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  • 1990-1994  (3.713)
  • 1980-1984  (2.447)
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  • 1
    Digitale Medien
    Digitale Medien
    Histomorphological aspects of vascular anastomosis established by laser (1991)
    Springer
    Lasers in medical science 6 (1991), S. 363-366 
    Details
    ISSN: 1435-604X
    Schlagwort(e): Laser vascular welding ; Tissue fusion ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Physik , Technik allgemein
    Notizen: Abstract The central problem in microsurgery is the reconstruction of small vessels. The long operating time, foreign body granuloma formation around the suture material as well as aneurysmal alterations of the vessel wall after conventional suture technique make the search for alternatives indispensable. Some of these disadvantages can be avoided as demonstrated by our animal experiments and histological examinations in laser-assisted anastomosing. The aim of this study is to show these aspects in connection with laser application and compare them with conventional suture techniques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02030894
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  • 2
    Digitale Medien
    Digitale Medien
    Organ-specific crystalline structures of ferritin cores inβ-thalassemia/hemoglobin E (1991)
    Springer
    BioMetals 4 (1991), S. 162-165 
    Details
    ISSN: 1572-8773
    Schlagwort(e): Ferritin ; Thalassemia ; Ferrihydrite ; Crystallinity ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The cores of ferritins isolated from different organs of human subjects withβ-thalassemia/hemoglobin E (β-thal/HbE) disease have different size distributions and crystallinities depending on the source organ. These patients have not been treated by hypertransfusion regimen or iron chelation therapy.β-Thal/HbE spleens and livers yield ferritin cores which are less crystalline than those isolated from normal spleens and livers, reflecting the more rapid deposition of iron in the diseased state. Ferritins isolated from the hearts and pancreases ofβ-thal/HbE subjects were found to have larger, more crystalline cores than those from theβ-thal/HbE livers and spleens, possibly as a consequence of the role of the heart and pancreas as long-term iron deposition sites in this iron overload pathology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01141308
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  • 3
    Digitale Medien
    Digitale Medien
    Claws of cilia: Further observation of ciliated epithelium in neurenteric cyst (1991)
    Springer
    Virchows Archiv 418 (1991), S. 263-265 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Neurenteric cyst ; Enterogenous cyst ; Cilia ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Claw-like projections and related structures on cilium tips in neurenteric cyst epithelium are described. The ciliary claws are about 20 nm in length and just beneath them four parallel electron-dense areas or lines are discernible. Similar structures were also observed in another case of neurenteric cyst. These structures are very similar to those reported previously, and it is suggested that they are commonly present in various ciliated epithelia in Man.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01606065
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  • 4
    Digitale Medien
    Digitale Medien
    Alveolar soft-part sarcoma of the uterine corpus: Histological, immunocytochemical and ultrastructural study of a case (1991)
    Springer
    Virchows Archiv 418 (1991), S. 467-471 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Alveolar soft-part sarcoma ; Uterus ; Myometrium ; Immunocytochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A case of alveolar soft-part sarcoma located in the uterine corpus is reported. It was an incidental finding in the hysterectomy specimen of a 40-year-old woman. Light and electron microscopic examination revealed periodic-acid-Schiff-positive, diastase-resistant, membrane-bound cytoplasmic granules and crystalloids. Tumour cells expressed immunoreactivity with vimentin, desmin, cytokeratins, NK1/C3 and HMB-45 antibodies. Four years postoperatively, the patient is still alive without evidence of disease. Differential diagnoses, immunocytochemistry and clinical management of uterine alveolar soft-part sarcoma are discussed and the literature reviewed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01605935
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  • 5
    Digitale Medien
    Digitale Medien
    Glucagonomas of transgenic mice express a wide range of general neuroendocrine markers and bioactive peptides (1991)
    Springer
    Virchows Archiv 419 (1991), S. 115-129 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Transgenic mice ; Glucagonomas ; Immunohistochemistry ; Electron microscopy ; Radioimmunoassay
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Pancreatic tumours of transgenic mice carrying a glucagon-promoted simian virus 40 (SV40) T antigen oncogene have been analysed by histological, histochemical, ultrastructural and radioimmunological means. Seven transgenic mice were examined revealing dysplastic and neoplastic lesions in the endocrine pancreas. Four tumours were identified, one of which metastasized to periadrenal spaces and paravertebral lymph nodes. Benign tumours were composed of argyrophilic, endocrine cells reactive to a range of antibodies against neuroendocrine markers (neuron-specific enolase, protein gene product 9.5, chromogranin A, synaptophysin and protein 7B2) and different fragments of the proglucagon molecule (glucagon, glicentin, glucagon-like polypeptides 1 and 2). A few tumour cells expressed pancreatic polypeptide, somatostatin or insulin. Conventional ultrastructural analysis and immunogold labelling revealed typical glucagon-immunoreactive alpha granules which co-stored glicentin and glucagon-like polypeptides 1 and 2. The malignant primary tumour and its metastases were composed mainly of cells which did not show immunoreactivity for neuroendocrine markers or peptides. Atypical, glucagon-immunogold labelled granules were detected at electron microscopy in differentiated tumour cells and C-type retroviral particles in the largest tumour population of degranulated cells. The transgene-encoded oncoprotein SV40 large T-antigen was detected in the nuclei of well-differentiated tumour cells and in alpha cells of some dysplastic islets. All tumour-bearing mice showed high levels of circulating glucagon-like immunoreactivity. Transgenic mice harbouring the glucagon-promoted SV40 T antigen oncogene may provide a model for human glucagonoma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01600225
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  • 6
    Digitale Medien
    Digitale Medien
    The pathobiology of salivary gland (1991)
    Springer
    Virchows Archiv 418 (1991), S. 387-400 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Submandibular gland ; Tissue culture ; Electron microscopy ; Proliferating cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Fragments of rat submandibular gland (organoids) which maintained the topological organization of the parent tissue were cultured in a three-dimensional collagen gel matrix for up to 30 days. At 48 h, vigorous peripheral outgrowth had occurred around each organoid. This was accompanied by central necrosis and the bridging of adjacent organoids. By day 5, large cyst-like spaces occupied the centre of many organoids. Bromodeoxyuridine labelling indicated that a considerable proportion of the lining cells were proliferating. Organoid growth peaked at between 5 and 10 days. Thereafter, the number of viable colonies and proliferating cells declined. Addition of isoproterenol after 24 h culture resulted in marked morphological alterations, with earlier and more prolific outgrowth and a greater tendency for organoids to flatten and grow out over the surface of the gel with squamous differentiation. Ultrastructurally, nuclear and cytoplasmic features of isoproterenol-treated and untreated cultures were similar. The secretory granules and extensive rough endoplasmic reticulum of terminal tubule cells, evident in organoids immediately after isolation, were infrequent after 24 h and absent by 48 h. Similar alterations occurred in the few acinar cells, so by 5 days the cultures were composed entirely of a uniform population of primitive, dedifferentiated cells. Further uses of this culture systems will include the study of diseases and disorders of the salivary glands as well as normal growth and differentiation pathways.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01605924
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  • 7
    Digitale Medien
    Digitale Medien
    Degeneration of the corticopontine tract in olivopontocerebellar atrophy (1991)
    Springer
    Virchows Archiv 418 (1991), S. 99-103 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Corticopontine tract degeneration ; Olivopontocerebellar atrophy ; Electron microscopy ; Morphometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Nine cases of sporadic olivopontocerebellar atrophy [Déjérine-Thomas type, multisystemic atrophy (MSA)] were examined histologically and electron microscopically with special reference to the corticopontine tract. Five of nine cases showed degeneration of the myelinated nerve fibres in this tract. More severe degeneration of the fibres at the level of the pons than the crus cerebri indicates that degeneration of the fibres may start axodistally. Electron microscopy revealed selective involvement of large fibres in olivopontocerebellar atrophy, in contrast to unselective axonal atrophy in dentatorubropallidoluysian atrophy. The problem whether the degeneration of the tract is primary or secondary due to the loss of the pontine neurons remains open. We believe the former to be most likely. Degeneration of the corticopontine fibres should be added to the list of neuropathological findings in sporadic olivopontocerebellar atrophy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01600284
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  • 8
    Digitale Medien
    Digitale Medien
    Large cell anaplastic lymphoma: Evaluation of immunophenotype on paraffin and frozen sections in comparison with ultrastructural features (1991)
    Springer
    Virchows Archiv 418 (1991), S. 427-433 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Large cell anaplastic lymphoma ; Electron microscopy ; Immunophenotyping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Eleven cases of large cell anaplastic lymphoma (T typen=5, B typen=4, 0 typen=2) were investigated using electron microscopy and immunophenotyping on formalin-fixed paraffin sections and frozen sections of fresh tissue, to determine whether morphological criteria exist for the discrimination of T, B, and 0 phenotypes. Tumour cell lineage could not be established from ultrastructural features. On paraffin material monoclonal B-cell markers Ki-B5 and L-26 served as reliable tools for recognizing the B phenotype of large cell anaplastic lymphomas (previously determined on fresh material), whereas monoclonal antibodies MT1 (CD43) and UCHL1 (CD45RO) were of limited value in lineage determination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01605929
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  • 9
    Digitale Medien
    Digitale Medien
    Ultrastructural lipid and glycoconjugate cytochemistry of membranous lipodystrophy (Nasu-Hakola disease) (1991)
    Springer
    Virchows Archiv 419 (1991), S. 137-142 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Membranous lipodystrophy ; Nasu-Hakola disease ; Lipid and glyconconjugate ; Cytochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In order to assess the lipid and glycoconjugate characteristics of membranous lipodystrophy, a 29-year-old male with this disease was studied using an ultrastructural cytochemical approach. The specific membranocystic lesions of the disease are composed of cystic spaces and the lining membranes. The membranes were observed to have a two-layered character: microtubular structures in the layer adjacent to the spaces and a central amorphous zone. Lipid staining and the lipase digestion test revealed triglycerides localized not only in the cystic spaces but also in the microtubular structures. Lectin histochemical examintion of carbohydrate components demonstrated thatMaclura pomifera agglutinin bound strongly to the membranes, whileGriffonia simplicifolia I,G. simplicifolia II,Concanavalia ensiformis andTriticum vulgaris agglutinin reacted weakly. Our results indicate the presence of triglycerides and carbohydrates with mainlyα-D-galactose residues in the distinctive membranocystic lesions, in particular in the microtubular structures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01600227
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  • 10
    Digitale Medien
    Digitale Medien
    Photodynamic therapy of bladder cancer —uptake and phototoxicity of photosan in vitro (1991)
    Springer
    Urological research 19 (1991), S. 353-356 
    Details
    ISSN: 1434-0879
    Schlagwort(e): Bladder cancer ; Electron microscopy ; Photodynamic therapy ; Photosan ; Phototoxicity ; Tumor selectivity ; Video fluorescence microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The uptake of photosan and the intracellular sites of photoradiation-induced damage were investigated in vitro in bladder carcinoma cells and in normal bladder cells. Cells were examined by phase contrast, fluorescence and electron microscopy. The concentration of photosan, measured in μg/106 cells, showed a good correlation to the incubation time. At all incubation times, control cells showed a lower uptake when compared with tumor cells. Following photodynamic therapy (PDT), phase-contrast microscopy revealed marked changes in tumor cells, whereas only minor effects could be detected at the cell membrane of the control cells. Following PDT, most of the investigated cells showed onanges of the mitochondria and cytoplasma. These changes consisted of dissolution of the cristae, predominantly in the central part of the mitochondria. Twenty-four hours after PDT the shape of the mitochondria had changed markedly and the cristae were found to be completely destroyed. Moreover, the cystoplasma showed numerous vacuoles, and the number of mitochondria was decreased compared to non-treated cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00310149
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  • 11
    Digitale Medien
    Digitale Medien
    Widely distributed Bunina bodies and spheroids in a case of atypical sporadic amyotrophic lateral sclerosis (1991)
    Springer
    Acta neuropathologica 81 (1991), S. 349-353 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Amyotrophic lateral sclerosis ; Bunina body ; Clarke's nucleus ; Onuf's nucleus ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We report the autopsy findings of an 81-year-old patient with short-course sporadic amyotrophic lateral sclerosis lasting approximately 5 months. Pathological findings were probably very early. Light microscopy showed abundant eosinophilic Bunina type inclusions widely distributed not only in the motor neurons of the spinal cord and brain stem but also in neurons of the Onuf's and Clarke's nuclei. Fine structural study revealed that the inclusions seen in the Clarke's nuclei were identical to Bunina bodies observed in anterior horn cells. A direct connection between axonal swelling and perikaryon was often seen in the facial and hypoglossal nuclei and in the spinal cord. Ubiquitin-positive Lewy body-like inclusions and central chromatolysis-like changes were also found in the anterior horn cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305880
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  • 12
    Digitale Medien
    Digitale Medien
    Distribution of synapses on an intracellularly labeled small pyramidal neuron in the cat motor cortex (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 313-318 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Pyramidal neurons ; Motor cortex ; Synapses ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The morphological characteristics and distribution of synapses on a small pyramidal neuron in layer III of the cat motor cortex have been studied by combining intracellular HRP staining and electron microscopic examination. The stained neuron showed spiny apical and basal dendritic profiles under the light microscope, and exhibited the morphological features of a pyramidal neuron. Ultrastructural analysis indicated that about 80% of the presynaptic terminals formed asymmetrical synapses with spines of distal apical and basal dendrites. On proximal apical dendrites, 64% of the synapses were found to make contact with spines, and 16.7% of the synapses were of symmetrical type and formed with dendritic shafts. Two types of terminal could be identified on the soma; they were alternately located and established symmetrical and asymmetrical synaptic contacts respectively. Possible functional implications are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01673266
