The role of astrocytes in multiple sclerosis pathogenesis. / Participación de los astrocitos en la patogénesis de la esclerosis múltiple.

INTRODUCTION: Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system (CNS), in which astrocytes play an important role as CNS immune cells. However, the activity of astrocytes as antigen-presenting cells (APC) continues to be subject to debate. DEVELOPMENT: This review analyses the existing evidence on the participation of astrocytes in CNS inflammation in MS and on several mechanisms that modify astrocyte activity in the disease. CONCLUSIONS: Astrocytes play a crucial role in the pathogenesis of MS because they express toll-like receptors (TLR) and major histocompatibility complex (MHC) classI andII. In addition, astrocytes participate in regulating the blood-brain barrier (BBB) and in modulating T cell activity through the production of cytokines. Future studies should focus on the role of astrocytes in order to find new therapeutic targets for the treatment of MS.

Entropic profiles of DNA sequences through chaos-game-derived images.

A new method to determine entropic profiles in DNA sequences is presented. It is based on the chaos-game representation (CGR) of gene structure, a technique which produces a fractal-like picture of DNA sequences. First, the CGR image was divided into squares 4-m in size (m being the desired resolution), and the point density counted. Second, appropriate intervals were adjusted, and then a histogram of densities was prepared. Third, Shannon's formula was applied to the probability-distribution histogram, thus obtaining a new entropic estimate for DNA sequences, the histogram entropy, a measurement that goes with the level of constraints on the DNA sequence. Lastly, the entropic profile for the sequence was drawn, by considering the entropies at each resolution level, thus providing a way to summarize the complexity of large genomic regions or even entire genomes at different resolution levels. The application of the method to DNA sequences reveals that entropic profiles obtained in this way, as opposed to previously published ones, clearly discriminate between random and natural DNA sequences. Entropic profiles also show a different degree of variability within and between genomes. The results of these analyses are discussed in relation both to the genome compartmentalization in vertebrates and to the differential action of compositional and/or functional constraints on DNA sequences.

[Angiodysplasia of the colon. Apropos of 2 cases]. / Angiodisplasia de colon. A propósito de dos observaciones.

Angiodysplasia of the colon is a vascular lesion which involves the arterioles, venules and small venous vessels; usually it is a lesion of the aged and presents with rectorrhagia, melena or chronic anemia due to chronic blood loss. We present two cases of angiodysplasia of the colon in two female patients in the eighth decade of their lives, treated in the Servicio de Cirugía del Hospital Universitario Virgen Macarena de Sevilla. We emphasize the value of the angiographic study for the diagnosis of this lesion, and also the usefulness of isotopic study with labeled erythrocytes for the localization. The treatment of choice is surgical resection of the affected area. It was performed in both patients. One of them died.