Decrease In Heat Production Research Articles

The role of macrophage and adipocyte mitochondrial dysfunction in the pathogenesis of obesity.

Obesity has emerged as a prominent global public health concern, leading to the development of numerous metabolic disorders such as cardiovascular diseases, type-2 diabetes mellitus (T2DM), sleep apnea and several system diseases. It is widely recognized that obesity is characterized by a state of inflammation, with immune cells-particularly macrophages-playing a significant role in its pathogenesis through the production of inflammatory cytokines and activation of corresponding pathways. In addition to their immune functions, macrophages have also been implicated in lipogenesis. Additionally, the mitochondrial disorders existed in macrophages commonly, leading to decreased heat production. Meantime, adipocytes have mitochondrial dysfunction and damage which affect thermogenesis and insulin resistance. Therefore, enhancing our comprehension of the role of macrophages and mitochondrial dysfunction in both macrophages and adipose tissue will facilitate the identification of potential therapeutic targets for addressing this condition.

Performance of air source heat pump units with different wettability evaporators

The air source heat pumps (ASHPs) for winter heating have the advantages of high efficiency and environmental protection. However, the outside evaporator’s frosting negatively impacts the performance of heat pump systems in low-temperature and high-humidity environments. In this paper, we fabricated the superhydrophobic evaporator and mounted it on a commercial ASHP unit, expanding the use of superhydrophobic surface modification technology from heat exchangers in the laboratory to the ASHP units. Then we investigated the operating characteristics of two ASHP units equipped with hydrophilic and superhydrophobic evaporators respectively under six distinct outdoor and indoor environmental conditions experimentally. In the non-frosting conditions, film condensation formed on the surface of the hydrophilic evaporator and the evaporation temperature decreased with the formation of water film, resulting in a decrease in heat production and COP. In the frosting conditions, the time of forming the frost layers with the same thickness on the superhydrophobic surface was more than 4 times longer than that on the hydrophilic surface. The COP of the superhydrophobic evaporator unit was improved by 2.9% to 8.2% under the non-frosting conditions, by 11.5% under the continuous heating conditions and by 14.28% when the hydrophilic unit performed two defrosting cycles, respectively. During the period in which the hydrophilic evaporator unit completed two frosting/defrosting cycles, the energy loss coefficient caused by the defrosting process was 31.65% compared to the superhydrophobic evaporator unit. This work extended the experimental method of superhydrophobic heat exchanger, contributing to the application of superhydrophobic finned-tube evaporators in ASHP units.

The efficiency of dodecafluoro-2-methylpentan-3-one in suppressing NCM 811 lithium-ion battery fire

With the increase in the specific energy of lithium-ion batteries (LIBs), fire accidents occur more frequently; however, the effective and clean suppression of LIB fires remains a challenge. In the present work, the efficiency of dodecafluoro-2-methylpentan-3-one (C6F12O) in suppressing high energy density (HED) ternary LIB fires is experimentally investigated. It is found that C6F12O can efficiently extinguish the HED battery and its module fire. As the flow rate increases, the extinguishment time decreases and the peak temperature decreases, but the cooling efficiency for the long-term process is reduced. When the C6F12O spray can completely cover the thermal runaway (TR) area, its extinguishing and cooling effect is the best. For the HED module, the application of C6F12O effectively increases the TR trigger temperature, reduces the TR peak temperature, and decreases heat production. The application of water mist enhances the cooling of extinguished LIBs, the combination of C6F12O and water mist extends the TR propagation time of the fully charged LIB module to 1.4 times that without suppression, and the total TR heat production is reduced by 1423.1 kJ. These results provide guidance for the design of inhibitor volume fractions for HED LIB fires.

