Measurement Of Oxygen Consumption Research Articles

Measured Oxygen Consumption During Pediatric Cardiac Catheterization is More Accurate than Assumed Oxygen Consumption.

When calculating cardiac index (C.I.) by the Fick method, oxygen consumption (VO2) is often unknown, so assumed values are typically used. This practiceintroduces a knownsource of inaccuracy into the calculation. Using a measured VO2 (mVO2) from the CARESCAPE E-sCAiOVX module provides an alternative that may improve accuracy of C.I. calculations. Our aim is to validate this measurement in a general pediatric catheterization population and compare its accuracywith assumed VO2 (aVO2).mVO2 was recorded for all patients undergoing cardiac catheterization with general anesthesia and controlled ventilation during the study period. mVO2 was compared to the reference VO2 (refVO2) determined by the reverse Fick method using cardiac MRI (cMRI) or thermodilution (TD) as a reference standard for measurement of C.I. when available. 193 VO2 measurements were obtained, including 71 with a corresponding cMRI or TD measure of cardiac index for validation. mVO2 demonstrated satisfactory concordance and correlation with the TD- or cMRI-derived refVO2 (ρc = 0.73, r2 = 0.63) with a mean bias of -3.2% (SD ± 17.3%). Assumed VO2 demonstrated much weaker concordance and correlation with refVO2 (ρc = 0.28, r2 = 0.31) with a mean bias of + 27.5% (SD ± 30.0%). Subgroup analysis of patients < 36months of age demonstrated that error in mVO2 was not significantly different from that observed in older patients. Many previously reported prediction models for assuming VO2 performed poorly in this younger age range. Measured oxygen consumption using the E-sCAiOVX module is significantly more accurate than assumed VO2 when compared to TD- or cMRI-derived VO2 in a pediatric catheterization lab.

Interest of ergospirometry in the management of thoracic oncology surgery

Abstract Funding Acknowledgements Type of funding sources: None. Background A cardiopulmonary exercise testing (CPET) is recommended before a resection of a primary pulmonary nodule by surgical approach for patients at risk (with abnormal spirometry). The maximal oxygen consumption measurement (VO2max) evaluates the morbidity/mortality and allows to orient the surgical choice towards a lobectomy or a cuneiform resection. However, the VO2 max can be influenced by some parameters as patient’s motivation, overweight, …. Purpose The objective of this work is therefore to identify other complementary predictive factors of cardiopulmonary exercise test (CPET) in at-risk patients population with abnormal pulmonary function tests. Methods 211 subjects who underwent thoracic surgery for non-small cell lung cancer (NSCLC) between 2016 and 2020 at Erasmus Hospital and performed a CPET were analyzed and divided into 2 groups (G1 At Risk: n = 159: 10 mL/min/kg &amp;lt; VO2max &amp;lt; 20 mL/min/kg; G2 Control: n = 52: VO2max ≥ 20 mL/min/kg). Anthropological, biometric, clinical, and intraoperative data were collected based on the medical record. Results The risk group (G1) had a reduced VO2max associated with a higher VE/VCO2 slope. However, the 30-day and 1-year mortality as well as the number of minor and major complications were comparable to the control group (G2) because of the screening and the operative choices. All groups combined, VO2max was predictive of major complications (OR = 0.98, p = 0.04) and VE/VCO2 slope emerged as a predictor of total and minor postoperative complications (OR = 1.07, p = 0.0054 and respectively OR = 1.05, p = 0.046). Patients with a slope ≥ 34.5 had a higher incidence of total complications (OR = 3.16, p = 0.0004). In a subgroup with medium operative risk (VO2max between 15 and 20 mL/min/kg), VE/VCO2 slope was predictive of total complications (OR = 1.09, p = 0.02) whereas VO2max was predictive of major complications (OR = 0.97, p = 0.04).

C47 ADAPTATION OF THE PULMONARY CIRCULATION AND OF THE RIGHT HEART IN INTRACARDIAC INVETERATE SHUNTS: UNDER PRESSURE OR LET IT FLOW?

Abstract Congenital heart disease can be associated with pulmonary hypertension (PH) development and heart right remodelling. Nevertheless, the adaptation of the pulmonary circulation and of the right heart can be extremely heterogeneous, so that an accurate diagnostic work up may be advisable when an intracardiac shunt is suspected. Case Presentation A 53 years old woman, with no relevant clinical history and asymptomatic, was incidentally found to have clinical, ECG and echocardiographic signs of PH, and was referred to our Center. Diagnostic and Therapeutic Work Up Echocardiography showed: normal left ventricle (LV 3D volumes 88/35 ml), mild left atrial dilatation (39 ml/m2); severe right chambers dilatation (RV 3D 347/124 ml, EF 3D 62%, AD 116 ml/m2), moderate tricuspid regurgitation with a regurgitant jet velocity of 2.9 m/s. Right heart catheterization showed normal pulmonary pressures at rest (mPAP 20, PAWP 5 mmHg), extremely high pulmonary blood flow (Qp 29 L/min, calculated with the direct Fick method), with normal pulmonary vascular resistance (PVR 0.5 WU). During the oxymetric run, a step up in hemoglobin saturation between superior vena cava and right atrium (from 74 to 97%) was found, with a Qp/Qs ratio of 5.5. During exercise, Qp reserve was normal, suggesting a normal contractile reserve function of RV despite the extreme dilatation. Additionally, the patient did not develop exercise PH and exercise capacity was normal, based on a measured oxygen consumption (VO2) at peak of 24 ml/kg/min (104% of predicted). Angio–CT of the chest was performed, confirming the presence of a sinus venosus atrial septal defect. The patient was then referred for surgical correction. Conclusion Echocardiography signs are useful to direct correctly diagnostic work up. A severe RV dilatation with normal systolic function in an asymptomatic middle age woman should raise the possibility of an intracardiac shunt. Despite a large intracardiac shunt with a high Qp/Qs ratio for decades, PVR was normal, confirming that individual predisposition may play a role in the development of PH in pre–tricuspid shunts. Exercise test showed an optimal RV reserve, suggesting a low cardiac surgery risk.

