Vascularization of the gastrointestinal tract of the bottlenose dolphin (Tursiops truncatus, Montagu 1821)

Odontocetes primarily rely on fish, cephalopods, and crustaceans as their main source of nutrition. In the digestive system, their polygastric complex exhibits similarities to that of their closest terrestrial relatives such as cows, sheep, and giraffes, while the entero-colic tract shares similarities with terrestrial carnivores. The morphology, caliber, and structure of the odontocete intestine are relatively constant, and, since there is no caecum, a distinction between the small and large intestine and their respective subdivisions is difficult. To address this issue, we used the intestinal vascularization pattern, specifically the course and branching of the celiac artery (CA) and the cranial and caudal mesenteric arteries (CrMA and CdMA). A series of pictures and dissections of 10 bottlenose dolphins (Tursiops truncatus) were analyzed. Additionally, we performed a cast by injecting colored polyurethane foam in both arteries and veins to measure the caliber of the arteries and clarify their monopodial or dichotomous branching. Our results showed the presence of multiple duodenal arteries (DAs) detaching from the CA. The CrMA gave origin to multiple jejunal arteries, an ileocolic artery (ICA), and, in six cases, a CdMA. In four specimens, the CdMA directly originated from the abdominal aorta. The ICA gave rise to the mesenteric ileal branches (MIB) and mesenteric anti-ileal branches and the right colic arteries (RCA) and the middle colic arteries. From the CdMA originated the left colic and cranial rectal arteries (LCA and CrRA). The measurements revealed a mixed monopodial and dichotomous branching scheme. The analysis of the arteries and their branching gave us an instrument, based on comparative anatomy, to distinguish between the different intestinal compartments. We used the midpoint of anastomoses between MIB and RCA to indicate the border between the small and the large intestine, and the midpoint of anastomoses between LCA and CrRA, to tell the colon from the rectum. This pattern suggested an elongation of the duodenum and a shortening of the colic tract that is still present in this species. These findings might be related to the crucial need to possess a long duodenal tract to digest prey ingested whole without chewing. A short aboral part is also functional to avoid gas-producing colic fermentation. The rare origin of the CdMA on the CrMA might instead be a consequence of the cranial thrust of the abdominopelvic organs related to the loss of the pelvic girdle that occurred during the evolution of cetaceans.

Functional Expression Profile of Voltage-Gated K(+) Channel Subunits in Rat Small Mesenteric Arteries

Multiple K v channel complexes contribute to total K v current in numerous cell types and usually subserve different physiological functions. Identifying the complete compliment of functional K v channel subunits in cells is a prerequisite to understanding regulatory function. It was the goal of this work to determine the complete K v subunit compliment that contribute to functional K v currents in rat small mesenteric artery (SMA) myocytes as a prelude to studying channel regulation. Using RNA prepared from freshly dispersed myocytes, high levels of K v 1.2, 1.5, and 2.1 and lower levels of K v 7.4 α-subunit expressions were demonstrated by quantitative PCR and confirmed by Western blotting. Selective inhibitors correolide (K v 1; COR), stromatoxin (K v 2.1; ScTx), and linopirdine (K v 7.4; LINO) decreased K v current at +40 mV in SMA by 46 ± 4, 48 ± 4, and 6.5 ± 2 %, respectively, and K v current in SMA was insensitive to α-dendrotoxin. Contractions of SMA segments pretreated with 100 nmol/L phenylephrine were enhanced by 27 ± 3, 30 ± 8, and 7 ± 3 % of the response to 120 mmol/L KCl by COR, ScTX, and LINO, respectively. The presence of K v 6.1, 9.3, β1.1, and β1.2 was demonstrated by RT-PCR using myocyte RNA with expressions of K vβ1.2 and K v 9.3 about tenfold higher than K vβ1.1 and K v 6.1, respectively. Selective inhibitors of K v 1.3, 3.4, 4.1, and 4.3 channels also found at the RNA and/or protein level had no significant effect on K v current or contraction. These results suggest that K v current in rat SMA myocytes are dominated equally by two major components consisting of K v 1.2-1.5-β1.2 and K v 2.1-9.3 channels along with a smaller contribution from K v 7.4 channels but differences in voltage dependence of activation allows all three to provide significant contributions to SMA function at physiological voltages.

Emphasizing mesenteric blood vessels in laparoscopic colon cancer surgery video images

This study aims to reduce surgeon burden by emphasising mesenteric blood vessels buried in the mesentery using image processing techniques.We have developed an image processing system that can be connected to a laparoscope. The first step of the method is superficial vessel deletion using an opening process. Next, the mesenteric blood vessels are extracted by multiple regression analysis using hue, saturation, and value color space information in the image. Finally, the enhanced regions are determined by areas obtained by a labeling process. Although examples with both true and false positives are observed, the proposed technique demonstrates sufficient accuracy.

An extremely uncommon variant of left hepatic artery arising from the superior mesenteric artery

We report a new variation of the left hepatic artery arising from the superior mesenteric artery. The variant was discovered during radiological examinations in a patient presenting with ruptured hepatocellular carcinoma of the left liver lobe. Anatomical description was based on CT-scan and angiographic analysis. When present the left hepatic artery originates from the left gastric artery, with an incidence of 12-34 %. Knowledge of left hepatic artery anatomy is mandatory to optimize surgical and radiological management in complex clinical situations.

A microfluidic platform for probing small artery structure and function

Although pathologic changes to the structure and function of small blood vessels are hallmarks of various cardiovascular diseases, limitations of conventional investigation methods (i.e. pressure myography) have prohibited a comprehensive understanding of the underlying mechanisms. We developed a microfluidic device to facilitate assessment of resistance artery structure and function under physiological conditions (37 degrees C, 45 mmHg transmural pressure). The platform allows for on-chip fixation, long-term culture and fully automated acquisition of up to ten dose-response sequences of intact mouse mesenteric artery segments (diameter approximately 250 micrometres and length approximately 1.5 mm) in a well-defined microenvironment. Even abluminal application of phenylephrine or acetylcholine (homogeneous condition) yielded dose-response relationships virtually identical to conventional myography. Unilateral application of phenylephrine (heterogeneous condition) limited constriction to the drug-exposed side, suggesting a lack of circumferential communication. The microfluidic platform allows us to address new fundamental biological questions, replaces a manually demanding procedure with a scalable approach and may enable organ-based screens to be routinely performed during drug development.

Short-term angiotensin-1 receptor antagonism in type 2 diabetic Goto-Kakizaki rats normalizes endothelin-1-induced mesenteric artery contraction

Endothelin (ET)-1 and angiotensin II (Ang II) are likely candidates for a key role in diabetic vascular complications. We demonstrated previously that an enhanced ET-1-induced contraction is present in mesenteric arteries from Goto-Kakizaki (GK) rats at the chronic stage of type 2 diabetes. Here, we investigated whether short-term treatment of such rats with losartan, an angiotensin type 1 receptor antagonist, might normalize the ET-1-induced contraction. In mesenteric arteries from GK rats at the chronic stage (34-38 weeks) (vs. those from age-matched control Wistar rats): (1) the ET-1-induced contraction was enhanced, (2) the levels of ET-1 and Ang II were increased, (3) ET-1-stimulated ERK2 phosphorylation was increased, and (4) the ACh-induced endothelium-dependent relaxation was reduced. Mesenteric arteries isolated from such GK rats following treatment with losartan (25mg/kg/day for 2 weeks) exhibited reduced ET-1- and Ang II-induced contractions, suppressed ET-1-stimulated ERK phosphorylation, and increased ACh-induced relaxation, while the rats exhibited normalized plasma NO metabolism and their mesenteric arteries exhibited increased basal NO formation. However, such losartan treatment did not alter the increased levels of ET-1 and Ang II seen in GK mesenteric arteries. Our data suggest that within the timescale studied here, losartan normalizes ET-1-induced mesenteric artery contraction through a suppression of ERK activities and/or by normalizing endothelial function.

