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Cytotoxic effects of various quinone compounds are thought to be due to the formation of semiquinone free radicals. Hydroquinone and 1,2,4-benzenetriol in the presence of copper ions release from glutamate or DNA aldehydic products capable of reacting with 2-thiobarbituric acid (TBA). The formation of TBA reactive products (TBAR) was greater in the presence of 1,2,4-benzenetriol in comparison with hydroquinone. Complete inhibition of formation of TBAR from glutamate by 1,2,4-benzenetriol and copper was observed in the presence of catalase, thiourea and mannitol. Albumin and superoxide dismutase offered substantial protection. Complete protection of formation of TBAR from DNA was observed in the presence of catalase and thiourea. Presence of albumin, mannitol and superoxide dismutase caused only partial inhibition. The formation of TBAR from glutamate or DNA is dependent on copper ion concentration. The present data indicate that hydroquinone and 1,2,4-benzenetriol in the presence of copper ions can lead to the formation of reactive hydroxyl radicals which can release TBAR from glutamate or DNA. 相似文献
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AG Nettetal 《MedR Medizinrecht》2007,25(11):664-666
Abstrakt 1. Nimmt ein Patient einen ihm von seinem (Zahn-)Arzt einger?umten Exklusiv-Termin nicht wahr, obwohl er auf dessen Eigenschaft
ausdrücklich hingewiesen wurde, so hat er dem (Zahn-)Arzt den Behandlungsausfall abzüglich eines angemessenen Eigenanteils
des (Zahn-)Arztes zu ersetzen.
2. Die Ersatzpflicht tritt auch dann ein, wenn der Patient den Termin nicht in der in dem Behandlungsvertrag vorgesehenen
Frist absagt. Eine hierfür seitens des (Zahn-)Arztes bestimmte Frist von zwei Tagen vor Behandlungsbeginn stellt sich für
den Patienten grunds?tzlich auch nicht als unangemessene Benachteiligung i.S. des § 307 BGB dar.
3. Ein Anspruch des Arztes entf?llt auch bei nur mündlicher Vereinbarung nicht unter dem Gesichtspunkt des § 4 Abs. 5b BMV-Z,
denn diese Vorschrift ist teleologisch dahin zu reduzieren, dass nur zahn?rztliche Honoraransprüche aus erfolgten Behandlungen
schriftlich vereinbart werden müssen. Soweit es jedoch um einen vertraglichen Anspruch wegen einer Leistungsst?rung geht,
vermag das Schriftformerfordernis des § 4 Abs. 5b BMV-Z grunds?tzlich nicht einzugreifen. (Leits?tze des Bearbeiters) 相似文献
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Early during rat thymus ontogeny, an important proportion of thymocytes
expresses IL-2R and contains IL-2 mRNA. To investigate the role of the
IL-2-IL-2R complex in rat T cell maturation, we supplied either recombinant
rat IL-2 or blocking anti-CD25 mAb to rat fetal thymus organ cultures
(FTOC) under several experimental conditions. The IL-2 treatment initially
stimulated the growth of thymocytes and, as a result, induced T cell
differentiation, but the continuous addition of IL-2 to rat FTOC, as well
as the anti-CD25 administration, resulted in cell number decrease and
inhibition of thymocyte maturation. These results indicate that immature
rat thymocytes bear functional high- affinity IL-2R and that IL-2 promotes
T cell differentiation as a consequence of its capacity to stimulate cell
proliferation. Modifications in TCR alpha beta repertoire and increased
numbers of NKR- P1+ cells, largely NK cells, were also observed in
IL-2-treated FTOC. Furthermore, IL-2-responsiveness of different thymocyte
subsets changed throughout thymic ontogeny. Immature CD4-CD8-cells
responded to IL-2 in two stages, early in thymus development and around
birth, in correlation with the maturation of two distinct waves of thymic
cell progenitors. Mature CD8+ thymocytes maximally responded to IL-2 around
birth, supporting a role for IL-2 in the increased proliferation of mature
thymocytes observed in vivo in the perinatal period. Taken together, these
findings support a role for IL-2 in rat T cell development.
相似文献
10.
Cytotoxicity of atracurium and of its metabolites was tested in vitro.Exposure of isolated rat hepatocytes to atracurium produced cellular damage evidenced by extrusion of an intracellular enzyme, lactate dehydrogenase (LDH), into the incubation medium. Leakage of LDH was directly related to the concentration of atracurium in the medium (250 to 800 μM). If the spontaneous degradation of atracurium (presumably via Hofmann elimination) was first carried out in vitroand the degradation products subsequently added to the isolated hepatocytes, the leakage of LDH was also dose-dependent but larger than that observed after the addition of the parent drug. When l-cysteine was admixed to the products of the spontaneous degradation of atracurium prior to their addition to the liver cells, no leakage of LDH was observed. The results are compatible with the working hypothesis that atracurium itself and, even more so, acrylates formed in Hofmann elimination of atracurium, are reactive toward nucleophiles and damage the cells by alkylating nucleophiles present in cellular membranes. Antecedent covalent binding of acrylates to the nucleophile cysteine, i.e., the formation of acrylatecysteine adducts, saturated the reactive capacity of acrylates for nucleophiles and thus prevented the reactive metabolites from alkylating the endogenous nucleophiles. Possible clinical consequences resulting from in vivogeneration of reactive metabolites are not clear at the present time but are projected to be related to (a) the dose of atracurium administered, (b) the amount of acrylates generated, (c) the functional importance of the endogenous nucleophiles alkylated, and (d) the pathway and the speed of detoxification of atracurium and its metabolites. 相似文献