Figure 2.
Real-time measurements of hydrogen (H2) and methane (CH4) production in mice within indirect calorimetry system. (a) Illustration of the indirect calorimetry system extended for H2 and CH4 measurements. Direction of air flow in the tubing is shown in blue, new gas sensors are shown in green. For clarity, tube lengths are not to scale (all equal) and food and drink containers with sensors are not shown, nor are the infrared beam bars for activity measurements. (b) Ambient concentrations of H2 and CH4 (left y-axis, ppm) and O2 and CO2 (right y-axis, %) were recorded in an empty (reference) cage at 20 min intervals for 24 h. (c) Gas concentrations in a cage occupied by a chow-fed female adult mouse were measured and compared to the corresponding concentrations in the reference cage and expressed as delta values. White and grey areas in panels b and c represent the inactive light and active dark phase for the animal, respectively. ZT, Zeitgeber time.