Species relative abundance and direction of introgression in oaks.

Successful hybridisation and subsequent introgression lead to the transfer of genetic material across species boundaries. In this process, species relative abundance can play a significant role. If one species is less abundant than the other, its females will receive many heterospecific gametes, increasing mate-recognition errors and thus hybridisation rate. Moreover, first-generation hybrids will also more likely mate with the more abundant species, leading to asymmetric introgression. These predictions have important fundamental consequences, especially during biological invasions or when a rare species threatened by extinction is surrounded by individuals from a related species. However, experimental tests in nature of the importance of the relative abundance of each species on hybridisation dynamics remain scarce. We assess here the impact of species relative abundance on hybridisation dynamics among four species from the European white oak species complex. A total of 2107 oak trees were genotyped at 10 microsatellite markers and Bayesian clustering methods were used to identify reference trees of each species. We then used these reference trees to simulate purebred and hybrid genotypes to determine optimal threshold for genetic assignment. With this approach, we found widespread evidence of hybridisation between all studied oak species, with high occurrence of hybrids, varying from 11% to 31% according to stand and sampling strategies. This finding suggests that hybridisation is a common phenomenon that plays a significant role in evolution of this oak species complex. In addition, we demonstrate a strong impact of species abundance on both hybridisation rate and introgression directionality.

[Osteogenesis imperfecta and aortic incompetence. One case with pathological findings. Review of the literature (author's transl)]. / Ostéogenèse imparfaite et insuffisance aortique. Une observation avec documents anatomiques. Revue de la littérature.

Cardiovascular manifestations of Lobstein's disease are rare, probably unrecognized, and determining factors for the final prognosis, the most frequent lesion being aortic incompetence. The eleventh case to be reported with pathological findings in the literature is described. This complication is usually found in men, blood regurgitation being large in amount, symptomatic, and progressive. Its mechanism is related less to dilatation of the aorta and its ring than to valvular changes, they being frequently bicuspid and dysplasic. Histological findings, not however pathognomonic, are myxoid degeneration in the valves and parietal cystic necrosis in the aortic wall. Apart from the absence of an aneurysm and aortic dissection, macro- and microscopic lesions are similar to those observed in Marfan's syndrome and osteogenesis imperfecta. Operative therapy was employed in all eleven cases, with three postoperative deaths and three later deaths. Certain complications arise from uncontrollable severe hemorrhage, which justifies the use of valve heterografts not requiring antivitamin K administration.

[Blood digoxin and treatment of heart failure in aged patients]. / Digoxinémie et traitement de l'insuffisance cardiaque du sujet âgé

Serum digoxin level was determined by radioimmunoassay in 76 elderly in-patients (age: 76.1 +/- 1.0) which were treated by digoxin without any evidence of toxicity. Digoxin levels was related to blood nitrogen (p less than 0,01); on the other hand, no relationship between others factors influencing the digoxin bioavailability (age, body weight, associated drug) and digoxin levels could be found. Therapeutic effectiveness, as estimated by ventricular rate and signs and symptoms, was not dependent of digoxin levels. In patients with higher functional class (III and IV NYHA), however, digoxin level was generally demonstrated to be increased. Digoxin levels were lower in patients with coronary heart disease (1.71 +/- 0,22 ng/ml; n = 16) than in patients with right ventricle overload (2.94 +/- 0,74 mg/ml; n + 7 - p less than 0.05). Because of the very large scattering of digoxin levels, digoxin determination seems to be useful in measuring individual bioavailability and therapeutic effectiveness, and leading to the best base line of any individual treatment.