Bioaccumulation and interrelationship of manganese and zinc in horse mussel Modiolus modiolus fromEastern Canada

ABSTRACT:   Bioaccumulation and distribution of Mn and Zn in the total softtissues, digestive glands, residuals and adductor muscles of thehorse mussel Modiolus modiolus from three sites, includingindustrialized and non-industrialized locations in Eastern Canada,were investigated. Extremely high digestive gland metal concentrationswere found in individual mussels, as high as 1819 µg/gMn wet weight and 1964 µg/g Zn wet weight,with mean values from 358 to 404 µg/gMn and from 399 to 614 µg/g Zn for thecollection sites. High Mn to Zn interrelationships were observed inall types of tissues and at all sites. Between different tissues,Zn was interrelated by linear relationships, and Mn was best describedby power curve relationships for all tissue types. In the totalsoft tissue, Mn and Zn interrelations were fitted to power regressioncurves with different slopes between the three study sites. Thisindicated that horse mussel was exposed to different metal levels inthe environments and could be useful for monitoring these metals.The uptake of both metals at extremely high concentrations, thelack of regulation and the occurrence of interactions all suggest thatMn and Zn may play a biological role in horse mussels. Zn and Mninteractions, surprisingly, were not disrupted at the very highconcentrations of either metal, which proves that the mechanism ofmetal interactions does not involve a detoxification role.     

The Effect of Resuscitation Technique and Pre-Arrest State of Oxygenation on Blood–Gas Values during Cardiopulmonary Resuscitation in Dogs

Large mongrel dogs were anesthetized, instrumented, and subjected to electrically induced ventricular fibrillation after breathing either 100% oxygen (O2) or 10% O2 and 90% nitrogen for 10 minutes before arrest. Four minutes after arrest, open chest cardiopulmonary resuscitation (CPR) or intermittent abdominal compression closed chest CPR was initiated and continued for 20 minutes, at which time defibrillation was attempted. Central arterial and mixed venous blood samples were collected serially for the measurement of pH, carbon dioxide partial pressure (PCO2), and O2 partial pressure (PO2), and calculation of bicarbonate concentration and base excess. Mixed venous blood was collected serially for the measurement of lactate concentration. Hemodynamically variable resuscitation techniques and pre-arrest hypoxia or hyperoxia did not significantly influence blood-gas values during CPR. Mixed venous lactate concentrations after 20 minutes of CPR were significantly higher when hypoxia preceded the arrest and when intermittent abdominal compression closed chest CPR was used for resuscitation. Mixed venous PCO2 was significantly higher than arterial PCO2 in all dogs during CPR but was not significantly different before arrest.