Regional brain monoamine concentrations and their alterations in bovine hypomagnesaemic tetany experimentally induced by a magnesium-deficient diet

Monoamines are important brain neurotransmitters. An investigation was carried out to determine if hypomagnesaemic tetany was associated with alterations in regional brain monoamine concentrations in bovines. The results, established in cows with normal magnesium status, demonstrated that regional differences existed in the distribution and concentration of brain monoamines in the adult bovine, which were similar to those in other species. In magnesium-deficient cows, severe hypomagnesaemia and lowered cerebrospinal fluid (CSF) magnesium concentrations were associated with significant alterations in monoamine concentrations in some brain regions. Alterations in 3,4-dihydroxyphenylalanine (DOPA) and dihydroxyphenylacetic acid (DOPAC) concentrations in the corpus striatum, and dopamine (DA) in the cerebral cortex and cerebellum were recorded. These regions play an important role in both voluntary and involuntary motor function, and therefore these alterations may play a role in the aetiology of hypomagnesaemic tetany. However, there was no significant change in DA concentrations in the corpus striatum (the main dopaminergic region in the brain) associated with hypomagnesaemia. In addition, a significantly lower norepinephrine (NE) concentration in the corpus striatum of hypomagnesaemic animals was also recorded. Norephinephrine is generally excitatory and therefore lowered NE concentrations would be expected to result in depression rather than stimulation of motor function.     

Comparison of brain PrPd distribution in ovine BSE and scrapie

Scrapie and bovine spongiform encephalopathy (BSE) are both prion diseases affecting ruminants, and these diseases do not share the same public health concerns. Surveillance of the BSE agent in small ruminants has been a great challenge, and the recent identification of diverse prion diseases in ruminants has led to the development of new methods for strain typing. In our study, using immunohistochemistry (IHC), we assessed the distribution of PrP(d) in the brains of 2 experimentally BSE-infected sheep with the ARQ/ARQ genotype. Distribution of PrP(d) in the brain, from the spinal cord to the frontal cortex, was remarkably similar in the 2 sheep despite different inoculation routes and incubation periods. Comparatively, overall PrP(d) brain distribution, evaluated by IHC, in 19 scrapie cases with the ARQ/ARQ, ARQ/VRQ, and VRQ/VRQ genotypes, in some cases showed similarities to the experimentally BSE-infected sheep. There was no exclusive neuroanatomical site with a characteristic and specific PrP(d) type of accumulation induced by the BSE agent. However, a detailed analysis of the topography, types, and intensity of PrP(d) deposits in the frontal cortex, striatum, piriform cortex, hippocampus, mesencephalon, and cerebellum allowed the BSE-affected sheep group to be distinguished from the 19 scrapie cases analyzed in our study. These results strengthen and emphasize the potential interest of PrP(d) brain mapping to help in identifying prion strains in small ruminants.     

Different gradients for neurotransmitter metabolites and protein in horse cerebrospinal fluid

The serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA) and the dopamine metabolite, homovanillic acid (HVA) in the cerebrospinal fluid (CSF) of seven clinically normal horses were evaluated with reverse phase high pressure liquid chromatography and electrochemical detection. Comparisons of the neurotransmitter metabolite concentrations were made on CSF collected simultaneously from the atlanto-occipital and lumbosacral regions. There were significantly higher amounts of 5-HIAA and HVA in atlanto-occipital CSF than in lumbosacral CSF. Mean 5-HIAA concentrations in atlanto-occipital and lumbosacral CSF were 206.1±37.0 nmol/L and 68.5±12.6 nmol/L, respectively. The mean HVA concentration in atlanto-occipital CSF was 254.4±50.4 nmol/L. No HVA was detected in lumbosacral CSF. In contrast, significantly greater protein concentrations were present in lumbosacral CSF than in atlanto-occipital CSF. Lumbosacral and atlanto-occipital CSF contained 32.1±3.7 mg protein/dl and 25.0±1.3 mg protein/dl, respectively. Thus, between the atlanto-occipital and lumbosacral space of the horses, a rostrocaudal gradient existed for neurotransmitter metabolites and a caudorostral gradient existed for protein.     

