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At least 1,405 records · Page 78Linked to original sources
PubMed1991

Direct vasopressor effect of recombinant human erythropoietin on renal resistance vessels.

The contractile properties of recombinant human erythropoietin (rHuEPO) on isolated resistance vessels of renal and mesenteric vascular beds were studied in an in vitro model using a small vessel myograph. Under isometric conditions, rHuEPO caused a contraction of this vasculature in a concentration range between 10 U/ml and 200 U/ml. A maximal active wall tension of 1.52 +/- 0.19 mN/mm was obtained under a rHuEPO dose of 200 U/ml. In Ca2+ free solution, the pressor response to high rHuEPO-concentrations was attenuated, and the response to low rHuEPO concentrations was abolished. In the presence of verapamil, phentolamine and saralasin, rHuEPO-induced contractions were not affected significantly. A dose-dependent vasodilatation of mounted vasculature to acetylcholine (ACh) indicated that endothelium remained intact in our preparations. rHuEPO-induced vessel contraction was not abrogated after an enzymatical removal of endothelium by collagenase, confirming that the described contractile responses are endothelial independent. These findings suggest that a direct vasopressor effect of rHuEPO on proximal resistance vessels may contribute to development of hypertension seen in rHuEPO-treated hemodialysis patients.

Animals↗
PubMed1996

Noradrenaline-induced depolarization is smaller in isobaric compared to isometric preparations of rat mesenteric small arteries.

The hypothesis was tested that wall tension can influence the membrane potential response to noradrenaline (NA) using isometric and isobaric vessel preparations of rat mesenteric small arteries. The resting membrane potential was significantly less negative in the isobaric (-49.7+/-0.5 mV, S.E.M., n=12 vessels) compared to the isometric preparation (-56.1+/-0.7 mV, n=10), although there was no difference in wall tension. The depolarization induced by 10(-5) M NA was 2.6-fold smaller in the isobaric preparation, where wall tension decreased, compared to the isometric preparation, where wall tension increased. Since wall tension decreases under isobaric conditions, but increases under isometric conditions, the latter finding can be explained by assuming that part of the NA-induced membrane potential change is wall tension dependent.

Animals↗
PubMed2004

Activation of fibrinolysis and coagulation in non-occlusive intestinal ischaemia in a pig model.

The present study was carried out to explore the dynamics of the fibrinolytic and coagulation systems during non-occlusive intestinal ischaemia in a porcine model. Nineteen pigs underwent laparotomy. The inferior mesenteric artery and the collateral vessels to the rectum were ligated. The superior mesenteric artery (SMA) was isolated at its origin from the aorta, and constriction and flowmeter devices were applied. The blood flow of the SMA was reduced to cause ischaemia in the distal colon within the pHi interval 6.9-7.1. Fibrinogen, soluble fibrin, D-dimer, tissue plasminogen activator/plasminogen activator inhibitor-1 (tPA/PAI-1) complex and albumin were measured. Corrections for pig D-dimer and albumin were performed. Fibrinogen decreased significantly after laparotomy (P < 0.0001) and further after constriction of the SMA (P < 0.05), whereas soluble fibrin increased significantly (P < 0.005) after constriction of the SMA. The tPA/PAI-1 complex increased significantly after laparotomy (P < 0.05) and, after constriction of the SMA, the values first tended to decrease (P = 0.06) and then to increase (P = 0.056). The need to calibrate assays of human plasma proteins when applying them to experimental pig models was demonstrated. After constriction of the SMA, there was a rapidly reversed peak in the coagulation marker soluble fibrin and a strong tendency of alteration of the fibrinolytic marker tPA/PAI-1 complex.

Animals↗
PubMed1996

The importance of the hyperpolarizing mechanism increases as the vessel size decreases in endothelium-dependent relaxations in rat mesenteric circulation.

