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At least 307 records · Page 17Linked to original sources
PubMed2001

Mechanisms of the increased pressor response to vasopressors in the mesenteric bed of nitric oxide-deficient hypertensive rats.

In the present study we analyzed mesenteric vascular reactivity of chronic nitric oxide (NO)-deficient hypertensive rats (NW-nitro-L-Arginine Methyl Ester, L-NAME, 50 mg/kg/day, oral, 3 weeks). Perfusion pressure changes in response to cumulative additions of methoxamine and KCl were significantly increased in the mesenteric vessels of the L-NAME-treated as compared with vessels of the controls. Verapamil reduced the responses to methoxamine, but those of the hypertensive rats were still enhanced. In contrast, responses to KCl were almost completely abolished by verapamil. In mesenteric vessels perfused with zero calcium and high-potassium Krebs, pressor responses to the re-addition of calcium were also significantly enhanced in the hypertensive rats compared to the controls. Vasodilator responses to acetylcholine in KCl-preconstricted vessels, while still significant, were reduced in the L-NAME-treated rats. In this case, acute inhibition of NO blocked the vasodilator responses to acetylcholine and abolished the differences between the two groups. In methoxamine-preconstricted vessels and in the presence of acute inhibition of NO and prostaglandins, vasodilator responses to acetylcholine were significantly greater in the hypertensive vessels than in controls. In conclusion, the mesenteric vessels of L-NAME hypertensive rats show an enhanced response to vasopressors which is related to calcium entry. These data also reveal the existence of an enhanced role of a NO and prostaglandin-independent vasodilator factor, probably endothelium-derived hyperpolarizing factor that may play a compensatory role in the deficiency of NO.

Acetylcholine↗
PubMedDate not supplied

Effect of felodipine, a new dihydropyridine vasodilator, on contractile responses to potassium, noradrenaline, and calcium in mesenteric resistance vessels of the rat.

The effect of felodipine [4-(2,3-dichloro-phenyl)-1,4-dihydro-2,6-dimethyl-3-ethoxycarbonyl-5- methoxycarbonylpyridine on the contractile responses of mesenteric resistance vessels denervated in vitro was investigated. Sustained contractions of this vessel type were totally dependent on extracellular calcium. Felodipine (10-(15)-10-(9)M) had a concentration-dependent inhibitory action on contraction induced by maximal potassium (125 mM) and noradrenaline (10-(5)M) stimulation. Felodipine was more potent and more selective than D600 and nifedipine. Potassium and noradrenaline concentration-response characteristics were insurmountably antagonized by felodipine, the potassium sensitivity of vessels being unaffected while noradrenaline sensitivity was decreased. In calcium-depleted vessels, felodipine in all concentrations tested produced insurmountable antagonism of the potassium-activated calcium concentration-response characteristics, whereas the antagonism in low concentrations (10-(15)-10-(11)M) was surmountable in noradrenaline-activated vessels. Felodipine 10-(9) M blocked the response of potassium-activated vessels almost completely, whereas approximately 50% of the response of noradrenaline-activated vessels persisted. The results of this investigation indicate that the effect of felodipine may be caused primarily by selective inhibiton of responses evoked by membrane depolarization.

Animals↗
PubMed1990

Effect of neuropeptide Y on vasodilation mediated by calcitonin gene-related peptide (CGRP)-containing nerves in the mesenteric resistance vessel of the rat.

The role of neuropeptide Y (NPY) in the neurotransmission of calcitonin gene-related peptide (CGRP)-containing vasodilator nerves was investigated in perfused mesenteric vascular beds of the rat with active tone. NPY (5 and 10 nM) significantly inhibited the neurogenic vasodilation induced by perivascular nerve stimulation (1-8 Hz). However, NPY had no effect on vasodilation in response to bolus infusion of rat CGRP (10 and 100 pmol). These results suggest that NPY modulates the release of CGRP from CGRP-containing nerves in mesenteric resistance vessels.

