Effects of antifreeze protein from Lolium perenne L. (LpAFP) in the vitrification of in vitro-produced bovine embryos.

In the present study, the cryoprotective effects of Lolium perenne antifreeze protein (LpAFP) on the vitrification of bovine embryos were evaluated. In vitro-produced blastocysts were divided into two groups: the control group (CG) without the addition of LpAFP and the treatment group (TG) with the addition of 500 ng/ml of LpAFP in the equilibrium and vitrification solution. Vitrification was carried out by transferring the blastocysts to the equilibrium solution [7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO)] for 2 min and then to the vitrification solution (15% EG, 15% DMSO and 0.5M sucrose). The blastocysts were deposited on a cryotop device and submerged in liquid nitrogen. Warming was carried out in three steps in solutions with different sucrose concentrations (1.0, 0.5, and 0.0 M, respectively). Embryos were evaluated for re-expansion/hatching, the total cell count, and ultrastructural analysis. There was no significant difference in the re-expansion rate 24 h after warming; however, there was variation (P < 0.05) in the hatching rate in the TG and the total number of cells 24 h after warming was higher in the TG (114.87 ± 7.24) when compared with the CG (91.81 ± 4.94). The ultrastructural analysis showed changes in organelles related to the vitrification process but, in the TG, there was less damage to mitochondria and rough endoplasmic reticulum compared with the CG. In conclusion, the addition of 500 ng/ml of LpAFP during the vitrification of in vitro-produced bovine embryos improved the hatching rate and total cell number of blastocysts after warming and mitigated intracellular damage.

Intermittency properties in a temporal lobe epilepsy model.

Neuronal synchronization is important for communication between brain regions and plays a key role in learning. However, changes in connectivity can lead to hyper-synchronized states related to epileptic seizures that occur intermittently with asynchronous states. The activity-regulated cytoskeleton-associated protein (ARC) is related to synaptic alterations which can lead to epilepsy. Induction of status epilepticus in rodent models causes the appearance of intense ARC immunoreactive neurons (IAINs), which present a higher number of connections and conductance intensity than non-IAINs. This alteration might contribute to abnormal epileptic seizure activity. In this work, we investigated how IAINs connectivity influences the firing pattern and synchronization in neural networks. Firstly, we showed the appearance of synchronized burst patterns due to the emergence of IAINs. Second, we described how the increase of IAINs connectivity favors the appearance of intermittent up and down activities associated with synchronous bursts and asynchronous spikes, respectively. Once the intermittent activity was properly characterized, we applied the optogenetics control of the high synchronous activities in the intermittent regime. To do this, we considered that 1% of neurons were transfected and became photosensitive. We observed that optogenetics methods to control synchronized burst patterns are effective when IAINs are chosen as photosensitive, but not effective in non-IAINs. Therefore, our analyses suggest that IAINs play a pivotal role in both the generation and suppression of highly synchronized activities.

Large coefficient of variation of inter-spike intervals induced by noise current in the resonate-and-fire model neuron.

Neuronal spike variability is a statistical property associated with the noise environment. Considering a linearised Hodgkin-Huxley model, we investigate how large spike variability can be induced in a typical stellate cell when submitted to constant and noise current amplitudes. For low noise current, we observe only periodic firing (active) or silence activities. For intermediate noise values, in addition to only active or inactive periods, we also identify a single transition from an initial spike-train (active) to silence dynamics over time, where the spike variability is low. However, for high noise current, we find intermittent active and silence periods with different values. The spike intervals during active and silent states follow the exponential distribution, which is similar to the Poisson process. For non-maximal noise current, we observe the highest values of inter-spike variability. Our results suggest sub-threshold oscillations as a possible mechanism for the appearance of high spike variability in a single neuron due to noise currents.

Joint regression modeling of location and scale parameters of the skew t distribution with application in soil chemistry data.

