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C F Louis

Publications and source records attributed to C F Louis.

At least 55 records · Page 3Linked to original sources
PubMed1994

Tissue distribution of ryanodine receptor isoforms and alleles determined by reverse transcription polymerase chain reaction.

The tissue distribution of mRNA for ryanodine receptor (ryr) isoforms in various porcine tissues has been determined using the reverse transcription-polymerase chain reaction (RT-PCR). First strand cDNA was synthesized from total tissue RNA with reverse transcriptase and random hexamer primers. PCR primers were selected to amplify an approximately 500-base pair segment from homologous regions near the 5' end of the skeletal (ryr1), cardiac (ryr2), or brain (ryr3) ryr cDNA sequences. The specific amplification of each of the ryr isoforms was confirmed by restriction enzyme mapping and DNA sequencing. A ryr1 RT-PCR product was identified in skeletal muscle and esophagus, a ryr2 RT-PCR product was identified in cardiac muscle, aorta and esophagus, and a ryr3 RT-PCR product was identified in skeletal and cardiac muscle, aorta, esophagus, adrenal gland, small intestine, and lung. All three ryr isoforms were identified throughout the brain, including the parietal, frontal, and temporal lobes of the cerebrum, thalamus/hypothalamus, cerebellum, and brain stem. The normal (Arg615) and mutant (Cys615) ryr1 alleles were expressed in the brains of normal and malignant hyperthermia susceptible pigs, respectively. These results thus demonstrate expression of two ryr isoforms in each type of striated muscle, and all ryr isoforms in a number of regions of the nervous system. The wide distribution of ryr1 in the brain provides a possible neurogenic etiology of malignant hyperthermia.

Alleles↗
PubMed1994

Cyclic ADP-ribose does not affect cardiac or skeletal muscle ryanodine receptors.

The cardiac muscle isoform of the ryanodine receptor/Ca2+ release channel (RYR) has been proposed to be an important target of cyclic ADP-ribose (cADPR) action in mammalian cells. However, we now demonstrate that neither cADPR (0.1-5 microM), nor the related metabolites beta-NAD+ (0.1-30 mM) and ADP-ribose (0.1-5 microM), affected cardiac RYR activity as determined by [3H]ryanodine binding to cardiac sarcoplasmic reticulum (SR) vesicles. Similarly, cADPR (1 microM) failed to activate single cardiac RYR channels in planar lipid bilayers. Skeletal muscle SR [3H]ryanodine binding was also unaffected by cADPR (up to 30 microM). These results argue against a direct role for the well-characterized RYRs of cardiac or skeletal muscle in mediating cADPR-activated Ca2+ release.

Adenosine Diphosphate Ribose↗
PubMed1994

Nodulin 26, a nodule-specific symbiosome membrane protein from soybean, is an ion channel.

Nodulin 26 is an integral symbiosome membrane protein of nitrogen-fixing soybean nodules. Nodulin 26 is a member of a family of structurally homologous membrane proteins with diverse transport functions. Thus, it has been proposed to be involved in symbiosome membrane transport. Despite this claim, there has not been any evidence that nodulin 26 has a transport activity. In this study, nodulin 26 was purified from soybean nodules by a non-denaturing protocol and was reconstituted into liposomes for channel studies in planar lipid bilayers. Nodulin 26 readily incorporated into bilayers, forming single channels with a maximum unitary conductance of 3.1 nanosiemens (nS) in a recording buffer of 20 mM 3-(N-morpholino)propanesulfonate-NaOH, pH 7.4, 1 M KCl. Nodulin 26 also exhibited multiple, discreet lower conductance states ranging from 0.5 to 2.5 nS. Nodulin 26 channels were voltage-sensitive. The maximal 3.1-nS state was preferentially occupied at lower applied voltages, whereas the lower conductance states were more frequently occupied at higher voltage potentials. Nodulin 26 channels transported both cations and anions, but showed a weak selectivity for anions. These results represent the first purification and functional characterization of the nodulin 26 channel and support a role for this protein in symbiosome membrane transport.

Ion Channels↗
PubMed1994

Regulation of the sarcoplasmic reticulum ryanodine receptor by inorganic phosphate.

