[Alzheimer's disease lesions: from morphology to cell biology]

Four different approaches to Alzheimer disease changes have been successively applied, and allowed a permanent feed forward-feed back enrichment of knowledge: morphologists described neurofibrillary tangles, senile plaques, amyloid angiopathy; with the help of immunohistochemical and biochemical techniques, they recognised A beta- and tau-associated pathologies; this, in turn, allowed more precise analysis of the lesions, and permitted recognising new ones such as neuropil threads; molecular genetics and molecular biology provided new insights, allowing the discovery of additional pathologic proteins, the relevance of which to physiology and pathology of the nervous system has now to be settled down. The increasingly intricate complex of lesions of Alzheimer syndrome is reviewed. A more comprehensive understanding is urgently needed for initiating efficient therapeutic researches. It will require together continuing a multidisciplinary approach, and a renewal of research in neuropathology.

The significance of cortical pathology in progressive supranuclear palsy. Clinico-pathological data in 10 cases

Several observations suggest that the cortical lesions of progressive supranuclear palsy (PSP) play a role in the clinical symptoms and signs of the disease, although direct evidence for this is lacking. We addressed the significance of these lesions in a series of 10 cases of definite PSP. Tau positive cortical lesions were constant, and the mean density of neurofibrillary tangles (NFTs) was highest in the precentral and angular gyri. Their cortical distribution was singular: they were mainly located in the deepest cortical layers, affecting small as well as large neurons. They were weakly and rarely labelled with anti-ubiquitin antibodies. The tau metabolism impairment appeared more diffuse than previously thought, since neuropil threads, tau positive astrocytic tangles and oligodendroglial inclusions were also seen in the cortex and the subcortical structures. A factorial analysis of NFT density in cortex and subcortex isolated two factors, cortical and subcortical, both linked to the pedunculopontine nucleus. This suggests a prominent role of this nucleus in the spread of the lesions. A pathological subgroup exhibited mild lesions in the pedunculopontine nucleus, which were always associated with mild cortical density of NFTs. In this subgroup, the clinical data were unusual: absence of oculomotor palsy and axial rigidity in one case, of dementia in another, and presence of tremor at rest in the third case. The presence of cortical NFTs could be related to the selective involvement of cortical pathways perhaps connected with the pedunculopontine nucleus.

Inconstant apolipoprotein E (ApoE)-like immunoreactivity in amyloid beta protein deposits: relationship with APOE genotype in aging brain and Alzheimer's disease

The aim of this study was to analyze the relationship between apolipoprotein E (ApoE) and amyloid beta-protein (A beta) deposits in 29 brains from a series of elderly women, whose intellectual status had been prospectively assessed by the Blessed test score (BTS). In three cases the APOE genotype was epsilon 3/4, in one epsilon 2/2, in 25 epsilon 3/3. ApoE-like immunoreactive lesions resembling a classic senile plaque (ApoE-SP) or a diffuse deposit (ApoE-DD) were quantitatively assessed in the first temporal gyrus (Brodmann's area 22). The density of ApoE-positive deposits (ApoE-SP+ApoE-DD) was correlated with BTS (negative correlation R2 = 0.36, P = 0.0006). The correlation of the density of ApoE-DD with BTS (R2 = 0.26, P = 0.0051) was weaker than that of ApoE-SP (R2 = 0.50, P < 0.0001). The density of ApoE deposits was correlated with that of A beta-immunoreactive lesions (positive correlation R2 = 0.57, P < 0.0001). ApoE immunohistochemistry labeled fewer deposits than A beta immunohistochemistry but showed as many senile plaques (ApoE-SP) as tau immunohistochemistry and the Gallyas and Bodian techniques. Two of the three cases with the epsilon 3/4 allele had Alzheimer's disease (AD) with numerous ApoE-immunoreactive senile plaques. In contrast, the brain of the third epsilon 3/4 case, whose intellectual status was normal, contained numerous A beta deposits but lacked ApoE-like immunoreactivity. The presence of ApoE may, thus, not be a prerequisite for A beta deposition, even in cases with the epsilon 3/4 allele. The density of ApoE-SP peaked in layer III, whereas that of ApoE-DD was maximal in deeper cortical layers. This contrast in the laminar distribution indicates that only some ApoE-DD may evolve into ApoE-SP. ApoE deposition was linked to the intellectual decline and was constant in the most severely demented patients, in whom numerous ApoE-positive (and A beta-positive) neuritic plaques were surrounded by dystrophic neurites. ApoE may accumulate in neuritic senile plaques during the progression of AD.

