In Vitro Dedifferentiation of Melanocytes from Adult Epidermis

In previous work we described a novel culture technique using a cholera toxin and PMA-free medium (Mel-mix) for obtaining pure melanocyte cultures from human adult epidermis. In Mel-mix medium the cultured melanocytes are bipolar, unpigmented and highly proliferative. Further characterization of the cultured melanocytes revealed the disappearance of c-Kit and TRP-1 and induction of nestin expression, indicating that melanocytes dedifferentiated in this in vitro culture. Cholera toxin and PMA were able to induce c-Kit and TRP-1 protein expressions in the cells, reversing dedifferentiation. TRP-1 mRNA expression was induced in dedifferentiated melanocytes by UV-B irradiated keratinocyte supernatants, however direct UV-B irradiation of the cells resulted in further decrease of TRP-1 mRNA expression. These dedifferentiated, easily accessible cultured melanocytes provide a good model for studying melanocyte differentiation and possibly transdifferentiation. Because melanocytes in Mel-mix medium can be cultured with human serum as the only supplement, this culture system is also suitable for autologous cell transplantation

Nest desertion is not predicted by cuckoldry in the Eurasian penduline tit

Engagement in extra-pair copulations is an example of the abundant conflicting interests between males and females over reproduction. Potential benefits for females and the risk of cuckoldry for males are expected to have important implications on the evolution of parental care. However, whether parents adjust parental care in response to parentage remains unclear. In Eurasian penduline tits Remiz pendulinus, which are small polygamous songbirds, parental care is carried out either by the male or by the female. In addition, one third of clutches is deserted by both male and female. Desertion takes place during the egg-laying phase. Using genotypes of nine microsatellite loci of 443 offspring and 211 adults, we test whether extra-pair paternity predicts parental care. We expect males to be more likely to desert cuckolded broods, whereas we expect females, if they obtain benefits from having multiple sires, to be more likely to care for broods with multiple paternity. Our results suggest that parental care is not adjusted to parentage on an ecological timescale. Furthermore, we found that male attractiveness does not predict cuckoldry, and we found no evidence for indirect benefits for females (i.e., increased growth rates or heterozygosity of extra-pair offspring). We argue that male Eurasian penduline tits may not be able to assess the risk of cuckoldry; thus, a direct association with parental care is unlikely to evolve. However, timing of desertion (i.e., when to desert during the egg-laying phase) may be influenced by the risk of cuckoldry. Future work applying extensive gene sequencing and quantitative genetics is likely to further our understanding of how selection may influence the association between parentage and parental care

Molecular Basis of Repolarization Reserve Differences between Dogs and Man

Dog models are often used for clinically related electrophysiology research, but their appropriateness and limitations are unclear. This study compared repolarization reserve and its molecular basis in dogs vs humans. Rapid (IKr) and slow (IKs) delayed rectifier and inward rectifier (IK1) K+ currents were measured in cardiomyocytes from normal dog and human tissue-donor hearts. IK1, IKr and IKs blocking effects on action potential duration (APD) were studied on human and dog papillary muscle preparations. Gene expression was measured by real time PCR. IKr densities were similar in dog and man (0.37\ub10.03 pA/pF vs 0.29\ub10.05 pA/pF, P=ns). IK1 was ~3-fold greater in canine vs human cells (eg at \u201360 mV: 1.72\ub10.07 pA/pF vs 0.65\ub10.1 pA/pF*; n=21\u201328, *P<0.05), and IKs was ~4-fold greater in dog cardiomyocytes (eg at ~40 mV: 0.72\ub10.11 pA/pF vs human 0.18\ub10.03 pA/pF*, n=10\u201315). IK1 inhibition (Ba2+) marginally increased APD in humans (by 4.8 \ub1 1.5 %) but caused larger increases in dogs (17.9 \ub1 2.1 %*). In contrast, IKr inhibition caused remarkable APD prolongation in humans (44 \ub1 4 %) versus dogs (16 \ub1 2 %*). IK1-inhibition potentiated APD-prolonging actions of IKr-blockade more in dogs (APD-increase augmented by 55%) than in humans (APD-increase enhanced by 33%) and IKs-inhibition enhanced APD-prolonging actions of IKr-blockade more in dogs (APD-increase augmented by 20%) than in humans (APD-increase enhanced by 9%), confirming the role of IK1 and IKs in limiting IKr-blocking effects in dogs. Kir2.1 subunit mRNA was significantly more abundant in dog compared to human (by ~4 fold), while Kir2.2, Kir2.3, Kir2.4, the IKr-subunit ERG and Ito-subunits (Kv1.4, Kv4.3 and KChIP2) were expressed at similar levels. One IKs-related gene (KvLQT1) was similarly expressed, while minK was more abundant (~ 7-fold) in dogs than humans. Smaller IK1 and IKs, possibly due to differential expression of the IK1 \u3b2-subunit Kir2.1 and the IKs \u3b2-subunit minK, limit repolarization reserve and exaggerate APD-prolongation by IKr-block in humans compared to dogs. These findings provide insights into species-specific determinants of responses to repolarization stress and are relevant to relating findings in dog studies to clinical phenomena in man