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Introducción: La ecografía cerebral transfontanelar es una herramienta fundamental para monitorizar el tamaño de los ventrículos en los recién nacidos prematuros y tiene como ventajas su accesibilidad y que no usa radiaciones ionizantes. Al considerar el tamaño ventricular normal, es esencial tener medidas de referencia basadas en poblaciones de la misma edad. El objetivo de este artículo es presentar las medidas de referencia obtenidas de una muestra de neonatos prematuros de nuestro centro.

In this work, we report on the characterization by Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy of nanoparticulate iron phases and their precursors synthesized by a wet chemical route within the framework of a silicate matrix (sepiolite). These results show that the nature and location of the different iron species within the sepiolite structure are dependent on the conditions of the wet chemical preparation and, specifically, on the pH value of the acidic treatment to which the sepiolite powder was subjected prior to the impregnation with the iron(III)-containing solution. A subsequent thermal treatment at 500 °C (2 h) of the iron-containing sepiolites in a reducing H2/Ar atmosphere leads to the formation of different iron-reduced species. The nature of these reduced species is also dependent on the initial acidic treatment of the sepiolite. So, in the case of the iron-containing materials produced after treatment in strong acidic conditions of the original sepiolite, the reducing conditions bring about the formation of a significant amount of metallic iron nanoparticles. These metallic iron nanoparticles have been shown to be strongly resistant to oxidation at high temperatures. In the case of milder acidic initial conditions, the reduced samples do not contain metallic iron particles but mainly nonstoichiometric Fe3O4nanoparticles.

Magnetite nanoparticles with two different sizes, 5 and 17 nm, have been prepared by the decomposition of organic precursors in an organic media in the presence of oleic acid. The particles were characterized by TEM, X-ray diffraction, and IR and Mössbauer spectroscopy to clarify their structural and physicochemical properties. The samples consist of noninteracting magnetite nanoparticles in both cases with a more uniform size distribution and higher crystal order degree than particles of similar sizes prepared by coprecipitation. A controlled heat treatment of the samples in air leads to the transformation of magnetite to maghemite, which can be followed by the appearance of many IR bands forbidden for a spinel structure. In addition to that, an important reduction of saturation magnetization and coercivity at low temperature takes place whenever the oleic acid is preserved. Finally, Mössbauer spectra at different temperatures clearly show the effect of the nature of the iron oxide phase, the particle size, particle interactions, and structural order at the surface in both magnetite and maghemite as a consequence of oleic coating.

The mechanisms accounting for T cell depletion in AIDS patients are not yet fully understood, nor are the roles of host factors in HIV pathogenesis. We show here that an ongoing humoral immune response to HIV gp120 can sensitize non-infected cells towards apoptosis. Thus, i.v. injection of 1 μg recombinant(r) gp120 into gp120-immunized human CD4-transgenic mice (huCD4 Tg), which express huCD4 on both T and B cells, results in T and B cell depletion in peripheral blood and lymphoid tissues. On day 6 after a bolus injection of gp120, the numbers of peripheral T cells and B cells in gp120-immunized huCD4 Tg decreased sevenfold and two- to threefold, respectively. Annexin V staining revealed a higher percentage of early apoptotic cells on day 1 of gp120 i.v. injection from gp120-primed huCD4 Tg spleens compared to gp120-primed controls. Boosting the primed huCD4 Tg mice with soluble gp120 and hen egg-white lysozyme led to lower secondary titers to both antigens than found in controls. Furthermore, splenocytes from gp120-pretreated immunized huCD4 Tg had a lower level of stimulation in response to anti-CD3 treatment. These in vivo results are consistent with in vitro data demonstrating that cross-linking CD4 on splenocytes of huCD4 Tg by rgp120SF2 and anti-gp120 not only sensitizes T cells for apoptosis, but also induces apoptosis per se, and suggest that anti-gp120 responsiveness can contribute to T cell depletion in AIDS.