Effects of feeding blends of grains naturally contaminated with Fusarium mycotoxins on brain regional neurochemistry of starter pigs and broiler chickens

Two experiments were conducted to compare the effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on brain regional neurochemistry of starter pigs and broiler chickens. A polymeric glucomannan mycotoxin adsorbent (GM polymer) was also tested for its efficacy in preventing Fusarium mycotoxicoses. In Exp. 1, a total of 150 starter pigs (initial weight = 9.3+/-1.1 kg) were fed five diets (six pens of five pigs per diet) for 21 d. Diets (as-fed basis) included control, 17% contaminated grains, 24.5% contaminated grains, 24.5% contaminated grains + 0.2% GM polymer, and a pair-fed control for comparison with pigs receiving 24.5% contaminated grains. In Exp. 2,360 1-d-old male broiler chicks were fed for 56 d one of four diets containing the same source of contaminated grains as was fed to pigs. The diets included control, 37% contaminated grains, 58% contaminated grains, and 58% contaminated grains + 0.2% GM polymer (as fed). Neurotransmitter concentrations in the cortex, hypothalamus, and pons were analyzed by HPLC. The following brain neurotransmitter alterations (P < or = 0.05) were observed. In pigs, inclusion of contaminated grains in the diet 1) linearly increased cortex 5-hydroxytryptamine (5HT, serotonin) concentrations, while linearly decreasing hypothalamic tryptophan concentrations; 2) quadratically increased hypothalamic and pons 5-hydroxyindoleacetic acid (5HIAA):5HT ratios, whereas the ratio decreased linearly in the cortex; and 3) linearly increased the ratio of hypothalamic 3,4-dihydroxyphenylacetic acid:dopamine (DA) concentrations, whereas hypothalamic norepinephrine (NRE) and pons DA and homovanillic acid (HVA) concentrations linearly decreased. In broiler chickens, inclusion of contaminated grains in the diet 1) linearly increased concentrations of 5HT and 5HIAA in the pons and 5HT concentrations in the cortex; 2) linearly decreased 5HIAA:5HT ratio; and 3) linearly increased pons NRE, 3-methoxy-4-hydroxyphenylethylene glycol, DA, and HVA concentrations. Supplementation of GM polymer to the contaminated diet decreased (P < 0.05) 5HT and 5HIAA concentrations in the cortex of pigs. It was concluded that the differences in alterations of brain neurochemistry might explain the species differences in the severity of Fusarium mycotoxin-induced feed refusal.     

Slaughter methods: electroencephalographic (EEG) studies on spinal cord section, decapitation and gross trauma of the brain in lambs

By means of electroencephalograms (EEG), attempts were made to determine when insensibility could be presumed in five lambs, two subjected to immobilisation by the punctilla method, two decapitated and one shot by a captive bolt in the poll region. Section of approximately 80% of the spinal cord by the punctilla method had no apparent effect on sensibility and the technique was considered to be inhumane. The EEG obtained from a decapitated bead showed no obvious change in pattern for eight seconds and subsequent changes were similar to those associated with exsanguination only. Thus no evidence was obtained to indicate that decapitation causes immediate insensibility, neither was the belief substantiated that severance of the spinal cord, during the slaughter of sheep, hastens the onset of insensibility. These results also provide additional evidence on the inhumane nature of punctilla slaughter of cattle. The animal shot with a captive bolt in the poll region, as opposed to the frontal region, showed EEG activity for 78 seconds.     

Antinociceptive effects of low dose lumbosacral epidural ropivacaine in healthy ponies

The objective of this study was to evaluate the safety and efficacy of low dose lumbosacral epidural ropivacaine in ponies. Antinociceptive effects of epidural ropivacaine were evaluated by means of mechanical nociceptive thresholds (MNTs) at several spinal levels in conscious ponies. The effects of ropivacaine on nociceptive afferent transmission to the spinal cord were also assessed by measuring spinal cord somatosensory evoked potentials (SSEPs) in anaesthetised ponies. Ataxia scores were determined in conscious ponies to assess the effects on motor function. A randomised, placebo controlled, double blind cross-over design was used. Low dose lumbosacral epidural ropivacaine led to increases in MNTs at various anatomical locations with a maximum effect at the lumbosacral and sacrococcygeal regions, both with respect to increase in threshold and duration of effect. Analysis of SSEPs showed that epidural ropivacaine influenced both Aβ- and Aδ-mediated afferent transmission to the spinal cord at the level of the lumbosacral junction. Ponies showed mild ataxia after low dose lumbosacral epidural ropivacaine, but all ponies remained standing. Application of low dose lumbosacral epidural ropivacaine provided safe and efficacious antinociceptive effects in conscious and anaesthetised ponies, and could therefore be a valuable addition to multimodal analgesic protocols in Equidae.     

