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  • 1
    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.
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  • 2
    ISSN: 1432-2307
    Keywords: Dupuytren's contracture ; Collagen ; Thermal stability and shrinkage ; X-ray diffraction ; Electronmicroscopy ; Aminoacid-analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Anhand experimenteller Daten über eine multifaktorielle Erniedrigung der Thermostabilität des Kollagens wird für die Dupuytrensche Kontraktur der folgende Pathomechanismus zur Diskussion gestellt: 1. durch Vererbung oder Erkrankung eingeleitete Schwächung der Fasern der Palmaraponeurose; 2. durch Summation mechanischer, d.h. traumatischer Einflüsse zusätzliche Beeinträchtigung physikalischer Kollageneigenschaften: 3. hierdurch ausgelöste etappenweise Verkürzung entlasteter Fascienfasern bei Körpertemperatur; 4. Stabilisierung der eingetretenen Verkürzung (Kontraktur) durch Kollagenneubildung. Dieser Deutungsversuch wird durch licht- und polarisationsoptische, elektronenmikroskopische, röntgenographische sowie chemische Untersuchungsergebnisse gestützt.
    Notes: Summary Regarding experimental data on the multi-factorial reduction of the thermostability of collagen, the following sequence of the mechanism of Dupuytren's contracture is discussed: 1. Hereditary or acquired weakness of fibres of the palmar fascia 2. Further disturbance of the physical property of collagen by the cumulative effects of mechanical, i.e. traumatic, influence. 3. By this means an induced stepwise shrinkage of released fascial fibres in body temperature. 4. Stabilisation of the shortening (contracture) by development of collagen. This hypothesis is supported by histological, polarizing-microscopic, electron-microscopic and chemical results.
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  • 3
    ISSN: 1432-2307
    Keywords: Biomechanics ; Cyclic loading ; Collagen ; Connective tissue ; Disordered fibrillar structure ; Electron-microscopy ; Elongation-growth ; Gliding mechanism ; Mechanical analogy ; Pathobiomechanics ; Synchrotron radiation ; Viscoelastic behaviour ; X-ray diffraction ; Tendons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Eine unter Zugbelastung begrenzte Parallelverschieblichkeit sich überlappender Untereinheiten (Fibrillen und Subfibrillen) wird als ein wesentliches Merkmal des Ordnungsprinzips kollagener Fasern angegeben. Das viskoelastische Verhalten von menschlichem und tierischem Sehnenkollagen wird anhand kombinierter mechanischer, röntgenographischer und morphologischer Meßdaten beschrieben und mit dem Ordnungsprinzip der Fasern korreliert. Das Vorliegen parallel verschieblicher Untereinheiten wird durch Retardations- und Relaxationsversuche in Kombination mit Kurzzeitbeugungsmessungen unter Einsatz der Synchrotronstrahlung bewiesen und mit der dämpfenden Eigenschaft der Sehnenfasern in Zusammenhang gebracht. Für die elastische Eigenschaft der Sehnenfasern wird die Rückstellkraft deformierter helikaler und nichthelikaler Molekülketten verantwortlich gemacht. Das Längenwachstum von Sehnenfasern wird mit dem Gleitvermögen von Untereinheiten korreliert. Der auf eine Verbesserung der Zueinanderausrichtung potentieller Bindungspartner beruhende Konditionierungseffekt einer zyklischen Faserbelastung ist an weniger gut formierten Einheiten besonders auffällig und entsprechend an jugendlichen Sehnenfasern größer als an alten. Die stoßartige Belastung einer Sehnenfaser aus der Ruhephase führt zu größeren molekularen Deformationen als nachfolgende gleichhohe Belastungen und kann fibrilläre Gefügestörungen hervorrufen. Es wird eine Modellkonstruktion zur Simulation mechanischer Eigenschaften von Kollagen beschrieben und für einige Beispiele durchgerechnet.
