Recoveries of rat lymph FA after administration of specific structured 13C-TAG

The potential of the specific structured TAG MLM [where M = caprylic acid (8:0) and L = linoleic acid (18:2n-6)] is the simultaneous delivery of energy and EFA. Compared with long-chain TAG (LLL), they may be more rapidly hydrolyzed and absorbed. This study examined the lymphatic recoveries of intragastrically administered L*L*L*, M*M*M*, ML*M, and ML*L* (where * = 13C-labeled FA) in rats. Lymph lipids were separated into lipid classes and analyzed by GC combustion isotope ratio MS. The recoveries of lymph TAG 18:2n-6 8 h after administration of L*L*L*, ML*M, and ML*L* were 38.6, 48.4, and 49.1%, respectively, whereas after 24 h the recoveries were approximately 50% in all experimental groups. The exogenous contribution to lymph TAG 18:2n-6 was approximately 80 and 60% at maximum absorption of the specific structured TAG and L*L*L*, respectively, 3-6 h after administration. The tendency toward more rapid recovery of exogenous long-chain FA following administration of specific structured TAG compared with long-chain TAG was probably due to fast hydrolysis. The lymphatic recovery of 8:0 was 2.2% 24 h after administration of M*M*M*. This minor lymphatic recovery of exogenous 8:0 was probably due to low stimulation of chylomicron formation. These results demonstrate tendencies toward faster lymphatic recovery of long-chain FA after administration of specific structured TAG compared with long-chain TAG.

Dietary long-chain PUFA in the form of TAG or phospholipids influence lymph lipoprotein size and composition in piglets

Several sources of long-chain PUFA (LCP) are currently available for infant formula supplementation. These oils differ in their FA composition, the chemical form of the FA esters [TAG or phospholipids (PL)], and presence of other lipid components. These differences may affect LCP absorption, distribution, and metabolic fate after ingestion. The purpose of this study was to evaluate the influence of different chemical forms of dietary LCP on the composition of lymph lipoproteins. Eighteen pigs (5 d old) were bottle-fed different diets for 2 wk: a control diet (C), a diet containing LCP as TAG from tuna and fungal oils (TF-TAG), or a diet containing LCP as PL from egg yolk (E-PL). We measured lipid and FA composition of lymph, main lymph fractions (TAG or PL), and the particle size of lymph lipoproteins. The average diameter of lymph lipoproteins was significantly lower in the E-PL group compared with the control and TF-TAG groups (C: 3902 +/- 384 A; TF-TAG: 3773 +/- 384 A; E-PL: 2370 +/- 185 A). Arachidonic acid and DHA contents in lymph and lymph-TAG were significantly higher in the TF-TAG group compared to the E-PL group (0.50 +/- 0.03 and 0.24 +/- 0.03 g/100 g vs. 0.29 +/- 0.04 and 0.12 +/- 0.03 g/100 g, respectively). The addition to the diet of LCP in the form of TAG or PL affected the size of intestinal lipoproteins and also led to a different distribution of these FA in lymph lipoproteins.

Stimulation of regional lymphatic and blood flow by epicutaneous oxazolone

The application of the epicutaneous antigen oxazolone results in persistent induration and erythema; however, the relative changes in lymph and blood flow in the inflammatory skin are largely unknown. To define the contribution of lymph and blood flow to the clinical appearance of cutaneous inflammation, we studied the sheep ear after the application of oxazolone. As a model for the study of these changes, the sheep ear had several experimental advantages: 1) a simplified superficial vascular network, 2) defined lymphatic drainage, and 3) an avascular and alymphatic cartilaginous barrier. Lymph flow was continuously monitored by cannulation of the prescapular efferent lymph duct. Blood flow, as reflected by cutaneous erythema, was noninvasively measured by use of a visible-spectrum spectrophotometer. The application of the epicutaneous oxazolone resulted in increased ear thickness for >7 days. The lymph flow from the oxazolone-stimulated ear peaked between 24 and 48 h after oxazolone stimulation. Spectrophotometric evaluation indicated that the cutaneous erythema peaked 72-96 h after application of oxazolone. Corrosion casting and scanning electron microscopy of the microcirculation at 96 h after antigen stimulation demonstrated significant dilatation of the superficial vascular network. These results suggest a biphasic response to oxazolone stimulation: 1) an early increase in vascular permeability associated with increased lymph flow and 2) a subsequent increase in relative blood flow associated with a dilated inflammatory microcirculation.

Somatostatin analog treatment of a cervical thoracic duct fistula

BACKGROUND

Reoperation for recurrent thyroid cancer poses an increased risk of complications, including thoracic duct fistula. Treatment of this complication is controversial. A survey of thoracic literature reports the use of somatostatin analog, whereas no cases have reported the use of this therapy in cases arising from neck dissection.