A novel presenilin 1 mutation resulting in familial Alzheimer's disease with an onset age of 29 years

We have identified a novel Alzheimer's disease family in which affected subjects had a very young age of onset (range 29-35 years). Neuropathological confirmation of the diagnosis was obtained for one patient. Molecular analysis shows that within this family the disease results from a missense mutation at codon 235 of the presenilin 1 (PS-1) gene. Two patients had exhibited generalized tonico-clonic seizures several years before the onset of dementia. Whether this particular clinical feature is a consequence of the PS-1 mutation remains to be established. The Leu235Pro mutation is, to our knowledge, the PS-1 mutation associated with the youngest age of AD onset, which suggests that it has a drastic effect on PS-1 function.

Beta AP deposition and head trauma

Head trauma is considered to be a risk factor for Alzheimer's disease, because a high prevalence of beta AP deposits has repeatedly been reported in patients who died within a few days following head injury. To evaluate this statement, we undertook two studies using immunohistochemistry for beta AP and found a surprisingly low prevalence of beta AP diffuse deposits. We first selected 23 patients aged 17-63 years, who died 0-76 days after head trauma. Using beta AP antibody at the usual dilution (1:100), we did not find any deposits. With a high concentration of antibody (dilution 1:2) we found beta AP diffuse deposits in one 46-year-old case. In a second study, 17 patients aged 60-79 years old, who died 1-35 days after head injury, were compared to a control group. We did not find any significant difference in the density of beta AP diffuse deposits between cases and controls using usual dilutions of beta AP antibody. The density of beta AP diffuse deposits was linked only to aging and the presence of senile plaques.

Spinocerebellar ataxia 3 and Machado-Joseph disease: clinical, molecular, and neuropathological features

Patients with spinocerebellar ataxia 3 (SCA3) and Machado-Joseph disease (MJD) carry an expanded CAG repeat in the MJD1 gene. One hundred twenty families of different geographic origin with autosomal dominant cerebellar ataxia (ADCA) type I were tested. Thirty-four families (126 patients) carried an expanded CAG repeat. The expanded and the normal allele did not overlap and the repeat was unstable during transmission, with variation in the size of the CAG length ranging from -8 to +5 and a mean expansion of 0.86 repeats without differences according to the parental sex. There was a combined effect of the number of CAG repeats of the expanded and normal allele on the age at onset, which accounted for 70% of its variability. The length of the CAG repeat influenced the frequency of clinical signs associated with cerebellar ataxia, such as abnormal tendon reflexes or decreased vibration sense, whereas the interindividual variation of supranuclear ophthalmoplegia, sphincter and swallowing difficulties, and amyotrophy was mostly determined by different disease durations. We compared the clinical profile of 91 SCA3/MJD patients with 51 SCA1 and 32 SCA2 patients. There were striking differences between the SCA3/MJD and SCA2 but not with SCA1 groups of patients. Despite their clinical similarities, distinct neuropathological features were observed in 2 SCA3/MJD and 2 SCA1 patients.