Sediment oxygen consumption in Antarctic subglacial environments

AbstractOxygen consumption in aquatic sediments is an indicator of overall biological activity of the ecosystem. As such, rates of sedimentary oxygen utilization are well documented for much of the open oceans and freshwater lakes. However, there are few direct measurements of sedimentary oxygen consumption from Antarctic subglacial aquatic sediments. We report the first microsensor oxygen profiles and derived sedimentary oxygen consumption rates from beneath the Ross Ice Shelf and a subglacial lake beneath the West Antarctic Ice Sheet. Rates of oxygen consumption in these two environments are relatively low, but comparable to those reported from ice‐free polar oceans and oligotrophic Arctic lakes. Our study demonstrates the presence of oxygen within Antarctic subglacial aquatic sediments and its importance for oxygen‐consuming microorganisms living in these ecosystems.

Ru(II) Oxygen Sensors for Co(III) Complexes and Amphotericin B Antifungal Activity Detection by Phosphorescence Optical Respirometry.

The measurement of oxygen consumption is an important element in the understanding of an organism's metabolic state. Oxygen is also a phosphorescence quencher, which allows the evaluation of phosphorescence emitted by oxygen sensors. Two Ru(II)-based oxygen-sensitive sensors were used to study the effect of chemical compounds [(1) = [CoCl2(dap)2]Cl, and (2) = [CoCl2(en)2]Cl (AmB = amphotericin B) against reference and clinical strains of Candida albicans. The tris-[(4,7-diphenyl-1,10-phenanthroline)ruthenium(II)] chloride ([Ru(DPP)3]Cl2) (Box) adsorbed onto the DavisilTM silica gel was embedded in the silicone rubber Lactite NuvaSil® 5091 and the coating on the bottom of 96-well plates. The water-soluble oxygen sensor (BsOx = tris-[(4,7-diphenyl-1,10-phenanthrolinedisulphonic acid disodium)ruthenium(II)] chloride 'x' hydrate = {Ru[DPP(SO3Na)2]3}Cl2 = water molecules were omitted in the BsOx formula) was synthesized and characterized by RP-UHPLC, LCMS, MALDI, elemental analysis, ATR, UV-Vis, 1H NMR, and TG/IR techniques. The microbiological studies were performed in the environment of RPMI broth and blood serum. Both Ru(II)-based sensors turned out to be useful in the study of the activity of Co(III) complexes and the commercial antifungal drug amphotericin B. In addition, a new activity of the oxygen sensor, the soluble Ru(II) complex BsOx, was demonstrated, which is a mixture with amphotericin B that caused a significant increase in its antifungal activity. Thus, it is also possible to demonstrate the synergistic effect of compounds active against the microorganisms under study.

Investigating respiratory simplification caused by prenatal RAGE upregulation

Receptors for advanced glycation end-products (RAGE) are multi-ligand cell surface receptors of the immunoglobulin superfamily predominantly expressed by lung epithelium. Previous experiments showed that RAGE upregulation throughout pregnancy caused significant fetal lung hypoplasia via elevated apoptosis and misregulation of the transcription factors thyroid transcription factor 1 (TTF1) and forkhead box protein A2 (Fox-A2). Our current research focused on characterizing the contributors to these abnormalities. We confirmed poor development of murine lungs through a time course of RAGE upregulation from conception to sacrifice on embryonic day (E)15.5, E16.5, E17.5, E18.5, and specific upregulation from E15.5 to E18.5 only. H&amp;E staining confirmed significant simplification. We hypothesized that this malformation was in part due to aberrant levels of inflammation and apoptosis. Blotting revealed significantly increased levels of phosphorylated AKT and ERK1/2 in RAGE TG pups which cause NF-κB mediated transcription of inflammatory genes. Due to potential roles for these signaling intermediates, we sought to assess RAGE-mediated impact on mitochondrial efficiency. Oxidative phosphorylation was assessed in lungs from RAGE TG pups and controls by measuring oxygen consumption per unit mass when lungs were exposed to the substrates malate, glutamate, ADP, succinate, and FCCP which activate sequential components of the electron transport chain. We discovered significantly increased levels of oxidative phosphorylation in transgenic pups compared to controls. Levels of ATP and reactive oxidative species (ROS) in relation to altered oxidative phosphorylation and inflammation provided additional mechanistic clarity. These results support the importance of proper RAGE regulation in the development of lung tissue and elucidate mechanisms possibly causing such damage. This work was supported by funding from the National Institutes of Health (NIH 1R15-HL152257, PRR and JAA). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

