Neuronal autophagy and aggresomes constitute a consistent part of neurodegeneration in experimental scrapie

We describe here a variety of autophagous forms encountered in the terminal stages of two models of scrapie in hamsters. We also show that the number of autophagic vacuoles increased through the incubation period in the 263K strain scrapie model. In addition, we demonstrated for the first time the presence of aggresomes in the neuronal cytoplasm in scrapie-affected hamster brains. We observed neuronal autophagic vacuoles in different stages of formation in the same specimens. However, this description is based on the subjective grading of the severity of changes, which may or may not equate to the stage of development. First, a part of the neuronal cytoplasm was sequestered by membranes (phagophores) and that part of the cytoplasm confined by membranes often exhibited increased electron density. The intracytoplasmic membranes multiplied in a labyrinth-like manner. The area taken up by autophagic vacuoles expanded and eventually a large proportion of the cytoplasm was transformed into an agglomeration mass of autophagic vacuoles. Occasionally a large but single autophagic vacuole was visible. Autophagic vacuoles developed not only in the neuronal perikarya but also in neuronal processes, eventually replacing the whole cross-section of affected neurites.Generally,there were few qualitative differences between these two models but hamsters inoculated with the 263K strain had more severe changes. In a few specimens there were round electron-dense structures that we identified as aggresomes. Aggresomes are not membrane-bound and were found in the cytoplasm of a few neurons.

The infrequent simultaneous genetic alterations in glioblastoma multiforme (LOH 10, 17, 19q, TP53 mutation and EGFR amplification) with short clinical course

We described the case of an unusual, complex genetic alteration in 57 year-old male patient with glioblastoma multiforme (GBM) with short survival (6 and half months). Alterations consisted of p53 mutation, LOH 10, LOH 17, LOH 19q and EGFR amplification. LOH1p, LOH 9 and LOH 13 were negative. Immunohistochemical study did not correlate with molecular results. The overexpression of TP53 protein and RB protein was detected only in small percentage of cells and interestingly the overexpression of EGFR was present only focally. Immnunostainings for PTEN, P16, PI3-K were negative. Additionally, we observed an overexpression of IGFB2 protein. This case indicates the accumulation of molecular changes in glioblastoma multiforme in patient with short survival.

Glioneuronal-mesenchymal tumour with malignant transformation

We report a case of a 10-year-old girl with a tumour of the right temporoparietal region of the brain. The tumour consisted of three morphologically distinct portions: a well-differentiated one containing a mixture of a ganglioglioma with adipocytic-like cells and focal chondroid metaplasia, a separate island with neurocytic differentiation, and the malignant one, which exhibited an organoid pattern (trabecular and festooned) of primitive neuroectodemal tumour (PNET). We hypothesize that the latter component originated from the multicomponental glioneuronal tumour with mesenchymal differentiation and thus that lesion constituted an unusual example of malignant transformation of low-grade glioneuronal neoplasm.

Severe, early and selective loss of a subpopulation of GABAergic inhibitory neurons in experimental transmissible spongiform encephalopathies

Little is known about the pathogenetic basis of characteristic symptoms in transmissible spongiform encephalopathies (TSEs) such as myoclonus and characteristic EEG hyperactivity. We investigated the GABAergic system and its subpopulations in mice inoculated with experimental scrapie (ME7, RML, 22A strains) and Creutzfeldt-Jakob disease (CJD; Fujisaki strain), to study damage to inhibitory neurons. Since recent studies have shown electrophysiological changes in prion protein (PrP) knockout mice, we also studied mice lacking or overexpressing the PrP gene. Antibodies against glutamic acid decarboxylase (GAD), parvalbumin (PV), calbindin (CB), and calretinin (CR) were used to stain GABAergic neurons, and isolectin-B4 to stain perineuronal nets around PV+ neurons. In scrapie infected mice, cortical PV+ neurons were severely reduced while CB+ and CR+ neurons were well preserved. In CJD inoculated mice, loss of PV+ neurons was severe and occurred very early after inoculation. PrP-/- and tg20 mice showed normal appearance of PV, CB, CR, GAD+ neurons and their neuropil, and of isolectin-B4+ perineuronal nets. The early, severe and selective loss of cortical PV+ neurons in experimental scrapie and CJD suggest selective loss of PV+ GABAergic neurons as important event during disease development, possibly as one basis of excitatory symptoms in TSEs.

