Immunocytochemical characteristics of elbow, knee and ankle muscles of the five-toed jerboa (Allactaga elater).
Biochemical adaptations of limb myofibres to intensive bipedal hopping were investigated using the five-toed jerboa Allactaga elater as a model in comparison with the rat. Immunofluorescence methods included immunoreactivity to anti-fast and anti-slow MHC and troponin I. There is no specialization of triceps caput mediale for postural function in the minute non-locomotor forelimbs, unlike quadruped mammals. The various elbow extensor heads and the flexor muscles are alike with regard to fibre type population and cross-sectional areas of each type of fibre. The extensor muscle in the elongated hindlimbs of the five-toed jerboa, at both the knee and the ankle joints, differ from each other extensively. One head, made up of an extremely high percentage of type I, fatigue-resistant fibres, is suited to postural function. Two extensor heads at each joint contain a very high percentage of type IIB fibres (having the greatest maximal velocity of contraction) and are able to produce the powerful acceleration needed to trigger the leap. The relative cross-sectional areas of the myofibres are characteristic of hopping locomotion: predominance in number of one type of myofibre in a muscle accompanies greater cross-sectional area, which increases muscle efficiency in either postural or accelerative function of the muscle.
Jouffroy
F K
FK
Unité Mixte de Recherche C.N.R.S 8570, Laboratoire d'Anatomie Comparée, Museum National d'Histoire Naturelle, Paris, France. fkjouffr@mnhn.fr
Medina
M F
MF
Renous
S
S
Gasc
J P
JP
D000222:Adaptation, Physiological; D000818:Animals; D005552:Forelimb; D006614:Hindlimb; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000737:chemistry*; D009218:Myosins / Q000032:analysis; D012377:Rodentia / Q000378:metabolism / Q000502:physiology*; D019210:Troponin I / Q000032:analysis
D019210:Troponin I; D009218:Myosins