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  • Articles: DFG German National Licenses  (4,486)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 239-242 
    ISSN: 1432-0827
    Keywords: Bone ; Magnetic field ; IR light ; Light absorption constant ; Efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Enhancement of photovoltage has been found in bone and its two major constituents when placed in a magnetic field in standard Hall geometry. Infrared light has been used for carrier excitation. From data obtained in this manner, values for the light absorption constant, extinction constant, mass absorption constant, and efficiency have been estimated. All these parameters increase with the increase of magnetic field. A possible explanation for the observed phenomena is presented.
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  • 2
    ISSN: 1432-0827
    Keywords: Vitamin D ; Vitamin D deficiency ; Cartilage ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To test the importance of 24-hydroxylation of vitamin D3 on bone mineralization, rat pups born to vitamin D-deficient females were given either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3 for 16 days beginning at the time of weaning. Following such treatment analysis of blood samples revealed no detectable 24R,25-(OH)2D3 and 1,25-(OH)2D3 in the rats given the difluoro compound while revealing the expected 24,24-difluoro-25-hydroxyvitamin D3 and 24,24-difluoro-1,25-dihydroxyvitamin D3. The rats given 25-hydroxyvitamin D3 had the expected levels of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3. Following sacrifice at day 17, postweaning bone mineralization and modeling were studied in long bones using histological methods. Bones taken from vitamin D-deficient rats at the beginning and end of the experimental period had lesions typical of rickets. These included wide growth plates, excessive amounts of osteoid, and metaphyseal fibrosis. Following treatment with either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3, bone mineralization returned to normal. Growth plate widths and the amount of osteoid on bone surfaces were both substantially reduced and to a similar degree in both treatment groups. Normal cartilage core formation and trabecularization of the metaphyseal primary spongiosa were also restored to a similar degree in both groups. In effect, no difference was observed in any bone parameter studied between the 25-hydroxyvitamin D3- and the 24,24-difluoro-25-hydroxyvitamin D3-treated animals. These results provide strong evidence that 24-hydroxylation of the vitamin D molecule plays little or no role in the modeling and mineralization of bone.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 655-661 
    ISSN: 1432-0827
    Keywords: 1,25-Dihydroxyvitamin D3 ; 25-Hydroxyvitamin D3 ; 24,25-Dihydroxyvitamin D3 ; Receptors ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The hormonal metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], exerts its biological effects by binding to a cytosolic receptor protein. Such a protein has been demonstrated in vitamin D3 target organs including fetal rat calvariae and more recently in rat osteogenic sarcoma cells. In this study we have compared the binding of 25-hydroxyvitamin D3 [25(OH)D3] and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] to that of 1,25-(OH)2D3 in fetal rat calvariae and osteogenic sarcoma (OS) cells. Sucrose density sedimentation, DNA-cellulose chromatography, and intracellular uptake studies have been employed to evaluate these interactions. In cytosol preparations from calvariae, [3H]-1,25(OH)2D3 bound to a 3.3S macromolecule and to a much greater extent to a 5.8S macromolecule while both [3H]25(OH)D3 and [3H]24,25(OH)2D3 bound to the 5.8S macromolecule. By incubating intact calvariae and OS cells with labeled metabolites and thus establishing binding intracellularly prior to cell disruption, we have found that the 3.3S protein which has high specificity for 1,25(OH)2D3 occurs inside the cells; the 5.8S protein, however, does not occur inside the cells but is generated after cell disruption. The [3H]-1,25(OH)2D3-receptor complex adsorbed to DNA-cellulose and was eluted from this affinity resin at 0.28M KCl. In contrast, [3H]25(OH)D3 and [3H]-24,25(OH)2D3 binding activity did not adsorb to DNA-cellulose. We conclude that, in contrast to the 3.3S protein, the 5.8S macromolecule does not fulfill receptor criteria but is rather generated by the experimental manipulation of the bone cells. Our data suggest that the vitamin D3 actions on bone are mediated only via the 3.3S receptor, and hence quantitative but not qualitative differences of the effects of the various metabolites are feasible.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 43 (1981), S. 451-454 
    ISSN: 1432-1106
    Keywords: Monocular deprivation ; Cortico-geniculate projections ; Visual cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 16 cats monocularly deprived from 2 to 3 weeks of age, we studied 53 striate cortical cells which were identified as projecting to the dorsal lateral geniculate nucleus (LGN) on the basis of antidromic activation from LGN and of histological localization within cortical layer VI. As in the normal cat, these cortico-geniculate cells could be classified as slow, intermediate or fast, according to their axonal conduction velocities. The sampling ratio of the slow cells (mostly unresponsive to visual stimuli) was much higher than normal. On the other hand, the ratio of the intermediate (one half were simple cells) and fast cells (all except one were complex cells) was significantly lower than the norm. Also, the average axonal conduction velocities of the complex and simple cells were significantly slower than normal. These results suggest that normal maturation of cortico-geniculate cells, particularly fast and intermediate ones, is retarded or arrested by monocular visual deprivation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 44 (1981), S. 41-56 
    ISSN: 1432-1106
    Keywords: Eye movements ; Dark-rearing ; Cat ; Vestibulo-ocular reflex ; Optokinetic nystagmus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cats reared in total darkness to adulthood have abnormal eye movements. A spontaneous nystagmus is found in the dark before any visual experience. The eye movements evoked by vestibular or optokinetic stimulation are less effective at compensation than for a normal cat. The vestibuloocular reflex (VOR) has a low gain (around 0.3) and a frequency dependent phase relation. The efficiency of optokinetic nystagmus (OKN) is poorer than for a normal cat, except for downwards stimulus movement which is followed better than normal. OKN is poorest in response to a stimulus viewed monocularly moving in the nasal to temporal direction. Neither VOR nor OKN of a dark-reared cat recover in efficiency within 5 months of the animal being brought into the light. A normal cat put into the dark for 135 days shows none of these abnormalities except an occasional spontaneous nystagmus.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 42 (1981), S. 73-80 
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Vestibulo-ocular responses ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Unilateral lesions of the superior colliculus were made in normal cats. Following the operation, animals exhibited a typical neglect for contralateral visual space and forced circling toward the ipsilateral side. Optokinetic nystagmus was decreased for a stimulus moving toward the ipsilateral side, particularly in the temporal-to-nasal direction when the eye contralateral to the lesion was stimulated alone. — 2. When tested in the dark, animals exhibited a strong imbalance of their vestibulo-ocular responses (VOR) to velocity steps or to sinusoidal oscillations. Rotation of the animal toward the ipsilateral side produced a VOR with a higher gain, and a shorter phase-lead than in pre-operative controls. VOR was decreased in the opposite direction to a smaller extent, however. The overall asymmetry between the two sides at the post-operative stage was about 40%. — 3. In two animals, spontaneous nystagmus was present in the dark with the fast phase toward the ipsilateral side. — 4. Visual suppression of VOR was abolished during ipsiversive rotation and was still present during contraversive rotation. — 5. The effects of unilateral colliculectomy on VOR were transient. Spontaneous nystagmus disappeared in 3 days. VOR asymmetry in the dark was no longer present after 2–3 weeks. Loss of visual VOR suppression persisted for a few more days. — 6. Superior colliculus exerts a tonic control on static and dynamic components of VOR. This control may mediate part of VOR visual modulation and provide a substitutive input for compensation of pathological VOR asymmetry.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 7 (1981), S. 191-196 
    ISSN: 1432-2161
    Keywords: Fluoroscopy ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fluoroscopically positioned spot films are widely used in gastrointestinal and chest roentgenography. Little or no mention is made of the diagnostic use of fluoroscopic spot filming for skeletal roentgenography in major texts or recent literature, and a rough survey of practicing radiologists showed us that such procedure was frequently underutilized or not utilized. While skeletal pathology is usually depicted quite accurately by plain radiographs there are times when a problem may be rapidly and simply clarified by fluoroscopically positioned spot films. In an attempt to assess the value of fluoroscopy for evaluation of musculoskeletal problems, we reviewed 46 cases in which fluoroscopically positioned spot films were obtained.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 391 (1981), S. 323-335 
    ISSN: 1432-2307
    Keywords: Malignant fibrous histiocytoma ; Bone ; Ultrastructural cytology ; Myoblastic differentiation ; Undifferentiated mesenchymal stem cell ; Relationship to osteosarcoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Malignant fibrous histiocytoma (MFH) of bone is a well-defined tumor by light microscopy but no agreement has been achieved concerning its histogenesis. We present the light and electron microscopic findings of four cases of MFH of bone. In case 1 multiple bone tumors were observed and in case 4 the tumor developed after irradiation. It was our aim to document the cytological variability and to arrange the findings in a histogenetic concept of primary intraosseous MFH. We observed some undifferentiated cells but mainly histiocyte- and fibroblast-like cells including intermediate forms, and several types of giant cells. We should emphasize the fact that there were also some large cells with a light microscopic resemblance to rhabdomyoblasts and with electron microscopic characteristics of myoblastic differentiation. From the ultrastructural point of view, therefore, MFHs seem to derive from a primitive mesenchymal stem cell rather than from the ordinary histiocyte. It is suggested that osteosarcoma and MFH of bone may have a common progenitor cell but it is important to make a clear clinico-pathological distinction between the tumors because of differing biological behavior.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Urological research 9 (1981), S. 115-121 
    ISSN: 1434-0879
    Keywords: Heat coagulation ; in situ freezing ; Tissue repair ; Kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Autoradiographic investigations on kidney cells were performed after focal cryolesions (-180 to-196°C) and focal heat application (740°C). Cells were studied 12 h to 30 days after the lesions had been produced. In the damaged granulation tissue the percentage of radioactively labelled fibroblasts as well as the percentage distribution of leucocytes, monocytes, macrophages, lymphocytes, fibroblasts and fibrocytes and the mean cell concentration were determined. There were no significant differences in the leucocytic and monocytic cell reactions after the two types of physical injuries. However, the percentage of fibroblasts, fibrocytes and macrophages was higher and the percentage of lymphocytes lower after cryonecrosis when compared to heat application. The cell concentration increased during the last 2 weeks of the experimental time after a thermolesion. The labelling index of the wound fibroblasts was significantly higher after the 10th day after thermonecrosis than after in situ freezing. The increased cellular activity 2 to 4 weeks after heat coagulation of the kidney was probably induced by the delayed resorption of the carbonised necrotic tissue. The reduced phagocytic activity of macrophages might have depended on alteration and modification of molecular cell structures which were different after heat application or freezing. The different lymphocytic reaction seems to be the consequence of different immune responses of the lymphatic system. It is suggested that focal thermolesions may have a stimulatory effect on the cell-mediated immune response and that focal cryonecrosis may induce an increase in humoral immune response.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0568
    Keywords: Thalamus ; Ultrastructure ; Cat ; Quantitative analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of the ventrobasal complex (VB) of the cat thalamus was investigated in order to compare the data with those obtained in other thalamic nuclei. New data are described regarding the identification of Golgi II type neurons and several forms of axo-somatic synapses. By means of a quantitative analysis the number of different profiles, distribution of interprofile contacts, synaptic densities and degree of synaptic input of the two main cell-types were defined. The quantitative data obtained in the VB complex were compared with values for the lateral geniculate body (CGL), nucleus anterior ventralis (AV-non-sensory relay thalamic nucleus) and nucleus lateralis posterior-pulvinar complex (LP-PU-associative thalamic nucleus). The quantitative data reveal that: 1. The occurrence of RL terminals is equal in the two relay nuclei (VB and AV) and three-fold higher than in the LP-PU. 2. The percentage ratio of specific terminals (RL) in the total surface area in the relay nuclei is three-fold higher than in the LP-PU. 3. The RL→D synapses are twice as numerous in the relay nuclei as in the associative nucleus. 4. The density of synaptic RS profiles in VB is half of that found in LP-Pu. 5. In the thalamic relay nuclei the number of synaptic contacts on Golgi II type neurons is one-third of the synaptic supply of relay neurons; in the LP-Pu the amount of synaptic contacts on Golgi II type neuron approaches the synaptic supply of projective neurons.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 111-117 
    ISSN: 1432-0827
    Keywords: Calcium-deficient hydroxyapatite ; Amorphous calcium phosphate ; Bone ; Radial distribution function ; Carbonate apatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary When amorphous calcium phosphate (ACP) was transformed to crystalline hydroxyapatite (HA) in a series of aqueous slurry concentrations ranging from low to high, the higher slurry concentrations produced more Ca-deficient HA as measured by Ca/P ratio and heat-produced pyrophosphate. We feel that the excess solution phosphate produced in the higher slurry transformations results in lower Ca/P ratio HA. It has been suggested that an ACP is the precursor to bone apatite. Regulation of the in vivo ACP slurry concentration could then control the stoichiometry and, therefore, the metabolic activity of bone apatite. X-ray radial distribution function (RDF) analyses showed that CO 3 2− substitution in HA creates far greater structural distortions than do Ca deficiencies. The latter, however, do produce small, but observable, structural distortions when compared to stoichiometric HA. It now seems clear that the RDF of bone apatite can be modeled by a synthetic, Ca-deficient, CO 3 2− -containing HA.