To better understand the mechanisms regulating myoplasmic Ca2+ during muscle activity, we have examined the effect of inorganic phosphate (P(i)) on the ryanodine receptor (RyR) Ca2+ release channel of the sarcoplasmic reticulum (SR). We report that P(i) at concentrations reached in exercising skeletal muscle (3-30 mM) produced a dose-dependent stimulation of ryanodine binding to skeletal muscle SR. Ryanodine binding was increased by 84% in the presence of 30 mM P(i) with half-maximal stimulation at 4 mM P(i). In contrast to its effect on skeletal muscle SR, ryanodine binding to cardiac muscle SR was not stimulated by P(i) (3-30 mM). Stimulation of ryanodine binding to skeletal muscle SR was maximal in the presence of micromolar Ca2+ and was associated with an increased affinity of the RyR for ryanodine (Kd = 204 nM in the absence, versus 107 nM in the presence of 10 mM P(i)). P(i) (10 mM) also increased the rate of Ca2+ release from 45Ca(2+)-filled skeletal muscle SR vesicles by 50% in the presence of micromolar Ca2+. Conversely, arsenate and sulfate (10 mM) had no effect on either ryanodine binding or Ca(2+)-induced Ca2+ release, demonstrating the specificity of the P(i) effect. Single-channel recordings of purified skeletal muscle SR RyR incorporated into planar lipid bilayers showed that addition of 10 mM P(i) to the cis chamber increased the open probability of the channel by 91%. These results demonstrate that concentrations of P(i) which occur in vivo during exercise significantly stimulate the in vitro activity of the skeletal muscle RyR Ca2+ release channel.

Animals↗
PubMed1994

Ion selectivity of porcine skeletal muscle Ca2+ release channels is unaffected by the Arg615 to Cys615 mutation.

The Arg615 to Cys615 mutation of the sarcoplasmic reticulum (SR) Ca2+ release channel of malignant hyperthermia susceptible (MHS) pigs results in a decreased sensitivity of the channel to inhibitory Ca2+ concentrations. To investigate whether this mutation also affects the ion selectivity filter of the channel, the monovalent cation conductances and ion permeability ratios of single Ca2+ release channels incorporated into planar lipid bilayers were compared. Monovalent cation conductances in symmetrical solutions were: Li+, 183 pS +/- 3 (n = 21); Na+, 474 pS +/- 6 (n = 29); K+, 771 pS +/- 7 (n = 29); Rb+, 502 pS +/- 10 (n = 22); and Cs+, 527 pS +/- 5 (n = 16). The single-channel conductances of MHS and normal Ca2+ release channel were not significantly different for any of the monovalent cations tested. Permeability ratios measured under biionic conditions had the permeability sequence Ca2+ >> Li+ > Na+ > K+ > or Rb+ > Cs+, with no significant difference noted between MHS and normal channels. This systematic examination of the conduction properties of the pig skeletal muscle Ca2+ release channel indicated a higher Ca2+ selectivity (PCa2+:Pk+ approximately 15.5) than the sixfold Ca2+ selectivity previously reported for rabbit skeletal (Smith et al., 1988) or sheep cardiac muscle (Tinker et al., 1992) Ca2+ release channels. These results also indicate that although Ca2+ regulation of Ca2+ release channel activity is altered, the Arg615 to Cys615 mutation of the porcine Ca2+ release channel does not affect the conductance or ion selectivity properties of the channel.

Animals↗
PubMed1994

Volatile anesthetics inhibit dihydropyridine binding to malignant hyperthermia-susceptible and normal pig skeletal muscle membranes.

BACKGROUND: Surface membrane dihydropyridine receptor Ca2+ channels may play a role in the response of malignant hyperthermia-susceptible skeletal muscle to volatile anesthetics. METHODS: We determined the effect of halothane, enflurane, and isoflurane on the binding of the Ca2+ channel blocker PN200-110 to skeletal muscle membranes isolated from malignant hyperthermia-susceptible and normal pigs. RESULTS: In the presence of 0.4 mM halothane, the maximal [3H]PN200-110 binding to both normal and malignant hyperthermia membranes was reduced by 37-43% (P < 0.05). There was no difference in the equilibrium constant for the halothane-dependent inhibition of [3H]PN200-110 binding to these two types of membranes. There also was no significant difference among halothane, enflurane, or isoflurane in their ability to inhibit [3H]PN200-110 binding to either normal or malignant hyperthermia membranes. CONCLUSIONS: Volatile anesthetics inhibit the binding of PN200-110 to skeletal muscle membranes by decreasing the number of functionally active dihydropyridine receptor proteins. This inhibition is similar for membranes isolated from both normal and malignant hyperthermia-susceptible muscle, thus providing no evidence for a halothane-induced functional defect in this protein in malignant hyperthermia-susceptible muscle. However, the results of this study also indicate that the mechanism by which volatile anesthetics decrease surface membrane Ca2+ currents in skeletal muscle is by reducing the number of functional dihydropyridine receptor Ca2+ channels.