Endothelium-dependent relaxations are achieved by a combination of endothelium-derived prostacyclin (PGI2), nitric oxide (NO), and endothelium-derived hyperpolarizing factor (EDHF). However, it remains to be fully clarified whether the relative contribution of these three mechanisms to endothelium-dependent relaxations varies as a function of the vessel size. This study was designed to clarify this point. Acetylcholine (ACh)-induced endothelium-dependent relaxations were examined in isolated blood vessels taken from the aorta and the proximal and distal mesenteric arteries of the rat. The contributions of PGI2, NO, and EDHF were evaluated by the inhibitory effects of indomethacin, N omega-nitro-L-arginine methyl ester (L-NAME) in the presence of indomethacin, and KCl in the presence of indomethacin and L-NAME, respectively. The membrane potentials were recorded with microelectrodes. The expression of endothelial No synthase (eNOS) was examined by both immunostaining and immunoblotting. The contribution of PGI2 was negligible in three different-sized blood vessels. The contribution of NO was most prominent in the aorta, whereas that of EDHF was most prominent in the distal mesenteric arteries. The resting membrane potential was significantly deeper and the ACh-induced hyperpolarization was greater in the distal mesenteric arteries than those in the aorta. The expression of eNOS was the highest in the aorta and the lowest in the distal mesenteric arteries. These results indicate that the importance of EDHF increases as the vessel size decreases in endothelium-dependent relaxations in the rat mesenteric circulation.

Acetylcholine↗
PubMedDate not supplied

Systolically gated 3D phase contrast MRA of mesenteric arteries in suspected mesenteric ischemia.

OBJECTIVE: Our goal was to assess the value of MRA for detecting stenoses in the celiac (CA) and superior mesenteric (SMA) arteries in patients suspected of having chronic mesenteric ischemia, using an optimized systolically gated 3D phase contrast technique. MATERIALS AND METHODS: In an initial study in 24 patients who underwent conventional angiography of the abdominal vessels for different clinical indications, a 3D phase contrast MRA technique (3D-PCA) was evaluated and optimized to image the CAs and SMAs. Subsequently, a prospective study was performed to assess the value of systolically gated 3D-PCA in evaluation of the mesenteric arteries in 10 patients with signs and symptoms of chronic mesenteric ischemia. Intraarterial digital subtraction angiography and surgical findings were used as the reference standard. RESULTS: In the initial study, systolic gating appeared to be essential in imaging the SMA on 3D-PCA. In 10 patients suspected of mesenteric ischemia, systolically gated 3D-PCA identified significant proximal disease in the two mesenteric vessels in 4 patients. These patients underwent sucessful reconstruction of their stenotic vessels. CONCLUSION: Cardiac-gated MRA may become a useful tool in selection of patients suspected of having mesenteric ischemia who may benefit from surgery.

Adult↗
PubMed1990

The presence of pinworms (Enterobius sp.) in the mesenteric lymph nodes, liver and lungs of a chimpanzee, Pan troglodytes.

This report describes a case of fatal enterobiasis caused by Enterobius sp. in the mesenteric lymph nodes, lymphatic vessels of mesentery, blood vessels of the liver and lungs of a chimpanzee from Qingdao Zoo, China. Based on pathological findings, it is likely that the pinworms obtained access to these organs via the lymphatic or haematogenous pathway. As far as we are aware, this is the first reported case of Enterobius sp. in the mesenteric lymph nodes and blood vessels of the lungs and veins of the hepatic triad in a chimpanzee.

Animals↗
PubMed1999

Mechanisms of hypoxic vasodilatation of isolated rat mesenteric arteries: a comparison with metabolic inhibition.

