Shapes and structures of biological rhythms: Variability of phenotypes in two strains of mice and their progeny

The patterns of creatine-phosphokinase and alkaline-phosphatase activities, white blood cells counts and urea-nitrogen concentration were assessed in males and females of two mice strains (BALB/c, c57BL/6J) and in their one-sided cross F1 progeny. All animals were exposed to a 12:12 light:dark regimen. The patterns were analyzed to elucidate the rhythm basic parameters: period, acrophase, mesor and amplitude and three additional characteristics: relative amplitude, rate of change of the relative amplitude and the area under the curve. Analysis of the rhythms' structure showed that most patterns possess more than one period component (compound rhythms). Strain and gender differences were revealed in some patterns even under identical environmental signals. The versatility of the F1 group patterns suggests that each parameter is governed by separate multiple or polygenic systems. Such organization enables multitude phenotypes of compound rhythms which endows the organism with physiological advantage by optimizing its functions to cope with a multitude of environmental signals.