Acetylcholinesterase activity and lipid peroxidation in the brain and spinal cord of rats infected with Trypanosoma evansi

Neurological and locomotor clinical signs are described in animals infected with Trypanosoma evansi. These disturbances may be related to changes in the amount of acetylcholine (neurotransmitter) in the synaptic cleft. Therefore, changes in acetylcholinesterase (AChE) activity and lipid peroxidation in brain and spinal cord of T. evansi-infected rats were investigated. Each rat was intraperitoneally infected with 10(6) trypomastigotes kept in fresh (group A; n=13) and cryopreserved blood (group B; n=13). Thirteen served as uninfected (not-infected; group C). In days 4 and 30 post-infection (PI) the rats were anesthetized and subsequently decapitated to obtain the brain and the spinal cord (between vertebrae L1 and S2). The brain was removed and dissected (cerebellum, cerebral cortex, striatum and hippocampus) to measure the activity of AChE and lipid peroxidation, determined by TBARS levels. To verify if T. evansi was present in the central nervous system (CNS), brain structures of three rats of each group were processed by PCR T. evansi-specific. AChE activity was significantly increased in all brain structures and decrease in spinal cord in infected rats in 4 PI (P<0.05). The levels of TBARS were decreased in the brain structures, differently from spinal cord, which showed increased lipid peroxidation in 4 PI. The AChE activity in striatum, cerebral cortex, hippocampus and spinal cord reduced concomitantly with the increase of the enzyme in cerebellum of the infected rats (P<0.05), and the TBARS levels increased in cerebellum, striatum and spinal cord of infected rats compared to non-infected animals in 30 PI. The PCR was positive for T. evansi in all structures of the brain, confirming the presence of the parasite in the CNS. Based on the results, we conclude that the changes in AChE activity and lipid peroxidation in the CNS are induced by infection with T. evansi, suggesting that the parasite interferes with the cholinergic neurotransmission in this experimental condition.     

Biochemical and histological changes in the hypothalamus in hormone-stimulated sheep]

The effects were investigated of a hormonal preparation of serum gonadotrophin (SC) on neurosecretion, PAS-positive mucopolysaccharides and on histological changes in the third cerebral ventricle; at the same time variations were determined of catecholamine concentrations of ependyma surface in the hypothalamic regions that control directly reproductive functions in ewes of the Merino and Wallachian breeds in the oestrus period. Ewe oestrus was synchronized by insertion of Ageline (Spofa) sponges into the vagina. A dose of 2000 IU of serum gonadotrophin (Bioveta, Ivanovice in Haná) was administered to stimulate the ewes (n = 30). Twelve ewes of the Wallachian breed, six control and six test ones, were used for radioenzymatic detection of catecholamines (Catechola test, Prague). The brains were segmented immediately after bleeding and samples were taken from the eminentia medialis, area preoptica and corpus mamillare pursuant to the stereotactic configuration of the sheep hypothalamus (Welento et al., 1968). The brains of ten ewes of the Merino breed, four control and six test ones, and of eight ewes of the Wallachian breed (four control and four test ones) were used for histological treatment. For the purposes of a histological study, the brains were treated with current histological methods. The amount of neurosecretory material was assessed by light microscopy (Nakahara, 1963). Samples for the study of ependyma of the lower part of the third cerebral ventricle were examined in a scanning electron microscope. The obtained results demonstrate a statistically significant decrease by 36.4% (P less than 0.05) in epinephrin concentrations in the area preoptica of hypothalamus after SG administration (Fig. 3), in comparison with the control group. A decrease in norepinephrin concentration in the corpus mamillare (Fig. 4) was statistically significant (P less than 0.001). The dose of 2000 IU SG influenced most markedly catecholamine concentrations in the eminentia medialis (Fig. 5), where a statistically significant decrease in epinephrin and norepinephrin concentration was observed (P less than 0.01). Dopamine concentrations also decreased significantly (P less than 0.05) in the eminentia medialis (Fig. 5). Following the hormonal stimulation, a significant increase in dopamine and epinephrin concentrations was observed in the hypophysis of sheep (Fig. 6; P less than 0.05) and in the epiphysis there was a significant decrease in epinephrin and dopamine concentration (P less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)     