1. Hypoxia (PO2 < 5 mmHg) decreased vessel tone in isolated rat mesenteric arteries precontracted with either high [K+] or the thromboxane analogue U46619. This response was not altered by N-nitro-L-arginine (L-NA) and indomethacin. 2. Simultaneous measurement of pHi and tension showed that the decrease in vessel tone was accompanied by an intracellular acidification. Similar reductions in tone and pHi were observed with the metabolic inhibitors 2,4-dinitrophenol (DNP) and sodium azide. 3. The presence of the lactate transport inhibitor alpha-cyano-4-hydroxy-cinnamic acid (CHC) increased the magnitude of the acidification and resulted in a significantly faster reduction in tone in response to hypoxia. Addition of CHC to normoxic tissues caused both a vasodilatation and a reduction of pHi. 4. A decrease in pHi induced on washout of ammonium chloride (NH4Cl) resulted in an increase in tone. 5. Relaxation to hypoxia or metabolic inhibition was unaffected when the change in pHi was neutralized by addition of the weak base trimethylamine (TMA). 6. It is concluded that severe hypoxia decreases tone in isolated rat mesenteric arteries by a mechanism which is independent of nitric oxide and prostaglandins. Both severe hypoxia and metabolic inhibition reduced pHi, although this does not appear to be contributing to the changes in tone observed.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

Endothelium-dependent and endothelium-independent effects of adenosine diphosphate in renovascular hypertension.

Norepinephrine-induced responses in isolated perfused mesenteric vascular bed from normotensive and renovascular hypertensive rats were examined in the presence of adenosine diphosphate (ADP, 2 x 10(-6) M). Responses to norepinephrine were significantly greater in vessels from hypertensive rats. Norepinephrine-induced contractions increased after the removal of endothelium. N omega-Nitro-L-arginine (L-NOARG), a potent inhibitor of nitric oxide formation, similarly increased contractions. The greatest responses were obtained, however, after treatment of the vascular segments with methylene blue. The presence of ADP caused significant endothelium-dependent decreases in contractions. Although decreases caused by ADP in vessels with endothelium after treatment with L-NOARG were not statistically significant, a tendency to decreased responses seems to suggest that L-NOARG diminishes but does not completely prevent the effect of ADP in mesenteric vessels. Methylene blue partially reduced the endothelium-dependent ADP-induced relaxant effects in sham-operated nephrectomized rats. A tendency to increased contractions to norepinephrine was observed in the presence of ADP after removal of endothelium. Thus, in the mesenteric resistance arteries of the rat under stimulation by ADP, it appears that nitric oxide released from L-arginine and the activity of soluble guanylate cyclase account only in part for the endothelium-dependent decreased responses to norepinephrine. When nitric oxide formation or soluble guanylate cyclase activity are depressed simultaneously with endothelium damage, ADP released from platelets or red blood cells may be an important factor that acts synergically with vasoconstrictor stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1980

[Anatomy and topography of adult human mesenteric lymph nodes].

Topography, number and age changes of the mesenteric lymph nodes in the small intestine have been studied in 40 corpses of both sex at the age of 21-90 years. The mesenteric lymph nodes, their afferent and deferent vessels have been revealed by the method of intersticial injection of coloured masses into the small intestinal wall, as well as by a direct injection of the lymph nodes studied in the mesentery. Variability in the total number of the mesenteric lymph nodes has been demonstrated; topographic borders of separate groups of the mesenteric lymph nodes have been stated; topography of the lymph nodes as regards the mesenteric blood vessels has been described. Quantitative changes (total and group) in the mesenteric lymph nodes with age in grown-up persons have been demonstrated.

Adult↗
PubMed1990

Endothelin-1 and U46619 potentiate selectively the venous responses to nerve stimulation within the perfused superior mesenteric vascular bed of the rat.

The effects were examined of endothelin-1 and U46619 on the responses to perivascular nerve stimulation of the simultaneously perfused arterial and venous vessels of the superior mesenteric arterial bed of the rat. Stimulation of the nerves at 4-16 Hz for 30 s caused frequency dependent constrictions of both the arterial and venous vessels similar to those produced by bolus doses of exogenous noradrenaline (0.1-10 nmol). Infusion of either endothelin-1 (0.1 nM) or U46619 (1-3 nM) caused small (less than or equal to 5 mmHg) increases in arterial and venous perfusion pressures and selectively potentiated the venous, but not arterial, responses to nerve stimulation. Conversely, endothelin-1 and U46619 potentiated the responses of both the arterial and venous vessels to exogenous noradrenaline. Thus, as reported previously for the arterial vessels of the rat mesentery, the isolated venous vessels constrict to perivascular nerve stimulation in a frequency dependent manner. In addition, endothelin-1 and U46619 potentiate selectively the effects of nerve stimulation on the veins.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Neuro-muscular transmission in blood vessels: phasic and tonic components. An in-vitro study of mesenteric arteries of the rat.

