Theodor Meynert (1833-1892), pioneer and visionary of brain research.

Theodor Meynert (1833-1892) was the first scientist to perceive brain research as an interdisciplinary project, documented by his own fundamental contributions as a selfstanding enterprise and presented with comprehensive objectives of research. Meynert was born in Dresden and lived in Vienna from the age of 8. In a steep career, he reached high professional recognition: Aged 37, he took charge of the management of the 1st Psychiatric Clinic, established especially for him; he exerted competent influence in the so-called 2nd Viennese School of Medicine and at international level. The focal points of his scientific work have been anatomy and histology of cerebrum and brainstem, topography and functional relations of the main connecting fiber systems, also demonstrated by precisely interpreted clinipathological obaservations. Among his timely findings should be stressed: the stratified texture, cellular architecture and regional differentiation of the cerebral cortex as a basis of present cytoarchitectonics and of cortical localisation theory, e.g., regarding speech defects. Intending to establish psychiatry as an exact science on the basis of brain pathology, Meynert formulated a program which anticipates the targets designed by today's biological psychiatry. The vital and psychic dynamics of the brain he interpreted in critical speculation along the lines of the contemporary philosophy of nature. Meynert combined his ingenious exact findings with results of the upcoming neurophysiology, neurochemistry and neuropsychology into a prodigious coherent system representing the complexity of the human brain-world relationship. These achievements reveal Meynert as the founder of scientific brain research.

Neuropathology and genetics of Pelizaeus-Merzbacher disease.

The recent history of Pelizaeus-Merzbacher Disease (PMD) demonstrates paradigmatically the impact of basic biological research on clinical neurology and brain pathology: this rare and peculiar hereditary disease has become one of the best known disorders of its kind, through a cooperative research effort in neuropathology, human genetics, neurochemistry and molecular biology. PMD, a genetic dysmyelination restricted to the CNS, has been identified as a disease that involves the X chromosome-linked gene for myelin proteolipid protein (PLP), a major structural myelin component. Today more than 30 different mutations in this gene have been defined and associated with PMD or the clinically distinct form X-linked spastic paraplegia type-2 (SPG-2). Improved scanning techniques, specifically the non-invasive magnetic resonance imaging (MRI), allow its early diagnosis in the heterogeneous group of CNS myelin deficiencies. These remarkable achievements have, at the same time, caused a problem for disease classification. Myelin disorders have been grouped in the past on the basis of clinical and neuropathological criteria, creating a system that has now to be reconciled with molecular-genetic data.

[Neuropathology in the neurosciences. A system in transition]. / Die Neuropathologie in den Neurowissenschaften. Ein System im Wandel.

Neuropathology (Np) is a full member of the neurosciences. As a basic neuroscience it is directed to the behaviour of nervous tissues under pathogenic conditions. The theoretical and methodical core of Np concerns the morphological features of pathological disorders and processes of the nervous system. The goal of Np data presentation is an objective description of the structural changes; their time course as processes, and if possible their causal constellations. Complementary to this analytical task is that of reconstructing the pathological process and at a higher level the conception of pathomorphological entities, e.g. as syndromes. Clinical Np is an alliance of Np with neurology, psychiatry and neurosurgery for representing the structural basis of diseases and the role of morphology in diagnosis and clinical management. Prerequisite for the proper functioning of Np is an integration with these other specialist fields. The clinical neuropathologist therefore has to be in certain respects also a neurologist. The same is true of the alliances of Np with other neurosciences, which is already reflected in recent neuropathological methodology. Detailed training programs are necessary for clinical Np, covering all aspects of its medical and social implications. Enough options should be offered for horizontal flexibility of curricula, futherance of secondary special training and support of good unconventional approaches by junior scientists.

Synaptic pathology in Alzheimer's disease: immunological data for markers of synaptic and large dense-core vesicles.

We have analysed several markers for small synaptic vesicles (synaptin-synaptophysin, p65 and SV2) and large dense-core vesicles (chromogranin A, secretogranin II/chromogranin C) in the brains of patients with Alzheimer's disease, and normal controls by immunoblotting and immunohistochemistry. In comparison to age-matched controls the levels of all three synaptic vesicle markers were decreased in temporal cortex of Alzheimer patients. On the other hand, the levels of chromogranin A were increased, and those of secretogranin II lowered. This resulted in a significant increase of the ratios of chromogranin A to synaptophysin, p65 or SV2 and of that for chromogranin A to secretogranin II. These increases were significantly correlated to clinical severity of dementia and extent of neuropathological changes. By immunohistochemistry a high percentage of senile plaques was found to contain chromogranin A-reactive dystrophic neurites, whereas synaptophysin reactivity within plaques was rare. These results indicate that the number of synaptic vesicles is lowered in Alzheimer's disease, and that one component of large dense-core vesicles, i.e. chromogranin A, is elevated. We, thus, suggest that in Alzheimer's brain distinct changes occur for both types of synaptic organelles.