Animals↗
PubMed1980

An increased calcium sensitivity of mesenteric resistance vessels in young and adult spontaneously hypertensive rats.

1. We have measured the calcium sensitivity in response to noradrenaline stimulation and potassium depolarization of isolated segments of 100 to 200 micrometer mesenteric resistance vessels from spontaneously hypertensive (SHR) and control Wistar-Kyoto rats. The rats were either young (4 wk) or adult (4 months), that is of ages before or after the SHRs had developed elevated blood pressure. Experiments were performed under conditions in which the effect of noradrenaline uptake by, and the potassium-induced noradrenaline release from, the nerve terminals in the vessel walls was eliminated. 2. The response of the SHR and WKY vessels to noradrenaline under conditions where only the extracellular calcium appeared to have been removed was similar. When subsequently stimulated maximally by noradrenaline, the calcium-sensitivity of the SHR vessels (Ca-ED50 approximately or equal to 0.1 mM) was greater than that of the WKY vessels (Ca-ED50 approximately or equal to 0.2 mM). When depolarized by potassium, all vessels were less sensitive to calcium and there was little difference in the calcium sensitivity of SHR and WKY vessels in either age group (Ca-ED50 approximately or equal to 0.8 mM). 3. The results suggest that whereas the potassium (potential)-dependent calcium permeability of the SHR smooth muscle cell membrane is normal, the noradrenaline-induced calcium permeability is abnormally high. The presence of this abnormality in the vessels from the young SHRs suggests that it may be a factor involved in the aetiology of hypertension in the SHR.

Aging↗
PubMed1993

Superior mesenteric arteriovenous fistula: report of a case and review of the literature.

Iatrogenic arteriovenous fistula of the superior mesenteric vessels is rare, with only 22 cases being documented. We report herein a case of a 63-year-old man with an iatrogenic arteriovenous fistula which developed after a small bowel resection for intestinal tuberculosis. The patient was admitted to our hospital for a gastric ulcer, at which time an ultrasonogram demonstrated cystic dilatation of the superior mesenteric vein, proving to be an arteriovenous fistula of the mesenteric vessels. An angiogram of the superior mesenteric vessels subsequently confirmed this diagnosis and resection of the fistula was performed, followed by an uneventful recovery. Iatrogenic mesenteric arteriovenous fistula with no presenting symptoms, as in our case, is uncommon and surgery performed before the development of associated portal hypertension should achieve good results. A review of the literature follows the report of this case.

Arteriovenous Fistula↗
PubMed1984

Extracellular Ca2+ dependence and diltiazem inhibition of contraction in rabbit conduit arteries and mesenteric resistance vessels.

The dependence of norepinephrine-(NE-) and high potassium (80 mM K) depolarization-induced contractions on extracellular versus intracellular calcium (Ca2+) pools was studied in strips of rabbit superior mesenteric artery and its branches, and in perfused mesenteric resistance vessels. 80 mM K contractions were abolished in the presence of 0 Ca2+ 2 mM EGTA in all arteries studied, whereas 10(-5) M NE-induced contractions and stimulated 45Ca efflux in 0 Ca2+ 2 mM EGTA decreased in a graded fashion from proximal to distal arteries. These data indicate a decreasing release of intracellular Ca2+ and an increasing dependence on extracellular Ca2+ for NE-induced contractions as one proceeds from proximal to distal arteries. This pattern was paralleled by increasing sensitivity of NE-induced contractions to inhibition by diltiazem (10(-9)-10(-4) M) from proximal to distal arteries, while inhibition of 80 mM K contractions was similar in all vessels. 45Ca influx induced by 10(-5) M NE in the resistance vessels, wherein the NE does not release intracellular Ca2+, is approximately 10,000-fold more sensitive to the action of diltiazem than that in the aorta. However, when the aorta is activated by 10(-8) M NE, it becomes more sensitive to inhibition by diltiazem than when it is activated by 10(-5) M NE. The former NE concentration does not release intracellular Ca2+ in the aorta, whereas the latter does. Thus, it appears that NE-induced 45Ca influx is most susceptible to inhibition by diltiazem when the NE has not also released intracellular Ca2+. We suggest that the release of intracellular Ca2+ by NE may make its stimulated Ca2+ influx less susceptible to inhibition by diltiazem.

