16 research outputs found

    Desenvolvimento morfológico dos ovários em embriões e fetos bovinos da raça Nelore Morphological development of the ovaries in embryos and fetuses of Nelore breed

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    Investigaram-se os eventos morfológicos relacionados ao desenvolvimento pré-natal de ovários de 81 embriões e fetos da raça Nelore, coletados em frigoríficos, com idades variando de 26 a 240 dias pós-fecundação. Observou-se formação da crista gonádica e presença de células germinativas em seu interior aos 29 e 34 dias, respectivamente. As oogônias e folículos primordiais, ao contrário dos folículos em crescimento, apresentaram diferenças significativas de diâmetro nos vários períodos estudados. Verificou-se correlação positiva (P<0,05) entre o diâmetro das oogônias e de seus núcleos, bem como entre o diâmetro dos folículos primordiais e em crescimento com seus oócitos e respectivos núcleos. A gônada apresentou-se completamente formada aos 40 dias. Folículos primordiais, em crescimento e antrais surgiram, aproximadamente, aos 95, 140 e 180 dias, respectivamente. Na raça Nelore, a oogênese tem início e duração semelhante à de raças taurinas, mas apresenta como peculiaridade a antecipação do surgimento da foliculogênese.<br>The morphologic events related to the prenatal development of the ovaries in 81 Nelore breed embryos and fetuses gathered in a local slaughterhouse, with age range from 26 to 240 days following fecundation were studied. The age of fetuses was estimated from measures taken in the cranium-caudal direction. The sex was identified from macroscopic observations and using Polymerase Chain Reaction (PCR) technique. For histology the gonads were fixed in Bouin’s fluid for 24 hours and 5 µm thick section’s were stained with hematoxylin-eosin. Formation of gonadal ridge and presence of germinal cells were found within it at 29 and 34 days, respectively. Oogonia and primordial follicles, unlike the growing follicles, exhibited significant differences in diameter in the various periods studied. Positive correlation (P<0.05) was found between the diameter of oogonia and their nucleus as well as between primordial and growing follicles with their oocytes and respective nuclei. The gonad was fully formed at 40 days. Primordial follicles, in the growing stage, and antral follicles first appeared, approximately at 95, 140, and 180 days, respectively. Despite the onset and duration of oogenesis being similar to that of taurine breeds, folliculogenesis initiates at an early stages in the Nelore breed

    Interaction of double-stranded DNA inside single-walled carbon nanotubes

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    Deoxyribonucleic acid (DNA) is the genetic material for all living organisms, and as a nanostructure offers the means to create novel nanoscale devices. In this paper, we investigate the interaction of deoxyribonucleic acid inside single-walled carbon nanotubes. Using classical applied mathematical modeling, we derive explicit analytical expressions for the encapsulation of DNA inside single-walled carbon nanotubes. We adopt the 6–12 Lennard–Jones potential function together with the continuous approach to determine the preferred minimum energy position of the dsDNA molecule inside a single-walled carbon nanotube, so as to predict its location with reference to the cross-section of the carbon nanotube. An analytical expression is obtained in terms of hypergeometric functions which provides a computationally rapid procedure to determine critical numerical values. We observe that the double-strand DNA can be encapsulated inside a single-walled carbon nanotube with a radius larger than 12.30 Å, and we show that the optimal single-walled carbon nanotube to enclose a double-stranded DNA has radius 12.8 Å.Mansoor H. Alshehri; Barry J. Cox; James M. Hil

    Surface Modification by Graft Polymerization

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