Porcine Stress Syndrome Research Articles

The use of in vivo magnetic resonance imaging and spectroscopy to study porcine stress syndrome in young, halothane-susceptible pigs: Preliminary results

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) studies on young, halothane-susceptible pigs (4 wk old) are reported. The proton image shows distinct changes in shape of the hindleg muscle as the stress syndrome develops. Simultaneous evaluations of the "free water" content by volume selective spectroscopy shows an increase of about 40% after onset of the syndrome. The in vivo phosphorus spectrum obtained as a function of time before and after the stress event clearly shows a drop in phosphocreatine with simultaneous increase in inorganic phosphate. A drop in pH can also be detected after some delay. This study illustrates the broad applicability of noninvasive MRI and MRS in investigations of porcine stress syndrome. Key words: PSS, porcine stress syndrome, MRI, magnetic resonance imaging, 31P MRS, phosphorus-31 magnetic resonance spectroscopy

Use of a DNA-based test for the mutation associated with porcine stress syndrome (malignant hyperthermia) in 10,000 breeding swine

Summary: To test the hypothesis that the mutation associated with porcine stress syndrome (pss; malignant hyperthermia) was present in a large proportion of North American and English swine, a simple and rapid laboratory protocol was used for cost-effective, large-scale diagnosis of susceptibility to pss. This pss test was applied to 10,245 breeding swine of various breeds from 129 farms in the United States, Canada, and England. Approximately 1 of 5 swine was a heterozygous carrier of the pss mutation, with approximately 1% being homozygotes. Prevalence of the pss mutation was 97% for 58 Pietrain, 35% for 1,962 Landrace, 15% for 718 Duroc, 19% for 720 Large White, 14% for 496 Hampshire, 19% for 1,727 Yorkshire, and 16% for 3,446 crossbred swine. The pss gene frequencies for these breeds were 0.72, 0.19, 0.08, 0.10, 0.07, 0.10, and 0.09, respectively. In addition to these breeds, we have identified the pss mutation in Poland China and Berkshire breeds. These gene frequencies were 30 to 75% lower in Canadian swine than in US swine, with the exception of Yorkshires, for which the gene frequency was threefold higher in Canadian swine. English swine were similarly, or more so, affected than were US swine. Accuracy was estimated at > 99%. Cost to perform the test was < $20/ animal. Depending on the perceived net balance of deleterious and beneficial effects of the mutation, the pss test could be used to eradicate the pss mutation from herds, or for controlled expression of the mutation.

In vivo 31P NMR spectroscopy studies of halothane induced porcine stress syndrome. No effect of C-phenyl N-tert-butyl nitrone (PBN).

Porcine stress syndrome (PSS) which is an example of malignant hyperthermia (MH) in swine has previously been attributed to oxidative stress primarily due to an inherited antioxidant abnormality in MH susceptible (MHS) animals. C-phenyl-N-tert-butyl nitrone (PBN), a free radical spin trap, was selected to investigate whether free radicals are involved in MH. If free radicals cause the MH stress attack, then PBN should alter the time required for the onset of the stress attack, or perhaps protect the animal from experiencing the stress attack. In vivo phosphorus-31 (31P) magnetic resonance spectroscopy (MRS) was used to monitor metabolism in three to four week old normal and MHS piglets administered halothane as the stress challenge. Malignant hyperthermia was not reproducibly induced by halothane anesthesia. For those animals which did develop MH a dramatic fall in the level of PCr and a rise in the level of Pi was detected by 31P MRS. Intravenous administration of PBN prior to halothane exposure had no effect on the number of animals experiencing the stress attack. PBN does not appear to prevent, delay or reverse the onset of halothane-induced MH in three to four week old MHS piglets. The primary events leading to the MH syndrome do not appear to be influenced by the intervention of the type of free radicals normally trapped by PBN.