Animals↗
PubMed1998

Quantitative analysis of calcitonin gene-related peptide- and neuropeptide Y-immunoreactive nerve fibers in mesenteric blood vessels of rats irradiated with cobalt-60 gamma rays.

The effects of 60Co gamma rays on calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers and neuropeptide Y (NPY)-immunoreactive nerve fibers were examined in mesenteric blood vessels of rats. Using a free-floating immunostaining streptavidin-biotin peroxidase complex method combined with a nickel-enhancement technique, we found that the distribution pattern of these two peptidergic nerve fibers in superior mesenteric arteries and superior mesenteric veins did not change, while the densities of CGRP-immunoreactive nerve fibers and NPY-immunoreactive nerve fibers in superior mesenteric arteries and veins varied with the time after irradiation. The results suggested that CGRP and NPY may be important in the development and elimination of radiation-induced injury.

Animals↗
PubMed1997

Mesenteric vasculopathy in intestinal tuberculosis.

BACKGROUND: Involvement of mesenteric vessels in intestinal tuberculosis and its role in the pathogenesis of the intestinal changes have not been studied histologically. AIM: To study mesenteric vessels in patients undergoing surgery for complications of intestinal tuberculosis. METHODS: Resected intestinal specimens from 68 patients presenting with intestinal perforation and intestinal obstruction were examined; involvement of the major mesenteric vessels was evaluated. RESULTS: Granulomas were seen in the vessel wall in one case and near the vessel wall in 11 cases, intraluminal thrombi were seen in 23 cases, and subintimal fibrosis in nine cases. Perivascular cuffing was seen in intramural and subserosal vessels in ten cases. CONCLUSIONS: Changes in the vessel wall may lead to gut ischemia, which may contribute to the development of strictures and stercoral perforation in intestinal tuberculosis.

Adolescent↗
PubMed2001

Laser pulse impact on rat mesenteric blood vessels in relation to laser treatment of port wine stain.

BACKGROUND AND OBJECTIVE: To study the impact of laser pulses on animal microvasculature as a model for laser treatment of port wine stains. STUDY DESIGN/MATERIALS AND METHODS: Rat mesenteric blood vessels were irradiated with a laser pulse (585 nm, 0.2-0.6 ms pulse duration, 0.5-30 J/cm(2) radiant exposure). Video microscopy was used to assess vessel dilation, formation of intravascular thrombi, bubble formation, and vessel rupture. Changes in reflection during a laser pulse were measured by simultaneously recording the temporal behavior of the incident and reflected signals. RESULTS: A threshold radiant exposure of approximately 3 J/cm(2) was found for changes in optical properties of blood in vivo, confirming previous in vitro results. Often, laser exposure induced a significant increase in vessel diameter, up to three times the initial diameter for venules and four times for arterioles, within 200 ms after laser exposure. Arterioles were more likely to dilate than venules. Sometimes, immediately after the pulse, round structures, interpreted as being gas bubbles, were seen within the vessel lumen. CONCLUSIONS: A variety of phenomena can occur when blood vessels of sizes comparable to those in port wine stains are irradiated with laser pulses as used in port wine stain treatment. Thrombus formation and vessel rupture have been described before from histological sections of laser-irradiated port wine stains. However, vessel dilation and formation of non-transient gas bubbles as found in this study have not been described before.

Animals↗
PubMed1992

Fish oil feeding selectively attenuates contractile responses to noradrenaline and electrical stimulation in the perfused mesenteric resistance vessels of spontaneously hypertensive rats.

