To cool or not to cool? Intestinal coccidians disrupt the behavioral hypothermia of lizards in response to tick infestation.

It is generally accepted that parasites exert negative effects on their hosts and that natural selection favors specific host responses that mitigate this impact. It is also known that some components of the host immune system often co-evolve with parasite antigens resulting in a host-parasite arms race. In addition to immunological components of the anti-parasitic response, host behavioral responses are also important in this arms race and natural selection may favor avoidance strategies that preclude contact with parasites, or shifts in the host's thermoregulatory strategy to combat active infections (e.g., behavioral fever). Ticks are widespread parasites with direct and indirect costs on their vertebrate hosts. Their saliva provokes hemolysis in the blood of their hosts and can transmit a plethora of tick-borne pathogens. We enquired whether tick infestation by Ixodes pacificus can provoke a thermoregulatory response in Sceloporus occidentalis. For this, we compared the thermoregulatory behavior of tick-infested lizards against tick-infested lizards co-infected with two different species of coccidians (Lankesterella occidentalis and Acroeimeria sceloporis). After this, lizards were kept in individual terraria with a basking spot and fed ad libitum. We found that tick-infested lizards sought cooler temperatures in proportion to their tick load, and this response was independent of the co-infection status by L. occidentalis. This was consistent in April and June (when tick loads were significantly lower) and suggests a conservative strategy to save energy which might have been selected to overcome tick infestations during phenological peaks of this parasite. However, this behavior was not observed in lizards co-infected with A. sceloporis, suggesting that co-infection with this intestinal parasite prompt lizards to be active. Cost of tick infestation was confirmed because housed lizards lost weight at a constant ratio to initial tick load, independently of other infections. The broader implications of these findings are discussed in the context of climate change.

[Displacement of the instantaneous center of rotation of the humeral head during abduction: implication for scapulohumeral muscular function]. / Déplacement des centres instantanés de rotation de l'epaule au cours de i'abduction: implication sur la fonction des muscles scapulo-huméraux.

PURPOSE OF THE STUDY: To date, studies of glenohumeral stress forces have been based on the notion of a unique center of rotation situated at the geometric center of the humeral head. Early work, e.g. Fisher et al in 1977, suggested that the instantaneous center of rotation can migrate during abduction producing muscle vectors with variable moments and consequently variable stress forces. We conducted a kinematic analysis of the shoulder forces during continuous movement. MATERIAL AND METHODS: An imaging device commonly used for angiography enabled acquisition of one image per second during a continuous movement of abduction. Images were obtained for twenty healthy shoulders in ten subjects. RESULTS: The instantaneous center of rotation was not situated at the geometric center of the humeral head. Although interindividual variability was significant, the preferential positions of the instantaneous center of rotation implied a constant reproducible succession of gliding, rolling, and translation in variable proportions during the abduction movement. When the same movement was performed with a 3500g load held in the hand, the ICR migrated towards the upper part of the humeral head implying a predominance of the rolling motion over the gliding and translation motions. Between 40 degrees and 60 degrees glenohumeral abduction, the instantaneous center of rotation exhibited a metaphyseal displacement producing a longer lever arm for the supaspinatus and an abduction function for the infraspinatus and the subscapularis, unrecognized to date. After 60 degrees, medialization of the instantaneous center of rotation lengthened the lever arm of the deltoid. DISCUSSION: A valid analysis of the glenohumeral stress forces must take into consideration the localization of the instantaneous center of rotation. In the clinical setting, our findings demonstrate that the infraspinatus and the subscapularis play an important role which must be considered both in surgery and in rehabilitation.

Contribution to the vascular origin of the unicameral bone cyst.

Vascular occlusion between bone cyst and intramedullary venous system seems to be the primum movens in the genesis of a unicameral bone cyst. High speed injection of saline and alternative aspiration injection of the cyst fluid and reaming of the medullary cavity clearly open vascular channels connecting the bone cyst to the intramedullary venous system. This was monitored by pre- and postmanipulative radiographs. This technique was employed in 12 patients with a unicameral bone cyst. All but one went on to healing with increasing diameter of the cortical bone and filling of the cystic cavity.

[Reflections on the anterior cruciate ligament (A.C.L.) and clinical implications]. / Considérations sur le ligament croisé antérieur (L.C.A.) et implications cliniques.

This report documents experiments on the front, crossed ligament undertaken after dissection of 17 human knees. The form, direction, constitution, and even the various diameters and tibial and femoral bone insertion surfaces of the ligament were all studied. Various cross-section experiments were undertaken to reveal the physio-pathological aspects. Greater tibial insertion area and diameter along with a more oblique orthogonal projection on the tibial correspond to the need to better spread the constraints. It is concluded that varying degrees of tension in function of the position of the knee, and knowledge of the various lengths and diameters of the ligament permit a better understanding of the prosthetic replacement surgery required.

[Internal tibial pain in runners]. / Douleurs tibiales internes chez les coureurs à pieds.

Certain pains located along the internal boundary of the tibia in its middle third appear sometimes in young athletes who have come to racing comparatively late. The pains improve with rest, but nevertheless end up by being subintrant. The worst pain is located at the tibial insertion point of the common flexor of the toes, and of the soleus muscle. An accentuation of tarsal pronation often accompanies the pain syndrome, this in turn sometimes being accompanied by excessive valgisation of the back of the foot. Torsion disorders of the lower limb are another component of the picture. Intensive training and certain propulsion exercises on tiptoe seem to trigger off these disorders. Radiography can show moniliform cortical adaptations. Bone scintigraphies using marked technetate mainly show the areas of longitudinal hypercaptation on the internal boundary of the tibia. Pain is triggered off by the excessive use of the common flexor of the toes and by partial rupture of the aponeurosis at the point of tibial insertion of the soleus. The pressure measurements of the deep posterior space do not suggest a lodge syndrome; however, certain histopathological pictures do suggest the existence of an ischemical phenomenon. The orthopaedic treatment is based on an understanding of the deficient mechanisms functioning during foot pressure on the ground in racing. Corrective footwear and slow, gradual training techniques can help with these problems. Sometimes the pains become resistant to all conservative treatment and will respond favourably to an aponeurotomy associated with partial disinsertion of the soleus and common flexor of the toes.

[Medial tibial pain in runners]. / Douleurs tibiales internes chez les coureurs à pied.

Pain at the site of the tibial insertion of the flexor digitorum longus and the soleus near the middle third of the medial border of the tibia may be encountered in young athletes, who have usually started to run in late adolescence. Heel valgus, abnormal mid-foot pronation and excessive tibial torsion may be seen in association. The symptoms are brought on after excessive training. Radiographs may show cortical thickening at the site of the pain, and a bone scan may demonstrate a mild increase in the uptake of the isotope at this site. The pain appears to be related to a strain of the attachment of the flexor digitorum longus and the aponeurotic insertion of the soleus into the tibia. The pressure in the deep posterior compartment of the tibia is normal. Histological examination of specimens from the flexor digitorum longus may demonstrate ischaemic changes in the muscle. Treatment is based on an understanding of the biomechanics of the foot in running, modification of training methods and the use of suitable orthotics. If these measures fail, partial division of the aponeurotic attachment of soleus and freeing of the insertion of the flexor digitorum longus is usually successful.