Anesthetics↗
PubMed1994

Anions that potentiate excitation-contraction coupling may mimic effect of phosphate on Ca2+ release channel.

Perchlorate is one of a group of inorganic anions that potentiate excitation-contraction coupling in skeletal muscle. We have compared the effect of perchlorate on the sarcoplasmic reticulum (SR) Ca(2+)-release channel with the effect of inorganic phosphate (Pi), an anion which accumulates in skeletal muscle during exercise. Perchlorate and Pi (10-20 mM) stimulated Ca2+ release from SR vesicles 2- to 3-fold, respectively, and increased ryanodine binding to SR vesicles 1.5-fold. Stimulation of SR Ca(2+)-release channel activity by both perchlorate and Pi was maximal in the presence of micromolar Ca2+ and was associated with an increased affinity of the channel for ryanodine. Other anions known to potentiate muscle contraction (thiocyanate, iodide, and nitrate) also stimulated skeletal muscle SR Ca2+ release and ryanodine binding, as did the Pi analogue vanadate. However, none of the inorganic anions examined altered ryanodine binding to cardiac muscle SR. These results confirm that the SR Ca(2+)-release channel may be a primary site at which perchlorate and other potentiating anions affect skeletal muscle excitation-contraction coupling. In addition, these results demonstrate that the action of these anions on the SR Ca(2+)-release channel resembles that of Pi, a potential endogenous regulator of this channel.

Animals↗
PubMed1994

Skeletal muscle junctional membrane protein content in pigs with different ryanodine receptor genotypes.

The content of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase, transverse tubule dihydropyridine receptor (DHPR), and SR ryanodine receptor (RyR) was determined in muscle of pigs homozygous for the normal RyR allele and homozygous or heterozygous for the malignant hyperthermia-susceptible (MHS) RyR allele. Total muscle membranes isolated from 1-day-old pigs of the three different genotypes did not differ in the content of any of these proteins. However, at 28 days of age, crude membranes and total muscle homogenates from homozygous MHS pigs exhibited only 61-81% of the [3H]PN 200-110 or [3H]ryanodine binding of identical preparations isolated from normal pigs; these MHS membranes also contained only 50% of the normal content of each of the DHPR subunits. The crude membranes and muscle homogenates from heterozygous pigs were intermediate to both types of homozygotes in terms of [3H]PN 200-110 binding, [3H]ryanodine binding, and the content of the DHPR subunits. However, membrane preparations enriched in triadic junctional proteins isolated from 3- to 4-mo-old pigs of the three different genotypes did not differ in their [3H]PN 200-110 binding, [3H]ryanodine binding, or Ca(2+)-ATPase activities. We conclude that, although the stoichiometry of the RyR to DHPR is not altered, the presence of the MHS RyR allele during muscle development results in a decreased relative content of these two proteins. This is probably due to a lower junctional membrane content and may be an important ultrastructural consequence of the altered sarcoplasmic Ca2+ regulation in MHS muscle.

Animals↗
PubMed1994

Caffeine stimulation of malignant hyperthermia-susceptible sarcoplasmic reticulum Ca2+ release channel.

The altered caffeine sensitivity of malignant hyperthermia-susceptible (MHS) muscle contracture is one basis of the diagnostic test for this syndrome. To determine whether the Arg615-to-Cys615 mutation of the porcine sarcoplasmic reticulum (SR) Ca2+ release channel is directly responsible for this altered caffeine sensitivity, the single-channel kinetics of purified MHS and normal pig Ca2+ release channels were examined. Initial studies demonstrated that decreasing the pH of the medium in either the cis- or trans-chamber decreased the Ca2+ release channel percent open time (Po). The half-inhibitory pH of MHS channels (6.86 +/- 0.04, n = 17) was significantly different from that of normal channels (7.08 +/- 0.07, n = 14). At pH 7.4, in either 7 or 0.12 microM Ca2+, MHS channel Po was not significantly different from that of normal channels over the range 0-10 mM caffeine. Although at pH 6.8 in 7 microM Ca2+ MHS channel Po was greater than that of normal channels over the range 0-20 mM caffeine, the difference could be eliminated by dividing each mean MHS Po by a scaling factor of 3.2. Thus the MHS Ca2+ release channel mutation does not appear to be directly responsible for the altered caffeine sensitivity of MHS pig muscle contracture. Rather, this altered caffeine sensitivity may result from an altered resting myoplasmic Ca2+ concentration or the altered pH and Ca2+ sensitivity of Ca2+ release channel Po of MHS muscle.

