The role of the extrinsic thoracic limb muscles in equine locomotion

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 ± 17 mm) fascicles, arranged at about 45° to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb

Circadiane slaap-waakritmestoornissen

Circadiane slaap-waakritmestoornissen zijn slaap-waakverstoringen met een afwijkend 24-uurspatroon in de slaap-waakafwisseling. In de psychiatrische praktijk komt de vertraagd slaap-waakritmestoornis (DSPD) veruit het vaakst voor. De prevalentieschatting van DSPD in de algemene bevolking varieert van 0,1 tot 3 %, oplopend bij jongeren tot 16 %. Klachten zijn problemen met op de gewenste tijd in slaap vallen en ’s morgens niet op tijd wakker kunnen worden, met slaperigheid en vermoeidheid overdag. Op de gewenste, late tijd wordt wel normaal geslapen. Naar schatting 40 % van de mensen met DSPD heeft ook een psychiatrische diagnose, zoals een stemmings-, angst- of middelengerelateerde stoornis. Therapie van vooral vertraagd slaap-waakritmestoornissen moet zich richten op een gedragsmatige slaapbehandeling in combinatie met weinig licht in de avond, lichttherapie in de ochtend en eventueel een lage dosis melatonine zo’n 5 uur voor het in slaap vallen

Unravelling the pathogenesis of myasthenia gravis.

Myasthenia gravis is a relatively rare neurological disease that is associated with loss of the acetylcholine receptors that initiate muscle contraction. This results in muscle weakness, which can be life-threatening. The story of how both the physiological basis of the disease and the role of acetylcholine-receptor-specific antibodies were determined is a classic example of the application of basic science to clinical medicine, and it has provided a model for defining other antibody-mediated disorders of the peripheral and central nervous systems