Simulations of time harmonic blood flow in the Mesenteric artery: comparing finite element and lattice Boltzmann methods

BACKGROUND

Systolic blood flow has been simulated in the abdominal aorta and the superior mesenteric artery. The simulations were carried out using two different computational hemodynamic methods: the finite element method to solve the Navier Stokes equations and the lattice Boltzmann method.

RESULTS

We have validated the lattice Boltzmann method for systolic flows by comparing the velocity and pressure profiles of simulated blood flow between methods. We have also analyzed flow-specific characteristics such as the formation of a vortex at curvatures and traces of flow.

CONCLUSION

The lattice Boltzmann Method is as accurate as a Navier Stokes solver for computing complex blood flows. As such it is a good alternative for computational hemodynamics, certainly in situation where coupling to other models is required.

The Use of Fluorescent Nuclear Dyes for the Study of Blood Vessel Structure and Function: Novel Applications of Existing Techniques

We have used nuclear fluorescent dyes to develop a technique for the study of vascular structure and function. Nuclear stained blood vessels, viewed with the appropriate filter sets, can be studied in great detail. Only the nuclei of the cells which form the walls are visible and so their positions relative to one another as well as their viability can be quickly assessed. The dyes are not toxic, therefore when the vessel contracts or relaxes, the changes in position of the nuclei can be monitored. In this paper we describe two original applications of fluorescent nuclear dyes in vascular research.

Vascular function of MGH and MGL mice, two strains which differ by a genetic variation of magnesium metabolism

Mg deficiency is considered as a risk factor of cardiovascular disorders like hypertension and atherosclerosis. MGH and MGL mice, selected for high and low Mg status, are animal models which present variations of Mg metabolism of genetic origin. The cardiovascular functions of these mice have never been studied. In this study, the arterial blood pressure of MGH and MGL strains was measured by plethysmography. Morphology and reactivity to vasoconstrictor agents were also investigated by a pressurized and perfused system in mesenteric resistance artery. It is shown that: (1) MGH mice presented a higher plasma Mg concentration than MGL; (2) arterial blood pressure and heart rates were similar between the two groups; (3) media thickness, media cross-sectional area, and internal and external diameters were smaller in pressurized mesenteric resistance arteries from MGH mice than in those from MGL mice; (4) the vasoconstriction induced by vasopressin (but not norepinephrine) was higher in the mesenteric arteries from MGH mice than in those from MGL ones. In summary, MGH mice as compared to MGL mice present differences in arterial geometry and higher reactivity to vasopressin without repercussions on arterial blood pressure. The real repercussion of these observations on the cardiovascular system of the MGH and MGL models is at present unknown. More experiments are needed to clarify the influence of differences in Mg metabolism of genetic origin on cardiovascular function.

A model of blood flow in the mesenteric arterial system

Background

There are some early clinical indicators of cardiac ischemia, most notably a change in a person's electrocardiogram. Less well understood, but potentially just as dangerous, is ischemia that develops in the gastrointestinal system. Such ischemia is difficult to diagnose without angiography (an invasive and time-consuming procedure) mainly due to the highly unspecific nature of the disease.

Understanding how perfusion is affected during ischemic conditions can be a useful clinical tool which can help clinicians during the diagnosis process. As a first step towards this final goal, a computational model of the gastrointestinal system has been developed and used to simulate realistic blood flow during normal conditions.

Methods

An anatomically and biophysically based model of the major mesenteric arteries has been developed to be used to simulate normal blood flows. The computational mesh used for the simulations has been generated using data from the Visible Human project. The 3D Navier-Stokes equations that govern flow within this mesh have been simplified to an efficient 1D scheme. This scheme, together with a constitutive pressure-radius relationship, has been solved numerically for pressure, vessel radius and velocity for the entire mesenteric arterial network.

Results

The computational model developed shows close agreement with physiologically realistic geometries other researchers have recorded in vivo. Using this model as a framework, results were analyzed for the four distinct phases of the cardiac cycle – diastole, isovolumic contraction, ejection and isovolumic relaxation. Profiles showing the temporally varying pressure and velocity for a periodic input varying between 10.2 kPa (77 mmHg) and 14.6 kPa (110 mmHg) at the abdominal aorta are presented. An analytical solution has been developed to model blood flow in tapering vessels and when compared with the numerical solution, showed excellent agreement.

Conclusion

An anatomically and physiologically realistic computational model of the major mesenteric arteries has been developed for the gastrointestinal system. Using this model, blood flow has been simulated which show physiologically realistic flow profiles.

Arterial variants in pancreatic adenocarcinoma

Surgery remains the only curative option for the treatment of pancreatic adenocarcinoma. Local tumor resectability depends on a number of factors, but most importantly, the relationship of the tumor to adjacent arterial structures. For example, surgery is rarely performed when the tumor involves the celiac axis or the superior mesenteric artery. Unexpected variant arterial anatomy or tumor involvement of aberrant arteries may complicate pancreatic surgery. The classic visceral arterial anatomy occurs in only 55%-60% of the population, with one or more variant vessels occurring in the remaining population. Knowledge of both variant and normal anatomy is essential for accurate preoperative planning. We describe here the arterial variant anatomy of the pancreas and its identification by multidetector CT imaging, with and without the aid of post-processed volume-rendered images.

Effects of h1-calponin ablation on the contractile properties of bladder versus vascular smooth muscle in mice lacking SM-B myosin

The functional significance of smooth muscle-specific h1-calponin up-regulation in the smooth muscle contractility of SM-B null mice was studied by generating double knockout mice lacking both h1-calponin and SM-B myosin. The double knockout mice appear healthy, reproduce well and do not show any smooth muscle pathology. Loss of h1-calponin in the SM-B null mice bladder resulted in increased maximal shortening velocity (V(max)) and steady-state force generation. The force dilatation pressure, which was decreased in the SM-B null mesenteric vessels, was restored to wild-type levels in the double knockout vessels. In contrast, the half-time to maximal constriction was significantly increased in the double knockout vessels similar to that of SM-B null mice and indicating decreased shortening velocity in the double knockout vessels. Biochemical analyses showed that there is a significant reduction in smooth muscle alpha-actin levels, whereas h-caldesmon levels are increased in the double knockout bladder and mesenteric vessels, suggesting that these changes may also partly contribute to the altered contractile function. Taken together, our studies suggest that up-regulation of h1-calponin in the SM-B null mice may be necessary to maintain a reduced level of cross-bridge cycling over time in the absence of SM-B myosin and play an important role in regulating the smooth muscle contraction.

Ca2+ signaling in mouse mesenteric small arteries: myogenic tone and adrenergic vasoconstriction

Arteries that have developed myogenic tone (MT) are in a markedly different physiological state compared with those that have not, with higher cytosolic [Ca(2+)] and altered activity of several signal transduction pathways. In this study, we sought to determine whether alpha(1)-adrenoceptor-induced Ca(2+) signaling is different in pressurized arteries that have spontaneously developed MT (the presumptive physiological state) compared with those that have not (a common experimental state). At 32 degrees C and intraluminal pressure of 70 mmHg, cytoplasmic [Ca(2+)] was steady in most smooth muscle cells (SMCs). In a minority of cells (34%), however, at least one propagating Ca(2+) wave occurred. alpha(1)-Adrenoceptor activation (phenylephrine, PE; 0.1-10.0 microM) caused strong vasoconstriction and markedly increased the frequency of Ca(2+) waves (in virtually all cells). However, when cytosolic [Ca(2+)] was elevated experimentally in these arteries ([K(+)] 20 mM), PE failed to elicit Ca(2+) waves, although it did elevate [Ca(2+)] (F/F(0)) further and caused further vasoconstriction. During development of MT, the cytosolic [Ca(2+)] (F/F(0)) in individual SMCs increased, Ca(2+) waves disappeared (from SMCs that had them), and small Ca(2+) ripples (frequency approximately 0.05 Hz) appeared in approximately 13% of cells. PE elicited only spatially uniform increases in [Ca(2+)] and a smaller change in diameter (than in the absence of MT). Nevertheless, when cytosolic [Ca(2+)] and MT were decreased by nifedipine (1 microM), PE did elicit Ca(2+) waves. Thus alpha(1)-adrenoceptor-mediated Ca(2+) signaling is markedly different in arteries with and without MT, perhaps due to the elevated [Ca(2+)], and may have a different molecular basis. alpha(1)-Adrenoceptor-induced vasoconstriction may be supported either by Ca(2+) waves or by steady elevation of cytoplasmic [Ca(2+)], depending on the amount of MT.

