Abnormal calcium signalling and the caffeine–halothane contracture test

Figures

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  Fig 1. Caffeine-halothane contracture test and clinical index. A, contractile force of muscle strips in response to 2 mM caffeine vs. force in response to 3 vol% halothane. B, same data in logarithmic scales. Results in the blue region are "normal"; patients qualify as HN. The HS region maps forces excessive ("positive") for both caffeine and halothane. Tests in region labeled HH had discrepant results, positive for halothane but not caffeine. No patients had the reciprocal results (the HC region was empty). The correlation between forces induced by caffeine and halothane was high (r2 = 0.73). In both panels the short dashed line represents equal forces in response to both agonists. FH in HS were generally much greater than in HH. C, Clinical Index, plotted vs. FC and FH. The highest values of the index are found in HH patients. The index averages were significantly higher than in HN but the difference between HH and HS was not significant (statistics in Supplemental Table 1). Special symbols identify patients with pathogenic mutations (Supplemental Table 2). In B, the abscissae have a small random number added (−0.018 > r < 0.018, smaller than the precision of the measurement) to…

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  Fig 2. Spontaneous Ca2+ events in a myotube from a MH-susceptible patient (Patient #22, diagnosed as HS). Images taken at 326 ms intervals. Spark-like spontaneous events are seen throughout; a propagating wave is first imaged at 1630 ms.

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  Fig 3. A, Images of [Ca2+]cyto illustrating the normal response to stimulation. B, Ca2+ release flux calculated from [Ca2+]cyto. Field stimulus applied before 3rd panel. Images taken at 500 ms intervals. The response is immediate, brief and synchronous throughout the cell. (Patient I.D. #9, diagnosed as HN). C, response to a train of pulses (represented schematically at top) in a myotube from another HN patient to show strict association of calcium response to electrical stimulus.

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  Fig 4. Waves and spikes in response to electrical stimulus. A, cytosolic Ca2+ wave and B, Ca2+ release flux. The first frame, resting fluorescence at an expanded intensity scale, reveals multiple nuclei. A brief field stimulus was applied at time 0. Arrows in second panel indicate the immediate response to the stimulus, better seen as flux in B. A large increase in [Ca2+] develops later. The Ca2+ flux takes the form of a cell-wide wave that propagates right-to-left at 90 µm s−1. Patient #9, diagnosed as HS. C-D, example of "spiking" after a stimulus. C, time course of cell-averaged fluorescence after a single stimulus (trace at top); an immediate response is followed by large fast-rising spikes. Patient #31, diagnosed as HH. D, [Ca2+]cyto transients and E, corresponding Ca2+ release flux after a stimulus applied at time 0. Unlike the wave in A, activation of release is fast, repeated, and covers homogeneously large sections of cells. Different myotubes may reactivate at different times. Patient #40, diagnosed as HH.

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  Fig 5. The calcium Index and principal components. A, calcium index, plotted vs. forces in caffeine-halothane contracture test (CHCT). Note that the highest values are found among HH. Special symbols mark the only patients with disease-causing or disease-associated mutations. B, Ca2+ and clinical indexes compared. The regression line has a slope of 0.58. r2 = 0.49. B, 2-dimensional principal component analysis. Symbols represent patients, plotted by their principal components 1 and 2. In this plot HH is notably more separated from the other classes than in the graph of panel B. The centers of mass of the group distributions are located by colour-corresponding stars. They align approximately with the axis of principal component 1 (x axis). The dashed line is a tentative border, placed by eye, between a region of normal cell-level phenotype and one of abnormal phenotype. While most HS patients lie on the "normal" side of the line, all but two of the HH patients occupy the "abnormal" region. Two HH outliers are identified by patient ID # next to the symbol. Crosses within symbols identify patients with no personal or family MH history, present in every group.