Retinal photoreceptor damage produced in guinea pigs by tunicamycin

Corynetoxins, members of the tunicamycin group of antibiotics, produce a severe and frequently fatal neurological disorder in ruminant livestock, and guinea pigs are a useful model to study the pathology and pathogenesis of this disease. The aim of this study was to determine whether tunicamycin produced ocular damage in this species, which could have pharmacotherapeutic and diagnostic value. Four 8-week-old guinea pigs were treated with tunicamycin, and two control animals were given the drug vehicle only. Guinea pigs were injected subcutaneously with 400 μg/kg of tunicamycin, in dimethyl sulphoxide, and killed 48 h post-injection. The eyes were then examined by light microscopy. Immunohistochemistry for rhodopsin was also performed. The principal pathological finding was marked retinal photoreceptor damage, which was characterised by disruption and disorganisation of rods, sometimes progressing to necrosis and separation of the outer segment. The cytoplasm of some rods was focally distended by accumulated, proteinaceous material. Rhodopsin immunopositivity in injured rods was markedly diminished and associated with shrinkage and shortening of the injured rod's outer segment. Ocular pathology, in the form of reproducible and extensive retinal photoreceptor damage, was found in guinea pigs given tunicamycin, extending the range of species found to be susceptible to this toxic injury. The guinea pig could prove to be a good animal model to test potential therapeutic interventions, and as brain lesions are often minimal and liver pathology non-specific in intoxicated ruminants, any spontaneously arising ophthalmic injury found in these species could be diagnostically useful.

Large felid leucoencephalomyelopathy in a Sumatran tiger (Panthera tigris sumatrae) from an Australian zoo

CASE REPORT

The clinicopathological features of a case consistent with large felid leucoencephalomyelopathy are described in a 19-year-old, zoo-based Sumatran tiger in which degenerative vertebral disease, renal insufficiency, diaphragmatic hernia and cataracts were comorbid. The principal presenting sign was ataxia, with concurrent deterioration of vertebral stiffness and vision loss. Histological features included marked destruction of the white matter, the formation of large, bizarre astrocytes and accumulation of numerous foamy macrophages (gitter cells). Immunohistochemical investigation of reactive astrocytes revealed several different cytoplasmic proteins.

CONCLUSION

This is the first reported case of large felid leucoencephalomyelopathy in Australia.

Abstract P6-03-02: Budesonide and colesevelam reduce neratinib-induced diarrhea in a rat model

Background: Neratinib (Puma Biotechnology Inc.) is an irreversible pan-HER tyrosine kinase inhibitor approved for use as extended adjuvant therapy in women with early-stage HER2+ breast cancer. Diarrhea is the main adverse event of neratinib; grade 3 events are common in the absence of antidiarrheal prophylaxis (40%) [Chan et al. Lancet Oncol 2016]. To investigate the underlying pathogenic mechanisms and to explore possible targets for its prevention, we developed a reproducible rat model of neratinib-induced diarrhea. Findings from the model indicated that neratinib-induced diarrhea is multifactorial, involving anatomical disruption and mucosal inflammation in the ileum and colon [Secombe et al. Asia Pac J Clin Oncol 2017]. We investigated the effects of budesonide, a locally-acting corticosteroid used for gastrointestinal conditions, and colesevelam, a bile acid sequestrant, on neratinib-associated diarrhea and intestinal changes in this model.

Methods: Male albino Wistar rats were randomly allocated to vehicle control (5% DMSO/1% carboxymethyl cellulose), neratinib 50 mg/kg alone or combined with budesonide 1 mg/kg or colesevelam 300 mg/kg by oral gavage for 14 or 28 days. Diarrhea severity was graded daily [0, no diarrhea; 1, mild; 2, moderate; 3, severe]. A tissue injury score was assigned based on validated histological criteria (villus fusion and atrophy, disruption of brush border and enterocytes, crypt losses/architectural disruption, crypt cell disruption, infiltration of polymorphonuclear cells/lymphocytes, dilation of lymphatics/capillaries, edema). Inflammation was assessed using multiplex cytokine/chemokine ELISA.Fecal bile acids were measured in pooled fecal samples over an 8-hour period.

Results: Findings at 28 days:

VariableControl (n=16)Neratinib (n=16)Neratinib + budesonide (n=16)Neratinib + colesevelam (n=16)Incidence of diarrhea, %Grade 137.5000Grade 212.587.5100100Grade 3012.500Mean±SEM days with grade 2 diarrhea0.1±0.115.8±2.710.0±1.0*10.0±2.1*Median (range) tissue injury scoreDistal ileum0.5 (0–2.0)4.0 (3.0–5.0)††3.0 (2.0–4.0)3.0 (2.0–4.0)†Proximal colon2.0 (0–3.0)5.0 (4.0–6.0)††3.0 (2.0–5.0)*3.0 (2.0–5.0)Distal colon0.5 (0–2.0)2.5 (2.0–4.0)††1.0 (0–2.0)*1.5 (0–2.0)Median (range) cytokine levelsaIleumIFN-γ27 (15–48)49 (39–67)†43 (29–55)–IL-463 (15–111)223 (109–318)464 (309–559)**–IL-1021 (14–54)32 (10–84)60 (52–89)*–ColonIFN-γ22 (6–32)16 (12–22)16 (6–19)–IL-4147 (88–270)165 (15–327)345 (170–433)*–IL-1054 (18–128)55 (37–96)47 (43–60)–Mean±SEM total fecal bile acids, umol/mg3.5±0.43.9±0.2–5.5±0.4††*ang/ml (IFN-γ); pg/ml (IL-4, IL-10); *p<0.05, **p<0.005 vs neratinib; †p<0.05, ††p<0.005 vs control; IFN, interferon; IL, interleukin; SEM, standard error of the mean