IFNγ Augments the Oxygen Consumption Rate and Metabolism in Monocytes Partially Through P2X7

BackgroundInterferon-gamma (IFNγ) is a pleiotropic cytokine crucial for immune responses to intracellular pathogens. IFNγ causes transcriptional changes that lead to increased production of reactive oxygen species (ROS) which promote microbial killing. IFNγ increases the oxygen consumption rate (OCR), ROS production, as well as NAD salvage, all through transcription regulation by STAT1. The ATP-gated, purinergic pore P2X7 has been identified as an ion channel that allows for the influx of Ca2+ and Na+ and the efflux of K+, as well as playing a role in the processing and release of proinflammatory cytokines in macrophages. P2X7 appears to play a role in IFNγ-induced metabolic reprogramming in monocytes as well as the increase in ROS production. MethodsWe used a Seahorse Extracellular Flux analyzer to measure oxygen consumption (as an indicator of ROS production), medium acidification, and kinetics in human monocytes in response to IFNγ or inhibitors before and after PMA activation. We used small molecule inhibitors to block NAD salvage and P2X7 pathways. We also used flow cytometry to measure protein expression, using anti-P2X7 antibodies. ResultsIFNγ activation led to doubling of expression level of the purinergic pore P2X7 on monocytes as shown by flow cytometry. Inhibition of the STAT1-dependent nicotinamide phosphoribosyltransferase (NAMPT) by daporinad led to a reduction of OCR by 67%. Addition of NAD to NAMPT blocked cells circumvented the blockade and restored normal OCR. Interestingly, inhibition of P2X7 by AZ-11645373 in the setting of NADcomplemented NAMPT blockade led to ~50% reduction of OCR. In the absence of NAMPT inhibition, P2X7 blockade alone leads to about 15% reduction in OCR; in the setting of IFNγ-stimulated OCR, the reduction was 25%. ConclusionsP2X7 expression increases in monocytes following IFNγ-activation, and its patency facilitates NAD-dependent OCR. In the setting of NAMPT blockade, P2X7 plays an important role in trafficking NAD or its metabolites into cells and allowing oxygen consumption following IFNγ stimulation. Blockade of P2X7 leads to reduced OCR, which diminished even further upon IFNγ stimulation and NAMPT blockade. The ability to augment OCR through P2X7 may contribute to control of intracellular pathogens.

PO-01-124 THE CALCIUM HANDLING MACHINERY IS REMODELED IN FRIEDREICH’S ATAXIA

Friedreich's ataxia (FA) is an inherited neurodegenerative disorder that causes progressive nervous system damage. FA is caused by a deficiency in the frataxin protein due to an expansion of GAA repeats in the first intron of the frataxin gene. Reduced frataxin protein expression is thought to negatively affect mitochondrial function, leading to increased oxidative damage. Although FA is considered a neurodegenerative disorder, it is not completely understood why most patients present with left ventricular systolic dysfunction and die from cardiac events. The objective of our study is to determine whether the abnormal calcium handling machinery is a molecular mechanism that perpetuates cardiac dysfunction in FA. We used the frataxin knock-out (KO) mouse model of FA as well as human heart samples from donors with FA and from unaffected donors. The expression of calcium handling machinery proteins was assessed with proteomics and western blot. In left ventricular myocytes from KO and WT mice, the IonOptix system was used for calcium imaging, the seahorse assay was utilized to measure oxygen consumption rate (OCR) and confocal imaging was used to quantify the mitochondrial membrane potential (Δψm), and reactive oxygen species (ROS). ECG and echocardiography were used to assess cardiac function in the mice. In the proteomic analysis and western blot, SERCA2, Ryr2 and CaMKII were significantly downregulated, and the mitochondrial calcium handling proteins voltage-dependent anion channel and mitochondrial calcium uniporter were significantly upregulated in left ventricular tissue from humans with FA and from KO mice. On the ECG, the RR, PR, QRS, and QTc intervals were significantly longer in the KO mice. Echocardiography showed that the ejection fraction and fractional shortening were significantly decreased and left ventricular wall thickness and diameter were significantly increased in the KO mice. Moreover, the calcium transient decay was significantly prolonged in ventricular myocytes from KO mice compared to WT. Additionally, the Δψm was significantly depolarized, the OCR was significantly decreased, and ROS levels were significantly elevated in left ventricular myocytes from KO compared to WT. The development of left ventricular contractile dysfunction in FA is associated with reduced expression of calcium handling proteins, abnormal calcium cycling, and mitochondrial dysfunction.

