Portable Unit for Metabolic Analysis

The Portable Unit for Metabolic Analysis (PUMA) is an instrument that measures several quantities indicative of human metabolic function. Specifically, this instrument makes time-resolved measurements of temperature, pressure, flow, and the partial pressures of oxygen and carbon dioxide in breath during both inhalation and exhalation. Portable instruments for measuring these quantities have been commercially available, but the response times of those instruments are too long to enable temporal resolution of phenomena on the time scales of human respiration cycles. In contrast, the response time of the PUMA is significantly shorter than characteristic times of human respiration phenomena, making it possible to analyze varying metabolic parameters, not only on sequential breath cycles but also at successive phases of inhalation and exhalation within the same breath cycle. In operation, the PUMA is positioned to sample breath near the subject s mouth. Commercial off-the-shelf sensors are used for three of the measurements: a miniature pressure transducer for pressure, a thermistor for temperature, and an ultrasonic sensor for flow. Sensors developed at Glenn Research Center are used for measuring the partial pressures of oxygen and carbon dioxide: The carbon dioxide sensor exploits the relatively strong absorption of infrared light by carbon dioxide. Light from an infrared source passes through the stream of inhaled or exhaled gas and is focused on an infrared- sensitive photodetector. The oxygen sensor exploits the effect of oxygen in quenching the fluorescence of ruthenium-doped organic molecules in a dye on the tip of an optical fiber. A blue laser diode is used to excite the fluorescence, and the optical fiber carries the fluorescent light to a photodiode, the temporal variation of the output of which bears a known relationship with the rate of quenching of fluorescence and, hence, with the partial pressure of oxygen. The outputs of the sensors are digitized, preprocessed by a small onboard computer, and then sent wirelessly to a desktop computer, where the collected data are analyzed and displayed. In addition to the raw data on temperature, pressure, flow, and mole fractions of oxygen and carbon dioxide, the display can include volumetric oxygen consumption, volumetric carbon dioxide production, respiratory equivalent ratio, and volumetric flow rate of exhaled gas

miR-223 targets IL-1β production and is decreased in synovial fluid monocytes from arthritis patients

Aim: The aim of this study was to identify miRNA that target infl ammatory pathways during arthritis. Specifi cally we are interested in production of the key infl ammatory cytokine IL-1β, which is generated by a complex of proteins known as the infl ammasome.<p></p> Methods: Synovial fl uid monocytes were isolated from patients with rheumatoid or psoriatic arthritis and analysis of miRNA expression was performed. NLRP3, a key component of the infl ammasome, was identifi ed as a potential target of miR-223 and this was validated by several approaches.<p></p> Results: We have identifi ed the fi rst miRNA that targets an infl ammasome complex. This is miR-223, which has a single, highly conserved binding site in the NLRP3 3′UTR. miR-223 expression decreases as monocytes differentiate into macrophages, and NLRP3 protein increases during this time. However overexpression of miR-223 prevents accumulation of endogenous NLRP3 protein levels, as for monocytic Thp-1 cells differentiated into macrophages with PMA. NLRP3 function was also impacted by miR-223, with decreased IL-1β production after stimulation with nigericin or uric acid crystals, but not poly dAdT (AIM2) or salmonella (NLRC4). Consistent with this, mice lacking miR-223 are reported to have spontaneous infl ammatory disease associated with increased NLRP3 protein expression. miR-223 is known to be decreased in type 2 diabetes, Crohn’s disease, and now we show a specifi c decrease in synovial monocytes from rheumatoid and psoriatic arthritis patients. All of these diseases are associated with increased IL-1β and the effect of miR-223 on NLRP3 could be a mechanism to account for this.<p></p> Conclusions: In summary we have identifi ed an endogenous miRNA that limits NLRP3 infl ammatory capacity during myeloid differentiation, and is decreased in synovial fl uid monocytes from patients with rheumatoid or psoriatic arthritis.<p></p&gt