自体静脉移植后管壁超微结构的变化

目的　探讨自体静脉移植后内皮形态特征和中膜SMC增生特点 ,为静脉搭桥后再狭窄的防治提供资料。方法　兔 18只 ,随机分 6组 ,均作模拟血管搭桥手术 ,即将颈外静脉移植于颈总动脉 ,术后取材 ,光电镜观察。结果　移植后 1～ 4周管壁渐增厚 ,4～ 6周时达最厚 ,随后管壁不再继续增厚。对照侧静脉无微绒毛梭形内皮被移植段具有丰富微绒毛呈不同形态的内皮细胞所替代。移植后 1～ 2周 ,SMC肌丝和致密体减少 ,与合成和分泌有关的细胞器异常丰富 ,SMC从收缩型转变成合成型 ,四周时分泌型细胞器略有减少 ,但细胞间的胶原纤维明显增多。第 6～ 12周 ,SMC又渐从分泌型向收缩型转变。结论　自体静脉移植后 4～ 6周管壁厚度达高峰 ,内皮微绒毛增多。中膜SMC在 1～ 2周转型增殖最明显。提示术后 2周内是药物抑制SMC增殖的良机     

Age-related changes in vascular adrenergic signaling: clinical and mechanistic implications

A large and growing segment of the general population are age 65 or older, and this percentage will continue to rise. Primary care of this population has, and is becoming a priority for clinicians. Hypertension, orthostatic hypotension, arterial insufficiency, and atherosclerosis are common disorders in the elderly that lead to significant morbidity and mortality. One common factor to these conditions is an age-related decline in beta-adrenergic receptor (beta-AR)-mediated function and subsequent cAMP generation. Presently, there is no single cellular factor that can explain this age-related decline, and thus the primary cause of this homeostatic imbalance is yet to be identified. However, the etiology is clearly associated with an age-related change in the ability of beta-AR receptor to respond to agonist at the cellular level. This article will review what is presently understood regarding the molecular and biochemical basis of age-impaired beta-AR receptor-mediated signaling. A fundamental understanding of why beta-AR-mediated vasorelaxation is impaired with age will provide new insights and innovative strategies for the management of the multiple clinical disorders that effect older people.     

Effects of isoproterenol on adrenergic constriction in vascular smooth muscle.

A series of isolated segments of carotid arteries from Dutch-belted, adult, male rabbits were studied with respect to their response to a beta receptor agonist. Segments of 3-cm length were mounted in a chamber with constant surrounding temperature and pressure and perfused at constant pressure. Inflow pressure, outflow pressure, and flow rate were measured, and values of resistance (R) were calculated. Subsequent to control R, each vessel was exposed to a vasoconstricting concentration of either norepinephrine (NE: 10(-8), 10(-9), 10(-10) M) or potassium (K+: 100mM, 50 mM) followed by three doses of the beta-adrenergic agonist, isoproterenol (IP: 10(-7), 10(-6), 10(-5)M) administered simultaneously with each constrictor. R was not altered by IP during NE infusion but was significantly increased at all levels of IP during both K+ infusions. When the K+ series was repeated with alpha blockade, IP did not alter R. Thus, beta receptors do not appear to be functionally present in the adult rabbit carotid artery.     

Membrane activation of smooth muscle from rabbit basilar artery by dopamine

Intracellular membrane potential (E_m) and force development were measured in rabbit basilar artery to help elucidate the mechanism of action of dopamine in this preparation. There was a strong correlation between membrane depolarization and contraction (r=0.95) between 3×10^–7 M to 10^–4 M dopamine. When the vascular muscle cells were depolarized by elevating [K]_o there was a E_m dependent decrease in force development in response to dopamine. Significant reduction of dopamine stimulated force development was observed when the vessel was depolarized by 5–6 mV by excess extracellular K⁺ and 90% inhibition was seen when the artery was depolarized to –20mv. When Ca⁺⁺ influx was blocked, dopamine no longer induced force development. Such findings suggest that dopamine cotracts rabbit basilar artery by a mechanism involving membrane depolarization. This process may involve an influx of extracellular Ca⁺⁺ through voltage sensitive channels.     

