Amyloid plaques in transmissible spongiform encephalopathies (prion diseases)

Amyloid plaques are encountered in all cases of kuru and Gerstmann-Straussler-Scheinker disease (GSS) and in some 10-15% of sporadic Creutzfeldt-Jakob disease (sCJD) cases. In variant Creutzfeldt-Jakob (vCJD) the particular type of plaque known as "florid" or "daisy" plaque exists in 100% of cases. By electron microscopy several types of amyloid plaque were delineated, corresponding to those seen by PrP immunohistochemistry. Unicentric "kuru" plaques consisted of stellate arrangements (stars or cores) of amyloid bundles emanating from a dense interwoven centre. A proportion of kuru plaques formed very dense stars, reminiscent of sea urchins in shape. Others presented a looser pattern. Amyloid stars were enveloped by astrocytic processes. High-power electron micrographs revealed that amyloid bundles were concealed within grooves of obscure cellular origin. Interestingly, basement membranes lined with electron-dense material were observed at the periphery of many amyloid plaques of GSS. Dystrophic neurites were seen only rarely. Microglial cells formed a significant part of the amyloid plaques. Occasionally clusters composed of several kuru plaques were found. These were intermediate forms to multi-centric plaques, which consisted of several merging stellate cores. Smaller amyloid deposits surrounded larger cores. In contrast to the kuru plaques, associated with a limited number of dystrophic neurites (DN), numerous such structures were seen at the periphery. The DN were filled with abnormal organelles such as electron-dense bodies, multi-vesicular bodies and multilamellar bodies and thus were indistinguishable from those seen in scrapie and CJD or Alzheimer's disease, except that they did not contain paired helical filaments (PHF). Instead, piled neurofilaments were often detected in the centres of DN. Similar DN were observed but these were not associated with any plaques. The last and, by the same token, the rarest type of plaque was the purely neuritic plaque. These consisted of large areas filled with DN of different sizes and shapes (sometimes bizarre) but not amyloid bundles. Analogously to the kuru and multi-centric plaques, astrocytic processes were observed at the periphery. By means of light microscopy and semi-thin (1 microm) sections discrete PrP-immunopositive plaques were observed (data not shown), in the subependymal region but not in the deep brain neuroparenchyma, in both 263K and 22C-H scrapie-infected hamster brains. These plaques were not discernible by routine haematoxylin and eosin staining. Ultrastructurally, plaques were recognised as areas of low electron density containing haphazardly-oriented fibrils which, when immunogold techniques were applied, were heavily decorated with PrP-conjugated gold particles.

Doppel: the prion's double

Doppel (Dpl) is a PrP-like protein, coded by a gene named PRND, located near the PRNP (prion proten coding gene) locus. Human Dpl is a 179-amino acid protein showing approximately 25% sequence identity with the carboxyproximal two thirds of the human cellular prion protein (PrPC). A comparison of the structures of Dpl and PrP(C) reveals similarities in the secondary structure and topology. Apart from their structural similarities, the PrP and Dpl proteins seem to have different functions. The Prnd gene is expressed in mouse embryos; in adult mice its transcripts are present in heart, mammary gland, spleen, testes and, in contrast to Prnp, only at very low levels in the adult CNS. Moreover, the Dpl protein is not capable of enhancing the propagation of the pathological prion protein (PrP(Sc)). The Dpl protein has been identified as a regulator of acrosome function and male gametogenesis. The human PRND open reading frame has been shown to contain polymorphic codons, but research on a correlation between the PRND polymorphic sequences and neurodegenerative disorders carried out to date in different populations have shown contradictory results. Therefore, the role of the PRND gene in CJD and other diseases still remains unexplained.

Echigo-1: a panencephalopathic strain of Creutzfeldt-Jakob disease. II. Ultrastructural studies in hamsters

In this and a companion paper we present immunohistochemical and ultrastructural data on hamsters infected with the Echigo-1 strain of Creutzfeldt-Jakob disease. Ultrastructurally, two types of vacuoles were readily discriminated in the brain: the grey matter vacuoles of spongiform change and intramyelin vacuoles. The vacuoles were always membrane-bound; the membranes were single or double. The axons were entirely missing from the plane of the sections or, if visible, were shrunken and attached to the innermost layer of the myelin. It was noteworthy that some vacuoles indented cell bodies or processes and thus were reminiscent of the intraneuronal vacuoles typical for natural scrapie, BSE and CWD in ungulates and cervids but not of the vacuoles encountered in rodent models of scrapie and CJD. We also noticed vacuoles distending myelinated fibres in which the axons had become dystrophic. Some axons underwent Wallerian degeneration while others met the criteria for dystrophic neuritis. Both alterations existed in the same areas. Typical dystrophic neurites contained abnormal subcellular organelles, mainly electron-dense lysosomal inclusions. Other neurites contained numerous multi-vesicular bodies and autophagic vacuoles. Nuclear paracrystalline rod-like inclusions were occasionally visible in neurons while other inclusions comprised spiroplasma-like inclusions in synaptic boutons. The robust cellular reactions consisted of reactive astrocytes and macrophages filled with cellular debris. It is of note that complex autophagic vacuoles were observed in the cytoplasm of neurons.

