Tubulovesicular structures: what are they really?

The tubulovesicular structures (TVS) are the only structures unique at the level of thin-section electron microscopy for all TSEs so far examined. They were first described in NIH Swiss mice infected intracerebrally with the "Chandler" strain of scrapie by David-Ferreira et al. in 1968 [Proc. Soc. Exp. Biol. Med. 127:313-320]. TVS were described as "particles and rods ranging in diameter from 320 to 360 A(o)." The exact topology of TVS is not entirely clear. In most published electron micrographs, TVS appeared as spheres measuring between 20 and 40 nm in diameter. The number of neuritic processes containing TVS increases through the incubation period and has been shown to correlate with the incubation period and titre of infectivity in three longitudinal disease studies of scrapie and CJD. These studies, therefore, suggest that TVS may represent a primary pathogenetic event rather than a pathological product of disease. The predominant theory of the scrapie agent is now the "prion hypothesis" and its derivatives, which implies that a conformationally altered abnormal isoform (PrP(Sc) or PrP*) of a normal cellular membrane glycoprotein (PrP(c)) is the agent and its accumulation merely mimicks replication. If an abnormal fraction of PrP is indeed the infectious agent, (although it is no longer suggested in some quarters that protease resistant fraction of PrP(Sc) is the agent). The absence of stainable PrP in TVS, however, would indicate that they are not the ultrastructural correlate of the agent. However, TVS appear to be specific and unique to the TSEs, appearing before the earliest pathological changes and increasing in line with incubation period or titre. The very existence of TVS and their correlation with infectivity, therefore, urgently needs an explanation.

Molecular analysis of PRNP gene in Polish population and in Creutzfeldt-Jakob disease

In our study we have examined allelic variation of codon 129 among the Polish population as well as Polish and Dutch CJD cases. The open reading frame of the PrP gene was amplified using the polymerase chain reaction (PCR). PCR product was digested with Nsp I and Mae II endonucleases and separated by 2% agarose gel electrophoresis and, finally, sequenced by the Sanger dideoxy-mediated chain-termination method. To obtain population data we have screened 109 unrelated Polish adults. There were 45% of methionine homozygotes, 16% of valine homozygotes and 3% of heterozygotes. Among Polish CJD cases, 75% were methionine homozygous, 12.5% were valine homozygous and 12.5% were heterozygous, whereas among Dutch CJD cases it was 29% of Met/Met and 71% of Met/Val genotypes.

Neuronal loss and apoptosis in experimental Creutzfeldt-Jakob disease in mice

One of the hallmarks of prion disease--neuronal cell loss, may be accomplished by apoptosis. The aim of this study was to estimate the neuronal cell loss in mice brains with experimental Creutzfeldt-Jakob disease (CJD) and control mice in the comparison with the apoptosis appeared by in situ end labelling (TUNEL) in function of time of post-incubation period and developing of the spongiform changes. The number of neurons was considerably lower in terminally sick animals (20-21 week of incubation period) than in control mice. The mean value of loss of neuronal cell was 32%. The greatest loss (55%) of neurons was noted in the septal nuclei of the paraterminal body and the least lost (16%) in the hypothalamus. We report here, that apoptotic cells are readily detectable in CJD-affected mice brains in time-dependt manner after infection of Fujisaki strain, but the number of apoptotic cells detected by in situ end labelling does not well correlate with the extensiveness of neuronal loss. The degree of apoptosis corresponds to the well developed spongiform changes.