1. The mechanism of the antihypertensive effects of n-3 fatty acids were examined in spontaneously hypertensive rats (SHR) by feeding 'Max EPA' fish oil or hydrogenated coconut oil and determining the responses of perfused mesenteric resistance vessels to various contractile agents and peri-arterial nerve stimulation. 2. Fish oil feeding for 4 weeks caused a decrease in the responses to exogenous noradrenaline and electrical nerve stimulations but had no significant effect on vasopressin and KCl (80 mmol/L) induced contractions. 3. These results provide direct evidence for specific attenuation of vascular responses to sympatho-adrenal stimulation in resistance vessels following fish oil feeding and may account for the antihypertensive effects seen in humans and in some forms of hypertension in rats.

Animals↗
PubMed1980

Effect of sodium-potassium-dependent ATPase inhibition on noradrenaline-activated calcium sensitivity of mesenteric resistance vessels in adult spontaneously hypertensive rats.

1. We have investigated the noradrenaline-activated calcium sensitivity of 150 micrometer mesenteric resistance blood vessels from spontaneously hypertensive and control Wistar-Kyoto rats. 2. Under control conditions the spontaneously hypertensive rat blood vessels had a greater calcium sensitivity than the Wistar-Kyoto rat vessels. 3. In the presence of 1 mmol of ouabain/l, a treatment known to inhibit the sodium-potassium-dependent ATPase, the responses of the spontaneously hypertensive rat blood vessels were reduced more than those of the Wistar-Kyoto rat blood vessels, so that the responses of spontaneously hypertensive rat and Wistar-Kyoto rat blood vessels were then similar. 4. Similar results were obtained by removing external potassium, a procedure which should also inhibit the sodium-potassium-ATPase. 5. The results suggest that the greater noradrenaline-activated calcium sensitivity of spontaneously hypertensive rat blood vessels may be associated with an increased sodium-potassium-ATPase activity.

Animals↗
PubMed2002

Kit-like immunopositive cells in sheep mesenteric lymphatic vessels.

Recent electrophysiological studies have suggested that there is a subpopulation of cells in lymphatic vessels which act as pacemakers controlling the characteristic spontaneous contractile activity in this tissue. In this study, electron microscopy and immunohistochemical techniques were used on sheep mesenteric lymphatic vessels to investigate the morphology of the cells comprising the lymphatic wall. The smooth muscle cells were not orientated in circular and longitudinal layers as is seen in the gastrointestinal tract, but were arranged in bundles which interlock and cross over in a basket-weave fashion. Antibodies to Kit and vimentin, which are widely used to label specialised pacemaking cells in the gastrointestinal tract (known as interstitial cells of Cajal), demonstrated the existence of an axially orientated subpopulation of cells lying between the endothelium and the bulk of the smooth muscle. Examination of this area using electron microscopy showed cells which were electron dense compared to the underlying smooth muscle and contained caveolae, Golgi complexes, mitochondria, 10-nm filaments, a well-developed endoplasmic reticulum and a basal lamina. The smooth muscle cells typically contained caveolae, dense bodies, mitochondria, abundant filaments, sER and basal laminae. Cells dispersed for patch-clamp studies were also stained for vimentin and myosin. Myosin-staining cells had the typical spindle appearance of smooth muscle cells whereas the vimentin-positive cells could either be branched or more closely resemble the smooth muscle cells. The present study provides the first morphological evidence that specialised cells exist within the vascular system which have the ultrastructural characteristics of pacemaker cells in other tissues and are vimentin and Kit positive.

Animals↗
PubMed1983

Decreased relaxation of isolated mesenteric resistance vessels from 2-kidney, 1 clip Goldblatt hypertensive rats.

