Efeito da suplementação com aditivos nutricionais sobre características de crescimento de bovinos da raça Nelore em Testes de Desempenho de Touros Jovens.

Objetivou-se com este estudo avaliar o efeito da suplementação, com diferentes tipos de aditivos, sobre características de crescimento de bovinos da raça Nelore em Testes de Desempenho de Touros Jovens. Foram avaliadas três provas de ganho em peso (PGP 1, PGP 2 e PGP 3). Em cada PGP, foi utilizado um aditivo diferente, tanto no período da seca quanto das águas. Dessa forma, os aditivos utilizados foram: PGP 1, monensina sódica; PGP 2, probiótico; e, PGP 3, virginiamicina. O valor genético dos animais foi predito pelo método da máxima verossimilhança restrita, o qual foi subtraído de sua respectiva pesagem, de forma que todos os animais apresentassem valor genético igual à zero. As análises de dados longitudinais foram realizadas utilizando o método de medidas repetidas no tempo. Os animais suplementados com monensina sódica e virginiamicina apresentaram os maiores pesos médios. Entretanto, os animais alimentados com o aditivo virginiamicina no suplemento, apresentaram maior velocidade de crescimento e desenvolvimento. Portanto, a utilização de virginiamicina promoveu incrementos positivos tanto no peso quando ganho em peso diário dos animais participantes dos Testes de Desempenho de Touros Jovens

Desenvolvimento de estrutura de Kartcross

A estrutura de um kartcross é um dos elementos com maior importância neste tipo de veículos, pois para além de agregar e suportar os restantes componentes, é o componente que permite a proteção do ocupante do veículo. Nesta tese foi concebida uma estrutura para um veículo kartcross, de acordo com o regulamento da Federação Internacional do Automóvel (FIA). Foram tidos em consideração os principais requisitos regulamentares para o desenvolvimento de uma estrutura homologável. Foi efetuado um estudo de simulação estrutural por elementos finitos, para avaliar o seu desempenho mecânico e verificar se a estrutura cumpre com os requisitos de segurança, em particular a célula de sobrevivência, de acordo com as condições definidas no regulamento da FIA. Foi também efetuado um estudo simplificado de otimização estrutural com vista a melhorar o seu desempenho no que respeita à resistência e à rigidez à torção.The structure of a kartcross is one of the most important elements in this type of vehicle, because besides adding and supporting the other components, it is the component that allows the protection of the occupant of the vehicle. In this thesis a structure for a kartcross vehicle was conceived, according to the regulation of the International Automobile Federation (FIA). The main regulatory requirements for the development of an approvable have been taken into account. A finite element structural simulation study was carried out to assess its mechanical performance and to verify that it meets the safety conditions of the survival cell according to the conditions defined in the FIA regulation. A simplified structural optimization study has also been carried out to improve its performance, in particular with regard to strength and torsional stiffness.

Prevalence of Coxielle Burnetii anbitodies in Danish Dairy herds

<p>Abstract</p> <p>During recent years in Denmark higher rates of antibodies to <it>Coxiella burnetii </it>have been detected in animals and humans than previously reported. A study based on bulk tank milk samples from 100 randomly selected dairy herds was performed to estimate the prevalence and geographical distribution of antibody positive dairy herds. Using the CHEKIT Q-Fever Antibody ELISA Test Kit (IDEXX), the study demonstrated a prevalence of 59% antibody positive herds, 11% antibody intermediate herds and 30% antibody negative herds based on the instructions provided by the manufacturer. The geographical distribution does not indicate a relationship between the regional density of dairy farms and the prevalence of antibody positive dairy farms. The result supports the hypothesis of an increase in the prevalence of positive dairy herds compared to previous years.</p

