经右股动脉行肾动脉下腹主动脉腔内球囊阻断血流的应用解剖学研究

目的探讨经右股动脉入路应用球囊导管阻断肾动脉下腹主动脉的可行性。方法解剖50例健康成人尸体标本（其中男性33例,女性17例）,测量身高;分别经血管腔内测量肾动脉下腹主动脉至右股动脉腹股沟韧带平面的长度,采用sPSs12．0统计学软件分析身高与血管长度之间的关系。结果身高与肾动脉下腹主动脉至右股动脉腹股沟韧带平面的长度之间存在直线回归及较强的相关关系。结论经右股动脉入路行血管腔内球囊阻断肾动脉下腹主动脉对于腹主动脉瘤,特别是破裂腹主动脉瘤是一个可行的安全阻断血流的方法,为临床工作提供了一个新的思路和方法。     

Dynamic model of the short-term regulation of arterial pressure in the cat

The purpose of this study was to characterise the dynamics of the short-term control of arterial pressure in the cat with the aid of a model consisting of a nonlinear negative-feedback control system. The arterial system was described by a three element windkessel model (peripheral resistance, R, aortic characteristic impedance, R_c, and total arterial compliance, C). The resistance regulation was represented by a second-order system with static gain G_R, a damping factor σ and an undamped natural frequency ω_n. The resistance gain, G_R, and the windkessel parameters were obtained from measurements of aortic and venous pressures and cardiac output in two steady states. The parameters σ and ω_n were estimated from mean pressure and mean flow during the transient from control to the new steady state. Pressure reductions averaged 10 per cent and resistance changes averaged 12 per cent. Average windkessel model parameters in the control condition were: C=(25·9±6·1) 10⁻⁶ g⁻¹ cm⁴ s², R_c=(2·51±0·53) 10³ g cm⁻⁴ s⁻¹, R=(40·9±9·8) 10³ g cm⁻⁴ s⁻¹. Average estimates of parameters of the resistance regulator were: G_R=(4·14±2·38) 10⁻³ min ml⁻¹, ω_n = 1·0 ± 1·0 rad s⁻¹, σ=0·41±0·19. A satisfactory fit was found between model predicted and measured pressure. The results suggest that the dynamic short-term control of pressure is underdamped and oscillatory. The amplitude of these oscillations is affected by arterial compliance, suggesting an interaction between the arterial system and short-term resistance regulation.     

Are isolated femoral resistance vessels or tail arteries good models for the hindquarter vasculature of spontaneously hypertensive rats?

We have investigated the extent to which the properties of small arteries from the hindquarters of spontaneously hypertensive rats (SHRs) are consistent with the characteristics of perfused SHR hindquarter preparations (for which the relaxed vascular resistance, the reactivity and the sensitivity are reported to be increased). We have therefore compared the in vitro morphological and pharmacological properties of a femoral resistance vessel (i. d. ca 200 μm) and of the tail artery (i. d. ca 600 μm) from SHRs with those from control Wistar-Kyoto rats (WKYs). When relaxed, for any given wall tension, the internal circumference of the SHR resistance vessels was reduced, but that of the SHR tail artery was normal. When activated with 10 μM noradrenaline, the SHR resistance vessels had an increased calcium sensitivity, but the calcium sensitivity of the SHR tail arteries was normal. However, the maximum response of both types of SHR vessels was such that the vessels would have been able to contract against increased transmural pressure. The noradrenaline sensitivity of the SHR resistance vessels was normal but the SHR tail arteries had a decreased sensitivity. The results suggest that the femoral resistance vessel is in general a better model for the hindquarter vasculature than the tail artery.     

