Lewy bodies contain epitopes both shared and distinct from Alzheimer neurofibrillary tangles

Most of the identified constituents of the filamentous inclusions characteristic of the neurodegenerative diseases of aging are derived from the cytoskeleton. This study was undertaken to define immunocytochemically the cytoskeletal constituents of the filamentous cytopathologic marker of idiopathic Parkinson disease, the Lewy body (LB). An array of antibodies specific to neurofilaments, tubulin, microtubule associated proteins (tau, MAP1 and MAP2) and Alzheimer neurofibrillary tangles (NFT) were used to immunostain sections containing LB. All the antibodies to tubulin, MAP1 and MAP2 and the majority of the antibodies to neurofilaments and NFT recognized LB. The two monoclonal antibodies to NFT that recognize LB also react with ubiquitin, which has been identified in NFT. The prominent NFT component, tau, is apparently not incorporated into LB. These findings suggest that the presence of tau might not be a prerequisite to the formation of abnormal filaments. Therefore, although LB contain elements of neurofilaments, microtubules and ubiquitin, as do other abnormal neuronal filaments, they are distinct in composition. These distinctive and shared features may provide useful insights regarding the mechanisms underlying the formation of filaments in LB as well as those of other neuronal inclusions.

Phosphorylation of neurofilaments is altered in amyotrophic lateral sclerosis

We used a library of monoclonal antibodies (Mab) that distinguish phosphorylated (P+) and non-phosphorylated (P-) neurofilament (NF) epitopes to examine phosphorylation of NF in lower motor neurons of patients with amyotrophic lateral sclerosis (ALS), of neurologically normal controls of different ages, and of patients with central chromatolysis due to injuries to motor root axons. Monoclonal antibodies directed to P+ NF immunostained five to ten times more neuronal perikarya in ALS than in age-matched controls. Spheroids, which are NF containing axonal enlargements, found in significantly greater number in proximal axons in ALS, were also intensely immunostained with Mab to P+ NF. Moreover, anterior root axons in five of eleven cases of ALS reacted only with the Mab to P+ NF, while both P- and P+ NF were present in motor roots from controls. In control groups, the number of neuronal perikarya and spheroids that immunoreacted with the Mab to P+ NF increased moderately with age. Chromatolytic lower motor neurons were recognized by Mab to P+ NF. Our results show that the process of phosphorylation is altered in ALS. We propose that phosphorylation of NF in ALS occurs prematurely and that it is more likely to be associated with an impairment of NF transport than to be part of a chromatolytic reaction of lower motor neurons.

Alz 50 recognizes abnormal filaments in Alzheimer's disease and progressive supranuclear palsy

The monoclonal antibody Alz 50 recognizes a 68-kDa protein present in large amounts in cerebral tissue of patients with Alzheimer's disease (AD). We used light and electron microscopic as well as quantitative immunochemical techniques to compare distribution, characteristics, and amount of Alz 50 antigen in the tegmental nuclei of the pons of subjects with progressive supranuclear palsy (PSP) and subjects with AD. In both conditions Alz 50 antigen was found in neurons with and without neurofibrillary tangles (NFT). In NFT-bearing neurons the antigen was located in the filamentous components of NFT in both diseases, i.e., in straight filaments forming the NFT in PSP and in paired helical filaments components of the NFT in AD. In neurons lacking NFT the antigen was associated with straight filaments of various sizes, but the straight filaments were generally thinner than those of PSP. On immunoblots of both PSP and AD tissues, Alz 50 recognized a set of bands between 68 and 35 kDa which were not present in control tissue. The amount of Alz 50 antigen in AD tissue was estimated to be 10 times higher than that present in PSP tissue. The higher amount of Alz 50 antigen in AD tissue correlates with the more severe fibrillary pathology in this disease than in PSP. We propose that the Alz 50 antigen, although possibly related to tau proteins, distinguishes neurons that are forming abnormal filaments.