Trophic effect of the sympathetic nervous system on vascular smooth muscle

While the vasomotor effect of the sympathetic nervous system (SNS) on the arterial wall is well recognized, its trophic function is not. It is the aim of these studies to demonstrate this all-important function as it relates to the vascular muscle. Although the exact mechanism by which sympathetic nerve impulses influence the metabolism of the vessel wall is unknown, effects of sympathectomy can be demonstrated. Several lines of evidence indicate that chronic absence of sympathetic innervation in rabbits increases collagen synthesis and decreases activity of tricarboxylic acid cycle enzymes in the vascular wall. When chemically sympathectomized rabbits were fed a 1% cholesterol dietary supplement for 80 days, the aortas of these rabbits contained significantly more cholesterol and total lipids than those from fully innervated controls in spite of insignificant differences in plasma lipids. In a subsequent series of experiments we analyzed the efficacy of the SNS in two strains of pigeons. White Carneau (WC) pigeons are known by their susceptibility to atherosclerosis of the aorta while Show Racer (SR) pigeons are not. Our results demonstrate that the abdominal aorta of WC pigeons has less sympathetic innervation and it declines faster with age than that of SR pigeons. The results of the described studies documenting the direct trophic influence of the SNS on the arterial wall are reinforced by the similarity to the vessel wall changes induced by partial sympathectomy and natural aging. Various phases of this work were done in collaboration with Drs. N. Alexander, D. Amiel, C.M. Bloor, M. Chvapil, J.D. Turner and T. Zemplenyi.     

Age-related loss of proliferative activity of human vascular smooth muscle cells in culture

This work studied the proliferation activity in cultures of vascular smooth muscle cells (SMC) from individuals of different ages. The cells derived from arteries of 12 donors of both sexes from 45 to 91 years of age. The main parameter considered was the 'proliferation rate' (cells grown per day in the different culture passages) taking into account the age of the donor. No significant relationship between age of the donor and the cell life in proliferation was found. On the contrary, the mean time of passage duration for reaching the maximum of proliferation as well as its 'efficiency' (maximum of proliferation rate registered/mean time of passage duration) show a statistically significant dependence on the age of the donor. Furthermore, the proliferation rate measured in each passage is statistically significant related to donor age. The regressions obtained show a similar negative slope (VC 4%). Considering the first five culture passages, the regression crosses the x-axis at the age of 105.6+/-11.7 years. This age in which no proliferative activity of human SMC would be expected lies near the limit of maximum life potential for human beings. Our results suggest that with advancing donor age there is an increasing number of senescent SMC either primarily transferred or appeared in the culture. Vascular SMC of individuals whose life is near the end would almost be all senescent and therefore show extremely low proliferation rates in the culture. If the proliferative activity of arterial SMC is a condition for atherogenesis, the proportion of senescent cells would be inversely related to the propensity of developing the atheroma because of the inability of these cells to divide.     

Effects of a β1-selective adrenergic agonist in normal human volunteers

Summary In healthy volunteers, the effects of prenalterol, a new ₁-adrenoceptor agonist, on renal hemodynamics, excretory function, plasma-renin-activity, plasma cAMP concentration, and plasma and urinary norepinephrine were studied. Besides an increase in blood pressure, which was adjusted to about 20 mmHg above the resting values, and an increase of heart rate, prenalterol induced only transient decreases of urinary volume and free water clearance and in increase of sodium excretion. The other parameters measured did not change. Thus prenalterol mainly exerts positiv inotropic and chronotropic effects and does not affect renal circulation.     

