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  • 1995-1999  (1,049)
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  • 1995  (1,049)
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  • 1995-1999  (1,049)
  • 1980-1984
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  • 1930-1934
  • 1860-1869  (432)
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  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructural alterations and environmental exposure influence the opiate concentrations in hair of drug addicts (1995)
    Springer
    International journal of legal medicine 107 (1995), S. 301-305 
    Details
    ISSN: 1437-1596
    Keywords: Hair ; Opiates ; Drug monitoring ; Ultrastructure ; Environmental conditions ; Hair damage Cosmetic treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract Hair samples were taken at autopsy from the head of 1 male and 1 female subject both known as drug abusers. Some of the strands were bleached by in-vitro cosmetic treatment. The bleached hair as well as the original hair samples were partly exposed to water or soil prior to further investigations and drug monitoring. The exposure times were 4 weeks or 6 months for water and 6 months for soil. The hair fibers were examined by transmission electron microscope (TEM) and by scanning electron microscope (SEM) investigations. The electron microscope studies confirmed that all experimental conditions had produced morphological alterations in the hair fibers. After exposure to water or to soil for 6 months as well as after storage of the clipped bleached hair in tap water at room temperature for 4 weeks, drug monitoring of formerly positive hair samples gave negative results. After storage of natural hair in soil or in water for 4 weeks the opiate levels had dramatically decreased. The samples were screened by fluorescence polarization immunoassay after enzymatic digestion. The results were confirmed by GC/MS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246877
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  • 2
    Electronic Resource
    Electronic Resource
    A histological study on experimental autoimmune myocarditis with special reference to initiation of the disease and cardiac dendritic cells (1995)
    Springer
    Virchows Archiv 426 (1995), S. 493-500 
    Details
    ISSN: 1432-2307
    Keywords: Autoimmune myocarditis ; Cardiac myosin ; Dendritic cell ; Macrophage ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The precise mechanism of myosin-induced autoimmune myocarditis is unknown. The purpose of the present study was to define the immunohistological and ultrastructural characteristics of the infiltrating cells, especially in the initial phase of the myocarditis. It was demonstrated that OX6-positive dendritic cells first infiltrated the cardiocytes on day 13 after immunization. After day 17, OX6-positive cells, which possessed elongated irregular-shaped processes on the cell surface but contained few phago-lysosomes in the cytoplasm, were located at the margin of an inflammatory field and inserted their processes into the sarcoplasm of cardiocytes. The central portion of the inflammatory field was occupied by ED1-positive inflammatory macrophages, which were rich in phagosomes and which were in contact with degenerating cardiocytes. No evidence was obtained which suggested that lymphocytes directly injured the cardiocytes. These results demonstrated ultrastructural evidence that the type of infiltrating cell that first injures cardiocytes is the cardiac dendritic cell. Inflammatory macrophages thereafter serve as scavengers of degenerating cardiocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193173
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure and immunoreactivity of dystrophic axons indicate a different pathogenesis of Hallervorden-Spatz disease and infantile neuroaxonal dystrophy (1995)
    Springer
    Virchows Archiv 427 (1995), S. 415-421 
    Details
    ISSN: 1432-2307
    Keywords: Hallervorden-Spatz disease ; Infantile neuroaxonal dystrophy ; Axonal dystrophy ; Ultrastructure ; Cytoskeletal proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An immunohistochemical and ultrastructural analysis of dystrophic axons (DAs) in the brain and peripheral nerve of a patient with familial infantile neuroaxonal dystrophy (INAD) and in the brain of a patient with familial Hallervorden-Spatz Disease (HSD) revealed prevalent membrano-tubular or granulo-vesicular profiles with a graded pattern of evolution in INAD, while dense bodies, vesicles and amorphous material were pressent in HSD. DAs immunoreactivity with τ-protein and 200 kDa-neurofilament antibodies was stronger in HSD than in INAD. In both cases immunohistochemistry was positive for ubiquitin and negative for β-tubulin and β-amyloid. Distinct ultrastructural features and immunoreactivity pattern of cytoskeletal components suggest different pathogenetic mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199391
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  • 4
    Electronic Resource
    Electronic Resource
    Gastrointestinal autonomic nerve tumours and their separation from other gastrointestinal stromal tumours: an ultrastructural and immunohistochemical study of seven cases (1995)
    Springer
    Virchows Archiv 426 (1995), S. 27-35 
    Details
    ISSN: 1432-2307
    Keywords: Gastrointestinal autonomic nerve tumours ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Gastrointestinal stromal tumours (GIST) represent a heterogeneous group whose classification frequently requires ultrastructural and immunohistochemical studies. In a retrospective study of the ultrastructural findings of 24 gastrointestinal stromal tumours, whose light microscopic study has yielded ambiguous results and in which accurate diagnosis had required ultrastructural support, seven were found to have the characteristics of gastrointestinal autonomic nerve (GAN) tumours. In all of them the diagnosis was based on the presence of dendritic processes with dense neuroendocrine granules. Immunohistochemically, the seven tumours were negative for smooth-muscle markers. All stained positively for vimentin. NSE, chromogranin, and synaptophysin were positive in most of them, while S-100 protein was positive only in two cases. We present the ultrastructural and immunohistochemical features of seven GANT against the background of the GISTs of our series. We conclude that GAN tumours cannot be diagnosed by light microscopy alone but this tumour group displays characteristic electron microscopic and immunohistochemical features and appears to represent a distinct type of GIST.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194695
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  • 5
    Electronic Resource
    Electronic Resource
    Immunogold labelling of paired helical filaments and amyloid fibrils by specific monoclonal and polyclonal antibodies (1995)
    Springer
    Acta neuropathologica 90 (1995), S. 441-447 
    Details
    ISSN: 1432-0533
    Keywords: Key words Alzheimer's disease ; Neurofibrillary ; tangles ; Amyloid ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Senile plaque and paired helical filament (PHF) formation are characteristic of Alzheimer's disease, but the mechanisms leading to these lesions still remain unclear. To understand them better, we have performed different immunolabellings of amyloid protein and PHF. We describe a very specific immunodetection of PHF with AD2, a monoclonal antibody directed against a hyperphosphorylated epitope of PHF-tau, and use double immunolabelling to show that PHF and plaque amyloid are discretely labelled by different antibodies. We also discuss different mechanisms of PHF maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294803
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  • 6
    Electronic Resource
    Electronic Resource
    Familial amyloid polyneuropathy associated with transthyretin Gly42 mutation: a quantitative light and electron microscopic study of the peripheral nervous system (1995)
    Springer
    Acta neuropathologica 90 (1995), S. 516-525 
    Details
    ISSN: 1432-0533
    Keywords: Key words Familial amyloid polyneuropathy ; Transthyretin ; Ultrastructure ; Lectin histochemistry ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We performed extensive quantitative analyses of the peripheral nervous system (PNS) of two siblings with familial amyloid polyneuropathy (FAP) caused by a transthyretin (TTR) Gly42 mutation. Pronounced amyloid deposition was found in the sympathetic ganglia (SyG), dorsal root ganglia (DRG) and throughout the length of the peripheral nerve fibers with some accentuation in the more proximal portion. There was severe neuronal loss in the SyG and DRG together with nerve fiber depletion in the nerve trunk, while only a small amount of amyloid deposition with mild fiber loss was seen in the spinal roots. Sprouts of regenerating axons were very scanty even in the spinal nerves or roots. A teased fiber study mainly showed demyelinating fibers, but axonal degeneration was also present throughout peripheral nerves. An electron microscopic study showed fine amyloid fibrils in direct contact with the axoplasmic membrane of demyelinated axons and destruction of axons in some areas. Amyloid deposition within the PNS in this type of FAP resembled that in type I FAP (TTR Met30). However, direct axonal damage by amyloid fibrils appeared to be more prominent in our cases than in type I FAP. Lectin histochemistry using Ulex europaeus agglutinin I demonstrated preferential depletion of small neurons in the DRG and their primary afferent fibers in the spinal dorsal horn. Primary axonal degeneration and ganglionopathy due to amyloid deposition appear to be the pathogenetic mechanisms for peripheral neuropathy in this type of FAP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294814
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  • 7
    Electronic Resource
    Electronic Resource
    A monoclonal antibody that recognizes a carbohydrate epitope of human protoplasmic astrocytes (1995)
    Springer
    Acta neuropathologica 91 (1995), S. 23-30 
    Details
    ISSN: 1432-0533
    Keywords: Key words Protoplasmic astrocyte ; Secondary ; lysosome ; Immunohistochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract By hybridizing mouse myeloma cells with spleen cells from a BALB/c mouse immunized with the glial cell-rich fraction prepared from an autopsied human brain, we established a hybridoma that produces a monoclonal antibody to protoplasmic astrocytes (PA). The antibody, named PRAS-1, consistently labeled cytoplasm of PA with a granular pattern. In a few cases, the cytoplasmic processes of several astrocytes in gray and white matter were also stained. The immunoreactivity was lost after periodic acid treatment or methylation, showing that the epitope is composed of a carbohydrate. The cytoplasmic reaction was resistant to protease digestion and lost after incubation in an organic solvent, suggesting that a glycolipid is the antigen. On the other hand, the reaction in the processes disappeared upon protease digestion. Ultrastructurally, the immunoreaction was localized to secondary lysosomes. Cross-reactivity was noted on a small number of incidental neurons, corpora amylacea, hepatocytes and esophageal epithelial cells. A long period of formalin fixation did not deteriorate the antigenicity. PRAS-1 was demonstrated to detect PA immunohistochemically on paraffin sections, and may be applicable to further investigations into development or neoplasms of human astrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050388
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  • 8
    Electronic Resource
    Electronic Resource
    Familial amyloid polyneuropathy associated with transthyretin Gly42 mutation: a quantitative light and electron microscopic study of the peripheral nervous system (1995)
    Springer
    Acta neuropathologica 90 (1995), S. 516-525 
    Details
    ISSN: 1432-0533
    Keywords: Familial amyloid polyneuropathy ; Transthyretin ; Ultrastructure ; Lectin histochemistry ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We performed extensive quantitative analyses of the peripheral nervous system (PNS) of two siblings with familial amyloid polyneuropathy (FAP) caused by a transthyretin (TTR) Gly42 mutation. Pronounced amyloid deposition was found in the sympathetic ganglia (SyG), dorsal root ganglia (DRG) and throughout the length of the peripheral nerve fibers with some accentuation in the more proximal portion. There was severe neuronal loss in the SyG and DRG together with nerve fiber depletion in the nerve trunk, while only a small amount of amyloid deposition with mild fiber loss was seen in the spinal roots. Sprouts of regenerating axons were very scanty even in the spinal nerves or roots. A teased fiber study mainly showed demyelinating fibers, but axonal degeneration was also present throughout peripheral nerves. An electron microscopic study showed fine amyloid fibrils in direct contact with the axoplasmic membrane of demyelinated axons and destruction of axons in some areas. Amyloid deposition within the PNS in this type of FAP resembled that in type I FAP (TTR Met30). However, direct axonal damage by amyloid fibrils appeared to be more prominent in our cases than in type I FAP. Lectin histochemistry using Ulex europaeus agglutinin I demonstrated preferential depletion of small neurons in the DRG and their primary afferent fibers in the spinal dorsal horn. Primary axonal degeneration and ganglionopathy due to amyloid deposition appear to be the pathogenetic mechanisms for peripheral neuropathy in this type of FAP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294814
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  • 9
    Electronic Resource
    Electronic Resource
    Apoptotic process of cerebellar degeneration in experimental methylmercury intoxication of rats (1995)
    Springer
    Acta neuropathologica 91 (1995), S. 72-77 
    Details
    ISSN: 1432-0533
    Keywords: Key words Cerebellar degeneration ; Methylmercury ; intoxication ; Apoptosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This report deals with the mechanism involved in the cerebellar degeneration following experimental methylmercury poisoning of male Wistar rats. The cerebellar granule cells of animals that exhibited typical hind leg paresis were shrunken and displayed marked nuclear pyknosis. At the ultrastructural level, the nuclei of these cells were condensed and fragmented, features which are characteristic of apoptosis. In situ staining for DNA strand breaks revealed that the pyknotic nuclei were positively labeled. DNA fragmentation was confirmed by agarose gel electrophoresis; a ladder pattern of multiples of approximately 200-base pair fragments, typical of apoptosis, was observed with the cerebellar DNA of the methylmercury-treated animals. These observations suggest that the degeneration of cerebellar granule cells by alkyl mercury compounds involves an apoptotic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050394
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  • 10
    Electronic Resource
    Electronic Resource
    Immunogold labelling of paired helical filaments and amyloid fibrils by specific monoclonal and polyclonal antibodies (1995)
    Springer
    Acta neuropathologica 90 (1995), S. 441-447 
    Details
    ISSN: 1432-0533
    Keywords: Alzheimer's disease ; Neurofibrillary tangles ; Amyloid ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Senile plaque and paired helical filament (PHF) formation are characteristic of Alzheimer's disease, but the mechanisms leading to these lesions still remain unclear. To understand them better, we have performed different immunolabellings of amyloid protein and PHF. We describe a very specific immunodetection of PHF with AD2, a monoclonal antibody directed against a hyperphosphorylated epitope of PHF-tau, and use double immunolabelling to show that PHF and plaque amyloid are discretely labbeled by different antibodies. We also discuss different mechanisms of PHF maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294803
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  • 11
    Electronic Resource
    Electronic Resource
    Subcortical microtubule network separates the periplasm from the endoplasm and is responsible for maintaining the position of accessory nuclei in hymenopteran oocytes (1995)
    Springer
    Development genes and evolution 205 (1995), S. 54-61 
    Details
    ISSN: 1432-041X
    Keywords: Oogenesis ; Cytoskeleton ; Accessory nuclei ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oocytes of hymenopterans are equipped with peculiar organelles termed accessory nuclei. These organelles originate from the germinal vesicle (oocyte nucleus) and gather preferentially at the anterior pole. To gain insight into the mechanism of uneven (asymmetrical) distribution of accessory nuclei, the organization of the microtubule cytoskeleton in the oocytes of two hymenopterans Chrysis ignita and Cosmoconus meridionator has been studied. It is shown that during late previtellogenesis two networks of microtubules are present along the contact zone between the oocyte and enveloping follicular epithelium. The external one is associated with belt desmosomes connecting neighbouring follicular cells. The internal network is composed of randomly orientated microtubules and separates transparent, organelle-free periplasm from the endoplasm. All cellular organelles and the germinal vesicle are localized in the endoplasm. Accessory nuclei are accumulated in the anterior endoplasm; they always lie in direct contact with the subcortical network. Treatment with colchicine results in the disappearance of the periplasm as well as in the redistribution of cellular organelles including accessory nuclei. Presented findings suggest that subcortical microtubules play an important role in the positioning of accessory nuclei throughout the ooplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188843
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  • 12
    Electronic Resource
    Electronic Resource
    Die hämatopoietische Stammzelle des Menschen Funktion und Morphologie* (1995)
    Springer
    Der Pathologe 16 (1995), S. 1-10 
    Details
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Hämatopoietische Stammzellen ; CD 34+-Progenitorzellen ; Morphologie ; Ultrastruktur ; Antigenität ; Funktion ; Key words Haematopoietic stem cells ; CD 34+ progenitor cells ; Morphology ; Ultrastructure ; Antigen expression ; Function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Pluripotential haematopoietic stem cells and their progeny, the so-called committed precursor cells, i. e., progenitor cells which are already lineage-restricted, may be identified by the membrane-bound expression of CD 34. In accordance with this peculiar property it became possible to enrich and characterize primitive precursor cells by using different methods of cell separation techniques, which involved fluorescence staining or ferro-magnetic particles bound to CD 34 antibodies. Recently conducted studies demonstrate that CD 34-positive (CD 34+) stem cells of the peripheral blood represent a relatively uniform cell population with almost round nuclei, a finely dispersed chromatin pattern and a small portion of weakly basophilic cytoplasm. From the cytological viewpoint they resemble so-called large stimulated lymphocytes (virocytes). Ultrastructural studies are compatible with a paucity of organelles and a lymphoid character of these progenitors. In comparison, the stem cell population, derived from the bone marrow consists of more heterogeneous elements. These are generally larger and reveal an admixture of fairly immature as well as more differentiated cells, sharing bean-shaped or indented nuclei with prominent nucleoli and a more extended cytoplasm. CD 34+ progenitors from the peripheral blood and those from the bone marrow display a co-expression of CD 43 (MT1) and CD 45 (LCA). Furthermore, different subpopulations exhibit – dependent on their origin (blood/bone marrow) and to a various extent – lineage-restricted markers like CD 33, CD 38, CD 61, CD 20, CD 11a/c, glycophorin C und CD 15 (LeuM 1). The recently developed immuno- and ferromagnetic enrichment methods for CD 34+ progenitor cells are considered innovative tools for modern oncology. These techniques play an important role in the treatment of haematological malignancies and advanced tumours in the context of autologous and, although so far rarely applied, heterologous stem cell transplantation procedures.