Sustained mitochondrial dysfunction in male, but not female Spontaneous Hypertensive Rats (SHR) corresponds with delayed renal recovery from ischemic injury

Acute kidney injury (AKI) due to ischemia-reperfusion (IR) is a serious and frequent complication in hospital settings with high mortality rates. The mechanisms mediating renal IR injury and leading to increased risk of later developing cardiovascular and renal diseases in either sex remain poorly understood. We previously reported that there is sex difference in renal recovery from IR where males have a delayed recovery vs females. Mitochondrial dysfunction plays a pivotal role in the pathogenesis of AKI in males, resulting in abnormal kidney repair and disease progression. However, the impact of IR on mitochondrial function in females has not been examined. The goal of the current study was to test the hypothesis that IR results in greater sustained mitochondrial dysfunction in males vs. females corresponds to delayed recovery of renal function in males. 13-week-old male and female SHR were subjected to sham or 30-minute warm bilateral IR. Subsets of rats were euthanized 1- or 7-days post-IR (n=6/group). Blood was collected to measure kidney function. The right kidney was dissected and processed for electron microscopy (EM) to assess mitochondrial structure, histological analysis of renal structure, and measurement of mitochondrial DNA (mtDNA) copy number via RT-PCR. Tubular cells were isolated from the left kidney to measure oxygen consumption rate (OCR) to assess mitochondrial respiration using Seahorse XFe24 Extracellular Flex Analyzer. IR increased plasma creatinine (Pcr) in male and female SHR vs. respective sham controls 1-day post-IR (PIR =0.0001; Psex✕IR=0.2). Pcr remained elevated in male, but not female, SHR 7 days post-IR (Pcr: PIR =0.03; Psex✕IR=0.04). OCR was reduced in male and female tubules 1 day post IR (PIR =0.001; Psex=0.94) and remained reduced only in tubules from males 7 days post-IR (PIR =0.0001; Psex✕IR=0.0001). Consistent with decreased OCR, EM revealed swollen round mitochondria, reduced mitochondria density with complete loss of cristae membranes vs. sham controls 1-day post-IR in both sexes, which was sustained 7 days post-IR only in males. Mitochondrial DNA copy number and peroxisome proliferator-activator receptor-y coactivator (PGC-1α) mRNA expression was also reduced 1-day post-IR in both sexes (PIR =0.05; Psex✕IR=0.59) and remained down only in males 7 days post-IR (PIR =0.02; Psex✕IR=0.001). In conclusion, our data demonstrate that there is sex difference in mitochondria after renal IR. Males have sustained mitochondrial dysfunction with delayed renal recovery compared to females. Further studies will be carried out to better understand the direct impact of mitochondria dysfunction on renal recovery post-IR in male and females. This work was supported by career development grant from AHA (20CDA35310362) to R Mohamed; National Institutes of Health (1P01HL134604-01 and R01 HL127091 to J. C. Sullivan. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Comparing effects of microplastic exposure, FPOM resource quality, and consumer density on the response of a freshwater particle feeder and associated ecosystem processes

Fine particulate organic matter (FPOM) is an important basal resource in stream ecosystems for deposit- and filter-feeding macroinvertebrates (collectively ‘particle feeders’). Microplastics (MP) share many characteristics with FPOM (e.g. size range, surface area to volume ratios) and are potentially consumed by particle feeders. Accordingly, MP contamination of natural FPOM pools might affect particle feeder growth and survival, particularly when background FPOM resource quality is low, or intraspecific competition is high. We conducted a microcosm experiment to evaluate how a realistic (1400 particles/kg sediment) polyethylene MP (ø = 45–53 µm) concentration interacts with FPOM (ø = 63–250 µm) resource quality (low versus high nutrient content) and consumer density (10 versus 20 individuals per microcosm) to affect growth and survival of larval Chironomus riparius (Diptera: Chironomidae), a model particle feeder. We additionally quantified community respiration, based on three hour measurements of oxygen consumption in the microcosms at the end of the experiment. MP exposure reduced larval body lengths by 26.7%, but only under the low consumer density treatment. MPs reduced community respiration by 26.2%, but only in the absence of chironomids, indicating an impact on microbial respiration. In comparison, low resource quality and high consumer density were associated with 53.5–70.2% reductions in community respiration, chironomid body length and/or body mass. These results suggest that effects of contamination of FPOM with MPs at environmentally realistic concentrations on the life histories of particle feeders such as C. riparius might be limited, especially relative to the effects of resource quality and consumer density. However, the reduction in microbial respiration when MPs were present highlights the need for further research addressing MP impacts on microbes, given their key roles in ecosystem functioning.

The impact of selected abiotic factors on Artemia hatching process through real-time observation of oxygen changes in a microfluidic platform

Current studies on abiotic impacts on Artemia, a crustacean which is widely used in aquaculture, and ecotoxicology, often focus on endpoint analysis (e.g., hatching rates, survival). Here, we demonstrate that a mechanistic understanding can be obtained through measurement of oxygen consumption in real-time over an extended time period in a microfluidic platform. The platform enables high level control of the microenvironment and direct observation of morphological changes. As a demonstration, temperature and salinity are chosen to represent critical abiotic parameters that are also threatened by climate change. The hatching process of Artemia consists of four different stages: hydration, differentiation, emergence, and hatching. Different temperatures (20, 35, and 30 °C) and salinities (0, 25, 50, and 75 ppt) are shown to significantly alter the duration of hatching stages, metabolic rates, and hatchability. Specifically, the metabolic resumption of dormant Artemia cysts was significantly enhanced at higher temperatures and moderate salinity, however, the time needed for this resumption was only dependent on higher temperatures. Hatchability was inversely related to the duration of the differentiation stage of hatching, which persisted longer at lower temperatures and salinities. The current approach of investigation of metabolism and corresponding physical changes can be employed to study hatching processes of other aquatic species, even those with low metabolic rate.