In regression model applications, the errors may frequently present a symmetric shape. In such cases, the normal and Student t distributions are commonly used. In this paper, we shall be concerned only to model heavy-tailed, skewed errors and absence of variance homogeneity with two regression structures based on the skew t distribution. We consider a classic analysis for the parameters of the proposed model. We perform a diagnostic analysis based on global influence and quantile residuals. For different parameter settings and sample sizes, various simulation results are obtained and compared to evaluate the performance of the skew t regression. Further, we illustrate the usefulness of the new regression by means of a real data set (amount of potassium in different soil areas) from a study carried out at the Department of Soil Science of the Luiz de Queiroz School of Agriculture, University of São Paulo.

Intake, digestibility, ingestive behavior and performance of goats fed spineless cactus genotypes resistant to carmine cochineal / Consumo, digestibilidade, comportamento ingestivo e desempenho de caprinos alimentados com genótipos de palma forrageira resistentes à cochonilha-do-carmim

The objective was to evaluate the intake and digestibility of nutrients, ingestive behavior, and performance of goats fed with spineless cactus genotypes resistant to carmine cochineal (Miúda or Orelha de Elefante Mexicana (OEM). Thirty castrated male goats, without defined breed, aged 12 to 14 months, with an average body weight of 19.0±2.8kg, were distributed in a completely randomized design among three treatments (Control - Tifton hay, Miúda, and OEM) and ten replicates; the initial weight was considered as the covariate. The intake of organic matter (OM), neutral detergent fiber (NDF) was highest in the control treatment, while the intake of NFC was higher in the OEM diet. Treatments containing forage cactus showed the highest digestibility of DM, OM, and NFC. The animals fed the control diet spent more time on rumination and total chewing, but the time spent feeding or feeding efficiency, and performance did not differ. The use of spineless cactus genotypes resistant to carmine cochineal (Miúda and Orelha de Elefante Mexicana) in a diet for goats, in the amount of 450g/kg of DM does not interfere with the performance of the animals and improves the digestibility of OM and NFC.(AU)

Objetivou-se com o presente estudo avaliar o consumo e a digestibilidade de nutrientes, o comportamento ingestivo e o desempenho de caprinos alimentados com genótipos de palma forrageira resistentes à cochonilha-carmim (miúda ou orelha-de-elefante-mexicana (OEM). Trinta cabritos machos, castrados, sem raça definida, com idades entre 12 e 14 meses e peso corporal médio de 19,0±2,8kg, foram distribuídos em delineamento inteiramente ao acaso, em três tratamentos (controle - feno de tifton; miúda e OEM) e 10 repetições; o peso inicial foi considerado a covariável. O consumo de matéria orgânica (MO) e de fibra em detergente neutro (FDN) foi maior no tratamento controle; enquanto a ingestão de CNF foi maior na dieta OEM. Tratamentos contendo palma forrageira apresentaram as maiores digestibilidades de MS, MO e CNF. Os animais alimentados com a dieta controle gastaram mais tempo em ruminação e em mastigação total, mas o tempo gasto com alimentação ou a eficiência alimentar e o desempenho não diferiram. A utilização de genótipos de palma forrageira resistentes à cochonilha-carmim (miúda e orelha-de-elefante-mexicana) na dieta de caprinos, na quantidade de 450g/kg de MS, não interfere no desempenho dos animais e melhora a digestibilidade de MO e CNF.(AU)

Leptin decreases apoptosis and promotes the activation of primordial follicles through the phosphatidylinositol-3-kinase/protein kinase B pathway in cultured ovine ovarian tissue.