Fatigue behaviour of Nitinol peripheral stents: The role of plaque shape studied with computational structural analyses

Fatigue resistance of Nitinol stents implanted into femoro-popliteal arteries is a critical issue for the particular biomechanical environment of this district. Hip and knee joint movements due to the cyclic daily activity expose the superficial femoral artery (SFA), and therefore the implanted stents, to quite large and cyclic deformations influencing stent fatigue resistance. Objective of this work is to provide a tool based on finite element analysis able to evaluate the biomechanical effect of SFA on stent fatigue resistance. Computer simulations of the treatment of stenotic vessel by angioplasty and stenting and of the subsequent in vivo loading conditions (axial compression and bending) were carried out. Three different stenotic vessel models were defined, by keeping a constant stenosis rate and changing the plaque sharpness and number of stenoses. The fatigue behaviour was analysed comparing the amplitude and mean value distribution of the first principal strain in the whole stent for the different simulated conditions. Results showed that the maximum mean strain is similar in all the models, while the alternating strain is related to both plaque shape and loading conditions. In conclusion, this study confirms the requisite of replicating in vivo loading conditions. It also reveals the importance of taking into account the thickness variation of the vessel in the stenotic zone in the assessment of the stent fatigue resistance.     

Dynamic pressure-flow diagrams and impedance in experimental arterial stenosis and in stenotic atherosclerosis

Dynamic pressure-flow diagrams were generated by plotting instantaneous pulsatile pressure versus pulsatile flow measured 2 to 3 cm proximal to a graded arterial stenosis in the dog femoral artery. The slope of the major axis of the diagram was defined as the pulse impedance (Z _P).Z _p under steady-state and vasodilated conditions was linearly related to the large vessel impedance (Z _l) calculated independently as the average vascular input impedance modulus from 3 to 19 Hz, and linearly related to the hydraulic resistance of the stenosis. In a separate study,Z _p andZ _l each were shown to be greater in patients with severe femoral artery stenotic atherosclerosis than in control patents, and unchanged during vasodilation. In addition,Z _p andZ _l were reduced following femoral-to-popliteal bypass procedures. In summary, dynamic pressure-flow diagrams provide an easy-to-obtain index of the effective vascular hydraulic input impedance in stenotic arteries, and an index of the severity of distal arterial stenosis. This research has been supported in part by the North Carolina Heart Association (Grant-in-Aid 1974-75-A-62) and the Environmental Protection Agency, Chapel Hill, North Carolina.     

Cable properties of external intercostal muscle fibres from myotonic and nonmyotonic goats

1. In preparations of about 200 fibres each from thirty-nine biopsies of external intercostal muscle taken from nine myotonic and six nonmyotonic goats, cable properties were determined at 38 degrees C for individual fibres with a pair of intracellular micro-electrodes.2. In each preparation the mean fibre dimensions, determined histologically and corrected for shrinkage, were used to calculate the mean membrane resistance, R(m), fibre capacitance, C(t), and myoplasmic resistivity, R(i). In the 124 nonmyotonic fibres the mean values were: R(m), 1897 Omega.cm(2), C(t), 4.1 muF/cm(2), and R(i), 112 Omega.cm. In 151 myotonic fibres R(m) was 5589 Omega.cm(2), C(t), 4.4 muF/cm(2), and R(i), 103 Omega.cm.3. Conductance of the fibre core times unit length increased with cross-sectional area, and fibre capacitance per unit length increased with perimeter. There was little correlation of membrane resistance per unit length of fibre with either fibre perimeter or resting potential.4. The principal abnormality of cable properties in the myotonic fibre is its threefold higher membrane resistance, which accounts for its decreased electrical current rheobase.     