    Notes: Zusammenfassung Hämatopoietische Stammzellen, d. h. Progenitorzellen, die bereits in Richtung einer bestimmten Zellreihe festgelegt sind, lassen sich immunzytochemisch durch Nachweis der membranständigen Expression von CD 34 darstellen. Aufgrund dieser Eigenschaft ist es möglich geworden, Vorläuferzellen durch unterschiedliche Zellseparationsverfahren anzureichern und genauer zu charakterisieren. Neuere Untersuchungen zeigen, daß CD 34-positive (CD 34+-) Stammzellen des Blutes einer relativ uniformen Zellpopulation angehören. Zytologisch deuten sie in Routinefärbungen Aspekte sog. lymphoider Reizformen bzw. Virozyten an. Ultrastrukturelle Untersuchungen bestätigen den relativ organellenarmen Charakter der Progenitorzellen. Vergleichsweise stellt sich die entsprechende Zellpopulation aus dem Knochenmark als wesentlich heterogeneres Zellgemisch dar. Sowohl die CD 34+-Stammzellen des Blutes wie des Knochenmarks weisen eine Expression von CD 43 (MT1) und CD 45 (LCA) auf. Weiterhin zeigen Subpopulationen in Abhängigkeit von ihrem Vorkommen (Peripherie/Knochenmark) und in unterschiedlicher Ausprägung linienspezifische Marker. Die kürzlich entwickelten, v. a. immunomagnetischen Anreicherungsverfahren für CD 34+-Stammzellen stellen bedeutende Perspektiven für die moderne Onkologie dar. Sie sind insbesondere für die Therapie hämatologischer Neoplasien und fortgeschrittener maligner Tumoren im Rahmen von Stammzelltransplantationen, von größter klinischer Bedeutung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002920050070
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  • 13
    Electronic Resource
    Electronic Resource
    Ultrastructural characterization of apospory in Panicum maximum (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 197-204 
    Details
    ISSN: 1432-2145
    Keywords: Apomixis ; Apospory ; Aposporous initial ; Aposporous embryo sac ; Ultrastructure ; Panicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucellar ultrastructure of apomictic Panicum maximum was analyzed during the meiocytic stage and during aposporous embryo sac formation. At pachytene the megameiocyte shows a random cell organelle distribution and sometimes only an incomplete micropylar callose wall. The chalazal nucellar cells are meristematic until the tetrad stage. They can turn into initial cells of aposporous embryo sacs. The aposporous initials can be recognized by their increased cell size, large nucleus, and the presence of many vesicles. The cell wall is thin with few plasmodesmata. If only a sexual embryo sac is formed, the nucellar cells retain their meristematic character. The aposporous initial cell is somewhat comparable to a vacuolated functional megaspore. It shows large vacuoles around the central nucleus and is surrounded by a thick cell wall without plasmodesmata. In the mature aposporous embryo sac the structure of the cells of the egg apparatus is similar to each other. In the chalazal part of the egg apparatus the cell walls are thin and do not hamper the transfer of sperm cells. Structural and functional aspects of nucellar cell differentiation and aposporous and sexual embryo sac development are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228937
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  • 14
    Electronic Resource
    Electronic Resource
    Aluminium causes nutrient imbalance and structural changes in the needles of Scots pine without inducing clear root injuries (1995)
    Springer
    Trees 9 (1995), S. 134-142 
    Details
    ISSN: 1432-2285
    Keywords: Pinus sylvestris L. ; Aluminium ; Nutrients ; Mycorrhiza ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of aluminium chloride (AICI3) treatments (50 and 150 mg/l) on 3-year-old Scots pine (Pinus sylvestris L.) seedlings were studied in a sand culture during 2 growing periods in an open field experiment. Even by the end of the first growing period, a decline was observed in the concentrations of Ca, Mg and P within the needles, and of Ca and Mg in the roots. After the second growing period, increased N and K concentrations were observed in the needles of Al-treated seedlings. Both the needles and roots of Al-treated seedlings showed, after the second growing period, a decline in growth and increased concentrations of AI as the amount of AICI3 in the nutrient solution increased. Al-induced changes in needle structure were found to be symptomatic of a nutrient imbalance, particularly of Mg and P. Al-stress did not result in any observable changes in root anatomy or in the number of mycorrhizas. Scots pine proved to be rather resistant to Al-stress, indicating that direct Al-injuries are not likely in the field, though Al-stress may be a contributing factor in the formation of nutrient imbalances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02418202
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  • 15
    Electronic Resource
    Electronic Resource
    Mitochondrial abnormalities of muscle tissue in mice with juvenile visceral steatosis associated with systemic carnitine deficiency (1995)
    Springer
    Virchows Archiv 426 (1995), S. 271-279 
    Details
    ISSN: 1432-2307
    Keywords: JVS mouse ; Systemic carnitine deficiency ; Mitochondrial abnormality ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A mouse with juvenile visceral steatosis (the JVS mouse) has been recognized as a novel animal model for systemic carnitine deficiency. We examined cardiac, skeletal and smooth muscle cells in JVS and control mice by light and electron microscopy. Cardiac and skeletal muscle cells of these mice at 4 weeks of age exhibited a ragged-red appearance after trichrome staining. Electron microscopy, demonstrated increased numbers of mitochondria and lipid droplets in the cells. Compression or distortion of the myofibril bundles, primarily due to the increased number of mitochondria, suggests the possible existence of a functional disturbance of the cardiac and skeletal muscle. In the urinary bladder, only one or two large lipid droplets and slightly increased number of mitochondria were recognized in the perinuclear region of the smooth muscle cells. At 8 weeks of age, the mouse enzyme histochemistry specific for mitochondria, such as cytochrome c oxidase and succinic dehydrogenase, and oil red O staining, confirmed further increases in the number of mitochondria and lipid droplets in the heart. However, the accumulation of these organelles in the skeletal and smooth muscle cells was no greater than that noted in JVS mice at 4 weeks of age. In the cardiac muscle cells, autolysosomes or autophagic vacuoles containing electron-dense membranous, lamellar or whorled structures closely associated with mitochondria and pseudoinclusion bodies in the nucleus were recognized, and bundles of myofibrils were buried under numerous mitochondria, suggesting the existence of disturbed contractile function in the heart of JVS mice. These results indicate that this murine strain associated with systemic carnitine deficiency exhibits a generalized mitochondrial abnormality in the muscle system especially in the heart.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191365
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  • 16
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in the lung in Niemann-Pick type C mouse (1995)
    Springer
    Virchows Archiv 427 (1995), S. 77-83 
    Details
    ISSN: 1432-2307
    Keywords: Niemann-Pick disease ; Mouse ; Lung ; Electron microscope ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The biochemical and morphological aspects of BALB/c mice with many features of the Niemann-Pick disease type C in man (NP-C mouse) have been studied extensively. However, the pulmonary pathology has not been studied extensively and we describe here some unique ultrastructural features of the lung in the NP-C mouse. Ultrastructurally, macrophages in younger mice contained osmiophilic dense granules and annulolamellar structures, but larger multilamellar concentric structures increased in the macrophages of older mice. In contrast, endothelial cells and type I pneumocytes showed membrane-bound bodies with dense granules and vesicular or vesiculogranular structures as well as amorphous materials. Type II pneumocytes were unremarkable throughout. Our study suggests that endothelial cells and type I pneumocytes are the major site of metabolic derangement resulting in pronounced morphological changes with granular and round membranous structures in the lungs of NP-C mouse. Alveolar macrophages with multilamellar concentric structures may be a result of disturbed disposal of surfactant material from type II pneumocytes rather than that from storage material of type I pneumocyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203741
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  • 17
    Electronic Resource
    Electronic Resource
    Differences in synaptic output between excitatory and inhibitory motoneurons in a crayfish muscle (1995)
    Springer
    Cell & tissue research 280 (1995), S. 513-518 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Axo-axonal synapse ; Neuromuscular synapse ; Motoneuron ; Ultrastructure ; Procambarus clarkii (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A pair of antagonistic motoneurons, one excitatory and one inhibitory, innervates the distal accessory flexor muscle in the walking limb of the crayfish Pro- cambarus clarkii. The number and size of synapses formed by these two axons on the muscle fibers (neuromuscular synapses) and on each other (axo-axonal synapses) were estimated using thin-section electron microscopy. Although profiles of nerve terminals of the two axons occur in roughly equal proportions, the frequency of occurrence of neuromuscular synapses differed markedly: 73% were excitatory and 27% were inhibitory. However, inhibitory synapses were 4–5 times larger than excitatory ones, and consequently, the total contact areas devoted to neuromuscular synapses were similar for both axons. Axo-axonal synapses were predominantly from the inhibitory axon to the excitatory axon (86%), and a few were from the excitatory axon to the inhibitory axon (14%). The role of the inhibitory axo-axonal synapse is presynaptic inhibition, but that of the excitatory axo-axonal synapse is not known. The differences in size of neuromuscular synapses between the two axons may reflect intrinsic determinants of the neuron, while the similarity in total synaptic area may reflect retrograde influences from the muscle for regulating synapse number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318355
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  • 18
    Electronic Resource
    Electronic Resource
    Evolution and ultrastructure of the bovine spermatogonia precursor cell line (1995)
    Springer
    Cell & tissue research 281 (1995), S. 249-259 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Stem cells ; Testis ; PGP 9.5 ; Ultrastructure ; Tubular whole-mounts ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The spermatogonial stem cell line in prepubertal and adult bovine testis was studied by electron microscopy and protein gene product 9.5 immunohistochemistry. Three successive spermatogonia precursor cell configurations were observed. Small basal stem cells were found to possess a spherical shape and nuclei with two to three nucleoli. They were observed in prepubertal testes (25 and 30 weeks) and in low numbers during all the stages of the seminiferous epithelial cycle in the adult. Aggregated spermatogonia precursor cells are the dominating germ cell type in the 25-week-old and 30-week-old calf. In the adult seminiferous epithelium, they cause expansion of the basal tubular compartment as they form dense groups containing up to 15 cells. These groups are observed concomitantly with cycling A-spermatogonia and preleptotenes at the beginning of spermatocytogenesis. At the end of A-spermatogonia propagation, the aggregated spermatogonia precursor cells separate and intermingle with cycling A-spermatogonia. The spermatogonia precursor cells can later be found together with I-spermatogonia as members of an interconnected cellular network of medium-sized cells. When the I-spermatogonia divide to form the smaller B-spermatogonia, the precursor cells, which stay connected with the cycling spermatogonial population, pass through a growth phase. They can now be considered as committed spermatogonia precursor cells and are continuously being transformed into A1-spermatogonia to start a new round of spermatocytogenesis. Ultrastructurally, all members of the precursor cell line are similar. However, a number of features have been found to show a quantitative increase (endoplasmic reticulum, mitochondria) or to exhibit a rising degree of complexity (nucleolus) during the progression from basal stem cells to committed spermatogonia precursor cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583394
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  • 19
    Electronic Resource
    Electronic Resource
    Evolution and ultrastructure of the bovine spermatogonia precursor cell line (1995)
    Springer
    Cell & tissue research 281 (1995), S. 249-259 
    Details
    ISSN: 1432-0878
    Keywords: Stem cells ; Testis ; PGP 9.5 ; Ultrastructure ; Tubular ; Whole-mounts ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The spermatogonial stem cell line in prepubertal and adult bovine testis was studied by electron microscopy and protein gene product 9.5 immunohistochemistry. Three successive spermatogonia precursor cell configurations were observed. Small basal stem cells were found to possess a spherical shape and nuclei with two to three nucleoli. They were observed in prepubertal testes (25 and 30 weeks) and in low numbers during all the stages of the seminiferous epithelial cycle in the adult. Aggregated spermatogonia precursor cells are the dominating germ cell type in the 25-week-old and 30-week-old calf. In the adult seminiferous epithelium, they cause expansion of the basal tubular compartment as they form dense groups containing up to 15 cells. These groups are observed concomitantly with cycling A-spermatogonia and preleptotenes at the beginning of spermatocytogenesis. At the end of A-spermatogonia propagation, the aggregated spermatogonia precursor cells separate and intermingle with cycling A-spermatogonia. The spermatogonia precursor cells can later be found together with I-spermatogonia as members of an interconnected cellular network of medium-sized cells. When the I-spermatogonia divide to form the smaller B-spermatogonia, the precursor cells, which stay connected with the cycling spermatogonial population, pass through a growth phase. They can now be considered as committed spermatogonia precursor cells and are continuously being transformed into A1-spermatogonia to start a new round of spermatocytogenesis. Ultrastructurally, all members of the precursor cell line are similar. However, a number of features have been found to show a quantitative increase (endoplasmic reticulum, mitochondria) or to exhibit a rising degree of complexity (nucleolus) during the progression from basal stem cells to committed spermatogonia precursor cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583394
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  • 20
    Electronic Resource
    Electronic Resource
    Immunocytochemical characterization of a new marker of fibrous and reactive astrocytes (1995)
    Springer
    Cell & tissue research 283 (1995), S. 39-49 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Mab 6.17 ; Reactive astrocyte ; Diencephalon ; Spinal cord ; Confocal microscopy ; Ultrastructure ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A specific monoclonal antiserum (Mab 6.17) inducing a strong immunostaining of the neuromuscular junction has been used to detect the possible occurrence of the corresponding antigen throughout the intact or lesioned central nervous system of adult rats. In intact animals, 6.17-immunolabeling was essentially detected in astrocyte-like structures located in white matter fasciculi of the brain, such as the optic tract, corpus callosum, fornix, and in the white matter of the spinal cord. The astroglial nature of such 6.17-immunolabeled profiles was verified by performing double or triple immunofluorescent labeling with Mab 6.17 and with specific antisera against astrocytic markers, such as S100 protein, glial fibrillary acidic protein and vimentin. In the white matter, all the structures reactive to Mab 6.17 were also reactive to antibodies against S100 protein, glial fibrillary acidic protein and vimentin. On the other hand, astrocytes of the grey matter that were immunoreactive to S100 and glial fibrillary acidic protein but negative to vimentin, were devoid of 6.17-immunoreactivity. After lesions including stab wound through the diencephalon or transection of the spinal cord, a marked increase of 6.17-immunostaining was noted in the regions surrounding the lesions. In these regions, 6.17-immunolabeling was associated with S100-, GFAP- and vimentin-positive astrocytes constituting the glial scar. The ultrastructural localization of 6.17-immunoreactivity indicated that, similar to glial fibrillary acidic protein and vimentin, the recognized antigen was mainly associated with gliofilaments. These observations indicate that, in the central nervous system of adult rats, Mab 6.17 recognizes a molecule associated with gliofilaments, which is essentially associated to reactive astrocytes expressing high levels of vimentin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050510
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  • 21
    Electronic Resource
    Electronic Resource
    Ultrastructural and time-lapse observations of intraepithelial lymphocytes in the small intestine of the guinea pig: their possible role in the removal of effete enterocytes (1995)
    Springer
    Cell & tissue research 280 (1995), S. 491-497 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Intestine ; small ; Intraepithelial lymphocytes ; Microcinematography ; Ultrastructure ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In previous ultrastructural studies we have shown that at the tip of intestinal villi in guinea pigs, effete enterocytes are separated into two portions: a thin apical cytoplasm to be exfoliated into the lumen and a major basal portion to be ingested by lamina propria macrophages. During this process, intraepithelially disposed, large granular lymphocytes interdigitate with enterocytes in a complex manner. In the present study, the relation between the enterocytes and the lymphocytes in the villous epithelium of the guinea pig small intestine is described by use of transmission and scanning electron microscopy in an attempt to visualize the roles and activities of the lymphocytes more clearly. The lymphocytes project numerous pointed processes into effete enterocytes, even piercing them. Enterocytes are deeply indented or perforated, probably as a result of the encroaching lymphocyte processes. Some enterocytes are separated into apical and basal portions by numerous large excavations in the cytoplasm. These findings indicate that repeated perforating penetration of the lymphocytes induces cell cleavage. Supporting this supposition, our microcinematographic observations demonstrate the alternate protrusion and withdrawal of processes of lymphocytes. The processes advance with a pointed end, and subsequently, retract with a rounded end in a cycle of 8–18 seconds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318353
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  • 22
    Electronic Resource
    Electronic Resource
    Ultrastructural studies of the myenteric plexus and smooth muscle in organotypic cultures of the guinea-pig small intestine (1995)
    Springer
    Cell & tissue research 280 (1995), S. 627-637 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Myenteric plexus ; Smooth muscle ; Organotypic culture ; Ultrastructure ; Intestine ; small ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. External muscle and myenteric plexus from the small intestine of adult guinea-pigs were maintained in vitro for 3 or 6 days. Myenteric neurons and smooth muscle cells from such organotypic cultures were examined at the electron-microscopic level. An intact basal lamina was found around the myenteric ganglia and internodal strands. Neuronal membranes, nuclei and subcellular organelles appeared to be well preserved in cultured tissues and ribosomes were abundant. Dogiel type-II neurons were distinguishable by their elongated electron-dense mitochondria, numerous lysosomes and high densities of ribosomes. Vesiculated nerve profiles contained combinations of differently shaped vesicles. Synaptic membrane specializations were found between vesiculated nerve profiles and nerve processes and cell bodies. The majority of nerve fibres were well preserved in the myenteric ganglia, in internodal strands and in bundles running between circular muscle cells. No detectable changes were found in the ultrastructure of the somata and processes of glial cells. Longitudinal and circular muscle cells from cultured tissue had clearly defined membranes with some close associations with neighbouring muscle cells. Caveolae occurred in rows that ran parallel to the long axis of the muscle cells. These results indicate that the ultrastructural features of enteric neurons and smooth muscle of the guinea-pig small intestine are well preserved in organotypic culture.