Effects of meat quality and storage on the breakdown of adenosine triphosphate in muscle from swine

The quality of pork is dependent on animal genotype, pre-slaughter handling, processing, maturation, and storage. We investigated the pattern of adenosine triphosphate (ATP) breakdown as it related to these factors. Samples of the thoracis portion of the longissimus dorsi muscle were obtained from 19 randomly selected German Landrace-Pietrain crossbreed swine. Based on their 40 min post-mortem pH and electrical conductances, three groups were classified: (1) PSE meat, pH ≤ 5·6 and conductance >10 mS (n = 7); (2) intermediate quality, pH 5·6–6·0 and conductance between 4 and 10 mS (n = 5); and (3) normal quality, pH ≥ 6·0 and conductance < mS (n = 7). Hence, the animals investigated included those susceptible to malignant hyperthermia (porcine stress-syndrome). Twenty-four hours post mortem samples were evaluated for the following parameters: ATP metabolism, pH values, electrical conductance, meat colour, water binding capacity, shear force and general composition (i.e. total protein, fat, mineral and water contents). Muscle composition was the same in each group, but for the other parameters there were clear differences. Following different storage periods and conditions (1 or 5 days at 4°C and 27 days at −18°C), the degree of ATP metabolism as well as general meat quality (i.e. including sensory evaluation) were reassessed. Samples from the pre-selected groups became less discernible following prolonged storage. In all animals, the pattern of ATP breakdown was similar, the major metabolites including inosine monophosphate, hypoxanthine, adenosine monophosphate, and inosine. The degree of breakdown was dependent on the duration and temperature of storage, but not on animal type. The muscular samples for the intermediate and normal muscle groups, which were stored for 27 days at −18°C, were given the highest sensory evaluation scores. The simple HPLC measurement of ATP metabolism was considered as a useful means to assess appropriate storage.

Effect of porcine stress syndrome on the solubility and degradation of myofibrillar/cytoskeletal proteins.

This study examined the effect of stress classification (stress-positive, stress-carrier, stress-negative) of pigs on selected properties of postmortem muscle, including protein solubility and degradation of proteins such as titin. Longissimus muscle samples were removed 45 min postslaughter, divided into samples, and stored at 0 to 2 degrees C for analysis at 0, 1, 3, 5, and 7 d postmortem. Whole-muscle samples (homogenates) and purified myofibrils were prepared from each sample for analysis by SDS-PAGE. A portion of each muscle sample also was extracted 1) with a low-ionic-strength solution to obtain a sarcoplasmic protein fraction and 2) with two different high-ionic-strength solutions to obtain a myofibrillar/cytoskeletal protein fraction for measurement of protein solubility and for analysis of extracts by SDS-PAGE. No significant differences were observed between muscle from stress-negative and stress-carrier animals in this study. Sarcoplasmic (P less than .05) and myofibrillar/cytoskeletal (P less than .01) protein solubility was lower in muscle samples from stress-positive animals than in muscle samples from stress-carrier and stress-negative animals at all postmortem times studied. The high molecular weight protein titin was degraded more slowly postmortem in muscle from stress-positive than in muscle from stress-negative animals, as observed by SDS-PAGE analysis of whole-muscle samples (homogenates) an myofibrils. The combination of lowered protein solubility and reduced rate of postmortem degradation of structural proteins such as titin may explain, at least in part, the reduced quality and protein functionality of muscle from stress-positive pigs.

Biotechnology transfer: A pig breeding company perspective

Abstract Development in 1991 of a test for the mutant gene responsible for porcine stress syndrome is the first example of biotechnology transfer to the pig breeding industry since artificial insemination in the 1950s. Technology has been transferred from the fields of statistics, computer science, electronics and human medicine to pig breeders over the past two decades. Cryopreservation of sperm and eggs, a practical method for sexing semen and non‐surgical embryo transfer procedures are needed for the full potential of artificial insemination and embryo transfer to be realized. Gene mapping may reveal presently unknown genes of major importance for selection and (or) transgenic manipulation. Transgenic pigs have been produced successfully and the greatest challenge will be to identify and isolate genes having large effects, either on traits included in current selection programs or on novel traits, specific metabolic processes affecting meat quality, disease resistance, structural soundness, pig behavio...

Porcine stress syndrome: An animal model for the neuroleptic malignant syndrome?

The porcine stress syndrome is a genetic disorder of swine which, like neuroleptic malignant syndrome, is characterized by hyperthermia, muscle rigidity, and autonomic dysfunction. We investigated the porcine stress syndrome as a possible animal model for neuroleptic malignant syndrome in two ways. First, we administered haloperidol and lithium carbonate, alone and in combination, to susceptible and resistant swine. Second, we attempted to prevent the syndrome by pretreating animals with bromocriptine. Porcine stress syndrome was induced in 2 of 3 susceptible and 1 of 3 resistant swine by combined treatment with lithium and haloperidol, but was not triggered by treatment with lithium or haloperidol alone. Pretreatment with bromocriptine conferred no protection against the syndrome.

