Responses of human basilar arteries to vasoactive intestinal polypeptide

The responses to 9 X 10(-7) M vasoactive intestinal polypeptide (VIP) by isolated human basilar arteries of 30 individuals were studied to further elucidate the role the peptide might play in modifying cerebrovascular tone normally and in disease. In most experiments the artery was precontracted with prostaglandin F2 alpha (PGF2 alpha), either with 1 or 2 X 10(-6) M or with 10(-5) M PGF2 alpha. The course of action to VIP was observed for 15 min following its application to the contracted vessel. Some arteries failed to respond to VIP (13%), otherwise the arteries relaxed 44% when the contraction was induced by 10(-5) M PGF2 alpha and 67.6% after the lower concentrations of PGF2 alpha. There was no significant decrement in the vasorelaxant effect of VIP throughout the period of observation. A second and third application of VIP to the precontracted artery produced significantly less of an effect than the first, but no consistent progressive pattern of tachyphylaxis was evident. In additional experiments, indomethacin (10(-5) M) did not prevent the vasorelaxant effect of VIP, suggesting that prostanoid synthesis was not involved. Pretreatment of the artery with VIP did not prevent the contractions generated by 10, 30, 50 and 90 mM KCl while antithrombin III (1.2 X 10(-7) M) did, indicating fundamental differences between these two vasorelaxants. In conclusion, VIP will inhibit contraction of isolated human cerebral arteries for prolong periods and could be a significant factor regulating cerebral blood flow in humans.     

Numerical simulations of the blood flow through vertebral arteries

Vertebral arteries are two arteries whose structure and location in human body result in development of special flow conditions. For some of the arteries, one can observe a significant difference between flow rates in the left and the right arteries during ultrasonography diagnosis. Usually the reason of such a difference was connected with pathology of the artery in which a smaller flow rate was detected. Simulations of the flow through the selected type of the vertebral artery geometry for twenty five cases of artery diameters have been carried out. The main aim of the presented experiment was to visualize the flow in the region of vertebral arteries junction in the origin of the basilar artery. It is extremely difficult to examine this part of human circulation system, thus numerical experiments may be helpful in understanding the phenomena occurring when two relatively large arteries join together to form one vessel. The obtained results have shown that an individual configuration and diameters of particular arteries can exert an influence on the flow in them and affect a significant difference between flow rates for vertebral arteries. It has been assumed in the investigations that modelled arteries were absolutely normal, without any pathology. In the numerical experiment, the non-Newtonian model of blood was employed.     

Endothelium-independent and -dependent contractions induced by endothelin-1 in canine basilar arteries

Endothelium-dependence of contractile responses to endothelin-1 was examined in isolated canine basilar arteries. Within 2 hrs after mounting tissue preparations, endothelin-1 (10(-9) M) caused a monophasic tonic contraction that developed very slowly and was sustained in intact and endothelium-removed arteries. More than 5 hrs after tissue mounting, endothelin-1 (10(-9) M) caused a biphasic contraction consisting of phasic and tonic components in intact arteries, and caused a monophasic tonic contraction in endothelium-removed arteries. This phasic component was significantly decreased by aspirin (5 x 10(-5) M,), OKY-046 (10(-5) M) (a TXA2 synthetase inhibitor) and ONO-3708 (10(-8) M) (a TXA2 antagonist). The present experiments demonstrate that endothelin-1 causes an endothelium-independent tonic contraction and an endothelium-dependent phasic contraction in canine basilar arteries, and suggest that TXA2 plays a role as an endothelium-derived contracting factor.     

Contractile responses to rat urotensin II in resting and depolarized basilar arteries

The effects of human urotensin II (hUII) on the vascular tone of different animal species has been studied extensively. However, little has been reported on the vasoactive effects of rat urotensin (rUII) in murine models. The aim of the present study was to investigate the effects of rUII on vasoreactivity in rat basilar arteries. Basilar arteries from adult male Wistar rats (300–350 g) were isolated, cut in rings, and mounted on a small vessel myograph to measure isometric tension. rUII concentrations were studied in both resting and depolarized state. To remove endothelial nitric oxide effects from the rUII response, we treated selected arterial rings with N_ω-nitro-L-arginine methyl ester (L-NAME). 10 μM rUII produced a potent vasoconstrictor response in rat basilar arteries with intact endothelium, while isometric forces remained unaffected in arterial rings treated with lower rUII concentrations. Although L-NAME did not have a significant effect on 10 μM rUII-evoked contraction, it slightly increased arterial ring contraction elicited by 1 μM rUII. In depolarized arteries, dose-dependent rUII increased depolarization-induced contractions. This effect was suppressed by L-NAME. Our results show that the rat basilar artery has a vasoconstrictor response to rUII. The most potent vasoconstrictor effect was produced by lower doses of rUII (0.1 and 1 μM) in depolarized arteries with intact endothelium. This effect could facilitate arterial vasospasm in vascular pathophysiological processes such as subarachnoid hemorrhage and hypertension, when sustained depolarization and L-type Ca²⁺ channel activation are present.     