Patient-Derived 3D Models for Preclinical Drug Response Evaluation in Neuroblastoma

Abstract Background Neuroblastoma is the most common solid childhood tumor outside the central nervous system. Metastatic and relapsed disease in neuroblastoma patients still has a poor prognosis. New treatment methods to improve therapy and outcomes for patients with advanced neuroblastoma are urgently needed. However, clinical trials currently only allow for testing few substances in even fewer patients. This increases the need to improve and advance preclinical tumor models to preselect favorable candidates for novel therapeutics. Aims This study investigates the advantages and limitations of using bioreactor-based perfused 3D models in for preclinical drug testing in solid tumors exemplified in neuroblastoma. Methods We established perfused bioreactor-based 3D models using neuroblastoma cell lines and tissue slice-culture and evaluated cell viability. Several inhibitors against hypoxia-related factors, associated with tumor progression, were tested including Aqb011 against aquaporin 1 (AQP1) and SLC-0111 against carbonic-anhydrase IX (CAIX). Isothermal microcalorimetry was used for measuring real time thermogenesis in 3D cell and tissue constructs. Results 3D neuroblastoma cell constructs presented with similar morphological features compared to neuroblastoma cells in intact tumor tissue featuring small, round and blue cells. Perfused neuroblastoma slice-culture maintained its primary structure in the bioreactor for up to 10 days. Both 3D neuroblastoma cell constructs and neuroblastoma tissue responded to inhibition with significant decrease of thermogenesis measured by microcalorimetry, if the correlating hypoxic factor (AQP1 or CAXI) was expressed. The AQP1 inhibitor Aqb011 and the CAIX inhibitor SLC-0111 decrease heat production of 3D neuroblastoma cultures. Conclusions We newly establish two preclinical models for neuroblastoma cells and tissue in a 3D structure. Drug response monitoring can be applied in these models using isothermal microcalorimetry. Monitoring times can be increased by use of the perfused bioreactor. Our models are an important first step to preclinically evaluate new drugs using patient-derived tumor tissue exemplified for neuroblastoma.

Effects of natural-gas blending on ignition delay and pollutant emission of diesel fuel for the condition of homogenous charge compression ignition engine

• Effects of blending of natural gas (NG) with diesel fuel were investigated. • Major properties of diesel were measured at 40 bar and its surrogate fuel was formulated. • Blending of NG reduces pollutant emission with slight decrease in heat production. • Ignition timing is changed by NG blending, but, it is not significant. • The optimal mixture ratio of NG in the dual fuel is suggested in HCCI engines. Burning of dual fuel of diesel and natural gas is a promising technique in compression ignition engine in the aspects of fuel economy and reduced emission. Effects of blending of natural gas with diesel fuel are investigated numerically and experimentally with respect to ignition delay, heat production, and pollutant emission. First, major properties of diesel are measured at high pressure of 40 bar, which is an engine-relevant condition, and thereby, a surrogate fuel with higher accuracy is formulated, which has properties closer to diesel than the other existing surrogate fuels. Especially, as one of key properties, high molecular weight of diesel is considered critically in formulating a surrogate fuel. Ignition delay times of several mixtures of diesel and natural gas (NG), of which mixture ratios of 100/0%, 60/40%, and 20/80%, are measured by a shock tube in the ranges of temperature from 770 K to 1,000 K and of equivalence ratios from 0.5 to 2.0. Measured ignition delay is compared with that calculated by numerical simulations with the surrogate fuel formulated in this study for its validation. Finally, combustion simulations of HCCI (homogeneous charge compression ignition) are conducted with the mixture of diesel and NG and compared with available experimental data. And thereby, optimal mixture ratio of the dual fuel is suggested in terms of ignition time and pollutant emission acceptable in HCCI engines.