Animals↗
PubMed1994

Cell-to-cell communication in a differentiating ovine lens culture system.

PURPOSE: This study was performed to determine whether the junctions between both the epithelial and the differentiating fiber-like cells of ovine lens cultures, like gap junctions in other tissues, exhibit cell-to-cell communication that is inhibited by n-octanol, and to determine whether lens connexins and the fiber cell membrane proteins MP20 and MP26 are expressed by these ovine lens cell cultures. METHODS: Cells were injected with Lucifer yellow CH to measure cell-to-cell communication. Antibodies to connexin-related lens membrane protein MP70, connexin 43 (Cx43), and connexin 46 (Cx46) and to membrane proteins MP20 and MP26 were used to immunofluorescently label lens cultures and probe Western blots of membranes isolated from lens cultures. RESULTS: Both epithelial cells and differentiating clear cells exhibited cell-to-cell transfer of Lucifer yellow that was inhibited by n-octanol. Although a Cx43 antibody immunofluorescently labeled small plaques between the epithelial cells, an MP70 antibody labeled large plaques as well as small punctate areas of the differentiating fiber-like cells. It is interesting that Cx43 and MP70 were frequently present in the same plaques at cell interfaces between epithelial cells as well as some of the larger plaques on the differentiating fiber-like cells. Cx46 and MP70 antibodies labeled the same plaques in membranes of differentiating fiber-like cells and late-stage epithelial cells. The electrophoretic mobility of all three connexin proteins was modified after treatment with alkaline phosphatase. Immunohistochemical staining of these differentiating regions and Western immunoblotting of purified membranes derived from differentiated cultures also showed the presence of MP20 and MP26. CONCLUSIONS: The different cell types in the ovine lens culture exhibit gap junction-mediated cell-to-cell communication that is likely effected by one or more of the connexin proteins.

1-Octanol↗
PubMed1993

Protein and lipid rotational dynamics in cardiac and skeletal sarcoplasmic reticulum detected by EPR and phosphorescence anisotropy.

We have used time-resolved phosphorescence anisotropy and electron paramagnetic resonance (EPR) spectroscopy to detect the rotational dynamics of the Ca-ATPase and its associated lipids in dog cardiac sarcoplasmic reticulum (DCSR), in comparison with rabbit skeletal SR (RSSR), in order to obtain insight into the physical bases for different activities and regulation in the two systems. Protein rotational motions were studied with time-resolved phosphorescence anisotropy (TPA) of erythrosin isothiocyanate (ERITC) and saturation-transfer EPR (ST-EPR) of a maleimide spin-label (MSL). Both labels were attached selectively and rigidly to the Ca-ATPase. Lipid rotational motions were studied with conventional EPR of stearic acid spin-labels. As in previous studies on RSSR, the phosphorescence anisotropy decays of both preparations at 4 degrees C were multiexponential, due to the presence of different oligomeric species. The rotational correlation times for the different rotating species were similar for the two preparations, but the total decay amplitude was substantially less for cardiac SR, indicating that more of the Ca-ATPase molecules are in large aggregates in DCSR. ST-EPR spectra confirmed that the Ca-ATPase is less rotationally mobile in DCSR than in RSSR. Lipid probe mobility and fatty acid composition were very similar in the two preparations, indicating that the large differences observed in protein mobility are not due to differences in lipid fluidity. We conclude that the higher restriction in protein mobility observed by both ST-EPR and TPA is due to more extensive protein-protein interactions in DCSR than in RSSR.

Animals↗
PubMed1993

Localization and functional role of the calmodulin-binding domain of phospholamban in cardiac sarcoplasmic reticulum vesicles.

