The effect of temperature and body size on electron transport system activity in freshwater zooplankton

1978 ◽  
Vol 56 (4) ◽  
pp. 634-642 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Organic Compounds ◽  
Transport System ◽  
Environmental Temperature ◽  
Electron Transport System ◽  
Effect Of Temperature ◽  
Unit Weight ◽  
Succinate Oxidation ◽  
Ets Activity

Electron transport system (ETS) activity in Mysis relicta, Limnocalanus macrurus, and surface zooplankton was measured by following the rate of reduction of cytochrome c in the presence of NADH, succinate, or NADPH. The steady-state kinetics indicate that NADPH is oxidized by a different ETS from NADH and succinate, and more than one system may exist for the oxidation of NADH and succinate in surface zooplankton. The NADPH requiring ETS which, because of its higher Km, presumably does not reduce cytochrome c in vivo, is probably equivalent to the microsomal NADPH requiring ETS from vertebrates and insects used in the detoxification of organic compounds. ETS activity is affected by both environmental temperature and size of the organism, with environmental temperature affecting both the total activity of the enthalpy of activation of the system. Larger organisms have a lower activity per unit weight compared with smaller animals. Because the effects of temperature and size are roughly similar for NADPH oxidation and NADH or succinate oxidation, the ratio of NADPH to either NADH or succinate oxidation may be a useful indicator of exposure to toxic organic compounds.

Electron transport system activity in Daphnia and crayfish

1977 ◽  
Vol 55 (5) ◽  
pp. 847-854 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Transport System ◽  
Electron Transport System ◽  
Toxic Substances ◽  
Ets Activity ◽  
Cytochrome C Reductase ◽  
Orconectes Propinquus ◽  
Cytochrome C Reduction ◽  
Nadph Cytochrome C Reductase

The activity of the electron transport system (ETS) in Daphnia magna and the crayfish Orconectes propinquus was estimated by measuring NADH-, succinate-, and NADPH-cytochrome c reductase. The activity of the total ETS was also measured by following NADH oxidation, and by measuring the rate of cytochrome c reduction upon addition of cyanide after a steady state between cytochrome c reductase (EC 1.6.99.3) and cytochrome oxidase (EC 1.9.3.1) had been reached. ETS activity is highest in crayfish gill when NADH or succinate is used as substrate, and highest in crayfish hepatopancreas when NADPH is used. Michaelis–Menten constants for NADH, NADPH, and cytochrome c are comparable with some of the lower values reported for mammalian systems. The usefulness of the ETS assay in the study of toxic substances is discussed.

A comparison of electron transport system activity in stream and beaver pond sediments

1995 ◽  
Vol 52 (6) ◽  
pp. 1318-1326 ◽  
Author(s):  
M. S. Songster-Alpin ◽  
R. L. Klotz
Keyword(s):  
Electron Transport ◽  
Transport System ◽  
Unit Length ◽  
New York State ◽  
Dry Weight ◽  
Electron Transport System ◽  
Beaver Pond ◽  
Tetrazolium Chloride ◽  
Ets Activity ◽  
Beaver Ponds

Electron transport system (ETS) activity of sediments as an indication of microbial metabolic activity was measured at four beaver pond sites in central New York State. ETS activity, an indication of microbial biomass and respiration, was measured as the reduction of 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) to INT-formazan. Since INT can be reduced by both aerobes and anaerobes, the total microbial respiratory activity in the sediments was measured. The ETS activity increased from means of 11.1–65.0 μg O2∙g−1 dry weight∙h−1 at the free-flowing upstream reaches to means of 221.2–262.6 μg O2∙g−1 dry weight∙h−1 within the beaver ponds. ETS activity decreased with increased depth of sediment probably because of the loss of aerobic activity. When ETS activity was expressed on a per unit area basis (grams O2 per square metre per hour), the increase from upstream reaches to the ponds ranged from 13- to 35-fold. This difference increased to 460- to 2180-fold when the activity was expressed per unit length of stream (micrograms O2 per metre per hour). These data showed that beaver ponds greatly increased microbial activity along streams, likely resulting in changes in biogeochemical cycles controlled directly or indirectly by microorganisms.

The multiple roles of the mitochondrion of the malarial parasite

Parasitology ◽  
2004 ◽  
Vol 129 (5) ◽  
pp. 511-524 ◽  
Author(s):  
J. KRUNGKRAI
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Transport System ◽  
Antimalarial Drug ◽  
Tricarboxylic Acid Cycle ◽  
Coenzyme Q ◽  
Complex Iii ◽  
Electron Transport System ◽  
Complex Ii ◽  
Dehydrogenase Complex

Mitochondria of the malaria parasitePlasmodium falciparumare morphologically different between the asexual and sexual blood stages (gametocytes). In this paper recent findings of mitochondrial heterogeneity are reviewed based on their ultrastructural characteristics, metabolic activities and the differential expression of their genes in these 2 blood stages of the parasite. The existence of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II), cytochrome c reductase (complex III) and cytochrome c oxidase (complex IV) suggests that the biochemically active electron transport system operates in this parasite. There is also an alternative electron transport branch pathway, including an anaerobic function of complex II. One of the functional roles of the mitochondrion in the parasite is the coordination of pyrimidine biosynthesis, the electron transport system and oxygen utilization via dihydroorotate dehydrogenase and coenzyme Q. Complete sets of genes encoding enzymes of the tricarboxylic acid cycle and the ATP synthase complex are predicted fromP. falciparumgenomics information. Other metabolic roles of this organelle include membrane potential maintenance, haem and coenzyme Q biosynthesis, and oxidative phosphorylation. Furthermore, the mitochondrion may be a chemotherapeutic target for antimalarial drug development. The antimalarial drug atovaquone targets the mitochondrion.

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