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Oxygen uptake kinetics

Lara-Antonia Beer, Helma Tatge, Nicole Reich, Michel Tenspolde, Alexandra Olling, Sebastian Goy, Klemens Rottner, Alexi Kirilov Alekov, Ralf Gerhard
Toxin A and Toxin B (TcdA/TcdB) are large glucosyltransferases produced by Clostridium difficile. TcdB but not TcdA induces reactive oxygen species (ROS)-mediated early cell death when applied at high concentrations. We found that non-glucosylated Rac1 is essential for induction of early cell death since inhibition of Rac1 impedes this effect. Early cell death only occurs when TcdB is rapidly endocytosed. This was shown by generation of chimeras using the trunk of TcdB from a hypervirulent strain. TcdB from hypervirulent strain has been described to translocate from endosomes at higher pH values and thus, meaning faster than reference type TcdB...
June 14, 2018: Cellular Microbiology
Luis Antonio Pereira de Lima, Maxime Raison, Sofiane Achiche, Ricardo Dantas de Lucas
The human oxygen uptake (VO2 ) response to step-like increases in work rate is currently modeled by a First Order System Multi-Exponential (FOME) arrangement. Due to their first order nature, none of FOME model's exponentials is able to model an overshoot in the oxygen uptake kinetics (OVO2 K). Nevertheless, OVO2 K phenomena are observed in the fundamental component of trained individuals' step responses. We hypothesized that a Mixed Multi-Exponential (MiME) model, where the fundamental component is modeled with a second instead of a first order system, would present a better overall performance than that of the traditional FOME model in fitting VO2 on-kinetics at all work rates, either presenting or not OVO2 K...
June 14, 2018: Journal of Applied Physiology
Xiao Zhang, Ranjan K Dash, Elizabeth R Jacobs, Amadou K S Camara, Anne V Clough, Said H Audi
Integrated computational modeling provides a mechanistic and quantitative framework for describing lung mitochondrial bioenergetics. Thus, the objective of this study was to develop and validate a thermodynamically-constrained integrated computational model of the bioenergetics of isolated lung mitochondria. The model incorporates the major biochemical reactions and transport processes in lung mitochondria. A general framework was developed to model those biochemical reactions and transport processes. Intrinsic model parameters such as binding constants were estimated using previously published isolated enzymes and transporters kinetic data...
2018: PloS One
M Ethan MacDonald, Avery J L Berman, Erin L Mazerolle, Rebecca J Williams, G Bruce Pike
A new method is proposed for obtaining cerebral perfusion measurements whereby blood oxygen level dependent (BOLD) MRI is used to dynamically monitor hyperoxia-induced changes in the concentration of deoxygenated hemoglobin in the cerebral vasculature. The data is processed using kinetic modeling to yield perfusion metrics, namely: cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). Ten healthy human subjects were continuously imaged with BOLD sequence while a hyperoxic (70% O2 ) state was interspersed with baseline periods of normoxia...
May 28, 2018: NeuroImage
Claudia Miranda, Paulina Ibacache, Edgardo Opazo, Juan Rojas, Marcelo Cano
BACKGROUND: The evaluation of cardiorespiratory fitness (RCC) using maximal or peak oxygen consumption (VO2), requires a high level of effort in obese patients. We propose a method to evaluate RCC using constant and moderate loads, called VO2 kinetics (tau). AIM: To determine the relationship between tau and peak VO2 in patients with obesity. MATERIAL AND METHODS: Forty patients (87% females) aged 37 ± 12 years and with a body mass index (BMI) of 34...
January 2018: Revista Médica de Chile
Shalini Verma, Jamal Ali Moiz, Shahnawaz Anwer, Ahmad H Alghadir, Mohammed Ejaz Hussain
BACKGROUND: Cardiac autonomic neuropathy is a commonly overlooked complication of type 2 diabetes mellitus (T2DM) characterized by an imbalance between sympathetic and parasympathetic supply to the heart, which contributes to cardiovascular morbidity and mortality. T2DM has also been shown to negatively influence oxygen kinetics and increase oxidative stress, which may be linked to the development of various chronic complications. Aerobic training has been reported to improve oxygen uptake, antioxidant defense, and cardiac autonomic function in T2DM; however, the effects of varying doses of exercise on these variables are not known...
May 24, 2018: Trials
Dejana Popovic, Nikhil Kumar, Sundeep Chaudhry, Akshay Bagai, Ross Arena, Naresh Kumar
PURPOSE: Improvements in cardiorespiratory fitness (VO2peak) post-cardiac rehabilitation (post-CR) are used to gauge therapeutic efficacy. The aim of the present study was to assess the effect of supervised CR on other cardiopulmonary exercise testing (CPX) variables, specifically those that reflect ventilatory efficiency and VO2 changes in relation to changes in work rate (WR). METHODS: Patients (n = 142; mean age 63 ± 9 y; 23% female) with coronary artery disease (CAD) participated in supervised CR for 3 to 6 mo completing 60 ± 17 sessions (range: 32-96 sessions), with intensity derived from the baseline CPX...
