Utilidad de la estación unipodal en la valoración del riesgo de caídas / Utility of one-leg balance in evaluation of the risk of falls

Objetivo: comparar los resultados obtenidos en la estación unipodal con el análisis del equilibrio estático mediante posturografía. Métodos: 59 sujetos mayores de 64 años. Se evaluó la estación unipodal y el Modified Clinical Test for the Sensory Interaction on Balance mediante el posturógrafo Balance Master (Neurocom®). Grupo A: sujetos que no realizaron la estación unipodal, y grupo B: los que sí pudieron realizarla. Resultados: grupo A: 37,2% (22). Grupo B: 62,6% (37). Sobre una superficie dura y con los ojos abiertos, el centro de gravedad del grupo A se desplazó 0,4 grados/s (0,28-0,6) y el del grupo B 0,2 grados/s (0,1-0,3) (p = 0,01). Sobre una superficie firme y con los ojos cerrados, el centro de gravedad del grupo A se desplazó 0,5 grados/s (0,3-0,8) y el del grupo B 0,3 grados/s (0,1-0,4) (p = 0,002). Sobre una superficie almohadillada y con los ojos abiertos, el centro de gravedad del grupo A se desplazó 1,1 grados/s (0,90-1,60) y el del grupo B 0,9 grados/s (0,73-1,3) (p = 0,045). Sobre una superficie almohadillada y con los ojos cerrados, el centro de gravedad del grupo A se desplazó 6 grados/ s (4-6) y el del grupo B 2,3 grados/s (1,63-3,08) (p < 0,001). Conclusiones: los sujetos de edad avanzada capaces de mantener la estación unipodal durante al menos 5 s muestran un menor desplazamiento de su centro de gravedad que los que no lo consiguen. Los resultados se mantienen cuando se suprimen las aferencias visual y propioceptiva (AU)

Aims: to compare posturographic test with One-Leg Balance test in the elderly. Methods: we studied 59 healthy men and women living in the community who were at least 65 years of age. All of them were evaluated with One–Leg Balance (defined as the ability to stand on one leg unsupported for 5 seconds) and Modifies Clinical Test for the Sensory Interaction on Balance by the Balance Master (Neurocom®). We distributed the patients in two groups. Group A included those who couldn’t perform one-leg balance and group B those who could perform it. Results: 62.6% of subjects could perform one-leg balance and 37.2% could not perform it. On a firm surface with opened eyes, the A group made a variation of 0.4 deg/s (0.28-0.6) in the gravity center position and the B group 0,2 deg/s (0.1-0.3) (p = 0.010). On a firm surface with closed eyes, the A group made a variation of 0.5 deg/s (0.3-0.8) and the B group 0.3 deg/s (0.1- 0.4) (p = 0.002). On a foam surface with open eyes, the A group made a variation of their gravity center position of 1.10 deg/s (0.90-1.60) and the B group 0.9 deg/s (0.73-1.30) (p = 0.045). On a foam surface with closed eyes the A group made a variation of their gravity center position of 6 deg/s (4-6) and the B group 2.3 deg/s (1.63-3.08) (p < 0.001). Conclusions: elderly patients who can perform one-leg balance, make less variations of their gravity centre. The results are the same when visual and propioceptive afferences are suppressed (AU)

Transfer RNA binding to 80S ribosomes from yeast: evidence for three sites.

The number of tRNA binding sites in 80S ribosomes from Saccharomyces cerevisiae was assessed by means of tRNA saturation and translocation experiments. In the absence of cognate mRNA yeast ribosomes could bind 0.6 [32P]tRNA(Phe) per 80S while poly(U) programmed ribosomes accepted up to 1.7 tRNA(Phe) molecules per 80S or 0.5 molecules of Ac[14C]Phe-tRNA(Phe) per 80S. Compared with the known features of E. coli ribosomes these binding values indicated both the presence of three tRNA binding sites and the validity of the exclusion principle for peptidyl-tRNA binding to yeast ribosomes. Upon EF-2 dependent translocation of a complex containing deacyl-tRNA in the P-site and AcPHe-tRNA in the A-site, the deacylated tRNA does not leave the ribosome quantitatively. This observation suggests the presence of an E site in 80S ribosomes which is functionally equivalent to the one previously characterized in prokaryotic systems.

Effect of superoxide dismutase and catalase, given separately, on myocardial "stunning".

