The mechanical effects of 3 lower leg muscles during inversion

The mechanical effects of 3 lower leg muscles during

inversion

Citation for published version (APA):

Huson, A., Janssen, J. D., Spoor, C. W., Leeuwen, van, J. L., & Ottevanger, E. J. C. (1988). The mechanical effects of 3 lower leg muscles during inversion. Journal of Anatomy, 158(JUN), 210-210.

Document status and date: Published: 01/01/1988

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Proceedings

ofthe Anatomical Society of

Irradiation of control C57BI/10 mousemuscles slightly diminished their growth but did not affect their histological appearance.

Exposure of mdx muscles to irradiation greatly reduced their rate of growth and abolished histological signs of muscle fibre regeneration. Surviving muscle fibres became progressively interspersed by fibrous and fattyconnective tissue, afeatureof DMDmuscle. These changeswere

not evident in identically treated non-myopathic muscle.

Thus, differences betweenthemdx and DMD myopathiesare partially attributableto thehigh regenerative capacity ofmouseskeletalmuscle: inhibition of this regeneration in the mdxmouse

yieldsa valuable experimental model ofDMD. These findings highlight the difficulty, in animal modelsof human disease, of determining whether any difference lies in the primary lesion or in

the species-specific reaction to thatprimary lesion.

30. The mechanical effects ofthree lower leg muscles during inversion. By A. HUSON, E. J.C. OTTEVANGER, C. W. SPOOR, J. L. VAN LEEUWEN, A. A. H. J. SAUREN* and J. D. JANSSEN*.

Department of Anatomy, University ofLeiden, The Netherlands, and *Faculty ofMechanical Engineering, Eindhoven University ofTechnology, Eindhoven, The Netherlands

An experimental set-up has been developed formeasuring reaction forces on the foot. Seven vertical and three horizontal forces can be simultaneously measured. The foot is loaded with a vertical force whereasinversionof the foot is evoked by applyingamoment abouta vertical axis

to the lower leg and/orsimulating isometric aswellasisotonic muscle forces. The magnitude of the input moment changes during inversion. These changes are recorded and the resulting moment-rotation anglecurve is specificfor the tarsal mechanism under study. A similarcurveis

found if muscular forceswith aninversioneffect aresimulated. Differentmuscles, however, may modify the moment-rotation angle curves in a different way. These modifications reflect the

mechanical effectivenessofthe muscles concernedasinvertorsorevertors.Inthiswaytheanterior

tibialis,

posteriortibialisand peroneuslongus muscles have been compared. Preliminary analysis of the force data (1) showedtheoccurrenceofpreconditioning phenomena in the moment-rotation angle curve during repeated inversion ofthe

foot;

(2) revealed the amount of relaxation in the statically loaded long tendons of the three muscles compared; and (3) demonstrated the mechanical effectiveness ofthe three above-mentioned lower leg muscles during inversion and eversion of the foot. Under the experimental conditions of the measuring set-up the tibialis anterior muscle provedto bea poorinvertor, whereas the tibialisposterior muscle hadapowerful inversion effect and the peroneus longus muscle illustrated its eversion effect. The experimental set-up may quantify themechanical effects oftendon transfer in orthopaedic surgery.

31. Evidencethatdendritesof hamster geniculateneuronsestablishcontactwithretinalaxonsinthe optic tract at the timeand atthe site of emission ofretinogeniculatebranches. By P. G. BHIDE, A. R.

LIEBERMAN

andD.0. FROST*. Department of Anatomy, UniversityCollege London, and *Section ofNeuroanatomy, Yale University (Fig. 4)

Retinal axons reach thesuperior colliculus (SC) by embryonicday 12 (E12). Enroute theypass

over the surface to the diencephalon, but not until E14 or later do branches emerge, to enter diencephalic nuclei such as the dorsal lateral geniculate nucleus (dLGN). Itis not known what induces these axonstobranch, butwehave shown previously that the branching periodcoincides with the appearanceinthe optictract,closetobranch sites, of transient synapticcontactsbetween retinal axons and dendritic invaginations thereof (Bhide et al. J. Anat. 152, 1987). Here we demonstrate the probable nature and sourceofthe invaginatingdendrites.

Brains were removedfromhamsterpupsbetween birth(PO) andP21andaslabofdiencephalon placed in oxygenated Ringer. A small deposit ofHRP was placed in the dLGN by stabbing its lateral surface with a micropipettecoated with HRP. Twotofive hours later the tissuewasfixed

andVibratome sections(c. 100

,um)

processed for LM and EM-HRP histochemistry usingDAB as chromogen.

Most neurons within thesiteofHRPdeposition and individual orsmall clusters ofneurons at

its periphery were heavilylabelled with HRP: manywere verycompletelyvisualised. Inthe early postnatal period laterallydirected dendritesof cells withsomatalocatedatvariabledepthswithin dLGN commonly enteredand terminated within the optic tract: thesecells resembled immature projection cells (Fig. 4; OT= optic tract). The extensionof labelled dendrites into the optictract has beenconfirmed by EM.

Thus processes of immaturegeniculate relayneuronsestablish precocioussynapticcontactwith retinocollicular axons coursingthrough the overlying optic tract, at the time atwhich, andclose