Synthesis of two marine farnesylacetones that dilate the basilar arteries of rabbits

We have synthesized novel vasodilatation farnesylacetones 1 and 2, which are major active constituents of Sargassum siliquastrum collected from the coast of the East Sea in Korea, in 9 steps. A test of the vasodilatation effect of synthetic intermediates and their deprotected compounds on the basilar arteries of rabbits revealed that 14 and 14-1 have a similar dilation effect as their target marine natural products 1 and 2.     

Biomechanical properties of canine vertebral and internal carotid arteries

In order to understand the participation of the geometrical and elastic properties of the large cerebral arteries in the maintenance of brain circulatory homeostasis, biomechanical properties of isolated internal carotid artery (extracranial part) and vertebral artery (intrathoracic part) were investigated both in a relaxed and in an activated (3x 10(-6) mol.l-1 norepinephrine) state of the smooth muscle. Quasi-static large deformation mechanical test was carried out by means of changing the intraluminal pressure slowly (2.5 mmHg.sec-1) and cyclicly in a range of 0-250 mmHg at in vivo length while external diameter was recorded continuously as a function of the intraluminal pressure. Maximum active tangential strain was found to be -2.7 +/- 1.6% at 70 mmHg for the internal carotid artery, and -5.9 +/- 1.1% at 100 mmHg for the vertebral artery. Incremental elastic modulus decreased and distensibility increased in both arteries following smooth muscle activation, these alterations, however, were larger in the case of the vertebral artery. A U-shaped characteristic impedance of vertebral artery was found both in relaxed and in constricted states of this vessel. Minimum values for the relaxed and the activated segments were found at 90 mmHg and 120 mmHg, respectively. These results support the hypothesis that certain biomechanical properties of the large arteries, like impedance, can be regarded as controlled variables that may contribute to the optimization of circulatory functions.     

Surgical anatomy of the anastomotic branch between the occipital and vertebral arteries

Using anatomical material of mature persons and, for the first time, that of newborns, the discovered well developed anastomotic branch between the occipital and vertebral arteries can be considered as an anatomical variant of the vascular system, important for the collateral blood circulation. Similar branch in mature persons can also serve as an intermediate link for transmitting irritation at the neck osteochondrosis along the periarterial plexuses from the vertebral artery to the occipital one, that results in reflectory pains in the posterior area of the neck.     

Involvement of protein kinases on the upregulation of endothelin receptors in rat basilar and mesenteric arteries

Endothelin(B) (ET(B)) receptors are upregulated in experimental stroke or after 24 hrs of organ culture. This upregulation is manifested both as stronger contraction and as an increase in ET(B) receptor messenger RNA (mRNA) levels. The present study was designed to evaluate the importance of protein kinases (c-Jun N-terminal kinase [JNK], protein kinase C [PKC], and extracellular signal-regulated kinase [ERK1/2]) in ET(B) receptor upregulation after organ culture. Rat basilar and mesenteric arteries were incubated for 24 hrs in Dulbecco's modified Eagle's medium (DMEM) with or without the PKC inhibitor, RO-31-7549; the ERK1/2 inhibitor, SB386023; or the JNK inhibitor, SP600125, added 3, 6, or 12 hrs after initiation of incubation. Subsequently, vessel segments were mounted in myographs and the contractile responses to ET-1 and sarafotoxin 6c were studied. The ET(B) and ET(A) receptor mRNA levels were determined with a real-time polymerase chain reaction (PCR). The cellular localization and protein level of ET(B) receptors were evaluated by immunohistochemistry. The PKC and ERK1/2 inhibitors attenuated the contraction induced by S6c in the basilar arteries more than in the mesenteric arteries. The efficiency of the inhibitors was proportional to the incubation time. Real-time PCR showed a decrease in the ET(B) receptor mRNA levels in arteries treated with PKC or ERK inhibitors. The JNK inhibitor had a significant inhibitory effect on ET(B) receptor upregulation in the basilar arteries. Immunohistochemistry revealed that the ET(B) receptor upregulation occured in the smooth-muscle cells and that it had the same pattern as in the quantitative PCR. Our results show that the PKC, ERK1/2, and JNK are more important for the upregulation of contractile ET(B) receptors in cerebral arteries compared with mesenteric arteries. ERK1/2 seems to be more important for the ET(B) receptor upregulation, as compared with PKC and JNK. The evaluation of the time dependency suggests that the phenomenon can be reversed even after its initiation.     

Species variations in the relaxation of tail arteries to electrical stimulation

Relaxation in response to electrical stimulation has been studied in isolated tail arteries from rats, cats and pigs. Electrical stimulation elicited contractile responses in unstimulated strips, but caused frequency-dependent relaxations in tail arteries from all species studied, following contractile responses by various agents. The order of susceptibility to the relaxant effect of electrical stimulation in arteries from all three species was pig greater than cat greater than rat. Relaxations to electrical stimulation were unaffected by prior treatment of arteries with atropine, propranolol, tetrodotoxin, indomethacin, ouabain, pyrilamine and chemical denervation with 6-hydroxy-dopamine, but were prevented, dose-dependently, by cimetidine and aminophylline (antagonists of histamine H2-receptor and adenosine P1-receptor, respectively). The results suggest that relaxation of tail arteries from the rat, cat and pig in response to electrical stimulation is modulated by histamine and adenosine.     

