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Among all the regulatory homeostatic networks in vertebrates, the activation of the hypothalamic-pituitaryadrenal axis during the stress response, has gained considerable attention, and the measurement of fecal glucocorticoids (FGC) has become an invaluable tool to assess adrenocortical activity related to stressful events in wild and captive animals. However, the use of FGC requires the validation of measurement techniques and the proper selection of the specific hormone according to the study species. The main objective of this study was to identify the dominant glucocorticoid (GC) hormone in the stress response of black-tailed prairie dogs (Cynomys ludovicianus) in an arid grassland of Chihuahua, Mexico. A capture stress challenge in the field was developed to determine if the levels of glucocorticoids (cortisol and corticosterone) both in serum and fecal samples could be attributed to stress in Cynomys ludovicianus. The samples were analysed with the technique of liquid phase radioimmunoassay , and this study showed that both cortisol and corticosterone are present at measurable levels in serum and fecal samples of black-tailed prairie dogs. We found that both GCs were present in similar concentrations in serum, however, corticosterone concentration in fecal samples was higher than cortisol. Likewise, biochemical validations performed in this study to test the assay reached acceptable levels of reliability. Therefore, we confirm that fecal analysis can be implemented as a method to measure stress responses in wild prairie dogs.

A detailed thermodynamic analysis has been carried out of large-scale coal gasification-based power plant cycles with near zero CO2 emissions, integrated with chemical looping combustion (CLC). Syngas from coal gasification is oxidized in dynamically operated packed bed reactors (PBRs), generating a CO2-rich stream ready for sequestration. PBRs have recently been proposed for CLC as an alternative for an interconnected fluidized bed reactors system operated at high pressure, to circumvent difficulties associated with solids circulation and gas/solid separation at high temperature and pressure. However, in view of the dynamic operation, the heat management in PBRs needs to be carefully assessed, since it affects the temperature and gas flow rates at the reactor outlet during the different cycles. The present work investigates the effect on plant performance of two different PBRs heat management strategies proposed in a previous work, with the aim of avoiding problems related to oxygen carriers featuring low reduction kinetics at moderate temperatures. The system is designed to achieve full integration of the steam cycle with the other units of the plants in order to improve the overall plant efficiency. A sensitivity analysis on the CLC operating pressure, the steam cycle parameters and the effect of syngas dilution with exhaust recirculation and steam addition was performed. The mass and energy balances of the integrated plant are presented in detail and the plant performance is compared with reference technologies. The net electric efficiency approaches 41% (based on the coal LHV) with a CO2 capture efficiency over 97%. Moreover, it has been found that the heat management strategies adopted do not significantly affect the maximum net electric efficiency, even if different power shares between the gas and steam turbines are obtained, with consequent implications in the plant design and economics.

In group-living animals, competition for a scarce resource often results in the formation of dominance hierarchies. Dominant individuals garner more of that resource for themselves through the use of aggression, forcing subordinates to rely on nonaggressive strategies to secure it. Stealing from dominants is common, but subordinate thieves can risk attack if caught. How, then, do subordinates decide when and where to steal? We explored whether the opportunity to learn about the location and availability of food might facilitate food-stealing attempts by male blue gouramis, Trichogaster trichopterus , a freshwater tropical fish. Our results show that subordinates were able to use learned cues to mount highly effective ‘sneaky’ tactics. By anticipating food location and availability, subordinates reduced the number of attacks they received as well as the amount of time they spent fleeing from dominants. More importantly, however, our results revealed unexpected plasticity in the cognitive mechanisms underlying this learning: like privately trained dominants, privately trained subordinates learned to approach food cues directly; however, on the very first occasion that subordinates were tested with a dominant present, they dramatically altered their previously learned direct approach to food cues, immediately adopting a different, sneaky tactic instead. Thus, subordinates were able to combine information about previous learning, namely an ‘expectancy’ of food, with the probability of future attack and adjust their food-getting strategy accordingly.