[Differential diagnosis of dementia diseases. A prospective clinical study with neuropathologic diagnostic verification]. / Die Differentialdiagnose der Demenzerkrankungen. Eine prospektive klinische Untersuchung mit neuropathologischer Diagnosestellung.

We present clinico-pathological correlations for a consecutive series of 44 demented patients in the Vienna longitudinal study on dementia. Prospective clinical diagnosis used the DSM-III-R and the NINCDS-ADRDA criteria. Not only the clinical, but also the neuropathological diagnosis of DAT is based on exclusion criteria, and depends on the interpretation of minimal vascular lesions. Although we did not exclude atypical cases from the study, 80% of diagnoses could be validated at autopsy. Nevertheless, our set of clinical criteria needs further validation in patients in the earliest stages of dementia.

Cytoskeleton pathology in Alzheimer's disease and related disorders.

The reported findings suggest that ubiquitination of pathological proteinaceous intracytoplasmic inclusions is not at all specific of AD. On the contrary it appears to be a general biochemical marker for disorders in the degradation of a variety of cytoskeletal and other cytoplasmic proteins. The pattern of affected cytoskeletal components is not specific of AD/SDAT tangles. Tau definitely is present also in PSP tangles and possibly in Pick bodies but not in Lewy bodies. Therefore it has to be considered that the intracytoplasmic accumulation of cytoskeletal protein/ubiquitin complexes in itself is a rather unspecific cellular reaction pattern, possibly a secondary reaction to cell injury of many types, especially, however, of neuronal aging. Nevertheless, the manifestation of NFT in an excessive quantity, intensity, and dynamics with severe concomitant lesions as in AD/SDAT undoubtedly is a true pathological and in this sense a disease-specific change.

[Astroglial dystrophies]. / Astrogliale Dystrophien.

An account is given of the concept of glial dystrophies (SEITELBERGER 1970), with reference being made to the astroglial syndromes involved, that is to the complex of astroglial dystrophy (AD). Basic research more recently conducted on the physiology of astroglia seem to support the assumption that astroglia represents a particular pattern of cytochemical processes and regulations which, in response to disturbance, is likely to cause characteristic and quite often selective morphological alterations. A distinction is made between 3 sub-groups of AD, that is AD proper in a more limited sense, gliovasal dystrophy (GVD), and glioneuronal dystrophy (GND). In this context, the most common forms of astroglial alterations are discussed in keeping with the above definition. The Rosenthal fibre is defined as a disorder of the astroglial cytoskeleton which may grow manifest as reactive or systemic alterations, depending on expression. The various forms of abnormal astrocytes in hepatogenic AD were found to differ from each other in both morphology and immunocytochemical reactivity, according to their particular pathogenetic patterns. Presenile glial dystrophy is a senile disease that is characterised by massive numerical increase in astrocytes, primarily at the corticomedullary interface and is accompanied by diffuse cerebral atrophy but only minor nerve cell alterations. It is thus an entity in its own right, apart from Pick's and Alzheimer's diseases. A selective astroglial oedema may be experimentally induced in regions of epileptic hyperactivity of nerve cells by systemic administration of kainic acid. It is in conformity with the functional linkage of astrocytes with cerebral vessels and neurons that AD is quite often associated with alterations of these structures, as well: GVD and GND.(ABSTRACT TRUNCATED AT 250 WORDS)

Some mechanisms of brain edema studied in a kainic acid model.