For many years noradrenaline was considered to be the exclusive transmitter released from sympathetic nerves. However, during recent years both ATP and NPY have been suggested to be co-transmitters to noradrenaline in these nerves. The present study aimed to investigate the functional relationship between these suggested transmitters during nerve stimulation with different frequencies and in different extracellular calcium concentrations. Also the importance of the pattern of nerve stimulation and the potentiation of the neurogenic response after a period of high-frequency nerve stimulation were investigated. Contractions caused by nerve stimulation and applied agonists were investigated in segments of small mesenteric arteries from rat. The biophysical, electrophysiological, and pharmacological properties of these vessels are well characterized in previous studies. The rapid contraction caused by a single nerve stimulus, the "single twitch", and the initial, phasic contraction caused by high-frequency nerve stimulation were only slightly affected by alpha-adrenoceptor blockade with prazosin, whereas the tonic response to high-frequency stimulation was markedly reduced. The phasic responses and those to low-frequency nerve stimulation thus appear to be due mainly to a non-adrenergic transmitter. After inhibiting the response to exogenous ATP by alpha beta-methylene ATP, the response to single impulses and to low-frequency nerve stimulation were markedly reduced, while those to high-frequency stimulation were unaffected. This suggests that ATP acts as a true transmitter in sympathetic nerves, being responsible mainly for rapid responses to low-frequency stimulation, and for the initial part of responses to high-frequency stimulation. When alpha beta-methylene ATP and prazosin were given in combination, no contraction was obtained during nerve stimulation at any frequency. However, if in this situation a contraction was induced by e.g. exogenous vasopressin, field stimulation caused a further, slow contraction. This additional response was undoubtedly neurogenic, but required high-frequency nerve stimulation. The response to nerve stimulation was found to be calcium-dependent, the calcium-dependency being more pronounced at low than at high stimulation frequencies. A continuous, high-frequency (8-16 Hz) nerve stimulation could greatly (5-15 fold) enhance the response to subsequent low-frequency nerve stimulation. This potentiation increased with the frequency of the conditioning stimulation and, within limits, with the number of impulses delivered. Also the extracellular calcium concentration during the conditioning stimulation determined the magnitude of the potentiation. This post-tetanic potentiation has many characteristics in common with the post-tetanic potentiation studied in the central and somatomotor nervous system.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

A comparison of vasopressin and noradrenaline on oxygen uptake by perfused rat hindlimb, kidney, intestine and mesenteric arcade suggests that it is in part due to contractile work by blood vessels.

1. The rat hindlimb, kidney and intestine were each perfused in a nonrecirculating mode at 25 degrees C using an artificial perfusate (initial pressure 85 +/- 5 mmHg) and the effects of vasopressin and noradrenaline on oxygen uptake and perfusion pressure determined. 2. Both vasopressin (K0.5 = 0.1 nM) and noradrenaline (K0.5 = 2 nM) increased oxygen uptake as well as perfusion pressure by the perfused hindlimb; changes in oxygen uptake were closely matched by changes in pressure. The maximum increase in oxygen uptake was approx. 9 mumol/hr per g wet wt of hindlimb. 3. The perfused kidney also responded to vasopressin and noradrenaline with parallel increases in oxygen uptake and perfusion pressure for each agent. The largest increase in oxygen uptake was approx. 30 mumol/hr per g wet wt but this was not maximal. 4. Vasopressin increased oxygen uptake and pressure by the perfused intestine over the range 0.01-2 nM, but the changes in pressure only became significant at doses greater than 0.1 nM. 5. Noradrenaline inhibited oxygen uptake and increased perfusion pressure in a dose-dependent manner at pharmacological concentrations (greater than 30 nM) when shunting of perfusate may have contributed to unperfused regions. 6. A network of mesenteric blood vessels estimated to contain approx. 6% vascular tissue by weight, with the remainder white fat cells, lymphatics and connective tissue, was also perfused. 7. Vasopressin (K0.5 = 0.3 nM) and noradrenaline (K0.5 = 30 nM) each increased oxygen uptake and perfusion pressure in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