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  • 13
    Digitale Medien
    Digitale Medien
    The costo-uterine muscle of the rat (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 337-343 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Costo-uterine muscle ; Innervation ; Fluorescence histochemistry ; Electron microscopy ; Morphometry ; Rat (Wistar)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The costo-uterine muscle provides a skeletal attachment to the longitudinal myometrial layer of the uterine horn. In this study we investigated the possibility that the muscle is responsive to sex steroid hormones. In rats of 4 weeks of age, injected with oestradiol for 5 days, the cross-sectional area of nucleated muscle cell profiles was significantly increased. A significant increase in the sectional area of muscle cells was also demonstrated in the costo-uterine muscle of 16-week-old rats, on the 20th day of gestation, compared with nonpregnant rats in dioestrus and of the same age. In oestrogen-treated and in pregnant rats, there was also an increase in muscle cell length. As to the innervation of the costo-uterine muscle, in glyoxylic acid-treated whole-mount and cryostat preparations, we found not only perivascular nerve fibres, but also a few nerve fibres innervating the muscle proper. The pattern of innervation was unchanged after oestrogen treatment and during pregnancy. In the electron microscope, axonal varicosities were observed in the proximity of both vascular and non-vascular muscle cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00957895
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  • 14
    Digitale Medien
    Digitale Medien
    Ultrastructural changes in the gracile nucleus of the rat after sciatic nerve transection (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 591-604 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Spinal nerves ; Dorsal column nuclei ; Nerve degeneration ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ultrastructural changes in the gracile nucleus of the rat have been examined after peripheral nerve injury. The sciatic nerve of adult rats was transected at mid-thigh level, and after survival times ranging from 1 day to 32 weeks sections from the gracile nucleus were prepared for electron microscopic examination. Unoperated animals served as controls. Atypical profiles were regularly observed in the experimental cases at post-operative survival times from 3 days up to 32 weeks. It was sometimes not possible to classify these as pre-terminal axons or terminals, because synaptic contacts could not be identified. The two most common changes throughout the entire post-operative period were greatly expanded myelinated axons, or unmyelinated profiles containing numerous mitochondria, osmiophilic dense bodies and vacuoles. Atypical profiles were occasionally observed in unoperated control animals. The results clearly show that various types of degenerative changes occur in the gracile nucleus after peripheral nerve injury. These changes differ markedly from previously described transganglionic changes in other systems. It cannot be excluded that some of the changes reflect growth-related reactions, although the typical features of axon regeneration could not be found.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00942581
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  • 15
    Digitale Medien
    Digitale Medien
    Elucidation of three-dimensional ultrastructure of Hirano bodies by the quick-freeze, deep-etch and replica method (1991)
    Springer
    Acta neuropathologica 81 (1991), S. 248-254 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Hirano bodies ; Unit lamellae ; Alzheimer's disease ; Rapid-freeze, deep-etch and replica ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To clarify the yet controversial fine structure of Hirano bodies, we made three-dimensional observations of the tissues from the right hippocampus obtained at autopsy of elderly patients by the quick-freeze, deep-etch and replica method. The basic structure of Hirano bodies was a unit lamella, a closely attached pair of sheets composed of parallel-running smooth filaments, 10 to 12 nm in diameter with 12-nm interspaces. In the unit lamella, filaments from each of the overlapping sheets crossed obliquely at acute or obtuse angles to form lattice-like meshworks. The unit lamellae were arranged in a folded, waved or concentric manner, and connected or supported by cross-linking filaments of the same width. The distance between these unit lamellae was about 50 nm. Occasionally the sheets were separated or fused making layers of one to three sheets. At the periphery of the bodies parallel filaments were dispersed into individual filaments of similar size or directly attached to the cytoplasmic membrane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305865
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  • 16
    Digitale Medien
    Digitale Medien
    Light and electron microscopic and immunohistochemical observations of the Onuf's nucleus of amyotrophic lateral sclerosis (1991)
    Springer
    Acta neuropathologica 81 (1991), S. 610-614 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Amyotrophic lateral sclerosis ; Bunina body ; Onuf's nucleus ; Ubiquitin ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We examined the Onufrowicz nucleus (Onuf's nucleus) of ten sporadic amyotrophic lateral sclerosis (ALS) patients with light and electron microscopic and immunohistochemical methods. Neurons in the Onuf's nucleus of ALS patients were better preserved than those in anterior horn cells. However, some showed morphological changes in the nucleus, namely, central chromatolytic changes, Bunina bodies, ubiquitin-positive filaments and spheroids. The Onuf's neurons of ALS patients showed more argentophilia than those of non-ALS patients. Electron microscopic observations revealed that neurofilaments were relatively more numerous in the Onuf's neurons of ALS patients. Bunina bodies and degenerated neurites were also seen in the Onuf's nucleus. In conclusion, the Onuf's nucleus in sporadic ALS patients showed some morphological changes similar to those noted in anterior horn cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00296370
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  • 17
    Digitale Medien
    Digitale Medien
    Ultrastructure of diffuse plaques in senile dementia of the Alzheimer type: comparison with primitive plaques (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 13-20 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Alzheimer-type dementia ; Senile plaques ; Amyloid β/A4 protein ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We compared the ultrastructure between diffuse and primitive plaques in the brains of senile dementia, using pairs of routine electron microscopic ultrathin sections and adjacent semithin sections, which were immunolabeled for β protein. In the frontal cortex, amyloid fibrils were rarely seen in a minority of diffuse plaques, suggesting an initial stage of the diffuse plaques. A majority of the diffuse plaques had electrondense material and/or amyloid fibrils between cell processes in part of but not the entire β/A4-immunoreactive areas. Small degenerating neurites were often seen with apparent amyloid fibrils in the diffuse plaques, and these were considered to be in an advanced stage. The size and number of degenerating neurites were proportional to the amount of amyloid. Bundles of amyloid fibrils were occasionally surrounded by astroglial processes forming gap junctions. Neurons were found within some diffuse plaques, but capillaries were rarely seen. In contrast, in the temporal cortex, the diffuse plaques were smaller, and even these small ones had apparent amyloid fibrils. The amount of amyloid correlated significantly with plaque size in the temporal cortices, but not in the frontal cortices. Most of the diffuse plaques of the frontal lobe remained as advanced diffuse plaques (apparent amyloid with occasional astroglia and some degenerating neurites) for a long time, and did not transformed into primitive plaques, whereas the temporal diffuse plaques tended to transform into primitive plaques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00310918
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  • 18
    Digitale Medien
    Digitale Medien
    Microtubule bundles in fish cerebellar Purkinje cells (1991)
    Springer
    Anatomy and embryology 183 (1991), S. 105-110 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Initial axon segment ; Microtubules ; Cross-bridges ; Golgi apparatus ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The initial axon segments and the cell bodies of Purkinje cells were examined in electron microscopic serial sections and toluidine blue semithin sections of goldfish cerebellum. We observed two characteristic cytoplasmic features different from those of other vertebrate neurons. 1. The areas of Nissl substance and Golgi apparatus are sharply divided in the periphery and center of the cytoplasm. 2. Microtubules fasciculated by cross-bridges in the axon hillock and initial axon segment remain bundled in the perikaryon, pass near the eccentric nucleus, and enter into the Golgi area of the central cytoplasm, where they are surrounded by mitochondria. We suggest that the intracellular fasciculated microtubules may establish a prepared pathway for fast anterograde and retrograde transport to and from the Golgi area of the cell body.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00174390
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  • 19
    Digitale Medien
    Digitale Medien
    Elastic-like tissue, a new component of the renal glomerular capillary wall in a cartilaginous fish (1991)
    Springer
    Anatomy and embryology 183 (1991), S. 475-481 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Elastic-like tissue ; Elasmobranch ; Glomerular capillary wall ; Kidney ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Elastic-like tissue composed of tubular microfibrils continuous with, and disappearing into, amorphous material is present in the connective tissue space of the glomerular capillary wall of the river ray (freshwater elasmobranch) kidney. The amorphous material is stained by tannic acid but not by uranyl acetate. Structures with similar morphology and staining characteristics are also found in the subendothelial connective tissue layer of renal arteries in this species. Comparative ultrastructural observations of kidneys from marine rays show elastic-like tissue in the arterial wall but not in the glomerular vessels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00186436
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  • 20
    Digitale Medien
    Digitale Medien
    Immunohistochemistry of primitive neuroectodermal tumors in infants with special emphasis on cytokeratin expression (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 494-501 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Primitive neuroectodermal tumor ; Cytokeratin immunohistochemistry ; Double labelling ; Electron microscopy ; Immunoblotting
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Eleven primitive neuroectodermal tumor (PNET) biopsies from infants under the age of 3 years were studied for the presence of various differentiation markers for neuroectodermal stem cells. Special emphasis was placed on the expression of cytokeratin proteins. The tumor cells expressed different cytokeratin proteins (CK8, CK13, CK18, CK19, KL1, AE1/AE3, MNF16) in 3 of 11 cases. These cases were furthermore characterized by a strong expression of glial fibrillary acidic protein, S-100 protein and vimentin. Vimentin and cytokeratin proteins were co-expressed; cross-reactivity between these two intermediate filaments could be excluded by immunoblotting. It is noteworthy that the three positive tumors were all from infants in their 1st year. We assume that PNETs in early infancy are characterized by a particularly wide range of differentiation patterns. The presence of cytokeratin proteins in these cases seems to be associated with the expression of vimentin and must be regarded as an indicator of an early developmental stage of the tumor cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00293384
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  • 21
    Digitale Medien
    Digitale Medien
    Recessive ichthyosis congenita type II (1991)
    Springer
    Archives of dermatological research 283 (1991), S. 211-218 
    Details
    ISSN: 1432-069X
    Schlagwort(e): Ichthyosis ; Histopathology ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the hetereogeneous group of recessive congenital ichthyoses the disorder of desquamation seems to be a basic problem. Desquamation is strongly dependent on the normal lipid metabolism of the keratinocytes. We describe a group of patients who have a typical clinical picture of large scale ichthyosis and cholesterol clefts in the thickened corneal layer, evidencing a disturbance of the lipid metabolism of the skin. The corneocytes also show a thin or absent cornified envelope, which could indicate a disturbance of protein synthesis. These patients have a severe ichthyosis, but good general health and no associated symptoms. This disorder has recently been named ‘ichthyosis congenita type II’ by the Heidelberg group on the basis of electron microscopic findings. According to the present examination this group corresponds clinically to the currently used diagnosis ‘lamellar ichthyosis’.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01106104
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  • 22
    Digitale Medien
    Digitale Medien
    The effect of the proteolytic enzyme savinase on human plantar skin in vitro (1991)
    Springer
    Archives of dermatological research 283 (1991), S. 377-381 
    Details
    ISSN: 1432-069X
    Schlagwort(e): Savinase ; Proteolytic enzyme ; Human plantar skin ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of the proteolytic enzyme savinase on human plantar skin in vitro was examined by light and electron microscopy to elucidate the morphological involvement of activated savinase in human epidermis. Light microscopic examination of incubated skin fragments demonstrated that the histological changes produced by savinase in the epidermis, including the stratum corneum, depended upon pH value, enzyme concentration and incubation time. After incubation in 0.1% savinase in phosphate buffer, pH 8.0, for 2 h at 35
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00371819
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  • 23
    Digitale Medien
    Digitale Medien
    Ultrastructure of giant and small thalamic terminals of cortical origin: a study of the projections from the barrel cortex in mice using Phaseolus vulgaris leuco-agglutinin (PHA-L) (1991)
    Springer
    Experimental brain research 87 (1991), S. 159-172 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Corticothalamic projection ; Somatosensory system ; Barrel ; Phaseolus vulgaris ; leucoagglutinin ; Electron microscopy ; Mouse ; Synaptic glomerulus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary By means of tracing with the lectin Phaseolusvulgaris leucoagglutinin (PHA-L), we examined in the thalamus of the mouse, the axon terminals of fibers originating in the barrel cortex. Vibratome sections of the brain were subjected to PHA-L immunocytochemistry and processed for light and electron microscopy. We observed small (0.5–0.8 μm in diameter) varicosities of labeled fibers in the nucleus ventrobasalis (VB) and the nucleus posterior (PO) as well as labeled giant terminals (3–5 μm in diameter) in PO. The analysis involved examination of serial sections and computer-aided reconstruction of several terminals. The small varicosities in VB appear to be small axon terminals forming distinct asymmetric synapses with small dendritic profiles. Some labeled terminals are apposed to, but not synaptically related with, the cell bodies of neurons in VB that are retrogradely labeled with PHA-L. The small varicosities seen with the light microscope in PO are terminals forming asymmetric synapses with dendritic shafts. The giant terminals in PO appear as large, vesicle-filled profiles forming part of synaptic glomeruli, i.e. complexes of one corticothalamic terminal engulfing several excrescences of a single dendrite. A giant terminal forms several asymmetric synapses (about 8) with these excrescences, as well as numerous (up to 15) puncta adhaerentia. The glomeruli are enveloped in glial lamellae, and they are often found at the bifurcations of primary dendritic segments. We suggest that the small terminals in VB are in the service of feedback signalling from the barrel cortex to its principal thalamic relay nucleus; the functional importance of this projection may reside in increased spatio-temporal discrimination. We interpret the giant terminals in PO as elements serving feed-forward processing, allowing the barrel cortex to influence, via PO, parts of the motor pathway modulating the animal's ongoing behavior.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228517