Kainic acid (KA) is a potent neuroexcitatory drug widely used in the experimental study of seizure activity. Subcutaneous injection of KA into rats (10 mg/kg in saline 10 mg/ml; pH 7.0) induced longlasting status epilepticus followed by damage of CNS tissue in the entorhinal/pyriform cortex and in the hippocampus. The studies covered by this report demonstrated the formation of cytotoxic brain edema characterized by massive swelling of perineuronal and perivascular astroglia with microcirculation disturbance after KA injection, resulting in parenchymal necrosis of the affected region; furthermore perivenous hemorrhages and necroses corresponding to herniation lesions of the brain appear. Tracer studies with Na-fluorescein, Evans blue, albumin, and horseradish peroxidase revealed only a mild increase in the permeability of cerebral vessels, topographically unrelated to areas of brain edema. Treatment of brain edema with dexamethasone did not influence the incidence and severity of edematous brain damage. Treatment with mannitol, however, completely prevented the lesion in 54% of animals injected with KA. The present results indicate that brain edema plays an important role in the pathogenesis of epileptic brain damage following systemic KA intoxication. It is suggested that in this model brain edema develops due to massive ionic imbalance caused by KA induced persistent neuronal excitation. In addition the model demonstrates the possible pathogenetic role of selective astrocytic swelling in the production of local hippocampal ischemia followed by herniation and its sequels. Such pathology originating from astrocytes probably may occur also in closed brain injury.

Tau and ubiquitin immunoreactivity at different stages of formation of Alzheimer neurofibrillary tangles.

In his original 1911 publication Alois Alzheimer classified neurofibrillary tangles (ANT) into three morphologically defined subgroups according to their stage of maturation. The present study shows that changes in the morphological appearance of ANT during their maturation process are accompanied by changes in their antigenic profile. As shown by several immunocytochemical studies these abnormal phosphorylated microtubule-associated protein tau and of ubiquitin. In this study, immunoreactivity for the altered tau is not only seen in a subset of tangles but also in the cytoplasm of some nerve cells lacking ANT, which we believe to be at a stage of neuronal alteration preceding the formation of compact tangles (Stage 0 tangles). Similar numbers of Stage 0 tangles are present in the brains of age-matched non-demented individuals as in Alzheimer cases, but are absent in young controls lacking ANT. In extracellular "ghost tangles", the ultimate stage of neurofibrillary degeneration, immunoreactivity for tau is accessible to antibodies only when tissue sections are pretreated with formic acid to uncover the binding sites. In contrast to tau, presence/accessibility of an epitope residing on residues 50-65 of ubiquitin recognized by a monoclonal antibody raised to paired helical filaments (3-39) increases during the maturation of ANT and is most pronounced in "ghost tangles". Appearance/uncovering of the 3-39 epitope and masking of tau reactivity during tangle maturation may reflect degradation or conformational changes in the pathological filaments due to their aging and the final loss of their parent nerve cells.

An antigenic profile of Lewy bodies: immunocytochemical indication for protein phosphorylation and ubiquitination.

An antigenic profile of subcortical and cortical Lewy bodies was determined in the presence or absence of neurofibrillary tangles in the same brain using antisera and monoclonal antibodies to various cytoskeletal elements as well as to determinants not present in the normal cytoskeleton. The cores of many Lewy bodies were strongly reactive with a monoclonal antibody to paired helical filaments which has been shown to recognize ubiquitin. This antibody also stained Marinesco bodies in the same tissue sections. Two monoclonal antibodies to phosphorylated epitopes of neurofilament proteins (SM I 31, SM I 34) stained the peripheries of about 40% of all discernable Lewy bodies on untreated paraffin sections. Reactivity with a monoclonal antibody to neurofilaments (SM I 33) appeared only after pretreatment of the sections with phosphatase. Lewy bodies did not bind antibodies to tau protein. Our results show that, as previously shown for neurofibrillary tangles, Lewy bodies also contain ubiquitin. The uncovering of neurofilament epitopes by treatment with phosphatase indicates that abnormal phosphorylation of cytoskeletal elements may play a role in the pathogenesis of the Lewy body.

Accumulation of abnormally phosphorylated tau precedes the formation of neurofibrillary tangles in Alzheimer's disease.

