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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 39 (1977), S. 81-88 
    ISSN: 1432-0533
    Keywords: Neuropathy in cats ; Thallium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A method of poisoning cats with thallium is described. The chief functional disturbances in the nervous system are hypotonia and ataxia. The pathological changes are confined to the central and peripheral axons of primary sensory neurones and are of the ‘dying back’ type. No motor nerve fibre degeneration was found in this species. While extensive degeneration of sensory nerves was found, those in muscle were apparently unaffected. The significance of this anomalous finding is discussed in relation to the mechanism of the ‘dying back’ process.
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  • 2
    ISSN: 1432-0533
    Keywords: Isoniazid ; Neuropathy ; Intoxication ; Dying back ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Large single doses of isoniazid by mouth (1–2 g/kg) have been shown to produce in rats Wallerian degeneration visible with the light microscope from the third day onwards. By contrast, changes in axons are seen from 24 h onwards by electron microscopy. The earliest ultrastructural changes are associated with vacuoles appearing between axon and Schwann cells. These are large and focal, and often compress the axon. The adjacent axon may show changes in smooth ER, and in microtubular arrangement. Alterations in smooth membranes and in mitochondria are visible in Schwann cell cytoplasm, not necessarily related to the vacuole formation and axonal features. It is suggested that INH neuropathy is essentially a multifocal axonal lesion.
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  • 3
    ISSN: 1432-0533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats were given 2,5-hexanediol, a metabolite of n-hexane, in the drinking water until they developed a marked degree of paresis over about 7 weeks and were then allowed to recover naturally. The time course and the manner of removal of the neurofilamentous masses accumulated within axons caused by the intoxication were followed by electron microscopy over the subsequent 8 weeks. The neurofilamentous masses slowly disappeared completely from the axons of this tract, without there being any degeneration, over 6–7 weeks. They disappeared first from the fibres in the brachium of the superior colliculus, perhaps by transport towards the terminals, and later from the axons within the superior colliculus itself. Particularly in preterminal fibres in the superior colliculus the filamentous accumulations became permeated by a network of smooth endoplasmic reticulum which may have played a part in the removal of the filaments. Accumulations of mitochondria and dense bodies in preterminal regionsm presumed to be caused by obstruction to retrograde transport, disappearedpari passu with loss of the filaments. The significance of these events in relation to neurofilament metabolism is discussed.
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  • 4
    ISSN: 1432-0533
    Keywords: Cisplatin ; Rat spinal ganglia ; Nucleolar segregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cisplatin given in doses of 0.5–2 mg to Wistar and to Sprague-Dawley rats produced nucleolar segregation of the dense fibrillar from the granular component in spinal root ganglion cells. The nucleolar segregation, found to the same extent in large and small neurons, was confirmed by specific silver staining and by electron microscopy. After repeated doses of 1 mg or 0.5 mg, up to 40% of affected nucleoli were observed by light microscopy. Focal clearing of the nucleoplasm of nuclei also occurred. Disorganisation of ribosomes was found in more severely intoxicated animals, especially in large light cells with shrinkage of the Nissl substance and apparent increase in neurofilaments, the latter occasionally distending the initial segment of the axon, but never extending further. Hypertrophy of the satellite cells with increase in the perineuronal intercellular spaces, often associated with irregular, scalloped nuclear and cell outlines, suggested that neuron shrinkage had occurred. This was confirmed by morphometry and marked alterations were found in nucleolar-to-nuclear and nucleolar-to-cell diameter ratios, nuclear and cell diameters were also somewhat reduced without change in the nucleus-to-cell ratios. Peripheral sensory nerve degeneration was not seen, and the animals died from non-neural causes. The probable role of these events in the production of sensory neuropathy is discussed.
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  • 5
    ISSN: 1432-0533
    Keywords: Rat ; Mongolian gerbil ; Trimethyltin ; Dense bodies ; Golgi appratus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The different responses of neurons with distinctive variations in morphology and function, confirm earlier observations of the lack of uniformity in the reaction of nerve cells to trimethyltin. Thus, hippocampal pyramidal and cortical neurons in both rat and Mongolian gerbil (M. unguiculatus) show abundant lysosomal dense bodies and disorganisation of the protein-synthesising apparatus. Cerebellar Purkinje cells in gerbil, but not in rat, show striking increases in smooth membrane systems, while dense bodies are insignificant in both species; large motor-type neurons in brain stem and spinal cord in both species do not accumulate dense bodies, but their rough endoplasmic reticulum (RER) may undergo intense vacuolation with or without subsequent cell death; and by contrast, spinal ganglion cells of both species may form an excess of dense bodies and, in the gerbil, vacuolation of RER. In contrast with these varied responses to trimethyltin most neurons, large and small, in both species regularly undergo striking vacuolation of the Golgi apparatus in the earliest phase of the intoxication, a constant feature that probably reflects the site of the primary cytotoxic lesion; all other changes we consider are secondary to such damage to the Golgi apparatus, however this may come about. These observations are discussed in relation to earlier reports of the variable effects of trimethyltin and with the metabolic changes reported in trimethyltin intoxication that in general accord with these morphological conclusions.
