Interdisciplinary perspectives on infectious diseases, 2010
Prion disorders are infectious, neurodegenerative diseases that affect humans and animals. Suscep... more Prion disorders are infectious, neurodegenerative diseases that affect humans and animals. Susceptibility to some prion diseases such as kuru or the new variant of Creutzfeldt-Jakob disease in humans and scrapie in sheep and goats is influenced by polymorphisms of the coding region of the prion protein gene, while other prion disorders such as fatal familial insomnia, familial Creutzfeldt-Jakob disease, or Gerstmann-Straussler-Scheinker disease in humans have an underlying inherited genetic basis. Several prion strains have been demonstrated experimentally in rodents and sheep. The progression and pathogenesis of disease is influenced by both genetic differences in the prion protein and prion strain. Some prion diseases only affect the central nervous system whereas others involve the peripheral organs prior to neuroinvasion. Many experiments undertaken in different species and using different prion strains have postulated common pathways of neuroinvasion. It is suggested that prion...
Following a severe outbreak of clinical scrapie in 2006-2007, a large dairy goat herd was culled ... more Following a severe outbreak of clinical scrapie in 2006-2007, a large dairy goat herd was culled and 200 animals were selected for post-mortem examinations in order to ascertain the prevalence of infection, the effect of age, breed and PRNP genotype on the susceptibility to scrapie, the tissue distribution of diseaseassociated PrP (PrP(d)), and the comparative efficiency of different diagnostic methods. As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the prevalence of preclinical infection was very high (72/200; 36.0%), with most infected animals being positive for PrP(d) in lymphoreticular system (LRS) tissues (68/72; 94.4%) compared to those that were positive in brain samples (38/72; 52.8%). The retropharyngeal lymph node and the palatine tonsil showed the highest frequency of PrP(d) accumulation (87.3% and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid tissue (RAMALT) was positive in only 30 (41.7%) of the infected goats. However, the efficiency of rectal and palatine tonsil biopsies taken shortly before necropsy was similar. The probability of brain and RAMALT being positive directly correlated with the spread of PrP(d) within the LRS. The prevalence of infection was influenced by PRNP genetics at codon 142 and by the age of the goats: methionine carriers older than 60 months showed a much lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last showed prevalence values similar to isoleucine homozygotes of any age (40/80; 50.0%). Two of seven goats with definite signs of scrapie were negative for PrP(d) in brain but positive in LRS tissues, and one goat showed biochemical and IHC features of PrP(d) different from all other infected goats. The results of this study have implications for surveillance and control policies for scrapie in goats.
The distribution of PrP(BSE) in the brain of nine confirmed BSE field cases was analyzed using im... more The distribution of PrP(BSE) in the brain of nine confirmed BSE field cases was analyzed using immunohistochemistry and compared to the levels of PrP(BSE) determined by two rapid tests (Prionics-Check WESTERN and Prionics-Check LIA). Each brain was dissected into 16 areas: spinal cord, medulla oblongata, pons, mesencephalon, thalamus, hippocampus, cerebellar vermis, cerebellar medulla, cerebellar hemispheres, occipital cortex, temporal cortex, parietal cortex, striatum, frontal cortex, piriform lobe and olfactory bulbs. The highest levels of PrP(BSE) were detected in the medulla oblongata, spinal cord and pons, and correspondingly both rapid tests showed 100% correlation with the immunohistochemistry with regard to sensitivity and specificity. Some inconsistencies between the levels of PrP(BSE) determined either by immunohistochemistry or by the rapid tests were found in brain areas with medium to low levels of PrP(BSE). These brain areas included the cerebellar hemisphere, olfactory bulb, and the temporal and parietal cortices. A brain PrP(BSE) distribution curve (BPDC) was designed by plotting the PrP(BSE) signals obtained from the two rapid tests versus the anatomical region along the caudal-rostral axis of the brain. Comparison of the BPDC of the nine BSE cases showed that all cases had a similar PrP(BSE) distribution in the brain but with variable intensities, which could be explained by different stages in the progression of the disease. We propose that the BPDC could be used as a tool to differentiate classical cases of BSE from the recently identified atypical BSE cases.
