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PubMed1995

Evidence that the L-arginine pathway plays a role in the regulation of pumping activity in bovine mesenteric lymphatic vessels.

The objective of this study was to investigate the role of the L-arginine pathway in the regulation of lymphatic pumping. Bovine mesenteric lymphatic vessels (8 to 12 cm in length containing four to six lymphangions) were immersed in an organ bath with input provided by a reservoir filled with Krebs solution. The vessels were stimulated to pump by applying a 6 cm H2O transmural pressure. The addition of 10(-7)-10(-4) M oxyhemoglobin, NG-monomethyl-L-arginine (L-NMMA), or methylene blue to the reservoir resulted in a reduction in lymphatic pumping. L-Arginine (10(-7)-10(-4) M) had no effect on spontaneous pumping activity. However, L-arginine reversed the inhibition caused by oxyhemoglobin and L-NMMA. When tested between 10(-7) and 10(-6) M, sodium nitroprusside (sNP) had variable effects on lymphatics. sNP depressed pumping in approximately 2/3 of the vessels and increased pumping in the remaining 1/3 of ducts. When the results were meaned, sNP caused a significant depression in activity. However, the lower concentration of sNP (10(-7) M) was able to reverse the inhibitory effects of oxyhemoglobin, L-NMMA, and methylene blue whereas the higher concentration (10(-6) M) caused further reductions in pumping activity. These results suggest that bovine lymphatic vessels produce nitric oxide or a related compound. L-Arginine metabolites appear to facilitate the pumping response by an as yet undefined mechanism.

Animals↗

PubMed1984

Thrombus formation in lymphatic vessels associated with Brugia malayi.

Lymph thrombi within affected afferent lymphatic vessels of cats infected with Brugia malayi were examined by scanning electron microscopy. Thrombi were made up of alternating layers of fibrin strands and cells, many of which were intact erythrocytes. The endothelial lining of the vessel wall near the site of thrombus attachment showed transition from normal endothelial cells to a flattened syncytium in which individual endothelial cells could not be distinguished. Imprints of cells, including erythrocytes, were visible in the vessel wall at the point of thrombus attachment. Damage to the endothelial lining may be a factor in the initiation of thrombus formation.

Animals↗

PubMed1998

A physiologic function for p-glycoprotein (MDR-1) during the migration of dendritic cells from skin via afferent lymphatic vessels.

P-glycoprotein (MDR-1) is a well-known transporter that mediates efflux of chemotherapeutic agents from the intracellular milieu and thereby contributes to drug resistance. MDR-1 also is expressed by nonmalignant cells, including leukocytes, but physiologic functions for MDR-1 are poorly defined. Using an initial screening assay that included >100 mAbs, we observed that neutralizing mAbs MRK16, UIC2, and 4E3 against MDR-1 specifically and potently blocked basal-to-apical transendothelial migration of mononuclear phagocytes, a process that may mimic their migration into lymphatic vessels. Antagonists of MDR-1 then were used in a model of authentic lymphatic clearance. In this model, antigen-presenting dendritic cells (DC) migrate out of explants of cultured human skin and into the culture medium via dermal lymphatic vessels. DC and T cells derived from skin expressed MDR-1 on their surfaces. Addition of anti-MDR-1 mAbs MRK16, UIC2, or the MDR-1 antagonist verapamil to skin explants at the onset of culture inhibited the appearance of DC, and accompanying T cells, in the culture medium by approximately 70%. Isotype-matched control mAbs against other DC molecules including CD18, CD31, and major histocompatibility complex I did not block. In the presence of MDR-1 antagonists, epidermal DC were retained in the epidermis, in contrast to control conditions. In summary, this work identifies a physiologic function for MDR-1 during the mobilization of DC and begins to elucidate how these critical antigen-presenting cells migrate from the periphery to lymph nodes to initiate T lymphocyte-mediated immunity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

Substance P and gastrin releasing peptide in bovine mesenteric lymphatic vessels: chemical characterization and action.

