PERSISTANCE DE CARACTERES ONTOGÉNIQUES DANS LE MUSCLE MASSÉTER ADULTE

During embryonic and foetal development, the masseter is formed from two successive generations of muscle fibers in a manner which is very similar to that which has been previously described for other skeletal muscles. This phenotypeis characterised by the persisten ce of ontogenic myosin isoforms ( embryonic and foetal myosin heavy chains, embryonic light chain) and by the presence of two distinct populations of fibers : small diameter fibers which coexpress theembryonic, foetal and fast isoforms of the myosin heavy chains but never express the slow isoform; large diameter fibers which express the slow myosin heavy chain either exclusively or in variable associations with the other isoforms.These characteristics of the human masseter muscle probably correspond not only to its embryological origin and its special innervation, but also to the functional constraints to which it is submitted after birth.Le développement du masséter s'effectue pendaQt la vie embryo-fa:tale en deux générations de fibres suivant un schéma tres comparable a la plupart des a u tres muscles de l 'organisme. Apres la naissance, un phénotype particulier se caractérise par l'expression persistante d'isoformes ontogéniques de la myosine (isoformes embryonnaire et fa:tale des chaines lourdes, isoforme embryonnaire des chaines légeres) et par l'individualisation de deux populations de fibres: de petite taille coexprimant les isoformes embryonnaire, fa:tale et rapide des chaines lourdes de la myosine mais n'exprimant pas l'isoforme lente; de grande taille exprimant l'isoforme lente des chaines lourdes de la myosine seule ou diversement associée aux autres isoformes.II est vraisemblable que les spécificités du masséter humain traduisent non seulement son origine embryologique et son innervation particuliere mais également les contraintes fonctionnelles qu'il subit apres la naissance

The first appearance of Meckel's cartilage in the fetus (Article in French)

Meckel's cartilage plays an important role in the topographical organisation and in the differentiation of the facial structure during the embryonal and even much later during the foetal period. Our observations on serial sections carried out in two human foetuses aged 12 and 16 weeks indicate that the two dorsal (tympanic) and ventral (mandibular) branches of Meckel's cartilage are perfectly defined at 16 weeks. In the dorsal branch, the primordia of the incus and of head of the malleus are still composed on non-ossified cartilage. In the ventral branch, it is also possible to describe at 16 weeks three posterior, medial and anterior parts which are composed of cartilage. The initiating role played by the ventral part of Meckel's cartilage on the ossification of the mandible leads during the embryonal period to the formation of the mandibular primary growth center, which is therefore clearly defined in our first stage at 12 weeks. The partial fibrous evolution and the regression of the major part of the ventral branch of Meckel's cartilage only start after 16 weeks of intrauterine life

Factors associated with prolonged length of stay for elective hepatobiliary and neurosurgery patients: a retrospective medical record review

Abstract Background Patients with prolonged length of hospital stay (LOS) not only increase their risks of nosocomial infections but also deny other patients access to inpatient care. Hepatobiliary (HPB) malignancies have some of highest incidences in East and Southeast Asia and the management of patients undergoing HPB surgeries have yet to be standardized. With improved neurosurgery techniques for intracranial aneurysms and tumors, neurosurgeries (NS) can be expected to increase. Elective surgeries account for far more operations than emergencies surgeries. Thus, with potentially increased numbers of elective HPB and NS, this study seeks to explore perioperative factors associated with prolonged LOS for these patients to improve safety and quality of practice. Methods A retrospective cross-sectional medical record review study from January 2014 to January 2015 was conducted at a 1250-bed tertiary academic hospital in Singapore. All elective HPB and NS patients over 18 years old were included in the study except day and emergency surgeries, resulting in 150 and 166 patients respectively. Prolonged LOS was defined as above median LOS based on the complexity of the surgical procedure. The predictor variables were preoperative, intraoperative, and postoperative factors. Student’s t-test and stepwise logistic regression analyses were conducted to determine which factors were associated with prolonged LOS. Results Factors associated with prolonged LOS for the HPB sample were age and admission after 5 pm but for the NS sample, they were functional status, referral to occupational therapy, and the number of hospital-acquired infections. Conclusion Our findings indicate that preoperative factors had the greatest association with prolonged LOS for HPB and NS elective surgeries even after adjusting for surgical complexity, suggesting that patient safety and quality of care may be improved with better pre-surgery patient preparation and admission practices