METHODS

We report a 16-year-old girl with recurrent papillary thyroid cancer who had a persistent lymphatic-cutaneous fistula develop after repeat modified left neck dissection. Despite conservative management, drainage persisted for 2 months. A regimen was begun that included TPN and injections of a somatostatin analog.

RESULTS

Treatment with a somatostatin analog resulted in an immediate attenuation of drainage and subsequent closure of the fistula after 16 days of treatment.

CONCLUSION

The use of somatostatin analog can increase the success of conservative management of thoracic duct fistulae.

Lipid-based formulations for intestinal lymphatic delivery

The current state of the art of intestinal lymphatic transport is given by reviewing the more recent publications, which have utilized lipid-based vehicles. The results published often show variable trends depending on, the design of the vehicle, the components used, the physicochemical properties of the drug, the animal model and experimental techniques, these variables often make direct comparisons difficult. Traditionally intestinal lymphatic delivery has been expressed as a percentage of the dose transported in the lymph. Using this parameter results obtained to date, with lipid-based vehicles, are somewhat disappointing maximising at approximately 20-30%, for highly lipophilic compounds including DDT and halofantrine (Hf). Recent data, monitoring Hf, in a fed versus fasted dog study, have shown that a higher degree of lymphatic transport is possible (>50% dose) in the postprandial state, this study should result in stimulating renewed interest in the potential of achieving significant levels of lymphatic targeting. Although some relevant features controlling lymphatic transport have been identified over the years a deeper appreciation of all the mechanisms, which is vital for therapeutic exploitation of lymphatic transport, is still unrealized. This review analyses the success and limitations of a formulation approach using lipid-based vehicles and highlights potential areas for further research.

Effects of resuscitation with hydroxyethyl starch (HES) on pulmonary hemodynamics and lung lymph balance in hemorrhagic sheep; comparative study of low and high molecular HES

Synthetic starch solution, such as hydroxyethyl starch (HES), has been used clinically to restore cardiovascular volume in patients with hemorrhagic shock. Several HES solutions are available clinically, but each HES has a broad range of molecular mass fractions. We performed comparative studies of extremely low and high molecular HES to evaluate the effects of these HES solutions on lung lymph filtration during resuscitation. We prepared awake sheep with vascular monitoring and lung lymph fistulas. After baseline measurements, animals were bled from an arterial line to maintain shock. After 2 h of hemorrhagic period, the following three solutions were infused over 1 h, respectively. Experiment (Exp) 1 (n=6); low molecular HES; (molecular weight (MW) 70000, substitution fractions 0.5-0.55, Exp 2 (n=6); high molecular HES; (MW 450000, substitution fractions 0.65). Exp 3 (n=6); normal saline (NS). The quantity of solution was determined as the same volume of blood lost to induce hemorrhagic situation in each animal (Exp 1; 940+/-36 ml, Exp 2; 910+/-50 ml, Exp 3; 920+/-42 ml). Both low and high molecular HES could restore the systemic artery pressure and cardiac output, and significantly increased pulmonary microvascular pressure equally, which were significantly higher than those in normal saline. However, actual oncotic pressure gradient (plasma-lymph) rose transiently during low molecular HES infusion, while high molecular HES widened the oncotic pressure gradient even after the cessation of the infusion. Lung lymph flow during and after resuscitation with low molecular HES and NS rose significantly from the pre-shock baseline. There was no significant difference in increased lung lymph flow between low molecular HES and NS. However, lung lymph flow after high molecular HES was significantly less than that after low molecular HES. These data suggest that low molecular HES is as useful a plasma substitute as high molecular HES, but has a possibility to increase lung lymph filtration during the early phase of resuscitation.

Egg phosphatidylcholine decreases the lymphatic absorption of cholesterol in rats

