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R I Carp

Publications and source records attributed to R I Carp.

At least 19 recordsLinked to original sources
PubMed1992

Demonstration of scrapie strain diversity in infected PC12 cells.

Scrapie strain replication in the nerve growth factor-induced, differentiated PC12 cell culture system was examined. Differences in replication between mouse-derived agents were demonstrated, with the 139A scrapie strain yielding 100- to 1000-fold higher levels of infectivity than the ME7 scrapie strain. Replication was not detected in PC12 cells infected with either the hamster-derived 263K or rat-derived 139R scrapie strains. Studies on the neurotransmitters in infected PC12 cells demonstrated that the adrenergic pathway was unchanged but the cholinergic pathway was altered. Furthermore, the degree of alteration correlated with the level of scrapie strain replication. Comparison of infectivity titres and enzymatic changes in ME7-infected PC12 cells with those in Chandler agent-infected mouse neuroblastoma cells suggests that the significant changes in neurotransmitter levels in cultures exhibiting low titres of infectivity involve factors in addition to strain replication. The variation in the range of scrapie strain replication in PC12 cells is discussed in relationship to species barrier, cell targeting, genetic susceptibility and species strain specificity. These studies further emphasize the value of the PC12 cell model system in examining the scrapie strain-host cell interaction and in addition support the concept of variation among scrapie strains.

Acetylcholinesterase↗
PubMed1991

Scrapie-associated prion protein accumulates in astrocytes during scrapie infection.

In the course of scrapie, a transmissible spongiform encephalopathy caused by an unconventional agent, a normal cellular protein is converted to an abnormal form that copurifies with infectivity and aggregates to form deposits of amyloid. We have used immunocytochemistry and methods that enhance detection of amyloidogenic proteins to investigate the types of cells in the central nervous system which are involved in the formation of the abnormal scrapie-associated protein. We show that this protein accumulates in astrocytes prior to the cardinal neuropathological changes in scrapie--astrogliosis, vacuolation, neuron loss, and amyloid deposition. These findings implicate the astrocyte in the formation of the scrapie isoform of the prion protein and amyloid in scrapie and suggest that this cell type might also be involved in the replication of the scrapie agent.

Amyloid↗
PubMed1991

Scrapie-infected spleens: analysis of infectivity, scrapie-associated fibrils, and protease-resistant proteins.

Scrapie-associated fibrils (SAF) and protease-resistant proteins (PrP) were isolated from spleens and brains of clinical animals (mice and hamsters) from three scrapie agent-host strain combinations, and their concentrations were compared with infectivity levels. The spleens of infected animals contained lower levels of infectivity, PrP, and SAF than did brains. Regardless of the route of infection, both SAF and infectivity were detected in spleen before brain. Infectivity increased in brains and spleens of 139A-infected mice before the detection and increase in SAF, suggesting that the synthesis of SAF and PrP may not be the limiting factor in agent replication. In contrast to those in ME7- and 263K-infected animals, the Western blot profiles for PrP from brain and spleen of 139A-infected mice exhibited distinct differences. Results indicate that SAF and PrP found in the spleens are both organ- and scrapie strain-specific.

Animals↗
PubMed1991

Variation in the characteristics of 10 mouse-passaged scrapie lines derived from five scrapie-positive sheep.

Ten mouse-passaged scrapie lines were initiated from five sheep with clinical scrapie. Of the lines, five were initiated and passaged exclusively in mice with the s7s7 genotype and the remaining five lines were initiated in mice with the p7p7 genotype, with two of these lines subsequently being passaged exclusively in p7p7 mice and two being passaged mainly in p7p7 mice. Lines were passaged three or four times and two parameters were compared: incubation period and the induction of a weight increase during the preclinical period. Considerable variation in the incubation periods was found between the different passage lines at similar passage levels, with a range in s7s7 mice of 113 days to greater than 450 days and a range in p7p7 mice of 219 days to greater than 500 days. All of the lines passaged exclusively in s7s7 mice had shorter incubation periods in this mouse genotype than in p7p7 mice, whereas of the five lines initiated in p7p7 mice, two had shorter incubation periods in p7p7 mouse strains. C57BL mice were used as the indicator strain and most of the lines caused an increase in weight during the preclinical phase of disease compared to control mice injected with normal brain homogenates. For both parameters, incubation period and preclinical weight increase, differences were seen in lines that had identical passage histories, suggesting that an informational molecule separate from host genomic material must specify scrapie strain differences.

