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Malignant Hyperthermia (MH) has been shown to be due to an inherited disorder in cellular membrane systems, which also seem to be affected by halothane. With the erythrocyte osmotic fragility test we tried to find out if the erythrocyte membrane can serve as a diagnostic tool in malignant hyperthermia and as a model for halothane effects on membranes. We obtained MH susceptible and MH resistant pigs and their crossbreeds. The MH susceptible pigs showed the greatest degree of haemolysis in the erythrocyte osmotic fragility test. Furthermore, halothane increased haemolysis more in the erythrocytes of MH susceptible pigs. The MH resistant pigs were only slightly affected in both and the crossbreeds showed intermediate results. The variance occurring within one halothane group could be used to add a further distinguishing characteristic apart from the discrete halothane challenge test and so enable selection within a pure halothane group. Zusammenfassung Die osmotische Fragilität von Erythrozyten bei Maligner Hyperthermie und Effekte von Halothan Die Maligne Hyperthermie (MH) ist eine hereditäre Störung zellulärer Membransysteme, welche auch durch Halothan beeinflußbar sind. Durch die Bestimmung der osmotischen Resistenz wollten wir herausfinden, ob die Erythrozytenmembran dazu dienen kann, den Halothaneffekt auf Membranen zu simulieren und als diagnostisches Mittel zur Aufdeckung von maligner Hyperthermie zu fungieren. Wir untersuchten MH-empfindliche und MH-resistente Schweine sowie deren reziproke Kreuzungen. Die MH-empfindlichen Schweine zeigten nicht nur die höchste Hämolyserate im Test, sondern auch die höchste Empfindlichkeit gegenüber Halothan. Die MH-resistenten Schweine zeigten nur geringe Hämolyse und Halothanempfindlichkeit, während sich die Kreuzungstiere intermediär verhielten. Durch die relativ weite Streuung innerhalb einer Gruppe von Halothan-Reagenten kann die Bestimmung der osmotischen Fragilität ein kontinuierliches Merkmal zum qualitativen Halothantest hinzufügen und somit eine Selektion auch innerhalb einer Halothan-Gruppe ermöglichen. [ABSTRACT FROM AUTHOR]

The nucleotide sequence data referred to in this paper have been submitted to GenBank and have been assigned the accession number X97040.c-myc is an ubiquitous nuclear phosphoprotein involved in the regulation of cell-growth, differentiation and apoptosis. Higher nuclear levels of c-myc block adipogenesis and trigger the onset of myogenesis and folliculogenesis. The c-myc proto-oncogene has the potential of a mediator between second messengers such as calcium and cAMP and gene expression. As both are involved in stress-susceptibility and carcass quality in the pig, this study investigates associations between c-myc genotypes and carcass quality traits as well as interactions with the Ryr1 genotype in this species. An association between c-myc and carcass fat traits was evident, but did not reach genome-wide significance levels. Significance niveaus, explained variance and mean differences between the homozygotes of the Ryr1-gene which clearly decreased from the AA-genotype to the BB-genotype of c-myc are indicating a gene interaction between both genes. Mean differences in lean percentage (expressed in SD) decreased by 89.2% in ME × PI and by 86.3% in WS × PI. The existing but weakly developed significances of the association between c-myc and carcass fat traits are discussed under the aspect of epistatic nullification. [ABSTRACT FROM AUTHOR]