Echigo-1: a panencephalopathic strain of Creutzfeldt-Jakob disease: ultrastructural studies of the optic nerve

The Echigo-1 strain of CJD was isolated by Mori and colleagues (1989) from a case of 33-year-old female with a panencephalopathic type of CJD. An incubation period following intracerebral inoculation of hamsters with 10% cleared suspension of the Echigo-1-affected brain was approximately six months. We report here ultrastructural changes which are comparable with those in the white matter of another panencephalopathic type of CJD, the Fujisaki strain of CJD (GSS) passaged in mice. Vacuoles developed within myelinated axons: within axoplasm or within the myelin sheath and these were accompanied by exuberant reaction of macrophages and hypertrophic astrocytes. Axons underwent Wallerian degeneration and dystrophic neurites were also seen. Most important, we observed proliferation of inner mesaxons. Cross-sectional profiles of innumerable myelinated fibers contained membranous organelles which were continuous with the inner lamellae of the oligodendroglial cells. These unusual proliferations of inner mesaxon formed whorls and elaborated loops. In some axons, proliferation was so severe that loops of mesaxon filled the whole cross-section of the axon. Occasionally, we observed intrusion of the membranous tongue of the inner mesaxon into axoplasm. This study presents a second panencephalopathic model of CJD available in small laboratory rodents. It is important because this is the only such model in hamsters and it may be used for comparative studies of different strains of agent in the same host; thus far only mouse and hamster model have been available for comparative studies.

Cytogenetic and proliferative potentials in meningiomas

Cytogenetic analysis and Ki-67 staining index (SI) were performed on the series of 51 meningiomas, to estimate the relationship between the extent of chromosomal changes and the growth potential of tumors. The tumors were classified according to histological subtype (22 meningiotheliomatous, 15 transitional, 12 fibroblastic and 2 angiomatous) and grade (40 benign, 5 atypical and 6 malignant ones). There was no significant difference in the complexity of chromosomal changes among the histologically distinct tumor subtypes. In contrast, there was a significant association between the number of chromosomal abnormalities and tumor grade. Normal karyotypes were found in 50% and complex in 20% of benign tumors. All grade II or III tumors revealed complex karotype. The tumors classified as benign revealed significantly lower mean Ki-67 SI than atypical or malignant ones (1.6%, 7.4% and 14.7%, respectively). However, within tumors classified as benign, mean Ki-67 SI of these with normal or simple karyotypic changes did not differ significantly from those with complex karyotype (1.6% and 0.9%, respectively). Thus, the extent of genome abnormalities in meningiomas, measured on the chromosomal level, does not relate directly to their proliferative potential.

January 2000: 12 year old boy with recent onset seizures

A 12-year old boy presented with new onset of seizures and a CT scan showed a left frontal lobe tumor which was removed completely. Neuropathological examination showed a pleomorphic ganglion cell tumor with necrosi, and endothelial proliferation. The diagnosis was extraventricular atypical neurocytic neoplasm ("cystic ganglioneurocytoma").

Clinicopathological analysis of pilocytic astrocytomas and gangliogliomas in children

We present here a clinico-pathological analysis of 58 pilocytic astrocytomas (PA) and 11 gangliogliomas (GG) based on an analysis of neuronal markers (GFAP, SYN, NFP) in these two groups of neoplasms. During the retrospective review of 58 cases recognized primarily as PA, 11 verified neoplasms demonstrated strong reaction for SYN or NFP or for both antibodies. These cases were reclassified as gangliogliomas. None of 11 tumors recognized as GG were further reclassified as PA. The overall 5-year survival was 88.89% in PA and 70.00% in GG group.

Electron microscopy in diagnosis of tumors of the nervous system

An abbreviated catalogue of major categories of brain tumors and ultrastructural findings regarding these neoplasms are presented in short review.

Dysembryoplastic neuroepithelial tumor (DNT): an ultrastructural study of six cases

