665 research outputs found
Differentiation and radiosensitivity of hemopoietic stem cells of mice during hypokinesia
The potential for differentiation and radiosensitivity of the stem hemopoietic cells (KOE) under conditions of initial and later hypokinesia is examined. It is established that in the initial period of hypokinesia (3 days) when a stress reaction prevails, changes occur in the erythroid differentiation and radiosensitivity of KOE. This effect is associated with redistribution of T-lymphocytes that increase in number in the bone marrow of mice during hypokinesia. At later periods of hypokinesia (30 days) when changes in the organism are related to hypokinesia proper, differentiation and radiosensitivity of KOE were normalized
Non-equilibrium theory of the allele frequency spectrum
A forward diffusion equation describing the evolution of the allele frequency
spectrum is presented. The influx of mutations is accounted for by imposing a
suitable boundary condition. For a Wright-Fisher diffusion with or without
selection and varying population size, the boundary condition is , where is the frequency
spectrum of derived alleles at independent loci at time and is
the relative population size at time . When population size and selection
intensity are independent of time, the forward equation is equivalent to the
backwards diffusion usually used to derive the frequency spectrum, but the
forward equation allows computation of the time dependence of the spectrum both
before an equilibrium is attained and when population size and selection
intensity vary with time. From the diffusion equation, we derive a set of
ordinary differential equations for the moments of and express the
expected spectrum of a finite sample in terms of those moments. We illustrate
the use of the forward equation by considering neutral and selected alleles in
a highly simplified model of human history. For example, we show that
approximately 30% of the expected heterozygosity of neutral loci is
attributable to mutations that arose since the onset of population growth in
roughly the last years.Comment: 24 pages, 7 figures, updated to accomodate referees' suggestions, to
appear in Theoretical Population Biolog
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