RESUMEN
A population-based analysis of progressive multifocal leukoencephalopathy (PML) showed PML frequencies of 5.1% among patients with AIDS and 0.07% among patients with hematologic malignancies, but similar clinical features of PML in both groups. Sequencing of the p53 gene, exon 4, showed heterozygosity (Arg-Pro) at codon 72 in five of six PML patients. These findings indicate that frequencies of non-AIDS- and AIDS-related PML differ markedly but p53 polymorphisms may influence the occurrence of PML in both groups.
Asunto(s)
Síndrome de Inmunodeficiencia Adquirida/complicaciones , Leucoencefalopatía Multifocal Progresiva/complicaciones , Leucoencefalopatía Multifocal Progresiva/genética , Proteína p53 Supresora de Tumor/genética , Adulto , Encéfalo/patología , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Polimorfismo Genético/genéticaRESUMEN
The North American beluga whale Delphinapterus leucas population has been divided into a number of putative geographical stocks based upon migration routes and areas of summer concentration. Nucleotide sequences of the mitochondrial DNA (mtDNA) control region were used to assess whether these geographical stocks are genetically distinct. Beluga whale samples from 25 sites were collected primarily from aboriginal subsistence hunts across North America from 1984 to 1994. Thirty-nine mtDNA haplotypes were identified in 628 beluga samples. No differences were found in the distribution of haplotypes between male and female beluga whales at any sampling site. These haplotypes segregated into two distinct assemblages in both a haplotype network and a neighbour-joining tree. The haplotype assemblages and a geographically disjunct distribution that suggests postglacial recolonization of the North American Arctic from two different refugia. An analysis of molecular variance based on haplotype relationships and frequency indicated genetic heterogeneity among beluga whale summering groups (P < or = 0.001). Sequence divergence estimates between sampling sites also indicated geographical differentiation, particularly between samples taken at east Hudson Bay or St Lawrence River and the western or central Arctic. The results of this study show a high degree of philopatry to specific summering areas by this highly mobile animal.
Asunto(s)
Variación Genética , Genética de Población , Ballenas/genética , Animales , ADN Mitocondrial/genética , Femenino , Haplotipos , Masculino , América del NorteRESUMEN
We have studied by autoradiography the effects of 1,3-diaminopropane (DAP) upon cellular proliferation in a number of tissues in vivo in the rat. DAP is a structural analogue of the naturally occurring polyamine putrescine, and is believed to block cellular polyamine synthesis by supressing the induction of ornithine decarboxylase (the rate-limiting enzyme for polyamine biosynthesis). The continuous infusion of DAP into rats that had been partially hepatectomised prevented the subsequent waves of spermidine and DNA synthesis from taking place in the regenerating liver. The inhibition of DNA synthesis is accounted for primarily by a block in the entry of hepatocytes into S phase and not by a reduction in the rate of DNA synthesis itself. In contrast to the regenerating liver, DAP exerted minimal effects upon the proliferation of the gut epithelium and bone marrow elements. The proliferation of stem cells of these latter tissues, which are normally in a state of rapid and continuous proliferation unlike the liver, is thus much more resistant to perturbations in polyamine biosynthesis and function. DAP is consequently unable to arrest and so protect normal rapidly proliferating tissues from damage caused by anti-cancer drugs (e.g. hydroxyurea) that kill only proliferating cells. DAP cannot therefore be employed to selectively protect normal cells but not tumour cells from cytotoxic damage according to a principle we have previously established in tissue culture.