Variant CJD (vCJD) and bovine spongiform encephalopathy (BSE): 10 and 20 years on: part 1

From 1986 more than 184,000 cattle in the UK and islands (of which >1,880 have been detected by active surveillance using rapid tests) and approaching 5,500 elsewhere have been confirmed with BSE. The original 1988 ban on the use of ruminant-derived protein in ruminant feed has been upgraded and now prohibits the use of any processed animal protein in feed for any farmed food animal. As a result of rigorous enforcement this reinforced ban is now regarded as fully effective from 1 Aug. 1996. Reasons are given for the substantial slippage that occurred initially and for the small but diminishing number of cases that have occurred in cattle born after 1 Aug. 1996. The 1989 offal ban, initially introduced to protect public health, has likewise been progressively strengthened and since 1995 has been effectively enforced by the Meat Hygiene Service, thus protecting the consumer. It is now extended as the specified risk material (SRM) ban throughout the EU. BSE continues to decline towards elimination in the UK and is being dealt with effectively in other Member States of the European Union (EU) and Switzerland with an extensive (and very expensive) range of edicts. The improving situation in the EU has encouraged the EC to draft a TSE Roadmap outlining possible reduction in control measures whilst still protecting the consumer. The situation on a global basis still causes concern as, although cases are less frequent than in the UK, surveillance, legislation and enforcement are not clearly as extensive and effective as in the EU. The risk of primary transmission of BSE to man from cattle to cause variant CJD (vCJD) is examined with reference to up-to-date assessments of bovine tissue infectivity and is now regarded as unlikely in the EU and Switzerland.

Variant CJD (vCJD) and bovine spongiform encephalopathy (BSE): 10 and 20 years on: part 2

Up until February 2006, variant CJD (vCJD), the human disease associated with transmission of BSE from cattle, has been confirmed in 160 patients resident in the UK and 28 elsewhere, some of whom have never visited the UK. Cases have been reported in France (16 cases), Ireland (3), USA (2), Canada, Italy, Japan, The Netherlands, Portugal, Saudi Arabia and Spain (1 each). The presumed main period of hazard for ingestion of the BSE agent in bovine products in the UK is 1984-89, or perhaps up to 1995-6 but at a reduced level. Debated incubation periods for vCJD are discussed, with special reference to the wide, but currently reducing, range of predicted further primary cases in the UK. The primary disease seems to be preferentially acquired by, and expressed in, relatively young people. All but one of the British cases examined so far were homozygous for methionine at the polymorphic codon 129 of the prion protein PRNP gene. Tests of appendix specimens from large numbers of otherwise normal subjects at the time of appendicectomy have revealed lymphoreticular accumulations of PrP(Sc) in a few samples. Furthermore, three patients who died of vCJD had appendices removed by appendicectomy whilst healthy. Two of these appendices were retrospectively shown to be positive for PrP(Sc) and one removed 10 years before clinical onset was negative. This has led to worries regarding the possibility of pre-clinical or sub-clinical prion-associated disease in an unknown proportion of the population. To date, there has been no known association of primary vCJD with occupation, medicines, immunising agents, gelatine, or surgery (including the use of catgut sutures), or exposure to bovine products other than by ingestion. There is much concern that human-to-human (secondary) vCJD infection is transferred by blood transfusion. A possible risk is also perceived from infected blood products, human organs and tissues, or via contaminated surgical instruments or devices though, so far as is known, no cases have yet arisen in this way. Steps have been taken to reduce the risks and much research is in hand in this field. Continued TSE surveillance, the maintenance of adequate preventive controls, attention to possible parenteral challenges, and further research studies are of paramount importance.