Modeling Subsurface Performance of a Geothermal Reservoir Using Machine Learning

Geothermal power plants typically show decreasing heat and power production rates over time. Mitigation strategies include optimizing the management of existing wells—increasing or decreasing the fluid flow rates across the wells—and drilling new wells at appropriate locations. The latter is expensive, time-consuming, and subject to many engineering constraints, but the former is a viable mechanism for periodic adjustment of the available fluid allocations. In this study, we describe a new approach combining reservoir modeling and machine learning to produce models that enable such a strategy. Our computational approach allows us, first, to translate sets of potential flow rates for the active wells into reservoir-wide estimates of produced energy, and second, to find optimal flow allocations among the studied sets. In our computational experiments, we utilize collections of simulations for a specific reservoir (which capture subsurface characterization and realize history matching) along with machine learning models that predict temperature and pressure timeseries for production wells. We evaluate this approach using an “open-source” reservoir we have constructed that captures many of the characteristics of Brady Hot Springs, a commercially operational geothermal field in Nevada, USA. Selected results from a reservoir model of Brady Hot Springs itself are presented to show successful application to an existing system. In both cases, energy predictions prove to be highly accurate: all observed prediction errors do not exceed 3.68% for temperatures and 4.75% for pressures. In a cumulative energy estimation, we observe prediction errors that are less than 4.04%. A typical reservoir simulation for Brady Hot Springs completes in approximately 4 h, whereas our machine learning models yield accurate 20-year predictions for temperatures, pressures, and produced energy in 0.9 s. This paper aims to demonstrate how the models and techniques from our study can be applied to achieve rapid exploration of controlled parameters and optimization of other geothermal reservoirs.

PSXII-19 Organ and cellular contributions to heat production in Brahman and Angus steers

Abstract Reductions in basal metabolism and growth rate appear to contribute to decreased heat production of Bos indicus breeds. Lower metabolic rate may be due to smaller organ size and lower metabolic activity. Liver and heart account for high percentage of metabolic activity relative to their weight, and at a cellular level, mitochondria are responsible for producing energy for cellular maintenance. Our objective was to determine liver and heart weight and evaluate expression of key mitochondrial proteins in Bos indicus (80–100% Brahman) and Bos taurus (80–100% Angus) steers. Steers (n = 14 per breed) were harvested at the university meat laboratory. After evisceration, livers and hearts were weighed, and samples were frozen in liquid nitrogen for further analyses. Western blotting was used to determine expression of proteins in mitochondrial energy production: citrate synthase, a marker of mitochondria content; succinate dehydrogenase B (SDH-B), complex II; cytochrome c oxidase subunit IV, complex IV; and ATP synthase subunit 5A (ATP5A), complex V. Data were analyzed using an unpaired t-test in SAS-JMP. Although steers were similar age at slaughter (P = 0.84), Brahman steers weighed less (P < 0.0001) and thus produced lighter carcasses (P < 0.0001) and smaller livers and hearts (P < 0.0001). On a relative basis (kg organ/kg BW), Brahman tended to possess smaller hearts (P = 0.06) and smaller livers (P = 0.03). Expression of mitochondria proteins in heart did not differ between breeds (P > 0.3). However, Brahman exhibited lower expression of SDH-B (P = 0.005) but tended to have higher expression of ATP5A (P = 0.07) in liver. Altogether, this supports that smaller organ size is a contributing factor to lower heat production in heat-tolerant Brahman steers, and shifts in mitochondria protein expression in liver may impact energy metabolism at the cellular level.

Dietary Iron Deficiency Modulates Adipocyte Iron Homeostasis, Adaptive Thermogenesis, and Obesity in C57BL/6 Mice

BackgroundAdaptive thermogenesis is an iron-demanding pathway, significantly contributing to whole-body energy expenditure. However, the effects of iron-deficient diets on adaptive thermogenesis and obesity remain unknown. ObjectivesWe aimed to determine the impact of dietary iron deficiency on iron homeostasis in adipocytes, adaptive thermogenic capacity, and metabolic consequences in obesity. MethodsC57BL/6 male mice were assigned to either the iron-adequate (IA, 35 ppm) or the iron-deficient group (ID, 3 ppm) at weaning. Upon 8 wk of age, both IA and ID groups received an isocaloric high-fat diet (45% kcal from fat) for 10 wk, maintaining the same iron content. Mice (n = 8) were used to determine the iron status at the systemic and tissue levels and lipid metabolism and inflammatory signaling in adipose tissue. The same mice were used to evaluate cold tolerance (4°C) for 3 h. For assessing adaptive thermogenesis, mice (n = 5) received an intraperitoneal injection of β3-adrenoceptor agonist CL316243 (CL) for 5 d. ResultsCompared with the IA group, the ID group had nonanemic iron deficiency, lower serum ferritin (42.8%, P < 0.01), and greater weight gain (8.67%, P < 0.05) and insulin resistance (159%, P < 0.01), partly due to reduced AMP-activated protein kinase activation (61.0%, P < 0.05). Upon cold exposure, the ID group maintained a core body temperature 2°C lower than the IA group. The ID group had lower iron content (47.0%, P < 0.01) in the inguinal adipose tissue (iWAT) than the IA group, which was associated with impaired adaptive thermogenesis. In response to CL, ID mice showed decreased heat production (P < 0.01) and defective upregulation of beige adipocyte-specific markers, including uncoupling protein 1 (41.1%, P < 0.001), transferrin receptor 1 (47.5%, P < 0.001), and mitochondrial respiratory chain complexes (P < 0.05) compared with IA mice. ConclusionsDietary iron deficiency deregulates iron balance in the iWAT and impairs adaptive thermogenesis, thereby escalating the diet-induced weight gain in C57BL/6 mice.