Conclusions: Budesonide and colesevelam reduced duration of neratinib-induced diarrhea and prevented severe diarrhea. Budesonide also reduced histopathological injury and inflammation via preservation of intestinal morphology and upregulation of anti-inflammatory cytokines in the ileum and colon. The phase II CONTROL study (Clinicaltrials.gov NCT02400476) is currently investigating the effects of adding budesonide or colestipol to loperamide prophylaxis in the prevention of neratinib-induced diarrhea and will help to determine the clinical relevance of our observations.

Citation Format: Bowen JM, Secombe KR, Ball IA, Shirren J, Wignall AD, Finnie JW, Olek E, Martin D, Lalani AS, Keefe D. Budesonide and colesevelam reduce neratinib-induced diarrhea in a rat model [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-03-02.

Primary, congenital neuroaxonal dystrophy with peripheral nerve demyelination in Merino-Border Leicester × Polled Dorset lambs

CASE REPORT

Clinicopathological features of neuroaxonal dystrophy (NAD) in newborn, Merino-Border Leicester × Polled Dorset lambs are described. The affected lambs were unable to walk at birth and microscopic examination of brainstem and spinal cord sections revealed bilaterally symmetrical accumulations of axonal swellings (spheroids), the histological hallmark of primary NAD. The neurological deficit was also exacerbated by myelin loss and secondary axonal degeneration, particularly in the spinal cord and sciatic nerves, but also, to a more limited extent, in brainstem and spinal nerves.

CONCLUSIONS

Although lambs previously diagnosed with NAD have ranged in age from 2 days to 7 months, this is believed to be the first report of congenital NAD in this species. Moreover, the present cases are the only ones in which peripheral nerve demyelination has been found.

Avian Riboflavin Deficiency: An Acquired Tomaculous Neuropathy

The finding of tomacula, focal areas of sausage-shaped hypermyelination in peripheral nerves, is reported for the first time in avian riboflavin deficiency. Day-old, meat-type chickens were fed a riboflavin-deficient diet (1.8 mg/kg) and were killed on postnatal days 6, 11, 16, and 21, while control chickens were fed a conventional diet containing 5.0 mg/kg riboflavin. Tomacula were found in sciatic and brachial nerves from day 11 onward, became more frequent and prominent with increasing time, and preceded the onset of segmental demyelination.

Temporal Sequence of Autolysis in the Cerebellar Cortex of the Mouse

This study examined the temporal sequence of post-mortem changes in the cerebellar cortical granular and Purkinje cell layers of mice kept at a constant ambient temperature for up to 4 weeks. Nuclei of granule cell microneurons became pyknotic early after death, increasing progressively until, by 7 days, widespread nuclear lysis resulted in marked cellular depletion of the granular layer. Purkinje cells were relatively unaltered until about 96 h post mortem, at which time there was shrinkage and multivacuolation of the amphophilic cytoplasm, nuclear hyperchromasia and, sometimes, a perinuclear clear space. By 7 days, Purkinje cells had hypereosinophilic cytoplasm and frequent nuclear pyknosis. By 2 weeks after death, Purkinje cells showed homogenization, the cytoplasm being uniformly eosinophilic, progressing to a 'ghost-like' appearance in which the cytoplasm had pale eosinophilic staining with indistinct cell boundaries, and nuclei often absent. The results of this study could assist in differentiating post-mortem autolysis from ante-mortem lesions in the cerebellar cortex and determining the post-mortem interval. Moreover, this information could be useful when interpreting brain lesions in valuable mice found dead unexpectedly during the course of biomedical experiments.

Axonal Spheroid Accumulation In the Brainstem and Spinal Cord of A Young Angus Cow with Ataxia

CASE REPORT

An 18-month-old Angus cow presented with rapidly developing ataxia and subsequently died. The finding of large numbers of axonal spheroids in brainstem nuclei and spinal cord grey matter, bilaterally symmetrical in distribution, was consistent with a histopathological diagnosis of neuroaxonal dystrophy (NAD). Most of the axonal swellings were immunopositive to amyloid precursor protein, suggesting that interruption to axonal flow was important in their genesis.

CONCLUSIONS

The topographical distribution of axonal spheroids in the brain and spinal cord in this bovine case closely resembled that found in the ovine neurodegenerative disorder termed NAD, in which axonal swellings are the major pathological feature. This appears to be the first reported case of this type of NAD in cattle. The aetiology of the spheroidal aggregations in this case was not determined. There was no evidence from the case history or neuropathology to indicate whether the axonal spheroids in this case involved an acquired or heritable aetiology.

Forensic Pathology of Traumatic Brain Injury

Traumatic brain injury constitutes a significant proportion of cases requiring forensic examination, and it encompasses (1) blunt, nonmissile head injury, especially involving motor vehicle accidents, and (2) penetrating, missile injury produced by a range of high- and lower-velocity projectiles. This review examines the complex pathophysiology and biomechanics of both types of neurotrauma and assesses the macroscopic and histologic features of component lesions, which may be used to determine the cause and manner of death resulting from an intentional assault or accident. Estimation of the survival time postinjury by pathologic examination is also important where malicious head injury is suspected, in an attempt to ascertain a time at which the traumatic event might have been committed, thereby evaluating the authenticity of statements made by the alleged perpetrator.

