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Hall JK, Bates JHT, Krishnan R, Kim JH, Deng Y, Lutchen KR, Suki B. Elucidating the interaction between stretch and stiffness using an agent-based spring network model of progressive pulmonary fibrosis. FRONTIERS IN NETWORK PHYSIOLOGY 2024; 4:1396383. [PMID: 38840902 PMCID: PMC11150662 DOI: 10.3389/fnetp.2024.1396383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 05/01/2024] [Indexed: 06/07/2024]
Abstract
Pulmonary fibrosis is a deadly disease that involves the dysregulation of fibroblasts and myofibroblasts, which are mechanosensitive. Previous computational models have succeeded in modeling stiffness-mediated fibroblasts behaviors; however, these models have neglected to consider stretch-mediated behaviors, especially stretch-sensitive channels and the stretch-mediated release of latent TGF-β. Here, we develop and explore an agent-based model and spring network model hybrid that is capable of recapitulating both stiffness and stretch. Using the model, we evaluate the role of mechanical signaling in homeostasis and disease progression during self-healing and fibrosis, respectively. We develop the model such that there is a fibrotic threshold near which the network tends towards instability and fibrosis or below which the network tends to heal. The healing response is due to the stretch signal, whereas the fibrotic response occurs when the stiffness signal overpowers the stretch signal, creating a positive feedback loop. We also find that by changing the proportional weights of the stretch and stiffness signals, we observe heterogeneity in pathological network structure similar to that seen in human IPF tissue. The system also shows emergent behavior and bifurcations: whether the network will heal or turn fibrotic depends on the initial network organization of the damage, clearly demonstrating structure's pivotal role in healing or fibrosis of the overall network. In summary, these results strongly suggest that the mechanical signaling present in the lungs combined with network effects contribute to both homeostasis and disease progression.
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Affiliation(s)
- Joseph K. Hall
- Department of Biomedical Engineering, Boston University, Boston, MA, United States
| | - Jason H. T. Bates
- Department of Medicine, University of Vermont, Burlington, VT, United States
| | - Ramaswamy Krishnan
- Center for Vascular Biology Research, Department of Emergency Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
| | - Jae Hun Kim
- Department of Biomedical Engineering, Boston University, Boston, MA, United States
| | - Yuqing Deng
- Department of Mechanical Engineering, Boston University, Boston, MA, United States
| | - Kenneth R. Lutchen
- Department of Biomedical Engineering, Boston University, Boston, MA, United States
| | - Béla Suki
- Department of Biomedical Engineering, Boston University, Boston, MA, United States
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2
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Leija RG, Curl CC, Arevalo JA, Osmond AD, Duong JJ, Huie MJ, Masharani U, Brooks GA. Enteric and systemic postprandial lactate shuttle phases and dietary carbohydrate carbon flow in humans. Nat Metab 2024; 6:670-677. [PMID: 38388706 PMCID: PMC11052717 DOI: 10.1038/s42255-024-00993-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 01/24/2024] [Indexed: 02/24/2024]
Abstract
Dietary glucose in excess is stored in the liver in the form of glycogen. As opposed to direct conversion of glucose into glycogen, the hypothesis of the postprandial lactate shuttle (PLS) proposes that dietary glucose uptake is metabolized to lactate in the gut, thereby being transferred to the liver for glycogen storage. In the present study, we provide evidence of a PLS in young healthy men and women. Overnight fasted participants underwent an oral glucose tolerance test, and arterialized lactate concentration and rate of appearance were determined. The concentration of lactate in the blood rose before the concentration of glucose, thus providing evidence of an enteric PLS. Secondary increments in the concentration of lactate in the blood and its rate of appearance coincided with those of glucose, which indicates the presence of a larger, secondary, systemic PLS phase driven by hepatic glucose release. The present study challenges the notion that lactate production is the result of hypoxia in skeletal muscles, because our work indicates that glycolysis proceeds to lactate in fully aerobic tissues and dietary carbohydrate is processed via lactate shuttling. Our study proposes that, in humans, lactate is a major vehicle for carbohydrate carbon distribution and metabolism.
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Affiliation(s)
- Robert G Leija
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Casey C Curl
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Jose A Arevalo
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Adam D Osmond
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Justin J Duong
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Melvin J Huie
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Umesh Masharani
- Department of Medicine, University of California, San Francisco, CA, USA
| | - George A Brooks
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, CA, USA.
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3
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Douglas J, Carter CW, Wills PR. HetMM: A Michaelis-Menten model for non-homogeneous enzyme mixtures. iScience 2024; 27:108977. [PMID: 38333698 PMCID: PMC10850774 DOI: 10.1016/j.isci.2024.108977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/21/2023] [Accepted: 01/16/2024] [Indexed: 02/10/2024] Open
Abstract
The Michaelis-Menten model requires its reaction velocities to come from a preparation of homogeneous enzymes, with identical or near-identical catalytic activities. However, this condition is not always met. We introduce a kinetic model that relaxes this requirement, by assuming there are an unknown number of enzyme species drawn from a probability distribution whose standard deviation is estimated. Through simulation studies, we demonstrate the method accurately discriminates between homogeneous and heterogeneous data, even with moderate levels of experimental error. We applied this model to three homogeneous and three heterogeneous biological systems, showing that the standard and heterogeneous models outperform respectively. Lastly, we show that heterogeneity is not readily distinguished from negatively cooperative binding under the Hill model. These two distinct attributes-inequality in catalytic ability and interference between binding sites-yield similar Michaelis-Menten curves that are not readily resolved without further experimentation. Our user-friendly software package allows homogeneity testing and parameter estimation.
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Affiliation(s)
- Jordan Douglas
- Department of Physics, The University of Auckland, Auckland 1010, New Zealand
- Centre for Computational Evolution, The University of Auckland, Auckland 1010, New Zealand
| | - Charles W. Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Peter R. Wills
- Department of Physics, The University of Auckland, Auckland 1010, New Zealand
- Centre for Computational Evolution, The University of Auckland, Auckland 1010, New Zealand
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4
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Fuadah YN, Qauli AI, Marcellinus A, Pramudito MA, Lim KM. Machine learning approach to evaluate TdP risk of drugs using cardiac electrophysiological model including inter-individual variability. Front Physiol 2023; 14:1266084. [PMID: 37860622 PMCID: PMC10584148 DOI: 10.3389/fphys.2023.1266084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 09/20/2023] [Indexed: 10/21/2023] Open
Abstract
Introduction: Predicting ventricular arrhythmia Torsade de Pointes (TdP) caused by drug-induced cardiotoxicity is essential in drug development. Several studies used single biomarkers such as qNet and Repolarization Abnormality (RA) in a single cardiac cell model to evaluate TdP risk. However, a single biomarker may not encompass the full range of factors contributing to TdP risk, leading to divergent TdP risk prediction outcomes, mainly when evaluated using unseen data. We addressed this issue by utilizing multi-in silico features from a population of human ventricular cell models that could capture a representation of the underlying mechanisms contributing to TdP risk to provide a more reliable assessment of drug-induced cardiotoxicity. Method: We generated a virtual population of human ventricular cell models using a modified O'Hara-Rudy model, allowing inter-individual variation. IC 50 and Hill coefficients from 67 drugs were used as input to simulate drug effects on cardiac cells. Fourteen features (dVm dt repol , dVm dt max , Vm peak , Vm resting , APD tri , APD 90 , APD 50 , Ca peak , Ca diastole , Ca tri , CaD 90 , CaD 50 , qNet, qInward) could be generated from the simulation and used as input to several machine learning models, including k-nearest neighbor (KNN), Random Forest (RF), XGBoost, and Artificial Neural Networks (ANN). Optimization of the machine learning model was performed using a grid search to select the best parameter of the proposed model. We applied five-fold cross-validation while training the model with 42 drugs and evaluated the model's performance with test data from 25 drugs. Result: The proposed ANN model showed the highest performance in predicting the TdP risk of drugs by providing an accuracy of 0.923 (0.908-0.937), sensitivity of 0.926 (0.909-0.942), specificity of 0.921 (0.906-0.935), and AUC score of 0.964 (0.954-0.975). Discussion and conclusion: According to the performance results, combining the electrophysiological model including inter-individual variation and optimization of machine learning showed good generalization ability when evaluated using the unseen dataset and produced a reliable drug-induced TdP risk prediction system.
