Non-invasive evaluation of buccal respiratory chain enzyme dysfunction in mitochondrial disease: comparison with studies in muscle biopsy.

Making a diagnosis of mitochondrial disease (MD) is extremely challenging and often employs the analysis of respiratory complex (RC) activities in biopsied skeletal muscle. Given both the invasive nature and expense of biopsied-muscle based testing for mitochondrial defects, buccal swab enzyme analysis has been explored as an alternative approach to the more invasive muscle biopsy. Case studies have recently suggested that buccal swabs from patients can be used to accurately assess mitochondrial enzyme activities including RC I and RC IV using a dipstick methodology combined with spectrophotometric analysis. In this study, forty patients with suspected MD who have previously been found to have significant defects in either RC I or RC IV in skeletal muscle were assessed by buccal swab analysis and compared to enzyme values obtained with unaffected controls (n=106) in the same age range. Buccal citrate synthase was used as an indicator of overall mitochondrial content, correlating well with overall buccal mitochondrial frataxin levels and was found to be elevated above control levels in 28% of the patients in this cohort. Of 26 cases with significant muscle RC I deficiency, 20 displayed significantly reduced levels of buccal RC I activity. All 7 of the patients with muscle RC IV deficiency showed significant buccal RC IV defect and 6 of the 7 patients with combined defects in muscle RC I and IV activity levels also exhibited analogous deficiencies in both buccal RC I and RC IV activities. In conclusion, the relatively high correlation (over 82%) of buccal and muscle RC deficiencies further supports the validity of this non-invasive approach as a potentially useful tool in the diagnosis of MD.

An hypothesis on the consolidation and PGE1-induced deconsolidation of a platelet plug.

UNLABELLED: Consolidation is the final stage in haemostasis in which a platelet plug blocking a bleeding area of a vessel: (a) becomes impermeable to circulating plasma proteins and (b) contracts to resist blood pressure. HYPOTHESIS: The impermeabilization step of consolidation is accomplished through fluid uptake by the platelets from a hydrated intercellular glue formed during thrombin activation. Dehydration occurs through inhibition of the Na+,K+-ATPase of platelets with sodium and water uptake. However, and uniquely, due to the high cellular density of the platelet plug, access of peripheral plasma fluids to the plug is limited forcing the platelets to take up preferentially the fluid of interplatelet space. The increased adhesion properties of the dehydrated glue simultaneously furthers a decreased hydraulic permeability and an improved coupling of the contractile forces among platelets. In 'Deconsolidation', the fluid uptake process can be reversed and amplified by agents that increase cAMP, reactivating the Na+,K+-ATPase and expressing CFTR or equivalent Cl- secretory channels that force the extrusion of fluid from the platelets, with rehydration of the intercellular polymer and a large increase in the interplatelet space.