Neuroaxonal dystrophy in Merino-Border Leicester × Polled Dorset lambs

CASE REPORT

The clinicopathological features of neuroaxonal dystrophy (NAD) in 2 lambs are described. Of 40 Merino-Border Leicester × Polled Dorset lambs on a property in north-eastern Victoria, 4 presented with marked ataxia and listlessness, and 2 affected animals (2 days and 2 weeks of age, respectively) of both sexes were necropsied. Numerous axonal swellings (spheroids) were found in the central nervous system, particularly in brainstem nuclei and spinal cord grey matter, and there was severe spinal cord demyelination.

CONCLUSIONS

This is the first report of NAD in such crossbred lambs; the affected animals were much younger than in previously described cases of ovine NAD and myelin loss was of much greater magnitude than previously reported.

Loss of endothelial barrier antigen immunoreactivity as a marker of Clostridium perfringens type D epsilon toxin-induced microvascular damage in rat brain

The epsilon toxin elaborated by Clostridium perfringens type D in the intestine of domestic livestock is principally responsible for the neurological disease produced after its absorption in excessive quantities into the systemic circulation. The fundamental basis of the cerebral damage induced by epsilon toxin appears to be microvascular injury with ensuing severe, diffuse vasogenic oedema. Endothelial barrier antigen (EBA), which is normally expressed by virtually all capillaries and venules in the rat brain, was used in this study as a marker of blood-brain barrier (BBB) integrity. After exposure to high levels of circulating epsilon toxin, there was substantial loss of EBA in many brain microvessels, attended by widespread plasma albumin extravasation. These results support microvascular injury and subsequent BBB breakdown as a key factor in the pathogenesis of epsilon toxin-induced neurological disease.

Comparative neuropathology of ovine enterotoxemia produced by Clostridium perfringens type D wild-type strain CN1020 and its genetically modified derivatives

Clostridium perfringens type D causes enterotoxemia in sheep and goats. The disease is mediated by epsilon toxin (ETX), which affects the cerebrovascular endothelium, increasing vascular permeability and leading to cerebral edema. In the present study, we compared the distribution and severity of the cerebrovascular changes induced in lambs by C. perfringens type D strain CN1020, its isogenic etx null mutant, and the ETX-producing complemented mutant. We also applied histochemical and immunohistochemical markers to further characterize the brain lesions induced by ETX. Both ETX-producing strains induced extensive cerebrovascular damage that did not differ significantly between each other in nature, neuroanatomic distribution, or severity. By contrast, lambs inoculated with the etx mutant or sterile, nontoxic culture medium did not develop detectable brain lesions, confirming that the neuropathologic effects observed in these infections are dependent on ETX production. Lambs treated with the wild-type and complemented strains showed perivascular and mural vascular edema, as well as serum albumin extravasation, particularly severe in the cerebral white matter, midbrain, medulla oblongata, and cerebellum. Brains of animals inoculated with the ETX-producing strains showed decreased expression of glial fibrillary acidic protein and increased expression of aquaporin-4 in the end-feet processes of the astrocytes around blood vessels. Early axonal injury was demonstrated with anti-amyloid precursor protein immunohistochemistry. Perivascular accumulation of macrophages/microglia with intracytoplasmic albumin globules was also observed in these animals. This study demonstrates that ETX is responsible for the major cerebrovascular changes in C. perfringens type D-induced disease.

Neuroinflammation: beneficial and detrimental effects after traumatic brain injury

Traumatic brain injury (TBI) is the major cause of death and severe disability in young adults and infants worldwide and many survivors also have mild to moderate neurological deficits which impair their lives. This review highlights the primary and secondary lesions constituting craniocerebral trauma and the main elements of neuroinflammation, one of the most important secondary events evolving after the initial traumatic insult. Neuroinflammation has dual and opposing roles in outcome after TBI, being both beneficial and harmful, its effects often differing between the acute and more delayed phases after injury. Since each patient with TBI has a unique and complex pattern of cerebral damage, developing pharmacological intervention strategies targeted at the multiple cellular and molecular events in the neuroinflammatory cascade is difficult. While there have been very few successful outcomes to date in human clinical trials of drugs developed to treat TBI in general, those that have been devised to modulate neuroinflammation are discussed.

Congenital dyserythropoietic anaemia and dyskeratosis in Australian Poll Hereford calves

Congenital dyserythropoietic anaemia (CDA) is a heterogeneous group of rare genetic disorders that in humans is characterised by ineffective haematopoiesis with morphological abnormalities in erythroid precursor cells and secondary iron overload. In the 1990s, a syndrome of CDA with dyskeratosis and progressive alopecia was reported in Poll Hereford calves in Canada and the USA. We report the clinical and pathological findings in two Poll Hereford calves with this syndrome from separate properties in South Australia. The animals had a variably severe anaemia, associated with abnormal nucleated red blood cells in peripheral blood, and large numbers of rubricytes and metarubricytes with a characteristic nuclear ultrastructure in the bone marrow. Both calves were born with a wiry hair coat and a progressively 'dirty-faced' appearance associated with hyperkeratosis and dyskeratosis (apoptosis).

