Critical appraisal of pathology transmission in the α-synuclein fibril model of Lewy body disorders

Lewy body disorders are characterized by the emergence of α-synucleinopathy in many parts of the central and peripheral nervous systems, including in the telencephalon. Dense α-synuclein+ pathology appears in regio inferior of the hippocampus in both Parkinson's disease and dementia with Lewy bodies and may disturb cognitive function. The preformed α-synuclein fibril model of Parkinson's disease is growing in use, given its potential for seeding the self-propagating spread of α-synucleinopathy throughout the mammalian brain. Although it is often assumed that the spread occurs through neuroanatomical connections, this is generally not examined vis-à-vis the uptake and transport of tract-tracers infused at precisely the same stereotaxic coordinates. As the neuronal connections of the hippocampus are historically well defined, we examined the first-order spread of α-synucleinopathy three months following fibril infusions centered in the mouse regio inferior (CA2+CA3), and contrasted this to retrograde and anterograde transport of the established tract-tracers FluoroGold and biotinylated dextran amines (BDA). Massive hippocampal α-synucleinopathy was insufficient to elicit memory deficits or loss of cells and synaptic markers in this model of early disease processes. However, dense α-synuclein+ inclusions in the fascia dentata were negatively correlated with memory capacity. A modest compensatory increase in synaptophysin was evident in the stratum radiatum of cornu Ammonis in fibril-infused animals, and synaptophysin expression correlated inversely with memory function in fibril but not PBS-infused mice. No changes in synapsin I/II expression were observed. The spread of α-synucleinopathy was somewhat, but not entirely consistent with FluoroGold and BDA axonal transport, suggesting that variables other than innervation density also contribute to the materialization of α-synucleinopathy. For example, layer II entorhinal neurons of the perforant pathway exhibited somal α-synuclein+ inclusions as well as retrogradely labeled FluoroGold+ somata. However, some afferent brain regions displayed dense retrograde FluoroGold label and no α-synuclein+ inclusions (e.g. medial septum/diagonal band), supporting the selective vulnerability hypothesis. The pattern of inclusions on the contralateral side was consistent with specific spread through commissural connections (e.g. stratum pyramidale of CA3), but again, not all commissural projections exhibited α-synucleinopathy (e.g. hilar mossy cells). The topographical extent of inclusions is displayed here in high-resolution images that afford viewers a rich opportunity to dissect the potential spread of pathology through neural circuitry. Finally, the results of this expository study were leveraged to highlight the challenges and limitations of working with preformed α-synuclein fibrils.

Exploring the early steps of amyloid peptide aggregation by computers

The assembly of normally soluble proteins into amyloid fibrils is a hallmark of neurodegenerative diseases. Because protein aggregation is very complex, involving a variety of oligomeric metastable intermediates, the detailed aggregation paths and structural characterization of the intermediates remain to be determined. Yet, there is strong evidence that these oligomers, which form early in the process of fibrillogenesis, are cytotoxic. In this paper, we review our current understanding of the underlying factors that promote the aggregation of peptides into amyloid fibrils. We focus here on the structural and dynamic aspects of the aggregation as observed in state-of-the-art computer simulations of amyloid-forming peptides with an emphasis on the activation-relaxation technique.

[Correlation between changes in the nerve fiber layer and examination of the visual field using automatic perimetry in diagnosing primary open angle glaucoma]

PURPOSE

To analyse the correlation between changes in the nerve fiber layer and the appearance of defects in the visual field in primary open angle glaucoma (POAG).

MATERIAL

and methods: Digital image processing of the nerve fiber layer and examination of the visual field (30-2 Humphrey) was performed in 450 patients. The conditions for obtaining the digital images are presented.

RESULTS

Defects of the nerve fiber layer were evaluated qualitatively and quantitatively using automatic perimetry and the correlation was estimated. The results are discussed.

CONCLUSION

Examination of patients suspected of having POAG is much more precise when using both techniques performed the same day. Thus it will be possible to save time for: early diagnosis, monitoring the treatment, limiting the progression of glaucoma.

