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Philip C. Withers - One of the best experts on this subject based on the ideXlab platform.
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Lung ventilation is an effector of the baroreflex in the cane toad (Rhinella marina)
The FASEB Journal, 2012Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:Lung ventilation plays an important role for regulating Lymph flux in anurans by changing the compliance of Lymph Sacs that surround the lungs during changes in lung volume. Because Lymph mobilizat...
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Lymph flux rates from various Lymph Sacs in the cane toad Rhinella marina: an experimental evaluation of the roles of compliance, skeletal muscles and the lungs in the movement of Lymph
Journal of Experimental Biology, 2010Co-Authors: Stanley S. Hillman, Michael S. Hedrick, Robert C. Drewes, Philip C. WithersAbstract:A new method for quantitatively determining Lymph flux from various Lymphatic Sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C i V i= C f V f following injection of Evans Blue into specific Lymph Sacs and measuring its appearance in the venous circulation. The apparent Lymph volume was 57 ml kg–1. The greatest rate of Lymph return (0.5–0.8 ml kg–1 min–1) and best linear fit of Evans Blue appearance in the circulation with time followed injections into the subvertebral Lymph sac, which has direct connections to both the anterior and posterior pairs of Lymphatic hearts. Rate of Lymph flux from the pair of posterior Lymph hearts was three times greater than the anterior pair. Rates of Lymph flux were only influenced by injection volume in the crural Lymph Sacs, implicating Lymph sac compliance as the source of the pressure for Lymph movement from these Sacs. Femoral Lymph sac fluxes were decreased by 60% following ablation of the tendons of the sphincter ani cloacalis, abdominal crenators and piriformis. This supports a role for these muscles in generating the pressure for vertical Lymph movement. Femoral Lymph sac fluxes were also decreased by 70% by the insertion of a coil in the subvertebral Lymph sac, preventing normal compression and expansion of this sac by the lungs. This supports a role for lung ventilation in generating the pressure for vertical movement of Lymph. Contrary to previous hypotheses, fluxes from the brachial sac were not influenced by insertion of the coil into the subvertebral sac. A haemorrhage equivalent to 50% of the blood volume did not change Lymph flux rates from the femoral Lymph Sacs. These data provide the first experimental evidence that actual Lymph fluxes in the cane toad Rhinella marina depend on Lymph sac compliance, contraction of specific skeletal muscles and lung ventilation to move Lymph laterally and vertically to the dorsally located Lymphatic hearts.
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unique role of skeletal muscle contraction in vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Robert C. Drewes, Stanley S. Hillman, Michael S. Hedrick, Philip C. WithersAbstract:SUMMARY Electromyographic (EMG) activity of skeletal muscles that either insert on the skin or are associated with the margins of subcutaneous Lymph Sacs was monitored for two species of anurans, Chaunus marinus and Lithobates catesbeiana (formerly Bufo marinus and Rana catesbeiana ). Our hypothesis was that contraction of these muscles varies the volume, and hence pressure, within these Lymph Sacs, and that this pressure is responsible for moving Lymph from ventral, gravitationally dependent reaches of the body to dorsally located Lymph hearts. EMG activity of M. piriformis, M. gracilis minor, M. abdominal crenator, M. tensor fasciae latae, M. sphincter ani cloacalis, M. cutaneous pectoris and M. cutaneous dorsi was synchronous with pressure changes in their associated Lymph Sacs. These muscles contracted synchronously, and the pressures generated within the Lymph Sacs were sufficient to move Lymph vertically against gravity to the Lymph hearts. The pressure relationships were complex; both negative and positive pressures were recorded during a contractile event, a pattern consistent with the addition and loss of Lymphatic fluid to the Lymph Sacs. Severing the tendons of some of the muscles led to Lymph pooling in gravitationally dependent Lymph Sacs. These data are the first to: (1) describe a function for many of these skeletal muscles; (2) document the role of skeletal muscles in vertical Lymph movement in anurans; and (3) reinterpret the role of the urostyle, a bony element of the anuran pelvic girdle.
