Search

BACKGROUND This study was carried out to evaluate the effects of a long-term high-fat diet on lipids and lipoproteins composition in thoracic duct lymph in pigs. MATERIAL AND METHODS We examined lymph taken from the thoracic duct from 24 female white sharp-ear pigs, divided into 3 experimental groups fed different diets for 12 months: (a) the control group, fed the standard balanced diet; (b) the HFD group, fed an unbalanced, high-fat diet, and (c) the reversal diet group (RD), fed an unbalanced, high-fat diet for 9 months and then a standard balanced diet for 3 months. RESULTS Lymph analysis after 12 months of fixed diets revealed significantly higher concentration of proteins in the HFD group in comparison to the control and RD groups. Examination of lymph lipoproteins fractions showed that the high-fat diet in the HFD group in comparison to control group caused an increase in cholesterol, phospholipids, and proteins content within HDL and chylomicrons. There were also more proteins within HDL in the HFD group in comparison to the RD group and more triglycerides within chylomicrons in the HFD group in comparison to the control group. CONCLUSIONS A long-term high-fat diet resulted in changed structure of HDL and chylomicrons in the thoracic duct lymph. Alterations in HDL composition suggest that a high-fat diet enhances reverses cholesterol transport. Changes in chylomicrons structure show the adaptation to more intense transport of dietary fat from the intestine to the liver under the influence of a high-fat diet. Reversal to a standard balanced diet had the opposite effects.

Purpose: Oxycholesterols (OCs) are produced from cholesterol by oxidation of the steroidal backbone and side-chain. OCs are present in blood and evidence suggests their involvement in disease development and progression. However, limited information is available regarding the absorption mechanisms and relative absorption rates of dietary OCs. Although ezetimibe is known to inhibit intestinal cholesterol absorption via Niemann-Pick C1-Like 1 (NPC1L1), whether it also inhibits dietary OC absorption is unclear., Methods: We investigated the effects of ezetimibe on OC absorption in rats fed an OC-rich diet containing 10 different OCs. We collected lymphatic fluid using permanent cannulation of the thoracic duct and quantified OC levels., Results: Ezetimibe treatment significantly reduced the apparent absorption of 5β,6β-epoxycholesterol (5,6β-epoxy) and its levels in the proximal intestinal mucosa in OC-fed rats. Using in silico analyses, the binding energy of NPC1L1 N-terminal domain (NPC1L1-NTD) and 5,6β-epoxy was found to be similar to that of NPC1L1-NTD and cholesterol, suggesting that polar uncharged amino acids located in the steroidal part of 5,6β-epoxy were involved., Conclusion: Our results indicate that ezetimibe-mediated inhibition of dietary OC absorption varies depending on the specific OC, and only the absorption of 5,6β-epoxy is significantly reduced.

Background: Chylothorax is a rare condition which can be associated with malignant lymphoproliferative disorders (LPDs). We retrospectively analyzed the results of the conservative treatment of 10 patients with persistent non-traumatic malignant chylothorax., Results: Conservative treatment lead to a decline of chylothorax after mean of 66 days and consisted of the treatment of the underlying disease and of simultaneous long-term supportive care (drainage of the thoracic cavity, dietary measures and nutrition management). In most cases (80%), chylothorax disappeared only after a successful therapeutic response of the underlying disease. Low-dose radiotherapy had very good effects in two patients., Conclusion: Conservative treatment of malignant chylothorax can be considered a suitable method. Based on our results, successful treatment of the lymphoproliferative disorder seems to be a very important factor for the disappearance of chylothorax.

We studied hormone levels in the thoracic duct lymph and expression of miRNA involved in the pathogenesis of breast cancer induced in rats by intramammary injection of N-methyl-Nnitrosourea. The correlations between miRNA expression and hormone levels depended on the type of treatment.

Shear-dependent inhibition of lymphatic thoracic duct (TD) contractility is principally mediated by nitric oxide (NO). Endothelial dysfunction and poor NO bioavailability are hallmarks of vasculature dysfunction in states of insulin resistance and metabolic syndrome (MetSyn). We tested the hypothesis that flow-dependent regulation of lymphatic contractility is impaired under conditions of MetSyn. We utilized a 7-wk high-fructose-fed male Sprague-Dawley rat model of MetSyn and determined the stretch- and flow-dependent contractile responses in an isobaric ex vivo TD preparation. TD diameters were tracked and contractile parameters were determined in response to different transmural pressures, imposed flow, exogenous NO stimulation by S-nitro-N-acetylpenicillamine (SNAP), and inhibition of NO synthase (NOS) by l-nitro-arginine methyl ester (l-NAME) and the reactive oxygen species (ROS) scavenging molecule 4-hydroxy-tempo (tempol). Expression of endothelial NO synthase (eNOS) in TD was determined using Western blot. Approximately 25% of the normal flow-mediated inhibition of contraction frequency was lost in TDs isolated from MetSyn rats despite a comparable SNAP response. Inhibition of NOS with l-NAME abolished the differences in the shear-dependent contraction frequency regulation between control and MetSyn TDs, whereas tempol did not restore the flow responses in MetSyn TDs. We found a significant reduction in eNOS expression in MetSyn TDs suggesting that diminished NO production is partially responsible for impaired flow response. Thus our data provide the first evidence that MetSyn conditions diminish eNOS expression in TD endothelium, thereby affecting the flow-mediated changes in TD lymphatic function., (Copyright © 2016 the American Physiological Society.)

