Turbidity based methods, however, assume a linear relationship between test organism growth and absorbance [3]. Also, if turbidity is interpreted visually, results can differ from person to person. OSI-906 research buy All chemical or physical processes either generate or consume heat. This can be measured using isothermal microcalorimetry (IMC). The heat flow rate is
proportional to the reaction rate, and the total heat produced in some time t is proportional to the extent of the reaction taking place in time t. Based on these principles, IMC is a universal tool for real-time evaluation of rate processes in small (e.g. 3–20 ml) ampoules, AMN-107 chemical structure including processes involving cultured cells [4]. In IMC the net heat flow generated by any biological or non-biological chemical or physical processes taking place within the ampoule is continuously measured while the ampoule is kept at constant temperature. IMC instruments can be calibrated with an internal precision heater or with reactions of known heat-flow. However, the instruments measure the net heat flow produced by all processes taking place in an ampoule. Therefore, in order to correctly interpret the measurements, the user must have 4SC-202 datasheet knowledge of what processes are taking place and have, if necessary, an
experimental means for accounting for heat flow from processes not of interest. A prime example is chemical breakdown of the medium in which a process of interest is taking place. Besides being a universal rate process measurement tool, IMC also has the advantage that it is entirely passive. Therefore the specimen is not disturbed in any way during measurement, and after measurement the contents of ampoule can be evaluated by any other means desired. More information is available in a review by Lewis and Daniels (the senior author) giving a detailed description of the nature, advantages and limitations of IMC, including its use in evaluating cellular processes involving bioactive Cyclic nucleotide phosphodiesterase materials [4]. In 1996, the senior author began reporting his experience using isothermal micro-nano
calorimetry to evaluate the activity of cultured cells- response of cultured macrophages to implant material particles [5]. However, microcalorimetry has been long-used to study metabolism of cultured cells. James reviewed work in cellular microcalorimetry in 1987 [6] and reported a paper by Hill in 1918 as the earliest employing microcalorimetry to study bacteria. In 1977, Ripa et al. [7] evaluated microcalorimetry as tool for the evaluation of blood culture media. In the study, the influence of additives on blood culture could be determined much faster and easier compared to traditional media evaluation methods. Based on their data, Ripa et al. [7] suggested the use of microcalorimetry as tool to evaluate the inhibitory or stimulatory influence of various compounds. Later, another study used microcalorimetry to detect the growth of microorganisms [8].