Le syndrome de Marcus Gunn est une affection génétique, rare et d'étiopathogénie obscure. Il se traduit par la rétraction de la paupière supérieure ptosée lors d'un mouvement de la mâchoire inférieure. Cas n̊ 1 : Un garçon, âgé de 16 ans, sans antécédents pathologiques notables, présentait une ptose fluctuante de la paupière supérieure gauche, constatée à la naissance. Elle était associée à une baisse progressive de l'acuité visuelle. L'examen neurologique retrouva : Un ptosis à gauche avec paralysie du droit supérieur Une rétraction de la paupière supérieure lors de l'ouverture de la bouche et à la mastication. L'examen ophtalmologique objectiva une amblyopie à gauche. Le test de Lancaster mit en évidence une paralysie des muscles droit supérieur et petit oblique gauches. Cas n̊ 2 : Une fillette âgée de 8 ans, sans antécédents pathologiques particuliers, présentait un ptosis fluctuant, de l'œil droit, depuis l'âge de 6 mois qui apparaissait lors des mouvements de succion. L'examen retrouva : un ptosis partiel de l'œil droit avec phénomène de Marcus Gunn, un aspect ovalaire des pupilles. L'examen ophtalmologique était sans anomalies. Cas n̊ 3 : Une femme, âgée de 27 ans, sans antécédents médicaux notables, consultait pour rétraction de la paupière supérieure gauche qui accompagnait de façon synergique les mouvements de mastication. L'examen retrouva : un ptosis fluctuant, modéré et isolé avec phénomène de MG. Ce phénomène touche certains sujets atteints de ptosis congénital, souvent unilatéral ; c'est le cas de nos patients. Il répond à une transmission autosomique dominante ; nos cas sont sporadiques. Les hypothèses étiopathogéniques sont multiples. L'anomalie palpébrale résulte, probablement, d'une innervation, aberrante, du muscle releveur de la paupière supérieure, par des branches du nerf trijumeau, qui s'égarent sur le nerf oculomoteur commun. Le syndrome de Marcus Gunn associe un ptosis congénital et des syncinésies mandibulo-palpébrales. Il est dû, probablement, à une innervation, erratique, du muscle releveur de la paupière supérieure, par les branches du trijumeau.

Stimulation of the rat exocrine pancreas by cerulein induces a variety of cellular processes, some of which require the expenditure of energy. In this study, changes in the amounts of various energy metabolites, including creatine phosphate (PCr), ATP, and ADP were determined by high-resolution 31P NMR spectroscopy. The spectrum of a perchloric acid extract of pancreas from the 48 h fasted rat was taken as a reference for comparison of 31P NMR spectra recorded after stimulation by cerulein. The NMR results obtained from rat pancreas stimulated in vivo by cerulein (3, 5, 10, 20, 40 min) were compared to those determined by HPLC. We show that during hormonal stimulation, the relative concentrations of PCr in the pancreas of the fasted rat rise significantly (p less than 0.02), reach a maximum at 10 min, fall between the 10th and 20th min, and then return to the relatively low levels observed in controls. On the other hand, the relative concentrations of ATP fall during the first 10 min after stimulation by cerulein, then rise significantly between the 10th and 20th min, whereas the levels of ADP rise during the first 10 min and fall between the 10th and 20th min. The energy required for exocytosis was assumed to be supplied by ATP synthesized in acinar cells. The 31P NMR results indicated that this ATP was derived from phosphorylation of ADP by PCr, and that large amounts of PCr are synthesized during the first minutes after cerulein stimulation. In addition, a significant rise in glycerophosphocholine was observed after cerulein stimulation, which was attributed to an enhanced catabolism of membranes and an increase in phospholipid turnover. Injection of cerulein antagonists, such as asperlicin or lorglumide, inhibited the effects of cerulein stimulation on energy metabolites. Furthermore, no changes were observed after injection of secretin, a hormone that stimulates secretion of bicarbonate. However, the analog of cerulein, pentagastrin, produced the same effects as cerulein, although to a lesser extent.

Low-resolution proton nuclear magnetic resonance (1H NMR) analysis of the pancreas of rats stimulated with caerulein, a cholecystokinin analog, was found to differ from that of control rats either fed ad libitum or fasted for two days. The hormonal stimulation induced (a) an increase in the longitudinal relaxation time TI; (b) a 'H NMR peak situated at 1.8 ± 0.2 ppm from the resonance peak of tissular water. This resonance peak was not observed in the pancreas of fasted rats, although it could just be detected in the pancreas of rats fed ad libitum. These features were not observed after injection of lorglumide, an antagonist of cholecystokinin, followed by caerulein stimulation. On the other hand, stimulation with secretin induced a slight increase in T1 but did not lead to the appearance of the 1.8 ± 0.2 ppm peak. The 1.8 ± 0.2 ppm resonance peak thus appears to be related to the hormone-stimulated state of the exocrine pancreas and might be a useful indicator of the physiological state of exocrine pancreatic tissue. From ultrastructural examination of pancreatic cells and 1H NMR studies of solutions of the major membrane phospholipids in rat plasma, we concluded that the 1.8 ± 0.2 ppm resonance peak stemmed from an alteration in the metabolism of membrane phospholipids and/or an increase in membrane fluidity after stimulation of acinar cells by caerulein.