Molecular analysis of chromosome 1, 10 and 19 abnormalities in human oligodendroglial tumors: relationship between frequency of LOH grade, age and gender

BACKGROUND

Loss of heterozygosity (LOH) on 1p and 19q is observed in most oligodendroglial tumors. LOH on 10q appears to be less common in these tumors as compared to other gliomas.

PATIENTS AND METHODS

We reviewed 14 patients with oligodendroglial tumors (10 low-grade and 4 anaplastic oligodendroglioma) to evaluate the frequency of LOH on 1p, 10q and 19q and correlate it with tumor grade and patients' age and gender; 5 loci on 1p and 5 on 19q as well as 4 on 10q were analyzed for LOH using PCR techniques.

RESULTS

LOH on 1p together with 19q was detected in 6 tumors, 1 tumor showed deletion of 19q accompanied with deletion on 10q. Deletion on 1p was associated with deletion of 19q (p < 0.005) and mutual associations among deletions at loci on 19q (p < 0.05) were found. Patients with LOH on 1p were younger on average than patients with retained heterozygosity (p = 0.05). Grade II oligodendrogliomas predominated among younger patients (p < 0.01) while grade III oligodendrogliomas predominated among women (p < 0.005). No association between LOH on 1p nor 19q and tumor grade or patients' gender was found.

CONCLUSION

Our study provides several clinically interesting findings and further supports the hypothesis of chromosome 1p and 19q involvement in the oligodendroglial cancerogenesis.

[Analyses of 14-3-3 protein in the cerebrospinal fluid in Creutzfeldt-Jakob disease. Preliminary report]

BACKGROUND AND PURPOSE

Definitive diagnosis of Creutzfeldt-Jakob disease (CJD) is possible only after neuropathological confirmation; there are no non-invasive tests which allow to definitely diagnose CJD pre mortem. The only one biochemical marker included in the diagnostic criteria for CJD approved by WHO is an elevated level of 14-3-3 protein in the cerebrospinal fluid (CSF). The aim of the study was to introduce 14-3-3 analysis for a routine diagnostics of CJD in Poland and to optimise the Western blotting technique used in the Reference Centre of Prion Diseases in Lodz.

MATERIAL AND METHODS

We analysed 33 samples of CSF: 17 from patients suspected of CJD (2 definitive, 2 probable, 4 possible, 11 others), and 16 controls (from patients with other neurological diseases). CSF samples were analysed using the Western blotting method and commercially available antibodies (Santa Cruz). We used 2 methods of CSF preparation: with and without lyophilization, and 2 different anti-14-3-3 antibodies: rabbit polyclonal and mouse monoclonal antibodies.

RESULTS

We found 14-3-3 protein in both definitive sCJD cases and in one probable case. Among other samples, we obtained a positive result only in one patient with alcohol abuse history and in samples of CSF contaminated with erythrocytes.

CONCLUSIONS

The Western blotting test for 14-3-3 protein in CSF is useful for diagnosis of CJD, but only when considered in an appropriate clinical context, together with other diagnostic criteria. Contamination of CSF with erythrocytes can cause false positive results. Analysis of a non-lyophilised CSF and detection of 14-3-3 protein using the mouse monoclonal antibody gave the most reliable results.

