sentences:  Examples include
  
  
  Deficiency of ATR expression in adult mice leads to the appearance of age-related alterations such as hair graying, hair loss, kyphosis (rounded upper back), osteoporosis and thymic involution.Furthermore, there are dramatic reductions with age in tissue-specific stem and progenitor cells, and exhaustion of tissue renewal and homeostatic capacity.There was also an early and permanent loss of spermatogenesis.