Amount Of Lymph Research Articles

Structure and physiology of the lymphatic vasculature

The lymphatic vascular system is a highly organized network of structurally and functionally connected specialized lymphatic vessels of various sizes and lymph nodes that perform metabolic and transport functions. Lymph is a blood plasma filtrate that comprises antigen-presenting cells and lymphocytes. Via lymph, excess fluid and extravasated proteins are removed from the tissues. The lymphatic system supports an extracellular fluid homeostasis that is favorable for optimal tissue functioning by removing substances that result from metabolism or cell death, as well as optimizing immunity against bacteria, viruses and other antigens. Although the lymphatic vasculature is not formally considered part of the immune system, it is crucial for the traffic of antigens and immune cells. In addition, lymphatic endothelial cells can supply antigens and express factors that modulate immune responses. After an inflammatory stimulus, endothelial cells produce chemokines, which recruit immune cells to the lymph nodes. Unlike the circulatory system with a centralized pump, the movement of lymph through the network of lymphatic vessels is provided by forces that stimulate the initial formation of lymph in the tissues and the ability of the lymphatic vessels and nodes to rhythmically contract, providing increased pressure and lymph movement in the proximal direction. Since the metabolic rate in various organs and tissues varies significantly depending on the functional state of the tissue, the blood flow through the tissue and the amount of lymph formed also change significantly. The lymphatic vasculature has several circuits for regulating lymph flow. This review provides a comprehensive overview of the important results obtained over the past century and discusses the molecular and physiological control of the transport function of lymphatic vessels and nodes.

Pressure within the thoracic duct modulates lymph composition

The amount of lymph received by the thoracic duct depends on each contributing organ's ability to produce interstitial fluid and generate a pressure differential moving lymph into the central lymphatic circulation. It has been reported that varying the pressure within the thoracic duct could alter each organ's contribution to thoracic duct flow. The thoracic duct above the diaphragm was cannulated to obtain lymph from the liver, gut, and lower body. Pressure within the thoracic duct was elevated serially by increasing the lymphatic cannula outflow height. This caused lymph protein concentration to increase while chyle concentration (measured by absorbance) decreased. The data demonstrate that as thoracic duct pressure increases, the percentage contribution of gut lymph flow (as represented by chyle concentration) decreases while the contribution of lymph originating within the liver (as indicated by higher protein concentration) increases. We conclude that pressure variation within the central lymphatic system affects the amount of lymph or edema fluid leaving any given organ.

Effects of tetrahydrolipstatin, a lipase inhibitor, on absorption of fat from the intestine of the rat

Tetrahydrolipstatin (THL) derived by hydrogenation from lipstatin, a lipase inhibitor produced by Streptomyces toxytricini, has been shown to inhibit in vitro the activity of all three lipases secreted to the gastro-intestinal tract; gastric lipase, pancreatic lipase and carboxylester lipase (cholesterol ester hydrolase). The effects of THL on intestinal absorption of fat (transport to the thoracic duct chyle) has now been investigated after intraduodenal infusion in a rat model. Absorption of label from oleic acid when administered with monoolein in micellar bile salt solution was not affected by THL in concentrations up to 10 −4 M calculated on the volume of the aqueous phase. Absorption of free cholesterol in micellar bile salt solution of the lipolytic products of triolein; oleic acid and monoolein, is not significantly affected at a concentration of THL of 10 −4 M. Absorption of cholesterol from cholesteryl oleate under the same conditions is almost completely inhibited. The results indicate that absorption of free cholesterol is not dependent on the activity of pancreatic cholesterol ester hydrolase. The absorption of emulsified triolein was not significantly affected by 10 −5 M THL but decreased to around 30% of the controls by a concentration 10-times higher. There was no significant decrease of cholesterol absorption when administered in emulsified triolein while absorption of cholesteryl oleate was reduced at both concentrations of THL and almost completely at 10 −4 M. Radioactivity from [2- 14C]THL when administered emulsified in triolein was recovered in urine, bile and thoracic duct lymph to 10–14, 8–13 and 1–3%, respectively, largely independent on dose administered. Label from [1″- 14C]THL was recovered in the same amounts in lymph but much less in bile and urine indicating that the amino acid moiety has been split off early in the absorption process.

THE ROLE OF THE LYMPHATIC SYSTEM IN THE ABSORPTION OF WATER FROM THE INTESTINE OF THE RAT

The flow and composition of lymph in the cisterna chyli and mesenteric lymphatic vessel of the restrained conscious rat has been studied in relation to the ingestion of 5 ml. of water and isotonic saline. In both cases the lymph flow increases and the protein concentration of the lymph falls; the time relationships are, however, different. When water is taken, the response begins in a few minutes and is over in 30 minutes; when saline is taken, the response begins in 15 minutes and is over in 60 minutes. The excess amount of lymph recovered during the responses is about 0·8 ml. These studies, and studies with tritiated water, suggest that during the first 10 minutes after rats drink water there is a transient bulk flow of fluid from the intestinal lumen into the intestinal lymphatics. The intestinal lymphatics seem to act as an overflow system during the absorption of hypotonic fluid.