Mesenteric Flow Research Articles

Functional adaptation of bovine mesenteric lymphatic vessels to mesenteric venous hypertension

Lymph flow is the primary mechanism for returning interstitial fluid to the blood circulation. Currently, the adaptive response of lymphatic vessels to mesenteric venous hypertension is not known. This study sought to determine the functional responses of postnodal mesenteric lymphatic vessels. We surgically occluded bovine mesenteric veins to create mesenteric venous hypertension to elevate mesenteric lymph flow. Three days after surgery, postnodal mesenteric lymphatic vessels from mesenteric venous hypertension (MVH; n = 7) and sham surgery (Sham; n = 6) group animals were evaluated and compared. Contraction frequency (MVH: 2.98 ± 0.75 min(-1); Sham: 5.42 ± 0.81 min(-1)) and fractional pump flow (MVH: 1.14 ± 0.30 min(-1); Sham: 2.39 ± 0.32 min(-1)) were significantly lower in the venous occlusion group. These results indicate that postnodal mesenteric lymphatic vessels adapt to mesenteric venous hypertension by reducing intrinsic contractile activity.

Distinct from its canonical effects, deletion of IL-12p40 induces cholangitis and fibrosis in interleukin-2Rα−/− mice

The IL-12 family modulates T cell mediated autoimmune diseases and GWAS in PBC have suggested a critical role of IL-12 and its subunits in modulating portal inflammation. We have taken advantage of an aggressive model of portal inflammation and colitis in IL-2Rα−/− mice to study the specific role of IL-12 and, in particular, the immunobiology of p40−/−IL-2Rα−/− mice. Colonies of IL-2Rα+/−, IL-2Rα−/− and p40−/−IL-2Rα−/− mice were studied for the natural history of immunopathology in liver and colon using histology and immunohistochemistry. Further, to focus on mechanisms, liver, spleen and mesenteric lymph node flow cytometry was employed to identify specific phenotypes; cytokine analysis on inflammatory cell populations was compared between groups. Finally, Real-Time PCR was used to focus on the genes involved in hepatic fibrosis. Surprisingly, p40−/−IL-2Rα−/− mice manifest more severe portal inflammation and bile duct damage, including signs of portal hypertension and liver fibrosis, but a significant reduction in colitis. Indeed, p40−/−IL-2Rα−/− mice reveal a profound hepatic CD8+ T cell infiltrate, whose major component are effector memory cells as well as enhanced hepatic Th1 but reduced Th17 responses. These observations were confirmed by Real-Time PCR analysis of fibrosis-related genes in the liver. Distinct from its canonical effects, IL-12p40 plays a critical role in autoimmune cholangitis, including hepatic fibrosis. These data take on striking significance for any proposed human trials that modulate the IL-12p40 pathway in human PBC.

Mast Cell-Directed Recruitment of MHC Class II Positive Cells and Eosinophils Towards Mesenteric Lymphatic Vessels in Adulthood and Elderly

Aging impairs mesenteric lymph flow, which is crucial for fluid and macromolecule homeostasis, fat absorption, and immune function. Previously, we demonstrated that mast cells (MCs) line mesenteric lymphatic vessels (MLVs) with a greater degree of basal activation of MCs in aged mesentery. The number of intact MCs available to react acutely to inflammatory stimuli was decreased with age. However, the role of mast cells in recruiting other immune cells towards MLVs and its aging-associated alterations has not been explored before in great detail. In this study we treated live mesenteric tissue isolated from Sprague Dawley (SD) rats, as well as adult 9-mo and aged 24-mo Fischer-344 (F-344) rats for 2 hours with MC activators (48/80 and Substance P) and performed whole mount IHC and vital dye staining of the mesenteric segments containing MLVs to identify immune cell recruitment towards MLVs after mast cell (MC) activation. Number of major histocompatibility complex (MHC) class II positive APCs and eosinophils near MLVs was counted and compared between treatments and ages. With greater density of MCs near MLVs, we for the first time demonstrated that mesenteric MC activation by compound 48/80 and Substance P resulted in recruitment of MHC class II positive cells and eosinophils towards MLVs. This effect was reduced in cromolyn-injected rats, thus confirming that MCs are necessary for such recruitment. The immune cell presence near MLVs after MC activation was reduced in aged tissues. We link these findings to our previous report of lesser number of intact MCs available for initiating an acute immune response in aged mesentery. Cumulatively, these findings serve as the first step in study of the aging-associated mechanisms that link MCs, lymphatic vessels, and disordered immune function in the elderly.