Role of long-range repulsive forces in organizing axonal neurofilament distributions: evidence from mice deficient in myelin-associated glycoprotein

When the axon of a motor neuron is sectioned and visualized by electron microscopy, a two-dimensional distribution of neurofilaments (NFs) with nonrandom spacing is revealed; this ordered arrangement implies the presence of physical interactions between the NFs. To gain insight into the molecular basis of this organization, we characterized NF distributions from mouse sciatic nerve cross sections using two statistical mechanical measures: radial distribution functions and occupancy probability distributions. Our analysis shows that NF organization may be described in terms of effective pairwise interactions. In addition, we show that these statistical mechanical measures can detect differences in NF architecture between wild-type and myelin-associated glycoprotein null mutant mice. These differences are age dependent, with marked contrast between the NF distributions by 9 months of age. Finally, using Monte Carlo simulations, we compare the experimental results with predictions for models in which adjacent NFs interact through rigid cross bridges, deformable cross bridges, and long-range repulsive forces. Among the models tested, a model in which the filaments interact through a long-range repulsive force is most consistent with the results of our analysis.

Neuroarchitecture of the auditory cortex in the rufous horseshoe bat (Rhinolophus rouxi)

This study describes the location and anatomical subdivisions of the auditory cortex of the horseshoe bat, Rhinolophus rouxi. The basic cyto- and myeloarchitectural features and cytochrome oxidase reactivity patterns are evaluated in brains where auditory fields have been previously established neurophysiologically (Radtke-Schuller and Schuller 1995). Thus, the neuroanatomical findings from these brains and additional analyzed material are related to neurophysiological characteristics. The neocortex of Rhinolophus shows a typical mammalian six-layered organization. It is poorly laminated, has a low density of granular elements, a wide layer I, and a phylogenetically old pyramidal cell type in a sharply accentuated layer II. These features are generally considered 'primitive' or conservative. Frontal, parietal, temporal and occipital regions can be distinguished. In the temporal cortex, layers III and IV are found to be markedly thicker than layer V, in contrast to the parietal region, where a prominent layer V, containing a high concentration of large pyramidal cells is the most outstanding feature. The entire temporal region, most of the parietal and parts of the occipital region are responsive to auditory stimuli. The primary auditory field corresponds to most of the temporal region. The fields of the parietal region almost completely coincide with the dorsal fields of the auditory cortex. Border zones between the temporal, parietal, and occipital regions correspond to the posterior auditory field. The non-primary fields of the auditory cortex occupy a larger area of the bat's neocortex than the primary field. The accentuated neuroarchitectural features, like cortical thickness and staining intensity, are shown to coincide with the physiological representation of biologically significant parameters.

Alpha2-macroglobulin associates with beta-amyloid peptide and prevents fibril formation

We have used the yeast two-hybrid system to isolate cDNAs encoding proteins that specifically interact with the 42-aa beta-amyloid peptide (Abeta), a major constituent of senile plaques in Alzheimer's disease. The carboxy terminus of alpha2-macroglobulin (alpha2M), a proteinase inhibitor released in response to inflammatory stimuli, was identified as a strong and specific interactor of Abeta, utilizing this system. Direct evidence for this interaction was obtained by co-immunoprecipitation of alpha2M with Abeta from the yeast cell, and by formation of SDS-resistant Abeta complexes in polyacrylamide gels by using synthetic Abeta and purified alpha2M. The association of Abeta with alpha2M and various purified amyloid binding proteins was assessed by employing a method measuring protein-protein interactions in liquid phase. The dissociation constant by this technique for the alpha2M-Abeta association using labeled purified proteins was measured (Kd = 350 nM). Electron microscopy showed that a 1:8 ratio of alpha2M to Abeta prevented fibril formation in solution; the same ratio to Abeta of another acute phase protein, alpha1-antichymotrypsin, was not active in preventing fibril formation in vitro. These results were corroborated by data obtained from an in vitro aggregation assay employing Thioflavine T. The interaction of alpha2M with Abeta suggests new pathway(s) for the clearance of the soluble amyloid peptide.