This study evaluated the effects of leptin on primordial follicle survival and activation after in vitro culture of ovine ovarian tissue and if leptin acts through the phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) pathway. Ovarian fragments were fixed for histology (fresh control) or cultured for 7 days in control medium (α-MEM+) alone or supplemented with leptin (1, 5, 10, 25 or 50 ng/ml). Follicle morphology, activation and apoptosis were analyzed. Next, the fragments were cultured in the medium that showed the best results in the absence or the presence of the PI3K inhibitor (LY294002), and immunohistostaining of p-Akt protein was assessed. After culture, the percentage of normal follicles decreased (P < 0.05) in all treatments compared with the fresh control. Moreover, control medium and 1 ng/ml leptin had similar (P > 0.05) percentages of normal follicles, which were significantly higher than those in other treatments. However, culture with 1 ng/ml leptin maintained apoptosis similarly (P > 0.05) to that of the fresh control and lower (P < 0.05) than that in α-MEM+. Leptin did not influence follicle activation (P > 0.05) compared with the control medium (α-MEM+). Culture in 1 ng/ml leptin with LY294002 decreased the normal follicles and increased apoptosis, inhibited follicle activation (P < 0.05), and reduced p-Akt immunostaining, compared with the medium containing 1 ng/ml leptin without PI3K inhibitor. In conclusion, leptin at 1 ng/ml reduces apoptosis and promotes the activation of primordial follicles compared with the fresh control after in vitro culture of ovine ovarian tissue possibly through the PI3K/Akt pathway.

Metabolic dynamics of native lambs fed with Tifton 85 hay or Maniçoba hay associated with the spineless cactus / Dinâmica metabólica de cordeiros nativos alimentados com feno de capim-tifton 85 ou feno de maniçoba associados à palma forrageira

The objective of this study was to evaluate the metabolic response of native lambs fed Tifton 85 hay (Cynodon dactylon) or Maniçoba hay (Manihot pseudoglaziovii) associated with spineless cactus (Nopalea cochenillifera Salm Dyck). Sixteen Morada Nova lambs were used, with a mean initial weight of 19.36±1.48kg, distributed in a randomized block design, with two treatments and eight replications. Dry matter intake was higher for lambs fed Maniçoba hay compared to Tifton hay, while the body weight at slaughter was not influenced by diets. Regarding the blood metabolites, only the serum concentration of urea was influenced, with higher value observed in the lambs that fed the diet containing Tifton hay. When analyzing blood biomarkers, in the different biweekly collections, a linear increase in the blood concentration of urea, glucose, fructosamine, alkaline phosphatase and sodium was observed, as well as a quadratic effect for serum potassium. The other blood metabolites were not influenced in function of the collection days. The replacement of Tifton 85 hay for Maniçoba hay does not cause negative changes in the dynamics of different biomarkers and presents itself as a promising forage resource.(AU)

O objetivo deste trabalho foi avaliar a resposta metabólica de cordeiros nativos alimentados com feno de capim-tifton 85 (Cynodon dactylon) ou feno de maniçoba (Manihot pseudoglaziovii) associados à palma forrageira (Nopalea cochenillifera Salm Dyck). Foram utilizados 16 cordeiros Morada Nova, com peso inicial médio de 19,36±1,48kg, distribuídos em delineamento de blocos ao acaso, com dois tratamentos e oito repetições. O consumo de matéria seca foi maior nos cordeiros alimentados com feno de maniçoba em comparação ao feno de tifton, enquanto o peso corporal ao abate não foi influenciado pelas dietas. Em relação aos metabólitos sanguíneos, apenas a concentração sérica de ureia foi influenciada, com maior valor observado nos cordeiros que ingeriram a dieta contendo feno de capim-tifton. Quando foi realizada a análise dos biomarcadores sanguíneos nas diferentes coletas quinzenais, foi observado aumento linear nas concentrações sanguíneas de ureia, glicose, frutosamina, fosfatase alcalina e sódio, e efeito quadrático para o potássio sérico. Os demais metabólitos sanguíneos não foram influenciados em função dos dias de coleta. A substituição do feno de tifton 85 por feno de maniçoba influencia positivamente o metabolismo de cordeiros sem causar alterações na dinâmica dos diferentes biomarcadores e se apresenta como um promissor recurso forrageiro.(AU)