Canine stress syndrome/malignant hyperthermia susceptibility: calcium-homeostasis defect in muscle and lymphocytes

This study provides the first comprehensive characterisation of the calcium (Ca) homeostasis defects found in muscle and lymphocytes of a malignant hyperthermia (MH)-susceptible dog. Novel findings regarding this dog are reported, compared to controls. First, a canine stress syndrome occurs, analogous to the porcine stress syndrome; susceptibility can be identified by exercise challenge testing. Secondly, caffeine causes Ca release from muscle sarcoplasmic reticulum in a greater amount and at a greater rate. Thirdly, there is a compensatory increase in Ca sequestration by sarcoplasmic reticulum. Fourthly, lymphocytes have lower cytosolic-free Ca and a greater ability to prevent Ca increase. Halothane increases Ca by a greater amount and rate. Fifthly, muscle is more resistant to the contracture-producing effects of caffeine, as occurs in the non-rigid variant of MH susceptibility in man. This resistance, despite increased caffeine-induced release through the Ca channel, may be attributable to increased Ca sequestration by sarcoplasmic reticulum. Finally, erythrocyte osmotic fragility and creatine kinase tests fail to distinguish between the MH-susceptible dog and controls.

Intravenous catheterisation of conventional pigs without application of antimicrobial agents.

In six experiments 43 castrated male conventional pigs weighing 25-41 kg were catheterised by inserting a cannula via the jugular vein into the cranal caval vein. The catheters were taped to the spinal neck region where the tap stops were located. Antimicrobial agents were not applied. One pig died 32 hour after surgery from Porcine Stress Syndrome. The catheters remained patent for at least nine days in 38 of the remaining 42 animals (90%). In two animals the catheter by mistake was not inserted into the jugular vein. Two animals got catheters with a one-way blockage four days after surgery. In these animals autopsy revealed thrombosis and phlebitis of the occluded vein and a valve-like thrombus at the tip of the catheters. In seven of the 43 pigs the effects of anaesthesia, surgery and catherisation were followed using rectal temperature and haematological and some blood biochemical parameters for nine days after the surgery. It is concluded that this catheterisation technique, without application of antimicrobial agents, can be used well for experimental infections and pharmacokinetic studies.

Vitamin E and vitamin C supplementation and stress-susceptible pigs: Effects of halothane and pharmacologically induced muscle contractions

Stress-susceptible pigs were offered selenium-adequate diets containing either 20 IU vitamin E kg −1 or 260 IU vitamin E kg −1 and 500 mg vitamin C kg −1. Performance characteristics and carcase quality were not different between the two groups. During the feeding trial the pigs were exposed to halothane and “myostress”. Plasma pyruvate kinase, creatine kinase and thiobarbituric-acid reactive substances were used as indicators of damage to cell membranes. Subsequent to halothane intubation and to “myostress” injection antioxidant supplementation had a highly significant protective effect on cell membrane integrity. These results are compatible with previous suggestions that the porcine stress syndrome reflects an antioxidant abnormality which may be ameliorated by increasing the antioxidant content of the ration.

Effects of pH and ATP Concentrations on the Heat Contracture of Glycerinated Single Fibers of Rabbit Psoas Muscle

ABSTRACTThe occurrence of heat contracture of glycerinated single fiber of rabbit psoas muscle was investigated in relaxing solutions with varying pH values and ATP concentrations. The threshold temperature for inducing heat contracture of single muscle fibers in relaxing solutions decreases with increasing pH values and decreasing ATP concentrations. There seems to be a relationship between heat contracture of muscle fibers and the tremor of skeletal muscle of porcine stress syndrome. Also, there seems to be a relationship between the heat contracture and alkaline rigor development.

Blood catecholamines in response to handling in normal and stress-susceptible swine

Venous blood was collected from porcine stress syndrome (PSS)-susceptible ( n=23) and -resistant ( n=55) 3-month-old Landrace pigs. Susceptibility to PSS was determined by the halothane test and resistance was confirmed by the halothane succinylcholine test, which were performed after the blood sampling procedure. Plasma levels of norepinephrine and epinephrine (pg ml −1) were determined by high performance liquid chromatography (HPLC) with electrochemical detection. Norepinephrine levels ( X± SEM ) were significantly higher in the PSS-susceptible pigs (993±109) than in their PSS-resistant (573±41) counterparts. The levels of epinephrine on the other hand, were the same in both groups, 168±14 for the PSS-resistant group and 186±31 for the PSS-susceptible group. It was concluded that PSS-susceptible animals experience a significantly higher noradrenergic sympathetic response to handling stress associated with routine blood collection.