Animals↗
PubMed1991

Neuropathological changes in scrapie and Alzheimer's disease are associated with increased expression of apolipoprotein E and cathepsin D in astrocytes.

With the rationale that the neuropathological similarities between scrapie and Alzheimer's disease reflect convergent pathological mechanisms involving altered gene expression, we set out to identify molecular events involved in both processes, using scrapie as a model to study the time course of these changes. We differentially screened a cDNA library constructed from scrapie-infected mice to identify mRNAs that increase or decrease during disease and discovered in this way two mRNAs that are increased in scrapie and Alzheimer's disease. These mRNAs were subsequently shown by sequence analysis to encode apolipoprotein E and cathepsin D (EC 3.4.23.5). Using in situ hybridization and immunocytochemistry to define the cellular and anatomic pathology of altered gene expression, we found that in both diseases the increase in apolipoprotein E and cathepsin D mRNAs and proteins occurred in activated astrocytes. In scrapie, the increase in gene expression occurred soon after the amyloid-forming abnormal isoform of the prion protein has been shown to accumulate in astrocytes. In Alzheimer's disease, the increased expression of cathepsin D also occurred in association with beta-amyloid. These studies reveal some of the molecular antecedents of neuropathological changes in scrapie and Alzheimer's disease and accord new prominence to the role of astrocytes in neurodegenerative conditions.

Aged↗
PubMed1990

Incubation periods and histopathological changes in mice injected stereotaxically in different brain areas with the 87V scrapie strain.

After stereotaxic injection into five different brain areas (cortex, caudate nucleus, substantia nigra, thalamus and cerebellum) of IM mice with the 87V scrapie strain, the cerebellum had the shortest incubation period. The vacuolation pattern was similar regardless of the area injected with extensive vacuolation in the thalamus, mesencephalon and hypothalamus. The pattern of amyloid plaques differed markedly depending on the area injected. In particular, no plaques were seen anywhere in the brain after injection into intact cerebellum, whereas injection into the four cerebral areas yielded plaques in the forebrain but not in the cerebellum. The incubation period after injection into bisected cerebella was much longer than after injection into intact cerebella. Mice injected on one side of bisected cerebellum had amyloid plaques in the forebrain but not in the cerebellum. There is a discussion of the finding that, although no plaques and virtually no vacuolation were seen in the cerebellum, the shortest incubation period occurred after injection into intact cerebellum.

Amyloid↗
PubMed1990

Pancreatic lesions and hypoglycemia-hyperinsulinemia in scrapie-injected hamsters.

Hamsters injected intracerebrally with scrapie strains 139H or 22CH or with normal hamster brain were assessed for body weight periodically throughout the incubation period. Animals injected with the scrapie strains became obese before the appearance of the motor changes that are indicative of the start of clinical disease. During the latter part of the incubation period and during clinical disease, animals were hypoglycemic and showed marked hyperinsulinemia. At autopsy, there was marked hyperplasia and hypertrophy of the cells of the islets of Langerhans. Thyroid, adrenal glands, liver, and kidney also were enlarged. The data suggest a severe endocrinopathy and point to new areas of pathologic and clinical changes that can be assigned to unconventional slow infections.

Animals↗
PubMed1990

Vacuolization, incubation period and survival time analyses in three mouse genotypes injected stereotactically in three brain regions with the 22L scrapie strain.

In previous studies we showed that C57BL mice injected stereotactically in the cerebellum with the 22L scrapie strain had a significantly shorter incubation period than those injected with the same agent in other brain regions. In mice injected in the cerebellum, vacuolization was limited to the cerebellum, medulla and mesencephalon, whereas injection into forebrain regions resulted in vacuolization in all brain regions. The studies suggested that the cerebellum had a selective vulnerability for 22L. In this study we examined the interaction between host genotype and selective vulnerability of specific brain regions. The mouse gene that has the most profound effect on pathogenesis, particularly incubation period, is termed Sinc (scrapie incubation). Groups of mice with three genotypes of Sinc (s7s7, p7p7 and their F1 cross, s7p7) were injected with 22L into the cerebral cortex, thalamus or cerebellum. Analysis of incubation periods showed that, regardless of the host genotype, the cerebellum injection group had a significantly shorter incubation period than groups injected in other regions. After cerebellum injection vacuolization was limited to the cerebellum, medulla and mesencephalon in all three host genotypes. The location of vacuoles within the cerebellum differed depending upon the host strain. Vacuolization developed almost exclusively in grey matter in s7s7 mice, mainly in white matter in p7p7 mice, and in both grey and white matter in F1 mice. These results demonstrate that the selective vulnerability of the cerebellum to induction of clinical disease by 22L does not depend on host genotype, but host genotype does affect lesion distribution within the cerebellum.

