Antiestrogen therapies affect tissue homeostasis of the gerbil (Meriones unguiculatus) female prostate and ovaries

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The present work aims to evaluate the response of the adult gerbil female prostate (paraurethral glands) and ovaries to short-term exposure to antiestrogenic agents, consisting of daily oral doses of letrozole (1 mg kg(-1) day(-1)) or intradermal doses of tamoxifen (1 mg/kg) every other day for 21 days. The serum levels of testosterone and estradiol were monitored, and the prostates and ovaries collected for structural, ultrastructural, and immunocytochemical analyses. The letrozole treatment resulted in increases of serum testosterone levels and secretory activity as well as in glandular hyperplasia and dysplastic growth, simulating the effects caused by the exogenous androgens. The effects caused by tamoxifen indicate that this endocrine agent acted as an estrogenic agonist on the prostate, causing glandular hypertrophy, secretory activity decrease, and the development of prostatic lesions. Therefore, it is possible to conclude that the letrozole and tamoxifen therapies result in a series of complex effects that endanger the physiology of hormone-dependent organs, including the female prostate and ovaries. The hormonal imbalance caused by administration of these drugs resulted in considerable changes in prostatic morphology, in a manner very similar to what occurs during the development of prostatic lesions in aged postmenopausal women. Thus, these therapies must be chosen carefully since long-term treatments can result in female prostate dysplasic lesions.794674685Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq [301111/05-7]FAPESP [02/12942-6

Theoretical description of the colossal entropic magnetocaloric effect: Application to MnAs

We report on the theoretical investigations into the recently discovered colossal entropy change in MnAs under magnetic-field change in an isothermal process. The phenomenological model takes into account the exchange-Zeeman interactions, magnetoelastic interactions, the external pressure effect, and the magnetic-field dependence of the lattice entropy. The results show the fundamental role of the lattice entropy in the colossal entropy change for the MnAs compound. The best model parameters and their variation with pressure were determined.73

Pressure-induced colossal magnetocaloric effect in MnAs

To present day, the maximum magnetocaloric effect (MCE) at room temperature for a magnetic field change of 5 T is 40 J/(kg K) for MnAs. In this Letter we present colossal MCE measurements on MnAs under pressure, reaching values up to 267 J/(kg K), far greater than the magnetic limit arising from the assumption of magnetic field independence of the lattice and electronic entropy contributions. The origin of the effect is the contribution to the entropy variation coming from the lattice through the magnetoelastic coupling.932

Ambient pressure colossal magnetocaloric effect tuned by composition in Mn1-xFexAs

The magnetocaloric effect (MCE) is the basis for magnetic refrigeration, and can replace conventional gas compression technology due to its superior efficiency and environment friendliness(1-3). MCE materials must exhibit a large temperature variation in response to an adiabatic magnetic-field variation and a large isothermal entropic effect is also expected. In this respect, MnAs shows the colossal MCE, but the effect appears under high pressures(4). In this work, we report on the properties of Mn1-xFexAs that exhibit the colossal effect at ambient pressure. The MCE peak varies from 285K to 310K depending on the Fe concentration. Although a large thermal hysteresis is observed, the colossal effect at ambient pressure brings layered magnetic regenerators with huge refrigerating power closer to practical applications around room temperature.51080280

A General Approach to First Order Phase Transitions and the Anomalous Behavior of Coexisting Phases in the Magnetic Case

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)First order phase transitions for materials with exotic properties are usually believed to happen at fixed values of the intensive parameters (such as pressure, temperature, etc.) characterizing their properties. It is also considered that the extensive properties of the phases (such as entropy, volume, etc.) have discontinuities at the transition point, but that for each phase the intensive parameters remain constant during the transition. These features are a hallmark for systems described by two thermodynamic degrees of freedom. In this work it is shown that first order phase transitions must be understood in the broader framework of thermodynamic systems described by three or more degrees of freedom. This means that the transitions occur along intervals of the intensive parameters, that the properties of the phases coexisting during the transition may show peculiar behaviors characteristic of each system, and that a generalized Clausius-Clapeyron equation must be obeyed. These features for the magnetic case are confirmed, and it is shown that experimental calorimetric data agree well with the magnetic Clausius-Clapeyron equation for MnAs. An estimate for the point in the temperature-field plane where the first order magnetic transition turns to a second order one is obtained (the critical parameters) for MnAs and Gd(5)Ge(2)Si(2) compounds. Anomalous behavior of the volumes of the coexisting phases during the magnetic first order transition is measured, and it is shown that the anomalies for the individual phases are hidden in the behavior of the global properties as the volume.196942949Fundacao de Amparo Pesquisa do Estado deConselho Nacional de Desenvolvimento CientificoCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)U.S. Department of EnergyOffice of ScienceOffice of Basic Energy Sciences [DE-AC02-06CH11357]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Office of Basic Energy Sciences [DE-AC02-06CH11357