    Notes: Summary A limited glide of overlapping subunits of collagen fibres under stretching forces represents a characteristic feature of the system. The viscoelastic behaviour of human and animal tendon collagen is described simultaneously by mechanical, morphological and X-ray data and correlated with the structural principle of the fibres. The existence of gliding subunits is proven by retardation- and relaxation-experiments in combination with short-time-x-ray-measurements by synchrotron-radiation. This behaviour may explain the damping properties of tendons. The retractive force of deformed helical and nonhelical molecular chains is generally thought to be responsible for the elasticity of the system. Length-increase of tendons during growth may be also correlated with the gliding processes. The so called conditioning-effect is due to an improved arrangement of possible reacting groups by cyclic stretch which can be well demonstrated on low ordered samples and is therefore greater in the case of juvenile specimens than in older ones. A quick first stretch causes greater molecular deformations than further stretches of the same strength, and may lead to disordered domains in the structure. A mathematical model for the simulation of the mechanical properties is given and was used for the calculation of some examples.
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  • 4
    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.
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  • 5
    ISSN: 0020-708X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
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  • 6
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In Exzisaten aus dem Rupturbereich von Sehnen wurden fibrilläre Gefügestörungen in der Art von Knickdeformationen beobachtet, die einen Vergleich mit Deformationen in experimentell überdehnten und entspannten Kollagenfasern zulassen. Auf die mögliche Bedeutung für die Pathomechanik der Sehnenruptur wird hingewiesen.
    Notes: Summary Areas of disordered fibrillar structure similar to kinking deformities have been observed in specimens from ruptured tendons. It seems possible to compare this phenomenon with experimentally produced deformations. The significance for the pathomechanics of tendon rupture is discussed.
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  • 7
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Experimentelle Untersuchungen zeigen, daß überdehntes Kollagen Änderungen seiner Zugfestigkeit und seines Ordnungszustandes erfährt. Je nach Belastung und Vernetzungsgrad zeigen die nach Dehnung entspannten Fibrillen Aufspleißungen in mehr oder weniger einheitliche Bündel aus Subfibrillen oder umschriebene Abknickungen. Der Mechanismus der Knickdeformationen wird analysiert. Auf einen möglichen Zusammenhang zwischen Knickdeformation und Sehnenruptur wird hingewiesen. Die Untersuchungsergebnisse werden belegt durch die Bestimmung mechanischer Größen und der Thermostabilität der Proben sowie ihres Ordnungszustandes mit Hilfe der Röntgenbeugung und Elektronenmikroskopie.
    Notes: Summary The affect of stretch on collagen was investigated. Alterations of mechanical dimensions and thermostability of fibrils were measured and changes in fine structure determined by x-ray diffraction and electronmicroscopy. Collagen underwent changes both in tensile strength and fine structure following stretch beyond the physiological range. The severity of these changes depended both on the degree of stretch and the cross-link density of the collagen. Fibrils either became split into bundles consisting of subfibrillar units or showed circumscribed kinking deformities. The mechanism producing kinking was investigated. It is possible that a connection exists between fibrillar kinking and tendon rupture.
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  • 8
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Zusammenfassung Im Grenzfall der kurzen schwachen rein elektrischen Einzellinse nehmen die Gleichungen für die elektronenoptischen Bildfehler eine übersichtliche Form an.
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  • 9
    ISSN: 1615-6110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 110 (1963), S. 608-612 
    ISSN: 1615-6110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Zusammenfassung Decalepidanthus H.Riedl, gen. nov. und dessen einzige ArtD. sericophyllus H.Riedl, s p. n. werden beschrieben. Die neue Gattung gehört zur TribusBorraginoideae-Lithospermeae, nimmt aber durch den Besitz von zehn Hohlschuppen nahe der Korollbasis und die weit aus der Korolle ragenden Stamina eine Sonderstellung innerhalb dieser Gruppe ein. Die Struktur derBorraginoideae wird im Zusammenhang mit der Stellung vonDecalepidanthus erörtert und ein retikulates Entwicklungsschema angenommen.
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