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lung ventilation contributes to vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P <0.001) relationships between lung pressure and Lymph sac pressures ( r 2 =0.19–0.72), indicating that pulmonary pressure is transmitted to the highly compliant Lymph Sacs that surround the lungs. Subvertebral sac pressure of resting animals was not significantly different between L. catesbeiana (518±282 Pa) and C. marinus (459±111 Pa). Brachial sac compliance (ml kPa –1 kg –1 ) also did not differ between the two species (33.6±5.0 in L. catesbeiana and 37.0±9.4 in C. marinus ). During expiration (lung deflation), reductions in expanding subvertebral sac pressure are communicated to the brachial Lymph sac. Changes in brachial and pubic Lymph sac pressures were correlated almost entirely during expiration rather than inspiration. The change in brachial sac pressure during expiration was 235±43 Pa for C. marinus and 215±50 Pa for L. catesbeiana , which is of sufficient magnitude to move Lymph the estimated 0.5–1.0 cm vertical distance from the forelimb to the vicinity of the anterior Lymph hearts. We suggest that Lymph is moved during expiration to the subvertebral sac from anterior and posterior Lymph Sacs. During lung inflation, increased Lymph sac pressure moves Lymph to axillary regions, where Lymph hearts can return Lymph to the vascular space. Consequently, pulmonary ventilation has an important role for Lymph movement and, hence, blood volume regulation in anurans.
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Lung ventilation contributes to vertical Lymph movement in anurans.
Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P
Stanley S. Hillman - One of the best experts on this subject based on the ideXlab platform.
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Lung ventilation is an effector of the baroreflex in the cane toad (Rhinella marina)
The FASEB Journal, 2012Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:Lung ventilation plays an important role for regulating Lymph flux in anurans by changing the compliance of Lymph Sacs that surround the lungs during changes in lung volume. Because Lymph mobilizat...
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Lymph flux rates from various Lymph Sacs in the cane toad Rhinella marina: an experimental evaluation of the roles of compliance, skeletal muscles and the lungs in the movement of Lymph
Journal of Experimental Biology, 2010Co-Authors: Stanley S. Hillman, Michael S. Hedrick, Robert C. Drewes, Philip C. WithersAbstract:A new method for quantitatively determining Lymph flux from various Lymphatic Sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C i V i= C f V f following injection of Evans Blue into specific Lymph Sacs and measuring its appearance in the venous circulation. The apparent Lymph volume was 57 ml kg–1. The greatest rate of Lymph return (0.5–0.8 ml kg–1 min–1) and best linear fit of Evans Blue appearance in the circulation with time followed injections into the subvertebral Lymph sac, which has direct connections to both the anterior and posterior pairs of Lymphatic hearts. Rate of Lymph flux from the pair of posterior Lymph hearts was three times greater than the anterior pair. Rates of Lymph flux were only influenced by injection volume in the crural Lymph Sacs, implicating Lymph sac compliance as the source of the pressure for Lymph movement from these Sacs. Femoral Lymph sac fluxes were decreased by 60% following ablation of the tendons of the sphincter ani cloacalis, abdominal crenators and piriformis. This supports a role for these muscles in generating the pressure for vertical Lymph movement. Femoral Lymph sac fluxes were also decreased by 70% by the insertion of a coil in the subvertebral Lymph sac, preventing normal compression and expansion of this sac by the lungs. This supports a role for lung ventilation in generating the pressure for vertical movement of Lymph. Contrary to previous hypotheses, fluxes from the brachial sac were not influenced by insertion of the coil into the subvertebral sac. A haemorrhage equivalent to 50% of the blood volume did not change Lymph flux rates from the femoral Lymph Sacs. These data provide the first experimental evidence that actual Lymph fluxes in the cane toad Rhinella marina depend on Lymph sac compliance, contraction of specific skeletal muscles and lung ventilation to move Lymph laterally and vertically to the dorsally located Lymphatic hearts.
