Critical environmental limits for young, healthy adults (PSU HEAT)

Critical environmental limits are those combinations of ambient temperature and humidity above which heat balance cannot be maintained for a given metabolic heat production, limiting exposure time and placing individuals at increased risk of heat-related illness. The aim of the present study was to establish those limits in young (18-34 yr) healthy adults during low-intensity activity approximating the metabolic demand of activities of daily living. Twenty-five (12 men/13 women) subjects were exposed to progressive heat stress in an environmental chamber at two rates of metabolic heat production chosen to represent minimal activity (MinAct) or light ambulation (LightAmb). Progressive heat stress was performed with either (1) constant dry-bulb temperature (Tdb) and increasing ambient water vapor pressure (Pa) (Pcrit trials; 36, 38, or 40 °C), or (2) constant Pa and increasing Tdb (Tcrit trials; 12, 16, or 20 mmHg). Each subject was tested during MinAct and LightAmb in 2-3 experimental conditions in random order, for a total of 4-6 trials per participant. Higher metabolic heat production (p < 0.001) during LightAmb compared to MinAct trials resulted in significantly lower critical environmental limits across all Pcrit and Tcrit conditions (all p < 0.001). These data, presented graphically herein on a psychrometric chart, are the first to define critical environmental limits for young adults during activity resembling those of light household tasks or other activities of daily living, and can be used to develop guidelines, policy decisions, and evidence-based alert communications to minimize the deleterious impacts of extreme heat events.

Aerobic glycolysis in cancer cells supplies ATP while preventing excess metabolic thermogenesis

A general feature of cancer metabolism is ATP regeneration via substrate-level phosphorylation even under normoxic conditions (aerobic glycolysis). However, it is unclear why cancer cells prefer the inefficient aerobic glycolysis over the highly efficient process of oxidative phosphorylation for ATP regeneration. Here, we show that a beneficial aspect of aerobic glycolysis is that it reduces metabolic heat generation during ATP regeneration. 13C-metabolic flux analysis of 12 cultured cancer cell lines and in silico metabolic simulation revealed that metabolic heat production during ATP regeneration via aerobic glycolysis was considerably lesser than that produced via oxidative phosphorylation. The dependency on aerobic glycolysis was partly alleviated upon culturing under low temperatures. In conclusion, thermogenesis is required for maintaining thermal homeostasis and can govern aerobic glycolysis in cancer cells.

CONTROL OF INTRAOPERATIVE SHIVERING UNDER SPINAL ANAESTHESIA- A PROSPECTIVE RANDOMIZED COMPARATIVE STUDY OF NALBUPHINE WITH TRAMADOL

spinal anesthesia is a widely used technique for both elective and emergency surgeries. Shivering is one of the most commonly recognized complications of the central neuraxial blockade because of impairment of thermoregulatory control, reported in 40%-70% of the patients undergoing surgery under spinal anaesthesia. Post-anesthetic shivering is defined as an involuntary,spontaneous,rhythmic oscillating muscle hyperactivity that increases metabolic heat production up to 600% after anesthesia. Shivering during neuraxial anesthesia is a common issue that could have possibly adverse impacts, for example, increased oxygen consumption, carbon dioxide production, lung ventilation and cardiac work, as well as causing diminished mixed venous oxygen saturation. Spinal anesthesia impedes the thermoregulatory system by restraining tonic vasoconstriction which assumes significant role in the regulation of temperature

PSII-6 Electronically controlled cooling pads improve litter growth and thermoregulatory measures and increase total heat production in heat stressed lactating sows

Heat stress (HS) decreases lactation output in sows due to an attempt to reduce metabolic heat production; however, this negatively affects litter growth performance. Therefore, the study objective was to determine whether electronically controlled cooling pads (ECP) would improve indirect measures of lactation output (e.g., metabolic heat production) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg) and litters were assigned to either an ECP (n = 6) or a non-functional ECP (NECP; n = 6) and placed into farrowing crates within indirect calorimeters from d 3.7 ± 0.5 to d 18.7 ± 0.5 of lactation. Litters were standardized across all sows (11.4 ± 0.7 piglets/litter), and sows were provided ad libitum feed and water. All sows were exposed to cyclical HS (28.27 ± 1.42°C nighttime to 35.14 ± 0.70°C daytime). On d 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine total heat production (THP). Body temperature (TB), was measured hourly using vaginal implants, and respiration rate (RR) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Litter weights were obtained at birth and weaning. An overall decrease (P &lt; 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40°C) was observed in ECP versus NECP sows. An increase in THP (P &lt; 0.01; 20.4%) and THP/kg0.75 (P &lt; 0.01; 23.1%) was observed for ECP when compared to NECP sows and litters. Litter growth rate was increased (P &lt; 0.01; 20.8%) in ECP versus NECP sows. In summary, the use of ECP improves litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical heat stress.

Evaluation of the Accuracy and Safety of a Portable Metabolic Heat Conformation-Based Non-invasive Glucose Meter: A Multicentre Clinical Study. (Preprint)

BACKGROUND Non-invasive blood glucose measurement is expected to be an ideal way for glucose monitoring, although most of the methods are under study and yet to be verified in large-scale clinical trials. OBJECTIVE We intend to evaluate the stability, accuracy of the metabolic heat conformation (MHC)-based non-invasive glucometer in a multicentre, self-controlled clinical trial. This device obtained the first medical device registration certificate awarded by the National Medical Products Administration of China (NMPA). METHODS The clinical study was conducted at three sites on 200 subjects who received glucose measurement with a non-invasive glucometer, the Contour Plus blood glucose monitoring system, and venous plasma glucose (VPG) measurements, in a fasted state and at 2 and 4 hours after meals. Trial Registration: ChiCTR1900020523. RESULTS The non-invasive and VPG measurements showed 93.9% (95% CI, 91.7–95.6%) of the values in zone A + B in a Consensus Error Grid. The measurements obtained in a fasted state and at 2 hours after meals are more accurate, with 99.0% and 97.0% of the values in zone A + B, respectively. The proportion of values in zone A + B and the correlation coefficients in subjects who did not receive insulin were 3.1% and 0.0596 higher than in those who received insulin. The accuracy of the non-invasive glucometer was influenced by the level of islet cell function and insulin resistance, which had a correlation coefficient with the MARD of -0.0961 (p=0.020) and -0.1577 (p=0.00012), respectively. CONCLUSIONS The MHC-based non-invasive glucometer demonstrates generally high stability and accuracy in the glucose monitoring of diabetic patients. The calculation model needs to be further explored and optimised for patients with different diabetes subtypes, levels of insulin resistance and insulin secretion capacity. CLINICALTRIAL the name of the trial registry : A multi-center study for evaluating the accuracy and safety of noninvasive glucose meter in people with diabetes or impaired glucose regulation (impaired fasting glucose and impaired glucose tolerance), using an experimental test system as a reference. registration number : ChiCTR1900020523 URL : https://www.chictr.org.cn/showproj.aspx?proj=33857