Bistability and Hopf bifurcation of a tritrophic system with Holling functional responses.

In this paper we analyze the dynamics of a tritrophic food chain, with functional responses of Holling type III and II for the mesopredator and superpredator respectively and logistic growth rate for the prey. We show that there are parameter conditions for which the system has up to three equilibrium points. When three equilibrium points appear we show that each one of them exhibits a supercritical Hopf bifurcation. Moreover we can also show that there is a set of parameters for which the system exhibits a simultaneous Hopf bifurcation.

Necrotizing granulomatous vasculitis in advanced HIV infection.

We describe the first case of granulomatous necrotizing vasculitis not restricted to the central nervous system in an HIV-infected patient. No mycobacteria or drugs potentially associated with granuloma formation were involved in this patient, suggesting that the cause of this vasculitis was probably autoimmune. The development of granulomatous vascular inflammation in this patient with less than 200 CD4 cells/microl might have been due to immune overactivation. After starting potent antiretroviral therapy a profound immune deactivation was observed and the vasculitis did not relapse.

Interferon alpha induction of metallothionein in rat liver is not linked to interleukin-1, interleukin-6, or tumor necrosis factor alpha.

Synthesis of metallothionein (MT) is induced by interferon-alpha (IFN-alpha) in vitro and in vivo. In addition, IFN-alpha promotes redistribution of zinc (Zn) from the plasma to the liver in mice. However, it is not clear if IFN-alpha induces hepatic MT synthesis directly or indirectly via liberation of other cytokines. In order to address this issue, we determined hepatic MT levels, Zn concentration in plasma, liver, and urine, and plasma levels interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNFalpha) in rats following intramuscular injection of human IFN-alpha (1.5 x 10(6) UI/m(2)). Animals were housed in metabolic cages and sacrificed at various times after IFN-alpha administration. Zn concentrations in serum, urine, and hepatic tissue were determined by atomic absorption spectrophotometry. MT protein was measured using the MT silver saturation method and expression of MT-1 and MT-2 mRNA was measured by RT-PCR. Plasma levels of rat IL-1, IL-6, and TNFalpha were determined using an ELISA method. Hepatic MT levels began to increase at 2 h following IFN-alpha administration and reached maximum levels at 12 h post-treatment. Induction of MT gene expression was confirmed by increases in MT-1 and MT-2 mRNA levels 6, 12, and 18 h after IFN-alpha administration. IFN-alpha treatment also resulted in biphasic increases in hepatic Zn, with levels peaking at 2 h, the time-point when MT levels are first increased, and again at 18 h. Concurrently, there were decreases in serum Zn levels at these time points, suggesting IFN-alpha induced movement of Zn from the blood to hepatic tissue. The decrease in serum Zn was not due to increased excretion since urinary Zn levels were unaffected following IFN-alpha treatment. IFN-alpha administration had no effect on plasma IL-1, IL-6, and TNFalpha levels. These results show that IFN-alpha promotes the increase of hepatic MT levels and plasma/liver redistribution directly, without IL-1, IL-6, or TNFalpha participation.

Evaluación geriátrica integral en pacientes hospitalizados / Integral Geriatric evaluation in hospitalized patients

Antecedentes: durante la hospitalización de los pacientes geriátricos, no se toma en cuenta su estado funcional, cognoscitivo y psíquico; la evaluación sistemática mediante pruebas de estas variables revela estados de dependencia física, alteraciones cognoscitivas y depresión. Objetivo: conocer la frecuencia de las alteraciones cognoscitivas y la depresión en los pacientes geriátricos. Material y métodos: se realizaron cuatro evaluaciones: índice de actividades de la vida cotidiana, escala de actividades instrumentales de la vida cotidiana, miniexamen del estado mental y, por último, la escala de Hamilton. Se determinó la media, la desviación estándar y el coeficiente de variación, y se hizo un cálculo de correlación entre la demencia y la depresión. Resultados: se incluyeron 135 pacientes, 85 (62 por ciento) hombres y 50 (37 por ciento) mujeres. En el índice de actividades de la vida cotidiana se ubicaron 86 (63 por ciento) pacientes con independencia, 30 (22 por ciento) con independencia y cierta ayuda y 19 (14 por ciento) con dependencia. En la escala de actividades instrumentales de la vida cotidiana se encontraron 123 (91 por ciento) pacientes que no necesitaban ayuda, 19 (14 por ciento) que la necesitaban y 2 (1.4 por ciento) dependientes. La depresión no se manifestó en 31 (22 por ciento) pacientes, fue leve en 90 (66 por ciento) y moderada en 14 (10.3 por ciento); su forma severa no ocurrió. Las alteraciones cognoscitivas estuvieron ausentes en 87 (64.4 por ciento) pacientes, fueron leves en 25 (18.5 por ciento) y moderadas en 8 (5.9 por ciento). La correlación de Pearson entre demencia y depresión no se estableció estadísticamente. Conclusiones: las alteraciones cognoscitivas, la depresión y la dependencia física en la población estudiada obliga a realizar en forma sistemática estas pruebas a todos los pacientes geriátricos hospitalizados.