正常直肠系膜横径的MRI解剖学研究

目的　基于核磁共振图像探讨正常成人直肠系膜横径及其影响因素。 方法　收集100例符合纳入标准的行盆腔MRI检查的成人临床资料进行回顾性分析。其中，男性42例，女性58例，年龄27~83岁。在轴位T1W1图像的精囊腺/子宫体层面上，测量直肠系膜最大横径、直肠最大横径、膀胱最大横径、双侧股骨头间距、前腹壁皮下脂肪厚度及女性子宫最大横径；对直肠系膜横径与其他测量指标之间的相关性进行统计学分析。 结果　（1）58例女性中，直肠系膜最大横径为（7.15±0.97）cm，子宫最大横径为（5.86±0.61）cm。直肠系膜横径与子宫横径无统计学相关性（P>0.05）。（2）合并男性、女性数据进行统计学分析。直肠系膜最大横径为（7.15±0.87）cm，直肠最大横径为（2.84±0.74）cm，膀胱最大横径为（8.58±1.66）cm，双侧股骨头间距为（12.79±0.96）cm，前腹壁皮下脂肪厚度为（2.01±0.76）cm。直肠系膜横径与性别、年龄以及膀胱横径无统计学相关性（P>0.05）；直肠系膜横径与前腹壁皮下脂肪厚度、直肠横径、双侧股骨头间距存在线性正相关（t=3.807、2.612、2.002，P<0.05）。以直肠系膜最大横径（Y）为应变量，前腹壁皮下脂肪厚度（X1）、直肠横径（X2）、双侧股骨头间距（X3）为自变量，得回归方程为：Y=3.500+0.389 X1+0.275 X2+0.163 X3，P<0.05，R2=0.522。 结论　直肠系膜横径与双侧股骨头间距、前腹壁皮下脂肪厚度及直肠横径有关。直肠系膜横径的观察和测量，可为直肠病变的诊疗提供影像学依据。     

Development of an in vivo tissue-engineered vascular graft with designed wall thickness (biotube type C) based on a novel caged mold

Small-diameter biotube vascular grafts developed by in-body tissue architecture had high patency at implantation into rabbit carotid arteries or rat abdominal aortas. However, the thin walls (34 ± 14 μm) of the original biotubes made their implantation difficult into areas with low blood flow volumes or low blood pressure due to insufficient mechanical strength to maintain luminal shape. In this study, caged molds with several windows were designed to prepare more robust biotubes. The molds were assembled with silicone tubes (external diameter 2 mm) and cylindrical covers (outer diameter 7 mm) with 12 linear windows (1 × 9 mm). After the molds were embedded into beagle dorsal subcutaneous pouches for 4 weeks, type C (cage) biotubes were obtained by completely extracting the surrounding connective tissues from the molds and removing the molds. The biotube walls (778 ± 31 μm) were formed at the aperture (width 1 mm) between the silicone rods and the covers by connective cell migration through the windows of the covers. Excellent mechanical properties (external pressure resistance, approximately 4 times higher than beagle native femoral arteries; burst strength, approximately 2 times higher than original biotubes) were obtained. In the acute phase of implantation of the biotubes into beagle femoral arteries, perfect patency was obtained with little stenosis and no aneurysmal dilation. The type C biotubes may be useful for implantation into peripheral arteries or veins in addition to aortas.     

Non-invasive evaluation of the conduit function and the buffering function of large arteries in man.

The purpose of this study was to validate a two-dimensional (2D) echography coupled range-gated Doppler system for the non-invasive measurement of internal diameter, blood flow velocity, and pulse wave velocity of peripheral arteries, such as the common carotid artery (CCA), femoral artery (FA), and brachial artery (BA) in man. The array of the ultrasonic system and the Doppler probe were attached and formed a fixed angle (38 degrees 30'). The artery was firstly visualized using the echo-graphic array probe in order to position the Doppler beam. Then, the range-gated Doppler system was used to measure both internal diameter and blood flow velocity with the sample volume position covering the internal diameter. Using a hydraulic device, there was an obvious correlation between the calculated and the measured velocities (r = 0.98). Normal values of diameter, blood flow velocity and blood flow were measured in 18 healthy volunteers. The means (+/- 1 standard deviation) was as follows: diameter, CCA = 0.636 +/- 0.027 cm, FA = 0.843 +/- 0.074 cm, BA = 0.302 +/- 0.052 cm; flow velocity, CCA = 19.5 +/- 2.1 cm s-1, FA = 11.4 +/- 1.2 cm s-1, BA = 6.7 +/- 1.0 cm s-1. Blood flows were as follows: CCA, 370.6 +/- 42.5 ml mn-1, FA 387.0 +/- 75.0 ml mn-1 and BA (wrist occlusion) 29.8 +/- 12.5 ml mn-1. The intra-observer reproducibilities for CCA, FA and BA were respectively: for diameter, 4.9%, 4.12% and 14.8%; for velocity, 8.9%, 10.6% and 10.2%. The inter-observer reproducibilities were respectively: for diameter, 5.6%, 5.4% and 11.3% for velocity, 6.5%, 5.7% and 6.3%. Simultaneous determinations of pulse wave velocity from blood flow velocity recording allowed estimations of the distensibility of these arteries. Finally, the coupled echo and range-gated Doppler system permitted non-invasive evaluation of blood flow calculated as the product of the vessel cross-sectional area and measured blood velocity and also of arterial compliance as the ratio of the cross-sectional area and the square of pulse wave velocity. Such estimations of the conduit and buffering functions of peripheral large arteries in man were shown to be more accurate for the common carotid and the femoral arteries than for the brachial artery.     

