Aluminum accumulation in a lotic mayfly at low pH—A laboratory study

1990 ◽  
Vol 19 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Kjell G. Frick ◽  
Jan Herrmann
2020 ◽  
Vol 259 ◽  
pp. 108813
Author(s):  
Lucélia Borgo ◽  
Flávio Henrique Rabêlo ◽  
Giselle Carvalho ◽  
Thiago Ramires ◽  
Ana Julia Righetto ◽  
...  

2005 ◽  
Vol 62 (10) ◽  
pp. 2303-2311 ◽  
Author(s):  
Anna R Winter ◽  
Joel W Nichols ◽  
Richard C Playle

Juvenile rainbow trout (Oncorhynchus mykiss) (∼0.6 g) were exposed to 3 µmol Al·L–1 in ion-poor water adjusted to pH 4–10 in the absence or presence of natural organic matter (NOM). Aluminum accumulation by trout gills was highest at pH 6–8, there was moderate Al accumulation by trout gills at pH 5 and 9, and trout at pH 4 and 10 did not accumulate any Al on their gills. NOM at 5 mg C·L–1 eliminated Al accumulation by trout gills at all water pHs. These results are explained by NOM complexing Al and keeping Al in solution but off the gills, by H+ competition with Al3+ at low pH, by poor binding of the Al(OH)4– anion to negatively charged gills at high pH, and by polymerization and precipitation of Al onto the gills at intermediate water pH, especially if water pH in the gill micro environment is considered. Increased fish mortality at pH 10 in the presence of NOM is explained by the indirect effect of NOM tying up the limited amount of Ca in the ion-poor water.


Author(s):  
J. Quatacker ◽  
W. De Potter

Mucopolysaccharides have been demonstrated biochemically in catecholamine-containing subcellular particles in different rat, cat and ox tissues. As catecholamine-containing granules seem to arise from the Golgi apparatus and some also from the axoplasmic reticulum we examined wether carbohydrate macromolecules could be detected in the small and large dense core vesicles and in structures related to them. To this purpose superior cervical ganglia and irises from rabbit and cat and coeliac ganglia and their axons from dog were subjected to the chromaffin reaction to show the distribution of catecholamine-containing granules. Some material was also embedded in glycolmethacrylate (GMA) and stained with phosphotungstic acid (PTA) at low pH for the detection of carbohydrate macromolecules.The chromaffin reaction in the perikarya reveals mainly large dense core vesicles, but in the axon hillock, the axons and the terminals, the small dense core vesicles are more prominent. In the axons the small granules are sometimes seen inside a reticular network (fig. 1).


Author(s):  
D.E. Brownlee ◽  
A.L. Albee

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.


2008 ◽  
Vol 13 (4) ◽  
pp. 239-247 ◽  
Author(s):  
David De Cremer ◽  
Barbara C. Schouten

The present research examined the idea that the effectiveness of apologies on promoting fairness perceptions depends on how meaningful and sincere the apology is experienced. More precisely, it was predicted that apologies are more effective when they are communicated by an authority being respectful to others. A study using a cross-sectional organizational survey showed that an apology (relative to giving no apology) revealed higher fairness perceptions, but only so when the authority was respectful rather than disrespectful. In a subsequent experimental laboratory study the same interaction effect (as in Study 1) on fairness perceptions was found. In addition, a similar interaction effect also emerged on participants’ self-evaluations in terms of relational appreciation (i.e., feeling valued and likeable). Finally, these self-evaluations accounted (at least partly) for the interactive effect on fairness perceptions.


1964 ◽  
Vol 11 (01) ◽  
pp. 085-093
Author(s):  
W. F Blatt ◽  
JL Gray ◽  
H Jensen

SummaryA sensitive tool has been described for measuring fibrinolysis in reconstituted systems using thrombelastography. Activator mixtures with no appreciable proteolytic activity can similarly be tested in this system when the fibrinogen utilized has sufficient plasminogen present. Exposure of human plasminstreptokinase mixtures formed at pH 7.0 to acid conditions produced a striking loss of activator activity which could not be ascribed to low pH lability of the components, nor to plasmin action on the SK at pH 2.0. This is additional evidence for the hypothesis that human plasmin interacts with SK to form a complex capable of converting human and bovine plasminogen to plasmin.


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