Increased Velocity Storage in Subjects with Meniere's Disease.

OBJECTIVE: Velocity storage mechanism is a multisensory rotation estimator; it compensates for errors in the information provided by the peripheral vestibular organs by means of an adjustment in the duration of the vestibular signal. The aim of this study was to determine the activity of the velocity storage mechanism in the presence of a labyrinthine disorder, using galvanic vestibular stimulation to cause direct activation of the vestibular afferent neurons. MATERIALS AND METHODS: Forty-one subjects with definite Meniere's disease (MD) and 36 healthy volunteers were evaluated using a 20-s galvanic vestibular stimulation. RESULTS: We found a post-stimulus nystagmus overshoot exclusively in subjects with MD (47% in subjects with unilateral disease and 82% in subjects with bilateral disease), but no overshoot in healthy subjects. CONCLUSION: Because post-stimulus nystagmus overshoot is caused by the velocity storage mechanism, this finding suggests an increase in the velocity storage in subjects with a labyrinthine disease.

New clinical and toxicological scenario of gammaglutamyltranspeptidase.

After the discovery of gammaglutamyltranspeptidase in 1950 by Hanes, the significance of its increased levels in clinical practice has mainly been focused on ethanol toxicity, and also some neoplasms and biliary tract obstruction. More recently, attention has swift to the metabolic functions of this enzyme, as a neutralizer of oxygen free radicals and as a glutathione donor to the cell. High serum levels of gammaglutamyltranspeptidase is known to occur when oxidative stress is increased, or associated with several vascular risk factors and the insulin resistance syndrome, as an early marker of diabetes. There are also a number of drugs that induce the expression of the tissue enzyme (microsomes) with the result of high serum levels without structural damage to the liver. Because it is a ubiquitous enzyme, a very high number of causes can be involved, that may be difficult to recognize. Finally, because glutathione is necessary to conjugate a number of chemical compounds, from an epidemiological and toxicological perspective, the enzyme might be useful as a biomarker of several ambient toxins.In this review we want to emphasize the increasing clinical and diagnostic significance of this enzyme discovered half a century ago.

Nueva singladura clínica y toxicológica de la gammaglutamiltranspeptidasa / New clinical and toxicological scenario of gammaglutamyltranspeptidase

Desde su descubrimiento en 1950 por Hanes, la enzima gammaglutamiltranspeptidasa, al menos en medicina clínica, se ha vinculado casi en exclusiva, al valor de su aumento en la toxicidad por etanol y, en menor medida, de la existencia de ciertas neoplasias y de bloqueo de la vía biliar. Más recientemente, menudean trabajos acerca de su papel metabólico, mediando la neutralización de radicales libres de oxígeno y aprovisionando de glutatión a las células. El nivel sérico de gammaglutamiltranspeptidasa es expresivo de estrés oxidativo aumentado y se ha asociado a diversos factores de riesgo cardiovascular y a componentes del síndrome de resistencia a la insulina, de modo que sería un biomarcador precoz para el desarrollo de diabetes. Por otro lado numerosos fármacos inducen la enzima tisular (microsomas) pudiendo dar elevaciones séricas que no suponen daño estructural a nivel hepático. Su ubicuidad anátomo-citológica hace que pueda aumentar en suero en numerosos procesos, siendo por ello en ocasiones dificultoso patentizar su origen. Finalmente, desde un ángulo epidemiológico y toxicológico, siendo que el glutatión es necesario para conjugar diversas sustancias químicas, la enzima resultaría un biomarcador, entre otros, de numerosas sustancias nocivas medioambientales. Se incide en conjunto en este ensanchamiento del significado clínico y diagnóstico de una enzima que se creía suficientemente conocida desde hace medio siglo en que se descubrió(AU)

After the discovery of gammaglutamyltranspeptidase in 1950 by Hanes, the significance of its increased levels in clinical practice has mainly been focused on ethanol toxicity, and also some neoplasms and biliary tract obstruction. More recently, attention has swift to the metabolic functions of this enzyme, as a neutralizer of oxygen free radicals and as a glutathione donor to the cell. High serum levels of gammaglutamyltranspeptidase is known to occur when oxidative stress is increased, or associated with several vascular risk factors and the insulin resistance syndrome, as an early marker of diabetes. There are also a number of drugs that induce the expression of the tissue enzyme (microsomes) with the result of high serum levels without structural damage to the liver. Because it is a ubiquitous enzyme, a very high number of causes can be involved, that may be difficult to recognize. Finally, because glutathione is necessary to conjugate a number of chemical compounds, from an epidemiological and toxicological perspective, the enzyme might be useful as a biomarker of seve - ral ambient toxins. In this review we want to emphasize the increasing clinical and diagnostic significance of this enzyme discovered half a century ago(AU)