The role of thoracic epidural anesthesia in severe acute pancreatitis

In animal studies of severe acute pancreatitis, thoracic epidural anesthesia appears to enhance the splanchnic circulation, improve end-organ perfusion, and favorably influence mortality. The application of thoracic epidurals in the critically ill human patient is less clear. Methodological difficulties in reliably assessing mesenteric flow have hampered progress, and clinical concerns surrounding this potentially attractive therapeutic modality remain unanswered. Future research needs to focus on the impact of epidural anesthesia on basic human physiological pmeters to help direct further randomized studies in human disease.

Low-Dose Vasopressin Improves Cardiac Function in Newborn Piglets With Acute Hypoxia-Reoxygenation

Cardiovascular dysfunction in asphyxiated neonates contributes significantly to their morbidity and mortality. We have recently shown that a low-dose vasopressin infusion (0.005 - 0.01 units/kg per hour) may improve myocardial oxygen transport balance in a swine model of neonatal hypoxia-reoxygenation. We aimed to compare the systemic and regional hemodynamic effects of low-dose vasopressin to dobutamine, a synthetic beta-adrenoreceptor agonist. Piglets (1 - 5 days old, 1.6 - 2.2 kg) were anesthetized and instrumented to continuously monitor systemic hemodynamic parameters, including cardiac output and mesenteric flow indices. After 2 h of hypoxia (10% - 15% O2), piglets had normoxic reoxygenation for 4 h. In a blinded randomized fashion, piglets received infusion of either vasopressin (0.01 units/kg per hour started at 30 min of reoxygenation) or dobutamine (20 μg/kg per minute started at 2 h of reoxygenation) (n = 8 per group). Hypoxia-reoxygenation controls (placebo, n = 8) and sham-operated (n = 5) piglets were also studied. Tissue lactate, glutathione, glutathione disulfide, and lipid hydroperoxides levels and histology of the left ventricle and the small bowel were analyzed. Plasma was also analyzed for troponin-I and intestinal fatty acid-binding protein levels. Piglets subjected to hypoxia-reoxygenation had cardiogenic shock and metabolic acidosis, which improved on reoxygenation. During recovery, cardiac output and mesenteric flows gradually deteriorated and were increased similarly in vasopressin- and dobutamine-treated piglets (P < 0.05 vs. controls). Plasma troponin-I and left ventricular lactate levels were lower in the vasopressin and dobutamine groups (P < 0.05 vs. controls), with no difference in the histological analysis among groups. The intestinal GSSG/GSH ratio and lipid hydroperoxides level were lower in the vasopressin and dobutamine groups (P < 0.05 vs. controls). This study is the first to demonstrate that a low-dose vasopressin infusion used in the setting of neonatal swine model of hypoxia-reoxygenation is associated with an improvement in cardiac output and mesenteric perfusion.

Effects of exogenous vasoactive intestinal peptide on mesenteric lymph pathway during early intestinal ischemia–reperfusion injury in rats

Mesenteric lymph pathway serves as the primary route by which gut injury leads to systemic inflammation and distant organ injury. The inflammation of the intestinal tract is partially mediated by vasoactive intestinal peptide (VIP). Therefore, the aim of this study was to test whether exogenous VIP affects mesenteric lymph pathway during early intestinal ischemia–reperfusion (IIR) injury. Rats were randomized into control, control+VIP, IIR and IIR+VIP groups. The observation of mesenteric lymph flow was carried out by cannulation of mesenteric lymphatics. The distribution of in vivo lymphocyte trafficking was performed by 51Cr labeled lymphocytes and was measured by γ-counter. Endotoxin concentration was assayed using the limulus test kit and TNF-α level was detected by ELISA. When IIR injury treated with VIP, the volumes of lymph flow increased by 80%, which caused the number of lymphocytes exiting in mesenteric lymphatic increased by 50% while the proportion of 51Cr-lymphocytes in Peyer's patches, intestinal effector tissues, mesenteric nodes, large intestine, stomach decreased by 58%, 51%, 58%, 63%, 64% respectively at the 6th h after reperfusion following intestinal ischemia. Meanwhile, endotoxin and TNF-α levels in intestinal lymph decreased by 51% and 83%. These results suggest that exogenous VIP ameliorates IIR induced splanchnic organ damage via inhibition of toxic mediators reaching systemic circulation and reinforcement of the effective immune responses in gut-associated lymphoid tissues (GALT).