Objective: Lymphatic endothelial dysfunction underlies the pathogenesis of many chronic inflammatory disorders. The proinflammatory cytokine tumor necrosis factor (TNF) is known for its role in disrupting the function of the lymphatic vasculature. This study investigates the ability of apolipoprotein (apo) A-I, the principal apolipoprotein of high-density lipoproteins, to preserve the normal function of lymphatic endothelial cells treated with TNF., Approach and Results: TNF decreased the ability of lymphatic endothelial cells to form tube-like structures. Preincubation of lymphatic endothelial cells with apoA-I attenuated the TNF-mediated inhibition of tube formation in a concentration-dependent manner. In addition, apoA-I reversed the TNF-mediated suppression of lymphatic endothelial cell migration and lymphatic outgrowth in thoracic duct rings. ApoA-I also abrogated the negative effect of TNF on lymphatic neovascularization in an ATP-binding cassette transporter A1-dependent manner. At the molecular level, this involved downregulation of TNF receptor-1 and the conservation of prospero-related homeobox gene-1 expression, a master regulator of lymphangiogenesis. ApoA-I also re-established the normal phenotype of the lymphatic network in the diaphragms of human TNF transgenic mice., Conclusions: ApoA-I restores the neovascularization capacity of the lymphatic system during TNF-mediated inflammation. This study provides a proof-of-concept that high-density lipoprotein-based therapeutic strategies may attenuate chronic inflammation via its action on lymphatic vasculature., (© 2015 American Heart Association, Inc.)

Calcium channel blockers (CCB) are widely prescribed anti-hypertensive agents. The commonest side-effect, peripheral oedema, is attributed to a larger arterial than venous dilatation causing increased fluid filtration. Whether CCB treatment is detrimental to human lymphatic vessel function and thereby exacerbates oedema formation is unknown. We observed that spontaneous lymphatic contractions in isolated human vessels (thoracic duct and mesenteric lymphatics) maintained under isometric conditions were inhibited by therapeutic concentrations (nanomolar) of the CCB nifedipine while higher than therapeutic concentrations of verapamil (micromolar) were necessary to inhibit activity. Nifedipine also inhibited spontaneous action potentials measured by sharp microelectrodes. Furthermore, noradrenaline did not elicit normal increases in lymphatic vessel tone when maximal constriction was reduced to 29.4 ± 4.9% of control in the presence of 20 nmol l(-1) nifedipine. Transcripts for the L-type calcium channel gene CACNA1C were consistently detected from human thoracic duct samples examined and the CaV1.2 protein was localized by immunoreactivity to lymphatic smooth muscle cells. While human lymphatics ex vivo were highly sensitive to nifedipine, this was not apparent in vivo when nifedipine was compared to placebo in a randomized, double-blinded clinical trial: conversely, lymphatic vessel contraction frequency was increased and refill time was faster despite all subjects achieving target nifedipine plasma concentrations. We conclude that human lymphatic vessels are highly sensitive to nifedipine in vitro but that care must be taken when extrapolating in vitro observations of lymphatic vessel function to the clinical situation, as similar changes in lymphatic function were not evident in our clinical trial comparing nifedipine treatment to placebo., (© 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society.)

Objective: To radiographically and histologically evaluate the effects of photodynamic therapy on the cisterna chyli in rats., Study Design: Experimental study., Animals: Adult male Sprague-Dawley rats (n = 60)., Methods: Cecal lymph nodes were injected with the photodynamic compound verteporfin. A 690 nm, 500 mW diode laser was then directed at the area of the cisterna chyli for either 0, 1.5, or 3 minutes. Cisterna chyli patency was evaluated using lymphography, and histologic changes were evaluated on postoperative Days 1, 3, 5, 7, and 14., Results: Histologically, minimal to marked injury to the cisternal and/or pericisternal tissues was present in all treated rats at all time periods. Radiographically, 8/20 cisternae were occluded in the 1.5-minute treatment group (including 1/4 on Day 1, 2/4 on Day 3, 3/4 on Day 5, 0/4 on Day 7, and 2/4 on Day 14), and 9/20 cisternae were occluded in the 3-minute treatment group (including 0/4 on Day 1, 1/4 on Day 3, 3/4 on Day 5, 3/4 on Day 7, and 2/4 on Day 14). There was minimal to no histologic evidence of tissue injury in control rats. All control cisternae were radiographically open., Conclusions: Further investigations into the timing of laser application and light dose, or alternative photodynamic agents are required to limit injury to adjacent tissues and to improve the effectiveness of cisternal photoablation., (© Copyright 2014 by The American College of Veterinary Surgeons.)