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    URL: http://dx.doi.org/10.1007/BF00318365
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  • 23
    Electronic Resource
    Electronic Resource
    Seasonal changes in hepatocyte ultrastructure correlated with the cyclic synthesis of secretory proteins in the winter flounder (Pleuronectes americanus) (1995)
    Springer
    Cell & tissue research 281 (1995), S. 153-161 
    Details
    ISSN: 1432-0878
    Keywords: Liver ; Ultrastructure ; Antifreeze ; Proteins ; Secretion ; Lipid ; Flounder, Pleuronectes americanus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Liver tissue was sampled from flounder (Pleuronectes americanus) throughout the year with the intention of documenting changes in the ultrastructure coincident with the production and secretion of antifreeze proteins. In the winter, hepatocytes are dedicated to the production of these proteins and, in the female, also reproductive proteins. In both sexes, liver cells in the summer contain abundant lipid and glycogen stores. In the female, there is a conspicuous hepatocyte transformation from a fat-filled cell in the summer to one with well-developed rough endoplasmic reticulum in the winter. Large amounts of rough endoplasmic reticulum (11.2 mg/gm) were recovered after subcellular fractionation of female wintertime liver. The increased appearance of secretory organelles and the high number of nucleolar profiles observed in winter animals is consistent with the elevated demand for protein secretion and synthesis in both sexes. The fractional volumes occupied by lipid droplets and mitochondria were different when comparisons were made between sex and season. Females contained a greater volume of lipid than did males, and summer animals contained more lipid than those in winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307969
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  • 24
    Electronic Resource
    Electronic Resource
    Glycosaminoglycans in porcine lung: an ultrastructural study using Cupromeronic Blue (1995)
    Springer
    Cell & tissue research 281 (1995), S. 473-483 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Glycosaminoglycans ; Cupromeronic Blue ; Lung ; Connective tissue ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Glycosaminoglycans (GAGs) are essential components of the extracellular matrix contributing to the mechanical properties of connective tissues as well as to cell recognition and growth regulation. The ultrastructural localization of GAGs in porcine lung was studied by means of the dye Cupromeronic Blue in the presence of 0.3 M MgCl2 according to Scott’s critical electrolyte concentration technique. GAGs were observed in locations described as follows. Pleura: Dermatan sulphate (DS) and chondroitin sulphate (CS) attached in the region of the d-band of collagen fibrils, interconnecting the fibrils; heparan sulphate (HS) at the surface of elastic fibers and in the basement membrane of the mesothelium and blood vessels. Bronchial cartilage: Abundant amounts of GAGs were observed in three zones: pericellular, in the intercellular matrix and at the perichondrial collagen. By enzyme digestion a superficial cartilage layer with predominantly CS could be distinguished from a deep zone with CS and keratan sulphate. The structure of the large aggregating cartilage proteoglycan was confirmed in situ. Airway epithelium: HS at the whole surface of cilia and microvilli and in the basement membrane of the epithelial cells. Alveolar wall: CS/DS at collagen fibrils, HS at the surface of elastic fibers and in the basement membranes of epithelium and endothelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050442
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  • 25
    Electronic Resource
    Electronic Resource
    Glycosaminoglycans in porcine lung: an ultrastructural study using Cupromeronic Blue (1995)
    Springer
    Cell & tissue research 281 (1995), S. 473-483 
    Details
    ISSN: 1432-0878
    Keywords: Glycosaminoglycans ; Cupromeronic Blue ; Lung ; Connective tissue ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Glycosaminoglycans (GAGs) are essential components of the extracellular matrix contributing to the mechanical properties of connective tissues as well as to cell recognition and growth regulation. The ultrastructural localization of GAGs in porcine lung was studied by means of the dye Cupromeronic Blue in the presence of 0.3 M MgCl2 according to Scott's critical electrolyte concentration technique. GAGs were observed in locations described as follows. Pleura: Dermatan sulphate (DS) and chondroitin sulphate (CS) attached in the region of the d-band of collagen fibrils, interconnecting the fibrils; heparan sulphate (HS) at the surface of elastic fibers and in the basement membrane of the mesothelium and blood vessels. Bronchial cartilage: Abundant amounts of GAGs were observed in three zones: pericellular, in the intercellular matrix and at the perichondrial collagen. By enzyme digestion a superficial cartilage layer with predominantly CS could be distinguished from a deep zone with CS and keratan sulphate. The structure of the large aggregating cartilage proteoglycan was confirmed in situ. Airway epithelium: HS at the whole surface of cilia and microvilli and in the basement membrane of the epithelial cells. Alveolar wall: CS/DS at collagen fibrils, HS at the surface of elastic fibers and in the basement membranes of epithelium and endothelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417864
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  • 26
    Electronic Resource
    Electronic Resource
    The larval development of lateral musculature in gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax (1995)
    Springer
    Cell & tissue research 280 (1995), S. 217-224 
    Details
    ISSN: 1432-0878
    Keywords: Ultrastructure ; Muscle growth ; Hypertrophy ; Hyperplasia ; Histochemistry ; Fish ; Sparus aurata, Dicentrarchus labrax (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Fibre-type differentiation of the lateral musculature has been studied in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval development. Histochemical and ultrastructural techniques show two presumptive muscle layers and two germinative zones of presumptive myoblasts. At hatching, myotomal muscle consists of a monolayer of thin undifferentiated cells near the skin (first germinative zone) overlying another mono-layer of small diameter fibres extending hypaxially and epaxially away from the transverse septum. Below this, there is a much thicker, deep layer of fibres, generally large in diameter and polygonal in shape. The presumptive myoblasts are located between these two layers of fibres in the second germinative zone. Initially, the superficial and deep muscle fibres show high and low myosin ATPase activity, respectively. Both layers grow by generating new fibres from the two mentioned germinative zones. At the end of larval life, the superficial layer changes its histochemical profile from high to low myosin ATPase activity and, at the same time, intermediate or pink muscle fibres can be observed by oxidative activity (the NADH-TR reaction). Morphometric analysis shows a significant increase in mean fibre diameter during successive ages, as shown by the Student's t-test (hypertrophic growth). Skewness and kurtosis values of fibre diameters point to the generation of a new fibre population from the germinative zones (hyperplastic growth).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307792
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  • 27
    Electronic Resource
    Electronic Resource
    Ultrastructural and time-lapse observations of intraepithelial lymphocytes in the small intestine of the guinea pig: their possible role in the removal of effete enterocytes (1995)
    Springer
    Cell & tissue research 280 (1995), S. 491-497 
    Details
    ISSN: 1432-0878
    Keywords: Intestine, small ; Intraepithelial lymphocytes ; Microcinematography ; Ultrastructure ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In previous ultrastructural studies we have shown that at the tip of intestinal villi in guinea pigs, effete enterocytes are separated into two portions: a thin apical cytoplasm to be exfoliated into the lumen and a major basal portion to be ingested by lamina propria macrophages. During this process, intraepithelially disposed, large granular lymphocytes interdigitate with enterocytes in a complex manner. In the present study, the relation between the enterocytes and the lymphocytes in the villous epithelium of the guinea pig small intestine is described by use of transmission and scanning electron microscopy in an attempt to visualize the roles and activities of the lymphocytes more clearly. The lymphocytes project numerous pointed processes into effete enterocytes, even piercing them. Enterocytes are deeply indented or perforated, probably as a result of the encroaching lymphocyte processes. Some enterocytes are separated into apical and basal portions by numerous large excavations in the cytoplasm. These findings indicate that repeated perforating penetration of the lymphocytes induces cell cleavage. Supporting this supposition, our microcinematographic observations demonstrate the alternate protrusion and withdrawal of processes of lymphocytes. The processes advance with a pointed end, and subsequently, retract with a rounded end in a cycle of 8–18 seconds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318353
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  • 28
    Electronic Resource
    Electronic Resource
    Ultrastructural studies of the myenteric plexus and smooth muscle in organotypic cultures of the guinea-pig small intestine (1995)
    Springer
    Cell & tissue research 280 (1995), S. 627-637 
    Details
    ISSN: 1432-0878
    Keywords: Myenteric plexus ; Smooth muscle ; Organotypic culture ; Ultrastructure ; Intestine, small ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract External muscle and myenteric plexus from the small intestine of adult guinea-pigs were maintained in vitro for 3 or 6 days. Myenteric neurons and smooth muscle cells from such organotypic cultures were examined at the electron-microscopic level. An intact basal lamina was found around the myenteric ganglia and internodal strands. Neuronal membranes, nuclei and subcellular organelles appeared to be well preserved in cultured tissues and ribosomes were abundant. Dogiel type-II neurons were distinguishable by their elongated electron-dense mitochondria, numerous lysosomes and high densities of ribosomes. Vesiculated nerve profiles contained combinations of differently shaped vesicles. Synaptic membrane specializations were found between vesiculated nerve profiles and nerve processes and cell bodies. The majority of nerve fibres were well preserved in the myenteric ganglia, in internodal strands and in bundles running between circular muscle cells. No detectable changes were found in the ultrastructure of the somata and processes of glial cells. Longitudinal and circular muscle cells from cultured tissue had clearly defined membranes with some close associations with neighbouring muscle cells. Caveolae occurred in rows that ran parallel to the long axis of the muscle cells. These results indicate that the ultrastructural features of enteric neurons and smooth muscle of the guinea-pig small intestine are well preserved in organotypic culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318365
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  • 29
    Electronic Resource
    Electronic Resource
    Seasonal changes in hepatocyte ultrastructure correlated with the cyclic synthesis of secretory proteins in the winter flounder (Pleuronectes americanus) (1995)
    Springer
    Cell & tissue research 281 (1995), S. 153-161 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Liver ; Ultrastructure ; Antifreeze ; Proteins ; Secretion ; Lipid ; Flounder ; Pleuronectes americanus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Liver tissue was sampled from flounder (Pleuronectes americanus) throughout the year with the in-tention of documenting changes in the ultrastructure coincident with the production and secretion of antifreeze proteins. In the winter, hepatocytes are dedicated to the production of these proteins and, in the female, also reproductive proteins. In both sexes, liver cells in the summer contain abundant lipid and glycogen stores. In the female, there is a conspicuous hepatocyte transformation from a fat-filled cell in the summer to one with well- developed rough endoplasmic reticulum in the winter. Large amounts of rough endoplasmic reticulum (11.2 mg/gm) were recovered after subcellular fractionation of female wintertime liver. The increased appearance of secretory organelles and the high number of nucleolar profiles observed in winter animals is consistent with the elevated demand for protein secretion and synthesis in both sexes. The fractional volumes occupied by lipid droplets and mitochondria were different when comparisons were made between sex and season. Females contained a greater volume of lipid than did males, and summer animals contained more lipid than those in winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307969
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  • 30
    Electronic Resource
    Electronic Resource
    Ultrastructural characterization of the sexually dimorphic medial preoptic nucleus of male Japanese quail (1995)
    Springer
    Cell & tissue research 279 (1995), S. 517-527 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Avian brain ; Preoptic nucleus ; Sexual behaviour ; Ultrastructure ; Sexual dimorphism ; Coturnix japonica (Aves ; Phasianiformes)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The medial preoptic nucleus is a sexually dimorphic structure whose cytoarchitecture, afferent and efferent connections, and functions have been previously described. No detailed ultrastructural study has, however, been perfomed to date. Here we describe the ultrastructural organization of this important preoptic structure of the male quail. Neuronal cell bodies of the medial preoptic nucleus generally show extensive development of protein-synthesis-related organelles (rough endoplasmic reticulum, polysomes), and of secretory structures (Golgi complexes, secretory vesicles, dense bodies). Previous morphometrical studies at the light-microscopical level have demonstrated the presence of a medial and a lateral neuronal population distinguished by the size of their cell bodies (the medial neurons are smaller than the lateral neurons). The present ultrastructural investigation confirms the difference in size, but no difference has been observed in the ultrastructural organization of the neurons. In both the medial and the lateral part, the nucleus is characterized by a large variety of cell bodies, including some that, on the basis of their ultrastructure, can be considered as putative peptidergic neurons. Close contacts are frequently observed between adjacent cell bodies that are normally arranged in clusters. Various types of synaptic endings are also present, suggesting a rich supply of nerve fibers. A few glial cells are scattered within the nucleus. In view of the crucial role of this region in regulating quail sexual behavior, the large heterogeneity of neurons and of afferent nervous fibers suggest that this region might have an important role in the integration of information arriving from different brain regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050311
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  • 31
    Electronic Resource
    Electronic Resource
    Fine structural study of interstitial cells associated with the deep muscular plexus of the rat small intestine, with special reference to the intestinal pacemaker cells (1995)
    Springer
    Cell & tissue research 282 (1995), S. 129-134 
    Details
    ISSN: 1432-0878
    Keywords: Small intestine ; Pacemaker ; Interstitial cell ; Ultrastructure ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two types of interstitial cells have been demonstrated in close association in the deep muscular plexus of rat small intestine, by electron microscopy. Cells of the first type are characterized by a fibroblastic ultrastructure, i.e. a well-developed granular endoplasmic reticulum, Golgi apparatus and absence of the basal lamina. They form a few small gap junctions with the circular muscle cells and show close contact with axon terminals containing many synaptic vesicles. They may play a role in conducting electrical signals in the muscle tissue. Cells of the second type are characterized by many large gap junctions that interconnect with each other and with the circular muscle cells. Their cytoplasm is rich in cell organells, including mitochondria, granular endoplasmic reticulum and Golgi apparatus. They show some resemblance to the smooth muscle cells and have an incomplete basal lamina, caveolae and subsurface cisterns. However, they do not contain an organized contractile apparatus, although many intermediate filaments are present in their processes. They also show close contacts with axon terminals containing synaptic vesicles. These gap-junction-rich cells may be regular components of the intestinal tract and may be involved in the pacemaking activity of intestinal movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319139
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  • 32
    Electronic Resource
    Electronic Resource
    Ultrastructural study of the presence of vasoactive intestinal polypeptide and serotonin in mucosal nerve fibres and endocrine cells of the intestine of goldfish (Carassius auratus) and tilapia (Oreochromis mossambicus) (1995)
    Springer
    Cell & tissue research 283 (1995), S. 143-150 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Vasoactive intestinal polypeptide (VIP) ; Serotonin ; Ultrastructure ; Immunogold label ; Mucosal nerves ; Goldfish ; Carassius auratus ; Tilapia ; Oreochromis mossambicus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In order to establish a possible role of vasoactive intestinal polypeptide (VIP) and serotonin as (neuro)transmitters involved in the regulation of fish intestinal epithelium, we studied the presence of VIP and serotonin at the ultrastructural level in the intestinal mucosa of tilapia and goldfish. A low percentage of varicosities near the basal membrane of the tilapia intestinal epithelium was found to label for VIP or for serotonin, whereas in the goldfish, this percentage was much higher. The varicosities usually contained large granular and small clear vesicles. Immunogold labeling indicated that serotonin and VIP were localized in the large granular vesicles. Unlabeled large granular vesicles and small clear vesicles were usually also present in varicosities with serotonin- or VIP-labeled vesicles. In the goldfish, the serotonin-labeled varicosities were close to the epithelial cells, and direct contacts between serotonin-labeled nerve fibres and epithelial cells could sometimes be visualized. However, synaptic membrane specializations were never observed. In tilapia, the distance between the VIP- or serotonin-labeled varicosities and the epithelial cells was large (more than 2 μm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050522
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  • 33
    Electronic Resource
    Electronic Resource
    Fine structural study of interstitial cells associated with the deep muscular plexus of the rat small intestine, with special reference to the intestinal pacemaker cells (1995)
    Springer
    Cell & tissue research 282 (1995), S. 129-134 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Small intestine ; Pacemaker ; Interstitial cell ; Ultrastructure ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Two types of interstitial cells have been demonstrated in close association in the deep muscular plexus of rat small intestine, by electron microscopy. Cells of the first type are characterized by a fibroblastic ultrastructure, i.e. a well-developed granular endoplasmic reticulum, Golgi apparatus and absence of the basal lamina. They form a few small gap junctions with the circular muscle cells and show close contact with axon terminals containing many synaptic vesicles. They may play a role in conducting electrical signals in the muscle tissue. Cells of the second type are characterized by many large gap junctions that interconnect with each other and with the circular muscle cells. Their cytoplasm is rich in cell organells, including mitochondria, granular endoplasmic reticulum and Golgi apparatus. They show some resemblance to the smooth muscle cells and have an incomplete basal lamina, caveolae and subsurface cisterns. However, they do not contain an organized contractile apparatus, although many intermediate filaments are present in their processes. They also show close contacts with axon terminals containing synaptic vesicles. These gap-junction-rich cells may be regular components of the intestinal tract and may be involved in the pacemaking activity of intestinal movement.