Alcoholic extracts of bovine mesenteric lymphatic vessels were assayed for the presence of SP, GRP, VIP, PHI, GIP and NT using specific radioimmunoassays. SP and GRP immunoreactivities were detected at concentrations of 190 +/- 20 and 1,000 +/- 130 pg.g-1, respectively. No significant levels of immunoreactivity were detected for any of the other peptides. SP and GRP immunoreactivities coeluted with their synthetic counterparts from both Sephadex G-50 and reversed phase HPLC columns. Synthetic SP (10(-9)-10(-7) M) and the naturally occurring analogue of GRP, bombesin (10(-9)-10(-7) M), increased spontaneous contraction rate in isolated vessel segments. This excitatory effect was not blocked by the alpha-adrenoceptor antagonist phentolamine (3 x 10(-6) M).

Animals↗

PubMed2005

[An experimental model of the lymphatic vessels transplantation].

The aim of this work is to describe a procedure of primary reconstruction of the lymphatic vessels on a model of heterotopic intestine transplantation in a rat. Both the donor and the recipient part of the procedure are described in a detail, as well as diagnostic methods of postoperative patency of the lympahatic anastomosis. In the end, the authors' own trial group is presented. However, no statistically significant differences were detected in histological findings of the intestinal graft rejection in rats with lymphatic anastomosis, compared with the control group.

Anastomosis, Surgical↗

PubMed1989

[Structure of the excretory ducts, intraorganic lymphatic vessels, tissue canals and intercellular space of various organs (data of scanning electron microscopy injection replicas)].

Architectonics of the biliary canaliculi and intrahepatic ducts systems, as well as intraorganic urinary pathways in white rats have been investigated by means of scanning electron microscopy of injection replica. Acinar structure of the intralobular part of the biliary bed has been proved. Anastomoses between the biliary canaliculi of the neighbouring lobules have been demonstrated. A useful method for obtaining injection replica of the intraorganic lymphatic vessels is filling of the ductal system of the parenchymatous organs with solid resins (methylmethacrylate+) under a high (nonphysiological) pressure. Casts of periportal and paravenous hepatic lymphatic vessels have been obtained. An ability of methylmethacrylate to replicate intercellular and connective tissue spaces is verified. Casts of the perisinusoid spaces (Disse) are obtained for the first time.

Animals↗

PubMed2002

Morphometric analysis of lymphatic vessels in primary biliary cirrhosis.

The purpose of this study was to elucidate the morphometric changes occurring in hepatic lymphatics in primary biliary cirrhosis (PBC). The lymphatic vessels were stained intensely by enzyme-histochemistry for 5'-nucleotidase while blood vessels stained well for alkaline phosphatase (ALP). We performed a morphometric analysis to estimate the number of lymphatic and blood vessels and their areas, using computer graphics software (NIH Image). Both the number of lymphatics and their areas in specimens in patients with PBC at an early stage were found to have increased. Neither the number nor the areas of the blood vessels showed any obvious relationship with the degree of fibrosis of PBC. Our results clarified that the sizes and number of lymphatics are increased even in the early stage of PBC. This is thought to be due to increased lymph production, which is caused by disturbance of the microcirculation associated with portal hypertension.

Journal Article↗

PubMed2001

Expression of vascular endothelial growth factor receptor 3 in blood and lymphatic vessels of lung adenocarcinoma.