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Affiliation(s)
- Yunendah Nur Fuadah
- Computational Medicine Lab, Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
- School of Electrical Engineering, Telkom University, Bandung, Indonesia
| | - Ali Ikhsanul Qauli
- Computational Medicine Lab, Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
- Department of Engineering, Faculty of Advanced Technology and Multidiscipline, Universitas Airlangga, Surabaya, Jawa Timur, Indonesia
| | - Aroli Marcellinus
- Computational Medicine Lab, Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
| | - Muhammad Adnan Pramudito
- Computational Medicine Lab, Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
| | - Ki Moo Lim
- Computational Medicine Lab, Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
- Computational Medicine Lab, Department of Medical IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
- Meta Heart Co., Ltd., Gumi, Republic of Korea
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5
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Yue Z, Li C, Voth GA. The role of conformational change and key glutamic acid residues in the ClC-ec1 antiporter. Biophys J 2023; 122:1068-1085. [PMID: 36698313 PMCID: PMC10111279 DOI: 10.1016/j.bpj.2023.01.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 01/16/2023] [Accepted: 01/20/2023] [Indexed: 01/26/2023] Open
Abstract
The triple glutamine (Q) mutant (QQQ) structure of a Cl-/H+ antiporter from Escherichia coli (ClC-ec1) displaying a novel backbone arrangement has been used to challenge the long-held notion that Cl-/H+ antiporters do not operate through large conformational motions. The QQQ mutant substitutes the glutamine residue for an external glutamate E148, an internal glutamate E203, and a third glutamate E113 that hydrogen-bonds with E203. However, it is unknown if QQQ represents a physiologically relevant state, as well as how the protonation of the wild-type glutamates relates to the global dynamics. We herein apply continuous constant-pH molecular dynamics to investigate the H+-coupled dynamics of ClC-ec1. Although any large-scale conformational rearrangement upon acidification would be due to the accumulation of excess charge within the protein, protonation of the glutamates significantly impacts mainly the local structure and dynamics. Despite the fact that the extracellular pore enlarges at acidic pHs, an occluded ClC-ec1 within the active pH range of 3.5-7.5 requires a protonated E148 to facilitate extracellular Cl- release. E203 is also involved in the intracellular H+ transfer as an H+ acceptor. The water wire connection of E148 with the intracellular solution is regulated by the charge states of the E113/E203 dyad with coupled proton titration. However, the dynamics extracted from our simulations are not QQQ-like, indicating that the QQQ mutant does not represent the behavior of the wild-type ClC-ec1. These findings reinforce the necessity of having a protonatable residue at the E203 position in ClC-ec1 and suggest that a higher level of complexity exists for the intracellular H+ transfer in Cl-/H+ antiporters.
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Affiliation(s)
- Zhi Yue
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois
| | - Chenghan Li
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois.
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6
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Electron transfer in protein modifications: from detection to imaging. Sci China Chem 2023. [DOI: 10.1007/s11426-022-1417-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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7
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A century of exercise physiology: key concepts in muscle energetics. Eur J Appl Physiol 2023; 123:25-42. [PMID: 36271943 DOI: 10.1007/s00421-022-05070-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/07/2022] [Indexed: 01/07/2023]
Abstract
In the mid-nineteenth century, the concept of muscle behaving like a stretched spring was developed. This elastic model of contraction predicted that the energy available to perform work was established at the start of a contraction. Despite several studies showing evidence inconsistent with the elastic model, it persisted into the twentieth century. In 1923, W. O. Fenn published a paper in which he presented evidence that appeared to clearly refute the elastic model. Fenn showed that when a muscle performs work it produces more heat than when contracting isometrically. He proposed that energy for performing work was only made available in a muscle as and when that work was performed. However, his ideas were not adopted and it was only after 15 years of technical developments that in 1938 A. V. Hill performed experiments that conclusively disproved the elastic model and supported Fenn's conclusions. Hill showed that the rate of heat production increased as a muscle made the transition from isometric to working contraction. Understanding the basis of the phenomenon observed by Fenn and Hill required another 40 years in which the processes that generate force and work in muscle and the associated scheme of biochemical reactions were established. Demonstration of the biochemical equivalent of Hill's observations-changes in rate of ATP splitting when performing work-in 1999 was possible through further technical advances. The concept that the energy, from ATP splitting, required to perform work is dynamically modulated in accord with the loads a muscle encounters when contracting is key to understanding muscle energetics.
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8
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Tracing the lactate shuttle to the mitochondrial reticulum. EXPERIMENTAL & MOLECULAR MEDICINE 2022; 54:1332-1347. [PMID: 36075947 PMCID: PMC9534995 DOI: 10.1038/s12276-022-00802-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 01/02/2022] [Accepted: 01/05/2022] [Indexed: 11/10/2022]
Abstract
Isotope tracer infusion studies employing lactate, glucose, glycerol, and fatty acid isotope tracers were central to the deduction and demonstration of the Lactate Shuttle at the whole-body level. In concert with the ability to perform tissue metabolite concentration measurements, as well as determinations of unidirectional and net metabolite exchanges by means of arterial–venous difference (a-v) and blood flow measurements across tissue beds including skeletal muscle, the heart and the brain, lactate shuttling within organs and tissues was made evident. From an extensive body of work on men and women, resting or exercising, before or after endurance training, at sea level or high altitude, we now know that Organ–Organ, Cell–Cell, and Intracellular Lactate Shuttles operate continuously. By means of lactate shuttling, fuel-energy substrates can be exchanged between producer (driver) cells, such as those in skeletal muscle, and consumer (recipient) cells, such as those in the brain, heart, muscle, liver and kidneys. Within tissues, lactate can be exchanged between white and red fibers within a muscle bed and between astrocytes and neurons in the brain. Within cells, lactate can be exchanged between the cytosol and mitochondria and between the cytosol and peroxisomes. Lactate shuttling between driver and recipient cells depends on concentration gradients created by the mitochondrial respiratory apparatus in recipient cells for oxidative disposal of lactate. Studies using isotope tracer technologies have significantly improved understanding of how lactate, a metabolite produced as fuel during normal metabolism and in response to exercise, moves or ‘shuttles’ throughout the body. George Brooks and colleagues at the University of California, Berkeley, USA, reviewed the history of the understanding of lactate shuttling, which has largely been informed by human studies using isotope tracer infusions during rest and exercise. Such research highlights continuous organ–organ, cell–cell, and intracellular lactate shuttling. Lactate moves between producer cells such as skeletal muscle cells and consumer cells in tissues including the heart and brain, where it is preferred over glucose as an energy source. Shuttling depends on lactate concentration gradients created by mitochondrial networks in recipient cells. Lactate is disposed of via oxidation.