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    URL: http://dx.doi.org/10.1007/BF00319139
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    Electronic Resource
    Differences in synaptic output between excitatory and inhibitory motoneurons in a crayfish muscle (1995)
    Springer
    Cell & tissue research 280 (1995), S. 513-518 
    Details
    ISSN: 1432-0878
    Keywords: Axo-axonal synapse ; Neuromuscular synapse ; Motoneuron ; Ultrastructure ; Procambarus clarkii (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A pair of antagonistic motoneurons, one excitatory and one inhibitory, innervates the distal accessory flexor muscle in the walking limb of the crayfish Procambarus clarkii. The number and size of synapses formed by these two axons on the muscle fibers (neuromuscular synapses) and on each other (axo-axonal synapses) were estimated using thin-section electron microscopy. Although profiles of nerve terminals of the two axons occur in roughly equal proportions, the frequency of occurrence of neuromuscular synapses differed markedly: 73% were excitatory and 27% were inhibitory. However, inhibitory synapses were 4–5 times larger than excitatory ones, and consequently, the total contact areas devoted to neuromuscular synapses were similar for both axons. Axo-axonal synapses were predominantly from the inhibitory axon to the excitatory axon (86%), and a few were from the excitatory axon to the inhibitory axon (14%). The role of the inhibitory axo-axonal synapse is presynaptic inhibition, but that of the excitatory axo-axonal synapse is not known. The differences in size of neuromuscular synapses between the two axons may reflect intrinsic determinants of the neuron, while the similarity in total synaptic area may reflect retrograde influences from the muscle for regulating synapse number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318355
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  • 35
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    Electronic Resource
    Ultrastructural localisation of NADPH-diaphorase in the chick thymic medulla (1995)
    Springer
    Cell & tissue research 279 (1995), S. 405-409 
    Details
    ISSN: 1432-0878
    Keywords: NADPH-diaphorase ; Nitric oxide ; Thymic medulla ; Ultrastructure ; Chick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Nicotinamide-adenine-dinucleotide phosphate-diaphorase positive cells in the chick thymus were studied at the electron-microscopic level. The formazan, a marker for the enzyme nitric oxide synthase, labelled cystic, undifferentiated, endocrine-like and myoid cells in the medulla. Some lymphoid and reticulo-epithelial cells were also lightly labelled. The reaction product was predominantly bound to the membranes of the endoplasmic reticulum in all the cells labelled and also to the nuclear envelope and outer membrane of mitochondria. The Golgi apparatus and the plasma membrane were free of the reaction product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318498
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  • 36
    Electronic Resource
    Electronic Resource
    Ultrastructural localisation of NADPH-diaphorase in the chick thymic medulla (1995)
    Springer
    Cell & tissue research 279 (1995), S. 405-409 
    Details
    ISSN: 1432-0878
    Keywords: Key words: NADPH-diaphorase ; Nitric oxide ; Thymic medulla ; Ultrastructure ; Chick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Nicotinamide-adenine-dinucleotide phosphate-diaphorase positive cells in the chick thymus were studied at the electron-microscopic level. The formazan, a marker for the enzyme nitric oxide synthase, labelled cystic, undifferentiated, endocrine-like and myoid cells in the medulla. Some lymphoid and reticulo-epithelial cells were also lightly labelled. The reaction product was predominantly bound to the membranes of the endoplasmic reticulum in all the cells labelled and also to the nuclear envelope and outer membrane of mitochondria. The Golgi apparatus and the plasma membrane were free of the reaction product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050297
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  • 37
    Electronic Resource
    Electronic Resource
    Ultrastructural characterization of the sexually dimorphic medial preoptic nucleus of male Japanese quail (1995)
    Springer
    Cell & tissue research 279 (1995), S. 517-527 
    Details
    ISSN: 1432-0878
    Keywords: Avian brain ; Preoptic nucleus ; Sexual behaviour ; Ultrastructure ; Sexual dimorphism ; coturnix japonica (Aves, Phasianiformes)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The medial preoptic nucleus is a sexually dimorphic structure whose cytoarchitecture, afferent and efferent connections, and functions have been previously described. No detailed ultrastructural study has, however, been perfomed to date. Here we describe the ultrastructural organization of this important preoptic structure of the male quail. Neuronal cell bodies of the medial preoptic nucleus generally show extensive development of protein-synthesis-related organelles (rough endoplasmic reticulum, polysomes), and of secretory structures (Golgi complexes, secretory vesicles, dense bodies). Previous morphometrical studies at the light-microscopical level have demonstrated the presence of a medial and a lateral neuronal population distinguished by the size of their cell bodies (the medial neurons are smaller than the lateral neurons). The present ultrastructural investigation confirms the difference in size, but no difference has been observed in the ultrastructural organization of the neurons. In both the medial and the lateral part, the nucleus is characterized by a large variety of cell bodies, including some that, on the basis of their ultrastructure, can be considered as putative peptidergic neurons. Close contacts are frequently observed between adjacent cell bodies that are normally arranged in clusters. Various types of synaptic endings are also present, suggesting a rich supply of nerve fibers. A few glial cells are scattered within the nucleus. In view of the crucial role of this region in regulating quail sexual behavior, the large heterogeneity of neurons and of afferent nervous fibers suggest that this region might have an important role in the integration of information arriving from different brain regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318164
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  • 38
    Electronic Resource
    Electronic Resource
    Immunogold labelling of estradiol receptor in MCF7 cells (1995)
    Springer
    Cell & tissue research 279 (1995), S. 445-452 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Estradiol receptor ; Breast cancer cells ; Cell culture ; Ultrastructure ; Electron microscopy ; Immunohistochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The distribution of estradiol receptor in serial sections of estradiol-deprived and estradiol-stimulated MCF7 cells was studied by using mouse monoclonal antibodies reacting with different domains of the receptor and goat-antimouse IgG/6 nm gold. In the nucleus and the cytoplasm of estradiol-deprived cells, the receptor was detected by all three monoclonals (13H2, HT 65 and MA1-310). The antibodies 13H2 and MA1-310 detected receptor associated to the microfilament bundles in the cytoplasm. Higher densities of antireceptor attachment to the nuclear areas were accompanied by a reduction in the attachment to the cytoplasm after estradiol stimulation of the cells. The results confirm earlier observations on the presence of cytoplasmic estrogen receptor in estradiol-deprived cells and support the premise of an es- tradiol-induced translocation of this ligand-dependent transcription regulator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050303
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  • 39
    Electronic Resource
    Electronic Resource
    Immunogold labelling of estradiol receptor in MCF7 cells (1995)
    Springer
    Cell & tissue research 279 (1995), S. 445-452 
    Details
    ISSN: 1432-0878
    Keywords: Estradiol receptor ; Breast cancer cells ; Cell culture ; Ultrastructure ; Electron microscopy ; Immunohistochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution of estradiol receptor in serial sections of estradiol-deprived and estradiol-stimulated MCF7 cells was studied by using mouse monoclonal antibodies reacting with different domains of the receptor and goat-antimouse IgG/6 nm gold. In the nucleus and the cytoplasm of estradiol-deprived cells, the receptor was detected by all three monoclonals (13H2, HT 65 and MA1-310). The antibodies 13H2 and MA1-310 detected receptor associated to the microfilament bundles in the cytoplasm. Higher densities of antireceptor attachment to the nuclear areas were accompanied by a reduction in the attachment to the cytoplasm after estradiol stimulation of the cells. The results confirm earlier observations on the presence of cytoplasmic estrogen receptor in estradiol-deprived cells and support the premise of an estradiol-induced translocation of this ligand-dependent transcription regulator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318156
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  • 40
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    Electronic Resource
    Cells of the photoreceptor line in the pineal organ of an adult marsupial, Didelphis albiventris (1995)
    Springer
    Cell & tissue research 282 (1995), S. 363-366 
    Details
    ISSN: 1432-0878
    Keywords: Pineal organ ; Pinealocytes ; Secretory rudimentary photoreceptors ; Ultrastructure ; Didelphis albiventris (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We report the presence of atypical pinealocytes as components of epiphyseal follicles in the adult South American opossum Didelphis albiventris. Their main characteristic is a bulbous-shaped apical cytoplasmic extension which protrudes towards the follicular lumen among the microvilli and cilia of neighbouring ependymal cells. They resemble the photoreceptor-like pinealocytes of sauropsids and developing photoreceptors in the retina of newborn mammals. Morphological characteristics enable us to classify them as cells of the receptor line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319126
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  • 41
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    Electronic Resource
    Cells of the photoreceptor line in the pineal organ of an adult marsupial, Didelphis albiventris (1995)
    Springer
    Cell & tissue research 282 (1995), S. 363-366 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Pineal organ ; Pinealocytes ; Secretory rudimentary photoreceptors ; Ultrastructure ; Didelphis albiventris (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We report the presence of atypical pinealo-cytes as components of epiphyseal follicles in the adult South American opossum Didelphis albiventris. Their main characteristic is a bulbous-shaped apical cytoplasmic extension which protrudes towards the follicular lumen among the microvilli and cilia of neighbouring ependymal cells. They resemble the photoreceptor-like pinealocytes of sauropsids and developing photoreceptors in the retina of newborn mammals. Morphological characteristics enable us to classify them as cells of the receptor line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050487
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  • 42
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    Electronic Resource
    Comparative anatomy and ultrastructure of active and dormant vascular cambium in rhizome ofBotrychium ternatum (1995)
    Springer
    Journal of plant research 108 (1995), S. 149-159 
    Details
    ISSN: 1618-0860
    Keywords: Anatomy ; Botrychium ternatum ; Rhizome ; Ultrastructure ; Vascular cambium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vascular cambium ofBotrychium ternatum rhizome varied according to age, position and season was studied by light and electron microscopy. Cambium at the 6th internode (6-year-old cambium) had the greatest number of active cambial cells in August and September, thus it was in the most active stage. The active cells were characterized by the presence of a large vacuole, few storage materials such as starch grains within plastids or lipid droplets, a thin tangential wall; and various cell organelles in the thin peripheral layer of cytoplasm. When the 6-year-old cambium reached its dormant season after November, the dormant cells were filled with numerous storage materials and had few cell organelles. Our observations suggested that the initiation and cessation of cambial activity may be correlated with the annual life cycle of this plant: the vegetative and reproductive leaves began to emerge in June and July, respectively, and the sporophyll withered in November after the spore dispersal. Most cambial cells at the 10th internode, which remained in a dormant state throughout the year, were filled with numerous storage materials. Our results indicated that the activity of vascular cambium in the 10th internode was determinate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02344339
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  • 43
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    Electronic Resource
    Cellular changes during the acquisition of embryogenic potential in isolated pollen grains ofNicotiana tabacum (1995)
    Springer
    Protoplasma 186 (1995), S. 220-230 
    Details
    ISSN: 1615-6102
    Keywords: Embryogenesis ; In vitro culture ; Isolated pollen ; Nicotiana tabacum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We used electron microscopical techniques to study ultrastructural changes during the acquisition of embryogenic competence in immature pollen grains ofNicotiana tabacum, isolated at the early- or mid-bicellular stage and cultured in vitro under starvation conditions. Cytoplasmic and nuclear changes during the starvation treatment are reported. Dedifferentiation of plastids, dilation of the wall of the generative cell, the appearance of a large vacuole, loss of nuclear pores in the vegetative nucleus, changes in chromatin and nucleolar structure, and a decrease in the size of the nucleolus were observed. We suggest that these events are the first step in the switch from generative to vegetative generation during pollen embryogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281332
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  • 44
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    Electronic Resource
    Accumulation of vismione A in regenerated plants ofVismia guianensis DC (1995)
    Springer
    Protoplasma 189 (1995), S. 9-16 
    Details
    ISSN: 1615-6102
    Keywords: Metabolite accumulation ; Vismia guianensis ; Callus cultures ; Plant regeneration ; Ultrastructure ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The accumulation and tissue localization of antitumoral vismione A in the in vitro regenerated plants ofVismia guianensis DC. were investigated. Chemical and light and electron-microscope analyses revealed that vismione A, detected as phenolic black globules in the vacuoles, was accumulated in the leaf, mainly in the palisade, and in small amounts in the primary body of the stem (epidermis and first cortical layer). Vismione A is neither present in the secretory cavities and ducts of the leaf nor in the secretory ducts of the stem. In the leaves of the regenerated plants, the amount of vismione A reached 0.5% FW, compared to 0.1% in the leaves of the parent plant. The optimization of the in vitro regeneration of plants was obtained in MS medium enriched with BAP (1 ppm). The best results for the rooting of regenerated plants were achieved with MS medium containing half-strength salts and 10−5 MIBA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280287
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  • 45
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    Electronic Resource
    Low-density lipoproteins inhibit histamine and NaNO2 relaxations of the coronary vasculature and reduce contractile function in isolated rat hearts (1995)
    Springer
    Heart and vessels 10 (1995), S. 249-257 
    Details
    ISSN: 1615-2573
    Keywords: LDL ; Rat heart ; Ultrastructure ; Coronary vasculature ; Contractile function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study we examined the action of native and oxidized low-density lipoproteins (LDL) on coronary vascular and cardiac function and ultrastructure in rat hearts perfused isovolumically in the Langendorff mode. Responses of the coronary resistance vessels to the endothelium-dependent vasodilator, histamine, and the endothelium-independent vasodilator, NaNO2, were measured together with contractile function (rate-pressure product) before and after perfusion for 20 min with native — or oxidized-LDL at a concentration of 100 µg protein/ml. Ultrastructural damage was assessed via electron microscopy of perfusion-fixed heart specimens. When compared to findings in untreated, control hearts, both native and oxidized LDL significantly reduced the responsiveness of the coronary resistance vessels to histamine and NaNO2, by about 50%. The rate-pressure product was decreased more by oxidized-LDL (41%) than by native-LDL (26%). Electron microscopy showed no ultrastructural abnormalities in the vasculature or myocytes of control hearts. The administration of both native- and oxidized-LDL caused distortion of endothelial cells, increased levels of pinocytotic vesicles in both endothelial and smooth muscle cells, detachment of blood vessels from surrounding tissue, and some regions of myocyte injury with evidence of mitochondrial injury and fluid accumulation. Our results show that both native- and oxidized-LDL are toxic to the isolated heart preparation. They inhibit coronary vascular responsiveness to vasodilators, reduce contractile function, and produce damage to cardiac ultrastructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01744904
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  • 46
    Electronic Resource
    Electronic Resource
    Usefulness of electron microscopy in the diagnosis of cardiac sarcoidosis (1995)
    Springer
    Heart and vessels 10 (1995), S. 275-278 
    Details
    ISSN: 1615-2573
    Keywords: Sarcoidosis ; Heart ; Endomyocardial biopsy ; Epithelioid cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A 49-year-old man with cardiac sarcoidosis is presented. He suffered from congestive heart failure, and left ventricular asynergy and reduced function was evident by echocardiogram and left ventriculogram. A light microscopic examination of the endomyocardial biopsy revealed nonspecific myocarditis without giant cells or noncaseating granulomas. Under an electron microscope, however, several epithelioid cells were found in the specimen. The serum level of lysozyme was elevated. The patient had a past history of sarcoidosis of the eyes and lungs 22 years previously. Cardiac diseases presenting epithelioid cells other than sarcoidosis were clinically ruled out. Thus, the diagnosis of cardic sarcoidosis was made based on both clinical and ultrastructural findings, and corticosteroid therapy was initiated. In the second biopsy, performed 4 months later, a noncaseating granuloma was found. Generally, the incidence of histological diagnosis of cardiac sarcoidosis by light microscopy is relatively low in endomyocardial biopsy specimens. The present case suggests that the addition of an ultrastructural examination may improve the diagnostic usefulness of the endomyocardial biopsy in cardiac sarcoidosis, since electron microscopy can clearly identify the presence of even one epithelioid cell.
