Structured lipids improve fat absorption in normal and malabsorbing rats.
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The presence of medium-chain fatty acids in dietary fatty acid as well as the triacylglycerol structure may influence the absorption and lymphatic transport of fatty acids. We compared the lymphatic transport and recovery of fatty acids from four intragastrically administered fats based on rapeseed oil and decanoic acid in two rat models of normal absorption and malabsorption, respectively. The fats were: 1) a fat with a regiospecific structure, 2) a similar fat but with a random distribution of fatty acids in the triacylglycerol molecule, 3) a physical mixture of tridecanoin and rapeseed oil and 4) rapeseed oil as control. Lymph samples were collected for 24 h. Significantly higher recoveries were observed of total fatty acids, oleic acid, linoleic acid and linolenic acid from the specific oil in malabsorbing rats and of linoleic acid in normal rats fed specific oil compared with those fed rapeseed oil. Furthermore, the recoveries of oleic acid and linolenic acid from the specific oil in normal rats were higher than those from the other oils. In malabsorbing rats, the transport of all fats was approximately 90% less than that of normal rats. The present study demonstrates improved hydrolysis and absorption of the specific oil compared with the other oils examined both in rats with normal absorption and in rats with malabsorption. (+info)
Lymph-borne chemokines and other low molecular weight molecules reach high endothelial venules via specialized conduits while a functional barrier limits access to the lymphocyte microenvironments in lymph node cortex.
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Lymph-borne, soluble factors (e.g., chemokines and others) influence lymphocyte recirculation and endothelial phenotype at high endothelial venules (HEVs) in lymph node cortex. Yet the route lymph-borne soluble molecules travel from the subcapsular sinus to the HEVs is unclear. Therefore, we injected subcutaneously into mice and rats a wide variety of fluorophore-labeled, soluble molecules and examined their distribution in the draining lymph nodes. Rather than percolating throughout the draining lymph node, all molecules, including microbial lipopolysaccharide, were very visible in the subcapsular and medullary sinuses but were largely excluded from the cortical lymphocyte microenvironments. Exclusion prevailed even during the acute lymph node enlargement accompanying viral infection. However, low molecular mass (MW) molecules, including chemokines, did gain entry into the cortex, but in a very defined manner. Low MW, fluorophore-labeled molecules highlighted the subcapsular sinus, the reticular fibers, and the abluminal and luminal surfaces of the associated HEVs. These low MW molecules were in the fibers of the reticular network, a meshwork of collagen fibers ensheathed by fibroblastic reticular cells that connects the subcapsular sinus floor and the HEVs by intertwining with their basement membranes. Thus, low MW, lymph-borne molecules, including chemokines, traveled rapidly from the subcapsular sinus to the HEVs using the reticular network as a conduit. (+info)
Vascular endothelial growth factor receptors in the regulation of angiogenesis and lymphangiogenesis.
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VEGFR-1 (Flt-1), VEGFR-2 (KDR) and VEGFR-3 (Flt4) are endothelial specific receptor tyrosine kinases, regulated by members of the vascular endothelial growth factor family. VEGFRs are indispensable for embryonic vascular development, and are involved in the regulation of many aspects of physiological and pathological angiogenesis. VEGF-C and VEGF-D, as ligands for VEGFR-3 are also capable of stimulating lymphangiogenesis and at least VEGF-C can enhance lymphatic metastasis. Recent studies have shown that missense mutations within the VEGFR-3 tyrosine kinase domain are associated with human hereditary lymphedema, suggesting an important role for this receptor in the development of the lymphatic vasculature. (+info)
Pulmonary vascular changes associated with isolated mitral stenosis in India.
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Pulmonary vascular changes were studied in 100 cases of isolated mitral stenosis; these included 90 patients in whom lung biopsies were obtained at valvotomy and 10 patients who came to necropsy. Medial thickness of the pulmonary arteries was measured in each case and in 12 cases was correlated with the haemodynamic data. Most patients were young, 78 being 30 years of age or less and 42 under 20 years or less. Males predominated 2:1. All patients with mitral stenosis showed varying degrees of vascular and other associated parenchymal changes. The most conspicuous were those observed in the muscular branches of the pulmonary artery in which the media was thickened in all cases, moderately in 44 and considerably in 28 cases. Dilation lesions representing grade 4 lesions of hypertensive pulmonary vascular disease (Heath and Edwards, 1958), hitherto not described in mitral stenosis, were observed in 4 cases. The intima was found to be frequently abnormal, showing oedema, fibrosis, and, more importantly, variable degrees of muscularization, often suggesting the incipient formation of a second media. Arteries and arterioles were often occluded by thrombi in various stages of organization, and the freshly formed channels tended to acquire a muscular lining. Arterioles were muscularized in all cases, and in many there was a pronounced intimal proliferation. Other changes included medial hypertrophy in the veins and and occasional muscularization and dilatation of the lymphatics. A notable feature was hypertrophy of the musculature of the bronchiolo-alvelar system seen in a majority of cases. The alveolar walls showed variable degrees of thickening and fibrosis, intimal proliferation of alveolar capillaries, and "epithelialization" of alveoli. Haemosiderosis was present in 70 cases. On the whole the more severe changes were observed more often in the younger subjects, further supporting the observation that rheumatic mitral stenosis in India commonly affects the juvenile age groups and is characterized by association with severe pulmonary hypertension. Medial hypertrophy was proportional to the level of pulmonary artery pressure. (+info)
Structure, function, and molecular control of the skin lymphatic system.