Spatial orientation of extraocular muscle EMG responses to tilt in the rabbit during postnatal development

Unanaesthetized pigmented rabbits 2–45 days of age were gradually tilted (15° steps) over 360° around three orthogonal body axes. The multiunit electromyogram activity of superior rectus (SR) and superior oblique (SO) extraocular muscles was recorded with chronically implanted pairs of fine wire electrodes after each tilt step. The integrated EMG activity of the extraocular muscles in response to static tilt stimulation was trigonometrically related to tilt angle in all age groups. Each eye muscle was characterized by a typical locus of tilt positions which resulted in maximum integrated EMG activity. This locus was described by a vector of tonic vestibular activation (TVA) within the head coordinate system. The orientation of these TVA vectors within the coordinate system of the rabbit's head and, therefore, the coordination of tonic eye muscle activation in response to the position of the animal in the gravitational field did not change with postnatal age in the rabbit. Therefore, eye muscles are already capable of responding to static vestibular stimulation for the stabilization of gaze when visual information becomes available to the rabbit pups. The EMG responses to static tilt stimulation were principally determined by the scalar product of the gravity vector and the muscle's TVA vector. The response of the extraocular muscles to this effective gravitational stimulus was unchanged during the postnatal development of the rabbit: excitatory stimuli resulted in an approximately linear increase of the integrated EMG activity, inhibitory stimuli resulted in a smaller decrease to a minimum value. The correlation between the effective strength of excitatory gravity stimuli and the EMG activity of the extraocular muscles increased significantly at the time of postnatal eye opening. Since the strongest responses of SR and SO to static tilt were observed in intermediate roll-pitch positions that correspond closely to the planes of the vertical semicircular canals, a common reference frame for the cooperation of maculo-ocular and ampullo-ocular reactions is suggested.     

缺氧对兔胸主动脉平滑肌细胞增殖的影响

目的: 观察缺氧对培养的兔胸主动脉平滑肌细胞增殖的影响及其可能的机制。方法: 采用析因实验设计, 测定在正常或缺氧环境下, 不同浓度的胎牛血清对培养的血管平滑肌细胞数量、[³H]-TdR掺入量、MTT比色以及细胞cGMP水平的影响; 透射电镜观察细胞超微结构。结果: 缺氧组平滑肌细胞的数量、[³H]-TdR掺入量以及MTT比色显著多于常氧组(P<0.01); 电镜下可见缺氧组较正常组细胞器发达, 可见大量分泌胞, 少量髓样变线粒体; 缺氧组平滑肌细胞内的cGMP浓度明显高于常氧组。结论: 缺氧可促进血管平滑肌细胞DNA合成, 促进细胞增殖, 可能与提高细胞内的cGMP水平有关。     

Pituitary adenylate cyclase activating polypeptide induces vascular relaxation and inhibits nonvascular smooth muscle activity in the rabbit female genital tract

In vitro effects of two bioactive forms of pituitary adenylate cyclase activating polypeptide (PACAP): PACAP–38 and PACAP–27 were studied on rabbit vascular and non–vascular smooth muscle. Segments of the ovarian artery and muscle strips from the fallopian tube were used. Two series of experiments were performed on vessels: the dose–response relationship of PACAP–38 (10–10–7 M) was established on noradrenaline– (NA, 10–6 M) contracted vessels. In the other set of experiments the contractile effect of 10–8–10–4 M NA added cumulatively, was studied on arterial segments incubated with PACAP–38 (10–7 M), PACAP–27 (10–7 M) or VIP (10–7 M). The effect of PACAP–38, PACAP–27 and VIP (10–10–10–⁶ M) was investigated on spontaneously contracting smooth muscle of the fallopian tube. Longitudinally as well as transversally cut specimens were investigated. PACAP–38 produced a significant dose–related relaxation on the NA–precontracted vessels. However, pre–incubation of the vessels with 10–7 M PACAP–38, PACAP–27 and vaso active intestinal polypeptide (VIP) did not induce a general rightward shift of the NA concentration–response curves, although a tendency to inhibition in the low–dose interval was observed. The peptides caused a significant, dose–dependent inhibition of both frequency and amplitude on the fallopian tube smooth muscle activity. The effects of the three peptides on longitudinally as well as transversally cut specimens were alike.     