Astrocytic aerobic glycolysis provides lactate to support neuronal oxidative metabolism in the hippocampus.

Under physiological conditions, the energetic demand of the brain is met by glucose oxidation. However, ample evidence suggests that lactate produced by astrocytes through aerobic glycolysis may also be an oxidative fuel, highlighting the metabolic compartmentalization between neural cells. Herein, we investigate the roles of glucose and lactate in oxidative metabolism in hippocampal slices, a model that preserves neuron-glia interactions. To this purpose, we used high-resolution respirometry to measure oxygen consumption (O2 flux) at the whole tissue level and amperometric lactate microbiosensors to evaluate the concentration dynamics of extracellular lactate. We found that lactate is produced from glucose and transported to the extracellular space by neural cells in hippocampal tissue. Under resting conditions, endogenous lactate was used by neurons to support oxidative metabolism, which was boosted by exogenously added lactate even in the presence of excess glucose. Depolarization of hippocampal tissue with high K+ significantly increased the rate of oxidative phosphorylation, which was accompanied by a transient decrease in extracellular lactate concentration. Both effects were reverted by inhibition of the neuronal lactate transporter, monocarboxylate transporters 2 (MCT2), supporting the concept of an inward flux of lactate to neurons to fuel oxidative metabolism. We conclude that astrocytes are the main source of extracellular lactate which is used by neurons to fuel oxidative metabolism, both under resting and stimulated conditions.

Impact of atmospheric pressure variations on aerobic biodegradation test.

Biodegradation rate is an important index to evaluate the environmental risk of chemicals, which is usually determined by measuring oxygen consumption through respirometer in a biodegradation test. However, atmospheric pressure variations affect reactor oxygen concentration and oxygen volume recorded by respirometer in biodegradation test, and the parameters of reactor volume and test material amount amplify its effect. Atmospheric pressure variation >1 kPa could introduce >20% underestimation in biodegradation rate when a small amount of test material (0.04-0.2 g per 100 g of inoculum) and high reactor volume (2-4 L) were used according to the international standards. A 5 kPa drop in atmospheric pressure leads to a 6% decrease in headspace oxygen concentration in the reactor, which could subsequently inhibit biodegradation microbials and decrease the biodegradation rate by 30%. Moreover, the biodegradation process (oxygen consumption rate) could be accelerated/delayed several times by atmospheric pressure variations compared to the process without variations when the oxygen consumption rate was <5 mL h-1 in a 0.5 or 1 L reactor and <10 mL h-1 in a 2-L reactor. Mitigating the effects of atmospheric pressure variations on biodegradation test includes lowering the reactor volume, increasing the test material amount and recording atmospheric pressure for further modification.

Abstract 5341: Data mining of PubChem bioassay data reveals OXPHOS inhibitors with anti-cancer activity

Abstract High Grade Serous Ovarian Cancer (HGSOC) is a fatal disease that is typically detected at an advanced stage when there are limited modalities for effective treatment. Treatment efficacy against cancer is dependent on tumor metabolism and its adaptation for most therapies. Warburg effect is an important adaptation found in tumors where cells primarily catabolize glucose even in presence of sufficient oxygen and nutrients. Nevertheless, recent evidence suggests cells in tumor microenvironments remain dependent on mitochondrial ATP production via oxidative phosphorylation (OXPHOS). OXPHOS also represents a major metabolic pathway in cancer stem cells and tumor cells of relapse patients. Molecular signatures of glycolysis and OXPHOS are both detected in tumors. This points to the OXPHOS pathway as a potential therapeutic target in cancer. Here we apply a data mining approach to identify OXPHOS inhibitors to evaluate as candidates for therapies against HGSOC. High-Throughput Screening (HTS) on mechanistic targets like OXPHOS are cost prohibitive for academic laboratories. As an alternative, we deployed a data mining pipeline to find active chemical classes among 8415 available OXPHOS-related bioassays in the PubChem data repository. Active compound clusters frequently contain α,β-unsaturated carbonyl groups, which are also observed in both endogenous quinone electron carriers and atovaquone–a potent inhibitor of OXPHOS. Out of 312041 unique compounds tested in the assays, we selected 6 representative molecules from each of the 6 largest active chemical clusters to test for OXPHOS inhibition, ROS production, and reduced cancer cell proliferation. We assayed cell viability (MTT) to check for proliferation of human (OVCAR3, OVCAR5, OVISE) and mouse (ID8) ovarian cancer cells against 6 compounds, Oryzalin, Allylyestrenol, Esbiothrin, Lacidipine, Coumatetralyl, and CID929419 (MLS000713029), 72 h post treatment. ID8 and OVCAR5 significantly decreased cell proliferation after Lacidipine and Oryzalin treatment. Significant increase in intracellular ROS, a frequent consequence of OXPHOS inhibition, was observed in all cell lines after Lacidipine treatment. Elevated ROS was also observed in ID8 and OVISE cells after Esbiothrin treatment. To confirm OXPHOS inhibition as the mechanism of action, we performed Mito Stress Test on the Seahorse Analyzer and measured Oxygen Consumption Rate. Treatment with Oryzalin, Allylyestrenol, Esbiothrin, and Lacidipine significantly decreased basal respiration rate and ATP production in ID8 and OVCAR3 cells. This suggests that 4 of the 6 compound classes prioritized by the data mining pipeline inhibits OXPHOS in ovarian cancer cells. Thus, our pipeline provides an efficient alternative to HTS for identifying OXPHOS inhibitors. Next, we plan to test the in-vivo efficacy of these drugs against ovarian tumors in a mouse model and investigate their molecular mechanisms. Citation Format: Sejal T. Sharma, Liping Feng, Nicha Boonpattrawong, Lisa M. Barroilhet, Manish Patankar, Spencer S. Ericksen. Data mining of PubChem bioassay data reveals OXPHOS inhibitors with anti-cancer activity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5341.