Flujo mesentérico en un modelo experimental por isquemia-reperfusión en ratas

IntroductionMaintained acute occlusion followed by reperfusion of the superior mesenteric artery (SMA) in a few hours can trigger irreversible bowel damage. The aim of the study was to determine the changes in mesenteric flow measured by colour Doppler Ultrasound and correlating with histological lesions in an experimental model of ischaemia-reperfusion. Method and materialThree groups of Sprague-Dawley 17 day-old rats were studied (control, ischemia and reperfusion). The model used was ischaemia-reperfusion over the SMA. Intra-abdominal ultrasound was then performed. The parameters recorded were: Maximum systolic velocity (MSV), pulsatility index (PI), resistance (RI) and systole-diastole (S/D). The histological variables were: intestinal lesion (Wallace/Keenan-Chiu scale), morphometrics (mean villus height [MVH]), and goblet cells. The Spearman (rs) correlation was used. ResultsThe MSV in the reperfusion group was 74.3cm/s, the PI 7.33 and S/D 25.75 in the SMA, which were higher than the controls (41.35cm/s; 3.12 and 12.45, respectively). A direct association (P<.01) was found between MSV, PI and S/D regarding: Wallace/Kennan scoring system (rs = 0.655; rs = 0.593; rs = 0.63) and the Chiu (rs = 0.569; rs = 0.522; rs = 0.47). While the correlation was the reverse (P<.01) when associated with the MVH (rs = –0,495; rs = –0,452; rs = –0,459) and goblet cells of the colon (rs = –0,525; rs = –0,45; rs = –0,518). ConclusionsThe reperfusion phase increased mesenteric flow expressed by the MSV and PI and could significantly predict the potential bowel damage at macroscopic and microscopic level.

Role of mesenteric lymph pathway in the effects of exogenous somatostatin against early intestinal injury after ischemia–reperfusion in rats

Intestinal ischemia–reperfusion (I/R)-induced gut injury remains a challenge for critically ill patients. This study aims to test whether mesenteric lymph pathway is involved in intestinal I/R injury and whether somatostatin (SST) affects mesenteric lymph pathway after mesenteric reperfusion. Intestinal I/R rats were treated with SST-14 by intravenous injection combined with intraperitoneal injection before occlusion of the SMA until the end of the experiment. When intestinal I/R injury treated with SST, the volumes of mesenteric lymph flow at the 6th h after reperfusion following intestinal ischemia were increased ([0.55±0.24] ml/h vs [0.25±0.09] ml/h, p<0.05) and the number of intestinal lymphocytes per milliliter ([2.30±0.72]×107/ml vs [1.16±0.63]×107/ml, p<0.05) was also increased, which caused the number of intestinal lymphocytes output at the same period of time was significantly increased compared with intestinal I/R group ([1.33±0.88]×107/h vs [0.28±0.15]×107/h, p<0.05). Meanwhile, the number of 51Cr-lymphocytes migration from systemic circulation to the effector sites in GALT was significantly increased ([1.93±0.23]×105/h vs [0.90±0.25]×105/h, p<0.05), although the percentage of 51Cr-lymphocytes in the effector sites ([1.45±0.26]% vs [3.23±1.69]%, p<0.05) was sharply decreased compared with intestinal I/R group. The accompanying decreases of the endotoxin concentration ([0.038±0.017] EU/mL vs [0.110±0.028] EU/mL, compared with intestinal I/R group p<0.05) and the TNF-α levels ([37.50±10.45] ρg/ml) vs ([74.93±14.77] ρg/ml), compared with intestinal I/R group p<0.05) in mesenteric lymph and the improvement of vital organ dysfunction happened during the early intestinal I/R injury. Suppression of gut-derived toxic mediators reaching systemic circulation and increases of the number of lymphocytes homing to the effector sites in GALT to strengthen the effective immune responses in intestinal mucosa account for the protective effects of exogenous SST against early intestinal I/R injury.