Influence of neuronal location on antigenic properties of neurofibrillary tangles

We quantitatively assessed the antigenic properties of the neurofibrillary tangles (NFT) located in neurons of the tegmental nuclei of the pontine raphe in progressive supranuclear palsy (PSP) and Alzheimer's disease (AD). These properties were then compared with those of NFT of AD located in hippocampal neurons. Antibodies known to react with cortical NFT of AD were used to stain sections from PSP, AD, and control cases. The reaction with the straight filaments of NFT of PSP and with the paired helical filaments of pontine NFT of AD was ascertained by immunoelectron microscopy. The results show that, despite the ultrastructural difference, straight filaments in NFT of PSP and paired helical filaments in NFT of AD share antigenic properties when they are located in the same neuronal population. In contrast, paired helical filaments located in the cerebral cortex are antigenically different from those in pontine nuclei. Location, more than structure, may play a role as determinant of antigenic properties in straight filaments of PSP and paired helical filaments of AD.

Ubiquitin is associated with abnormal cytoplasmic filaments characteristic of neurodegenerative diseases

Several degenerative diseases of the nervous system are characterized by the presence of neuronal inclusions. Most of these inclusions are made of abnormal filaments and share epitopes with cytoskeletal proteins. One of these inclusions, the neurofibrillary tangle of Alzheimer disease, has recently been shown to contain ubiquitin, a regulatory protein thought to play a role in the degradation of abnormal proteins. We carried out light and electron microscopic immunocytochemistry with several polyclonal and monoclonal antibodies to investigate the presence of ubiquitin in neuronal inclusions of neurodegenerative diseases. Ubiquitin was present not only in paired helical filaments that form the neurofibrillary tangle of Alzheimer disease, but also in the filamentous components of the inclusion characteristic of Parkinson disease, Pick disease, and progressive supranuclear palsy. In contrast, ubiquitin was not detected in other neuronal inclusions often found in aging and in Alzheimer disease, such as Hirano bodies and granulovacuolar degeneration. Reactivity with monoclonal antibodies suggests differences in the ubiquitin-acceptor proteins present in the inclusions studied. It is concluded that ubiquitin is selectively present in neuronal inclusions of degenerative diseases.

Paramyosin and actin in schistosomal teguments

Schistosomes are blood-dwelling trematode parasites that infect 200 million people in developing countries. The critical role served by the tegument in immune evasion and parasite homeostasis suggests that a detailed knowledge of tegumental components would be helpful in the design of new drugs and the production of vaccines. We demonstrate here, by immunoelectron microscopy, that the cytoskeletal proteins actin and paramyosin are organized into major tegumental structures of Schistosoma mansoni. The surface spines are composed of paracrystalline arrays of actin filaments. Actin is also present in areas recovering from damage, implying an important role for this structural protein in tegumental repair. Paramyosin exists predominantly in the tegument in a non-filamentous form, the membrane-bounded elongate bodies. The localization of this protein to the tegument of the parasite is the likely basis for resistance to S. mansoni observed in mice immunized with paramyosin (refs 1, 2 and T. P. Flanigen et al., in preparation).

Ultrastructural localization of erythrocyte cytoskeletal and integral membrane proteins in Plasmodium falciparum-infected erythrocytes

The distributions of ankyrin, spectrin, band 3, and glycophorin A were examined in Plasmodium falciparum-infected erythrocytes by immunoelectron microscopy to determine whether movement of parasite proteins and membrane vesicles between the parasitophorous vacuole membrane and erythrocyte surface membrane involves internalization of host membrane skeleton proteins. Monospecific rabbit antisera to spectrin, band 3 and ankyrin and a mouse monoclonal antibody to glycophorin A reacted with these erythrocyte proteins in infected and uninfected human erythrocytes by immunoblotting. Cross-reacting malarial proteins were not detected. The rabbit sera also failed to immunoprecipitate [3H]isoleucine labeled malarial proteins from Triton X-100 and sodium dodecyl sulfate (SDS) extracts of infected erythrocytes. These three antibodies as well as the monoclonal antibody to glycophorin A bound to the membrane skeleton of infected and uninfected erythrocytes. The parasitophorous vacuole membrane was devoid of bound antibody, a result indicating that this membrane contains little, if any, of these host membrane proteins. With ring-, trophozoite- and schizont-infected erythrocytes, spectrin, band 3 and glycophorin A were absent from intracellular membranes including Maurer's clefts and other vesicles in the erythrocyte cytoplasm. In contrast, Maurer's clefts were specifically labeled by anti-ankyrin antibody. There was a slight, corresponding decrease in labeling of the membrane skeleton of infected erythrocytes. A second, morphologically distinct population of circular, vesicle-like membranes in the erythrocyte cytoplasm was not labeled with anti-ankyrin antibody. We conclude that membrane movement between the host erythrocyte surface membrane and parasitophorous vacuole membrane involves preferential sorting of ankyrin into a subpopulation of cytoplasmic membranes.