May 11, 2018: Journal of Cardiopulmonary Rehabilitation and Prevention
Wen Ping Deng, Jie Zhang, Zhi Jian Zhang, Shao Chang Hu, Jin Rong Guo, Yuan Qiu Liu, Fan Qian Kong, Yi Zhang
The stable hydrogen and oxygen isotopes are environmental isotopes, which widely exist in various kinds of water. Their relative abundance variation in water can indicate the water circulation and mechanism of water use in plant. This research selected two major kinds of greening tree species, evergreen coniferous Platycladus orientalis and deciduous broad-leaved Quercus variabilis, in Beijing mountainous area, and the water movement process in soil-plant-atmosphere continuum was investigated by the variation characteristics analysis of stable hydrogen and oxygen isotope compositions in precipitation, soil water, groundwater, plant stem water and leaf water...
July 18, 2017: Ying Yong Sheng Tai Xue Bao, the Journal of Applied Ecology
Anthony Birat, Pierre Bourdier, Enzo Piponnier, Anthony J Blazevich, Hugo Maciejewski, Pascale Duché, Sébastien Ratel
The aim of this study was to determine whether prepubertal children are metabolically comparable to well-trained adult endurance athletes and if this translates into similar fatigue rates during high-intensity exercise in both populations. On two different occasions, 12 prepubertal boys (10.5 ± 1.1 y), 12 untrained men (21.2 ± 1.5 y), and 13 endurance male athletes (21.5 ± 2.7 y) completed an incremental test to determine the power output at VO2max (PVO2max ) and a Wingate test to evaluate the maximal anaerobic power (Pmax ) and relative decrement in power output (i...
2018: Frontiers in Physiology
Roy K Aaron, Jennifer R Racine, Anne Voisinet, Peter Evangelista, Jonathan P Dyke
OBJECTIVE: The hypothesis of this study is that human subchondral bone exhibits abnormal patterns of perfusion in osteoarthritis (OA) that can be characterized by kinetic parameters of blood flow using dynamic contrast enhanced (DCE) MRI. DESIGN: Fifteen subjects with advanced OA of the knee and 7 control subjects without OA were studied at 1.5 Tesla with DCE-MRI. Region of interest (ROIs) analysis of pharmacokinetic perfusion parameters were used to examine initial uptake and washout of the contrast agent in the lateral tibial plateau...
April 30, 2018: Osteoarthritis and Cartilage
Andrea Baschieri, Benedetta Del Secco, Nelsi Zaccheroni, Luca Valgimigli, Riccardo Amorati
Metal nanoparticles are reported to be toxic due to the generation of free radicals at their surface. Relatively inert thiol-capped gold nanoparticles (AuNPs) have been reported to induce radical formation in the presence of hydroperoxides, which would conflict with their potential use as inert scaffolds for the design of novel nano-antioxidants. With the aim of clarifying this aspect, we investigated the pro-oxidant activity of dodecanethiol-capped AuNPs (∼5 nm diameter), prepared through the Brust-Schiffrin synthesis, by oxygen-uptake kinetic studies...
April 24, 2018: Chemistry: a European Journal
Jayita Chopra, Ramkrishna Sen
Lipid accumulation in oleaginous yeast is generally induced by nitrogen starvation, while oxygen saturation can influence biomass growth. Systematic shake flask studies that help in identifying the right nitrogen source and relate its uptake kinetics to lipid biosynthesis under varying oxygen saturation conditions are very essential for addressing the bioprocessing-related issues, which are envisaged to occur in the fermenter scale production. In the present study, lipid bioaccumulation by P. guilliermondii at varying C:N ratios and oxygen transfer conditions (assessed in terms of kL a) was investigated in shake flasks using a pre-optimized N-source and a two-stage inoculum formulated in a hybrid medium...
April 20, 2018: Bioprocess and Biosystems Engineering
Mitchell A George, Kaitlin M McLay, Patricia K Doyle-Baker, Raylene A Reimer, Juan M Murias
Although aging has been associated to slower [Formula: see text]O2 kinetics, some evidence indicates that fitness status and not aging per se might modulate this response. The main goal of this study was to examine the [Formula: see text]O2 , deoxygenated hemoglobin+myoglobin (deoxy-[Hb+Mb]) kinetics, and the NIRS-derived vascular reperfusion responses in older compared to young men of different training levels (i.e., inactive, recreationally active, and endurance trained). Ten young inactive [YI; 26 ± 5 yrs...
