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11.
Miroslav Makek Hans Jörg Leu 《Virchows Archiv : an international journal of pathology》1982,397(3):241-250
Summary We present the case of a sacrococcygeal chordoma which recurred 15 years after the radical removal as a soft tissue tumor in the gluteal musculature. This tumor consisted of two parts: a chordoma without symptoms of aggressive cellular proliferation and a malignant fibrous histiocytoma. During the following 4 years several local recurrences of the malignant fibrous histiocytoma occurred in the gluteal musculature. The patient finally died of lung metastases. No chordoma tumor tissue was found in the lungs, in the gluteal musculature or in the sacrococcygeal bone area. Histology including electron microscopy revealed no proof of a transition of chordoma into malignant fibrous histiocytoma. It must be assumed that the secondary soft tissue tumor originated from residual chordoma cells which were implanted during the operation of the primary tumor. It remains unclear whether the malignant fibrous histiocytoma arose from mesenchymal stromal cells within the chordoma or directly from primitive neuroectodermal chorda cells which possess the ability to differentiate into a variety of cell types including mesenchymal cells. 相似文献
12.
In the reaction of triisobutylene with AlBr3/DBr system, backbone isomerization and formation of higher oligomers takes place, in addition to deuteration. Both reactions are explained by the cleavage of the backbone bonds of the intermediate carbonium ions. The fragments formed can react with other components of the reaction system. The possible role of these reactions in the mechanism of termination and chain transfer in the cationic polymerization of isobutylene is discussed briefly. 相似文献
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15.
Miroslav Marek Michael Roman Danica Dosko
ilov Svatopluk Pokorný 《Macromolecular chemistry and physics.》1986,187(10):2337-2344
The polymerization of 3-chloro-2-methyl-1-propene was investigated at temperatures between 0 and ?80°C, using AlCl3 and AlBr3 as initiators. The molecular weights of the resulting oily products depend on the polymerization temperature and varied in the range of the number-average molecular weight M?n = 400–620. The course of polymerization was studied and the characteristic groupings in the oligomeris were identified by means of 1H NMR and 13C NMR spectroscopy. Based on the results the mechanism of partial reactions was discussed to explain the new type of propagation in the cationic polymerization. 相似文献
16.
An investigation was made on the effect of some n-alkyl halides (n-butyl fluoride, n-butyl chloride, and n-butyl bromide) and some benzyl halides (benzyl fluoride, benzyl chloride, and benzyl bromide) on the polymerization of isobutene in heptane, catalyzed by aluminium iodide. It was found that n-butyl fluoride and benzyl halides raise the rate of polymerization considerably. It was also established, from the dependence of the rate of polymerization and of the molecular weights on the concentration of alkyl halides and aluminium iodide, that alkyl halides do not act as cocatalysts, but that the increase in the rate of polymerization is due to the formation of catalytically active products of halogen exchange between aluminium iodide and alkyl halides. The results are discussed in terms of our present knowledge concerning the polymerization of isobutene with catalytic systems consisting of two FRIEDEL-CRAFTS halides. 相似文献
17.
Ivana Vančurová Miroslav Flieger Jindřich Volc Milan J. Beneš Jana Novotná Jiří Neužil Vladislav Běhal 《Journal of basic microbiology》1987,27(9):529-533
Anhydrotetracycline oxygenase was purified both by affinity chromatography and by hydrophobic interaction chromatography. Molecular weight of anhydrotetracycline oxygenase was determined to be 115,000 by Sephadex G-200 gel filtration. Using preparative isoelectric focusing the isoelectric point of the enzyme was estimated to be 5.3. The enzyme showed a sensitivity to thiol-specific inhibitors. During the hydrophobic interaction purification step, the activity dropped considerably. Reactivation occurred when a heat treated crude extract was added to the reaction mixture. 相似文献
18.