Animals↗
PubMed1990

Pathogenesis and pathology of scrapie after stereotactic injection of strain 22L in intact and bisected cerebella.

The mechanisms involved in the spread of scrapie within the brain remain unclear. To examine this issue the 22L scrapie strain was injected in one side of the cerebellum of mice in which the cerebellum had been bisected prior to injection. Another group of animals received the same injection into intact cerebella, i.e. without prior bisection. We found that bisection of the cerebella delayed the spread of scrapie agent from the injection site to the contralateral side of the cerebellum and that the occurrence of vacuolization was not as extensive and was markedly delayed in the uninjected side compared to its occurrence after injection in the intact cerebellum. Replication of agent in an area preceded the development of vacuolization in that area by several weeks. There was marked loss of Purkinje cells on the injected side of bisected cerebella, with no loss seen on the uninjected side. The incubation period of scrapie disease in mice injected after cerebellar bisection was significantly longer than after the injection of intact cerebella. The results in this study suggest that the scrapie agent spreads along intact nerve cell tracts, probably by axonal transport.

Animals↗
PubMed1990

Further characterization of scrapie replication in PC12 cells.

The rat pheochromocytoma cell line, PC12, undergoes neuron-like morphological, biochemical and electrophysiological differentiation, in the presence of low concentrations of nerve growth factor (NGF). NGF-treated PC12 cells have been shown previously to support 139A scrapie agent replication. In the present report we extended these findings and analysed the cellular conditions necessary for agent replication. Following the infection of differentiated PC12 cells, scrapie replicated to relatively high titres as determined by an incubation period assay. The removal of NGF, which causes the gradual dedifferentiation of PC12 cells, resulted in the inability of scrapie to replicate. The scrapie infectivity detected in PC12 cultures is cell-associated and not released into the medium. Cells in infected cultures did not show any change in morphology when compared to cells in mock-infected cultures. Titration studies of scrapie infectivity in PC12 cells have indicated that up to 4 LD50 units per cell can be obtained although a yield of 1 LD50 per cell was more common. Using an approximate m.o.i. of 1, only differentiated PC12 cells supported 139A scrapie agent replication when compared to two other differentiated, neuronal cell types, indicating that PC12 cells are more susceptible to agent replication. These studies support further the suitability of using differentiated PC12 cells as an in vitro model to study scrapie agent replication.

Adrenal Gland Neoplasms↗
PubMed1989

Scrapie-induced alterations in glucose tolerance in mice.

Certain scrapie strains cause obesity in several strains of mice. The potential association between obesity and altered glucose tolerance was assessed by monitoring body weight and glucose tolerance throughout the incubation period in scrapie strain-mouse strain combinations that do and do not produce obesity. Virtually all obese mice showed reduced glucose tolerance as shown by significantly higher blood glucose levels 2 h after a glucose overload. Mice injected with a scrapie strain that did not cause obesity showed normal tolerance. The scrapie infectivity titre of the pancreas of obese mice clinically affected with scrapie was very low. Adrenalectomy prevented both the increase in weight and aberrant glucose tolerance but had no other effect on the course of the disease. Following increasing dilution of the inoculum, the increase in body weight and the development of aberrant glucose tolerance reached an end-point that was similar to that of scrapie infectivity. The system described provides an inducible model of obesity with altered glucose tolerance.

Adrenalectomy↗
PubMed1989

Classic genetics of scrapie.

Many years ago, observations of natural scrapie revealed differences in clinical manifestations and in the areas of the brain that showed the most intense histopathological changes. In experimental work with scrapie in mice two fundamental points were established in early studies: (1) A mouse gene, termed Sinc for scrapie incubation, affects the length of the incubation period. (2) In a single strain of mice, incubation periods of different "strains" of scrapie can differ by as much as 3-4 fold, e.g., the incubation period of the ME7 scrapie strain in C57BL mice is approximately 122 days, whereas the incubation period for the 22A strain is 360 days. From this "classic" beginning our knowledge about the parameters influenced by genetic characteristics of both host and agent have expanded. In a number of instances, initial examination of an aspect of host-agent interaction has subsequently revealed surprising influences of informational molecules from both host and agent. A partial list of the parameters under genetic control follows: (1) The extent of vacuolation in various regions of the brain; (2) The quantity of amyloid plaques in the brain; (3) The occurrence of increased weight in the preclinical phase of disease; (4) The development of aberrant glucose tolerance; (5) The area of the brain which yields the shortest incubation period after stereotaxic injection; and (6) The physical-chemical and immunological characteristics of scrapie associated fibrils. In several well documented instances differences between scrapie strains were evident after repeated passages of the strains in the same host strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Influence of stereotaxically injected scrapie on neurotransmitter systems of mouse cerebellum.