This study was conducted to determine the effects of phosphatidylcholine (PC) from different sources on intestinal absorption of cholesterol. Male Sprague-Dawley rats were fed an AIN-93G diet containing soybean oil for 4 wk. Each rat with lymph cannula was infused via a duodenal catheter at 3.0 mL/h for 8 h with a lipid emulsion [in micromol: 451.8 triolein, 27.8 kBq 14C-cholesterol (CH), 20.7 CH, 3.6 alpha-tocopherol, and 100 PC in 24 mL PBS, pH 6.6]. The PC in the lipid emulsion was egg PC (EPC), hydrogenated egg PC (HPC), or soy PC (SPC). The EPC in the lipid emulsion markedly lowered the lymphatic absorption of 14C-CH (24.7 +/- 2.5% dose) compared with SPC (34.9 +/- 1.2%) and a lipid emulsion containing no PC (NPC) (30.8 +/- 2.0%). The HPC further lowered the absorption of 14C-CH to 21.1 +/- 1.4% dose. The outputs of phospholipid were unaffected by the source of PC infused (EPC, 32.2 +/- 1.7; HPC, 31.8 +/- 1.6; and SPC, 32.9 +/- 1.8 micromol/8 h). Compared with NPC (595.0 +/- 59.5 micromol), the total output of fatty acids over 8 h was increased significantly by SPC (685.4 +/- 55.8 micromol), but decreased by HPC (467.7 +/- 28.4 micromol). The total lymphatic output of oleic acid (18:1), the major fatty acid infused in the form of triolein, did not differ among the NPC (448.0 +/- 58.2 micromol/8 h), SPC (457.9 +/- 52.3 micromol/8 h) and EPC (412.9 +/- 20.8 micromol/8 h) groups, but was significantly lower in the HPC group (262.0 +/- 24.1 micromol/8 h). The findings provide the first evidence that EPC markedly lowers the lymphatic absorption of cholesterol under in vivo conditions. The inhibitory effect of EPC appears to be due to the higher degree of saturation of its acyl groups relative to SPC, suggesting that the intestinal absorption of egg cholesterol may be reduced by the presence of PC in egg yolk.

Correction of lymph circulation during immediate hypersensitivity reaction

We measured lymph flow rate in the thoracic lymphatic duct of dogs with anaphylactic shock receiving mono- or combination therapy with norepinephrine and hydrocortisone. Intensification of lymph circulation improved resorption and transport of metabolic products from the interstitial space through lymphatic vessels and stimulated exchange processes in the blood and tissues during allergic alterations.

Detergent inhibits 70-90% of responses to intravenous endotoxin in awake sheep

Sheep have reactive pulmonary intravascular macrophages, which are essential for the marked pulmonary vascular response to infusions of small quantities of endotoxin. In another species with reactive pulmonary intravascular macrophages, horses, our laboratory found that an intravenous biosafe detergent, tyloxapol, inhibited some systemic and pulmonary responses to endotoxin (Longworth KE, Smith BL, Staub NC, Steffey EP, and Serikov V. Am J Vet Res 57: 1063-1066, 1996). We determined whether the same detergent would inhibit endotoxin responses in awake sheep. In 10 awake, instrumented sheep with chronic lung lymph fistulas, we did a control experiment by intravenously infusing 1 microg/kg Escherichia coli endotoxin. One week later, we gave 40 micromol/kg tyloxapol intravenously 1-4 h before infusing the same dose of endotoxin. In these paired studies, we compared pulmonary hemodynamics, lung lymph dynamics, body temperature, circulating leukocyte concentrations, and circulating tumor necrosis factor for 6 h. In all 10 sheep, tyloxapol blocked 80-90% of the pulmonary responses and 70-90% of the systemic responses. Tyloxapol is safe, inexpensive, easy to use, and effective immediately. It may be a clinically useful approach to contravening many of the effects of endotoxemia, in humans as well as animals.

Lymph osmolality and rehydration from NaCl solutions by toads, Bufo marinus

Toads, Bufo marinus, allowed to maintain an ad libitum state of hydration were dehydrated by 10 15% of their standard weight and allowed to rehydrate from either deionized water or from 10 or 50 mmol l(-1) NaCl solutions. Toads rehydrating from the dilute salt solutions recovered a larger fraction of their standard weight than did toads rehydrating from deionized water despite there being a reduced osmotic gradient. Amiloride did not reduce water gain from these solutions. Water uptake from 100 mmol l(-1) sucrose and 50 mmol l(-1) Na gluconate was reduced relative to deionized water by a fraction predicted from the osmotic gradient. Thus, the presence of both Na+ and Cl- are required for the augmentation of water gain from dilute salt solutions. Toads allowed to rehydrate from 120 mmol l(-1) NaCl for 180 min recovered nearly as much water as toads rehydrating from deionized water for 120 min and the lymph osmolality was not reduced relative to the dehydrated condition. The recovery of water from the salt solution was greater than that predicted from the reduced osmotic gradient and amiloride partially inhibited the rehydration from 120 mmol l(-1) NaCl. Solute coupled water transport can therefore be demonstrated in living animals but only from a NaCl solution that is nearly isoosmotic with the lymph. The mechanism for enhanced water gain from dilute salt solutions remains unresolved.