Effects of hormone replacement therapy on postmenopausal uterine myoma

OBJECTIVES: To evaluate the effects of sequential continuous hormone replacement therapy (HRT) on myoma size and on pulsatility index (PI) of uterine arteries and to verify the correlation between uterine artery flow impedance and the growth rate of myoma in women receiving HRT. METHODS: In a prospective 1-year study 60 postmenopausal women were enrolled into three study-groups to receive continuous transdermal 17beta-oestradiol 0.05 mg/day plus nomegestrolo acetate 5 mg/day sequentially added: 20 patients (group A) unaffected by uterine myomas, 20 patients (group B) with single asymptomatic myoma <3 cm/14 cm3, 20 patients (group C) with single asymptomatic myoma >3 cm/14 cm3. The changes in myoma volume and in PI were assessed by means of transvaginal ultrasonographic scan every 3 months. The patients with myoma were divided into two subgroups: quiescent myoma (B1, C1) and growing myoma (B2, C2). RESULTS: No significant increase of uterine fibroids volume was found after 1-year HRT (24.14+/-20.02-->28.81+/-30.02 cm3). Six out of eight myomas growing during HRT belonged to group C. The uterine artery basal PI value of group A was significantly higher (P<0.01) than the corresponding PI in group B and C. At 3 months follow-up, uterine artery PI was significantly higher (P<0.01) than the basal value in both group B (1.70+/-0.22-->1.88+/-0.16) and C (1.59+/-0.28-->1.92+/-0.21). The baseline PI values in group B1 and C1 were significantly higher than the baseline values observed in group B2 and C2 (1.76+/-0.17 vs. 1.32+/-0.02, 1.76+/-0.16 vs. 1.24+/-0.08) and significantly lower than those observed in group A (2.39+/-0.47). After 3 months of HRT, the PI values were not significantly higher than the baseline values in groups B1 and C2 (1.76+/-0.17-->1.90+/-0.17; 1.24+/-0.08-->1.74+/-0.16), while they were significantly higher in group C1 (1.76+/-0.16-->2.01+/-0.17). CONCLUSIONS: Sequential continuous HRT does not increase the volume of the uterine myoma. The findings of very low resistance index in the uterine arteries of women with growing myoma may indicate the risk of growth of the neoplasia during HRT. The assessment of PI in the uterine arteries could be helpful in predicting the growth rate of the myomas before starting HRT.     

A mechanical model lung for hydraulic testing of total liquid ventilation circuits

