'Fishy' make-up on the hook for mercury exposure: a case series / Maquillaje 'sospechoso' de anzuelo para la exposición al mercurio: un estudio de serie de casos

OBJECTIVE: This report examines the source and outcome of four Barbadian women with extremely high hair mercury concentrations (361-5617 ug/g inorganic mercury) due to topical application of mercury containing skin-lightening cosmetics. METHODS: Inorganic hair and urine mercury analysis was done at the toxicological centre laboratory of the Institut National de Santé Publique du Québec (Standard Council of Canada accredited). The clinical examinations were performed on location at the Queen Elizabeth Hospital of Barbados. RESULTS: Urine samples [7-135 ug/L, normal < 2 ug/L] revealed elevated mercury concentrations signifying systemic exposure. Reported symptoms during the clinical examination were consistent but nonspecific to chronic mercury exposure. CONCLUSION: Evidently, cosmetics containing dangerous levels of mercury are still available for purchase in Barbados and should be entirely banned.

OBJETIVO: Este reporte examina la fuente y evolución clínica de cuatro mujeres barbadenses con concentraciones de mercurio extremadamente altas (mercurio inorgánico de 361-5617 ug/g) en el pelo debido a la aplicación tópica de cosméticos para el aclaramiento de la piel, que contienen mercurio. MÉTODOS: Se realizó un análisis del mercurio inorgánico en el cabello y la orina, en el laboratorio del centro toxicológico del Institut National de Santé Publique du Quebec (acreditado por el Consejo de Normalización de Canadá). Los exámenes clínicos fueron realizados en el Hospital Queen Elizabeth de Barbados. RESULTADOS: Las muestras de orina [7-135 ug/L, normal < 2 ug/L] revelaron concentraciones elevadas de mercurio, indicando una exposición sistémica. Los síntomas reportados durante el examen clínico se correspondían, aunque no deforma específica, con una exposición crónica al mercurio. CONCLUSIÓN: Evidentemente, cosméticos que contienen niveles peligrosos de mercurio se hallan todavía disponibles a la venta en Barbados, y deben ser totalmente prohibidos.

'Fishy' Make-up on the Hook for Mercury Exposure: A Case Series.

OBJECTIVE: This report examines the source and outcome of four Barbadian women with extremely high hair mercury concentrations (361-5617 µg/g inorganic mercury) due to topical application of mercury containing skin-lightening cosmetics. METHODS: Inorganic hair and urine mercury analysis was done at the toxicological centre laboratory of the Institut National de Santé Publique du Québec (Standard Council of Canada accredited). The clinical examinations were performed on location at the Queen Elizabeth Hospital of Barbados. RESULTS: Urine samples [7-135 µg/L, normal < 2 µg/L] revealed elevated mercury concentrations signifying systemic exposure. Reported symptoms during the clinical examination were consistent but nonspecific to chronic mercury exposure. CONCLUSION: Evidently, cosmetics containing dangerous levels of mercury are still available for purchase in Barbados and should be entirely banned.

Chronic mercury exposure examined with a computer-based tremor system.

Tremor is being increasingly evaluated by quantitative computer-based systems to differentiate its causes. In this study, a group of mercury-exposed workers were assessed to determine whether tremor characteristics differed by exposure level. Workers were classified into two groups: those with an average urine mercury concentration below the American Conference of Government Industrial Hygienist Biological Exposure Index of 35 micrograms/g creatinine, and those with an average urine mercury concentration above the Biological Exposure Index. Tremor characteristics (including intensity, harmonic index, center frequency, standard deviation of the center frequency, and tremor index) were measured and recorded with a computer-based tremor system. Sixteen of 17 workers who were potentially exposed to mercury participated in the study. Three workers had a mean urine mercury concentration of 27.0 micrograms/g-creatinine and were assigned to the low-exposure group, and 13 workers had a mean urine mercury concentration of 200.2 micrograms/g-creatinine and were assigned to the high-exposure group. There was a statistically significant difference in the tremor index (which compiles five individual tremor parameters into a single value) between the two groups (P = 0.04; Wilcoxon's rank sum test). Other tremor characteristics did not differ significantly between the groups. Tremor index may be more useful than measures of individual tremor parameters in differentiating normal from subclinical pathological tremors among groups of workers with chronic mercury exposure.

Effect of temperature on motor responses in organophosphate intoxication.

We studied the effect of temperature on median motor responses in a 41-year-old man with organophosphate intoxication. At 32 degrees C, a normal amplitude compound motor action potential (CMAP) and a smaller spontaneous repetitive discharge (SRMAP) were present. With warming to 39 degrees C, the CMAP amplitude decreased 20%, while the SRMAP amplitude decreased 33%. With cooling to 14 degrees C, the CMAP amplitude decreased 9%, while the SRMAP became unobtainable. Possible mechanisms for these findings are discussed.

Co-operative interactions between troponin-tropomyosin units extend the length of the thin filament in skeletal muscle.

Ca2+ binding to troponin C (TnC), a subunit of the thin filament regulatory strand, activates vertebrate skeletal muscle contraction. Tension, however, increases with Ca2+ too abruptly to be the result of binding to sites on individual TnCs. Because extraction of one TnC on average per regulatory strand dramatically reduces the slope of the tension/Ca2+ relationship, we proposed that all 26 troponin-tropomyosin complexes of the regulatory strand form a co-operative system. This study of permeabilized (chemically skinned) rabbit psoas fibers analyzes the extraction time-course, the distribution of extraction sites on regulatory strands and the effects of extraction on the co-operativity of the tension/Ca2+ relationship. Two components of TnC are resolved in the time-course of extraction: a "rapidly extracting" component that can be selectively removed without affecting tension or co-operativity, and a "slow extracting" component whose loss reduces tension and co-operativity. Extraction of [14C]TnC shows that the slowly extracting component is lost randomly, so that, after removal of 5% of the TnC, most extracted strands have lost one TnC. Extraction interrupts the transmission of co-operativity by dividing the regulatory strand into smaller, independent co-operative systems; it reduces tension by preventing Ca2+ activation of TnC-depleted regulatory units. Co-operativity of the tension/Ca2+ relationship is modeled with the concerted-transition formalism for intact systems of 26 regulatory units, and for the smaller systems in extracted fibers.