Colloidal diffusion inside a spherical cell.

The hydrodynamic hindering of a single-particle dynamics under total confinement is measured by optical microscopy. The three-dimensional trajectories of single-colloidal particles confined in spherical water globules of sizes only a few times the particle's diameter are tracked as they sample the entire volume of the globule. The hydrodynamic interactions between the particle and the spherical wall produce a dependence of the short-time diffusion on the particle's distance to the surface and an asymmetry in the radial and tangential components of the local diffusion coefficient, with the diffusion along the tangential direction being faster than along the radial direction. The latter decreasing close to the wall while the former being practically constant.

[Radiosurgery in the treatment of brain cavernomas. Experience with 17 lesions treated in 15 patients]. / La radiochirurgie dans le traitement des cavernomes. Expérience de 17 lésions traitées chez 15 patients.

The aim of this study is to assess the efficiency of radiosurgery (RS) in the treatment of brain cavernomas. The series included intra-axial 17 lesions in 15 patients, 10 women and 5 men. Eleven were infratentorial lesions (brain stem and cerebellum) and 6 supratentorial (thalamus, hippocampus, brain cortex and paraventricular region). Fifteen lesions bled once or twice. Two lesions revealed by focal epilepsy displayed a rim of hemosiderin on MRI. RS was performed for all 17 lesions. The risk of morbidity was considered too high for surgery in 13 patients and 2 patients wished to be treated by RS. RS was delivered by a 6 MeV linear accelerator with a conic collimators device. Stereotactic localization and dosimetry were carried out with STP system 3.O (Fischer-Liebinger TM, Germany). Doses ranged between 16 and 23 Gy, the lower doses being delivered to brain stem lesions. All the lesions received a single fraction isocentric radiation. Lesion volumes ranged between 0.7 and 4.7 cm(3). Twelve lesions disappeared on MRI, the volume reduced (50-80%) in 3 lesions, and did not change in 2 lesions. Volume reduction was significant (P<0.01, P<0.001). In the follow up, 4 patients experienced bleeding, 1 of them died. Edema diagnosed in 2 patients at 3 and 13 months was treated by corticosteroids. The risk of hemorrhage without treatment in this group of patients was estimated about 34.45% a year. Hemorrhage incidence observed after RS was 7.17% (significant with P<0.01, P<0.001). At the end of follow up, 12 patients were symptom-free, 2 had sequels from bleeding, 1 patient died. Radiosurgery is an efficient treatment of cavernomas leading to a total disappearance of 70% of the lesions and significantly reducing the risk of new hemorrhages.

[Abundance and body size of Menippe mercenaria (Crustacea: Brachyura), in artificial refuges in Quintana Roo, Mexico]. / Abundancia y tallas de Menippe mercenaria (Crustacea: Brachyura), en refugios artificiales en Quintana Roo, México.

In Florida and Cuba the stone crab Menippe mercenaria (Say, 1818) is under strong fishing-pressure; nevertheless in the Mexican Caribbean it is considered as sub-utilized and poorly known resource. Artificial shelters ("condominios cubanos") were used to study relative abundance, age structure, claw length-carapace amplitude relation, and population in three seasons and four sectors at Bahía Ascension, Quintana Roo, Mexico. The abundance varied according to the sector and sampling season: population was higher in the south and during the north wind ("Nortes") season (January to March). The carapace amplitude was directly proportional to claw length (r2 = 0.83, 0.97 and 0.89; p < 0.05 in females, males and total, respectively). The results suggest that specimens with 37.5 and 67.5 mm of carapace amplitude are the most limited regarding refuge availability in the Bay.

[Biomass and density of 2 seagrass species in southern Quintana Roo, Mexico]. / Biomasa y densidad de dos especies de pastos marinos en el sur de Quintana Roo, México.

The biomass and productivity of a seagrass community are useful for determining the ecological status of the coast. Leaf biomass and shoot density in beds of Thalassia testudinum Banks & Sol. ex K. D. Koenig, were compared for two environments in the Mexican Caribbean coast (N = 6 quadrants/site) in November 1998. Shoot and leaf biomass values were lower in the mangrove-associated meadow than in the reef lagoon meadow. This could be related to the higher percentage of epiphytes on the leaves. In addition, T. testudinum had more biomass than Syringodium filiforme Kütz in the reef lagoon.

[Myocardial infarction caused by cold beverage drinking after strenuous physical exercise]. / Infarto del miocardio provocado por ingesta de bebida fría inmediatamente después de ejercicio físico intenso.

A case of acute myocardial infarction in a 36 years old patient is presented. Maleness was male, as the only mayor coronary risk factor. He had myocardial infarction associated with ingestion of cold beverage after strenuous physical exercise. A coronariographic study was done postmyocardial infarction, which showed a mild obstruction of the LAD. The most likely cause of the coronary event in this case is coronary spasm and atherosclerosis. A review of the literature on this subject is made.