We report six cases od DNT with a detailed ultrastructural characteristics. The patient age ranged from 7 to 16 years (mean 12), the location was temporal in three cases and frontal, temporooccipital and parietooccipital in each of one remaining cases. The predominant clinical feature in each case was history of episodes of intractable seizures. Histopathologically, the neoplasms were multinodular, each nodule was well-circumscribed and was composed of glioneuronal elements embedded in the variable amount of myxoid matrix. The oligodendroglial-like cells (OLC) predominated in the nodules with some accompanying mature neurons. The nodules were frequently surrounded by small calcifications which could be found also within the tumors. OLCs were immunoreactive for S-100 protein and neurons had the expression of synaptophysin and neurofilament proteins. Ultrastructurally, each tumor consisted of three major elements: neoplastic cells (OLC), elongated processes forming neuropil-like structure and expanded "mucoid" extracellular space: the latter gave an impression of cellular elements floating within it. Neoplastic cells had round, oval or elongated nuclei, no discernible nucleoli and a relatively narrow rim of the cytoplasm. Some nuclei were irregular and invaginated and pseudoinclusions were observed; a part of cytoplasm sequestered within pseudoinclusions often appeared degenerated with large blabs and electron-lucent vesicles, some of these contained in turn semicircular profiles of unknown significance. The second element consisted of innumerable cellular processes. Some of these were elongated and formed stacks connected by symmetrical symmetric or asymmetric adhesive plaque junctions. The others had shorter "neck" containing microtubules, these extended into bullous extensions. Dense-cored vesicles were occasionally observed, in both cytoplasm of neoplastic cells and within processes. In one cell, cross-sectioned annulate lamellae were found. In cytoplasm of a few cells, unusual inclusions reminiscent ribosome-lamellae complexes were observed. These were cylindrical resembling "laboratory tubes" with a cone-like endings. At higher power, walls of the "tubes" resolved into layered structures composed of several laminae; between laminae, ribosome-like structures were visible.

Proton magnetic resonance spectroscopy of primary pediatric brain tumors: neuropathological correlation

Forty-five children with primary brain tumors were evaluated by in vivo proton magnetic resonance spectroscopy (MRS) with the aim of detecting correlations between the obtained spectra and tumor malignancy and histology. All investigations were performed using a 1.5 T MR scanner (Picker) with point-resolved spectroscopic (PRESS) sequence (TR 1600 ms, TE 270 ms, NEX 256). Spectra were analyzed for N-acetylaspartate (NAA), choline containing-compounds (Cho), creatine and phosphocreatine (Cr) and lactate (Lac). The Cho/NAA ratio was the most useful parameter for differentiating between normal brain, benign and malignant tumors as well as discriminating the three main groups of pediatric brain tumors namely pilocytic astrocytoma, ependymoma and medulloblastoma. Proton MRS appears to be an important noninvasive technique in the differential diagnosis of pediatric brain tumors.

The ultrastructural study of primary intracranial germ tumors

We describe here ultrastructural and clinicopathological features of five primary intracranial germinomas. By electron microscopy, two major tumor components were defined as large, well differentiated tumor cells and non-neoplastic cells such as macrophages, astrocytes and lymphocytes. Nuclei of tumor cells were round to oval, often presented irregularly contoured nuclear membranes with oval indentations and, occasionally, cytoplasmic invagination. Some of them constituted unusual conformational changes of nuclear membranes rarely described as intranuclear pockets. Desmosome-like intercellular junctions were observed in several neoplastic cells. The nucleoli were composed of a loose, fragmented nucleolonema, whereas elongated, anastomosing and rope-like nucleolonemas, described previously as characteristic for germinomas were not seen. Most tumor cells had villous cytoplasmic projections sometimes intermingled with similar projections of macrophages. Cytoplasm contained a moderate number of mitochondria, a few lysosomes, annulate lamellae, centrioles and glycogen particles. The other distinct components of tumor were lymphocytes, macrophages and astrocytes. Scattered astrocytes typically contained abundant glial filaments adjacent to primary tumor cell. A filopodia-like processes of macrophages often interspersed between other cells, were very prominent features of germinomas. Small lymphocytes were found scattered between the tumor cells, single or in clusters.