We have previously shown decreased pulmonary lymph flow in our lamb model of chronically increased pulmonary blood flow, created by the in utero placement of an 8-mm aortopulmonary shunt. The purpose of this study was to test the hypothesis that abnormal lymphatic function in shunt lambs is due to impaired lymphatic endothelial nitric oxide (NO)-cGMP signaling resulting in increased lymphatic vascular constriction and/or impaired relaxation. Thoracic duct rings were isolated from 4-wk-old shunt (n = 7) and normal (n = 7) lambs to determine length-tension properties, vascular reactivity, and endothelial NO synthase protein. At baseline, shunt thoracic duct rings had 2.6-fold higher peak to peak tension and a 2-fold increase in the strength of contractions compared with normal rings (P < 0.05). In response to norepinephrine, shunt thoracic duct rings had a 2.4-fold increase in vascular tone compared with normal rings (P < 0.05) and impaired relaxation in response to the endothelium-dependent dilator acetylcholine (63% vs. 13%, P < 0.05). In vivo, inhaled NO (40 ppm) increased pulmonary lymph flow (normalized for resistance) ∼1.5-fold in both normal and shunt lambs (P < 0.05). Inhaled NO exposure increased bioavailable NO [nitrite/nitrate (NOx); ∼2.5-fold in normal lambs and ∼3.4-fold in shunt lambs] and cGMP (∼2.5-fold in both) in the pulmonary lymph effluent (P < 0.05). Chronic exposure to increased pulmonary blood flow is associated with pulmonary lymphatic endothelial injury that disrupts NO-cGMP signaling, leading to increased resting vasoconstriction, increased maximal strength of contraction, and impaired endothelium-dependent relaxation. Inhaled NO increases pulmonary lymph NOx and cGMP levels and pulmonary lymph flow in normal and shunt lambs. Therapies that augment NO-cGMP signaling within the lymphatic system may provide benefits, warranting further study.

The contractile activity of muscle cells lining the walls of collecting lymphatics is responsible for generating and regulating flow within the lymphatic system. Activation of PKC signaling contributes to the regulation of smooth muscle contraction by enhancing sensitivity of the contractile apparatus to Ca(2+). It is currently unknown whether PKC signaling contributes to the regulation of lymphatic muscle contraction. We hypothesized that the activation of PKC signaling would increase the sensitivity of the lymphatic myofilament to Ca(2+). To test this hypothesis, we determined the effects of PKC activation with phorbol esters [PMA or phorbol dibutyrate (PDBu)] on the contractile behavior of α-toxin-permeabilized rat mesenteric and cervical lymphatics or the thoracic duct. The addition of PMA or PDBu induced a significant increase in the contractile force of submaximally activated α-toxin-permeabilized lymphatic muscle independent of a change in intracellular Ca(2+) concentration, and the Ca(2+)-force relationship of lymphatic muscle was significantly left shifted, indicating greater myofilament Ca(2+) sensitivity. Phorbol esters increased the maximal rate of force development, whereas the rate of relaxation was reduced. Western blot and immunohistochemistry data indicated that the initial rapid increase in tension development after stimulation by PDBu was associated with myosin light chain (MLC)20 phosphorylation; however, the later, steady-state Ca(2+) sensitization of permeabilized lymphatic muscle was not associated with increased phosphorylation of MLC20 at Ser(19), 17-kDa C-kinase-potentiated protein phosphatase-1 inhibitor at Thr(38), or caldesmon at Ser(789). Thus, these data indicate that PKC-dependent Ca(2+) sensitization of lymphatic muscle may involve MLC20 phosphorylation-dependent and -independent mechanism(s).

Purpose: Elderly patients with esophageal cancer who are not candidates for chemoradiation may benefit from targeted agents; hence erlotinib combined with radiotherapy was evaluated in this trial., Materials and Methods: Patients >65 years with carcinoma of the thoracic esophagus or gastroesophageal junction who were not eligible for platinum-based treatment received erlotinib daily for 1 year starting on day 1 of radiotherapy [50.4 Gy days 1-28 (Mon-Fri) at 1.8 Gy per fraction]. Response was assessed by endoscopy and computed tomography. The primary endpoint was overall survival (OS), and secondary endpoints were complete response, progression-free survival (PFS) and toxicity., Results: The ECOG performance status in the 17 study patients was 0,1 and 2 in 2, 12 and 3 patients, respectively; 1, 5, 7 and 4 patients were in stage I, II, III and IV, respectively; adenocarcinoma was noted in 16 patients and squamous cell carcinoma in 1; there were 3 current, 12 past and 2 never smokers. Median OS was 7.3 months (95% confidence interval, CI: 3.8-22.3) with 14 deaths. There were 2 mucosal complete responses, 1 residual carcinoma in situ and 3 partial endoscopic responses in 9 patients who had endoscopy after radiotherapy. Estimated PFS was 4.5 months (95% CI: 2.4-7.3). Progression was distant (n = 3), locoregional (n = 6), unknown (n = 5) and too early (n = 3). Estimated 1-year survival was 29% (95% CI: 11-51%), 5 patients lived >12 months. Treatment-related toxicities of grade 3-4 occurred in 5 patients. Patients with epidermal growth factor receptor amplification and never smokers had the longest OS (22.3 and 16.6 months, respectively)., Conclusions: Erlotinib with radiotherapy is tolerable and warrants further biomarker-driven evaluation in this population., (Copyright © 2013 S. Karger AG, Basel.)

Guar gum has a well-recognized hypolipidemic effect. This effect is thought to be due to the physicochemical properties of guar gum, which may cause changes in adsorption of lipids or the viscosity of the intestinal contents. Guar gum is a non-specific absorption inhibitor of any type of lipid-soluble compound. Permanent lymph duct cannulation was performed on rats to investigate the effects of dietary guar gum on lymph flow and lipid transport. Rats fed a 5% guar gum diet were compared with those fed a 5% cellulose diet, and lymph was collected after feeding. The water-holding capacity (WHC), settling volume in water (SV), and viscosity of guar gum were compared with those of cellulose. Rats fed with the guar gum diet had significantly lower lymph flow and lymphatic lipid transport than did rats fed with the cellulose diet. The WHC, SV, and viscosity of guar gum were significantly higher than those of cellulose. We propose that dietary guar gum reduces lymph flow and thereby diminishes lipid transport by means of its physicochemical properties related to water behavior in the intestine.

