Physiological mechanisms of thermoregulation in reptiles: a review

The thermal dependence of biochemical reaction rates means that many animals regulate their body temperature so that fluctuations in body temperature are small compared to environmental temperature fluctuations. Thermoregulation is a complex process that involves sensing of the environment, and subsequent processing of the environmental information. We suggest that the physiological mechanisms that facilitate thermoregulation transcend phylogenetic boundaries. Reptiles are primarily used as model organisms for ecological and evolutionary research and, unlike in mammals, the physiological basis of many aspects in thermoregulation remains obscure. Here, we review recent research on regulation of body temperature, thermoreception, body temperature set-points, and cardiovascular control of heating and cooling in reptiles. The aim of this review is to place physiological thermoregulation of reptiles in a wider phylogenetic context. Future research on reptilian thermoregulation should focus on the pathways that connect peripheral sensing to central processing which will ultimately lead to the thermoregulatory response.

CXCR4/SDF1 interaction inhibits the primordial to primary follicle transition in the neonatal mouse ovary

The molecular mechanisms behind the entry of the primordial follicle into the growing follicle pool remain poorly understood. To investigate this process further, a microarray-based comparison was undertaken between 2-day postpartum mouse ovaries consisting of primordial follicles/naked oocytes only and those with both primordial follicles and newly activated follicles (7-day postpartum). Gene candidates identified included the chemoattractive cytokine stromal derived factor-1 (SDF1) and its receptor CXCR4. SDF1 and CXCR4 have been implicated in a variety of physiological processes including the migration of embryonic germ cells to the gonads. SDF1-alpha expression increased with the developmental stage of the follicle. Embryonic expression was found to be dichotomous post-genii cell migration, with low expression in the female. Immunohistochemical studies nonetheless indicate that the autocrine pattern of expression ligand and receptor begins during embryonic life. Addition of recombinant SDF1-alpha to neonatal mouse ovaries in vitro resulted in significantly higher follicle densities than for control ovaries. TUNEL analysis indicated no detectable difference in populations of apoptotic cells of treated or control ovaries. Treated ovaries also contained a significantly lower percentage of activated follicles as determined by measurement of oocyte diameter and morphological analysis. Treatment of cultured ovaries with an inhibitor of SDF1-alpha, AMD3100, ablated the effect of SDF1-alpha. By retaining follicles in an unactivated state, SDF1/CXCR4 signaling may play an important role in maintaining the size and longevity of the primordial follicle pool. (c) 2006 Elsevier Inc. All rights reserved.

Ethanol prevents NMDA receptor reduction by maternal separation in neonatal rat hippocampus

We measured the effects of ethanol on glutamate receptor levels in the hippocampus of neonatal Wistar rats using a vapor chamber model. Two control groups were used; a normal suckle group and a maternal separation group. Levels of NMDA receptors were not significantly altered in ethanol-treated animals compared to the normal suckle control group, as shown by [H-3]MK-801 binding and Western blot analysis. However, MK-801 binding and NR1 subunit immunoreactivity were greatly reduced in the hippocampus of separation control animals. Neither ethanol treatment nor maternal separation altered levels of GluR1 or GluR2(4). These results have serious implications for the importance of maternal contact for normal brain development.

Measuring parent satisfaction with a neonatal hearing screening program

The primary aim of the present study was to investigate parent satisfaction with a neonatal hearing screening program through use of a valid and reliable questionnaire developed for this purpose (Parent Satisfaction Questionnaire with Neonatal Hearing Screening Program; PSQ-NHSP). Eighty parents whose children had received hearing screening participated in this study. High levels of satisfaction were reported with more than 90% of parents satisfied with all aspects of the program. The PSQ-NHSP was analyzed for validity and reliability and demonstrated excellent internal consistency reliability (sigma = 0.94) and excellent test-retest reliability (rho = 0.97). Content validity of the PSQ-NHSP was partially established by reviewing available literature on parent satisfaction studies in other pediatric health-care service programs. Construct validity of the PSQ-NHSP was indicated by a significant positive relationship between overall satisfaction and the three specific dimensions in the questionnaire. The satisfaction questionnaire was found to be a useful instrument for identifying service shortfalls, and routine use of the PSQ-NHSP in other neonatal hearing screening programs is recommended.

Neonatal neurodevelopment outcomes following tocolysis with glycerol trinitrate patches

Objective: The object of this study was to determine the effects of maternal tocolysis with glycerol trinitrate (GTN) patches on the neurodevelopment of infants. Study design: This was a randomized, multicenter, controlled trial comparing the efficacy of GTN patches with standard beta 2 agonist as tocolytic therapy. The previously reported outcomes of this study indicated no difference in neonatal mortality or morbidity to hospital discharge. One hundred fifty-six surviving infants from 2 Australian centers were psychometrically assessed using the Griffiths Mental development Scales (revised) at 18 months of age. Results: There was no difference in psychometric performance between those infants enrolled in either the GTN (81 infants) or beta 2 agonist (75 infants) arm of the study. Conclusion: This randomized trial supports no significant difference between GTN patches in comparison with standard beta 2 agonist for tocolytic therapy. The results underscore the association between premature labor and adverse infant outcomes. (c) 2006 Mosby, Inc. All rights reserved.