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Metabolic flux between organs measured by arteriovenous metabolite gradients. EXPERIMENTAL & MOLECULAR MEDICINE 2022; 54:1354-1366. [PMID: 36075951 PMCID: PMC9534916 DOI: 10.1038/s12276-022-00803-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/15/2022] [Accepted: 03/04/2022] [Indexed: 12/15/2022]
Abstract
Mammalian organs convert dietary nutrients into circulating metabolites and share them to maintain whole-body metabolic homeostasis. While the concentrations of circulating metabolites have been frequently measured in a variety of pathophysiological conditions, the exchange flux of circulating metabolites between organs is not easily measurable due to technical difficulties. Isotope tracing is useful for measuring such fluxes for a metabolite of interest, but the shuffling of isotopic atoms between metabolites requires mathematical modeling. Arteriovenous metabolite gradient measurements can complement isotope tracing to infer organ-specific net fluxes of many metabolites simultaneously. Here, we review the historical development of arteriovenous measurements and discuss their advantages and limitations with key example studies that have revealed metabolite exchange flux between organs in diverse pathophysiological contexts.
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Colburn TD, Weber RE, Hageman KS, Caldwell JT, Schulze KM, Ade CJ, Behnke BJ, Poole DC, Musch TI. Vascular ATP-sensitive K + channels support maximal aerobic capacity and critical speed via convective and diffusive O 2 transport. J Physiol 2020; 598:4843-4858. [PMID: 32798233 PMCID: PMC7874302 DOI: 10.1113/jp280232] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 08/13/2020] [Indexed: 12/26/2022] Open
Abstract
KEY POINTS Oral sulphonylureas, widely prescribed for diabetes, inhibit pancreatic ATP-sensitive K+ (KATP ) channels to increase insulin release. However, KATP channels are also located within vascular (endothelium and smooth muscle) and muscle (cardiac and skeletal) tissue. We evaluated left ventricular function at rest, maximal aerobic capacity ( V ̇ O2 max) and submaximal exercise tolerance (i.e. speed-duration relationship) during treadmill running in rats, before and after systemic KATP channel inhibition via glibenclamide. Glibenclamide impaired critical speed proportionally more than V ̇ O2 max but did not alter resting cardiac output. Vascular KATP channel function (topical glibenclamide superfused onto hindlimb skeletal muscle) resolved a decreased blood flow and interstitial PO2 during twitch contractions reflecting impaired O2 delivery-to-utilization matching. Our findings demonstrate that systemic KATP channel inhibition reduces V ̇ O2 max and critical speed during treadmill running in rats due, in part, to impaired convective and diffusive O2 delivery, and thus V ̇ O2 , especially within fast-twitch oxidative skeletal muscle. ABSTRACT Vascular ATP-sensitive K+ (KATP ) channels support skeletal muscle blood flow and microvascular oxygen delivery-to-utilization matching during exercise. However, oral sulphonylurea treatment for diabetes inhibits pancreatic KATP channels to enhance insulin release. Herein we tested the hypotheses that: i) systemic KATP channel inhibition via glibenclamide (GLI; 10 mg kg-1 i.p.) would decrease cardiac output at rest (echocardiography), maximal aerobic capacity ( V ̇ O2 max) and the speed-duration relationship (i.e. lower critical speed (CS)) during treadmill running; and ii) local KATP channel inhibition (5 mg kg-1 GLI superfusion) would decrease blood flow (15 µm microspheres), interstitial space oxygen pressures (PO2 is; phosphorescence quenching) and convective and diffusive O2 transport ( Q ̇ O2 and DO2 , respectively; Fick Principle and Law of Diffusion) in contracting fast-twitch oxidative mixed gastrocnemius muscle (MG: 9% type I+IIa fibres). At rest, GLI slowed left ventricular relaxation (2.11 ± 0.59 vs. 1.70 ± 0.23 cm s-1 ) and decreased heart rate (321 ± 23 vs. 304 ± 22 bpm, both P < 0.05) while cardiac output remained unaltered (219 ± 64 vs. 197 ± 39 ml min-1 , P > 0.05). During exercise, GLI reduced V ̇ O2 max (71.5 ± 3.1 vs. 67.9 ± 4.8 ml kg-1 min-1 ) and CS (35.9 ± 2.4 vs. 31.9 ± 3.1 m min-1 , both P < 0.05). Local KATP channel inhibition decreased MG blood flow (52 ± 25 vs. 34 ± 13 ml min-1 100 g tissue-1 ) and PO2 isnadir (5.9 ± 0.9 vs. 4.7 ± 1.1 mmHg) during twitch contractions. Furthermore, MG V ̇ O2 was reduced via impaired Q ̇ O2 and DO2 (P < 0.05 for each). Collectively, these data support that vascular KATP channels help sustain submaximal exercise tolerance in healthy rats. For patients taking sulfonylureas, KATP channel inhibition may exacerbate exercise intolerance.