Deposition of the prion protein (PrP) during the evolution of experimental Creutzfeldt-Jakob disease

We studied the immunocytochemical distribution of the prion or proteinase-resistant protein (PrP) during the evolution of experimental Creutzfeldt-Jakob disease (CJD) in mice. Fifty-one brains were collected up to 22 weeks following intracerebral inoculation with the Fujisaki strain of the CJD agent. Slides were also immunostained for apolipoprotein E (apoE) and glial fibrillary acidic protein. Vacuolar changes with focal astrocytosis first occurred around the needle track at week 2 and later spread along white matter tracks. Until week 12, changes were asymmetrical, affecting more the side of inoculation. Spongiform change and astrogliosis spread subsequently to the gray matter. Time course and intensity of spongiform change and immunocytochemistry for PrP were discrepant: in most brain regions, severe vacuolation preceded immunocytochemically detectable PrP accumulation. PrP deposits in form of small dots were first detectable at week 6 in the area surrounding the needle track. After week 7, plaque-like amorphous PrP deposits were observed in white matter pathways. Finally, PrP was detectable also in basal ganglia and in the dorsal hippocampus (week 13) and in the neocortex (week 17), as the synaptic type of PrP immunopositivity. In the hippocampus, diffuse PrP deposits paralleled spongiform change, while in the cortex severe vacuolation was accompanied only by weak synaptic PrP deposits. Immunocytochemically detectable apoE was restricted to compact plaque-type PrP deposits after week 15. We conclude that disease-specific neuropathology spreads from the needle track along white matter pathways towards the gray matter; in this model, there is some discrepancy between development of tissue pathology and immunocytochemically detectable deposition of PrP. Immunocytochemically detectable apoE deposition follows PrP accumulation.

The ultrastructural study of primary intracranial germ cell tumours

We describe here ultrastructural and clinicopathological features of five primary intracranial germinomas. By electron microscopy, two major tumour components were defined as large, well differentiated tumour cells and non-neoplastic cells such as macrophages, astrocytes and lymphocytes. Nuclei of the tumour cells often presented irregularly contoured nuclear membranes with oval indentations and, occasionally, cytoplasmic invagination. Some of them constituted unusual conformational changes of nuclear membranes rarely described as intranuclear pockets. Desmosome-like intercellular junctions were observed in several neoplastic cells. Nucleoli were composed of a loose, fragmented nucleolonema whereas elongated, anastomosing and rope-like nucleolonemas, described previously as characteristic for germinomas were not seen. Typically, the cytoplasm contained glycogen particles. Most tumour cells had villous cytoplasmic projections sometimes intermingled with similar projections of macrophages. Scattered astrocytes typically containing abundant glial filaments were adjacent to primary tumour cells.

Biologic heterogeneity of angiomatous meningiomas

Three angiomatous meningiomas, classified histologically as benign, were analyzed cytogenetically and examined for the expression of EGF/PDGF and their receptors by immunohistochemistry. An accumulation of p53 protein and the presence of mutations in exons 5-8 of the p53 gene in neoplastic cells were also determined. In one tumour, chromosome studies revealed near diploid karyotype with the loss of chromosome 22. Two other meningiomas revealed tetraploid karyotypes with the presence of telomeric associations and a wide spectrum of numerical, complex chromosome aberrations. Moderate EGF and EGFR immunoreactivity was found in three and one meningioma, respectively. All tumours exhibited diffuse PDGF and PDGFR-beta expression. No p53 gene mutations were found, but one tumour expressed strong and dispersed p53 immunopositivity. This findings reflect the biological heterogeneity of angiomatous meningiomas.

Mutations of TP53, amplification of EGFR, MDM2 and CDK4, and deletions of CDKN2A in malignant astrocytomas

We investigated the frequency and mutual relationship of molecular alterations in 33 malignant astrocytomas (28 glioblastomas and 5 anaplastic astrocytomas). The genetic alterations analyzed were: deletion of CDKN2a/p16 gene, TP53 mutations, and amplification of EGFR, MDM2 and CDK4. The most common genetic alteration was EGFR amplification which was revealed in 15 cases (45%). TP53 mutation was identified in 9 cases (27%) and CDKN2/p16 deletion was detected in 13 cases (41%). Either MDM2 and CDK4 amplifications were less frequent, as they were identified in 4 (12%) and 1 (3%) case, respectively. Of the 15 cases showing the amplification of EGFR, 9 had CDKN2/p16 deletion (60%, p = 0.04). On the other hand, CDKN2/p16 deletion and EGFR amplification rarely occurred with TP53 mutations (2 of 14 cases with CDKN2/p16 deletion, 14%). These results confirm the existence of at least two different pathways leading to the formation of a glioblastoma.