Partial submergence: An undescribed behavioral adjustment for thermoregulation at high ambient temperature in Aeshnidae

Many insects including odonates thermoregulate using a combination of behavioral and physiological mechanisms. At high ambient temperature (Ta), these mechanisms include decreased heat production and increased heat loss. Heat production can be reduced by decreasing activity. Heat loss can be enhanced by perching in a shaded microhabitat where temperature is cooler than in the surrounding environment. Aeshnids, which are intermittent endotherms, increase heat loss at high Ta; also by increasing hemolymph circulation from the thorax, where most metabolic heat is produced, to the abdomen, where it dissipates to the environment by convection. While studying two aeshnid species (Anax junius and Rhionaeschna multicolor) at a Sonoran Desert (Arizona, USA) stream, I observed partially submerged mature individuals of both sexes of these species. This heretofore undescribed behavior was seen only at Ta; ≥ 43 °C and almost exclusively during the hottest part of the day (15:00–17:00 hr), when the daily difference between Ta; and water temperature (Tw) was, on average, largest. A cooling effect of partial submergence behavior on body temperature would, therefore, presumably be most effective also during this period. Several percher species of libellulids were present at the study site. These dragonflies are not known to use endothermy for thermoregulation or to increase hemolymph circulation to the abdomen to dissipate heat at high Ta;, and none was ever observed to partially submerge. It is suggested in aeshnids that partial submergence at high Ta; serves a thermoregulatory function by facilitating body heat dissipation from the abdomen.

Serum proteomics analysis reveals the thermal fitness of crossbred dairy buffalo to chronic heat stress.

Chronic heat stress (CHS) reduces the production efficiency of the buffalo dairy industry. Relatively low-abundance proteins with particular functions in biological processes are changed by CHS. The present study aimed to quantify the differences in low-abundance proteins of crossbred dairy buffaloes under CHS and thermal-neutral (TN) conditions. With label-free quantification, 344 low-abundance proteins were identified in serum. Of these, 17 differentially expressed low-abundance proteins with known functions were detected, and six of the differentially expressed proteins related to heat stress were validated with parallel reaction monitoring. Lipase (LPL), glutathione peroxidase 3 (GPX3), cathelicidin-2 (CATHL2), ceruloplasmin (CP), and hemoglobin subunit alpha 1 (HBA1) cooperatively played roles in the thermal fitness of dairy buffalo by decreasing heat production and increasing blood oxygen delivery. Also, dairy buffaloes may adapt to CHS and hypoxia with high levels of RBCs, HBA1 and CP to increase blood oxygen delivery capacity.

Holmium:Yttrium-Aluminum-Garnet Laser Pulse Type Affects Irrigation Temperatures in a Benchtop Ureteral Model.