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Affiliation(s)
- Trenton D Colburn
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Ramona E Weber
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
| | - K Sue Hageman
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Jacob T Caldwell
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Kiana M Schulze
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Carl J Ade
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Brad J Behnke
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
| | - David C Poole
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Timothy I Musch
- Department of Kinesiology, Kansas State University, Manhattan, KS, 66506, USA
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
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Lanctôt CM, Al-Sid-Cheikh M, Catarino AI, Cresswell T, Danis B, Karapanagioti HK, Mincer T, Oberhänsli F, Swarzenski P, Tolosa I, Metian M. Application of nuclear techniques to environmental plastics research. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 192:368-375. [PMID: 30045000 DOI: 10.1016/j.jenvrad.2018.07.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 07/18/2018] [Accepted: 07/18/2018] [Indexed: 06/08/2023]
Abstract
Plastic pollution is ubiquitous in aquatic environments and its potential impacts to wildlife and humans present a growing global concern. Despite recent efforts in understanding environmental impacts associated with plastic pollution, considerable uncertainties still exist regarding the true risks of nano- and micro-sized plastics (<5 mm). The challenges faced in this field largely relate to the methodological and analytical limitations associated with studying plastic debris at low (environmentally relevant) concentrations. The present paper highlights how radiotracing techniques that are commonly applied to trace the fate and behaviour of chemicals and particles in various systems, can contribute towards addressing several important and outstanding questions in environmental plastic pollution research. Specifically, we discuss the use of radiolabeled microplastics and/or chemicals for 1) determining sorption/desorption kinetics of a range of contaminants to different types of plastics under varying conditions, 2) understanding the influence of microplastics on contaminant and nutrient bioaccumulation in aquatic organisms, and 3) assessing biokinetics, biodistribution, trophic transfer and potential biological impacts of microplastic at realistic concentrations. Radiotracer techniques are uniquely suited for this research because of their sensitivity, accuracy and capacity to measure relevant parameters over time. Obtaining precise and timely information on the fate of plastic particles and co-contaminants in wildlife has widespread applications towards effective monitoring programmes and environmental management strategies.
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Affiliation(s)
- Chantal M Lanctôt
- Environment Laboratories, International Atomic Energy Agency, 4a, Quai Antoine Ier, 98000 Principality of Monaco, Monaco; Australian Rivers Institute, Griffith University, Gold Coast Campus, QLD 4215, Australia.
| | - Maya Al-Sid-Cheikh
- University of Plymouth, School of Biological and Marine Sciences, Drake Circus, Plymouth PL4 8AA, UK.
| | - Ana I Catarino
- The School of Energy, Geoscience, Infrastructure and Society, Institute of Life and Earth Sciences, Centre for Marine Biodiversity and Biotechnology, Heriot-Watt University, Edinburgh, UK.
| | - Tom Cresswell
- Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001, Kirrawee DC, NSW 2232, Australia.
| | - Bruno Danis
- Marine Biology Lab, CP160/15, Université Libre de Bruxelles (ULB) 50, Brussels, Belgium.
| | | | - Tracy Mincer
- Woods Hole Oceanographic Institution, 45 Water Street, Wood Hole, MA, 02543, USA.
| | - François Oberhänsli
- Environment Laboratories, International Atomic Energy Agency, 4a, Quai Antoine Ier, 98000 Principality of Monaco, Monaco.
| | - Peter Swarzenski
- Environment Laboratories, International Atomic Energy Agency, 4a, Quai Antoine Ier, 98000 Principality of Monaco, Monaco.
| | - Imma Tolosa
- Environment Laboratories, International Atomic Energy Agency, 4a, Quai Antoine Ier, 98000 Principality of Monaco, Monaco.
| | - Marc Metian
- Environment Laboratories, International Atomic Energy Agency, 4a, Quai Antoine Ier, 98000 Principality of Monaco, Monaco.
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Hoffman JIE. The history of the microsphere method for measuring blood flows with special reference to myocardial blood flow: a personal memoir. Am J Physiol Heart Circ Physiol 2017; 312:H705-H710. [PMID: 28130341 DOI: 10.1152/ajpheart.00834.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/09/2017] [Accepted: 01/19/2017] [Indexed: 11/22/2022]
Abstract
We use many types of equipment and technologies to make our measurements but give little thought to how they developed. Evolution was once described as a series of recoils from blind alleys, and this is exemplified by the gradual development of the microsphere method of measuring blood flows. The microsphere method is one of the most frequently used methods for measuring blood flow to organs and portions of organs. The method can measure myocardial blood flow with reasonable accuracy (within 10%) down to samples weighing >50 mg but probably will not do so for samples weighing 1-10 mg. Microspheres with diameters from 10 to 15 μm provide the best compromise between accurate flow measurement and retention in tissue. Radioactive labels have been almst entirely replaced by fluorescent labels, but colored microspheres and neutron-activated labels are also used.NEW & NOTEWORTHY The contributions of the various individuals who developed the microsphere method of measuring regional blood flows and how these advances took place are brought to light in this paper.
