Biomedical subjects
James Barnett
Publications and source records attributed to James Barnett.
Variations in aggrecan structure modulate its susceptibility to aggrecanases.
Proteoglycan aggregates and purified aggrecan from adult and fetal bovine cartilage and adult and neonatal human cartilage were subjected to in vitro degradation by recombinant aggrecanase-1 and aggrecanase-2. The ability of the aggrecanases to cleave within the aggrecan IGD (interglobular domain) and CS2 domain (chondroitin sulphate-rich domain 2) was monitored by SDS/PAGE and immunoblotting. Aggrecanase-2 showed a similar ability to cleave within the IGD of adult and immature aggrecan, whereas aggrecanase-1 was less efficient in cleavage in the IGD of immature aggrecan, for both the bovine and the human substrates. Both aggrecanases showed a similar ability to cleave within the CS2 domain of bovine aggrecan irrespective of age, but showed a much lower ability to cleave within the CS2 domain of human aggrecan. Equivalent results were obtained whether aggrecan was present in isolation or as part of proteoglycan aggregates. When proteoglycan aggregates were used, neither aggrecanase was able to cleave link protein. Thus, for aggrecan cleavage by aggrecanases, variations in cleavage efficiency exist with respect to the species and age of the animal from which the aggrecan is derived and the type of aggrecanase being used.
Maintaining oxygenation via demand oxygen delivery during rest and exercise.
BACKGROUND: Oxygen-conserving devices have been the foundation of highly portable oxygen systems that enable hypoxemic chronic lung disease patients to live active lives. Pulsing demand oxygen delivery systems (DODS) can adequately oxygenate most patients at rest and usually during exercise. However, some patients desaturate during exercise at DODS settings equivalent to continuous-flow oxygen. OBJECTIVE: Determine if design enhancements of the Oxymatic 401 DODS (including increased sensitivity, earlier inspiratory delivery, larger pulse volume, modified pulse contour, and higher settings) better maintain blood oxygen saturation (measured via pulse oximetry [S(pO2)]) in patients who severely desaturate during exercise. METHODS: We compared patients receiving DODS oxygen and patients receiving continuous-flow oxygen, during both rest and iso-exercise. SETTING: This study was conducted in the Pulmonary Rehabilitation Program at Mission Hospital, Regional Medical Center, Mission Viejo, California. SUBJECTS: We studied 10 patients with chronic lung disease and difficulty maintaining exercise S(pO2) with DODS. Nine patients had chronic obstructive pulmonary disease and one had restrictive lung disease. The group's (mean +/- SD) demographic and physiologic values included: age 67 +/- 7 y, forced expiratory volume in the first second 0.79 +/- 0.3 L, forced vital capacity 1.7 +/- 0.7 L, and S(pO2) 88%. INTERVENTIONS: Resting S(pO2) was measured during continuous oxygen flow and during DODS, at identical settings. S(pO2) was allowed to stabilize at each level before recording. During treadmill exercise at identical work loads we measured continuous flow and DODS S(pO2) at the same settings. If the DODS S(pO2) was less than during the equivalent continuous flow, the DODS setting was increased for another treadmill trial. RESULTS: At rest the DODS was equivalent to continuous flow: S(pO2) was 93.7 +/- 2.1% with DODS and 93.8 +/- 1.9% with continuous flow. During exercise at corresponding settings DODS S(pO2) was 90.5 +/- 3.8% and continuous-flow S(pO2) was 93.1 +/- 3.1%. Six subjects had S(pO2) > 90%, with 4 of them achieving equivalency. At higher DODS settings S(pO2) became equivalent: 92.5 +/- 2.8%. The DODS oxygen-use efficiency advantage was 6.7-fold at rest and 5.6-fold during exercise, except with subjects who required a higher exercise DODS setting, with whom the DODS advantage was 4.3-fold. CONCLUSIONS: The redesigned Oxymatic 401 DODS maintains adequate S(pO2) during rest and exercise, but some patients require the higher delivery settings. We recommend that all patients prescribed DODS undergo exercise evaluation with the prescribed DODS to ensure efficacy and determine the DODS settings required to maintain S(pO2) at the prescribed limits.