The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
J. Menage - One of the best experts on this subject based on the ideXlab platform.
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The Fluid Content of the human intervertebral disc. Comparison between Fluid Content and swelling pressure profiles of discs removed at surgery and those taken postmortem.
Spine, 1992Co-Authors: Brian Johnstone, Jill P. G. Urban, Sally Roberts, J. MenageAbstract:The Fluid Content of the disc, which governs its mechanical response and biological behavior, varies with external load. Because load on the disc changes after death, the Fluid Content and swelling pressure profiles of human discs taken at autopsy were measured, and compared with discs removed during surgical procedures. In general, discs taken at surgery had a lower Fluid Content in the nucleus and a higher Fluid Content in the outer anulus than discs removed at autopsy. In discs removed at surgery, the swelling pressure of the nucleus was higher than that of the anulus, whereas in autopsy discs the swelling pressure profile was flat. These changes are though to result from changes in load after death, and could influence the results of in vitro mechanical tests on the disc.
William A Fajman - One of the best experts on this subject based on the ideXlab platform.
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An in vivo MRI study of the changes in volume (and Fluid Content) of the lumbar intervertebral disc after overnight bed rest and during an 8-hour walking protocol.
Journal of spinal disorders & techniques, 2002Co-Authors: John A Malko, William C Hutton, William A FajmanAbstract:Summary: Magnetic resonance imaging (MRI) was used to measure the changes in the volume (and Fluid Content) of the lumbar intervertebral discs (L1–L2, L2–L3, L3–L4, L4–L5) in five normal subjects. For each subject, MRI scans were taken at the end of a normal day and again on the following morning (after a night's bed rest). Ten further scans were taken during an 8-h protocol consisting of alternate periods of walking (40 min) and scanning (10 min). On average, 1) disc volume increased by 10.6% during overnight bed rest, which corresponds to a gain of about 0.9 cm3 of Fluid; 2) the rate of disc volume decrease during the 8-h walking protocol was 0.96 × 10−3 cm3/min; and 3) after 8 h (using our walking/scanning protocol), the disc volume did not decrease to the volume measured at the end of the previous day.
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an in vivo magnetic resonance imaging study of changes in the volume and Fluid Content of the lumbar intervertebral discs during a simulated diurnal load cycle
Spine, 1999Co-Authors: John A Malko, William C Hutton, William A FajmanAbstract:Study Design. Magnetic resonance imaging was used to measure the changes in volume of the lumbar intervertebrai disc in vivo during a load cycle. Objectives. To measure changes in volume of the lumbar intervertebral disc during a load cycle and relate these changes to changes in Fluid Content. of Background Data. There have been very few experiments conducted to measure the volume and Fluid changes in intervertebral discs in vivo. Methods. Five healthy subjects were recruited (aged 27, 29, 31, 34, and 52 years) in a study using magnetic resonance imaging to measure the changes in volume of the lumbar intervertebral disc m vivo, during a load cycle. The experiment was designed to simulate a diurnal load cycle, but over less time. The load cycle consisted of bed rest, followed by walking with a 20-kg backpack for 3 hours, followed by bed rest for 3 hours. Magnetic resonance imaging scans of the lumbar spine were obtained 10 times during this load cycle. The disc volume was calculated by summing the disc area contained in each slice of the scan. The changes in volume of the discs (L2-L3, L3-L4, and L4-L5) recorded at the 10 times were then related to the Fluid changes. Results. Load-induced changes in disc volume can be detected and measured using MR imaging. The average volume increase 3 hours after removing a highly compressive load was 5.4%. The water Content of the nucleus and anulus in the disc of the young human is said to be approximately 80% and 70%, respectively. If the disc gained 5.4% of its initial total volume, and assuming that the initial Fluid Content was approximately 75%, then it gained approximately 7% (i.e., 5.4%/75% × 100% - 7%) of its Fluid. Conclusions. Load-induced changes in disc volume can be detected and measured using magnetic resonance imaging.
Niels H Secher - One of the best experts on this subject based on the ideXlab platform.