[Symptomatic aneurysm of the right gastroepiploic artery. Case report and review of the literature].

Aneurysms of the splanchnic arteries have rarely been reported. Aneurysms of the splenic artery are the most common aneurysms of the splanchnic vessels, followed by the hepatic and the mesenteric artery. Aneurysms of the gastroepiploic vessels show an incidence of only 0.4%. Due to a rupture rate of nearly 90% they are of great clinical importance. Therefore treatment is indicated for every diagnosed aneurysm of the gastroepiploic artery. While for ruptured aneurysms a conventional operation is inevitable, for asymptomatic aneurysms laparoscopic or interventional therapy is an alternative.

Abdomen, Acute↗
PubMed1997

Diameter variability and microvascular flow resistance.

Microvessels are known to exhibit irregular shapes, deviating substantially from an idealized cylindrical tube geometry. Such irregularities must be taken into account in calculating microvascular flow resistance and may add to the observation that flow resistance in living microvessels in vivo is about twice that predicted on the basis of tube flow studies in vitro. The present study was aimed at providing a comprehensive database describing the apparent diameter variability for all segments of a complete microvascular network in the rat mesentery and assessing the impact of this variability on segmental flow resistance and the pressure drop across the network. Diameters were estimated by intravital microscopy at axial intervals of 20 microns along the 546 vessel segments of a mesenteric microvessel network, resulting in 6,319 separate diameter measurements. The amplitude of diameter variations in individual vessel segments decreased from approximately 15% of the mean vessel diameter in the smallest segments (approximately 5 microns diam) to approximately 5% in the largest segments (approximately 60 microns diam). Segmental hindrance was estimated to be 10-23% higher than calculated from arithmetic mean diameter, depending on the model used to estimate the hydrodynamically effective segment diameter. The overall pressure drop across the network calculated using a mathematical flow simulation was increased by 7-13.5%. This increase in flow resistance can explain approximately 10% of the observed discrepancy between flow resistance in vivo and in vitro.

Animals↗
PubMed1981

Manifestations of carcinoma of the uncinate process by means of superior mesenteric arteriography.

Identification of carcinoma arising in the uncinate region of the pancreas is difficult because of the peculiar topographic relationship of this lesion with adjacent structures. Among the various diagnostic procedures performed upon ten patients with this malignant lesion, superior mesenteric arteriography provided the most helpful information, including signs of invasion in the main trunk of the superior mesenteric artery and vein and in the proximal portion of the jejunal arteries. A clearer visualization of these vascular involvements was attained in the right posterior oblique projection rather than in the anteroposterior projection. On the contrary, the arterial and portal vessels belonging to the celiac territory, such as superior pancreaticoduodenal arteries, dorsal pancreatic artery, gastroduodenal artery, splenic vein and portal vein, were almost free of involvement. At laparotomy, almost all of the patients had direct extension of the tumor to the superior mesenteric vessels, forming a cancerous core in the root of mesentery. All died of cachexia within six months after a palliative surgical procedure. Serial roentgenograms of superior mesenteric artery, especially taken in the oblique projection, are the best means of confirming carcinoma of the uncinate process, for which only a few available methods have been established to evaluate the clinical aspects.

Adenocarcinoma↗
PubMed2003

Pregnancy enhances the angiotensin (Ang)-(1-7) vasodilator response in mesenteric arteries and increases the renal concentration and urinary excretion of Ang-(1-7).

