In vitro melanocyte-stimulating hormone (MSH) stimulates melanogenesis in some, but not all, melanocytes and melanoma cells. In an attempt to explain this variation in response to alpha MSH, we examined cyclic adenosine monophosphate (cAMP) accumulation, tyrosinase activity, and melanin production in primary (1 degree) murine B16 melanoma cells and in two B16 cell lines (B16 F1 and B16 F10) that are known to respond to alpha MSH. In vivo all three B16 melanoma cell types produced pigmented tumours. In vitro alpha MSH increased tyrosinase activity and melanin content in the F1 and F10 cells but not in the B16 1 degree cells. alpha MSH, however, increased cAMP production in all three cell types, confirming that the inability of B16 1 degree cells to produce melanin in response to alpha MSH is not due to a lack of alpha MSH receptors or cAMP response to alpha MSH. Further, we present evidence for a separate pathway of melanogenesis that is independent of cAMP as calmodulin antagonists, which do not elevate cAMP, increased tyrosinase activity, and melanin production in both 1 degree and F1 cells.

Animals↗

PubMedDate not supplied

Intensive dance practice. Repercussions on growth and puberty.

To determine the effect of intensive sports training on growth and puberty, we studied a group of 97 young female dancers longitudinally for 5 years. We studied the changes in their heights, weights, and pubertal developments and compared these findings with those of a control group. We found that 15 (16%) dancers who started dance training had noticeably decreased growth velocity during the prepuberty stage after the beginning of ballet practice compared with the control group. This group had the same average training time compared with the other dancers, but these dancers were the slimmest and had the most inadequate nutritional intake. Puberty in dancers was delayed compared with the controls. We found that moderately intensive dance practice can lead to eating disorders and weight control early in childhood, with consequences that are poorly known. Weight and height statistics of children who practice individual sports involving body aesthetics must be monitored to detect early anomalies.

Adolescent↗