Massive LINE-1 retrotransposon enrichment in tamarins of the Cebidae family (Platyrrhini, Primates) and its significance for genome evolution

To study heterochromatin distribution differences among tamarins, we applied LINE-1 probes using fluorescence in situ hybridization onto chromosomes of Saguinus mystax, Leontocebus fuscicollis, and Leontopithecus rosalia with the aim to investigate possible evolutionary implications. LINE-1 repeats were shown to be involved in genome architecture and in the occurrence of chromosomal rearrangements in many vertebrates. We found bright LINE-1 probe signals at centromeric or pericentromeric areas, GC rich, on almost all chromosomes in three tamarin species. We also found non-centromeric signals along chromosome arms. In a phylogenetic perspective, we analyzed the pattern of LINE-1 distribution considering human chromosomal homologies and C banding patterns. Our data indicate that LINE-1 centromeric expansions and accumulation presumably arose in a common tamarin ancestor and that the presence of LINE-1 at the junction of human chromosome associations is presumably linked to interchromosomal rearrangements. For example, we found bright centromeric signals as well as non-centromeric signals on chromosomes 1 and 2, in all species analyzed, in correspondence to human chromosome associations 13/9/22 and 20/17/13, which are synapomorphic for all tamarins. Furthermore, we found other faint signals that could be apomorphisms linked both to intrachromosomal rearrangements as well as to retro-transposition events. Our results confirm that the three species have similar karyotypes but small differences in LINE-1 and heterochromatin amplification and distribution; in particular on chromosome pairs 19–22, where we show the occurrence of small inversions, in agreement with previous classic cytogenetic hypothese

Molecular cytogenetic insights to the phylogenetic affinities of the giraffe (<I>Giraffa camelopardalis</I>) and pronghorn (<I>Antilocapra americana</I>)

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Postnatal lung function after prenatal steroid treatment in sheep: Effect of gender

The effect of fetal gender on postnatal lung function and response to prenatal steroid exposure were examined retrospectively in a group of 115 preterm lambs. Fetuses received a single intramuscular injection of 0.5 mg/kg betamethasone alone or in conjunction with L-thyroxine 48 h before delivery at 128-d gestational age. Control animals received an equivalent volume of saline. After delivery, respiratory mechanics and blood gas parameters were recorded for 40 min. Deflation pressure volume curves were constructed in excised lungs. Right upper lobes from a randomly selected subgroup of control animals were examined morphometrically. Control (saline-treated) females were able to be ventilated at lower ventilatory pressures with equivalent tidal volumes and more efficient gas exchange. There were no gender differences in compliance, conductance, or excised lung volumes for saline-treated animals. More efficient gas exchange in females could not be explained by thinner alveolar septa or greater alveolar surface area. After hormone treatment, both males and females exhibited significant improvements in respiratory mechanics, gas exchange, and an increase in alveolar surfactant concentration. However, females exhibited a significantly greater improvement than males for compliance, conductance, excised lung volume, and arterial oxygen partial pressure. These data provide a comprehensive description of gender differences in postnatal lung function and response to steroid treatment in preterm animals, and support clinical findings of sexual dimorphism