It is now well accepted that the endocrine system can be strongly influenced by the immunological status of the body. This laboratory has provided documented evidence that the rat thymus produces a biologically active secretion, with a molecular weight of approximately 30 kDa, that augments the gonadotrophin-releasing hormone (GnRH) stimulated secretion of gonadotrophins by isolated pituitary cells in culture. To determine the cells of origin of the factor involved, the reticulo-epithelial cells from the thymus were incubated in vitro to provide media for the examination of possible effects on the secretion of gonadotrophins by the rat pituitary. The enrichment of the culture with reticulo-epithelial cells was confirmed using anticytokeratins antibodies. It was found that the addition of such conditioned medium increased the secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), with a greater effect on the former. The increment in gonadotrophin secretion was time- and dose-dependent. This same conditioned medium also potentiated the effect of GnRH on the cultured pituitary cells. The fractionation of thymic-conditioned medium using selective molecular membrane filters, provided evidence that the active factor or factors involved in the enhanced secretion of gonadotrophins are larger than 10 kDa MW. Present findings show that thymic reticulo-epithelial cells are responsible for this activity.

This report describes the influences of fetal serum and gonadotropins on the development and function of chick testicular cells in a culture system that allows long term control of culture conditions. Testis of new born male chicks were dissociated and cultured in different conditions and the production of testosterone measured by RIA. 1. 1.|To investigate the effect of serum the cells were wither cultured in a defined medium composed by Dulbecco's modified medium (DMM) plus 0.1% albumin or media containing DMM plus 10% fetal bovine serum (FBS). The presence of serum increased protein content of the cultures, but no differences were found in basal testosterone production. When hCG (2IU/ml) was added to both culture media, the increment in testosterone production hence produced, was greater when cells were cultured in defined medium. 2. 2.|Cells were precultured for 24 hr in either defined serum media with or without hCG. The media were then replaced with DMM plus BSA and 1-methyl 3-isobutyl xanthine (IBMX) in the presence or absence of hCG and cells further incubated for 2 hr. Addition of hCG increased testosterone production by cells cultured in defined medium and enhanced its subsequent response to hCG stimulation. Cells cultured in serum medium maintained their ability to respond to hCG, but the addition of this hormone to the medium, abolished the response to further hCG-stimulation. 3. 3.|hCG caused a dose-related increased in testosterone production by cells cultured in defined and serum containing media, but concentrations of hCG above 2 IU/ml depressed testosterone production in the latter group. 4. 4.|Cells cultured in defined medium were incubated for 6 hr either with or without FSH of different purity grade. Both preparations stimulated the production of testosterone, the pure one being less effective than the LH-contaminated one. 5. 5.|Cells cultured in defined medium were incubated for 6 hr either with or without FSH and further stimulated with hCG (2 IU/ml). A significant increment in the response to hCG was observed when cells had been exposed to FSH. Present results show that FBS influences the function and development of chick testis cells in culture. Since both FSH and hCG modified testosterone secretion, a role for gonadotropins in the functional capacity of neonatal Leydig cells is also suggested.

Corticosterone (1 μg/g) was administered to the pregnant rat mother at 17, 18 and 19 days of gestation. The pups were killed at birth or at 6 or 12 days of age and the morphological and biochemical development of the brain, with special emphasis in the cerebellum was studied. The brain and cerebellar weight was slightly diminished in the corticosterone treated animals. Corticosterone produced changes in the pattern of development of the cerebellar layers, causing an accelerated decrement of the external granular layer at 12 days of life. The total protein content of the cerebellum was increased in the hormone treated pups at birth, 6 and 12 postnatal days. Newborn corticosterone treated animals showed a decreased DNA content, but this phenomenon was completely reversed at 12 days. It was concluded that corticosterone given to the pregnant mother influences the time pattern of the development of the brain and the cerebellum.

An interrelationship between immune and reproductive systems has been postulated, and involves, among others, bidirectional effects between gonads and thymus. To this effect a rat thymus fraction of about 28000 mol wt has been reported to inhibit the effect of hCG on in vitro suspension of Leydig cells. We have investigated the antigonadotropin activity of thymus extracts on rat testis receptors. Acetonic powder obtained from thymus of 14 day-old rats was separated by molecular sieve chromatography. The effect of the collected fractions on the 125 I-hCG binding to receptor sites in rat testes was evaluated. A fraction corresponding to 27000–28000 mol wt named thymus factor (TF), was found to inhibit the binding activity of 125 I-hCG to its testicular receptor. The inhibitory effect of TF on hCG binding is dose related. By Scatchard analysis a competitive interaction at the receptor level between TF and hCG was demonstrated. The Ka values of hCG binding were diminished in the presence of TF while no significative changes were detected in the number of receptor sites. Present results strongly suggest a modulation function of TF at the testis receptor level.