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Affiliation(s)
- Julien I E Hoffman
- Department of Pediatrics, University of California, San Francisco, California
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5
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Modeling to link regional myocardial work, metabolism and blood flows. Ann Biomed Eng 2012; 40:2379-98. [PMID: 22915334 DOI: 10.1007/s10439-012-0613-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 06/21/2012] [Indexed: 12/13/2022]
Abstract
Given the mono-functional, highly coordinated processes of cardiac excitation and contraction, the observations that regional myocardial blood flows, rMBF, are broadly heterogeneous has provoked much attention, but a clear explanation has not emerged. In isolated and in vivo heart studies the total coronary flow is found to be proportional to the rate-pressure product (systolic mean blood pressure times heart rate), a measure of external cardiac work. The same relationship might be expected on a local basis: more work requires more flow. The validity of this expectation has never been demonstrated experimentally. In this article we review the concepts linking cellular excitation and contractile work to cellular energetics and ATP demand, substrate utilization, oxygen demand, vasoregulation, and local blood flow. Mathematical models of these processes are now rather well developed. We propose that the construction of an integrated model encompassing the biophysics, biochemistry and physiology of cardiomyocyte contraction, then combined with a detailed three-dimensional structuring of the fiber bundle and sheet arrangements of the heart as a whole will frame an hypothesis that can be quantitatively evaluated to settle the prime issue: Does local work drive local flow in a predictable fashion that explains the heterogeneity? While in one sense one can feel content that work drives flow is irrefutable, the are no cardiac contractile models that demonstrate the required heterogeneity in local strain-stress-work; quite the contrary, cardiac contraction models have tended toward trying to show that work should be uniform. The object of this review is to argue that uniformity of work does not occur, and is impossible in any case, and that further experimentation and analysis are necessary to test the hypothesis.
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Gussakovsky E, Kuzio B, Yang Y, Kupriyanov V. Fluorescence imaging to quantify the fluorescent microspheres in cardiac tissue. JOURNAL OF BIOPHOTONICS 2011; 4:277-287. [PMID: 20672303 DOI: 10.1002/jbio.201000057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
To quantify the fluorescent microsphere (FM) content in cardiac tissue, which is an indicative of blood flow, fluorescence imaging of both sides of the pig heart slice was employed. Despite the light scattering inside the tissue and contributions from multiple tissue layers to the total emission, it is shown that the fluorescence intensity at any pixel is proportional to the FM content and the fluorescence image may be transformed to the image of the FM concentration. A convenient standard for the emission-FM concentration transformation is proposed. The approach has several advantages in comparison with the traditional "digestion & extraction" method such as: non-destructiveness, high spatial resolution, high throughput, repeatability and simplicity of operation.
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Affiliation(s)
- Eugene Gussakovsky
- National Research Council Institute for Biodiagnostics, Winnipeg, Manitoba R3B1Y6 Canada.
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On the Emission Intensity of Fluorescent Microspheres in Cardiac Tissue Images. J Fluoresc 2010; 20:857-63. [DOI: 10.1007/s10895-010-0629-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Accepted: 02/08/2010] [Indexed: 10/19/2022]
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Mitala CM, Wang Y, Borland LM, Jung M, Shand S, Watkins S, Weber SG, Michael AC. Impact of microdialysis probes on vasculature and dopamine in the rat striatum: a combined fluorescence and voltammetric study. J Neurosci Methods 2008; 174:177-85. [PMID: 18674561 DOI: 10.1016/j.jneumeth.2008.06.034] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 06/25/2008] [Accepted: 06/26/2008] [Indexed: 11/25/2022]
Abstract
Measuring extracellular dopamine in the brain of living animals by means of microdialysis and/or voltammetry is a route towards understanding both normal brain function and pathology. Previous reports, however, suggest that the tissue response to implantation of devices may affect the outcome of the measurements. To address the source of the tissue response and its impact on striatal dopamine systems microdialysis probes were placed in the striatum of anesthetized rats. Images obtained by dual-label fluorescence microscopy show signs of ischemia and opening of the blood-brain barrier near the probe tracks. Opening of the blood-brain barrier was further examined by determining dialysate concentrations of carbi-DOPA, a drug that normally does not penetrate the brain. Although carbi-DOPA was recovered in brain dialysate, it did not alter dialysate dopamine levels or evoked dopamine release as measured by voltammetry near the probes. Microdialysis probes also significantly diminished the effect of intrastriatal infusion of kynurenate on extracellular dopamine levels as measured by voltammetry near the probes.