[Electrochemical detoxication of the lymph in the treatment of patients with suppurative-resorptive endotoxicosis]

A new method for lymph detoxication in patients with pyoresorptive endotoxicosis is proposed. The method is based on electrochemical oxidation of the lymph, is simple and cheap. After 4-h exposure of the lymph with 0.04% sodium hypochlorite the concentration of the main toxic metabolites appreciably decreased, while the levels of total protein and leukocytes changed negligibly. Electrochemical detoxication of the lymph was used in the treatment of 13 patients with pyoresorptive endotoxicosis and led to improvement of the clinical status and rapid decrease in the levels of the major toxic metabolites, which was particularly expressed 3 days after the treatment. No negative effects were observed. Hence, electrochemical detoxication of the lymph appreciably improved the results of treatment of patients with cholestatic endotoxicosis.

Lymph draining from foot joints in rheumatoid arthritis provides insight into local cytokine and chemokine production and transport to lymph nodes

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by inflammatory reactions in joints and adjacent tissues unaccompanied by clinically evident changes in lymphatics and lymph nodes draining the inflamed areas. The explanation for this phenomenon, which contrasts with infectious processes in joints and soft tissues that evoke major changes in the lymphatic system, is unclear. To determine which inflammatory factors produced in the joints of RA patients are transported in lymph to lymph nodes, we measured levels of immunoglobulins, cytokines, and chemokines in prenodal lymph from the foot joints of RA patients and quantified their rate of transport to regional lymph nodes.

METHODS

Lymph was collected from the cannulated lymphatics draining the foot joints, tendons, fascia, and skin of 20 RA patients. Lymph flow rate and concentrations of proteins and immunoglobulins were measured. Cytokine and chemokine levels were quantified by enzyme-linked immunosorbent assays. Results were compared with those obtained in 20 control subjects.

RESULTS

In the cannulated vessel, the mean +/- SEM lymph flow rate in RA patients was almost 2-fold that in control subjects (22.6 +/- 3.2 ml/24 hours versus 13.2 +/- 1.1 ml/24 hours; P < 0.01). Lymph concentrations of total protein, IgG, and IgM were 1.80 +/- 0.14 gm/dl, 384 +/- 45 mg/dl, and 32.0 +/- 1.5 mg/dl, respectively, in RA patients and 1.66 +/- 0.14 gm/dl, 238 +/- 32 mg/dl, and 15.0 +/- 1.3 mg/dl, respectively, in control subjects. The corresponding lymph:serum (L:S) ratios were 0.21 +/- 0.02, 0.22 +/- 0.02, and 0.15 +/- 0.02, respectively, in RA patients and 0.22 +/- 0.02, 0.19 +/- 0.02, and 0.11 +/- 0.02, respectively, in control subjects. The L:S ratios of <1 and the absence of significant differences between groups suggested a lack of local production of immunoglobulins. In RA patients, lymph concentrations (in pg/ml) were as follows: interleukin-1beta (IL-1beta) 14.8 +/- 3.9, IL-6 511 +/- 143, tumor necrosis factor alpha (TNFalpha) 9.9 +/- 1.1, IL-1 receptor antagonist (IL-1Ra) 4,274 +/- 737, IL-10 13.3 +/- 4.4, IL-8 846 +/- 174, IL-15 6.2 +/- 0.9, granulocyte-macrophage colony-stimulating factor (GM-CSF) 2.30 +/- 0.15, vascular endothelial growth factor (VEGF) 80.4 +/- 8.6, and macrophage inflammatory protein 1alpha (MIP-1alpha) 171 +/- 34. In control subjects, these values were as follows: IL-1beta 1.50 +/- 0.25, IL-6 79.0 +/- 14.6, TNFalpha 4.4 +/- 1.1, IL-1Ra 208 +/- 52, IL-10 0.0, IL-8 216 +/- 83, IL-15 5.00 +/- 0.45, GM-CSF 0.40 +/- 0.05, VEGF 42.0 +/- 2.4, and MIP-1alpha 3.4 +/- 1.7 (P < 0.05 versus RA patients for all except IL-15). The L:S ratio was >1 in all RA patient samples for IL-1beta, IL-6, IL-1Ra, IL-8, GM-CSF, IL-10, IL-15, TNFalpha, and MIP-1alpha, indicating local production of cytokines. Great variability in lymph cytokine concentrations, presumably reflecting differences in the intensity of local inflammation, was not reflected in serum cytokine concentrations. Intravenously infused methylprednisolone decreased lymph cytokine levels to normal within 12 hours. In contrast, their concentrations in serum showed little or no change.