Gerstmann-Sträussler-Scheinker disease. I. Human diseases

Gerstmann-Sträussler-Scheinker disease (GSS) is a slowly progressive hereditary autosomal dominant disease (OMIM: 137440) and the first human transmissible spongiform encephalopathy (TSE) in which a mutation in a gene encoding for prion protein (PrP) was discovered. Its true prevalence is difficult to estimate but figures within the range of 1-10/100,000,000 are quoted. GSS is defined as a neurodegenerative disease "in family with dominantly inherited progressive ataxia and/or dementia): encephalo(myelo)pathy with multi-centric PrP plaques". In this review, we summarise data on all the families with GSS. The hallmark of the GSS neuropathology is the multi-centric plaque but the pattern varies between families. In the second part of this review the experimental data using experimental models of GSS in transgenic mice are summarised as well as structural biology of mutated PrP in GSS.

Echigo-1: a panencephalopathic strain of creutzfeldt-jakob disease. I. neuropathological and immunohistochemical studies

We demonstrate an unusually intensive accumulation of prion protein (PrP) on neuronal membranes in hamsters infected with the Echigo-1 panencephalopathic strain of Creutzfeldt-Jakob disease. This stands in strong contrast with the poor vacuolation in this model. Several distinct patterns of PrP(TSE) deposit were observed in the brain. The first type consisted of a fine granular "synaptic"/diffuse type of accumulation which, especially in the cerebral cortex, appeared laminar. Deposits frequently coalesced to form plaque-like structures. The second pattern consisted of perivascular plaque-like accumulations. When a vessel was cut longitudinally, these formed long linear arrays of plaques and smaller globules. The third, and most striking, consisted of perineuronal deposits. These formed small dots and coarser globules which were densely situated on the neuronal membrane on both cell bodies and their processes.

Immunohistochemical investigations of the prion protein accumulation in human spongiform encephalopathies. Special report II

Creutzfeldt-Jakob disease (CJD) in a proportion of cases may have nonspecific clinical signs and symptoms and no characteristic neuroimaging and EEG picture. Thus, neuropathological studies are mandatory for a diagnosis. However, spongiform change, neuronal loss and astrocyte proliferation--the hallmarks of prion diseases, may also be absent or variable. In such cases, the diagnosis should be supported by the detection of prion protein (PrP) by Western blotting or immunohistochemistry (ICC). PrP may not be visualised under "regular" conditions, but it is unmasked following pretreatment procedures: incubation in formic acid or guanidine thiocyanate, microwave treatment, and hydrated or hydrolytic autoclaving, and these methods were included in standard diagnostic procedures in several different protocols. The aim of this study was to compare the effectiveness of these pretreatment methods and to introduce an optimal protocol for our laboratory. For this purpose, we used brain sections of 11 cases of CJD, 1 case of Gerstmann-Sträussler-Scheinker syndrome (GSS), 1 case of kuru and 3 control brains. For pretreatment we used the hydrated and hydrolytic autoclaving and incubation with formic acid. Immunostaining was performed with monoclonal 3F4 antibody against PrP. The best results were achieved with hydrolytic autoclaving. By this procedure we were able to detect the "synaptic" type of PrP accumulation in all CJD cases, as well as in GSS and kuru, while with other two methods the signal was weaker or even absent.

Ultrastructural changes in the optic nerves of rodents with experimental Creutzfeldt-Jakob Disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS) or scrapie

This report describes the ultrastructural changes in the optic nerves of (1) hamsters infected with the Echigo-1 strain of Creutzfeldt-Jakob disease (CJD), (2) hamsters infected with the 263K or 22C-H strain of scrapie, and (3) mice infected with the Fujisaki strain of Gerstmann-Sträussler-Scheinker disease (GSS). Vacuolation of myelinated fibres was present in the myelin sheaths, with splitting of myelin lamellae. These vacuoles contained typical secondary vacuoles and curled membrane fragments. Myelinated fibre vacuolation was also accompanied by an exuberant cellular reaction consisting of macrophages containing numerous mitochondria, abundant rough endoplasmic reticulum, and secondary lysosomes filled with digested myelin debris and other electron-dense material. Within macrophages, myelin fragments undergoing active digestion, lyre-like bodies and paracrystalline inclusions were frequently noted. Astrocytes and their processes were prominent; glial filaments and many mitochondria were readily detected. Proliferation of inner mesaxons was observed. Cross-sectional profiles of innumerable myelinated fibres contained membranous organelles continuous with the inner lamellae of the oligodendroglial cells. The proliferations of inner mesaxons formed whorls and loops, and intrusion of the membranous tongue of the inner mesaxon into the axoplasm was occasionally observed; dystrophic neurites were relatively numerous. In mice infected with the Fujisaki strain of GSS, fibres had undergone demyelination with stripping of the myelin lamellae, while others showed vesicular myelin degeneration.

