The effect of technical conditions and storage medium composition on the phosphomonoesters to inorganic phosphate ratio determined by 31P nuclear magnetic resonance spectroscopy in rabbit kidney.

Using 31P nuclear magnetic resonance spectroscopy, we compared the state of the high-energy phosphates in rabbit kidneys stored at 4 degrees C for 24 hr with 3 different solutions: Ringer (Rg), University of Wisconsin (UW), and Euro-Collins (EC) solutions. We found the highest phosphomonoester/inorganic phosphate (MP:Pi) ratio in the group of kidneys stored in the Rg solution (Rg, 0.93 +/- 0.04; UW, 0.36 +/- 0.02; EC, 0.28 +/- 0.02). This medium has been demonstrated in previous physiological studies to give poor results in terms of organ preservation compared to the solutions that mimic the "intracellular" fluid, such as the EC and UW solutions. Because the commonly used cold storage solutions contain phosphates, which superimpose on the intracellular Pi and, thus, can distort the results, we attempted to eliminate the contaminating solution around the kidney and in the vasculature by flushing the kidney with a phosphate-free solution (Rg). The MP:Pi ratio increased in the UW and EC groups (UW, 0.82 +/- 0.04; EC, 0.64 +/- 0.04) in identical proportion in the 2 groups. It remained highest in the Rg group (1.02 +/- 0.03). Comparisons of data before and after flush showed that external phosphate contamination was not predominant. There was no equilibrium in phosphate distribution between intra- and extracellular spaces at 24 hr of storage. We conclude that the validity of the MP:Pi ratio, as a viability index of renal transplant, might have to be restricted to comparisons of kidneys preserved in the same storage conditions. Therefore, it would be necessary to establish normal and pathological values of this ratio for each cold storage solution.

Modeling paternal attentiveness: distressed pups evoke differential neurobiological and behavioral responses in paternal and nonpaternal mice.

With the exception of parturition and lactation, male California deer mice (Peromyscus californicus) exhibit the same parental responses toward offspring as conspecific females. A closely related species, Peromyscus maniculatus, however, rarely exhibits paternal responses. In the current study, a comparative species approach was used to assess paternal responses in both Peromyscus species with varying levels of paternal experience (biological fathers, pup-exposed virgins, and pup-naïve virgins). Of special interest was the persistence of the males to direct their attention toward a distressed pup housed in a small enclosure (i.e., a barrier existed between males and pups). In addition to pup-directed responses, non-pup-directed responses such as grooming, resting and jumping were recorded. Subsequently, all animals' brains were assessed for fos-immunoreactivity (ir) in several areas previously associated with the paternal brain circuit. Overall, P. californicus exhibited more pup-directed responses as well as less fos-ir in brain areas involved in emotional integration and processing such as the insula and anterior cingulate. In addition to increased activation of emotional regulatory areas, P. maniculatus males, observed to direct their behavior away from the pup, exhibited higher fos-ir in the nucleus accumbens (involved in goal acquisition), perhaps due to a heightened motivation to avoid the pups. Interestingly, experience with pups altered the lateral septum and amygdala activation of P. maniculatus to levels similar to P. californicus biological fathers. Finally, fos-ir was increased in the medial preoptic area, involved in the maintenance of maternal behavior, in the biological fathers of both species. Thus, although biological predispositions toward pup-directed behaviors were observed in P. californicus males, evidence of a few shifts toward the paternal neural activation profile was apparent in P. maniculatus males. Specifically, modifications in fear responses and social processing may represent the cornerstones of the gradual shift from social tentativeness to social attentiveness in the presence of pups.

Fatherhood alters behavioural and neural responsiveness in a spatial task.

The hormones and experiences of pregnancy, parturition and lactation have been shown to dramatically remodel the female rat's hippocampus, potentially enhancing behaviours critical for meeting the increased demands of motherhood. Previous work in our laboratory has also suggested that pup exposure, apart from pregnancy and lactation, constitutes an important influence on ancillary maternal behaviour (e.g. foraging behaviour). In the present study, we press the parental model further by examining the effect of pup exposure on the hippocampus of males from a biparental mouse species, the California mice (Peromyscus californicus). Males were either Fathers (i.e. first-time fathers housed with a female from mating until 7 days after parturition), pup-exposed virgins (PEV; i.e. sexually naïve males briefly exposed to pups daily for 7 days) or Virgins (i.e. never exposed to females or pups). A dry-land maze (DLM), as used for assessing spatial learning, was employed to determine the foraging abilities of the males. The results indicated that, on the most challenging day of testing (i.e. acquisition day), California mouse Fathers demonstrated superior memory for the task compared to PEVs and Virgins. In addition to the behavioural data, significantly more fos-immunoreactivity was observed in the CA1, CA3 and dentate gyrus regions of the hippocampi of Fathers than PEVs or Virgins in response to the probe trial. Additionally, a trend for altered performance on the DLM was observed in the PEVs on the last day of testing, which was accompanied by the highest levels of nestin-immunoreactivity, an indicant of neuroplasticity, of the three groups. In summary, these data suggest that, in accordance with previous observations of maternal rats, the paternal brain is similarly influenced by parental experience, as demonstrated by accompanying modifications to relevant neurobiological and behavioural responses.