Comparative approach to understanding traumatic injury in the immature, postnatal brain of domestic animals

Traumatic brain injury (TBI) is a frequent occurrence in veterinary medicine, but the mechanisms leading to brain damage after a head impact are incompletely understood, particularly in the postnatal immature and still developing nervous system. This paper reviews neurotrauma studies, largely in paediatric humans and experimental animal models, in order to outline the pathophysiological and biomechanical events likely to be operative in head trauma involving domestic animal species in the postnatal period, as there is almost no other information available in the veterinary literature. Predicting the outcome of TBI is particularly difficult at this developmental time, in large part because recovery is influenced by the stage of brain maturation and neuroplasticity. An important part of the clinical management of TBI is the differentiation of primary brain damage, which occurs at the moment of head impact and is largely refractory to treatment, from the cascade of secondary events, which evolve over time and are potentially preventable and amenable to therapeutic intervention. An understanding of the causes and consequences of secondary brain damage such as hypoxia-ischaemia, brain swelling, elevated intracranial pressure, and infection is critical to limiting the resulting brain injury.

Neuropathological changes in a lamb model of non-accidental head injury (the shaken baby syndrome)

Non-accidental head injury (NAHI), also termed the "shaken baby syndrome", is a major cause of death and severe neurological dysfunction in children under three years of age, but it is debated whether shaking alone is sufficient to produce brain injury and mortality or whether an additional head impact is required. In an attempt to resolve this question, we used a lamb model of NAHI since these animals have a relatively large gyrencephalic brain and weak neck muscles resembling those of a human infant. Three anaesthetised lambs of lower body weight than others in the experimental group died unexpectedly after being shaken, proving that shaking alone can be lethal. In these lambs, axonal injury, neuronal reaction and albumin extravasation were widely distributed in the hemispheric white matter, brainstem and at the craniocervical junction, and of much greater magnitude than in higher body weight lambs which did not die. Moreover, in the eyes of these shaken lambs, there was damage to retinal inner nuclear layer neurons, mild, patchy ganglion cell axonal injury, widespread Muller glial reaction, and uveal albumin extravasation. This study proved that shaking of a subset of lambs can result in death, without an additional head impact being required.

Neuroaxonal dystrophy in Australian Merino lambs

Neuroaxonal dystrophy (NAD) is a morphological abnormality in man and animals that is characterized by the occurrence of numerous axonal swellings (spheroids) in the nervous system. NAD has been described in Suffolk lambs in the USA, Merino lambs in Australia and several breeds of sheep in New Zealand. This paper describes the clinicopathological changes of only the second occurrence of NAD reported in Merino lambs. There were some features (myelin loss, gliosis and visual impairment) in these Australian cases that have not been reported previously in ovine NAD. Application of immunohistochemical markers of axonal transport suggested that disruption of this transport mechanism contributed to spheroid development.

A Rosenthal Fiber Encephalomyelopathy Resembling Alexander’s Disease in 3 Sheep

We report an encephalomyelopathy in three 18-month-old Merino sheep with features of adult-onset Alexander’s disease (AD), a human primary astrocytic disorder. The signature histologic finding was the presence of numerous hypereosinophilic, intra-astrocytic inclusions (Rosenthal fibers), mainly in perivascular, subpial, and subependymal sites, especially in the caudal brain stem and spinal cord. Although AD usually results from mutations in the glial fibrillary acidic protein ( GFAP) gene, no such mutation was detected in these sheep. However, the annual clinical presentation of this disorder in a few sheep in the affected flock is suggestive of a familial pattern of occurrence.

Alzheimer type II astrocytes in the brains of pigs with salt poisoning (water deprivation/intoxication)

The finding of Alzheimer type II astrocytes, in addition to the pathognomonic combination of laminar cerebrocortical necrosis and eosinophil infiltration, in the brains of pigs is reported for the first time in cases of indirect salt poisoning following water deprivation.

Selective Vulnerability of Peripheral Nerves in Avian Riboflavin Deficiency Demyelinating Polyneuropathy

Riboflavin (vitamin B2) deficiency in young chickens produces a demyelinating peripheral neuropathy. In this study, day-old broiler meat chickens were fed a riboflavin-deficient diet (1.8 mg/kg) and killed on posthatch days 6, 11, 16, 21, and 31, while control chickens were given a conventional diet containing 5.0 mg/kg riboflavin. Pathologic changes were found in sciatic, cervical, and lumbar spinal nerves of riboflavin-deficient chickens from day 11 onwards, characterized by endoneurial oedema, hypertrophic Schwann cells, tomacula (redundant myelin swellings), demyelination/remyelination, lipid deposition, and fibroblastic onion bulb formation. Similar changes were also found in large and medium intramuscular nerves, although they were less severe in the latter. However, by contrast, ventral and dorsal spinal nerve roots, distal intramuscular nerves, and subcutaneous nerves were normal at all time points examined. These findings demonstrate, for the first time, that riboflavin deficiency in young, rapidly growing chickens produces selective injury to peripheral nerve trunks, with relative sparing of spinal nerve roots and distal nerve branches to muscle and skin. These novel findings suggest that the response of Schwann cells in peripheral nerves with riboflavin deficiency differs because either there are subsets of these cells in, or there is variability in access of nutrients to, different sites within the nerves.

