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Biomedical subjects

R I Carp

Publications and source records attributed to R I Carp.

At least 55 records · Page 3Linked to original sources
PubMed1994

Effect of infection with the 139H scrapie strain on the number, area and/or location of hypothalamic CRF- and VP-immunostained neurons.

Scrapie is a transmissible neurodegenerative disease which shares some characteristics with Alzheimer disease (AD). Recent studies show abnormal enlargement of the adrenal glands and kidneys in 139H-affected hamsters. Using immunocytochemical techniques with antibodies to corticotropin-releasing factor (CRF) and vasopressin (VP), we observed the following: (1) a significantly higher number of CRF-immunostained neurons in the preoptic nucleus of hypothalamus of 139H-affected hamsters than controls; (2) the area of VP-immunostained (ir-VP) neurons in the lateral hypothalamus, which includes the internuclear group of magnocellular neurons and the nucleus circularis, was significantly lower for 139H-affected hamsters than for controls; and (3) no significant difference between 139H-affected and control hamsters with regard to the number of ir-VP neurons in the dorsal-medial hypothalamus (DMH), including the paraventricular hypothalamus, or the supraoptic nuclei. However, the population of ir-VP neurons in the DMH shifted to the anterior part of the hypothalamus in 139H-affected hamsters. Three-dimensional models of the immunostaining were prepared and these provide clear depictions of the changes noted. The changes in the CRF and VP systems in 139H-affected hamsters suggest that the neuroendocrine system can be affected by unconventional slow infections.

Animals↗
PubMed1994

Concentration and distribution of infectivity and PrPSc following partial denaturation of a mouse-adapted and a hamster-adapted scrapie strain.

PrPSc is a specific protein marker for slow infectious diseases known as the transmissible subacute spongiform encephalopathies. Although PrPSc is closely associated with infectivity, it is not known if it is the infectious agent itself, a component of the agent or merely adventitiously associated with infectivity. In the present study we demonstrate that the resistance of PrPSc to partial denaturation and of infectivity to inactivation differs markedly for two scrapie strains. Proteinase K treatment or electrophoretic analysis of partially denatured PrPSc preparations reveal a dissociation between infectivity and demonstrable PrPSc. Our findings support other evidence that not all PrPSc is required for infectivity. Our studies combined with previous biological analyses suggest that PrPSc cannot be the sole component associated with the infectious agent.

Animals↗
PubMed1994

Interaction of scrapie agent and cells of the lymphoreticular system.

The current study focused on the role of lymphoid elements of the lymphoreticular system in scrapie pathogenesis. In the first experiment, adherent and non-adherent splenocytes from mice infected with the 139A scrapie strain were prepared. The level of infectivity on a per cell basis was significantly higher in the adherent cell population. In a second set of experiments, thymocytes, unfractionated splenocytes, T-cell enriched and T-cell depleted fractions of splenocytes were infected in vitro with ME7 scrapie strain. There was no evidence of replication of scrapie in ME7-exposed cells in any of the preparations during the first 5-14 days post-exposure. In assays done 5 days after infection, most of the infectivity was cell-associated. These data suggest that lymphoid cells are not involved in scrapie replication. The level of IgA in the serum of 139A-infected mice was markedly reduced compared to the levels in mice injected with normal mouse brain homogenate or with the ME7 scrapie strain. The reduction in IgA levels in 139A-infected mice was evident at each of the 4 time points tested. The final experiment dealt with the question of scrapie replication in the lymphoreticular organs in mouse strains with different incubation periods for 139A after intraperitoneal injection. The results in this experiment suggest that the difference in incubation periods is related to differences in time of access of infection to the central nervous system rather than to differences in the ability of agent to replicate in spleen.

Animals↗
PubMed1994

Histopathological changes in the islets of Langerhans in scrapie 139H-affected hamsters.

Previous studies showed that the 139H strain of scrapie injected into hamsters caused obesity, a marked hypertrophy of the islets of Langerhans, generalized endocrinopathy and marked hypoglycaemia-hyperinsulinaemia. In the current study, female weanling Syrian hamsters (LVG/LAK strain) were inoculated intracerebrally with scrapie strain 139H or 263K, or with normal hamster brain. Sections of the pancreas stained with haematoxylin and eosin or Gomori's one-step trichrome were examined by light microscopy. The 139H-affected hamsters showed extensive vacuolization, cellular hypertrophy, cellular atrophy, cytoplasmic vesicles and nuclear pathological changes in the islets of Langerhans. Also observed were abnormal structures, termed blood vessel cores, in the islets of 139H-affected hamsters. These structures were almost always centrally located within islets and were surrounded by B cells, some of which were abnormally elongated. None of these pathological changes were seen in the islets of Langerhans in control or 263K-affected hamsters. The level of scrapie-specific protease resistant protein (PrPSc) in pancreas was much lower than that in brain, a finding consistent with previous data showing low scrapie infectivity titres in pancreas.