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  • 12
    ISSN: 1432-0827
    Keywords: Phosphoprotein ; Bone ; 31P-NMR ; Phosphoserine ; Phosphothreonine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Fractionation of the EDTA-soluble, noncollagenous proteins of the organic matrix of chicken bone by Sephadex G-100 molecular sieving has revealed that the majority of the organic phosphorus is present in two fractions, from one of which a homogeneous phosphoprotein has been isolated. The purified phosphoprotein has an apparent molecular weight of 12,000 and contains bothO-phosphoserine andO-phosphothreonine.31P-NMR spectroscopy demonstrates that all of the organic phosphorus exists in the form of phosphomonoesters which have an average pK2 of 6.8. The phosphoprotein is highly acidic due to its high content of dicarboxylic acids in addition to the presence of organic phosphorus. The characteristic amino acid composition of the phosphoprotein establishes its noncollagenous nature and highlights the differences among bone, dentin, and enamel phosphoproteins. The absence ofγ-carboxyglutamic acid distinguishes it from osteocalcin, the noncollagenousγ-carboxyglutamic acid-containing peptide of bone matrix.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 455-457 
    ISSN: 1432-0827
    Keywords: Bone ; Osteoporosis ; Diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The bone mineral status of fifty-one children with diabetes mellitus was studied by single photon absorptiometry. The mean bone mineral content was 13% below values predicted by age, sex, height, and weight. Those children whose diabetes was one year or less in duration were as osteopenic as those whose diabetes was of longer duration. The demineralized children received a higher daily insulin dose than the others. No association was noted between the degree of skeletal demineralization and sex, statural growth, renal function, and serum calcium and phosphorus. No significant changes in bone mineral content were noted longitudinally.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 57-69 
    ISSN: 1432-0827
    Keywords: Thallium ; Chondrodystrophy ; Cartilage ; Bone ; Matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Using the transmission electron microscope, we sought to describe the morphology of thallium sulfate-induced chondrodystrophy in chick embryos. There was cell death and degeneration in all zones of growth cartilage, but the cells and matrix of the hypertrophic zone were the most severely affected. Ultrastructural changes of the hypertrophic chondrocytes consisted of alteration of the cytoplasmic contents and of the intercellular matrix; the cell membrane was smooth and without cytoplasmic extensions. The cytoplasm was filled with dilated rough endoplasmic reticulum, vacuoles of varying sizes and contents, and lipidlike bodies with electron-dense granules; mineral crystals, collagen, and degenerating mitochondria were present. The matrix showed only spotty calcification and a reduced number of dense bodies, vesicles, and granules. The cells appeared to have failed to exteriorize cell products across the plasmalemma. Failure to exteriorize cell products and to form cytoplasmic processes reduced the number of potential nucleation sites for calcification. The ultrastructure of osteocytes was much less affected.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 89-99 
    ISSN: 1432-0827
    Keywords: Soluble proteoglycans ; Resistant proteoglycans ; Collagen ; Bone ; Cartilage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Soluble proteoglycans (SPG) were extracted from bovine (BCC) and human (HCC) costal cartilages by the dissociative method using 4 M guanidinium chloride (GuHCl). Proteoglycans which are resistant to extraction (RPG) were obtained following collagenase digestion or hydroxylamine treatment of the cartilage residues. Similarly, SPG were extracted from bovine metaphyseal and cortical bone using EDTA. The RPG were extracted from the bones using hydroxylamine. Density gradient fractionation under dissociative conditions of cartilage SPG and RPG followed by chromatography on Sepharose 2B revealed that A1D1 RPG are smaller than the SPG. SPG reacted with either collagenase or hydroxylamine are also smaller than the parent SPG. A1D1 fractions obtained from BCC-SPG and RPG or from mixtures of SPG and acid-soluble collagen are free of hydroxyproline. Hydroxyproline is not completely separated from HCC-RPG. Density gradient fractionation of bone proteoglycans and Sepharose chromatography of the A1 and A1D1 fractions showed that those obtained from metaphysis are larger than those from cortical bone. This was attributed to the presence of calcified cartilage in metaphyseal bone. The A1D1 fractions of the metaphyseal proteoglycans seemed to undergo self-association since this fraction is larger than the A1 fraction from which it is derived. Cortical bone proteoglycans do not behave similarly. Density gradient purification under dissociative conditions failed to separate hydroxyproline from the proteoglycans obtained from bone. It is hypothesized that in bone proteoglycans and collagen might be linked.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 567-574 
    ISSN: 1432-0827
    Keywords: Bone ; Femur ; Age ; Mineral ; Apatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary It has previously been observed that after the third decade of life the tensile strength of bone decreases faster than its density [1], indicating that some microstructural change occurs in bone with advancing age. In order to try to elucidate this observation, the orientation and particle size of the mineral phase of bone have been studied with respect to age. Samples were taken from femora varying in age from 13 to 97 years. The results show that the degree of preferred orientation does not vary with age after the first decade of life. However, the percentage of small particles increased up to the fourth decade of life and thereafter decreased, a pattern of change similar to that observed for bone strength. It would seem to indicate that an increase in mineral particle size is a factor that contributes to the loss of bone strength and that an increased percentage of large particles in the later years of life could, along with osteoporosis, help to explain the increased fragility in the bones of the elderly.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 369-374 
    ISSN: 1432-0827
    Keywords: Histomorphometry ; Bone ; Reproducibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To study bone histomorphometry reproducibility in normal subjects, we performed during orthopedic surgery bone biopsies in 16 post-menopausal women. Each woman had four bone biopsies, two at the usual site in the iliac crest, one on the left and one on the right side, and two other biopsies just behind the usual site, one at each side. We performed measurements of trabecular bone volume, relative osteoid volume, osteoid surfaces, osteoclastic resorption surfaces and calcification front. The average values of the 16 patients were compared, on the one hand, two by two, by a student test, and on the other hand, by a variance analysis. By these two methods the results showed no significant difference between the average values of the 16 patients at each location for any of the histomorphometric parameters studied. However, there was a location variation which was estimated by the intra-individual variation for a given patient. On the other hand, we calculated from the variance analysis the location variance for a group of 10 to 100 patients. In any case all the parameters had a location variation which was high for osteoclastic resorption surfaces and relative osteoid volume when expressed in % of the absolute value of these parameters. The variation of the trabecular bone volume was 0–46. 15% (95% confident limit interval) in a single patient and the hypothetical value of the location variation was 41.6% for a group of 10 patients and 13.0% for a group of 100 patients.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 441-444 
    ISSN: 1432-0827
    Keywords: Bone ; Diffusion ; H2O ; Ions ; Vitamin D ; Diphosphonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The rates of diffusion of small ions and neutral molecules through isolated calvaria have been determined. Compared with data published on self-diffusion and diffusion through cartilage, H2O, 3-O-methylglucose, lactate, sulfate, and methylamine diffuse at approximately 2/3 the expected rate. Diffusion of H2O and sulfate was unaffected by the administration of the diphosphonate 1-hydroxyethane-1,1-diphosphonate (EHDP), although phosphate fluxes are markedly diminished. Diffusion of water was nearly doubled by vitamin D deficiency. A 1-week treatment with 1,25(OH)2D3 had no effect on H2O diffusion while returning calcium influx to normal. It is concluded that bone matrix permits a flow of small neutral and ionized molecules nearly comparable to that in cartilage. When changes in calcium and phosphate influx are observed, they can be ascribed to the exchange properties of bone mineral and not to changes in matrix permeability.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 499-504 
    ISSN: 1432-0827
    Keywords: Bone ; Collagen ; Density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The density of a bovine cortical bone matrix sample was found in water, several ethanol-water solutions, and in the dried state. Previously the density of the same mineralized bone was found fresh and when desiccated. The volume in each state was estimated from the dimensional changes axially, tangentially, and radially. Confirmation was found by determining the density of dried specimens upon immersion in xylene. The amount of imbibed xylene provided an estimate of the free pore volume in the dried matrix. The volume fraction of the solid constituent, S, in the wet matrix was found to be 0.57, from which the density of S in various solutions was calculated. Density of wet matrix in 0.15 M saline: 1.180 g/cc; for dried matrix, 1.246 g/cc. Density of wet S in saline: 1.33 g/cc; for dried S, 1.42 g/cc, which matches published values for collagen molecules. Dimensional changes between wet and dried state of matrix match published values for artificially cross-linked rat tail tendon fibers. Axially: 1.04, by area: 2.27; by volume: 2.62. Estimate of intrafibrillar volume, assuming 80% of mineral is within fibrils: 0.73 cc/g dry collagen.
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  • 20
    Electronic Resource
    Electronic Resource
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    Calcified tissue international 33 (1981), S. 631-639 
    ISSN: 1432-0827
    Keywords: Bone ; Osteopenia ; Noninvasive monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Radiological techniques were utilized for monitoring progressive changes in compact bone in the tibia of monkeys during experimentally induced osteopenia. Bone mass loss in the tibia during restraint was evaluated from radiographs, from bone mineral analysis, and from images reconstructed from gamma ray computerized tomography. The losses during 6 months of restraint tended to occur predominantly in the proximal tibia and were characterized by subperiosteal bone loss, intracortical striations, and scalloped endosteal surfaces. Bone mineral content in the cross section of the tibia declined 17–21%. Tomography demonstrated endosteal widening and reduced mineral content per unit of thickness of cortical bone. In 6 months of recovery, the mineral content of the proximal tibia remained depressed. Effects of the dynamic environment on local-regional changes in various skeletal areas are discussed.
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  • 21
    Electronic Resource
    Electronic Resource
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    Calcified tissue international 33 (1981), S. 35-39 
    ISSN: 1432-0827
    Keywords: Copper ; Resorption ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An investigation of the role of copper in bone metabolism was undertaken. Explanted calvaria from 6-day-old mice were grown for 48 h in medium with and without the addition of copper sulfate. Active resorption was found to be significantly inhibited in the presence of copper sulfate concentrations of 10−6M and above. Copper sulfate concentrations of 10−5M and above inhibited hydroxyproline, protein, and DNA synthesis. Lower concentrations were ineffective. The effect of 5 × 10−6M copper sulfate on resorption was reversible. Several other compounds were tested for similar effects and at 5 × 10−6M were found to inhibit bone resorption in the order: copper sulfate 〉 brown gold chloride 〉 sodium aurothiomalate 〉 zinc sulfate 〉 sodium sulfate. The copper sulfate effect was twice that of sodium aurothiomalate, and sodium sulfate was not significantly inhibitory. The results suggest that the high serum copper levels associated with rheumatoid arthritis may reflect the activity of a hypothetical control mechanism of bone resorption. In the diseased state this would act to restore the normal rate of bone resorption.