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Affiliation(s)
- Christina M Mitala
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, United States
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9
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Bartoli CR, Okabe K, Akiyama I, Coull B, Godleski JJ. Repeat microsphere delivery for serial measurement of regional blood perfusion in the chronically instrumented, conscious canine. J Surg Res 2007; 145:135-41. [PMID: 17632127 PMCID: PMC2277484 DOI: 10.1016/j.jss.2007.04.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 04/09/2007] [Accepted: 04/09/2007] [Indexed: 10/23/2022]
Abstract
INTRODUCTION For chronic, repeat hemodynamic studies in conscious dogs, we designed and tested a chronically instrumented canine microsphere delivery model. The goals of this study were (1) to investigate the accuracy of repeated estimations of blood perfusion using fluorescent-labeled microspheres and (2) to develop and validate a chronic preparation that permits consecutive estimations in the same conscious animal over an extended protocol. METHODS Via thoracotomy, nine dogs were instrumented with left atrial appendage and aortic vascular access catheters connected to subcutaneous vascular access ports. Four animals received seven serial injections of 1.6 million 15 microm microspheres (total: 11.2 million), and five animals received 8 serial injections of 2.25 million microspheres (total: 18 million) over the course of 11 or 18 wk. RESULTS All catheters have remained bidirectionally patent during protocol for 14.9 +/- 0.8 (mean +/- SEM) wk. Sphere accumulation did not significantly alter global myocardial (P = 0.69, P = 0.25), renal (P = 0.92, P = 0.12), hepatic (P = 0.84, P = 0.32), or splenic (P = 0.33, P = 0.70) blood perfusion in either set of animals. CONCLUSIONS Catheters remained bidirectionally patent for months, did not interfere with the hemodynamic responses of the preparation, and allowed repeat percutaneous injection of microspheres and withdrawal of reference arterial blood from within conscious canines. Eight serial injections totaling 18 million microspheres over 18 weeks did not alter regional myocardial, hepatic, renal, or splenic blood flow. This dependable, chronic, percutaneous arterial access preparation provides a means for examining acute and long-term effects of pathophysiological, pharmaceutical, and environmental influences on regional arterial blood flow in conscious, large animals.
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Affiliation(s)
- Carlo R Bartoli
- Department of Environmental Health, Harvard School of Public Health, Boston, MA 02215, USA.
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10
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Glenny RW, Bernard SL, Luchtel DL, Neradilek B, Polissar NL. The spatial-temporal redistribution of pulmonary blood flow with postnatal growth. J Appl Physiol (1985) 2007; 102:1281-8. [PMID: 17095640 DOI: 10.1152/japplphysiol.00632.2006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The pulmonary vascular tree undergoes remarkable postnatal development and remodeling. While a number of studies have characterized longitudinal changes in vascular function with growth, none have explored regional patterns of vascular remodeling. We therefore studied six neonatal pigs to see how regional blood flow changes with growth. We selected pigs because of their rapid growth and their similarities to human development with respect to the pulmonary vascular tree. Fluorescent microspheres of varying colors were injected into the pulmonary circulation to mark regional blood on days 3, 12, 27, 43, and 71 after birth. The animals were awake and in the prone posture for all injections. The lungs were subsequently removed, air dried, and sectioned into ∼2-cm3 pieces. Flow on each injection day was determined for each piece. Despite the increase in the hydrostatic gradient in the lung with growth, there was a strong correlation between blood flow to the same lung piece when compared on days 3 and 71 (0.73 ± 0.12). Although a dorsal-ventral gradient of perfusion did not exist on day 3, blood flow increased more in the dorsal region by day 12 and then gradually became more uniform by day 71. Although most of the lung pieces did not show any discernable pattern of blood flow redistribution, there were spatial patterns of blood flow redistribution that were similar across animals. Our findings suggest that local mechanisms, shared across animals, guide regional changes in vascular resistance or vasoregulation during postnatal development. In the pig, these mechanisms act to produce more uniform flow in the normal posture for an ambulating quadruped. The stimuli for these changes have not yet been identified.
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Affiliation(s)
- Robb W Glenny
- Division of Pulmonary and Critical Care Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA.
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11
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Athanasopoulos AN, Economopoulou M, Orlova VV, Sobke A, Schneider D, Weber H, Augustin HG, Eming SA, Schubert U, Linn T, Nawroth PP, Hussain M, Hammes HP, Herrmann M, Preissner KT, Chavakis T. The extracellular adherence protein (Eap) of Staphylococcus aureus inhibits wound healing by interfering with host defense and repair mechanisms. Blood 2006; 107:2720-7. [PMID: 16317095 PMCID: PMC1895382 DOI: 10.1182/blood-2005-08-3140] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 11/14/2005] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is a major human pathogen interfering with host-cell functions. Impaired wound healing is often observed in S aureus-infected wounds, yet, the underlying mechanisms are poorly defined. Here, we identify the extracellular adherence protein (Eap) of S aureus to be responsible for impaired wound healing. In a mouse wound-healing model wound closure was inhibited in the presence of wild-type S aureus and this effect was reversible when the wounds were incubated with an isogenic Eap-deficient strain. Isolated Eap also delayed wound closure. In the presence of Eap, recruitment of inflammatory cells to the wound site as well as neovascularization of the wound were prevented. In vitro, Eap significantly reduced intercellular adhesion molecule 1 (ICAM-1)-dependent leukocyte-endothelial interactions and diminished the consequent activation of the proinflammatory transcription factor nuclear factor kappaB (NFkappaB) in leukocytes associated with a decrease in expression of tissue factor. Moreover, Eap blocked alphav-integrin-mediated endothelial-cell migration and capillary tube formation, and neovascularization in matrigels in vivo. Collectively, the potent anti-inflammatory and antiangiogenic properties of Eap provide an underlying mechanism that may explain the impaired wound healing in S aureus-infected wounds. Eap may also serve as a lead compound for new anti-inflammatory and antiangiogenic therapies in several pathologies.
