Shiver me XXXX ! Elucidating @entity22405 's role in shivering thermogenesis.

@entity5442 @entity19 @entity3986 @entity22405 @entity400
UNASSIGNED: Shivering frequency scales predictably with body mass and is 10 times higher in a @entity19 than a moose. The link between shivering frequency and body mass may lie in the tuning of muscle elastic properties. @entity22405 functions as a muscle 'spring', so shivering frequency may be linked to @entity22405 's structure. The @entity3986 with @entity5442 (mdm) @entity19 is characterized by a deletion in @entity22405 's N2A region. @entity19 that are homozygous for the mdm mutation have a lower body mass, stiffer gait and reduced lifespan compared with their wild-type and heterozygous siblings. We characterized thermoregulation in these @entity19 by measuring metabolic rate and @entity400 frequency during shivering. Mutants were heterothermic at ambient temperatures of 20-37  C while wild-type and heterozygous @entity19 were homeothermic. Metabolic rate increased at smaller temperature differentials (i.e. the difference between body and ambient temperatures) in mutants than in non-mutants. The difference between observed @entity400 frequencies and shivering frequencies predicted by body mass was significantly larger for mutant @entity19 than for wild-type or heterozygous @entity19 , even after accounting for differences in body temperature. Together, the heterothermy in mutants, the increase in metabolic rate at low temperature differentials and the decreased @entity400 frequency demonstrate the thermoregulatory challenges faced by @entity19 with the mdm mutation. Oscillatory frequency is proportional to the square root of stiffness, and we observed that mutants had lower active muscle stiffness in vitro. The lower @entity400 frequencies in mutants are consistent with reduced active muscle stiffness and suggest that @entity22405 affects the tuning of shivering frequency.
