Structure of Lymphatic Valves in the Spinotrapezius Muscle of the Rat

Mazzoni, Michelle C.; Skalak, Thomas C.; Schmid‐Schönbein, Geert W.

doi:10.1159/000158707

Cited by 33 publications

(35 citation statements)

References 6 publications

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“…Collagen was observed only at the insertion points and buttresses of the valves and at the outer wall of the vessel, suggesting that this regional differentiation provides structural support for the valve leaflets and vessel. The buttresses are believed to support the leaflets, allowing rapid and complete closure of the valve during retrograde flow while preventing valve inversion (Mazzoni et al, 21 ). Previous studies on lymphatic valve structure yielded mixed results.…”

Section: Discussionmentioning

confidence: 99%

Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

Rahbar

Weimer

Gibbs

et al. 2012

Lymphatic Research and Biology

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Background: Lymph flow depends on both the rate of lymph production by tissues and the extent of passive and active pumping. Here we aim to characterize the passive mechanical properties of a lymphangion in both midlymphangion and valve segments to assess regional differences along a lymphangion, as well as evaluating its structural composition. Methods and Results: Mesenteric lymphatic vessels were isolated and cannulated in a microchamber for pressure-diameter (P-D) testing. Vessels were inflated from 0 to 20 cmH 2 O at a rate of 4 cmH 2 O/min, and vessel diameter was continuously tracked, using an inverted microscope, video camera, and custom LabVIEW program, at both mid-lymphangion and valve segments. Isolated lymphatic vessels were also pressure-fixed at 2 and 7 cmH 2 O and imaged using a nonlinear optical microscope (NLOM) to obtain collagen and elastin structural information. We observed a highly nonlinear P-D response at low pressures (3-5 cmH 2 O), which was modeled using a three-parameter constitutive equation. No significant difference in the passive P-D response was observed between mid-lymphangion and valve regions. NLOM imaging revealed an inner elastin layer and outer collagen layer at all locations. Lymphatic valve leaflets were predominantly elastin with thick axially oriented collagen bands at the insertion points. Conclusions: We observed a highly nonlinear P-D response at low pressures (3-5 cmH 2 O) and developed the first constitutive equation to describe the passive P-D response for a lymphangion. The passive P-D response did not vary among regions, in agreement with the composition of elastin and collagen in the lymphatic wall.

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Section: Discussionmentioning

confidence: 99%

Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

Rahbar

Weimer

Gibbs

et al. 2012

Lymphatic Research and Biology

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“…Because of the much higher v* e during diaphragmatic skeletal muscle than v* i during spontaneous lymphatic smooth muscle contraction, the corresponding wall shear stress increased almost 15 times more during extrinsic pumping, likely representing an important determinant of the transition from a bidirectional to unidirectional intraluminal flux. Indeed, for very low Reynold's numbers, intraluminal valve closure depends upon pressure drop and viscous forces alone (16); the high forward v* e attained during skeletal muscle contraction might rise both these parameters enough to trigger closure of the intraluminal valve thus preventing lymph backflow, and favoring unidirectional forward flow. On the contrary, the extremely low v* i observed with spontaneous contraction alone would not be able to set the conditions favorable to backward valve closure, thus resulting in significant backflow and slow forward propulsion.…”

Section: Ajp-heart Circ Physiolmentioning

confidence: 99%

Lymph flow pattern in pleural diaphragmatic lymphatics during intrinsic and extrinsic isotonic contraction

Moriondo

Solari

Marcozzi

et al. 2016

American Journal of Physiology-Heart and Circulatory Physiology

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Moriondo A, Solari E, Marcozzi C, Negrini D. Lymph flow pattern in pleural diaphragmatic lymphatics during intrinsic and extrinsic isotonic contraction. Am J Physiol Heart Circ Physiol 310: H60 -H70, 2016. First published October 29, 2015 doi:10.1152/ajpheart.00640.2015.-Peripheral rat diaphragmatic lymphatic vessels, endowed with intrinsic spontaneous contractility, were in vivo filled with fluorescent dextrans and microspheres and subsequently studied ex vivo in excised diaphragmatic samples. Changes in diameter and lymph velocity were detected, in a vessel segment, during spontaneous lymphatic smooth muscle contraction and upon activation, through electrical whole-field stimulation, of diaphragmatic skeletal muscle fibers. During intrinsic contraction lymph flowed both forward and backward, with a net forward propulsion of 14.1 Ϯ 2.9 m at an average net forward speed of 18.0 Ϯ 3.6 m/s. Each skeletal muscle contraction sustained a net forward-lymph displacement of 441.9 Ϯ 159.2 m at an average velocity of 339.9 Ϯ 122.7 m/s, values significantly higher than those documented during spontaneous contraction. The flow velocity profile was parabolic during both spontaneous and skeletal muscle contraction, and the shear stress calculated at the vessel wall at the highest instantaneous velocity never exceeded 0.25 dyne/cm 2 . Therefore, we propose that the synchronous contraction of diaphragmatic skeletal muscle fibers recruited at every inspiratory act dramatically enhances diaphragmatic lymph propulsion, whereas the spontaneous lymphatic contractility might, at least in the diaphragm, be essential in organizing the pattern of flow redistribution within the diaphragmatic lymphatic circuit. Moreover, the very low shear stress values observed in diaphragmatic lymphatics suggest that, in contrast with other contractile lymphatic networks, a likely interplay between intrinsic and extrinsic mechanisms be based on a mechanical and/or electrical connection rather than on nitric oxide release. lymph propulsion; tissue stress; spontaneous lymphatic contractility NEW AND NOTEWORTHYIn diaphragmatic lymphatics, flow velocity and lymph flow were more than two order of magnitude greater during contraction of diaphragmatic skeletal muscle than during spontaneous contraction of lymphatic smooth muscles, suggesting a marginal role of the latter in setting lymph flow in rhythmically moving, thoracic tissues.THE PLEURAL DIAPHRAGMATIC lymphatic system is composed of linear lymphatic vessels preferentially located in the tendineous and the medial muscular portion of the diaphragm, and of a more complex net of loop-like structures interconnected by short linear tracts and preferentially located at the most peripheral diaphragmatic rim (18). Given the strategic role played by pleural lymphatics in setting the correct pleural fluid volume and subatmospheric pressure required to maintain the normal lung chest wall coupling (29), much effort has been spent in the study of the inner regulatory mechanisms of lymph drainage and propulsion in th...

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“…[24][25][26][27][28][29][30][31] These important structures are a hallmark of the lymphatic network and their proper function depends upon some unique properties of the lymphatic. 24,26,29,30,32,33 The function of the lymphatic valves is thought to be driven by the pressures and flow of fluid across them, given their unique structure. …”

Section: The Secondary Lymphatic Valve Systemmentioning

confidence: 99%