Aquaporin-4 in acute cerebral edema produced by Clostridium perfringens type D epsilon toxin

Sheep, particularly lambs, with high circulating levels of Clostridium perfringens type D epsilon toxin develop severe neurologic signs and often die suddenly. On microscopic examination, in the brain, there is microvascular endothelial injury and diffuse vasogenic edema. The aquaporin (AQP) family of membrane water-channel proteins, especially AQP-4, is important in the regulation of water balance in the brain and facilitates reabsorption of excess fluid. In rats given epsilon toxin, generalized cerebral edema was demonstrated by marked albumin extravasation and was correlated with widespread upregulation of AQP-4 in astrocytes. These results suggest that AQP-4 has a role in the clearance of edema fluid from brains damaged by this clostridial toxin.

Novel fibroblastic onion bulbs in a demyelinating avian peripheral neuropathy produced by riboflavin deficiency

The finding of novel fibroblastic onion bulb-like structures in peripheral nerves is reported for the first time in avian riboflavin deficiency. Day old broiler meat chickens were fed a riboflavin deficient diet (1.8 mg/kg) and were killed on postnatal days 6, 11, 16, 21 and 31, whereas control chickens were fed a conventional diet containing 5.0 mg/kg riboflavin. The fibroblastic onion bulb-like structures were found in sciatic and brachial nerves from day 11 onwards and consisted of long cytoplasmic processes of hypertrophied fibroblasts surrounding demyelinated, remyelinated and normally myelinated axons. The fibroblast cytoplasmic processes often enveloped more than one nerve fibre to produce a unique compound-like onion bulb structure. These onion bulb-like structures occurred early in the course of segmental demyelination at the same time as tomacula formation and became increasingly more prominent in the later stages of demyelination and remyelination. The molecular basis of formation of these unique structures requires further study as to the basis of the attraction of the fibroblast processes to nerve fibres associated with myelinating Schwann cells. The model may also be useful in investigating the role of endoneurial fibroblasts in endoneurial fibrosis as the early fibroblastic response in the onion bulbs is distinct from the more usual fibroblastic deposition of collagen in end-stage peripheral nerve disease.

Early paranodal myelin swellings (tomacula) in an avian riboflavin deficiency model of demyelinating neuropathy

INTRODUCTION

Disruption of the complex architectural and molecular organization of the paranodal region of myelinated peripheral nerve fiber may initiate the evolving time dependent process of segmental demyelination. In support of this notion was the finding of focal paranodal myelin swellings (tomacula) due to redundant folding of myelin sheaths, early in the time course of an avian riboflavin deficiency model of demyelinating neuropathy.

METHODS

Newborn broiler meat chickens were maintained either on a routine diet containing 5.0 mg/kg riboflavin (control group) or a riboflavin-deficient diet containing 1.8 mg/kg riboflavin. Riboflavin concentrations in the liver were measured at postnatal day 11. Peripheral nerves were morphologically examined at days 6, 11, 16 and 21 using light and electron microscopy and teased nerve fiber techniques.

RESULTS

Riboflavin-deficient chickens showed signs of a neuropathy from days 8 and pathological examination of peripheral nerves revealed a demyelinating neuropathy with paranodal tomacula formation starting on day 11. Paranodal tomacula consisted of redundant myelin infoldings or outfoldings, increased in size and frequency after day 11. After day 16, the paranodal swellings showed prominent degenerative changes accompanied by an increased frequency of myelinated fibers showing demyelination.

CONCLUSION

Tomacula due to redundant myelin folds are generally considered a remyelination phenomenon, yet in this avian riboflavin deficiency model of demyelination, the paranodal tomacula occurred early in the course of demyelination.

Neuropathological changes produced by non-penetrating percussive captive bolt stunning of cattle

A blunt, non-missile head injury inflicted by a non-penetrating captive bolt pistol in cattle at slaughter resulted in immediate loss of consciousness, a depressed fracture of the frontal bone and widespread subarachnoid haemorrhage, particularly beneath the impact site, in the temporal and frontal lobes, and around the brainstem. There was also invariably petechial haemorrhage in the basal ganglia and thalamus. The large concussive force applied to the cranium by the stunner was probably responsible for rendering the animal insensible and the vascular damage produced by this force and the sudden ventrocaudal acceleration of the brain after impact. These findings supported the use of this mode of stunning, followed by exsanguination, as an acceptable form of slaughter of cattle in abattoirs.

Apoptosis in liver damage produced by tunicamycin

OBJECTIVE

To determine whether apoptosis contributes to hepatocyte loss in tunicamycin poisoning.

DESIGN

Groups of four guinea pigs were given 400 microg/kg of tunicamycin subcutaneously and killed at 24 h intervals up to 72 h post-injection. Livers were examined by routine histological methods and ancillary techniques (TUNEL staining, endonuclease activation, caspase activity, and electron microscopy) to ascertain whether any hepatocyte injury was apoptotic.

RESULTS

Many hepatocytes exposed to tunicamycin showed evidence of apoptosis in the form of nuclear karyorrhexis with chromatin margination and crescent formation, TUNEL-positivity, DNA laddering, elevated caspase activity and apoptotic body formation.

CONCLUSION

Tunicamycin caused the death of many hepatocytes in the livers of guinea pigs by apoptosis.