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    URL: http://dx.doi.org/10.1007/BF01744907
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  • 47
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    Electronic Resource
    Ultrastructural studies on the embryo sac ofViscum minimum I. Megasporogenesis (1995)
    Springer
    Protoplasma 185 (1995), S. 93-105 
    Details
    ISSN: 1615-6102
    Keywords: Embryo sac ; Embryogenesis ; Megasporogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes taking place during megasporogenesis of a mistletoe (Viscum minimum) were examined at both light and electron microscopy levels. No distinct ovules, integuments, or ovarian cavity are present at any stage of development. The multicellular archesporium originates in the center of a solid ovary. Several functional megasporocytes are developed from the archesporial cells, either adjacent to each other or separated by unspecialized cells. The megasporocyte is much larger than surrounding cells, is invested by a thick wall, and possesses a large nucleus and amyloplasts. Although plasmodesmata are absent even between the adjacent megasporocytes, cells enter meiosis simultaneously. Following meiosis a linear tetrad is formed. Double and treble linear tetrads are frequently observed. The development of the embryo sac conforms to the monosporic or Polygonum type of megasporogenesis. However, the bisporic or Allium type of development is occasionally observed in preparations. Factors determining the pattern of development are discussed. As in other plant species which follow the monosporic type of development, only one functional megaspore cell undergoes further development while others degenerate. Unlike the healthy functional megaspore cell, the degenerating cells have large starch grains and electron-dense cytoplasm. At a later stage of development, the degraded cells are absorbed by the surrounding tissue.
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    URL: http://dx.doi.org/10.1007/BF01272757
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  • 48
    Electronic Resource
    Electronic Resource
    Endoplasmic reticulum as a storage site for allergenic proteins in pollen grains of several Oleaceae (1995)
    Springer
    Protoplasma 187 (1995), S. 111-116 
    Details
    ISSN: 1615-6102
    Keywords: Allergenic protein ; Oleaceae ; Pollen ; Endoplasmic reticulum ; Immuno-localization ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of mature pollen grains of several Oleaceae species (Olea europaea, Fraxinus excelsior, Syringa vulgaris, Ligustrum vulgare, andForsythia suspensa) was studied and the immunolocalization of Ole e I, the major allergen of olige pollen, was determined by immunogold labelling. The five Oleaceae pollens studied here showed different intensities of labelling. The Ole e I allergen was localized throughout the rough endoplasmic reticulum. The absence of gold particles in other cell compartments, such as nuclei, pastids, mitochondria, dictyosomes, lipid bodies, and cell wall, as well as the absence of labelling in control preparations, indicate the specificity of immunolocalization. We conclude that endoplasmic reticulum of the mature pollen grain is a storage site for allergenic proteins and is probably also involved in their synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280238
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  • 49
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    Electronic Resource
    Electron microscopic studies onNosema mesnili Paillot (Microsporidia: Nosematidae) infecting the Malpighian tubules ofPieris canidia larva (1995)
    Springer
    Protoplasma 186 (1995), S. 142-148 
    Details
    ISSN: 1615-6102
    Keywords: Pieris canidia ; Nosema mesnili ; Microsporidia ; Lepidoptera ; Pieridae ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of a microsporidiumNosema mesnili found in the Malpighian tubules ofPieris canidia is described. The life cycle includes meronts, sporonts, sporoblasts, and spores, with typical diplokaryon in each stage. The first two stages are amorphous forms with the former having a thinner cell wall. The spore has 11 coils of the polar filament. This protozoan is a chronic pathogen to its insect host and might have potential as a biological control agent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281324
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  • 50
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    Ultrastructure of microsporogenesis and microgametogenesis inArabidopsis thaliana (L.) Heynh. ecotype Wassilewskija (Brassicaceae) (1995)
    Springer
    Protoplasma 185 (1995), S. 7-21 
    Details
    ISSN: 1615-6102
    Keywords: Arabidopsis thaliana ; Microgametogenesis ; Microsporogenesis ; Pollen development ; Tapetal cells ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The process of microsporogenesis and microgametogenesis was studied at the ultrastructural level in wild-typeArabidopsis thaliana ecotype Wassilewskija to provide a basis for comparison with nuclear male-sterile mutants of the same ecotype. From the earliest stage studied to mature pollen just prior to anther dehiscence, microsporocyte/microspore/pollen development follows the general pattern seen in most angiosperms. The tapetum is of the secretory type with loss of the tapetal cell walls beginning at about the time of microsporocyte meiosis. Wall loss exhibits polarity with the tapetal protoplasts becoming located at a distance from the inner tangential walls first, followed by an increase in distance from the radial walls beginning at the interior edge and progressing outward. The inner tangential and radial tapetal walls are completely degenerated by the microspore tetrad stage. Unlike other members of the Brassicaceae that have been studied, the tapetal cells ofA. thaliana Wassilewskija also lose their outer tangential walls, and secretion occurs from all sides of the cells. Exine wall precursors are secreted from the tapetal cells in a process that appears to involve dilation of individual endoplasmic reticulum cisternae that fuse with the tapetal cell membrane and release their contents into the locule. Following completion of the exine, the tapetal cell plastids develop membranebound inclusions with osmiophilic and electron-transparent regions. The plastids undergo ultrastructural changes that suggest breakdown of the inclusion membranes followed by release of their contents into the locule prior to the complete degeneration of the tapetal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01272749
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  • 51
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    Electronic Resource
    Early cellular events during induction of carrot explants with 2,4-D (1995)
    Springer
    Protoplasma 185 (1995), S. 28-36 
    Details
    ISSN: 1615-6102
    Keywords: Carrot hypocotyl explant ; Flow cytometry ; Somatic embryogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cellular events occurring in carrot hypocotyl explants during long-term and pulse treatment with 2,4-D were followed using different techniques (light and transmission electron microscopy, flow cytometry, PCNA staining). Different morphogenetic pathways were induced under the various experimental conditions. Nevertheless, in the explants the activated cells were the same (provascular cells) and they showed very similar structural and ultrastructural changes. The long-term treatment with 2,4-D induced rapid re-activation of the cell cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01272751
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  • 52
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    Cellular changes during heat shock induction and embryo development of cultured microspores ofBrassica napus cv. Topas (1995)
    Springer
    Protoplasma 185 (1995), S. 106-112 
    Details
    ISSN: 1615-6102
    Keywords: Brassica napus ; Embryogenesis ; Heat shock ; Induction ; Microspore embryogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Brassica napus cv. Topas microspores, isolated and cultured near the time of the first pollen mitosis and subjected to a heat treatment of 24 h, can be induced to develop into haploid embryos. This is a study of microspore structure during induction and embryo determination. Early during the 32.5 °C incubation period the nucleus moved away from the edge of the cell, and granules, 30 to 60 nm in diameter, appeared in the mitochondria and as a cluster in the cytoplasm. Cells divided symmetrically and at the end of the heat treatment, acquired the features of induced bicellular structures described previously. The features persisted as the cells divided randomly within the exine for 4–7 days following heat induction. Multicellular structures released from the exine underwent periclinal divisions resulting in protoderm differentiation of the globular embryo, thus determining embryo development. The cytoplasm of early heart-stage embryos contains abundant polyribosomes. Non-embryogenic development was indicated by large accumulations of starch and/or lipid and thickened cell walls or an unorganized pattern of cell division following release of the multicellular structures from the exine. Embryogenesis is discussed in terms of induction, embryo determination and development.
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    URL: http://dx.doi.org/10.1007/BF01272758
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  • 53
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    Electronic Resource
    Disturbance of the secretory pathway inMicrasterias denticulata by tunicamycin and cyclopiazonic acid (1995)
    Springer
    Protoplasma 189 (1995), S. 173-179 
    Details
    ISSN: 1615-6102
    Keywords: Cyclopiazonic acid ; Golgi apparatus ; Micrasterias ; Secretory pathway ; Tunicamycin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Both tunicamycin, an inhibitor of N-linked glycosylation of proteins, and cyclopiazonic acid, which inhibits the Ca2+-dependent ATPase in the ER, influence the secretory pathway at the ER level and lead to a cessation of cell growth inMicrasterias. Electron microscopical investigations reveal that the mode of action of the two inhibitors differs. While tunicamycin treatment results in a disintegration of the Golgi bodies into small vesicles, cyclopiazonic acid prevents products being supplied from the ER, resulting in the dilatation of ER cisternae and a reduction in the number of Golgi cisternae, combined with a loss of dictyosomal activity. The disturbed cell wall formation under tunicamycin indicates that N-linked glycosylation of proteins is required for normal cell growth inMicrasterias. Moreover, our studies reveal that changes in cytoplasmic free calcium concentration, as a consequence of ATPase inhibition in the ER by cyclopiazonic acid, may inhibit wall material secretion by interrupting the normal ER-dictyosome association.
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    URL: http://dx.doi.org/10.1007/BF01280171
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    Studies on turfgrass snow mold caused byTyphula ishikariensis. II. Microscopical observation of infected bentgrass leaves (1995)
    Springer
    Mycoscience 36 (1995), S. 179-185 
    Details
    ISSN: 1618-2545
    Keywords: Turfgrass snow mold ; Typhula ishikariensis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light and transmission electron microscopy revealed thatTyphula ishikariensis penetrated into bentgrass leaves either through cuticles or stomata either by single hyphae or infection cushions formed on host surfaces. Time course study on infected leaves showed that penetration through stomatal subsidiary cells and their adjacent cells seemed to occur earlier than that through epidermal cells located farther from stomata. More than 30% of epidermal cells were infected by 10 days after inoculation. When hyphae penetrated through an intact cuticle of epidermal cells, they seemed to dissolve host cell walls enzymatically at penetration sites. Physical pressure also seemed to be involved in penetration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268555
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    Plasticity of gonad development in hermaphroditic sparids: ovotestis ontogeny in a protandric species, Lithognathus mormyrus (1995)
    Springer
    Environmental biology of fishes 43 (1995), S. 255-267 
    Details
    ISSN: 1573-5133
    Keywords: Gonadogenesis ; Early germ cell ; Teleost ; Ultrastructure ; Fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Heterosexual gonad development in a sparid species, Lithognathus mormyrus, was studied by histological and cytological examination, during the first three years of life. Gonad bisexuality is achieved after two months of development, according to the cytological dynamics known in sparids. In one-year-old fishes, a variability in the gonad morphology of the juvenile is shown: three different types of ovotestis have been identified within the same cohort: ovotestes with testicular prevalence (25%), testicular and ovarian equivalence (20%), and ovarian prevalence (55%). This morphological variability of the juvenille ovotestes was consistent with the histological analysis of the sexual structure of the adult stock at the first sexual maturity, which constituted 55.5% of functional males (stemming from the first types of ovotestis) and 44.5% of primary females (from the third type). The plasticity of sexual expression in sparids is emphasized, revealing the potentialities of the ovotestis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00005857
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  • 56
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    Inverted ductal papilloma of minor salivary gland origin: morphological aspects and cytokeratin expression (1995)
    Springer
    European archives of oto-rhino-laryngology and head & neck 252 (1995), S. 370-373 
    Details
    ISSN: 1434-4726
    Keywords: Salivary gland tumors ; Inverted ductal papilloma ; Ultrastructure ; Cytokeratin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ultrastructural features and cytokeratin expression of inverted ductal papillomas of minor salivary gland origin were studied. Under the electron microscope, an increased number of desmosomes and mucus-like granules in some cells were the most striking features. Immuno-histochemical study revealed that tumor cells displayed strongly positive reactions with cytokeratins 13 and 14, and less strong reactions with cytokeratins 7, 8, 18 and 5D3. These results support the hypothesis that an inverted ductal papilloma can be derived from the proximal portion of a salivary gland excretory duct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178280
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  • 57
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    Determination of viability of cryopreserved cartilage grafts (1995)
    Springer
    European archives of oto-rhino-laryngology and head & neck 252 (1995), S. 30-34 
    Details
    ISSN: 1434-4726
    Keywords: Cartilage grafting ; Cryopreservation ; Cell biology ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Although transplantation of preserved cartilage has assumed a role of great importance in reconstructive surgery, there are many divergent and contradictory opinions with regard to the outcome of cryopreserved cartilage. This study was formulated to assess the functional state of chondrocytes after cryopreservation. Freeze injury and survival were studied using the trypan blue dye exclusion test, functional assay for cell adhesion and transmission electron microscopy. The methods applied clearly proved that a greater part of the cartilage cells was irreversibly damaged by cryopreservation. Findings demonstrated that cryopreserved cartilage remained non-viable and was not ablt to originate new cartilage. Thus, such cartilage will be reconstruction of parts of the skeleton subject to mechanical stress. The feasibility of cryopreservation techniques for providing vital cartilage substitutes needs further evaluation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171437
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    Mitteilungen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 778-778 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780323
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  • 59
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    Stereoselective Partial Synthesis of (+)-Pisiferic Acid (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 818-832 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (+)-Pisiferic acid (1), an antibiotic active against Gram-negative and Gram-positive bacteria, was synthesized starting from dehydroabietic acid (2) or abietic acid (26). The terpene ring system was functionalized and a Barton reaction used to oxidize Me(20). The intermediates of this photochemical reaction were isolated and characterized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780404
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  • 60
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    Oligodeoxyribonucleotides Containing 4-Aminobenzimidazole in Place of Adenine: Solid-phase synthesis and base pairing (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 833-846 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligonucleotides containing 4-aminobenzimidazole 2′-deoxyribofuranoside (1,3-dideaza-2′-deoxyadenosine; c1c3Ad, 1) were synthesized. For this purpose, various NH2-protecting groups were investigated, and the [(9H-fluoren-9-yl)methoxy]carbonyl group was selected for phosphoramidite protection (→ 4c). Apart from the phosphoramidite 3, the phosphonate 2 was prepared. Compound 1 was incorporated in a homooligonuclectide as well as in oligomers containing naturally occurring nucleosides. The Tm values and the thermodynamic data of various duplexes (11 · 10, 17 · 10, 18 · 10) containing 4-aminobenzimidazole were determined. Although d[(c1c3A)20] (11) does not form a Hoogsteen duplex with d(T20) (10) as observed with d[(c1A)20], it destabilizes the Watson-Crick duplexes to a much smaller extent than it was expected from a bulged loop structure. Apparently, 4-aminobenz-imidazole interacts with regular nucleoside residues within a Watson-Crick duplex structure, most likely by vertical stacking. According to the low basicity of the amino group, only weak H-bonding is expected.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780405
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  • 61
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    Über die Biosynthese von γ-Dodecanolacton in reifenden Früchten: Aroma-Komponenten der Erdbeere (Fragaria ananassa) und des Pfirsichs (Prunus persica) (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 847-856 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Biosynthesis of γ-Dodecanolactone in Ripening Fruits: Flavor Constituents from Strawberries (Fragaria ananassa) and Peaches (Prunus persica)Administration of deuterium-labelled 9,10-expoxy[8,8-2H2]heptadecanoic acid 8a/b and 9,10-dihydroxy-[8,8-2H2]methylheptadecanoate 9 as lower analogues of oleic acid 1 to ripening fruits of strawberries (Fragaria ananassa) and peaches (Prunus persica) results in the emission of labelled γ-undecanolactone (5) as the lower analog of γ-dodecanolactone (2). The transformation proceeds with loss of a single D-atom from C(8) of the precursors. Early precursors, like the C17-epoxy-acids 8a/b yield (4R)-γ-undecanolactone (5) of high enantiomeric purity, while later intermediates results in (4R)-γ-undecanolactone (5) of low purity. The data support a biosynthetic sequence involving the consecutive action of an epoxide hydrolase and β-oxidation to generate the correct chain length of the lactone percursor. The final steps proceed via cyclization of the 3,4-dihydroxyundecanoic acid 13 to the 3-hydroxy-γ-undecanolactone 14. Elimination of H2O and reduction of the intermediate γ-undec-2-enolactone 15 terminate the biosynthesis of 5. The sequence is representative for the biosynthesis of naturally occurring γ-dodecanolactone (2).
