Reply to: Revisiting life history and morphological proxies for early mammaliaform metabolic rates

Non peer reviewe

Reptile-like physiology in Early Jurassic stem-mammals

Despite considerable advances in knowledge of the anatomy, ecology and evolution of early mammals, far less is known about their physiology. Evidence is contradictory concerning the timing and fossil groups in which mammalian endothermy arose. To determine the state of metabolic evolution in two of the earliest stem-mammals, the Early Jurassic Morganucodon and Kuehneotherium, we use separate proxies for basal and maximum metabolic rate. Here we report, using synchrotron X-ray tomographic imaging of incremental tooth cementum, that they had maximum lifespans considerably longer than comparably sized living mammals, but similar to those of reptiles, and so they likely had reptilian-level basal metabolic rates. Measurements of femoral nutrient foramina show Morganucodon had blood flow rates intermediate between living mammals and reptiles, suggesting maximum metabolic rates increased evolutionarily before basal metabolic rates. Stem mammals lacked the elevated endothermic metabolism of living mammals, highlighting the mosaic nature of mammalian physiological evolution. Modern mammals are endothermic, but it has not been clear when this type of metabolism evolved. Here, Newham et al. analyse tooth and bone structure in Early Jurassic stem-mammal fossils to estimate lifespan and blood flow rates, which inform about basal and maximum metabolic rates, respectively, and show these stem-mammals had metabolic rates closer to modern ectothermic reptiles than to endothermic mammals.Peer reviewe

Interpreting the Status of an Underground Coal Mine Heating for Valid Risk Management and Control

The status of an underground coal mine heating event is predominantly assessed based on gas sampling results from the affected area. The gas samples can be obtained in a number of different ways, but for accurate determination of the gases present analysis is normally performed using gas chromatography. Several gas indicators have been identified from past experiences that are used in combination to determine a Trigger Action Response Plan for individual mines. The upper levels of the Trigger Action Response Plan contain more urgent actions in response to the assessed level of advanced heating, with the ultimate level being withdrawal from the mine. Once this point is reached the only action that can be taken to control the event has to be done remotely and also, once activated it is difficult to re-enter the mine. Recent experience of a heating event provides new data that demonstrates the importance of understanding and interpreting the status of hot spot development to risk management and control applied by an Incident Management Team. This paper discusses the use of gas trending, including the development of: a new gas indicator ratio that is very sensitive to the heating status and control measures applied; and a hot spot tracking diagram that provides a good visual representation of the heating status and the response to actions taken

Quadriceps function, proprioceptive acuity and functional performance in healthy young, middle-aged and elderly subjects

BACKGROUND: Muscle functions to generate force-producing movement and also has a role in proprioception. If ageing compromises these sensorimotor functions of muscle, the ability of older subjects to detect and correct postural sway may be impeded, resulting in impairment of functional performance. METHOD: To see if age-related changes occurred and, if so, what their effects might be. Quadriceps strength, proprioception, postural stability and functional performance were assessed in young (n = 20, mean age 23 years), middle-aged (n = 10, mean age 56 years) and elderly (n = 15, mean age 72 years) subjects. RESULTS: With increasing age there were decreases in quadriceps strength (r = -0.511; P < 0.001), acuity of joint position sense (r = -0.603; P < 0.001) and postural stability (ANOVA < 0.002) during stance conditions which placed a greater reliance on muscle proprioceptors. These changes may decrease postural stability confidence, resulting in impaired performance of common activities of daily living (r = 0.635; P < 0.001). CONCLUSIONS: The age-related deterioration in sensorimotor function of muscle may contribute to the increased fear and frequency of falls in elderly subjects, thereby decreasing independence

Sensorimotor changes and functional performance in patients with knee osteoarthritis

OBJECTIVE: Muscles are essential components of our sensorimotor system that help maintain balance and perform a smooth gait, but it is unclear whether arthritic damage adversely affects muscle sensorimotor function. Quadriceps sensorimotor function in patients with knee osteoarthritis (OA) was investigated, and whether these changes were associated with impairment of functional performance. METHODS: Quadriceps strength, voluntary activation, and proprioceptive acuity (joint position sense acuity) were assessed in 103 patients with knee OA and compared with 25 healthy control subjects. In addition, their postural stability, objective functional performance (the aggregate time for four activities of daily living), and disabilities (lequesne index) were also investigated. RESULTS: Compared with the control subjects, the patients with knee OA had weaker quadriceps (differences between group mean 100N, CI 136, 63N), poorer voluntary activation (20% CI 13, 25%) that was associated with quadriceps weakness, and impaired acuity of knee joint position sense (1.28 degrees, CI 0.84, 1.73 degrees). As a group the patients were more unstable (p = 0.0017), disabled (10, CI 7, 11), and had poorer functional performance (19.6 seconds, CI 14.3, 24.9 seconds). The most important predictors of disability were objective functional performance and quadriceps strength. CONCLUSIONS: In patients with knee OA, articular damage may reduce quadriceps motoneurone excitability, which decreases voluntary quadriceps activation thus contributing to quadriceps weakness, and diminishes proprioceptive acuity. The arthrogenic impairment in quadriceps sensorimotor function and decreased postural stability was associated with reduced functional performance of the patients