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  • 24
    Digitale Medien
    Digitale Medien
    The fine structure of serotonin and tyrosine hydroxylase immunoreactive terminals in the ventral posterior thalamic nucleus of cat and monkey (1991)
    Springer
    Experimental brain research 85 (1991), S. 507-518 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Serotonin ; Tyrosine hydroxylase ; Electron microscopy ; Thalamus ; Cat ; Monkey
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Immunocytochemical methods have been combined with serial thin section analysis to study the synaptic organization of serotonin (5-HT) and tyrosine hydroxylase (TH) immunoreactive terminals in the ventral posterior nucleus of the cat and monkey thalamus. One hundred 5-HT immunoreactive terminals from the cat and approximately forty 5-HT and TH immunoreactive terminals from the monkey were selected for analysis in serial thin sections. Only 7–10% of the immunoreactive terminals could be revealed to form conventional synaptic contacts. Most of these could be identified as the asymmetrical type. Dendritic shafts belonging to relay neurons were the major targets of these monoamine immunoreactive terminals. The remainder made intimate membrane associations with relay cell dendrites and somata or with presynaptic dendrites of interneurons, but no overt membrane specializations could be detected. The present results suggest that the modulation of thalamocortical relay function by brainstem monoamine pathways in the somatosensory thalamus may occur by release of transmitters at atypical contact sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00231734
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  • 25
    Digitale Medien
    Digitale Medien
    Corneal edema induced by bis (tributyltin) oxide (1991)
    Springer
    Archives of toxicology 65 (1991), S. 651-655 
    Details
    ISSN: 1432-0738
    Schlagwort(e): Bis (tributyltin) oxide ; Corneal edema ; Electron microscopy ; X-ray microanalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Comeal edema induced by bis (tributyltin) oxide (TBTO) was studied with an electron microscope and the accumulation sites of tin were determined with an X-ray microanalyzer. Male Wistar rats received an intramuscular injection of 0.5 ml/kg TBTO. After time intervals of 2,4, 6, 8, 10, 12 h after injection, corneas were isolated and provided for electron microscopy. Corneas from untreated rats served as controls. Marked swelling of mitochondria in the corneal endothelial cells occurred at 4 h after TBTO injection. The corneal edema appeared in the endothelial layer and the stroma at 6 h after injection. By X-ray microanalysis, Sn peaks were obtained from swollen mitochondria in the endothelial cells. At 12 h after TBTO injection, edematous swelling of the corneal tissue became more advanced. These results indicated that parenterally administered TBTO accumulated in the mitochondria of corneal endothelial cells. The direct toxic effects of TBTO on the mitochondria might cause the interference with active pump function of endothelial cells and induced the corneal edema.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02098031
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  • 26
    Digitale Medien
    Digitale Medien
    In vitro and in vivo uptake of nickel sulfides by rat lymphocytes (1991)
    Springer
    Archives of toxicology 65 (1991), S. 324-329 
    Details
    ISSN: 1432-0738
    Schlagwort(e): αNi3S2 ; βNiS ; Rat lymphocytes ; Electron microscopy ; Energy dispersive spectrometry ; Sulfur phosphorus shift ; Biological transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The uptake, the biological transformation and the interaction with cellular constituents of αNi3S2 and βNiS have been studied in vitro and in vivo on rat lymphocytes. βNiS crystals are phagocytized in vitro and no structural degradation is observed within the first 3 days of exposure. Energy dispersive spectrometry (EDS) reveals a slight dissolution characterized by the loss of sulfur. αNi3S2 is degraded in the extracellular space to minute particles (50–100 nm) covering the cell membrane. Smaller intracellular particles (10–30 nm) are found selectively bound to mitochondria, endoplasmic reticulum, Golgi vesicles, nuclear membranes, and the euchromatinic part of nuclei. EDS analyses reveal that the particles bound to cell membranes and euchromatin no longer contain sulfur but phosphorus and nickel as inorganic compounds. This observation suggests the formation of a Ni/P complex with the phosphate groups either of membranous phospholipids or of nuclear RNA or DNA. A similar uptake and transformation process of αNi3S2 is observed on lymphocytes after in vivo incubation. This leads us to consider lymphocytes as target cells, as compared with other cell types where the αNi3S2 uptake occurs only partially. The present findings show a difference of uptake and biological transformation between αNi3S2 and βNiS. The identical results obtained after in vitro and in vivo bioassays enhance the in vitro experiments, at least for this cell type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01968967
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  • 27
    Digitale Medien
    Digitale Medien
    Surface reconstruction from stereoscopy and “shape from shading” in SEM images (1991)
    Springer
    Machine vision and applications 4 (1991), S. 271-285 
    Details
    ISSN: 1432-1769
    Schlagwort(e): Electron microscopy ; three-dimensional vision ; surface reconstruction ; stereo ; shape from shading ; dynamic programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract The computational reconstruction of surface topographies from scanning electron microscope (SEM) images has been extensively investigated in the past, but fundamental image processing problems still exist. Since conventional approaches adapted from general-purpose image processing have not sufficiently met the requirements in terms of resolution and reliability, we have explored combining different methods to obtain better results. This paper presents a least-squares combination of conventional stereoscopy with “shape from shading” and a way of obtaining self-consistent surface profiles from stereoscopy and “stereo-intrinsic shape from shading” using dynamic programming techniques. Results are presented showing how this combined analysis of multi-sensorial data yields improvements of the reconstructed surface topography that cannot be obtained from individual sensor signals alone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01815304
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  • 28
    Digitale Medien
    Digitale Medien
    Structural aspects of the soluble NAD-dependent hydrogenase isolated from Alcaligenes eutrophus H16 and from Nocardia opaca 1b (1991)
    Springer
    Archives of microbiology 155 (1991), S. 303-308 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Soluble NAD-dependent hydrogenase ; Alcaligenes eutrophus ; Nocardia opaca ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The soluble NAD-dependent hydrogenase (hydrogen-NAD oxidoreductase, EC 1.12.1.2), consisting of four non-identical subunits, was isolated from Alcaligenes eutrophus H16 and from Nocardia opaca 1b and analyzed by a HPLC gel permeation technique and electron microscopy. The tetrameric enzyme particles from both origins, as determined from negatively stained electron microscopic samples, were found to be elongated and very similar in shape and size. The A. eutrophus enzyme was measured in more detail. It exhibited dimensions of 12.7 nm by 5.5 nm (axial ratio 2.3:1). Dissociation into smaller particles and unspecific aggregation combined with partial inactivation were observed in the presence of the inhibitor NADH. Kept in buffer without added nickel, the enzyme was partially dissociated. Reassociation of tetramers without restored enzyme activity was achieved by addition of 0.5 mM NiCl2. A working model for the structural organization of the tetrameric enzyme particle is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00252217
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  • 29
    Digitale Medien
    Digitale Medien
    Serotonergic effects on carbonic anhydrase activity in the choroid plexus (1991)
    Springer
    Child's nervous system 7 (1991), S. 442-447 
    Details
    ISSN: 1433-0350
    Schlagwort(e): Acetazolamide ; Carbonic anhydrase activity ; Choroid plexus ; Electron microscopy ; Serotonin ; Tetrabenazine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The carbonic anhydrase (CA) activities in the choroid plexus of dogs were investigated by electron microscopy, and the effects of 5-hydroxytryptophan (5-HTP) on them were examined to elucidate the participation of serotonin in the production of cerebrospinal fluid. The reaction products yielded by the method employed proved to be CA activity by elimination tests using acetazolamide (Diamox). Following administration of 5-HTP, the CA activities fell to 43.3% of the control value, that is, approximately 56% of the CA activities in the choroid plexus were affected by serotonin. When tetrabenazine (TBZ) was administered, the CA activities in the choroid plexus decreased to 22.4% of the control value. These results suggest that the CA activity in the choroid plexus is remarkably suppressed when nervous control of the choroid plexus is disturbed by the administration of a monoamine denervator such as TBZ. The present data indicate that the serotonergic inhibitory effect on the CA activity in the choroid plexus may be less predominant than that of TBZ and acetazolamide.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00263186
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  • 30
    Digitale Medien
    Digitale Medien
    A cytochemical and immunocytochemical study of DNA distribution in spermatid nuclei of mouse, rabbit, and bull (1991)
    Springer
    Cell & tissue research 265 (1991), S. 517-525 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Spermiogenesis ; Spermatids ; DNA ; Immunocytochemistry ; Electron microscopy ; Bovine ; Mouse ; Rabbit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary DNA distribution in mouse, rabbit and bull spermatids was analyzed by electron microscopy, after using a Feulgen-like HCl-osmium ammine procedure, and after immunocytochemistry with anti-DNA antibodies. In addition, nucleic acids were visualized with the intercalating dye ethidium bromide and phosphotungstic acid. The parts of DNA displaying a beta helix configuration (possibly A-T rich parts) were identified by epifluorescence microscopy after staining with Hoechst 33258. In all 3 species, young spermatid nuclei were seen to have large areas poor in DNA, as well as DNA-rich areas, which were mostly concentrated into a peripheral layer close to the acrosome and into one or several masses, displaying species-specific locations. These DNA-rich areas were stained with Hoechst 33258. Elongating spermatid nuclei contained homogeneously distributed DNA, and this was evident following both immunocytochemistry and nucleic acid histochemistry in all 3 species. However, the distribution appeared more heterogeneous after the Feulgen-like procedure, and was accompanied by a disappearance of Hoechst-fluorescence. In fully elongated spermatids, all nuclear areas stained with Hoechst 33258, while the 3 other techniques labeled either all or species-specific parts of the condensed chromatin. The reasons for these variable reactions are discussed in terms of technique specificities, DNA configuration and nucleoprotein moiety replacements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00340875
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  • 31
    Digitale Medien
    Digitale Medien
    Transient expression of a calcium-binding protein (spot 35-calbindin) and its mRNA in the immature pituicytes of embryonic rats (1991)
    Springer
    Cell & tissue research 266 (1991), S. 325-330 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Calbindin ; Neurohypophysis ; Development, ontogenetic ; Immunohistochemistry ; In-situ hybridization ; Electron microscopy ; Rat (Wistar)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Spot 35 protein is a Ca-binding protein originating from the rat cerebellum; it is now referred to spot 35-calbindin. This protein is expressed in immature pituicytes of the neurohypophyseal anlage in the E11–E18 rat embryo. The gene expression of spot 35-calbindin was detected by in-situ hybridization analysis only at stage E11–E12. Profiles of spot 35-positive nerve fibers of a neurosecretory nature were found in anlage at stage E16. At this stage, some immature pituicytes are partially immunopositive for spot 35-calbindin only in their peripheral cytoplasm; others are immunonegative. At birth and thereafter through adulthood, abundant nerve fibers are the sole structures immunoreactive for spot 35-calbindin; all the pituicytes are immunonegative, resulting in a light-microscopic appearance of numerous immunonegative round profiles, corresponding to pituicytes, and capillaries embedded in the granularly immunostained neurohypophysis. The present findings suggest that, during specific embryonic stages, immature pituicytes exert some as yet unidentified roles related to Ca-mediated functions involving the expression of spot 35-calbindin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318188
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  • 32
    Digitale Medien
    Digitale Medien
    Development of the basal lamina in xenografted human carcinomas: an ultrastructural and immunohistochemical study (1991)
    Springer
    Cell & tissue research 266 (1991), S. 563-578 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Xenografted human carcinomas ; Basal lamina ; Development, following heterotransplantation ; Electron microscopy ; Immunofluorescence microscopy ; Man ; Mouse (NMRI, nu/nu)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The development of the basal lamina (BL), the key structure of the basement membrane (BM), was investigated in three xenografted human carcinomas of the sigmoid colon (CA 1), the lung (L 261), and the hypopharynx (H-Stg 1) following heterotransplantation to athymic mice. The study involved the use of electron microscopy and indirect immunofluorescence techniques employing highly specific antibodies against the intrinsic BL components, heparan sulfate proteoglycan, laminin and type-IV collagen. Following transplantation, the extracellular matrix material of the transplanted tumors decomposed and was phagocytozed by invading macrophages within 1 to 2 days. During this stage, no specific binding of the applied antibodies to BL components could be detected within the xenografts. Following the ingrowth of host-derived connective tissue between days 2 to 6, small fluorescence-positive granules appeared within the cytoplasm and around those tumor cells that were located close to the invaded strands of connective tissue. Ultrastructurally, typical secretory granules were detectable in the cytoplasm of many xenografted carcinoma cells. Thereafter, a tannic acid-positive, patchy material appeared in the extracellular space of CA 1 and L 261 and aggregated to form small fragments of a discontinuous BL. In the H-Stg 1 xenografts, this material assembled to form continuous mono-, bi- and multilayered structures. Large amounts of excess BL material remained accumulated in the L 261 and H-Stg 1 xenografts until the end of the observation period (day 24). These findings reveal that discontinuities of the BL occur independent of the active invasion processes of tumor cells, since xenografted human carcinomas neither grow invasively nor metastasize in nude mice. Moreover, they confirm that these discontinuities are not caused by a quantitatively insufficient production of BL material, but rather arise from qualitative imbalances of the composition of the synthesized BL material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318598
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  • 33
    Digitale Medien
    Digitale Medien
    Initiation of acellular extrinsic fiber cementum on human teeth (1991)
    Springer