Effect of Rolipram on in vitro maturation, gene expression and embryonic development in bovines / Efeito de rolipram na maturação in vitro, expressão gênica e desenvolvimento embrionário em bovinos

The aim of this work was to evaluate the effect of the Rolipram during the maturation of bovine oocytes and gene expression of embryos produced in vitro. Bovine ovaries were collected in slaughterhouse. The COCs were selected and divided into 5 groups: Control 0 time; Control: IVM for 24 hours; Rolipram treatments with IVM blocking for 24 hours in maturation medium containing (100, 150 and 200µM). After 24 hours all groups were reseated in IVM for another 24 hours. Subsequently COCs were subjected to the same IVM system and fertilized, being checked for cleavage post fertilization and for blastocyst. In addition, performed expression of the following genes: Mater, BMP15 and Bax. No difference was found in gene expression. Of oocytes evaluated shortly after follicular aspiration, 79.00% were in GV, GVBD, MI, while 13.40%, were in MII and 7.60%, D/NI. Significant difference was observed in different concentrations (T100, T200 and T150µM) in oocytes that have reached the MII phase compared to control treatments (P= 0.003). Differences were observed in cleavage rate (P< 0.05) between T150 and T200 when compared to the C/24 Group. A high difference was observed on blastocyst rate (P< 0.001) among treatments compared to the control group.(AU)

O objetivo deste trabalho foi avaliar o efeito do rolipram durante a maturação de oócitos bovinos, expressão gênica e embriões produzidos in vitro. Os ovários bovinos foram coletados no matadouro. Os COCs foram selecionados e divididos em cinco grupos: controle 0 tempo; controle: MIV por 24 horas; tratamentos rolipram com bloqueio MIV por 24 horas em meio de maturação contendo 100, 150 e 200µM. Após 24 horas, todos os grupos foram recolocados em MIV por mais 24 horas. Subsequentemente COCs foram submetidos ao mesmo sistema MIV e fertilizados, sendo avaliada a taxa de clivagem e de blastocisto, além da expressão dos seguintes genes: Mater, BMP15 e Bax. Nenhuma diferença foi observada na expressão gênica. Dos oócitos avaliados logo após a aspiração folicular, 79,0% estavam em GV, GVBD, MI, enquanto 13,40% estavam em MII, e 7,60% em D/NI. A diferença significativa foi observada em diferentes concentrações (T100, T200 e T150µM) em oócitos que atingiram a fase MII em comparação aos tratamentos de controle (P=0,3). Diferenças foram observadas nas taxas de clivagem (P<0,5) entre T150 e T200 quando comparadas com as taxas do grupo C/24. Uma grande diferença foi observada na taxa de blastocisto (P<0,1) entre os tratamentos em relação ao grupo controle.(AU)

Effects of leptin on the follicular development and mitochondrial activity of ovine isolated early antral follicles cultured in vitro.

This study evaluated the effect of leptin on the in vitro culture of isolated sheep early antral follicles. Early antral follicles (300-450 µm) were isolated and cultured for 12 days in tissue culture medium 199 (TCM 199) supplemented with glutamine, hypoxanthine, transferrin, insulin, selenium, ascorbic acid, bovine serum albumin (BSA) and recombinant follicle stimulating hormone (rFSH) (TCM 199+: control medium) or TCM 199+ supplemented with 2 or 10 ng/mL leptin. After culture, oocytes were subjected to in vitro maturation (IVM). The parameters analyzed were morphology, extrusion rate, follicular diameter, growth and fully-grown oocytes (oocytes ≥110 µm) rates. After IVM, reactive oxygen species (ROS) levels, mitochondrial activity, meiotic stages and meiotic resumption rates were also analyzed. After 12 days of culture, the concentration of 2 ng/mL of leptin showed a higher percentage of morphologically normal follicles, fully-grown oocytes (≥110 µm), active mitochondria and meiotic resumption compared to the control medium (TCM 199+; P < 0.05) but did not differ when compared to leptin concentration of 10 ng/mL (P > 0.05). After culturing, no significant differences existed among treatments in terms of the follicle diameter and ROS levels. In conclusion, the addition of 2 ng/mL leptin to the base culture medium is capable of improving follicular survival, oocyte growth, mitochondrial activity and meiotic resumption after the in vitro culture of isolated sheep early antral follicles.