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Kingma JG, Simard D, Rouleau JR. Comparison of Neutron Activated and Radiolabeled Microsphere Methods for Measurement of Transmural Myocardial Blood Flow in Dogs. J Thromb Thrombolysis 2005; 19:201-8. [PMID: 16082608 DOI: 10.1007/s11239-005-1201-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND The 'gold standard' radioactive microsphere (RM) technique for measurement of organ blood flow under various experimental conditions is inaccessible to many researchers due to increasing environmental concerns regarding safety and disposal of low-level radioactive waste materials. A new method using neutron activated microspheres (NAM) has recently been described. METHODS We compared regional myocardial blood flows using the new formulation STERIspheres (NAM; 15.0 +/- 0.1 [SD] microm; density 1.5 gr/mL) with RM (15.0 +/- 0.1 [SD] microm; density 1.5 gr/mL) under different experimental conditions during acute ischemia-reperfusion injury in dogs. Random paired combinations of four different RM and NAM were co-injected into the left atrium during autoregulation, coronary occlusion and flow-mediated hyperemia (reperfusion) in the same animal. The left ventricle was divided into non-ischemic and ischemic regions and further subdivided into endocardial, mid-myocardial and epicardial portions. After gamma-counting, blood and myocardial tissue samples (n = 180) were dried and then shipped to a core facility for neutron activation and analysis. NAM-RM blood flow data were directly compared by ANOVA and regression analysis; Bland and Altman analysis was also performed to assess mean differences in blood flow with NAM-RM. RESULTS A direct relation for blood flow between NAM-RM was observed; the slope of the relation (1.17 RM +/- 0.04 [SEE]) was different from unity but the intercept (0.06 +/- 0.06 [SEE]) was not different from the origin. Intermethod mean differences were minimal between NAM-RM in the low to normal range of blood flow and were increased at the higher blood flow levels the latter being of minor physiological consequence. A direct relation for endo/epicardial blood flow ratios between NAM-RM was also observed; the slope of the relation (0.98 RM +/- 0.04 [SEE]) and the intercept (0.03 +/- 0.06 [SEE]) were not different from unity or the origin, respectively. CONCLUSIONS RESULTS show that in addition to limiting production of radioactive waste materials, NAM accurately measure myocardial blood flow, endocardial/epicardial and ischemic/non-ischemic blood flow distributions over a wide range. We compared myocardial blood flows using paired combinations of neutron activated (NAM) and the 'gold standard' radiolabeled microspheres (RM) co-injected during autoregulation, coronary occlusion and flow-mediated hyperemia in an in situ canine ischemia-reperfusion preparation. A direct relation for blood flow and endo/epicardial blood flow ratios between NAM-RM was observed; intermethod mean differences between NAM-RM were minimal in the low to normal blood flow range but increased at higher blood flow levels. These results indicate that NAM accurately measure myocardial blood flow and its transmural distribution in addition to limiting unnecessary production of radioactive laboratory waste products.
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Affiliation(s)
- John G Kingma
- Institut Universitaire de Cardiologie et Pneumologie, Department of Medicine, Laval University, Quebec City, Quebec, G1K 7P4.
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Alders DJC, Groeneveld ABJ, de Kanter FJJ, van Beek JHGM. Myocardial O2 consumption in porcine left ventricle is heterogeneously distributed in parallel to heterogeneous O2 delivery. Am J Physiol Heart Circ Physiol 2004; 287:H1353-61. [PMID: 15142850 DOI: 10.1152/ajpheart.00338.2003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myocardial blood flow is unevenly distributed, but the cause of this heterogeneity is unknown. Heterogeneous blood flow may reflect heterogeneity of oxygen demand. The aim of the present study was to assess the relation between oxygen consumption and blood flow in small tissue regions in porcine left ventricle. In seven male, anesthetized, open-chest pigs, local oxygen consumption was quantitated by computational model analysis of the incorporation of 13C in glutamate via the tricarboxylic acid cycle during timed infusion of [13C]acetate into the left anterior descending coronary artery. Blood flow was measured with radioactive microspheres before and during acetate infusion. High-resolution nuclear magnetic resonance 13C spectra were obtained from extracts of tissue samples (159 mg mean dry wt) taken at the end of the acetate infusion. Mean regional myocardial blood flow was stable [5.0 ± 1.6 (SD) and 5.0 ± 1.4 ml·min−1·g dry wt−1 before and after 30 min of acetate infusion, respectively]. Mean left ventricular oxygen consumption measured with the NMR method was 18.6 ± 7.7 μmol·min−1·g dry wt−1 and correlated well ( r = 0.85, P = 0.02, n = 7) with oxygen consumption calculated from blood flow, hemoglobin, and blood gas measurements (mean 22.8 ± 4.7 μmol·min−1·g dry wt−1). Local blood flow and oxygen consumption were significantly correlated ( r = 0.63 for pooled normalized data, P < 0.0001, n = 60). We calculate that, in the heart at normal workload, the variance of left ventricular oxygen delivery at submilliliter resolution is explained for 43% by heterogeneity in oxygen demand.