A new model lung (ML), designed to reproduce the tracheal pressure vs. fluid flow relationship in animals undergoing total liquid ventilation (TLV) trials, was developed to be used as a mock bench test for neonatal TLV circuits. The ML is based on a linear inertance-resistance-compliance (LRC) lumped-parameter model of the respiratory system with different resistance values for inspiration (R insp ) or expiration (R exp ). The resistant element was set up using polypropylene hollow fibres packed inside a tube. A passive one-way valve was used to control the resistance cross-section area provided for the liquid to generate different values for R insp or R exp , each adjustable by regulating the active length of the respective fibre pack. The compliant element consists of a cylindrical column reservoir, in which bars of different diameter were inserted to adjust compliance (C). The inertial phenomena occurring in the central airways during TLV were reproduced by specifically dimensioned conduits into which the endotracheal tube connecting the TLV circuit to the ML was inserted. A number of elements with different inertances (L) were used to simulate different sized airways. A linear pressure drop-to-flow rate relationship was obtained for flow rates up to 5 l/min. The measured C (0.8 to 1.3 mL cmH2O (-1) kg(-1)), R insp (90 to 850 cmH2O s l(-1)), and R exp (50 to 400 cmH2O s l(-1)) were in agreement with the literature concerning animals weighing from 1 to 12 kg. Moreover, features observed in data acquired during in vivo TLV sessions, such as pressure oscillations due to fluid inertia in the upper airways, were similarly obtained in vitro thanks to the inertial element in the ML.     

Ultrasound of the abdomen in endurance athletes

This project evaluated, if athletes show adaption of their abdominal organs in response to endurance training. Abdominal sonography was performed in 26 sedentary male subjects [CO; age: 26 (SD 5) years; mass (BM): 78.7 (SD 10.6) kg; lean body mass [LBM): 67.1 (SD 7.4) kg; height (HE): 183 (SD 6) cm, individual anaerobic threshold (cycle ergometry; IAT): 2.1 (SD 0.1) W·kg^–1], 14 moderately endurance trained athletes [EA1; age: 27 (SD 4) years; BM: 74.0 (SD 5.9) kg; LBM: 64.6 (SD 4.5) kg; HE: 178 (SD 5) cm, IAT: 3.0 (SD 0.5) W·kg^–1] and 27 well endurance trained athletes [EA2; age: 27 (SD 4) years; BM: 72.1 (SD 4.3) kg; LBM: 65.4 (SD 3.2) kg; HE: 179 (SD 4) cm, IAT: 3.7 (SD 0.4) W·kg^–1]. One subject of EA2 had cholecystolithiasis and another one renal redoublication, 3 persons showed uncomplicated parapelvine or subcapsular renal cysts (CO, EA1). The transverse area of the large abdominal arteries (abdominal aorta, common iliac arteries) was significantly greater in EA2 than in both EA1 and CO and partly greater in EA1 than in CO. Also, the ratios of sagittal and transverse diameters of the left and right lobes of the liver to LBM showed higher values for EA2 than for both EA1 and CO. These results indicate morphological adaptive processes of the great abdominal arteries in endurance athletes.     

Age-related changes in dorsal root ganglia,circulating and vascular calcitonin gene-related peptide (CGRP) concentrations in female rats: Effect of female sex steroid hormones

The aim of the present study is to investigate whether immunoreactive (I) calcitonin gene-related peptide (CGRP) content is decreased in plasma and mesenteric arteries (resistance arteries) in middle-aged rats and if so, whether sex steroid hormones enhance I-CGRP in middle-aged female rats. We also examined whether vascular CGRP receptor components, calcitonin receptor like receptor (CRLR) and receptor activity modifying protein 1 (RAMP₁) are elevated by sex steroid hormones treatment in middle-aged female rats. Young adult (3 months old) and middle-aged (10–12 months old) ovariectomized rats were treated subcutaneously with estradiol-17β (E₂; 2 mg), progesterone (P₄; 5 mg), E₂ + P₄ (2 mg + 20 mg) or placebo (control). Radioimmunoassay and Western blot analysis were performed to measure I-CGRP content and CGRP receptor components in dorsal root ganglia (DRG), in resistance arteries and in plasma. Immunofluorescent staining methods were employed to determine cellular localization of CRLR, RAMP₁ in resistance arteries. Our data demonstrated that I-CGRP content was significantly (p < 0.05) lower in the plasma and resistance arteries of middle-aged female rats compared to young controls. Both RAMP₁ and CRLR were concentrated in vascular endothelium and the underlying smooth muscle cells. RAMP₁ but not CRLR appeared to be decreased in middle-aged rat vasculature. Chronic perfusion of sex steroid hormones to ovariectomized rats: (1) significantly (p < 0.05) elevated I-CGRP in the DRG and in the plasma, and (2) significantly elevated RAMP₁ (p < 0.05) but did not alter CRLR in resistance arteries. These data suggest that female sex steroid treatment enhances I-CGRP and its receptors, and thus regulate the blood pressure in aged female rats.     