Disturbances of the gamma-aminobutyric acid (GABA) neurotransmitter system have been implicated i... more Disturbances of the gamma-aminobutyric acid (GABA) neurotransmitter system have been implicated in chronic degenerative neurological disease. Cognitive dysfunction and neuron loss are features in older dogs. GABAergic neurons also show immunoreactivity for specific calcium-binding proteins. Immunohistochemistry was used to study the neuronal expression of calbindin D-28k and parvalbumin in different areas of the brain in 13 dogs, aged between 2 and 13.5 years. Calbindin expression was found only in the cerebellum. There were significant differences in the quantity and distribution of neurons expressing these proteins between geriatric and adult brains. Parvalbumin- and calbindin-expressing neurons are relatively sensitive to degeneration in the cerebellum of older dogs. Parvalbumin labelling was associated with dystrophic structures that are commonly associated with ageing.
A neuropathological study of Holstein-Friesian calves with spinal muscular atrophy (SMA) demonstr... more A neuropathological study of Holstein-Friesian calves with spinal muscular atrophy (SMA) demonstrated decreased numbers of motor neurons in the brachial and lumbo-sacral regions of the spinal cord, together with swelling and accumulation of phosphorylated neurofilaments, and neuronophagia in most of the remaining motor neurons. The pyramidal tracts, motor cortex and thalamus were not affected. Synaptophysin immunohistochemistry revealed a marked reduction of punctate terminals but only around swollen neurones, suggesting loss of terminal afferents on motor neurons at advanced stages of the degenerative process. An immunohistochemical study of proteins linked with cell death and cell survival demonstrated reduced expression of Fas, Fas-L, Bcl-2 and Bax in swollen motor neurons. Punctate cytochrome C immunoreactivity, consistent with mitochondrial localization, was detected in the soma of normal motor neurons, but not in swollen motor neurons. Finally, no labelling of motor neurons with antibodies to cleaved (active) caspase-3 (17kD) was detected, suggesting a lack of involvement of the apoptotic pathways in motor neuron death. Taken together, the present findings point to necrosis as a major cause of motor neuron death in the advanced stages of SMA in Holstein-Friesian calves.
A young female domestic short-hair cat presented with neurological signs consistent with a multif... more A young female domestic short-hair cat presented with neurological signs consistent with a multifocal encephalic lesion (depressed mental status, head tilt to the right, cervical ventroflexion, head tremors, tetraparesis, conscious propioceptive deficits in all four limbs and visual deficits). No gross lesions were seen at necropsy. On light microscopical examination lesions were found only in the brain and cervical spinal cord. A generalized vacuolation of the grey matter of the brain was observed. Special staining techniques, immunohistochemistry, lectin affinity histochemistry and ultrastructural studies were performed to characterize the lesion; preservation of the white matter and a reactive astrogliosis were demonstrated. Feline retroviruses and PrPsc were not detected. Ultrastructurally, a dilatation of intracytoplasmic membrane-bounded organelles with membrane disruption and dendritic and somatic swelling was found in astrocytes and neurons. The age of the animal and histological changes suggested a novel, possibly congenital, spongiform degeneration of the brain and cervical spinal cord.
The classical prion diseases (e.g. scrapie of sheep and goats and bovine spongiform encephalopath... more The classical prion diseases (e.g. scrapie of sheep and goats and bovine spongiform encephalopathy of cattle) are characterized by the accumulation of abnormal forms of the prion protein (PrP), usually recognized by their relative resistance to proteolysis compared with the physiological cellular forms of PrP. However, novel prion diseases have been detected in sheep, cattle and man, in which the abnormal PrP has less resistance to proteolysis than identified previously. These more subtle differences between abnormal and normal forms of PrP can be problematic in routine diagnostic tests and raise questions in respect of the range of PrP disorders. Abnormal accumulations of PrP in atypical and classical prion diseases can be recognized by immunohistochemistry. To determine whether altered PrP expression or trafficking might occur in nosological entities not previously connected with prion disease, the brains of sheep affected with diverse neurological conditions were examined for evidence of altered PrP labelling. Such altered immunolabelling was detected in association with either basic lesions or specific diseases. Some reactive glial cells and degenerate neurons found in several different recognized disorders and non-specific inflammatory processes were associated with abnormal PrP labelling, which was absent from brains of healthy, age-matched sheep. The results agree with previous indications that normal PrP function may be linked with the oxidative stress response, but the data also suggest that PrP functions are more extensive than simple protective responses against stress insults.