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9
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Barclay CJ, Curtin NA. The legacy of A. V. Hill's Nobel Prize winning work on muscle energetics. J Physiol 2022; 600:1555-1578. [PMID: 35114037 PMCID: PMC9304278 DOI: 10.1113/jp281556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 01/24/2022] [Indexed: 11/08/2022] Open
Abstract
A. V. Hill was awarded the 1922 Nobel Prize, jointly with Otto Meyerhof, for Physiology or Medicine for his work on energetic aspects of muscle contraction. Hill used his considerable mathematical and experimental skills to investigate the relationships among muscle mechanics, biochemistry and heat production. The main ideas of the work for which the Nobel Prize was awarded were superseded within a decade and the legacy of Hill and Meyerhof's Nobel work was not a set of persistent, influential ideas but rather was a prolonged period of extraordinary activity that advanced the understanding of how muscles work far beyond the concepts that led to the Nobel Prize. Hill pioneered the integration of mathematics into the study of physiology and pharmacology. Particular aspects of Hill's own work that remain in common use in muscle physiology include mathematical descriptions of the relationships between muscle force output and shortening velocity and between force output and calcium concentration and the model of muscle as a contractile element in series with an elastic element. We describe some of the characteristics of Hill's broader scientific activities and then outline how Hill's work on muscle energetics was extended after 1922, as a result of Hill's own work and that of others, to the present day. Abstract figure legend. A. V. Hill's scientific legacy. Vertical from the base. A. V. Hill (pictured) and his colleague Otto Meyerhof shared the 1922 Nobel Prize for Physiology or Medicine. Seven enduring elements of Hill's legacy to muscle physiology are shown. Arrows link concepts and approaches to related disciplines where they have been foundational and highly influential. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- C J Barclay
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia
| | - N A Curtin
- Cardio-Respiratory Interface, NHLI, Imperial College London, London, SW7 2AZ, UK
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10
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Sato Y, Takinoue M. Capsule-like DNA Hydrogels with Patterns Formed by Lateral Phase Separation of DNA Nanostructures. JACS AU 2022; 2:159-168. [PMID: 35098232 PMCID: PMC8790810 DOI: 10.1021/jacsau.1c00450] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Indexed: 05/03/2023]
Abstract
Phase separation is a key phenomenon in artificial cell construction. Recent studies have shown that the liquid-liquid phase separation of designed-DNA nanostructures induces the formation of liquid-like condensates that eventually become hydrogels by lowering the solution temperature. As a compartmental capsule is an essential artificial cell structure, many studies have focused on the lateral phase separation of artificial lipid vesicles. However, controlling phase separation using a molecular design approach remains challenging. Here, we present the lateral liquid-liquid phase separation of DNA nanostructures that leads to the formation of phase-separated capsule-like hydrogels. We designed three types of DNA nanostructures (two orthogonal and a linker nanostructure) that were adsorbed onto an interface of water-in-oil (W/O) droplets via electrostatic interactions. The phase separation of DNA nanostructures led to the formation of hydrogels with bicontinuous, patch, and mix patterns, due to the immiscibility of liquid-like DNA during the self-assembly process. The frequency of appearance of these patterns was altered by designing DNA sequences and altering the mixing ratio of the nanostructures. We constructed a phase diagram for the capsule-like DNA hydrogels by investigating pattern formation under various conditions. The phase-separated DNA hydrogels did not only form on the W/O droplet interface but also on the inner leaflet of lipid vesicles. Notably, the capsule-like hydrogels were extracted into an aqueous solution, maintaining the patterns formed by the lateral phase separation. In addition, the extracted hydrogels were successfully combined with enzymatic reactions, which induced their degradation. Our results provide a method for the design and control of phase-separated hydrogel capsules using sequence-designed DNAs. We envision that by incorporating various DNA nanodevices into DNA hydrogel capsules, the capsules will gain molecular sensing, chemical-information processing, and mechanochemical actuating functions, allowing the construction of functional molecular systems.
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Affiliation(s)
- Yusuke Sato
- Frontier
Research Institute for Interdisciplinary Sciences, Tohoku University, Miyagi 980-8579, Japan
- Department
of Computer Science, Tokyo Institute of
Technology, Kanagawa 226-8502, Japan
| | - Masahiro Takinoue
- Department
of Computer Science, Tokyo Institute of
Technology, Kanagawa 226-8502, Japan
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11
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Garcia CK, Renteria LI, Leite-Santos G, Leon LR, Laitano O. Exertional heat stroke: pathophysiology and risk factors. BMJ MEDICINE 2022; 1:e000239. [PMID: 36936589 PMCID: PMC9978764 DOI: 10.1136/bmjmed-2022-000239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 09/06/2022] [Indexed: 12/31/2022]
Abstract
Exertional heat stroke, the third leading cause of mortality in athletes during physical activity, is the most severe manifestation of exertional heat illnesses. Exertional heat stroke is characterised by central nervous system dysfunction in people with hyperthermia during physical activity and can be influenced by environmental factors such as heatwaves, which extend the incidence of exertional heat stroke beyond athletics only. Epidemiological data indicate mortality rates of about 27%, and survivors display long term negative health consequences ranging from neurological to cardiovascular dysfunction. The pathophysiology of exertional heat stroke involves thermoregulatory and cardiovascular overload, resulting in severe hyperthermia and subsequent multiorgan injury due to a systemic inflammatory response syndrome and coagulopathy. Research about risk factors for exertional heat stroke remains limited, but dehydration, sex differences, ageing, body composition, and previous illness are thought to increase risk. Immediate cooling remains the most effective treatment strategy. In this review, we provide an overview of the current literature emphasising the pathophysiology and risk factors of exertional heat stroke, highlighting gaps in knowledge with the objective to stimulate future research.
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Affiliation(s)
- Christian K Garcia
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Liliana I Renteria
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL, USA
| | - Gabriel Leite-Santos
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL, USA
| | - Lisa R Leon
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Orlando Laitano
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
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12
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Laitano O, Oki K, Leon LR. The Role of Skeletal Muscles in Exertional Heat Stroke Pathophysiology. Int J Sports Med 2021; 42:673-681. [PMID: 33772503 DOI: 10.1055/a-1400-9754] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The active participation of skeletal muscles is a unique characteristic of exertional heat stroke. Nevertheless, the only well-documented link between skeletal muscle activities and exertional heat stroke pathophysiology is the extensive muscle damage (e. g., rhabdomyolysis) and subsequent leakage of intramuscular content into the circulation of exertional heat stroke victims. Here, we will present and discuss rarely explored roles of skeletal muscles in the context of exertional heat stroke pathophysiology and recovery. This includes an overview of heat production that contributes to severe hyperthermia and the synthesis and secretion of bioactive molecules, such as cytokines, chemokines and acute phase proteins. These molecules can alter the overall inflammatory status from pro- to anti-inflammatory, affecting other organ systems and influencing recovery. The activation of innate immunity can determine whether a victim is ready to return to physical activity or experiences a prolonged convalescence. We also provide a brief discussion on whether heat acclimation can shift skeletal muscle secretory phenotype to prevent or aid recovery from exertional heat stroke. We conclude that skeletal muscles should be considered as a key organ system in exertional heat stroke pathophysiology.