Spatial growth and pattern formation in the small intestine microvascular bed from larval to adult Xenopus laevis: a scanning electron microscope study of microvascular corrosion casts

The microvascular anatomy of the small intestine of metamorphosing tadpoles of the South African Clawed Toad, Xenopus laevis (Daudin) is studied from developmental stages 55 to 65 and in adults by scanning electron microscopy (SEM) of vascular corrosion casts (VCCs) and light microscopy. Up to stage 62, VCCs reveal a dense two-dimensional vascular network ensheating the intestinal tube, whose proximal portion forms a clockwise spiralling outer and its distal portion an anti-clockwise spiralling inner coil. Vessels of the intestinal network impose flat and run circularly to slightly obliquely. Locally, dense capillary plexus with small "holes" indicating ongoing intussusceptive microvascular growth (IMG) and vessel maturation, are present. The typhlosole, an invagination along the proximal portion of the small intestine, reveals a dense capillary bed with locally ongoing IMG. VCCs of stages 62/63 for the first time reveal a three-dimensional vascular bed with longitudinal intestinal folds of varying size and heights greatly enlarging the luminal exchange area of the intestinal tube. From stage 65 onwards, longitudinal intestinal folds undulate and, though smaller in size and less mature as indicated in VCCs by the presence of wider, sinus-like vessels with small "holes" interposed between, closely resemble the intestinal folds present in the small intestine of adult Xenopus. Our data suggest that maturation of the vascular pattern in the small intestine of X. laevis tadpoles takes place successively after stages 62-63, and growth during this period is preferentially by intussusception.

Differential Distribution of Mechanosensitive Nonselective Cation Channels in Systemic and Pulmonary Arterial Myocytes of Rabbits

The mechanosensitive nonselective cation channel (NSC(MS)) is a key player in vascular myogenic contraction. The functional channel density and pressure sensitivity of NSC(MS) in vascular myocytes were compared between pulmonary and systemic arteries (coronary, mesenteric and cerebral arteries) in the rabbit. In cell-attached condition, a negative pressure via patch pipettes commonly activated NSC(MS) with weak voltage dependence. The threshold pressure for activation was lower, and the density of NSC(MS) was higher in the pulmonary than the systemic arteries. When the pulmonary arteries were divided into small-diameter (outer diameter, OD < 0.5 mm) and large-diameter (OD > 1.5 mm) arteries, the low threshold and high density of NSC(MS) were observed only in small-diameter ones. No such difference was observed between the small- and large-diameter coronary arteries. The higher stretch sensitivity and denser functional expression of NSC(MS) in small pulmonary arteries might suggest an adaptive tuning for the relatively low pulmonary blood pressure in vivo.

Macroscopic and microscopic intermesenteric communications

The aim of this study was to describe all levels of the intermesenteric communications because of their importance in vascular diseases of the colon. The connections of superior and inferior mesenteric networks are very important in cases of acute or chronic obstruction to prevent ischemia and necrosis. Angiograms of mesenteric arteries were studied (40), cadaverous large intestine samples with mesentery and feeding vessels were dissected (36) or injected with India ink solution (24) or methylmetacrylate Mercox (41). In 7.9 % of cases an intermesenteric connection was described, named anastomosis intermesenterica accessoria and classified according to Pikkieff's(1) proposal. The marginal artery in the left colic flexure forms an arch called Riolan's arcade(2) or Haller's anastomosis(3) and is present in 95 % of cases. Infrequent anastomosis between straight vessels and mighty plexuses in the intestinal wall were registered. There are no regional differences when compared to the rest of colon.

A case of nonrotation of the midgut with a middle mesenteric artery

In 2002, we came across a very rare case of nonrotation of the midgut with a middle mesenteric artery (MM) (tentative name). It was found in a 73-year-old Japanese female cadaver donated for student dissection at Kumamoto University. In this case, the small intestine occupied the right half of the abdominal cavity and the large intestine occupied the left half. The caecum was situated on the anterior inferior part of the abdominal cavity near the midline. The duodenum (Du) was fused to the posterior abdominal wall. The small intestine except the Du and the ascending colon were suspended from the posterior abdominal wall by the mesentery, but the remainder of the colon was fused to the left posterior abdominal wall. In addition, an anomalous branch arose from the abdominal aorta between the superior and inferior mesenteric arteries (SM and IM) in this case. It chiefly supplied the ascending and the transverse colons and anastomosed with the SM and IM, respectively, through the marginal arteries. It is very rare that these anomalies appear simultaneously in one body. In this case, it is difficult to declare that the existence of the MM directly caused the nonrotation of the midgut, but it is reasonable to suppose some kind of relation between them.

Anastomosis of Riolan Revisited

The eponym anastomosis of Riolan suggests that Jean Riolan (1580-1657), a famous 17th century French anatomist, was the first to describe this mesenteric arterial connection between the superior and inferior mesenteric arteries. Riolan was a strong defender of traditional Galenic doctrine in medicine and proved a vigorous opponent of the new concept of the circulation of blood as exposed by William Harvey (1578-1657). As confirmed by examining his anatomy book published in 1649, it is unlikely that Riolan would have conceived an arterial collateral pathway in the mesocolon. He probably had observed vascular arcades running along the inner border of the colon. It was not until 1743 that Albrecht von Haller (1708-1777) gave a detailed description of the anatomy of the mesenteric arteries, referring to the arterial collateral connection between the superior and inferior mesenteric arteries as the Arcus Riolani in honor of an old master of anatomy.

A rare variation of the coeliac trunk

The hepatic, splenic and Left gastric arteries are considered as the "main classic branches" of the coeliac trunk. During the routine dissections in the laboratory of the Anatomy Department in a 62-year-old male cadaver, a rare variation, a coeliacomesenteric trunk was observed. This trunk gave rise to the left gastric, the common hepatic, the splenic, the left gastro-epiploic, the right and left inferior phrenic arteries. The developmental and clinical significance of this anomalous vessel is discussed.

Arterial structural changes in rats immunized by AT1-receptor peptide

Accumulating evidence suggests that anti-AT1 (angiotensin II receptor type 1) receptor antibodies are involved in the pathogenesis of hypertension. We assessed the hypothesis that changes in vascular structure could be induced in rats immunized with AT1-receptor peptide. In this study, an animal model was made by immunizing Wistar rats aged 4 weeks with the synthetic peptide corresponding to the second extracellular peptide of human AT1 as the antigen and raising them for 1 year, while monitoring their blood pressure, heart rate, and anti-AT1-receptor antibodies. A year later the aorta and mesenteric artery of the immunized rats were collected to detect their structural changes. Anti-AT1-receptor antibodies purified by affinity chromatography were prepared to detect their effect on vascular smooth muscle cell (VSMC) proliferation by the method of bromodeoxyuridine incorporation and cell cycle distribution, and their effect on the expression of VSMC c-jun and c-fos mRNA by reverse transcription-polymerase chain reaction and Western blot. Anti-AT1-receptor antibodies were detected in immunized rats throughout the year without significant changes in blood pressure or heart rate, but pathological changes in the arteries were noted at the end of the study period. Purified anti-AT1-receptor antibodies improved proliferation of VSMC and upregulated c-jun expression, which were both attenuated by losartan. In summary, anti-AT1-receptor antibodies can be prepared by active immunization with the peptide of AT1 as the antigen, without changes in blood pressure or heart rate. Anti-AT1-receptor antibodies may play a role in hypertension through upregulation of c-jun expression, thus improving VSMC proliferation and finally inducing vascular recombination.

