RESUMO
The genus Psammolestes within the subfamily Triatominae and tribe Rhodniini comprises the species Psammolestes arthuri, Psammolestes coreodes, and Psammolestes tertius, all potential vectors of Chagas disease. A feature of Psammolestes is their close association with birds, which makes them an interesting model for evolutionary studies. We analyzed cytogenetically Psammolestes spp., with the aim of contributing to the genetic and evolutionary knowledge of these vectors. All species of the Psammolestes showed the same chromosomal characteristics: chromocenter formed only by sex chromosomes X and Y, karyotype 2n = 22 and constitutive heterochromatin, and AT base pairs restricted to the sex chromosome Y. These results corroborate the monophyly of the genus and lead to the hypothesis that during the derivation of P. tertius, P. coreodes, and P. arthuri from their common ancestor, there was no reorganization in the number or structure of chromosomes.
Assuntos
Doença de Chagas/transmissão , Cromossomos de Insetos/química , Especiação Genética , Insetos Vetores/genética , Filogenia , Triatominae/genética , Animais , Pareamento de Bases , Aves/parasitologia , Doença de Chagas/epidemiologia , Doença de Chagas/parasitologia , Cromossomos de Insetos/ultraestrutura , Heterocromatina/química , Heterocromatina/ultraestrutura , Humanos , Insetos Vetores/classificação , Insetos Vetores/parasitologia , Cariótipo , América Latina/epidemiologia , Triatominae/classificação , Triatominae/parasitologia , Trypanosoma cruzi/patogenicidade , Cromossomo X/química , Cromossomo X/ultraestrutura , Cromossomo Y/química , Cromossomo Y/ultraestruturaRESUMO
Sperm dimensions and the question of whether X and Y chromosome-bearing sperm differ in size or shape has been of great interest, especially for the development of alternative methods to sort or classify sperm cells. The aim of the present study was to evaluate possible differences in the shape and size of the sperm head between X and Y chromosome-bearing sperm by atomic force microscopy (AFM). One ejaculate per bull (nâ=â4) was used. Each ejaculate was separated into four fractions: non-sexed (NS), sexed for X-sperm (SX), sexed for Y-sperm (SY) and a pooling of SX and SY samples (SXY). Using AFM, 400 sperm heads per group were measured. Twenty three structural features were assessed including one-, two- and three-dimensional parameters and shape descriptors. These measurements determine the micro- to nanoscale features of X- and Y-bearing chromosomes in sperm cells. No differences were observed for any individual variables between SX and SY groups. Next, a simultaneous evaluation of all features using statistical discriminant analysis was performed to determine if it was possible to distinguish to which group belong each individual cells. This analysis clearly showed, a distinct separation of NS, SXY, SX and SY groups. The recognition of this structural possibility to distinguish between X and Y sperm cell might improve the understanding of sperm cells biology. These results indicated that the associations of several structural measurements of the sperm cell head are promising candidates for development of a new method of sperm sexing.
Assuntos
Forma Celular/fisiologia , Tamanho Celular , Microscopia de Força Atômica/veterinária , Análise para Determinação do Sexo/métodos , Cabeça do Espermatozoide/ultraestrutura , Cromossomo X/química , Cromossomo Y/química , Animais , Bovinos , Separação Celular/métodos , Separação Celular/veterinária , Análise Discriminante , Modelos Lineares , Masculino , Microscopia de Força Atômica/métodos , Cabeça do Espermatozoide/químicaRESUMO
Australia is thought of as the home of marsupials, but South America has 60 or so species of these interesting mammals. The genome of one of these, the South American grey short-tailed opossum, Monodelphis domestica, has just been sequenced and published in June.1 The high quality 6x coverage is the first marsupial genome completed, pipping the 2x coverage of the Australian tammar wallaby at the post by half a year. The opossum genome has an unusual structure with fewer chromosomes than the human genome (9 pairs versus 23 pairs) but a longer total length (3.4 billion versus 3 billion bases). The opossum autosomes, like those of all marsupials, are extremely large but, in contrast, the X chromosome is only 76 Mb long. The opossum genome has turned up several surprises and provided critical new information on the evolution of mammalian genomes.