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  • 22
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    International archives of occupational and environmental health 48 (1981), S. 173-177 
    ISSN: 1432-1246
    Keywords: Bone ; Lead ; Soil ; Past exposure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The lead concentrations in the bones of skeletons of mediaeval inhabitants of England were found to be greatly in excess of those of contemporary populations and greater than could be reasonably accounted for by the probable levels of lead exposure during life. The concentrations of lead in the soil in the immediate vicinity of the skeletons approximated to the concentrations found in the bones, and it was considered that over the centuries the two had come into approximate equilibrium. The results from other studies are compared with those of the present one, and it is concluded that palaeontological remains offer doubtful criteria for the in-vivo assessment of lead exposure in past populations.
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  • 23
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    Experimental brain research 41 (1981), S. 233-246 
    ISSN: 1432-1106
    Keywords: Cat ; Ventral tegmental area ; Locus ceruleus ; Parabrachial nuclei ; Horseradish peroxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Thirty-three cat brains with injections of horseradish peroxidase in various regions of the cerebral cortex were screened for afferent projections from the ventral tegmental area, the locus ceruleus, and the parabrachial nuclei. All three structures were found to project to rather divergent parts of the cortex, including regions in the posterior half of the hemisphere. These results, especially for the ventral tegmental area and, to a lesser degree, for the parabrachial neurons, disagree with most of the target loci of established cortical afferents in the rat. Though our results might be attributed to species differences in the cortical innervation of brain stem structures, we prefer explanations which emphasize different densities in the distribution of brain stem afferents to the cortex, and/or which suggest different cortical targets of catecholaminergic and noncatecholaminergic neurons.
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  • 24
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex ; Optokinetic nystagmus ; Vestibular habituation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1.Unilateral habituation of the vestibuloocular reflex was produced in adult cats stimulated by repeated unidirectional velocity steps (vestibular training) or by a continuously moving visual surround (optokinetic training). — 2. Unidirectional vestibular training produced a strong asymmetry of vestibuloocular responses (VOR). Responses to velocity steps applied to the “trained” labyrinth were decreased both in gain and in time-constant. This effect generalized to responses to sinusoidal oscillations (0.03 Hz to 0.1 Hz), i.e. to a stimulus not used during training. — No spontaneous nystagmus was ever observed in spite of the dynamic VOR asymmetry. — 3. Unilateral vestibular habituation produced by vestibular training appeared to be a long-lasting phenomenon. It was still present 10 days after the end of training. — 4. Optokinetic responses were not affected by vestibular training. — 5. Unidirectional optokinetic training produced an increase in the slow phase velocity of optokinetic nystagmus (OKN) by about 25% in both directions. This effect did not persist for more than a few minutes. A marked spontaneous nystagmus was recorded in the dark after each session of optokinetic training, with a slow phase in the direction opposite to the previous OKN. — 6. VOR in response to velocity steps and to sinusoidal oscillations were decreased unilaterally after optokinetic training. This effect was of short duration, however, and disappeared within the interval between training sessions. This lack of retention contrasted with the prolonged effect of vestibular training.
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  • 25
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    Experimental brain research 42 (1981), S. 442-452 
    ISSN: 1432-1106
    Keywords: Chemoreceptors ; C Fibers ; Vagal nerves ; Gastro-duodenal Region ; Microelectrode technique ; Cat ; Chémorécepteurs ; Fibres C ; Nerfs vagues ; Région Gastro-duodénale ; Technique des ; Microélectrodes ; Chat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé La sensibilité vagale aux hydrates de carbone (glucose en particulier) et aux acides (acide chlorhydrique et acide acétique) a été étudiée dans la région gastro-duodénale chez des chats anesthésiés. Les potentiels d'action ont été enregistrés dans le ganglion plexiforme droit au moyen de microélectrodes extracellulaires. Des récepteurs, sélectivement sensibles soit aux hydrates de carbone, soit aux acides, ont été ainsi mis en évidence. Ces récepteurs doivent donc être considérés comme de véritables glucorécepteurs et acidorécepteurs. Les deux types de chémorécepteurs, silencieux au départ, présentent une fréquence de décharge basse qui varie entre 2 et 14 imp/s pour les acido-récepteurs et entre 2 et 30 imp/s pour les glucorécepteurs. Les réponses peuvent être irrégulières ou régulières et durer plusieurs minutes; leur latence est faible (entre 1 et 20 s) pour les deux types de chémorécepteurs, ce qui suggère une localisation dans la muqueuse ou au voisinage de celleci. Les fibres connectées aux glucorécepteurs et aux acido-récepteurs ont une vitesse de conduction qui varie entre 0,8 et 1,2 m/s: elles sont donc amyéliniques. L'enregistrement de l'activité électromyographique de la région gastro-duodénale a permis de montrer que les acido-récepteurs et les glucorécepteurs interviennent dans la régulation de la motilité gastrique et duodénale, l'effet le plus marqué étant une diminution du rythme électrique de base de l'estomac.
    Notes: Summary Vagal sensitivity to carbohydrates (mainly glucose) and to acids (hydrochloric and acetic acids) was studied in the gastro-duodenal region of anesthetized cats. Action potentials were recorded extracellularly from the nodose ganglion by means of glass microelectrodes. Receptors responding to glucose perfusion were found at this level as well as receptors stimulated by acid perfusion. It is shown that each type of receptor was activated by only one kind of stimulus (carbohydrates and acids, respectively). These receptors must thus be considered as true glucoreceptors or acido-receptors. Being silent before activation, these two types of chemoreceptors discharged at a frequency that varied from 2 to 14 imp/s for the acido-receptors, and from 2 to 30 imp/s for the glucoreceptors. The response could be irregular or regular and might last several minutes. Its latency was short (between 1 and 20 s for both types of chemoreceptors. It was therefore supposed that they were located in the mucosa or neighboring structures. From the conduction velocities (0.8–1.2 m/s), it was concluded that fibers originating from the acidoand glucoreceptors belonged to the C type. Recording of the electromyographic activity from the gastro-duodenal region demonstrated that the gluco- and acido-receptors are involved in the regulation of motility of the gastric and duodenal regions.
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  • 26
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    Experimental brain research 43 (1981), S. 25-33 
    ISSN: 1432-1106
    Keywords: Cat ; LP-pulvinar complex ; MIN ; Visual texture ; Receptive field properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Multiple visual field representations are contained within the feline LP-pulvinar complex; regions differentiated by their afferent and efferent connectivity patterns as the striate-, tecto- and retino-recipient zones. Cell responses from these visuotopic zones were investigated in immobilized cats under N2O/O2 supplemented with pentobarbitone or Althesin, using spot, bar and textured stimuli. Response fields recorded within the LP-pulvinar complex were classified as diffuse, concentric, movement-, direction- or orientation-sensitive. Concentric receptive fields were further classified as sustained (X), transient (Y) or tonic/phasic W-cells. Direction-and movement-sensitive cells predominated in the striate- and tecto-recipient zones, respectively. Motion of noise fields, or noise bars against an identical stationary noise background elicited vigorous responses from cells in the striate zone, many showing a preference for noise stimuli. In contrast, cells from the tectal zone and other divisions of the LP-pulvinar complex were insensitive to noise. The retino-recipient zone at the lateral margin of the pulvinar nucleus was characterized by cells with concentric receptive fields, the majority exhibiting properties similar to W-cells in the LGNd. The evidence supports the notion of functional subdivision within the LP-pulvinar complex corresponding to the visuotopically organized regions defined by their connectivity patterns. Consideration of the retino-recipient zone as an extension of the LGNd-MIN complex is discussed.
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  • 27
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    Experimental brain research 43 (1981), S. 101-103 
    ISSN: 1432-1106
    Keywords: Cat ; Pyramidal tract ; Corticospinal system ; Locomotion ; Stepping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied the pattern of stepping in cats, before and after the placement of lesions in the corticospinal system. We found a deficit after the lesions, which was characterized by increased extension of the involved hindlimbs during the stance (E2–E3) phase of the step cycle. This deficit lasted two weeks or less. It may reflect loss of inhibitory influences upon extensor motoneuron pools.
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  • 28
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    Experimental brain research 43 (1981), S. 413-418 
    ISSN: 1432-1106
    Keywords: Gracile nucleus ; Plasticity ; Somatotopy ; Agenetic defect ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The somatotopic representation of the hindlimb in the gracile nucleus was studied in two cats who had a congenital defect of one hindfoot. The defect comprised all of the foot downward from and including the heel, and the distal third of tibia and fibula. The part of the sciatic nerve normally supplying the lower hindlimb and the hindfoot was reduced in diameter by one third. The motoneurones corresponding to the absent muscles were lacking and replaced by glial elements. The cross-sectional area of the dorsal columns at segment S2 was reduced by more than 20%. The gracile nuclei, in contrast, were not reduced in size. Only the diameter of its neurones was significantly smaller. Electrophysiological single and multi-neurone recordings revealed an altered somatotopic representation in the gracile nucleus on the defective side. The nuclear area normally representing the missing parts of the body surface now received input from the stump. There was no nuclear area devoid of afferent input, and there was no input in the gracile from the forelimb or from the contralateral side. It is concluded that the remaining parts of the leg project onto the gracile nucleus in an ordered fashion, sharing the entire nucleus according to their present afferent fibres.
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  • 29
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    Experimental brain research 43 (1981), S. 422-428 
    ISSN: 1432-1106
    Keywords: Retinal ganglion cells ; Cat ; Rod and cone mediated receptive fields ; Receptive field size/shape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Receptive field centres of cat retinal ganglion cells, as mediated by rod and by cone inputs, were mapped as contours of iso-sensitivity at a mid-mesopic adapting luminance using, respec-tively, 452 nm-blue and 578 nm-yellow narrow-band lights at an intensity 1 log unit above threshold for the most sensitive locus. Based on the sizes and shapes of mapped rod and cone centres for 74 ganglion cells, four receptive field centre categories were distinguished. Cone and rod centres were usually elliptical, and in almost 60% of cells the major axis through the receptive field centre was oriented within ±20 ° of horizontal. In 69%, rod and cone centres were non-concentric, 66% had larger rod than cone centres — area ratios ranging from 0.6 ∶ 1 to 2.9 ∶ 1, and in only two cases was the rod centre actually smaller than the cone centre.
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  • 30
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    Experimental brain research 41 (1981), S. 301-309 
    ISSN: 1432-1106
    Keywords: Cat ; Auditory ; Localization ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses of single neurones in the inferior colliculus of anaesthetized adult cats and kittens were studied using best-frequency stimuli of varying interaural intensity difference (IID). Two broad classes of neurone, distinguished by the predominant type of input from each ear, were examined. One class of cells received predominantly excitatory input from each ear (EE cells). The other class were excited by monaural stimulation of the contralateral ear and showed no response to monaural stimulation of the ipsilateral ear, but inhibition of the excitatory response by simultaneous ipsilateral stimulation (EI cells). Fourteen of the 18 adult EI cells showed marked changes in discharge rate with variation in IID. Adult EI cells showed low response variability and were insensitive to changes in average binaural intensity. In all cases of IID sensitivity, the onset component of the response was less sensitive to IID than the sustained component. Eight out of ten EE cells were insensitive to IID over the range tested. Cells of high best-frequency in kittens younger than 28 days showed irregular changes in discharge rate with variation in IID and wide response variability. Some low-frequency EI cells in young kittens showed sensitivity to IID, but it is unlikely that these could be involved in sound localization as their frequency response was inappropriate. Many cells in kittens aged 31–40 days showed monotonic, adult-like IID functions, but the response variability of these cells remained higher than that of adult cat neurones. These data provide evidence for a developmental change of binaural interaction in the cat.