Background: The lymphatic system plays a critical role in the body's fluid and protein homeostasis, immune regulation, and dietary fat absorption. One of the major pathologies of the lymphatic system is primary lymphedema, which occurs in approximately 0.6% of live births and is caused by missing or impaired lymphatic vessels. Although there is a great need for medical intervention into diseases of the lymphatic system, very little is known about its development or how it maintains integrity over time. Recent studies have suggested that biophysical components, such as local extracellular fluid flow, may be important factors during initiation of lymphangiogenesis. We hypothesize that interstitial fluid flow functions as an important morphoregulator during developmental lymphangiogenesis., Methods and Results: In the present study we use pharmacological agents and a mutant fish line to modulate interstitial flow. Our data confirm that a sufficient increase or decrease in interstitial flow can profoundly affect lymphatic patterning and may result in a lymphedema-like phenotype. Proper interstitial flow appears to be necessary during LEC migration for proper lymphatic development., Conclusions: These results support the contention that interstitial flow is an important morphoregulator of developmental lymphangiogenesis.

The current study characterizes the mechanical properties of the human thoracic duct and demonstrates a role for adrenoceptors, thromboxane, and endothelin receptors in human lymph vessel function. With ethical permission and informed consent, portions of the thoracic duct (2-5 cm) were resected and retrieved at T(7)-T(9) during esophageal and cardia cancer surgery. Ring segments (2 mm long) were mounted in a myograph for isometric tension (N/m) measurement. The diameter-tension relationship was established using ducts from 10 individuals. Peak active tension of 6.24 +/- 0.75 N/m was observed with a corresponding passive tension of 3.11 +/- 0.67 N/m and average internal diameter of 2.21 mm. The equivalent active and passive transmural pressures by LaPlace's law were 47.3 +/- 4.7 and 20.6 +/- 3.2 mmHg, respectively. Subsequently, pharmacology was performed on rings from 15 ducts that were normalized by stretching them until an equivalent pressure of 21 mmHg was calculable from the wall tension. At low concentrations, norepinephrine, endothelin-1, and the thromboxane-A(2) analog U-46619 evoked phasic contractions (analogous to lymphatic pumping), whereas at higher contractions they induced tonic activity (maximum tension values of 4.46 +/- 0.63, 5.90 +/- 1.4, and 6.78 +/- 1.4 N/m, respectively). Spontaneous activity was observed in 44% of ducts while 51% of all the segments produced phasic contractions after agonist application. Acetylcholine and bradykinin relaxed norepinephrine preconstrictions by approximately 20% and approximately 40%, respectively. These results demonstrate that the human thoracic duct can develop wall tensions that permit contractility to be maintained across a wide range of transmural pressures and that isolated ducts contract in response to important vasoactive agents.

Administration of black-tea polyphenols (BTP) simultaneously reduced lymphatic recovery of both (3)H-cholesterol and (14)C-trioleoylglycerol in rats that were cannulated in the thoracic duct. BTP decreased the in vitro micellar solubility of cholesterol in a dose-dependent manner. When purified theaflavins, which are components of BTP, were used, theaflavin-monogallates (TFMGs), theaflavin-3-gallate (TF3G), and theaflavin-3'-gallate (TF3'G) were effective in eliminating cholesterol from bile salt micelles in vitro. Theaflavin (TF) and theaflavin-3,3'-digallate (TFDG) had no effect on the micellar solubility of cholesterol. The concentration of bile acid in the micelles was not influenced by the addition of any BTPs or theaflavins. These results suggest that the reduction of micellar cholesterol by BTP could be important to reducing cholesterol absorption.

We investigated the pivotal roles of glucose and its transporter in the regulation of mechanical activity of isolated rat thoracic ducts and then examined whether mitochondrial ATP-sensitive K(+) channels (mitoK(ATP)) are involved in those responses. In the absence of extracellular glucose, the thoracic ducts showed pump activity during 120 min. Extracellular glucose caused a dose-dependent increase in the frequency of pump activity and a constriction in the thoracic ducts. Pump activity of the thoracic ducts in 0 mm glucose was completely inhibited in the presence of chlorogenic acid (an inhibitor of glucose-6-phosphatase). Cytochalasin B, an inhibitor of facilitative glucose transporter (GLUT), or phlorizin, an inhibitor of sodium-dependent glucose cotransporter (SGLT), significantly reduced the frequency of pump activity and dilated the thoracic ducts. A decrease in the frequency of pump activity induced by 5-hydroxydecanoate (5-HD, a selective blocker of mitoK(ATP)) was completely reversed by ruthenium red (an inhibitor of Ca(2+) uniporter in mitochondria). Diazoxide (a selective opener of mitoK(ATP)) significantly increased the frequency of pump activity. Carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP, a protonophore of mitochondrial proton pump action) significantly reduced the frequency of pump activity and dilated the thoracic ducts. Collectively, these findings suggest that glucose derived from intracellular glycogen and/or through GLUT/SGLT in lymphatic smooth muscles contributes to the regulation of the pump activity of isolated rat thoracic ducts, and that mitoK(ATP) in the cells may partially serve as a modulator of the mechanical functions associated with mitochondrial Ca(2+) uptake.