Cumulative contractile responses to norepinephrine (NE), their potentiation with cocaine and their inhibition by diltiazem, cumulative relaxation responses to adenosine and acetylcholine, and contractile responses to 140 mM K+ were studied in isolated mesenteric resistance vessels (ca 175 mu internal diameter) from 2-kidney, 1 clip (2K-1C) Goldblatt hypertensive Wistar rats (2 week duration) and sham-operated controls. No difference in calculated internal diameter, NE sensitivity (before or after inclusion of cocaine in the bath), maximum NE-induced tension, or rate of relaxation after NE washout was found between the two groups. However, the contractile responses to NE in the presence of diltiazem were greater, and acetylcholine and adenosine were less effective in relaxing NE-induced contractions in vessels from 2K-1C Goldblatt hypertensive rats. Depolarization with 140 mM K+ induced equivalent contractions in the two groups and were inhibited to the same extent by 10(-6) M phentolamine, indicating that the contribution of catecholamines released from sympathetic nerve endings by the 140 mM K+ to the K+ induced contraction was equivalent in the two groups. Decreased relaxation of NE-induced contractions reflects a functional alteration in vascular smooth muscle of resistance vessels from 2K-1C rats that may contribute to the development of elevated total peripheral resistance in this model of hypertension.

Acetylcholine↗
PubMedDate not supplied

[Ultrasonography of changes in the retroperitoneal vessels and perivascular spaces during retroviral infection: preliminary results].

The abdomen in patients with acquired immunodeficiency syndrome (AIDS) is subject to various damage. In AIDS patients, manifestations in the retroperitoneal region, including apparent changes in the pancreas, kidney and lymph nodes, have been well described in the radiological literature. However, abnormalities of the vessels and perivascular spaces have not been well investigated in this syndrome. We performed abdominal sonography in 10 patients who were seropositive for HIV. They had no history of known risk factors such as drug abuse or homosexuality. Also, 4 healthy male controls were examined for comparison. Our aim was to demonstrate and to characterize the pathological changes of the retroperitoneal vessels and perivascular spaces from sonographic observations. The sonographic evaluation included determination of the morphologic and dynamic aspects of the aorta, vena cava and superior mesenteric vessels. The echostructure of the perivascular spaces was analyzed. In this prospective and preliminary study, we have not considered the presence of an AIDS condition. We have precisely analyzed the upper umbilical areas. In all cases, there were supposed to be the same landmarks. The sonographic scans were obtained through the left renal and mesenteric vessel areas, essentially through axial scans. In all 10 patients, sonography showed at least two abnormalities. Three patients had abnormal echostructural changes in all the sites. The images showed echostructural disorganization with poor definition and "fuzzy" and "dirty" aspects of the retroperitoneal vessels and perivascular spaces. The aorta was normal in 2 patients and abnormal in 8 patients with diminished hyperechography and regularity of the aortal wall. The aortic diameter was smaller than 1.5 cm in 7 cases, with a significant attenuation of the beating of the aorta. Despite these abnormalities, the aorta had a normal left paramedian position ahead of the rachis. The inferior vena cava was normal in 1 case and abnormal in 9 cases with diminished hyperechography and regularity of the wall. The vena cava position was normal in 4 cases, displaced in 6, and laminated in 3. The superior mesenteric vessels were abnormal in 8 cases, with poorly defined aims in 6, an indefinite position in 2, and spreading in 2. Adenopathy was present in 6 patients, multiple in 5 and singular in 1 case. A retrocaval location was always observed. A perivascular infiltration and thickening was noted which was diffuse in 6 cases and micronodular in 1 case. From our observations, we conclude that these echostructural changes could be related to AIDS. However, further studies are necessary to confirm these observations and to determine if this sonographic pattern may be seen during the course of the disease. This is the first study to our knowledge which stressed the echostructural changes of the retroperitoneal vessels and perivascular spaces in patients with AIDS.

Abdomen↗
PubMed2005

Effects of chloride substitution in isolated mesenteric blood vessels from Dahl normotensive and hypertensive rats.