Abnormal turning behaviour, GABAergic inhibition and the degeneration of astrocytes in ovine Tribulus terrestris motor neuron disease

OBJECTIVE: To observe the clinical signs of sheep affected by Tribulus terrestris motor neuron disease, to ascertain their response to striatal dopamine reducing drugs, and to examine their brains and spinal cords for microscopic changes. PROCEDURES: Twenty-eight sheep displaying well developed clinical signs of the disorder were observed. Twenty-two of these and 22 normal sheep were then randomly allocated to three groups and treated with diazepam, chlorpromazine, or xylazine. The time that it took an animal to return to a standing position following drug administration was recorded. The brain and complete spinal cord were removed from each of the other six affected sheep and fixed in formalin. Brains were sectioned throughout at 5 mm intervals and spinal cords at 10 mm intervals. All tissues were paraffin embedded and examined by light microscopy. A few samples were examined by electron microscopy. RESULTS: Clinical signs included postural asymmetry with a right:left body-side dominance within the group of 50:50, unequal flaccid paresis in the pelvic limbs, extensor muscle atrophy and adduction of the weaker pelvic limb, and concurrent abduction of the stronger. Forward motion followed either a fixed left or right hand curved trajectory, the sheep no longer being able to choose which. Twelve animals intermittently displayed rotational behaviour that involved loss of postural balance without locomotor activation. The administration of diazepam, chlorpromazine, or xylazine caused limb paresis and sedation, with affected sheep being slower than normal sheep by factors of 8, 3 and 2 respectively, to return to a standing position. There were scattered areas of mild Wallerian degeneration throughout the spinal cord, and in both the brain and the cord there were small numbers of degenerate astrocytes containing novel cytoplasmic pigment granules. CONCLUSIONS: Affected sheep had a dysfunction in the control of directional change and this provides a new insight into the normal mechanism for 'turning' in quadrupeds. Directional change requires a functional asymmetry or lateralisation within the upper motor neuron to accommodate a difference in the rate of forward progression of each body side and, simultaneously, a lateral shift of the centre of gravity. The sensitivity of affected sheep to diazepam is consistent with a pre-existing elevation in GABAergic neuronal inhibition, probably as a result of a reduction in glutamatergic neuronal excitation. The cytoplasmic pigment found in degenerate astrocytes was novel and its presence in the brain nuclei known to contribute to turning behaviour could have aetiological significance. The motor output of the basal ganglia in Tribulus neurotoxicity appeared to be excessively inhibitory to the pelvic limb extensor muscles and was asymmetric, causing fixation of the turning posture but not locomotor activation. An intoxication of specific purine sensitive, glutamate releasing astrocytes, located in nuclei controlling turning, was suspected.     

Protozoan encephalomyelitis causing pelvic limb paresis in a yearling sheep

A pelvic limb paresis of 6 weeks duration in a yearling sheep resulted from protozoan encephalomyelitis involving the spinal cord at the thoracolumbar junction. An elevated lumbosacral cerebrospinal fluid protein concentration but normal cisternal cerebrospinal fluid protein concentration indicated the presence of a thoracolumbar inflammatory lesion resulting in cord compression which obstructed the rostral flow of the cerebrospinal fluid. Under general anaesthesia, myelography at the lumbo-sacral site demonstrated blockage to the rostral flow of contrast medium at T13/L1. At necropsy, there were no gross pathological changes at T13/L1, but histopathology revealed non-tract specific lymphocytic perivascular cuffing, axonal swelling and oedema in the spinal cord, characteristic of a protozoal encephalomyelitis. No parasites were detected in the multiple spinal cord sections examined but immunocytochemistry identified antigens cross-reactive with Sarcocystis spp. antigens in glial cells in these lesions.     

The use of two mixtures of ketamine and xylazine to immobilise free ranging Bennetts wallabies

Two mixtures of ketamine and xylazine were evaluated as immobilising agents for the capture of free ranging Bennetts wallabies (Protemnodon rufogrisea). The wallabies were given either a dose of 150 mg ketamine and 187.5 mg xylazine (mixture 1), or a dose of 160 mg ketamine and 80 mg xylazine (mixture 2) by intramuscular injection using a projectile syringe. The quality of induction and immobilisation was similar with both mixtures, although immobilisation occurred more rapidly and lasted longer with mixture 1. Respiration was not depressed and blood gas levels were not significantly changed from normal. Bradycardia was produced but no other arrhythmias were recorded. There was a slight fall in mean arterial pressure. Cloacal temperature was not altered to a significant degree. Recovery was good in the unstimulated animal and no side effects were observed. Mixture 1 was preferred owing to its more rapid immobilising effect.     