The meandering mesenteric artery: a historic review and surgical implications

PURPOSE

The aim of this study was to review the literature regarding collateral mesenteric circulation with emphasis on the mesenteric meandering artery (of Moskowitz). Standard vascular embryology and anatomy are described as are the collateral mesenteric vessels that can develop with arterial stenosis or occlusion. A discussion on the correct usage of terms for describing mesenteric collateral vessels follows.

METHODS

We undertook review of the historical literature to discuss the surgical implications of the meandering mesenteric artery.

RESULTS

Despite a long history of study by anatomists and surgeons, confusion still persists regarding both the number and correct descriptive terminology of the collateral mesenteric vessels.

CONCLUSIONS

The use of the vague historic term "arc of Riolan" should be discarded for the more precise term "meandering mesenteric artery." The meandering mesenteric artery should routinely be preserved in all surgical procedures, to include resection for cancer, given its critical function in providing collateral mesenteric circulation. Further evaluation in the asymptomatic patient, however, is unnecessary.

Volume flow estimation in the precapillary mesenteric microvasculature in vivo and the principle of constant pressure gradient

Volume flow was estimated from axial erythrocyte velocity measurements in 30 mesenteric microvessels of 6 rabbits and was compared to Murray's law predictions. The diameters of capillaries and precapillary arterioles ranged between 5.6 and 12 microm. The significant pulsating flow component existing in these microvessels was taken into account by measuring instantaneous axial blood velocity throughout the course of a cardiac cycle and then averaging over the period. In addition, the effect of the velocity profile variation with diameter was taken into account, for the first time, by using a profile factor function. According to Murray's law, the relation between blood volume flow and diameter is governed by a 'cube' law. Curve fitting to volume flow and diameter data pairs for rabbits, showed a dependence of volume flow on diameter raised to the 4th power (with a correlation coefficient equal to 0.97). The above result supports the hypothesis that, in the precapillary part of microvasculature, the principle of constant longitudinal pressure gradient rather than the principle of minimum work may be valid.

Heteromultimeric Kv1 channels contribute to myogenic control of arterial diameter

Inhibition of vascular smooth muscle (VSM) delayed rectifier K+ channels (K(DR)) by 4-aminopyridine (4-AP; 200 micromol/L) or correolide (1 micromol/L), a selective inhibitor of Kv1 channels, enhanced myogenic contraction of rat mesenteric arteries (RMAs) in response to increases in intraluminal pressure. The molecular identity of K(DR) of RMA myocytes was characterized using RT-PCR, real-time PCR, and immunocytochemistry. Transcripts encoding the pore-forming Kvalpha subunits, Kv1.2, Kv1.4, Kv1.5, and Kv1.6, were identified and confirmed at the protein level with subunit-specific antibodies. Kvbeta transcript (beta1.1, beta1.2, beta1.3, and beta2.1) expression was also identified. Kv1.5 message was approximately 2-fold more abundant than that for Kv1.2 and Kv1.6. Transcripts encoding these three Kv1alpha subunits were approximately 2-fold more abundant in 1st/2nd order conduit compared with 4th order resistance RMAs, and Kvbeta1 was 8-fold higher than Kvbeta2 message. RMA K(DR) activated positive to -50 mV, exhibited incomplete inactivation, and were inhibited by 4-AP and correolide. However, neither alpha-dendrotoxin or kappa-dendrotoxin affected RMA K(DR), implicating the presence of Kv1.5 in all channels and the absence of Kv1.1, respectively. Currents mediated by channels because of coexpression of Kv1.2, Kv1.5, Kv1.6, and Kvbeta1.2 in human embryonic kidney 293 cells had biophysical and pharmacological properties similar to those of RMA K(DR). It is concluded that K(DR) channels composed of heteromultimers of Kv1 subunits play a critical role in myogenic control of arterial diameter.

Developmental expression of endothelin receptors in postnatal swine mesenteric artery

Studies were conducted to determine whether endothelin (ET) ETA and ETB receptor protein and mRNA expression is developmentally regulated in the postnatal swine mesenteric circulation. To this end, Western blotting and real-time reverse PCR were performed on protein and total RNA isolated from the mesenteric artery harvested from 3-, 10-, and 30-d-old swine. Western blot analysis revealed that ETA and ETB receptor protein expression in the swine mesenteric artery decreased over the age range studied; thus, ETA and ETB receptor protein expression was significantly greater in the 3-d-old group then progressively declined over the first postnatal month. Similar to the Western data, real-time PCR analysis revealed that ETA and ETB receptor mRNA expression also decreased over the age range studied; thus, ETA and ETB receptor mRNA expression was significantly greater in the 3-d-old group then progressively declined over the first postnatal month. Immunohistochemistry localized the ETA receptor to the vascular smooth muscle and the ETB receptor to the endothelial cell layer. Additionally, we report a partial cDNA sequence for the swine ETB receptor. We conclude that ETA and ETB receptor protein and mRNA expression is developmentally regulated in the postnatal swine mesenteric artery, being expressed to a greater degree in younger animals.

Depolarization-induced calcium influx in rat mesenteric small arterioles is mediated exclusively via mibefradil-sensitive calcium channels

1. In this study, intracellular Ca(2+) was measured as the Fura-2 ratio (R) of fluorescence excited at 340 and 380 nm (F(340)/F(380)) in nonpressurized rat mesenteric small arterioles ( (lumen diameter) 10-25 microm). 2. The response to depolarization using 75 mm KCl was an increase in R from a baseline of 0.96+/-0.01 ([Ca(2+)](i) approximately 74 nm) to 1.04+/-0.01 ( approximately 128 nm) (n=80). The response to 75 mm K(+) was reversibly abolished in Ca(2+)-free physiological saline solution, whereas phentolamine (10 microm) or tetrodotoxin (1 microm) had no effects. LaCl(3) (200 microm) inhibited 61+/-9% of the response. 3. A [K(+)]-response curve indicated that the Ca(2+) response was activated between 15 and 25 mm K(+). The data suggest that the Ca(2+) response was caused by the activation of voltage-dependent Ca(2+) channels. 4. Mibefradil use dependently inhibited the Ca(2+) response to 75 mm K(+) by 29+/-2% (100 nm), 73+/-7% (1 microm) or 89+/-7% (10 microm). Pimozide (500 nm) use dependently inhibited the Ca(2+) response by 85+/-1%. 5. Nifedipine (1 microm) inhibited the Ca(2+) response to 75 mm K(+) by 41+/-12%. The response was not inhibited by calciseptine (500 nm), omega-agatoxin IVA (100 nm), omega-conotoxin MVIIA (500 nm), or SNX-482 (100 nm). 6. Using reverse transcriptase-polymerase chain reaction, it was shown that neither Ca(V)2.1a (P-type) nor Ca(V)2.1b (Q-type) voltage-dependent Ca(2+) channels were expressed in mesenteric arterioles, whereas the Ca(V)3.1 (T-type) channel was expressed. Furthermore, no amplification products were detected when using specific primers for the beta(1b), beta(2), or beta(3) auxiliary subunits of high-voltage-activated Ca(2+) channels. 7. The results suggest that the voltage-dependent Ca(2+) channel activated by sustained depolarization in mesenteric arterioles does not classify as any of the high-voltage-activated channels (L-, P/Q-, N-, or R-type), but is likely to be a T-type channel. The possibility that the sustained Ca(2+) influx observed was the result of a T-type window current is discussed.