Pathogenesis of brain damage produced in sheep by Clostridium perfringens type D epsilon toxin: a review

Microvascular endothelial damage by the epsilon toxin of Clostridium perfringens type D appears to be the fundamental cause of cerebral parenchymal injury and lesions occur in a seemingly dose- and time-dependent manner. Large doses of circulating toxin produce a severe, generalised, vasogenic cerebral oedema and an acute or peracute clinical course to death. With lower doses of toxin, or in partially immune sheep, focal necrosis, often bilaterally symmetrical, occurs in certain selectively vulnerable brain regions, which appear to become fewer as the toxin dose is reduced. These cases follow a more protracted clinical course, but death is the usual outcome. The precise pathogenesis of the focal brain damage found in subacutely intoxicated sheep is unresolved, but several possible mechanisms are discussed.

Brain damage in pigs produced by impact with a non-penetrating captive bolt pistol

OBJECTIVE

To assess the effect of impact with a nonpenetrating captive bolt pistol in pigs by studying the resulting traumatic brain injury (TBI) and to compare the pathological changes with those found previously in the brains of sheep using a similar experimental paradigm.

PROCEDURE

The unrestrained heads of six, anaesthetised, 7- to 8-week-old, Large White pigs were impacted in the temporal region with a nonpenetrating captive bolt pistol. Four hours postimpact, brains were perfusion-fixed with 4% paraformaldehyde. Coronal sections from six levels along the brain were cut and stained with haematoxylin and eosin and immunohistochemically for amyloid precursor protein, a sensitive marker of axonal injury (AI) in the brain after trauma.

RESULTS

TBI in pigs was characterised only by very mild AI, whereas AI in sheep after captive bolt impact to the same head region was much more severe and widely distributed and often associated with vascular damage such as contusions, subarachnoid and intraparenchymal haemorrhage.

CONCLUSIONS

TBI in pigs was much less severe than in sheep after non-penetrating mechanical impact of similar magnitude, confirming the importance of interspecies differences in determining an appropriate physical method of euthanasia.

Traumatic brain injury

Animal models have played a critical role in elucidating the complex pathogenesis of traumatic brain injury, the major cause of death and disability in young adults in Western countries. This review discusses how different types of animal models are useful for the study of neuropathologic processes in traumatic, blunt, nonmissile head injury.

Brain damage in sheep from penetrating captive bolt stunning

OBJECTIVE

To determine the severity and distribution of structural changes in the brains of adult sheep stunned by penetrating captive bolt.

PROCEDURE

The unconstrained heads of ten, anaesthetised, unhorned, 2-year-old Merino sheep were impacted at the summit of the head with a penetrating captive bolt pistol. Six sheep were ventilated and four received no respiratory support. Two hours after impact, brains from the six ventilated sheep were perfusion-fixed with 4% paraformaldehyde. Sixteen whole, serial coronal sections from each brain were stained with haematoxylin and eosin and immunohistochemically for amyloid precursor protein, a sensitive marker of axonal and neuronal reaction in the brain after trauma. Pathological changes in these brains were then quantified by morphometric analysis.

RESULTS

Structural change in all impacted brains was a mixture of focal injury around the wound track and more widely distributed damage in the cerebral hemispheres, cerebellum and brainstem, but varied considerably in severity between individual sheep. All nonventilated sheep died rapidly following respiratory arrest.

CONCLUSIONS

After penetrating captive bolt stunning, damage to the central reticular formation, axonal connections, and the cortical mantle is the likely reason for failure of respiratory control and traumatic loss of consciousness.

Effect of tunicamycin on hepatocytes in vitro

Cultured rat hepatocytes exposed to tunicamycin, a substance biologically indistinguishable from the corynetoxin responsible for a toxic hepatocerebral disorder in Australian ruminant livestock, had degenerative changes characterized by marked cytoplasmic lipid accumulation and dilatation of cisternae of rough endoplasmic reticulum or necrosis. The findings, which resemble those found previously in vivo after tunicamycin administration, suggest that, after gaining ready access to liver parenchyma via leaky hepatic sinusoids, tunicamycin directly damages the hepatocytes.

Toxin-induced vasogenic cerebral oedema in a rat model

Vasogenic cerebral oedema (VCO) was induced in Hooded Wistar rats by intraperitoneal injection of Clostridium perfringens type D epsilon prototoxin. Animals were killed, 1 h to 14 d postinjection, by perfusion fixation under general anaesthesia. VCO was detected by the presence of endogenous albumin in the brain, visualised by immunocytochemistry. As early as 1 h postinjection, albumin was detected in the walls of cerebral microvessels. Maximal diffuse leakage within the neural parenchyma was seen at 24 and 48 h and immunoreactivity was still present at 4 d. At 7 d only few foci were seen, and at 14 d albumin distribution was similar to that in controls. Ultrastructural assessment of the microvessels showed swelling of many astrocytic processes and abnormalities of the endothelial cells varying from swelling with loss of cytoplasmic organelles to cells showing increased electron density. Immunostaining for the endothelial barrier antigen (EBA) showed strongly immunoreactive vessels throughout normal brains. Experimental animals showed partial reduction in EBA expression, most evident at 24 and 48 h, with gradual recovery to normal by 14 d. The exact role that EBA plays in the intact BBB remains obscure.