Ultrastructural pathology of prion diseases revisited: brain biopsy studies

We report here a detailed ultrastructural comparison of brain biopsies from 13 cases of Creutzfeldt-Jakob disease (CJD) and from one case of fatal familial insomnia (FFI). The latter disease has not heretofore benefited from ultrastructural study. In particular, we searched for tubulovesicular structures (TVS), 35-nm particles regarded as the only disease-specific structures at the level of thin-section electron microscopy. Our material consisted of brain biopsies obtained by open surgery from one FFI case from a new French family, one case of variant CJD (vCJD), nine cases of sporadic CJD (sCJD), two cases of iatrogenic (human growth hormone) CJD and one case of hereditary CJD (Val203Iso). The ultrastructural picture of the cerebral cortex of the FFI patient was virtually indistinguishable from that of CJD. TVS were found, albeit only after prolonged search. Typical spongiform change was observed, consisting of intracellular membrane-bound vacuoles containing secondary chambers (vacuoles within vacuoles) and amorphous material. Neuronal degeneration was widespread: some processes contained degenerating mitochondria and lysosomal electron-dense bodies and these met the criteria for neuroaxonal dystrophy. Other processes contained branching cisterns; still others were filled with electron-dense masses and amorphous vesicles. The overall ultrastructural appearance of variant CJD was similar to that of FFI cerebral cortex, except for a much higher number of cellular processes containing TVS. We detected TVS in the majority of sCJD cases that, in addition to typical spongiform change and robust astrocytic reaction, showed widespread neuritic and synaptic degeneration and autophagic vacuoles. We conclude that TVS are readily found in FFI, vCJD and sCJD and that widespread neuritic degeneration is a part of ultrastructural pathology in prion diseases.

Polymorphisms within the prion (PrP) and prion-like protein (Doppel) genes in AD

The authors present a study on the association of PRNP and PRND gene polymorphisms with the occurrence and age at onset of Alzheimer's disease (AD). DNA from 79 Polish patients with probable AD and 107 healthy control subjects was studied. The PRNP codon 129 homozygosity seemed to be associated with the occurrence of AD: In AD patients, the percentage of Val/Val and Met/Met genotypes was higher than in the control subjects. A significant difference appeared also between early-onset (<70 years) and late-onset (> or = 70 years) AD patients in the PRND genotypes.

Plasma levels of alpha beta peptides are altered in amnestic mild cognitive impairment but not in sporadic Alzheimer's disease

Plasma alpha beta levels have been examined in sporadic Alzheimer's disease yielding conflicting results; both no difference and an increase in plasma concentrations of alpha beta42 and alpha beta40 in sporadic cases of AD as compared to controls have been reported. Elevated plasma alpha beta42 levels may be detected several years before the onset of symptoms (in mild cognitive impairment stadium). Levels of alpha beta40 and alpha beta42 were measured in plasma from 54 patients with AD, 39 subjects with MCI and 35 controls using a commercially available ELISA. Mean plasma alpha beta42 levels were significantly higher in MCI as compared to both AD (P < 0.001) and control subjects (P < 0.001), while alpha beta40 did not differ between the groups. No correlations were observed between alpha beta levels and age, MMSE scores or gender. According to ROC curve analysis the maximum accuracy in discriminating MCI versus both controls and AD subjects has been achieved using a cut-off value of 3.8.

Microglial cells in neurodegenerative disorders

Microglia are resident immune cells of the CNS. They are involved in the pathogenesis of diverse neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, prion diseases as well as multiple sclerosis, amyotrophic lateral sclerosis and AIDS dementia complex. It is widely accepted that microglia contribute to the neurodegeneration through a release of a variety of proinflammatory substances. In fact, they are not the only cells which contribute to immunological processes inside the nervous system. The CNS is composed of different cell populations that answer to pathological factors and influence each other and modulate their reactions. These complex interactions are responsible for the development of brain pathology. This paper reviews the available information on microglial cells contribution to AD, PD and prion diseases development.