We describe two innovative ideas in the treatment of iatrogenic chyle leak. The first is the early use of a pancreatic lipase inhibitor (Orlistat) to reduce fat absorption and chyle production, with consequent faster fistula healing. The second is the treatment of these patients at home in the community by district nurses backed by the hospital staff. This domiciliary approach has a positive psychological effect on the patient, permits the patient to take responsibility for their treatment, and reduces hospital length of stay minimising patient exposure to nosocomial infections.

The objectives of this study were to evaluate the physiological importance of the flow and shear generated by phasic contractions of lymphatic vessels and the mechanisms responsible for the influences of such shear on lymphatic pumping. Lymphatic segments of the rat thoracic duct were isolated, cannulated and pressurized. The diastolic diameters were measured in phasically non-active segments. The diastolic and systolic diameters, half-relaxation time (HRT), contraction frequency, ejection fraction and fractional pump flow were determined in phasically active segments. Since imposed flow was excluded, flow and shear occurred only as a result of the intrinsic contractions in phasically active segments whereas in phasically non-active segments contraction-generated flow and shear were absent. The influences of incrementally increased transmural pressure (from 1 to 5 cmH(2)O) were examined in control conditions and after NO synthase blockade (l-NAME 10(-4) m) or cyclooxygenase blockade (indomethacin 10(-5) m). The spontaneous phasic contractions produced a flow-dependent diastolic relaxation. This reduction of the lymphatic tone is a regulatory mechanism that maintains pumping in thoracic duct in an energy-saving/efficient mode: it improves diastolic filling (enhanced lusitropy - lowering HRT), makes lymphatic contractions stronger (enhanced inotropy - higher contraction amplitude) and propels more fluid forward during each contraction (elevated ejection fraction) while decreasing contraction frequency (reduced chronotropy). The findings also demonstrated that the NO pathway, not the cyclooxygenase pathway is responsible for this reduction of lymphatic tone and is the prevailing pathway responsible for the self-regulatory adjustment of thoracic duct pumping to changes in lymph flow pattern.

We investigated the short-term effects of a phosphodiesterase III inhibitor (Olprinone) on hemodynamics and thoracic duct lymph flow in anesthetized open-chest sheep with heart failure induced by endothelin-1 (cardiogenic shock). Ultrasound transit-time flow probes were attached to the thoracic duct, the ascending aorta and the renal artery. Arterial, pulmonary and central venous pressures were monitored. Endothelin-1 was infused intravenously at a dosage that reduced cardiac output to 50% or more of baseline (n=11). The effects of Olprinone were examined (n=5) by intravenous infusion after endothelin-1 administration. Other sheep (n=6) were used as controls. Olprinone significantly increased cardiac output that had been decreased by endothelin-1 and further increased thoracic duct flow that had been increased by endothelin-1. Increased arterial and pulmonary pressures induced by endothelin-1 administration were rapidly decreased by Olprinone. Renal arterial flow and central venous pressure were, however, unchanged by Olprinone. Overall, Olprinone acutely improved experimental cardiogenic shock (heart failure) induced by endothelin-1, and maintained thoracic duct lymph flow at a high level after endothelin-1 administration.

We investigated the effects of vascular endothelial growth factor (VEGF(165)) on [Ca(2+)](i)-transient in cultured lymphatic endothelial cells (LEC) and mechanical activity of isolated dog thoracic ducts. VEGF (0.1-10 ng/ml) caused a dose-dependent increase of the [Ca(2+)](i) in LEC. Pretreatment with 10(-5) M genistein or 5x10(-6) M herbimycin A produced a significant reduction of the VEGF-induced [Ca(2+)](i)-transient. In the presence of 10(-6) M thapsigargin, VEGF caused no significant effect on the [Ca(2+)](i)-transient. Pretreatment with Ca(2+)-free solution containing 0.1 mM EGTA produced no significant effect on the peak increase of [Ca(2+)](i) induced by 0.1 or 10 ng/ml VEGF, but significantly depressed the sustained part of [Ca(2+)](i) observed at the higher concentration of VEGF. The VEGF (0.1-10 ng/ml) caused a significant dilation of the isolated lymph vessels with intact endothelium, which were precontracted with U46,619. The 10 ng/ml VEGF-induced dilation was significantly reduced by 3 x 10(-5) M N(omega)-nitro-L-arginine methyl ester (L-NAME). The action of L-NAME was inhibited by the simultaneous application of 10(-3) M L-arginine. Mechanical rubbing of the endothelium also caused significant inhibition of the VEGF-induced dilation. The findings suggest that VEGF(165) may activate the receptor-related tyrosine kinase and cause the release of Ca(2+) from the inositol 1,4, 5-triphosphate-sensitive intracellular Ca(2+) stores in LEC. VEGF(165) also produces endothelium-dependent nitric oxide-mediated dilation of the precontracted isolated lymph vessels.