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  • 6
    ISSN: 1432-0533
    Keywords: Isoniazid ; Motor end plate ; Partial denervation ; Botulinum toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Chronic dosing of rats with isoniazid (INH) leads to an increase in the incidence of short “spontaneous” sprouts on motor end plates in the rat sternocostalis muscle. After partial denervation there is a slight increase in terminal sprouting after 1 week of dosing: this changes to a significant decrease from 2 to 6 weeks of dosing. The same is noted after local botulinum toxin injection, and in both conditions sprout length is significantly reduced. In vitro studies show that glutathione, cysteine and cystathionine all increase the incidence of short, “spontaneous” sprouts from end plates, while homocysteine and cystine have no effect. These findings are interpreted in the light of the hypothesis that in INH intoxication there may be a reduction of available axonal glutathione and cysteine due to inhibition of the pyridoxal phosphate-dependent enzymes cystathionine synthetase and cystathioninase.
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  • 7
    ISSN: 1432-0533
    Keywords: Key words 1 ; 3-Dinitrobenzene ; Modulation of ; glio-vascular lesions ; Neurotoxicity ; Bifenthrin tremor ; Energy deprivation syndromes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To test the hypothesis that altered neuronal activity may influence the extent and severity of the glio-vascular lesions produced by 1,3-dinitrobenzene (DNB), rats were either given the tremorgenic pyrethroid, Bifenthrin, or anaesthetised during various dosing schedules of DNB. When compared with controls dosed only with DNB, Bifenthrin tremor made both the ataxia and other functional effects caused by DNB more pronounced. Lesions in the brain stem were made significantly more severe and widespread across three dose levels of DNB. Centres such as facial nuclei, motor nuclei of fifth nerve, subthalamic nuclei and mamillary bodies, not damaged by DNB alone, were also affected in some animals. In contrast, general anaesthesia by either isoflurane ur urethane decreased the severity of the lesions, this being more pronounced with urethane. The character of the tissue changes, however, was not altered by these additional procedures. These findings support the suggestion that neuronal activity is one important determinant of the selective vulnerability of sensitive brain stem nuclei to glio-vascular damage from DNB intoxication.
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  • 8
    ISSN: 1432-0533
    Keywords: Organic Mercury ; Neuropathy ; Toxicology ; Neuronal ; Degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats have been poisoned with methyl-mercury-dicyandiamide at two different dose levels, 5 mg/kg body weight or 7.5 mg/kg daily for 8 consecutive days. The morphological changes in peripheral nerves and the central nervous system are largely restricted to primary sensory cells of spinal ganglia, and to a lesser extent to the granular cells of the cerebellum. There were clearly two grades of cell damage, either whole cell death or whole fibre death; there is no evidence to suggest that partial fibre death could occur, at least not at the two dose levels used. No definite indications were found for this neuropathy being a ‘dying back’ process, for the nerve fibres appeared to degenerate contemporaneously along their whole extent.
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  • 9
    ISSN: 1432-0533
    Keywords: Co-Radiation ; Spinal Cord ; Rat ; Cell Proliferation ; p-Bromophenylacetylurea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats were irradiated with doses of 1 000–3 000 rads to the cervical spinal cord and subsequently given a paralytic dose of p-Bromophenylacetylurea. The nuclear populations in the degenerating dorsal columns were determined and it was found that a significant suppression of cell proliferation occurred after all three dose levels. The cell populations in the shielded parts of the tracts rostral to the irradiated zone were not affected.
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  • 10
    ISSN: 1432-0533
    Keywords: Autoradiography ; 3H Uridine ; Methyl mercury intoxication ; Spinal ganglion neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The uptake of3H-uridine into rat spinal ganglion neurones has been followed by autoradiography for up to 48 h after its intravenous injection. Labelling of nucleoli and of nuclei reached a peak within 1 h and then declined. Nuclear labelling returned to background levels by 24 h, but nucleolar labelling was still significant after 48 h. Animals dosed with methyl mercury chloride (7.5 mg/kg daily) showed no change in labelling rate in nucleolus or nucleus after 1, 2, or 4 doses. After 8 doses there was severe reduction in labelling in both nucleolus and nucleus; this amount causes extensive loss of axons, loss of some cell bodies and a marked reduction in amino acid incorporation into proteins. On recovery after a further 8 days, labelling levels returned to normal. It is concluded that at the time when loss of ribosomes occurs from the cytoplasm methyl mercury is more likely to be directly disturbing ribosomal structure than RNA synthesis, for methyl mercury causes marked changes in ribosomal organisation after 4 doses, but disturbances to RNA synthesis do not occur until the 8th dose.
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