    Cell & tissue research 263 (1991), S. 311-324 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Dental root surface ; Periodontal fiber fringe ; Dentino-cemental junction ; Electron microscopy ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The development of acellular extrinsic fiber cementum (AEFC) has never before been studied in human teeth. We have therefore examined the initiation of AEFC in the form of a collagenous fiber fringe and its attachment to the underlying dentinal matrix, in precisely selected, erupting human premolars with roots developed to 50%–60% of their final length. Freshly extracted teeth were prefixed in Karnovsky's fixative, decalcified in EDTA and subdivided into about 10 blocks each, cut from the mesial and distal root surfaces, vertical to and along the root axis. The blocks were postfixed in osmium tetroxide, embedded in Epon and cut for light- and electron-microscopic investigation. Starting at the advancing edge of the root, within a region extending about 1 mm coronal to this edge, fibroblast-like cells were seen closely covering the external root surface. Along the first 100 μm from the root edge, these cells extended cytoplasmic processes and contacted the dentinal collagen fibrils. Between these cells and the dentinal matrix, new collagen fibrils and very short collagen fibers gradually developed. Within the second 100 μm from the root edge, this resulted in the formation of a cell-fiber fringe network. Newly formed fibers of the fringe were directly attached to the non-mineralized matrix containing dentinal collagen fibrils and could be distinguished from the latter by differences in fibril orientation. During the process of dentin mineralization, the transitional zone between the fiber-fringe base and the dentinal matrix, i.e., the future dentino-cemental junction, also mineralized. It is suggested that this fiber fringe is the base of AEFC, which later increases in thickness by fiber extension and subsequent mineralization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318773
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  • 34
    Digitale Medien
    Digitale Medien
    Establishment of acellular extrinsic fiber cementum on human teeth (1991)
    Springer
    Cell & tissue research 263 (1991), S. 325-336 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Cementum ; Fiber fringe ; Periodontal ligament fibers ; Dentino-cemental junction ; Electron microscopy ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The present study describes for the first time the development of early acellular extrinsic fiber cementum (AEFC) until its establishment on human teeth. Precisely selected premolars with roots developed to 50%–100% of their final length were prefixed in Karnovsky's fixative and most of them were decalcified in EDTA. Their roots were subdivided into about 10 blocks each, cut from the mesial and distal root surfaces. Following osmication, these blocks were embedded in Epon and sectioned for light-and transmission electron microscopy. Some blocks were cut non-demineralized. From semithin stained sections, the density of the collagenous fiber fringe protruding from the root surface was measured by using the Videoplan-system. After initiation of this fiber fringe and its attachment to the dentinal root surface followed by mineralization, the fringe gradually increased in length and subsequently became mineralized. Fringe elongation and the advancement of the mineralization front appeared to progress proportionally. Thus, in all stages of AEFC development, a short fiber fringe covered the mineralized AEFC. Its density remained constant, irrespective of AEFC thickness. The latter gradually increased and reached an early maximum of 15–20 μm in the cervical region. At this stage, the AEFC fringe appeared to fuse with the future dentogingival or other collagen fibers of the tooth supporting apparatus. Mineralization of the fringe commenced with isolated, spherical or globular centers, which later fused with the mineralization front and became incorporated in AEFC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318774
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  • 35
    Digitale Medien
    Digitale Medien
    Ultrastructural study of a cytoplasmic bridge connecting a pair of erythroblasts in mice (1991)
    Springer
    Cell & tissue research 264 (1991), S. 215-219 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Erythroblast ; Cytokinesis ; Cytoplasmic bridge ; Fetal liver ; Erythropoiesis ; Electron microscopy ; dd Mice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A unique cytoplasmic connection between erythroblasts was studied by electron microscopy in mouse hemopoietic tissues (fetal liver, fetal and neonatal spleen and adult bone marrow). Many pairs of interphase erythroblasts were connected by a “cytoplasmic bridge” that was very thin and sometimes long in comparison with telophase bridges. The stage of maturation of the cells in a pair was similar. Small numbers of microtubules ran along the cytoplasmic bridge; a mid-body was not seen. The plasma membrane at approximately the middle of the bridge bulged to form a ring-shaped ridge filled with dense amorphous substances; this was called a “bulging ring”. Thus, the cytoplasmic bridge between erythroblasts did not morphologically correspond to the telophase bridge in the usual cytokinesis. Cytoplasmic bridges were observed in various differentiating stages of erythroblasts, whereas other cell types of the hemopoietic lineage did not have such a bridge. The cytoplasmic bridge is unique to erythroblasts and provides an evidence for the atypical cytokinesis of the erythroblastic lineage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00313958
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  • 36
    Digitale Medien
    Digitale Medien
    Regulation of nuclear membrane assembly and maintenance during in vitro maturation of mouse oocytes: role of pyruvate and protein synthesis (1991)
    Springer
    Cell & tissue research 265 (1991), S. 105-112 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Oocytes ; Meiosis ; Energy metabolism ; Protein synthesis ; Nuclear envelope ; Electron microscopy ; Mouse (Swiss)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In the absence of a suitable energy source, mouse oocytes cultured in vitro resume, but fail to complete, meiotic maturation. However, little is known about the underlying mechanisms leading to this meiotic failure. We utilized pyruvate-deficient medium to test for the role of pyruvate throughout the meiotic maturation process. Germinal vesicle-stage (GV) oocytes underwent germinal vesicle breakdown (GVBD), but failed to form a polar body when cultured continuously in pyruvate-free medium. However, when GV oocytes were preincubated for 4 h in pyruvate-free medium containing dibutyryl cyclic adenosine monophosphate (dbcAMP) and then cultured in pyruvate-free medium, GVBD was markedly inhibited. Preincubation of GV oocytes in dbcAMP and cycloheximide, followed by culture in cycloheximide only, also inhibited GVBD. A longer preincubation period was required in the cycloheximide-dbcAMP case (12 h) than in pyruvate-free-dbcAMP medium situation (4 h). Strikingly, reassembly of the nuclear membrane without polar body formation was observed following GVBD in oocytes continuously cultured in pyruvate-free medium. The reassembled nuclear membrane increased in size with continued culture, and it surrounded partially-decondensed chromatin. Nuclear membrane reassembly also occurred in oocytes which had undergone GVBD during continuous culture in medium containing only cycloheximide. Reformation of nuclear membranes after GVBD was confirmed by electron-microscopic analyses of oocytes cultured in pyruvate-free medium or in the presence of cycloheximide. We conclude that both pyruvate and protein synthesis are required for nuclear membrane disassembly, whereas lack of pyruvate or protein synthesis is associated with interruption of the metaphase state and reassembly of the nuclear membrane. The evidence suggests that assembly and maintenance of an intact nucleus and its disintegration are all amenable to regulation by pyruvate, possibly via mechanism(s) involving protein synthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318144
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  • 37
    Digitale Medien
    Digitale Medien
    Barrier membranes at the outer surface of the brain of an elasmobranch, Raja erinacea (1991)
    Springer
    Cell & tissue research 265 (1991), S. 113-120 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Blood-brain barrier ; Glia ; Meninges ; Electron microscopy ; Skate, Raja erinacea (Elasmobranchii)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary This report gives the results of the first electron-microscopic examination of the cell layers covering the outer brain surface and the inner surface of the cartilaginous skull in the skate, Raja erinacea. The perivascular glial blood-brain barrier — a characteristic of elasmobranchs — extends to the outer surface of the brain. This outer barrier layer is surrounded, in turn, by a subarachnoid compartment (depth: 30–40 μm), containing loose connective tissue and blood vessels; by an arachnoid-like epithelium (10–15 cell layers), impermeable to horseradish peroxidase; and, by perimeningeal fluid, a fluid with a slow turnover rate and a protein composition different from plasma. The inside of the skull, facing the perimeningeal fluid, is covered by a multilayered (10–15 layers) cuboidal epithelium, also impermeable to horseradish peroxidase. Closely apposed cells in the luminal layer of this epithelium have apical microvilli and numerous vesicular profiles, containing material of moderate electron density. These observations may explain, in terms of structure, the regulated protein content of perimeningeal fluid and the restricted exchange of solutes between brain and perimeningeal fluid in elasmobranchs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318145
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  • 38
    Digitale Medien
    Digitale Medien
    Structural heterogeneity of the basement membrane in the rat proximal tubule (1991)
    Springer
    Cell & tissue research 266 (1991), S. 11-22 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Basement membrane ; Proximal tubule ; Hydraulic pressure ; Mechanical stress ; Electron microscopy ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructure of the basement membrane of the rat proximal tubule was observed by transmission electron microscopy after the use of a cold dehydration technique. The basement membrane of the P1 segment is thick and possesses several structural specializations that are rare in other basement membranes; these include intraepithelial ridges, dense bars, and basement membrane vesicles. The intraepithelial ridges are found in the intercellular spaces between interdigitating processes of the proximal tubule cells. The ridges and the interdigitating processes run circumferentially around the tubule. The dense bars are frequently found in the intraepithelial ridges. They are especially prominent on the concave side of the tubular bends and to a lesser extent near sites where intracellular actin filaments anchor onto the basal cell membranes. The basement membrane vesicles are bounded by unit membranes; they are variable in both their electron density and their size. They are usually found in association with dense bars, and the grade of their accumulation is positively correlated with the development of the dense bars. These three specializations have no topographical relationship with the interstitial structures, such as fibrobalasts and collagen fibrils. The specializations are best developed on the concave side of tubular bends where the circumferential stresses caused by the intraluminal hydraulic pressure are presumably the largest; we therefore propose that they are an adaptation to, or a manifestation of, the increased wall stress in the proximal tubule.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00678706
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  • 39
    Digitale Medien
    Digitale Medien
    An immunocytochemical study of the endocrine pancreas in the Australian fat-tailed dunnart (Sminthopsis crassicaudata) (1991)
    Springer
    Cell & tissue research 263 (1991), S. 195-198 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Pancreas, endocrine ; Islets of Langerhans ; Immunocytochemistry ; Endocrine cells four types ; Electron microscopy ; Sminthopsis crassicaudata (Marsupialia)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The endocrine pancreas of the Australian fattailed dunnart, Sminthopsis crassicaudata, was investigated by means of electron-microscopic immunocytochemistry using the protein A-gold technique on London resin (LR) white-embedded tissue. The primary antibodies used were raised against insulin, glucagon, somatostatin and pancreatic polypeptide. The morphology of the secretory granules differed in the four cell types. The insulin cells are pleomorphic, and the secretory granules composed of an electron-dense core surrounded by an electron-lucen halo. The glucago cells possess granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells have large, less dense secretory granules. The pancreatic polypeptide cells show small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by immunocytochemical data at the light-or preferably electron-microscopic level. Recent developments in immuno-electron-microscopic techniques have contributed to a better knowledge of cells responsible for the secretion of a wide variety of hormones, as in this study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318415
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  • 40
    Digitale Medien
    Digitale Medien
    Quantitative analysis of regional variability in the distribution of transverse tubules in rabbit myocardium (1991)
    Springer
    Cell & tissue research 264 (1991), S. 293-298 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Transverse (T-) tubules ; Muscle, cardiac ; Electron microscopy ; Morphometry ; Rabbit (Lagomorpha)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The goal of the present investigation was to compare quantitatively the distribution of T-tubules between regions of the myocardium. The volume fraction and surface density of T-tubules in rabbit right atrial free wall, left atrial free wall, right ventricular free wall, left ventricular free wall, right ventricular papillary muscle, and left ventricular papillary muscle were measured using established, electron-microscopic, morphometric techniques. T-tubules were delineated using wheat-germ agglutinin conjugated to horseradish peroxidase as a tracer. No significant differences were found in the morphometric parameters between any two ventricular samples or between atrial samples. Furthermore, little difference between T-tubule volume fraction or surface density was found between individual animals for any given site. Both volume fraction and surface density of ventricular T-tubules were more than ten-times their values in atrial tissue (volume fraction: 3.43%±0.35 vs. 0.20±0.09; surface density: 2.46 μm2/μm3±0.11 vs 0.10±0.04). Measurements show that there is greater variation of T-tubule volume fraction and surface density within atrial samples than within ventricular samples. This suggests greater inhomogeneity in T-tubule distribution in atrial myocardium than in ventricular myocardium. Morphometric data also indicate that the mean diameter of atrial T-tubules is greater than that of ventricular T-tubules while qualitative observations show that atrial T-tubules are distributed less regularly and have a larger longitudinal component to their organization than those in the ventricular myocardium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00313966
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  • 41
    Digitale Medien
    Digitale Medien
    Nerve growth factor receptor-like immunoreactivity in primary and permanent canine tooth pulps of the cat (1991)
    Springer
    Cell & tissue research 264 (1991), S. 321-328 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Tooth pulp ; NGF receptor ; Calcitonin gene-related peptide ; Substance P ; Neuropeptide Y ; Immunocytochemistry ; Electron microscopy ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The distribution of nerve growth factor receptor (NGF receptor)-like immunoreactivity in pulps of developing primary and mature permanent cat canine teeth was examined, by use of a monoclonal antibody against NGF receptor detected by fluorescence immunohistochemistry and pre-embedding immunocytochemical light- and electron microscopy. Both primary and permanent pulps contained a vast number of NGF receptor-like immunoreactive nerves. Immunolabelling appeared to be localized both to axons and Schwann cells. In addition, many blood vessel walls in immature primary tooth pulps showed NGF receptor-like immunoreactivity, in contrast to permanent pulps where blood vessels rarely were NGF receptor-immunoreactive. Double-labelling immunofluorescence experiments revealed that in the permanent pulp a majority of the NGF receptor-positive nerves also showed calcitonin gene-related peptide (CGRP)-like immunoreactivity, and many showed substance P-like immunoreactivity. However, nerve fibers with neuropeptide Y-like immunoreactivity lacked NGF receptor-like immunoreactivity. In developing primary tooth pulps fewer NGF receptor-positive nerves were CGRP-like immunoreactive or substance P-like immunoreactive, as compared to the permanent pulp. Neuropeptide Y-like immunoreactive nerve fibers were not detected in the primary tooth pulp. The results suggest a role for nerve growth factor in both developing and mature sensory nerves of the tooth pulp.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00313969
