Lack of a differential radiation response for proliferative and non-proliferative rat thyroid cells (FRTL-5) in vitro.

FRTL-5 rat thyroid epithelial cells maintain normal thyroid function and morphology in vitro, exhibit an absolute requirement for thyroid stimulating hormone (TSH) for proliferation and display radiation dose response characteristics indistinguishable from those of rat thyroid epithelial cells in vivo (Rad. Res. 105:138-146, 1986). In TSH-free medium cells remain in a non-proliferative, yet viable, state for prolonged periods of time and respond to TSH re-stimulation by a return to exponential growth. Flow cytometric analysis using two-step acridine orange (AO) staining revealed an accumulation of cells in the G1 phase of the cell cycle accompanied by a pronounced reduction in red fluorescence (indicative of RNA content) in FRTL-5 cells cultured in the absence of TSH. The response of proliferative and non-proliferative FRTL-5 cells to single dose, split dose and fractionated radiation was compared to determine whether proliferative status was an important response determinant. The response of FRTL-5 cells was not influenced by proliferative status at the time of irradiation. Additionally, dose response was not altered by variable (12 hr-8 days) non-proliferative intervals before or after irradiation. As revealed by split dose experiments, the rate and extent of sublethal damage repair was likewise similar for proliferative and non-proliferative cells. Multifraction experiments employing three fractions separated by 6 hr intervals indicate that non-proliferative FRTL-5 cells completely repair sublethal damage between fractions. These results indicate that the radiation response of FRTL-5 cells is not influenced by the proliferative status of the cells prior to or post-irradiation.

Progress in the management of childhood brain tumors.

The authors have attempted to summarize the contributions that have been made towards improvements in the management of children with brain tumors by the development of sophisticated imaging tools for diagnosis, by the development of more sophisticated and versatile neurosurgical tools, by refinements in radiation therapy delivery equipment and techniques, and by the introduction of chemotherapy into therapy regimens. Overall, the interaction of all of these modalities is stressed, culminating in a comprehensive multidisciplinary approach to the management of children with brain tumors.

Brain tumors in children. II. Advances in neurosurgery and radiation oncology.

In this article, the contributions of neurosurgery and radiation oncology to the management of childhood brain tumors are described. Progress in a particular discipline rarely occurs in an isolated fashion, and it is clear that neurosurgical advances owe much to similar advances in anesthesiology, neuroradiology, and intensive care management. These advances in various disciplines have all permitted bolder yet safer attempts at radical resection by the neurosurgeon. The goal of radical surgical resection is cure in the case of low-grade brain tumors. However, even in those situations where surgery alone cannot be curative, the reduction of tumor bulk facilitates the task of both radiation therapy and chemotherapy, with improvement in progression-free survival as well as overall survival. For those tumors that cannot be cured by surgical resection alone, the standard of therapy thereafter still remains irradiation of the residual tumor. It is clear that the single major advance in the treatment of childhood medulloblastoma has been Cushing's recognition of the value of craniospinal irradiation. Refinements in radiation machines and treatment planning have permitted more accurate delivery of radiation therapy with a slight reduction in toxicity. Newer approaches, such as hyperfractionated irradiation and interstitial irradiation, attempt to improve therapeutic efficacy while minimizing toxicity. Nevertheless, as more children are surviving their brain tumors following surgery and radiation therapy, the price of the successful therapy is being increasingly realized in terms of developmental deficits, particularly in the very young child. It is the desire of all those involved in the management of children with primary brain tumors to seek alternative approaches to wide-field irradiation of the brain in children with high-grade tumors.

Aggregation pheromone of the male granary weevil,Sitophilus granarius (L.).

Evidence for a male-produced aggregation pheromone inSitophilus granarius is reported. Hexane extracts of Tenax®-trapped volatiles from males held on wheat were attractive to both sexes in a multiple-choice olfactometer and pitfall bioassay chamber. A quantitative relationship existed between days of insect exposure on disks and degree of responsiveness. The maximum response was to 35 insect-day-equivalents. Diel-related activity showed both sexes responsive during photophase and nonresponsive during scotophase.