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unique role of skeletal muscle contraction in vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Robert C. Drewes, Stanley S. Hillman, Michael S. Hedrick, Philip C. WithersAbstract:SUMMARY Electromyographic (EMG) activity of skeletal muscles that either insert on the skin or are associated with the margins of subcutaneous Lymph Sacs was monitored for two species of anurans, Chaunus marinus and Lithobates catesbeiana (formerly Bufo marinus and Rana catesbeiana ). Our hypothesis was that contraction of these muscles varies the volume, and hence pressure, within these Lymph Sacs, and that this pressure is responsible for moving Lymph from ventral, gravitationally dependent reaches of the body to dorsally located Lymph hearts. EMG activity of M. piriformis, M. gracilis minor, M. abdominal crenator, M. tensor fasciae latae, M. sphincter ani cloacalis, M. cutaneous pectoris and M. cutaneous dorsi was synchronous with pressure changes in their associated Lymph Sacs. These muscles contracted synchronously, and the pressures generated within the Lymph Sacs were sufficient to move Lymph vertically against gravity to the Lymph hearts. The pressure relationships were complex; both negative and positive pressures were recorded during a contractile event, a pattern consistent with the addition and loss of Lymphatic fluid to the Lymph Sacs. Severing the tendons of some of the muscles led to Lymph pooling in gravitationally dependent Lymph Sacs. These data are the first to: (1) describe a function for many of these skeletal muscles; (2) document the role of skeletal muscles in vertical Lymph movement in anurans; and (3) reinterpret the role of the urostyle, a bony element of the anuran pelvic girdle.
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lung ventilation contributes to vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P <0.001) relationships between lung pressure and Lymph sac pressures ( r 2 =0.19–0.72), indicating that pulmonary pressure is transmitted to the highly compliant Lymph Sacs that surround the lungs. Subvertebral sac pressure of resting animals was not significantly different between L. catesbeiana (518±282 Pa) and C. marinus (459±111 Pa). Brachial sac compliance (ml kPa –1 kg –1 ) also did not differ between the two species (33.6±5.0 in L. catesbeiana and 37.0±9.4 in C. marinus ). During expiration (lung deflation), reductions in expanding subvertebral sac pressure are communicated to the brachial Lymph sac. Changes in brachial and pubic Lymph sac pressures were correlated almost entirely during expiration rather than inspiration. The change in brachial sac pressure during expiration was 235±43 Pa for C. marinus and 215±50 Pa for L. catesbeiana , which is of sufficient magnitude to move Lymph the estimated 0.5–1.0 cm vertical distance from the forelimb to the vicinity of the anterior Lymph hearts. We suggest that Lymph is moved during expiration to the subvertebral sac from anterior and posterior Lymph Sacs. During lung inflation, increased Lymph sac pressure moves Lymph to axillary regions, where Lymph hearts can return Lymph to the vascular space. Consequently, pulmonary ventilation has an important role for Lymph movement and, hence, blood volume regulation in anurans.
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Lung ventilation contributes to vertical Lymph movement in anurans.
Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P
Michael S. Hedrick - One of the best experts on this subject based on the ideXlab platform.
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Visualising Lymph movement in anuran amphibians with computed tomography
Journal of Experimental Biology, 2014Co-Authors: Michael S. Hedrick, Kasper Hansen, Tobias Wang, Henrik Lauridsen, Jesper Thygesen, Michael PedersenAbstract:Lymph flux rates in anuran amphibians are high relative to those of other vertebrates owing to ‘leaky’ capillaries and a high interstitial compliance. Lymph movement is accomplished primarily by specialised Lymph muscles and lung ventilation that move Lymph through highly compartmentalised Lymph Sacs to the dorsally located Lymph hearts, which are responsible for pumping Lymph into the circulatory system; however, it is unclear how Lymph reaches the Lymph hearts. We used computed tomography (CT) to visualise an iodinated contrast agent, injected into various Lymph Sacs, through the Lymph system in cane toads ( Rhinella marina ). We observed vertical movement of contrast agent from Lymph Sacs as predicted, but the precise pathways were sometimes unexpected. These visual results confirm predictions regarding Lymph movement, but also provide some novel findings regarding the pathways for Lymph movement and establish CT as a useful technique for visualising Lymph movement in amphibians.
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Lung ventilation is an effector of the baroreflex in the cane toad (Rhinella marina)
The FASEB Journal, 2012Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:Lung ventilation plays an important role for regulating Lymph flux in anurans by changing the compliance of Lymph Sacs that surround the lungs during changes in lung volume. Because Lymph mobilizat...