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  • 42
    Digitale Medien
    Digitale Medien
    Effects of prolonged sodium restriction on the morphology and function of rat adrenocortical autotransplants (1991)
    Springer
    Cell & tissue research 265 (1991), S. 35-41 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Adrenal autotransplants ; Sodium restriction ; Mineralocorticoid hormones ; Electron microscopy ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Regenerated adrenocortical nodules were obtained by implanting fragments of the capsular tissue of excised adrenal glands into the musculus gracilis of rats (Belloni et al. 1990). Five months after the operation, operated rats showed a normal basal blood level of corticosterone, but a very low concentration of circulating aldosterone associated with a slightly increased plasma renin activity (PRA). Regenerated nodules were well encapsulated and some septa extended into the parenchyma from the connective-tissue capsule. The majority of parenchymal cells were similar to those of the zonae fasciculata and reticularis of the normal adrenal gland, while zona glomerulosa-like cells were exclusively located around septa (juxta-septal zone; JZ). In vitro studies demonstrated that nodules were functioning as far as glucocorticoid production was concerned, while mineralocorticoid yield was very low. Prolonged sodium restriction significantly increased PRA and plasma aldosterone concentration, and provoked a marked hypertrophy of JZ, which was due to increases in both the number and average volume of JZ cells. Accordingly, the in vitro basal production of aldosterone and other 18-hydroxylated steroids was notably enhanced. The plasma level of corticosterone, as well as zona fasciculata/reticularis-like cells and in vitro production of glucocorticoids by regenerated nodules were not affected. These findings, indicating that autotransplanted adrenocortical nodules respond to a prolonged sodium restriction similar to the normal adrenal glands, suggest that the relative deficit in mineralocorticoid production is not due to an intrinsic defect of the zona glomerulosa-like JZ, but is probably caused by the impairment of its adequate stimulation under basal conditions. The hypothesis is advanced that the lack of splanchnic nerve supply and chromaffin medullary tissue in regenerated nodules may be the cause of such an impairment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00318136
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  • 43
    Digitale Medien
    Digitale Medien
    The endocrine pancreas of glucagon-and somatostatin-immunized rabbits (1991)
    Springer
    Cell & tissue research 265 (1991), S. 261-273 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Endocrine pancreas ; Immunization ; Insulin ; Glucagon ; Somatostatin ; Electron microscopy ; Rabbit (Chinchilla, Ch: b Ch)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An active or passive immunization against hormones and the subsequent neutralization of hormones by circulating antibodies is a valuable tool for the identification of hormonal action. To recognize presumed local (autocrine, paracrine) effects exerted by pancreatic hormones, the endocrine pancreas of rabbits was investigated electron-microscopically after long-term immunization against glucagon or somatostatin. Glucagon immunization resulted in hyperplasia and hypertrophy of glucagon- (A-) cells and in their increased metabolic activities: They showed prominent nucleoli, increased amounts of endoplasmic reticulum, Golgi areas, and mitochondria. These changes were paralleled by alterations in secretion granules (increased size, decreased hormonal content), increased numbers of lysosomes (crinophagic bodies), and an increment of the filamentous system. Basically, these findings point to an autocrine regulation of A-cells. Following somatostatin immunization, somatostatin- (D-) cells were hyperplastic but unchanged in their metabolic state. Instead, insulin-(B-) cells and A-cells exhibited equivalents of increased cellular activities (parameters, see above). This stimulation most probably is caused by cancelled paracrine (inhibitory) effects of somatostatin. The changes observed after both immunizations were differently expressed in morphologically heterogeneous islet types (size, angioarchitecture, cellular composition, microtopology of the various cell types). It is concluded, therefore, that the regulation of islets is not uniform. Autocrine and paracrine effects exerted by islet hormones are of different significance in individual islets, or they interfere differently with other regulatory signals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00398074
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  • 44
    Digitale Medien
    Digitale Medien
    Morphological and cytochemical studies of the effects of ecdysteroids in a lepidopteran cell line (IAL-PID2) (1991)
    Springer
    Cell & tissue research 265 (1991), S. 361-369 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Electron microscopy ; Scanning electron microscopy ; Lectin-gold particles ; Cytology ; Glycoproteins ; Imaginal discs ; Tissue culture ; Plodia interpunctella (Insecta)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The Indian meal-moth cell line, IAL-PID2, established from larval wing discs was examined from the 250th to the 300th passages. The cultured cells retain various structural and functional qualities of epidermal cells. Under hormone-free conditions PID2 cells grow as a monolayer of round or spindle-shaped cells. They appear as weakly active epidermal cells. The endoplasmic reticulum and Golgi apparatus are poorly developed and secretory activity is reduced. Culture conditions resulted in considerable cellular expansions, abundance of storage products (glycogen, lipids), and hypertrophy of the lysosomal system. The PID2 cell line retains the ability to respond to ecdysteroids; 20-hydroxyecdysone treatment (2×10-6 M) triggered morphogenetic and secretory processes. Cells formed pseudoepithelial aggregates interconnected and linked by desmosome-like structures. The hormone-stimulated cells are involved in the biosynthesis of N-acetyl-D-glucosamine-rich glycoproteins. The glycosylation sites were located, by use of WGA-gold particles, on cellular expansions and all along the plasma membrane. The possible significance of these glycoproteins is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00398084
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  • 45
    Digitale Medien
    Digitale Medien
    Electron microscopic changes and edema after nine hours' perfusion of isolated canine hearts (1991)
    Springer
    Heart and vessels 6 (1991), S. 203-210 
    Details
    ISSN: 1615-2573
    Schlagwort(e): Isolated heart ; Extended perfusion ; Oxygen-carrying solutions ; Electron microscopy ; Preservation and edema
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In a comparative study, we investigated whether or not removed and non-beating hearts could be preserved in vitro by continuous perfusion with oxygen-carrying solutions (blood, perfluoro-carbon emulsion) and simultaneous substitution with specific substrates. We used 18 mongrel dogs subdivided into 2 groups (1st group: perfluorocarbon emulsion; 2nd group: blood); the perfusion time was 9 h. In addition to parameters to control the medium of the perfusion solution, we measured parameters that would allow us to assess the success of the extended perfusion. These parameters were high-energy phosphates and, in particular, electron optical analysis. At the end of the perfusion period, electron optical analysis revealed a mild and reversible ischemic reaction by the myocardial cells in both groups. However, statistical analysis showed (1) a significant increase in the ischemic reaction for both groups over the perfusion period (P=0.02), and (2) a significant, even more pronounced ischemic reaction in the subendocardial myocardium (P=0.025). It should be noted that distinctly interstitial edema developed during the perfusion period and that this would appear to be a fairly critical problem with extended continuous isolated heart perfusion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02125098
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  • 46
    Digitale Medien
    Digitale Medien
    Patterns of cortical and perinuclear microtubule organization in meristematic root cells ofAdiantum capillus veneris (1991)
    Springer
    Protoplasma 165 (1991), S. 173-188 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Adiantum capillus veneris ; Meristematic root cells ; Microtubule organization ; Immunofluorescence microscopy ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The interphase meristematic root cells ofAdiantum capillus venerispossess a well developed cytoskeleton of cortical microtubules (Mts), which disappear at prophase. The preprophase-prophase cells display a well organized preprophase microtubule band (PMB) and a perinuclear Mt system. The observations favour the suggestion that the cell edges included in the PMB cortical zone possess a Mt organizing capacity and thus play an important role in PMB formation. The perinuclear Mts are probably organized on the nuclear surface. The preprophase-prophase nuclei often form protrusions towards the PMB cortical zone and the spindle poles, assuming a conical or rhomboid shape. Mts may be involved in this nuclear shaping. Reinstallation of cortical Mts in dividing cells begins about the middle of cytokinesis with the reappearance of short Mts on the cell surface. When cytokinesis terminates, numerous Mts line the postcytokinetic daughter wall. Many of them converge or form clusters in the cytoplasm occupying the junctions of the new and the old walls. In the examined fern, the cortical Mt arrays seem to be initiated in the cortex of post-cytokinetic root cells. A transitory radial perinuclear Mt array, comparable to that found in post-telophase root cells of flowering plants, was not observed inA. capillus veneris.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01322288
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  • 47
    Digitale Medien
    Digitale Medien
    Repair of 8-methoxypsoralen photoinduced cross-links in yeast (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 335-344 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; DNA interstrand cross-links ; DNA repair ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The repair of interstrand cross-links induced by 8-methoxypsoralen plus UVA (365 nm) radiation DNA was analyzed in diploid strains of the yeast Saccharomyces cerevisiae. The strains employed were the wild-type D7 and derivatives homozygous for the rad18-1 or the rad3-12 mutation. Alkaline step-elution and electron microscopy were performed to follow the process of induction and removal of photoinduced crosslinks. In accordance with previous reports, the D7 rad3-12 strain failed to remove the induced lesions and could not incise cross-links. The strain D7 rad18-1 was nearly as efficient in the removal of 8-MOP photoadducts after 2 h of post-treatment incubation as the D7 RAD+ wild-type strain. However, as demonstrated by alkaline step-elution and electron microscopic analysis, the first incision step at DNA cross-links was three times more effective in D7 rad18-1 than in D7 RAD+. This is consistent with the hypothesis that the RAD18 gene product is involved in the filling of gaps resulting from persistent non-informational DNA lesions generated by the endonucleolytic processing of DNA cross-links. Absence of this gene product may lead to extensive strand breakage and decreased recognition of such lesions by structural repair systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00260625
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  • 48
    Digitale Medien
    Digitale Medien
    Mechanism of the damage to myelinated axons in experimental Creutzfeldt-Jakob disease in mice: An ultrastructural study (1991)
    Springer
    European journal of epidemiology 7 (1991), S. 545-550 
    Details
    ISSN: 1573-7284
    Schlagwort(e): Creutzfeldt-Jakob disease ; Electron microscopy ; Myelinated axon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We report the ultrastructural pathology of myelinated axons in mice infected experimentally with the Fujisaki strain of Creutzfeldt-Jakob disease (CJD). Initially the myelin sheath was separated into several concentric bands, and cellular processes penetrated between layers of myelin and lifted away the outermost lamella. Then a complicated labyrinth of the concentric cellular processes, clearly belonging to either astrocytes or macrophages, invested myelinated axons. In terminal stages axons completely denuded of myelin were seen in the center of concentric networks of cellular processes. Myelin remnants were seen within astrocytes and macrophages. We conclude that the mechanism(s) of damage to myelinated axons in CID may be similar to that operating in immunologically mediated demyelinating disorders.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00143137
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  • 49
    Digitale Medien
    Digitale Medien
    Merkel cell carcinoma of the head and neck associated with Bowen's disease (1991)
    Springer
    European archives of oto-rhino-laryngology and head & neck 248 (1991), S. 436-441 
    Details
    ISSN: 1434-4726
    Schlagwort(e): Merkel cell carcinoma ; Neuroendocrine carcinoma ; Bowen's disease ; Immunohistochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The Merkel cell carcinoma occurs primarily in the skin of the head and neck, and develops in the dermis with a trabecular growth pattern. Immunohistochemistry reveals positive staining for neuron-specific enolase, neurofilaments, cytokeratin and chromogranin A. Electron microscopically, the tumor cells contain dense-core granules, spinous cytoplasmic processes, desmosomes, zonulae adherentes and paranuclear filament aggregates besides frequent mitoses, focal necroses and lymphocyte and plasma cell infiltrates. The Merkel cell carcinoma is often co-existent with other malignancies such as squamous cell carcinoma or, as in the present study, with Bowen's disease. The definite diagnosis of the Merkel cell carcinoma can be effected only by electron microscopic examination of the tumor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00627629
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  • 50
    Digitale Medien
    Digitale Medien
    Point group symmetry and cartesian force constant redundancy (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 19-29 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A procedure for identifying redundancy in the Cartesian force constant matrix is described, and a prescription is given for generating the entire matrix of second derivatives from the minimal set of information. A proof is supplied which demonstrates that the number of nonredundant rows corresponding to a symmetry unique atom is necessarily less than three if the atom is invariant with respect to a symmetry operation of the point group other than the identity or inversion. Furthermore, only one row is required if the atom lies on a threefold or higher-order rotation axis. An application of the procedure to the evaluation of harmonic force constants by numerical differentiation of gradient vectors is briefly described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390105
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  • 51
    Digitale Medien
    Digitale Medien
    An intermediate neglect of differential overlap model for second-row transition metal species (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 31-45 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An intermediate neglect of differential overlap (INDO) model for elements of the second transition series is described. Values of exponents for the radial portion of the Slater basis atomic orbitals, the orbital ionization energies, and the beta (or bonding) parameters for these elements are reported. Use of the model to investigate equilibrium geometries, relative energy ordering of geometric isomers, spectroscopic transition energies, energy ordering of state wave functions of different symmetry, trends in dipole moments, and equilibrium stretching frequencies is reported. The results indicate that the INDO method is capable of yielding quality results for species containing atoms of the second transition series.
