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A new calorimetric technique is described that allows high-throughput heat production rate measurements on small biological tissue samples. The technique is based on the widely used thermopile chip technology combined with an innovative method for precise transport and positioning of samples of different biological materials at the thermal power detector inside the calorimeter. The new transport and positioning technique is a combination of fluidic and mechanical transport, where the latter is realized by a magneto-motor drive. The transport facility ensures good diffusive oxygen penetration into the sample, which is essential for highly metabolically active materials. The proper functioning of the device is demonstrated by measuring the heat production of metabolically active brown adipose tissue, biopsied tegu lizard muscle, and live Drosophila larvae at different stages and temperatures. [ABSTRACT FROM AUTHOR]

Ca2+ signaling in trypanosomatids is an important component of energy metabolism regulation and therefore, cytosolic Ca2+ concentration is finely regulated by Ca2+ transport through the plasma membrane and Ca2+ uptake and release by intracellular organelles. To maintain intracellular Ca2+ homeostasis with different gradients of the ion within the cellular compartments, there is an energy cost and also energy dissipation in the form of heat. Using an innovative segmented fusion technique of a chip-calorimeter and CRISPR/Cas9 knockout (–KO) Trypanosoma cruzi cell lines, we evaluated the heat generation during Ca2+ uptake by digitonin-permeabilized T. cruzi epimastigotes, a system consisting of Ca2+ uptake predominantly by mitochondria and acidocalcisomes. We used three T. cruzi epimastigotes cell lines: control cells denominated scrambled, cells with the absence of the pyruvate dehydrogenase phosphatase (TcPDP-KO) and cells lacking mitochondrial Ca2+ uptake via the mitochondrial calcium uniporter (TcMCU-KO), that presented, in this respective order, decreasing rates and capacities of Ca2+ uptake. TcPDP-KO cells exhibited the lowest heat production following Ca2+ addition, which may be due to its lower mitochondrial oxidative phosphorylation capacity and lower ATP availability for acidocalcisomal Ca2+ uptake. Scrambled and TcMCU-KO cells exhibited similar Ca2+-induced heat effects, which correlates with a higher ATP-dependent acidocalcisomal Ca2+ uptake in these cells. Our results show evidences that mitochondrial Ca2+ transport via the uniporter is minimally heat dissipative, while ATPase pumps in acidocalcisomes possess a predominant contribution to the heat generated during Ca2+ uptake. [ABSTRACT FROM AUTHOR]

The development of the segment-flow technology has considerably extended the application range of miniaturized calorimeters. The transport of samples in aqueous µL segments by a water-immiscible carrier liquid enables the investigation of aggregated, complex biological samples in flow-through. The protection from contaminations of the fluidics of the calorimeter by the carrier liquid is an excellent precondition for the design of efficient automatic experiment protocols. In this paper, a new operation mode of this technique is presented, which allows the measurement of fast transient heat-dissipating processes using a chip calorimeter. Heat dissipation is initiated by the merging of separate µL-sample-segments arriving successively at the measuring chamber. The potential of the segment fusion technique was demonstrated here using two different applications. First, we showed the use of this method for an automatic screening of the strength of receptor–substrate interactions by the measurement of the heat of the adduct formation of carbohydrate octyl ß-d-glucopyranoside and three different receptor molecules. Next, we used the method for the determination of transient heat effects in the seconds range allowing the investigation of metabolic processes in Trypanosoma cruzi cells induced by Ca2+ ions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new calorimetric technique is described which allows the measurement of metabolic heat rates in biological materials which are triggered by changes in the oxygen tension. It uses the high permeability for oxygen of a thin-walled Teflon flow channel of a chip calorimeter in order to adjust variable but defined oxygen concentrations in the samples. Using this technique, for the first time, the heat production rate of sickle cell erythrocytes (SS-RBCs) in sickled and non-sickled state could be compared. To measure heat rate changes in real time when sickled SS-RBCs return to the non-sickled state, the heat dissipation was measured during the re-oxygenation of the cell samples which had been treated before under anoxic conditions. We found higher heat production rate of the blood cells in non-sickled state, which is in agreement with the reported increased glucose uptake. [ABSTRACT FROM AUTHOR]

Rapid detection of antibiotic resistances of clinical bacterial strains would allow an early selective antibiotic therapy and a faster intervention and implementation of infection control measurements. In clinical practice, however, conventional antibiotic susceptibility tests of bacteria often need 24 h until the results are obtained. The metabolic heat production of bacteria is an excellent possibility to record their physiological activities and could therefore be used for a rapid discrimination of bacterial strains which are resistant or non-resistant to antibiotics and also to lytic bacteriophages, respectively. Unfortunately, conventional calorimeters suffer from need of comparably large volumes of bacterial suspensions are characterised by slow operation and high costs which restrict their application in clinical laboratories. The present paper demonstrates that a new type of calorimeters developed on silicon-chip technology enables the detection of antibiotic resistances on a minute-timescale. For this reasons, a prototype chip calorimeter was used which sensitivity is 20 nW related to the heat production of about 10 bacteria. For a clear discrimination of antibiotic resistance about 10 bacteria are required. The antibiotic resistances and susceptibilities of different strains of Staphylococcus aureus to cefoxitin and the sensitivities of S. aureus DSM 18421 and E. coli DSM 498 to a mixture of two bacteriophages were studied. Comparing the heat productions of cultures incubated with antibiotics or bacteriophages to those without these antibacterial preparations enabled a clear discrimination of resistant and non-resistant strains already after totally 2 h. [ABSTRACT FROM AUTHOR]