Ionic mechanism for contractile response to hyposmotic challenge in canine basilar arteries

A hyposmotic challenge elicited contraction of isolated canine basilar arteries. The contractile response was nearly abolished by the removal of extracellular Ca²⁺ and by the voltage-dependent Ca²⁺ channel (VDCC) blocker nicardipine, but it was unaffected by thapsigargin, which depletes intracellular Ca²⁺ stores. The contraction was also inhibited by Gd³⁺ and ruthenium red, cation channel blockers, and Cl^– channel blockers DIDS and niflumic acid. The reduction of extracellular Cl^– concentrations enhanced the hypotonically induced contraction. Patch-clamp analysis showed that a hyposmotic challenge activated outwardly rectifying whole cell currents in isolated canine basilar artery myocytes. The reversal potential of the current was shifted toward negative potentials by reductions in intracellular Cl^– concentration, indicating that the currents were carried by Cl^–. Moreover, the currents were abolished by 10 mM BAPTA in the pipette solution and by the removal of extracellular Ca²⁺. Taken together, these results suggest that a hyposmotic challenge activates cation channels, which presumably cause Ca²⁺ influx, thereby activating Ca²⁺-activated Cl^– channels. The subsequent membrane depolarization is likely to increase Ca²⁺ influx through VDCC and elicit contraction. stretch-activated cation channels; Ca²⁺-activated Cl^– channels; voltage-dependent Ca²⁺ channels; large-conductance Ca²⁺-activated K⁺ channels; gadolinium     

MSCTA对基底动脉变异的初步研究及其临床意义

目的:研究MSCT血管成像对基底动脉变异的诊断价值,并探讨其临床意义.方法:回顾性分析MSCT血管成像诊断基底动脉变异120例.所有患者均采用GELightSpeed64层螺旋CT对其头颈部动脉进行CT血管成像扫描,将获得的原始数据传入AW4.2P后处理工作站,血管重建技术包括容积再现(VR)、最大密度投影(MIP)、多平面重建(MPR)及曲面重建(CPR),影像分析采用智能血管分析与目测法相结合.结果:基底动脉走行弯曲50例(42%),包括左侧凸30例(25%)、右侧凸例15例(占12.5%)、S型凸5例(3.5%);基底动脉起止点变异47例(39.3%),其中起点变异35例(29.3%)、终点变异12例(10%);基底动脉形态变异14例(11.7%),其中开窗型lO例(8.3%)、管径粗大2例(占1.7%)、管径细小2例(1.7%);基底动脉主要分支变异9例(7.5%).结论:MSCT血管成像是一种无创性诊断基底动脉变异的有效方法,能够解释临床上部分不明原因的基底动脉供血不足,具有重要的临床意义.     

Bacterial variations on the methionine salvage pathway

Background  

The thiomethyl group of S-adenosylmethionine is often recycled as methionine from methylthioadenosine. The corresponding pathway has been unravelled in Bacillus subtilis. However methylthioadenosine is subjected to alternative degradative pathways depending on the organism.     

Effect of variations in pressure and flow on the geometry of isolated canine carotid arteries

A study is described in which the effects of hemodynamics on arterial geometry are investigated in vitro. A novel perfusion apparatus is employed to deliver pulsatile flow through excised canine carotid arteries under carefully controlled conditions. Data of perfused vessel diameter and arterial wall thickness are derived from the radial displacement of the pulsating vessel as measured using a scanning laser micrometer whose accuracy is determined to be 0.0125 mm (0.0005 in). The results of 30 perfusion experiments suggest that the hemodynamic variables of transmural pressure, pulse pressure and flow rate influence vessel size and radial strain. The physiologic implications of these findings are discussed.     

Surgical management of chronic occlusive disease of the aortic arch vessels and vertebral arteries.

Occlusive disease of the aortic arch vessels is relatively rare and often missed initially. Of 41 patients treated surgically for this condition over a 10-year period 38 had arteriosclerotic lesions, 2 had symptoms secondary to vasculitis (Takayasu''s arteritis) and 1 had a radiation injury to a subclavian artery. In 22 cases the left subclavian artery was involved; the right subclavian and innominate arteries were the next most commonly affected. Only four vertebral stenoses were treated. Most patients presented with a combination of arm and hindbrain ischemia that was shown radiologically to be associated with a subclavian steal syndrome, but in some only isolated arm symptoms or severe vertigo alone was experienced. There was a difference in blood pressure between the arms of at least 20 mm Hg in 88% of the patients. The treatment for 28 patients was creation of a carotid-subclavian bypass, for 6 the placement of a bypass graft from the ascending aorta to the subclavian or carotid artery or both, for a 3 a subclavian endarterectomy and for 4 vertebral angioplasty. There were no operative deaths, and 90% of the grafts were patent 1 to 72 months later. however, only 30 (73%) of the patients were asymptomatic and 9 (22%) had improved.