Neuronal differentiation of retinoblastoma cells induced by medium conditioned by human RPE cells

Tumor cells can be induced to differentiate in vitro by biochemical manipulation of their culture environment. In the studies described here, the effects of medium conditioned by human retinal pigmented epithelial (RPE) cells on Y79 human retinoblastoma cells have been examined. RPE-conditioned medium in conjunction with laminin and a poly-D-lysine substratum is observed to induce neuronal differentiation of Y79 cells. The cells extend long cellular processes and exhibit immunologically detectable neurotypic properties. In contrast, control Y79 cells not exposed to medium conditioned by RPE cells exhibit only infrequent neuronal phenotypes. This response of Y79 cells to RPE-conditioned medium indicates that factors secreted by RPE cells can act as inducers of neuronal differentiation in retinoblastoma cells and suggest that such factors may be of importance in the development and differentiation of the neural retina.

Polypeptide composition of paired helical filaments

Immunocytochemical studies using antibodies to cytoskeletal proteins have provided conflicting data on the components of paired helical filaments (PHF), due solely to immunological cross-reactivities. To avoid such ambiguity, we developed a protein chemical approach to the identification of the PHF components. After treatment with formic acid, PHF were digested with lysylendopeptidase and the resultant peptides were separated by HPLC. All major peaks were analysed for their amino acid compositions and sequences. From the PHF digest, proteolytic fragments of ubiquitin, tau and beta protein were sequenced. Ubiquitin in PHF appears to be in a conjugated form, while its target protein remains unidentified. Tau is integrated into PHF at the site of its carboxyl third. The presence of beta protein fragments is best interpreted as being due to contamination of amyloid filaments in the PHF preparation. Thus, ubiquitin and tau are the two definite components of PHF.

The repeat region of microtubule-associated protein tau forms part of the core of the paired helical filament of Alzheimer's disease

The paired helical filament, the principal component of the neurofibrillary tangles characteristic of Alzheimer's disease, is shown to consist of two structurally distinct parts. An external fuzzy region can be removed by pronase treatment to leave a pronase-resistant morphologically recognizable core. A monoclonal antibody has been raised which both decorates the core and labels peptide fragments extracted from the core. Amino acid sequence derived from such peptides was used to design oligonucleotide probes with which cDNA libraries were screened and clones coding for the corresponding proteins were isolated. The sequences proved to code for two isoforms of human microtubule-associated protein tau, which contained respectively three or four tandem repeats of 31 or 32 amino acids each with a characteristic Pro-Gly-Gly-Gly motif. The patterns of mRNA expression for the two isoforms were found to be stage and cell-type specific but were apparently unaltered in Alzheimer's disease. The repeat region of tau is believed to be the microtubule binding domain and it is this region of the molecule which is tightly and specifically bound in the core of the paired helical filament.

Morphology and distribution of neurons in the retinal ganglion cell layer of the adult tammar wallaby--Macropus eugenii

The morphology of the ganglion cell layer of the adult tammar wallaby has been examined from Nissl-stained retinal flatmounts. From this material, neurons have been classed as ganglion cells or displaced amacrine cells according to the disposition of Nissl substance. A further subdivision of ganglion cells into a separate group of alphalike cells was assisted by determining the range of soma sizes in neurofibrillar-stained flatmounts, a method which, in the cat, has revealed the presence of alpha cells. Isodensity contour maps prepared from the Nissl-stained flatmounts show a well-developed visual streak and an area centralis in the total neuronal population. A similar pattern was also found in the ganglion cells, thus confirming Tancred's (J. Comp. Neurol. 196:585-603, '81) finding, and, as well, in the alphalike ganglion cells and the displaced amacrine cells. The relative proportions of ganglion cells to displaced amacrines (GC:DA) were evaluated from isodensity profiles drawn along and vertical to the visual streak for the two cell types and also from maps showing the variation in the GC:DA ratio throughout the retina. A comparison with results published for other species shows that the visual streak development in the tammar wallaby is consistent with the expectations of the "terrain" theory and that, in its relative proportion of displaced amacrines, the tammar closely resembles the rabbit but contrasts sharply with the cat, which has half as many ganglion cells and three times as many displaced amacrines as the other two species.