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Affiliation(s)
- Orlando Laitano
- Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, United States
| | - Kentaro Oki
- Thermal & Mountain Medicine Devision, United States Army Research Institute of Environmental Medicine, Natick, United States
| | - Lisa R Leon
- Thermal & Mountain Medicine Devision, United States Army Research Institute of Environmental Medicine, Natick, United States
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13
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Poole DC, Rossiter HB, Brooks GA, Gladden LB. The anaerobic threshold: 50+ years of controversy. J Physiol 2020; 599:737-767. [PMID: 33112439 DOI: 10.1113/jp279963] [Citation(s) in RCA: 138] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 10/16/2020] [Indexed: 12/23/2022] Open
Abstract
The anaerobic threshold (AT) remains a widely recognized, and contentious, concept in exercise physiology and medicine. As conceived by Karlman Wasserman, the AT coalesced the increase of blood lactate concentration ([La- ]), during a progressive exercise test, with an excess pulmonary carbon dioxide output ( V ̇ C O 2 ). Its principal tenets were: limiting oxygen (O2 ) delivery to exercising muscle→increased glycolysis, La- and H+ production→decreased muscle and blood pH→with increased H+ buffered by blood [HCO3 - ]→increased CO2 release from blood→increased V ̇ C O 2 and pulmonary ventilation. This schema stimulated scientific scrutiny which challenged the fundamental premise that muscle anoxia was requisite for increased muscle and blood [La- ]. It is now recognized that insufficient O2 is not the primary basis for lactataemia. Increased production and utilization of La- represent the response to increased glycolytic flux elicited by increasing work rate, and determine the oxygen uptake ( V ̇ O 2 ) at which La- accumulates in the arterial blood (the lactate threshold; LT). However, the threshold for a sustained non-oxidative contribution to exercise energetics is the critical power, which occurs at a metabolic rate often far above the LT and separates heavy from very heavy/severe-intensity exercise. Lactate is now appreciated as a crucial energy source, major gluconeogenic precursor and signalling molecule but there is no ipso facto evidence for muscle dysoxia or anoxia. Non-invasive estimation of LT using the gas exchange threshold (non-linear increase of V ̇ C O 2 versus V ̇ O 2 ) remains important in exercise training and in the clinic, but its conceptual basis should now be understood in light of lactate shuttle biology.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, and The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - George A Brooks
- Department of Integrative Biology, Exercise Physiology Laboratory, University of California, Berkeley, CA, USA
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14
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Bayer P, Matena A, Beuck C. NMR Spectroscopy of supramolecular chemistry on protein surfaces. Beilstein J Org Chem 2020; 16:2505-2522. [PMID: 33093929 PMCID: PMC7554676 DOI: 10.3762/bjoc.16.203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 09/18/2020] [Indexed: 01/17/2023] Open
Abstract
As one of the few analytical methods that offer atomic resolution, NMR spectroscopy is a valuable tool to study the interaction of proteins with their interaction partners, both biomolecules and synthetic ligands. In recent years, the focus in chemistry has kept expanding from targeting small binding pockets in proteins to recognizing patches on protein surfaces, mostly via supramolecular chemistry, with the goal to modulate protein–protein interactions. Here we present NMR methods that have been applied to characterize these molecular interactions and discuss the challenges of this endeavor.
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Affiliation(s)
- Peter Bayer
- Structural and Medicinal Biochemistry, University of Duisburg-Essen, Universitätsstr. 1-5, 45141 Essen, Germany
| | - Anja Matena
- Structural and Medicinal Biochemistry, University of Duisburg-Essen, Universitätsstr. 1-5, 45141 Essen, Germany
| | - Christine Beuck
- Structural and Medicinal Biochemistry, University of Duisburg-Essen, Universitätsstr. 1-5, 45141 Essen, Germany
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Thompson AJ, Marks LH, Goudie MJ, Rojas-Pena A, Handa H, Potkay JA. A small-scale, rolled-membrane microfluidic artificial lung designed towards future large area manufacturing. BIOMICROFLUIDICS 2017; 11:024113. [PMID: 28798849 PMCID: PMC5533476 DOI: 10.1063/1.4979676] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 03/22/2017] [Indexed: 05/22/2023]
Abstract
Artificial lungs have been used in the clinic for multiple decades to supplement patient pulmonary function. Recently, small-scale microfluidic artificial lungs (μAL) have been demonstrated with large surface area to blood volume ratios, biomimetic blood flow paths, and pressure drops compatible with pumpless operation. Initial small-scale microfluidic devices with blood flow rates in the μl/min to ml/min range have exhibited excellent gas transfer efficiencies; however, current manufacturing techniques may not be suitable for scaling up to human applications. Here, we present a new manufacturing technology for a microfluidic artificial lung in which the structure is assembled via a continuous "rolling" and bonding procedure from a single, patterned layer of polydimethyl siloxane (PDMS). This method is demonstrated in a small-scale four-layer device, but is expected to easily scale to larger area devices. The presented devices have a biomimetic branching blood flow network, 10 μm tall artificial capillaries, and a 66 μm thick gas transfer membrane. Gas transfer efficiency in blood was evaluated over a range of blood flow rates (0.1-1.25 ml/min) for two different sweep gases (pure O2, atmospheric air). The achieved gas transfer data closely follow predicted theoretical values for oxygenation and CO2 removal, while pressure drop is marginally higher than predicted. This work is the first step in developing a scalable method for creating large area microfluidic artificial lungs. Although designed for microfluidic artificial lungs, the presented technique is expected to result in the first manufacturing method capable of simply and easily creating large area microfluidic devices from PDMS.
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Affiliation(s)
| | - L H Marks
- VA Ann Arbor Healthcare System, Ann Arbor, Michigan 48105, USA
| | - M J Goudie
- College of Engineering, University of Georgia, Athens, Georgia 30602, USA
| | - A Rojas-Pena
- Department of Surgery, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - H Handa
- College of Engineering, University of Georgia, Athens, Georgia 30602, USA
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In-depth neuropharmacokinetic analysis of antipsychotics based on a novel approach to estimate unbound target-site concentration in CNS regions: link to spatial receptor occupancy. Mol Psychiatry 2016; 21:1527-1536. [PMID: 26809840 DOI: 10.1038/mp.2015.229] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 11/30/2015] [Accepted: 12/15/2015] [Indexed: 12/24/2022]
Abstract
The current study provides a novel in-depth assessment of the extent of antipsychotic drugs transport across the blood-brain barrier (BBB) into various brain regions, as well as across the blood-spinal cord barrier (BSCB) and the blood-cerebrospinal fluid barrier (BCSFB). This is combined with an estimation of cellular barrier transport and a systematic evaluation of nonspecific brain tissue binding. The study is based on the new Combinatory Mapping Approach (CMA), here further developed for the assessment of unbound drug neuropharmacokinetics in regions of interest (ROI), referred as CMA-ROI. We show that differences exist between regions in both BBB transport and in brain tissue binding. The most dramatic spatial differences in BBB transport were found for the P-glycoprotein substrates risperidone (5.4-fold) and paliperidone (4-fold). A higher level of transporter-mediated protection was observed in the cerebellum compared with other brain regions with a more pronounced efflux for quetiapine, risperidone and paliperidone. The highest BBB penetration was documented in the frontal cortex, striatum and hippocampus (haloperidol, olanzapine), indicating potential influx mechanisms. BSCB transport was in general characterized by more efficient efflux compared with the brain regions. Regional tissue binding was significantly different for haloperidol, clozapine, risperidone and quetiapine (maximally 1.9-fold). Spatial differences in local unbound concentrations were found to significantly influence cortical 5-HT2A receptor occupancy for risperidone and olanzapine. In conclusion, the observed regional differences in BBB penetration may potentially be important factors contributing to variations in therapeutic effect and side effect profiles among antipsychotic drugs.