Determination of Krogh Coefficient for Oxygen Consumption Measurement from Thin Slices of Rodent Cortical Tissue Using a Fick's Law Model of Diffusion.

To investigate the impact of experimental interventions on living biological tissue, ex vivo rodent brain slices are often used as a more controllable alternative to a live animal model. However, for meaningful results, the biological sample must be known to be healthy and viable. One of the gold-standard approaches to identifying tissue viability status is to measure the rate of tissue oxygen consumption under specific controlled conditions. Here, we work with thin (400 μm) slices of mouse cortical brain tissue which are sustained by a steady flow of oxygenated artificial cerebralspinal fluid (aCSF) at room temperature. To quantify tissue oxygen consumption (Q), we measure oxygen partial pressure (pO2) as a function of probe depth. The curvature of the obtained parabolic (or parabola-like) pO2 profiles can be used to extract Q, providing one knows the Krogh coefficient Kt, for the tissue. The oxygen trends are well described by a Fick's law diffusion-consumption model developed by Ivanova and Simeonov, and expressed in terms of ratio (Q/K), being the rate of oxygen consumption in tissue divided by the Krogh coefficient (oxygen diffusivity × oxygen solubility) for tissue. If the fluid immediately adjacent to the tissue can be assumed to be stationary (i.e., nonflowing), one may invoke conservation of oxygen flux K·(∂P/∂x) across the interface to deduce (Kt/Kf), the ratio of Krogh coefficients for tissue and fluid. Using published interpolation formulas for the effect of salt content and temperature on oxygen diffusivity and solubility for pure water, we estimate Kf, the Krogh coefficient for aCSF, and hence deduce the Kt coefficient for tissue. We distinguish experimental uncertainty from natural biological variability by using pairs of repeated profiles at the same tissue location. We report a dimensionless Krogh ratio (Kt/Kf)=0.562±0.088 (mean ± SD), corresponding to a Krogh coefficient Kt=(1.29±0.21)×10-14 mol/(m·s·Pa) for mouse cortical tissue at room temperature, but acknowledge the experimental limitation of being unable to verify that the fluid boundary layer is truly stationary. We compare our results with those reported in the literature, and comment on the challenges and ambiguities caused by the extensive use of 'biologically convenient' non-SI units for tissue Krogh coefficient.

Heart Rate Recovery Assessed by Cardiopulmonary Exercise Testing in Patients with Cardiovascular Disease: Relationship with Prognosis

The use of exercise testing has expanded in recent decades and there is a wealth of information examining the prognostic significance of exercise variables, such as peak oxygen consumption or ventilatory measures whilst exercising. However, a paucity of research has investigated the use of recovery-derived parameters after exercise cessation. Heart rate recovery (HRR) has been considered a measure of the function of the autonomic nervous system and its dysfunction is associated with cardiovascular risk. We aim to provide an overview of the literature surrounding HRR and its prognostic significance in patients with cardiovascular disease undertaking an exercise test. In December 2020, searches of PubMed, Scopus, and ScienceDirect were performed using key search terms and Boolean operators. Articles were manually screened and selected as per the inclusion criteria. Nineteen articles met inclusion criteria and were reviewed. Disagreement exists in methodologies used for measuring and assessing HRR. However, HRR provides prognostic mortality information for use in clinical practice. HRR is a simple, non-invasive measure which independently predicts mortality in patients with heart failure and coronary artery disease; HRR should be routinely incorporated into clinical exercise testing.

Abstract P6-11-15: Lipid accumulation in residual triple negative breast cancer cells surviving chemotherapy treatment

