Age-related qualitative shift in emotional behaviour : paradoxical findings after re-exposure of rats in the elevated-plus maze

Several variables, including age, are known to influence anxiety. Previous exposure to the elevated-plus maze (EPM) is known to modify emotional behaviour as retesting in the EPM at a standard age of 3 months increases open-arm avoidance and attenuates the effects of anxiolytic drugs. This study analysed whether similar results are obtained when older animals are subjected to these experimental paradigms. Overall, increasing age was associated with more signs of anxiety. Additionally, we observed a paradoxical behaviour pattern in aged-subjects that were re-exposed to the EPM, with mid-aged and old rats failing to display open arm avoidance (OAA) in the second trial; this qualitative shift in emotional behaviour was not associated with decreased locomotion. An examination of how age influences responsiveness to anxiolytic drugs, with or without previous maze experience, was also conducted. Midazolam (0.5 and 1 mg/kg) proved anxiolytic in maize-naive young animals; in marked contrast, in older animals midazolam at 1 mg/kg resulted in sedation but not anxiolyis. One trial tolerance to midazolam was evident in animals of both ages that were subjected to a second EPM trial; the latter phenomenon was apparently accentuated in older animals as they do not show open arm avoidance upon re-exposure to the EPM. These data suggest that the age-associated ‘resistance’ to anxiolytic drugs might be related to a qualitative shift in emotional behaviour

Seasonal Changes in Chemical Composition, Preference and In Sacco Degradation of Eight Different Fodder Tree leaves

Livestock farmers in the Coastal Savannah of Ghana cut and feed leaves of various naturally occurring fodder tree species to supplement livestock diets, especially in the dry season. The aim of this study was to determine the seasonal changes in chemical composition, rumen degradation characteristics and preference of sheep for eight common indigenous fodder tree leaves, and ascertain their contribution to livestock production. Fodder leaves from Albizzia lebbek (AL), Baphia nitida (BN), Blighia sapida (BS), Ficus exasperata (FE), Ficus polita (FP), Morinda lucida (ML), Moringa oleifera (MO) and Spondias mombin (SM) were used. Fresh leaves were sampled in the wet and dry seasons to determine changes in seasonal chemical composition. Four Djallonke sheep (two males and two females) of average weight of 27.3 kg ±0.22 were offered fresh fodder leaves in a cafeteria system to determine preference. In sacco dry matter (DM) degradation was determined using four fistulated sheep in a repeated atin suare design. Seasonal D crude protein C acid detergent fire D neutral detergent fire D and lignin content of the fodder leaves ranged fro 319.7 to 862.7 g kg-1, 150.0 to 359.2 g kg -1 D . to . g g -1 DM , 277.5 to 718.3 g kg -1 DM and . to . g g-1 DM respectively. Crude protein content of, AL and FP were higher for the wet season than dry season but BS had similar trend for both seasons. The soluble and potentially degradable fractions of D ranged from 113.3-216.8 and 142.9-627.7 g kg-1. It is concluded that the four most preferred fodder species were AL, FE, SM and MO. Their CP contents regardless of the season were higher than the minimum level considered as adeuate for oderate ruinant production. t is epected that these fodder leaves ill contriute to ypass protein and nitrogen retention and suseuently lead to eight gain hen fed to sheep

Morphological correlates of corticosteroid-induced changes in prefrontal cortex-dependent behaviors

Imbalances in the corticosteroid milieu have been implicated in several neuropsychiatric disorders, including depression and schizo-phrenia. Prefrontal cortex (PFC) dysfunction is also a hallmark of these conditions, causing impairments in executive functions such as behavioral flexibility and working memory. Recent studies have suggested that the PFC might be influenced by corticosteroids released during stress. To test this possibility, we assessed spatial working memory and behavioral flexibility in rats submitted to chronic adrenalectomy or treatment with corticosterone (25 mg/kg) or the synthetic glucocorticoid dexamethasone (300 μg/kg); the behavioral analysis was complemented by stereological evaluation of the PFC (prelimbic, infralimbic, and anterior cingulate regions), the adjacent retrosplenial and motor cortices, and the hippocampal formation. Dexamethasone treatment resulted in a pronounced impairment in working memory and behavioral flexibility, effects that correlated with neuronal loss and atrophy of layer II of the infralimbic, prelimbic, and cingulate cortices. Exposure to corticosterone produced milder impairments in behavioral flexibility, but not in working memory, and reduced the volume of layer II of all prefrontal areas. Interestingly, adrenalectomy-induced deleterious effects only became apparent on the reverse learning task and were not associated with structural alterations in the PFC. None of the experimental procedures influenced the morphology of retrosplenial or motor cortices, but stereological measurements confirmed previously observed effects of corticosteroids on hippocampal structure. Our results describe, for the first time, that imbalances in the corticosteroid environment can induce degeneration of specific layers of the PFC; these changes appear to be the morphological correlate of corticosteroid-induced impairment of PFC-dependent behavior(s).German Academic Exchange - grant Acções Integradas Luso-Alemãs.Portuguese Rectors’ Conference