Effect of global system for mobile communication (gsm)-like radiofrequency fields on vascular permeability in mouse brain

The effect of global system for mobile communication (GSM) radiofrequency fields on vascular permeability in the brain was studied using a purpose-designed exposure system at 898.4 MHz. Mice (n= 30) were given a single far field, whole body exposure for 60 minutes at a specific absorption rate of 4 W/kg. Control mice were also sham-exposed (n = 10) or permitted free movement in a cage (n = 10) to exclude any stress-related effects. Vascular permeability changes were detected using albumin immunohistochemistry and the efficacy of this vascular tracer was confirmed with a positive control group exposed to a clostridial toxin known to increase vascular permeability in the brain. No significant difference in albumin extravasation was detected between any of the groups at the light microscope level using the albumin marker.

Clostridium perfringens prototoxin-induced alteration of endothelial barrier antigen (EBA) immunoreactivity at the blood-brain barrier (BBB)

It has been reported that the severe cerebral edema produced in experimental animals by Clostridium perfringens (Cl p) type D epsilon toxin can be prevented by prior treatment with its precursor prototoxin due to competitive binding to endothelial cells (ECs) at the blood-brain barrier (BBB). In this study we investigate the effects of the prototoxin on the BBB, without added toxin. The integrity of the BBB was assessed by its ability to prevent leakage of endogenous albumin. ECs at the BBB were studied by immunocytochemistry for any alteration in the endothelial barrier antigen (EBA), a molecular marker for the intact BBB. Immunocytochemistry showed rapid but mild opening of the BBB to endogenous albumin. Light and electron immunocytochemistry showed qualitative and quantitative reduction in EBA immunoreactivity, with a spectrum of changes at time intervals from 1 h to 14 days post-prototoxin injection. Some vessels with ultrastructural changes and widening of the perivascular space retained EBA immunoreactivity. Many vessels showed partial or complete loss of EBA staining with minimal widening of the perivascular space and edema. Recovery of EBA expression was still incomplete at 14 days postinjection. This is the first report to show endothelial cell damage, mild reversible cerebral edema, and alteration in BBB markers following administration of Cl p prototoxin. This model of mild brain edema may be useful for BBB studies.

Effect of impact on different regions of the head of lambs

The heads of anaesthetized lambs aged 4-5 weeks were subjected to impact (temporal, frontal or occipital) of constant strength with a humane stunner. Two hours later, the brains were perfusion-fixed with 4% paraformaldehyde and serial whole coronal slices processed by routine methods. Sections were stained with haematoxylin and eosin or labelled with a monoclonal antibody to amyloid precursor protein, a sensitive marker of axonal injury and neuronal reaction. Microscopical evaluation of axonal, neuronal and vascular damage was performed with a quantitative grid system. Frontal impact produced the greatest damage, followed by occipital then temporal impact. An unusual lesion found in the majority of lambs subjected to impact was multifocal necrosis of the cerebellar granular layer. The findings should assist clinicians in evaluating the probable outcome of traumatic head injury in domestic animals.

Upregulation of neuronal amyloid precursor protein (APP) and APP mRNA following magnesium sulphate (MgSO4) therapy in traumatic brain injury

The aim of this study was to assess and quantitate topographically the effects of posttraumatic intravenous magnesium sulphate (MgSO4) on neuronal perikaryal APP antigen and messenger RNA (mRNA) expression in sheep brains 2 h after a controlled focal head impact. The percentage brain area with APP immunoreactive neuronal perikarya was 71, 56, 27.5 and 5.5%, respectively, in MgSO4-treated head-injured animals, head-injured animals without any treatment, MgSO4 treated nonimpacted animals, and nontreated nonimpacted control sheep. Although there was no statistically significant difference in APP immunoreactive neuronal perikarya in the MgSO4-treated HI group (mean 71%) compared to the HI group without any treatment (mean 56%), northern analysis showed that there was a 2.3-+/-0.2-fold increase in APP mRNA in the thalamus of treated impacted animals compared to untreated impacted animals (p < 0.005). However, MgSO4 treated nonimpacted control animals also showed a 1.6-+/-0.1-fold increase in APP mRNA compared to untreated nonimpacted controls (p < 0.005). MgSO4 therapy results in upregulation of neuronal APP mRNA and APP expression that is quantitatively greater following a focal head impact.

Axonal and neuronal amyloid precursor protein immunoreactivity in the brains of guinea pigs given tunicamycin

Amyloid precursor protein (APP) immunocytochemistry was used to study axonal and neuronal changes in guinea pig brains exposed to tunicamycin. Substantial axonal injury was found in ischemic-hypoxic foci and more generally, but this injury was not readily appreciable in conventionally stained sections. Neuronal perikaryal APP expression was also widely distributed, possibly as an acute phase response to this neurotoxin.

Evaluation of brain damage resulting from penetrating and non-penetrating captive bolt stunning using lambs

OBJECTIVE

To compare the brain damage in sheep resulting from penetrating and non-penetrating captive bolt stunning.

DESIGN

The unrestrained heads of anaesthetised lambs were impacted in the temporal region with penetrating and non-penetrating captive bolt pistols (humane stunners) using a constant charge. Two hours after head impact, brains were perfusion-fixed with 4% paraformaldehyde. Coronal sections were stained with haematoxylin and eosin and immunohistochemically for amyloid precursor protein, a sensitive marker of axonal and neuronal reaction in brains after trauma. Pathological changes in these brains were then quantified by morphometric analysis.