Limited proteolysis and affinity-labeling techniques have been used to localize the calmodulin-binding domain of phospholamban, the major substrate for both cAMP- and calmodulin-dependent protein kinases in cardiac sarcoplasmic reticulum (SR). SR vesicles, treated with increasing concentrations of trypsin (likely hydrolyzing at Arg-25 in the cytoplasmic region of phospholamban), exhibited a subsequent loss of both cAMP- and calmodulin-dependent phosphorylation, as well as calmodulin affinity-labeling of phospholamban. When SR vesicles were treated with increasing concentrations of chymotrypsin (which likely cleaves at Tyr-6 of phospholamban) there was no effect on the cAMP-dependent phosphorylation of phospholamban. However, similar concentrations of chymotrypsin resulted in a loss of both calmodulin affinity-labeling and calmodulin-dependent phosphorylation of phospholamban (at Thr-17). When SR vesicles were treated with increasing concentrations of Endoproteinase Lys-C (which hydrolyzes phospholamban at Lys-3) both the calmodulin affinity-labeling and the calmodulin-dependent, but not the cAMP-dependent, phosphorylation of phospholamban were inhibited. These data were complemented by 1H-NMR studies on the complex formed by calmodulin and a phospholamban peptide. These data suggest that binding of calmodulin to phospholamban may be an essential intermediate step in the calmodulin-dependent phosphorylation of phospholamban.

Affinity Labels↗
PubMed1993

Phosphorylation of the porcine skeletal and cardiac muscle sarcoplasmic reticulum ryanodine receptor.

Porcine skeletal and cardiac muscle sarcoplasmic reticulum (SR) vesicle fractions enriched in the ryanodine receptor were phosphorylated in the presence of [gamma-32P]MgATP and either exogenous cAMP-dependent protein kinase (cAMP-PK), or Ca2+ plus calmodulin. Phosphorylation of the cardiac muscle ryanodine receptor in the presence of either cAMP-PK or calmodulin (6.4 and 10.6 pmol Pi/mg SR respectively) was approximately equal to or twice the [3H]ryanodine binding activity of this preparation (5.2 pmol/mg). Furthermore, cardiac muscle ryanodine receptor Pi incorporation catalyzed by cAMP-PK and calmodulin was approximately additive. In skeletal muscle SR, however, the level of cAMP-PK or calmodulin catalyzed phosphorylation of the intact ryanodine receptor (0.2 or 2.9 pmol Pi/mg SR, respectively) was much less than the [3H]ryanodine binding activity of this fraction (11.6 pmol/mg). Furthermore, Pi incorporation into the intact skeletal muscle ryanodine receptor was 3-8-fold less than that incorporated into a component of slightly lower M(r). Although this latter component comigrated with an immunoreactive fragment of the ryanodine receptor on polyacrylamide gels, it did not appear to be derived from the ryanodine receptor. We conclude that the significant phosphorylation of the cardiac muscle SR ryanodine receptor indicates a likely physiological role for protein kinase-mediated regulation of this Ca(2+)-channel. In contrast, the minimal phosphorylation of the skeletal muscle SR ryanodine receptor indicates that such a role of protein kinases is unlikely in this tissue.

Animals↗
PubMed1993

Cloning and expression of a major rat lens membrane protein, MP20.

The lens contains a major membrane protein with an apparent molecular weight of 18 kDa and which has been referred to as MP18 [Louis et al. (1989). J. Biol. Chem. 264, 19967-73]. We have cloned a rat MP20 cDNA that appears to be identical to this previously described protein based on sequence homology. The predicted protein sequence has characteristics typical of an integral membrane protein and a molecular mass of 19637. The transcripts for MP20 appear to be lens specific as indicated by RNA analysis; Southern blot analysis indicates that MP20 is coded for by a single gene with possibly a single intron in its coding sequence. The expression of transcripts for several lens membrane proteins (MP20, MP26 and alpha 3-gap junctions) was compared in 1.5 month bovine fetal and 4-6 month post-natal calf lenses. The transcript levels for these proteins were more abundant in fetal lenses than in calf lenses indicating a possible developmental regulation of the transcripts for these three lens-specific membrane proteins. The MP20 cDNA was expressed in a heterologous mammalian cell culture system in which the majority of the protein was integrated into membranous structures localized near the nucleus; there was little incorporation of MP20 into the cell plasma membrane as detected by immunofluorescence. This system should prove useful for both the isolation and purification of MP20, and will enable study of its properties under defined conditions.