Immunocytochemical studies of neurofilament antigens in the neurofibrillary pathology induced by aluminum

Intrathecal administration of aluminum salts induces accumulation of neurofilaments in axons and perikarya of motor neurons and is associated with impaired axonal transport of neurofilament proteins. Because phosphorylation of the 200-kilodalton (kd) neurofilament protein, thought to be a major component of the sidearms, seems to be important in interactions of neurofilaments with other cytoskeletal elements, we have postulated that aluminum may produce neurofibrillary pathology by altering patterns of neurofilament phosphorylation. To test this hypothesis, antibodies against phosphorylated and non-phosphorylated neurofilament epitopes were used for immunocytochemical analysis of spinal cord sections from aluminum-injected rabbits. In control animals, phosphorylated 200-kd neurofilament proteins were not demonstrable in perikarya of motor neurons. In experimental rabbits, perikarya and proximal axons of affected motor neurons showed striking accumulations of immunoreactivity of one phosphorylated epitope. The presence of phosphorylated 200-kd neurofilament proteins in these regions may have important consequences for the organization of the cytoskeleton and for the transport of neurofilaments. A similar, but not identical, pattern of accumulation of phosphorylated neurofilament immunoreactivity has recently been observed in neurofibrillary tangles in Alzheimer's disease.

Brain glutamate decarboxylase and cholinergic enzyme activities in scrapie

C57BL/6J mice, age 6-8 weeks were inoculated intracerebrally with brain homogenate from mice previously infected with the 139A strain of scrapie; control mice were identically treated with brain homogenate from non-infected normal mice. The activities of choline acetyltransferase (CAT), acetyl cholinesterase (AChE), and glutamic acid decarboxylase (GAD) were determined in the forebrain and hindbrain of these animals after 67, 126 and 151 days post-inoculation. There were no significant differences in the activities of CAT and GAD between scrapie and control mice at early, middle or late stages of the disease in the scrapie-infected animals; there was an about 20% decline in AChE activity in the scrapie brain.

Schwann cells fail to differentiate when co-cultured in contact with PC12 neurites

Schwann cells derived from mouse or rat dorsal root ganglia (DRG) were co-cultured with either DRG neurons or nerve growth factor (NGF)-responsive PC12 pheochromocytoma cells for up to 7 weeks. When Schwann cells were grown in the presence of DRG neurites, they displayed normal ensheathing behavior and produced basal laminae and small diameter collagen fibrils within 5-19 days in vitro. However, when Schwann cells were co-cultured in direct contact with PC12 cells and without DRG neurons, they largely failed to ensheath PC12 neurites, and failed to assemble either basal lamina or small diameter collagen fibrils at any point during 7 weeks. Schwann cell proliferation continued in the presence of PC12 neurites, indicating that PC12 cells produced a mitogenic activity for Schwann cells functionally similar to previously described neurite-associated activities. These results demonstrate that Schwann cell contact with PC12 cells does not elicit the final morphogenetic events in Schwann cells (ensheathment, basal lamina formation and collagen fibril assembly) that normally occur when Schwann cells are co-cultured in contact with DRG neurons.

Alzheimer's disease

Significant progress has been made in identifying changes in cholinergic, monoaminergic, and peptidergic neurotransmitter systems in the brains of individuals with Alzheimer's disease. Moreover, neurobiological approaches are beginning to reveal the relationships between these neurotransmitter abnormalities and histological hallmarks of the disease, i.e. neurofibrillary tangles, senile plaques, and loss of specific populations of nerve cells. However, to date, the clinical consequences of these specific neurotransmitter changes remain to be elucidated, the cause of this disorder has not been identified, and no effective therapy is yet available.

Morphology and distribution of Alzheimer neuritic (senile) and amyloid plaques in striatum and diencephalon

Mapping of striatal and diencephalic plaque distribution was conducted in 25 cases of dementia of the Alzheimer type. This analysis was carried out by fluorescence microscopy of paraffin-embedded tissue sections treated with Thioflavine S as fluorochrome. Consistent differences in plaque morphology and density between nuclei and fiber tracts were observed. Striatal and pallidal distribution was uneven, with plaque aggregation near and within certain fiber tracts: capsules, medullary laminae, and radial fasciculi. Diencephalic plaques showed also preferred aggregation near and within fiber tracts and within the intralaminar nuclei. The different subcortical plaque morphologies observed according to the nuclear or fiber tract location of the amyloid plaque, indicates that the peripheral ("halo") portion of the plaque is determined by the neurophil response to the primary event: the amyloid deposit. No correlation was observed between the distribution of plaques and any particular neurotransmitter system. In that respect, plaques were present within the nucleus basalis. Neurofibrillary tangle distribution was also seen to be dissociated from plaque distribution.