RESULTS

The skull was fractured in 50% of lambs after a non-penetrating head impact and in all animals after a penetrating head wound. Impact contusions were present in 80% of lambs receiving a non-penetrating head injury and in all of those with a penetrating wound. Total contusion area was similar in both groups. Amyloid precursor protein-positive axons and neurons, and haemorrhage, were widely distributed in the brain after both head impact types, but there was no statistically significant difference between the two groups. Multifocal necrosis of the cerebellar granular layer was found in all lambs with non-penetrating head injury, but in none with a penetrating injury.

CONCLUSIONS

The structural brain damage, a mixture of focal and diffuse injury, produced by penetrating and non-penetrating captive bolt pistols was overall similar and of sufficient severity to suggest that both types of weapon are acceptable for euthanasia.

Alpha-mannosidosis in the guinea pig: a new animal model for lysosomal storage disorders

Alpha-mannosidosis is a lysosomal storage disorder resulting from deficient activity of lysosomal alpha-mannosidase. It has been described previously in humans, cattle, and cats, and is characterized in all of these species principally by neuronal storage leading to progressive mental deterioration. Two guinea pigs with stunted growth, progressive mental dullness, behavioral abnormalities, and abnormal posture and gait, showed a deficiency of acidic alpha-mannosidase activity in leukocytes, plasma, fibroblasts, and whole liver extracts. Fractionation of liver demonstrated a deficiency of lysosomal (acidic) alpha-mannosidase activity. Thin layer chromatography of urine and tissue extracts confirmed the diagnosis by demonstrating a pattern of excreted and stored oligosaccharides almost identical to that of urine from a human alpha-mannosidosis patient. Widespread neuronal vacuolation was observed throughout the CNS, including the cerebral cortex, hippocampus, thalamus, cerebellum, midbrain, pons, medulla, and the dorsal and ventral horns of the spinal cord. Lysosomal vacuolation also occurred in many other visceral tissues and was particularly severe in pancreas, thyroid, epididymis, and peripheral ganglion. Axonal spheroids were observed in some brain regions, but gliosis and demyelination were not observed. Ultrastructurally, most vacuoles in both the CNS and visceral tissues were lucent or contained fine fibrillar or flocculent material. Rare large neurons in the cerebral cortex contained fine membranous structures. Skeletal abnormalities were very mild. Alpha-mannosidosis in the guinea pig closely resembles the human disease and will provide a convenient model for investigation of new therapeutic strategies for neuronal storage diseases, such as enzyme replacement and gene replacement therapies.

Upregulation of amyloid precursor protein messenger RNA in response to traumatic brain injury: an ovine head impact model

There is evidence that the amyloid precursor protein (APP) plays an important role in neuronal growth and synaptic plasticity and that its increased expression following traumatic brain injury represents an acute phase response to trauma. We hypothesized that the previously described increased APP expression in response to injury (Van den Heuvel et al., Acta Neurochir. Suppl. 71, 209-211) is due to increased mRNA expression and addressed this by examining the expression of APP mRNA and APP within neuronal cell bodies over time in an ovine head impact model. Twenty-five anesthetized and ventilated 2-year-old Merino ewes sustained a left temporal head impact using a humane stunner and 9 normal sheep were used as nonimpact controls. Following postimpact survival periods of 15, 30, 45, 60, and 120 min, brains were perfusion fixed in 4% paraformaldehyde and examined according to standard neuropathological protocol. APP mRNA and antigen expression were examined in 5-microm sections by nonisotopic in situ hybridization and APP immunocytochemistry. The percentage of brain area with APP immunoreactivity within neuronal cell bodies in the impacted animals increased with time from a mean of 7.5% at 15 min to 54.5% at 2 h. Control brains showed only very small numbers of weakly APP-positive neuronal cell bodies ranging from 2 to 14% (mean 7%). Increased expression of APP mRNA was first evident in impacted hemispheres at 30 min after impact and progressively increased over time to involve neurons in all sampled regions of the brain, suggesting increased transcription of APP. In contrast, APP mRNA was undetectable in tissue from nonimpacted sheep. These data show that APP mRNA and antigen expression are sensitive early indicators of neuronal injury with widespread upregulation occurring as early as 30 min after head impact.

Neuronal damage produced in rat brains by Clostridium perfringens type D epsilon toxin

This paper reports neuronal changes in rat brains subacutely intoxicated with Copyright Clostridium perfringens type D epsilon toxin. Neuronal damage was characterized by either (1) progressive cytoplasmic vacuolation leading to necrosis, or (2) shrunken hyperchromatic cells with nuclear pyknosis. The neuronal injury was also often bilaterally symmetrical, particularly in the brainstem. These findings suggest that, after gaining access to brain tissue by producing an increase in vascular permeability, epsilon toxin later exerts a directly cytotoxic effect on neurons.

Multifocal cerebellar granular layer necrosis in traumatically head-injured lambs

In a blunt, nonmissile, head impact model of traumatic brain injury in 4-5-week-old Merino lambs, multiple foci of internal granular layer necrosis were found in all 10 impacted animals. This lesion has not previously been reported after human or animal head injury. Temporal lobe impact contusions, predominantly microscopic (8/10) and contralateral contusions (2/10), parenchymal (10/10) and subarachnoid (10/10) hemorrhage, and widely distributed axonal injury were also observed. Although the precise pathogenesis of this focal granule cell necrosis and often attendant red cell change in Purkinje cells was unclear, an ischemic etiology due to trauma-related vascular damage is postulated.