CONCLUSION

High lymph concentrations of cyto kines and chemokines, exceeding those in serum, were found in RA patients. The L:S concentration ratios of > 1 indicate the local production of these cytokines and chemokines in the inflamed tissues. High flow rates of lymph containing high cytokine concentrations through the regional lymph nodes are likely to affect node lymphocytes and dendritic cells. Analysis of cytokines in lymph should provide insight into events in inflamed tissues in RA and in regional lymph nodes.

Beta-adrenergic agonist therapy accelerates the resolution of hydrostatic pulmonary edema in sheep and rats

To determine whether beta-adrenergic agonist therapy increases alveolar liquid clearance during the resolution phase of hydrostatic pulmonary edema, we studied alveolar and lung liquid clearance in two animal models of hydrostatic pulmonary edema. Hydrostatic pulmonary edema was induced in sheep by acutely elevating left atrial pressure to 25 cmH(2)O and instilling 6 ml/kg body wt isotonic 5% albumin (prepared from bovine albumin) in normal saline into the distal air spaces of each lung. After 1 h, sheep were treated with a nebulized beta-agonist (salmeterol) or nebulized saline (controls), and left atrial pressure was then returned to normal. beta-Agonist therapy resulted in a 60% increase in alveolar liquid clearance over 3 h (P < 0.001). Because the rate of alveolar fluid clearance in rats is closer to human rates, we studied beta-agonist therapy in rats, with hydrostatic pulmonary edema induced by volume overload (40% body wt infusion of Ringer lactate). beta-Agonist therapy resulted in a significant decrease in excess lung water (P < 0.01) and significant improvement in arterial blood gases by 2 h (P < 0.03). These preclinical experimental studies support the need for controlled clinical trials to determine whether beta-adrenergic agonist therapy would be of value in accelerating the resolution of hydrostatic pulmonary edema in patients.

[A new method for detoxifying the lymph in patients with cholestatic endotoxicosis]

A method is proposed for lymph detoxication in patients with cholestatic endotoxicosis by indirect electrochemical oxidation. The method is simple and cheap. After the treatment of the toxic lymph with the solution of sodium chloride during 4 hours the concentration of main toxic metabolites in it was substantially decreased while the total protein content was practically not changed. Under study were the results of using electrochemical lymph detoxication in 11 patients with cholestatic endotoxicosis which was followed by better condition of the patients and by faster dynamics of lowering the level of the main toxic metabolites.

Lung lymph response to overinfusion with hydroxyethyl starch in sheep. Comparative studies of high and low molecular weight compounds

BACKGROUND

Several hydroxyethyl starch (HES) solutions are available clinically. We performed comparative studies of low and high molecular weight HES to evaluate the effects on lung lymph flow in sheep, to see the difference in the types of HES.

METHODS

We prepared awake sheep with vascular monitorings and lung lymph fistulas. We measured systemic artery pressure (Psa), pulmonary artery pressure (Ppa), and left atrial pressure (Pla) continuously. Cardiac output (CO) was measured every 30 min. Lung lymph flow (Qlym) was collected every 15 min. After baseline measurements, two HES solutions were infused over 2 h, respectively. Experiment 1 (n=6): low molecular weight HES (MW 70 000, substitution ratio 0.5-0.55), Experiment 2 (n=5): high molecular weight HES (MW 450 000, substitution ratio 0.7).

RESULTS

Both low and high molecular HES behaved similarly as a volume expander, increasing Psa, CO, Pla and Ppa, and decreasing hematocrit. In addition, the actual oncotic pressure gradient (plasma - lymph) was widened after the start of either low or high molecular HES, but the value for high molecular HES was significantly higher than that for low molecular HES. Qlym of low molecular HES rose significantly from the baseline and the percent increase in Qlym for low molecular HES was significantly higher than that for high molecular HES.

CONCLUSION

These data suggest that low molecular HES is as useful a plasma substitute as high molecular HES, but may increase lung fluid filtration in the overinfused state.

Flow reduces the amplitude and increases the frequency of lymphatic vasomotion: role of endothelial prostanoids