Neuropathological findings in a case of coexistent progressive supranuclear palsy and Alzheimer's disease

A 66-year-old man was investigated for increasing forgetfulness and frequent falls. Following appropriate investigations, the cause was presumed to be senile dementia of the Alzheimer type. He was reviewed one year later and found to have impaired vertical gaze and a hoarse voice. Progressive dementia, nuchal rigidity, anarthria, and sphincteric incontinence developed subsequently. A diagnosis of progressive supranuclear palsy was made. He died four years after the initial assessment. Neuropathological examination revealed changes characteristic of progressive supranuclear palsy, and suggestive of Alzheimer's disease. Globose tangles, granulovacuolar bodies and gliosis were present in the midbrain, the pons, the dentate nucleus of the cerebellum, and the globus pallidus. Senile plaques and occasional neurofibrillary tangles and granulovacuolar bodies were found in the hippocampus, amygdala, and temporal cortex. The coexistence of two disease processes resulting in dementia is discussed.

[The biochemistry of cerebral aging in man and in experimental models (author's transl)]

The biochemistry of cerebral aging in man is very little known. Two theories form the basis of current studies: the purely genetic theory and the catastrophic error theory (which explains senescence by a series of errors affecting protein synthesis). Whatever the mechanisms envisaged, they result in abnormalities in the biochemical structures of membranes and of cellular metabolism. However, senescence is not a chance phenomenon and certain regions, certain circuits, certain cells and certain metabolisms are more resistant than others. Cholinergic and catecholaminergic pathways are affected more than GABAergic and serotoninergic pathways. The substratum of the morphological lesions seen during senescence is poorly understood. Neurofilaments arranged in spirals characteristic of neurofibrillary degeneration have been isolated and partially analysed. There is no animal model which reproduces all the morphological changes seen in man. However, certain biochemical, structural and metabolic changes are sufficiently well reproduced in rodents in which changes in catecholamine would also seem to exist.

Alterations in protein synthetic capability of nerve cells in Alzheimer's disease

Cytoplasmic RNA content, nuclear and nucleolar volume are all significantly reduced in nerve cells of the temporal cortex in cases of Alzheimer's disease, examined both at diagnostic craniotomy and post mortem, when compared with non=demented control cases of similar age. On average, at necropsy, all three parameters are equally reduced by about 40-50%, but in biopsy cases, nuclear volume is decreased by the greatest amount (43%), followed by nucleolar volume is decreased by the greatest amount (43%), followed by nucleolar volume (36%), and cytoplasmic RNA (26%). These findings indicate that a change in protein synthesis occurs daily in the course of Alzheimer's disease which may result from a primary alteration within the nuclear apparatus.

Lewy bodies in the presence of Alzheimer's disease

Large numbers of Lewy bodies in the substantia nigra were found in a case of Alzheimer's disease. Parkinsonian symptoms were not recognized. The patient appears to be an example of an association recognized by Woodard but not yet understood. The case is discussed in the context of reported relationships between Parkinson's disease or "Lewy body disease" and dementia, on the one hand, and reports linking various forms of psychoses with an unusually high incidence of Lewy bodies, on the other.

[Progressive myoclonic encephalopathy in dialysis patients. Clinical, electroencephalographic and neuropathological study. Pathogenetic discussion]

Clinical and Neuropathological data on sixteen cases of progressive myoclonic encephalopathy are reported. This neurological syndrome appears after an average duration of thirty two months of haemodialysis and leads to death in four and a half months, and is characterized by myoclonus, speech disorder, epileptic seizures, and mental-status changes. At first, clinical signs and symptoms are related to haemodialysis, later they become permanent. An early diagnosis is based on EEG which is the only useful laboratory test, demonstrating bisynchronous slow-wave bursts. The caracteristic histopathologic findings are neuronal depopulation, lipofuscin accumulation, and appearance of Neurofibrillary degeneration, especially in Motor cortex, red nucleus and dentato-olivary systems. It seems to be justified to attribute P.M.D.E. to aluminium chronic poisonning; the source of the aluminium intoxication is not aluminium containing phosphate-binding gels but intravenously administreted tape-water. The intracellular binding of aluminium is shown from a histochemical study employing fluorescent stain Morin.