A chloride-bicarbonate exchanging anion carrier in vascular smooth muscle of the rabbit

Cl^– efflux into various incubation media (PSS) was studied in pieces of rabbit aortae loaded with³⁶Cl. Replacement of HCO ₃ ^– /CO₂ by HEPES/O₂ in the PSS increased the rate of Cl^– efflux by a factor of 2.4. This effect was suppressed in Cl^–-free PSS containing isethionate, propionate, or benzenesulfonate, but not in NO ₃ ^– -PSS, or Br^–-PSS. The stimulant effect of HCO ₃ ^– withdrawal on Cl^– efflux was reduced by 140 M DIDS, but not by 1 mM furosemide. The Cl^– effux was temperature-dependent (Q₁₀=2.3–2.5), and it was not affected on depolarisation by high [K⁺]₀. — The [Cl^–]_i of rabbit aorta determined by uptake studies with³⁶Cl, decreased slightly (by 15%) below controls in PSS containing 140 M DIDS, but drastically (from 32.6 to 13.5 mM, i.e. by 59%) in PSS containing 1 mM furosemide. — Withdrawal of HCO ₃ ^– /CO₂ depolarized rabbit pulmonary artery in standard PSS and in Br^–-PSS or NO ₃ ^– -PSS, but not in benzenesulfonate-PSS. — The pH_i of rabbit aorta determined by the distribution of (¹⁴C)-DMO, increased in Cl^–-free PSS containing isethionate or glucuronate. — It is concluded that transport mechanisms play a major role in the distribution of Cl^– in vascular smooth muscle, and that a membrane anion carrier operates in this tissue which can transport Cl^– and HCO ₃ ^– across the cell membrane. This mechanism seems to be involved in the regulation of pH_i. However, the known high [Cl^–]_i of vascular smooth muscle is rather mediated by the furosemide-sensitive Na–K–Cl cotransport than by this anion carrier.Supported by the Deutsche Forschungsgemeinschaft. Parts of this study have been reported to the German Physiological and Pharmacological Societies (Kreye and Gertheimer 1982; Kreye et al. 1984a, b), and at the First International Congress on Diuretics, Miami/USA (Kreye et al. 1984c)     

Potassium induced relaxation of vascular smooth muscle: A possible mechanism of exercise hyperaemia

Summary The relaxing effect of small increases in extracellular K⁺-concentration ([K⁺]₀) on helical strip preparations of the rat aorta, activated by 2 g norepinephrine/l, was investigated by simultaneously recording mechanical and extracellular mass electrical activity, the latter from two different points. The results of 148 separate experiments show that increases in [K⁺]₀ in a range between 2.7 and 12.7 mM produce decreases in tension corresponding to vasodilation in vivo. The relaxing effect of increasing [K⁺]₀ is temporary, lasting from 30–200 sec, after which propagation of excitation is improved. The temporary relaxation was not present in any of the 66 experiments in which [K⁺]₀ was increased to more than 13 mM; rather, an immediate increase in tension always occurred. The K⁺-relaxation is shown to be a result of a temporary impairment or block of conduction. Hyperpolarization as a result of increasing conductance quotient g_Kg_Na is discussed as a possible factor in these changes.This word was supported by the Deutsche Forschungsgemeinschaft (Bi 122/3).with the technical assistance of Jutta Nöring     

失血性休克大鼠血管平滑肌收缩功能变化研究

目的：研究失血性休克后大鼠胸主动脉血管平滑肌收缩功能变化并初步探讨其可能机制。方法：采用生物张力换能器及生理记录仪等技术体外测定失血性休克大鼠在休克后2 h、4 h VSM环对去甲肾上腺素（NE）、苯肾上腺素（PE）、咖啡因（caffeine）及氯化钾（KCl）等的收缩反应张力。结果：VSM环在休克后2 h、4 h对NE的最大反应张力分别为对照组的76.17%和66.50%；休克2 h后对高浓度（大于20 mmol/L）K⁺ 和20 mmol/L caffeine的反应张力明显下降；休克后4 h对 3×10^-6 mol/L PE的反应张力亦显著下降。结论：失血性休克后大鼠VSM收缩功能下降，反应性降低，其初步机制可能部分与休克后VSM细胞胞外钙内流及胞内钙释放功能下降等有关。     

Neuropeptide Y (NPY) co-exists with tyrosine hydroxylase and potentiates the adrenergic contractile response of vascular smooth muscle in the human uterine artery.