Effect of mast cell activation on immune cell trafficking towards mesenteric lymphatic vessels and its aging‐associated alterations

Aging impairs mesenteric lymph flow, which is crucial for fluid and macromolecule homeostasis, fat absorption, and immune function. Previously, we had demonstrated that mast cells line mesenteric lymphatic vessels (MLV) with a greater degree of basal activation of mast cells in aged mesentery. The number of intact mast cells available to react acutely to inflammatory stimuli was decreased with age. In this study we treated live mesenteric tissue isolated from adult and aged F‐344 rats for 2 hours with mast cell activators and performed whole mount IHC and vital dye staining to identify immune cell recruitment towards MLV after mast cell activation. Number of immune cells near MLV was counted and compared between treatments and ages. With greater density of mast cells near MLV, we demonstrated that mesenteric mast cell activation by Compound 48/80 &amp; Substance P resulted in migration of MHC II positive cells and eosinophils towards MLV. This effect was reduced in cromolyn pre‐injected rats. The immune cell recruitment towards MLV after mast cell activation was reduced in aged tissues. We link these findings to our previous report of lesser number of intact mast cells available for initiating an acute immune response in aged mesentery. These findings serve as first step in study of the aging‐associated mechanisms that potentially link mast cells and disordered immune function in the elderly. NIH R01 AG030578, HL094269.

Lymphatic Muscle Cells in Rat Mesenteric Lymphatic Vessels of Various Ages

Recent studies on aging-associated changes in mesenteric lymph flow in situ demonstrated predominance of the severe negative chronotropic effect of aging on the contractility of aged mesenteric lymphatic vessels (MLV). At the same time, contraction amplitude of the aged vessels was only slightly diminished by aging and can be rapidly stimulated within 5-15 minutes. However, the detailed quantitative evaluation of potential aging-associated changes in muscle cells investiture in MLV has never been performed. In this study we, for the first time, performed detailed evaluation of muscle cells investiture in MLV in reference to the position of lymphatic valve in different zones of lymphangion within various age groups (3-mo, 9-mo and 24-mo Fischer-344 rats). Using visual and quantitative analyses of the images of MLV immunohistochemically labeled for actin, we confirmed that the zones located close upstream (pre-valve zones) and above lymphatic valves (valve zones) possess the lowest investiture of lymphatic muscle cells. Most of the high muscle cells investiture zones exist downstream to the lymphatic valve (post-valve zones). The muscle cells investiture of these zones is not affected by aging, while pre-valve and valve zones demonstrate significant aging-associated decrease in muscle cells investiture. The low muscle cells investiture zones in lymphatic vessels consist of predominantly longitudinally oriented muscle cells which are positioned in pre-valve and valve zones and connect adjacent lymphangions. These cells may provide important functional impact on the biomechanics of the lymphatic valve gating and electrical coupling between lymphangions, while their aging-associated changes may delimit adaptive reserves of aged lymphatic vessels.

Dopexamine can attenuate the inflammatory response and protect against organ injury in the absence of significant effects on hemodynamics or regional microvascular flow

IntroductionThe effects of dopexamine, a β2-agonist, on perioperative and sepsis-related hemodynamic, microvascular, immune, and organ dysfunction are controversial and poorly understood. We investigated these effects in a rodent model of laparotomy and endotoxemia.MethodsIn two experiments, 80 male Wistar rats underwent laparotomy. In 64 rats, this was followed by administration of endotoxin; the remainder (16) underwent sham endotoxemia. Endotoxemic animals received either dopexamine at 0.5, 1, or 2 μg/kg/min or 0.9% saline vehicle (controls) as resuscitation fluid. The effects of dopexamine on global hemodynamics, mesenteric regional microvascular flow, renal and hepatic function and immune activation were evaluated.ResultsEndotoxin administration was associated with a systemic inflammatory response (increased plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10, as well as cell-adhesion molecules CD11a and CD11b), and increased pulmonary myeloperoxidase (MPO) activity (indicating pulmonary leukocyte infiltration), whereas biochemical changes demonstrated lactic acidosis with significant renal and hepatic injury. Dopexamine administration was associated with less-severe lactic acidosis (pooled dopexamine versus controls, (lactate, 2.2 mM ± 0.2 mM versus 4.0 mM ± 0.5 mM; P < 0.001) and reductions in the systemic inflammatory response (pooled dopexamine versus control, 4 hour (TNF-α): 324 pg/ml ± 93 pg/ml versus 97 pg/ml ± 14 pg/ml, p < 0.01), pulmonary myeloperoxidase (MPO) activity, and hepatic and renal injury (pooled dopexamine versus control (ALT): 81 IU/L ± 4 IU/L versus 138 IU/L ± 25 IU/L; P < 0.05; (creatinine): 49.4 μM ± 3.9 μM versus 76.2 μM ± 9.8 μM; P < 0.005). However, in this study, clinically relevant doses of dopexamine were not associated with clinically significant changes in MAP, CI, or gut regional microvascular flow.ConclusionsIn this model, dopexamine can attenuate the systemic inflammatory response, reduce tissue leukocyte infiltration, and protect against organ injury at doses that do not alter global hemodynamics or regional microvascular flow. These findings suggest that immunomodulatory effects of catecholamines may be clinically significant when used in critically ill surgical patients and are independent of their hemodynamic actions.

