title: Periodic oscillations in leukopoiesis models with two delays.
abstract: The term leukopoiesis describes processes leading to the production and regulation of white blood cells. It is based on stem cells differentiation and may exhibit abnormalities resulting in severe diseases, such as cyclical neutropenia and leukemias. We consider a nonlinear system of two equations, describing the evolution of a stem cell population and the resulting white blood cell population. Two delays appear in this model to describe the cell cycle duration of the stem cell population and the time required to produce white blood cells. We establish sufficient conditions for the asymptotic stability of the unique nontrivial positive steady state of the model by analysing roots of a second degree exponential polynomial characteristic equation with delay-dependent coefficients. We also prove the existence of a Hopf bifurcation which leads to periodic solutions. Numerical simulations of the model with parameter values reported in the literature demonstrate that periodic oscillations (with short and long periods) agree with observations of cyclical neutropenia in patients.
authors.affiliation: Laboratoire de Mathématiques Appliquées UMR 5142, Université de Pau et des Pays de l'Adour, Avenue de l'Université, 64000 Pau, France. mostafa.adimy@univ-pau.fr <mostafa.adimy@univ-pau.fr>
authors.forename: Mostafa
authors.initials: M
authors.lastname: Adimy
authors.forename: Fabien
authors.initials: F
authors.lastname: Crauste
authors.forename: Shigui
authors.initials: S
authors.lastname: Ruan
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D006412:Hematopoietic Stem Cells / Q000166:cytology; D019891:Leukopoiesis / Q000502:physiology*; D008954:Models, Biological; D013997:Time Factors