Failure of 5-thio-D-glucose to alter cell survival in irradiated or unirradiated EMT6 tumors

The antineoplastic effects of the glucose analog 5-thio-D-glucose (5TG) were tested using EMT6 mouse mammary tumors in vivo and EMT6 cells in cell culture. In vitro, 5TG selectively killed hypoxic EMT6 cells. However, administration of 5TG to mice bearing EMT6 tumors produced no significant toxicity to the cells of unirradiated tumors and did not alter the survival of cells in irradiated tumors. Fasting the mice to lower blood glucose concentrations before administration of 5TG increased the toxicity of the drug to the mice, but did not allow more efficacious treatment of the tumors. The data provided no evidence that 5-thio-D-glucose can be used effectively for the treatment of solid tumors, either as a cytotoxic agent or as a radiosensitizer.     

Why do snow geese adopt eggs?

Nesting female lesser snow geese (Anser caerulescens caerulescens)usually adopt eggs that are laid adjacent to their nests bypotential intraspecific nest parasites. The host female rollsthe parasite’s egg up into the nest, using the same behaviorpatterns used to retrieve her own eggs if they are displacedfrom the nest. The reproductive consequences of adopting eggsare unclear. We consider three selective scenarios that mightmaintain adoption behavior in geese: (1) egg adoption is ofno reproductive consequence to the host; (2) egg adoption augmentshost reproductive success relative to that of unparasitizednests; and (3) egg adoption is making the best of a bad situation,once a female’s options are constrained by the presenceof an egg adjacent to the nest; we also consider (4) the possibilitythat adoption, if not concordant with the selective regime,is maladaptive. Nest parasitism is costly to the host, makinghypotheses 1 and 2 unlikely. However, adopting eggs significantlydecreases the risk of total nest failure during laying, morethan offsetting other probable host costs. This is consistentwith hypothesis 3. Experiments show that geese have limitedabilities to retrieve eggs, which accounts for most cases ofnonadoption of nearby eggs. We conclude that adoption of eggsis an adaptive trait, a form of nest protection. Adopting eggsis the best option within the species’ repertoire to thethreat to nest survival created when a parasite lays an eggnext to the nest. [Behav Ecol 1991;2:181-187]