Simple co-precipitation of trace elements on the oxinate precipitate is usually insufficient for quantitative recovery at the ppb levels. An additional 30 to 100% of some trace elements can be recovered on the AC phase if an AC adsorption step is included in the enrichment procedure (17).The procedure has been used for the analysis of environmental and laboratory samples in combination with XRF (17), INAA, and SSMS.
ACKNOWLEDGMENTThanks are due to H. Nullens and J. De Bonder for helpful computer evaluations and to J. Hoste, who made the neutron activation analysis possible.
Abstract-The functional inhibitory characteristics of the angiotensin II type 1 receptor blockers (ARB) candesartan; irbesartan; and losartan and its active metabolite EXP 3174 (EXP) were studied in rabbit aortic strips and rat portal vein preparations in vitro. Moreover, plasma-protein binding was determined, and the binding was high (Ͼ98.5%) for all ARBs. These values were needed to relate the concentrations of the ARBs used in vitro to the nonprotein bound concentrations in clinical use. In both vascular preparations, candesartan caused a marked decrease in the maximal contractile response of the angiotensin II (Ang II) concentration-response curve. Losartan, EXP, and irbesartan caused a rightward parallel shift without any major effects on the maximal response to Ang II. The inhibitory effect of candesartan developed slowly (maximal effect after Ͼ30 minutes) and lasted Ͼ2 hours despite repeated washing of the vessels. The effect of losartan, irbesartan, and EXP had a faster onset, and most of the inhibitory effect disappeared after washing. The duration of the inhibitory effects of the ARBs were not related to lipophilicity of the compounds. Cooling of the rat portal vein preparations to 4°C before administration of candesartan prevented the persistent inhibition of Ang II response seen at 37°C. For the other ARBs studied, the magnitude of inhibition and the speed of recovery of the Ang II response were independent of the incubation temperature before washing. In addition, when candesartan was given to conscious rats, the inhibitory effect on Ang II-induced blood pressure responses persisted during the 24-hour period despite nondetectable plasma concentrations of candesartan at 24 hours. [1][2][3] The tolerability of these compounds seems to be better than that of other antihypertensives, whereas the blood pressure-lowering effect is about the same as for angiotensin-converting enzyme inhibitors and calcium antagonists. 1-3 Regarding efficacy of different ARBs, candesartan and irbesartan were shown to be more effective than losartan in lowering 24-hour blood pressure (BP) in mildly to moderately hypertensive patients. 4,5 Candesartan was described to dissociate slowly from AT 1 -receptors in cell membrane preparations and to cause a more persistent inhibition of the angiotensin II (Ang II)-mediated vascular contractile response when compared with losartan. 6 In isolated vascular preparations from the rabbit, losartan caused a parallel rightward shift in the concentration-effect curves for Ang II, 7 whereas candesartan caused a marked suppression of the maximum contractile response to Ang II. 1,6 Thus ARBs may differ in their antagonism of the Ang II-mediated response, causing surmountable or insurmountable antagonism. 8 The mechanism of the insurmountable antagonism of candesartan and the long-lasting duration of effect is not clear, although it may be related to its slow dissociation from the receptor. 1,6 The aim of our study was to investigate the functional inhibitory characteristics of different ARBs. ...
The biological effects of effluents from pulp industries, especially from bleaching processes, on aquatic ecosystems were studied in a joint biological/chemical project field consisting of several sub-projects. The principal study was devoted to the effects of biologically active chlorinated organic compounds.
A receiving body of water for pulp bleach plant effluents at the Gulf of Bothnia was chosen for the three year study. Near the effluent outlet the fish biomass was low, and the species composition of the fish community had changed. Perch (Perca fluviatilis L.) exhibited reduced reproduction and disturbed physiology in all parts of the receiving body of water. The effluent also affected the diversity, biomass and distribution of invertebrates and plants. To further study the effects, fish and benthic-living organisms were exposed in the laboratory to sediment from the receiving water and to various mixtures of bleach plant effluents. The level of extractable organic chlorine (EOC1) of the perch decreased along a gradient from the effluent outlet towards the open sea. In sediment outside the Swedish coast, the level of EOC1 and the occurrence of compounds related to bleach mill effluents indicated a distribution of such substances over large areas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.