Interdisciplinary perspectives on infectious diseases, 2010
Prion disorders are infectious, neurodegenerative diseases that affect humans and animals. Suscep... more Prion disorders are infectious, neurodegenerative diseases that affect humans and animals. Susceptibility to some prion diseases such as kuru or the new variant of Creutzfeldt-Jakob disease in humans and scrapie in sheep and goats is influenced by polymorphisms of the coding region of the prion protein gene, while other prion disorders such as fatal familial insomnia, familial Creutzfeldt-Jakob disease, or Gerstmann-Straussler-Scheinker disease in humans have an underlying inherited genetic basis. Several prion strains have been demonstrated experimentally in rodents and sheep. The progression and pathogenesis of disease is influenced by both genetic differences in the prion protein and prion strain. Some prion diseases only affect the central nervous system whereas others involve the peripheral organs prior to neuroinvasion. Many experiments undertaken in different species and using different prion strains have postulated common pathways of neuroinvasion. It is suggested that prion...
Following a severe outbreak of clinical scrapie in 2006-2007, a large dairy goat herd was culled ... more Following a severe outbreak of clinical scrapie in 2006-2007, a large dairy goat herd was culled and 200 animals were selected for post-mortem examinations in order to ascertain the prevalence of infection, the effect of age, breed and PRNP genotype on the susceptibility to scrapie, the tissue distribution of diseaseassociated PrP (PrP(d)), and the comparative efficiency of different diagnostic methods. As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the prevalence of preclinical infection was very high (72/200; 36.0%), with most infected animals being positive for PrP(d) in lymphoreticular system (LRS) tissues (68/72; 94.4%) compared to those that were positive in brain samples (38/72; 52.8%). The retropharyngeal lymph node and the palatine tonsil showed the highest frequency of PrP(d) accumulation (87.3% and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid tissue (RAMALT) was positive in only 30 (41.7%) of the infected goats. However, the efficiency of rectal and palatine tonsil biopsies taken shortly before necropsy was similar. The probability of brain and RAMALT being positive directly correlated with the spread of PrP(d) within the LRS. The prevalence of infection was influenced by PRNP genetics at codon 142 and by the age of the goats: methionine carriers older than 60 months showed a much lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last showed prevalence values similar to isoleucine homozygotes of any age (40/80; 50.0%). Two of seven goats with definite signs of scrapie were negative for PrP(d) in brain but positive in LRS tissues, and one goat showed biochemical and IHC features of PrP(d) different from all other infected goats. The results of this study have implications for surveillance and control policies for scrapie in goats.
The distribution of PrP(BSE) in the brain of nine confirmed BSE field cases was analyzed using im... more The distribution of PrP(BSE) in the brain of nine confirmed BSE field cases was analyzed using immunohistochemistry and compared to the levels of PrP(BSE) determined by two rapid tests (Prionics-Check WESTERN and Prionics-Check LIA). Each brain was dissected into 16 areas: spinal cord, medulla oblongata, pons, mesencephalon, thalamus, hippocampus, cerebellar vermis, cerebellar medulla, cerebellar hemispheres, occipital cortex, temporal cortex, parietal cortex, striatum, frontal cortex, piriform lobe and olfactory bulbs. The highest levels of PrP(BSE) were detected in the medulla oblongata, spinal cord and pons, and correspondingly both rapid tests showed 100% correlation with the immunohistochemistry with regard to sensitivity and specificity. Some inconsistencies between the levels of PrP(BSE) determined either by immunohistochemistry or by the rapid tests were found in brain areas with medium to low levels of PrP(BSE). These brain areas included the cerebellar hemisphere, olfactory bulb, and the temporal and parietal cortices. A brain PrP(BSE) distribution curve (BPDC) was designed by plotting the PrP(BSE) signals obtained from the two rapid tests versus the anatomical region along the caudal-rostral axis of the brain. Comparison of the BPDC of the nine BSE cases showed that all cases had a similar PrP(BSE) distribution in the brain but with variable intensities, which could be explained by different stages in the progression of the disease. We propose that the BPDC could be used as a tool to differentiate classical cases of BSE from the recently identified atypical BSE cases.