Abstract Background: Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype for which limited targeted therapies are available. Therefore, conventional chemotherapy remains the backbone of standard neoadjuvant treatment (NACT) for TNBC patients. Unfortunately, ~45% of patients will have substantial residual tumor burden post neoadjuvant chemotherapy, leading to poor prognoses (PMID: 28135148). Recently, it has been demonstrated that mitochondrial oxidative phosphorylation (oxphos) is upregulated and is a therapeutic vulnerability in chemoresistant TNBC (PMID: 30996079; Baek et al., BioRxiv doi.org/10.1101/2022.02.25.481996). However, mechanisms driving increased oxphos in chemoresistant TNBC are not understood. Upregulated fatty acid (FA) metabolism is a common adaptation in tumors, providing an energy source through fatty acid β-oxidation (FAO), and promoting lipid accumulation after fatty acid synthesis (FAS) when energy needs are met. Chemotherapy can induce oxidative stress through the generation of reactive oxygen species. Cancer cells adapt to these damaging molecules by increasing de novo lipogenesis, resulting in the accumulation of lipid droplets (LDs) in the cytosol (PMID: 32782526, 20876798). We hypothesize that TNBC cells metabolically adapt to the stress of NACT by upregulating lipid metabolic pathways, providing highly energetic molecules that can be utilized to drive oxphos in chemoresistant TNBC. Methods: Using orthotopic patient-derived xenograft (PDX) models of TNBC (PIM001-P, PMID: 30996079, HCI-010, PMID: 22019887; WHIM14, PMID:24055055), we are measuring protein levels of fatty acid synthase (FASN) in vehicle tumors vs residual tumors surviving treatment with the standard front-line neoadjuvant chemotherapy regimens (Adriamycin plus cyclophosphamide (AC), docetaxel, carboplatin, or docetaxel+carboplatin) using immunohistochemistry (IHC). Vectra 3 microscopy (Akoya) is being used to quantify tumor cell-specific staining. We complemented our IHC analysis with reverse-phase protein array (RPPA). To assess LD accumulation in residual PDX tumors, we conducted transmission electron microscopy (TEM). To complement these PDX studies, we modeled the residual tumor metabolic state in cultured human TNBC cells. Following treatment with the IC50 of standard chemotherapeutic agents (AC, carboplatin, paclitaxel, docetaxel), we assessed oxphos by measuring oxygen consumption rate (OCR) using a Seahorse Bioanalyzer (Agilent). Further, we tested LD accumulation using LipidTOX staining. In ongoing studies, we are measuring incorporation of 13C palmitate into the tricarboxylic acid cycle (TCA) prior to and following chemotherapy treatments to assess if lipids fuel mitochondrial metabolism in residual TNBC cells. Results/Discussion: IHC in the PIM001-P PDX model after in vivo AC treatment revealed increased levels of FASN in post-AC residual tumors compared to the treatment-naive tumors. Further, key proteins involved in fatty acid synthesis, FASN and Acetyl-CoA carboxylase, were significantly increased in residual PIM001-P cells that survived AC compared to vehicle by RPPA. TEM analysis of the HCI-010 PDX revealed significantly more LDs in carboplatin-treated tumors compared to vehicle. This finding was supported by increased LDs observed in TNBC cell lines treated with NACT compared to vehicle in our LipidTOX analyses. Taken together, these data indicate that NACT induces increased expression of key lipid metabolism proteins and accumulation of cytosolic LDs. Our future experiments will reveal if chemoresistant TNBC cells preferentially utilize and incorporate lipids into the tricarboxylic acid cycle, in turn driving oxphos. These data have the potential to provide rationale for the incorporation of FAO/LD inhibitors in sequential combinations with conventional chemotherapies to more effectively kill TNBC cells that are chemo-refractory. Citation Format: Katherine E. Pendleton, Mokryun L. Baek, Junegoo Lee, Lin Tan, Hannah L. Johnson, Lacey E. Dobrolecki, James P. Barrish, Michael T. Lewis, Philip L. Lorenzi, Fabio Stossi, Gloria V. Echeverria. Lipid accumulation in residual triple negative breast cancer cells surviving chemotherapy treatment [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-11-15.

Toucans’ ostentatious beaks do not expand their thermoneutral zone

Some birds are just instantly recognisable. From elegant flamingos with graceful necks to toco toucans (Ramphastos toco) with their jet-black plumage and distinctive beaks, some birds just stand out from the dowdy crowd. And the toucan's outsized beak comes in handy for retrieving fruit and cracking nuts. But Glenn Tattersall from Brock University, Canada, explains that the toucan's outrageous bill also doubles as a radiator; he recalls how, in the 2000s, Augusto Abe (Sao Paulo State University, Brazil) put him on to the possibility that the birds may use their beaks to regulate their body temperature. However, warm-blooded creatures mainly prefer living at temperatures where they expend little energy to remain warm or keep cool, known as their thermoneutral zone. Denis Andrade, Jussara Chaves (both from Sao Paulo State University) and Tattersall wondered whether the toucans’ ostentatious beaks could expand the range of temperatures over which the birds live at relatively little cost to maintain their body temperature.Collecting six toucans, Chaves settled the birds in Andrade's lab at the Universidade Estadual Paulista, Brazil. Then each night, she placed individual birds into a temperature-controlled chamber – set at temperatures from 0 to 35°C, spanning the 10–25°C temperature range where they expend little energy to remain warm – and measured their oxygen consumption to find out how much energy they used to regulate their temperature when hot and chilly. Then, Chaves repeated the oxygen consumption measurements, but this time she prevented the birds from using their beaks like a radiator by placing a snuggly fitting felt jacket over each beak, which allowed the birds to open their beaks if they got warm and needed to pant, while preventing their beaks from absorbing or losing heat to regulate their temperature. If the beaks were allowing the birds to expand the range of temperatures over which they could live a relatively low-cost life, then the felt beak-jacket would alter the temperatures at which the birds began using more energy to keep warm or cool.But the beak-jacket didn't extend or reduce the temperature range over which the birds live comfortably. Their thermoneutral zone is not extended by their radiator beaks.The team also reviewed how the birds slept in cold conditions and realised that the chilliest birds with unjacketed beaks tucked their beaks beneath their wing feathers, in addition to shutting off the blood supply to the beak, to keep warm. However, as the temperatures rose above 30°C, the birds’ naked beaks came into their own. The toucans with felt jacketed beaks used 20% more energy than those without beak-jackets, probably because they were panting to keep cool. ‘Our estimate is that the beneficial consequence of being able to access the normal heat exchange through the bill at 35°C corresponds to ∼32% of basal metabolic rate’, Tattersall explains.So, the toucan's beak can work both ways. ‘It promotes heat dissipation quite efficiently, but under conditions of high solar radiation it may also be a window to undesired heat gain’, says Andrade. And the team suspects that the toucans’ ability to absorb heat through their impressive beaks as they go about their daily business could limit how long they spend foraging for food, forcing them to seek shade at the peak of the day to avoid overheating.