The neuropathologic diagnostic criteria of frontal lobe dementia revisited. A study of ten consecutive cases

Ten successive cases from the Neuropathology Laboratory of La Salpêtrière Hospital in Paris, were selected on the presence of: dementia and prominent symptoms and signs of the frontal type; a degenerative disease without markers other than Pick cells, Pick bodies or ubiquitin-labelled non argyrophilic inclusions. We propose the following steps to diagnose the degenerative dementia associated with symptoms and signs of the frontal type: 1. If there is severe frontotemporal atrophy, severe neuronal loss and astrogliosis, many ballooned neurons and characteristic inclusions that are both tau and ubiquitin positive, the diagnosis is Pick disease. 2. If signs of motor involvement (sometimes unnoticed by the clinician) are present with mild cortical atrophy and mild spongiosis of layers II-III, the diagnosis of frontal lobe degeneration associated with motor neuron disease is warranted. Ubiquitin positive inclusions are useful, but non specific, markers. 3. When there are neither Pick inclusions nor motor neuron disease, the diagnosis may be frontal lobe atrophy lacking distinctive histology.

Mutations affecting the mitochondrial genes encoding the cytochrome oxidase subunit I and apocytochrome b of Chlamydomonas reinhardtii

Mitochondrial mutants of the green alga Chlamydomonas reinhardtii that are inactivated in the cytochrome pathway of respiration have previously been isolated. Despite the fact that the alternative oxidase pathway is still active the mutants have lost the capacity to grow heterotrophically (dark + acetate) and display reduced growth under mixotrophic conditions (light + acetate). In crosses between wild-type and mutant cells, the meiotic progeny only inherit the character transmitted by the mt- parent, which indicates that the mutations are located in the 15.8 kb linear mitochondrial genome. Two new mutants (dum-18 and dum-19) have now been isolated and characterized genetically, biochemically and at the molecular level. In addition, two previously isolated mutants (dum-11 and dum-15) were characterized in more detail. dum-11 contains two types of deleted mitochondrial DNA molecules: 15.1 kb monomers lacking the subterminal part of the genome, downstream of codon 147 of the apocytochrome b (COB) gene, and dimers resulting from head-to-head fusion of asymmetrically deleted monomers (15.1 and 9.5 kb DNA molecules, respectively). As in the wild type, the three other mutants contain only 15.8 kb mitochondrial DNA molecules. dum-15 is mutated at codon 140 of the COB gene, a serine (TCT) being changed into a tyrosine (TAC). dum-18 and dum-19 both inactivate cytochrome c oxidase, as a result of frameshift mutations (addition or deletion of 1 bp) at codons 145 and 152, respectively, of the COX1 gene encoding subunit I of cytochrome c oxidase. In a total of ten respiratory deficient mitochondrial mutants characterized thus far, only mutations located in COB or COX1 have been isolated.(ABSTRACT TRUNCATED AT 250 WORDS)

Marked phenotypic heterogeneity associated with expansion of a CAG repeat sequence at the spinocerebellar ataxia 3/Machado-Joseph disease locus

The spinocerebellar ataxia 3 locus (SCA3) for type I autosomal dominant cerebellar ataxia (ADCA type I), a clinically and genetically heterogeneous group of neurodegenerative disorders, has been mapped to chromosome 14q32.1. ADCA type I patients from families segregating SCA3 share clinical features in common with those with Machado-Joseph disease (MJD), the gene of which maps to the same region. We show here that the disease gene segregating in each of three French ADCA type I kindreds and in a French family with neuropathological findings suggesting the ataxochoreic form of dentatorubropallidoluysian atrophy carries an expanded CAG repeat sequence located at the same locus as that for MJD. Analysis of the mutation in these families shows a strong negative correlation between size of the expanded CAG repeat and age at onset of clinical disease. Instability of the expanded triplet repeat was not found to be affected by sex of the parent transmitting the mutation. Evidence was found for somatic and gonadal mosaicism for alleles carrying expanded trinucleotide repeats.