Vascular endothelial growth factor receptor 3 (VEGFR-3) has been proposed as a marker for lymphatic endothelial cells. This study investigated the expression of VEGFR-3 in the tumour vessels of lung adenocarcinoma and evaluated whether VEGFR-3 staining was useful for identifying lymphatic vessels within the tumour stroma. It also explored whether active growth of lymphatic vessels occurred in lung adenocarcinoma. Formalin-fixed, paraffin-embedded specimens obtained from 60 cases of lung adenocarcinoma, including five cases of pure bronchiolo-alveolar carcinoma (BAC) without stromal, vascular, and pleural invasion, were examined. No VEGFR-3-positive vessels were observed in pure BAC, but varying numbers of VEGFR-3-positive vessels were found in 39 of 55 (70.9%) invasive adenocarcinomas. A comparison of serial sections stained for VEGFR-3, CD31, and laminin-1 showed that most of the VEGFR-3-positive vessels appeared to be blood vessels (CD31-positive, laminin-1-positive), but some had the characteristics of lymphatic vessels (variable staining for CD31, little or no staining for laminin-1). VEGFR-3 staining highlighted lymphatic invasion by cancer cells; this invasion could not be detected by CD31 or haematoxylin and eosin (H&E) staining. Active growth of lymphatic vessels (as indicated by nuclear Ki-67 labelling of the endothelium) was observed in five tumours, four of which showed a high level of lymphatic invasion by cancer cells. It was concluded that VEGFR-3 immunostaining did not discriminate clearly between vascular and lymphatic endothelial cells, since expression of VEGFR-3 can be up-regulated in tumour blood vessels. However, VEGFR-3 staining combined with laminin-1 and CD31 staining would be useful for identifying lymphatic vessels and their invasion by tumour cells in a more objective way. Finally, proliferation of lymphatic endothelial cells may occur in association with lymphatic invasion by cancer cells.

Adenocarcinoma↗

PubMed2000

Functional anatomy of lymphatic vessels under the aspect of tumor invasion.

In the human body there are about 800 lymph nodes, of which 300 are located in the head and neck area. The lymphatic system begins with initial finger-shaped lymphatic vessels consisting of valveless lymphatic capillaries and precollectors with valves. The precollectors become collectors and transport the lymph to the so-called lymph stems. These vessels lead into the right and left lymphatic duct and into the jugular trunk of the head and neck region. At the end they join into the blood circulation at the junction point of the jugular and subclavian veins. On the basis of the morphology of the initial lymphatics, these are probably the main port of entry of tumor cells. Investigations demonstrate the active invasion into the lymphatic system of melanoma cells. The preference of melanoma cells to adhere to the extracellular fibronectin of the endothelial cells may be a reason for the privileged invasion of the melanoma cells in the lymphatic system, because the extracellular matrix is not protected by a continuous basal lamina like blood vessels. Based on the directed movement of melanoma cells towards the fiber felt, there might be regulative mechanisms influencing the process of targeted adhesion.

Endothelium, Lymphatic↗

PubMed1980

Scanning electron microscopic study of canine lymphatic vessels and their valves.

The morphology of canine thoracic duct, peripheral collecting lymphatics and their valves was determined using scanning and transmission electron microscopy (SEM and TEM). Information from surface and subsurface structures was derived simultaneously in the SEM by using a heavy metal stain combined with backscattered electron imaging. The peripheral lymphatics and thoracic duct were covered by a continuous sheet of endotheial cells, the nuclei of which were slighly raised, avoid in shape with coarsely granular chromatin and long axes oriented parallel to the direction of flow. The immediate subendothelial connective tissue in the thoracic duct was primarily smooth muscle, whereas in the peripheral lymphatics reticular and elastic fibres predominated. Valves were seen in both peripheral and central lymphatics. These were covered with endothelium similar to the collecting lymphatic vessels, were usually bicuspid and had cusps that inserted either at a single point or overlapped prior to a wide based insertion. A complex network of connective tissue and elastic fibres was seen in valves and in the vessel walls adjacent to the valves. The similarities and dissimilarities of the SEM appearances of lymphatics arteries and veins are discussed.

Animals↗

PubMed2002

Vascular endothelial growth factors C and D and their VEGFR-2 and 3 receptors in blood and lymphatic vessels in healthy and arthritic synovium.