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  • 31
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    Experimental brain research 41 (1981), S. 329-337 
    ISSN: 1432-1106
    Keywords: Caudate nucleus ; Golgi/EM ; Corticocaudate projection ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A combined Golgi/electron microscopic technique was used to investigate the fine structure and synaptology of Golgi-stained spiny neurons in the caudate nucleus of the cat. In order to study the termination sites of cortical afferents on Golgistained spiny neurons, cortical fibres were caused to degenerate by making extensive cortical lesions 3 days prior to fixation of the animals. When examined in the electron microscope, perikarya of labelled spiny neurons have a round nucleus, a few mitochondria and microtubules, and a poorly developed Golgi apparatus and rough endoplasmic reticulum. Only rarely are axo-somatic contacts seen. Labelled dendrites exhibit a moderate number of microtubules and sometimes elongated mitochondria. Numerous labelled spines are seen in the vicinity of their parent dendrites. They are contacted by smaller type I and type III boutons and larger type IV boutons (Hassler et al. 1978). Large boutons filled with clear round vesicles establish symmetric contacts with labelled dendritic shafts. Degenerating boutons of cortical afferents are seen in contact with spines and, more rarely, with dendritic shafts of Golgi-stained spiny neurons. All degenerating boutons synapsing with labelled structures are found some distance from the cell body. No contacts of degenerating cortical boutons with the soma or with stem dendrites of Golgi-stained spiny neurons are found.
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  • 32
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    Experimental brain research 42 (1981), S. 196-202 
    ISSN: 1432-1106
    Keywords: Retina ; Sampling theorem ; Brisk, X and Y, ganglion cells ; Cat ; Visual acuity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The relationship of brisk transient and brisk-sustained unit cut-off frequencies to their respective array cut-off frequencies has been calculated by means of sampling theory from the corresponding α and β-mode cell densities at various retinal eccentricities. Interpretation of the results depends on whether on and off cells of each class are functionally homogeneous or heterogeneous populations. In agreement with expectations from sampling theory for a system involved in resolution tasks, it is found that the brisk-sustained system has less potential for undersampling and spurious imagery than the brisk-transient system, which is thought to play a different role. The brisk-sustained array could avoid such aliasing altogether if it is functionally heterogeneous. The differences between the two systems are similar to those between insect eyes respectively optimised for high resolution vision or the detection of high velocity image motion.
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  • 33
    ISSN: 1432-1106
    Keywords: Oculomotricity ; Lateral rectus and retractor bulbi motoneurones ; Infraorbital nerve ; Vibrissal pad ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses from lateral rectus, medial rectus and retractor bulbi nerves were obtained following electrical stimulation of the vibrissal pad of the cat. Discharges in afferent fibres dissected from the infraorbital nerve were recorded during movements of the vibrissae and following electrical stimulation of the vibrissal pad. Both stimuli activated the same population of Aα fibers. Intracellular records were obtained from lateral rectus motoneurones identified antidromically in the principal abducens nucleus and from retractor bulbi motoneurones similarly identified in the accessory abducens nucleus. EPSPs (3 mV) were recorded in lateral rectus motoneurones following electrical stimulation of the ipsilateral vibrissal pad at a latency of 3.5 ms. Large-amplitude disynaptic EPSPs (15 mV) were recorded in retractor bulbi motoneurones following the same vibrissal stimulation. The synaptic excitation evoked in both lateral rectus and retractor bulbi motoneurones through stimulation of the ipsilateral vibrissal pad induced an early retraction followed by an abduction of the eye ball. The hypothesis is that the vibrissal message might complement other sensory modalities in the generation of patterned eye movements.
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  • 34
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    Experimental brain research 44 (1981), S. 431-436 
    ISSN: 1432-1106
    Keywords: Cat ; Visual cortex ; Orientation columns ; Deoxyglucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three-dimensional reconstructions of the orientation column system were obtained from the visual cortex of four cats using the deoxyglucose technique. One cat had normal visual experience, one was monocularly deprived and two had selective experience with vertical and horizontal contours, respectively. In areas 17 and 18 orientation columns form a remarkably regular system of equally spaced parallel bands whose trajectory is orthogonal to the borderline between areas 17 and 18. This topographic organization is resistant to manipulations of early visual experience.
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  • 35
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    Experimental brain research 44 (1981), S. 437-440 
    ISSN: 1432-1106
    Keywords: Response variability ; Visual cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The relationship between the variance and mean rate of discharges of simple cells in the cat striate cortex has been examined when mean rate was varied by changing either stimulus spatial frequency or contrast. In both cases, the variance was related to the mean discharge rate by an exponent of about 1.15; the relation was thus roughly linear. The discharge variance was on average 1.7 times the mean rate for data obtained from measurements of the neurones' spatial frequency tuning curves, and 1.48 times the mean for data from the response-contrast determination. However, this difference was not statistically significant.
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    Experimental brain research 41 (1981), S. 420-426 
    ISSN: 1432-1106
    Keywords: Vestibular nystagmus ; Cat ; Visual suppression ; Vertical asymmetries ; Nystagmus vestibulaire ; Chat ; Suppression visuelle ; Asymétries verticales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Chez le chat, l'asymétrie des réponses nystagmiques verticales à une rotation autour d'un axe interaural a été caractérisée en mesurant la fréquence de battement et le gain du réflexe vestibulooculaire dans chaque sens vers le haut et vers le bas. Des variations sinusoïdales de la vitesse de la tête, ou des échelons de vitesse ont été exercés dans trois conditions visuelles: à l'obscurité (stimulation vestibulaire pure); à la lumière (stimulation mixte vestibulaire et optocinétique); et enfin, alors qu'un miroir placé devant l'animal et solidaire du mouvement de sa tête lui fournissait une référence visuelle stable (vision stabilisée). Dans les trois conditions, la fréquence de battement et le gain du nystagmus vers le bas (désigné par le sens des phases rapides) sont plus grands que ceux du nystagmus vers le haut. A l'obscurité, les caractéristiques des nystagmus postrotatoires suggèrent une constante de temps plus longue pour le réflexe vestibulo-oculaire vers le bas que vers le haut. A la lumière, les deux stimulations agissent synergiquement. En vision stabilisée, la suppression du nystagmus s'exerce préférentiellement sur le nystagmus haut, ce qui appuie l'hypothèse d'une addition algébrique des effets des deux stimulations.
    Notes: Summary In the cat, the asymmetry of vertical nystagmus in response to a rotation around the Yaxis has been characterized by measuring the beat frequency and gain of vestibulo-ocular reflexes in each direction (upward and downward). Sinusoidal variations of head velocity or velocity steps have been applied under three visual conditions (a) in darkness (pure vestibular stimulation); (b) in the light (mixed vestibular and optokinetic stimulation); (c) with a mirror placed in front of the animal; since the mirror image moved with the head, the animal was provided with a stable visual cue (stabilized vision). In all three conditions, beat frequency and gain were greater for downward than for upward nystagmus (the direction refers to that of the quick phase). In darkness, the characteristics of postrotatory nystagmus suggested a greater time constant for downward than for upward vestibulo-ocular reflexes. In the light, both stimuli acted synergistically. In stabilized vision, upward vestibular nystagmus was preferentially suppressed, suggesting an algebraic summation of the effects arising from both kinds of stimuli.
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    Experimental brain research 42 (1981), S. 89-98 
    ISSN: 1432-1106
    Keywords: Receptive field ; Single unit ; Striate cortex ; Simple cell ; Cat ; Model stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The receptive field organization of simple cells was studied by analyzing interaction effects between two stationary flashing light stimuli. One stimulus was positioned in the most responsive part of the receptive field to produce activity against which the effects of the other stimulus in various positions of the visual field could be determined. The receptive field was subdivided into an elongated center and elongated antagonistic flanks. The effects on the flanks were always considerably stronger on one side. Powerful flank suppression could be elicited within a region which usually was only slightly wider than the receptive field center. The suppression was just as stimulus specific as the activation of the center and occurred only by light ON or OFF. The cells were classified into ON-dominant and OFF-dominant depending on the kind of response found in the center. In ON-dominant cells the strong flank suppression occurred only by light ON, and light OFF produced enhancement. Correspondingly, the strong flank suppression occurred only by light OFF in OFF-dominant cells. This is consistent with the interpretation that simple cells have excitatory and inhibitory input from the same type of cells in the lateral geniculate nucleus (LGN), i.e., only from ON-center or OFF-center cells. The small size of the area where strong flank suppression occurred shows that inhibition comes from a few LGN cells rather than from a large pool of cells. A model for simple cell receptive fields presuming overlapping but acentric excitatory and inhibitory fields with input to both fields from either ON- or OFF-center LGN cells was tested by computer simulation and shown to fit the experimental data.
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    Experimental brain research 42 (1981), S. 99-107 
    ISSN: 1432-1106
    Keywords: Receptive field ; Single unit ; Striate cortex ; Complex cells ; Cat ; Model simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The receptive field organization of complex cells was studied by analyzing interaction effects between two stationary flashing light stimuli. One was placed in the most responsive part of the receptive field to produce activity against which effects of the other in different visual field positions could be determined. The receptive field was spatially organized into antagonistic center and flanks just like the fields of simple cells. However, both center and flanks were found within the receptive field area where a single slit evoked discharge. Center and flanks were elongated along the optimal stimulus orientation. The flanks were displaced from the center normal to optimal stimulus orientation. In the center, ON- and OFF-responses were usually about equal in strength and the maximum ON- and OFF-responses occurred in about the same position. This shows that complex cells are activated by input from both ON- and OFF-center cells in the lateral geniculate nucleus (LGN) where the receptive field centers of the LGN cells overlap closely. This explains most of the specific features of complex cells, e.g., the spatially overlapping ON- and OFF-zones, the large response field, the repetitive firing when a slit moves over the receptive field, and the marked non-linear spatial summation. Strong flank suppression occurred with both ON and OFF. The effects were usually stronger on one side of the center. Maximal suppression occurred on the same side with both ON and OFF. This is consistent with the interpretation that complex cells are inhibited by input from both LGN ON- and OFF-center cells with overlapping receptive field centers. A model presuming that complex cells have overlapping but acentric excitatory and inhibitory fields was tested by computer simulation and shown to fit the experimental data. This is the same model as presented for simple cells in the preceding paper (Heggelund 1980), except that the excitatory and inhibitory fields of simple cells have input from either ON- or OFF-center LGN cells, whereas in complex cells they have input from both types.
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  • 39
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    Experimental brain research 42 (1981), S. 146-157 
    ISSN: 1432-1106
    Keywords: Nucleus tractus opticus ; Visual response ; Direction specificity ; Optokinetic nystagmus ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary All cells in the nucleus of the optic tract (NOT) of the cat, that Bcould be activated antidromically from the inferior olive, were shown to be direction-specific, as influenced by horizontal movements of an extensive visual stimulus. Cells in the left NOT were activated by leftward and inhibited by rightward movement, while those in the right NOT were activated by rightward and inhibited by leftward movement. Vertical movements did not modulate the spontaneous activity of the cells. The mean spontaneous discharge rate in 50 NOT cells was 30 spikes/s. This direction-specific response was maintained over a broad velocity range (〈0.1 ° – 〉100 °/s). Velocities over 200 °/s could inhibit NOT cells regardless of stimulus direction. All cells in the NOT were driven by the contralateral eye, about half of them by the ipsilateral eye also. In addition, activation through the contralateral eye was stronger in most binocular units. Binocular cells preferred the same direction in the visual space through both eyes. An area approximately corresponding to the visual streak in the cat's retina projected most densely onto NOT cells. This included an extensive ipsilateral projection. No clear retinotopic order was seen. The most sensitive zone in the very large receptive fields (most diameters being 〉20 °) was along the horizontal zero meridian of the visual field. The retinal input to NOT cells was mediated by W-fibers. The striking similarities between the input characteristics of NOT-cells and optokinetic nystagmus are discussed. The direction selectivity and ocular dominance of the NOT system as a whole can provide a possible explanation for the directional asymmetry in the cat's optokinetic nystagmus when only one eye is stimulated.