[HIV and dementia: neuropathology]

Cognitive disorders associated with HIV infection may be due to focal lesions (lymphoma, toxoplasmosis, progressive multifocal leukoencephalitis, etc.), metabolic encephalopathy (e.g. hepatic insufficiency) or psychiatric disorders (depression). In the absence of such causes a "cognitive and motor syndrome associated with HIV infection" has been defined on clinical criteria (Working group of the American Academy of Neurology, 1991). This syndrome is not consistently associated with any specific lesion. Neither the multifocal encephalitis of HIV or CMV infection nor the diffuse leukoencephalopathy associated with HIV are the only causes. The existence of a neocortical neuronal loss has been suggested by several retrospective studies, but our prospective study has not shown cortical or subcortical atrophy. Measurement of neuronal density in Brodmann's areas 4,9 and 40 has not revealed a significant loss either global, by layer, or by column. The only constant lesion was gliosis of the cortex and white matter. Neuronal loss, therefore, is not indispensable to the occurrence of cognitive disorders in AIDS. The mechanism of dementia might be: dysfunction of cortical neurons (dendritic abnormalities, virus/neurotransmitter competition); subcortical dysfunction, as suggested by the high density of microglial nodules in that region; white matter lesions which could be due to abnormalities in the blood-brain barrier. The expression of cell adhesion molecules (VCAM-1, VLA-4, ICAM-1 and LFA-1) by endothelial cerebral cells is not significantly different in AIDS patients, demented or not, and in patients with multiple sclerosis. In contrast, the expression of VCAM-1 by astrocytes is significantly increased in demented AIDS patients compared with non demented ones.(ABSTRACT TRUNCATED AT 250 WORDS)

ApoE immunoreactivity and microglial cells in Alzheimer's disease brain

The spatial relationship of apolipoprotein E (apoE)-like immunoreactivity (IR) to amyloid beta-peptide (A beta), astrocytes and microglial cells in the brain of Alzheimer's disease was studied by double immunolabelling. Diffuse apoE-like IR was seen in A beta diffuse deposits, and markedly increased in the core of classic senile plaques. Microglial cells, sometimes immunoreactive for apoE, were frequent in areas of apoE-like IR, where they often grouped into clusters in the core of apoE-labelled senile plaques. Although astrocytic processes were seen within these senile plaques, the cell bodies were always at a distance from the core. None of these astrocytes expressed apoE-like IR. Microglial cells, some of them immunoreactive for apoE, were seen in the center of apoE-labelled senile plaques. These data suggest that microglial cells play a more significant role than astrocytes in apoE deposition in senile plaques of Alzheimer disease.

[Fatal familial insomnia and prion diseases]

Fatal familial insomnia has recently enlarged the group of prion diseases. The disease starts between 35 and 60 years of age, is inherited as an autosomic dominant trait, and leads to death within 7 to 32 months. Clinical symptoms and signs include insomnia dysautonomia, cognitive and motor alteration. The discrete topography of the lesions in fatal familial insomnia underlines the role of the thalamus in the regulation of the sleep-wake cycle. Atrophy, neuronal loss and gliosis are prominent in the anterior and dorsomedial nuclei of the thalamus. Spongiosis, which is usually found in prion diseases, is absent in fatal familial insomnia. An abnormal prion protein (PrPsc) is detected in the brain. There is a mutation at codon 178 of the gene encoding this protein. Fatal insomnia is distinct from Creutzfeldt-Jakob disease on clinical, histopathologic and molecular grounds. It provides new information about genetics of prion diseases which share the characteristics of being altogether inherited and, in most cases, transmissible. The recent finding of abnormal PrP in diffuse subcortical gliosis suggests that other degenerative disorders could actually be prion diseases.

Massive infarcts involving the territory of the anterior choroidal artery and cardioembolism

BACKGROUND AND PURPOSE

At neuropathological examination, the territory of the anterior choroidal artery is frequently found to be involved in massive infarcts of the internal carotid artery territory. The aim of our study was to analyze the clinical spectrum, the course, and the mechanism of these massive infarcts compared with the rare infarcts involving only the anterior choroidal artery territory.