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780406
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  • 62
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    Acyclic Tetraethynylethene Molecular Scaffolding: Multinanometer-sized linearly conjugated rods with the poly(triacetylene) backbone and cross-conjugated expanded dendralenes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 779-796 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatives of fully cross-conjugated tetraethynylethene (3,4-diethynylhex-3-ene-1,5-diyne) 1 are versatile precursors to multinanometer-sized molecular rods with all-C-backbones. Oxidative polymerization (CuCl, N,N,N′,N′-tetramethylethylenthylenediamine (TMEDA), O2) of the trans-bis-deprotected trans-bis(triisopropylsilyl)-protected tetraethynylethene 2 yielded, after end-capping with phenylacetylene, the remarkably stable, soluble oligomers 3-7 with a persilylethynylated poly(triacetylene) (PTA) backbone [—(C≡C—CR=CR—C≡C)n—] and a length of 19.4 (3), 26.8 (4), 34.3 (5), 41.8 (6), and 49.2 (7) Å (Scheme 1). These compounds underwent facile one-electron reductions with the number of reversible reduction steps being equal to the number of tetraethynylethene moieties in each molecular rod. Oxidative Eglinton-Glaser homo-coupling of tetraethynylethenes 8-10 with a single free ethynyl group provided the fully silyl-protected 3,4,9,10-tetraethynyl-substituted dodeca-3,9-diene-1,5,7,11-tetraynes 11-13 (Scheme 2) and, after alkyne deprotection, the novel hydrocarbon 14, a C20H6 isomer, and its partially silyl-protected derivative 15. Oxidative hetero-coupling between two different tetraethynylethene derivatives, one with a single and the other with two free terminal ethynyl groups, yielded the extended chromophores 16-21 composed of 3 or 4 tetraethynylethene moieties (Scheme 3). The linearly conjugated oligomers 16 and 17 with the PTA backbone are isomeric to 19 and 20, respectively, which are members of the cross-conjugated expanded dendralenes, i.e., dendralenes with butadiynediyl fragments inserted between each pair of double bonds [—(C≡C—C(=CR2)—C≡C)n—]. The electronic absorption spectra of these compounds were compared and analyzed in terms of the competition between linear and cross-conjugation in determining the extent of π-electron delocalization. Although steric factors on π-electron conjugation remain to be clarified, this analysis strongly suggests that cross-conjugation is not an efficient mechanism for π-electron delocalization. All extended acetylenic-olefinic chromophores considered in this study exhibited remarkably high stability and did not decompose when exposed to laboratory air and light for months. In agreement with this observation, electrochemical studies demonstrated that the compounds are difficult to oxidize with the oxidation potentials in THF (0.1M(Bu4N)PF6) being higher than 1.0 V (vs. the ferrocene/ferrocenium couple).
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780402
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    Optisch aktive 3-Amino-2H-azirine als Bausteine für enantiomerenreine α,α-disubstituierte α-Aminosäuren: Synthese des α-Methylphenylalanin-Synthons and Einbau in Modell-PeptideHerrn Professor Dr. Manfred Hesse zum 60. Geburtstag gewidmet (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 935-946 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically Active 3-Amino-2H-azirines as Synthons for Enantiomerically Pure αα-Disubstituted α-Amino Acids: Synthesis of the α-Methylphenylalanine Synthons and Some Model PeptidesThe synthesis of a novel 2-benzyl-2-methyl-3-amino-2H-azirine derivative with a chiral amino group is described. Chromatographic separation of the diastereoisomer mixture yielded the pure diastereoisomers 9a and 9b (Scheme 4) which are the D- and L-2-methylphenylalanine ((α-Me)Phe) synthons, respectively. The reaction of 9a and 9b with thiobenzoic acid and with Z-leucine yielded the monothiodiamides 10a and 10b (Scheme 5) and the dipeptide derivatives 11a and 11b (Scheme 6), respectively. Methanolysis of 11b yielded 12b. The absolute configuration of 10a was established by X-ray crystallography. The absolute configuration of (α-Me)Phe in 12b has been deduced from the known configuration of L-leucine.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780416
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  • 64
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    Reactivity of 5,10:8,14-Disecosteroids: An unusual rearrangement of cyclodecene-1,4-dione systems to five-membered-ring spiro-γ-lactones (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 891-898 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon heating in AcOH, the stereoisomeric (Z)- and (R)-6,9-dioxocyclodex-3-enyl derivatives, 5 and 6, respectively, obtained by HgO/I2 oxidation of 5-hydroxy-8-oxo-8,14-seco-5α-androstane-3β,17β-diyl diacetate (3), undergo an unusual intramolecular rearrangement to give the corresponding unsaturated (5R,9R)- and (5R,9S)-spiro-lactones 7 and 8, respectively. Hydroxylation of the C=C bond in 7 and 8, and subsequent glycol cleavage of the resulting diols 9 and 10 afforded the epimeric spiro-lactones (5R,9S)-11 and (5R,9R)-14, respectively, and in both cases, the ring-D-containing fragments 12 and 13.
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    URL: http://dx.doi.org/10.1002/hlca.19950780412
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    Mitteilungen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1036-1036 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780425
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  • 66
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    Glycosylidene Carbenes. Part 21. Synthesis of N-tosylglycono-1,4-lactone hydrazones as precursors of glycofuranosylidene carbenes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1020-1035 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N′-(glycofuranosylidene)toluene-4-sulfonohydrazides 5 and 10 (Scheme 1) were prepared in good yields by oxidation (1,3-dibromo-5,5-dimethylhydantoin/Et3N) of the N′-glycosyltoluene-4-sulfonohydrazides 4 and 9, which were obtained from 2,3,5-tri-O-benzyl-D-ribose (3) and 2,3,5-tri-O-benzyl-D-arabinose (8), respectively, and toluene-4-sulfonohydrazide. The analogous naphthalene-2-sulfonohydrazides 7 and 12 were similarly prepared from 3 and 8 via 6 and 11. Photolysis in the presence of phenol of the sodium salt 15 (Scheme 2), best generated in situ, yielded the anomeric glycosides 16, some 5, and traces of the glycosides (1R)/(1S)-17. Photolysis of 15 in THF gave the sulfones α-D/β-D-18. Photolysis of 15 (quartz filter) and dimethyl fumarate led to a single cyclopropane 19, the sulfones α-D/β-D-18, and the N-(ribofuranosyl)-N′-(ribofuranosylidene)toluene-4-sulfonohydrazide 20. Similarly, N-phenylmaleimide afforded the cyclopropanes 21 and 22. Photolysis of the sodium salt of 10 and phenol afforded the anomeric glycosides α-D/β-D-23, the C-glycoside 24, and the sulfone 25. Photolytic glycosidation of 15 with N6-benzyladenine gave the two nucleosides 26 and 27 (Scheme 3).
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    Erstes Beispiel einer H-Verschiebung in ‘Thiocarbonyl-aminiden’ (N-(Alkylidensulfonio)aminiden)Es sind auch die Bezeichnungen Thiocarbonyl-imid, Thion-S-imid und Sulfin-imid gebräuchlich.Teilweise von G.M. an der Jahresversammlung der Polnischen Chemischen Gesellschaft in Warschau, September 1994, vorgetragen.Herrn Professor Albert Eschenmoser zum 70. Geburtstag gewidmet (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1067-1078 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: First Example of an H-Shift in ‘Thiocarbonyl Aminides’ (N-(Alkylidenesulfonio)aminides)Reaction of benzyl azide (15a) with the sterically hindered C=S group of 4,4-dimethyl-1,3-thiazole-5(4H)-thiones 14 (Scheme 3) and 1,1,3,3-tetramethylindane-2-thione (17, Scheme 4) at 80° leads to the corresponding imines in high yield, without formation of any by-product. In contrast, 15a and 2,2,4,4-tetramethyl-3-thioxocyclobutanone (7) under the same conditions yielded, in addition to imine 19, products 20a and 21 (Scheme 5). For the formation of 20a, a reaction mechanism via [1,4]-H shift in the intermediate ‘thiocarbonyl aminides’ 23 is proposed (Scheme 6). Product 21 as well as the dithiazole derivative 22, which is formed only in the reaction with 4-nitrobenzyl azide (15c), are formal adducts of the dipole 23. Whereas precedents are known for the formation of cycloadducts of type 22, the pathway to 21 is not known. Two possible mechanisms of its formation are proposed in Schemes 8 and 9.
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    Synthetic Attempts towards Polymers with Pentafulvene Structural UnitsFulvenes and Fulvalenes, Part 69; Part 68: [1]; short communication: [2]. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1091-1105 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic attempts towards fully conjugated polymers 9 with pentafulvene-diyl structural units are described. Cationic polymerization of pentafulvenes 1a (R = X = Me) and 1b (R = X = MeS) nearly quantitatively gives polymers 8a and 8b with typical Mn and Mw values of 38800 and 53750, respectively, for 8a, and 12000 and 35900, respectively, for 8b. Key step of the conversion 8a → 9a (Scheme 6) is a quantitative bromination 8a → 32a, the structure of 32a being confirmed by analytical data as well as by spectroscopic comparison with model compound 23. Best results in view of two-fold the HBr elimination 32a → 9a are obtained with Et3N, but so far elimination has not been complete. Synthetic sequences are optimized with model compound 21 (Scheme 4). Here again, bromination 21 → 23 is quantitative, while two-fold HBr elimination 23 → 22 with Et3N proceeds in 51% yield. Dibromide 23 easily undergoes HBr elimination followed by a Br shift to give bromide 29. Contrary to cationic polymerization, anionic polymerization of simple pentafulvenes 1 to 2 (which would be attractive in view of the conjugated polymers 3) is not successful: For pentafulvene 1b (R = X = MeS), the main reaction is Diels-Alder-type dimerization 1b → 15b (Scheme 2), even under anionic conditions.
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    Kupfer(II)-chlorid-katalysierte ‘Carben-Dimerisierung’ von 1-Halogeno-1-Lithiocyclopropanen: Ein einfacher Zugang zu Bi(cyclopropylidenen)Herrn Prof. Dr. Richard Neidlein zum 65. Geburtstag gewidmet14. Mitt. über Kupplungsreaktionen, 13. Mitt.: [1] (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1144-1165 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copper(II)-Chloride Catalyzed ‘Carbene Dimerization’ of 1-Halogeno-1-lithiocyclopropanes: A Simple Access to Bi(cyclopropylidenes)A series of 13 bi(cyclopropylidenes) 11 are prepared in a simple one-pot reaction by halogeno-lithio exchange between 1,1-dibromocyclopropanes 1a-n and BuLi, in most cases at -95°, to give 1-bromo-1-lithiocyclopropanes 2a-n, followed by treatment with CuCl2 at low temperature and a simple workup at room temperature (Scheme 3c and Table 1). The yields of bi(cyclopropylidenes) 11 strongly depend on reaction parameters, as explicitly shown for the conversion 1f →→ 11f (Tables 2-8). Mixed couplings between two different carbenoids are possible (Scheme 4), while diastereoselectivity of the active transition-metal complex seems to be low. The structures of bi(cyclopropylidenes) 11 are confirmed by spectroscopic data as well as by X-ray analysis of an isolated crystalline diastereoisomer of 11k (Fig. 1).
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    Design, synthesis, and anti- Trypanosoma cruzi evaluation of a new class of cell-growth inhibitors structurally related to Fenoxycarb (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1207-1214 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several compounds, structurally related to the insect-growth regulator Fenoxycarb (1), were designed and synthesized. These compounds were tested as growth inhibitors of Trypanosoma cruzi cells (epimastigotes). Compounds 6, 16, 18, and 22 were very active against T. cruzi making them promising good candidates either for blood-bank sterilization of Chagas'-disease surveillance, while compounds 11, 12, 13, and 19 showed a moderate degree of activity.