Dietary medium-chain triglycerides promote oral allergic sensitization and orally induced anaphylaxis to peanut protein in mice

The prevalence of peanut allergies is increasing. Peanuts and many other allergen sources contain significant amounts of triglycerides, which affect absorption of antigens but have unknown effects on sensitization and anaphylaxis. We recently reported that dietary medium-chain triglycerides (MCTs), which bypass mesenteric lymph and directly enter portal blood, reduce intestinal antigen absorption into blood compared with long-chain triglycerides (LCTs), which stimulate mesenteric lymph flow and are absorbed in chylomicrons through mesenteric lymph. We sought to test how dietary MCTs affect food allergy. C3H/HeJ mice were fed peanut butter protein in MCT, LCT (peanut oil), or LCT plus an inhibitor of chylomicron formation (Pluronic L81). Peanut-specific antibodies in plasma, responses of the mice to antigen challenges, and intestinal epithelial cytokine expression were subsequently measured. MCT suppressed antigen absorption into blood but stimulated absorption into Peyer patches. A single gavage of peanut protein with MCT, as well as prolonged feeding in MCT-based diets, caused spontaneous allergic sensitization. MCT-sensitized mice experienced IgG-dependent anaphylaxis on systemic challenge and IgE-dependent anaphylaxis on oral challenge. MCT feeding stimulated jejunal-epithelial thymic stromal lymphopoietin, Il25, and Il33 expression compared with that seen after LCT feeding and promoted T(H)2 cytokine responses in splenocytes. Moreover, oral challenges of sensitized mice with antigen in MCT significantly aggravated anaphylaxis compared with challenges with the LCT. Importantly, the effects of MCTs could be mimicked by adding Pluronic L81 to LCTs, and in vitro assays indicated that chylomicrons prevent basophil activation. Dietary MCTs promote allergic sensitization and anaphylaxis by affecting antigen absorption and availability and by stimulating T(H)2 responses.

86 Low-Dose Vasopressin is Cardioprotective in an Acute Swine Model of Neonatal Hypoxia-Reoxygenation

BackgroundCardiovascular dysfunction, a consequence of perinatal asphyxia, contributes significantly to its morbidity and mortality. The use of vasopressin, an endogenous hormone commonly given to adults with refractory shock, in neonates...

Renoportal anastomosis in right lobe living donor liver transplantation: report of a case

End-stage liver disease is often accompanied by thrombosis of the portal vein and the formation of splanchnic collateral vessels. Successful liver transplantation in such situations is more likely if the surgeon uses a strategy to establish a graft inflow. A 59-year-old male with a decompensated liver secondary to idiopathic portal hypertension underwent living donor liver transplantation (LDLT) using a right lobe liver graft donated from his son. His portal venous trunk was atrophied and a splenorenal shunt drained the mesenteric venous flow into the systemic circulation. LDLT was performed with renoportal anastomosis (RPA) using his right internal jugular vein as an interposed venous graft, without dissecting the collateral vessels. Although he developed temporary functional hyperbilirubinemia, he was discharged from the hospital 23 days after LDLT. This case suggests that RPA is a useful technique to manage patients with an obstructed portal vein and a splenorenal shunt.