Effect of pressure on transmural fluid flow in different de-endothelialised arteries

The effect of pressure on filtration across different de-endothelialised arteries has been studied experimentally and the existing theoretical model is validated. Segments of different arteries are excised, de-endotheliaslised and cannulated. Bovine serum albumin Krebs solution is used as perfusate. Transmural water flux is measured by following the movement of an air bubble in a calibrated capillary, which connects the artery to a pressure reservoir; the pressure of which is varied. The hydraulic conductivity L_p is calculated from the flux values. Using available experimental parameters in the case of the thoracic and abdominal aorta, a theoretical model is validated using the experimental results. As the elastic constant for the carotid artery is not available, the theoretical model is used to calculate the elastic constant at different transmural pressures. The values calculated are in the range −4·9×10⁻⁸ to −5·7×10⁻⁹ cm² dyne⁻¹ between 50 and 135 mm Hg. Both theoretical and experimental results show a decrease in L_p values with an increase in transmural pressure for the thoracic and abdominal aorta, whereas a different trend is observed in the case of the carotid artery. The L_p values increase at 90 mm Hg, as compared with 50 mm Hg, and with a further increase in transmural pressure the values decrease.     

正常直肠系膜横径的MRI解剖学研究

目的　基于核磁共振图像探讨正常成人直肠系膜横径及其影响因素。 方法　收集100例符合纳入标准的行盆腔MRI检查的成人临床资料进行回顾性分析。其中,男性42例,女性58例,年龄27~83岁。在轴位T1W1图像的精囊腺/子宫体层面上,测量直肠系膜最大横径、直肠最大横径、膀胱最大横径、双侧股骨头间距、前腹壁皮下脂肪厚度及女性子宫最大横径;对直肠系膜横径与其他测量指标之间的相关性进行统计学分析。 结果　（1）58例女性中,直肠系膜最大横径为（7.15±0.97）cm,子宫最大横径为（5.86±0.61）cm。直肠系膜横径与子宫横径无统计学相关性（P>0.05）。（2）合并男性、女性数据进行统计学分析。直肠系膜最大横径为（7.15±0.87）cm,直肠最大横径为（2.84±0.74）cm,膀胱最大横径为（8.58±1.66）cm,双侧股骨头间距为（12.79±0.96）cm,前腹壁皮下脂肪厚度为（2.01±0.76）cm。直肠系膜横径与性别、年龄以及膀胱横径无统计学相关性（P>0.05）;直肠系膜横径与前腹壁皮下脂肪厚度、直肠横径、双侧股骨头间距存在线性正相关（t=3.807、2.612、2.002,P<0.05）。以直肠系膜最大横径（Y）为应变量,前腹壁皮下脂肪厚度（X1）、直肠横径（X2）、双侧股骨头间距（X3）为自变量,得回归方程为：Y=3.500+0.389 X1+0.275 X2+0.163 X3,P<0.05,R2=0.522。 结论　直肠系膜横径与双侧股骨头间距、前腹壁皮下脂肪厚度及直肠横径有关。直肠系膜横径的观察和测量,可为直肠病变的诊疗提供影像学依据。     

Use of Input Impedance to Determine Changes in the Resistance of Arterial Vessels at Different Levels in Feline Femoral Bed