2018: Frontiers in Physiology
Daniel A Keir, Donald H Paterson, John M Kowalchuk, Juan M Murias
Despite compelling evidence to the contrary, the view that oxygen uptake (V̇O2) increases linearly with exercise intensity (e.g. power output, speed) until reaching its maximum (V̇O2max) persists within the exercise physiology literature. This viewpoint implies that the V̇O2 response at any constant-intensity is predictable from a ramp-incremental exercise test. However, the V̇O2 versus task-specific exercise intensity relationship constructed from ramp-incremental versus constant-intensity exercise are not equivalent preventing the use of V̇O2 responses from one domain to predict those of the other...
March 23, 2018: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
Philipp S Orekhov, Ekaterina G Kholina, Marine E Bozdaganyan, Alexey M Nesterenko, Ilya B Kovalenko, Marina G Strakhovskaya
Phthalocyanines are aromatic macrocyclic compounds, which are structurally related to porphyrins. In clinical practice, phthalocyanines are used in fluorescence imaging and photodynamic therapy of cancer and noncancer lesions. Certain forms of the substituted polycationic metallophthalocyanines have been previously shown to be active in photodynamic inactivation of both Gram-negative and Gram-positive bacteria; one of them is zinc octakis(cholinyl)phthalocyanine (ZnPcChol8+ ). However, the molecular details of how these compounds translocate across bacterial membranes still remain unclear...
April 12, 2018: Journal of Physical Chemistry. B
Robert T Mankowski, Victor M Niemeijer, Jasper P Jansen, Lotte Spraakman, Henk J Stam, Stephan F E Praet
Purpose: It is still equivocal whether oxygen uptake recovery kinetics are limited by oxygen delivery and can be improved by supplementary oxygen. The present study aimed to investigate whether measurements of muscle and pulmonary oxygen uptake kinetics can be used to assess oxygen delivery limitations in healthy subjects. Methods: Sixteen healthy young adults performed three sub-maximal exercise tests (6 min at 40% Wmax ) under hypoxic (14%O2 ), normoxic (21%O2 ) and hyperoxic (35%O2 ) conditions on separate days in randomized order...
June 2017: Journal of Exercise Science and Fitness
Dhissanuvach Chaikhot, Matthew J D Taylor, Florentina J Hettinga
An awareness of sex differences in gait can be beneficial for detecting the early stages of gait abnormalities that may lead to pathology. The same may be true for wheelchair propulsion. The aim of this study was to determine the effect of sex on wheelchair biomechanics and mechanical efficiency in novice young able-bodied wheelchair propulsion. Thirty men and 30 women received 12  min of familiarisation training. Subsequently, they performed two 10-m propulsion tests to evaluate comfortable speed (CS). Additionally, they performed a 4-min submaximal propulsion test on a treadmill at CS, 125% and 145% of CS...
March 13, 2018: European Journal of Sport Science
Cole S Bailey, Luke T Wooster, Mary Buswell, Sarvagna Patel, Paul P Pappagianopoulos, Kristian Bakken, Casey White, Melissa Tanguay, Jasmine B Blodgett, Aaron L Baggish, Rajeev Malhotra, Gregory D Lewis
OBJECTIVES: This study sought to characterize the functional and prognostic significance of oxygen uptake (VO2 ) kinetics following peak exercise in individuals with heart failure (HF). BACKGROUND: It is unknown to what extent patterns of VO2 recovery following exercise reflect circulatory response during exercise in HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF). METHODS: We investigated patients (30 HFpEF, 20 HFrEF, and 22 control subjects) who underwent cardiopulmonary exercise testing with invasive hemodynamic monitoring and a second distinct HF cohort (n = 106) who underwent noninvasive cardiopulmonary exercise testing with assessment of long-term outcomes...
April 2018: JACC. Heart Failure
Ross D Pollock, Katie A O'Brien, Lorna J Daniels, Kathrine B Nielsen, Anthea Rowlerson, Niharika A Duggal, Norman R Lazarus, Janet M Lord, Andrew Philp, Stephen D R Harridge
In this study, results are reported from the analyses of vastus lateralis muscle biopsy samples obtained from a subset (n = 90) of 125 previously phenotyped, highly active male and female cyclists aged 55-79 years in regard to age. We then subsequently attempted to uncover associations between the findings in muscle and in vivo physiological functions. Muscle fibre type and composition (ATPase histochemistry), size (morphometry), capillary density (immunohistochemistry) and mitochondrial protein content (Western blot) in relation to age were determined in the biopsy specimens...
April 2018: Aging Cell
Diamante Maresca, Teresa Zotta, Gianluigi Mauriello
Oxygen is considered one of the main factors affecting probiotic bacteria survival due to the induction of oxidative damages caused by the action of reactive oxygen species (ROS). It has been shown that oxidative stress resistance in lactic acid bacteria is strongly dependent on the type of cell metabolism. Shift from fermentative to respiratory metabolism (through the addition of heme and menaquinone and in presence of oxygen) was associated to increase in biomass, long-term survival, and production of antioxidant enzymes...
2018: Frontiers in Microbiology
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