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Affiliation(s)
- David J C Alders
- Institute for Cardiovascular Research, Vrije Universiteit, VU Medical Center, 1081 HV Amsterdam, The Netherlands
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14
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Decking UKM, Pai VM, Bennett E, Taylor JL, Fingas CD, Zanger K, Wen H, Balaban RS. High-resolution imaging reveals a limit in spatial resolution of blood flow measurements by microspheres. Am J Physiol Heart Circ Physiol 2004; 287:H1132-40. [PMID: 15117718 DOI: 10.1152/ajpheart.00119.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Density of 15-μm microspheres after left atrial application is the standard measure of regional perfusion. In the heart, substantial differences in microsphere density are seen at spatial resolutions <5 ml, implying perfusion heterogeneity. Microsphere deposition imaging permits a superior evaluation of the distribution pattern. Therefore, fluorescent microspheres (FMS) were applied, FMS deposition in the canine heart was imaged by epifluorescence microscopy in vitro, and the patterns were observed compared with MR images of iron oxide microspheres (IMS) obtained in vivo and in vitro. FMS deposition in myocardial slices revealed the following: 1) a nonrandom distribution, with sequentially applied FMS of different color stacked within the same vessel, 2) general FMS clustering, and 3) rather large areas devoid of FMS ( n = 3). This pattern was also seen in reconstructed three-dimensional images (<1 nl resolution) of FMS distribution ( n = 4). Surprisingly, the deposition pattern of sequentially applied FMS remained virtually identical over 3 days. Augmenting flow by intracoronary adenosine (>2 μM) enhanced local microsphere density, but did not alter the deposition pattern ( n = 3). The nonrandom, temporally stable pattern was quantitatively confirmed by a three-dimensional intermicrosphere distance analysis of sequentially applied FMS. T2-weighted short-axis MR images (2-μl resolution) of IMS revealed similar patterns in vivo and in vitro ( n = 6), as seen with FMS. The observed temporally stable microsphere patterns are not consistent with the notion that microsphere deposition is solely governed by blood flow. We propose that at high spatial resolution (<2 μl) structural aspects of the vascular network dominate microsphere distribution, resulting in the organized patterns observed.
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Affiliation(s)
- Ulrich K M Decking
- Department of Cardiovascular Physiology, Heinrich-Heine-University, 40225 Düsseldorf, Germany.
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15
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Matsumoto T, Tachibana H, Asano T, Takemoto M, Ogasawara Y, Umetani K, Kajiya F. Pattern differences between distributions of microregional myocardial flows in crystalloid- and blood-perfused rat hearts. Am J Physiol Heart Circ Physiol 2004; 286:H1331-8. [PMID: 14670811 DOI: 10.1152/ajpheart.00120.2003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regional myocardial flow distributions in Langendorff rat hearts under Tyrode and blood perfusion were assessed by tracer digital radiography (100-μm resolution). Flow distributions during baseline and maximal hyperemia following a 60-s flow cessation were evaluated by the coefficient of variation of regional flows (CV; related to global flow heterogeneity) and the correlation between adjacent regional flows (CA; inversely related to local flow randomness). These values were obtained for the original images (642 pixels) and for coarse-grained images (322, 162, and 82 blocks of nearby pixels). At a given point in time during baseline, both CV and CA were higher in blood ( n = 7) than in Tyrode perfusion ( n = 7) over all pixel aggregates ( P < 0.05, two-way ANOVA). During the maximal hyperemia, CV and CA were still significantly higher in blood ( n = 7) than in Tyrode perfusion ( n = 7); however, these values decreased substantially in blood perfusion and the CV and CA differences became smaller than those at baseline accordingly. During basal blood perfusion, the 60-s average flow distribution ( n = 7) showed a smaller CV and CA than those at a given point in time ( P < 0.05, two-way ANOVA). Coronary flow reserve was significantly higher in blood than in Tyrode perfusion. In conclusion, the flow heterogeneity and the local flow similarity are both higher in blood than in Tyrode perfusion, probably due to the different degree of coronary tone preservation and the presence or absence of blood corpuscles. Under blood perfusion, temporal flow fluctuations over 60-s order are largely involved in shaping microregional flow distributions.
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Affiliation(s)
- Takeshi Matsumoto
- Department of Medical Engineering and Systems Cardiology, Kawasaki Medical School, Kurashiki, Okayama 701-0192 Japan.