Mesenteric artery remodeling and effects of imidapril and irbesartan on it in spontaneously hypertensive rats

AIM: To investigate the remodeling of mesenteric artery and the expression of TGF-β₁, c-Jun in mesenteric artery and effects of imidapril and irbesartan on the remodeling in spontaneously hypertensive rats (SHR).

METHODS: Thirty SHR (male/female, 21/9), aged 13 wk, were randomly divided into 3 groups (7 male rats and 3 female rats each group): SHR group, imidapril group (imidapril 3 mg/kg·d was given in drinking water for 14 wk), and irbesartan group (irbesartan 50 mg/kg·d was given in drinking water foe 14 wk). Ten homogenous Wistar Kyoto rats, 5 males and 5 females, weighing 206 ± 49 g, were selected as normal control group (WKY group). Systolic pressure was measured on day 1, 2, 4, 6, 8, 10, 12 and 14 during the experiment and the rats were killed at the end of the experiment. Angiotensin II (Ang II) level in plasma and mesenteric arteries was measured by radioimmunoassay. The morphology of the secondary branches of mesenteric artery were examined by light microscopy and electron microscopy. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the expression of transforming growth factor TGF-β₁ and c-Jun mRNA.

RESULTS: Compared with imidapril group and irbesartan group, the blood pressure was remarkably increased in SHR group. Ang II level in plasma and mesenteric arteries in SHR group was the same or lower than that in WKY group, and was higher in irbesartan group and lower in imidapril group. The remodeling of mesenteric arteries in SHR group was mostly obvious among the 4 groups. The ratio of TGF-β₁ absorbed light value to GAPDH absorbed light value in the SHR group was 0.887 ± 0.019, which was significantly higher than that in WKY group, imidapril group, and irbesartan group with the ratios of 0.780 ± 0.018, 0.803 ± 0.005, and 0.847 ± 0.017, respectively (P < 0.01). Ang II level in plasma and mesenteric arteries in imidapril group was significantly lower than that in irbesartan group (P < 0.05). The c-Jun absorbed light value/GAPDH absorbed light value of mesenteric arteries in the SHR group was 0.850 ± 0.015, which was significantly higher than that in the WKY, imidapril, and irbesartan groups (0.582 ± 0.013, 0.743 ± 0.012, and 0.789 ± 0.013, respectively, P < 0.01), and was significantly lower in imidapril group than in irbesartan group (P < 0.05).

CONCLUSION: Imidapril and irbesartan can not only control blood pressure but also inhibit mesenteric arteries remodeling and mRNA expression of TGF-β₁, c-Jun in SHR. Imidapril is more effective than irbesartan.

Effect of age on mechanical properties of rat mesenteric small arteries

With aging, large arteries become stiffer and systolic blood pressure consequently increases. Less is known, however, about the age-related change in mechanics of small resistance arteries. The aim of this study was to determine whether aging plays a role in the stiffening of the small mesenteric arteries of rats. Intra-arterial systolic, diastolic, mean and pulse pressures were measured in male Wistar rats aged 2, 4, 15 and 26 months. The passive mechanical properties of the wall of isolated perfused and pressurized arterial segments of mesenteric small arteries were also investigated. Intra-arterial systolic, diastolic and mean blood pressures tended to decrease with age and were significantly lower in the oldest rats (26-month-old group). Pulse pressure was significantly higher in the 15- and 26-month-old groups than in the two younger groups. Under isobaric conditions, increasing age is associated with an outward hypertrophic remodeling of the mesenteric arteries. Under relaxed conditions, incremental distensibility in response to increasing intravascular pressure did not change with aging. As a function of strain (under isometric conditions), stress shifted to the left as age increased, indicating an age-related vascular stiffening. Under isobaric conditions or in relation to wall stress, the elastic modulus was greater in the adult 15-month-old rats than in the younger rats. These findings suggest that distensibility seems to be preserved with aging, despite stiffness of the wall components, probably by arterial wall geometric adaptation, which limits the pulse pressure damage. It is interesting to note that elastic modulus in mesenteric arteries from the oldest rats (26-month-old), examined in relation to wall stress and intravascular pressure, did not differ from that of the youngest rats, thus suggesting that elasticity of wall components had been restored.Key words: age, arteries, elastic modulus, stiffness, pressure.

Dopamine D 1 Receptor Augmentation of D 3 Receptor Action in Rat Aortic or Mesenteric Vascular Smooth Muscles

Dopamine is an important modulator of blood pressure, in part, by regulating vascular resistance. To test the hypothesis that D 1 and D 3 receptors interact in vascular smooth muscle cells, we studied A10 cells, a rat aortic smooth muscle cell line, and rat mesenteric arteries that express both dopamine receptor subtypes. Fenoldopam, a D 1 -like receptor agonist, increased both D 1 and D 3 receptor protein in a time-dependent and a concentration-dependent manner in A10 cells. The effect of fenoldopam was specific because a D 1 -like receptor antagonist, SCH23390 (10 −7 M/24 h), completely blocked the stimulatory effect of fenoldopam (10 −7 M/24 h) (D 3 receptor: control=21±1 density units [DU]); SCH23390=23±2 DU; fenoldopam=33±2 DU; fenoldopam+SCH23390=23±2 DU; n=10). D 1 and D 3 receptors physically interacted with each other because fenoldopam (10 −7 M/24 h) increased D 1 /D 3 receptor coimmunoprecipitation (35±5 versus 65±5 DU; n=8). A D 3 receptor agonist, PD128907, relaxed mesenteric arterial rings independent of the endothelium, effects that were blocked by a D 3 receptor antagonist, U99194A. Costimulation of D 1 and D 3 receptors led to additive vasorelaxation. We conclude that the D 1 receptor regulates the D 3 receptor by physical interaction and receptor expression. D 1 receptor stimulation augments D 3 receptor vasorelaxant effects. An interaction of D 1 and D 3 receptors may be involved in the regulation of blood pressure.

Configurational anatomy of the pancreas: its surgical relevance from ontogenetic and comparative-anatomical viewpoints

The structure of the adult human pancreas retains develop-mental traits in ontogenesis and comparative anatomy, under-standing of which greatly contributes to pancreatic surgical anatomy. The pyramidal process called the "auricle" or "ear"at the inferior margin of the neck suggests the vestige of the ontogenetic twist at the neck, resulting from bursal bulging with rotation of the pancreatic body and tail. This anatomical consideration serves to avoid inadvertent bleeding or pancreatic fistula during dissection of the right gastroepiploic arteryand vein at their roots. Recognition of embryonic rotation of the gastrointestinal tract eases detachment of the pancreati-coduodenal and jejunal vessels at their origins, enabling "reversed Kocherization" and complete resection of the mesoduodenum and upper mesojejunum. Embryological knowledge of vascular arcades of the pancreatic head serves as a guide for limited resection of the pancreas. The anterior inferior pancreaticoduodenal artery often runs behind, not in front of, the lower portion ("mentum" or "chin") of the pancreatic head, but still on the anterior leaflet of the embryonic mesoduodenum. The attachment of the adult pancreatic head to the duodenum occurs only at the major papilla of Vater and at the region around the minor papilla, which seems to be rational from ontogenetical and comparative-anatomical aspects. Knowledge of the pancreatic attachment helps when performing duodenum-preserving pancreatectomy and pancreas-sparing duodenectomy. The "lingula" or "small tongue", a pancreatic portion overlapping the common bile duct on the posterior aspect of the pancreas, is a key structure in resection of the extrahepatic bile duct.

Uterine artery structural and functional changes during pregnancy in tissue kallikrein-deficient mice

OBJECTIVE

Tissue kallikrein (TK) participates in acute flow-induced dilatation (FID) of large arteries. We investigated whether TK deficiency blunts FID and alters chronic flow-related arterial structural and functional changes in resistance-sized muscular arteries.

