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PubMed1997

Co-ordination of contractile activity in guinea-pig mesenteric lymphatics.

1. Intraluminally perfused lymphatic vessels from the mesentery of the guinea-pig were examined in vitro to investigate their contractile activity and the co-ordination of this activity between adjacent lymphangions. 2. Lymphangions constricted at fairly regular intervals and exhibited 'refractory' periods of up to 3 s during which constrictions did not occur. 3. The contractile activity of adjacent lymphangions was highly co-ordinated. 4. The smooth muscle was found to be continuous between the adjacent lymphangions for the majority of valve regions examined morphologically (52 of 63 preparations). 5. Mechanical and electrical coupling between adjacent lymphangions was indicated, as some lymphangions underwent transient dilatations just prior to constriction, whereas direct electrophysiological measurements showed that the smooth muscle of most adjacent lymphangions was electrically coupled across the valve (15 out of 20 pairs of lymphangions). 6. It is concluded that perfused lymphangions of guinea-pig mesenteric lymphatic vessels rhythmically constrict, with the contractile activity of adjacent lymphangions highly co-ordinated. The findings also indicate that transmission of both mechanical and electrical signals between the adjacent lymphangions contribute to the co-ordination of their contractile activity.

Animals↗
PubMedDate not supplied

Pancreatic adenocarcinoma: the different CT criteria for peripancreatic major arterial and venous invasion.

OBJECTIVE: To establish preliminarily the different diagnostic criteria for peripancreatic arterial and venous invasion in pancreatic carcinoma by comparing their multidetector-row computed tomography (MDCT) appearances with surgical exploration. METHODS: Among 101 patients with pancreatic carcinoma examined by MDCT, 54 candidates accepting surgery were preoperatively evaluated for vascular invasion based on CT signs (A-E): arterial embedment in tumor or venous obliteration; tumor involvement exceeding one-half of the circumference of the vessel; vessel wall irregularity; vessel caliber stenosis; teardrop superior mesenteric vein (SMV). The peripancreatic major vessels (n = 224) were examined carefully by surgeons during the operation. RESULTS: During surgical exploration, 78 vessels were found to be invaded. With sign A (B, C, or D) as the CT criterion for peripancreatic vascular invasion, the sensitivity of arterial and venous invasion was 66% (97%, 45%, or 41%) and 14% (49%, 63%, or 55%), respectively; the specificity of absence of arterial and venous invasion was 100% (91%, 99%, or 100%) and 100% (all 100%). In this study, there were 3 SMVs appearing teardrop (sign E), which were all confirmed to be invaded. CONCLUSIONS: It is recommended that the CT diagnostic criteria for arterial and venous invasion should be dealt with differently. The criteria of arterial invasion are the presence of sign A or the combination of sign B with one of signs C and D. The criteria of venous invasion are the presence of one of the following signs: sign A, sign B, sign C, sign D, and sign E.

Adult↗
PubMed1975

Dose-response relationships for arginine vasopressin and synthetic analogs on three types of rat blood vessels: possible evidence for regional differences in vasopressin receptor sites within a mammal.

These experiments were undertaken to determine the comparative relationships between chemical structure and biologic (contractile) activity of a series of vasopressin hormone analogs on different rat blood vessels (e.g., aorta, mesenteric arteriole and mesenteric venule). The functional contributions to, and interactions with, phenolic hydroxyl and aromatic groups as well as basicity in positions 2, 3 and 8, respectively, to or with hormone-receptor affinity and intrinsic (contractile) activity, were determined by analyzing the dose-response curves of five vasopressin peptides lacking one or more of these functional groups. The findings demonstrate that: 1) the structure-action relationships for vasopressin peptide-induced contractions on rat blood vessels vary with the particular type of macro- or microvessel (i.e., aorta, arteriole and venule); 2) the phenolic and aromatic groups in positions 2 and 3, respectively, are not only important for hormone-receptor affinity but intrinsic activity as well; 3) the potency (EC50) values for arginine vasopressin as well as the potencies and intrinsic activities of synthetic vasopressin analogs varied between the three different types of rat blood vessels examined; and 4) circulating levels (i.e., 10- minus 11- minus 10- minus 12 M) of [8-arginine]-vasopressin are capable of inducing contractile effects on mesenteric arterioles and venules. The quantitative data obtained in this study support the notion that a heterogeneity of the receptor, which subserves contraction, probably exists in blood vessels within and between vascular beds of a single mammalian species.