A sliver-gold impregnation technique for routine neuropathological use

A silver-gold impregnation technique for routine neuropathological use is presented. It is easy to perform, gives reproducible results and the ingredients are chemically well characterized. It has been successfully applied to formalin-fixed paraffin-embedded material from human brain, where nerve cell processes, neurofibrillary changes and melanin-containing neurons are distinctly visualized. Axons in peripheral nerves are impregnated and cross striations in muscle cells can also be demonstrated.

Neurofibrillary tangles in experimental neurolathyrism in rats induced by imino-dipropionitrile (IDPN). 1. Fine structural changes in the spinal cord and dorsal root ganglia

Anterior horns of the spinal cord from cervical and lumbar regions and dorsal root ganglia from these same levels were studied for ultrastructural changes in imino-dipropionitrile (IDPN) treated rats. Normal saline-injected rats, treated identically, served as controls for this study. In the spinal cord axonal balloons or dystrophic axons appeared in lightly myelinated or unmyelinated axons within 24 h after the third injection of IDPN. At this time hind leg paralysis had not yet developed. In addition to axonal changes, a few dendrites also showed neurofibrillary degeneration. Central chromatolytic changes were observed in most of the neurons, with evidence of generalized edema present within the cord. In the dorsal root ganglia axonal balloons were very prominent and showed neurofibrillary hypertrophy. Neurofibrillary material was also noted in the perikarya of medium-sized ganglion cells.

Motor neurone disease with neurofibrillary tangles in a Brazilian woman

The occurrence of neurofibrillary tangles in both the cerebral cortex and brain stem is typically seen in the Guam type of amyotrophic lateral sclerosis, but is exceedingly rare in the classical form of the disease. Only 3 cases of sporadic amyotrophic lateral sclerosis with such histopathologic features have so far been reported, all in the United States. A 49-year-old Brazilian woman had an 18-month history of amyotrophic lateral sclerosis involving predominantly the left-sided extremities with prominent bulbar signs. Autopysi disclosed moderate to severe loss of motor neurones in the hypoglossal nuclei and anterior spinal horns, absence of pyramidal tract demyelination, depigmentation of the substantia nigra and numerous neurofibrillary tangles in the hypothalamic region, parahippocampal gyrus, reticular substance of the mesencephalon and pons and in some brain stem nuclei. The topographical distribution of these changes was closely similar to that of Guamanian amyotrophic lateral sclerosis.

[Changes in the retino-tectal system of the turtle Testudo horsfieldi following enucleation]

Studies have been made on.morpho-functional changes in the optic nerve and midbrain tectum after enucleation of the tortoise T. horsfieldi. It was found that intensive degeneration of terminals which follows "dark" type (3--31/2 months after enucleation) corresponds to degeneration of myelinated fibers. Terminals degenerating accordingly to "light" type (2--3 months) presumably belong to unmyelinated fibers, which degenerate at this period in the nerve. Terminals which follow "vesicular" degeneration, survive up to 6--61/2 months, probably due to survival of some unmyelinated fibers in the nerve. During degeneration of the optic fibers, corresponding changes in amplitude-temporal parameters of the evoked potentials in the midbrain tectum were observed during electrical stimulation of the optic nerve. These changes include the increase of the interval between the stimulus and the peak of both components, as well as the decrease of the amplitude of the responses. These changes were originally observed 11/2--2 months after enucleation, becoming more evident at later stages; 6--61/2 months after enucleation, both components of the evoked potential disappeared almost simultaneously.

Frequency of Alzheimer's neurofibrillary tangles in the cerebral cortex in progressive supranuclear palsy (subcortical argyrophilic dystrophy)

The frequency of Alzheimer's neurofibrillary tangles was studied, employing large sections of the cerebral hemispheres, in the cerebral cortex in 2 cases of progressive supranuclear palsy. The majority of the neurofibrillary tangles were found in the smaller nerve cells of the third layer. The typical triangular form was rare, and most of them showed argyrophilic neurofibrillary filaments which coiled around the well-preserved nucleus. We concluded that their occurrence in the cerebral cortex is one of the morphological manifestations of the disease process.

