When It Is Personal

When Is It Coevolution?

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Puberty: when is it normal?

C lassically, the normal chronological age for pubertal onset is between 8 and 13 years in girls and 9 and 14 years in boys based on data from epidemiological studies from the 60’s (1). However, the age limit for pubertal timing is still a challenge (2,3). It is well known that puberty is a complex and multi factorial process that involves genetic, metabolic, socio economic, nutritional and eth...

When Senescence Is Optimal and When It Is Not

A simple model is developed that captures the main features of life reproduction, growth and maintenance. These features are determined by a single state variable, vitality. The resulting optimal life-history strategies are classified with respect to the course of their characteristic age-trajectory of mortality. It is shown that the range of optimal life histories is wide. The main factors tha...

When is it an osteoclast?

Using acid phosphatase as a marker, osteoclasts were examined from single sections of undemineralised iliac crest biopsies from patients with renal failure and from normal controls. Eighty one per cent of the cells from controls and 56% of the cells from patients with renal failure appeared to be non-nucleated or mononucleated. Serial sections showed, however, that 73% of the control cells were...

When is it an osteoclast?