OBJECTIVE: To localize vascular endothelial growth factor C (VEGF-C) and VEGF-D in synovial specimens in relation to their VEGFR-2 and VEGFR-3 receptors in blood and lymphatic vessels. METHODS: Immunohistochemical staining and messenger RNA analysis from control and arthritic synovial membrane specimens. RESULTS: Quantitative RT-PCR disclosed that VEGF-C mRNA copy numbers were higher than VEGF-D mRNA copy numbers in the rheumatoid arthritis (RA), osteoarthritis, and control patient groups studied (p < 0.01). Immunohistochemical staining localized VEGF-C to synovial lining cell layer, pericytes, and smooth muscle cells of blood vessels. The number of VEGF-C positive cells was increased in the synovial lining of ankylosing spondylitis (AS) and RA compared to control synovium. However, in contrast to control synovial lining, little if any VEGF-D was detected in AS or RA synovial lining. VEGFR-2 expressing stromal blood vessels, also positive for the vascular endothelial marker PAL-E and the basement membrane marker laminin, were more abundant in RA and AS than in controls. Interestingly, the lymphatic endothelial receptor VEGFR-3 was also expressed in most synovial vessels, especially in the sublining capillaries and venules. CONCLUSION: VEGF-C is strongly expressed in the hypertrophic synovial lining of arthritic joints, whereas VEGF-D expression is very low in AS and RA. The expression of VEGF-C and VEGF-D in pericytes and smooth muscle cells suggests that these factors may have a role in maintaining vascular homeostasis. The VEGF receptors VEGFR-2 and VEGFR-3 are present in most of the sublining blood vessels. The expression of the lymphatic marker VEGFR-3 in the sublining blood vessels may relate to fluid filtration and/or fenestrations. The relatively few lymphatic vessels along with increased vascular permeability in RA may contribute to the development of tissue edema and joint stiffness.

Arthritis↗

PubMed1997

Fine structure of the choroidal coat of the avian eye. Lymphatic vessels.

PURPOSE: To clarify the fine structure of the avian choroid and thus help explain the mechanisms for normal and abnormal eye function and growth. METHODS: Eyes from normal chickens and from experimental chickens subjected to unilateral paracentesis were fixed either by perfusion or in situ, with or without post-fixation by microwave irradiation, and then processed for light and electron microscopic analysis. RESULTS: The avian choroid contains thin-walled lacunae, whose fine structure is identical to that of lymphatic vessels. The lacunae are much smaller toward the anterior chamber and the Schlemm's canal than posteriorly in the eye bulb. Large lacunae are situated primarily in the suprachoroidea, and their blind-ended capillary branches enter the choriocapillaris and the walls of large veins. The walls of the large veins contain villous structures that protrude into their lumina and are penetrated by thin lacunar branches and by side lines of the venous lumen. In normal chickens, the lacunae usually are devoid of blood cells. After paracentesis of the anterior eye chamber, the lacunae become filled with erythrocytes on the side that was operated on, but not on the contralateral side. CONCLUSIONS: The authors propose that the lacunae of the avian choroid represent a system of posterior short lymphatic vessels, which drain intraocular fluids directly into the eye's venous system, and that the villous structures are sites of communication between lacunae and veins. The demonstration of a choroidal lymphatic system opens new insights into the processes of fluid removal, control of intraocular pressure, and regulation of choroidal thickness in the avian eye under normal and experimental conditions.

Animals↗

PubMed1991

The influence of afferent lymphatic vessel interruption on vascular addressin expression.