Element composition and biochemical components of Dirofilaria immitis

Element composition of whole canine heartworms (Dirofilaria immitis) was determined using inductively coupled argon plasma emission spectroscopy. The elements evaluated included Na, K, Ca, Mg, P, Al, B, Ba, Cu, Fe, Mn, Sr, Zn, As, and Pb. The only significant sex difference was calcium concentration which was higher in females. Amino acid analyses of body fluid revealed presence of nine essential and eight non-essential amino acids. Concentrations for male and female heartworms were not significantly different. The spectrum of amino acids was similar to that previously reported for canine plasma. Neurotransmitters or their metabolites detected in whole male and female heartworms using HPLC with electrochemical detector were epinephrine, dihydroxyphenylacetic acid, dopamine, and 5-hydroxyindoleacetic acid. Those not detected were norepinephrine, homovanillic acid, and 5-hydroxytryptamine.     

Protozoan encephalomyelitis causing pelvic limb paresis in a yearling sheep

A pelvic limb paresis of 6 weeks duration in a yearling sheep resulted from protozoan encephalomyelitis involving the spinal cord at the thoracolumbar junction. An elevated lumbosacral cerebrospinal fluid protein concentration but normal cisternal cerebrospinal fluid protein concentration indicated the presence of a thoracolumbar inflammatory lesion resulting in cord compression which obstructed the rostral flow of the cerebrospinal fluid. Under general anaesthesia, myelography at the lumbo-sacral site demonstrated blockage to the rostral flow of contrast medium at T₁₃L₁. At necropsy, there were no gross pathological changes at T₁₃/L₁, but histopathology revealed non-tract specific lymphocytic perivascular cuffing, axonal swelling and oedema in the spinal cord, characteristic of a protozoa1 encephalomyelitis. No parasites were detected in the multiple spinal cord sections examined but immunocytochemistry identified antigens cross-reactive with Sarcocystis spp. antigens in glial cells in these lesions.     

Chemical immobilisation of giraffe to facilitate short procedures

Objective To describe the chemical immobilisation of giraffe (Giraffa camelopardalis) for short procedures at Taronga Zoo. Design A clinical report. Animals Five giraffe. Procedure The weight of each animal was determined and pre-immobilisation fasting, careful preparation of the site, and planning were carried out prior to each procedure. Etorphine and acetylpromazine were used as the sole immobilising agents. During immobilisation, elevation of the head and constant monitoring of the heart rate, respiratory rate and temperature were employed; blood pressure and blood oxygen saturation (Sp₂) were monitored in one case 5. Intravenous fluids were administered. None of the animals was intubated, and supplemental oxygen was administered via an intranasal cannula in case 5. At the end of the procedures, diprenorphine was administered to reverse immobilisation. Results Induction times were 8 to 15 min. The mean heart rate, respiratory rate and rectal temperature were 58.6 beats per min, 12.2 breaths per min and 37.1°C₂ respectively. SpO₂ in case 5 increased to over 90% with the administration of supplemental oxygen. Recovery to standing after reversal of immobilisation was rapid (2 or 3 min) in three cases, but took 30 and 31 min in the other two. Conclusions Successful immobilisation of giraffe relies on consideration of all variables prior to and during the procedure. Careful selection and preparation of the venue and presence of sufficient numbers of adequately trained personnel are essential. Body weight determination allows accurate calculation of immobilising agent dose. Pre-immobilisation fasting followed by elevation of head and neck help preclude regurgitation and aspiration. Relevant vital signs monitoring, fluid replacement and oxygen supplementation promote cardiopulmonary homeostasis. Preoperative planning to ensure efficient performance of the procedure helps minimise recumbency time and increases the likelihood of a successful outcome.     