Amino Acid Sequence↗
PubMed1978

[Results of a microscopic study of several remains of the internal organs of Shandrin's mammoth].

The survived portion of an organ which topographically can be considered as a part of the lung, as well as a section of muscular tissue, perhaps that of the heart, has been studied. Under weak systems, the portion resembles the lung, spaces resembling alveoles, alveolar ducts and alveolar saccules are seen. "Alveolar" walls are stained dark grey by different methods; "alveoles" contain yellow granules, ferric components are not detected in them. The intestinal wall and that of the large vessel in the mesenteric cavity preserves a fibrillar carcass, fibrillar ultrastructure corresponding to collagen.

Animals↗
PubMed2003

Influence of dietary salt intake on the response of isolated perfused mesenteric veins of the dog to vasoactive agents.

BACKGROUND: Previous work has established that a high dietary salt intake results in enhanced arterial vasoconstrictor responses to stimulation with agonists. This investigation was designed to investigate the effects of dietary salt on the responses of isolated capacitance vessels (third order mesenteric veins). METHODS: Dogs were fed diets containing low, intermediate, and high levels of dietary salt (0.4, 3.0, and 6.0 mmol kg/day). The animals were killed, and lengths of mesenteric vein were mounted in a perfusion myograph with changes in lumenal diameter measured using a video tracking device. Responses to cumulative doses of norepinephrine (NE) and acetylcholine (Ach) were then determined. RESULTS: The vasoconstrictor responses to NE were greater in the veins from dogs on a high salt diet. Acetylcholine also caused venoconstriction that also was greater in the high salt group of animals. Responses to Ach were unaffected by N(omega)-nitro-L-arginine methyl ester but were abolished by atropine. CONCLUSIONS: These results indicate that mesenteric veins from dogs fed a high salt diet constrict more powerfully in response to agonists, which could contribute to the hypertensive effects of high intakes of dietary salt.

Acetylcholine↗
PubMed1995

Mevalonate availability affects human and rat resistance vessel function.

Previous data in rat conductance vessels indicated that cellular mevalonate contributes to vascular tone and systemic blood pressure control. Using exogenous mevalonate (M) or lovastatin, a 3-hydroxy-3-methyl-glutaryl CoA (HMG-CoA) reductase inhibitor (L), we characterized the role of mevalonate availability in resistance artery function, both in experimental animals and humans. Rat mesenteric artery resistance vessels (MARV, n = 9) were incubated for 48 h with either L, M, L + M, or vehicle (V) and tested for reactivity to NE, serotonin, acetylcholine, atrial natriuretic peptide, and sodium nitroprusside (SNP). Lovastatin increased sensitivity to NE (P < 0.03) and serotonin (P < 0.003), and significantly impaired the response to all three vasodilators. These effects were reversed by co-incubation with mevalonate. Mevalonate alone had no effect. In separate experiments, intravascular free Ca2+ concentration (ivfCa2+) was determined in fura-2AM loaded MARV. Basal ivfCa2+ was increased after a 48-h exposure to L (52.7 +/- 4.6 nM, L, vs. 29.7 +/- 2.4 nM, V, n = 12, P < 0.003), as were ivfCa2+ levels following stimulation with low (100 nM) NE concentrations. Similar ivfCa2+ concentrations were achieved during maximum contraction with NE (10 mM) in both groups. Human resistance arteries of human adipose tissue were also studied. Lovastatin increased the sensitivity to NE (ED50 = 372 +/- 56 nM, V, and 99 +/- 33 nM, L, P < 0.001) and significantly decreased the relaxation to acetylcholine and SNP of human vessels. We conclude that mevalonate availability directly contribute to resistance vessel function and vascular signal transduction systems in both experimental animals and humans. The study calls for the identification of non-sterol, mevalonate-derived vasoactive metabolites, and suggests that disorders of the mevalonate pathway can alter vascular tone and cause hypertension.

