Experimental investigation of preferential concentration in zooplankton swimming in turbulence.

Turbulence can cause particles to accumulate within specific regions of the flow. One mechanism responsible for this phenomenon, called preferential concentration, consists in particle-fluid interactions yielding inhomogeneous spatial distribution of particles into clusters or depleted regions due to density difference or finite-size effects. In the case of living particles such as plankton, clustering may also originate from their motility or from their behavioral response to turbulent forcing. Preferential concentration of plankton has attracted much attention, because it is a key determinant of encounter rates and therefore relevant for a wide range of ecological processes. However, most studies have focused on microscopic cells, and consequently the case of larger organisms remains poorly studied. Here, we use high-performance particle tracking and three-dimensional Voronoï analysis to test for the emergence of clustering in the spatial distribution of calanoid copepods, the most important metazoans in the oceans in terms of biomass. We found that neither inertia nor motility resulted in significant departure from a random Poisson process over a range of turbulence intensity from very strong to moderate. However, we observed weak clustering in calm water, which may originate from hydrodynamic and olfactory interactions between organisms. Our results improve our understanding of fluid-particle interactions in the zooplankton and have important implications for the modeling of their encounter rates in turbulence.

[Low-grade eosinophilic unclassified renal cell carcinoma, a recently proposed entity in the spectrum of eosinophilic renal cells tumors: Report of one case and discussion]. / Le carcinome rénal inclassé de bas grade à cellules éosinophiles, une entité récemment proposée dans le spectre des tumeurs rénales à cellules éosinophiles : étude d'un cas et discussion.

Low-grade eosinophilic unclassified renal cell carcinoma is a rare kidney tumor recently described, not included in the WHO classification, which is very close to oncocytoma. It is unknown to most pathologists and clinicians. From a histopathological point of view, this tumor is composed of oncocytic cells arranged in a diffuse and solid pattern, without cell nests, that makes it possible to differentiate it from oncocytoma, and expresses cytokeratin 7 (CK7) heterogeneously. We report a case with a cranial vault metastasis, and present the features to differentiate this entity from oncocytoma. Furthemore, we discuss about unclassified renal cell carcinomas with oncocytic cells.

Symmetry-breaking phase transitions in highly concentrated semen.

New experimental evidence of self-motion of a confined active suspension is presented. Depositing fresh semen sample in an annular shaped microfluidic chip leads to a spontaneous vortex state of the fluid at sufficiently large sperm concentration. The rotation occurs unpredictably clockwise or counterclockwise and is robust and stable. Furthermore, for highly active and concentrated semen, richer dynamics can occur such as self-sustained or damped rotation oscillations. Experimental results obtained with systematic dilution provide a clear evidence of a phase transition towards collective motion associated with local alignment of spermatozoa akin to the Vicsek model. A macroscopic theory based on previously derived self-organized hydrodynamics models is adapted to this context and provides predictions consistent with the observed stationary motion.

Nephron sparing surgery for renal cell carcinoma using selective renal parenchymal clamping.

PURPOSE: We describe a technical artifice facilitating nephron sparing surgery for renal cell carcinoma without clamping the renal pedicle. MATERIALS AND METHODS: Selective renal parenchymal clamping was performed using a large curved DeBakey aortic clamp placed around and sufficiently far from the tumor. The lesion was resected with a surrounding margin of normal renal parenchyma. The intrarenal vessels were suture ligated and the collecting system was closed as necessary. Time was not limited since the artery was not clamped. RESULTS: Ten patients with renal cell carcinoma in whom nephron sparing surgery was indicated underwent selective renal parenchymal clamping. The indication was elective in 8 patients and urgent in 2. The tumor was at the renal pole in 3 cases and peripheral in 7. Mean tumor size was 32 mm. (range 19 to 52). Blood loss was insignificant. Operative time was 81 minutes (range 61 to 125) and there were no perioperative or postoperative complications. CONCLUSIONS: Selective renal parenchymal clamping is a simple and efficient technical maneuver for facilitating nephron sparing surgery without pedicle dissection and clamping for renal peripheral or pole tumors. Neoplasm location and size are the limiting factors of this technique.

Coloepiploic mobilization during left radical nephrectomy for renal cell carcinoma is indicated to reduce the risk of iatrogenic splenectomy.

OBJECTIVES: To determine whether coloepiploic mobilization (CEM) is indicated to reduce the incidence of iatrogenic splenectomy during left radical nephrectomy for renal cell carcinoma. The incidence of iatrogenic splenectomy during a left nephrectomy is estimated to be between 1.4% and 24%. In a recent study, we reported that the incidence of iatrogenic splenectomy was 8% during a left nephrectomy performed for renal cell carcinoma through a transperitoneal anterior subcostal incision. METHODS: A left radical nephrectomy was performed in 233 consecutive patients for renal cell carcinoma through a transperitoneal anterior subcostal incision with a CEM procedure in which the left colonic flexure was completely detached from the epiploa. Perioperative and postoperative complications, including splenic injury, were noted in a database. The mean patient age was 51.3 years (range 21.3 to 90.2). The mean tumor size was 58 mm (range 15 to 230). RESULTS: An iatrogenic splenectomy was required in 3 patients, and in 1 patient, a splenic injury was treated conservatively. The incidence of iatrogenic splenectomy accompanying left radical nephrectomy was 1.3%. The mean operative time was 120 minutes (range 80 to 240). The mean time to normal gut motility was 3.4 days (range 2 to 11) and to discharge from the hospital it was 9.3 days (range 6 to 19). Regarding CEM, we did not observe any significant abdominal complications. CONCLUSIONS: The incidence of iatrogenic splenectomy during a left radical nephrectomy through a transperitoneal anterior subcostal incision may be reduced by performing the technique of CEM.