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  • 40
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    Experimental brain research 44 (1981), S. 177-186 
    ISSN: 1432-1106
    Keywords: Posture ; Movement ; Motor cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of postural support on posturo-kinetic co-ordination has been studied with a model of movement consisting of limb flexion induced by stimulation of the motor cortex in chronically implanted cats. To more easily quantify the responses by measuring the vertical forces exerted at the level of the four limbs, only weak stimuli were used, mainly triggering isometric motor activity. The aim of the study was to analyse the influence on the motor responses of various postural supports leading to a weight distribution between the limbs which differs from the normal situation. Three kinds of initial posture were tested. The first was obtained by directing the head of the cat to the left or to the right. The second type consisted in raising one or two of the platforms supporting the limbs. The third was obtained by adding a load to one of the limbs. The main results established in these conditions were the following: The latencies of the beginning of the movement and its associated postural adjustment, as revealed by the onset of force changes, were independent of the initial postural situation. Whatever the initial weight distribution, the amplitudes of force variations induced by given intensities of cortical stimulation were generally constant, though small variations of amplitude were noted in some cases. When there were changes in the response amplitudes, all four limbs were generally affected. The effect was observed whatever the limb concerned by modification of the support. This not only means that the postural responses depend on the amplitude of the movement but also that the amplitude of the movement itself may be modified according to perturbations affecting the postural limbs. Comparison of the present data with previous results leads to the hypothesis that a postural reference is taken into account in the determination of amplitudes of responses to cortical stimulation.
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    Naunyn-Schmiedeberg's archives of pharmacology 317 (1981), S. 357-363 
    ISSN: 1432-1912
    Keywords: Diuretics ; Amiloride ; Tizolemide ; MK-447 ; Tubular secretion ; Kidney ; Saluresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Using the modified Sperber technique in the hen the relationship between renal tubular secretion and urinary excretion of electrolytes of three alkaline diuretics was studied. The true tubular excetion fraction (TTEF) averaged 0.39, 0.60 and 0.01, respectively for amiloride, tizolemide and MK-447. Thus, there was extensive active tubular secretion of amiloride and especially of tizolemide, while a tubular secretion of MK-447 could not be established. The TTEF values of amiloride and tizolemide were significantly reduced by coadministration of mepiperphenidol (Darstine), an inhibitor of organic cation transport while these values were unaffected by the organic anion transport inhibitor novobiocin. Thus, amiloride and tizolemide are transferred from peritubular blood to the urine by an organic cation transport system, thereby significantly increasing the intraluminal concentration of the respective diuretic. This contributed significantly to the urinary electrolyte effects of each drug (in the case of amiloride a natriuretic and potassium-sparing effect and for tizolemide mainly a saluretic effect) since these effects were elcited predominantly on the ipsilateral side after renal portal infusion of the diuretic on one side and coinfusion of Darstine significantly reduced these excess excretions. Assuming a distal site of action, it seems therefore that a significant part of the renal electrolyte effects of amiloride (tizolemide) are coupled to its active tubular secretion and evoked from the luminal (urine) side of the avian nephron. In further support of a direct action of these diuretics on tubular cells, the renal clearances of 51-Cr-EDTA and 125-I-Na-o-iodohippurate were symmetrical during unilaterallity in electrolyte excretions. There was a small but significant ipsilateral excess saluresis after portal infusion of MK-447 that was not reduced by Darstine. This might be related to the higher concentrations of MK-447 in peritubular blood on the side of the infusion. It is suggested that MK-447 reaches its site(s) of action primarely by passive diffussion from the peritubular side of the nephron.
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  • 42
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    Pflügers Archiv 391 (1981), S. 226-230 
    ISSN: 1432-2013
    Keywords: Central chemosensitivity ; Morphology ; HRP ; Labelling ; Mapping ; Medulla oblongata ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A modified horseradish peroxidase labelling technique was used to study the distribution pattern of neurons in the central chemosensitive fields of the medulla oblongata of cats. In several cryosectioned medullae a mapping of superficially located HRP-labelled neurons was achieved. The distribution and configuration of the labelled neurons indicate that most of them belong to the nucleus paragigantocellularis lateralis. However, by varying the time of incubation it was possible to identify different types of neurons. On the basis of certain aspects of the HRP incorporation mode and neuronal topography a specific type of small-sized neurons has been identified. Some functional implications of these small neurons with respect to their possible chemosensitive activity are discussed.
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  • 43
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    Pediatric radiology 10 (1981), S. 207-209 
    ISSN: 1432-1998
    Keywords: Vascular malformation, kidney ; Cirsoid aneurysm ; Kidney ; Aneurysm, renal artery ; Hypertension, children ; Renal angiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two cases of congenital renal vascular malformation (cirsoid aneurysms) are reported. Both were associated with hypertension, and were detected by angiography. In one child, additional congenital intrarenal artery aneurysms were present. He became normotensive after heminephrectomy of the involved kidney.
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  • 44
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    Pflügers Archiv 389 (1981), S. 143-148 
    ISSN: 1432-2013
    Keywords: Retractor bulbi muscle ; Trigeminal afferents ; Oculomotricity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of vestibular and trigeminal stimulation on reflex responses of each slip of the retractor bulbi muscle were tested by recording the electromyogram. 1. In “encéphale isolé” cat, phasic electrical stimulation of the horizontal canal induced no response in the RB slips. Repetitive vestibular stimulation did not produce nystagmus in the RB muscle while strong muscular discharges were observed in the nystagmus lateral rectus muscle. 2. In anaesthetized cats, three trigeminal inputs elicited strong reflex responses in each slip of the RB muscle. Electrical stimulation of the vibrissae or the infra-orbital nerve evoked a two component reflex response (latencies: 5ms±0.5 and 14ms±2). Electrical stimulation of the supraorbital nerve elicited a single component reflex response (latency: 6ms±0.5). Electrical stimulation of the long ciliary nerves evoked a complex response with four components (latencies: 7.5ms±0.5, 10ms±2,15ms±2,20ms±2) 3. Pentobarbital and morphine produced lasting depression of the reflex responses of the RB muscle. The depressive effect of morphine was reversed by naloxone.
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  • 45
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    Pflügers Archiv 392 (1981), S. 34-39 
    ISSN: 1432-2013
    Keywords: Erythropoietin ; Erythropoiesis ; Kidney ; Hypoxia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Controversial hypotheses exist as to whether hypoxic kidneys produce biologically active erythropoietin (Ep) or an inactive erythropoietic factor that generates Ep from plasma protein in the blood. To clarify the role of the kidney in Ep production we attempted to extract Ep from kidneys of normal and of hypoxia exposed (6 h at 0.42 atm) Sprague-Dawley rats. Ep was measured in the microsomal fraction of kidney homogenates, using the exhypoxic polycythemic mouse assay for Ep. The Ep content was also determined in kidneys that were flushed free of blood with isotonic phosphate-buffer prior to extirpation. We found 0.04 U Ep/g in blood-depleted kidneys of normal rats. Upon exposure of the animals to hypoxia the Ep level increased to 0.92 U/g kidney. Ep levels were significantly higher in the kidney cortex than in the medulla. The erythropoietic activity in renal extracts was not enhanced after incubation of samples with homologous serum. Ep extracted from hypoxic kidneys behaved identically with plasma-Ep in the following biochemical tests: heat stability, affinity chromatography with wheat germ lectin, ion exchange chromatography, molecular sieve chromatography and neuraminidase inactivation. These studies support the hypothesis that kidney cortex cells are capable of producing biologically active Ep.
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  • 46
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    Archives of toxicology 48 (1981), S. 21-27 
    ISSN: 1432-0738
    Keywords: Rats intoxicated ; Lead acetate ; Copper chloride ; Zinc chloride ; D-penicillamine ; Lactate dehydrogenase ; Serum ; Kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Following subacute intoxication of rats with Pb-, Cu-, and Zn-salts (separately or in mixture) for 5 weeks, the chelating agent D-penicillamine was administered for 3 weeks. In the course of the 3-month experiment, lactate dehydrogenase (LDH) was estimated in serum and in cytoplasmic fraction of the kidney. Pb2+ treatment resulted in an increase of LDH activity, Cu2+ in a slight decrease, whereas Zn2+ had no effect, respectively. Mixture of these metals caused a significant rise in the enzymatic activity. Seven weeks after the stoppage of the administration of toxic substances, altered LDH activity, both in serum and in kidney returned to normal. D-penicillamine treatment was found to accelerate a restoration of the enzyme activity. In the experiments in vitro, Cu2+ inhibited significantly the kidney LDH activity, Pb2+ and Zn2+ being 100- and 400-times less efficient, respectively. Cu2+ inhibition was reversed by D-penicillamine, whereas inhibition of LDH by Zn2+ or Pb2+ was irreversible.
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  • 47
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    Archives of toxicology 49 (1981), S. 85-91 
    ISSN: 1432-0738
    Keywords: Rabbits ; Lead acetate ; Ultrastructure ; Kidney ; Proximal tubule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Electron microscopical studies were carried out on the kidneys of rabbits given s.c. injections of 0 (control), 0.25 or 0.50 mg lead acetate/kg b.w. 3 times a week during 14 weeks. At the end of the experimental period the animals had lead blood levels of 60, 500 and 600 μg/1 whole blood respectively. Treatment-related renal changes were found in the proximal tubules; they consisted of a dose-related increase in the amount of lysosomes in epithelial cells of the convoluted part, and of severely damaged cells and loss of brush border in the straight part. There was also an increase in lysosomal tubular inclusions, which are considered characteristic of lysosomes of the proximal tubular cells of the rabbit kidney. The significance of these findings for assessing the risk of occupational exposure to lead is briefly discussed.
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  • 48
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    Archives of toxicology 48 (1981), S. 167-172 
    ISSN: 1432-0738
    Keywords: Mercury bichloride ; Kidney ; Polyribosomes ; Protein-synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Polyribosome sedimentation pattern and their in vitro protein synthetic ability were investigated in kidneys of mice treated with a single injection of HgCl2. Mercury bichloride, after 1 h, evokes polyribosome disaggregation, the extent of which is logarithmically correlated with the dose in the range of 2.5–20 μmoles/kg. With the dose of 2.5 μmoles/kg the effect occurs after 1 h, it is maximal between 1 h and 3 h. After 6 h polyribosomes are reaggregated. Cyclohehimide pretreatment does not prevent the HgCl2 induced disaggregation of kidney polyribosomes. The cell-free system derived from kidneys of HgCl2 treated mice (10 μmoles/kg, 1 h) has a decreased protein synthetic ability. Both, in livers of mice treated with 20 μmoles/kg HgCl2 and in isolated rat's reticulocytes incubated with 20 μM HgCl2 during 1 h there were no apparent changes in the polyribosome sedimentation patterns.
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  • 49
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    Journal of cancer research and clinical oncology 101 (1981), S. 171-176 
    ISSN: 1432-1335
    Keywords: Chondrosarcoma ; Clear-cell chondrosarcoma ; Sarcoma ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Report of a case of clear-cell chondrosarcoma at the upper end of the left femur of a 32-year-old woman. She had two pathologic fractures during a period of 4 years. After the first fracture an excochleation and after the second fracture a resection were done. Two years after resection she had no local recurrence and was free from metastasis.