Variability in a permanent cyanobacterial bloom: species-specific responses to environmental drivers.

Cyanobacterial blooms are characterized by intense growth of one or few species that will dominate the phytoplankton community for periods of few months to an entire year or more. However, even during persistent blooms, important seasonal changes among dominant species can be observed. Pampulha reservoir is a tropical eutrophic reservoir presenting permanent blooms. To identify the main species in this environment, a closer analysis performed by microscopy and 16S-rRNA DGGE revealed Cylindrospermopsis raciborskii as highly dominant throughout the year. The second most abundant group comprised species belonging to the Microcystis genus. They followed a well-defined seasonal pattern described by interesting species-specific ecological trends. During thermal stratification in the rainy/warmer season, C. raciborskii dominated in the water column, while Microcystis spp. were abundant at the end of the dry season, a period characterized by higher total phosphorus concentrations. Phylogenetic analyses confirmed the two dominant taxa and their seasonal trends. The results showed that cyanobacteria major controlling factors were strongly species dependent, shifting from physical/climate related (stratification) to more chemical driven (nutrients/eutrophication). Identifying these drivers is therefore essential for the understanding of the bloom dynamics and the real risks associated with each species, and to eventually adopt the most appropriate and effective management strategies.

Recurrence quantification analysis for the identification of burst phase synchronisation.

In this work, we apply the spatial recurrence quantification analysis (RQA) to identify chaotic burst phase synchronisation in networks. We consider one neural network with small-world topology and another one composed of small-world subnetworks. The neuron dynamics is described by the Rulkov map, which is a two-dimensional map that has been used to model chaotic bursting neurons. We show that with the use of spatial RQA, it is possible to identify groups of synchronised neurons and determine their size. For the single network, we obtain an analytical expression for the spatial recurrence rate using a Gaussian approximation. In clustered networks, the spatial RQA allows the identification of phase synchronisation among neurons within and between the subnetworks. Our results imply that RQA can serve as a useful tool for studying phase synchronisation even in networks of networks.

Riddling: Chimera's dilemma.

We investigate the basin of attraction properties and its boundaries for chimera states in a circulant network of Hénon maps. It is known that coexisting basins of attraction lead to a hysteretic behaviour in the diagrams of the density of states as a function of a varying parameter. Chimera states, for which coherent and incoherent domains occur simultaneously, emerge as a consequence of the coexistence of basin of attractions for each state. Consequently, the distribution of chimera states can remain invariant by a parameter change, and it can also suffer subtle changes when one of the basins ceases to exist. A similar phenomenon is observed when perturbations are applied in the initial conditions. By means of the uncertainty exponent, we characterise the basin boundaries between the coherent and chimera states, and between the incoherent and chimera states. This way, we show that the density of chimera states can be not only moderately sensitive but also highly sensitive to initial conditions. This chimera's dilemma is a consequence of the fractal and riddled nature of the basin boundaries.

Synchronous behaviour in network model based on human cortico-cortical connections.

OBJECTIVE: We consider a network topology according to the cortico-cortical connection network of the human brain, where each cortical area is composed of a random network of adaptive exponential integrate-and-fire neurons. APPROACH: Depending on the parameters, this neuron model can exhibit spike or burst patterns. As a diagnostic tool to identify spike and burst patterns we utilise the coefficient of variation of the neuronal inter-spike interval. MAIN RESULTS: In our neuronal network, we verify the existence of spike and burst synchronisation in different cortical areas. SIGNIFICANCE: Our simulations show that the network arrangement, i.e. its rich-club organisation, plays an important role in the transition of the areas from desynchronous to synchronous behaviours.