Animals↗
PubMed1994

Hyperplasia and hypertrophy of B cells in the islets of Langerhans in hamsters infected with the 139H strain of scrapie.

Previous studies showed that in hamsters the 139H, but not the 263K, scrapie strain caused a marked increase in pancreatic size and led to obesity, hypoglycaemia and striking hyperinsulinaemia. In the preceding paper (Ye et al., 1994), the islets of Langerhans in 139H-affected hamsters showed cellular atrophy, fibrosis, cytoplasmic vesicles and nuclear pathological changes. In the present study, the profiles of pancreatic islets were classified into three sizes with an image analyzer. The number and total area covered by "small" islet profiles were less in 139H-affected than in normal hamsters. In contrast, the number and the area of "medium" and "large" islet profiles were significantly greater in 139H than in normal hamsters. With antibodies to insulin, glucagon, somatostatin and pancreatic polypeptide, the proportions of B, A, D and F cells were determined. With somatostatin-positive cells arbitrarily given a value of 1, the ratio of B:A:D:F cells in the islets was 27:5:1:0.04 in normal hamsters and 122:7:1:0.04 in 139H-affected hamsters. The increase in B cells would account for the islet enlargement and the hypoglycaemia-hyperinsulinaemia seen in 139H-affected hamsters.

Animals↗
PubMed1993

Increased expression of heat shock protein, transferrin, and beta 2-microglobulin in astrocytes during scrapie.

Scrapie is a slow infection and neurodegenerative disease of animals characterized pathologically by formation of amyloid, astrocytosis, vacuolation and injury and death of neurons. Our previous studies of scrapie point to: (i) a critical role for the astrocyte in responding to, and perhaps inadvertently contributing to, the neuropathological manifestations of infection; and (ii), the hypothesis that the astrocyte executes a programed response to neurological injury analogous to the stress response. The expression of genes encoding transferrin and beta 2-microglobulin has been shown to increase during scrapie and we sought in the studies reported here to determine whether this modulated expression would map to astrocytes. We also looked for changes in a heat shock protein that is induced in the stress response. We show that transferrin, beta 2-microglobulin and heat shock 72 kD protein all increase in astrocytes in the course of infection. We speculate in the discussion on the possible functions of these and other proteins in neurodegenerative processes and why these functions so frequently reside in the astrocyte.

Animals↗
PubMed1993

Analysis of host genetic control of scrapie-induced obesity.

The potential for induction of obesity during the preclinical phase of scrapie disease in mice was previously shown to be a function of both the strain of scrapie and the strain of inbred mouse. In the present study, host control of obesity induction by a scrapie strain was examined to determine if the effect were dependent on a single gene or multiple genes. The approach used was assessment of the pattern of weight induction in F1 and F2 crosses of parental inbred mouse strains that did or did not show a weight increase with a specific scrapie strain. Analyses of these data indicated that the induction of obesity was controlled by multiple host genes. In an unrelated observation, there was a correlation between the incubation period of a strain of scrapie in F2 generation mice and their coat color, i.e., the average incubation period of yellow-brown mice was significantly less than those of either black or white mice.

Animals↗
PubMed1993

Brain regional distribution of prion protein PrP27-30 in mice stereotaxically microinjected with different strains of scrapie.

Stereotaxic inoculation was used to examine the role of scrapie agent strain, inoculum, and injection site on the brain regional distribution of the prion protein, PrP27-30. Neither the type of inoculum nor the injection site influenced the distribution of PrP27-30 in brains of mice. Among the parameters examined, only the strain of agent affected the pattern of distribution and the yield of PrP27-30. Although mice injected into the cerebellum had the shortest incubation period, the cerebellum gave the lowest yield of the PrP27-30 among the seven brain regions examined. The positive correlation between PrP27-30 regional distribution and lesion profile (degree of vacuolation) reinforces the role of the PrPSC protein in scrapie pathogenesis.

Animals↗
PubMed1993

The role of antibodies to PrP in the diagnosis of transmissible spongiform encephalopathies.

Transmissible spongiform encephalopathies (TSE) are progressive degenerative disorders of the central nervous system. Efficient and accurate identification of these disorders is necessitated by their transmissibility and fatal prognosis. The availability of polyclonal and monoclonal antibodies to a TSE disease-specific protein marker PrPSC affords the sensitivity and specificity for immuno-diagnostic assays. The majority of PrPSC antigenic sites are species-directed, involve non-self sites and are common to both the normal host precursor (PrPC) and the modified disease form. The availability of these antigenic sites is highly restricted by conformational influences resulting in epitope-dependent restrictions on antibody binding. Diagnostic immunoassays for TSE have relied largely on immunocytochemistry and immunoblotting. Restrictions on epitope availability have lead to the formulation by several laboratories of a variety of techniques to unmask PrP specific epitopes. In addition, diagnosis requires the ability to detect PrPSC specifically in tissue which can also contain immuno-reactive PrPC. Immuno-detection techniques are discussed relative to their range of application, ease of interpretation, specificity and sensitivity.

Amino Acid Sequence↗
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↗