-
Lymph flux rates from various Lymph Sacs in the cane toad Rhinella marina: an experimental evaluation of the roles of compliance, skeletal muscles and the lungs in the movement of Lymph
Journal of Experimental Biology, 2010Co-Authors: Stanley S. Hillman, Michael S. Hedrick, Robert C. Drewes, Philip C. WithersAbstract:A new method for quantitatively determining Lymph flux from various Lymphatic Sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C i V i= C f V f following injection of Evans Blue into specific Lymph Sacs and measuring its appearance in the venous circulation. The apparent Lymph volume was 57 ml kg–1. The greatest rate of Lymph return (0.5–0.8 ml kg–1 min–1) and best linear fit of Evans Blue appearance in the circulation with time followed injections into the subvertebral Lymph sac, which has direct connections to both the anterior and posterior pairs of Lymphatic hearts. Rate of Lymph flux from the pair of posterior Lymph hearts was three times greater than the anterior pair. Rates of Lymph flux were only influenced by injection volume in the crural Lymph Sacs, implicating Lymph sac compliance as the source of the pressure for Lymph movement from these Sacs. Femoral Lymph sac fluxes were decreased by 60% following ablation of the tendons of the sphincter ani cloacalis, abdominal crenators and piriformis. This supports a role for these muscles in generating the pressure for vertical Lymph movement. Femoral Lymph sac fluxes were also decreased by 70% by the insertion of a coil in the subvertebral Lymph sac, preventing normal compression and expansion of this sac by the lungs. This supports a role for lung ventilation in generating the pressure for vertical movement of Lymph. Contrary to previous hypotheses, fluxes from the brachial sac were not influenced by insertion of the coil into the subvertebral sac. A haemorrhage equivalent to 50% of the blood volume did not change Lymph flux rates from the femoral Lymph Sacs. These data provide the first experimental evidence that actual Lymph fluxes in the cane toad Rhinella marina depend on Lymph sac compliance, contraction of specific skeletal muscles and lung ventilation to move Lymph laterally and vertically to the dorsally located Lymphatic hearts.
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unique role of skeletal muscle contraction in vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Robert C. Drewes, Stanley S. Hillman, Michael S. Hedrick, Philip C. WithersAbstract:SUMMARY Electromyographic (EMG) activity of skeletal muscles that either insert on the skin or are associated with the margins of subcutaneous Lymph Sacs was monitored for two species of anurans, Chaunus marinus and Lithobates catesbeiana (formerly Bufo marinus and Rana catesbeiana ). Our hypothesis was that contraction of these muscles varies the volume, and hence pressure, within these Lymph Sacs, and that this pressure is responsible for moving Lymph from ventral, gravitationally dependent reaches of the body to dorsally located Lymph hearts. EMG activity of M. piriformis, M. gracilis minor, M. abdominal crenator, M. tensor fasciae latae, M. sphincter ani cloacalis, M. cutaneous pectoris and M. cutaneous dorsi was synchronous with pressure changes in their associated Lymph Sacs. These muscles contracted synchronously, and the pressures generated within the Lymph Sacs were sufficient to move Lymph vertically against gravity to the Lymph hearts. The pressure relationships were complex; both negative and positive pressures were recorded during a contractile event, a pattern consistent with the addition and loss of Lymphatic fluid to the Lymph Sacs. Severing the tendons of some of the muscles led to Lymph pooling in gravitationally dependent Lymph Sacs. These data are the first to: (1) describe a function for many of these skeletal muscles; (2) document the role of skeletal muscles in vertical Lymph movement in anurans; and (3) reinterpret the role of the urostyle, a bony element of the anuran pelvic girdle.
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lung ventilation contributes to vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P <0.001) relationships between lung pressure and Lymph sac pressures ( r 2 =0.19–0.72), indicating that pulmonary pressure is transmitted to the highly compliant Lymph Sacs that surround the lungs. Subvertebral sac pressure of resting animals was not significantly different between L. catesbeiana (518±282 Pa) and C. marinus (459±111 Pa). Brachial sac compliance (ml kPa –1 kg –1 ) also did not differ between the two species (33.6±5.0 in L. catesbeiana and 37.0±9.4 in C. marinus ). During expiration (lung deflation), reductions in expanding subvertebral sac pressure are communicated to the brachial Lymph sac. Changes in brachial and pubic Lymph sac pressures were correlated almost entirely during expiration rather than inspiration. The change in brachial sac pressure during expiration was 235±43 Pa for C. marinus and 215±50 Pa for L. catesbeiana , which is of sufficient magnitude to move Lymph the estimated 0.5–1.0 cm vertical distance from the forelimb to the vicinity of the anterior Lymph hearts. We suggest that Lymph is moved during expiration to the subvertebral sac from anterior and posterior Lymph Sacs. During lung inflation, increased Lymph sac pressure moves Lymph to axillary regions, where Lymph hearts can return Lymph to the vascular space. Consequently, pulmonary ventilation has an important role for Lymph movement and, hence, blood volume regulation in anurans.
