Jean-Pierre Gasc

Gait parameters of treadmill versus overground locomotion in mouse

Many studies of interest in motor behaviour and motor impairment in mice use equally treadmill or track as a routine test. However, the literature in mammals shows a wide difference of results between the kinematics of treadmill and overground locomotion. To study these discrepancies, we analyzed the locomotion of adult SWISS-OF1 mice over a large range of velocities using treadmill and overground track. The use of a high-speed video camera combined with cinefluoroscopic equipment allowed us to quantify in detail the various space and time parameters of limb kinematics. The results show that mice maintain the same gait pattern in both conditions. However, they also demonstrate that during treadmill exercise mice always exhibit higher stride frequency and consequently lower stride length. The relationship of the stance time and the swing time against the stride frequency are still the same in both conditions. We conclude that the conflict related to the discrepancy between the proprioceptive, vestibular, and visual inputs contribute to an increase in the stride frequency during the treadmill locomotion.

Symmetrical and asymmetrical gaits in the mouse: patterns to increase velocity

The gaits of the adult SWISS mice during treadmill locomotion at velocities ranging from 15 to 85xa0cmxa0s−1 have been analysed using a high-speed video camera combined with cinefluoroscopic equipment. The sequences of locomotion were analysed to determine the various space and time parameters of limb kinematics. We found that velocity adjustments are accounted for differently by the stride frequency and the stride length if the animal showed a symmetrical or an asymmetrical gait. In symmetrical gaits, the increase of velocity is provided by an equal increase in the stride length and the stride frequency. In asymmetrical gaits, the increase in velocity is mainly assured by an increase in the stride frequency in velocities ranging from 15 to 29xa0cmxa0s−1. Above 68xa0cmxa0s−1, velocity increase is achieved by stride length increase. In velocities ranging from 29 to 68xa0cmxa0s−1, the contribution of both variables is equal as in symmetrical gaits. Both stance time and swing time shortening contributed to the increase of the stride frequency in both gaits, though with a major contribution from stance time decrease. The pattern of locomotion obtained in a normal mouse should be used as a template for studying locomotor control deficits after lesions or in different mutations affecting the nervous system.

Asymmetrical gaits of juvenile Crocodylus johnstoni, galloping Australian crocodiles

Seven juvenile individuals of the Australian species Crocodylus johnstoni from the Frankfurt Zoological Park were filmed on high-speed video, at 250 fields s −1 , whilst freely moving at various speeds in a long corridor. The sequences of locomotion were analysed to determine the various space and time parameters to characterize limb kinematics. We found that the animals use diverse patterns of asymmetrical gait, revealing great flexibility in limb co-ordination. In all these gaits, the forelimb strikes the ground first, in the couple made by diagonally opposite fore- and hindlimbs. Among these gaits, rotary gallop offers probably a high level of manoeuvrability, whereas transverse gallop resulted in a higher level of stability. Speed increase is achieved by half-bound and bound, the latter being the only gait used at velocities > 2 m s −1 . Speed was increased mainly by increasing the stride length of the fore- and hindlimbs by simultaneously increasing both its components, the step and swing lengths. However, in bound, the step length of each forelimb increased more than the swing length, resulting in a stronger thrust action, whereas swing length increased more than step length for the hindlimb, causing the centre of mass to accelerate forwards during its ballistic phase. The asymmetrical gaits of crocodiles such as Crocodylus johnstoni are probably not functionally equivalent to the transitional asymmetrical gaits exhibited by lizards when building up into a bipedal run. These gaits are also not entirely equivalent to mammalian gaits, despite the use of vertical movements of the vertebral axis in these crocodiles, favouring an erect dynamic posture.

High speed motion analysis of the predatory strike and fluorographic study of oesophageal deglutition in Vipera ammodytes : more than meets the eye

The predatory strike of Vipera ammodytes was analysed using high speed cinematography. Slow motion studies showed that the strike is a direct hit and that ensuing body postures are complex and occur within a very short time. Flawed strikes have been recorded and are discussed. Radiographic study of oesophageal deglutition demonstrated a lateral undulation of the cervical column resulting from metachronic contractions of body wall musculature, causing prey progress. Some comparative data on Bitis nasicornis and B.gabonica are given.

Six-legged walking by a bottom-dwelling fish

The hypothesis of a locomotor role for the free rays of Trigloporus lastoviza is supported by: (1) their periodic retraction and protraction during slow displacement over the substratum whenever the propulsive body wave responsible for swimming is not visible; (2) the integration of the rays individual cycles into a hexapod gait apparently generated by a metachronal impulse; and (3) the kinematic features of the longest free ray in relation to the bottom-walking velocity.

Intervention des membres dans la locomotion et le creusement du nid chez la tortue luth

La tortue luth (Dermochelys coriacea) adaptee a la vie pelagique, possede aussi un deplacement terrestre tout a fait original qui implique un systeme economique de traction du corps. Un repertoire precis de mouvements est utilise: mouvements periodiques et synchrones des membres anterieurs et posterieurs. Les mouvements qui interviennent dans le balayage de laire de ponte appartiennent egalement a ce meme repertoire. Par contre, les mouvements de creusement du nid, qui correspondent a une alternance dactivite des membres posterieurs suggerent la reactivation du patron moteur utilise par les tetrapodes.

Les données ontogénétiques peuvent-elles expliquer l'origine évolutive des Squamates apodes?

Resume Les etudes de morphologie comparative et fonctionnelle portant sur les Squamates serpentiformes ont permis de preciser les conditions dorigine de telles formes dans plusieurs lignees au cours de levolution. Nous presentons une hypothese generale qui synthetise celles recemment proposees par la Biologie du Developpement et la genetique moleculaire pour expliquer lapparition soudaine de ces formes apodes parmi les Tetrapodes.