Pythium insidiosum, the etiologic agent of pythiosis insidiosii, causes life-threatening infections in humans and animals. Previous studies of the epidemiology of this disease hypothesized about the possible life cycle of this oomycete. Details, however, were not provided on the steps required to cause infection. We investigated the life cycle ofP. insidiosum by inoculating pieces of equine skin and plant leaves and then studying the ensuing events with a scanning electron microscope. Our observations revealed that zoospores had a strong tropism for skin tissue, horse and human hair, and water lily and grass leaves and a weak attraction to a variety of other leaves. Encysted zoospores were observed on the favored leaves and skin. There they produced germ tubes and later abundant hyphal filaments that penetrated leaf tissues. Young sporangia had compact, thick wails. The sporangial wall was reduced to a fragile membrane when the sporangia had produced well-differentiated biflagellate zoospores. The encysted zoospores secreted an amorphous material that permitted the zoospores to adhere to skin and plant tissues. On the basis of these findings, a model to explain the life cycle ofP. insidiosum is proposed.

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We have studied the effect of Fe addition on the structural and magnetic transitions in the magnetic shape memory alloy Ni-Mn-Ga by substituting systematically each atomic species by Fe. Calorimetric and AC susceptibility measurements have been carried out in order to study the magnetic and structural transformation properties. We find that the addition of Fe modifies the structural and magnetic transformation temperatures. Magnetic transition temperatures are displaced to higher values when Fe is substituted into Ni-Mn-Ga, while martensitic and premartensitic transformation temperatures shift to lower values. Moreover, it has been found that the electron per atom concentration essentially governs the phase stability in the quaternary system. However, the observed scaling of transition temperatures with e/a differs from that reported in the related ternary system Ni-Mn-Ga.

Malathion and diazinon are two of the most commonly used organophosphorous (OP) agrochemicals. Several studies show that these pesticides exert several effects on mammalian spermatogenesis. Nevertheless, there are no studies concerning their effects on oogenesis. The objective of this study was to evaluate the effects of these insecticides on the viability of in vitro cultured mouse oocytes during the early oogenesis and to get a further understanding of the molecular mechanisms by which OP insecticides act and affect germinal cells. Oocytes were cultured from fetal ovaries for 10 days, when most oocytes had reached the diplotene stage (germinal vesicle stage). Cultures were exposed to different concentrations of malathion or diazinon for 24 h, and the effect on oocyte viability was assessed. Gene expression in oocytes exposed to the insecticides was analyzed by generating cDNA libraries and performing differential screenings. Results show a significant decrease in oocytes survival after 24-h exposure to 250 microM malathion or 900 nM diazinon, and the effect of these insecticides on the regulation of genes encoding proteins involved in transcription (BP75), translation (ribosomal protein S5), and mitochondrial function (cytochrome oxidase subunits I and III), providing evidence for OP insecticides as toxicants for mammals oocytes during the early oogenesis.