Inference of topology and the nature of synapses, and the flow of information in neuronal networks.

The characterization of neuronal connectivity is one of the most important matters in neuroscience. In this work, we show that a recently proposed informational quantity, the causal mutual information, employed with an appropriate methodology, can be used not only to correctly infer the direction of the underlying physical synapses, but also to identify their excitatory or inhibitory nature, considering easy to handle and measure bivariate time series. The success of our approach relies on a surprising property found in neuronal networks by which nonadjacent neurons do "understand" each other (positive mutual information), however, this exchange of information is not capable of causing effect (zero transfer entropy). Remarkably, inhibitory connections, responsible for enhancing synchronization, transfer more information than excitatory connections, known to enhance entropy in the network. We also demonstrate that our methodology can be used to correctly infer directionality of synapses even in the presence of dynamic and observational Gaussian noise, and is also successful in providing the effective directionality of intermodular connectivity, when only mean fields can be measured.

Dynamical characterization of transport barriers in nontwist Hamiltonian systems.

The turnstile provides us a useful tool to describe the flux in twist Hamiltonian systems. Thus, its determination allows us to find the areas where the trajectories flux through barriers. We show that the mechanism of the turnstile can increase the flux in nontwist Hamiltonian systems. A model which captures the essence of these systems is the standard nontwist map, introduced by del Castillo-Negrete and Morrison. For selected parameters of this map, we show that chaotic trajectories entering in resonances zones can be explained by turnstiles formed by a set of homoclinic points. We argue that for nontwist systems, if the heteroclinic points are sufficiently close, they can connect twin-islands chains. This provides us a scenario where the trajectories can cross the resonance zones and increase the flux. For these cases the escape basin boundaries are nontrivial, which demands the use of an appropriate characterization. We applied the uncertainty exponent and the entropies of the escape basin boundary in order to quantify the degree of unpredictability of the asymptotic trajectories.

Avaliação in vitro do sêmen congelado de carneiros com diluidor suplementado com miricetina / In vitro evaluation of ram sperm frozen with extender supplemented with myricetin

O objetivo deste estudo foi avaliar o efeito da suplementação do diluidor de congelação de sêmen ovino com o flavonoide miricetina contra os danos ocasionados aos espermatozoides. Oito pools de sêmen, obtidos de quatro reprodutores ovinos, foram congelados com diferentes concentrações de miricetina (0, 1, 10, 100 e 1000nM). Após o descongelamento, o sêmen foi avaliado quanto à cinética espermática, à integridade das membranas plasmática e acrossomal, ao potencial de membrana mitocondrial, aos níveis de ROS intracelular, à peroxidação lipídica e à estabilidade de membrana. Amostras tratadas com miricetina 10nM apresentaram menor percentual de células rápidas (P≤0,05), quando comparadas ao grupo miricetina 1000nM. Amostras do grupo controle apresentaram maior (P≤0,05) VAP que o grupo 10nM de miricetina, enquanto amostras criopreservadas com miricetina (10, 100 e 1000nM) evidenciaram maior (P<0,05) BCF, quando comparadas ao grupo controle. O grupo tratado com miricetina 1000nM apresentou maior percentual (P<0,05) de células com peroxidação lipídica, quando comparado ao grupo controle. Em conclusão, a suplementação do diluidor de criopreservação de sêmen ovino com 10 e 100nM de miricetina afeta a cinética espermática sem provocar alterações na estrutura geral do gameta, enquanto 1000nM de miricetina provoca mudanças na cinética associadas à danos peroxidativos.(AU)