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Soltesz K, Sturk C, Paskevicius A, Liao Q, Qin G, Sjoberg T, Steen S. Closed-Loop Prevention of Hypotension in the Heartbeating Brain-Dead Porcine Model. IEEE Trans Biomed Eng 2016; 64:1310-1317. [PMID: 27576237 DOI: 10.1109/tbme.2016.2602228] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Objective: The purpose of this paper is to demonstrate feasibility of a novel closed-loop controlled therapy for prevention of hypertension in the heartbeating brain-dead porcine model. METHODS Dynamic modeling and system identification were based on in vivo data. A robust controller design was obtained for the identified models. Disturbance attenuation properties and reliability of operation of the resulting control system were evaluated in vivo. RESULTS The control system responded both predictably and consistently to external disturbances. It was possible to prevent mean arterial pressure to fall below a user-specified reference throughout 24 h of completely autonomous operation. CONCLUSION Parameter variability in the identified models confirmed the benefit of closed-loop controlled administration of the proposed therapy. The evaluated robust controller was able to mitigate both process uncertainty and external disturbances. SIGNIFICANCE Prevention of hypertension is critical to the care of heartbeating brain-dead organ donors. Its automation would likely increase the fraction of organs suitable for transplantation from this patient group.
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Singh AK, Sen N, Chatterjee SK, Susan MABH. Kinetic study of oxidation of paracetamol by water-soluble colloidal MnO2 in the presence of an anionic surfactant. Colloid Polym Sci 2016. [DOI: 10.1007/s00396-016-3921-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Gorecki J, Gorecka JN, Nowakowski B, Ueno H, Yoshikawa K. How many enzyme molecules are needed for discrimination oriented applications? Phys Chem Chem Phys 2016; 18:20518-27. [PMID: 27405538 DOI: 10.1039/c6cp03860c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chemical reactions establish a molecular mechanism for information processing in living organisms. Here we consider a simple enzymatic reaction model that can be used to discriminate parameters characterizing periodic reagent inflow. Numerical simulations based on the kinetic equations show that there exist a range of inflow frequencies and amplitudes in which the time evolution of the system is very sensitive to small changes in the values of these parameters. However, the kinetic equations are derived for the thermodynamic limit, whereas in a real biological medium, like a cell, the number of enzyme molecules is an integer and finite. We use stochastic simulations to estimate discriminator reliability as a function of the number of enzyme molecules involved. For systems with 10 000 molecules the functionality predicted by kinetic equations is confirmed. If the number of molecules is decreased to 100, discrimination becomes unreliable.
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Affiliation(s)
- Jerzy Gorecki
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
| | - Joanna N Gorecka
- Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Bogdan Nowakowski
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland. and SGGW, Warsaw University of Life Sciences, Nowoursynowska 159, 02-776 Warsaw, Poland
| | - Hiroshi Ueno
- Faculty of Life and Medical Sciences, Doshisha University, Kyoto 610-0394, Japan
| | - Kenichi Yoshikawa
- Faculty of Life and Medical Sciences, Doshisha University, Kyoto 610-0394, Japan
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Singh AK, Sen N, Chatterjee SK, Singh NP. Micelle Catalyzed Oxidative Degradation of Paracetamol by Water Soluble Colloidal MnO2 in Acidic Medium. TENSIDE SURFACT DET 2016. [DOI: 10.3139/113.110436] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AbstractThe catalytic effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the MnO2-paracetamol (PCM) redox reaction has been examined spectrophotometrically in acidic medium at 298 K. The reaction demonstrates that the stoichiometric ratio of MnO2 and PCM is 1 : 1. The reaction exhibited first order kinetics with respect to [MnO2] and [PCM] but a negative fractional order was observed with respect to [H2SO4]. Various effects such as ionic strength, dielectric constant, [Mn(II)], [salts] and temperature have been studied. The catalytic effect of CTAB has been treated quantitatively by the well known Menger Portnoy and Piszkiewicz model. The values of binding constant (Ks), rate constant in the micellar phase (km), cooperativity index (n) and dissociation constant (KD) have also been calculated. From the several observations, a reaction mechanism has been proposed and the rate law has been derived. Applying the Arrhenius equation, various thermodynamic activation parameters have also been evaluated.
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Affiliation(s)
- Ajaya Kumar Singh
- 1Department of Chemistry, Govt.V.Y.T.PG. Auto. College Durg, Chhattisgarh, 491001, India
| | - Neelam Sen
- 1Department of Chemistry, Govt.V.Y.T.PG. Auto. College Durg, Chhattisgarh, 491001, India
| | - Som Kumar Chatterjee
- 2Department of Chemistry, N.R.M. Govt.Girls College Dhamtari, Chhattisgarh, 493773, India
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Indices of central aortic pressure waveform and ventricular function: an intimate conversation changing direction with age. J Hypertens 2016; 34:634-6. [PMID: 26934031 DOI: 10.1097/hjh.0000000000000883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Alcaraz A, Queralt-Martín M. On the different sources of cooperativity in pH titrating sites of a membrane protein channel. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2016; 39:29. [PMID: 26987733 PMCID: PMC7087919 DOI: 10.1140/epje/i2016-16029-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 01/06/2016] [Indexed: 06/05/2023]
Abstract
Cooperative interactions play a central role in the regulation of protein functions. Here we show that in multi-site systems like ion channels the application of the Hill formalism could require a combination of different experiments, even involving site-directed mutagenesis, to identify the different sources of cooperativity and to discriminate between genuine and apparent cooperativity. We discuss the implications for the channel function in the bacterial porins PorA (N. meningitidis) and OmpF (E. coli) and the viroporin SARS-CoV E.