Controversy persists regarding which oxygen metabolites are cytotoxic. Although the combination of superoxide dismutase (SOD) and catalase has been shown to attenuate postischemic myocardial dysfunction ("stunning"), it is unknown whether this beneficial effect is due to scavenging of O2-., H2O2, or both. Accordingly, 85 open-chest dogs underwent a 15-min occlusion of the left anterior descending coronary artery followed by 4 h of reperfusion. In phase A, dogs received an intravenous infusion of saline (group I), SOD (5 mg/kg, group II), catalase (12,000 U/kg, group III), or the combination of SOD and catalase (same doses, group IV). Recovery of regional myocardial function (assessed as systolic wall thickening) after reperfusion was significantly improved by the combination of SOD and catalase but not by SOD alone or catalase alone. To determine whether higher doses of enzymes are more effective, in phase B dogs received an intracoronary infusion of normal saline (group V), SOD in low dose (1.5 mg/kg, group VI), SOD in high dose (6.3 mg/kg plus 1.5 mg/kg iv, group VII), catalase in low dose (18,000 U/kg, group VIII), or catalase in high dose (240,000 U/kg plus 40,000 U/kg iv, group IX). Despite the fact that the local plasma levels of enzymes were considerably higher than those achieved in phase A, none of the treatments in phase B significantly enhanced recovery of contractile function. This study demonstrates that the combination of SOD and catalase is more effective than either enzyme alone in attenuating postischemic myocardial dysfunction and that increasing the doses of SOD or catalase does not provide additional protection. The results suggest that both O2-. and H2O2 contribute significantly to the pathogenesis of myocardial stunning after regional ischemia in the intact animal. Furthermore, the data imply that if SOD and catalase are to be used clinically to prevent postischemic dysfunction, protection may be achieved most effectively by combining the two enzymes.

Cyclic AMP in the Malpighian tubule fluid and in the urine of Rhodnius prolixus.

We demonstrate the presence of cyclic adenosine monophosphate (cAMP) in the fluid secreted by isolated Malpighian tubules of Rhodnius prolixus. In addition, we show that fifth-instar R. prolixus excrete cAMP in the urine after a meal of human blood. Nonstimulated isolated Malpighian tubules secrete small amounts of cAMP that increase about 10-fold after the addition of 5-hydroxytryptamine (5-HT). 5-HT is known to mimic R. prolixus diuretic hormone. The present findings demonstrate that 5-HT also acts via cAMP. The presence of cAMP in the rectal sac of the insect could be of importance in the differentiation of Trypanosoma cruzi and in the cycle of Chagas disease.

Postischemic mechanical and vascular dysfunction (myocardial "stunning" and microvascular "stunning") and the effects of calcium-channel blockers on ischemia/reperfusion injury.

The purpose of this review is to summarize current concepts regarding the sequelae of myocardial ischemia and reperfusion and the effects of calcium-channel blockers. This article will focus on three topics: (1) the phenomenon of postischemic myocardial dysfunction (myocardial "stunning"); (2) the phenomenon of postischemic vascular dysfunction (microvascular "stunning"); (3) the effects of calcium-channel blockers on myocardial ischemia and reperfusion injury.

Intracellular signaling transduction in the differentiation of Trypanosoma cruzi: role of cAMP.

We have studied the cell differentiation of Trypanosoma cruzi in an vitro system that allows the transformation of epimastigotes into metacyclic trypomastigotes. Intracellular cAMP levels of epimastigotes increased 3 fold prior to their differentiation into metacyclics where cAMP remained elevated 3.7 fold with respect to epimastigotes. We also observed a 3 fold increase in the specific activity of cAMP-binding of metacyclics crude homogenates. This activity resided in a cAMP-binding receptor protein (CARPT) which was different from the typical cAMP-binding subunits (RI and RII) of cAMP-dependent protein kinases, as shown by the use of polyclonal antibodies prepared against these two types of proteins. Anti-RI antibodies did not react with CARPT, and anti-RII antibodies gave a cross reaction with CARPT which was at least 1,000 fold less sensitive than the one shown by the homologous antigen. On Western blots CARPT displayed a major band with Mr = 87,000 instead of Mr = 56,000 for RII. These studies implicate that cAMP may act as a mediator of the cell differentiation of T. cruzi by a mechanism involving a novel type of cAMP-binding receptor.

Cyclic AMP as an inducer of the cell differentiation of Trypanosoma cruzi.

The addition to epimastigotes cultures of T. cruzi, of either cAMP, monobutyryl-cAMP, dibutyryl-cAMP, 8-Br-cAMP (at 2 mM each), or the cAMP-phosphodiesterase inhibitor, papaverine (0.2 mM), promoted the in vitro differentiation of these parasite forms into metacyclics. This effect of cAMP may also be exerted in vivo in the insect vector, since cAMP was detected in the urine and in the Malpighi secretion fluids of Rodnius prolixus.

Possible role of cAMP in the differentiation of Trypanosoma cruzi.

To assess the possible action of cAMP on the cell differentiation of Trypanosoma cruzi, we determined both cAMP levels and cAMP-binding activities of epimastigotes and trypomastigotes of this parasite. Trypomastigotes showed a 4-fold higher cAMP content and a 2.5-fold increase in the specific activity of a cAMP-binding protein with identical properties to that of epimastigotes. The high levels of cAMP present in trypomastigotes strongly suggest a role of this cyclic nucleotide on the differentiation of T. cruzi.