A comparison between the responses of neutral red and acridine orange: acridine orange should be preferential and alternative to neutral red as a dye for the monitoring of contaminants by means of biological sensors.

The acridine orange (AO) and neutral red (NR) dyes, commonly used as probes to measure the internal pH in acidic vesicles, are compared in this article. The comparison between the two dyes (arising from calculations taking into account their analytical constants) illustrated that the use of AO is preferential to that of NR because the AO response is sensitive over the whole pH range between 4.0 and 7.4, whereas the NR response is effective only between pHs 4.0 and 6.0. In addition, it became evident from the mitochondrial respiration response that NR, unlike AO, is a protonophore. When taken into consideration, these two properties suggest that AO is more suitable than NR as an indicator of toxicity measurements in water samples because the environmental toxic compounds induce pH changes in the acidic vesicles of biological structures that are used as environmental biosensors.

TCMS inhibits ATP synthesis in mitochondria: a systematic analysis of the inhibitory mechanism.

The interactions of the antifouling compound TCMS (2,3,5,6-tetrachloro-4-methylsulphonyl pyridine) with rat liver mitochondria have been investigated. The results indicate that the compound inhibits ATP synthesis. Further investigations regarding the ATP synthesis mechanism suggest that TCMS inhibits succinic dehydrogenase of the mitochondrial respiratory chain. As the respiratory chain is similar in all living organisms, it can be concluded that the toxic effect of TCMS most likely depend on the different bioavailability of the compound and on the different importance of mitochondria in the ATP production in the animal species.

Frozen mitochondria as rapid water quality bioassay.

A rapid and relatively low cost bioassay, usable in routine screening water test has been developed modifying the beef heart mitochondria test. In our experiments, mitochondria (FM22) were frozen at -22 degrees C, instead of -80 degrees C (FM80), and their applicability and sensitivity was verified. The oxygen consumption was measured by a Clark electrode that was interfaced to a PC to collect test analysis data. Blank tests were carried out to verify the oxygen consumption linear fitting. Toxicity tests were performed using pure organic and inorganic compounds, such to verify the FM22 sensitivity. A piecewise regression, through an Excel Macro, identified the break-point in the oxygen consumption and calculated the toxicity. The IC50s of the tested compounds were calculated and ranged from 0.123 to 0.173 mg/l for heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and from 0.572 to 10.545 mg/l for organics (benzene, DMSO, DDE, endrin, dichloromethane, chlorobenzene, 1,2-dichlorobenzene and 1,3-dichlorobenzene). Water effluent samples were then tested. The FM22 gave different toxic reactions to them. Water samples were characterised for heavy metals. The FM22 bioassay had a higher sensitivity than the FM80 and a high reproducibility in the toxicity test with pure compounds. The FM22 test was a good predictor of toxicity for water samples; the bioassay is easy, low cost and rapid, then usable for routine tests.