    Zusätzliches Material: 11 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390106
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  • 52
    Digitale Medien
    Digitale Medien
    Improved quadrature methods for three-center nuclear attraction integrals with exponential-type basis functions (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 625-645 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The numerical properties of a two-dimensional integral representation [J. Grotendorst and E.O. Steinborn, Phys. Rev. A 38, 3857 (1988)] of the three-center nuclear attraction integral with a special class of exponential-type orbitals (ETO'S), the B functions [E. Filter and E.O. Steinborn, Phys. Rev. A 18, 1 (1978)] are examined. B functions span the space of ETO'S. The commonly occurring ETO'S can be expressed in terms of simple finite sums of B functions. Hence, molecular integrals for other ETO'S, like the more common Slater-type orbitals, may be found as finite linear combinations of integrals with B functions. The main advantage of B functions is the simplicity of their Fourier transform that makes the derivation of relatively simple general formulas for molecular integrals with the Fourier transform method possible. The integrand of the integral representation mentioned above shows sharp peaks causing, in the case of highly asymmetric charge distributions, slow convergence of the quadrature method used by Grotendorst and Steinborn. New quadrature schemes are presented that use quadrature rules based on Möbius transformations. These rules are well suited for the numerical quadrature of functions that possess a sharp peak at or near a single boundary of integration [H.H.H. Homeier and E.O. Steinborn, J. Comput. Phys., 87, 61 (1990)]. Numerical results are presented that illustrate the fact that convergence of the new quadrature schemes is about a factor two faster in case of highly asymmetric charge distributions.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390409
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  • 53
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    Single-excitations-adapted molecular orbitals for a simplified description of electronic excited states (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 681-688 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An orbital transformation that minimizes the sum of the squares of the off-diagonal Hamiltonian elements between the singly excited configurations is described. The resulting single-excitations-adapted molecular orbitals (SEAMOS) are found to be very suitable for the description of electronic excited states. The test calculations on the singlet and triplet excited states of the N2, CO, and H2CO molecules are presented.
    Zusätzliches Material: 12 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390505
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  • 54
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    Digitale Medien
    Energy deposition mechanisms and biochemical aspects of DNA strand breaks by ionizing radiation (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 709-727 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theoretical model based on physical, chemical, and biochemical mechanisms has been presented to evaluate the yields of DNA strand breaks (single and double) as a function of linear energy transfer (LET) or -dE/dx. Energetic heavy charged particles are considered explicitly to provide a general theory for low- as well as for high-LET radiation. There are three main features of the calculation: (a) track structure considerations for the energy deposition pattern, (b) three-dimensional structure of DNA molecules to provide information on the exact location of damage, and (c) a Monte-Carlo scheme to simulate the diffusion processes of water radicals. To avoid the complexities of a cellular medium, an aqueous solution of DNA is considered in the calculation. When the results of the calculations are compared with experimental measurements of the yields of strand breaks in mammalian DNA (exposed in a cellular complex), reasonable agreement is obtained. However, only those experimental data have been compared where there were no enzyme repair processes. The method of calculation has also been extended to study breaks in higher-order structures of DNA molecules such as chromatin. Specific limitations of the present model have been pointed out for making further improvements.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390508
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  • 55
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    Digitale Medien
    Electronic aspects of LADH catalytic mechanismPaper presented at 29th Sanibel Symposia, 1989. (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 767-786 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Electronic aspects of the catalytic mechanism of liver alcohol dehydrogenase (LADH) are studied with the help of ab initio analytical gradient SCF MO methods. Three points are considered: (i) role of the catalytic zinc; (ii) geometry and electronic structure of the transition state for the hydride transfer reactions; and (iii) factors affecting the energy gap for the hydride transfer step, namely, substrate binding to zinc, reaction field, and serine 48 effects on the potential energy profile. The coordination sphere of the catalytic zinc has been modeled with an ammonia molecule and two SH- groups; complexes with CH3O-, CH3OH, and CH2O have been studied; a (6, 2, 2, 2, 1/6, 2, 1/3, 2) basis set has been used for Zn++; a (5, 2, 1, 1/3, 2) was used for oxygen, carbon, and sulfur; and a (3, 1) was used for hydrogen atoms. The hydride step was studied with two model systems: pyridinium cation/1,4-dihydropyridine coupled to the CH3O-/CH2O reaction, and cyclopropenyl cation/cyclopropene coupled to the CH3O-/CH2O system. For the latter, the role of Ser48 has been studied at the supermolecule level. The calculation on the hydride transfer step has been done at a 4-31G basis set level. The results obtained shed new light on the sources of catalytic activity of liver alcohol dehydrogenases.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390603
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  • 56
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    Digitale Medien
    Theoretical treatment of chemisorption using an Ab initio SCF Green-matrix formalism (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 839-849 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a treatment of chemisorption that uses the Green matrix of the surface and the admolecule, as well as a cluster calculation of a small surface cluster. Since full HF-SCF-band structures with nonlocal exchange are available now for larger systems for a couple of years, it is possible to treat the substrate surface and the admolecule on equal footing. This offers a natural way to solve the embedding problem. We have applied the formalism to the adsorption of H2 on beryllium and show that in contrast to cluster calculations there appears a binding, which is experimentally verified.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390608
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  • 57
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    Digitale Medien
    A study on the electronic spectra of vinylpyridines and 1,2-(dipyridyl)ethylenes. Molecular orbital calculations (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 211-226 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The electronic absorption spectra of 2-, 3-, and 4-vinylpyridines and 1,2-(2,3-dipyridyl), 1,2-(2,4-dipyridyl), 1,2-(3,4-dipyridyl), and 1,2-(4,4-dipyridyl) ethylenes have been investigated in polar and nonpolar solvents. A correlation has been made between the geometry of the molecule and the observed spectrum. Molecular orbital calculations have been carried out using the INDO/S—CI procedure and a limited geometry optimization. The solvent effect at the MO level has been calculated. MO calculations predicted the existence of nπ* transitions that were not observed experimentally. The wave functions of the different CI states were calculated. The experimental transition energy as well as oscillator strength corresponded satisfactorily with the calculated ones. The observed transitions were assigned according to the results of MO calculations.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390210
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  • 58
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    Digitale Medien
    Masthead (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390301
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  • 59
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    Digitale Medien
    The discovery of the chemical evolution of singlet oxygen. Some current chemical, photochemical, and biological applications (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 251-267 
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    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: From the speculations of G. N. Lewis in 1916, [J. Am. Chem. Soc. 38, 762 (1916)], the spectral predictions of R.S. Mulliken [Nature 122, 505 (1928)], and the quantum mechanical treatment by E. Hückel [Z. Phys. 60, 423 (1930)], the three lowest states of molecular oxygen (3Σg-, 1Δg, and 1Σg+) remained spectroscopic elusives until Gerhard and Lisa Herzberg [G. Herzberg, Nature 133, 759 (1934); L. Herzberg and G. Herzberg, Astrophys. J. 105, 353 (1947); G. Herzberg and L. Herzberg, Astrophys. J. 108, 167 (1948)], precisely defined them by observed infared transitions. The excited singlets remained of interest mainly to atmospheric spectroscopists and astrophysicists, and research on these species was scarce. The discovery in 1963 by A.U. Khan and M. Kasha [J. Chem. Phys. 39, 2105 (1963)] of the simple chemical production of singlet molecular oxygens by the aqueous reaction of hydrogen peroxide and hypochlorite released an explosion of research on the neglected species. Fifteen research symposia and research treatises confirm the broad range of chemical activities of singlet oxygen. The extension to biological systems is now proceeding, with surprising evidence of involvement of natural processes, including the action of singlet oxygen in white blood cell phagocytosis.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390305
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  • 60
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    Digitale Medien
    Polarization propagator calculation of spectroscopic properties of molecules (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 371-386 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We propose 10 desirable features or criteria for general purpose methods to be applied to the calculation of a range of spectroscopic properties. We discuss the second-order polarization propagator approximation (SOPPA) in light of these criteria by giving the actual computational expression used as well as a few numerical examples taken from the theory of NMR spectra (magnetic shieldings and spin-spin coupling constants). We demonstrate that SOPPA comes close to fulfilling these criteria.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390314
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  • 61
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    Digitale Medien
    High-resolution infrared analysis of the ν17 band of pyridine (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 423-436 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method for analyzing asymmetric top rovibrational bands displaying both blended and resolved features is described. The two-phase computational procedure uses a modified version of the asymmetric rotor-band contour program FASTPLOT to generate a preliminary set of upperstate spectroscopic constants. The parameters are subsequently refined by employing the assigned line-fitting formalism of the ASYROT program using both resolved and blended features. The technique is detailed in a comprehensive analysis of the ν17 band of pyridine. Inclusion of quartic centrifugal distortion constants was found to satisfactorily model a high-resolution (0.004 cm-1) spectrum of this band, yielding a standard deviation of 0.00137 cm-1. The variation in the rotational parameters with vibrational quantum number is examined in terms of possible weak rovibrational perturbations to the ν17 state. An ab initio calculation of the ν17/ν27 Coriolis coupling constant indicates the observed results are consistent with the interaction of these two vibrational states.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390318
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  • 62
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    Digitale Medien
    Announcement (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 521-521 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390324
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  • 63
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    Digitale Medien
    The system of harmonically interacting particles: An exact solution of the quantum-mechanical problem (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 173-181 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An original procedure has been developed to determine the eigenvalues and the eigenfunctions of quantum-mechanical many-body systems with a harmonic oscillator interaction. Exact solutions in the explicit form have been obtained for the case of systems containing three groups of identical particles. For the system containing two groups of identical particles, a solution in the adiabatic approximation has been obtained and compared with the exact one.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390207
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  • 64
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    Digitale Medien
    Fourth international conference on mathematical and computational chemistry (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 229-229 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390212
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  • 65
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    Digitale Medien
    Professor Michael Kasha (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 233-233 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390303
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  • 66
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    Digitale Medien
    Quantum chemical calculations on buckminsterfullerene and related structures. II. The electronic structure and spectra of some Cn and CnCa2+ cages (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 331-344 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390311
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  • 67
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    Digitale Medien
    International journal of quantum chemistry - A journal devoted to quantum theory and computations in chemistry, condensed matter physics, and biology. Editorial - program and policies (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 1-2 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390102
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  • 68
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    Digitale Medien
    Excited and ionized states of RuO4 and OsO4 studied by SAC and SAC-CI theories (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 93-113 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The excitation and ionization spectra of RuO4 and OsO4 are studied theoretically by the symmetry-adapted cluster (SAC) and SAC-CI theories. This is the attempt to assign whole of the spectra by ab initio calculations including electron correlations. In the ground state, electron correlations work to reduce the polarity of the M-O bond overestimated in the Hartree-Fock calculation. The Os-O bond is stronger than is the Ru-O bond, which is reflected in the differences of the excitation and ionization spectra of RuO4 and OsO4. The excitation energies of the experimental spectra are well reproduced by the SAC-CI theory, though the calculated intensities of some peaks are very small in comparison with the experiments. The outer-valence ionization spectra calculated by the SAC-CI theory agree well with the experimental photoelectron spectra. Some shake-up peaks that are accompanied with an electron-transfers from oxygen to metal are also calculated.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390110
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  • 69
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    Digitale Medien
    A comment on classical rainbow angles for atom-atom scattering (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 159-162 
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    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dependence of the rainbow angle on the depth of the potential well, the equilibrium distance, andthe force constant of the potential are discussed for several potential functions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390205
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  • 70
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    Digitale Medien
