Serial triple quantum sodium MRI during non-human primate focal brain ischemia.

Triple quantum (TQ) sodium MRI techniques with clinically acceptable 18-min data acquisition times were demonstrated in vivo in a nonhuman primate model of focal brain ischemia. Focal brain ischemia was induced in four animals using embolization coils to occlude the posterior cerebral artery, and a balloon catheter to occlude the middle cerebral artery. A statistically significant increase (P < 0.001) in the TQ sodium MRI signal intensity in the ischemic hemisphere relative to the contralateral hemisphere was seen at all time points in all four animals. This increased TQ sodium MRI signal intensity was demonstrated as early as 0.6 hr after the onset of ischemia. The TQ sodium MRI hyperintensity corresponded to the anatomical location of the ischemic cortex, as indicated by the registration of the TQ imaging data with anatomical proton MRI data. The results demonstrate that early after the onset of ischemia, there was an increase in the TQ signal intensity in the ischemic hemisphere, and a negligible change in the single quantum (SQ) signal intensity.

La homocisteína y la enfermedad cardiovascular / Homocysteine and cardiovascular disease

La homocisteína es un aminoácido sulfurado no esencial, que contiene un grupo tiol y se genera en casi todos los tejidos humanos, como producto del metabolismo de la metionina. Desde el a±o 1990, el estudio de Framingham reconoció la homocisteína (Hcy) como un posible factor de riesgo para enfermedad cardiovascular (ECV) y en el año 2003 lo declaró como factor de riesgo 'emergente'. La hiperhomocisteinemia se define como el aumento de los niveles plasmáticos de Hcy total(unida a proteínas más fracción libre), por encima de 15 μmol/L y se clasifica en tres niveles de severidad, moderado de 15-30 μmol/L, intermedio de 31-100 μmol/L y severo mayor de 100 μmol/L. La hiperhomocisteinemia puede producirse por una deficiencia enzimática en alguno de los pasos de su metabolismo, también se puede presentar por bajos niveles plasmáticos del ácido fólico y las vitaminas B6 y/o B12. La insuficiencia renal puede ser otra causa, debido a que el riñón es la ruta para eliminar la Hcy del plasma. La suplementación dietaria con ácido fólico reduce las concentraciones de Hcy en sangre en un 25 porciento, la suplementación con vitamina B12 en un 7 porciento, mientras que la suplementación con vitamina B6 no tiene efecto en esta disminución. Un estilo de vida saludable, una dieta balanceada con un moderado consumo de café y alcohol y dejar de fumar, contribuye en la reducción de los niveles plasmáticos de Hcy.

Homocysteine is a no essential sulfured aminoacid, that contains a thiol group in its structure. The homocysteineis produced in almost all human tissues for the methionine metabolism. In 1990, The Framingham study, demostrated that homocysteine (Hcy) could be a possible risk factor for cardiovascular disease. Since 2003 Hcy has been considered an “emergent” risk factor. The hiperhomocysteinemia is defined when plasmatic levels of total Hcy is above of 15 μmol/L. It`s classifiedaccording to three severity stages, moderate 15-30 μmol/L, intermediate 31-100 μmol/L and severe, higher than100 μmol/L. hiperhomocysteinemia can be produced by enzymatic deficiency in any of its metabolic routes, andalso due to low plasmatic levels of folic acid, vitamins B6 or B12 and renal failure, because kidney is the mainorgan to eliminate the Hcy from plasma. Folic acid diet supplementation could reduce Hcy blood concentrationabout 25%, and supplementation with vitamin B12 about 7%, however the supplementation with vitamin B6 hasnot shown any effect. Healthy life style, quit smoking, and balanced diet with a moderate consumption of coffee and alcohol may reduce Hcy plasmatic levels.

Triple/Single quantum filtered sodium MRI of acute brain ischemia.

The effectiveness of reperfusion therapies during acute brain ischemia depends on the viability of the underperfused tissue. Specifically, when the ischemic tissue is viable reperfusion leads to improved clinical outcome. However, when the ischemic tissue is non-viable, reperfusion therapy can lead to intra-cerebral hemorrhage and/or an accelerated rate of ischemia formation. Perfusion and diffusion weighted proton MRI (DW MRI) are well-established techniques for the early detection of brain ischemia but are unable to positively establish the viability of the tissue. Tissue sodium concentration (TSC) has been shown to exhibit a linear and reversible response for many hours after ischemia onset. Because sodium accumulation in tissue is closely related to its metabolic status, we believe that the rate of TSC accumulation during evolving ischemia could provide useful information about tissue viability during evolving ischemia. In this paper, we discuss the technical details leading to the application of triple quantum (TQ) sodium MRI for the monitoring of brain ischemia. The proposed methods are then demonstrated in a non-human primate model of temporary middle cerebral artery (MCA) occlusion.

Orientation, structure, wet-spinning, and molecular basis for supercontraction of spider dragline silk.

This manuscript reviews work from our laboratory that addresses the orientation, secondary structure, wet-spinning, and molecular basis for supercontraction of spider silk. It identifies the poly(alanine) runs as the crystalline regions, establishes the degree of orientation of these regions, and identifies the secondary structural elements of the conserved L-G-X-Q (X = G, S, or N) regions. It also describes methods for spinning very small amounts of protein polymers and it sets forth several molecular-level hypotheses concerning supercontraction.