The electrical stimulation-induced responses of isolated dog thoracic ducts were investigated using an organ bath technique. Electrical stimulation (0.7 ms in pulse width, 25 V in nominal voltage, 10 s in duration time, 1-32 Hz at frequency) produced frequency-related contractions in the lymphatic preparations. The contractions were abolished by pretreatment with tetrodotoxin (10(-7) M), guanethidine (10(-7), 10(-6) M), and bretylium (10(-7), 10(-6) M). Cocaine (10(-6) M) significantly potentiated the electrical stimulation-induced contractions. Phentolamine (10(-8)-10(-5) M), prazosin (10(-8)-10(-5) M), bunazosin (10(-6), 10(-5) M), yohimbine (10(-8)-10(-6) M) and rauwolscine (10(-8)-10(-6) M) also dose-dependently reduced the contractions. On the other hand, propranolol (10(-8)-10(-6) M), atropine (10(-6) M), hexamethonium (10(-6) M), aspirin (3 x 10(-5) M), N(omega)-nitro-L-arginine methyl ester (L-NAME) (3 x 10(-5) M) and L-NAME (3 x 10(-5) M) + L-arginine (10(-4) M) caused no significant effect on electrical stimulation-induced contractions. No significant difference in the electrical stimulation-induced responses was observed between the lymphatic preparations with and without an intact endothelium. The electrical stimulation caused only a small contraction with no relaxation in the thoracic duct preparation precontracted with 10(-8) M U46619. The small contraction was abolished by 10(-5) M phentolamine. These findings suggest that there exists alpha1- and alpha2-adrenoceptors-mediated excitatory innervation, but no NO-ergic inhibitory nerve fiber in dog thoracic ducts.

After antiorthostatic attitude of rats during 12 days, the contractile activity of their isolated lymphangions of the thoracic duct was studied. The amplitude of contractions was found to be decreased as well as the effects of serotonine, histamine, and acetylcholine, whereas that of adrenaline increased. The latter finding suggests enhancing of the activity of lymphatic vessels' adrenergic structures in antiorthostatic.

A piece of a human thoracic duct removed at operation was investigated in organ baths. The duct was cut in 8 ring segments each about 1mm long and isometric tension recorded. The segments were exposed to a potassium rich (124mM) Krebs buffer solution. In only two of the segments were contractions induced (7.2 and 1.0mN, respectively). Noradrenaline and the thromboxane mimetic U-46619 induced tonic and phasic contractions. At a noradrenaline concentration of 10(-5)M the phasic contractions had a frequency of 5 min-1. The highest frequency, 9 min-1, was recorded with 3 x 10(-10)M of U-46619 present in the bath. Noradrenaline had a mean Emax of 50% of the previous K+ (124mM)-induced contraction, and the mean pEC50-value was 6.7. The Emax and pEC50-values of U-46619 were 142% and 9.5, respectively. Postjunctional alpha-adrenoceptors and thromboxane A2-receptors may play a role in the contractility of the human thoracic duct.

In experiments on rabbits it was found that acute myocardial infarction (AMI) was associated with a disorder of the drainage function the lymphatic system and a drastic increase of the lymph toxicity. The administration of propranolol (obsidan), amiodaron (cordaron), lidocaine (xycaine), trimecaine (mesocaine), nitroglycerin, panangin and heparin exerted the pronounced stimulating action on the lymph outflow rate. Strophanthin-K, corglycon and digo in possessed the moderate lymphogenic effect. Novocainamide (procainamide), verapamil (isoptine) and panangin exerted no influence on the lymph outflow rate. The administration of the above mentioned drugs in the initial period of AMI sharply increased the toxic properties of the lymph; subsequently the lymph toxicity gradually decreased and was less than in control (in AMI treated with drugs).

Ring segments of dog thoracic ducts precontracted with a high concentration of norepinephrine (NE) relaxed in a concentration-dependent manner in response to acetylcholine (ACh) or sodium nitroprusside (SNP). Pretreatment with atropine inhibited the ACh-induced relaxation in a competitive manner. The Schild plot showed a slope of 1.1 +/- 0.2 and a pA2 value of 10.4 +/- 0.4 (n = 6 ring segments). Removal of endothelium caused a complete inhibition of the ACh-induced relaxations in precontracted dog thoracic ducts. ACh, which failed to relax precontraction of the ring segment when mounted separately, induced relaxation in the same preparation when it was mounted as a "sandwich" with the longitudinal strip. The ACh-induced relaxations in the lymphatic preparations with endothelium were suppressed or abolished by pretreatment with oxyhemoglobin (10(-6) and 10(-5) M), methylene blue (10(-6) and 10(-5) M), and NG-monomethyl-L-arginine (3 x 10(-5) M), but the relaxations were unaffected by aspirin (10(-5) M). Pretreatment with methylene blue (10(-5) M) also caused a significant reduction of the SNP-induced relaxations in the precontracted thoracic ducts. It may be concluded that ACh-induced relaxation in dog thoracic ducts precontracted with NE is mediated by high-affinity muscarinic receptors in the lymphatic endothelial cells. Also, stimulation of the endothelial muscarinic receptors liberates a transferable endothelium-derived relaxing factor, which results in the relaxation of the lymphatic smooth muscles via the accumulation of cellular guanosine 3',5'-cyclic monophosphate.

Prothoracic glands of the migratory locust Locusta migratoria during the postembryonnic development, are the biosynthetic source of ecdysone. The production of ecdysone by these glands in vitro has been used to evaluate the inhibitory activity of four cholesteryl derivatives with an allenic function on the side chain at C-22. These molecules were devised as potential inhibitors of hydroxylation at C-22 which is an obligate step in the biosynthesis of ecdysone. Three of the four molecules tested induce a marked depressory effect of the production of ecdysone. The effect of the compound with the higher activity was dose dependent and irreversible.