METHODS AND RESULTS

Vasomotor responses and structural parameters were determined in uterine arteries isolated from nonpregnant, 18- to 19-day pregnant, and 7-day postpartum TK-/- and TK+/+ littermate mice. In TK-/- mice, values of diameter, medial cross-sectional area (CSA), myogenic tone, and dilatation in response to acetylcholine were comparable to those values in TK+/+ mice, but FID (0 to 100 microL/min) was significantly reduced (55+/-4% versus 85+/-4% in TK+/+ mice). In both mouse strains, pregnancy resulted in significant increases in diameter and medial CSA and in the Nw-nitro-l-arginine methyl ester-sensitive component of FID. By 7 days after pregnancy, uterine arterial diameter and CSA values no longer differed from nonpregnant values, and FID was markedly reduced in TK-/- and TK+/+ mice.

CONCLUSIONS

These observations (1) confirm at the level of resistance arteries the key role of TK in FID and (2) indicate that TK deficiency does not compromise arterial remodeling and changes in the contribution of NO to FID during and after pregnancy.

Are there any structural alterations in a neovascularized jejunal segment by omentoenteropexy? A histologic and immunohistochemistry study

BACKGROUND/PURPOSE

Although the bowel neovascularization by omentoenteropexy seems to be a good alternative to bowel lengthening, there were no rigorous analyses about its histologic structure and intrinsic innervation. The aim of this study was a histologic and immunohistochemical analysis of a neovascularized jejune segment (NJS) by omentoenteropexy.

METHODS

An NJS was done by omentoenteropexy in 13 Wistar rats. Seven weeks afterward, the mesentery of the NJS was ligated and divided. The NJS was separated from the normal jejunum by proximal and distal complete sections. End-to-end anatomosis was done between NJS and normal jejunum to restore bowel continuity. Twenty-six rats were sham operated. At 10 weeks, specimens were taken, and H&E, S-100 protein, and neuron-specific enolase staining were done. The muscle layer thickness, mucosae layer, and myenteric plexus were analyzed. The statistical tests were the Mann-Whitney test, Friedman's test, and Spearman's correlation.

RESULTS

There was a significant increase in NJS diameter. The muscle layers and mucosa were greater in the study group. The average number of neurons per intestinal ganglion was significantly fewer in the NJS.

CONCLUSIONS

Omentoenteropexy provoked an increase in the diameter of NJS and contributed toward a reduction of the number of neurons in the myenteric plexus of NJS.

Endothelin antagonism on aldosterone-induced oxidative stress and vascular remodeling

Endothelin A (ETA) receptor blockade has prevented vascular remodeling in aldosterone and salt-induced hypertension. To evaluate effects of the ETA receptor antagonist, BMS 182874, compared with the aldosterone antagonist, spironolactone, on vascular remodeling in aldosterone-infused rats not exposed to a high salt diet, Sprague-Dawley rats were infused subcutaneously with aldosterone (0.75 microg/h) and treated with BMS 182874 (40 mg. kg-1. d-1), spironolactone, or hydralazine (both 25 mg. kg-1. d-1) while receiving a normal salt diet for 6 weeks. Aldosterone increased systolic BP (P<0.01), plasma endothelin (3.33+/-0.32 versus 1.85+/-0.40 pmol/L in control, P<0.05), systemic oxidative stress as shown by plasma thiobarbituric acid-reacting substances and vascular nicotinamide adenine dinucleotide phosphate (NADPH) activity. Aldosterone increased small artery media thickness (17.7+/-0.9 versus 13.6+/-0.8 microm in control, P<0.05) and media/lumen ratio (7.6+/-0.4 versus 5.5+/-0.4% in control, P<0.05), with growth index of 21% indicating hypertrophic remodeling. Laser confocal microscopy showed increased collagen and fibronectin deposition and intercellular adhesion molecule-1 (ICAM-1) content in the vessel wall of aldosterone-infused rats. The 3 treatments lowered BP, although hydralazine was slightly less effective. BMS 182874 and spironolactone decreased oxidative stress, normalized the hypertrophic remodeling, decreased collagen and fibronectin deposition, and reduced ICAM-1 abundance in the vascular wall of aldosterone-infused rats, whereas hydralazine only reduced NADPH activity in aorta but did not affect the remaining parameters. Vascular remodeling of small arteries occurs in aldosterone-infused rats exposed to a normal salt diet and may be mediated in part by ET-1 via stimulation of ETA receptors. Endothelin blockade may exert beneficial effects on vascular remodeling, fibrosis, oxidative stress, and adhesion molecule expression in aldosterone-induced hypertension.

Anatomical study of the pancreas in the house musk shrew (Suncus murinus), with special reference to the blood supply and innervation

To examine the macroscopic structure, blood supply, and innervation of the pancreas in the house musk shrew (Suncus murinus), we performed gross anatomical dissection and whole-mount immunostaining of the autonomic nerve of Suncus pancreases based on neurofilament protein (NFP) immunoreactivity. The adult Suncus pancreas is clearly separated into right and left lobes that are not fused. The right lobe of the Suncus pancreas is located in the dorsum of the duodenum and to the right of the common bile duct independently. The right lobe is supplied by branches of the superior mesenteric artery, and is innervated by branches that originate from the superior mesenteric plexus and run along the arterial branches of the superior mesenteric artery. The left lobe occupies 9/10 of the entire pancreas and is located to the left of the common bile duct. It is supplied mainly by branches of the splenic and common hepatic arteries, and is innervated by branches that originate from the celiac plexus and run along the splenic and common hepatic arteries. According to previous studies on the blood supply and innervation of the human pancreas, the right and left lobes of the Suncus pancreas correspond to the pancreatic parts derived from the ventral and dorsal pancreatic buds. The current results suggest that the Suncus pancreas is a suitable experimental model for studying the development of the human pancreas.

Pressure-induced activation of extracellular signal-regulated kinase 1/2 in small arteries

Extracellular signal-regulated kinase 1/2 (ERK1/2) may play a central signaling role in vascular remodeling. We investigated a possible combined role for the renin-angiotensin system and platelet-derived growth factor beta-receptor (PDGF-beta-R) in pressure-induced ERK1/2 activation in intact rat mesenteric small arteries. In an organ culture model, vessels were pressurized (70 mm Hg) for 1 hour plus a 5-minute intervention period. The intervention was either a rise in intraluminal pressure (up to 140 mm Hg) or challenge with angiotensin II (Ang II, 0.1 micromol/L) or PDGF-BB (30 microg/L). ERK1/2 activation was determined by Western blotting as formation of phosphorylated ERK1/2. All interventions caused ERK1/2 activation that was inhibited by the MEK inhibitor PD98059. The response to pressure was inhibited by an ACE inhibitor (perindoprilat), an Ang II receptor type 1 (R-AT1) antagonist (candesartan), and tyrosine kinase inhibitors (genistein, herbimycin A). An R-AT2 antagonist (PD123319) had no significant effect. Both a PDGF-receptor tyrosine kinase inhibitor (RPR101511A) and a neutralizing PDGF-beta-R antibody (AF385) inhibited the activation of ERK1/2 caused by PDGF-BB, Ang II, and pressure. That the latter interventions could indeed inhibit the PDGF-beta-R was supported by experiments with unmounted vessels in which PDGF-beta-R activation was measured by Western blot; both PDGF-BB and Ang II-mediated PDGF-beta-R activation were inhibited by RPR101511A and AF385. Immunohistochemistry showed that ERK1/2 and PDGF-beta-R was located in the adventitia, tunica media, and intima. The results suggest that pressure in rat mesenteric small arteries causes acute activation of ERK1/2 through pathways involving Ang II and PDGF-beta-R.

Cyclooxygenase-2 expression and role of vasoconstrictor prostanoids in small mesenteric arteries from patients with Crohn's disease

BACKGROUND

The present study investigates the vascular reactivity and the involvement of nitric oxide and prostanoids in regulating vasoconstriction of small mesenteric arteries from patients with Crohn's disease (CD) to understand the vascular component of this pathology.