The human uterine artery was studied by immunocytochemistry and in vitro pharmacology. Nerve fibres containing immunoreactivity for neuropeptide Y (NPY) were encountered in the media, adventitia, smooth muscle layers and surrounding the vasa vasorum. Approximately 50% of the nerve fibres containing NPY also stored immunoreactivity for tyrosine hydroxylase (TH) and TH activity was found in no other fibres. Noradrenaline (NA) contracted the isolated uterine artery in a concentration dependent manner. The presence of increasing doses of NPY shifted the concentration-response curve for NA to the left. Consequently the pD2-values were increased indicating a potentiation of the adrenergic effects induced by NPY. The results demonstrate the existence of NPY in adrenergic nerve fibres surrounding the human uterine artery. A close co-operation between NPY and NA in the neuronal control of smooth muscle is suggested.     

Local norepinephrine depletion and learning-related neuronal activity in cingulate cortex and anterior thalamus of rabbits

Summary Multi-unit neuronal activity was recorded in posterior cingulate cortex (area 29) and the anterior ventral (AV) thalamic nucleus during discriminative instrumental avoidance learning wherein a response (stepping in an activity wheel) to a 0.5-s tone (CS⁺) prevented a foot-shock 5 s after CS⁺ onset. Presentations of a different tone (CS^-) on 50% of the conditioning trials in an irregular sequence with the CS⁺ did not predict shock and thus required no response. Two groups of rabbits received intracranial micro-injections of 6-hydroxydopamine (6-OHDA) to locally deplete the NE in area 29 or the AV nucleus. Vehicle was injected in the non-depleted area in each group and a third group received vehicle injections in both areas. Dopamine neurons in subjects that received 6-OHDA were protected by pre-treatment with GBR-12909. Neuronal data were collected during two pre-training sessions in response to the tones only and when the tones and shock were presented unpaired. Thalamically depleted rabbits made more, and cortically depleted rabbits made fewer, avoidance responses than controls during the early stages of behavioral acquisition, and cortically depleted rabbits made fewer responses than controls and thalamically depleted rabbits during extinction testing administered after the completion of acquisition. One effect of NE depletion on neuronal activity was entirely local: elimination of neuronal sensitization effects (enhanced discharges elicited by tones during the unpaired tone-shock pre-training treatment relative to pre-training with tones only). Other neuronal effects of NE depletion were system-wide, i.e., they occurred whether the depletion was cortical or thalamic. These were: attenuation of area 29 tone-elicited neuronal discharges and enhancement of AV thalamic discharges before and during training; elimination in area 29 of neuronal discrimination between CS⁺ and CS^-, induced in controls by CS⁺-shock pairings in the first conditioning session; induction of this neuronal discrimination, not present in controls, in the AV nucleus during the first conditioning session; attenuation of discharge enhancements elicited in controls by unexpected stimuli (presentation of auditory stimuli different in quality and incidence from the CS⁺). Excepting the noted losses at the outset of training, the results did not support an involvement of NE in the production of cingulate cortical or AV thalamic excitatory and discriminative training-induced neuronal activity. The system-wide alterations due to NE depletion implicated NE in the processing of unexpected events and in the production of dynamic neuronal patterns relevant to mnemonic retrieval. Several of the depletion-related neuronal changes were similar to the effects of hippocampal formation (subicular) lesions, suggesting that NE-dependent functions in area 29 and the AV nucleus are governed by hippocampal efferents, which may control the release of NE in these areas.     

