Hydration and Nanoconfined Water: Insights from Computer Simulations.

The comprehension of the structure and behavior of water at interfaces and under nanoconfinement represents an issue of major concern in several central research areas like hydration, reaction dynamics and biology. From one side, water is known to play a dominant role in the structuring, the dynamics and the functionality of biological molecules, governing main processes like protein folding, protein binding and biological function. In turn, the same principles that rule biological organization at the molecular level are also operative for materials science processes that take place within a water environment, being responsible for the self-assembly of molecular structures to create synthetic supramolecular nanometrically-sized materials. Thus, the understanding of the principles of water hydration, including the development of a theory of hydrophobicity at the nanoscale, is imperative both from a fundamental and an applied standpoint. In this work we present some molecular dynamics studies of the structure and dynamics of water at different interfaces or confinement conditions, ranging from simple model hydrophobic interfaces with different geometrical constraints (in order to single out curvature effects), to self-assembled monolayers, proteins and phospholipid membranes. The tendency of the water molecules to sacrifice the lowest hydrogen bond (HB) coordination as possible at extended interfaces is revealed. This fact makes the first hydration layers to be highly oriented, in some situations even resembling the structure of hexagonal ice. A similar trend to maximize the number of HBs is shown to hold in cavity filling, with small subnanometric hydrophobic cavities remaining empty while larger cavities display an alternation of filled and dry states with a significant inner HB network. We also study interfaces with complex chemical and geometrical nature in order to determine how different conditions affect the local hydration properties. Thus, we show some results for protein hydration and, particularly, some preliminary studies on membrane hydration. Finally, calculations of a local hydrophobicity measure of relevance for binding and self-assembly are also presented. We then conclude with a few words of further emphasis on the relevance of this kind of knowledge to biology and to the design of new materials by highlighting the context-dependent and non-additive nature of different non-covalent interactions in an aqueous nanoenvironment, an issue that is usually greatly overlooked.

The superficial femoral vein: a valuable conduit for a short renal vein in kidney transplantation.

A variety of techniques have been developed to improve the problem with a short renal vein in kidney transplantation. Those techniques range from thorough mobilization of the recipient common and external iliac veins (iliac vein transposition) to donor vein elongation with a saphenous or gonadal vein or a polytetrafluoroethylene graft. Right renal vein extension using the inferior vena cava represents an excellent option for cadaveric kidney transplantation; however, for kidneys from living donors, that is not a suitable alternative. We present two cases where the superficial femoral vein was used as a conduit with good results; there was no additional morbidity for the patient. Although uncommon, renal vein extensions are sometimes needed in kidney transplantation. The superficial femoral vein comes close to representing the ideal conduit for a short renal vein when compared with a synthetic or an autologous graft due to its diameter and harvesting technique.

Biological relevance of the polymorphism in the CCR5 gene in refractory and non-refractory rheumatoid arthritis in Mexicans.

OBJECTIVE: The aim of this study was to analyze the frequencies of the CCR5 delta 32 deletion and HLA class II alleles in Mexican Amerindian populations and its relevance in the development and severity of RA. METHODS: We studied 212 Mexican Mestizo subjects (40 patients with refractory RA, 102 patients with non-refractory RA and 70 healthy individuals). At the same time, to evaluate the ethnicity of the CCR5 delta 32 deletion we also studied 192 individuals from three Mexican Amerindian populations (70 Mayo (Capomo) individuals, 61 Teenek individuals, and 61 Mazatecan Indians). The delta 32 deletion in the CCR5 structural gene and HLA-DRB1 were determined by a PCR-SSP and a PCR-SSO procedure, respectively. RESULTS: In the non-refractory RA group the CCR5 delta 32 gene frequency was 0.019 and the following genotype frequencies were observed: CCR5/CCR5 = 98.0%, CCR5/CCR5 delta 32 = 1.9% and CCR5 delta 32/CCR5 delta = 1.0%. In the refractory RA group the CCR5 delta 32 gene frequency was 0.025 and the genotype distribution was similar to that in the non-refractory RA group. The deletion was not detected in the Mexican Mestizo healthy group, or among the Teenek and Mayo Amerindians, all being individuals homozygous for the wild type allele. In the Mazatecan group the deletion frequency was 1.6% (g.f. = 0.016). We observed a significant increase in the frequency of the DRB1*07 allele in severe RA patients in relation to the non-severe RA group (p = 0.02, OR = 5.65, 95% CI = 0.95-43.05). CONCLUSION: Our results suggest that the CCR5 delta 32 deletion is not common in Mexican Amerindian populations and this study does not support an important role of CCR5 delta 32 in the pathogenesis of RA or a severe form of the disease in Mexicans.

[Epidemic outbreak of bacillary dysentery by "Shigella sonnei" in a kindergarten (author's transl)]. / Brote epidémico de disentería bacilar con Shigella sonnei en una guardería.

An epidemic outbreak, caused by "Shigella sonnei" in a kindergarten, affecting a high percentage of children aged two to seven years is described. On searching into the sensitivity is isolated strains to a wide range of antibiotics, it was observed that all them showed resistance to sulphonamides and a 57.19% were also resistant to phosphomycin. After doing the pertinent investigations and epidemiological analysis possible mechanisms of illness, transmission and dissemination are studied, evaluating the clinical symptoms that these children showed as well as the clinical course after treatment with ampicillin.