The Brazilian Wilms' Tumour Study Group carried out a hospital-based multicentre case-control study of potential risk factors for the disease between April 1987 and January 1989. The parents of 109 cases of Wilms' tumour (WT) were interviewed when they were admitted to hospital for diagnosis and treatment. Also interviewed were the parents of two controls per case, matched for age, sex and interviewer, who were admitted to the same or nearby hospitals for treatment of non-neoplastic conditions. Odds ratios adjusted for family income and parental education were calculated by conditional logistic regression. Among cases diagnosed before 25 months of age there was a marked gradient of increasing risk of WT with increasing maternal age at the time of the child's birth. There was no increased risk for cases diagnosed after 25 months of age. The effects of paternal age were less marked. Possible explanations for these results are discussed.
The mechanisms by which a protein searches its vast conformational space in order to attain its native fold in physiological times and to bind productively to relevant biological partners are not well understood. In particular, most proteins must be able alternate between at least one active conformational state and back to an inactive conformer, especially for the macromolecules that perform work and need to optimize ATP usage. This property may be invoked by a physical stimulus (temperature, radiation) or a chemical ligand. We have stimulated with temperature cycles two partners of an immune complex and revealed that properties of the external stimulus (period, phase) are also found in characteristics of the protein complex (i.e. periodic variation in its binding affinity). These results may be important for delineating in vitro the bases of molecular memory.
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