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  • 50
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    Naunyn-Schmiedeberg's archives of pharmacology 317 (1981), S. 168-172 
    ISSN: 1432-1912
    Keywords: Paraoxon ; Blood pressure ; Vertebral artery ; Central muscarinic receptors ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Application of paraoxon into the left vertebral artery (8–80 μg) or both the left and right vertebral artery (4–8 μg) of the anaesthetized cat evoked dose-dependent depressor effects, whereas heart rate was not influenced significantly. Also after systemic administration of paraoxon (150–825 μg·kg−1), while peripheral muscarinic receptors were blocked, depressor effects were still observed. Dose-response curves for the depressor response to paraoxon were established. Infusion of low doses of dexetimide via the vertebral artery prevented the hypotensive action of paraoxon. The distribution of this antimuscarinic drug in the brain was investigated. The depressor effect of paraoxon can be attributed to both a decrease in peripheral resistance and cardiac output. Decerebration and midcollicular transection were carried out in order to elucidate the site and mechanism of action. The depressor effect of paraoxon seems to be mediated by a central mechanism of action located within the lower brain stem. It is concluded that stimulation of muscarinic receptors in the pontomedullary region gives rise to the observed changes in haemodynamic parameters. Muscarinic receptors in the hypothalamus seem to be of minor importance for the hypotensive action of paraoxon.
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  • 51
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    Virchows Archiv 390 (1981), S. 193-204 
    ISSN: 1432-2307
    Keywords: Renin ; Kidney ; Segmental renal hypoplasia ; Hypertension ; Immunofluorescence ; Peroxidase anti-peroxidase (PAP)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distribuation of renin in two cases of segmental renal hypoplasia was investigated by immunofluorescence and the peroxidase anti-peroxidase (PAP) method using an anti-human renin antiserum. Renin-containing cells were found only in hypoplasic segments in the vicinity of altered glomeruli and small arteries. Well-preserved renal cortex and areas of chronic atrophic pyelonephritis failed to show any demonstrable site of renin production. Whatever is the mechanism of the disease, the characterization of large numbers of renin-containing cells in the affected kidney support a role for the renin-angiotensin system stimulation in this form of hypertension.
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  • 52
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    Cell & tissue research 216 (1981), S. 557-568 
    ISSN: 1432-0878
    Keywords: Electron microscopy ; Neuroglia ; Silver impregnation ; Brain ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The silver-impregnation procedure of Tsujiyama is suitable for demonstration of all three classical types of neuroglial cells; in the present study it was used for electron microscopic identification of neuroglial cells in the brain of the cat. The aim of the present study was 1) to determine impregnated structural correlates of neuroglial cells at the light- and electron-microscopic levels, and 2) to determine whether the method of Tsujiyama is applicable for the electron microscopic identification of the single types of neuroglial cells. Silver deposits were observed over the cytoplasm and processes of astrocytes where numerous glial filaments were present. Oligodendrocytes and microglial cells may be precisely differentiated by use of Tsujiyama's silver impregnation method at the electron microscopic level due to the pattern of silver-deposition in these two basic types of cells. This silver-impregnation method combined with electron microscopy is thus suitable for a precise identification of neuroglial cells; the technique may prove to be very helpful in identification of such categories of neuroglial cells that encompass also the images of cells which cannot be classified by use of the standard methods.
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  • 53
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    European archives of oto-rhino-laryngology and head & neck 233 (1981), S. 1-12 
    ISSN: 1434-4726
    Keywords: CM ; SP ; Hirnstamm-Reaktion ; Katze ; Entwicklung ; CM ; SP ; Brainstem response ; Cat ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The development of the surface-recorded cochlear and early neural potentials has been studied in the cat from birth to the 8th post-natal week. CM, SP, and each of the neural waves has a characteristic temporal developmental pattern and mature threshold. Wave IV is the most resistant to reduction in stimulus intensity levels, while the thresholds of both cochlear potentials are high. Animals with hereditary unilateral deafness constitute a most convenient model for the study of functional maturation in the auditory pathways, particularly with regard to precise latency estimations.
    Notes: Zusammenfassung Die Entwicklung der an der Oberfläche registrierten cochlearen und frühen neuralen Potentiale wurde bei der Katze von der Geburt bis zur 8. Woche studiert. CM, SP und jeder der neuralen Wellen haben ein charakteristisches altersbedingtes Entwicklungsmuster und eine Responsschwelle. Welle IV wird am wenigsten von einer Reduktion in der Stimulusintensität beeinflußt. Die Schwelle der beiden cochlearen Potentiale sind dagegen erhöht. Tiere mit angeborener einseitiger Taubheit sind bestens geeignet für das Studium der funktionellen Reifung der Gehörbahnen, besonders in bezug auf die exakten Latenzzeitmessungen.
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  • 54
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    European archives of oto-rhino-laryngology and head & neck 230 (1981), S. 251-255 
    ISSN: 1434-4726
    Keywords: Ganglion Scarpae ; Katze ; Labyrinthektomie ; Scarpa's ganglion ; Cat ; Labyrinthectomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary One year after membraneous labyrinthectomy in three cats a quantitative analysis of neurons in Scarpa's ganglion was performed under the light microscope. Total numbers of neurons were found 30% lower than in the respective contralateral ears. Although remaining perikarya showed signs of degeneration, such as shrinkage and vacuoles the proportions of large and small neurons remained unchanged after this procedure.
    Notes: Zusammenfassung Ein Jahr nach Labyrinthektomie wurde eine quantitative Analyse der Neuronen im Ganglion Scarpae der Katze durchgeführt. Die Gesamtzahl der Perikarya war 30% niedriger als in den unoperiert belassenen kontralateralen Ohren. Obwohl die verbleibenden Neuronen degenerative Veränderungen wie Schrumpfung und Vakuolen aufwiesen, waren die Anteile an großen und kleinen Neuronen unverändert.
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  • 55
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    Helvetica Chimica Acta 64 (1981) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 56
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isotope partition coefficient α between cyclohexane, cycloheptane and hydrogen has been determined between 80 and 180° and pressures around 1 atm. The values decrease with increasing deuterium content y of the hydrogen and can be expressed by the simple equation Ina = Δ S/R + (ΔH + δ · y)/RT with an error of ±1%. However it was not possible to achieve good agreement with theoretical calculations using a unique average value for the partition function of the hydrocarbon.
    Additional Material: 1 Ill.
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  • 57
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of reactions of p-chlorobenzenediazonium ions in aqueous buffer solutions (pH 9.0-10.6) under N2 (〈 5 ppb of O2) have been measured between 20 and 50°C. The formation of trans-diazotate is first-order with respect to the concentration of hydroxyl ions and to the equilibrium concentration of diazonium ions, if the diazonium ion⇄cis-diazotate equilibrium is considered as a fast prior equilibrium. This indicates that the p-chlorobenzenediazonium ion, in contrast to all previous investigations with the p-nitrobenzenediazonium ion and benzenediazonium ions carrying similar substituents with a -M effect, rearranges from the cis- to the trans-configuration as diazohydroxide and not as diazotate. The formation of trans-diazotate is catalyzed by carbonate and inhibited by hydrogen carbonate ions; mechanisms of these catalyses are discussed, and the solvent isotope effect KH2O/KD2O measured by an 1H-NMR. technique reported. The kinetics of the dediazoniations can be analyzed as a mixture of two reactions, a relatively fast first reaction, reaction A, which is responsible for about 5% of the total reaction, and a second reaction F. Both are first-order with respect to diazonium ion; reaction A is also first-order in hydroxyl ions. There are some indications that reaction A corresponds to the hydrolysis of the diazonium ion to give eventually amine and nitrite ions. Reaction F shows a complex dependence on hydroxyl ions; it is related to the homolytic dediazoniation.
    Additional Material: 10 Ill.
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  • 58
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 23Na-chemical shifts for the NaClO4 solute depend markedly upon the composition of binary solvent mixtures of THF with amines (pyridine, piperidine, pyrrolidine, aniline, propylamine, and isopropylamine). These changes, analyzed in a novel application of the Hill formalism, show equality of the intrinsic equilibrium constant K for the successive steps, upon displacement of THF from sodium coordination by one of these amines. The results, which are entirely consistent with tetracoordination of the sodium cation by these solvents, also indicate proportionality of the K values to the amine chemical shifts.
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  • 59
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    Helvetica Chimica Acta 64 (1981), S. 568-571 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenylglycine esters react with pyruvic acid to give α-methylsuccinic amides 9 instead of the expected Schiff bases 8, analogously to p-anisidine but unlike aniline.
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  • 60
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds have been isolated and their structures determined by X-ray crystallography. Their relative stability is discussed in terms of theory and experiment. The endo-adduct is the thermodynamically more stable one.
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  • 61
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    Helvetica Chimica Acta 64 (1981), S. 572-578 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Notes on the Synthesis of Sulfonated Derivatives of 5,6,7,8-Tetrahydro-1-naphthylamine and 5,6,7,8-Tetrahydro-2-naphthylamineSulfonation of 5,6,7,8-tetrahydro-1-naphthylamine (1) with sulfuric acid gave a mixture of 1-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (2), 4-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (13) and 4-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (3). The same reaction with 5,6,7,8-tetrahydro-2-naphthylamine (20) yielded 3-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (21); formation of 2-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (16) or of 3-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (24) was not observed. Treatment of 4-bromo-5,6,7,8-tetrahydro-1-naphthylamine (4) or of its 4-chloro analogue 5 with amidosulfuric acid gave 1-amino-4-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (9) and its 4-chloro analogue 10, respectively, which were dehalogenated to 2. Preparations of 13 and 24 were achieved by sulfonation of 5-nitro-1,2,3,4-tetrahydronaphthalene (14) and 6-nitro-1,2,3,4-tetrahydronaphthalene (22) to 4-nitro-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (15) and 3-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (23), respectively, followed by Béchamp reductions. The sulfonic acid 13 was also obtained by hydrogenolysis of 4-amino-1-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (11) or of its 1-chloro analogue 12; compounds 11 and 12 were synthesized from N-(4-bromo-5,6,7,8-tetrahydro-1-naphthyl)acetamide (7) and from its 4-chloro analogue 8, respectively, by sulfonation with oleum and subsequent hydrolysis. By ‘baking’ the hydrogensulfate salt of 1 or 20 compounds 3 and 21 were obtained, respectively. Synthesis of 16 was achieved by sulfur dioxide treatment of the diazonium chloride derived from 2-nitro-5,6,7,8-tetrahydro-1-naphthylamine (17) giving 2-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonyl chloride (18), followed by hydrolysis of 18 to the corresponding sulfonic acid 19 and final reduction.
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  • 62
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    Helvetica Chimica Acta 64 (1981), S. 1023-1025 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deprotonation of ethyl (E)-2-alkenoates 1, 3 and 4 yields after protonation the double bond migrated (3 Z)-isomers 5, 7 and 9 as major products. In contrast, deprotonation and reprotonation of ethyl (Z)-2-pentenoate (2) gives the (3 E)-isomer 6 exclusively. These findings are explained by reaction paths starting from different ester conformations.
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  • 63
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    Helvetica Chimica Acta 64 (1981), S. 1026-1031 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Route to 1, 3-Dicarbonyl Derivatives, Model Investigations on the A/B-Part of-3-Oxo-5α-steroidsStarting from 1 the 1, 3-dicarbonyl compounds 4a-d were synthetized via the enynes 2a-e and the relatively unstable epoxides 3a-d. The latter were reacted with 95% formic acid to gave 4a-d; small amounts of the furane derivatives 5a-c were identified as by-products in this last step. In the presence of catalytic amounts of HgSO4 the epoxides 3a-c yielded with 95% formic acid the furanes 5a-c, but no detectable amounts of 4a-c.