Parkinson's disease: distribution of Lewy bodies and monoamine neuron system

A systematic study of the central and peripheral nervous systems in 3 cases of Parkinson's disease has demonstrated that Lewy bodies are present in 27 nuclei. Of these 20 nuclei (12 pigmented and 8 unpigmented) are involved in 2 or all 3 cases. It is noticed that the distribution of Lewy bodies in Parkinson's disease described here corresponds surprisingly well to that of monoamine (dopamine, noradrenaline and serotonin) cell bodies demonstrated in rats by the histochemical fluorescence method. This correlation is similar to that of Alzheimer's neurofibillary changes in postencephalitic Parkinsonism as described by Ishii. Inasmuch as these viewpoints are also in agreement with preciously reported biochemical data on Parkinsonism, it is suggested that Parkinsonism (idiopathic and postencephalitic) should represent a system degeneration of monoamine neuron systems.

[Chief factors in the polyploidization of cerebellar Purkinje cells during chicken embryogenesis. I. Characteristics of the morphologic differentiation and growth of Purkinje cells]

The Purkinje cells of the cerebellum of chick embryos differentiating from the neuroblasts of the ventricular epithelium by the 10th day of development continue the process of morpho-functional specialization, which is characterized by formation of tigroid and neurofibrilles, by intensive growth of cells, decrease of nuclear-plasmatic and increase of nucleolar-nuclear relations. At the period of hatching the specialization of the Purkinje cells comes to an end.

Effects on the ventral spinocerebellar tract neurones from Deiters' nucleus and the medial longitudinal fascicle in the cat

Effects from the vestibulospinal tract (VST) and from fibres descending in the medial longitudinal fascicle (MLF) on the cells of origin of the ventral spinocerebellar tract (VSCT) have been studied with intracellular recording. Out of 110 VSCT neurones, the VST evoked monosynaptic EPSPs in 27, di- or polysynaptic EPSPs in 56 and disynaptic IPSPs in 26. In 93 tested VSCT cells, MLF stimulation evoked monosynaptic EPSPs in 26, monosynaptic IPSPs in 2, di- or polysynaptic EPSPs in 25 and disynaptic IPSPs in 21. Convergence of monosynaptic EPSPs from VST and MLF was found in a small proportion of cells whereas the two descending pathways evoked reciprocal effects in another small group of neurones. Convergence of monosynaptic EPSPs from VST or MLF and from group I afferents was also modest. In 9 VSCT neurones there was convergence of monosynaptic excitation and disynaptic inhibition from the vestibulospinal tract and the same pattern from MLF was recorded in 9 neurones. The results are discussed in view of the hypothesis that VSCT neurones carry information on the interneuronal ttransmission in the spinal cord.

Effect of zinc ions on structure and distribution of neurotubules (author's transl)

Being interested in factors stabilizing neurotubules (NTs) in situ, we decided to immerse short segments of fresh rat peripheral nerves in buffered solutions containing ZnCl2 in final concentrations up to 10-2 m prior to fixation with buffered osmium or glutaraldehyde, both containing ZnCl2. Zinc treatment resulted in a remarkable structural preservation of NTs after fixation with osmium, though they are not preserved by osmium fixation alone. Cross sections of myelinated nerve fibres show NTs arranged predominantly in compact groups. Within the groups NTs are surrounded or embedded in an electron dense fine granular material. The occurrence of incomplete C-shaped NTs and NT-like densities can be seen. NTs exhibit relatively constant distances and sometimes geometric patterns of arrangement. A lot of intertubule cross bridges and NTs with arms could be observed. In longitudinal section the bridge and arm spacing is seen to be periodic along the tubule axis at about 500 A. Zinc treatment of nerves fixed in glutaraldehyde resulted in the same ultrastructural alterations described above. The resistance of zinc-stabilized NTs to degradation by osmium and the ultrastructural changes induced by zinc are discussed. The results suggest that in the presence of zinc ions osmium-labile NTs are transformed--by disassembly and reassembly--to osmium-stabile microtubules that are not identical with preexisting ones.