ABSTRACT
We describe a chip calorimetric technique that allows the investigation of biological material under anoxic conditions in a micro-scale and in real time. Due to the fast oxygen exchange through the sample flow channel wall, the oxygen concentration inside the samples could be switched between atmospheric oxygen partial pressure to an oxygen concentration of 0.5% within less than 2 h. Using this technique, anaerobic processes in the energy metabolism of Trypanosoma cruzi could be studied directly. The comparison of the calorimetric and respirometric response of T. cruzi cells to the treatment with the mitochondrial inhibitors oligomycin and antimycin A and the uncoupler FCCP revealed that the respiration-related heat rate is superimposed by strong anaerobic contributions. Calorimetric measurements under anoxic conditions and with glycolytic inhibitors showed that anaerobic metabolic processes contribute from 30 to 40% to the overall heat production rate. Similar basal and antimycin A heat rates with cells under anoxic conditions indicated that the glycolytic rates are independent of the oxygen concentration which confirms the absence of the "Pasteur effect" in Trypanosomes. Graphical abstract.
Subject(s)
Calorimetry/methods , Energy Metabolism , Lab-On-A-Chip Devices , Trypanosoma cruzi/metabolism , Anaerobiosis , Antimycin A/pharmacology , Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone/pharmacology , Glycolysis/drug effects , Mitochondria/drug effects , Oligomycins/pharmacology , Oxygen/metabolism , Proton Ionophores/pharmacologyABSTRACT
Second-order calibration and multivariate spectroscopic-kinetic measurements in the visible region are proposed to improve the Jaffé method for creatinine assay. Analyses performed on synthetic mixtures containing bilirubin, glucose, and albumin confirm that second-order calibration is useful for creatinine determination in human serum. Quantitative determinations of creatinine with the parallel factor analysis (PARAFAC) and direct trilinear decomposition (TLD) methods were compared. It is shown that both methods can be used for creatinine determination in human serum, with an SEP (standard error of prediction) of 2.22 and coefficient of variability of 6.14% for PARAFAC, and an SEP of 2.38 and coefficient of variability of 6.57% for TLD [corrected].