Tissue-selective lymphocyte homing is directed in part by specialized vessels that define sites of lymphocyte exit from the blood. These vessels, the post capillary high endothelial venules (HEV), are found in organized lymphoid tissues, and at sites of chronic inflammation. Lymphocytes bearing specific receptors, called homing receptors, recognize and adhere to their putative ligands on high endothelial cells, the vascular addressins. After adhesion, lymphocytes enter organized lymphoid tissues by migrating through the endothelial cell wall. Cells and/or soluble factors arriving in lymph nodes by way of the afferent lymph supply have been implicated in the maintenance of HEV morphology and efficient lymphocyte homing. In the study reported here, we assessed the influence of afferent lymphatic vessel interruption on lymph node composition, organization of cellular elements; and on expression of vascular addressins. At 1 wk after occlusion of afferent lymphatic vessels, HEV became flat walled and expression of the peripheral lymph node addressin disappeared from the luminal aspect of most vessels, while being retained on the abluminal side. In addition, an HEV-specific differentiation marker, defined by mAb MECA-325, was undetectable at 7-d postocclusion. In vivo homing studies revealed that these modified vessels support minimal lymphocyte traffic from the blood. After occlusion, we observed dramatic changes in lymphocyte populations and at 7-d postsurgery, lymph nodes were populated predominantly by cells lacking the peripheral lymph node homing receptor LECAM-1. In addition, effects on nonlymphoid cells were observed: subcapsular sinus macrophages, defined by mAb MOMA-1, disappeared; and interdigitating dendritic cells, defined by mAb NLDC-145, were dramatically reduced. These data reveal that functioning afferent lymphatics are centrally involved in maintaining normal lymph node homeostasis.

Animals↗

PubMed1977

Lymphatic vessels of the human dental pulp.

Noncarious teeth obtained from individuals 15 to 50 years of age were used to study the lymphatic drainage of the human pulp. Thick sections (50 to 150 microns) were stained with iron hematoxylin for the demonstration of lymph and blood vessels. Lymph capillaries originated as blind sacs in the odontoblastic layer and in the pulp proper near the pulpo-odontoblastic border. They drained into small thin-walled collecting vessels that were irregular in shape and showed great variability in their drainage patterns. Communications between these vessels were very common. The larger conducting lymphatic vessels accompanied the blood vessels and nerves in their course through the pulp. They could be identified by their thin walls and small size. The large caliber lymphatic vessels contained valves, a structure not present in the veins of the same size. The conducting lymphatic vessels passed through the roots as individual units without draining into a large single vessel. The lymphatic vessels of the human pulp must be considered as a pathway for the removal of excessive tissue fluid in normal and diseased pulps.

Adolescent↗

PubMed2003

The same endothelial receptor controls lymphocyte traffic both in vascular and lymphatic vessels.

The mechanisms controlling the exit of lymphocytes from tissues via lymphatics are practically unknown. We have now identified a 270-300-kDa molecule designated common lymphatic endothelial and vascular endothelial receptor-1 (CLEVER-1) on human lymphatic endothelium and high endothelial venules. We show that it mediates binding of lymphocytes both to high endothelial venules and to lymphatic vessels. Moreover, blocking of the function of CLEVER-1 results in significant reduction of lymphocyte traffic in vivo. Notably, CLEVER-1 is also an inducible vascular adhesion molecule for other classes of leukocytes at sites of inflammation in peripheral tissues. These findings suggest that CLEVER-1 is involved in regulation of lymphocyte recirculation and migration of leukocytes to sites of inflammation and is a potential new target to control inflammation.

Animals↗

PubMed2004

Cyclopiazonic acid decreases spontaneous transient depolarizations in guinea pig mesenteric lymphatic vessels in endothelium-dependent and -independent manners.