The intraneuronal accumulation of paired helical filaments in the form of neurofibrillary tangles is one hallmark of the brain pathology in Alzheimer's disease. At certain predilection sites, a small number of similar lesions are also present in the brains of the majority of aged non-demented individuals. As suggested by several studies before, these abnormal cytoskeletal structures contain determinants of microtubule-associated protein tau and ubiquitin. The present study uses a morphological classification of neurofibrillary tangles into different stages of maturation, as suggested by Alzheimer in 1911, and shows by quantitative immunocytochemistry that early stages of neurofibrillary degeneration contain abnormally phosphorylated tau. Immunoreactivity for the altered tau is seen not only in tangles but also in the cytoplasm of some nerve cells lacking neurofibrillary tangles. Similar numbers of such immunoreactive neurons without tangles are present in age-matched non-demented individuals as in Alzheimer cases, but are absent in young controls. In contrast, incorporation of an epitope, recognized by a monoclonal antibody (3-39) raised to paired helical filaments, which is directed against a determinant residing in the 50-65 amino acid residue region of ubiquitin occurs late in the process of tangle maturation and is most pronounced in extracellular 'ghost tangles'. It is suggested that the accumulation of abnormally phosphorylated tau is one of the earliest cytoskeletal changes in the process of tangle formation. Exposure of certain ubiquitin epitopes in the pathological fibers may reflect an unsuccessful attempt of proteolytic degradation.

Effect of mannitol treatment on brain neurotransmitter markers in kainic acid-induced epilepsy.

The effect of mannitol treatment on the behavioural, morphological and neurochemical brain damage induced after subcutaneously applied kainic acid (10 mg/kg) was studied in the rat. Mannitol at a dose of 1.5 g/kg was injected intravenously 10 min, 1.5 h and 3 h respectively after kainic acid administration. A protective effect of mannitol was observed only when mannitol was given 1.5 h after kainic acid application, i.e. within the early phase of kainic acid-induced brain oedema development. At this time period, mannitol prevented the development of kainic acid-induced seizures as well as irreversible brain lesions and neurochemical changes, the latter being reduction of noradrenaline levels in amygdala/pyriform cortex measured 3 h, and reduction of glutamate decarboxylase and choline acetyltransferase activities measured 3 days after kainic acid treatment. Similarly loss of glutamate decarboxylase activity in dorsal hippocampus induced by kainic acid was prevented by mannitol treatment. It is concluded that by washing out brain oedema, mannitol treatment may prevent propagation of seizures and brain damage in the kainic acid model of epilepsy.

[Neuropathologic principles of senile dementia]. / Neuropathologische Grundlagen seniler Demenzen.

Several groups of senile dementias with differing causes and neurohistological substrates can be distinguished. Genetically determined Pick's disease produces severe neuronal atrophy; Alzheimer's disease is characterized by pathological neurofibrillary changes. Jakob-Creutzfeldt disease and Gerstmann-Sträussler-Scheinker disease are slow virus diseases induced by unconventional agents. These diseases, after an incubation time of several years, take the course of slowly progressive degenerative diseases of the central nervous system without inflammatory and specific immune reactions of the host organism. Regarding pathogenesis these diseases were interpreted as degenerative processes as long as their transmissibility was yet unknown. The fact that so-called slow virus diseases can also produce argyrophilic plaques is a further common feature of this group of diseases and human pathological aging processes. So far, however, there is no proof that Alzheimer's disease is caused by an unconventional agent. On the other hand, common features of the products of aging changes and of unconventional viral diseases are apparent. In this paper current knowledge of pathogenetic mechanisms in this rapidly developing field of research is presented. Some relevant factors of organic dementia are discussed: special characteristics of neuronal atrophy (functional role of dendrites); architectonics of cerebral atrophy (laminar versus modular atrophy); neurotransmitter changes (causes or sequels of dementia) and a possibly non-specific origin of senile plaques. Finally, the clinical relevance of neurobiological research into dementias is emphasized.

Neurofibrillary tangles in Alzheimer's disease and progressive supranuclear palsy: antigenic similarities and differences. Microtubule-associated protein tau antigenicity is prominent in all types of tangles.

The antigenic profile of neurofibrillary tangles (NFT) in Alzheimer's disease (AD), senile dementia of Alzheimer type (SDAT), progressive supranuclear palsy (PSP) and in non-demented aged humans was investigated by light and electron microscopic immunocytochemistry using antisera and monoclonal antibodies to tubulin, microtubule-associated proteins (MAP1, MAP2 and tau), neurofilament proteins and determinants unique to Alzheimer paired helical filaments (PHF). Antibodies to tau proteins labeled NFT in all cases investigated (AD, SDAT, PSP and non-demented aged humans). However, one monoclonal antibody to PHF recognized numerous tangles in AD/SDAT, but only a small minority of the PSP tangles. Antibodies to tubulin, MAP1, MAP2 and neurofilament proteins did not selectively stain NFT. Whereas pretreatment of sections with phosphatase was required for the detection of tangles with Tau-1 monoclonal antibody, digestion of sections with either phosphatase or pronase had no significant effect on the staining pattern obtained with the other antibodies. Our studies show that, as previously described for AD/SDAT, phosphorylated tau polypeptides are also a major antigenic determinant of tangles in PSP, indicating that tangle formation may follow a common pathogenetic pathway in neurofibrillary degenerations. There is, however, at least one epitope in AD/SDAT tangles which seems to be absent on, or at least inaccessible in, the 15-nm straight fibrils of PSP.