Enzyme activities of fatty acid oxidation and the respiratory chain in chronically stimulated fast-twitch muscle of the rabbit

Fast-twitch tibialis anterior muscle of the rabbit was subjected to chronic low-frequency (10 Hz, 10 h/day) stimulation for different time periods up to 28 days. Total cellular activities of carnitine: palmitoyl-CoA transferase, crotonase, 3-hydroxyacyl-CoA dehydrogenase, 3-keto-acyl-CoA thiolase, citrate synthase, NADH:cytochrome c oxidoreductase, succinate: cytochrome c oxidoreductase, and cytochrome c oxidase were measured in contralateral and stimulated muscles at various times. With the exception of crotonase, which increased only 1.6-fold after 28 days of stimulation, the other enzymes increased in parallel displaying 3-fold elevated absolute activities. These results, by supporting and extending our previous findings, indicate that the expression of the enzymes of the main metabolic systems of aerobic substrate oxidation, i.e. the citric acid cycle, the fatty acid oxidation and the respiratory chain, is regulated in a coordinate manner.     

人腹主动脉瘤平滑肌细胞表型变化

目的:研究腹主动脉瘤(AAA)中血管平滑肌细胞(VSMC)表型改变,探讨其在AAA发病中的作用。方法:选取人体AAA、动脉闭塞性疾病(AOD)和正常腹主动脉(NA)组织,采用α-肌动蛋白(α-SMA)、结蛋白(desmin)及肌球蛋白重链3种表型(SM1、SM2和SMemb)单克隆抗体,利用免疫组化及电镜技术,检测VSMC收缩型与合成型。结果:AOD及NA中VSMC以收缩表型α-SMA、desmin、SM1和SM2表达为主,SMemb在AOD的表达较低,而在NA无表达。AAA中VSMC以合成表型SMemb为主,α-SMA、SM1和SM2明显低于AOD及NA,desmin不表达;其中破裂者的SMemb和SM2低于非破裂者。结论:VSMC表型变化参与腹主动脉壁损伤重构,促进AAA形成和发展。     

Effect of adrenergic agonists on Ca2+-channel currents in single vascular smooth muscle cells

Ca²⁺-channel currents have been measured in enzymatically dispersed single smooth muscle cells of the rabbit ear artery using the whole-cell patch clamp technique. Inward currents were elicited by depolarizing test pulses from a holding potential of–50 mV. These currents were activated from–30 mV onward and reached full activation around 0 mV. -Adrenergic agonists did not affect the background current measured at the holding potential, but markedly reduced the peak amplitude of the voltageactivated Ca²⁺-channel currents. This -adrenergic inhibition also occurred in cells which were internally perfused with solutions containing either 10 M cAMP, 10M cGMP or 0.1 mM GTP, but became irreversible when the pipette solution contained a non-hydrolyzable GTP-analog. The action of -agonists on the voltage-activated Ca²⁺-channel currents was variable, and ranged from no effect at all to a 50% reduction of the current. It is concluded that -agonists do not open receptor-operated Ca²⁺-channels in these smooth muscle cells. The inhibition of the voltageactivated Ca²⁺-currents does not seem to be mediated through changes in cyclic nucleotide levels, but might be mediated through G-proteins. Its physiological relevance remains however unclear. The action of -agonists is consistent with their relaxing effect, but the reason for the nonuniform response has not been elucidated.     

兔眼角膜生物力学特性的年龄相关性

目的 利用兔眼角膜条的单轴拉伸实验数据,研究角膜生物力学特性与年龄的相关性。 方法 分别取3月龄和7~8月龄兔眼角膜条,实施单轴拉伸实验,获得实验数据;用指数模型和幂模型对应力 应变数据进行分析;用黏弹性力学模型对应力松弛数据进行分析。结果 兔眼角膜条呈现非线性黏弹性特征。在实验误差允许的范围内,不同月龄兔眼角膜条的非线性应力-应变关系差别不明显,7~8月龄兔眼角膜的切线模量略偏大,但其应力衰减得明显快。不同的拉伸速率对3月龄兔眼角膜条非线性应力-应变关系的影响不明显,但快速拉伸后的角膜条应力衰减明显变快。结论 兔眼角膜随月龄增加会轻微变硬,而角膜的松弛特性随月龄变化明显。