Robert C. Drewes - One of the best experts on this subject based on the ideXlab platform.
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Lung ventilation is an effector of the baroreflex in the cane toad (Rhinella marina)
The FASEB Journal, 2012Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:Lung ventilation plays an important role for regulating Lymph flux in anurans by changing the compliance of Lymph Sacs that surround the lungs during changes in lung volume. Because Lymph mobilizat...
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Lymph flux rates from various Lymph Sacs in the cane toad Rhinella marina: an experimental evaluation of the roles of compliance, skeletal muscles and the lungs in the movement of Lymph
Journal of Experimental Biology, 2010Co-Authors: Stanley S. Hillman, Michael S. Hedrick, Robert C. Drewes, Philip C. WithersAbstract:A new method for quantitatively determining Lymph flux from various Lymphatic Sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C i V i= C f V f following injection of Evans Blue into specific Lymph Sacs and measuring its appearance in the venous circulation. The apparent Lymph volume was 57 ml kg–1. The greatest rate of Lymph return (0.5–0.8 ml kg–1 min–1) and best linear fit of Evans Blue appearance in the circulation with time followed injections into the subvertebral Lymph sac, which has direct connections to both the anterior and posterior pairs of Lymphatic hearts. Rate of Lymph flux from the pair of posterior Lymph hearts was three times greater than the anterior pair. Rates of Lymph flux were only influenced by injection volume in the crural Lymph Sacs, implicating Lymph sac compliance as the source of the pressure for Lymph movement from these Sacs. Femoral Lymph sac fluxes were decreased by 60% following ablation of the tendons of the sphincter ani cloacalis, abdominal crenators and piriformis. This supports a role for these muscles in generating the pressure for vertical Lymph movement. Femoral Lymph sac fluxes were also decreased by 70% by the insertion of a coil in the subvertebral Lymph sac, preventing normal compression and expansion of this sac by the lungs. This supports a role for lung ventilation in generating the pressure for vertical movement of Lymph. Contrary to previous hypotheses, fluxes from the brachial sac were not influenced by insertion of the coil into the subvertebral sac. A haemorrhage equivalent to 50% of the blood volume did not change Lymph flux rates from the femoral Lymph Sacs. These data provide the first experimental evidence that actual Lymph fluxes in the cane toad Rhinella marina depend on Lymph sac compliance, contraction of specific skeletal muscles and lung ventilation to move Lymph laterally and vertically to the dorsally located Lymphatic hearts.
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unique role of skeletal muscle contraction in vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Robert C. Drewes, Stanley S. Hillman, Michael S. Hedrick, Philip C. WithersAbstract:SUMMARY Electromyographic (EMG) activity of skeletal muscles that either insert on the skin or are associated with the margins of subcutaneous Lymph Sacs was monitored for two species of anurans, Chaunus marinus and Lithobates catesbeiana (formerly Bufo marinus and Rana catesbeiana ). Our hypothesis was that contraction of these muscles varies the volume, and hence pressure, within these Lymph Sacs, and that this pressure is responsible for moving Lymph from ventral, gravitationally dependent reaches of the body to dorsally located Lymph hearts. EMG activity of M. piriformis, M. gracilis minor, M. abdominal crenator, M. tensor fasciae latae, M. sphincter ani cloacalis, M. cutaneous pectoris and M. cutaneous dorsi was synchronous with pressure changes in their associated Lymph Sacs. These muscles contracted synchronously, and the pressures generated within the Lymph Sacs were sufficient to move Lymph vertically against gravity to the Lymph hearts. The pressure relationships were complex; both negative and positive pressures were recorded during a contractile event, a pattern consistent with the addition and loss of Lymphatic fluid to the Lymph Sacs. Severing the tendons of some of the muscles led to Lymph pooling in gravitationally dependent Lymph Sacs. These data are the first to: (1) describe a function for many of these skeletal muscles; (2) document the role of skeletal muscles in vertical Lymph movement in anurans; and (3) reinterpret the role of the urostyle, a bony element of the anuran pelvic girdle.