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stroke volume of the heart and thoracic Fluid Content during head up and head down tilt in humans
Acta Anaesthesiologica Scandinavica, 2005Co-Authors: J J Van Lieshout, M P M Harms, F C Pott, M Jenstrup, Niels H SecherAbstract:BACKGROUND: The stroke volume (SV) of the heart depends on the diastolic volume but, for the intact organism, central pressures are applied widely to express the filling of the heart. METHODS: This study evaluates the interdependence of SV and thoracic electrical admittance of thoracic Fluid Content (TA) vs. the central venous (CVP), mean pulmonary artery (MPAP) and pulmonary artery wedge (PAWP) pressures during head-up (HUT) and head-down (HDT) tilt in nine healthy humans. RESULTS: From the supine position to 20 degrees HDT, SV [112 +/- 18 ml; mean +/- standard deviation (SD)], TA (30.8 +/- 7.1 mS) and CVP (3.6 +/- 0.9 mmHg) did not change significantly, whereas MPAP (from 13.9 +/- 2.7 to 16.1 +/- 2.5 mmHg) and PAWP (from 8.8 +/- 3.4 to 11.3 +/- 2.5 mmHg; P < 0.05) increased. Conversely, during 70 degrees HUT, SV (to 65 +/- 24 ml) decreased, together with CVP (to 0.9 +/- 1.4 mmHg; P < 0.001), MPAP (to 9.3 +/- 3.8 mmHg; P < 0.01), PAWP (to 0.7 +/- 3.3 mmHg; P < 0.001) and TA (to 26.7 +/- 6.8 mS; P < 0.01). However, from 20 to 50 min of HUT, SV decreased further (to 48 +/- 21 ml; P < 0.001), whereas the central pressures did not change significantly. CONCLUSIONS: During both HUT and HDT, SV of the heart changed with the thoracic Fluid Content rather than with the central vascular pressures. These findings confirm that the function of the heart relates to its volume rather than to its so-called filling pressures.
Brian Johnstone - One of the best experts on this subject based on the ideXlab platform.
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The Fluid Content of the human intervertebral disc. Comparison between Fluid Content and swelling pressure profiles of discs removed at surgery and those taken postmortem.
Spine, 1992Co-Authors: Brian Johnstone, Jill P. G. Urban, Sally Roberts, J. MenageAbstract:The Fluid Content of the disc, which governs its mechanical response and biological behavior, varies with external load. Because load on the disc changes after death, the Fluid Content and swelling pressure profiles of human discs taken at autopsy were measured, and compared with discs removed during surgical procedures. In general, discs taken at surgery had a lower Fluid Content in the nucleus and a higher Fluid Content in the outer anulus than discs removed at autopsy. In discs removed at surgery, the swelling pressure of the nucleus was higher than that of the anulus, whereas in autopsy discs the swelling pressure profile was flat. These changes are though to result from changes in load after death, and could influence the results of in vitro mechanical tests on the disc.
John A Malko - One of the best experts on this subject based on the ideXlab platform.
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An in vivo MRI study of the changes in volume (and Fluid Content) of the lumbar intervertebral disc after overnight bed rest and during an 8-hour walking protocol.
Journal of spinal disorders & techniques, 2002Co-Authors: John A Malko, William C Hutton, William A FajmanAbstract:Summary: Magnetic resonance imaging (MRI) was used to measure the changes in the volume (and Fluid Content) of the lumbar intervertebral discs (L1–L2, L2–L3, L3–L4, L4–L5) in five normal subjects. For each subject, MRI scans were taken at the end of a normal day and again on the following morning (after a night's bed rest). Ten further scans were taken during an 8-h protocol consisting of alternate periods of walking (40 min) and scanning (10 min). On average, 1) disc volume increased by 10.6% during overnight bed rest, which corresponds to a gain of about 0.9 cm3 of Fluid; 2) the rate of disc volume decrease during the 8-h walking protocol was 0.96 × 10−3 cm3/min; and 3) after 8 h (using our walking/scanning protocol), the disc volume did not decrease to the volume measured at the end of the previous day.
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an in vivo magnetic resonance imaging study of changes in the volume and Fluid Content of the lumbar intervertebral discs during a simulated diurnal load cycle
Spine, 1999Co-Authors: John A Malko, William C Hutton, William A FajmanAbstract:Study Design. Magnetic resonance imaging was used to measure the changes in volume of the lumbar intervertebrai disc in vivo during a load cycle. Objectives. To measure changes in volume of the lumbar intervertebral disc during a load cycle and relate these changes to changes in Fluid Content. of Background Data. There have been very few experiments conducted to measure the volume and Fluid changes in intervertebral discs in vivo. Methods. Five healthy subjects were recruited (aged 27, 29, 31, 34, and 52 years) in a study using magnetic resonance imaging to measure the changes in volume of the lumbar intervertebral disc m vivo, during a load cycle. The experiment was designed to simulate a diurnal load cycle, but over less time. The load cycle consisted of bed rest, followed by walking with a 20-kg backpack for 3 hours, followed by bed rest for 3 hours. Magnetic resonance imaging scans of the lumbar spine were obtained 10 times during this load cycle. The disc volume was calculated by summing the disc area contained in each slice of the scan. The changes in volume of the discs (L2-L3, L3-L4, and L4-L5) recorded at the 10 times were then related to the Fluid changes. Results. Load-induced changes in disc volume can be detected and measured using MR imaging. The average volume increase 3 hours after removing a highly compressive load was 5.4%. The water Content of the nucleus and anulus in the disc of the young human is said to be approximately 80% and 70%, respectively. If the disc gained 5.4% of its initial total volume, and assuming that the initial Fluid Content was approximately 75%, then it gained approximately 7% (i.e., 5.4%/75% × 100% - 7%) of its Fluid. Conclusions. Load-induced changes in disc volume can be detected and measured using magnetic resonance imaging.