Magnesium chloride alone or in combination with diazepam fails to prevent hippocampal damage following transient forebrain ischemia

In the central nervous system, magnesium ion (Mg2+) acts as an endogenous modulator of N-methyl-D-aspartate (NMDA)-coupled calcium channels, and may play a major role in the pathomechanisms of ischemic brain damage. In the present study, we investigated the effects of magnesium chloride (MgCl2, 2.5, 5.0 or 7.5 mmol/kg), either alone or in combination with diazepam (DZ), on ischemia-induced hippocampal cell death. Male Wistar rats (250-300 g) were subjected to transient forebrain ischemia for 15 min using the 4-vessel occlusion model. MgCl2 was applied systemically (sc) in single (1x, 2 h post-ischemia) or multiple doses (4x, 1, 2, 24 and 48 h post-ischemia). DZ was always given twice, at 1 and 2 h post-ischemia. Thus, ischemia-subjected rats were assigned to one of the following treatments: vehicle (0.1 ml/kg, N = 34), DZ (10 mg/kg, N = 24), MgCl2 (2.5 mmol/kg, N = 10), MgCl2 (5.0 mmol/kg, N = 17), MgCl2 (7.5 mmol/kg, N = 9) or MgCl2 (5 mmol/kg) + DZ (10 mg/kg, N = 14). Seven days after ischemia the brains were analyzed histologically. Fifteen minutes of ischemia caused massive pyramidal cell loss in the subiculum (90.3 percent) and CA1 (88.4 percent) sectors of the hippocampus, vehicle vs sham). Compared to the vehicle-treated group, all pharmacological treatments failed to attenuate the ischemia-induced death of both subiculum (lesion: 86.7-93.4 percent) and CA1 (lesion: 85.5-91.2 percent) pyramidal cells. Both DZ alone and DZ + MgCl2 reduced rectal temperature significantly. No animaldeath was observed after drug treatment. These data indicate that exogenous magnesium, when administered systemically post-ischemia even in different multiple dose schedules, alone or with diazepam, is not useful against the histopathological effects of transient global cerebral ischemia in rats

Efectos del pH y la concentración iónica sobre la infecciosidad del virus de la encefalitis equina venezolana / Effecs of pH and ionic concentration on VEE virus infection

El virus de la EEV a una temperatura de 37ºC sufre alteraciones en su nivel de infecciosidad, que varían según la concentración de la solución empleada. En buffer citrato 100 mM a pH 3,4 y 5, hay pérdida notable de la infecciosidad viral; cuando se usan concentraciones de 5 y 10 mM, a los mismos pH, no se observa ninguna variación en su nivel de infecciosidad. En presencia de soluciones diluídas de cloruro de magnesio pH 4 y a 77ºC, el virus es estable en su nivel de infecciosidad; lo que no se observa en las soluciones de elevada concentración (1 ó 2 M). Cuando se emplea una solución de MgSO4, no ocurre ninguna variación del nivel de infecciosidad del virus tratado en las mismas condiciones