Complement factors C1q and C3b in brains with Creutzfeldt-Jakob disease

Neuronal loss in Creutzfeldt-Jakob disease (CJD) is due to apoptosis and autophagy, however the apoptotic cell death may be related to the influence of cytokines. The role of complement system in induction of this process was recently postulated. In our study we examined the immunoreactivity for "early activation" complement factors C1q and C3b in the brains of the patients with CJD. We showed the positive immunoreactivity for C1q and C3b in neurons mainly in areas of spongiform change, in Purkinje cells, molecular layer and granular layer of cerebellum, and in prion protein positive plaques. The evident positive reactivity of two complement factors may suggest the role of complement system in neurodegeneration in CJD.

Molecular abnormalities in pediatric embryonal brain tumors--analysis of loss of heterozygosity on chromosomes 1, 5, 9, 10, 11, 16, 17 and 22

Embryonal tumors, the most common group of malignant brain tumors in childhood, are heterogeneous and have been associated with a large number of genetic abnormalities. The aim of this study was to comprehensively analyze loss of heterozygosity (LOH) on regions harboring suppressor genes (PTCH2, PTCH1, APC, PTEN, DMBT1, SUFU, AXIN1, hSNF5/INI1) and to study chromosomal regions in which deletions have been described most frequently (1p, 1q, 11p, 16p, 17p). Twenty-nine children (17 male and 12 female), aged from 1 year 13 years were included in this study. There were 24 medulloblastomas (MB) and 5 supratentorial primitive neuroectodermal tumors (sPNET). Tissue samples from 29 primary and 11 recurrent tumors were analyzed according to the LOH standard procedures, which were extended to include fluorescence in situ hybridization for detection of isochromosome 17q (i(17q)) and direct sequencing ofTP53 exon 4. LOH on 17p was found in 15 out of 29 tumors. FISH analysis identified the presence of i(17q) in 16 tumors. Comparison of LOH analysis and the FISH data indicated that alterations of 17p were related to be the introduction of an i(17q) formation. LOH on 10q and 9q was observed in 4 and 2 cases, respectively, and was associated with alterations of chromosome 17. These results indicated a connection between alterations of PTCH/SHH genes and abnormalities of chromosome 17. A deleted region on 22q, covering the hSNF5/INI1 locus, was observed in 3 tumors. Progression of the molecular changes occurred in 1 case of recurrent medulloblastoma. LOH on 10q and 17p was found in both primary and recurrent tumor, while losses on 11p, 16p, and 16q occurred only in the recurrent tumor. No evidence of alteration in TP53 exon 4 was identified.

Molecular heterogeneity of meningioma with INI1 mutation

BACKGROUND

INI1 (hSNF5) mutations are linked to rhabdoid tumours, but mutations in meningiomas with hot spot mutations in position 377 have also been reported.

AIMS

To analyse the INI1 gene in meningioma.

METHODS

Exons 1, 4, 5, and 9 of the INI1 gene were analysed by the polymerase chain reaction and direct sequencing in 80 meningiomas. For all cases, western blotting of the INI1 protein was performed.

RESULTS

Only one of the 80 samples showed a cytosine insertion in codon 376. This mutation changed the open reading frame in almost the whole exon 9 and resulted in a longer hSNF5 protein. Complex analysis of the above described tumour sample by western blotting, DNA sequencing, and loss of heterozygosity (LOH) analysis showed that this particular meningioma consisted of heterogeneic cellular components. One of these components had a mutated INI1 gene, whereas in the other component INI1 was intact.

CONCLUSIONS

INI1 mutation is a rare event in the molecular pathology of meningiomas. It is possible for the INI1 gene to be mutated in only a proportion of meningioma cells.

Bovine spongiform encephalopathy (BSE): the end of the beginning or the beginning of the end?