Cytoarchitecture, morphology, and lumbosacral spinal cord projections of the red nucleus in cattle

OBJECTIVE: To analyze the morphology, cytoarchitecture, and lumbosacral spinal cord projections of the red nucleus (RN) in cattle. ANIMALS: 8 healthy Friesian male calves. PROCEDURES: Anesthetized calves underwent a dorsal laminectomy at L5. Eight bilateral injections (lateral to the midline) of the neuronal retrograde fluorescent tracer fast blue (FB) were administered into the exposed lumbosacral portion of the spinal cord. A postsurgical calf survival time of 38 to 55 days was used. Following euthanasia, the midbrain and the L5-S2 spinal cord segments were removed. Nissl's method of staining was applied on paraffin-embedded and frozen sections of the midbrain. RESULTS: The mean length of the RN from the caudal to cranial end ranged from 6,680 to 8,640 microm. The magnocellular and parvicellular components of the RN were intermixed throughout the nucleus, but the former predominate at the caudal portion of the nucleus and the latter at the cranial portion with a gradual transitional zone. The FB-labeled neurons were found along the entire craniocaudal extension of the nucleus, mainly in its ventrolateral part. The number of FB-labeled neurons was determined in 4 calves, ranging from 191 to 1,469 (mean, 465). The mean cross-sectional area of the FB-labeled neurons was approximately 1,680 microm2. CONCLUSIONS AND CLINICAL RELEVANCE: In cattle, small, medium, and large RN neurons, located along the entire craniocaudal extension of the RN, contribute to the rubrospinal tract reaching the L6-S1 spinal cord segments. Thus, in cattle, as has been shown in cats, the RN parvicellular population also projects to the spinal cord.     

Use of magnetic motor-evoked potentials in horses with bilateral hind limb ataxia

OBJECTIVE: To determine the usefulness of magnetic motor-evoked potentials (MMEPs) for assessing the integrity of the cervical, thoracic, and thoracolumbar spinal cord in horses with bilateral hind limb ataxia. ANIMALS: 9 horses and 1 donkey with bilateral hind limb ataxia of various degrees. PROCEDURE: The motor cortex was stimulated magnetically, and MMEPs were recorded bilaterally from the extensor carpi radialis and cranial tibial muscles. RESULTS: In 5 horses and 1 donkey, MMEPs with normal onset latencies and peak-to-peak amplitude were recorded from the extensor carpi radialis muscles, whereas abnormal onset latencies and peak-to-peak amplitudes were recorded from the cranial tibial muscles. In these animals, a spinal cord lesion in the thoracic or thoracolumbar segments was suspected. In 4 horses, onset latencies and peak-to-peak amplitude of MMEPs recorded from the extensor carpi radialis and cranial tibial muscles were abnormal. In these horses, a cervical spinal cord lesion was suspected. CONCLUSIONS AND CLINICAL RELEVANCE: Transcranial magnetic stimulation can be considered a valuable diagnostic tool for assessing the integrity of the spinal cord, and MMEPs may be used for differentiating thoracic or thoracolumbar spinal cord lesions from mild cervical spinal cord lesions that cause ataxia in the hind limbs only.     

A survey of more than 11 years of neurologic diseases of ruminants with special reference to transmissible spongiform encephalopathies (TSEs) in Greece

The first cases of scrapie were detected in Greece in a flock of sheep in October 1986. All the animals of the affected flock and all sheep in two flocks that were in contact were killed and buried. A systematic investigation of all available cases with signs indicating a neurological disease started in sheep and goats in late 1986, as well as in cattle in 1989. The investigation was based on clinical examination, necropsy or macroscopical examination of the brain and viscera, and histological examination of the brain in all animals except those with coenurosis. Histological examinations of specimens from the spinal cord and other tissues, and if considered necessary bacteriological, toxicological and serological examinations were also carried out. In October 1997, scrapie was diagnosed in sheep of a second flock (a mixed flock of sheep and goats), grazing in a pasture close to the place where scrapie was initially detected. All animals of the second flock were also killed and buried. Diagnosis in the first flock was based on clinical signs and histological lesions, and in the second immunoblotting was also used. Distinctive lesions of scrapie were found in the brain and/or the spinal cord of eight sheep with clinical signs from the two flocks. The lesions were revealed in the brain stem and/or in the cervical spinal cord, and tended to be symmetrical. In one sheep, severe lesions in the cortex of cerebral hemispheres and of the cerebellum were also found. In the brain of two sheep from the second flock the pathological isoform of PrP protein was detected. Despite the eradication scheme applied, scrapie in sheep reappeared after 11 years in a place close to where it occurred initially. This may indicate that the effectiveness of the eradication scheme implemented was not adequate and additional approaches may be needed.     