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  • 64
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    Helvetica Chimica Acta 64 (1981), S. 1032-1039 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It was found that analysis of the 1H-NMR. signals (at 360 (preferably) and/or 100 MHz) of the protons at C (4) and of the equatorial α-proton at C (6), particularly when these are located in the 2-3 ppm region and therefore convenient for detection and identification, may be of valuable aid in the structural and configurational characterization of 5-hydroxy- and 5-acetoxy-steroids (unsubstituted or containing a hydroxy or acyloxy substituent at C (3)).
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  • 65
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterodiamantanes and Structurally Related Compounds. Part III. The Pentacyclic C11-Diethers 5, 13-Dioxapentacyclo [6.5.0.02,6.03,12.04,9]tridecane, 4, 13-Dioxapentacyclo [6.4.1.02,7.03,10.05,9]tridecane, and 3, 10-Dioxapentacyclo [7.3.1.02,7.04,12.06,11]tridecaneIn connection with the studies on heterodiamantanes and structurally related compounds the three novel pentacyclic diethers 3-5 were prepared starting from the cyclopentadienone dimer 6. All four compounds have as common features a central carbocyclic 6-membered ring with four axial alkyl substituents and two oxygen functions in 1, 4 position. The required eleventh C-atom was introduced by dichlorocarbene addition either to 6 ( → 7) (Scheme 2) or to 29 ( → 28) (Scheme 4).Diether 3 was obtained by reduction of 26 (Scheme 2), a suitable precursor prepared either by intramolecular addition (24 → 26; Scheme 2) or substitution (30 → 26, 31 → 26; Scheme 4), as well as by direct substitution (44 → 3, 42 → 3; Scheme 5). Diether 4 was the product of a direct substitution (39 → 4, 36 → 4; Scheme 5). The synthesis of diether 5 was achieved from the addition product 51 (resulting from the alcohols 47 and 48; Scheme 6).Diether 4 is the thermodynamically least stable of the three diethers 3-5. It was easily isomerized to 5 on treatment with concentrated sulfuric acid in benzene whereas 3 and 5 remained unchanged under these conditions.
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  • 66
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    Helvetica Chimica Acta 64 (1981), S. 1040-1057 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spherical Cryptates. Synthesis and Inclusion-Complexes of Spherical Macrotricyclic LigandsA general strategy for the synthesis of spherical macrotricyclic ligands has been developed. Four spherical cryptands, SC-24, SC-25, SC-26 and SC-27 have been obtained by this route. The synthesis and cation-complexing properties of these compounds are described in detail. Stability constants and cation exchange rates of the spherical cryptates obtained with alkali and alkaline-earth cations have been determined. Highly stable complexes are formed by SC-24; the Rb+ and Cs+ cryptates of SC-24 are the most stable complexes of these cations known to date. The size of the intramolecular cavity affects the complexation selectivity. The cation exchange rates are very slow, and the corresponding free energies of activation are even larger than, for macrobicyclic cryptates of similar stability. Both the high complex stabilities and the high activation energies required for cation exchange indicate a marked ‘spherical cryptate effect’ resulting from the highly connected nature of the molecular architecture of spherical macrotricyclic ligands.
    Additional Material: 6 Ill.
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  • 67
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    Helvetica Chimica Acta 64 (1981), S. 1058-1062 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of proton transfer from 2, 4-hexadiene, 1, 3-cycloheptadiene, cyclopentadiene and acetone to t-butoxide have been measured in the gas phase using pulsed-ion-cyclotron-resonance spectroscopy. The rate constants are (units of 10-10 cm3 molecule-1 s-1): 2.7 ± 0.4, 3.8 ± 0.4, 6.1 ± 0.7 and 10.8 ± 1.5, respectively. These results are analyzed in terms of the properties of the encounter complex and reaction transition states. The reaction profile for t-butoxide + cyclopentadiene is modeled using RRKM theory and an estimate for the central barrier height is obtained.
    Additional Material: 1 Ill.
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  • 68
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 2- and 3-Phenyl Substituted Alkylalkylidene Iminium Ions in the Gas PhaseThe collision-induced fragmentations of 2- and 3-phenyl substituted alkylalkylidene iminium ions are reported. Besides the homolytic cleavage of the azaallyl bond a nucleophilic attack of the unsubstituted phenyl group at the iminium function is observed in the gas phase, yielding carbonium ions such as cyclopropanspirobenzenium (3), indanylium (10) and indenylium ions (11).
    Additional Material: 1 Tab.
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  • 69
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modification of a previously reported synthesis of zeaxanthin (1), and routes to both zeaxanthin and rhodoxanthin (2) from α-ionone, are described.
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  • 70
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition metal complexes often have low-lying excited electronic states and, as a consequence, tend to be electronically labile, i.e., their electronic properties exhibit pronounced sensitivity to external perturbations. Often drastic changes in various spectroscopic properties indicating substantial electronic rearrangements can be induced be relatively weak intermolecular forces as provided by nonpolar solvents or solid molecular host lattices. This behaviour can be explained by crossing of potential surfaces in the vicinity of the absolute minimum. Many physical properties of a given orbitally (near-) degenerate system depend strongly on the relative magnitude of some characteristic parameters determining the shape of the ground Born-Oppenheimer potential surface(s), e.g. barrier height versus zero-point energy, distance between minima versus zero-point amplitude, energy difference between minima, etc. Typical examples are systems exhibiting Jahn-Teller activity, spin-crossover, mixed valence, exchange coupling and other types of electronic near-degeneracies. In paramagnetic systems changes in the electronic wavefunction can be most conveniently detected and analyzed by using EPR. spectroscopy.In paramagnetic sandwich complexes we studied two types of orbital degeneracies: Jahn-Teller degeneracies (d7-systems such as Co (cp)2, Ni(cp)2+ and Fe (cp) (bz), low-spin d5-systems such as Mn (cp)2) and low-spin/high-spin equilibria (d5-systems such as Mn (cp)2). By diluting these complexes and ring-substituted derivatives in a large variety of diamagnetic host systems we have been able to control the 6A/2E equilibrium of Mn (cp)2 by influencing the metal-to-ring distance and by changing the degree of ring alkylation; similarly we have been able to vary the relative weights of the two electronic states contributing to the two-fold degenerate electronic ground state of d5- and d7-systems to a large degree by variation of the local asymmetric fields offered by the lattice sites of the host systems.For comparison the electronic ground state properties of octahedral Cu(II) complexes with CuN6 CuO6 chromophores, of V (CO)6 and tetrahedral VCl4 were also studied by EPR. between 4K and room temperature in several host systems. Characteristic differences in the details of the temperature and host dependence of the EPR. spectra in all these electronically labile systems can be explained in terms of differences in the vibronic coupling type (E ⊗ e vs. T ⊗ e, t), the strength of linear and/or quadratic JT-coupling and the effects produced by spin-orbit coupling.
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  • 71
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of Porphine-type Nickel Complexes Containing Axially Oriented SidechainsThe structure of (±)-[1, 11-dimethoxy-10 H-HDP (2-)]nickel (3), the product of the thermodynamically controlled addition of methanol to [6 H-HDP]nickel-bis-(tetrafluoroborate) (1), was determined by X-ray analysis. The two methoxy groups in 3 are cis-oriented. The syntheses and spectroscopic properties of [1, 11-diethoxy-10 H-HDP (2-)]nickel (5), [1, 11-dineopentyloxy-10 H-HDP (2-)]nickel (6) as well as the bridged complexes [1, 11-pentamethylenedioxy-10 H-HDP (2-)]nickel (4) and [1, 11-(E)-2,3-(dimethyl-2-butenylenedioxy)-10 H-HDP (2-)]nickel (7) are described. Reaction of 1 with bromide ions or 4-methylpyridine leads to the formation of the corresponding hexacoordinated, paramagnetic complexes dibromo [6 H-HDP]-nickel (II) (8) and bis (4-methylpyridine)[6 H-HDP]nickel-bis (tetrafluoroborate) (9).
    Additional Material: 6 Ill.
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  • 72
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a flexible, stereocontrolled synthesis of enantiomerically pure substituted cyclopentenes and cyclopentanes - including 11α-hydroxy-13-oxaprostanoic acid 20 - (-)-quinic acid via an acyclic precursor 6 by an intramolecular aldolisation-dehydration reaction.
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  • 73
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute conformation of 7-chloro-5-phenyl-1-[(S)-α-phenylethyl]-1, 3-dihydro-2H-1, 4-benzodiazepin-2-one (1c) in crystal, and its inversion rate in solution were determined, enabling prognosis of direction of asymmetric induction during C(3)-alkylation.
    Additional Material: 1 Ill.
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  • 74
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Application of the α-Alkynone Cyclization: Synthesis of rac-Modhephenerac-Modhephene 1, the first sesquiterpene with a propellane C-skeleton and its epimer rac-epi-modhephene 27, were synthesized starting from bicyclo[3.3.0]oct-1(5)-en-2-one (2). The key step in the construction of the [3.3.3]-propellane system is an application of the α-alkynone cyclization, namely 3 → 4 and 11 → 14. The preferred formation of the propellanes 4 and 14 in this step shows that the insertion of the postulated alkylidene carbene intermediate into tertiary C,H-bonds outweighs the one into the secondary ring-C,H-bonds leading to 12/13 and 15/16, respectively. The two starting materials for the α-alkynone cyclization, 3 and 11, were prepared from 2 by the reactions shown in Scheme 3. The further elaboration and separation of the cyclization products 4 and 14 to rac-modhephene 1 and its epimer 27 are outlined in Scheme 5.
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  • 75
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    Helvetica Chimica Acta 64 (1981), S. 389-398 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transformations of 13 alcohols and 13 diols in the presence of a small amount dimethylsulfoxide (1/16 mol) were studied. Relationships were found between the type of the hydroxy compound and the selectivity of the transformation, and conclusions were drawn regarding the transformation mechanism. The ether formation observed with certain alcohols proceeds via a carbenium cation. The reaction conditions applied were found suitable for inducing water elimination from the ditertiary 1,2- and 1,3-diols (pinacol rearrangement, 1,2-elimination). From the 1,4- and 1,5-diols the corresponding oxacycloalkanes can be obtained in good yield. Cyclodehydration occurs by intramolecular nucleophilic substitution, via a concerted mechanism. The effect of DMSO is exerted directly, and protoncatalysis occurs simultaneously.
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  • 76
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    Helvetica Chimica Acta 64 (1981), S. 425-429 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Novel Example of Unsaturated Branched-chain Sugar Nucleoside: 3′-Deoxy-3′-methylidene-adenosineStarting from 5-O-benzoyl-3-C-methylidene-3-deoxy-1,2-O-isopropylidene-α-D-erythro-pentofuranose (11) the title compound 8 has been prepared. Its α-anomer (9) and the acyclic sugar nucleoside 10 have been obtained as by-products. Adenosine deaminase slowly deaminated 8, 9 being not affected. Compound 8 exhibited no antiviral activity, whereas one of its saturated analogues (13) inhibited the multiplication of the herpes-1 (HF) virus.
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  • 77
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    Helvetica Chimica Acta 64 (1981), S. 449-457 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational isomers of astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) from the flesh of salmon (Salmo salar and Oncorhynchus) caught at different places in Europe and Canada were isolated and analyzed as (-)-camphanic acid diesters by means of HPLC. The biological variation in the composition of the configurational isomers in seven fish was surprisingly similar: 78 to 85% of (3S, 3′S)-astaxanthin, 12 to 17% (3R, 3′R)-astaxanthin and 2 to 6% meso-astaxanthin.
    Additional Material: 5 Ill.
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  • 78
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An interactive system of programs has been developed to assist in structure elucidation based on mass spectral data. The program relies on algorithms for generating all the structural isomers that constitute alternative explanations of the observed data and it associates relative plausibility values with the different isomers. The structure assembly part of the program allows for the use of overlapping substructural components, such as substructures inferred from the appearance of particular ion patterns in the spectrum of an unknown compound. Mass spectrum interpretation procedures used with this structure assembly process could exploit any form of spectrum-substructure correlation scheme. In this work, the emphasis has been on the use of detailed and class specific spectrum-substructure correlations. Applications of the program are illustrated by means of an example analysis of the mass spectra of a variety of marine sterols.