Réponses Contractiles Aux Catécholamines des Artères Rénale et Iliaque en Présence d'Halothane Chez le Porc Sensible à l'Hyperthermie Maligne

SummaryContractile response to catecholamines in the presence of halothane of renal and iliac arterial rings in pigs susceptible to malignant hyperthermiaDuring halothane induced reaction in pigs susceptible to porcine stress syndrome, and consequently to malignant hyperthermia an unstable blood pressure is characteristic. The objectives of this study were to evaluate the m vitro reactivity of renal and iliac arteries to catecholamines, in the presence of halothane, of pigs susceptible to malignant hyperthermia. Logarithmically increased concentrations of epinephrine and norepinephrine produced vascular contraction of a sigmoid type, in a dose‐dependent fashion. The presence of 5 % halothane moderately inhibited the catecholaminergic response of renal arterial rings of malignant hyperthermia susceptible animals as a non‐specific antagonist.

A review of the relationships of pH with physical aspects of pork quality

The pH 1-index, defined as the percent of carcasses with pH < 6·0 at 45 min post-mortem (p-m), gives some indication of the likely incidence of pale, soft, exudative (PSE) pork at 24 h or more p-m. However, there is considerable variation between nations in the subjective definition of PSE. Thus, pH data show that subjectively-defined PSE pork from one country might be regarded as normal pork in another country, and vice versa. The paleness of pork is inversely proportional to pH. The data from conventional monochromatic reflectance photometers are almost linearly related to pH whereas the data from the Goefo meter and fibre-optic (FO) probes follow curvilinear relationships which may be logarithmic. In the visible spectrum, correlations of FO reflectance with pH and muscle structure are strongest towards 700 nm. The relationship of pH with exudate (bag-drip) is biphasic with fluid losses increasing from pH 7 to about 6·1, then staying constant at lower pHs. This biphasic pattern is also seen in some, but not all, methods in which exudate is measured by applied pressure or in which myofibrillar water-holding capacity is measured by centrifugation. Electrical impedance and its primary determinants (resistance and capacitance in parallel) are directly proportional to pH but follow curvilinear relationships. There is at least some theoretical understanding of the relationship of pH with exudate, but much remains to be learnt about the causal relationships of pH with paleness or softness. Many of the older published studies in the field are marred by a failure to separate genetic causes of low-pH (porcine stress syndrome) from environmental causes (preslaughter handling, slaughter and refrigeration).

Platelet alterations in porcine stress syndrome.

Platelets in blood collected from pigs identified as normal (21) or stress susceptible (25) on the basis of their response to halothane challenge, were subjected to electron microscopic examination in order to test whether the ultrastructural features of stress susceptible pigs exhibit any deviation from those of normal. The most striking feature of the platelets from stress susceptible pigs was the extent of dilatation of the open canalicular system (OCS). The difference in platelet morphology between normal and stress susceptible pigs was consistent regardless of the anticoagulants used for blood collection indicating that the platelet alteration may be an inherent component of the porcine stress syndrome.

Of man and pigs: Is malignant hyperthermia a stress‐related disorder?

AbstractMalignant hyperthermia (MH) is a very rare but frequently fatal complication of anaesthesia. The identification of susceptible patients depends on a family history of anaesthetic difficulties, increased serum creatine kinase activity and the pharmacological assessment of a muscle biopsy. Dantrolene has been introduced recently as a specific therapeutic agent for MH. Detailed investigation of MH in pigs has drawn attention to the possible role of circulating catecholamines in initiating and potentiating the syndrome. Only certain breeds of pigs develop MH and these breeds are also susceptible to the occurrence of the porcine stress syndrome (PSS) and pale, soft, exudative pork (PSEP). There is increasing evidence that isolated cases of ‘awake MH’ can be triggered by excessive fatigue, emotional stress and high environmental temperatures. It is possible that in some MH‐susceptible families death may occur from ventricular arrhythmias in emotional stressful situations, possibly associated with an underlying cardiomyopathy.