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Affiliation(s)
- Antonio Alcaraz
- Department of Physics, Laboratory of Molecular Biophysics, Universitat Jaume I, 12080, Castellón, Spain.
| | - María Queralt-Martín
- Department of Physics, Laboratory of Molecular Biophysics, Universitat Jaume I, 12080, Castellón, Spain
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23
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Loiselle DS, Johnston CM, Han JC, Nielsen PMF, Taberner AJ. Muscle heat: a window into the thermodynamics of a molecular machine. Am J Physiol Heart Circ Physiol 2015; 310:H311-25. [PMID: 26589327 DOI: 10.1152/ajpheart.00569.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/10/2015] [Indexed: 11/22/2022]
Abstract
The contraction of muscle is characterized by the development of force and movement (mechanics) together with the generation of heat (metabolism). Heat represents that component of the enthalpy of ATP hydrolysis that is not captured by the microscopic machinery of the cell for the performance of work. It arises from two conceptually and temporally distinct sources: initial metabolism and recovery metabolism. Initial metabolism comprises the hydrolysis of ATP and its rapid regeneration by hydrolysis of phosphocreatine (PCr) in the processes underlying excitation-contraction coupling and subsequent cross-bridge cycling and sliding of the contractile filaments. Recovery metabolism describes those process, both aerobic (mitochondrial) and anaerobic (cytoplasmic), that produce ATP, thereby allowing the regeneration of PCr from its hydrolysis products. An equivalent partitioning of muscle heat production is often invoked by muscle physiologists. In this formulation, total enthalpy expenditure is separated into external mechanical work (W) and heat (Q). Heat is again partitioned into three conceptually distinct components: basal, activation, and force dependent. In the following mini-review, we trace the development of these ideas in parallel with the development of measurement techniques for separating the various thermal components.
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Affiliation(s)
- Denis Scott Loiselle
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand; Department of Physiology, The University of Auckland, Auckland, New Zealand
| | | | - June-Chiew Han
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Poul Michael Fønss Nielsen
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand; Department of Engineering Science, The University of Auckland, Auckland, New Zealand; and
| | - Andrew James Taberner
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand; Department of Engineering Science, The University of Auckland, Auckland, New Zealand; and
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Mizeranschi A, Zheng H, Thompson P, Dubitzky W. Evaluating a common semi-mechanistic mathematical model of gene-regulatory networks. BMC SYSTEMS BIOLOGY 2015; 9 Suppl 5:S2. [PMID: 26356485 PMCID: PMC4565562 DOI: 10.1186/1752-0509-9-s5-s2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Modeling and simulation of gene-regulatory networks (GRNs) has become an important aspect of modern systems biology investigations into mechanisms underlying gene regulation. A key challenge in this area is the automated inference (reverse-engineering) of dynamic, mechanistic GRN models from gene expression time-course data. Common mathematical formalisms for representing such models capture two aspects simultaneously within a single parameter: (1) Whether or not a gene is regulated, and if so, the type of regulator (activator or repressor), and (2) the strength of influence of the regulator (if any) on the target or effector gene. To accommodate both roles, "generous" boundaries or limits for possible values of this parameter are commonly allowed in the reverse-engineering process. This approach has several important drawbacks. First, in the absence of good guidelines, there is no consensus on what limits are reasonable. Second, because the limits may vary greatly among different reverse-engineering experiments, the concrete values obtained for the models may differ considerably, and thus it is difficult to compare models. Third, if high values are chosen as limits, the search space of the model inference process becomes very large, adding unnecessary computational load to the already complex reverse-engineering process. In this study, we demonstrate that restricting the limits to the [−1, +1] interval is sufficient to represent the essential features of GRN systems and offers a reduction of the search space without loss of quality in the resulting models. To show this, we have carried out reverse-engineering studies on data generated from artificial and experimentally determined from real GRN systems.
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25
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Jeong JE, Kim B, Woo S, Hwang S, Bazan GC, Woo HY. Principal factors that determine the extension of detection range in molecular beacon aptamer/conjugated polyelectrolyte bioassays. Chem Sci 2015; 6:1887-1894. [PMID: 28706644 PMCID: PMC5494547 DOI: 10.1039/c4sc03258f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 12/22/2014] [Indexed: 01/09/2023] Open
Abstract
A strategy to extend the detection range of weakly-binding targets is reported that takes advantage of fluorescence resonance energy transfer (FRET)-based bioassays based on molecular beacon aptamers (MBAs) and cationic conjugated polyelectrolytes (CPEs). In comparison to other aptamer-target pairs, the aptamer-based adenosine triphosphate (ATP) detection assays are limited by the relatively weak binding between the two partners. In response, a series of MBAs were designed that have different stem stabilities while keeping the constant ATP-specific aptamer sequence in the loop part. The MBAs are labeled with a fluorophore and a quencher at both termini. In the absence of ATP, the hairpin MBAs can be opened by CPEs via a combination of electrostatic and hydrophobic interactions, showing a FRET-sensitized fluorophore signal. In the presence of ATP, the aptamer forms a G-quadruplex and the FRET signal decreases due to tighter contact between the fluorophore and quencher in the ATP/MBA/CPE triplex structure. The FRET-sensitized signal is inversely proportional to [ATP]. The extension of the detection range is determined by the competition between opening of the ATP/MBA G-quadruplex by CPEs and the composite influence by ATP/aptamer binding and the stem interactions. With increasing stem stability, the weak binding of ATP and its aptamer is successfully compensated to show the resistance to disruption by CPEs, resulting in a substantially broadened detection range (from millimolar up to nanomolar concentrations) and a remarkably improved limit of detection. From a general perspective, this strategy has the potential to be extended to other chemical- and biological-assays with low target binding affinity.
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Affiliation(s)
- Ji-Eun Jeong
- Department of Nanofusion Engineering , Department of Cogno-Mechatronics Engineering , Pusan National University , Miryang , Gyeongsangnam-do 627-706 , Republic of Korea .
| | - Boram Kim
- Department of Nanofusion Engineering , Department of Cogno-Mechatronics Engineering , Pusan National University , Miryang , Gyeongsangnam-do 627-706 , Republic of Korea .
| | - Shinjae Woo
- Department of Nanofusion Engineering , Department of Cogno-Mechatronics Engineering , Pusan National University , Miryang , Gyeongsangnam-do 627-706 , Republic of Korea .
| | - Sungu Hwang
- Department of Nanomechatronics Engineering , Pusan National University , Miryang , Gyeongsangnam-do 627-706 , Republic of Korea
| | - Guillermo C Bazan
- Department of Chemistry & Biochemistry , University of California , Santa Barbara , California 93106 , USA .
| | - Han Young Woo
- Department of Nanofusion Engineering , Department of Cogno-Mechatronics Engineering , Pusan National University , Miryang , Gyeongsangnam-do 627-706 , Republic of Korea .
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27
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Schurr A. Cerebral glycolysis: a century of persistent misunderstanding and misconception. Front Neurosci 2014; 8:360. [PMID: 25477776 PMCID: PMC4237041 DOI: 10.3389/fnins.2014.00360] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 10/21/2014] [Indexed: 11/18/2022] Open
Abstract
Since its discovery in 1780, lactate (lactic acid) has been blamed for almost any illness outcome in which its levels are elevated. Beginning in the mid-1980s, studies on both muscle and brain tissues, have suggested that lactate plays a role in bioenergetics. However, great skepticism and, at times, outright antagonism has been exhibited by many to any perceived role for this monocarboxylate in energy metabolism. The present review attempts to trace the negative attitudes about lactate to the first four or five decades of research on carbohydrate metabolism and its dogma according to which lactate is a useless anaerobic end-product of glycolysis. The main thrust here is the review of dozens of scientific publications, many by the leading scientists of their times, through the first half of the twentieth century. Consequently, it is concluded that there exists a barrier, described by Howard Margolis as “habit of mind,” that many scientists find impossible to cross. The term suggests “entrenched responses that ordinarily occur without conscious attention and that, even if noticed, are hard to change.” Habit of mind has undoubtedly played a major role in the above mentioned negative attitudes toward lactate. As early as the 1920s, scientists investigating brain carbohydrate metabolism had discovered that lactate can be oxidized by brain tissue preparations, yet their own habit of mind redirected them to believe that such an oxidation is simply a disposal mechanism of this “poisonous” compound. The last section of the review invites the reader to consider a postulated alternative glycolytic pathway in cerebral and, possibly, in most other tissues, where no distinction is being made between aerobic and anaerobic glycolysis; lactate is always the glycolytic end product. Aerobically, lactate is readily shuttled and transported into the mitochondrion, where it is converted to pyruvate via a mitochondrial lactate dehydrogenase (mLDH) and then is entered the tricarboxylic acid (TCA) cycle.