The 22L strain of scrapie was injected stereotaxically into the cerebellum of C57BL/6J mice to determine its effect on several cerebellar neurotransmitter systems during the early clinical stages of the disease. In this model vacuolar lesions are restricted to the cerebellum with no evidence of vacuolization in other brain regions. Although vacuolar lesions develop throughout all cell layers of the cerebellum, they are most severe in the granule cell layer. Modest but significant (P less than 0.01) reductions in cerebellar weight, glutamate decarboxylase activity, and in the affinity of the N6-[adenine-2,8-3H]cyclohexyladenosine binding sites, were observed in scrapie affected mice. The densities of the high- and low-affinity adenosine receptors were unaffected. Adenosine receptors in the cerebellum are highly localized to the axon terminals of the glutamatergic, GABA receptive granule cells. GABA, benzodiazepine, glutamate, and muscarinic cholinergic receptors were not significantly altered. In addition, the high-affinity uptake of glutamate, and the activity of choline acetyltransferase were not significantly changed. GABA high-affinity uptake was slightly increased. Even though the granule cell layer of the cerebellum had undergone severe vacuolation, only modest neurotransmitter changes were apparent. Although these results suggest a tenuous relationship between scrapie pathology and the integrity of neurotransmitter systems, it is possible that compensatory neurochemical changes in uncompromised neuronal populations may have masked potentially specific neurotransmitter effects.

Animals↗
PubMed1988

Multiple sclerosis etiology--an Epstein-Barr virus hypothesis.

The opinion has been expressed frequently in the literature that MS is caused by a combination of an environmental agent and genetic factors, possibly with an autoimmune component. However, the specific environmental agent has not as yet been identified. This paper describes cumulative circumstantial evidence which strongly points to a post-pubertal primary Epstein-Barr virus infection as this unidentified etiological event in the induction of MS disease.

Adolescent↗
PubMed1988

Adrenal involvement in scrapie-induced obesity.

In previous studies we found an increase in body weight during the preclinical phase of disease in certain scrapie strain-mouse strain combinations. The effect was augmented by injection into the hypothalamus. In the present study, we found an increase in food consumption (compared to the normal mouse brain injection group) for both the 139A and ME7 scrapie groups, although only the ME7 group showed an increase in body weight. In a scrapie strain-mouse strain combination that showed an increase in body weight, the adrenal gland was the only organ that showed a significant increase in weight. The titer of scrapie in the adrenals was comparatively low. Adrenalectomy prevented the increase in body weight in two strains of mice injected with the ME7 scrapie strain. The results suggest that scrapie-induced obesity depends on an effect of scrapie on the hypothalamic-pituitary-adrenal axis.

Adrenal Glands↗
PubMed1987

Ultrastructural observations of spinal cord lesions and blood-brain barrier changes in scrapie-infected mice.

Spinal cord samples from IM or VM mice injected intracerebrally with the 87V scrapie agent were examined ultrastructurally at the clinical stage of disease for changes in blood vessel permeability and for pathological alterations. In several animals, (3 of 16), massive changes were noted in the cervical spinal cords in the subependymal area of the cortical gray matter immediately surrounding the central canal including ependymal cell changes, the presence of amyloid plaque in close association with microglial cells, extensive neuropil vacuolation, the appearance of reactive astrocytes, degenerating neurites and vacuolated neurons. In those regions showing structural damage, localized increased permeability to horseradish peroxidase across the blood-brain barrier was noticed along with the appearance of numerous vesiculo-canalicular profiles in micro-blood vessel endothelial cells with extravasation of the tracer to the neuropil. Some damaged neurons appeared flooded with this tracer. These changes were not observed in either the thoracic or lumbar spinal cord regions. The occurrence of pathological changes in the spinal cords of a small percentage of intracerebrally injected mice was probably due to a high concentration of the scrapie agent which localized in the cervical spinal cord, presumably after entering the spinal fluid via the lateral ventricle at the time of injection.

Amyloid↗