Chemical composition, in vitro dry matter digestibility and Gas production of four browse species and their combinations used as feed for small ruminants

Browse species as complete feed for ruminants is uncommon. This may be due to low dry matter (DM) and high condensed tannins (CT) contents limiting its potential to influence weight gain. Drying however improves DM content and reduces CT levels and its astringency. The objective of this study was to determine chemical composition, in vitro parameters and to evaluate the potential benefits of feeding small ruminants on dried browse leaves and their combinations. The browse species were Albizzia lebbek, Gliricidia sepium, Moringa oleifera and Millettia thoningii. Rumen fluid was obtained from two fistulated forest type wethers for the in vitro evaluation. The DM, crude protein (CP), ash, CT, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose and lignin were 866-916 g/kg, 101-303 g/kg DM, 74.7-200 g/kg DM, 0.9-1.3 g/kg DM, 202-552 g/kg DM, 205-520 g/kg DM, 94-381 g/kg DM and 105-192 g/kg DM respectively. The organic matter digestibility (OMD), in vitro dry matter digestibility (IVDMD), in vitro gas production (IVGP), metabolisable energy (ME) and short chain fatty acids (SCFA) of the four browse species and their combinations recorded were 314.9-721.6 g/kg DM, 515.4-721 ml/g DM, 139-602 ml/g DM, 314.6-1406.9 ml/g DM and 3.1-14.4 ml/g DM respectively. There were positive associative effects shown by the combined browse leaves between IVDMD and IVGP. The regression analyses revealed that relationships between IVGP and CP and IVDMD and CT and all relationships between OMD, SCFA, ME and IVGP were significant (p<0.05). All the browse species and their combinations had IVDMD values of more than 500 g/kg DM and low gas production. The high CP and ash contents, low CTs, low to moderate fibre components, moderate to high IVDMD and low IVGP of the four browse species and their combinations make them potentially valuable as feed resources for small ruminant production

Limitation of electron mobility in modulation-doped In0.53Ga0.47As/InP quantum wells at low temperatures

The low-temperature electron mobility is investigated here for electrons confined in modulation-doped In0.53Ga0.47As/InP single symmetric quantum wells. The subband structure calculation is developed via variational method, both Schrodinger and Poisson equations being solved simultaneously with adequate heterointer- ¨ face matching conditions. With this in hands, the main electron scattering rates are computed, namely alloy disorder, remote ionized impurity, and interface roughness. As a result, interesting interchanges in these scattering rates were found by varying the well width and the spacer width, which show that some scattering mechanisms can surpass the alloy disorder scattering rate and come to limit the electron mobility, a behavior not reported in the literature

Zero-mode analysis of quantum statistical physics

We present a unified formulation for quantum statistical physics based on the representation of the density matrix as a functional integral. We identify the stochastic variable of the effective statistical theory that we derive as a boundary configuration and a zero mode relevant to the discussion of infrared physics. We illustrate our formulation by computing the partition function of an interacting one-dimensional quantum mechanical system at finite temperature from the path-integral representation for the density matrix. The method of calculation provides an alternative to the usual sum over periodic trajectories: it sums over paths with coincident endpoints, and includes non-vanishing boundary terms. An appropriately modified expansion into Matsubara modes provides a natural separation of the zero-mode physics. This feature may be useful in the treatment of infrared divergences that plague the perturbative approach in thermal field theory.Comment: 9 pages, 5 figure

On the influence of thermal hysteresis on the performance of thermomagnetic motors

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQAlthough thermal hysteresis might be a problem in the magnetocaloric refrigeration, the same is not necessarily true for thermomagnetic motor applications. This work presents a comparison of the magnetocaloric properties of materials with first order magnetic transition (having large or narrow thermal hysteresis) to those with second order magnetic transition, assessing the application of these materials in thermomagnetic motors through a thermodynamic approach. Results show that the larger the thermal hysteresis, the higher the specific work produced in a thermal cycle. This allows operation at higher temperature differences with high efficiency relative to Carnot efficiency, when compared with systems using narrow hysteresis and second order transition materials.1222415FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2015/26799-0Sem informaçã