A study was made of the isometric responses of isolated canine thoracic ducts to several physiological vasoactive substances. Contractions of the lymphatic smooth muscles were induced by epinephrine, norepinephrine, 5-hydroxytryptamine, histamine (HIS) and prostaglandin F2 alpha in a dose-dependent manner. The decreasing order of potency in the contractile responses was as follows: epinephrine greater than norepinephrine greater than 5-hydroxytryptamine much greater than HIS not equal to prostaglandin F2 alpha. There were no significant regional differences in the responses to vasoconstrictive agents. Phenylephrine, xylazine and clonidine caused a dose-dependent contraction in the lymphatic preparations. Prazosin (10(-8) to 10(-7) M) inhibited the phenylephrine-induced vasoconstriction in a competitive manner. Xylazine-induced responses were inhibited competitively by yohimbine (10(-8) to 10(-7) M). These results suggest that both alpha-1 and alpha-2 adrenoceptors are located on the lymphatic smooth muscles of canine thoracic ducts. On the other hand, acetylcholine, isoproterenol, HIS, adenosine and ATP caused dose-dependent relaxations in canine thoracic ducts precontracted by 10(-5) M norepinephrine. The decreasing order of potency in the relaxant responses was as follows: acetylcholine much greater than isoproterenol much greater than adenosine not equal to HIS not equal to ATP. There were no significant regional differences in the relaxant responses to the agents. Procaterol, salbutamol, dobutamine and denopamine caused a dose-dependent relaxation of isolated canine thoracic ducts. Propranolol (10(-9) to 10(-8) M) inhibited procaterol- and dobutamine-induced vasorelaxations in a competitive manner. Metoprolol (10(-8) to 10(-7) M) inhibited only the dobutamine-induced vasorelaxation, but did not significantly influence the procaterol-induced response.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous measurements of thoracic duct lymph flow and small intestinal lymph flow were carried out in mongrel dogs after the administration of mannitol, ethacrynic acid, furosemide and chlorothiazide. Thoracic duct lymph flow increased only after injection of mannitol. Intestinal lymph flow increased after injection of all diuretics except chlorothiazide. Furthermore, mannitol produced simultaneous increases in thoracic duct and intestinal lymph flows. The durations of response of the increased lymph flows from each lymph channel produced by mannitol were statistically identical. The durations of increased intestinal lymph flows observed with each drug were: 40+/-3 (S.E.), 43+/-2 and 38+/-2 minutes for mannitol, ethacrynic acid and furosemide, respectively. Mean arterial blood pressures and inferior vena cava pressures did not change from the control to the experimental state in any animal studied. Similarly measurements of serum and lymph sodium, potassium and protein concentrations were unchanged from the control to the experimental state. These studies demonstrate that mannitol simultaneously increases thoracic duct lymph flow as well as intestinal lymph flow. Secondly, the results suggest that the increases in thoracic duct lymph flow after ethacrynic acid and furosemide administration, observed in previous studies arose primarily from the small intestine.

The effect of an intravenous injection (2 ml/kg) of hyperoncotic (30 g%) Dextran (MW 60000) or Albumin on lymph formation and thoracic duct lymph flow was studied in 16 dogs. As a result of the injection, plasma colloid osmotic pressure increased, plasma volume increased due to fluid reabsorption from the extravascular compartment, and thus cardiac output became enhanced. Total body lymph formation was not affected as shown by an unchanged transcapillary disappearance rate of macromolecules. Thoracic duct lymph flow, however, was increased. The concomitant augmentation of lymph protein concentration and the elevated hepatic blood flow following the injection of hyperoncotic Dextran show that the increased thoracic duct lymph flow was probably brought about by an increase in hepatic lymph flow.

An earlier report proved that Daflon 500 mg constituted of 90% diosmin and 10% hesperidin exerts a lymphagogue effect on dogs. The aim of the present work is to investigate whether the lymphagogue effect of Daflon 500 mg is associated with an increase in pulsatile activity of lymphatic vessels. The investigation was carried out on mongrel dogs anaesthetised by pentobarbital (10 mg/kg); the lymph was collected by a fistula on the thoracic lymphatic duct; using this fistula the pulsatile activity of lymphatic vessels was estimated by Campbell and Health methodology. The lymphatic volume was measured every ten-minutes in graduated tubes for 2 hours and the pulsatile component of intralymphatic pressure (MPC) was estimated from measurements of the area (expressed in mm2) enclosed by the part of the tracing due to the pulsatile component during one minute. Daflon 500 mg was intravenously injected after having been dissolved in DMSO + TRIS; three doses were injected: 12.5, 6.25 and 3.125 mg/kg. Regarding the lymphagogue effect, Daflon 500 mg induced an increase in lymphatic flow correlated with the administered doses. The maximal 10-minute period lymphatic flows were 191% (12.5 mg/kg), 171% (6.25 mg/kg) and 91% (3.125 mg/kg); the peak of the effect was, in each case, reached between 20 and 25 minutes after the injection. Regarding the pulsatile activity, Daflon 500 mg induced an increase of MPC. The MPC was correlated with the increase in lymph flow (r = 0.877).