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Affiliation(s)
- Avital Schurr
- Department of Anesthesiology and Perioperative Medicine, University of Louisville School of Medicine Louisville, KY, USA
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Miller J, Melicher MS, Schepartz A. Positive allostery in metal ion binding by a cooperatively folded β-peptide bundle. J Am Chem Soc 2014; 136:14726-9. [PMID: 25290247 PMCID: PMC4210112 DOI: 10.1021/ja508872q] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Indexed: 01/19/2023]
Abstract
Metal ion binding is exploited by proteins in nature to catalyze reactions, bind molecules, and favor discrete structures, but it has not been demonstrated in β-peptides or their assemblies. Here we report the design, synthesis, and characterization of a β-peptide bundle that uniquely binds two Cd(II) ions in a distinct bicoordinate array. The two Cd(II) ions bind with positive allosteric cooperativity and increase the thermodynamic stability of the bundle by more than 50 °C. This system provides a unique, synthetic context to explore allosteric regulation and should pave the way to sophisticated molecular assemblies with catalytic and substrate-sensing functions that have historically not been available to de novo designed synthetic proteomimetics in water.
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Affiliation(s)
- Jonathan
P. Miller
- Department
of Chemistry and Department of Molecular, Cellular and Developmental
Biology, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Michael S. Melicher
- Department
of Chemistry and Department of Molecular, Cellular and Developmental
Biology, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Alanna Schepartz
- Department
of Chemistry and Department of Molecular, Cellular and Developmental
Biology, Yale University, New Haven, Connecticut 06520-8107, United States
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Novel 2,2′-bipyridine palladium(II) complexes with glycine derivatives: synthesis, characterization, cytotoxic assays and DNA-binding studies. JOURNAL OF THE IRANIAN CHEMICAL SOCIETY 2013. [DOI: 10.1007/s13738-013-0237-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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31
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Ackermann E, Weiel EM, Pfaff T, Drossel B. Boolean versus continuous dynamics in modules with two feedback loops. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2012; 35:107. [PMID: 23096153 DOI: 10.1140/epje/i2012-12107-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/20/2012] [Accepted: 09/26/2012] [Indexed: 06/01/2023]
Abstract
We investigate the dynamical behavior of simple networks, namely loops with an additional internal regulating connection. Continuous dynamics for mRNA and protein concentrations is compared to a Boolean model for gene activity. Using a generalized method and within a single framework, we study different continuous models and different types of regulatory functions, and establish conditions under which the system can display stable oscillations or stable fixed points. These conditions depend only on general features such as the degree of cooperativity of the regulating interactions and the logical structure of the interactions. There are no simple rules for deciding when Boolean and continuous dynamics agree with each other, but we identify several relevant criteria.
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Affiliation(s)
- Eva Ackermann
- Institut für Festkörperphysik, TU Darmstadt, Hochschulstraße 6, 64289, Darmstadt, Germany.
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Shanmugarajan S, Beeson CC, Reddy SV. Osteoclast inhibitory peptide-1 binding to the Fc gammaRIIB inhibits osteoclast differentiation. Endocrinology 2010; 151:4389-99. [PMID: 20610564 PMCID: PMC2940506 DOI: 10.1210/en.2010-0244] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Osteoclast inhibitory peptide-1 (OIP) is an autocrine/paracrine inhibitor of osteoclast differentiation, and mice that overexpress OIP-1 in osteoclast lineage cells develop an osteopetrosis bone phenotype. In this study, we show that OIP-1 binding to the Fc gamma receptor IIB (Fc gammaRIIB) inhibits osteoclast differentiation. Confocal microscopy revealed colocalization of OIP-1 with Fc gammaRIIB in osteoclasts, and we observed that OIP-1 carboxy-terminal GPI-linked peptide forms a 1:1 complex with recombinant Fc gammaRIIB protein with an affinity binding of a dissociation constant of approximately 4 microm. Immunoreceptor tyrosine-based activation motif (ITAM)-bearing adapter proteins (FcR gamma and DNAX-activating protein of molecular mass 12 kDa) are critical for osteoclast development, and OIP-1 transgenic mouse-derived preosteoclast cells demonstrated suppression (6-fold) of ITAM phosphorylation of FcR gamma but not DNAX-activating protein of molecular mass 12 kDa. Interestingly, these preosteoclast cells demonstrated increased levels (4-fold) of immunoreceptor tyrosine-based inhibitory motif phosphorylation of Fc gammaRIIB and Src homology 2-domain-containing proteins tyrosine phosphatase 1 activation. Further, OIP-1 mouse-derived preosteoclasts cells demonstrated inhibition of spleen tyrosine kinase activation (4.5-fold), compared with wild-type mice. These results suggest that cross-regulation of immunoreceptor tyrosine-based inhibitory motif and ITAM bearing Fc receptors may play a role in OIP-1 suppression of spleen tyrosine kinase activation and inhibition of osteoclast differentiation. Thus, OIP-1 is an important physiologic regulator of osteoclast development and may have therapeutic utility for bone diseases with high bone turnover.
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Affiliation(s)
- Srinivasan Shanmugarajan
- Charles P. Darby Children's Research Institute, Medical University of South Carolina, 173 Ashley Avenue, Charleston, South Carolina 29425, USA
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Torres Martin de Rosales R, Faiella M, Farquhar E, Que L, Andreozzi C, Pavone V, Maglio O, Nastri F, Lombardi A. Spectroscopic and metal-binding properties of DF3: an artificial protein able to accommodate different metal ions. J Biol Inorg Chem 2010; 15:717-28. [PMID: 20225070 DOI: 10.1007/s00775-010-0639-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 02/14/2010] [Indexed: 10/19/2022]
Abstract
The design, synthesis, and metal-binding properties of DF3, a new de novo designed di-iron protein model are described ("DF" represents due ferri, Italian for "two iron," "di-iron"). DF3 is the latest member of the DF family of synthetic proteins. They consist of helix-loop-helix hairpins, designed to dimerize and form an antiparallel four-helix bundle that encompasses a metal-binding site similar to those of non-heme carboxylate-bridged di-iron proteins. Unlike previous DF proteins, DF3 is highly soluble in water (up to 3 mM) and forms stable complexes with several metal ions (Zn, Co, and Mn), with the desired secondary structure and the expected stoichiometry of two ions per protein. UV-vis studies of Co(II) and Fe(III) complexes confirm a metal-binding environment similar to previous di-Co(II)- and di-Fe(III)-DF proteins, including the presence of a mu-oxo-di-Fe(III) unit. Interestingly, UV-vis, EPR, and resonance Raman studies suggest the interaction of a tyrosine adjacent to the di-Fe(III) center. The design of DF3 was aimed at increasing the accessibility of small molecules to the active site of the four-helix bundle. Indeed, binding of azide to the di-Fe(III) site demonstrates a more accessible metal site compared with previous DFs. In fact, fitting of the binding curve to the Hill equation allows us to quantify a 150% accessibility enhancement, with respect to DF2. All these results represent a significant step towards the development of a functional synthetic DF metalloprotein.