Apoptosis in non-astrocytic brain tumours in children

Apoptosis is a process of great significance in cell biology. It plays a crucial role in both physiological and pathological conditions. An example is a tumour growth that is based on a subtle balance between cell division and cell death. Previously necrosis was considered to be the major type of cell death in tumours. Many recent investigations have focused on apoptosis, a phenomenon of great importance, and it is this type of cell death that is frequently "chosen" by a moribund cell. The objects of our interest were central nervous system (CNS) tumours, in which we estimated the number of apoptotic cells and sought for any correlation between the intensity of apoptosis and other markers of proliferation. Therefore, we studied CD34, the marker of angiogenesis, and Ki67, the marker of cell proliferation. We investigated 19 medulloblastomas and 15 ependymomas, among which 6 were anaplastic. We used in-situ labelling of DNA fragments to detect apoptosis in paraffin-embedded tissues. The mean value of the apoptotic ratio (AR) for all examined brain tumours was 0.012 with a standard deviation (SD) of 0.032, for medulloblastomas 0.021 (SD 0.04), for ependymomas 0.001 (SD 0.002) and for anaplastic ependymomas 0.004 (SD 0.003).

Loss of chromosome 22 and proliferative potential in ependymomas

Fluorescence in situ hybridisation (FISH) analysis using total chromosome 22 painting and locus specific 22q11.2 (bcr locus) probes was performed on sections from archival paraffin-embedded tumours obtained from 28 patients diagnosed with either ependymoma, WHO grade 11 (18 cases) or anaplastic ependymoma, WHO grade 111 (10 cases). The Ki-67 labelling index (LI) analysis was carried out in parallel to estimate the tumours' proliferative potential. Loss of chromosome 22 was revealed in eleven (39%) ependymomas, seven (39%) WHO grade II and four (40%) anaplastic variants. Concurrent cytogenetic analysis was performed on 11 tumours to confirm the loss of chromosome 22 in four cases; clones with a loss of chromosome 22, which was identified by FISH, were not detected by standard cytogenetics in two samples. The loss of chromosome 22 was restricted either to the tumours' site or to sex or age of the patients studied. The Ki-67 LI ranged from 0.1 to 32.0% (mean 4.3%). Low-grade tumours significantly showed a lower mean Ki-67 LI than those classified as anaplastic tumours (3.1% and 6.4%, respectively). Additionally, the mean Ki-67 LI for ependymomas with a loss of chromosome 22 was significantly lower than that for tumours with chromosome 22 disomy (1.6% and 6.0%, respectively, p = 0.05), indicating that loss of chromosome 22 may be associated with the subset of ependymomas characterised by low proliferative capacities.

Posterior fossa tumours in children and adolescents. A clinicopathological study of 216 cases

Posterior fossa tumours are characteristics of paediatric population. This report is a study of 216 consecutive cases of neuropathologically verified brain tumours in children under the 18th year of age, who underwent surgery at the Polish Mother Memorial Hospital in Lódź, Poland, between 1990 and 2003. Children with posterior fossa tumours constituted 47% of all paediatric patients with brain tumours. Male-to-female ratio was 1.35:1, and the major peak in the incidence of tumours was observed between 4 and 6 years of age. The most common locations were the cerebellum along with the fourth ventricle (61.5%), cerebellar hemispheres (27.5%), and brain stem (7.5%). Astrocytic tumours (predominantly pilocytic astrocytomas) were the most common group of neoplasms (41.5%) followed by embryonal tumours (all but one medulloblastomas--34.5%), ependymal tumours (13%), and mixed neuronal-glial tumours (5.5%). Altogether, nineteen histological types of brain tumours were diagnosed in the analysed population. The location of tumours, age and sex were compared with those of previously published series of paediatric posterior fossa tumours.

Exuberant cellular reaction of the optic nerves in experimental Creutzfeldt-Jakob disease

We report here on the exuberant glial reaction in the optic nerves affected by prion diseases. Optic nerves from CJD- and GSS-, and scrapie-infected mice and hamsters showed severe pathology. These lesions were qualitatively indistinguishable from each other but were more intense in the Fujisaki model than in the hamsters inoculated with Echigo-1. Exuberant cellular reaction comprised of macrophages containing numerous mitochondria, abundant rough endoplasmic reticulum, and secondary lysosomes filled with digested myelin debris, electron-dense material and occasionally, entire myelin-bound vacuoles were readily observed in both models. Macrophages actively digesting myelin fragments and containing lyre-like bodies and paracrystalline inclusions were frequently noted. Some macrophages extended long filopodia to form labyrinth-like structures, and within a few macrophages, concentric arrays of cisterns and channels sequestrated part of the cytoplasm. An analogous network of narrow cisterns was seen to surround whole segments of the myelinated fibers.