Increased secretion of insulin and proliferation of islet β-cells in rats with mesenteric lymph duct ligation

Background & aimsIt has been suggested that intestinal lymph flow plays an important role in insulin secretion and glucose metabolism after meals. In this study, we investigated the influence of ligation of the mesenteric lymph duct on glucose metabolism and islet β-cells in rats. MethodsMale Sprague–Dawley rats (10weeks old) were divided into two groups: one underwent ligation of the mesenteric lymph duct above the cistern (ligation group), and the other underwent a sham operation (sham group). After 1 and 2weeks, fasting plasma concentrations of glucose, insulin, triglyceride, glucose-dependent insulinotropic polypeptide (GIP), and the active form of glucagon-like peptide-1 (GLP-1) were measured. At 2weeks after the operation, the oral glucose tolerance test (OGTT) and intravenous glucose tolerance test (IVGTT) were performed. After the rats had been sacrificed, the insulin content of the pancreas was measured and the proliferation of β-cells was assessed immunohistochemically using antibodies against insulin and Ki-67. ResultsDuring the OGTT, the ligation group showed a significant decrease in the plasma glucose concentration at 120min (p<0.05) and a significant increase in the plasma insulin concentration by more than 2-fold at 15min (p<0.01). On the other hand, the plasma GIP concentration was significantly decreased at 60min (p<0.01) in the ligated group, while the active form of GLP-1 showed a significantly higher level at 90min (1.7-fold; p<0.05) and 120min (2.5-fold; p<0.01). During the IVGTT, the plasma insulin concentration in the ligation group was significantly higher at 2min (more than 1.4-fold; p<0.05). Immunohistochemistry showed that the ratios of β-cell area/acinar cell area and β-cell area/islet area, and also β-cell proliferation, were significantly higher in the ligation group than in the sham group (p<0.05, p<0.01 and p<0.01, respectively). The insulin content per unit wet weight of pancreas was also significantly increased in the ligation group (p<0.05). ConclusionsIn rats with ligation of the mesenteric lymph duct, insulin secretion during the OGTT or IVGTT was higher, and the insulin content and β-cell proliferation in the pancreas were also increased. Our data show that mesenteric lymph duct flow has a role in glucose metabolism.

Mast cells in proximity of adult and aged mesenteric lymphatic vessels

Aging impairs mesenteric lymph flow, which is crucial for fluid and macromolecule homeostasis, fat absorption, and immunity. Differences in contractile behavior of aged isolated mesenteric lymphatic vessels (MLV) and those observed in situ suggest an important regulatory involvement of some cellular elements in the immediate surrounding environment of aged MLV. We used whole mount immunohistochemistry and vital staining to identify and characterize mast cells (MCs) surrounding MLV in adult and aged Fischer‐344 rats. Additionally, we investigated the aging‐associated differences in MCs activation in the mesenteric bed in control and treated conditions. We used mesenteric tissue segments for acute treatments with 48/80, and biological activators, and used Ruthenium Red staining to identify activated MCs. Degree of activation was assessed by the image analysis of activated cells in control and treated conditions. We found a greater degree of pre‐activation of MCs in control conditions in aged rats compared to adult animals. Such pre‐activated status of aged MCs reflects lesser ability of aged MCs and adjacent MLV to adequately react to acute stimulation in elderly. These findings serve as first step in investigations of the aging‐associated mechanisms that potentially link MCs function, inflammation, and functional contractile disturbances in aged MLV. NIH R01 AG030578, HL094269.

The effect of systemic anaphylaxis on mesenteric lymph flow in anesthetized rats

The anaphylaxis‐induced fluid extravasation in splanchnic vascular bed was determined by measuring the mesenteric lymph flow (Qlym) during anaphylactic shock in anesthetized rats. Blood pressure (BP), portal venous pressure (PVP), and Qlym were measured. An injection of the ovalbumin antigen into the sensitized rats (n=10) caused a decrease in BP from 125 to 37 mmHg at 10 min, while an increase in PVP by 21 cm H2O at 2 min. Qlym increased 3.3‐fold baseline at 2 min, followed by a return to the baseline within 12 min. The lymph protein concentrations increased after antigen, which indicated increased vascular permeability. In the non‐sensitized rats (n=10), PVP was mechanically increased in a manner similar to that of the antigen‐challenged rats. Unexpectedly, this PVP elevation caused a similar increase in Qlym, but the lymph protein concentration decreased. In separate sensitized rats (n=5), the mesenteric arterial flow was much decreased after antigen, as compared with the PVP elevated rats (n=5), suggesting reduced splanchnic vascular surface area during anaphylaxis. In conclusion, systemic anaphylaxis in rats causes an increase in Qlym by increased vascular hydrostatic pressure due to portal hypertension, and by increased vascular permeability. However, this increased extravasation is relatively small probably due to decreased vascular surface area, and is observed transiently only soon after antigen.