METHODS AND RESULTS

An increased production of proinflammatory cytokines (tumor necrosis factor-alpha and interleukins 1beta, 6, and 8) has been observed in biopsy specimens of inflammatory intestinal mucosa. However, contractile responses of small mesenteric arteries from CD patients in response to norepinephrine were not changed ex vivo when compared with controls. Exposure to either the nitric oxide synthase inhibitor N(G)-nitro-L-arginine or the cyclooxygenase (COX) inhibitor indomethacin did not modify contractions induced by norepinephrine in either control or CD patients. However, in the latter, the specific COX-2 inhibitor N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide significantly attenuated norepinephrine-induced vasoconstriction. Furthermore, immunohistochemical analysis showed marked COX-2 expression in the whole arterial wall of vessels from CD patients. Vessels from control patients exhibited weak COX-2 staining in the adventitial and endothelial layers only.

CONCLUSIONS

The above results provide direct evidence for COX-2 expression in small mesenteric arteries from CD patients. They also shed new light on the involvement of vasoconstrictor metabolites of COX in regulating contraction of these arteries. Of particular interest is the balance between vasoconstrictor products from COX-2 and unidentified vasodilatory products that maintained vascular reactivity in a physiological range despite an increase of circulatory cytokines in patients with CD.

Development of the myogenic response in postnatal intestine: role of PKC

Previous attempts to determine developmental changes in the vascular myogenic response have been confounded by the presence of competing vasoactive stimuli or the use of isolated vessels with markedly different baseline diameters. To circumvent these issues, small mesenteric arteries (diameter approximately 150 microm) from 1- and 10-day-old piglets were studied in vitro under no-flow conditions. In situ studies demonstrated that the intravascular pressure and diameter of these vessels were similar in both age groups, allowing an effective comparison of the myogenic response not obscured by differences in basal diameter. The pressure-diameter relationship was age specific. Thus, although small mesenteric arteries from both age groups demonstrated myogenic constriction in response to stepwise increases in pressure (0 to 100 mmHg, in 20-mmHg increments), the intensity of contraction was significantly greater in vessels from 1-day-old piglets particularly within the pressure range normally experienced by these vessels in situ. Attenuation or activation of PKC with calphostin C or indolactam, respectively, substantially altered the pressure-diameter relationship in 1-, but not 10-day-old arteries; thus calphostin C essentially eliminated the contractile response to pressure elevation in younger subjects, whereas indolactam significantly increased the intensity of the myogenic response and shifted its activation point to a lower pressure range. Immunoblots carried out on protein recovered from these arteries revealed the presence of alpha, beta, epsilon, iota, and lambda; notably, expression of the alpha- and epsilon-isoforms substantially decreased between postnatal days 1 and 10.

Altered structure and distensibility of arteries in salt-fed rats

BACKGROUND AND OBJECTIVES

Habitual high-sodium diet may cause stiffening of arteries. The aim of this study was to investigate the long-term effects of physiologically relevant high-sodium diet on the structure and distensibility of arteries in rats.

METHODS

Adult male Sprague-Dawley rats were fed 2% NaCl diet for 3 or 6 months; rats fed 0.7% NaCl diet were controls. Pressure-volume (distensibility) relationships were measured in the presence and absence of calcium in excised, in-vitro perfused segments of right carotid artery and of second order mesenteric arteries. The left carotid artery and the remaining mesenteric arteries of rats were perfused in situ with papaverine followed by fixative at 100 mmHg, and then embedded in epoxy for morphometric measurements.

RESULTS

The tail systolic blood pressure (SBP), and in subgroups of rats, the directly measured mean arterial pressure (MAP), of salt-fed rats at 3 and 6 months were unchanged. At 3 months, there was dilatation (increased lumen area) of both carotid and mesenteric arteries of salt-fed rats, without a change in distensibility. At 6 months, the lumen area of carotid arteries of salt-fed rats returned to control value (inward remodeling), and carotid artery distensibility remained unchanged. At 6 months, there was further dilatation (P <0.01) and reduced distensibility (P =0.01) of mesenteric arteries in salt-fed rats.

CONCLUSIONS

A three-fold increase in dietary sodium intake leads to dilatation of arteries in normotensive rats. When there is compensatory remodeling, the distensibility of arteries remains unchanged; when compensation is lacking, unopposed dilatation is associated with reduced distensibility.

Coexistence of multiple anomalies in the celiac-mesenteric arterial system

The origins and distribution of arteries of the celiac-mesenteric system were examined by dissection of 52 formalin-fixed human cadavers. Seventy-five percent of the cadavers exhibited the classic Michels' Type I hepatolienogastric pattern; 25% had different branching patterns. Multiple anomalies of the celiac-mesenteric arterial system were observed in one Caucasian female cadaver: a short lienogastric trunk; a common hepatic artery arising directly from the abdominal aorta; an anomalous course of the hepatic arteries; an accessory left hepatic artery arising from the left and right gastric arterial anastomosis along the lesser curvature of the stomach; a double cystic artery; a common inferior phrenic trunk arising from the celiac trunk; and an aberrant arterial channel connecting the proximal segments of the splenic and gastroduodenal arteries. A patent ductus venosus and an anomalous formation of the portal vein by the confluence of the splenic and superior and inferior mesenteric veins was also observed. Although single anomalies of the celiac-mesenteric arterial system are common, complex combinations, such as were observed in the present case, represent a significant deviation from the normal developmental pattern. There seems to be no report in the literature of such a combination of anomalies coexisting in one individual. The developmental and clinical significance of these anomalous vessels is discussed.

Canine mesenteric artery and vein convey no difference in the content of major contractile proteins

BACKGROUND

Mesenteric arteries and veins are composed of tonic smooth muscles and serve distinct functions in the peripheral circulation. However, the basis for the functional disparity of the resistive and capacitative parts of the mesenteric circulation is poorly understood. We studied potential differences in the expression levels of six contractile proteins in secondary and tertiary branches of the inferior mesenteric artery and vein along with differences in the vessel wall morphology.

RESULTS

Bright field and electron microscopy showed that both vessel walls had the same major structural elements. The arterial walls, however, had greater number, and more tightly assembled, smooth muscle cell layers compared to vein walls. The content of actin, myosin heavy chain, myosin light chain, and calponin was similar in the two blood vessels. The artery expressed higher amount of the actin-binding protein caldesmon than the vein (41.86 +/- 2.33 and 30.13 +/- 3.37 microg/mg respectively, n = 12). Although the total tropomyosin content was almost identical in both blood vessels, the alpha isoform dominated in the artery, while the beta isoform prevailed in the vein.

CONCLUSIONS

Canine mesenteric artery and vein differ in vessel wall morphology but do not convey differences in the expression levels of actin, myosin light chain, myosin heavy chain and calponin. The two vascular networks express distinct amounts of caldesmon and tropomyosin, which might contribute to the fine tuning of the contractile machinery in a manner consistent with the physiological functions of the two vascular networks.

MR angiography of the mesenteric vasculature

MRA has evolved from a research tool to a robust clinical diagnostic modality. In many centers worldwide, it is the technique of choice for evaluating patients with suspected CMI, assessing operability of patients with pancreatic cancer, and investigating the portal system. Evolving indications include the assessment of liver transplant patients before and after transplant and of living related liver transplant donors. The search for the bleeding source in patients with gastrointestinal hemorrhage may be an indication in the future, once intravascular contrast agents become available.