The purpose of this investigation was to examine the effect of Cl-free medium, nitric oxide synthase inhibitor (N nitro-L-arginine methyl ester; L-NAME), and Cl channel antagonist (niflumic acid), on alpha1-adrenoceptor (cirazoline) mediated responses in the isolated mesenteric blood vessels from Dahl salt-resistant normotensive (SRN) and salt-sensitive hypertensive (SSH) rats on a 4% salt diet for 7 weeks. Cirazoline produced dose-dependent vasoconstriction in blood vessels of SRN and SSH rats. Replacement of extracellular Cl with propionate ions significantly inhibited (P < 0.05) cirazoline-mediated vasoconstriction in SRN but not in SSH rats. Perfusion with L-NAME (10 microM) augmented responses to cirazoline in SRN but not in SSH rats. In Cl-free medium, addition of L-NAME had a biphasic effect on cirazoline responses; potentiation of responses at the lower doses and attenuation at the highest dose. Niflumic acid (10 microM) significantly inhibited cirazoline responses with the inhibition being more pronounced in SRN than SSH rats. The resting Em of smooth muscle cells was -68.0 +/- 4.2 mV (mean +/- SD; n = 87) and -67.2 +/- 4.8 mV (n = 88), in SRN and SSH rats, respectively. Perfusion with Cl-free medium produced a significant depolarization that was larger in smooth muscle cells of SSH (-57.4 +/- 4.8 mV, n = 38) than SRN (-61.3 +/- 5.4 mV, n = 35) rats, while L-NAME depolarized the smooth muscle cells of SRN (-62.1 +/- 6.5 mV, n = 36) but not SSH (-67.5 +/- 4.2 mV, n = 34) rats. The data supports the view that Cl handling and Ca-dependent Cl channels seem to undergo modification as a consequence of salt-induced hypertension. It is also possible that the modified role of nitric oxide on membrane potential may have a direct bearing on the changes observed in Cl handling in blood vessels of SRN versus SSH rats.

Animals↗
PubMed2005

[The effect of examination of enzymes in serum to diagnosis of acute mesenteric ischemia in rabbit].

OBJECTIVE: To study the change regulation of enzymes in serum for the diagnosis and treatment of acute mesenteric ischemia by earlier period. METHODS: Thirty-six of rabbits were divided into three groups included from artery, vein and artery with vein by interrupted in mesenteric vessels respectively and there was twelve rabbits in every groups. It was observed that ALT, AST, ALP, gamma-GT, CK, CK-MB, LDH in serum at mesenteric vessels pre-interrupted and post-interrupted 1, 3, 6, 9 h respectively and the bowel color variety was observed at the same time too. RESULTS: After 3 h from post-occluded of mesenteric vessels, among the three groups there was bowel infarction and ALT, AST, ALP, gamma-GT, LDH in serum all to obviously go up. CONCLUSION: It is beneficial to diagnosis of acute mesenteric ischemia at earlier by the examination of enzymes in serum.

Acute Disease↗
PubMed1983

Redundant nature of the vasopressin and renin--angiotensin systems in the control of mesenteric resistance vessels of the conscious fasted cat.

[1-deaminopenicillamine, 4-valine, 8-D-arginine]Vasopressin (DPVDAVP), a specific antagonist of the pressor activity of vasopressin, and teprotide, a converting enzyme inhibitor, were infused intravenously in conscious, fasted (24-30 h) but not water-deprived cats which had been implanted previously with flow probes on their superior mesenteric arteries and with arterial and venous cannulae. Infusion of DPVDAVP (20 micrograms/min) alone or teprotide (1 mg over 5 min) alone caused only small and statistically nonsignificant changes in mesenteric conductance and arterial pressure. However, infusion of DPVDAVP during the plateau phase of the response to teprotide or, conversely, administration of teprotide during the plateau phase of the response to DPVDAVP caused large increases in mesenteric conductance and small but significant decreases in arterial pressure. The results are consistent with the hypothesis that vasopressin and angiotensin are redundant overlapping mechanisms that play a significant role in the control of the mesenteric resistance vessels of the conscious fasted cat; when one system is inhibited, the other compensates to maintain resistance.

Animals↗