Helical Chirality: a Link between Local Interactions and Global Topology in DNA

DNA supercoiling plays a major role in many cellular functions. The global DNA conformation is however intimately linked to local DNA-DNA interactions influencing both the physical properties and the biological functions of the supercoiled molecule. Juxtaposition of DNA double helices in ubiquitous crossover arrangements participates in multiple functions such as recombination, gene regulation and DNA packaging. However, little is currently known about how the structure and stability of direct DNA-DNA interactions influence the topological state of DNA. Here, a crystallographic analysis shows that due to the intrinsic helical chirality of DNA, crossovers of opposite handedness exhibit markedly different geometries. While right-handed crossovers are self-fitted by sequence-specific groove-backbone interaction and bridging Mg2+ sites, left-handed crossovers are juxtaposed by groove-groove interaction. Our previous calculations have shown that the different geometries result in differential stabilisation in solution, in the presence of divalent cations. The present study reveals that the various topological states of the cell are associated with different inter-segmental interactions. While the unstable left-handed crossovers are exclusively formed in negatively supercoiled DNA, stable right-handed crossovers constitute the local signature of an unusual topological state in the cell, such as the positively supercoiled or relaxed DNA. These findings not only provide a simple mechanism for locally sensing the DNA topology but also lead to the prediction that, due to their different tertiary intra-molecular interactions, supercoiled molecules of opposite signs must display markedly different physical properties. Sticky inter-segmental interactions in positively supercoiled or relaxed DNA are expected to greatly slow down the slithering dynamics of DNA. We therefore suggest that the intrinsic helical chirality of DNA may have oriented the early evolutionary choices for DNA topology

Preferentially Quantized Linker DNA Lengths in Saccharomyces cerevisiae

The exact lengths of linker DNAs connecting adjacent nucleosomes specify the intrinsic three-dimensional structures of eukaryotic chromatin fibers. Some studies suggest that linker DNA lengths preferentially occur at certain quantized values, differing one from another by integral multiples of the DNA helical repeat, ∼10 bp; however, studies in the literature are inconsistent. Here, we investigate linker DNA length distributions in the yeast Saccharomyces cerevisiae genome, using two novel methods: a Fourier analysis of genomic dinucleotide periodicities adjacent to experimentally mapped nucleosomes and a duration hidden Markov model applied to experimentally defined dinucleosomes. Both methods reveal that linker DNA lengths in yeast are preferentially periodic at the DNA helical repeat (∼10 bp), obeying the forms 10n+5 bp (integer n). This 10 bp periodicity implies an ordered superhelical intrinsic structure for the average chromatin fiber in yeast

Continuous Requirement for the Clr4 Complex But Not RNAi for Centromeric Heterochromatin Assembly in Fission Yeast Harboring a Disrupted RITS Complex

Formation of centromeric heterochromatin in fission yeast requires the combined action of chromatin modifying enzymes and small RNAs derived from centromeric transcripts. Positive feedback mechanisms that link the RNAi pathway and the Clr4/Suv39h1 histone H3K9 methyltransferase complex (Clr-C) result in requirements for H3K9 methylation for full siRNA production and for siRNA production to achieve full histone methylation. Nonetheless, it has been proposed that the Argonaute protein, Ago1, is the key initial trigger for heterochromatin assembly via its association with Dicer-independent “priRNAs.” The RITS complex physically links Ago1 and the H3-K9me binding protein Chp1. Here we exploit an assay for heterochromatin assembly in which loss of silencing by deletion of RNAi or Clr-C components can be reversed by re-introduction of the deleted gene. We showed previously that a mutant version of the RITS complex (Tas3WG) that biochemically separates Ago1 from Chp1 and Tas3 proteins permits maintenance of heterochromatin, but prevents its formation when Clr4 is removed and re-introduced. Here we show that the block occurs with mutants in Clr-C, but not mutants in the RNAi pathway. Thus, Clr-C components, but not RNAi factors, play a more critical role in assembly when the integrity of RITS is disrupted. Consistent with previous reports, cells lacking Clr-C components completely lack H3K9me2 on centromeric DNA repeats, whereas RNAi pathway mutants accumulate low levels of H3K9me2. Further supporting the existence of RNAi–independent mechanisms for establishment of centromeric heterochromatin, overexpression of clr4+ in clr4Δago1Δ cells results in some de novo H3K9me2 accumulation at centromeres. These findings and our observation that ago1Δ and dcr1Δ mutants display indistinguishable low levels of H3K9me2 (in contrast to a previous report) challenge the model that priRNAs trigger heterochromatin formation. Instead, our results indicate that RNAi cooperates with RNAi–independent factors in the assembly of heterochromatin