Arachidonic acid metabolism in Ascidia ceratodes eggs: role of lipid peroxidation

1. Addition of arachidonic acid (AA) to Ascidia ceratodes oocyte homogenates results in its rapid oxidation to several polar products. 2. AA oxidation in homogenates has both calcium independent and calcium stimulated components. 3. Calcium or AA addition to an oocyte homogenate stimulates O2-consumption. 4. Stimulation of homogenate O2-consumption by AA and calcium is additive. 5. Intact eggs oxidize AA to products similar to those detected in vitro. 6. Quantitatively total AA oxidation was similar for unfertilized and fertilizing eggs and dividing embryos, while qualitative differences were detected for the three stages. 7. These results demonstrate the presence of lipoxygenase-like, peroxidizing activity, in Ascidia eggs that is capable of producing products potentially important to the control of early metabolic events during development.

Role of calmodulin in Plasmodium falciparum: implications for erythrocyte invasion by the merozoite

Calmodulin, a calcium-dependent modulator protein, was shown to be indispensable for in vitro growth of erythrocytic stages of the human malaria parasite, Plasmodium falciparum. When the potent calmodulin antagonists, W7, trifluoperazine (TFP) and R24571, were added to cultures of P. falciparum they inhibited invasion of erythrocytes by merozoites, as well as maturation of schizonts. W5, a chlorine-deficient analogue of W7, was a much weaker inhibitor than W7. The concentrations of W5, W7, TFP and R24571 needed to produce 50% inhibition of schizont maturation were 63.5, 19, 18 and 8.5 microM, respectively, while concentrations needed to inhibit 50% the appearance of ring forms were only 19.5, 7, 8.4 and 4.5 microM, respectively. All the antagonists were more effective at inhibiting the invasion of erythrocytes by merozoites than maturation of schizonts. Ca2+ depletion by EGTA also inhibited merozoite invasion of erythrocytes. Unlike W5, W7, TFP and R24571, cyclosporin A (CsA) showed marked inhibition of schizont maturation at concentrations that reduce ring form production. Immunoelectron microscopy showed that calmodulin was concentrated at the apical end of both free and intraerythrocytic merozoites. No anticalmodulin immunoreactivity was observed in merozoites grown in the presence of 10 microM TFP, although the other calmodulin antagonists and EGTA did not significantly affect the calmodulin location in merozoites. These results suggest that the accumulation of calmodulin at the apical end of merozoites plays an important role during their attachment to and/or invasion of the host erythrocyte, possibly through activation of Ca2+ dependent processes.

Immunocytochemical properties of Alzheimer straight filaments

In addition to paired helical filaments (PHF), the Alzheimer neurofibrillary tangle (NFT) contains straight filaments measuring 10-15 nm in width, as well as amorphous material. In previous immunoelectron microscopic studies, we have demonstrated that PHF and the amorphous material share antigens with the microtubule associated protein, tau, and the 200 kDa subunit of neurofilaments (NF). The present immunoelectron microscopic study focuses on the antigens present in the straight filaments contained in the NFT. Indirect and direct immunogold staining of Vibratome sections of Alzheimer hippocampus with a monoclonal antibody to NF200 kDa (1.1.1.) and polyclonal antibodies to NF, tau, and to PHF yielded intense and specific reaction with NFT. Within the same NFT both straight filaments and PHF were decorated by all the antibodies. Similarly decorated within NFT were filaments displaying a transitional form between straight filaments and PHF. Both PHF and straight filaments were also recognized by all the antibodies after extraction with an ionic detergent. These findings show that straight filaments contain most, if not all, of the antigens known to be present in PHF and share with PHF insolubility in ionic detergents. It is suggested that straight filaments result from alternative pathways of organization of the same components as form the PHF.

