Ingeborg van Leeuwen has developed a new tumour growth model. The model views the tumour as an integral part of the body. Existing models regard the tumour as an independent unit, separate from the host in which it grows. The tumour growth rate was found to be dependent on the age-dependent metabolic rate of the host. The model also established the relationship between the tumour growth process and the host's food intake.
Animals which follow a low-calorie diet have a higher life expectancy upon developing a tumour than animals without any dietary restrictions. The researcher also predicts that tumours generally develop faster in younger than in older hosts. This is because the energy available per cell decreases with age.
Van Leeuwen also developed a model that established the effect of food intake on growth and ageing. The model consists of two modules. The first describes the energy dynamics of an organism and provides equations for the feeding rate, fat content, change in body weight and metabolic rate. The second module describes the ageing of an organism. This description is based on the theory that ageing is the result of oxidative damage caused by free radicals. The two modules are linked together by the fact that the rate of production of free radicals depends on the metabolic rate, which in turn depends on the energy uptake and body size. In the end, a combination of the two modules results in an equation in which the life expectancy depends on the food consumption and body growth.
For fully-grown animals, the model simplifies to another, already well-known model. This enabled the researcher to ascertain how the parameters of this known model depend on the metabolic rate, feeding behaviour, and body size of the animals.
For further information please contact Dr Ingeborg M.M. van Leeuwen (Department of Theoretical Biology, Vrije Universiteit), tel. 31-204-446-959, e-mail: ingeborg@bio.vu.nl. The defence of the doctoral thesis took place on 9 December 2003. Dr Van Leeuwen's supervisor was Prof. S.A.L.M. Kooijman (tel. 31-204-447-130).
The research was funded by the Technology Foundation STW.