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16
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Anetzberger H, Thein E, Löffler G, Messmer K. Fluorescent microsphere method is suitable for chronic bone blood flow measurement: a long-term study after meniscectomy in rabbits. J Appl Physiol (1985) 2003; 96:1928-36. [PMID: 14698991 DOI: 10.1152/japplphysiol.00904.2003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The fluorescent microsphere (FM) method is considered a reliable technique to determine regional bone blood flow (RBBF) in acute experiments. In this study, we verified the accuracy and validity of this technique for measurement of RBBF in a long-term experiment and examined RBBF after meniscectomy. Twenty-four anesthetized female New Zealand white rabbits (3 groups, each n = 8) received consecutive left ventricular injections of FM in defined time intervals after meniscectomy: group 1 from preoperation to 3 wk postoperation; group 2 from 3 to 7 wk postoperation; and group 3 from 7 to 11 wk postoperation. To test the precision of the FM method, two FM species were injected simultaneously at the first and last measurement. After the experiment, humeri, femora, tibiae, and reference organs (kidney, lung, brain) were removed and dissected according to standardized protocols. Fluorescence was determined in each reference blood and tissue sample, and blood flow values were calculated. Blood flow in kidney, lung, and brain revealed no significant difference between right and left side and remained unchanged during the observation period, thus excluding errors due to shunting and dislodging of spheres in our experiments. Comparison of relative bone blood flow values obtained by simultaneously injected FM showed an excellent correlation at the first and last injection, indicating valid RBBF measurements in long-term experiments. We found a significant increase in RBBF 3 wk after meniscectomy in the right tibial condyles compared with the nonoperated left side. Similar changes were found in the femoral condyles. RBBF in other regions of tibia, femur, and humerus revealed no significant differences between right- and left-sided bone samples of the same region. Our results demonstrate that the FM method is valid for measuring RBBF in long-term experiments. In addition, we were able to demonstrate that meniscectomy leads to an increase in RBBF in the tibial condyles at a very early stage. This increase might be caused by stress-induced alterations of the subchondral bone.
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Affiliation(s)
- H Anetzberger
- Department of Orthopaedics, Klinikum Grosshadern, Ludwig-Maximilians University, 81377 Munich, Germany.
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17
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Anetzberger H, Thein E, Becker M, Walli AK, Messmer K. Validity of fluorescent microspheres method for bone blood flow measurement during intentional arterial hypotension. J Appl Physiol (1985) 2003; 95:1153-8. [PMID: 12730148 DOI: 10.1152/japplphysiol.00299.2003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this study, we compared bone blood flow values obtained by simultaneously injected fluorescent (FM) and radiolabeled microspheres (RM) at stepwise reduced arterial blood pressure. Ten anesthetized female New Zealand White rabbits received simultaneous left ventricular injections of FM and RM at 90, 70, and 50 mmHg mean arterial blood pressure (MAP). After the experiments, both kidneys and long bones of all four limbs were removed and dissected in a standardized manner. Radioactivity (corrected for decay, background, and spillover) and fluorescence were determined, and blood flow values were calculated. Relative blood flow values estimated for each bone sample by RM and FM were significantly correlated (r = 0.98, slope = 0.99, and intercept = 0.04 for 90 mmHg; r = 0.98, slope = 0.94, and intercept = 0.09 for 70 mmHg; r = 0.98, slope = 0.96, and intercept = 0.07 for 50 mmHg). Blood flow values (ml x min-1 x 100 g-1) of right and left bone samples determined at the different arterial blood pressures were identical. During moderate hypotension (70 mmHg MAP), blood flow in all bone samples remained unchanged compared with 90 mmHg MAP, whereas a significant decrease of bone blood flow was observed at severe hypotension (50 mmHg MAP). Our results demonstrate that the FM technique is valid for measuring bone blood flow. Differences in bone blood flow during altered hemodynamic conditions can be detected reliably. In addition, changes in bone blood flow during hypotension indicate that vasomotor control mechanisms, as well as cardiac output, play a role in setting bone blood flow.
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Affiliation(s)
- H Anetzberger
- Department of Orthopaedics, Ludwig-Maximilians University, 81377 Munich, Germany.
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18
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Conhaim RL, Watson KE, Heisey DM, Leverson GE, Harms BA. Perfusion heterogeneity in rat lungs assessed from the distribution of 4-microm-diameter latex particles. J Appl Physiol (1985) 2003; 94:420-8. [PMID: 12391079 DOI: 10.1152/japplphysiol.00700.2002] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary vascular perfusion has been shown to follow a fractal distribution down to a resolution of 0.5 cm(3) (5E11 microm(3)). We wanted to know whether this distribution continued down to tissue volumes equivalent to that of an alveolus (2E5 microm(3)). To investigate this, we used confocal microscopy to analyze the spatial distribution of 4-microm-diameter fluorescent latex particles trapped within rat lung microvessels. Particle distributions were analyzed in tissue volumes that ranged from 1.7E2 to 2.8E8 microm(3). The analysis resulted in fractal plots that consisted of two slopes. The left slope, encompassing tissue volumes less than 7E5 microm(3), had a fractal dimension of 1.50 +/- 0.03 (random distribution). The right slope, encompassing tissue volumes greater than 7E5 microm(3), had a fractal dimension of 1.29 +/- 0.04 (nonrandom distribution). The break point at 7E5 microm(3) corresponds closely to a tissue volume equivalent to that of one alveolus. We conclude that perfusion distribution is random at tissue volumes less than that of an alveolus and nonrandom at tissue volumes greater than that of an alveolus.