Adult↗
PubMed1998

The retroperitoneal resection margin and vessel involvement are important factors determining survival after pancreaticoduodenectomy for ductal adenocarcinoma of the head of the pancreas.

The prognosis of ductal adenocarcinoma of the pancreas is still poor. We analysed the factors that have a major influence on the survival of patients. Surgical specimens from 51 patients with ductal adenocarcinoma of the head of the pancreas were examined for tumour size, histological type, grade and local extension. In 7 patients the retroperitoneal resection margin was involved either macroscopically or histologically. Their mean survival was 10.6 months (1-17 months), compared with 22.7 months for the 44 patients with curative R0 resection. In 10 patients large vessels (portal and/or mesenteric vein) had to be resected; they survived for only 2-11 months, with a mean of 5 months (P<0.05). Non-R0-resected patients and patients in whom tumour-invaded vessels had to be resected constitute a high-risk group with a significantly shorter mean survival of 8.8 months, compared with 24.3 months for R0 resected patients without vessel invasion (P<0.05). Lymph node metastases were seen in 35 of 51 patients. Survival analysis based on nodal status revealed a mean survival of 33 months for patients staged as N0, 21.4 for N1a patients and 14 month for N1b patients. The differences were not statistically significant, however. Our data suggest that tumour invasion of the retroperitoneal resection margin and large vessel involvement are the major factors determining survival in patients with pancreatic cancer.

Aged↗
PubMed1981

Mesenteric desmoid tumors: sonographic and computed-tomographic appearance.

Sonographic and computed-tomographic (CT) findings in two patients with mesenteric desmoid tumors are reviewed. On ultrasound scans, mesenteric desmoids appear as well-circumscribed masses with scattered dense high-level echoes which correspond to mesenteric fat and vessels on the CT scan. Although these tumors appear well marginated on both ultrasound and CT scans, the pathologic examination shows microscopic invasion at the tumor margin in most cases. Differentiation from other mesenteric masses is discussed.

Adult↗
PubMed2004

Novel role for P2X receptor activation in endothelium-dependent vasodilation.

1 ATP is an important vasoactive mediator, which acts via two receptor classes: P2X and P2Y. Activation of P2X receptors has traditionally been associated with the well-characterised vasoconstrictor properties of ATP. 2 In the current study, we have shown that the P2X(1 & 3) receptor ligand, alpha, beta methylene ATP, induces vasodilation of rat isolated mesenteric arteries and that P2X1 receptors are abundantly expressed in the endothelium of these vessels. 3 Second-order rat mesenteric arteries were mounted in myographs and vasomotor responses recorded. Both ATP and alpha, beta methylene ATP induced a constriction followed by a vasodilation. The dilator effects of either ATP or alpha, beta methylene ATP were slower in onset than those induced by acetylcholine. By contrast, the traditional vasodilator P2Y ligand, ADP, induced vasodilation without contraction. 4 Vasodilation induced by alpha, beta methylene ATP was endothelial dependent, but was not affected by treatment of the vessels with L-NAME plus indomethacin alone. Dilation was, however, partially inhibited by the combination of apamin plus charybdotoxin and blocked by treating vessels with all four drugs. 5 Using confocal microscopy, P2X1 receptor immunoreactivity was localised to the endothelial, smooth muscle and adventitial layers of mesenteric vessels. P2X1 protein migrated as a primary band at around 50-60 kDa in vascular tissue. 6 These results show for the first time that P2X1 receptors are expressed on the endothelium and that a selective ligand of this receptor results in vasoconstriction followed by vasodilation. These observations have important implications for our understanding of the role of purines in biological responses.

Adenosine Triphosphate↗
PubMed1988

An autoradiographic study of muscarinic cholinoceptors in blood vessels: no localization on vascular endothelium.

