the host genome to the presence of the parasitic chromosome. Interestingly, the functions of these genes could explain some of the most important effects of B chromosomes, such as nucleotypic effects derived from the additional DNA they represent, chemical defense and detoxification, protein modification and response to stress, ovary function, and regulation of gene expression. Collectively, these changes uncover an intimate host-parasite interaction between A and B chromosomes during crucial steps of gene expression and protein function.

Cuidado enfermero en paciente posoperado de clipaje de aneurisma / Nursing care in postoperative patient of an aneurysm clipping

Introducción: los aneurismas cerebrales son dilataciones localizadas de la pared arterial, por lo general, se encuentran en puntos de bifurcación como las arterias grandes del polígono de Willis, las cuales tienen potencial de ruptura y traen consigo complicaciones serias, tales como el evento vascular cerebral (EVC) hemorrágico, en donde la mortalidad es del 66%. Debido al impacto que tiene dicha enfermedad, el profesional de enfermería requiere brindar cuidado integral a este grupo de pacientes,a través del uso del Proceso Cuidado Enfermero (PCE), el cual estádirigido hacia la planificación y el desarrollo de cuidados sistematizados, lógicos y racionales. Objetivo: desarrollar un plan de cuidado de enfermería mediante el uso de la taxonomía NANDA NIC NOC para un paciente posoperado de clipaje de aneurisma en base a la fisiopatología de la enfermedad y su intervención quirúrgica a partir de un caso clínico. Material y métodos: valoración por patrones funcionales de salud de un paciente posoperado de clipaje de aneurisma,revisión bibliográfica y elaboración del proceso cuidado enfermero (PCE) individualizado con el uso de la taxonomía NNN. Conclusión: el paciente neuroquirúrgico, representa un gran reto en el área de salud, por lo que, el profesional de enfermería debe responder a las necesidades sociales y propias de la disciplina para desempeñar un papel eficiente en la ejecución de un plan de cuidado individualizado, que permita el logro de resultados establecidos por el equipo multidisci-plinario.

Post-meiotic B chromosome expulsion, during spermiogenesis, in two grasshopper species.

Most supernumerary (B) chromosomes are parasitic elements carrying out an evolutionary arms race with the standard (A) chromosomes. A variety of weapons for attack and defense have evolved in both contending elements, the most conspicuous being B chromosome drive and A chromosome drive suppression. Here, we show for the first time that most microspermatids formed during spermiogenesis in two grasshopper species contain expulsed B chromosomes. By using DNA probes for B-specific satellite DNAs in Eumigus monticola and Eyprepocnemis plorans, and also 18S rDNA in the latter species, we were able to count the number of B chromosomes in standard spermatids submitted to fluorescence in situ hybridization, as well as visualizing B chromosomes inside most microspermatids. In E. plorans, the presence of B-carrying microspermatids in 1B males was associated with a significant decrease in the proportion of B-carrying standard spermatids. The fact that this decrease was apparent in elongating spermatids but not in round ones demonstrates that meiosis yields 1:1 proportions of 0B and 1B spermatids and hence that B elimination takes place post-meiotically, i.e., during spermiogenesis, implying a 5-25% decrease in B transmission rate. In E. monticola, the B chromosome is mitotically unstable and B number varies between cells within a same individual. A comparison of B frequency between round and elongating spermatids of a same individual revealed a significant 12.3% decrease. We conclude that B chromosome elimination during spermiogenesis is a defense weapon of the host genome to get rid of parasitic chromosomes.