Antibodies to the neuronal cytoskeleton are elicited by Alzheimer paired helical filament fractions

Antibodies were raised to paired helical filament (PHF) enriched fractions obtained from brains of individuals with Alzheimer disease by extraction with ionic detergent followed by sucrose gradient centrifugation. Electron microscopic examination showed that the fractions were enriched in Alzheimer PHF but contained also lipofuscin, amyloid, granular material and membranous elements. Analysis of these fractions with SDS-PAGE stained with Coomassie blue showed only a faint band at approximately 60 kDa while most of the material was excluded from the stacking gel. BALB/c mice were injected weekly with 100 or 200 micrograms of these fractions or corresponding fractions from age-matched control brains. The 3 mice injected with Alzheimer brain, but not the 5 mice injected with control brain fractions, produced antibodies that reacted with central and peripheral nervous system axons, Alzheimer neurofibrillary tangles in intact tissue as well as with isolated, SDS-treated paired helical filaments. In gel strips antibodies from all 3 mice injected with Alzheimer brain fractions reacted with the 200-kDa and 168-kDa but not the 68-kDa neurofilament subunits. The 3 antisera reacted also with some forms of the microtubule-associated protein tau. Adsorptions with the insoluble fraction from Alzheimer but not from control brains blocked staining of axons and NFT by all 3 antisera. Adsorption with highly purified neurofilament proteins or with a preparation containing the 200-kDa and 168-kDa neurofilament subunits blocked axon and NFT immunostaining only in one antiserum. Adsorptions with microtubule protein, heat-stable microtubule-associated protein, or a preparation of tau did not completely block immunostaining by any of the 3 antisera. These results demonstrate that fractions enriched with Alzheimer paired helical filaments contain insoluble neurofilament, tau and other yet unidentified antigens.

Filaments of Pick's bodies contain altered cytoskeletal elements

Pick's disease, a form of progressive senile dementia, is distinguished by the presence of neuronal inclusions known as Pick's bodies. The Pick's body consists mostly of sparse 10-20-nm straight filaments admixed with other cytoplasmic elements. This ultrastructural study was undertaken to establish which components of the Pick's body share epitopes with the normal neuronal cytoskeleton and with Alzheimer's paired helical filaments. Vibratome sections from postmortem brains of patients afflicted with Pick's disease were immunostained by means of polyclonal and monoclonal antibodies to neurofilaments, an antiserum to microtubule proteins not cross-reacting with neurofilaments, and an antiserum to Alzheimer's paired helical filaments. All the antibodies have been shown previously to react with Alzheimer's paired helical filaments. The peroxidase-antiperoxidase or indirect immunogold procedure was used for immunostaining. In addition, we used Bodian's silver stain, which has a high affinity for neurofilaments. At the electron-microscopic level the antibodies and Bodian's silver reacted with the straight filaments and some amorphous elements contained within the Pick's body. The following preadsorptions blocked the immunoreaction: neurofilament antibodies with neurofilaments; microtubule antibodies with microtubule protein or a preparation of the microtubule associate protein, tau; antibodies to paired helical filaments with Alzheimer's brain tissue. Treatment of brain tissue containing Pick's bodies with sodium dodecyl sulfate, a solvent of the normal neuronal cytoskeleton, did not dissolve straight 12-nm filaments. The detergent extracted filaments contained the same isotopes as the Pick's filaments in intact tissue. These results demonstrate that the straight filament components of the Pick's body contain the same neurofilament and microtubule epitopes as the Alzheimer's paired helical filaments and that the filaments share insolubility characteristics similar to those of the paired helical filaments. It is proposed that these two structures are related and are derived at least in part from altered components of the normal neuronal cytoskeleton.

Ubiquitin is detected in neurofibrillary tangles and senile plaque neurites of Alzheimer disease brains

Neurofibrillary tangles (NFT) and neurites associated with senile plaques (SP) in Alzheimer disease-affected brain tissues were specifically immunostained with affinity-purified antibody preparations directed against ubiquitin. In addition, a class of neurites seen in brain regions containing NFT and SP were also specifically stained. Cross-reactivity of the ubiquitin antisera for tau protein, neurofilament proteins, and high molecular weight microtubule-associated proteins (MAPs) were ruled out by (i) the inability of the ubiquitin antisera to stain these proteins in immunoblotting experiments and (ii) the inability of tau, neurofilament, and MAP preparations, when preincubated with the ubiquitin antisera, to inhibit the selective neurofibrillar staining observed. Our results are consistent with the suggestion that ubiquitin is covalently associated with the insoluble neurofibrillary material of NFT and SP. We propose that the ubiquitin-mediated degradative pathway may be ineffective in removing these fibrillar structures in Alzheimer disease brain.