[New aspects of senile and presenile dementia]. / Neue Aspekte der senilen und präsenilen Demenz.

Problems of research in dementia are presented. It is a matter both of structural disturbances in the texture of conditions which impair the texture of conditions of possible functions, as well as of actual functional disturbances of the brain. The numerous etiological and diagnostic aspects resulting from this show distinctly that the dementia does not exist. In the numerous dementias which appear as diseases of higher age, the distinction between true old age diseases (Alzheimer, Pick, progressive glial dystrophy) and the cerebrovascular dementias (multi-infarct-dementia, Binswanger's disease) is of importance. The classification of dementias may be carried out both by descriptive neuropathological criteria and by functional neuropathological criteria. This is demonstrated by way of examples.

Neuropathology of Rett syndrome.

Autopsy studies in 8 girls with the Rett syndrome dying between 4 and 15 years showed: Diffuse cerebral atrophy/micrencephaly, with a decrease in brain weight by 13.8 to 33.8% of age-matched controls, apparently related to the duration of the disorder; Mild, but inconsistent diffuse cortical atrophy without developmental disorders apart from occasional microdysgenesis (three cases), but increased amounts of neuronal lipofuscin, and occasional mild astrocytic gliosis; Mild, but inconsistent spongy changes in cerebral and cerebellar white matter, optic nerve (two cases), and myelinated fascicles of the brainstem tegmentum, without signs of dys- or demyelination, and apparently different from the spongy myelinopathy common to aminoacidopathies; Most conspicuous was an underpigmentation of the substantia nigra which contained many fewer well-pigmented neurons for age (53-73%), and fewer pigmented granules per neuron, while the total number of nigral neurons and the triphasic substructure of neuromelanin were normal for age. No pathologic changes were seen in locus coeruleus, nucleus basalis of Meynert, and nucleus dorsalis raphe; Electron microscopy of autopsy material from an 11-year-old girl showed increased amounts of neuronal lipofuscin without signs of a storage disorder. Reactive and degenerating axons in the caudate nucleus were possibly related to the nigral changes, suggesting some dysfunction of the dopaminergic nigro-striatal system, while the synaptic organization of the neostriatum appeared unaffected. Peripheral nerve from a patient dying in advanced stage showed increased numbers of unmyelinated (regenerated?) axons, with almost no demyelination and few remyelinated axons, suggesting axonal degeneration rather than hypomyelination, but exogenous factors (malnutrition) cannot be excluded. The pathogenetic mechanisms of the morphologic brain lesions and their relations to clinical and neurochemical findings in Rett syndrome are unknown and deserve further intensive investigations.

Kainic acid-induced seizures: dose-relationship of behavioural, neurochemical and histopathological changes.

Behavioural, neurochemical and histopathological changes induced by systemic injection of kainic acid were investigated at various doses of the neurotoxin (3, 6 and 10 mg/kg s.c.). There was a positive correlation between the dose of kainic acid and the extent of both the acute neurochemical changes 3 h after the injection (increases of 3,4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid levels and a decrease in noradrenaline levels in all brain regions investigated), the acute histopathological changes (shrinkage and condensation of nerve cells and brain oedema in the entire forebrain) and the extent of behavioural alterations (immobility, 'wet dog shakes' and limbic seizures). However, the slope of the dose-response curves was very steep. Late and irreversible alterations included losses of the enzyme markers glutamic acid decarboxylase and choline acetyltransferase and, histopathologically, incomplete parenchymal necrosis and haemorrhages. These changes, however, were restricted to a few brain regions, the most important being the hippocampus, amygdala, entorhinal and pyriform cortex, and olfactory bulb, and they were seen only in animals which had undergone severe convulsions. It is suggested that the irreversible brain lesions in this animal model of limbic (temporal lobe) epilepsy are not solely induced by a direct action of kainic acid, but may be caused--at least in part--by additional, secondary pathogenetic mechanisms.