In vitro labelling and autoradiographic techniques were used to examine the localization of [3H]quinuclidinyl benzilate ([3H]QNB) and [125I]4-iodo-QNB ([125I]4IQNB) to slide-mounted sections of rabbit aorta and pulmonary artery, cat aorta, pulmonary and superior mesenteric arteries. These vessels all respond to acetylcholine (ACh) with endothelium-dependent relaxation, yet there was no evidence for endothelium-related binding of either [3H]QNB or [125I]4IQNB. Muscarinic receptors were localized over the medial smooth muscle and, in the rabbit pulmonary artery, the density of binding increased towards the adventitia. Binding of either radioligand to sections of rabbit pulmonary artery was not affected by the muscarinic M1 receptor antagonist pirenzepine (20 nM) but was markedly reduced by the muscarinic M2 antagonist 4DAMP (4-diphenylacetoxy-N-methyl-piperidine methobromide) (1 nM). This study provides evidence for muscarinic receptors located directly on smooth muscle cells, indicating that endothelium-dependent relaxation to ACh results from an indirect mechanism involving smooth muscle muscarinic receptors.

Acetylcholine↗
PubMedDate not supplied

Changes in renal artery resistance after meal-induced splanchnic vasodilatation in cirrhotic patients.

PURPOSE: A relationship between vasomotor tone changes in mesenteric and renal vessels in cirrhotic patients has been suspected but remains controversial. The aim of this study was to assess by duplex Doppler sonography the changes in the circulatory resistance of the renal arteries and superior mesenteric artery (SMA) following meal-induced splanchnic vasodilatation. METHODS: Twenty-seven cirrhotic patients and 15 healthy volunteers with no hepatic or renal dysfunction were prospectively included in the study. The resistance index (RI) of the SMA and of the right and left renal arteries was measured by duplex Doppler sonography before and 30 minutes after ingestion of a standard 400-kcal balanced liquid meal. Values in controls and patients and values before and after the meal were compared, and correlations between RIs, Child-Pugh class (liver function), and creatinine clearance were assessed in cirrhotic patients. RESULTS: The fasting renal artery RI was greater in cirrhotic patients than in controls (p < 0.0001), but there was no difference in fasting SMA RIs. After the meal, there was a significant decrease in the SMA RI in controls (0.85 +/- 0.04 before versus 0.74 +/- 0.03 after meal, p = 0.0001) and in cirrhotic patients (0.85 +/- 0.04 before versus 0.77 +/- 0.04 after, p = 0.0001) and a significant increase in the renal artery RI (0.57 +/- 0.06 before versus 0.62 +/- 0.05 after in controls, p = 0.001; 0.68 +/- 0.07 before versus 0.70 +/- 0.07 after in cirrhotic patients, p = 0.001). No correlation was found in cirrhotic patients between the changes in renal artery RI and the postprandial SMA RI decrease, the Child-Pugh class, or the creatinine clearance. CONCLUSIONS: Meal-induced SMA vasodilatation (RI decrease) is associated with a marked increase in the renal artery RI, worsening the renal vasoconstriction in cirrhotic patients.

Adult↗
PubMed2000

Endothelin receptor antagonism ameliorates mast cell infiltration, vascular hypertrophy, and epidermal growth factor expression in experimental diabetes.

Vascular hypertrophy, a feature of experimental and human diabetes, has been implicated in the pathogenesis of the microvascular and macrovascular complications of the disease. In the present study, we sought to examine the role of endogenous endothelin and its relation to vascular growth factors in the mediation of vascular hypertrophy in experimental diabetes and to examine the contribution of mast cells to this process. Vessel morphology, endothelin, growth factor gene expression, and matrix deposition were studied in the mesenteric arteries of control and streptozotocin-induced diabetic Sprague-Dawley rats treated with or without the dual endothelin(A/B) receptor antagonist bosentan (100 mg x kg(-1) x d(-1)) during a 3-week period. Compared with control animals, diabetic animals had significant increases in vessel weight, wall-to-lumen ratio, mast cell infiltration, extracellular matrix deposition, and gene expression of epidermal growth factor (EGF) and transforming growth factor-beta(1). In diabetic, but not control, vessels, not only were EGF mRNA and endothelin present in endothelial cells, but also their expression was observed in adventitial mast cells. Immunoreactive endothelin was present in the media of mesenteric vessels of diabetic, but not control, animals. Bosentan treatment significantly reduced mesenteric weight, wall-to-lumen ratio, mast cell infiltration, matrix deposition, and EGF mRNA but did not prevent the overexpression of transforming growth factor-beta(1) mRNA in diabetic rats. These findings suggest that endogenous endothelin and EGF may play a role in diabetes-induced vascular hypertrophy and that mast cells may be pathogenetically involved in this process.