Bovine spongiform encephalopathy (BSE) is a zoonosis being the origin of variant Creutzfeldt-Jakob disease and an important cattle disease in its own right. This association has driven both the research into the disease and extensive epidemiological investigations of practical value. Not only has the occurrence of BSE has a serious effect on animal health and public health, it has also seriously interrupted trade in cattle and cattle products from affected countries. Since 2001, several additional European countries, Japan, Israel and Canada have reported BSE in native-born stock and this has led to a concern about the BSE status of countries that have imported cattle and cattle products from any affected country. A single case recently reported in the USA was in a cow imported from Canada, thus extending the risk of BSE occurrence into the North American continent as a whole. Extensive feed and offal bans have protected the food and feed chains in all countries with BSE, even though initially they tended to be leaky. Application of newly-developed, approved 'Rapid' tests for misfolded PrP in central nervous tissue of targeted, high-risk animals and slaughter cattle now provides the tools whereby the real incidence of the disease (and to a degree, infection) can be determined in an active surveillance programme. 'Rapid' testing also enables the progress of epidemics to be monitored in response to applied measures. In the EU, over 10 million cattle are tested annually. Analysis of the extensive data shows that it is the beginning of the end of the BSE epidemic in the UK; most European countries, Israel and Japan are close behind. The epidemic in North America (two cases to date) is at the beginning. Significant measures had already been adopted there to reduce the risk from recycling of infection via feed but it remains to be seen if they are watertight. Advice has been given to ensure that public health is protected and to monitor the epidemic by strategic use of approved 'Rapid' tests to determine that the epidemic is in fact trivial as believed, or otherwise to identify weaknesses in measures that can be corrected. It is imperative that all countries conduct risk assessments for BSE, follow the OIE recommendations and do not unreasonably disrupt international trade. There is a responsibility for all countries with BSE to ensure that infection is not exported to any country, particularly through live cattle and especially via meat-and-bone-meal, which is the acknowledged vehicle of transmission. There is also a responsibility placed upon all countries to protect, not only their cattle populations, but also their human populations from exposure to this economically important fatal disease. If all the advice is taken and measures enforced there is a prospect that BSE can be eliminated from countries and regions as a prelude to eradication from the world.

Astrocytes in transmissible spongiform encephalopathies (prion diseases)

Astrocytosis is one of the hallmarks of neuropathology of transmissible spongiform encephalopathies (TSEs) or prion diseases. In this review, we summarize data on astrocytic reaction, including naturally occurring or experimentally induced TSEs. A particular form of astrocytic reaction is known as gliocytosis and it is typical for experimental scrapie in mouse or in hamsters. Also, astrocytes participate in the formation of amyloid plaques. An interesting interaction between astrocytes and oligodendrocytes is discussed in detail as well as a particular form of astrocytic reaction in panencephalopathic form of TSEs.

An outline of the neuropathology of transmissible spongiform encephalopathies (prion diseases)

We review here the basic neuropathology of transmissible spongiform encephalopathies (TSE) or prion diseases. The classic hallmark of TSE neuropathology is a combination (in different proportions in different diseases) of spongiform change, astrocytosis, neuronal loss and amyloid plaques. Immunohistochemically, accumulation of the abnormal isoform of prion protein (PrP(sc) or PrP(d)) is regarded as a diagnostic for TSE. We also review the peculiarities of kuru, variant Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker disease.

Fate of myelinated fibres in the optic nerves in experimental Creutzfeldt-Jakob disease in rodents: an ultrastructural study

We report the ultrastructural appearances of myelinated fibres of the optic nerves from mice infected with the Fujisaki strain of Gerstmann-Sträussler-Scheinker (GSS) disease and from Echigo-1 strain of Creutzfeldt-Jakob disease (CJD). Optic nerves from CJD- and GSS-infected rodents showed severe pathological changes. Theses changes were qualitatively indistinguishable from each other but were more robust in the Fujisaki GSS model than in the hamsters inoculated with Echigo-1. The most characteristic finding was the distension with the attenuation of the myelin sheath forming a vacuole while shrunken axon was attached to the innermost layer of the myelin. With high power electron microscopy, we could observe the splitting of the myelin lamellae at the major dense or intraperiod lines to form complex openings that extended to line the vacuole. This finding suggests that myelin lamellae participate in the formation of vacuoles.

