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  • 1
    Electronic Resource
    Electronic Resource
    Ein bisher kaum bekanntes gliogenes Melanin des Gehirns („Cerebellares Gliamelanin“) (1978)
    Springer
    Virchows Archiv 380 (1978), S. 335-339 
    Details
    ISSN: 1432-2307
    Keywords: Melanin ; Glial Melanin ; Melanosis of the dentate nucleus ; Melanosis cerebelli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Melanosis of the dentate nucleus is an extremely rare condition in which pigment is formed within the cytoplasm and cytoplasmic processes of astrocytes in the dentate nucleus and the cerebellar granular cell layer. The pigment occurs as irregular polygonal structures of rather homogeneous appearance unlike granular neuromelanin located within neurons of the substantia nigra. The diameter of these pigment masses may reach 30 Μm or more. Their absorption of visible light increases steadily towards the shorter wavelengths, and the material is virtually opaque in the violet and ultraviolet region, resembling melanin in this respect. Since the absorption spectrum described by Rabl exhibited a small peak at 525 nm, he regarded the pigment as the hemoglobin derivative pentdyopent. We were unable, however, to confirm this observation. On X-ray diffraction the pigment produced a sharp reflex at 4.93 å as did synthetic melanin prepared from dopamine (but not melanin prepared from serotonin). These observations supported the assumption made by others based on histochemical evidence, that the pigment in the dentate nucleus may belong to the group of melanins. Presumably the glial melanin somehow arises from the metabolic pathway leading to DOPA. An astrocytic site of melanin formation other than in the cerebellum has not been previously described, and this melanin differs in appearance from the granular neuromelanin found in neurons in the substantia nigra. Thus “cerebellar glial melanin” contrasts with neuromelanin of the substantia nigra both in its site of formation and in its morphology. The underlying cause of the glial melanin formation in the cerebellum is not known. There are six cases in the world literature, 5 females and 1 male, ranging in age from 58 to 103 years. Involutional alterations in metabolism related to endocrine factors may possibly play an important part. To the best of our knowledge cerebellar melanosis is of no clinical relevance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431318
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  • 2
    Electronic Resource
    Electronic Resource
    Über Melanin und Melanosomen im ZNS im Vergleich zu extracerebralen Erscheinungsformen und synthetischem Melanin aus Dopamin und Serotonin (1979)
    Springer
    Acta neuropathologica 48 (1979), S. 177-188 
    Details
    ISSN: 1432-0533
    Keywords: Melanin ; Melanosomes ; Ultrastructure ; Infrared spectrophotometry ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Melanosomes and isolated melanosomal fragments (melanin particles) originating from gangliocytes (substantia nigra), astroglia (melanosis cerebelli), and melanocytes (melanotic meningeoma; metastases of melanoblastoma; melanosis thalami of the goat) were compared with synthetic melanins prepared from dopamine and serotonin, respectively. Samples were examined by electron microscopy, X-ray diffraction analysis according to Debye-Scherrer and by infrared spectrophotometry, and the results were evaluated with regard to characteristic features as they may relate to specific cell types or chemical structures. On electron microscopy all three types of melanosomes could be differentiated unequivocally as could the two synthetic melanins. Thus, there were similarities between synthetic melanin from dopamine and the gliogenic melanins of the cerebellum; the synthetic melanin from serotonin resembled melanin of melanocytes. X-ray diffraction analysis yielded 2-4 Debye diffraction rings with all human and synthetic samples, suggesting short range orders between 3.8 to 5 Å the sample obtained from a goat with thalamic melanosis showed a specific reflex pattern. While diffraction patterns of some melanins were partially identical, in particular that of melanin from dopamine and melanin of substantia nigra and dentate nucleus, respectively, they were different for the various melanocytic melanins. Further investigations are required to determine whether these differences are due to disparities in basic chemical structures or conformations or else, to particular compositional features of the various types of melanocytes as they arise from benign or malignant tumors or a specific species. Infrared spectrophotometry at higher wave numbers revealed the well known patterns of melanins, which are not, however, very suitable, for their further differentiation. At lower wave numbers (‘fingerprinting’) melanin of substantia nigra and the glial melanin in melanosis cerebelli yielded additional absorption bands of identical configuration. In contrast to melanin from dopamine, melanin from serotonin exhibited a closely similar absorption pattern in this spectral range, suggesting that the neuroectodermal melanins may contain a component possibly arising from serotonin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690518
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Maligner Granularzelltumor des Großhirnmarkes (1975)
    Springer
    Acta neuropathologica 32 (1975), S. 143-155 
    Details
    ISSN: 1432-0533
    Keywords: Cerebral Granular-Cell Tumor ; Abrikossoff's Tumor ; Nucleic Acids ; Polyploidy ; Protein Concentration ; Lipid Pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This is a report of the second known case of a primary malignant granular-cell tumor of the cerebral hemispherical white matter. Two cell types may be distinguished apparently representing different developmental stages of otherwise identical tumor cells. Quantitative histochemical and biochemical studies have shown that tumor cells were containing markedly elevated levels of DNA and RNA. Only few ribosomes and polysomes could be detected, however, by electron microscopy. While cytophotometry disclosed only slightly elevated cytoplasmic proteins, there was a distinct increase in total protein concentration of tumor tissue per unit weight, as measured by conventional techniques. It is suggested that this increase is mainly attributable to structural proteins of cellular and subcellular elements of multiplicating malignant cells. A ratio of RNA to DNA in excess of 1 was found for white matter derived from the central tumor, while the ratios of control tissue were lowered to values far below one due to postmortem changes greatly reducing tissue concentrations of RNA. No detailed characterization of RNA was attempted. The nuclear DNA content of tumor cells reached values equivalent to chromosomal hexadekaploidy. This was in sharp contrast to control data from an Abrikossoff tumor of the oral cavity and from a neurohypophyseal tumorette (“choristoma”), respectively, displaying diploidy only associated with a much lesser increase of cytoplasmic RNA and proteins. Qualitative lipid studies were consistent with a marked active demyelination of the tumor centre as indicated by a severe reduction of cerebrosides and sulfatides and the presence of cholesterol esters. In addition there was a striking loss of phosphatidylethanolamine and a lesser one of sphingomyelin of white matter of both the tumor-stricken and the contralateral unaffected hemispherical regions, possibly suggesting a generally disturbed metabolism of myelin. It is not clear whether these general changes were resulting from the presence of the unilateral tumor or from precocious cerebral involution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689568
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    Paper (German National Licenses)
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