Introduction: MOSES™ technology is a holmium:yttrium-aluminum-garnet laser pulse mode shown to minimize stone retropulsion. This may facilitate lithotripsy at higher power settings. However, power and heat production are proportional, and temperatures capable of tissue injury may occur during ureteroscopic lithotripsy. Although previous in vitro studies demonstrate the importance of irrigation and activation time on heat production, the impact of pulse type has not been evaluated. Methods: A flexible ureteroscope with a 365 μm laser fiber was placed in an 11/13 F access sheath inserted into a 50 mL saline bag to simulate a ureter, renal pelvis, and antegrade irrigant flow. A thermocouple was placed adjacent to the laser tip, and the laser fired for 30 seconds at 0.6 J/6 Hz, 0.8 J/8 Hz, 1 J/10 Hz, 1 J/20 Hz, and 0.2 J/70 Hz at irrigation pressure of 100 mmHg. Four runs were tested per setting using short pulse, long pulse (LP), MOSES-contact (MC), and MOSES-distance (MD) modes. The mean temperature changes (dT) were compared and thermal dose was calculated in cumulative equivalent minutes at 43°C (CEM43) using an adjusted baseline of 37°C. CEM43 ≥ 120 minutes was considered the tissue injury threshold. Results: At 0.8 J/8 Hz, LP produced the greatest dT, significantly higher than MC (p = 0.041). CEM43 did not exceed the injury threshold. At 1 J/10 Hz, dT was significantly higher for LP versus MC and MD (p = 0.024 and 0.045, respectively). Thermal dose remained below the injury threshold. No differences in dT were seen between pulse types at 0.6 J/6 Hz, 0.2 J/70 Hz, or 1 J/20 Hz. At 1 J/20 Hz, thermal dose exceeded the injury threshold for all pulse types within 3 seconds. Conclusions: Laser pulse type and length seemed to impact heat production in our ureteral model. LP produced significantly greater temperatures at 0.8 J/8 Hz and 1 J/10 Hz relative to MOSES settings. Fortunately, thermal dose remained safe at these settings. Both LP and MOSES technology have been shown to reduce stone retropulsion. At power ≤10 W, the latter may confer this advantage with decreased heat production.

The glycoprotein follistatin-like 1 promotes brown adipose thermogenesis

ObjectivesThe thermogenic brown adipose tissue (BAT) has been proposed as a potential target to prevent or treat obesity and related metabolic diseases. BAT secretes adipokines to regulate the thermogenic program in an autocrine or paracrine manner. Follistatin-like 1 (FSTL1), a glycoprotein involved in adipogenesis and obesity, however, the function of FSTL1 in BAT thermogenesis and in the regulation of systemic energy homeostasis are not fully understood. MethodsWhole-body ablation Fstl1 heterozygous mice (Fstl1+/−) and its littermates control were injected with CL316,243 to assess energy balance. A series of FSTL1 overexpression and knockdown experiments were carried out to evaluate its function in regulating thermogenic gene expression in brown adipocytes. ResultsFSTL1 expression was induced upon BAT activation during cold challenge or β3-adrenergic activation. FSTL1 haploinsufficiency in mice led to reduced thermogenic gene expression, impaired BAT recruitment, and decreased heat production. FSTL1 cell-autonomously promoted the β3-adrenergic signaling, which was required to upregulate PPARγ and UCP1 in brown adipocytes. Furthermore, only glycosylated FSTL1 could be secreted from brown adipocytes to induce the β3-adrenergic activation. ConclusionsOur results suggest FSTL1 as a novel stimulator of the β-adrenergic signaling and BAT thermogenesis.

Dopaminergic Projections to Raphe Pallidus Inhibit Brown Adipose Tissue Thermogenesis

