Akakus

Le petit massif de l’Akakus, en Libye, à faible distance du Tassili -moins de 100 km- est, comme le Tassili, constitué de pointements de grès d’âge primaire très déchiquetés par l’érosion éolienne, et de larges vallées ensablées. Il s’agit néanmoins d’une unité orogénique distincte, nettement délimitée à l’ouest : elle s’y termine en effet par une falaise abrupte, dominant la vallée du Tanezrouft, que suit la piste de Serdeles à Ghat. Les accès ne sont possibles que par l’est, où les vallées ..

Akakus

Le petit massif de l’Akakus, en Libye, à faible distance du Tassili -moins de 100 km- est, comme le Tassili, constitué de pointements de grès d’âge primaire très déchiquetés par l’érosion éolienne, et de larges vallées ensablées. Il s’agit néanmoins d’une unité orogénique distincte, nettement délimitée à l’ouest : elle s’y termine en effet par une falaise abrupte, dominant la vallée du Tanezrouft, que suit la piste de Serdeles à Ghat. Les accès ne sont possibles que par l’est, où les vallées ..

Bœuf (Préhistoire)

De nombreuses études avaient, tout au long du xixe siècle, décrit et nommé de multiples espèces ou sous-espèces de Bos. Sanson, par exemple, en dénombrait douze dans les seuls taurins. Au xxe siècle, une révision se fit : la Nomenclature en vigueur ne retient dans le sous-genre Bos, pour les animaux actuels, que trois sous-espèces (ou « types ») : le bœuf à bosse, B. indicus et deux types de « taurins », sans bosse : le B. primigenius ou bœuf à longues cornes (le longhorn) et le B. brachycero..

Biochemical analysis of the DNA unwinding and strand annealing activities catalyzed by human RECQ1

RecQ helicases play an important role in preserving genomic integrity, and their cellular roles in DNA repair, recombination, and replication have been of considerable interest. Of the five human RecQ helicases identified, three are associated with genetic disorders characterized by an elevated incidence of cancer or premature aging: Werner syndrome, Bloom syndrome, and Rothmund-Thomson syndrome. Although the biochemical properties and protein interactions of the WRN and BLM helicases defective in Werner syndrome and Bloom syndrome, respectively, have been extensively investigated, less information is available concerning the functions of the other human RecQ helicases. We have focused our attention on human RECQ1, a DNA helicase whose cellular functions remain largely uncharacterized. In this work, we have characterized the DNA substrate specificity and optimal cofactor requirements for efficient RECQ1-catalyzed DNA unwinding and determined that RECQ1 has certain properties that are distinct from those of other RecQ helicases. RECQ1 stably bound to a variety of DNA structures, enabling it to unwind a diverse set of DNA substrates. In addition to its DNA binding and helicase activities, RECQ1 catalyzed efficient strand annealing between complementary single-stranded DNA molecules. The ability of RECQ1 to promote strand annealing was modulated by ATP binding, which induced a conformational change in the protein. The enzymatic properties of the RECQ1 helicase and strand annealing activities are discussed in the context of proposed cellular DNA metabolic pathways that are important in the maintenance of genomic stability

A prominent β-hairpin structure in the winged-helix domain of RECQ1 is required for DNA unwinding and oligomer formation

RecQ helicases have attracted considerable interest in recent years due to their role in the suppression of genome instability and human diseases. These atypical helicases exert their function by resolving a number of highly specific DNA structures. The crystal structure of a truncated catalytic core of the human RECQ1 helicase (RECQ149–616) shows a prominent β-hairpin, with an aromatic residue (Y564) at the tip, located in the C-terminal winged-helix domain. Here, we show that the β-hairpin is required for the DNA unwinding and Holliday junction (HJ) resolution activity of full-length RECQ1, confirming that it represents an important determinant for the distinct substrate specificity of the five human RecQ helicases. In addition, we found that the β-hairpin is required for dimer formation in RECQ149–616 and tetramer formation in full-length RECQ1. We confirmed the presence of stable RECQ149–616 dimers in solution and demonstrated that dimer formation favours DNA unwinding; even though RECQ1 monomers are still active. Tetramers are instead necessary for more specialized activities such as HJ resolution and strand annealing. Interestingly, two independent protein–protein contacts are required for tetramer formation, one involves the β-hairpin and the other the N-terminus of RECQ1, suggesting a non-hierarchical mechanism of tetramer assembly

Robot-assisted versus laparoscopic pancreatoduodenectomy: a pan-European multicenter propensity-matched study

Background: The use of robot -assisted and laparoscopic pancreatoduodenectomy is increasing, yet large adjusted analyses that can be generalized internationally are lacking. This study aimed to compare outcomes after robot -assisted pancreatoduodenectomy and laparoscopic pancreatoduodenectomy in a pan-European cohort. Methods: An international multicenter retrospective study including patients after robot -assisted pancreatoduodenectomy and laparoscopic pancreatoduodenectomy from 50 centers in 12 European countries (2009-2020). Propensity score matching was performed in a 1:1 ratio. The primary outcome was major morbidity (Clavien-Dindo >= III). Results: Among 2,082 patients undergoing minimally invasive pancreatoduodenectomy, 1,006 underwent robot -assisted pancreatoduodenectomy and 1,076 laparoscopic pancreatoduodenectomy. After matching 812 versus 812 patients, the rates of major morbidity (31.9% vs 29.6%; P = .347) and 30-day/inhospital mortality (4.3% vs 4.6%; P = .904) did not differ significantly between robot -assisted pancreatoduodenectomy and laparoscopic pancreatoduodenectomy, respectively. Robot -assisted pancreatoduodenectomy was associated with a lower conversion rate (6.7% vs 18.0%; P < .001) and higher lymph node retrieval (16 vs 14; P = .003). Laparoscopic pancreatoduodenectomy was associated with shorter operation time (446 minutes versus 400 minutes; P < .001), and lower rates of postoperative pancreatic fistula grade B/C (19.0% vs 11.7%; P < .001), delayed gastric emptying grade B/C (21.4% vs 7.4%; P < .001), and a higher R0 -resection rate (73.2% vs 84.4%; P < .001). Conclusion: This European multicenter study found no differences in overall major morbidity and 30day/in-hospital mortality after robot -assisted pancreatoduodenectomy compared with laparoscopic pancreatoduodenectomy. Further, laparoscopic pancreatoduodenectomy was associated with a lower rate of postoperative pancreatic fistula, delayed gastric emptying, wound infection, shorter length of stay, and a higher R0 resection rate than robot -assisted pancreatoduodenectomy. In contrast, robot -assisted pancreatoduodenectomy was associated with a lower conversion rate and a higher number of retrieved lymph nodes as compared with laparoscopic pancreatoduodenectomy. (c) 2024 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)