Ultrastructural pathology of a Chilean case of tropical spastic paraparesis/human T-cell lymphotropic type I-associated myelopathy (TSP/HAM)

Human T-cell lymphotropic virus type I (HTLV-I), is the cause of endemic tropical spastic paraparesis (TSP) or HTLV-I-associated myelopathy (HAM). Because TSP/HAM is not a fatal disease, the neuropathology of this disease, albeit relatively well understood, is based on the examination of just a few incidental cases. Previously, we demonstrated peculiar lamellated structures, called "multilamellar bodies" (MLB). In this report, we present the ultrastructural neuropathology of a TSP/HAM case from Chile, with further detailed descriptions of MLB. It is tempting to suggest that MLB may represent specific ultrastructural markers of TSP/HAM. The pathology of the anterior and posterior horns was similar and was comprised of axonal degeneration, accompanied by extensive astrocytic gliosis. Lymphocytic infiltration, particularly observed as "cuffs" around blood vessels, was scattered among other cellular elements. Ultrastructurally, myelin sheaths were relatively well preserved, and some demyelinated but not remyelinated fibers were observed. Moreover, axons with abnormal accumulations of neurofilaments, suggestive of axonal degeneration, were detected. Several axons contained Hirano bodies. In many samples, glial processes replaced most of the remaining neuropil. In a few specimens of the anterior and posterior horns of the spinal cord, MLB were observed. These structures consisted of stacks of 30 to 40 electron-dense lamellae, which were interrupted by narrow electron-lucent spaces. All of the lamellae were immersed within an amorphous substance of intermediate density. Neurons of the dorsal root ganglia were basically normal except for increased lipofuscin accumulation. As in the spinal cord, myelinated axons were well preserved, but a few were demyelinated and surrounded by concentric arrays of Schwann cell membranes. Also, axons of the dorsal roots accumulated increased number of neurofilaments. Mast cells and Schwann cells were increased in number, the latter containing abundant pi granules and myelin fragments.

Neuroaxonal pathology in Creutzfeldt-Jakob disease

Neuroaxonal pathology has met little attention in transmissible spongiform encephalopathies. In brains of a series of 39 consecutive Creutzfeldt-Jakob disease (CJD) cases, we detected numerous abnormal neurites that labeled for neurofilament proteins (NFP) by immunocytochemistry. Three types of abnormally NFP-accumulating structures were more prominently observed in CJD brains than in age-matched control brains: 1. Neurons with NFP in their somata were seen in 29 CJD cases (74%), some appearing distended with eccentrically placed nuclei and homogenously stained cytoplasm. 2. Neuritic distensions (neuritic swellings, dystrophic neurites) were observed mainly in the white matter but also at the junction between gray and white matter. In some axons many such swellings could be traced along the visible part of the axonal segment. 3. Axonal spheroids were observed mainly in the medulla, predominantly but not exclusively in posterior nuclei, and were more numerous than in age-matched control brains. Several neurons, axons and spheroids demonstrated immunoreactivity for amyloid precursor protein. Their number was much smaller, however, than that of NFP-immunoreactive structures and varied from one or two immunopositive neurites per section to small clusters of beaded or spiral axons. Focal expression of apolipoprotein E in cells of microglial and astrocytic morphology was observed in areas with most pronounced axonal damage. We conclude that neuroaxonal pathology is a frequent and important part of brain lesioning in CJD, probably reflecting profound impairment of axonal transport.