BackgroundThe observations that patients with Parkinson's disease experience weight loss, while dopamine (DA) replacement therapy causes body weight gain, suggest that suppressing the DA system could stimulate energy expenditure. Peripheral administration of dopaminergic drugs decreases heat production by inhibition of brown adipose tissue (BAT) thermogenesis and by an increase in the threshold for muscular shivering. However, the exact neuroregulatory site through which DA modulates the activity of thermogenic thermoeffectors remains undefined.ResultsIn urethane/chloralose‐anesthetized, artificially‐ventilated rats, activation of type 2 or 3 dopamine receptors in the rostral raphe pallidus (rRPa) inhibits cold‐evoked BAT sympathetic activity, reduced BAT temperature and expired CO2, and produced hypotension and bradycardia. Anatomic evidence shows the co‐localization of TH and CTb immunoreactivities in neurons in the in the periventricular gray zona following injection of the retrograde tracer in the rRPa. These data indicate that this dopaminergic cell group projects to rRPa and is the likely source of the dopaminergic inhibition of BAT sympathetic activity.ConclusionOur data provide the first evidence that a DA input to the rRPa from periventricular gray zona modulates BAT thermogenesis and cardiovascular function. Modulating the dopaminergic input to rRPa could provide a novel therapeutic approach to promote fat oxidation, favor better glycaemic control, and accelerate weight loss.Support or Funding InformationNIH R01‐NS091066This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Genome-wide association of changes in swine feeding behaviour due to heat stress

BackgroundHeat stress has a negative impact on pork production, particularly during the grow-finish phase. As temperature increases, feeding behaviour changes in order for pigs to decrease heat production. The objective of this study was to identify genetic markers associated with changes in feeding behaviour due to heat stress. Feeding data were collected on 1154 grow-finish pigs using an electronic feeding system from July 2011 to March 2016. In this study, days were classified based on the maximum temperature humidity index (THI) during the day as “Normal” (< 23.33 °C), “Alert” (23.33 °C ≤ × < 26.11 °C), “Danger” (26.11 °C ≤ × < 28.88 °C), and “Emergency” (≥ 28.88 °C). Six hundred and eighty-one pigs that experienced more than one THI category were genotyped using a variety of SNP platforms, with final genotypes imputed to approximately 60,000 markers.ResultsA genome-wide association study (GWAS) for change in feeding behaviour between each pair of THI categories (six pairs) was conducted. Estimates of heritability for differences in feeding activity between each of the THI categories were low (0.02 ± 0.03) to moderate (0.21 ± 0.04). Sixty-six associations which explained more than 1% of the genomic variation for a trait were detected across the six GWAS, with the smallest number of associations detected in comparisons with Emergency THI. Gene ontology enrichment analysis showed that biological processes related to immune response and function were over-represented among the genes located in these regions.ConclusionsGenetic differences exist for changes in feeding behaviour induced by elevated ambient temperatures in grow-finish pigs. Selection for heat-tolerant grow-finish pigs should improve production efficiency during warm months in commercial production. Genetic variation in heat shock, stress response and immune function genes may be responsible for the observed differences in performance during heat stress events.

Numerical investigation of the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir: a case study of the Daming geothermal field in China.

The utilization of geothermal energy is clean and has great potential worldwide, and it is important to utilize geothermal energy in a sustainable manner. Mathematical modeling studies of geothermal reservoirs are important as they evaluate and quantify the complex multi-physical effects in geothermal reservoirs. However, previous modeling efforts lack the study focusing on the emission reduction efficiency and the deformation at geothermal wellbores caused by geothermal water extraction/circulation. Emission efficiency is rather relevant in geothermal projects introduced in areas characterized by elevated air pollution where the utilization of geothermal energy is as an alternative to burning fossil fuels. Deformation at geothermal wellbores is also relevant as significant deformation caused by water extraction can lead to geothermal wellbore instability and can consequently decrease the effectiveness of the heat extraction process in geothermal wells. In this study, the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir in Daming County, China, are numerically investigated based on a coupled multi-physical model. Relationships between the efficiency of emission reduction and heat extraction, deformation at geothermal well locations, and geothermal field parameters including well spacing, heat production rate, re-injection temperature, rock stiffness, and geothermal well placement patterns are analyzed. Results show that, although large heat production rates and low re-injection temperatures can lead to decreased heat production in the last 8years of heat extraction, they still improve the overall heat production capacity and emission reduction capacity. Also, the emission reduction capacity is positively correlated with the heat production capacity. Deformation at geothermal wellbore locations is alleviated by smaller well spacing, lower heat production rates, and smaller numbers of injectors in the well pattern, and by placing wells at locations with higher rock stiffness. Compared with the reference case with coal burning for heating purposes, the yearly emission reduction capacity can reach 1 × 107kg by switching to the direct utilization of geothermal energy in Daming field.