The aim of this study was to evaluate the effect of the supplementation of ram semen frozen with extender with the flavonoid myricetin against damage to sperm. Eight pools of semen obtained from four ram breeders, were frozen with different concentrations of myicetin (0, 1, 10, 100 and 1000nM). After thawing, the semen was evaluated for spermatic kinetics, plasma and acrosome membrane integrity, mitochondrial membrane potential, intracellular ROS levels, lipid peroxidation, and membrane stability. Samples treated with 10nM myricetin preserved a lower percentage of rapid cells (P≤0.05) when compared to the 1000nM myricetin group. Samples from the control group presented higher (P≤0.05) VAP than 10nM group of myricetin, while cryopreserved samples with myicetin (10, 100 and 1000nM) showed greater (P<0.05) BCF, when compared to control group. The group treated with 1000nM myricetin had a higher percentage (P<0.05) of cells with lipid peroxidation, when compared to the control group. In conclusion, supplementation of ram semen cryopreservation extender with 10 and 100nM myricetin affects sperm kinetics, without causing changes in the overall structure of the gamete, while 1000nM myricetin causes changes in the kinetics associated with peroxidative damage.(AU)

Estudo da vascularização folicular e do corpo lúteo de éguas cíclicas tratadas com extrato de pituitária equina utilizando ultrassom Doppler colorido / Study of follicular and corpus luteum vascularization in mares treated with Equine Pituitary Extract using ultrasound color Doppler

Informações sobre a vascularização da parede folicular e do corpo lúteo equino, associadas à superovulação, são escassas. Com o objetivo de avaliar o efeito superovulatório do extrato de pituitária equina (EPE) no fluxo sanguíneo folicular e luteal, foram utilizadas seis éguas Puro Sangue Árabe, em dois ciclos estrais (controle e tratamento). As éguas foram monitoradas diariamente por ultrassonografia modo B, até que os folículos atingissem diâmetro de 23mm (desvio). No ciclo tratamento, as éguas receberam 8mg de EPE, uma vez ao dia, por via IM, até que dois ou mais folículos atingissem o diâmetro entre 32 e 35mm. A ovulação foi induzida com acetato de deslorelina, quando os folículos atingiram, no mínimo, 35mm. No momento do desvio folicular, da indução da ovulação e do último exame pré-ovulatório, foi utilizada a ultrassonografia modo B para medir o diâmetro dos folículos e, no oitavo dia pós-ovulação, para a área do corpo lúteo (CL). Utilizou-se também ultrassonografia com Doppler colorido para avaliar a perfusão sanguínea da parede folicular e do parênquima luteal. No ciclo controle, foi realizado o mesmo procedimento, exceto pelo uso do EPE. Os dados foram submetidos à análise de variância, com nível de significância de 5%. Não foi observado efeito do EPE sobre o número de ovulações, o diâmetro dos folículos, a vascularização da parede folicular e a concentração sérica de estrógeno. Os animais, tratados ou não, apresentaram CLs funcionais, não havendo diferença na área do parênquima ou da vascularização luteal, nem na concentração sérica de progesterona, no oitavo dia após a ovulação. Foi observado que o EPE proporcionou um maior número de folículos subordinados no momento da indução da ovulação do folículo dominante (P ≤ 0,05). Embora esses folículos não tenham chegado a ovular, concluiu-se que o EPE atuou no crescimento de folículos, que podem ser utilizados em outras biotécnicas, como a transferência de oócitos, com maior aproveitamento da reserva folicular de ovários equinos.(AU)

Knowledge about follicle and corpus luteum vascularization associated with superovulation in mares is scarce. Aiming to evaluate the effect of equine pituitary extract (EPE) on superovulation, the experiment was conducted using six mares Purebred Arabian in two estrous cycles (control and treatment). The mares were synchronized, and monitored daily by ultrasound B mode until the follicles reached diameter ≤ 23 mm (deviation). In the treatment cycle, from the deviation, mares received 8 mg of EPE, once a day, intramuscularly, until two or more follicles reached a diameter between 32 and 35 mm. Ovulation was induced with deslorelin acetate when follicles reached at least 35 mm. At the time of follicular deviation, induction of ovulation and final preovulatory exam, it was used B-mode ultrasound to measure the diameter of follicles and on the eighth day after ovulation to measure the area of the corpus luteum (CL); color Doppler was also used to assess blood perfusion of the follicle wall and luteal parenchyma. In the control cycle was performed the same procedure except for the use of EPE. Data were subjected to analysis of variance, with 5% significance level. There was no effect of EPE on ovulation number, diameter of follicles, vascularity of the follicular wall and serum estrogen concentration. The animals treated or not, showed functional CLs, with no difference in parenchymal area or luteal vascularization, or in serum progesterone concentration on the eighth day after ovulation. It was observed that the EPE provided a greater number of subordinate follicles at the time of induction of ovulation of the dominant follicle. Although these follicles have failed to ovulate, it was concluded that EPE influenced the follicles growth, and it can be used in other biotechnologies, with greater utilization of equine ovarian follicular reserve.(AU)

