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.

Effect of prolonged cold exposure on components of the electron transport system

1960 ◽  
Vol 198 (4) ◽  
pp. 740-744 ◽  
Author(s):  
John P. Hannon
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Transport System ◽  
Cold Exposure ◽  
Liver Tissue ◽  
Succinic Dehydrogenase ◽  
Electron Transport System ◽  
Malic Dehydrogenase ◽  
Cytochrome C Reductase

The effect of 3–4 weeks exposure to 5° ± 1°C on the activity of enzymes associated with the electron transport system of rat liver and gastrocnemius muscle was investigated. The enzymes included lactic, succinic and malic dehydrogenase, DPNH-cytochrome c reductase and cytochrome oxidase. Cold exposure led to increased activities on the part of succinic and malic dehydrogenase and cytochrome oxidase. Muscle tissue exhibited a greater response in these components than liver tissue. Lactic dehydrogenase and DPNH-cytochrome c reductase activities were unaffected by cold exposure in either liver or muscle. Thyroxine, 2,4-dinitrophenol, phosphate and hexokinase-glucose stimulated the activity of succinic dehydrogenase activities of liver tissue, with hexokinase-glucose producing the greatest effect. The degree of stimulation by these agents was the same, however, for tissue from cold exposed animals as it was for controls. It was concluded that the increased tissue oxygen consumption in the cold-acclimatized rat was attributable to at least three mechanisms: a) an increased enzyme concentrations; b) a stimulation of latent enzyme activity; and c) an uncoupling of oxidative phosphorylation.

scholarly journals AN ELECTRON-TRANSPORT SYSTEM ASSOCIATED WITH THE OUTER MEMBRANE OF LIVER MITOCHONDRIA

1967 ◽  
Vol 32 (2) ◽  
pp. 415-438 ◽  
Author(s):  
Gian Luigi Sottocasa ◽  
Bo Kuylenstierna ◽  
Lars Ernster ◽  
Anders Bergstrand
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Outer Membrane ◽  
Respiratory Chain ◽  
Transport System ◽  
Cytochrome B5 ◽  
Liver Mitochondria ◽  
Electron Transport System ◽  
Cytochrome C Reductase ◽  
Nadh Cytochrome

Preparations of rat-liver mitochondria catalyze the oxidation of exogenous NADH by added cytochrome c or ferricyanide by a reaction that is insensitive to the respiratory chain inhibitors, antimycin A, amytal, and rotenone, and is not coupled to phosphorylation. Experiments with tritiated NADH are described which demonstrate that this "external" pathway of NADH oxidation resembles stereochemically the NADH-cytochrome c reductase system of liver microsomes, and differs from the respiratory chain-linked NADH dehydrogenase. Enzyme distributation data are presented which substantiate the conclusion that microsomal contamination cannot account for the rotenone-insensitive NADH-cytochrome c reductase activity observed with the mitochondria. A procedure is developed, based on swelling and shrinking of the mitochondria followed by sonication and density gradient centrifugation, which permits the separation of two particulate subfractions, one containing the bulk of the respiratory chain components, and the other the bulk of the rotenone-insensitive NADH-cytochrome c reductase system. Morphological evidence supports the conclusion that the former subfraction consists of mitochondria devoid of outer membrane, and that the latter represents derivatives of the outer membrane. The data indicate that the electron-transport system associated with the mitochondrial outer membrane involves catalytic components similar to, or identical with, the microsomal NADH-cytochrome b5 reductase and cytochrome b5.

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.

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.

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