On the radiogenic heat production of metamorphic, igneous, and sedimentary rocks

Sedimentary rocks cover ∼73% of the Earth's surface and metamorphic rocks account for approximately 91% of the crust by volume. Understanding the average behavior and variability of heat production for these rock types are vitally important for developing accurate models of lithospheric temperature. We analyze the heat production of ∼204,000 whole rock geochemical data to quantify how heat production of these rocks varies with respect to chemistry and their evolution during metamorphism. The heat production of metaigneous and metasedimentary rocks are similar to their respective protoliths. Igneous and metaigneous samples increase in heat production with increasing SiO2 and K2O, but decrease with increasing FeO, MgO and CaO. Sedimentary and metasedimentary rocks increase in heat production with increasing Al2O3, FeO, TiO2, and K2O but decrease with increasing CaO. For both igneous and sedimentary rocks, the heat production variations are largely correlated with processes that affect K2O concentration and covary with other major oxides as a consequence. Among sedimentary rocks, aluminous shales are the highest heat producing (2.9 μW m−3) whereas more common iron shales are lower heat producing (1.7 μW m−3). Pure quartzites and carbonates are the lowest heat producing sedimentary rocks. Globally, there is little definitive evidence for a decrease in heat production with increasing metamorphic grade. However, there remains the need for high resolution studies of heat production variations within individual protoliths that vary in metamorphic grade. These results improve estimates of heat production and natural variability of rocks that will allow for more accurate temperature models of the lithosphere.

Generation of Persister Cells of Pseudomonas aeruginosa and Staphylococcus aureus by Chemical Treatment and Evaluation of Their Susceptibility to Membrane-Targeting Agents.

Persister cells (PCs) are a subset of dormant, phenotypic variants of regular bacteria, highly tolerant to antibiotics. Generation of PCs in vivo may account for the recalcitrance of most chronic infections to antimicrobial treatment and demands for the identification of new antimicrobial agents able to target such cells. The present study explored the possibility to obtain in vitro PCs of Pseudomonas aeruginosa and Staphylococcus aureus at high efficiency through chemical treatment, and to test their susceptibility to structurally different antimicrobial peptides (AMPs) and two clinically used peptide-based antibiotics, colistin and daptomycin. The main mechanism of action of these molecules (i.e., membrane-perturbing activity) renders them potential candidates to act against dormant cells. Exposure of stationary-phase cultures to optimized concentrations of the uncoupling agent cyanide m-chlorophenylhydrazone (CCCP) was able to generate at high efficiency PCs exhibiting an antibiotic-tolerant phenotype toward different classes of antibiotics. The metabolic profile of CCCP-treated bacteria was investigated by monitoring bacterial heat production through isothermal microcalorimetry and by evaluating oxidoreductase activity by flow cytometry. CCCP-pretreated bacteria of both bacterial species underwent a substantial decrease in heat production and oxidoreductase activity, as compared to the untreated controls. After CCCP removal, induced persisters showed a delay in heat production that correlated with a lag phase before resumption of normal growth. The metabolic reactivation of bacteria coincided with their reversion to an antibiotic-sensitive phenotype. Interestingly, PCs generated by CCCP treatment resulted highly sensitive to three different membrane-targeting AMPs at levels comparable to those of CCCP-untreated bacteria. Colistin was also highly active against PCs of P. aeruginosa, while daptomycin killed PCs of S. aureus only at concentrations 32 to 64-fold higher than those of the tested AMPs. In conclusion, CCCP treatment was demonstrated to be a suitable method to generate in vitro PCs of medically important bacterial species at high efficiency. Importantly, unlike conventional antibiotics, structurally different AMPs were able to eradicate PCs suggesting that such molecules might represent valid templates for the development of new antimicrobials active against persisters.

Hypothermia induced by inhibition of fatty acid metabolism in anesthetized rats: contributions of the forebrain and vagal afferents.