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Direct observation of twisting steps during Rad51 polymerization on DNA. Proc Natl Acad Sci U S A 2009; 106:19239-44. [PMID: 19884492 DOI: 10.1073/pnas.0902234106] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The human recombinase hRad51 is a key protein for the maintenance of genome integrity and for cancer development. Polymerization and depolymerization of hRad51 on duplex DNA were studied here using a new generation of magnetic tweezers, measuring DNA twist in real time with a resolution of 5 degrees . Our results combined with earlier structural information suggest that DNA is somewhat less extended by hRad51 than by RecA (4.5 vs. 5.1 A per base pair) and untwisted by 18.2 degrees per base pair. They also confirm a stoichiometry of 3-4 bp per protein in the hRad51-dsDNA nucleoprotein filament. At odds with earlier claims, we show that after initial deposition of a multimeric nucleus, nucleoprotein filament growth occurs by addition/release of single proteins, involving DNA twisting steps of 65 degrees +/- 5 degrees. Simple numeric simulations show that this mechanism is an efficient way to minimize nucleoprotein filament defects. Nucleoprotein filament growth from a preformed nucleus was observed at hRad51 concentrations down to 10 nM, whereas nucleation was never observed below 100 nM in the same buffer. This behavior can be associated with the different stoichiometries of nucleation and growth. It may be instrumental in vivo to permit efficient continuation of strand exchange by hRad51 alone while requiring additional proteins such as Rad52 for its initiation, thus keeping the latter under the strict control of regulatory pathways.
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Pandey E, Upadhyay SK. Effect of micellar aggregates on the kinetics of oxidation of α-aminoacids by chloramine-T in perchloric acid medium. Colloids Surf A Physicochem Eng Asp 2005. [DOI: 10.1016/j.colsurfa.2005.05.029] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Murphy JC, Fox GE, Willson RC. Enhancement of anion-exchange chromatography of DNA using compaction agents. J Chromatogr A 2003; 984:215-21. [PMID: 12564692 DOI: 10.1016/s0021-9673(02)01814-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The use of adsorptive chromatography for preparative nucleic acid separations is often limited by low capacity. The possibility that the adsorbent surface area sterically accessible to nucleic acid molecules could be increased by reducing their radius of gyration with compaction agents has been investigated. The equilibrium adsorption capacity of Q Sepharose anion-exchange matrix for plasmid DNA at 600 mM NaCl was enhanced by up to ca. 40% in the presence of 2.5 mM spermine. In addition, compaction agent selectivity has been demonstrated. Spermine, for example, enhances the adsorption of both plasmid and genomic DNA, spermidine enhances binding only of plasmid, and hexamine cobalt enhances only the binding of genomic DNA. Compaction may be generally useful for enhancing adsorptive separations of nucleic acids.
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Affiliation(s)
- Jason C Murphy
- Department of Chemical Engineering, University of Houston, 4800 Calhoun Ave., Houston, TX 77004-4004, USA
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Abstract
Cooperativity, the departure from hyperbolic behaviour of the fractional saturation of a receptor at equilibrium (Y) for different values of ligand concentration (L), is an essential property of many physiological mechanisms and a first clue to the existence of conformational transitions and allosteric interactions. Here we investigate the properties of a simple and sensitive procedure to test and quantify cooperative behaviour. The measure of cooperativity involved is kappa = dK(L)/dL where K(L) = (1- Y) L/Y= [free sites]L/[occupied sites] is called the 'global dissociation quotient' Cooperative behaviour appears when kappa is not equal to 0, i.e., K(L) is a function of L. We have shown, for several equilibrium models of cooperative behaviour (e.g., Monod-Wyman-Changeux and Koshland-Némethy-Filmer), that K(L) can be expressed as the weighted average of the microscopic dissociation constants (K(i)) where the weights are the corresponding fractions of occupied sites (X(i)), K(L)= sigmaK(i)X(i). As a consequence, the change in the global dissociation quotient with ligand concentration for a dimer is kappa = (K1 - K2)dX1/dL. This result shows that the quantitative importance of a cooperative behaviour in a dimer depends on two factors: (i) the difference of the microscopic dissociation constants of the sites and (ii) the change in the fraction of occupied sites with ligand concentration. We analyze the generality of this unified view concluding that it would be fulfilled by every equilibrium model where there is a one-to-one relationship between free and occupied sites.
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Affiliation(s)
- L Acerenza
- Departamento de Biofísica, Facultad de Ciencias, Montevideo, Uruguay.
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Grady PG, Thomas LL. Characterization of cyclic-nucleotide phosphodiesterase activities in resting and N-formylmethionylleucylphenylalanine-stimulated human neutrophils. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 885:282-93. [PMID: 3004603 DOI: 10.1016/0167-4889(86)90243-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cyclic nucleotide phosphodiesterase activities in human neutrophils were characterized. Neutrophil sonicates exhibited high-affinity and low-affinity cAMP phosphodiesterase activities, with apparent Km values of 1.9 microM and 112 microM, respectively. No cGMP phosphodiesterase activity was detected. Approx. 70% of cAMP phosphodiesterase activity measured at 1 microM cAMP was present in the soluble subcellular fraction, and the remainder was localized in the particulate fraction. Chromatography of the soluble subcellular fraction on DE-52 ion-exchange resin yielded a low-affinity cAMP phosphodiesterase activity and a high-affinity cAMP phosphodiesterase activity. The soluble high-affinity cAMP phosphodiesterase activity exhibited moderate calmodulin sensitivity. After incubation of intact neutrophils with N-formylmethionylleucylphenylalanine (fMet-Leu-Phe), a 25-30% increase in the activity of the high-affinity cAMP phosphodiesterase activity was observed in the sonicate and in the soluble fraction. Maximal increases were achieved after 2 min of incubation and the increases persisted for at least 10 min. The increase in activity was independent of calmodulin and guanine nucleotide regulatory proteins. These results indicate that a soluble high-affinity cAMP phosphodiesterase comprises the majority of phosphodiesterase activity in neutrophils and that increases in this activity may contribute to the regulation of cAMP levels in neutrophils during activation.
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Abstract
Fat cells were preincubated for 2 h in the presence and absence of growth hormone (GH) and Dexamethasone (Dex) before the addition of increasing concentrations of either epinephrine, theophylline or glucagon and final incubation of the cells for an additional 5 minutes. GH and Dex increased by 85%, 28% and 72%, respectively, the cAMP levels reached in the sole presence of 10(-5)M epinephrine, 10(-2)M theophylline or 5 X 10(-5)M glucagon. An adenylate cyclase particulate preparation shows that epinephrine decreases Km from 2mM to 0.6 MM and increases Vmax and the strength of interaction value (n) from 0.91 to 1.75.
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Die Beziehungen zwischen der Wärmebildung und den im Muskel stattfindenden chemischen Prozessen. Rev Physiol Biochem Pharmacol 1916. [DOI: 10.1007/bf02355107] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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