Ultrastructural alterations in the optic nerve in transmissible spongiform encephalopathies or prion diseases--a review

The involvement of the visual system is well recognised in TSEs. The present review summarises the ultrastructural changes in the optic nerves in experimental infections of laboratory rodents with the agents of two human TSEs (CJD and GSS) and with two isolates of the scrapie agent. Vacuoles of myelinated fibres were found within myelin sheaths and themselves contained secondary vacuoles (vacuoles within other vacuoles) and curled membrane fragments not unlike the vacuoles in cerebral grey matter (see also: Spongiform change--an electron microscopic view; this issue). The myelin sheath had split either at the major dense line or at the intraperiod line. In addition, axons contained vacuoles within the axoplasm, corresponding to the typical spongiform vacuoles of grey matter. Vacuolation of myelinated fibres was accompanied by an exuberant cellular reaction consisting of macrophages containing numerous mitochondria, abundant rough endoplasmic reticulum and secondary lysosomes filled with digested myelin debris, electron-dense material and sometimes entire myelin-bounded vacuoles. Within macrophages myelin fragments undergoing active digestion were often seen, together with lyre-like bodies and paracrystalline inclusions. Astrocytes and their processes were prominent and glial filaments and many mitochondria were readily detected. Proliferation of the inner mesaxons was also seen. Cross-sectional profiles of many myelinated fibres contained membranous organelles continuous with the inner lamellae of the oligodendroglial cells. The inner mesaxon proliferations formed whorls and loops. In some axons proliferation was so severe that the mesaxonal loops filled the whole cross-section of the axon. Occasionally there was intrusion of the membranous tongue of the inner mesaxon into the axoplasm. Dystrophic neurites were relatively numerous. In GSS-infected animals some axons underwent demyelination with stripping of the myelin lamellae, while still others underwent vesicular myelin degeneration. It is of special note that in the cytoplasm of several cells as well as the axoplasm numerous autophagic vacuoles were seen.

Tubulovesicular structures--the ultrastructural hallmark for transmissible spongiform encephalopathies or prion diseases

Tubulovesicular structures (particles--TVS) are the only ultrastructural marker for all transmissible spongiform encephalopathies (TSEs) or prion disease as seen by thin section electron microscopy. The latter is stressed as opposed to negative-staining techniques. TVS are spheres or short rods of approximately 27-35 nm in diameter. What is particularly interesting, this size of TVS is also the size of filter cut-off as judged from ultrafiltration studies and the size of the smallest infectious unit as recently estaimated. TVS have been found in all naturally occurring and experimentally induced TSEs, including variant Creutzfeldt-Jakob disease and human familial TSEs--fatal familial insomnia and Gerstmann-Sträussler-Scheinker disease. In longitudinal studies, the number of neuronal processes containing TVS correlates roughly with the incubation period and with infectivity. Hence, they are readily found in hamsters infected with the 263K strain of scrapie but it is very difficult to find them in human TSEs where titre is lower. The composition of TVS is unknown but they are not composed of PrP. Their consistent presence in all TSEs suggests the role at least of TSE pathogenesis.

Molecular approaches to mechanisms of prion diseases

Prion diseases such as scrapie in sheep, bovine spongiform encephalopathy in cattle, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker disease and fatal familial insomnia in man are neurodegenerative disorders. In humans, the diseases can be sporadic, inherited, or acquired by infection. The underlying pathogenic event in prion diseases is a conformational modification of the cellular isoform prion protein (PrP(C)) to the pathogenic isoform (PrP(SC)) that accumulates in the central nervous system. However, in humans, in some inherited cases the pathological PrP is not PrP(Sc), but a transmembrane form of prion protein, (Ctm)PrP. Prion protein is encoded by the cellular gene, PRNP, which has been mapped to human chromosome 20p21. Familial prion diseases are thought to result from a change in structure of the prion protein produced by the mutated PRNP gene. Furthermore, polymorphic codon 129 of the PRNP gene encodes either methionine or valine and appears to influence the susceptibility of patients to iatrogenic and sporadic CJD as well as the neuropathological phenotype in these forms of CJD. Polymorphisms in the promoter region of PRNP gene or disturbances in prion protein metabolism, such as incorrect activity of cellular chaperones or proteasomes are considered as susceptibility factors in human prion diseases.