Fluid dynamic forces have substantial effects on the movement of lymph and activity of lymph vessels. The effect of increases in intraluminal flow on spontaneous pumping activity of isolated collecting lymphatics has not yet been characterized in a condition in which the intraluminal pressure is constant. Thus, in afferent lymph microvessels isolated from rat iliac lymph nodes, changes in maximum (Dmax) and minimum (Dmin) diameter to increases in perfusate flow were investigated in the presence of a constant perfusion pressure of 6 cmH2O. Intraluminal flow was elicited by increases in the difference between outflow and inflow pressures (Pdiff, from 0 to 6 cmH2O). Diameters were measured by videomicroscopy. In response to increases in perfusate flow, Dmax and Dmin of lymphatics decreased from 157.5 +/- 6.1 to 90.9 +/- 5.6 micron and from 91.9 +/- 5.3 to 66.3 +/- 3.6 micron, respectively, whereas vasomotion frequency increased from 18.0 +/- 0.7 min(-1) to 23.4 +/- 1.1 min(-1) (at Pdiff of 4 cmH2O). Removal of extracellular Ca2+ abolished spontaneous diameter oscillations; under these conditions the passive diameter of lymphatics was 216.0 +/- 7.1 micron and did not change in response to increases in perfusion. In the absence of endothelium, flow-induced changes in Dmax, Dmin, and oscillation frequency were eliminated. Nomega-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, did not affect flow-induced changes in diameter of lymphatics. In contrast, indomethacin, an inhibitor of prostaglandin synthesis, or SQ-29,548, a PGH2/thromboxane A2 (PGH2/TxA2) receptor blocker, inhibited the perfusion-induced reduction of Dmax and Dmin of lymphatics and also the increase in the frequency of vasomotion. These findings suggest that the sensitivity of lymphatic endothelium to increases in intraluminal flow could provide an important local intrinsic mechanism for the control of lymphatic resistance by release of constrictor prostanoids PGH2/TxA2.

A 21-aminosteroid, U-74006F, attenuates endotoxin-induced lung injury in awake sheep

The purpose of the present study was to examine the efficacy of U-74006F, a 21-aminosteroid, on lung dysfunction induced by endotoxaemia in awake sheep with lung lymph fistula and haemodynamic monitoring. We measured pulmonary haemodynamics, lung lymph balance, circulating leucocyte count, arterial blood gas tensions, and levels of thromboxane (Tx) B2 and 6-keto-prostaglandin (PG) F1 alpha in plasma and lung lymph. We performed two experiments. In experiment 1 (n = 6), we intravenously infused Escherichia coli lipopolysaccharide endotoxin (1 microgram/kg) over 30 min and observed the parameters over 5 h. In experiment 2 (n = 6), we pretreated sheep with an intravenous bolus of U-74006F (2 mg/kg) 30 min before the infusion of endotoxin in the same manner of experiment 1, and continuously infused U-74006F (0.5 mg/kg per h) over 5 h after the bolus during the experiment. The U-74006F significantly suppressed the early pulmonary hypertension, the late increase in pulmonary permeability and the elevations of TxB2 and 6-keto-PGF1 alpha levels in plasma and lung lymph during the early period following endotoxaemia, although the compound did not change the time course of leucocytopenia and hypoxaemia. These findings suggest that the administration of U-74006F attenuates the lung dysfunction induced by endotoxaemia in awake sheep.

[The mechanisms of the lymph-stimulating action of liposomes]

The mechanisms of lymph-stimulating action of different liposomes (lecithin-cholesterin, lecithin) were studied in the experiments on dogs. It has been shown an absence of interaction between changes in the lymph outflow rate and system circulation parameters when injecting any liposomes. Moreover, water and protein filtration from the vascular bed into the interstitial space was lowered due to liposomal injection. But oxygen tension in the muscular tissues remained on the level closed to the normal one. In contrast to the intravenous injection, the subcutaneous administration of liposomes has induced the stimulation of lymph outflow, which was more expressed on both volume (nearly by 40%) and duration (nearly by 50%). The experiments with limited and crossed blood flow have demonstrated a regional character of liposomal lymph-stimulating. The mechanisms of such liposomal action may be related to both direct action of liposomes on the lymphatic smooth muscle contractility in the lymphatic vessels and the increased lymph production in the site of liposomal injection due to free radical oxidation processes being limited in that area. The micellar form of phospholipids (essential) has demonstrated no lymph-stimulating action.

Alveolar epithelial fluid clearance persists in the presence of moderate left atrial hypertension in sheep