Synchronised firing patterns in a random network of adaptive exponential integrate-and-fire neuron model.

We have studied neuronal synchronisation in a random network of adaptive exponential integrate-and-fire neurons. We study how spiking or bursting synchronous behaviour appears as a function of the coupling strength and the probability of connections, by constructing parameter spaces that identify these synchronous behaviours from measurements of the inter-spike interval and the calculation of the order parameter. Moreover, we verify the robustness of synchronisation by applying an external perturbation to each neuron. The simulations show that bursting synchronisation is more robust than spike synchronisation.

Spike timing-dependent plasticity induces non-trivial topology in the brain.

We study the capacity of Hodgkin-Huxley neuron in a network to change temporarily or permanently their connections and behavior, the so called spike timing-dependent plasticity (STDP), as a function of their synchronous behavior. We consider STDP of excitatory and inhibitory synapses driven by Hebbian rules. We show that the final state of networks evolved by a STDP depend on the initial network configuration. Specifically, an initial all-to-all topology evolves to a complex topology. Moreover, external perturbations can induce co-existence of clusters, those whose neurons are synchronous and those whose neurons are desynchronous. This work reveals that STDP based on Hebbian rules leads to a change in the direction of the synapses between high and low frequency neurons, and therefore, Hebbian learning can be explained in terms of preferential attachment between these two diverse communities of neurons, those with low-frequency spiking neurons, and those with higher-frequency spiking neurons.

Effects of glycerol, equilibration time and antioxidants on post-thaw functional integrity of bovine spermatozoa directly obtained from epididymis.

This work aimed to evaluate the effect of stabilisation times, glycerol concentration, and the catalase and superoxide dismutase supplementation of diluent on parameters of frozen-thawed spermatozoa from epididymis of Nelore bulls: Experiment 1: spermatozoa diluted in Tris-egg yolk with glycerol (3%, 5% or 7%) and stabilisation times (0, 2 or 4 hr at 5°C); Experiment 2: Tris-egg yolk only, Tris-egg yolk with catalase (CAT, 50 or 100 U ml-1 ) or superoxide dismutase (SOD, 50 or 100 U ml-1 ). Frozen-thawed spermatozoa were evaluated for kinetic parameters, plasma membrane and acrosome integrity, mitochondrial activity and IVF capacity. ALH and BCF were affected (p < .05) by glycerol at 3% after 4-hr equilibration time and 7% after 2-hr equilibration time. Glycerol 3% had lower (p < .05) iPM and iAc after 4 hr. Glycerol 5% had greater (p < .05) hPMM after 4 hr and iAc after 2 hr than at 0 hr. SOD 100 U ml-1 had lower (p < .05) linearity and wobble compared to control group. No was observed differences to fertilisation rate (p < .05) among groups. In conclusion, glycerol 5% in Tris-egg yolk extender for 4 hr is suitable for the preservation of sperm kinetics and membrane integrity. CAT (50 and 100 U ml-1 ) or SOD (50-100 U ml-1 ) had no beneficial effects on sperm kinetics, plasma and acrosomal membrane integrity, mitochondrial activity or the capacity for IVF of frozen-thawed spermatozoa from epididymis of Nelore bulls.