Disturbances of the gamma-aminobutyric acid (GABA) neurotransmitter system have been implicated i... more Disturbances of the gamma-aminobutyric acid (GABA) neurotransmitter system have been implicated in chronic degenerative neurological disease. Cognitive dysfunction and neuron loss are features in older dogs. GABAergic neurons also show immunoreactivity for specific calcium-binding proteins. Immunohistochemistry was used to study the neuronal expression of calbindin D-28k and parvalbumin in different areas of the brain in 13 dogs, aged between 2 and 13.5 years. Calbindin expression was found only in the cerebellum. There were significant differences in the quantity and distribution of neurons expressing these proteins between geriatric and adult brains. Parvalbumin- and calbindin-expressing neurons are relatively sensitive to degeneration in the cerebellum of older dogs. Parvalbumin labelling was associated with dystrophic structures that are commonly associated with ageing.
A neuropathological study of Holstein-Friesian calves with spinal muscular atrophy (SMA) demonstr... more A neuropathological study of Holstein-Friesian calves with spinal muscular atrophy (SMA) demonstrated decreased numbers of motor neurons in the brachial and lumbo-sacral regions of the spinal cord, together with swelling and accumulation of phosphorylated neurofilaments, and neuronophagia in most of the remaining motor neurons. The pyramidal tracts, motor cortex and thalamus were not affected. Synaptophysin immunohistochemistry revealed a marked reduction of punctate terminals but only around swollen neurones, suggesting loss of terminal afferents on motor neurons at advanced stages of the degenerative process. An immunohistochemical study of proteins linked with cell death and cell survival demonstrated reduced expression of Fas, Fas-L, Bcl-2 and Bax in swollen motor neurons. Punctate cytochrome C immunoreactivity, consistent with mitochondrial localization, was detected in the soma of normal motor neurons, but not in swollen motor neurons. Finally, no labelling of motor neurons with antibodies to cleaved (active) caspase-3 (17kD) was detected, suggesting a lack of involvement of the apoptotic pathways in motor neuron death. Taken together, the present findings point to necrosis as a major cause of motor neuron death in the advanced stages of SMA in Holstein-Friesian calves.
A young female domestic short-hair cat presented with neurological signs consistent with a multif... more A young female domestic short-hair cat presented with neurological signs consistent with a multifocal encephalic lesion (depressed mental status, head tilt to the right, cervical ventroflexion, head tremors, tetraparesis, conscious propioceptive deficits in all four limbs and visual deficits). No gross lesions were seen at necropsy. On light microscopical examination lesions were found only in the brain and cervical spinal cord. A generalized vacuolation of the grey matter of the brain was observed. Special staining techniques, immunohistochemistry, lectin affinity histochemistry and ultrastructural studies were performed to characterize the lesion; preservation of the white matter and a reactive astrogliosis were demonstrated. Feline retroviruses and PrPsc were not detected. Ultrastructurally, a dilatation of intracytoplasmic membrane-bounded organelles with membrane disruption and dendritic and somatic swelling was found in astrocytes and neurons. The age of the animal and histological changes suggested a novel, possibly congenital, spongiform degeneration of the brain and cervical spinal cord.
The classical prion diseases (e.g. scrapie of sheep and goats and bovine spongiform encephalopath... more The classical prion diseases (e.g. scrapie of sheep and goats and bovine spongiform encephalopathy of cattle) are characterized by the accumulation of abnormal forms of the prion protein (PrP), usually recognized by their relative resistance to proteolysis compared with the physiological cellular forms of PrP. However, novel prion diseases have been detected in sheep, cattle and man, in which the abnormal PrP has less resistance to proteolysis than identified previously. These more subtle differences between abnormal and normal forms of PrP can be problematic in routine diagnostic tests and raise questions in respect of the range of PrP disorders. Abnormal accumulations of PrP in atypical and classical prion diseases can be recognized by immunohistochemistry. To determine whether altered PrP expression or trafficking might occur in nosological entities not previously connected with prion disease, the brains of sheep affected with diverse neurological conditions were examined for evidence of altered PrP labelling. Such altered immunolabelling was detected in association with either basic lesions or specific diseases. Some reactive glial cells and degenerate neurons found in several different recognized disorders and non-specific inflammatory processes were associated with abnormal PrP labelling, which was absent from brains of healthy, age-matched sheep. The results agree with previous indications that normal PrP function may be linked with the oxidative stress response, but the data also suggest that PrP functions are more extensive than simple protective responses against stress insults.
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