Spongiform change--an electron microscopic view

Spongiform change is a hallmark of transmissible spongiform encephalopathies (TSEs) in prion diseases. They are defined as small round or oval empty spaces in the neuropil. When confluent, they merge to form "morula-like" structures. Their neuroanatomical distribution and grading within each of defined neuroanatomical areas underlie the lesion profile method used to discriminate strains in rodents and in cattle. Ultrastructurally, vacuoles develop within neuronal elements. They are membrane-bound and contain secondary vacuoles and "curled" membrane fragments. Separate type of vacuoles are those develop within myelin sheath. Those vacuoles develop through complicated opening at the major-dense and intraperiod lines. The histogenesis of spongiform vacuoles is unclear and the only hypothesis that they develop through the formation of abnormal configuration of plasma membranes (ACPMs) has never been substantiated. We suggested that vacuoles may develop through process of autophagy.

Kuru: a half-opened window onto the landscape of neurodegenerative diseases

Kuru, the first human neurodegenerative disease classified as a transmissible spongiform encephalopathy (TSE), prion disease or, in the past, as a slow unconventional virus disease, was first reported to Western medicine in 1957 by Gajdusek and Zigas. A complete bibliography of kuru through 1975 has been published by Alpers et al. The solution of the kuru riddle opened a novel field of biomedical sciences and initiated more than a quarter of century of research that has already resulted in two Nobel prizes (to D. Carleton Gajdusek in 1976 and to Stanley B. Prusiner in 1997) and was linked to a third (to Kurt Wüthrich who determined the structure of the prion protein). Kuru research has impacted the concepts of nucleation-polymerization "protein cancers", and "conformational disorders". This paper is dedicated to Dr. Carleton Gajdusek on the occasion of his 80th birthday. "Kuru" in the Fore (Fig. 1) language means to shiver from fever or cold. The Fore used the noun of the kuru-verb to describe the always fatal disease which decimated their children and adult women but rarely men. It has been and still is restricted to natives of the Fore linguistic group at Papua New Guinea's Eastern Highlands and those neighboring linguistic groups which exchange women with Fore people (Auiana, Awa, Usurufa, Kanite, Keiagana, late, Kamano, Kimi; Fig. 2). Neighboring groups into which kuru-affected people did not settle through marriage or adoption, such as the Anga (Kukukuku), and remote lagaria, Kamano and Auiana people, were not affected. It seems that Kuru first appeared at or shortly after the turn of XX century in Uwami village of Keiagana people and spread to the Awande in the North Fore where the Uwami had social contacts. Within 20 years it had spread further into the Kasokana (in 1922 according to Lindebaum) and Miarasa villages of North Fore, and a decade later had reached the South Fore at the Wanikanto and Kamira villages. Kuru became endemic in all villages that it entered and became hyperendemic in the South Fore region. All native informants stressed the relatively recent origin of kuru. Interestingly enough, when kuru first appeared, it was considered poetically by Fore as similar to "the swaying of casuarinas tree" and kuru was labeled cassowary disease to stress the similarity between cassowary quills and "waving casuarinas fronds". Gajdusek first learned about kuru from Dr. Roy Scragg, director of Public Health in Port Mosby, who had already read a report sent by Dr. Vin Zigas to Dr. John Gunter in 1956. In March 1957, Gajdusek joined Zigas, who at that time was a medical patrol officer in Kainantu, Eastern Highland District of the Territory of Papua New Guinea.