In many studies, the functional state of vessels of different caliber was determined by fitting the lumped parameters of a mathematical model of the bed in order to fit the vascular input impedance (Z _in) data. However, reliability of the results obtained in such a way remains uncertain. In this study, we employed a mathematical model with seven lumped parameters and Z _in experimental data to analyze the distribution of resistance across the arterial bed of the hind limb in anesthetized cats, to test reliability of this distribution and to describe the process of ascending arterial dilation followed occlusion of iliac artery. The vascular bed was divided into three segments: large arteries, medium-sized arterial vessels and precapillary resistance vessels together with venous part of the bed. Based on the data of Z _in measured in a wide frequency range (from 0 to 150 Hz) we showed that pharmacologically induced constriction and dilation of the arterial microvessels were reflected in the model by the changes in the resistance of distal precapillary vessels only, whereas the local constriction or dilation of femoral and iliac arteries as well as artificial stenosis of the femoral artery resulted exclusively in the changes of the resistance describing the state of large arteries. Using the input impedance method we could demonstrate and quantitatively describe the process of ascending arterial dilation during the post-occlusion (reactive) hyperemia. All these results prove that the model of vascular bed with seven lumped elements used in combination with input hydraulic impedance data can be an effective tool permitted to quantitatively analyze the functional state of arterial vessels of different caliber and to describe the changes in resistance of arterial vessels during vascular reactions.     

Modulation of sympathetic neurotransmission by neuropeptide Y Y2 receptors in rats and guinea pigs

We have investigated the effect of the Y₂ receptor agonist (Y₂ agonist; N-acetyl [Leu^28,31] NPY 24-36), on contractions evoked by transmural electrical stimulation of sympathetic nerves of isolated arteries from a range of vascular beds in rats and guinea pigs. Contractions evoked by transmural stimulation of the rat renal, mesenteric and femoral arteries were significantly attenuated in the presence of the Y₂ agonist. In these arteries, contractions were significantly inhibited in the presence of an α-adrenoceptor antagonist (76–97%). So we conclude that these responses were primarily mediated by noradrenaline and that the Y₂ agonist attenuates the release of noradrenaline via presynaptic Y₂ receptors. Contractions of the rat carotid artery were not attenuated by the Y₂ agonist but were completely abolished in the presence of an α-adrenoceptor antagonist suggesting that in this artery the Y₂ agonist has no effect on release of noradrenaline. In the guinea pig, carotid arteries contractions evoked by transmural nerve stimulation were attenuated in the presence of the Y₂ agonist and inhibited by an α-adrenoceptor antagonist 75–87% suggesting that the Y₂ agonist attenuates the release of noradrenaline via presynaptic Y₂ receptors in this vessel. In the guinea pig femoral artery contractions evoked by transmural stimulation were not modified in the presence of the Y₂ agonist but were completely abolished in the presence of an α-adrenoceptor antagonist. This suggests that the Y₂ agonist does not modify noradrenaline release in this vessel. Contractions of the guinea pig mesenteric artery were significantly potentiated by the Y₂ agonist, possibly by potentiation of neuropeptide Y (NPY) at the Y₁ receptor. The Y₁ antagonist inhibited more than 70 % of the response, indicating that the majority of the contraction was mediated by NPY. The current study demonstrates heterogeneity of neurotransmitter substances in sympathetic nerves supplying vascular beds within and across species and in subsequent functional response.Supported by the National Health and medical Research Council of Australia.     

Electrical resistance of arterioles and venules in the hamster cheek pouch

The electrical resistance of the vascular endothelium was determined on single microvessels in the hamster cheek pouch in order to obtain information about this variable in a mammalian preparation. So far, the technique has only been applied to frog microvessels. The technique consists of injection of current into the vascular lumen via a microelectrode and recording of the ensuing intravascular potential distribution by a second microelectrode. Cable theory was used for the analysis. The average diameter of the vessels under study was 41 micron for arterioles and 28 micron for venules. The average resistance of the vessel wall at 37 degrees C was 19 omega cm2 and 3.3 omega cm2, respectively. For the venules this is somewhat lower than what has been recorded on muscle capillaries (Olesen & Crone 1983) in the frog at room temperature, whilst the values on arterioles are rather similar. The calculated sodium permeabilities, PNa+, were for arterioles 4 X 10(-5) cm X s-1 and for venules 23 X 10(-5) cm X s-1. The high permeability values for arterioles and venules indicate that the vascular exchange function may not be limited to capillaries only.     

腹壁穿支血管3D可视化模型的构建及意义

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