Control Limbs (control + limb)

Distribution by Scientific Domains


Selected Abstracts


Dynamic contrast-enhanced MRI of muscle perfusion combined with MR angiography of collateral artery growth in a femoral artery ligation model

NMR IN BIOMEDICINE, Issue 8 2007
Quido G. de Lussanet
Abstract To assess the use of MRI for evaluating changes in muscle blood flow and number of collateral arteries, serial dynamic contrast-enhanced MRI (DCE-MRI) was combined with high-spatial-resolution contrast-enhanced MR angiography (MRA) in a peripheral ischemia model. The combined MRI (DCE-MRI and MRA) protocol was performed serially in 15 male rabbits at 2,h (day 0+), 7 days, and 21 days after femoral artery ligation. In the anterior tibial and soleus muscle, changes in resting muscle blood flow determined as the endothelial transfer coefficient (Ktrans) and arterial inflow delay from DCE-MRI and changes in the number of sub-millimeter sized collateral arteries as scored with MRA were measured. Directly after ligation, Ktrans in the anterior tibial muscle was reduced to 23% of that in the control limb, then recovered to 81% on day 7, and to 85 % on day 21. Ktrans in the soleus muscle recovered from a reduction to 63% on day 0+, to 85% on day 7, and to 90% on day 21. The number of collaterals around the ligated femoral artery increased from 1.1 on day 0+ to 4.2 on day 7, and 6.0 on day 21 in the ligated limb only. Combined DCE-MRI and MRA allows non-invasive serial monitoring of changes in muscle blood flow and growth of sub-millimeter sized collateral arteries in a rabbit femoral artery ligation model. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Reductions in basal limb blood flow and vascular conductance with human ageing: role for augmented ,-adrenergic vasoconstriction

THE JOURNAL OF PHYSIOLOGY, Issue 3 2001
Frank A. Dinenno
1Basal whole-limb blood flow and vascular conductance decrease with age in men. We determined whether these age-associated changes in limb haemodynamics are mediated by tonically augmented sympathetic ,-adrenergic vasoconstriction. 2Seven young (28 ± 2 years; mean ±s.e.m.) and eight older (64 ± 2 years) healthy, normotensive adult men were studied. Baseline femoral artery blood flow (Doppler ultrasound) and calculated vascular conductance were 29 and 31 % lower, respectively, and vascular resistance was 53 % higher in the older men (all P < 0.001). 3Local (intra-femoral artery) ,-adrenergic receptor blockade with phentolamine evoked greater increases in femoral blood flow (105 ± 11 vs. 60 ± 6 %) and vascular conductance (125 ± 13 vs. 66 ± 7 %), and reductions in vascular resistance (55 ± 2 vs. 39 ± 3 %) in the experimental limb of the older compared with the young men (all P < 0.001). As a result, ,-adrenergic receptor blockade eliminated the significance of the age-associated differences in absolute levels of femoral blood flow (500 ± 51 vs. 551 ± 35 ml min,1), vascular conductance (6.02 ± 0.73 vs. 6.33 ± 0.26 U), and vascular resistance (0.17 ± 0.03 vs. 0.16 ± 0.01 U; P= 0.4,0.8, n.s.). Femoral haemodynamics in the control limb were unaffected by phentolamine administration in the contralateral (experimental) limb. Complete ,-adrenergic receptor blockade was demonstrated by the absence of vasoconstriction in the experimental limb in response to the cold pressor test. Local propranolol was administered to control for any ,-adrenergic effects of phentolamine. Propranolol did not affect haemodynamics in the experimental or control limbs. 4Our results indicate that the age-related reductions in basal limb blood flow and vascular conductance are mediated largely by chronically elevated sympathetic ,-adrenergic vasoconstriction. This may have important physiological and pathophysiological implications for the ageing human. [source]


The Effect of In Vivo Mechanical Loading on Estrogen Receptor , Expression in Rat Ulnar Osteocytes,,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2002
P. J. Ehrlich
Abstract The presence of estrogen receptor , (ER,) in osteocytes was identified immunocytochemically in transverse sections from 560 to 860 ,m distal to the midshaft of normal neonatal and adult male and female rat ulnas (n = 3 of each) and from adult male rat ulnas that had been exposed to 10 days of in vivo daily 10-minute periods of cyclic loading producing peak strains of either ,3000 (n = 3) or ,4000 microstrain (n = 5). Each animal ambulated normally between loading periods, and its contralateral ulna was used as a control. In animals in which limbs were subject to normal locomotor loading alone, 14 ±1.2% SEM of all osteocytes in each bone section were ER, positive. There was no influence of either gender (p = 0.725) or age (p = 0.577) and no interaction between them (p = 0.658). In bones in which normal locomotion was supplemented by short periods of artificial loading, fewer osteocytes expressed ER, (7.5 ± 0.91% SEM) than in contralateral control limbs, which received locomotor loading alone (14 ± 1.68% SEM; p = 0.01; median difference, 6.43; 95% CI, 2.60, 10.25). The distribution of osteocytes expressing ER, was uniform across all sections and thus did not reflect local peak strain magnitude. This suggests that osteocytes respond to strain as a population, rather than as individual strain-responsive cells. These data are consistent with the hypothesis that ER, is involved in bone cells' responses to mechanical strain. High strains appear to decrease ER, expression. In osteoporotic bone, the high strains assumed to accompany postmenopausal bone loss may reduce ER, levels and therefore impair the capacity for appropriate adaptive remodeling. [source]


Joint degeneration following closed intraarticular fracture in the mouse knee: A model of posttraumatic arthritis