Hirano body filaments contain actin and actin-associated proteins

Hirano bodies are eosinophilic, rod-shaped intraneuronal inclusions whose frequency increases with age and with Alzheimer's disease. To investigate their composition and possible relationship to the neuronal cytoskeleton, we employed immunocytochemistry and immunoelectronmicroscopy by using antisera to cytoskeletal proteins. The presence of actin, alpha-actinin, vinculin and tropomyosin was demonstrated diffusely throughout the Hirano body. The presence of these proteins supports the contention that Hirano bodies are derived from an abnormal organization of the neuronal cytoskeleton. The staining of Hirano bodies with fluorescent labelled phalloidin, a probe with a unique affinity for F-actin, indicates that the actin in Hirano bodies is in the F-state. Results of high voltage electron microscopy on 1.0 and 0.5 micron sections confirm the purely filamentous nature of Hirano bodies. These findings suggest that the mechanism of formation of Hirano bodies is different from that of the neurofibrillary tangle, another characteristic intraneuronal inclusion seen in Alzheimer patients.

Hirano bodies contain tau protein

Hirano bodies are intraneuronal inclusions whose frequency increases with age and Alzheimer's disease. These paracrystalline inclusions have been shown previously using immunocytochemistry to share epitopes with actin, tropomyosin, alpha-actinin and vinculin. Hirano bodies have not previously been demonstrated to share components with neurofibrillary tangles, another intraneuronal inclusion characteristic of Alzheimer's disease. In this study, we show that Hirano bodies bind antibodies to the microtubule-associated protein tau, a component of Alzheimer neurofibrillary tangles.

Coexistence of cytokeratin, vimentin and neurofilament protein in human choroid plexus. An immunohistochemical study of intermediate filaments in neuroepithelial tissues

The expression of intermediate filament proteins in human brain ependyma and choroid plexus epithelium has been studied by immunohistochemistry using a panel of monoclonal antibodies directed against all five classes of intermediate filaments. Ependymal cells express GFAP and vimentin filaments, whereas plexus epithelium simultaneously contains neurofilaments, cytokeratins and vimentin, a phenomenon not previously observed in normal cells in vivo. By means of specific antibodies we were able to establish that cytokeratins 8 and 18 but not 19 are present in plexus epithelium.

Microtubules are not altered in the dystrophic chicken

The association of an altered cytoplasmic microtubule complex in cells of the dystrophic chicken was investigated. Dystrophic chickens of lines 304 and 413 were compared with their genetically matched control, 412 (obtained from UC, Davis). Explants and trypsin-dissociated tissues were prepared from breast and heart muscles of chickens at 1, 3, 7, 14, 20, 40, 80 and 120 days ex ovo. The cells were cultured for 7 days and then processed for antitubulin immunofluorescence. Over 90% of the cells displayed an extensive cytoplasmic microtubule complex, although there was significant elevation of creatine phosphokinase in the dystrophic chickens after 20 days ex ovo. In both dystrophic and control preparations, one to two distinct functionally intact microtubule-organizing centers per cell were observed. Dystrophic and control chicken brain extracts demonstrated essentially the same extent of microtubule assembly as assayed by turbidity increase and protein in sedimentable polymer. SDS-PAGE revealed no significant differences in the microtubule proteins polymerized from the dystrophic and control brains. These results suggest that no significant alteration occurs in the structure, assembly or distribution of cytoplasmic microtubules in the cells of the dystrophic chicken.

Effect of cimetidine on digoxin disposition in peptic ulcer patients

Cimetidine inhibits the renal tubular secretion of creatinine and digoxin is partly excreted by the same pathway. In order to investigate a possible interaction between the two drugs, a randomized cross-over acute study has been conducted. Six patients with duodenal ulcers were given a single dose of digoxin (Dig) 0.75 mg i.v. with and without oral cimetidine 1200 mg/day. Cimetidine significantly reduced creatinine clearance from 157 to 132 ml/min. There was no significant difference in inulin clearance, 99.2 vs 97.5 ml/min, Dig elimination half life 53.9 vs 56.9 h, apparent volume of distribution 11.3 vs 11.6 l/kg, systemic clearance 2.42 vs 2.35 ml/min/kg, renal clearance 1.48 vs 1.62 ml/min/kg or urinary excretion of digoxin 49.5 vs 51.6% of dose without or with cimetidine. These results suggest that cimetidine does not influence the disposition of digoxin.