Medetomidine immobilisation and atipamezole reversal in large estuarine crocodiles (Crocodylus porosus) using metabolically scaled dosages

Background Restraint of large estuarine crocodiles is potentially dangerous. Neuromuscular blockers and other immobilising drugs have been used with variable results. Medetomidine has been reported as a reliable, repeatable and reversible immobilisation agent in small estuarine crocodilians. Methods and Results Two wild and two farmed male animals, between 3.05 and 4.6 m long, were hand‐injected into a triceps muscle with a metabolically scaled medetomidine dosage. Immobilisation occurred within 30 min. At the conclusion of the procedures, 70 min after medetomidine administration, three animals were injected with atipamezole IM into the opposite triceps muscle at a dosage based on body surface area. Reversal occurred within 5 min. The fourth animal was intubated prior to reversal of medetomidine and maintained on isoflurane anaesthesia for a gastrotomy. All animals were monitored closely post recovery and then regularly for at least 1 week. Conclusions Medetomidine at a metabolically scaled dosage delivered IM into the forelimb was effective for immobilising large estuarine crocodiles for at least 40 min. Atipamezole administered at a dosage calculated as a function of surface area effectively reversed this immobilisation.     

Hypothalamic neurotransmitter concentrations and meat quality in stressed pigs offered excess dietary tryptophan and tyrosine.

Pale, soft, exudative (PSE) pork occurs, for the most part, from environmental stress on the pig. Amino acid intake may be related to stress susceptibility through hormone and neurotransmitter induction. Two experiments were conducted to determine whether supplementation of 5 g of tryptophan (TRP) or 10 g of tyrosine (TYR) per kilogram of a 14% CP diet would alter the response of pigs to stress as measured by hypothalamic neurotransmitter concentrations and incidence of PSE. Twenty-four (Exp. 1) and 36 (Exp. 2) 92-kg pigs were offered one of three diets: control, TRP-, or TYR-supplemented for 5 d before slaughter. Dietary TRP or TYR supplementation in Exp. 1. doubled (P less than .05) plasma TRP and TYR concentrations, respectively, and increased (P less than .05) 5-hydroxytryptamine, dihydroxyphenyl ethylamine, dihydroxyphenyl acetic acid, and homovanillic acid concentrations in the hypothalamus. Pigs that exhibited stress at slaughter had lower (P less than .05) hypothalamic concentrations of epinephrine, norepinephrine, and 5-hydroxytryptamine. In Exp. 2, pigs were trucked 55 km to a commercial meat packing facility and slaughtered without a rest period. This handling procedure was designed to invoke a high incidence of PSE pork and thus be a strong test of treatments. Supplemental dietary amino acids seemed to alter the frequency distribution of the severity of PSE pork. These data indicate that dietary manipulation of amino acid precursors of neurotransmitters may offer a practical means of reducing stress response in swine.     

The effect of acute restraint stress on regional brain neurotransmitter levels in stress-susceptible pietrain pigs

Concentrations of noradrenaline (NA), adrenaline (A), dopamine (DA), 5-hydroxytryptamine (5-HT), the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and the main 5-HT metabolite 5-hydroxyindole-3-acetic acid (5-HIAA) were measured using HPLC in 16 brain areas of control and immobilized Pietrain pigs. The animals were immobilized for 15, 30 and 60 min in the prone position. Control pigs showed patterns of regional distribution of brain monoamines similar to those described for rats, dogs and Duroc pigs. However, the absolute values of NA and A in the hypothalamus and preoptic area were much higher than those in rats and dogs, but similar to those in Duroc pigs. The concentrations of dopamine and its metabolites DOPAC and HVA were highest in the caudate nucleus, the nucleus accumbens, the olfactory tubercle and the ventral tegmental area. The distributions of serotonin and its metabolite 5-HIAA were similar in all examined structures. DOPAC/DA and HVA/DA ratios were higher in the cornu ammonis, the hippocampus posterior and the raphe nuclei than in other structures, which suggests brain structure-related differences in dopamine turnover. The greatest decreases in NA and A content were observed in the hypothalamus, the preoptic area and the olfactory tuberculum during the first 30 min of immobilization stress. 5-HT turnover was increased in the raphe nuclei, while DA turnover was affected in the raphe nuclei, the septum, the substantia nigra and the olfactory tubercle. We suggest that acute immobilization stress caused differences in regional patterns of brain biogenic amines, thereby maintaining adequate transmitter levels during stress in stress-susceptible pigs.