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2007
Bridgette D. Furman
Abstract Posttraumatic arthritis is one of the most frequent causes of disability following joint trauma. The objective of this study was to develop a model of a closed articular fracture in the mouse knee joint to quantify the temporal sequence of joint degeneration in a model of posttraumatic arthritis. Closed intraarticular fractures were created in the tibial plateau of adult mice (C57BL/6) using a computer-controlled materials testing system and a custom-built indenter tip. Tibial plateau fractures were classified and imaged over time using high-resolution digital radiography. Animals were sacrificed at 2, 4, 8, and 50 weeks following fracture, and the experimental and contralateral control limbs were harvested for histology and micro-computed tomography (microCT) analysis. By radiographic analysis, tibial plateau fractures closely resembled clinical fractures. More complex and comminuted fractures correlated to significantly higher fracture energies. Histologic analysis demonstrated progressive joint degeneration as measured by a modified Mankin scale, with fibrillation and loss of proteoglycan in the articular cartilage. Subchondral bone thickening was also observed in experimental joints. The induction of a closed intraarticular fracture of the mouse tibial plateau generated a reproducible and clinically relevant joint injury that progressed to osteoarthritis-like changes by histologic and microCT evaluations. The ability to induce joint degeneration without an osteotomy or open arthrotomy provides a valuable new model for studying the natural sequelae of posttraumatic arthritis. Notably, the use of a murine model will facilitate the use of genetically modified animals for the investigation of specific genes implicated in the pathology of posttraumatic arthritis. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:578,592, 2007 [source]


Repair of rabbit segmental defects with the thrombin peptide, TP508

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2004
Michael R. Sheller
Abstract The synthetic peptide, TP508 (Chrysalin®), was delivered to rabbit segmental bone defects in biodegradable controlled-release PLGA microspheres to determine its potential efficacy for enhancing healing of non-critically and critically sized segmental defects. Non-critically sized radial defects were created in the forelimbs of New Zealand White rabbits, which were randomized into three treatment groups receiving 10, 50 and 100 ,g doses of TP508 in the right radius and control microspheres (without TP508) in the left radius. Torsional testing of the radii at six weeks showed a significant increase in ultimate torque, failure torque, ultimate energy, failure energy, and stiffness when treated with TP508 compared to controls (p < 0.01 for all measures). Thus, TP508 appeared to enhance or accelerate bone growth in these defects. In a second set of experiments, critically sized ulnar defects were created in the forelimbs of New Zealand White rabbits, which were randomized into two groups with each rabbit receiving microspheres with 100 or 200 ,g of TP508 into the right ulnar defect and control microspheres (without TP508) alone into the left ulnar defect. Bone healing was evaluated with plain radiographs, synchrotron-based microtomography, and mechanical testing. Radiographs of the rabbit limbs scored by three blinded, independent reviewers demonstrated a significantly higher degree of healing when treated with TP508 than their untreated control limbs (p < 0.05). Three-dimensional synchrotron tomography of a limited number of samples showed that the new bone in TP508-treated samples had a less porous surface appearance and open marrow spaces, suggesting progression of bone remodeling. Torsional testing of the ulnae at nine weeks showed a significant increase in maximum torque and failure energy when treated with TP508 compared to controls (p < 0.01 for both measures). These results suggest that TP508 in a controlled release delivery vehicle has the potential to enhance healing of segmental defects in both critically and non-critically sized defects. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]


Reductions in basal limb blood flow and vascular conductance with human ageing: role for augmented ,-adrenergic vasoconstriction

THE JOURNAL OF PHYSIOLOGY, Issue 3 2001
Frank A. Dinenno
1Basal whole-limb blood flow and vascular conductance decrease with age in men. We determined whether these age-associated changes in limb haemodynamics are mediated by tonically augmented sympathetic ,-adrenergic vasoconstriction. 2Seven young (28 ± 2 years; mean ±s.e.m.) and eight older (64 ± 2 years) healthy, normotensive adult men were studied. Baseline femoral artery blood flow (Doppler ultrasound) and calculated vascular conductance were 29 and 31 % lower, respectively, and vascular resistance was 53 % higher in the older men (all P < 0.001). 3Local (intra-femoral artery) ,-adrenergic receptor blockade with phentolamine evoked greater increases in femoral blood flow (105 ± 11 vs. 60 ± 6 %) and vascular conductance (125 ± 13 vs. 66 ± 7 %), and reductions in vascular resistance (55 ± 2 vs. 39 ± 3 %) in the experimental limb of the older compared with the young men (all P < 0.001). As a result, ,-adrenergic receptor blockade eliminated the significance of the age-associated differences in absolute levels of femoral blood flow (500 ± 51 vs. 551 ± 35 ml min,1), vascular conductance (6.02 ± 0.73 vs. 6.33 ± 0.26 U), and vascular resistance (0.17 ± 0.03 vs. 0.16 ± 0.01 U; P= 0.4,0.8, n.s.). Femoral haemodynamics in the control limb were unaffected by phentolamine administration in the contralateral (experimental) limb. Complete ,-adrenergic receptor blockade was demonstrated by the absence of vasoconstriction in the experimental limb in response to the cold pressor test. Local propranolol was administered to control for any ,-adrenergic effects of phentolamine. Propranolol did not affect haemodynamics in the experimental or control limbs. 4Our results indicate that the age-related reductions in basal limb blood flow and vascular conductance are mediated largely by chronically elevated sympathetic ,-adrenergic vasoconstriction. This may have important physiological and pathophysiological implications for the ageing human. [source]