Thermochemiluminescent assay of porcine, rat, and human erythrocytes for antioxidative deficiencies

The thermal induction of chemiluminescence of luminol-horseradish peroxidase-labeled erythrocytes from pigs, rats, and man was studied. The luminescent responses of rat, porcine, and human erythrocytes to heating were linear in respect to logs of counts per minute versus temperature. Landrace-Duroc crossbred pigs with a history of malignant hyperthermia (porcine stress syndrome) and Poland-China-miniature pigs inbred for malignant hyperthermia (MH) yielded erythrocytes with high-level thermochemiluminescence (TCL). Sprague-Dawley rat erythrocytes were intermediate in their production of TCL. Normal human and MH-resistant miniature swine erythrocytes produced low-level TCL. However, pretreatment of human erythrocytes with 1-chloro-2,4-dinitrobenzene (CDNB) resulted in high-level TCL. Furthermore, halothane enhanced the TCL of CDNB-treated human erythrocytes and Landrace-Duroc porcine erythrocytes that were not treated with CDNB. Red blood cells from pigs susceptible to the porcine stress syndrome demonstrated a TCL response very similar to CDNB-treated erythrocytes.

Further evidence on the inheritance of halothane reaction in pigs.

One thousand six hundred forty-one Pietrain, 163 Minnesota No. 1 and 158 Pietrain X Minnesota No. 1 crosses and their reciprocals were tested for porcine stress syndrome susceptibility using halothane gas between September 1975 and July 1981. The frequency of reactors in the Pietrain breed was 93.9%. Matings of reactor males to reactor females within the Pietrain breed resulted in 632 reactor and 14 nonreactor offspring. A boar, judged to be nonpenetrant on the basis of the halothane reaction of his parents and littermates, was shown by progeny test to be homozygous for the halothane allele. These data indicate that halothane sensitivity is due to a single autosomal recessive gene with a penetrance of about 98% and a frequency of .98 in this Pietrain herd. No halothane reactors were found in the 163 Minnesota No. 1 pigs tested. Only one Pietrain X Minnesota No. 1 gilt reacted positively to halothane and later, the same gilt produced both positive and negative offspring, indicating that she was most likely heterozygous. Blood group typing of 107 crossbred pigs provided insufficient information to predict accurately the halothane reaction, although some associations were observed between the A and H loci and halothane sensitivity. The time taken by Pietrain pigs to react to halothane was measured and recorded. Analysis of these data showed that progeny of some sires had significantly faster reaction times than others and that reaction time had decreased over the years. These results as well as other data presented here indicate the existence of certain modifier genes that influence halothane reaction.

Prediction of susceptibility to the porcine stress syndrome

An experiment designed to compare different predictors of porcine stress syndrome (PSS) was conducted. Animals were exposed to the anesthetic gas, halothane, and their reactions monitored to determine susceptibility or resistance to PSS. Two blood creatine phosphokinase (CPK) traits plus their logs10 were examined as predictors of PSS susceptibility. These were Sigma CPK, Antonik CPK, log Sigma CPK, and log Antonik CPK. The accuracy of these predictors varied from 87 percent to 91 percent in agreement with halothane-determined stress susceptibility. In addition, the relationship of PSS and blood types systems (AO,H) were studied. Two blood types, (+,-/-) and (-,+/+), were consistently stress susceptible while three blood types, (+,a/a), (+,a/c), and (+,c/-), were consistently stress resistant. However, one blood type (+,a/-) contained both stress-susceptible and stress-resistant individuals.

Performance Characteristics of Crossbred Pigs with Graded Percentages of Pietrain

Swine from two inbred lines, Minnesota No. 1 (F = .52) and Pietrain (F = .08), were used to produce 118 pigs representing graded percentages of Pietrain at 0, 25, 50, 62.5, 75, 87.5 and 100%. Incidence of the Porcine Stress Syndrome (PSS) was determined by halothane screening at about 100 d of age. Muscle quality and carcass leanness were determined at 90 kg live weight. Results of our study showed that halothane-identified PSS pigs can be used in crossing programs to increase lean meat production without loss in performance, if the females were not PSS-susceptible. Carcass length, mean backfat thickness, color score and average daily gain declined in performance, relative to Minnesota No. 1 pigs, as percentages of Pietrain increased. Linear increases were noted for loin weight, ham weight, loin eye area and ham and loin percentage with increased Pietrain percentage. PSS was absent in pigs that had up to and including 50% Pietrain. Heterosis was observed for carcass length (P<.01), mean backfat thickness (P<.05), dressing percentage (P<.05) and lean gain/kg of feed (P<.05). Differences for reciprocal differences were observed for loin weight (P<.05), ham and loin percentage (P<.05) and lean gain/kg of feed (P<.05). The advantage was for pigs that had Pietrain mothers.