(53/803)
The mechanisms of angiogenesis have been studied extensively over the past years. The focus, however, has been almost exclusively on blood vessels, whereas little effort has been directed toward understanding lymphangiogenesis and the role of lymphatic vessels in physiology and pathology. The lymphatic system, acting in concert with the blood vascular system, is of fundamental importance in maintaining tissue homeostasis, and disorders of the lymphatic system are common, often resulting in chronic, disabling conditions. This overview summarizes the most important aspects of the structure and function of the lymphatic system with emphasis on the skin lymphatic vasculature and the differences between blood and lymphatic vessels. Special attention has been given to the methods employed in research of the lymphatic system. Finally, we describe molecular mechanisms involved in the regulation of lymphangiogenesis. Vascular endothelial growth factor and vascular endothelial growth factor-C, expressed by distinct skin cell populations, play an important role in the molecular control of skin angiogenesis and lymphangiogenesis. (+info)
Stochastic regulation of cell migration from the efferent lymph to oxazolone-stimulated skin.
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The systemic immune response is a dynamic process involving the trafficking of lymphocytes from the Ag-stimulated lymph node to the peripheral tissue. Studies in sheep have demonstrated several phases of cell output in the efferent lymph after Ag stimulation. When skin contact sensitizers are used as Ag, the efferent lymph cell output peaks approximately 96 h after Ag stimulation and is temporally associated with the recruitment of cells into the skin. To investigate the relative contribution of this high-output phase of efferent lymphocytes to lymphocytic inflammation in the skin, we used a common contact sensitizer 2-phenyl-4-ethoxymethylene-5-oxazolone (oxazolone) to stimulate the skin and draining prescapular lymph node of adult sheep. The efferent lymph ducts draining the Ag-stimulated and contralateral control lymph nodes were cannulated throughout the experimental period. The lymphocytes leaving the lymph nodes during the 72-h period before maximum infiltration were differentially labeled with fluorescent tracers, reinjected into the arterial circulation, and tracked to the site of Ag stimulation. Quantitative tissue cytometry of the skin at the conclusion of the injection period (96 h after Ag stimulation) demonstrated more migratory cells derived from the Ag-stimulated lymph node than the contralateral control (median 18.5 vs 15.5 per field; p < 0.05). However, when corrected for total cell output of the lymph node, the Ag-stimulated migratory cells were 3.8-fold more prevalent in the skin than the contralateral control cells. These results suggest that the in situ immune response generally mirrors the frequency of recruitable lymphocytes in the peripheral blood. (+info)
Postembryonic hematopoiesis in Drosophila.
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We have investigated the blood cell types present in Drosophila at postembryonic stages and have analysed their modifications during development and under immune conditions. The anterior lobes of the larval hematopoietic organ or lymph gland contain numerous active secretory cells, plasmatocytes, few crystal cells, and a number of undifferentiated prohemocytes. The posterior lobes contain essentially prohemocytes. The blood cell population in larval hemolymph differs and consists mainly of plasmatocytes which are phagocytes, and of a low percentage of crystal cells which reportedly play a role in humoral melanisation. We show that the cells in the lymph gland can differentiate into a given blood cell lineage when solicited. Under normal nonimmune conditions, we observe a massive differentiation into active macrophages at the onset of metamorphosis in all lobes. Simultaneously, circulating plasmatocytes modify their adhesion and phagocytic properties to become pupal macrophages. All phagocytic cells participate in metamorphosis by ingesting doomed larval tissues. The most dramatic effect on larval hematopoiesis was observed following infestation by a parasitoid wasp. Cells within all lymph gland lobes, including prohemocytes from posterior lobes, massively differentiate into a new cell type specifically devoted to encapsulation, the lamellocyte. (+info)
A comparative study of anaerobic Coryneforms. Attempts to correlate their anti-tumour activity with their serological properties and ability to stimulate the lymphoreticular system.
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Various strains of anaerobic coryneforms and the closely related Propionibacteria have been compared in vivo with respect to their anti-tumour activity. Their effectiveness has been correlated with their serological relationship and to some extent with their ability to stimulate the lymphoreticular system. Organisms belonging to Corynebacterium acnes groups I and II and C. avidum group IV were active anti-tumour agents, although of varying effectiveness. These strains are serologically closely related and all produce a soluble cross-reacting antigen. The single C. granulosum group III strain which we tested, an unclassified coryneform, and the classical Propionibacteria did not cross-react with the main group and had little or no anti-tumour activity. At the high dose (0.7 mg) we used, all strains, whether they inhibited tumour development or not, enhanced clearance of colloidal carbon and stimulated production of an inflammatory peritoneal exudate; at lower dosage the results were too variable to permit valid comparison. At the higher dose anti-tumour activity of a strain appeared to correlate best with ability to produce splenomegally and decrease red cell volume in the blood. (+info)