Atypical case of sporadic Creutzfeldt-Jakob disease (CJD) in a young adult

The great concern exists that new variant of CJD (nvCJD) developed as a result of exposure to bovine spongiform encephalopathy (BSE)-infected meat products. Therefore, all cases of CJD in the young, as the one of ours are the matter of interest. The 21-year-old female developed a rapid progression of pyramidal, extrapyramidal and cerebellar signs, visual loss and psychiatric symptoms, leading to death in 16 weeks. The microscopic features were: a neuronal loss accentuated in cerebral cortex with extensive astroglia proliferation and spongiform changes. Immunohistochemical staining, revealed the presence of "synaptic" deposits of PrP in the cerebral cortex and in the cerebellum. No florid amyloid plaques were present. The case was diagnosed as a sporadic CJD, with some features of Heidenhein variant (visual symptoms) and corticostriatocerebellar category. The pathological findings excluded a nv CJD which is linked with BSE.

Progressive multifocal leukoencephalopathy (PML) and cerebral toxoplasmosis in an adult patient, with no symptoms of underlying immunosuppressing illness

We present a case of the coincidence of progressive multifocal leukoencephalopathy (PML) and central nervous system (CNS) toxoplasmosis in an adult patient, without a detectable cause of cell-mediated immunity impairment. The proper diagnosis was made postmortem on the basis of histological changes typical of both pathological processes. PML was characterized by the presence of subcortical focal demyelination, containing enlarged, densely basophilic oligodendrocyte nuclei, often with intranuclear inclusion, and bizarre astrocytes, mimicking neoplastic cells. PML was confirmed by detecting numerous papova virus particles in oligo- and astroglial nuclei by thin-section electron microscopy. Cerebral toxoplasmosis was characterized by the presence of multiple well-circumscribed necrotizing abscesses. Numerous Toxoplasma gondii (T. gondii) cysts and free, non-encysted protozoan parasites were found among the inflammatory infiltrates. The diagnosis of cerebral toxoplasmosis was further confirmed by immunocytochemistry. In order to detect putative immunosuppressive background underlying both pathological processes, HIV infection was taken into consideration, however, no histopathological changes indicative of AIDS either in the CNS or in the peripheral organs were eventually found. Moreover no HIV provirus genome was identified in the formalin-fixed, paraffin embedded brain tissue by the polymerase chain reaction (PCR). Current view on the selected aspects of the pathogenesis of both disorders were discussed.

Spinal cord pathology and viral burden in homosexuals and drug users with AIDS

Unless treated with effective antiretroviral therapy many AIDS patients develop a characteristic vacuolar myelopathy of the spinal cord associated with moderate clinical disability. Opinion is divided as to whether vacuolar myelopathy is causally linked to HIV myelitis. To investigate this further, spinal cord pathology was assessed in 41 drug users, 33 homosexual men and 16 other patients, all with AIDS. Previous work has shown that HIV encephalitis is more common in Edinburgh drug users than in homosexual men. In the present study HIV myelitis (10% overall) was more common in drug users (17%) than in homosexual men (3%) (P = 0.05), whereas the incidence of opportunistic infections (7% v. 9%) and lymphomas (2% v. 6%) was comparable in the two groups, but with a slight trend in the reverse direction, reflecting similar findings in the brain. However, moderate or severe vacuolar myelopathy was equally represented in both groups (20% of drug users and 21% of homosexual men). The HIV proviral load, assessed by polymerase chain reaction in frozen samples of thoracic spinal cord in 37 cases, correlated closely with the presence of giant cells and/or with immunocytochemical evidence of productive HIV infection. In 13 cases, the proviral load was measured in cervical, thoracic and lumbar samples and proved to be uniformly high or low in individual cases. This study provides no evidence for direct involvement of HIV, cytomegalovirus, papovavirus or human foamy virus in the pathogenesis of vacuolar myelopathy.