2-Mercaptoacetate (MA) is an antimetabolic drug that inhibits the utilization of fatty acids as an energy source. The intravenous injection of MA (1.2 mmol·kg-1) elicited an increase in tail skin temperature and a decrease in body core temperature in urethane-chloralose-anesthetized, neuromuscularly blocked, artificially ventilated rats, although administration of the same amount of NaCl did not. The respiratory exchange ratio was significantly higher after administration of MA than that after the saline treatment. On the other hand, heat production was increased by either the MA- or NaCl-injection, suggesting a nonspecific effect caused by the hyperosmolality of the solutions. These results indicate that the MA-induced hypothermia was caused by an increase in heat loss but not by a decrease in heat production. The amplitudes of heat loss responses to MA in rats fasted overnight were significantly smaller than those in fed ones, suggesting a mechanism for suppression of heat loss in the fasted state. Rats pretreated with vagotomy, capsaicin-induced desensitization of sensory nerve fibers or decerebration did not exhibit the MA-induced hypothermic responses. It is possible that the MA-induced heat loss and hypothermia were mediated by the vagal afferents and required the forebrain for the full expression of the responses.

Core Body Temperature Changes During Surgery and Nursing Management

The fact that surgical procedures and anaesthesia implementation affect thermoregulation, decrease heat production and increase heat loss cause hypothermia in the individual. This situation may create serious physiological problems both during and after the operation especially in risky patients. Surgical operation is a process threatening that body temperature of individual are maintained within required ranges due to the environment it is performed and requiring anesthesia application. Both general and local anesthesia’s suppress afferent and efferent control of thermoregulation. Additionally, surgery environment and exposure to surgical operation generally cause heat loss. Heat loss is a common during surgery. This is because the surgical environment transfers heat from the patient. Anesthesia decreases both heat production and thermoregulation capabilities of patients. Anesthesia also hardens the monitorization of body temperature. Hypothermia may cause complications such as fever, trembling, coldness and paleness in the skin, absent-mindedness, slowing in the metabolic speed, slowing in mental functions, bradycardia and rhythm disturbances, respiration slowing, coma and death. It is important for nurses to appreciate the physiological effects of hypothermia, which can cause complications in surgical patients in these settings. Furthermore accurate and careful monitoring of haemodynamic parameters. In this process the nurse may help maintain the individual’s body temperature by taking protective precautions through various methods before, during and after the operation and especially may protect the patient from various complications that may occur as a result of hypothermia.

2-Deoxy-D-glucose-induced hypothermia in anesthetized rats: Lack of forebrain contribution and critical involvement of the rostral raphe/parapyramidal regions of the medulla oblongata.

Systemic or central administration of 2-deoxy-d-glucose (2DG), a competitive inhibitor of glucose utilization, induces hypothermia in awake animals and humans. This response is mediated by the central nervous system, though the neural mechanism involved is largely unknown. In this study, I examined possible involvement of the forebrain, which contains the hypothalamic thermoregulatory center, and the medullary rostral raphe/parapyramidal regions (rRPa/PPy), which mediate hypoxia-induced heat-loss responses, in 2DG-induced hypothermia in urethane-chloralose-anesthetized, neuromuscularly blocked, artificially ventilated rats. The intravenous injection of 2DG (250mgkg(-1)) elicited an increase in tail skin temperature and decreases in body core temperature and the respiratory exchange ratio, though it did not induce any significant change in the metabolic rate. These results indicate that the hypothermic response was caused by an increase in heat loss, but not by a decrease in heat production and that it was accompanied by a decrease in carbohydrate utilization and/or an increase in lipid utilization as energy substrates. Complete surgical transection of the brainstem between the hypothalamus and the midbrain had no effect on the 2DG-induced hypothermic responses, suggesting that the hindbrain, but not the forebrain, was sufficient for the responses. However, pretreatment of the rRPa/PPy with the GABAA receptor blocker bicuculline methiodide, but not with vehicle saline, greatly attenuated the 2DG-induced responses, suggesting that the 2DG-induced hypothermia was mediated, at least in part, by GABAergic neurons in the hindbrain and activation of GABAA receptors on cutaneous sympathetic premotor neurons in the rRPa/PPy.