The vasoactive effect of angiotensin (Ang)-(1-7) in mesenteric resistance arteries together with its plasma and kidney concentration and urinary excretion was assessed in pregnant and virgin rats. Mesenteric arteries (230-290 microm) were mounted in a pressurized myograph system and Ang-(1-7) concentration-dependent response curves (10(-10)-10(-5) M) were determined in arteries preconstricted with endothelin-1 (10(-7) M). The Ang-(1-7) response was investigated in vessels with and without pretreatment with the Ang-(1-7) antagonist [D-[Ala(7)]-Ang-(1-7)] (10(-7) M). Ang-(1-7) caused a significantly enhanced, concentration-dependent dilation of mesenteric vessels (EC(50) = 2.7 nM) from pregnant compared with virgin female rats. D-[Ala(7)]-Ang-(1-7) eliminated the vasodilator effect of Ang-(1-7). There was no significant change in plasma concentration of Ang-(1-7) in pregnant animals. On the other hand, 24 h urinary excretion and kidney concentration of Ang-(1-7) were significantly higher in pregnant animals. The increased mesenteric dilation to Ang-(1-7) with enhanced kidney concentration and 24 h urinary excretion rate of Ang-(1-7) suggests an important role for this peptide in cardiovascular regulation during pregnancy.

Angiotensin I↗
PubMed1989

Superior mesenteric sympathetic tone in conscious renovascular hypertensive rats.

Blood flow in the superior mesenteric artery was observed with a chronically implanted electromagnetic flow probe in two-kidney, one-clip renovascular hypertensive rats (2K1C), one-kidney, one-clip renovascular hypertensive rats (1K1C), and normotensive control rats (NCR) in the conscious state. Arterial pressure was recorded with an indwelling catheter. Superior mesenteric resistance was calculated as arterial pressure divided by superior mesenteric flow. In all three groups of rats, superior mesenteric resistance remained almost unchanged when arterial pressure decreased markedly on ganglionic blockade with hexamethonium bromide. However, subsequent injection of a vasopressin antagonist (Manning compound) decreased superior mesenteric resistance significantly in 2K1C but not in 1K1C and NCR. Injection of vasopressin antagonist alone was without effect on arterial pressure and superior mesenteric flow in the three rat groups. Only 2K1C were judged to have appreciable sympathetic tone in resistance vessels of the superior mesenteric area, which was blocked by hexamethonium but compensated for by secondarily secreted vasopressin.

Animals↗
PubMed1997

Influence of cytochrome P-450 inhibitors on endothelium-dependent nitro-L-arginine-resistant relaxation and cromakalim-induced relaxation in rat mesenteric arteries.

In several blood vessels, endothelium-dependent vasorelaxation is in part mediated by an endothelium-derived hyperpolarizing factor (EDHF), the nature of which is as yet unknown. However, some evidence suggests that EDHF might be a cytochrome P-450-dependent monooxygenase metabolite of arachidonic acid. By using isometric tension measurements on rat main mesenteric arteries, the influence of four structurally and mechanistically different cytochrome P-450 inhibitors (proadifen, miconazole, 1-amino-benzotriazole, and 17-octadecynoic acid) was investigated on relaxations elicited by EDHF, assessed as the nitro-L-arginine-resistant component of acetylcholine-induced relaxation, and on relaxations provoked by the endothelium-independent potassium channel opener cromakalim. Proadifen (30 microM) inhibited the EDHF- as well as the cromakalim-induced relaxation, but not that elicited by nitroprusside. Also miconazole (30 microM) inhibited both the EDHF and the cromakalim-induced relaxation. On the other hand, 17-octadecynoic acid (5 microM) had no influence, and 1-aminobenzotriazole (1 mM) even potentiated EDHF- and cromakalim-induced relaxations. We conclude that the EDHF, released from the rat mesenteric artery by acetylcholine, is unlikely to be a cytochrome P-450-dependent monooxygenase metabolite of arachidonic acid and that proadifen and miconazole interfere with the action of cromakalim.

Acetylcholine↗