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    URL: http://dx.doi.org/10.1002/hlca.19950780513
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    Azetidin-3-ones from (S)-α-Amino Acids and Their Reactions with Nucleophiles: Preparation of some azetidine-containing amino-alcohol and amino-acid derivatives (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1238-1246 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of azetidin-3-ones 6-10, readily available from the amino acids L-alanine, L-phenylalanine, L-valine, L-lysine, and L-aspartic acid, via the corresponding diazo ketones, with nucleophilic reagents such as complex hydrides, Grignard compounds, an ester enolate, and a Wittig ylide give the expected products 11-19 in good yields and mostly in high diastereoselectivities. New amino-alcohol, γ-amino- and γ-amino-β-hydroxy-carboxylic-acid derivatives of known configurations are thus available.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780516
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    Solid-State Photocyclodimerization of 1-Thiocoumarin (= 2H-1-Benzothiopyran-2-one)Dedicated to Prof. Hans-Dieter Scharf, TU Aachen, on the occasion of his 65th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1079-1082 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation (λ 〉 390 nm) of 2H-1-benzothiopyran-2-one (1) in the solid state affords selectively 6aα,6bα,12bα,12cα -tetrahydrocyclobuta[1,2-c:4,3-c′]bis[1]benzothiopyran -6,7-dione (2), the head-to-head (HH) cis-cisoid-cis-dimer, while irradiation of 1 in the solid state using shorter wavelengths (λ 〉 340 nm) affords a mixture of all four cis-fused tricyclic dimers 2-5. These results represent a novel wavelength effect in solid-state photochemistry.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780504
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  • 73
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    7-Substituted 7-Deaza-2′-deoxyguanosines: Regioselective Halogenation of Pyrrolo[2,3-d]pyrimidine Nucleosides (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1083-1090 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 7-chloro-, 7-bromo-, and 7-iodo-substituted 7-deaza-2′-deoxyguanosine derivatives 2b-d is described. The regioselective 7-halogenation with N-halogenosuccinimides was accomplished using 7-[2-deoxy-3,5-O-di(2-methylpropanoyl)-β-D-erythro- pentofuranosyl]-2-(formylamino)-4-methoxy-7H-pyrrolo[2,3-d]- pyrimidine (4) as the common precursor. A one-pot reaction (2N aq. NaOH) of the halogenated intermediates 5a-c furnished the desired compounds. Also the 7-hexynyl derivative 2e of 7-deaza-2′-deoxyguanosine is described.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19950780505
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  • 74
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    Synthesis and 15N- and 17O-NMR Spectra of 5-Methyl(15N2)[O2,O4-17O2]uridine (= (15N2)[O2,O4-17O2]Ribosylthymine) (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1106-1111 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5-methyl(15N2)[O2,O4-17O2]uridine (= (15N2)[O2,O4-17O 2]ribosylthymine; 15) was synthesized and analyzed by 15N- and 17O-NMR spectroscopy. (15N2)Urea was condensed with 2,3-dibromo-2-methylpropanoyl chloride (3) and cyclized to form (15N2)thymine (5). After glycosidation, the 17O isotopes were introduced in two separate steps: hydrolytic ring opening of 2,5′-anhydro derivative 9 and hydrolysis of 3-nitro-1H-1,2,4-triazole derivative 12 with labelled water in the presence of a strong base. The 15N- and 17O-NMR spectra (Fig.) of 15 in phosphate-buffered water serve as references for heteronuclear NMR spectra of labelled RNA fragments.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780507
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  • 75
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    (±)-4-Amino-4,5-dideoxyribose, (±)-4-amino-4-deoxyerythrose, and (±)-dihydroxyproline derivatives from N-dienyl-γ-lactams (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1166-1177 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hetero-Diels-Alder cycloaddition of acylnitroso dienophile 4 with the N-(butadienyl)pyrrolidinone derivatives 2a, b led with complete regioselectivity to the oxazine adducts 5a, b (Scheme 1). Sequential osmylation, protection of the ensuing glycol, and reduction of the N—O bond gave the expected hemiaminals 11a, b which were characterized by their crystalline sulfite adducts 12a, b (Schemes 1 and 2). Deprotection and saponification of the latter led to aminodeoxyerythrose and to aminodeoxyribose derivatives as an equilibrium of pyrrolidinose equivalents, i.e., hemiaminals 14a, b, imines 14′a, b, and dimers 14″a,b, respectively (Scheme 3). Hydrocyanic acid addition to 11a, b led ultimately to the proline derivatives 16a, b (Scheme 2). Compound 11b proved to be an inhibitor of syncytium formation in AIDS-infected cells.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19950780510
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  • 76
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    Crystal Smectic-B Phase from a Mesomorphic Ferrocene Derivative (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1215-1218 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal properties of two ferrocene derivatives, substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene derivative 1 was found to be non-mesomorphic, the disubstituted ferrocene derivative 2 exhibited a crystal smectic-B phase. This result shows that ferrocene-containing thermotropic liquid crystals, despite the bulkiness of the metallocene core, are not limited to disordered calamitic phases.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780514
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    Oligosaccharide Analogues of Polysaccharides. Part 4. Synthesis of a monosaccharide-derived octamerDedicated to Albert Eschenmoser on the occasion of his 70th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1219-1237 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NaSMe in toluene leads to regioselective de-C-silylation of the bis[(trimethylsilyl)ethynyl]saccharide 2, but to decomposition of butadiynes such as 1 or 12. We have, therefore, combined the known reagent-controlled, regioselective desilylation of 2 and of 12 (AgNO2/KCN) with a substrate-controlled regioselective de-C-silylation, based on C-silyl groups of different size. This combination was studied with the fully protected 3 which was mono-desilylated to 4 or to 5 (Scheme 1). Triethylsilylation of 5 (→ 6) was followed by removal of the Me3Si group (→ 7), introduction of a (t-Bu)Me2Si group (→ 8) and removal of the Et3Si group yielded 9; these high-yielding transformations proceed with a high degree of selectivity. Iodination of 4 gave 10. The latter was coupled with 5 to the homodimer 11 and the heterodimer 12, which was desilylated to 13. The second building block for the tetramer was obtained by coupling 14 (from 7) with 5, leading to 15 and 16. Removal of the Me3Si group (→ 17) and iodination led to 18 which was coupled with 13 to the homotetramer 20 and the heterotetramer 19 (Scheme 2). Deprotection of 19 gave 21, which was, on the one hand, iodinated to 22, and, on the other hand, protected by the (t-Bu)Me2Si group (→ 23). Removal of the Et3Si group (→ 24) and coupling afforded the homooctamer 26 and the heterooctamer 25. Yields of iodination, silylation, and desilylation were consistently high, while heterocoupling proceeded in only 50-55%. Cleavage of the (i-Pr)3SiC and MeOCH2O groups of 11 (→ 27), 15 (→ 28), 20 (→ 29) and 26 (→ 30) proceeded in high yields (Scheme 3). Complete deprotection in two steps of the heterocoupling products 16 (→ 31 → 32), 19 (→ 33 → 34), and 25 (→ 35 → 36) gave the unprotected dimer 32, tetramer 34, and octamer 36 in high yields (Scheme 4). Only the dimer 32 is soluble in H2O; the 1H-NMR spectra of 32, 34, and 36 in (D6)DMSO (relatively low concentration) show no signs of association.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780515
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  • 78
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    From Colchicine and Some of Its Derivatives to 1,2,3,9,10-Pentamethoxybenzo[a]heptalenesDedicated to Albert Eschenmoser on the occasion of his 70th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1247-1277 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A two-step synthesis of 4-methylcolchicine (13), starting from colchicine (2), has been developed (Scheme 5). In three steps, 4-ethylcolchicine (28) is also accessible from 2 (Scheme 8). Colchicine (2) and its derivatives 13 and 28 have been transformed into the benzo[a]heptalene derivatives 9, 18, and 34, respectively, by Hofmann degradation of the corresponding deacetylcolchiceine 3, 19, and 29, respectively, followed by methylation of the two O-functions first with diazomethane and then with trimethoxonium tetrafluoroborate (Scheme 2 and 6). The thus formed tropylium salts gave, on deprotonation with Me3N in CHCl3, the expected pentamethoxybenzo[a]heptalenes 9, 18, and 34, respectively. X-Ray crystal-structure analysis of 9 (Fig.3) and 18 (Fig. 7), determination of the vicinal coupling constants of the H-atoms at the heptalene skeleton as well as the measurement of the racemization rate of the new benzo[a]heptalenes revealed a marked influence of the substituent at C(4) on the degree of twisting of the heptalene skeleton. The absolute configuration of the resolved heptalenes was deduced from their long-wavelength CD maxima around 350 nm. The heptalenes with a negative maximum in this range possess (7aP)-configuration.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780517
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    Die Reaktion von 1-Halogeno-1-Lithiocyclopropanen mit CuCl2: Konkurrenz zwischen ‘Carben-Dimerisierung’ und oxidativer Kupplung15. Mitt. über Kupplungsreaktionen, 14. Mitt. [1]. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1311-1324 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Reaction of 1-Halogeno-1-lithiocyclopropanes with CuCl2: Competition between ‘Carbene Dimerization’ and Oxidative CouplingThe 1-chloro-1-lithiocyclopropanes 2a-d react at low temperature with CuCl2 to give diastereoisomeric mixtures of oxidative-coupling products 5a-d and of ‘carbene dimers’ 6a-d. The relative amount of 5a-d increases with CuCl2 concentration and reaction time. Diastereoselectivity of the reaction seems to be low, and separation as well as spectroscopic structure assignment of single diastereoselectivity of the reaction seems to be low, and separation as well as spectroscopic structure assignment of single diastereoisomers are difficult. The conformational behavior of 1,1′-dichloro-1,1′-bi(cyclopropyls) 5c and 5d is discussed. Contrary to 2a-d, 1-bromo-1-lithiocyclopropanes normally react with CuCl2 to give ‘carbene dimers’ 6 and no coupling products 5. So far the only exception is 1-bromo-1-lithio-2-phenylcyclopropane 2e which in the presence of CuCl2 gives some percents of coupling products 5e besides carbene dimers 6b as main products. An X-ray structure analysis of the predominant diastereoisomer 5e was performed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780521
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780601
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    Two-State Reactivity in Organometallic Gas-Phase Ion ChemistryDedicated to Sir Derek H. R. Barton (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1393-1407 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In contrast to organic reactions, which can almost always be described in terms of a single multiplicity, in organometallic systems, quite often more than one state may be involved. The phenomenon of two states of different multiplicities that determine the minimum-energy pathway of a reaction is classified as two-state reactivity (TSR). As an example, the ion/molecule reactions of ‘bare’ transition-metal-monoxide cations with dihydrogen and hydrocarbons have been analyzed in terms of the corresponding potential-energy hypersurfaces. It turns out that, besides classical factors, such as the barrier heights, the spin-orbit coupling factor is essential, since curve crossing between the high- and low-spin states constitutes a distinct mechanistic step along the reaction coordinates. Thus, TSR may evolve as a new paradigm for describing the chemistry of coordinatively unsaturated transition-metal complexes. This concept may contribute to the understanding of organometallic chemistry in general and for the development of oxidation catalysts in particular.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780602
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    Bis-allylic Reactivity of the Funicolides, 5,8(17)-diunsaturated briarane diterpenes of the sea pen Funiculina quadrangularis from the tuscan archipelago, leading to 16-nortaxane derivativesPresented in part by A.G. at ‘Giornate di Chimica delle Sostanze Naturali’, Amalfi, 29 May-1 June 1994. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1465-1478 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Funicolides A-C (1-3), D (5), and E (7) and 7-epifunicolide A (4), new 5,8(17)-diunsaturated briarane diterpenes, as well as the known analogue brianthein W (6), were isolated from the pennatulacean coral Funiculina quadrangularis (PALLAS, 1766) collected in the Tuscan archipelago. Easy degradation under oxidative and/or basic conditions served to assign the ester groups at C(2) or C(14), while revealing bis-allylic reactivity at C(7) with formation of 16-nortaxane derivatives.
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    URL: http://dx.doi.org/10.1002/hlca.19950780606
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  • 83
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    4-Amino-1,5-dihydro-2H-pyrrol-2-one aus Bortrifluorid-katalysierten Umsetzungen von 3-Amino-2H-azirinen mit Carbonsäure-Derivaten (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1490-1498 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-Amino-1,5-dihydro-2H-pyrrol-2-ones from Boron Trifluoride Catalyzed Reactions of 3-Amino-2H-azirines with Carboxylic Acid DerivativesReaction of 3-amino-2H-azirines 1 with ethyl 2-nitroacetate (6a) in refluxing MeCN affords 4-amino-1,5-dihydro-2H-pyrrol-2-ones 7 and 3,6-diamino-2,5-dihydropyrazines 8, the dimerization product of 1 (Scheme 2). Thus, 6a reacts with 1 as a CH-acidic compound by C—C bond formation via C-nucleophilic attack of deprotonated 6a onto the amidinium-C-atom of protonated 1 (Scheme 5). The scope of this reaction seems to be rather limited as 1 and 2-substituted 2-nitroacetates do not give any products besides the azirine dimer 8 (see Table 1). Sodium enolates of carboxylic esters and carboxamides 11 react with 1 under BF3 catalysis to give 4-amino-1,5-dihydro-2H-pyrrol-2-ones 12 in 50-80% yield (Scheme 3, Table 2). In an analogous reaction, 3-amino-2H-pyrrole 13 is formed from 1c and the Li-enolate of acetophenone (Scheme 4). A reaction mechanism for the ring enlargement of 1 involving BF3 catalysis is proposed in Scheme 6.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19950780608
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    Preparation, Structure, and Properties of All Possible Cyclic Dimers (Diolides) of 3-Hydroxybutanoic Acid (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1525-1540 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In connection with the proposed structure of a trans-membrane cellular ion channel consisting of a complex between poly[(R)-3-hydroxy butanoate] (P(3-HB)) and calcium polyphosphate, CaPPi (ca. 150 units each), which is supposed to contain s-cis-bonds or even more highly strained ester conformations, we have prepared and studied the properties of the cyclic dimer of 3-HB, the diolide 1. All possible forms of 1, the rac-, the meso-, and the enantiomerically pure (R,R)- and (S,S)-compounds were prepared, purified, and characterized. The synthesis (Scheme 1) started from dimethyl succinate with the key step being the Baeyer-Villiger oxidation of the rac- and meso-2,5-dimethylcyclohexane-1,4-diones 5. The rac-diolide 1 was resolved by preparative chromatography on a Chiralcel OD column (Fig.1). The crystal structures of rac- 1 (Fig.3) and of meso- 1 (Fig.5) were determined by X-ray diffraction: the diolides 1 contain s-cis-ester bonds and an ester group with a conformation half way to the transition state of rotation (Fig.2). Strain energies for the diolides 1 of up to 17.8 kcal/mol are suggested. Accordingly, these compounds show reactivities similar to those of carboxylic-acid anhydrides or even acid chlorides. They cannot be chromatographed on silica gel, and they react with primary, secondary, and tertiary alcohols, and with amines to form derivatives of open chain 3-HB ‘dimers’, hydroxy acids 6, esters 7, and amides 8 (Scheme 2). The rate of acid-catalyzed ring opening of the diolides 1 with alcohols has been measured (Fig.6 and 7). From the results described, we conclude that it is unlikely for strained and reactive ester conformations to occur as part of ion channels through phospholipid bilayers of cells.
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    Structural and Photophysical Properties of Pseudo-Tricapped Trigonal Prismatic Lanthanide building blocks controlled by zinc(II) in heterodinuclear d—f complexes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1541-1566 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient combination of electrospray mass spectrometry (ES-MS), spectrophotometric and 1H-NMR titrations in solution is used to characterize the assembly of the segmental ligand 2-{6-[1-(3,5-dimethoxybenzyl)-1H-benzimidazol-2-yl]pyridin-2-yl}-1, 1′-dimethyl-5,5′-methylene-2′-(5-methylpyridin-2-yl)bis[1H- benzimidazole] (L2) with ZnII and 4f metal ions, LnIII. Ligand L2 reacts with Zn(ClO4)2 in MeCN to give successively [Zn(L2)2]2+, where the metal ion is coordinated by the tridentate binding units of the ligands, and the double-helical head-to-head complex [Zn2(L2)2]4+. When L2 reacts with Ln(ClO4)3 (Ln = La, Eu, Lu), LaIII only leads to a well-defined cylindrical C1-symmetrical homodinuclear head-to-tail complex [La2(L2)3]6+ in solution, while chemical-exchange processes prevent the 1H-NMR characterization of [Eu2(L2)3]6+, and LuIII gives complicated mixtures of complexes. However, stoichiometric amounts of LnIII (Ln = La, Ce, Pr, Nd, Sm, Eu, Tb, Y, Lu), ZnII, and L2 in a 1:1:3 ratio lead to the selective formation of the C3-symmetrical heterodinuclear complexes [LnZn(L2)3]5+ under thermodynamic control. Detailed NOE studies show that the ligands are wrapped about the C3 axis defined by the metal ions, and the separation of dipolar and contact contributions to the 1H-NMR paramagnetic shifts of the axial complexes [LnZn(L2)3]5+ (Ln = Ce, Pr, Nd, Sm, Eu) in MeCN establishes that ZnII occupies the pseudo-octahedral capping coordination site defined by the three bidentate binding units, while LnIII lies in the resulting ‘facial’ pseudo-tricapped trigonal prismatic site produced by the three remaining tridentate units. Photophysical measurements show that [LnZn(L2)3]5+ (Ln = Eu, Tb) are only weakly luminescent because of quenching processes associated with the C3-cylindrical structure of the complexes. The use of 3d metal ions to control and design isomerically pure ‘facial’ tricapped trigonal prismatic lanthanide building blocks is discussed together with the calculation of a new nephelauxetic parameter associated with heterocyclic N-atoms coordinated to LnIII.
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    URL: http://dx.doi.org/10.1002/hlca.19950780612
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    Preparation of the PdCl2 Complex of TADDOP, the Bis(diphenylphosphinite) of TADDOL: Use in enantioselective 1,3-diphenylallylations of nucleophiles and discussion of the mechanism (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1636-1650 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the tartrate-derived diol (R,R)-α,α,α′,α′-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (TADDOL) with chlorodiphenylphosphane gives a new bis(diphenylphosphanyl) ligand (TADDOP). The complex 4 formed with PdCl2 has been crystallized and its structure determined by X-ray diffraction (Fig.1). The complex is used for Pd-catalyzed enantioselective 1,3-diphenylallylations of various nucleophiles which give products with enantiomer ratios of up to 88:12 (Scheme 2). Crystallization procedures lead to the enantiomerically pure (〉 99:1) product 11 derived from dimethyl malonate. The structure of the TADDOP complex 4 is compared with those of other transition-metal complexes containing chelating bis(diphenylphosphanyl) ligands (Fig.2). A crystallographic data base search reveals that the structures of transition-metal complexes containing two Ph2P groups (superpositions in Fig.3) fall into one of two categories: one with approximate C2 symmetry and the other with C1 symmetry (20 and 19 examples, resp.). A mechanistic model is proposed which correlates the conformational chirality (δ or λ) of the four Ph groups' arrangement in such complexes with the topicity of nucleophile approach on Pd-bound trans,trans-1,3-diphenylallyl groups (Scheme 3 and Table).
