RESUMO
The increased inertia of very high-energy electrons (VHEEs) due to relativistic effects reduces scattering and enables irradiation of deep-seated tumours. However, entrance and exit doses are high for collimated or diverging beams. Here, we perform a study based on Monte Carlo simulations of focused VHEE beams in a water phantom, showing that dose can be concentrated into a small, well-defined volumetric element, which can be shaped or scanned to treat deep-seated tumours. The dose to surrounding tissue is distributed over a larger volume, which reduces peak surface and exit doses for a single beam by more than one order of magnitude compared with a collimated beam.
Assuntos
Simulação por Computador , Dosagem Radioterapêutica , Radioterapia/métodos , Elétrons , Método de Monte CarloRESUMO
The COL1 gene was isolated from Ophiostoma novo-ulmi using the techniques of insertional mutagenesis and plasmid rescue. Sequence analyses suggest that the COL1 gene encodes a unique protein of 826 amino acids with consensus-type RNA-binding domains, most similar to a putative protein from Schizosaccharomyces pombe which resembles the C-terminus of the Saccharomyces cerevisiae U4/U6 splicing factor PRP24. Disruption of the COL1 gene produced the yeast-like col1 mutant. The inability of the mutant to synthesize the COL1 gene product was confirmed by transcript analysis. Transformation of the col1 mutant with the COL1 gene restored the wild phenotype and production of the 4.0-kb mRNA. The results from this study demonstrate that the COL1 RNA-binding protein is associated with filamentous growth in O. novo-ulmi.
Assuntos
Ascomicetos/genética , Cinamatos , Genes Fúngicos/genética , Splicing de RNA , Proteínas de Ligação a RNA/genética , Proteínas de Saccharomyces cerevisiae , Leveduras/genética , Sequência de Aminoácidos , Ascomicetos/efeitos dos fármacos , Ascomicetos/crescimento & desenvolvimento , Northern Blotting , Divisão Celular/genética , Segregação de Cromossomos , DNA Complementar/química , DNA Complementar/genética , DNA Fúngico/química , DNA Fúngico/genética , Resistência Microbiana a Medicamentos , Proteínas Fúngicas , Teste de Complementação Genética , Higromicina B/análogos & derivados , Higromicina B/farmacologia , Dados de Sequência Molecular , Mutação , RNA Fúngico/genética , RNA Mensageiro/genética , Ribonucleoproteínas Nucleares Pequenas/genética , Saccharomyces cerevisiae/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Transformação GenéticaRESUMO
The button mushroom, Agaricus bisporus, is a commercially important cultivated filamentous fungus. During the last decade, the button mushroom industry has depended mainly on two strains (or derivatives of these two strains). Using one of these highly successful strains (strain U1) we examined the phenomenon of strain instability, specifically, the production of irreversible sectors. Three "stromatal" and three "fluffy" sectors were compared with a healthy type U1 strain and with a wild-collected isolate. Compost colonization and fruit body morphology were examined. The main objective of this study, however, was to examine the meiotic stability of the sectored phenotype. Single basidiospores were isolated and subjected to a grain bioassay in which the ability to produce sectors was measured. Our results were as follows: (i) basidiospore cultures obtained from a wild-collected isolate showed no tendency to produce sectors; (ii) approximately 5% of the basidiospore cultures obtained from healthy type U1 strains produced irreversible sectors in the grain bioassay; (iii) the five primary sectors examined produced basidiospore cultures, half of which produced normal-looking growth in the grain bioassay and half of which produced some degree of sectoring; and (iv) the one sectored isolate that represented the F2 generation gave ratios similar to the 1:1 ratio observed for the F1 cultures.