METHODS

Retrospective clinical examination and pathological study were performed in 35 patients with cerebral infarcts affecting at least the territory of the anterior choroidal artery.

RESULTS

In no patient had the involvement of the anterior choroidal territory infarcts been recognized clinically, nor had the triad of clinical signs (hemiplegia, hemianesthesia, and hemianopsia) classically seen in infarcts restricted to this territory been found alone. Impairment of consciousness, cognitive disorders, or oculomotor palsies had been found in addition to one or more signs of the triad. This was probably related to the involvement of other territories (94%), especially the middle cerebral artery territory (68%) and the posterior cerebral artery territory (20%). The concomitant involvement of several territories was due most frequently to an occlusion of the internal carotid artery, which was found at autopsy in 74% of the patients. These occlusions were often associated with cardioembolism (54%). In contrast, artery-to-artery embolism (17%) and small-artery disease (6%) were seldom found. Only two cases of infarcts restricted to the anterior choroidal artery territory were observed.

CONCLUSIONS

The involvement of the territory of the anterior choroidal artery in massive infarcts was due mainly to a cardioembolic occlusion of the internal carotid artery.

[Gliomatous meningitis of hemispheric tumors. Study of 22 cases in adults]

Twenty-two patients suffering from diffuse leptomeningeal gliomatosis (LG) were identified at the Salpêtrière Hospital between January 1989 and January 1994: 20 patients had a known primary supratentorial glioma when LG was diagnosed (8 glioblastomas, 5 anaplastic astrocytomas, 3 anaplasic oligodendrogliomas, 2 astrocytomas and 2 oligodendrogliomas); 2 patients had primary LG. The delay between the discovery of the primary tumour and the development of LG was 5 +/- 4 months in glioblastomas and 22 +/- 16 months for others gliomas. In 1/2 primary LG, autopsy demonstrated an hippocampic astrocytoma which was undetected pre-mortem even on MRI; in the second patient with primary LG no autopsy was obtained and the diagnosis was based on meningeal biopsy. An epidemiological study was made by comparing 13 LG with 275 supratentorial gliomas without LG who were seen during the same period. The incidence of symptomatic LG was 4.7% and was more frequent in anaplasic astrocytomas (6.5%) and anaplasic olidendrogliomas (11.4%) than in glioblastomas (3%) but the difference was not statistically significant. The age at diagnosis of LG was 56 +/- 11 years in glioblastomas and 41 +/- 7 in others gliomas, related to tumour histology. Among the 22 studied cases, only 27% had a meningeal syndrome; multifocal neurological involvement was present in 74% of patients combining at various degree signs of cerebral, cranial nerves and roots or spinal cord dysfunction. Contrast enhancing lesions in the meninges or ventricules on CT/MRI were found in 82% of cases and 45% had an hydrocephalus. In the CSF 94% of patients had a protein level over 1 milligram and 47% of them had a low glucose level < 2.7 mmol/l; malignant cells were found in 47% of cases. Among 11 patients who received radiotherapy and/or chemotherapy, 3 improved and 2 were stable and their survival ranged from 6 to 34+ months. Criteria allowing diagnosis of LG are defined and the therapeutic option are reviewed.

An international perspective on the prevalence of the Wernicke-Korsakoff syndrome

In the Western world previous studies have shown that the majority of cases of the Wernicke-Korsakoff syndrome (WKS), which is caused by thiamine deficiency, occur in alcoholics. However, in France, a country with one of the highest per capita consumptions of alcohol, the prevalence of the WKS was found to be only 0.4% in a small retrospective autopsy study. This figure is compared with data sent to the authors by a number of neuropathologists from the U.S.A., Europe, Scandinavia and Australia. There was no obvious correlation between the prevalence rates of the WKS, which were highest in Australia (2.8%-previously published), and per capita consumption of alcohol. Other issues such as diet, National programs for supplementation of foods with thiamine, and drinking habits are considered. The pathological diagnosis of the WKS can often be made on macroscopic examination of the brain after fixation in formalin. The mammillary bodies are smaller than normal in most cases of chronic WKS. However in this study it was found that the most common causes of small mammillary bodies were Alzheimer's disease and atrophy due to transneuronal degeneration secondary to lesions in the hippocampus.