Vascular perfusion limits mesenteric lymph flow during anaphylactic hypotension in rats

To determine fluid extravasation in the splanchnic vascular bed during anaphylactic hypotension, the mesenteric lymph flow (Q(lym)) was measured in anesthetized rats sensitized with ovalbumin, along with the systemic arterial pressure (P(sa)) and portal venous pressure (P(pv)). When the antigen was injected into the sensitized rats (n = 10), P(sa) decreased from 125 ± 4 to 37 ± 2 mmHg at 10 min with a gradual recovery, whereas P(pv) increased by 16 mmHg at 2 min and returned to the baseline at 10 min. Q(lym) increased 3.3-fold from the baseline of 0.023 ± 0.002 g/min to the peak levels of 0.075 ± 0.009 g/min at 2 min and returned to the baseline within 12 min. The lymph protein concentrations increased after antigen, a finding indicating increased vascular permeability. To determine the role of the P(pv) increase in the antigen-induced increase in Q(lym), P(pv) of the nonsensitized rats (n = 10) was mechanically elevated in a manner similar to that of the sensitized rats by compressing the portal vein near the hepatic hilus. Unexpectedly, P(pv) elevation alone produced a similar increase in Q(lym), with the peak comparable to that of the sensitized rats. This finding aroused a question why the antigen-induced increase in Q(lym) was limited despite the presence of increased vascular permeability. Thus the changes in splanchnic vascular surface area were assessed by measuring the mesenteric arterial flow. The mesenteric arterial flow was decreased much more in the sensitized rats (75%; n = 5) than the nonsensitized P(pv) elevated rats (50%; n = 5). In conclusion, mesenteric lymph flow increases transiently after antigen presumably due to increased capillary pressure of the splanchnic vascular bed via downstream P(pv) elevation and perfusion and increased vascular permeability in anesthetized rats. However, this increased extravasation is subsequently limited by decreases in vascular surface area and filtration pressure.

Successful aspiration and thrombolytic therapy for acute superior mesenteric artery occlusion

To report a case of acute superior mesenteric artery (SMA) embolism successfully treated with aspiration and pharmacological thrombolysis. A 74-year-old female was admitted to the hospital with acute abdominal pain 5 hours in duration. Computed tomography angiography revealed a complete embolic occlusion distal to the first jejunal branch of the SMA. Aspiration and local continuous thrombolysis with urokinase resulted in near complete revascularization of the mesenteric flow after 4 hours and almost complete restoration after 20 hours. The patient made a complete recovery and continues to do well on warfarin therapy after treatment. Aspiration and thrombolytic therapy can be an alternative treatment modality in surgical high risk patient.

Phase Contrast Magnetic Resonance Assessment of Volume of Abdominal Visceral Blood Flow in Newborn Infants

Background: Episodes of intestinal ischaemia are likely to be central to the pathogenesis of necrotising enterocolitis. Echocardiographic techniques can estimate volume of superior mesenteric artery(SMA) flow1, however these measures have not yet been validated. Phase Contrast Magnetic resonance(PCMR) techniques have been shown to provide repeatable quantifications of cardiac output and systemic perfusion in newborn infants2. The aim of this study was to assess the feasibility of performing PCMR assessments of abdominal visceral blood flow in newborn preterm infants. Methods: Scans were performed on 7 infants with median(range) gestation 34(30.3-37.7) weeks, weight at scan 1833(790-2800)grams using a Philips 3.0T scanner. PCMR slices(resolution-0.6/0.6/4mm,TR/TE-5.9/3.1ms) were placed at the proximal SMA and on the descending aorta(DAo) proximal to the celiac plexus and distal to the renal arteries(Figure). Flow was quantified using in-built software(ViewForum) incorporating automated vessel-edge detection Results: Intestinal flow was taken as SMA flow; visceral non-SMA(VnonSMA) flow was taken as proximal DAo - SMA - distal DAo (=celiac plexus plus inferior mesenteric and renal artery flow). Images were successfully obtained in all 7 infants. Median intestinal flow was 31.8(12.1-67.1)ml/kg/min, VnonSMA was 55.7(34.3-99)ml/kg/min. Conclusions: PCMR assessment of volume of SMA and visceral non-SMA blood flow is feasible in newborn infants. Further study is required to assess repeatability and correlation with echocardiography.