Animals↗
PubMed2005

A canine model to study the significance and hemodynamics of type II endoleaks.

OBJECTIVE: The clinical significance of Type 2 endoleak after endovascular repair of abdominal aortic aneurysms (AAA) remains incompletely delineated. This study describes the development of a novel canine model that allows for continuous monitoring of intraaneurysmal pressure in the setting of Type 2 endoleak. METHODS: Infrarenal AAA were created in 10 mongrel dogs by implanting a prosthetic aneurysm containing an intraluminal, solid-state, strain gauge pressure transducer which is able to measure pressures in both solid and liquid media. A segment of native aorta with two or more patent side branch vessels was reimplanted into the prosthetic aneurysm using a Carrel patch. Four animals had two lumbar vessels implanted; two had two lumbar vessels and the caudal mesenteric artery implanted, and four control animals had no vessels reimplanted. Retrograde flow in the aneurysmal side branches caused a Type 2 endoleak after the aneurysm was excluded from antegrade flow by deploying a stent graft. Both systemic and intra-sac pressures were measured daily for up to 90 days after endovascular exclusion and indexed to systemic pressure. Endoleak patency and flow were assessed with digital subtraction angiography, duplex ultrasound, and cine-magnetic resonance angiography (MRA). Histological characterization of the intraaneurysmal contents was performed. RESULTS: Before endovascular exclusion, the systolic, mean arterial, and pulse pressure within the aneurysmal sac closely matched that of the systemic circulation (systolic, 0.96 +/- 0.22; mean, 0.94 +/- 0.21; pulse pressure, 0.97 +/- 0.22) (R value, 0.97). Endovascular exclusion in animals with no collateral side branch vessels resulted in no endoleak and significantly reduced intraaneurysmal pressure when compared to systemic pressure, with systolic, mean arterial, and pulse pressure 0.172 +/- 0.05, 0.137 +/- 0.05, and 0.098 +/- 0.02, respectively (P < 0.001). In animals with Type 2 endoleaks, the pressures were lower than systemic pressure, but statistically significant in their difference from the control group. The systolic pressure of those with Type 2 endoleaks was 0.702 +/- 0.048; mean arterial pressure was 0.784 +/- 0.028, and pulse pressure was 0.406 +/- 0.031 when indexed to systemic pressure (P < 0.001). Cine-MRA and Duplex ultrasound documented persistent patency of the Type 2 endoleaks throughout the study period in animals with multiple side branches. CONCLUSION: Intraaneurysmal pressure in the setting of Type 2 endoleaks may be accurately determined using this canine model. Intraaneurysmal pressure is maintained at a significant level in the context of this retrograde collateral perfusion, suggesting that persistent Type 2 endoleaks are of clinical significance. This model may serve to allow further evaluation and characterization of Type 2 endoleaks.

Angiography, Digital Subtraction↗
PubMedDate not supplied

The effect of cisterna chyli ablation combined with thoracic duct ligation on abdominal lymphatic drainage.

OBJECTIVE: To evaluate the effect of cisterna chyli ablation (CCA) and thoracic duct ligation (TDL) on abdominal lymphatic drainage in normal dogs. STUDY DESIGN: Experimental study. ANIMALS: Nine female beagle dogs. METHODS: TDL was performed in 3 dogs and was combined with CCA (CCA-TDL) and local omentalization in 6 dogs. Contrast lymphangiography was attempted in all dogs immediately before and after TDL. Dogs were reanesthetized at 31-37 days for lymphatic studies by new methylene blue (NMB) injection into a mesenteric lymph node and by contrast lymphangiography. RESULTS: In 6 CCA-TDL dogs, 2 had direct shunting of contrast from the lymphatic system into major abdominal veins, 3 had contrast material that dissipated into abdominal vessels within the mesenteric root, and 1 had shunting into the azygous vein. NMB was not observed within the omental pedicle after CCA-TDL. Chylous drainage was by the azygous vein in all 3 TDL dogs. CONCLUSIONS: CCA-TDL disrupted chylous drainage to the thoracic duct and resulted in direct intraabdominal lymphaticovenous anastomoses identified by shunting of lymphatic flow directly into the abdominal vasculature in 5 of 6 CCA-TDL dogs. Omentalization of the cisternal ablation site was not beneficial in augmenting extrathoracic lymphatic drainage and is not recommended with CCA-TDL. CLINICAL RELEVANCE: CCA-TDL represents a novel approach to surgical redirection of chylous drainage to the venous circulation outside of the thorax and may be useful in the treatment of spontaneous chylothorax in the dog.

