Insulin-like growth factor II acts as an autocrine growth and motility factor in human rhabdomyosarcoma tumors

Rhabdomyosarcoma is the most common soft tissue sarcoma of childhood and appears to arise from developing striated muscle-forming cells. Since insulin-like growth factor II (IGF-II) is involved in normal muscle growth and maturation and elevated IGF-II mRNA levels have previously been reported in rhabdomyosarcomas, we have been studying the possible role of IGF-II in the unregulated growth and invasive potential of these embryonal tumors. In this study, we demonstrate that 13 of 14 rhabdomyosarcoma tumors express high levels of IGF-II mRNA relative to normal adult muscle and also express mRNA for the type I IGF receptors on their cell surface, the receptor thought to mediate the effects of IGF-II on muscle cells. We have established several rhabdomyosarcoma cell lines in mitogen-free media and demonstrate that these cells express type I IGF receptors on their cell surface and secrete IGF-II into the media. Exogenous IGF-II is able to stimulate cellular motility in these cell lines as assayed in a modified Boyden chamber. Finally, alpha IR-3, a type I receptor antagonist, inhibits the growth of these cell lines in serum-free media but does not inhibit IGF-II-induced motility of these cells. These data suggest that endogenously produced IGF-II functions as an autocrine growth and motility factor in many rhabdomyosarcoma tumors. The mitogenic actions of IGF-II are mediated through a domain of the type I IGF receptor that is blocked by alpha IR-3. IGF-II-induced motility may be mediated through an alternative signaling pathway.     

Differential regulation of fibronectin receptor subunit gene and cell surface expression in human peripheral blood T lymphocytes.

Members of the beta 1 subfamily of heterodimeric integrins, such as the fibronectin receptors alpha 5 beta 1 and alpha 4 beta 1, are expressed on human T lymphocytes. The presence of these two adhesion receptors on T lymphocytes suggests an involvement in cell-cell and cell-extracellular matrix interactions that may be important for the development of immune and inflammatory reactions. We have examined the cell surface expression of alpha 5, alpha 4, and beta 1 subunits on purified peripheral blood T lymphocytes before and after activation with Con A and PMA. Freshly isolated T lymphocytes contained distinct fractions expressing high or low levels of alpha 5 and beta 1. Only a high expressing T lymphocyte population was present after 72-h culture with Con A and PMA. Time course analysis indicated that the shift in alpha 5 and beta 1 expression occurred during the first 24 h after addition of activating agents and occurred in the absence of proliferation. In contrast to alpha 5 and beta 1, essentially all freshly isolated T lymphocytes expressed high levels of alpha 4. After 72-h culture with Con A and PMA, a wide distribution of alpha 4 expression was observed. Further experiments showed that after activation, a proportion of CD4-positive cells decreased their surface expression of alpha 4, but increased their surface expression of alpha 5 and beta 1. In contrast, most CD8-positive cells increased their surface expression of alpha 5, beta 1, and alpha 4 upon activation. An examination of mRNA levels in pan-T lymphocyte cultures after activation indicated that alpha 5 and alpha 4 mRNA expression decreased, whereas beta 1 mRNA expression was unchanged, in Con A/PMA-activated cells as compared to those cultured in medium alone. Our results indicate that T lymphocyte activating agents may differentially affect the expression of alpha 5 beta 1 and alpha 4 beta 1, thus providing a mechanism for the selective regulation of binding interactions that occur at sites of immune reactions.     

A technique for obtaining early life history data in pouched marsupials

Early developmental and demographic events in many marsupials occur in the mother's pouch out of animal managers' sight. Because pouch examination is perceived as being stressful both to animal and handler, the pouch has proven to be a formidable physical and psychological barrier to the study of early life history events in marsupials in zoos. Demographic and developmental data such as litter size at birth, secondary sex ratios, infant mortality rates, and early rates of growth and development, normally considered essential information for the development of breeding programs, are therefore essentially unavailable for most zoo populations of marsupials. Here we describe a technique for the safe and non-stressful examination of the pouches of small (< 2 kg) marsupials that enables the capture of such data. The technique, involving the use of transparent plastic tubes of slightly different diameters for restraining the animals and an otoscope for examining the pouch and its contents, has been very successfully applied to life history studies of four species at the National Zoological Park: Pseudocheirus peregrinus, Petaurus breviceps, Philander opossum, and Chironectes minimus.