Amino Acid Sequence↗
PubMed1993

Reconstitution of abnormalities in the malignant hyperthermia-susceptible pig ryanodine receptor.

Malignant hyperthermia-susceptible (MHS) pigs homozygous for the Cys615 ryanodine receptor allele demonstrate altered sarcoplasmic reticulum (SR) ryanodine binding and Ca2+ release channel regulatory properties when compared with normal pigs homozygous for the Arg615 allele. While solubilized in 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, the purified MHS and normal ryanodine receptors had a similar dissociation constant (Kd) for ryanodine, maximum binding, and Ca2+ concentration for half-maximal stimulation and inhibition of ryanodine binding (Ca2+(0.5)); however, after reconstitution into proteoliposomes, the purified MHS and normal receptors had Kd values for ryanodine of 75 and 150 nM, respectively, which were significantly different. The purified MHS and normal porcine ryanodine receptors also had similar single-channel Cs+ conductance, optimal cis-Ca2+ for channel opening, and cis-Ca2+(0.5) for channel activation. Significantly, at inactivating levels of cis-Ca2+ (> 0.1 mM), MHS channels had a greater open probability, a higher cis-Ca2+(0.5) for inhibition of channel opening (250 vs. 75 microM for MHS and normal, respectively), longer mean open times, and shorter mean closed times than did normal channels. We conclude that the mutation at residue 615 causes a detectable alteration in ryanodine receptor/Ca2+ channel activity and thus may represent the primary defect responsible for the altered SR Ca2+ regulation characteristic of MHS porcine muscle.

Animals↗
PubMed1993

Perchlorate potentiation of excitation-contraction coupling in mammalian skeletal muscles.

The action of perchlorate (ClO4-), an agonist of the voltage sensor in excitation-contraction (EC) coupling, has been examined using bundles of intact muscle cells, isolated membrane vesicles [sarcoplasmic reticulum (SR) and transverse tubule (TT)], and cultured myotubes. The effect of ClO4- on mechanical parameters was investigated in isolated murine limb muscles. The presence of ClO4- (5 or 10 mM) greatly increased twitch tension ( > 250%), slightly enhanced tetanic tension, and increased K contracture tension. K contracture thresholds of extensor digitorum longus (EDL, 40 mM K+) and soleus (30 mM K+) muscles were not altered by ClO4-. However, in whole cell patch clamp studies of mouse myotubes, contractile activation was shifted by approximately -10 mV by 10 mM ClO4-. To further define the site of alteration of EC coupling by ClO4-, studies were conducted with isolated porcine SR and TT vesicles and with cultured mouse myotubes. The rate constant of Ca-induced 45Ca release from SR vesicles was significantly increased by ClO4-. However, neither the affinity nor level of [3H]PN200-110 binding to TT vesicles was significantly affected by ClO4- concentrations that increased twitch tension. Furthermore, slow plasmalemmal Ca currents of myotubes recorded in the whole cell patch-clamp mode were enhanced by 10 mM ClO4-, and the current-voltage relationship was shifted approximately -7mV. Thus, in enhancing EC coupling in mammalian muscle, ClO4- may act at multiple sites including the SR Ca release channel and the TT Ca channel-voltage sensor.

Animals↗
PubMed1993

Relative accuracy of the halothane challenge test and a molecular genetic test in detecting the gene for porcine stress syndrome.

Pietrain swine homozygous for the hal gene (n) associated with porcine stress syndrome (PSS) and a Pietrain-derivative breed, Near Pietrain (NP), with a frequency of .31 for n, were mated to produce reciprocal F1, F2, and purebred NP litters. The halothane challenge test was performed on all 40 parents and 240 progeny to predict their hal genotype and PSS susceptibility. The DNA-based assay for a C to T mutation at base pair 1,843 of the skeletal muscle ryanodine receptor (ryr1) cDNA, which is very highly correlated with PSS, was also determined for these animals. The predicted hal genotypes observed in the progeny differed significantly from the expected Mendelian ratios, and the halothane challenge test consistently overestimated the n/n hal genotype. However, the ryr1 genotypes observed in the progeny did not differ significantly from the expected Mendelian ratios, and this DNA-based assay apparently misidentified only one of the 40 parents. The results of this study indicate that the assay for the ryr1 mutation more accurately predicts both the homozygous and heterozygous forms of the PSS gene than does the halothane challenge test.

Animals↗