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780703
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    Multiple Cyclopropanations of C70. Synthesis and characterization of bis-, tris-, and tetrakis-adducts and chiroptical properties of bis-adducts with chiral addends, including a recommendation for the configurational description of fullerene derivatives with a chiral addition pattern (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1673-1704 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The regioselectivity of multiple cyclopropanations of C70 with 2-bromopropanedioates in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base (Bingel reaction) was investigated in a systematic study. Bisadduct formation occurred preferentially at the 6—6 bonds formed by the most pyramidalized sp2-C-atoms at the two opposite poles of the fullerene and, in the reaction with achiral bis[(ethoxycarbonyl)methyl]2-bromopropanedioate (13a), yielded three constitutionally isomeric bis(methano)fullerenes (Scheme 2). Two of them, C2-symmetrical (±)-1 and (±)-2, are chiral; a fact which had not been considered in previous investigations. Formation of the third, C2v-symmetrical isomer 3 was observed for the first time. Configurational descriptions for fullerene derivatives which possess a chiral chromophore as a result of specific functionalization patterns are proposed. Cyclopropanations of C70 with optically active bis[(S)-1-phenylbutyl] 2-bromopropanedioate (13b) yielded five optically active, C2-symmetrical bis-adducts 7-11 which could be separated by preparative HPLC and fully characterized (Scheme 3, Fig.4). Compounds 7/8 and 9/10 represent two constitutionally isomeric pairs of diastereoisomers, and their circular dichroism (CD) spectra show pronounced Cotton effects mainly due to strong chiroptical contributions from the chirally functionalized fullerene chromophores (Fig.7). Since the addition patterns on the fullerene surface in each pair of diastereoisomers have an enantiomeric relationship, their CD spectra closely resemble those expected for two enantiomers. In the third constitutional isomer 11, the addition pattern on the fullerene surface is C2v-symmetrical, and optical activity only results from the chiral addends. Its CD spectrum shows weak Cotton effects mainly from induced circular dichroism originating from the perturbation of the achiral fullerene chromophore by the attached chiral addends. Addition of diethyl 2-bromopropanedioate (2 equiv.) to the C2-symmetrical racemic bis-adduct (±)-2 yielded a mixture of tris-adducts and one major, C2-symmetrical tetrakis-adduct (±)-4 which was isolated in pure form (Scheme 4). Starting from the achiral C2v-symmetrical bis-adduct 3, one single Cs-symmetrical tris-(5) and one C2v-symmetrical tetrakis-adduct (6) were obtained as major products which were isolated and fully characterized (Scheme 5). The regioselectivity for introduction of a second addend in the same hemisphere of C70 is high and resembles the preferred pattern of bis-addition seen in the functionalization of C60.
    Additional Material: 10 Ill.
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  • 88
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    From Epiraikovenal, an Instrumental Niche-Exploitation Sesquiterpenoid of Some Strains of the Marine Ciliated Protist euplotes raikovi, to an unusual intramolecular tele-dienone-olefin [2+2] photocycloadditionPresented in part by F.P. in a lecture at the School of Chemistry, University of Melbourne, on April 28, 1995. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1747-1754 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that strains of the marine ciliate Euplotes raikovi are subtly variable in their production of secondary metabolites. Strains GA8 and 39W from Mediterranean and SB8 from Californian coasts produce the sesquiterpenoid epiraikovenal (3), while strains GA8 and SB8 also produce secoepiraikovenal (4), which play an instrumental niche-exploitation role and have also taxonomic significance. Comparison of 3 and 4 with raikovenal (2) and its putative biogenetic precursor 1, which have similar roles in the conspecific strain Morl from Casablanca coast in the Atlantic Ocean, inspired us the first case of intramolecular tele-dienone-olefin [2+2] photocycloaddition, exemplified here by the transformation of 1 into ent-3. This served also to unequivocally clarify the stereochemical relationship between 3 and 2.
    Additional Material: 1 Tab.
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  • 89
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    Nucleotides. Part XLVPart XLIV: [1].. Synthesis of new (2′-5′)adenylate trimers, containing 5′-amino-5′-deoxyadenosine residues at the 5′-end of the oligoadenylate chain, and of its analogues, carrying a 9-[(2-hydroxyethoxy)methyl]adenine residue at the 2′-terminus (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1777-1784 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5′-amino-5′-deoxy-2′,3′-O-isopropylideneadenosine (4) was obtained in pure form from 2′,3′-O-isopropylideneadenosine (1), without isolation of intermediates 2 and 3. The 2-(4-nitrophenyl)ethoxycarbonyl group was used for protection of the NH2 functions of 4 (→7). The selective introduction of the palmitoyl (= hexadecanoyl) group into the 5′-N-position of 4 was achieved by its treatment with palmitoyl chloride in MeCN in the presence of Et3N (→5). The 3′-O-silyl derivatives 11 and 14 were isolated by column chromatography after treatment of the 2′,3′-O-deprotected compounds 8 and 9, respectively, with (tert-butyl)dimethylsilyl chloride and 1H-imidazole in pyridine. The corresponding phosphoramidites 16 and 17 were synthesized from nucleosides 11 and 14, respectively, and (cyanoethoxy)bis(diisopropylamino)phosphane in CH2Cl2. The trimeric (2′-5′)-linked adenylates 25 and 26 having the 5′-amino-5′-deoxyadenosine and 5′-deoxy-5′-(palmitoylamino)adenosine residue, respectively, at the 5′-end were prepared by the phosphoramidite method. Similarly, the corresponding 5′-amino derivatives 27 and 28 carrying the 9-[(2-hydroxyethoxy)methyl]adenine residue at the 2′-terminus, were obtained. The newly synthesized compounds were characterized by physical means. The synthesized trimers 25-28 were 3-, 15-, 25-, and 34-fold, respectively, more stable towards phosphodiesterase from Crotalus durissus than the trimer (2′-5′)ApApA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780711
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  • 90
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    Syntheses and Reactions of 1′,2′-Unsaturated 2′,3′-Seconucleoside Analogues (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1797-1805 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1′,2′-unsaturated 2′,3′-secoadenosine and 2′,3′-secouridine analogues were synthesized by the regioselective elimination of the corresponding 2′,3′-ditosylates, 2 and 18, respectively, under basic conditions. The observed regioselectivity may be explained by the higher acidity and, hence, preferential elimination of the anomeric H-C(1′) in comparison to H—C(4′). The retained (tol-4-yl)sulfonyloxy group at C(3′) of 3 allowed the preparation of the 3′-azido, 3′-chloro, and 3′-hydroxy derivatives 5-7 by nucleophilic substitution. ZnBr2 in dry CH2Cl2 was found to be successful in the removal (85%) of the trityl group without any cleavage of the acid-sensitive, ketene-derived N,O-ketal function. In the uridine series, base-promoted regioselective elimination (→19), nucleophilic displacement of the tosyl group by azide (→20), and debenzylation of the protected N(3)-imide function gave 1′,2′-unsaturated 5′-O-trityl-3′-azido-secouridine derivative 21. The same compound was also obtained by the elimination performed on 2,2′-anhydro-3′-azido-3′-azido-3′-deoxy-5′-O-2′,3′-secouridine (22) that reacted with KO(t-Bu) under opening of the oxazole ring and double-bond formation at C(1′).
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19950780714
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  • 91
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    On the Way to Glycoprocessing Inhibitors. Synthesis of an imidazo-L-xylo-piperidinose derivative (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1837-1842 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An eight-step synthetic sequence led from the known D-xylo-pentodialdose 8 to imidazo-L-xylo-piperidinose 15, the key steps being the build-up of imidazole compound 12 by a van Leusen methodology and the intramolecular SN2 ring closure of the O-triflated benzylidene derivative 13. xylo-Piperidinose 15 appears in a half-chair conformation like the oxocarbonium ions which are the postulated intermediates in the glycoprocessing of the pyranose polysaccharides. This bicyclic azasugar should be a glycosidase inhibitor.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780717
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  • 92
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    3′,4′-Diethynl-2′,3′,5′-trideoxy-5′-noruridine: A new self-polymerizable 2′-deoxyribonucleoside analogueDedicated to Prof. Dr. Richard Neidlein, Heidelberg, on the occasion of his 65th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1879-1886 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In 10 steps, 3′,4′-diethynyl-2′,3′,5′-trideoxy-5′-noruridine (14) was synthesized in 5% overall yield from commercial uridine, using conventional methods of nucleoside chemistry. As two functional groups capable to react with each other are present in the same molecule, the synthetic compound is able to form polymers, similar to the polynucleotides, by an acetylene coupling reaction.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780721
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  • 93
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    Synthesis of Thiophene-Substituted Spiropyrans and Spirooxazines, Precursors of Photochromic Polymers (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1887-1893 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of spiropyrans 11 and 12 and spirooxazines 13-17 containing a thiophene moiety is described. Two different synthetic approaches were used. The spectrokinetic properties of these new compounds are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780722
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  • 94
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    Nucleic-Acid Analogs with Restricted Conformational Flexibility in the Sugar-Phosphate Backbone (‘Bicyclo-DNA’). Part 5Part 4: [1].. Synthesis, Characterization, and Pairing Properties of Oligo-α-D-(bicyclodeoxynucleotides) of the Bases Adenine and Thymine (α-Bicyclo-DNA)Preliminary communication on α-Bicyclo-DNA: [2].Dedicated to Professor A. Eschenmoser on the occasion of his 70th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 2077-2096 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A conformational analysis of the (3′S,5′R)-2′-deoxy-3′,5′-ethano-α-D-ribonucleosides (a-D-bicyclodeoxynucleosides) based on the X-ray analysis of N4-benzoyl-α-D-(bicyclodeoxycytidine) 6 and on 1H-NMR analysis of the α-D-bicyclodeoxynucleoside derivatives 1-7 reveals a rigid sugar structure with the furanose units in the l′-exo/2′-endo conformation and the secondary OH groups on the carbocyclic ring in the pseudoequatorial orientation. Oligonucleotides consisting of α-D-bicyclothymidine and α-D-bicyclodeoxyadenosine were successfully synthesized from the corresponding nucleosides by phosphoramidite methodology on a DNA synthesizer. An evaluation of their pairing properties with complementary natural RNA and DNA by means of UV/melting curves and CD spectroscopy show the following characteristics: i) α-bcd(A10) and α-bcd(T10) (α = short form of α-D)efficiently form complexes with complementary natural DNA and RNA. The stability of these hybrids is comparable or slightly lower as those with natural β-d(A10) or β-d(T10)( β = short form ofβ-D). ii) The strand orientation in α-bicyclo-DNA/β-DNA duplexes is parallel as was deduced from UV/melting curves of decamers with nonsymmetric base sequences. iii) CD Spectroscopy shows significant structural differences between α-bicyclo-DNA/β-DNA duplexes compared to α-DNA/β-DNA duplexes. Furthermore, α-bicyclo-DNA is ca. 100-fold more resistant to the enzyme snake-venom phosphodiesterase with respect to β-DNA and about equally resistant as α-DNA.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780816
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  • 95
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    Selectivity in Rhodium(II)-Catalyzed Rearrangements of cycloprop-2-ene-1-carboxylates (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 129-144 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The course of the thermocatalytic rearrangement of cycloprop-2-ene-1-carboxylates in the presence of dirhodium(II) tetrakis(perfluorobutyrate) ([Rh2(pfb)4]) was investigated by varying the substituents of the cyclopropene ring. Product composition is markedly influenced by the number, nature, and position of the substituents, which determine the regio- and stereoselectivity of the cyclopropene-ring cleavage. A mechanism is proposed in which attack of the electrophilic RhII species is concerted with disrotatory ring opening of the incipient cyclopropyl cation and affords a metal-complexed vinylcarbene. The chemoselectivity of the latter is consistent with that of other carbenes generated in the presence of [Rh2(pfb)4].
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19950780113
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  • 96
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    Complete π-Facial Stereoselectivity in the TiCl4-Mediated [4 + 2] Cycloaddition of Cyclopentadiene to N,N′-fumaroyldi[(2R)-bornane-10,2-sultam] (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 145-150 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under the co-operative influence of two prosthetic groups, and independent of the TiCl4 concentration, complete and constant diastereofacial π-selection was achieved during the [4 + 2] cycloaddition of cyclopentadiene to N,N′-fumaroyl-di[(2R)-bornane-10,2-sultam] ((-)-1c); reactive conformations are discussed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780114
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  • 97
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    Preparation and Absolute Configuration of Some Iris Essential Oil Constituents of the 5-methylsafranic-acid seriesPresented in part at the XVth Conference on Isoprenoids, 20-25 September 1993, Zakopane, Poland. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 165-176 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The β-dienoate (+)-(5S)-13a (86% ee; meaning of α and β as in α- and β-irone, resp.) was obtained from (-)-(5S)-9a via acid-catalyzed dehydration of the diastereoisomer mixture of allylic tertiary alcohols (+)-(1S,5S)-15/(+)-(1R,5S)-15 (Scheme 3). Prolonged treatment gave clean isomerization via a [1,5]-H shift to the α-isomer (-)-(R)-16a with only slight racemization (76% ee; Scheme 4). In contrast, the SnCl4-catalyzed stereospecific cyclization of (+)-(Z)-6 to (-)-trans-8a (Scheme 2), followed by a diastereoselective epoxidation to (+)-11 gave, via acid-catalyzed dehydration of the intermediate allylic secondary alcohol (-)-12, the same ester (+)-13a (Scheme 3), but with poor optical purity (13% ee), due to an initial rapid [1,2]-H shift. The absolute configuration of (-)-16a-c was confirmed by chemical correlation with (-)-trans-19 (Scheme 4). 13C-NMR Assignments and absolute configurations of the intermediate esters, acids, aldehydes, and alcohols are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780116
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  • 98
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    Mitteilungen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 265-267 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780123
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  • 99
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780201
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  • 100
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    Synthesis of Polypropionate Fragments Containing Tertiary-Alcohol Moieties. Cross-aldolisations with lithium enolates of 7-oxabicyclo[2.2.1]heptan-2-one derivativesFor a preliminary report, see [1]. Part of the Ph.D. thesis of Ph. K., Ecole Polytechnique Fédérale de Lausanne, 1994. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 301-324 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Diels-Alder adduct of 2,4-dimethylfuran to 1-cyanovinyl (1′R)-camphanate ((+)-(1R,2S,4R)-2-exo-cyano-1,5-dimethyl-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl (1′R)-camphanate ((+)-1)) was converted into (+)-2,7-dideoxy-2,4-di-C-methyl-L-glycero- ((+)-6) and -D-glycero-L-altro-heptono-1,4-lactone ((+)-7), into (-)-(3R,4R,5R,6S)-3,4:5,7-bis(isopropylidenedioxy)-4,6-dimethylheptan-2-one ((-)-22), and into (+)-(2R,3R,4R,5S,6S)-3,4:5,6-bis(isopropylidenedioxy)-2,4-dimethylheptanal ((+)-34). Condensation of ((+)-34 with the lithium enolate of (-)-(1R,4R,5S,6R)-6-exo-[(tert-butyl)dimethylsilyloxy]-1,5-endo-dimethyl-7-oxabicyclo[2.2.1] heptan-2-one ((-)-38; derived from (+)-1) gave a 3:2 mixture of aldols (+)-39 and (+)-40 (mismatched pairs of a α-methyl-substituted aldehyde and (E)-enolate) whereas the reaction of (±)-34 with (±)-38 gave a 10:1 mixture of aldols (±)-41 and (±)-39. A single aldol, (-)-44, was obtained to condensing (+)-34 with the lithium enolate of (+)-(1S,4S,5S,6S)-5-exo-(benzyloxy)-1,5-endo-dimethyl-7-oxabicyclo[2.2.1]heptan-2-one ((+)-43; derived from (-)-(1S,2R,4S)-2-exo-cyano-1,5-dimethyl-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl (1′S)-camphanate ((-)-3)). All these cross-aldolisations are highly exo-face selective for the bicyclic ketones. The best stereochemical matching is obtained when the lithium enolates and α-methyl-substituted aldehydes can realize a ‘chelated transition state’ that obeys the Cram and Felkin-Anh models (steric effects). Polypropionate fragments containing eleven contiguous stereogenic centres and tertiary-alcohol moieties are thus prepared with high stereoselectivity in a convergent fashion. The chiral auxiliaries ((1R)- and (1S)-camphanic acid) are recovered at the beginning of the syntheses.
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    URL: http://dx.doi.org/10.1002/hlca.19950780205
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