The effect of moderate left atrial (LA) hypertension on alveolar liquid clearance (ALC) was investigated in anesthetized, ventilated sheep, surgically prepared to measure lung lymph flow as well as hemodynamics. To simulate alveolar edema, 3-4 ml/kg of isosmolar 5% albumin in Ringer lactate were instilled into each lower lobe, and ALC was measured. After 4 h of LA hypertension (24 cmH2O), ALC was similar to that in control sheep (31 +/- 3% with LA hypertension vs. 34 +/- 10% with normal LA pressure). Because plasma epinephrine levels were moderately elevated in the presence of LA hypertension, ALC was then studied in the presence of LA hypertension following bilateral adrenalectomy. Without endogenous release of epinephrine, ALC was significantly reduced compared with normal LA pressure (20 +/- 7% compared with 34 +/- 10%, P < 0.05). Thus endogenous catecholamines caused a submaximal stimulation of ALC in the presence of LA hypertension. Exogenous administration of aerosolized beta2-agonist therapy with salmeterol increased ALC in the presence of normal LA pressure but had no stimulatory effect in the presence of moderate LA hypertension. Therefore, we tested the hypothesis that endogenous release of atrial natriuretic factor (ANF) may downregulate alveolar epithelial Na+ and fluid transport in the presence of LA hypertension. There was a modest twofold increase in plasma ANF levels after LA hypertension. Additional in vitro studies demonstrated that, in the presence of beta2-agonist stimulation, ANF decreased Na+ pump activity (Na+-K+-ATPase) in isolated rat alveolar epithelial type II cells. ANF may downregulate vectorial Na+ and fluid transport stimulated by endogenous or exogenous beta-adrenergic agonist stimulation in the presence of LA hypertension. In summary, ALC continues even in the presence of moderate LA hypertension. Aerosolized beta2-adrenergic agonist therapy significantly increased ALC, but only when LA pressure was normal.

Biphasic insulin secretion during intravenous glucose tolerance test promotes optimal interstitial insulin profile

We examined the hindlimb lymph insulin profile during simulated intravenous glucose tolerance tests (IVGTTs) in anesthetized dogs to test the following hypotheses: 1) the biphasic insulin response to intravenous glucose can be seen as a priming bolus and a secondary infusion that effect a rapid stepwise increase in the interstitial insulin concentration and 2) the activation of glucose utilization (rate of glucose uptake [Rd]) during an IVGTT is more similar to the dynamics of the interstitial insulin profile than that of the arterial plasma. Three insulin profiles were infused: a normal biphasic pattern, a second phase infusion only, and a biphasic pattern with a fourfold greater first phase and a normal second phase. During the normal biphasic infusion, lymph insulin quickly reached and maintained a steady-state concentration (10 min, 26.42 +/- 0.86 microU/ml). With second phase only, it took lymph insulin 35 min to reach a steady state of lower concentration (13.13 +/- 0.46 microU/ml) than the normal. And with a fourfold greater first phase, lymph insulin plateaued quickly (16 min, 140.87 +/- 1.68 microU/ml), but for a shorter duration than the normal. For each profile, the time course of activation of Rd did not follow the time course of insulin in the plasma, but was more similar to that of insulin in the interstitial fluid. These results show that the biphasic response allows interstitial insulin to rapidly reach and maintain a steady state beneficial to activation and maintenance of glucose utilization.

Bronchial vascular contribution to lung lymph flow

The lymphatic vessels of the lung provide an important route for clearance of interstitial edema fluid filtered from pulmonary blood vessels. However, the importance of lung lymphatics for the removal of airway liquid filtered from the systemic circulation of the lung has not been demonstrated. We studied the contribution of the bronchial vasculature to lung lymph flow in anesthetized, ventilated sheep (n = 35). With the bronchial artery cannulated and perfused (control flow = 0.6 ml. min-1. kg-1), lymph flow from the efferent duct of the caudal mediastinal lymph node was measured 1) during increased bronchial vascular perfusion (300% of control flow); 2) with a hydrated interstitium induced by a 1-h period of left atrial hypertension and subsequent recovery, both with and without bronchial perfusion; and 3) during infusion (directly into the bronchial artery) of bradykinin, an inflammatory mediator known to cause changes in bronchial vascular permeability. Increased bronchial perfusion for 90 min resulted in an average 35% increase in lung lymph flow. During left atrial hypertension, the increase in lung lymph flow was significantly greater with bronchial perfusion (339% increase over baseline) than without bronchial perfusion (138% increase). Furthermore, recovery after left atrial hypertension was more complete after 90 min without bronchial perfusion (91%) than with bronchial perfusion (63%). Infusion of bradykinin into the bronchial artery resulted in a prompt and prolonged 107% increase in lung lymph flow. This was not seen if the same dose was infused into the pulmonary artery. Thus bronchial vascular transudate contributes significantly to lymph flow from the efferent duct of the caudal mediastinal lymph node. These results demonstrate that lymph vessels clear excess fluid from the airway wall and should be considered when evaluating the effect of vascular leak in airway obstruction.