Magnesium supplementation and deoxycorticosterone acetate--salt hypertension: effect on arterial mechanical properties and on activity of endothelin-1

The aim of this study was to show whether the decrease in blood pressure induced by Mg supplementation in deoxycorticosterone acetate - salt (DOCA-salt) hypertensive rats is associated with mechanical modifications of blood vessels and (or) changes in tissular production and (or) vasoconstrictor activity to endothelin-1. DOCA-salt treatment increased blood pressure, media thickness, cross-sectional area, and lumen diameter of carotid arteries. Distensibility and incremental elastic modulus versus stress were not altered in carotid arteries, suggesting that the DOCA-salt vessel wall adapts structurally to preserve its blood pressure buffering capacity. Magnesium supplementation attenuated DOCA-salt hypertension. In comparison with normotensive rats, systolic, mean, and pulse pressures were higher whereas diastolic pressure was not different in Mg-supplemented DOCA-salt rats. Magnesium supplementation did not significantly modify the elastic parameters of carotid arteries. In resistance mesenteric arteries, DOCA-salt hypertension induces an inward hypertrophic remodeling. Magnesium supplementation attenuates wall hypertrophy and increases lumen diameter to the normotensive diameter, suggesting a decrease in peripheral resistance. Magnesium supplementation normalizes the altered vasoconstrictor activity of endothelin-1 in mesenteric arteries and attenuates endothelin-1 overproduction in kidney, left ventricle, and aorta of DOCA-salt rats. These findings suggest that Mg supplementation prevents blood pressure elevation by attenuating peripheral resistance and by decreasing hypertrophic effect of endothelin-1 via inhibition of endothelin-1 production.

Age-related changes of dopamine receptor protein immunoreactivity in the rat mesenteric vascular tree

Dopamine D1-D5 receptor protein immunoreactivity and tyrosine hydroxylase (TH) immunoreactivity were investigated on the mesenteric arterial tree by immunohistochemistry. The density of various dopamine receptors and TH immunoreactivity was compared between young (6-month-old), adult (15-month-old) and senescent (24-month-old) Fischer 344 rats by computer-assisted microdensitometry. The dopamine D1-like (D1 and D5) receptors were localized on the tunica media of different sized mesenteric artery branches. The D2-like (D2, D3 and D4) receptors as well as TH immunoreactivity were localized only on the adventitia-media transitional zone of mesenteric arterial tree. Expression of the D1 and D5 receptors was decreased in both adult and senescent rats compared to the young rats, suggesting an age-related decline in these receptors. Of the D2-like receptors, the expression of the D2 receptor was decreased as a function of age, while the D3 receptor was unchanged in the senescent rats compared to the young rats. Expression of the D4 receptor was increased in adult, but was unchanged in the senescent rats compared to young animals. TH immunoreactivity was increased as a function of age. The above data suggest that reduction in the D1, D2 and D5 receptor expression may contribute to the deficiency in the dopamine-mediated vasorelaxation and hence blood flow in the mesenteric vascular tree in aging. The different sensitivity to aging of sympathetic neuroeffector junctions labeled by TH and of dopamine D2-like receptors that are known to be prejunctional, suggests that age-related changes of dopamine receptor expression in the mesenteric vasculature reflect more complicated mechanisms than simple up- or down-regulation phenomena.

Mesenteric paraganglioma: a case report and review of the literature

Approximately 5% to 10% of paragangliomas occur in extra-adrenal sites, which can extend from the upper cervical region to the pelvis, parallel to the autonomic nervous system. This distribution corresponds to the embryologic development of the paraganglia from neural crest cells. Rarely, extra-adrenal paragangliomas can also occur aberrantly outside this distribution. We report such a case of extra-adrenal paraganglioma occurring in the anterior mesentery in a 76-year-old man. Two case reports exist in the literature describing extra-adrenal paragangliomas in the posterior mesentery. Normal paraganglionic tissue has been described at the roots of the superior and inferior mesenteric arteries, theoretically explaining the origin of the posterior mesenteric paragangliomas. Our case can best be attributed to the ventral migration of paraganglionic tissue through these vessels to reach the anterior mesentery, where they could potentially give rise to paragangliomas in this site.

Selective microvascular dysfunction in mice lacking the gene encoding for desmin

The intermediate filament desmin has a key role in the integrity and contractility of skeletal and cardiac myocytes. Its absence or aggregation leads to cardiomyopathies. In arteries desmin is distributed heterogeneously; vascular disorders might also occur in its absence. We studied endothelial and muscular functions in arteries from mice lacking desmin (des-/-), compared with control (des+/+). Carotid and mesenteric resistance arteries were mounted in vitro in arteriographs. Desmin was located exclusively in smooth muscle cells. In arteries from des-/- mice, pressure-induced (myogenic) tone was unchanged, but agonist-induced tone decreased in resistance arteries (no change in large arteries). Flow (shear stress)- and acetylcholine-induced, endothelium-dependent dilation, as well as endothelium-independent dilation, were also decreased in resistance arteries. To our knowledge, this is the first study of vascular contractile and dilatory functions in arteries lacking desmin. Although vascular reactivity was normal in large arteries, it decreased strongly in small resistance arteries. Thus, desmin is required in vascular smooth muscle cells and in resistance arteries, for efficient control of vascular tone and consequently for an optimal blood flow supply. This microvascular defect found in the absence of desmin might play a major role in myopathies seen in desmin-related diseases.

Volume-rendered 3D CT of the mesenteric vasculature: normal anatomy, anatomic variants, and pathologic conditions

Multi-detector row computed tomography (CT) offers important advantages over more conventional imaging methods in the evaluation of the mesenteric vasculature. It allows faster scanning, which practically eliminates motion and breathing artifacts, as well as thinner collimation. These advances, coupled with rapid intravenous administration of contrast material, allow excellent opacification of the mesenteric arteries and veins. This improves the quality of the three-dimensional (3D) data sets, which in turn leads to improved 3D vascular maps and more accurate assessment of various conditions such as arterial or venous encasement in patients with pancreatic cancer, mesenteric ischemia, or inflammatory bowel disease. Three-dimensional multi-detector row CT also allows better visualization of arterial and venous branching, thereby improving detection of more distal vascular involvement. In addition, 3D multi-detector row CT may help detect hemodynamic changes in patients with active inflammation and hyperemia of a bowel segment because it can be used to measure bowel wall enhancement over time. Carcinoid tumors that have infiltrated the mesentery have a characteristic CT appearance, and other conditions such as lymphoma or sclerosing mesenteritis can also manifest as an infiltrating mass that envelops mesenteric vessels. Three-dimensional multi-detector row CT represents a significant advance in CT technology and can help ensure prompt, accurate evaluation of the mesenteric vasculature.

Blood pressure and mesenteric resistance arterial function after spaceflight

Ground studies indicate that spaceflight may diminish vascular contraction. To examine that possibility, vascular function was measured in spontaneously hypertensive rats immediately after an 18-day shuttle flight. Isolated mesenteric resistance arterial responses to cumulative additions of norepinephrine, acetylcholine, and sodium nitroprusside were measured using wire myography within 17 h of landing. After flight, maximal contraction to norepinephrine was attenuated (P < 0.001) as was relaxation to acetylcholine (P < 0.001) and sodium nitroprusside (P < 0.05). At high concentrations, acetylcholine caused vascular contraction in vessels from flight animals but not in vessels from vivarium control animals (P < 0.05). The results are consistent with data from ground studies and indicate that spaceflight causes both endothelial-dependent and endothelial-independent alterations in vascular function. The resulting decrement in vascular function may contribute to orthostatic intolerance after spaceflight.

The arterial supply of Meckel's diverticulum in geese (Anser anser domesticus)

This study was carried out to describe the arterial supply of Meckel's diverticulum (MD) in geese, using 36 adult healthy geese of both sexes, 50 to 52 weeks of age. The arterial supply of MD was classified into three types, In the first type, MD was supplied by a very distinct branch from the cranial mesenteric artery in 21 geese. In the second type, it was supplied by one terminal branch from the cranial mesenteric artery in 9 geese. In the third type, it was supplied both by one branch from the jejunal artery and by terminal branch from the cranial mesenteric artery in 6 geese. Based on the these types, we found significant differences (p < or = 0.01) in the length of MD between type I and II. The blood supply of the third type was observed more frequently in the male than in the female. Results from this study may contribute to the anatomical knowledge of arterial supply of MD in the geese.