Physiologic alterations of pH in vitro produce alterations of the oncotic pressure of both plasma and interstitial proteins, the effect being more marked in the latter. Therefore we postulated that by changing an animal's pH we could produce alterations in fluid distribution and affect the whole-body lymph flow rate. To test this hypothesis, we infused seven acutely nephrectomized anesthetized sheep with 2% body weight/volume isosmotic lactated Ringer's solution and bicarbonate (200 mEq) after a 30-minute control period. The fluid was infused over a 10-minute period with 20-minute recovery intervals. To another group of seven ewes, we infused the same volume of lactated Ringer's solution and hydrochloric acid (40 mEq). Throughout the experiment, we continuously measured arterial and venous pressures and lymph flow rate. Every 10 minutes we obtained samples for arterial pH, for hematocrit, and for plasma and lymph protein and osmolality. The infusion of bicarbonate was associated with a comparatively lower peak lymph flow rate (383% over baseline compared with 757% for acid infusion). Also the lymph flow rate after acid infusion started to increase approximately 5 minutes after the beginning of the infusion, as compared with approximately 10 minutes after the base infusion. Acid infusion did not increase arterial pressure, in contrast to the other infusions. The changes in pH obtained with the infusions were insignificant for the Ringer's infusion, +0.17 for the base, and -0.16 for the acid. The plasma/lymph protein concentration ratios at the end of the infusion were no different for acid or base: 112.4% +/- 4.4% and 101.9% +/- 5% (difference from control, mean +/- SEM) respectively (p greater than 0.1). In conclusion, minimal alterations of pH produced alterations in the cardiovascular and lymph flow rate responses to fluid challenge in anesthetized animals.

1. Simultaneous thoracic duct and hepatic lymph flows were measured in 29 mongrel dogs before and after the intravenous administration of mannitol, ethacrynic acid, frusemide and chlorothiazide in separate experiments. 2. Thoracic duct lymph flow increased significantly after each diuretic agent was administered. 3. Hepatic lymph flow increased only after ethacrynic acid and mannitol administration. Frusemide and chlorothiazide did not alter hepatic lymph flow. 4. These data show that increases in thoracic duct lymph flow after ethacrynic acid and mannitol arise partly from the liver, as well as from other organs.

Both pregnancy and estrogen administration are associated with a decrease in the systemic vasculature pressor response to angiotensin II infusion; however, the lymphatic vessel system response is not clear. In the present study we infused angiotensin II to nine nonpregnant splenectomized ewes with 0.1, 10, or 1,000 ng X kg-1 X min-1 for a 5-min period at each dose. At the lowest dose the mean arterial pressure increased from 10 to 20% over base line. At the highest dose, the left thoracic duct flow rate peaked at 361% 10 min after the infusion was started, whereas arterial pressure peaked at 183% of the control value. Peak lymph flow occurred 4-6 min after the maximal increase in mean systemic arterial pressure. Neither hematocrit nor venous pressure were altered at any of the doses administered. This suggests that the interstitial fluid space pressure remained unchanged and that the increase in lymph flow was not secondary to fluid transfer from the intravascular system. We postulate, therefore, that the effect of angiotensin II in the increase of lymph flow rate is by direct action on the lymphatic vessels themselves.

The effect of ganglionic blockade (GB) and subsequent i.v. infusion of adrenaline (AD), noradrenaline (NA), isoproterenol (IP), and angiotensin II (AII) on thoracic duct lymph flow (LF) and transcapillary escape rate of plasma proteins (FER) was studied in anaesthetized (Nembutal), paralyzed (pancuronium), and artificially ventilated dogs. The carotid artery, the external jugular vein, and the thoracic duct were cannulated. Following a control period, GB was performed by pentolinium tartrate and thereafter the other drugs were infused in a random sequence for 30-60 min with 1 h intervals. Mean arterial blood pressure was decreased from 125 to 90 mmHg by GB, it was increased by 36 mmHg by AD, 41 mmHg by NA, and 44 mmHg by AII, and was decreased by 27 mmHg by IP. LF was about 38 microliter/min/kg before GB and was not changed systematically by GB, because either the sympathetic tone was rather weak or the intrinsic contractions and the tone of lymphatics were reduced by GB. FER was not affected by GB. LF increased by 9 microliter/min/kg (control 36 microliter/min/kg) during AII infusion, probably due to increased lymph formation; the latter can be concluded from the 68% increase in FER. NA raised LF by 15 microliter/min/kg (control 44 microliter/min/kg) probably due to alpha-adrenergic stimulation of the intrinsic contractions of lymphatics; lymph formation seemed not to be affected because FER was not changed systematically. AD enhanced LF by 29 microliters/min/kg (control 39 microliters/min/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution of trephan blue in different organs and tissues and in the lymph was studied in acute experiments on 84 dogs after the infusion of 5% NaCl solution (0.5 mg/kg). The rise of the stain concentration in the intact dogs was the greatest in the liver, the kidney and the intestine. The osmotic shift caused by the intravenous infusion of the hypertonic NaCl solution increased the blood plasma hyaluronidase activity, reduced the maximal accumulation time of the stain in the tissues and led to a 1.5-2 fold elevation in the stain concentration in the organs.

The action of cordiamine and pentylene tetrazole upon the tonicity of the thoracic and jugular lymph trunks and the arterial pressure was studied in acute experiments on dogs by employing perfusion with Lock's solution under constant pressure. It is shown that pentylene tetrazole forces down, as a rule, the lymph vessels tone, while cordiamine primarily brings it up.

Calcium dobesilate increases thoracic duct lymph flow in both anesthetized and mobile guinea pigs. The marked lymphogogue action of this drug may explain in part the improvement in tissue survival with ischemic insult.

In acute experiments on 31 dogs, dilatation of the thoracic lymphatic duct on moderate (5--8 V) stimulation of afferents of the sciatic nerve and i. v. administration of noradrenaline (3--5 mcg/kg) was shown to be due to specific effects of excitation of the duct alpha-adrenoreceptors mainly. The alpha-adrenoreceptors seem to be represented in the thoracic duct in a much greater amount that the beta-adrenoreceptors. Stimulation of both types of the duct's adrenoreceptors leads to an increase in its capacity.