    A general treatment of vibration-rotation coordinates for triatomic molecules (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 183-196 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An exact, within the Born-Oppenheimer approximation, body-fixed Hamiltonian for the nuclear motions of a triatomic system is presented. This Hamiltonian is expressed in terms of two arbitrarily defined internal distances and the angle between them. The body-fixed axis system is related to these coordinates in a general fashion. Problems with singularities and the domain of the Hamiltonian are discussed using specific examples of axis embedding. A number of commonly used coordinate systems including Jacobi, bond-length-bond-angle, and Radau coordinates are special cases of this Hamiltonian. Sample calculations on the H2S molecule are presented using all these and other coordinate systems. The possibility of using this Hamiltonian for reactive scattering calculations is also discussed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390208
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  • 71
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    Digitale Medien
    International journal of quantum chemistry - a journal devoted to quantum theory and computations in chemistry, condensed matter physics, and biology. Editorial - Program and Policies (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 1-2 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560400102
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  • 72
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    Digitale Medien
    Quantum rigid dipole in a permanent electric field. I. Rigorous treatment (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 33-53 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A behavior of a quantum rigid and pointlike dipole in a permanent electric field is under study. A dependence of a number of librational energy levels on the strength of the electric field is investigated on the basis of some rigorous results for the appropriate normal Jacobian matrices.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560400106
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  • 73
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    Digitale Medien
    A BSSE-free SCF algorithm for intermolecular interactionsSupported in part by the Hungarian Research Fund (OTKA No. 785). (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 139-148 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A very simple modification of the usual (∼N4) SCF procedure is proposed, permitting the exclusion of basis set superposition errors (BSSE) in problems of intermolecular interactions. No a posteriori corrections are required. The results of this “CHA/F method” are numerically close to those of the Boys-Bernardi correction scheme but are free from the “overcompensation” characteristic of the latter at smaller distances.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560400112
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  • 74
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    Digitale Medien
    Symmetry adapted formulation of the generalized Brillouin theorem (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 243-264 
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    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The singly excited functions satisfying Brillouin theorem are expressed as linear combinations of configuration-state functions for any spin and spatial symmetries (atomic or molecular) and for any reference wave function. The generality of the formulation is ensured by the use of the irreducible tensor method that can be adapted to any symmetry point group of interest. The expansion coefficients are simply written as products of fractional parentage coefficients, spin- and orbit-recoupling coefficients, and phase factors. The formalism is illustrated for some atomic (Kh) and molecular (C∞v, C3v, and Td) configurations. Group theoretical techniques are also used to correlate the Brillouin conditions within a chain of groups.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560400207
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  • 75
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    Digitale Medien
    Quantum-Chemical modeling of catecholamine storage including continuum solvent effects (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 299-304 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A model for catecholamine storage in vesicles is analyzed within the SCRF-CNDO/2 approach including continuum solvent effects. The model considers the approach of cationic norepinephrine (NE) to a positively charged guanidinium moiety. Ion-pair formation is found for the whole range of dielectric constants. Even though stable states of H-bonded partners are found for large dielectric constants, this process is ruled out to occur because it involves too high energies. It appears that the medium's polarity is determinant in lowering the energy barrier between the ion-pair complex and the separated partners. Thus, as the medium dielectric constant increases, the equilibrium between the two states is enhanced.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560400303
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  • 76
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    Digitale Medien
    Announcement (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 519-519 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390323
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  • 77
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    Digitale Medien
    Dirac-Fock self-consistent field method for closed-shell molecules with kinetic balance and finite nuclear size (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 487-517 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a general method of implementing the kinetic balance condition within the Dirac-Fock (DF) self-consistent field (SCF) formalism for closed-shell molecular structure. We review the steps leading to the derivation of DF SCF equations for closed-shell molecules, particularly as formulated by Matsuoka et al. In the present approach, the large component of the molecular spinors are expanded in terms of atomic basis spinors of spherical-type Gaussian functions, with the small component related to the large component by the kinetic balance condition. It is shown that imposing the kinetic balance condition on geometric Gaussian-type basis functions allows us to obtain the Fock matrix elements, involving both the large and the small components, form the standard nonrelativistic Cartesian-type matrix elements. By using properties of orthogonal polynomials, the solid spherical harmonics are expressed in Cartesian form, thus providing a general basis for transformation of one- and two-electron-matrix elements, obtained from a Cartesian Gaussian-type basis, to a spherical Gaussian-type basis. The advantages of using kinetically balanced geometric Gaussian-type basis functions in molecular DF calculations including finite-size nucleus effects are emphasized. For the sake of completeness, we have added in an appendix corrections to the nuclear attraction matrix elements for the finite-size nucleus already derived by Matsuoka.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390322
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  • 78
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    Digitale Medien
    Ab initio MRD-CI calculations for breaking a chemical bond in a molecule in a crystal or other solid environment. III. Me2N—NO2 decomposition of dimethylnitramine in a large crystalline environment (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 541-560 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Recently we extended our strategy for MRD-CI (multireference double excitation-configuration interaction) calculations, based on localized/local orbitals and an “effective” CI Hamiltonian, for molecular decompositions of large molecules to breaking a chemical bond in a molecule in a crystalline or other solid environment.Our technique begins with an explicit quantum chemical SCF calculation for a reference molecule surrounded by a number of other molecules in the multipole environment of more distant neighbors. The resulting canonical molecular orbitals are then localized, and the localized occupied and virtual orbitals in the region of interest are included explicitly in the MRD-CI with the remainder of the occupied localized orbitals being folded into an “effective” CI Hamiltonian. The MRD-CI calculations are then carried out for breaking a bond in the reference molecule. This method is completely general in that the space treated explicitly, as well as the surrounding space, may contain voids, defects, deformations, dislocations, impurities, dopants, edges and surfaces, boundaries, etc.Dimethylnitramine is the smallest prototype of the energetic R2N - NO2 nitramines, such as the 6-member ring RDX or the 8-member ring HMX. Decomposition of energetic compounds is initiated in the solid by a breaking of the target bond. Thus, it is crucial to know the difference in energy between breaking a bond in an isolated energetic molecule versus in the molecule in a solid. In the present study, we have carried out MRD-CI calculations for the Me2N - NO2 dissociation of dimethylnitramine in a dimethylnitramine crystal. The cases we investigated were one dimethylnitramine molecule (surrounded by 53 and 685 neighboring dimethylnitramine molecules represented by multipoles), three dimethylnitramine molecules, and three dimethylnitramine molecules (surrounded by 683 neighbors). All multipoles were cumulative atomic multipoles up through quadrupoles. The MRD-CI calculations on dimethylnitramine required large numbers of reference configurations from which were allowed all single and double excitations.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390403
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  • 79
    Digitale Medien
    Digitale Medien
    Second-order polarization propagator calculations of dynamic dipole polarizabilities and C6 coefficients (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 667-679 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The frequency-dependent dipole polarizability, α(E), is calculated using the second-order polarization propagator approximation (SOPPA). We have shown how to express α(E) as a function of E2 and thus obtained a form of α(E) that can be used to compute C6-coefficients without invoking complex arithmetic. For He we find that SOPPA recovers a large fraction of the correlation contribution for all frequencies, whereas for H2 where the correlation contributions are much smaller and also basis set-dependent, we find a less definite trend of SOPPA relative to RPA.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390504
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  • 80
    Digitale Medien
    Digitale Medien
    Transition properties from multiple scattering X-Alpha Calculations: A study of NO2 (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 71-91 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The usefulness of the MS-Xα method for calculating molecular transition properties is investigated in a study of NO2. Two-dimensional potential surfaces are obtained in C2v symmetry for the X̃2A1/Ã2B2 system. Potential curves that approximately follow the asymmetric stretch coordinate are also presented: On investigation, no symmetry-broken solutions were found. At all nuclear geometries investigated, the muffin-tin sphere radii were chosen by an energy-minimization technique. The inclusion of corrections to the muffin-tin form of the Xα total energy is shown to be essential, if the computed surfaces are to be qualitatively correct. The transition dipole moment connecting the two states is evaluated as a function of nuclear coordinates, using the transition-state approximation. Finally, the radiative decay of a single vibronic level in NO2 is modeled and the relevance to experiment is discussed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390109
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  • 81
    Digitale Medien
    Digitale Medien
    Monohydration selectivity mechanism of alkali cations in the potassium channel of excitable biomembranes (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 131-147 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nonempirical quantum chemical method Hartree-Fock-Roothan LCAO SCF MO in a two-exponent Dunning basis with the use of an extended set of Gaussian functions by Huzinaga-Dunning with consideration of electron correlation according to the Meller-Plesset theory of excitations of the second order was used to study monohydrates of Li+, Na+, K+, and HCOO- ions. The indicated basis was supplemented with polarization functions of d-type on the O atom and of p-type on the hydrogen atom as well as with diffusion functions of p-type on the oxygen atom. It has been found that binding energies of the water molecule with Li+, Na+ appeared to be higher and with K+ lower than with HCOO- · H2O. Potential curve shapes of K+ + H2O and HCOO- + H2O reactions are shown to be similar. The molecular mechanism of K+ channel selectivity of an excitable membrane is explained on the basis of the obtained calculations.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390203
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  • 82
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    Digitale Medien
    Collision-induced emission of O2(b1Σg+ → a1Δg) in the gas phaseNRCC No. 31208. (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 287-298 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In flow tube studies of the quenching of O2(b1Σg+), broad band emission of O2(b):M collision complexes was found to appear under the discrete rotational lines of the 0-0 band of the b1Σg+ → a1Δg electric quadrupole transition at higher oxygen pressures and on addition of foreign gases. Bimolecular rate constants for the collision-induced emission processes have been derived from the ratio of the intensities of the discrete lines and the continuum as well as from low-resolution measurements of the relative intensities of the b → a and b → X bands as a function of O2 and added gas pressure. They range from ≈10-21 cm3 s-1 for He to ≈4 × 10-19 cm3 s-1 for PCl3 vapor.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390307
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  • 83
    Digitale Medien
    Digitale Medien
    A realistic model for curve crossing in diatomic molecules (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 523-539 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a model system for the study of curve-crossing situations in diatomic molecules. All model parameters are determined by the potential energy topology. No coupling functions are fitted. The standard approximation schemes (Born-Oppenheimer approximation, adiabatic approximation, and the generator coordinate approximation) are then applied. The result of these numerical experiments suggest that the generator coordinate approximation is able to remove 80%-90% of the nonadiabatic effect on all levels throughout the crossing region.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390402
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  • 84
    Digitale Medien
    Digitale Medien
    A partial recurrence relation for reduced class coefficients of the symmetric group (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 593-604 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An expression for the product of a single-cycle class [(1)N - P(p)]N and an arbitrary class [(1)l1(2)l … (N)lN]N of the symmetric group has recently been conjectured. This expression involves a sum over a relatively small number of reduced class sums, depending on p indices. A further conjecture is formulated and demonstrated, according to which reduced class coefficients (RCCS) involving cycles whose length is expressed by means of a single index can be related to corresponding coefficients in the product of [(1)N - P+1(p - 1)]N with an arbitrary class sum. Consequently, the problem of evaluating the general class sum product reduces to that of obtaining a relatively small set of fundamental RCCS containing no single-index cycles. The conjectures mentioned can be used to evaluate the product [(1)N - p(p)]N · [(1)N - q(q)]N in terms of fundamental RCCS that can all be obtained from the product [(r)]r · [(r)]r, where r = min(p, q). For the latter product, we use a result due to Boccara.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390406
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  • 85
    Digitale Medien
    Digitale Medien
    Masthead (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390501
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  • 86
    Digitale Medien
    Digitale Medien
    Structure reports for 1988. Edited by G. Ferguson and J. Trotter, metals and inorganic compounds, Vol. 55A, Kluwer, Dordrecht, 1989 (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 647-647 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560390410
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  • 87
    Digitale Medien
    Digitale Medien