Overexpression of a novel member of the mitochondrial carrier family rescues defects in both DNA and RNA metabolism in yeast mitochondria

The PIF1 and MRS2 gene products have previously been shown to be essential for mitochondrial DNA maintenance at elevated temperatures and mitochondrial group II intron splicing, respectively, in the yeast Saccharomyces cerevisiae. A multicopy suppressor capable of rescuing the respiratory deficient phenotype associated with null alleles of either gene has been isolated. This suppressor is a nuclear gene that was called RIM2/MRS12. The RIM2/MRS12 gene encodes a predicted protein of 377 amino acids that is essential for mitochondrial DNA metabolism and proper cell growth. Inactivation of this gene causes the total loss of mitochondrial DNA and, compared to wild-type rhoo controls, a slow-growth phenotype on media containing glucose. Analysis of the RIM2/MRS12 protein sequence suggests that RIM2/MRS12 encodes a novel member of the mitochondrial carrier family. In particular, a typical triplicate structure, where each repeat consists of two putative transmembrane segments separated by a hydrophilic loop, can be deduced from amino acid sequence comparisons and the hydropathy profile of RIM2/MRS12. Antibodies directed against the aminoterminus of RIM2/MRS12 detect this protein in mitochondria. The function of the RIM2/MRS12 protein and the substrates it might transport are discussed.

[Neuropathology of non conventional infectious agents or prions]

The neuropathological diagnosis of infections by non conventional agents relies on four lesions: astrocytic gliosis (cell hypertrophy and proliferation) usually contrasting with absent mononuclear cell infiltrates (lymphocytes, monocytes-macrophages, and/or microglia) revealed by conventional techniques, and neuronal loss in the most affected areas are little specific findings. Amyloid plaques that are inconstantly found, and spongiosis of gray matter, a characteristic and very frequent finding, are most specific. PrP immunohistochemistry brings additional data. The main diagnostic difficulties are emphasized, and guidelines for Pathological studies are recalled.

Monoamine vesicular uptake sites in patients with Parkinson's disease and Alzheimer's disease, as measured by tritiated dihydrotetrabenazine autoradiography

The monoaminergic innervation of the caudate nucleus, putamen and ventral striatum was investigated post mortem, in patients with Parkinson's and Alzheimer's disease as compared to control subjects, by autoradiographic detection of tritiated dihydrotetrabenazine (3H-TBZOH), a specific high affinity ligand of the vesicular monoamine transporter. The binding of 3H-TBZOH was specific and saturable (Kd 5.3 nM). In control striatum, the pattern of distribution of 3H-TBZOH binding was heterogeneous, with higher binding levels in the 'matrix' than in the 'striosome' compartment. Changes in ligand binding levels were observed in the pathological brains compared to controls. In Parkinson's disease (PD), characterized by a severe damage of mesostriatal dopaminergic neurons, the density of 3H-TBZOH binding was reduced. A severe decrease in 3H-TBZOH binding was observed in all parts of the striatum (caudate nucleus: -80%, putamen: -86%, ventral striatum: -94%) in PD brains. The data corroborate the deficiency in striatal dopaminergic transmission and suggest that in PD brains dopaminergic terminals have disappeared and/or no longer contain synaptic vesicles. In Alzheimer's disease (AD), 3H-TBZOH binding was significantly reduced by 57% in the ventral striatum and not in the caudate nucleus and putamen. The specific decrease of monoaminergic transporter levels in the ventral striatum confirm that this nucleus is a target area in AD.