Guinea pig mesenteric lymphatic vessels exhibit vasomotion through a pacemaker mechanism that involves intracellular Ca(2+) release and resultant spontaneous transient depolarizations (STDs) of the smooth muscle membrane potential. This study presents a detailed characterization of the effects of cyclopiazonic acid (CPA) on this pacemaker activity. Microelectrode recordings from smooth muscle in vessel segments revealed that application of CPA (1-10 microM) caused a hyperpolarization accompanied by a decrease in the frequency and amplitude of STDs. The CPA-induced hyperpolarization was abolished after destruction of the endothelium and in the presence of N(G)-nitro-L-arginine (100 microM) or 1H-[1,2,4]oxadiazolol-[4,3-a]quinoxaline-1-one (10 microM), which suggests a contribution of endothelium-derived nitric oxide (EDNO) in this response. In the absence of EDNO-induced effects, CPA decreased the frequency and amplitude of STDs recorded before and in the presence of the thromboxane A(2) mimetic U-46619, norepinephrine, or thimerosal. CPA abolished U-46619-induced vasomotion as determined by measurement of constriction-associated intracellular Ca2+ concentration using the ratiometric Ca2+ indicator fura-2. The endothelial actions of CPA were compared with those of ACh, which is known to cause EDNO release in this preparation. Although CPA and ACh both increased endothelial intracellular Ca2+ concentration and depolarized the membrane potential, the kinetics of action for both parameters were markedly slower for CPA than ACh. These results suggest that CPA first hyperpolarizes the lymphatic smooth muscle and decreases STD frequency and amplitude through endothelial release of EDNO, and second, consistent with the action of CPA to inhibit sarcoplasmic reticulum Ca2+-ATPase and deplete Ca2+ stores, it further reduces STD activity. Inhibition of the lymphatic smooth muscle pacemaker mechanism is thought to abolish agonist-induced vasomotion.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1990

[The rheological properties of the large lymphatic vessels].

The resiliency module of the cuff of the bull mesenteric lymphatic vessels' lymphangion in the circular direction within physiological limits of transmural pressure is, on the average, (3.1 +/- 0.4) x 10(4) H.m-2. The resiliency differential module depends on the functional state of smooth muscle cells. In maximal activation of the myocytes' contractile apparatus, the resiliency module of the muscle cuff increases by 1.7 times and, against the background of the myocytes relaxation, it decreases by 1.6 times. The valvular portion of the lymphangion is more rigid and its resiliency module changes rather insignificantly in contraction or relaxation of smooth muscle cells. High distensibility of the muscle cuff provides for the capacitance function and for the self-regulation of its pumping function. Rigid wall of the valvular portion eliminates the insufficiency of the valves at a high transmural pressure and maintains an efficient work of the valvular apparatus.

Animals↗

PubMed2005

Peritumoral lymphatic vessel density and vascular endothelial growth factor C expression in early-stage squamous cell carcinoma of the uterine cervix.

PURPOSE: Lymphatic invasion and nodal metastasis plays a major role in the spread of cervical cancer; however, little is known about the mechanisms whereby tumor cells enter the lymphatic system. EXPERIMENTAL DESIGN: We examined the intra- and peritumoral lymphatic vessel density (LVD) using D2-40 immunohistochemistry in 111 cervical squamous cell carcinomas and correlated them with vascular endothelial growth factor (VEGF)-C expression, clinicopathologic tumor features, and outcome. RESULTS: Compared with benign cervix, intratumoral and peritumoral LVD was significantly increased (P < 0.0001). Peritumoral LVD was significantly higher than intratumoral LVD (P = 0.009). High peritumoral, but not intratumoral, LVD showed significant correlation with high tumor stage, lymphatic invasion, and nodal metastasis. VEGF-C showed increased expression at the invasive edge compared with the center of tumors (P < 0.0001) and correlated with high peritumoral LVD, lymphatic invasion, and nodal metastasis. High peritumoral LVD and VEGF-C expression at the invasive edge of tumors were associated with poor overall and recurrence-free survival in univariate analysis. In multivariate analysis, peritumoral LVD was the only independent term predictive of overall survival. CONCLUSIONS: Our findings suggest a potential role for VEGF-C in tumor-induced lymphangiogenesis represented by high peritumoral LVD, which may be one of the mechanisms leading to lymphatic invasion and metastatic spread. High peritumoral LVD may be an independent prognostic factor in early-stage cervical cancer.

Carcinoma in Situ↗