Animals↗
PubMed1993

Length-tension characteristics of bovine tracheobronchial lymphatic smooth muscle.

Current information regarding the physiology of lymphatic smooth muscle is derived from experiments on mesenteric and thoracic duct lymph trunks. We hypothesized that tracheobronchial lymphatics share many of the same properties possessed by the mesenteric lymphatics, and examined the passive and active length-tension characteristics of the two. Fresh isolated lymph vessel rings were prepared from bovine mesenteric and tracheobronchial lymphatic collectors, mounted in organ baths, and connected to force-displacement transducers. Isometric contractions were induced by exposure to 65mM KCl-substituted perfusate after intermittent ring length changes. Active tension was calculated. Optimal vessel length was greater in tracheobronchial vessel rings, averaging 4.9 +/- 0.4mm vs 2.8 +/- 0.3mm in mesenteric rings (p < 0.001). Optimal resting tension and ATmax were similar for both truncal types, measuring 738 +/- 95mg and 2379 +/- 289mg in tracheobronchial vessel rings, and 625 +/- 108mg and 2501 +/- 320mg in mesenteric vessel rings, respectively. Stress developed at L(o) (optimal length) was similar for tracheobronchial (35.4 +/- 4.3mN mm-2) and mesenteric (26 +/- 4.3mN mm-2) lymphatics (P = N.S.). The data demonstrate that tracheobronchial lymph vessels are similar to mesenteric lymph vessels in their ability to generate significant stress, and suggest that these lymphatics participate in the regulation of lymph flow.

Animals↗
PubMed1992

Reactivity of small blood vessels in hypertension: relation with structural changes. State of the art lecture.

Small blood vessels, particularly small arteries of 150-300 microns in lumen diameter and larger arterioles of 50-150 microns in lumen diameter, are the most important location of the arterial bed that undergoes changes resulting in the increased peripheral resistance that characterizes elevated blood pressure. This article reviews these morphological and functional alterations of small blood vessels. Study of mesenteric small arteries with a lumen diameter of 220-260 microns revealed consistently a reduced external and lumen diameter in renal and deoxycorticosterone acetate-salt hypertensive rats early in the evolution of hypertension. The media of the vessel wall was significantly thickened in the hypertensive rats, and the media/lumen ratio was increased. Although the tension that developed in response to different vasoconstrictors was not elevated or was even decreased in hypertensive rats, exaggerated transmural pressures resulted in the isolated blood vessels as a consequence of the law of Laplace because of the narrowed lumen. Similar findings were obtained in small resistance arteries from subcutaneous gluteal biopsies of hypertensive humans. In arterioles, on the other hand, decreases in the density of blood vessels (rarefaction) and in vasomotion amplitude may play a more important role than reductions in lumen diameter. As a consequence of the design of small resistance blood vessels and as a result of functional and structural alterations, which may be primary to or a consequence of high blood pressure, the pressor effect of vasoconstrictors is amplified and interacts with other factors to contribute to the maintenance of elevated blood pressure even if the intrinsic response of vascular smooth muscle to these agents is not exaggerated.

Humans↗
PubMed1998

Extracranial giant cell arteritis.

Although giant cell arteritis (GCA) of the extracranial arteries is said to be relatively frequent, clinical manifestations are rarely recognized. We describe a case presenting with intestinal perforation who subsequently died with active GCA of the coronary, mesenteric and temporal vessels.

Aged↗