    Photochemische Reaktionen von Übergangsmetall-Organyl-Komplexen mit Olefinen, 3. [4 + 5]-Cycloaddition konjugierter Diene an Tricarbonyl(η5-2,4-dimethyl-2,4-pentadienyl)mangan (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 3-12 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Manganese-mediated cyclization ; Nine-membered carbocycles ; Manganese complexes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photochemical Reactions of Transition Metal Organyl Complexes with Olefines, 31). - [4 + 5] Cycloaddition of Conjugated Dienes to Tricarbonyl(η5-2,4-dimethyl-2,4-pentadienyl)manganeseTricarbonyl(η5-2,4-dimethyl-2,4-pentadienyl)manganese [1] reacts photochemically with the acyclic conjugated dienes 1,3-butadiene [A], 2-methyl-1,3-butadiene [B], (E)-1,3-pentadiene (C), (E,E)-2,4-hexadiene (D), 2,4-dimethyl-1,3-pentadiene (E), 2,4-hexadien-1-ol (F), and methyl 2,4-hexadienoate (G) in a formal [4 + 5] cycloaddition to give tricarbonylmanganese complexes with η3:2-2,6-cyclononadien-1-yl ligands (2A-2G). In addition, the reaction of 1 with A yields thermolabile [η3:2:2-1-(3-butene-1,2-diyl)-1,3-dimethyl-2,6-cyclononadiene]dicarbonylmanganese (3A) and E,E and E,Z isomers of [η3-1-(2-butene-1,1-diyl)-1,3-dimethyl-2,6-cyclononadiene]tetracarbonylmanganese (4A, 4A] as byproducts. Similarly, 1 reacts with B to form tetracarbonyl[η3-1-(3-methyl-2-butene-1,1-diyl)-1,3,6-trimethyl1-2,6-cyclononadiene]manganese (4B) in a side reaction. The crystal and molecular structures of tricarbonyl(η3:2-1,3,5,5,7-pentamethyl-2,6-cyclononadien-1-yl]manganese (2E) and of 3A are determined by X-ray structure analyses. In each of the formally octahedral complexes unusual long manganese-carbon bonds are found for one coordinated CC double bond of the hydrocarbon ligands.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240102
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  • 88
    Digitale Medien
    Digitale Medien
    Derivate des Borols, XVI Bis(borol)nickel-Komplexe2) (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 17-23 
    Details
    ISSN: 0009-2940
    Schlagwort(e): (Borole)nickel complexes ; Nucleophilic substitution at boron ; 1H-Borole ; Dihydro-1H-borolediide ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Derivatives of Borole, XVI1), - Bis(borole)nickel Complexes2)The dilithium 1-(dialkylamino)dihydroborolediides Li2[C4H4-BNR2] 2a, b: R = Me, Et) react with NiCl2 · DME to give bis(borole)nickel complexes Ni(C4H4BNR2)2. Nucleophilic substitution reactions are used to produce a large variety of derivatives Ni(C4H4BR)2 1 (e.g. R = H, tBu, F, Cl, Br, I, OH, OMe). Treatment of Ni(C4H4BCl)2 (tg) with LiO(CH2)3OLi in THF produces a polymer and a dinuclear complex (μ-{η5:η5-[(CH2)3(OBC4H4)2]}2Ni2 (3) which crystallizes from CH2Cl2 as solvate 3 · CH2Cl2. The complexes 1g and 3 · CH2Cl2 are characterized by X-ray diffraction work. Barriers to internal ring-ring rotation are measured by variable-temperature NMR spectroscopy. The B - H bond of Ni(C4H4BH)2 (1a) is remarkably inert and does not react with H2O or with carboxylic acids in THF at room temperature. With PhCHO slow formation of the benzyloxy compound Ni(C4H4BOCH2Ph)2 (1 m) is observed at 100°C. For typical complexes such as the phenyl derivative 1e cyclic voltammetry in CH2Cl2 reveals an irreversible oxidation at 1.32 and a quasi-reversible reduction at -1.37 V vs. SCE.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240104
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  • 89
    Digitale Medien
    Digitale Medien
    Derivate des Borols, XVII {η5-[1-(Diisopropylamino)borol]}metall-Komplexe: Synthesen, Protonierung, interne Rotation (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 25-29 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Borole complexes ; {η5-[1-(Diisopropylamino)borole]}metal complexes, internal rotation of, protonation of ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Derivatives of Borole, XVII1). - {η5-[1-(Diisopropylamino)borole]}metal Complexes: Syntheses, Protonation, Internal RotationNew complexes M(CO)4L (M = Cr, W), cis-M(CO)2L2 [M = Mo, W (not isolated)], and (COD)NiL have been prepared from the Diels-Alder dimer L2, where L is 1-(diisopropylamino)borole, C4H4BNiPr2. Complexes of L can be protonated at the nitrogen atom to give stable salts such as [Cr(CO)4(LH)]BF4, [Fe(CO)3(LH)]BF4, [(C6Me6)Ru(LH)]BF4, and [CpCo(LH)]BF4; B  -  N bond dissociation is not observed. Barriers to internal rotation have been determined by variable temperature NMR spectroscopy for Cr(CO)4L, (COD)NiL, and NiL2. Three processes have been identified: rotation of the NiPr2 group around the B  -  N bond, gear-mesh rotation of the isopropyl groups around the C  -  N bonds, and rotation of L with respect to the counter ligands.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240105
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  • 90
    Digitale Medien
    Digitale Medien
    Darstellung von (Perfluoralkyl)halogeno-1,3-diselenetanen aus entsprechenden Selenocarbonylfluoriden und Umsetzungen mit Bortrichlorid sowie Arsenpentafluorid1) (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 51-61 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Selenocarbonyl compounds, perfluorinated ; 1,3-Diselenetanes, perhalogenated ; 2-Selenabicyclo[2.2.1]hept-5-enes ; 1,3-Diselenetan-2-ylium hexafluoroarsenates ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preparation of (Perfluoroalkyl)halogeno-1,3-diselenetanes from the Corresponding Selenocarbonyl Fluorides and Reactions with Boron Trichloride or Arsenic Pentafluoride1)Reactions of Hg(SeRt)2 (Rt = C2F5, C3F7, CF3) with (C2H5)2 All or All3 in octamethylcyclotetrasiloxane produce the unstable perfluoroalkaneselenocarbonyl fluorides 1 [R1 = CF3 (1 a), C2F5 (1 b), CF3Se (1 c)]. These compounds are very reactive and polymerize to rubberlike products. On heating the polymers decompose almost quantitatively to the monomers or dimers. In CFCl3 solution 1 dimerizes at 20°C in sunlight to the corresponding cis/trans-1,3-diselenetanes 2. The structure of 2 b is determined by single crystal X-ray diffraction. Different selenocarbonyl derivatives add to unsymmetrically substituted 1,3-diselenetanes 3. 1 a and 1 b react with cyclopentadiene to form the [4 + 2] cycloaddition products 4a and 4c. Halogen exchange reactions take place between 2a  -  d and BCl3. The cis-isomers react much faster than the trans-isomers to give a mixture of cis-, trans-forms of 5. When 2c,d is treated with BCl3 it is possible to isolate and characterize the pure trans-isomer 2d, which is separated by preparative gas chromatography from 5c,d. Fluorine abstraction with formation of 1,3-diselenetan-2-ylium ions (6a  -  f) are accomplished by reactions of 2 or 3 with AsF5 in SO2.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240109
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  • 91
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    Digitale Medien
    Molecular Structure of Hg[C(COF)=SF2=O]2 (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 87-88 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Alkylidenesulfur difluoride oxide ; Carbon-sulfur double bond ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hg[C(COF) = SF2 = O]2 is prepared by the reaction of FCO — CH = SF2 = O with HgF2. This compound represents the third known example of an alkylidenesulfur difluoride oxide. Its molecular structure is the same as that of the most abundant of the three isomers of FCO-CH = SF2 = O. This is assumed to be the result of weak intramolecular Hg… O contacts. With the exception of the fluorine atoms bound to sulfur, all atoms lie approximately in one plane.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240114
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  • 92
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    Digitale Medien
    Asterane, XXII. Synthese eines doppelten Tetraasterans: Nonacyclo[10.8.0.02,11.04,9.04,19.06,17.07,16.09,14.014,19]eicosan (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 103-109 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Asteranes ; Cage compounds ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Asteranes, XXII1).  -  Synthesis of a Double Tetraasterane: Nonacyclo[10.8.0.02,11.04,9.04,19.06,17.07,16.09,14.014,19]eicosane1,4,5,8-Tetrahydronaphthalene-2,3-dicarboxylic anhydride (9) is dimerized by UV light in dioxane yielding four isomeric [2 + 2] adducts whose methyl ester derivatives are elucidated spectroscopically. The structures of the major products 14 and 16 have been confirmed by X-ray structure analysis. Degradation of the carboxylic groups of 14 afforded the title compound 5.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240118
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  • 93
    Digitale Medien
    Digitale Medien
    Darstellung aromatischer Fluor-Verbindungen durch nucleophilen Austausch von Nitro-Gruppen gegen Fluorid (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 157-162 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Fluoro compounds, aromatic ; Nitrite exchange by fluoride ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Aromatic Fluoro Compounds by Nucleophilic Exchange of Nitro Groups by FluorideThe synthesis of aromatic fluoro compounds from the respective nitro compounds by nucleophilic substitution of nitrite by fluoride is described. Reasonable yields in case of nonactivated nitro compounds are only obtained if the nitrite formed in the reaction is eliminated by acylation. 1-Fluoro-3-nitrobenzene (2) was obtained from 1,3-dinitrobenzene (1), and 1-fluoro-3,5-dinitrobenzene (9) as well as 1,3-difluoro-5-nitrobenzene (10) from 1,3,5-trinitrobenzene (8) in yields up to 92% by reaction of nitro compounds with potassium fluoride in sulfolane at 180 - 200°C in the presence of phthaloyl dichloride (6); 1,2-difluoro-4-nitrobenzene (12) was formed in 58% yield from 2,4-dinitro-1-fluorobenzene (11) in the presence of pyromellitoyl tetrachloride (13).
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240124
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  • 94
    Digitale Medien
    Digitale Medien
    Synthese und Struktur von Bis[bis(diisopropylamino)phosphino]chalkogeniden (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 13-16 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diphosphines, tetrakis(diisopropylamino) ; Phosphinous anhydrides ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and Structure of Bis[bis(diisopropylamino)phosphino]chalcogenidesPhosphorodiamidous chalcogeno-anhydrides [(R2N)2P]2X (R = Me2CH; X = S, Se, Te) (2a-c) have been obtained by insertion of elemental sulfur, selenium, or tellurium into the P-P bond of the corresponding diphosphane (1). The structure of 2a and 2c has been confirmed by an X-ray diffraction.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240103
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  • 95
    Digitale Medien
    Digitale Medien
    (Perfluoralkyl)(dimethylamino)sulfonium-hexafluoroarsenate (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 31-38 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Fluorosulfonium salts, reaction with nucleophiles ; (Perfluoroakyl)(dimethylamino)sulfonium salts, preparation and structures of ; Methoxysulfinyl hexafluoroarsenate, alkylation with ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (Perfluoroalkyl)(dimethylamino)sulfonium HexafluoroarsenatesMeN = S(CF3)2 (5) is alkylated by Me3O⊕ AsF⊖6 to Me2N-S(CF3)⊕2 AsF⊖6 (4). From 5 and MeOSO⊕ AsF⊖6 (6) MeOS(O)-N(Me)S(CF3)⊕2 AsF⊖6 (7) is formed as a relatively stable primary product. Decomposition of 7 gives the expected 4 only in poor yield. Nucleophilic substitution of the sulfur-bonded fluorine in CF3SF⊕2 AsF⊖6 (8) by Me3SiNMe2 yields CF3S(NMe2)⊕2 AsF⊖6 (9). Similarly, (CF3)2CFSF⊕2 AsF⊖6 (10) reacts with dimethyl(trimethylsilyl)amine to give (CF3)2CFS(NMe2)⊕2 AsF⊖6 (11). The structures of 4 and 9 are elucidated by X-ray analyses, and the influence of the substituents on the bonding is discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240106
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  • 96
    Digitale Medien
    Digitale Medien
    Übergangsmetall-Silyl-Komplexe, 36 Zur Frage von Gold-Gold-Wechselwirkungen bei Ph2P[CH2]1(2) PPh2 verbrückten zweikernigen Gold-Silyl-Komplexen (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 63-67 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Dinuclear gold complex ; Silyl complex ; Gold-gold interaction ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transition-Metal Silyl Complexes, 361).  -  On the Question of Gold-Gold Interactions in Ph2P[CH2]t(2)PPh2-Bridged Dinuclear Gold Silyl ComplexesDinuclear silyl gold complexes of the type dppm(AuSiR3)2 (1) or dppe(AuSiR3)2 (2) are prepared by the reaction of dppm-(AuCl)2 or dppe(AuCl)2 with two equivalents of LiSi(aryl)3 or LiSi(SiMe3)3 The complex dppe[AuSi(SiMe3)3]2 (2 c) exhibits crystallographic inversion symmetry, and therefore the distance between both gold atoms is a maximum. In dppm-(AuSiPh3)2 (1b) a gold-gold interaction between both gold atoms is observed [Au  -  Au 316.80(3) pm].
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240110
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  • 97
    Digitale Medien
    Digitale Medien
    Cyclobuten-Ringöffnung: Eine nützliche Reaktion zur Synthese doppelsträngiger Moleküle (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 149-156 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Cyclobutene, ring-opening ; Poly Diels-Alder reaction ; Molecules, double-stranded ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cyclobutene Ring Opening: A Useful Reaction for the Synthesis of Double-Stranded MoleculesSyntheses and ring-opening reactions of the compounds endo-5a - e and 9a - c, all containing cyclobutene rings, are described. From these experiments it is concluded that compound 9a is a useful AB-type Diels-Alder monomer for the synthesis of well-defined double-stranded molecules. The stereochemistry of the adducts endo-4b and endo-5d is determined by X-ray structure analysis.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240123
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  • 98
    Digitale Medien
    Digitale Medien
    Zur Reaktion von Dialkylphosphiten mit α-Enonen, I Synthese und Allyl-Umlagerung von (1-Hydroxy-2-alkenyl)- und (1-Hydroxy-2-cycloalkenyl)phosphonsäure-dimethylestern (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 175-184 
    Details
    ISSN: 0009-2940
    Schlagwort(e): α-Enones, regioselective 1,2-addition of dimethyl phosphite to ; Allylic rearrangement of dialkyl (1-hydroxy-2-alkenyl)phosphonates ; 1-Alkenylphosphonates, 3-acetyloxy- ; 1-Alkenylphosphonates, 3-hydroxy- ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Reaction of Dialkyl Phosphites with α-Enones, I. - Synthesis and Allylic Rearrangement of Dimethyl (1-Hydroxy-2-alkenyl)- and (1-Hydroxy-2-cycloalkenyl)phosphonatesVarious β,γ-unsaturated α-hydroxyphosphonates 3 are prepared in good yields by NaOCH3-catalyzed regioselective 1,2-addition of dimethyl phosphite to acyclic and cyclic α-enones at -35°C. On acid-catalyzed acetylation, the allylic α-hydroxyphosphonates 3 (R1, R2 + H) rearrange under thermodynamic control; yielding the new 3-acetyloxy-1-(cyclo)alkenyl derivatives 8, from which the transposed allylic alcohols 11 are readily obtained. Using shorter reaction times, acetylation of compounds 3 affords mixtures of 1- and 3-acetylated products, 10 and 8, respectively.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240126
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  • 99
    Digitale Medien
    Digitale Medien
    Trioxypentafulvenes, 2 synthesis of 1-substituted 2,3,6-trioxypentafulvenes (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 207-212 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 2,3,6-Trioxypentafulvenes ; Keto-enol tautomerism ; Push-pull system ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Syntheses of 2,3,6-trioxypentafulvenes with a free position at the ring are described, in which the protection of the C-3 hydroxy group as methoxy or acetoxy derivative has been required. The difference in the behavior of the title compounds in relation to the previously reported 1,4-disubstituted 2,3,6-trihydroxypentafulvenes 2a-e, which only exhibit enol forms, is discussed and attributed to the disappearance of the push-pull system formed by the C-3 enol group and the C-4 electron-withdrawing substituent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240131
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  • 100
    Digitale Medien
    Digitale Medien
    Neue O6-Makrocyclen mit 2,2-Bis(2-furyl)propan-Einheiten (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 233-235 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Hexaoxacyclotriacontadodecaenes ; Macrocycles ; 2,2-Bis(2-furyl)propane ; 2,5-Bis[1-(2-furyl)-1-methylethyl]furan ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New O6 Macrocycles with 2,2-Bis(2-furyl)propane UnitsThe macrocycles 3a and 6 are prepared in 29 and 16% yield by cyclization of dilithiated 2,2-bis(2-furyl)propane (1) and 2,5-bis[1-(2-furyl) 1-methylethyl]furan (5), respectively, with ethyl N,N-dimethylcarbamate (2).
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19911240135
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