Evidence for direct action of alloxan to induce insulin resistance at the cellular level

To determine whether long-term insulin deficiency alters insulin movement across the endothelium, plasma and lymph dynamics were assessed in dogs after alloxan (50 mg/kg; n = 8) or saline injection (n = 6). Glucose tolerance (KG) and acute insulin response were assessed by glucose injection before and 18 days after treatment. Two days later, hyperglycaemic (16.7 mmol/l) hyperinsulinaemic (60 pmol x min(-1) x kg(-1)) glucose clamps were carried out in a subset of dogs (n = 5 for each group), with simultaneous sampling of arterial blood and hindlimb lymph. Alloxan induced fasting hyperglycaemia (12.9 +/- 2.3 vs 5.7 +/- 0.2 mmol/l; p = 0.018 vs pre-treatment) and variable insulinopenia (62 +/- 14 vs 107 +/- 19 pmol/l; p = 0.079). The acute insulin response, however, was suppressed by alloxan (integrated insulin from 0-10 min: 155 +/- 113 vs 2745 +/- 541 pmol x l(-1) x 10 min(-1); p = 0.0027), resulting in pronounced glucose intolerance (KG: 0.99 +/- 0.19 vs 3.14 +/- 0.38 min(-1); p = 0.0002 vs dogs treated with saline). During clamps, steady state arterial insulin was higher in dogs treated with alloxan (688 +/- 60 vs 502 +/- 38 pmol/l; p = 0.023) due to a 25% reduction in insulin clearance (p = 0.045). Lymph insulin concentrations were also raised (361 +/- 15 vs 266 +/- 27 pmol/l; p = 0.023), such that the lymph to arterial ratio was unchanged by alloxan (0.539 +/- 0.022 vs 0.533 +/- 0.033; p = 0.87). Despite higher lymph insulin, glucose uptake (Rd) was significantly diminished after injection of alloxan (45.4 +/- 2.5 vs 64.3 +/- 6.5 micromol x min(-1) x kg(-1); p = 0.042). This was reflected in resistance of target tissues to the lymph insulin signal (deltaRd/ delta lymph insulin: 3.389 +/- 1.093 vs 11.635 +/- 2.057 x 10(-6) x l x min(-1) x kg(-1) x pmol(-1) x l(-1); p = 0.012) which correlated strongly with the KG (r = 0.86; p = 0.0001). In conclusion, alloxan induces insulinopenic diabetes, with glucose intolerance and insulin resistance at the target tissue level. Alloxan treatment, however, does not alter lymph insulin kinetics, indicating that insulin resistance of Type 1 (insulin-dependent) diabetes mellitus reflects direct impairment at the cellular level.

Inhaled nitric oxide reduces lung fluid filtration after endotoxin in awake sheep

We studied the effect on lung fluid filtration of 37.6 ppm inhaled nitric oxide (NO) imposed for 1 h 2.5 h after endotoxin in seven awake sheep, with seven control subjects. The effects of NO on the longitudinal distribution of pulmonary vascular resistance (PVR) before and after endotoxin were specifically addressed in six sheep. Following endotoxin, sheep developed respiratory distress; PaO2, the alveolar-arterial oxygen tension difference (AaPO2) and venous admixture (Q S/Q T) changed significantly, as did the pulmonary artery pressure (Ppa), PVR, and lung lymph flow (Q L). Inhaled NO reduced Ppa and PVR by 50%; Q L decreased from 7.8 +/- 0.34 ml/15 min to 4.7 +/- 0.80 ml/15 min (mean +/- SEM), and lymph protein clearance from 4.9 +/- 0.18 ml/15 min to 3.6 +/- 0.75 ml/15 min. Lymph/plasma protein concentration ratio (L/P) increased from 0.63 +/- 0.016 to 0.72 +/- 0.006, concomitant with the decrease in Q L. The L/P - Q L relationships shifted from left, at baseline, to the right during endotoxemia, as did the permeability surface product (PS) isolines. The rightward shift was significantly less in the NO group. Inhaled NO significantly improved PaO2, AaPO2, and Q S/Q T, reduced the increase in pulmonary microwedge pressure back to baseline and decreased upstream and downstream PVR at 3.0 through 4. 0 h. We conclude that, in sheep, inhaled NO reduces lung fluid filtration by decreasing microvascular pressure and apparently also by declining the enhanced microvascular permeability during the late phase of endotoxemia.

[The effect of dimethyl sulfoxide on the changes in the lymph microcirculation induced by staphylococcal toxin]

The effect of dimethyl sulfoxide (dimexid, DMSO) on the lymph microvessels of the rat mesentery was studied by vital biomicroscopy. It was found that 30% DMSO increases the tonus of intact lymph microvessels and stimulates their phase contractions. Action of the agent for more than 15 min leads to the development of lymphostasis. DMSO has a pronounced corrective effect on disorders of lymph microcirculation caused by the staphylococcal toxin. It removes the main lymphopathogenic effects of the poison and normalizes the drainage function of the lymphangions. The correcting effect of DMSO on lymph circulation is attended with attenuation of the fatal effect of the toxin.