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Affiliation(s)
- Robert L Conhaim
- Department of Surgery, University of Wisconsin-Madison, 53792-7375, USA.
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Bauer I, Bauer M. Small animal models of hemorrhagic shock-induced liver dysfunction. CURRENT PROTOCOLS IN TOXICOLOGY 2002; Chapter 14:Unit14.3. [PMID: 23045074 DOI: 10.1002/0471140856.tx1403s11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Blood loss and ensuing circulatory failure continues to be the leading cause of death between the ages of 1 and 45 in most western countries. Hepatocellular dysfunction is a key feature of the pathophysiological sequelae of trauma/hemorrhage in patients surviving the first hours and hemorrhagic hypotension has been widely used as a model for indirect liver injury in the critically ill. This unit describes a low-flow ischemia model of the liver due to hemorrhagic hypotension that can be used to produce a reproducible and graded injury to the pericentral region of the acinus, which is critical for metabolism of xenobiotics. This protocol allows for measurement of cardiac output and regional flow.
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Affiliation(s)
- Inge Bauer
- University of the Saarland, Homburg, Germany
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20
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Abstract
Precise measurements of regional myocardial blood flow heterogeneity had to be developed before one could seek causation for the heterogeneity. Deposition techniques (particles or molecular microspheres) are the most precise, but imaging techniques have begun to provide high enough resolution to allow in vivo studies. Assigning causation has been difficult. There is no apparent association with the regional concentrations of energy-related enzymes or substrates, but these are measures of status, not of metabolism. There is statistical correlation between flow and regional substrate uptake and utilization. Attribution of regional flow variation to vascular anatomy or to vasomotor control appears not to be causative on a long-term basis. The closest relationships appear to be with mechanical function, but one cannot say for sure whether this is related to ATP hydrolysis at the crossbridge or associated metabolic reactions such as calcium uptake by the sarcoplasmic reticulum.
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21
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Hoefer IE, van Royen N, Buschmann IR, Piek JJ, Schaper W. Time course of arteriogenesis following femoral artery occlusion in the rabbit. Cardiovasc Res 2001; 49:609-17. [PMID: 11166274 DOI: 10.1016/s0008-6363(00)00243-1] [Citation(s) in RCA: 154] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVE We examined the time course of arteriogenesis (collateral artery growth) after femoral artery ligation and the effect of monocyte chemoattractant protein-1 (MCP-1). METHODS New Zealand White rabbits received MCP-1 or phosphate buffered saline (PBS) for a 1-week period, either directly or 3 weeks after femoral artery ligation (non-ischemic model). A control group was studied with intact femoral arteries and another 1 min after acute femoral artery ligation. RESULTS Collateral conductance index significantly increased when MCP-1 treatment started directly after femoral artery ligation (acute occlusion: 0.94+/-0.19; without occlusion: 168.56+/-15.99; PBS: 4.10+/-0.48; MCP-1: 33.96+/-1.76 ml/min/100 mmHg). However, delayed onset of treatment 3 weeks after ligation and final study of conductance at 4 weeks showed no significant difference against a 4-week control (PBS: 79.08+/-7.24; MCP-1: 90.03+/-8.73 ml/min/100 mmHg). In these groups increased conductance indices were accompanied by a decrease in the number of visible collateral vessels (from 18 to 36 identifiable vessels at day 7 to about four at 21 days). CONCLUSION We conclude that the chemokine MCP-1 markedly accelerated collateral artery growth but did not alter its final extent above that reached spontaneously as a function of time. We show thus for the first time that a narrow time window exists for the responsiveness to the arteriogenic actions of MCP-1, a feature that MCP-1 may share with other growth factors. We show furthermore that the spontaneous adaptation by arteriogenesis stops when only about 50% of the vasodilatory reserve of the arterial bed before occlusion are reached. The superiority of few large arterial collaterals in their ability to conduct large amounts of blood flow per unit of pressure as compared to the angiogenic response where large numbers of small vessels are produced with minimal ability to allow mass transport of bulk flow is stressed.
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Affiliation(s)
- I E Hoefer
- Department of Experimental Cardiology, Max-Planck-Institute for Physiological and Clinical Research, Benekestr. 2, D-61231, Bad Nauheim, Germany.
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22
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Abstract
The art and science of the use of deposition markers for the estimation of blood flow distributions throughout the body and within organs is reviewed. Development of diffusible tracer techniques started 50 years ago. Twenty years later, radioactive 15 micron microspheres became the standard marker. Early studies on small animals, fetal sheep in 1967 and rats in 1976, provoked much of the technical development. Needs for avoiding the use of radioactivity, for having long lasting labels, and for providing higher spatial resolution, are driving the continuing exploration of newer techniques using colored and fluorescent microspheres and molecular deposition markers. Strengths and weaknesses of the various methods are compared.
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Affiliation(s)
- F W Prinzen
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
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