Paired helical filaments from Alzheimer disease patients contain cytoskeletal components

Neurofibrillary tangles from Alzheimer disease patients share antigenic determinants with neurofilaments and microtubule-associated proteins, as shown by light microscopy immunocytology. The present study addresses the issue of whether these determinants are located on the paired helical filaments or on other components of the neurofibrillary tangle. Sections from postmortem brains from Alzheimer disease patients were stained by using Bodian's silver method or immunostained by using poly- and monoclonal antibodies to neurofilaments and polyclonal antibodies to microtubules. Bodian's silver stain has an intense affinity for neurofibrillary tangles and has been shown to bind to specific domains of neurofilament subunits. The antibodies to neurofilaments used here immunostain most or all of the neurofibrillary tangles present in the sections whereas the antiserum to microtubule protein immunoreacted with about half of the neurofibrillary tangles. All of the antibodies as well as Bodian's silver stain reacted with the paired helical filaments. The epitopes that we have shown to be present in the paired helical filament, in contrast to the corresponding epitopes present in normal neuronal cytoskeleton, are insoluble in ionic detergent. It is concluded that these epitopes are integral components of the paired helical filaments and that, at least in part, paired helical filaments are derived from altered elements of the normal neuronal cytoskeleton.

Characterization of a Ca2+-stimulated lipid peroxidizing system in the sea urchin egg

Addition of calcium chloride to an egg homogenate of Strongylocentrotus purpuratus stimulates O2 consumption which is not inhibited by millimolar cyanide. Results strongly suggest that Ca2+-stimulated O2 consumption is at least partially the result of polyunsaturated fatty acid oxidation. First, addition of arachidonic acid (AA), or other polyunsaturated fatty acids, to the homogenate enhance Ca2+-stimulated O2 consumption; this enhancement, by AA, being coupled to its oxidation to a hydroxy fatty acid. Second, calcium stimulates a lipase activity in the homogenate that is capable of releasing free fatty acids. Third, Ca2+-stimulated O2 consumption and AA oxidation have virtually identical calcium requirements and pH optima. The sequence of events then is that upon calcium addition to the homogenate, lipase activity is increased which liberates free fatty acids. At the same time calcium also activates a polyunsaturated fatty acid oxygenase, possibly lipoxygenase, that converts the free fatty acids to hydroxy fatty acids. The possible physiological importance of this reaction is underscored by the high affinity for Ca2+ [approximately 10(-7)M], an ion known to increase above the required levels at fertilization. The pH activity profile also suggests possible physiological modulation because a pH change of 6.8 increasing to 7.2, as suggested to occur after fertilization, yields almost a twofold increase in O2 consumption. Egg homogenates from many other invertebrate species have the ability to oxidize AA in a Ca2+-dependent fashion. For the investigated species, the presence of Ca2+-stimulated O2 consumption and AA oxidation correlates with the presence of cyanide insensitive respiration in the intact egg.

Fertilization stimulates lipid peroxidation in the sea urchin egg

Arachidonic acid is rapidly taken-up by Strongylocentrotus purpuratus eggs and eventually incorporated into cellular lipids. During the first few minutes following fertilization the arachidonic acid that has not been incorporated into other lipid forms is oxidized to a hydroxy-fatty acid. In vivo, the time of arachidonic acid conversion coincides with the transient period of increased intracellular free calcium after fertilization. In vitro, this lipid peroxidizing activity has been shown to be initiated by micromolar calcium. Taken together with the presence of Ca2+-stimulated lipase, these results suggest that calcium regulates both the release of polyunsaturated fatty acids from cellular lipids and their subsequent oxidation. The physiological function of lipid hydroxides or hydroperoxides in sea urchin fertilization is unknown. A possibility is that they may be important in regulating the many membrane permeability changes occurring within minutes after fertilization.

Dressler's syndrome after right ventricular infarction

Undiagnosed myocardial infarction of the right ventricle presented as Dressler's syndrome. Radioisotopic diagnostic procedures including first-pass and multigated acquisition nuclear angiography ( MUGA ) and thallium-201 perfusion studies enabled a retroactive diagnosis of myocardial infarction, showed it to be in the right ventricle, and clarified the aetiology of the unexplained fever and pleuropericarditis.