-
lung ventilation contributes to vertical Lymph movement in anurans
The Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P <0.001) relationships between lung pressure and Lymph sac pressures ( r 2 =0.19–0.72), indicating that pulmonary pressure is transmitted to the highly compliant Lymph Sacs that surround the lungs. Subvertebral sac pressure of resting animals was not significantly different between L. catesbeiana (518±282 Pa) and C. marinus (459±111 Pa). Brachial sac compliance (ml kPa –1 kg –1 ) also did not differ between the two species (33.6±5.0 in L. catesbeiana and 37.0±9.4 in C. marinus ). During expiration (lung deflation), reductions in expanding subvertebral sac pressure are communicated to the brachial Lymph sac. Changes in brachial and pubic Lymph sac pressures were correlated almost entirely during expiration rather than inspiration. The change in brachial sac pressure during expiration was 235±43 Pa for C. marinus and 215±50 Pa for L. catesbeiana , which is of sufficient magnitude to move Lymph the estimated 0.5–1.0 cm vertical distance from the forelimb to the vicinity of the anterior Lymph hearts. We suggest that Lymph is moved during expiration to the subvertebral sac from anterior and posterior Lymph Sacs. During lung inflation, increased Lymph sac pressure moves Lymph to axillary regions, where Lymph hearts can return Lymph to the vascular space. Consequently, pulmonary ventilation has an important role for Lymph movement and, hence, blood volume regulation in anurans.
-
Lung ventilation contributes to vertical Lymph movement in anurans.
Journal of Experimental Biology, 2007Co-Authors: Michael S. Hedrick, Stanley S. Hillman, Robert C. Drewes, Philip C. WithersAbstract:SUMMARY Anurans (frogs and toads) generate Lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky9 vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located Lymph hearts. At present, it is unclear how Lymphatic fluid that accumulates in central body subcutaneous Lymph Sacs is moved to the anterior and posterior Lymph hearts in the axillary regions and how Lymph is moved, against gravity, to the dorsally located Lymph hearts. In this study, we tested the hypothesis that lung ventilation, through its consequent effects on Lymph sac pressure, contributes to the vertical movement of Lymphatic fluid in the cane toad ( Chaunus marinus ) and the North American bullfrog ( Lithobates catesbeiana ). We measured pressure in the dorsal, lateral and subvertebral Lymph Sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral Lymph sac, which adheres to the dorsal surface of the lungs, simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant ( P
Kari Alitalo - One of the best experts on this subject based on the ideXlab platform.
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Loss of Endothelial Tie1 Receptor Impairs Lymphatic Vessel Development-Brief Report
Arteriosclerosis thrombosis and vascular biology, 2009Co-Authors: Gabriela D'amico, Emilia Anne Korhonen, Marika Waltari, Pipsa Saharinen, Pirjo Laakkonen, Kari AlitaloAbstract:Objective— Studies of Tie1 gene-targeted embryos have demonstrated loss of blood vessel integrity, but the relevance of Tie1 in Lymphatic vasculature development is unknown. We tested the hypothesis that the swelling observed in Tie1 mutant embryos is associated with Lymphatic vascular defects. Methods and Results— We could extend the survival of the Tie1 -deficient embryos in the ICR background, which allowed us to study their Lymphatic vessel development. At embryonic day (E) 14.5, the Tie1 −/− embryos had edema and hemorrhages and began to die. Immunohistochemical analysis revealed that they have abnormal Lymph Sacs. Tie1 −/− mutants were swollen already at E12.5 without signs of hemorrhage. Their Lymph Sacs were abnormally patterned, suggesting that Lymphatic malformations precede the blood vascular defects. We generated mice with a conditional Cre/ lox P Tie1 neo locus and found that the homozygous Tie1 neo/neo hypomorphic embryos survived until E15.5 with Lymphatic malformations resembling those seen in the Tie1 −/− mutants. Conclusion— Our data show that loss of Tie1 results in Lymphatic vascular abnormalities that precede the blood vessel phenotype. These findings indicate that Tie1 is involved in Lymphangiogenesis and suggest differential requirements for Tie1 signaling in the two vascular compartments.