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  • 79
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective Modification of the Terminal Amide Group of Linear Polyamides via 2-Oxazolin-5-ones as IntermediatesTreatment of aqueous or alcoholic solutions of diamides of type 2 with HCl leads to the formation of amide-acids and amide-esters of type 3 (Scheme 1 and Table). It has been shown, that 2-oxazolin-5-ones of type 4 are intermediates of this selective transformation of the disubstituted terminal amide group. The selectivity of the transformation is demonstrated by the reaction sequence shown in Scheme 3. No selectivity has been observed in the acid-catalyzed hydrolysis of triamide 9 with a monosubstituted terminal amide group (Scheme 4). Hydrolysis of the optically active dipeptide derivatives (+)-(L)-13 and (+)-(L)-15 with HBr in nitromethane at 60-80° yields the pure enantiomer (+)-(L)-14 and (+)-(L)-16, respectively (Scheme 5), i.e., no racemization takes place under the reaction conditions.These results show the usefulness of the dimethylamide group as a protecting group for carboxylic acids for example in the peptide synthesis.
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  • 80
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 15N-CIDNP. spectra recorded during the reaction of diazonium cations with OH- in weakly alkaline aqueous solutions show that the dediazoniation is at least partially homolytic. The polarizations observed for the diazonium and trans-diazotate ions can be explained by reaction proceeding via a cage involving diazenyl and diazotate radicals using Kaptein's rules and simple intensity considerations.
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  • 81
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate have been studied in buffer solutions in the pH-range 9.0-10.0, ionic strength I = 0.10, at 20.0° in glass and polytetrafluoroethylene vessels. The presence of oxygen (〈5 ppb of O2, 60 to 100 ppb of O2, air, 〉 99% of O2) has a decisive influence on the rate and kinetic order of the dediazoniation. Iodoacetic acid inhibits the reaction, whereas p-chlorophenol has a catalytic effect, and in air and 〉99% of O2 it acts as an autocatalyst. The reaction is subject to general-base catalysis by water, hydroxyl ions, hydrogen carbonate and carbonate ions. The kinetic results are interpreted in conjunction with data concerning the reaction products [2] and a 15N-CIDNP. investigation of a related system [3]. Specific radical chain mechanisms are consistent with the results.
    Additional Material: 10 Ill.
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  • 82
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The product distribution of compounds 2, 3 and 4 formed in the electrohydrodimerization (EHD) of 1 was determined as function of the water content of the solvent (CH3CN). The presence of water favours the formation of the glycols 4 and reduces the relative amounts of 1,6-diketones 2 and hydroxyketones 3, as determined by GC./MS.-analysis.
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  • 83
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    Helvetica Chimica Acta 64 (1981), S. 1575-1578 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unusual propellane skeleton of the sesquiterpene modhephene (1) has been synthesized starting from cyclopentenone (2). The key step 6 → 7 is an efficient and highly stereoselective intramolecular thermal ene-reaction. Further elaboration of the propellane 7 gave the enone 10 which had been previously converted to (±)-modhephene (1) in three steps.
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  • 84
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present work a mixing-reaction model is developed to describe the influence of the space- and time-dependent concentration of the leaving group on the pre-equilibria of the reactants and thus on the product distribution of mixing-disguised reactions. The modelling is carried out using a typical example of such reactions, namely azo coupling, where the leaving group is a proton. For this reaction, the existence of characteristic sets of parameters is established, for which the product distribution does not depend on the initial pH-value. These sets of parameters define the isoselectivity points.
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  • 85
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: rac.-Ajmalicine (31) and 19-epi-ajmalicine (30) have been synthesized by a convergent route from the preformed D, E-ring moieties 25 and 27 and tryptophyl bromide. Two syntheses of the trans-1-benzoyl-3-vinyl-4-piperidineacetic acid (13), used in the preparation of 25 and 27, are also described.
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  • 86
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    Helvetica Chimica Acta 64 (1981), S. 1653-1662 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray Structure Analyses of Chiral Ionophores: The NH4NCS Complex of 9,9′-Spirobifluorene-22-crown-5In the crystalline NH4NCS complex of 9,9′-spirobifluorene-22-crown-5 (1) the NH4+ ion sits in the centre of the polyether ring, with distances of 2.92-3.15 Å to the five O-atoms and shows at least twofold orientational disorder. In one orientation, three H-atoms point toward O-atoms and the fourth to the N-atom of the anion situated 2.78 Å above the polyether ring. In another, only two H-bonds are formed. The mean planes of the two fluorene parts of the molecule are perpendicular to each other.Crystals of 2,2′-bis (hydroxymethyl)-9,9′-spirobifluorene (2), an intermediate for the synthesis of 1, contain occluded benzene, which cannot be removed under vacuum. X-ray analysis shows that the benzene molecule does not interact with the spirobifluorene in a specific way but merely occupies cages in the crystal packing.
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  • 87
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    Helvetica Chimica Acta 64 (1981), S. 1717-1717 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 88
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    Helvetica Chimica Acta 64 (1981) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 89
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    Helvetica Chimica Acta 64 (1981), S. 1717-1727 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N-diazo coupling of p-chloroaniline with p-chlorobenzenediazonium tetrafluoroborate in acetonitrile at 30° shows non-linear base catalysis by water. The results are interpreted in terms of the SE2 mechanism with rate-limiting proton loss at low base concentration; it is postulated, moreover that the reaction proceeds via transition states in which varying degrees of H-bonding from the amine and the intermediate ω-complex to different water species influence the initial step and the base catalysis.
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  • 90
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleotides. XV. Synthesis and Properties of 2′O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleoside-3′-phosphotriesters, Starting Materials for Oligonucleotide SynthesesThe syntheses of two types of fully blocked ribonucleoside 3′-phosphotriesters 6-14 have been achieved in excellent yields from 2′-O-t-butyldimethylsilyl-5′-O-monomethoxytrityl-ribonucleosides 1-5 by phosphorylation with 2-chloro- and 2,5-dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6, 8, 10, 12 and 14 and by p-nitrophenylethanol to 7, 9, 11 and 13. These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15-23 with free HO—C(5′) could be obtained by detritylation and the 3′-phosphodiester triethylammonium salts 24-32 by deblocking of the cyanoethyl and the 2,5-dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.-and NMR.-spectra as well as C, H, N elementary analyses.
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  • 91
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: XIV. Substituted β-Phenyl-ethyl Groups. New Blocking Groups for Oligonucleotide Syntheses by the Phosphotriester ApproachVarious o- and p-substituted β-phenylethanols (2-10) have been synthesized and investigated as blocking groups in the phosphotriester approach. A large number of 5′-O-tritylated thymidine-3′-phosphotriesters (13-36) with two different phosphate protecting groups have been prepared, characterized, and studied according to their chemical stability and usefullness for oligonucleotide syntheses. The combination of a 5′-O-monomethoxytrityl- and a 3′-(2,5-dichlorophenyl, p-nitrophenylethyl)-phosphate function as in 18 turned out to possess optimal properties as a monomeric nucleotide building block due to the fact that these blocking groups can be quantitatively and selectively be removed without harming each other by trifluoroacetic acid in chloroform to 41, by oximate to 42, and by DBU to 43. The base-catalyzed removal of the monosubstituted phenylethyl groups by DBU or DBN respectively as well as the disubstituted phenylethyl groups by triethylamine in aprotic solvents is a β-elimination process leading to phosphodiesters without attack on the P-center.
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  • 92
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various free radicals formed during UV.-irradiation of aliphatic dicarboxylic acids in aqueous and methanolic solution are identified by ESR.-spectroscopy. Their structures point to α-cleavage and photoreduction as the dominant primary photochemical decay processes. The relative contributions of these reactions to the overall photodecomposition depend on solvent and degree of α-alkylation of the acid. Emission ESR.-spectra are found for radicals formed by C, CO-bond cleavage of α-dimethyl substituted acids. The polarization is referred to the triplet mechanism of CIDEP. and indicates this cleavage reaction occurs from a triplet molecular state.
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  • 93
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    Helvetica Chimica Acta 64 (1981), S. 1910-1929 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature and solvent dependence of the ESR. spectra of a number of semiquinone- and semidione-type radicals have been investigated with the aim of obtaining structural and kinetic information about intramolecular hydrogen bonding. Systematic variation of the chemical structure of the radicals indicates that in many cases formation and/or exchange of intramolecular H-bonds is disturbed or even precluded by steric hindrance or concomitant dynamic processes, such as internal rotation and/or intermolecular proton exchange.
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  • 94
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1943-1948 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, surface activity and micelle formation of three novel cyanine dyes with amphiphilic character is described. It is illustrated by combined surface tension and absorption measurements that in one case self-assembly is highly cooperative leading to aggregates with unique absorption properties.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1964-1967 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Naturally occurring kaempferol 3-O-β-D-(6″-O-coumaroyl)glucopyranoside (tiliroside) has been synthesized thereby confirming its structure. This is the first acylated flavonoid glycoside to be synthesized.
    Type of Medium: Electronic Resource
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  • 96
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1968-1968 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 97
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Juliprosine, a Further Alkaloid Isolated from Prosopis juliflora A.DC.By catalytic hydrogenation of the second base juliprosine (2) isolated from Prosopis juliflora (Leguminosae) the hexahydroderivative 5 was formed. The same product was obtained also by catalytic hydrogenation of juliprosopine (1) of known structure. The absolute configuration of 2 was deduced by comparison of [M]D values of Prosopis alkaloids of known absolute configuration.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1985-1990 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,5-Octadiyne cation in its lowest excited state has been studied in the gas phase by laser-induced fluorescence and photoelectron-photon coincidence techniques. The excitation spectrum of the Ã2″←2A″ transition has been obtained and yields vibrational frequencies of some of the fundamentals for the excited cationic state. The fluorescence quantum yields and lifetimes at selected energies within the Ã2A″ state have been determined from the coincidence measurements. This provides quantitative data for the discussion of the relaxation behaviour of such an excited open-shell cation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2002-2021 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deprotonation of the 3-trialkylsilyloxy-1,4-diene 3a and subsequent electrophilic substitution of the non-isolated 3-trialkylsilyoxypentadienyllithium 4 gives the α- and γ-products 8 and/or 6 in good yields. Whereas alkylation of 4 proceeds with variable regioselectivity (Table 1) aldehydes and ketones attack preferentially the γ-position of 4 (Table 2). The desired γ-products 6 may be directly subjected to inter- and intramolecular [4 + 2]-additions as demonstrated by the reactions 5a (≡ 6d) → 7 and 6h → 19 (Schemes 4 and 12). Alternatively, smooth fluoride-promoted silylether-cleavage 6 → 11 (Scheme 8) provides a convenient approach to substituted vinyl ketones such as to the natural products 11f (Table 3). The stereoselective conversion 6k → 23 (Scheme 13) implies an endo-selective intramolecular Diels-Alder addition (26 → 23) and exemplifies the use of 4 as an equivalent of the hypothetical anion IV. Furthermore, some electrophilic substitutions of the hexadienyllithium 15 have been studied (Scheme 10).
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1937-1942 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zinctetramethylpyridylporphyrin (ZnTMPyP4+) in acidic aqueous solution sensitizes efficiently oxygen generation by visible light in the presence of acceptors such as Fe3+ - and Ag+-ions and colloidal RuO2/TiO2 redox catalyst. Hydrogen and oxygen are cogenerated under visible light illumination of ZnTMPyP4+ solutions when a bifunctional catalyst (Pt and RuO2 codeposited onto TiO2) is employed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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