Zuzana Kubová Miroslav Kuba Jaroslav Hubacek František VíT 《Documenta ophthalmologica. Advances in ophthalmology》1990,75(1):67-72
In 80 subjects the dependence of movement-onset visual evoked potentials on some measures of stimulation was examined, and these responses were compared with pattern-reversal visual evoked potentials to verify the effectiveness of pattern movement application for visual evoked potential acquisition. Horizontally moving vertical gratings were generated on a television screen. The typical movement-onset reactions were characterized by one marked negative peak only, with a peak time between 140 and 200ms. In all subjects the sufficient stimulus duration for acquisition of movement-onset-related visual evoked potentials was 100ms; in some cases it was only 20ms. Higher velocity (5.6°/s) produced higher amplitudes of movement-onset visual evoked potentials than did the lower velocity (2.8°/s). In 80% of subjects, the more distinct reactions were found in the leads from lateral occipital areas (in 60% from the right hemisphere), with no correlation to handedness of subjects. Unlike pattern-reversal visual evoked potentials, the movement-onset responses tended to be larger to extramacular stimulation (annular target of 5°–9°) than to macular stimulation (circular target of 5° diameter).Abbreviation PREP
pattern-reversal visual evoked potentials 相似文献
19.
Vladimir Macháň Štefan Vilček Miroslav Kalinčák Konštantín Barna 《European journal of nuclear medicine and molecular imaging》1980,5(1):39-43
A SORB-GEL method has been worked out for analysing 99mTc-labelled compounds which (in a few minutes) enables the pertechnetate content to be determined in a preparation. The method is based upon a different tupe of behaviour of 99mTc-labelled compound, pertechnetate in the columns packed with Sephadex G-10, and with alumina during elution with saline.Polythene syringes 4.7 cm long and 1 cm in diameter were used as chromotographic columns. A syringe packed with Sephadex G-10 transferred 0.1 ml of 99mTc-labelled compound into the column, and the activity of the column was then measured in the ionisation chamber. Using a syringe, 20 ml of saline was foreced through this column. The eluate was then removed. Using an injection needle, a second column, packed with alumina, was connected with the first. Similarly, a third column, packed with Sephadex G-10, was connected to the second. Through all of them 40 ml of saline was forced. The third column containing Sephadex G-10 was then disconnected and its activity was measured in the ionisation chamber. The pertechnetate content in the preparation was then calculated from the measured values.The method is suitable for determinating the free pertechnetate content in strong and weak chelate compounds and in particle preparations. 相似文献
20.
Abstract: The present experiments were undertaken in order to examine the effect of adenosine in isolated rat aorta, to investigate the possible role of intact endothelium and endothelial relaxing factors in this action and to determine which population of adenosine receptors is involved in rat aorta response to adenosine. Adenosine (0.1–300 μM) produced concentration‐dependent (intact rings: pD2=4.39±0.09) and endothelium‐independent (denuded rings: pD2=4.52±0.12) relaxation of isolated rat aorta. In the presence of high concentration of K+ (100 mM) adenosine‐evoked relaxation was significantly reduced (maximal relaxation in denuded rings: control – 92.1±9.8 versus K+– 54.4±5.0). Similar results were obtained after incubation of ouabain (100 μM) or glibenclamide (1 μM). In K+‐free solution, K+ (1–10 mM)‐induced rat aorta relaxant response was significantly inhibited by ouabain (100 μM). Application of indomethacin (10 μM), NG‐nitro‐L‐arginine (10 μM) or tetraethylammonium (500 μM) did not alter the adenosine‐elicited effect in rat aorta. 8‐(3‐Chlorostyril)‐caffeine (0.3–3 μM), a selective A2A‐receptor antagonist, significantly reduced adenosine‐induced relaxation of rat aorta in a concentration‐dependent manner (pKB=6.57). Conversely, 1,3‐dipropyl‐8‐cyclopentylxanthine (10 nM), an A1‐receptor antagonist, did not affect adenosine‐evoked dilatation. These results indicate that in isolated rat aorta, adenosine produces endothelium‐independent relaxation, which is most probably dependent upon activation of smooth muscle Na+/K+‐ATPase, and opening of ATP‐sensitive K+ channels, to a smaller extent. According to receptor analysis, vasorelaxant action of adenosine in rat aorta is partly induced by activation of smooth muscle adenosine A2A receptors. 相似文献