Influence of temperature on respiratory metabolism during early development of Totoaba macdonaldi

Environmental temperature can act as a positive or negative modulator of the physiology and metabolism of poikilothermic organisms. As a general rule, larvae and juveniles are more sensitive to temperature stress than adults, which represents a key factor that partly determines their development and growth in aquaculture. Therefore, this study analyzed the effect of exposure to temperatures of 21, 24, and 27°C on the respiratory metabolism (RM) of Totoaba macdonaldi in different developmental stages. For this purpose, eggs, larvae with 4, 6, 8, 14, and 22 days post-hatch (dph), and juveniles of 25 dph were exposed to the experimental temperatures for 5 h. After the exposure time, oxygen consumption measurements were performed. The results clearly show that temperature (21 to 27°C) has the greatest effect on RM in eggs and larvae at 4 and 22 dph (3.1 ± 0.3 to 4.3 ± 0.3 μmol O2 h-1 egg-1, 2.9 ± 0.3 to 10.5 ± 1.2 μmol O2 h-1 larvae-1 and 102.0 ± 6.4 to 189.8 ± 15.3 μmol O2 h-1 larvae-1, respectively). This thermal sensitivity was not observed from 6, 8, and 14 dph larvae and juveniles at 25 dph, where morphological development was the main factor that influencing the RM. Therefore, this study shows that temperature affects RM in different development stages of totoaba, beginning in the egg stage and intensifying once the larvae hatch until 22 dph. Understanding how temperature affects energy expenditure by measuring RM is essential to establish culture conditions that allow better physiological performance and growth in the early life stages of T. macdonaldi.

Abstract P512: Association Between Resting Rate Pressure Product and All-Cause Mortality Among United States Adults

Background: Rate pressure product (RPP) is a measure of myocardial oxygen consumption and often used to quantify cardiac exercise workload. We sought to determine whether resting RPP was associated with all-cause mortality in healthy U.S. adults. Methods: This was a nationally representative, retrospective cohort study of the 1999-2018 National Health and Nutrition Examination Survey (NHANES), linked to the National Death Index through 2019. We included adult, non-pregnant participants without cardiovascular disease, kidney dysfunction, hypertension, diabetes, or current chronotropic agent use. RPP was calculated as the product of mean systolic BP (of 3 sitting BPs) and resting heart rate, and classified into quintiles (Q1≤7300, Q2 [Ref]: 7300-8250, Q3: 8250-9200, Q4: 9200-10400, Q5: &gt;10400). We used multivariable Cox regression to estimate risk of all-cause mortality, adjusting for demographics, CVD risk factors, and comorbidities, and accounting for the survey design. Results: Among 19,954 participants (mean age 40y; 9,653 [48%] female; 8,056 [66%] non-Hispanic White), 1,013 died over a median follow-up of 10.3 years (IQR, 5.6-15.5). Adults in Q3-Q5 had significantly increased unadjusted risk of all-cause mortality compared to Q2 (HR [95% CI], Q1: 0.89 [0.50,1.58], Q3: 1.69 [1.06,2.72], Q4: 1.97 [1.16,3.34], Q5: 2.69 [1.71,4.22]). Adjustment for covariates attenuated risks of mortality but remained 61% higher for Q5 (Q2 [Ref], Q1: 1.02 [0.77,1.36], Q3: 1.09 [0.85,1.40], Q4: 1.22 [0.93,1.59], Q5: 1.61 [1.25,2.07]). When stratifying by gender, men, but not women, demonstrated increased risk of mortality in Q4 and Q5 (Women, Q4: 0.84 [0.54,1.31], Q5: 1.33 [0.89,1.98]; Men, Q4: 1.53 [1.07,2.18], Q5: 1.79 [1.30,2.46]). Conclusion: Healthy adult participants with a resting RPP greater than 10,400 had 61% higher risk of all-cause mortality compared to a RPP less than or equal to 7,300. This effect seems to be more pronounced in men than women. Further longitudinal studies are needed to understand the independent, predictive value of RPP and factors (e.g. aerobic activity) driving RPP.