Cytogenetic changes in two cases of subependymal giant-cell astrocytoma

Cytogenetic analysis of subependymal giant-cell astrocytomas (SEGAs) from two patients presenting the clinical symptoms of tuberous sclerosis complex (TSC) revealed clonal chromosomal changes, resulting in the partial loss of chromosome 22q in both tumors. Immunohistochemically, tumors exhibited features of glial differentiation, while ultrastructural studies identified the characteristic paracrystalline inclusions within the tumor cells. To our knowledge, it is the first cytogenetic description of SEGAs associated with TSC.

The ultrastructure of glial tumors of astrocytic lineage: a review

In order to complete the classical descriptions of astrocytic tumors, I report here ultrastructural findings regarding this group of neoplasms. Fibrillary astrocytomas consisted of a mixture of cell bodies and their processes. Nuclei were indented and contained various types of nuclear bodies or filamentous paracrystalline inclusions. The cytoplasm with innumerable glial filaments was observed. Gemistocytic cells contained slightly more indented peripherally located nuclei while the whole cytoplasm was densely filled with glial filaments. The typical cells for the granular part of the astrocytic tumors and the granular tumors of astrocytic lineage contained the intracytoplasmic bundles of glial filaments and membrane-bound autophagic vacuoles. Pilocytic astrocytes were in the typical way elongated and contained many glial filaments in parallel bundles. Hirano bodies were rarely seen. Rosenthal fibers consisted of large electron-dense granular or amorphous masses merging at the periphery with glial filaments. In a case of the pleomorphic xanthoastrocytoma the electron microscopy showed numerous astrocytes connected by many long plaque-like junctions or hemidesmosomes with dense bundles of collagen fibrils. The majority of the astrocytes were covered with basal laminae, forming a complicated labyrinth-like pattern invaginated in astrocytic cytoplasm. Other astrocytes included also numerous vacuoles containing myelin figures and whorls. In a case of the subependymal giant cell astrocytoma, giant cells contained innumerable glial filaments, numerous ribosomes, distended endoplasmic reticulum, electron-dense bodies and peculiar crystalloids. Secondary glioblastomas retained clear stigmata of astrocytic tumor but the nuclei seemed to be more intended, cisterns of the endoplasmic reticulum appeared to be distended and frequently intranuclear pseudoinclusions were observed.

Electron microscopic studies of the optic nerve in experimental scrapie and the panencephalopathic type of Creutzfeldt-Jakob disease

We report the optic nerve ultrastructural pathology in experimental scrapie and Creutzfeldt-Jakob disease. Vacuoles developed within myelinated axons contained typical secondary vacuoles and curled membranes. These were seen either within the axoplasm or within the myelin sheath which split either at the major dense line or at the intraperiod line. Spongiform changes were accompanied by an exuberant cellular reaction consisting of macrophages and hypertrophic astrocytes. Occasionally, vesicular myelin degeneration and coated vesicles in a close proximity to the myelin were observed.

The Echigo-1: a panencephalopathic strain of Creutzfeldt-Jakob disease: a passage to hamsters and ultrastructural studies

The Echigo-1 strain of Creutzfeldt-Jakob disease (CJD) was isolated by Mori and colleagues (1989) from a case of a 33-year-old female with a panencephalopathic type of CJD. We report here ultrastructural data on the first passage in this laboratory. The bulk of the lesions was localized to the brain stem and cervical cord. Neuropathology was extraordinarily florid but quantitatively not much different from that reported for other panencephalopathic model of CJD, the Fujisaki (Fakuoka-1) strain of CJD passaged in NIH Swiss mice. Two types of vacuoles were easy to discriminate: typical change and intramyelin vacuole which are encountered in otherwise typical polioencephalopathic models but in much lower number. Some axons underwent Wallerian degeneration, others met criteria of dystrophic neurites and both alteration existed in the same areas. In neurons, nuclear paracrystalline rod-like inclusions were visible; other inclusions comprised spiroplasma-like inclusions in synaptic boutons. Robust cellular reaction comprised of reactive astrocytes and macrophages filled with cellular debris.