Instrumental Control of Peripheral Vasomotor Responses in Children

In two experiments children acquired instrumental control over skin temperature with the aid visual feedback. In Experiment 1,3 out of 4 children learned to control the temperature difference their two hands. In Experiment 2. one of these children acquired significant control of the difference between two fingers of one hand. Such highly specific responses apparently reflect direct instrumental modification of the vasomotor system since generalized effects due to muscular tension or respiration could he ruled out.     

Prostaglandin E2- and α- or β-Adrenoceptor Mediated Interferences with 3H-Noradrenaline Secretion from Human Vasomotor Nerves: Comparison between Effects on Omental Arteries and Veins

In earlier work with human vasomotor nerves (Stjärne and Gripe 1973) it has been shown that the inhibition of ³H-NA secretion by exogenous N A, and the enhancement caused by the α-adrenoceptor antagonist phentolamine, occur even after blocking formation of prostaglandin E₂ (PGE₂) with 5,8,11,14-eicosatetraynoic acid (ETA). This shows that at least part of the α-adrenoceptor mediated control of NA secretion is independent of (not mediated by) endogenous PGE₂. In the same paper it was also shown that the inhibitory effect of exogenous PGE₂ on ³H-NA secretion persists in the presence of phentolamine, indicating that exogenous PGE₂ acts on a target in the nerves different from that of NA (Stjärne 1973).     

Contractility,Muscle Mass and Agonist Sensitivity of Isolated Portal Veins from Normo- and Hypertensive Rats

Properties of the longitudinal smooth muscle of portal veins from normotensive Wistar rats, adult (NCR) and young (NCR_y); spontaneously hypertensive Okamoto rats, adult (SHR) and young (SHR_y); and adult Wistar rats with renal hypertension (RHR) were studied in vitro and histologically. Some aortic strips from SHR and SHR_y were compared with controls. In response to noradrenaline (NA) and acetylcholine (ACh) greater maximum force was developed by veins from all hypertensive groups than by those from control rats. Cross-sectional area of the longitudinal muscle of veins from SHR but not SHR nor RHR was greater than control. Maximum stress in response to agonists was greater in both SHR and RHR than NCR. ED_so-values for NA and ACh were lower in portal veins from SHR than NCR but not from RHR nor SHR_y compared to controls. Denervation did not abolish any of the differences between SHR and NCR. Aortic strips from SHR developed less maximum force to NA and ED₅₀ was greater than those from NCR. i.e. opposite to the findings in portal veins. Low levels of external Ca^2- reveal altered calcium handling in veins from SHR compared to controls. It is concluded that portal veins from hypertensive rats are functionally different from those of normotensive rats and differ in SHR compared to RHR. It is suggested that the altered functional properties of portal vein, but not of aorta, in several respects resemble those of arterial resistance vessels. The implications of these findings are discussed in terms of mechanisms of hypertension in these animal models.     

The Effects of Discrimination Training on Voluntary Control of Cephalic Vasomotor Activity

The present study was conducted to test Brener's calibration theory of visceral learning. It was hypothesized that training in discrimination of cephalic vasomotor responses would enhance acquisition of voluntary and biofeedback control of cephalic vasomotor response. Four groups were given discrimination training to detect either constriction, dilation, both constriction and dilation, or given false feedback. All groups were then given biofeedback training in constriction. All groups were assessed on discrimination accuracy, acquisition of biofeedback control of constriction, and voluntary control of dilation and constriction. The results indicated that discrimination of cephalic vasomotor responses can be learned and that this skill facilitates the acquisition of biofeedback and voluntary control of vasomotor responses. This facilitation occurs only if discrimination training is given for the specific response to be learned. The data suggest that discrimination of the relevant response is a necessary but not sufficient condition for acquisition of voluntary control in biofeedback learning.     

Generation of Schwann Cell-Derived Multipotent Neurospheres Isolated from Intact Sciatic Nerve

Schwann cells (SCs) are the supporting cells of the peripheral nervous system and originate from the neural crest. They play a unique role in the regeneration of injured peripheral nerves and have themselves a highly unstable phenotype as demonstrated by their unexpectedly broad differentiation potential. Thus, SCs can be considered as dormant, multipotent neural crest-derived progenitors or stem cells. Upon injury they de-differentiate via cellular reprogramming, re-enter the cell cycle and participate in the regeneration of the nerve. Here we describe a protocol for efficient generation of neurospheres from intact adult rat and murine sciatic nerve without the need of experimental in vivo pre-degeneration of the nerve prior to Schwann cell isolation. After isolation and removal of the connective tissue, the nerves are initially plated on poly-D-lysine coated cell culture plates followed by migration of the cells up to 80?% confluence and a subsequent switch to serum-free medium leading to formation of multipotent neurospheres. In this context, migration of SCs from the isolated nerve, followed by serum-free cultivation of isolated SCs as neurospheres mimics the injury and reprograms fully differentiated SCs into a multipotent, neural crest-derived stem cell phenotype. This protocol allows reproducible generation of multipotent Schwann cell-derived neurospheres from sciatic nerve through cellular reprogramming by culture, potentially marking a starting point for future detailed investigations of the de-differentiation process.     

急性心肌冬眠时心脏交感神经功能的变化

目的探讨急性心肌冬眠时心脏交感神经功能的变化。方法采用大鼠离体心脏急性心肌冬眠模型,测定急性心肌冬眠时电场刺激引起心脏去甲肾上腺素(NA)的释放,并观察复灌后的酪胺反应。结果电场刺激引起的NA的溢出在心肌冬眠组、对照组和复灌组分别为3.24±1.27、76.89±27.65和80.30±23.86pmol/g.min,复灌30min时,酪胺引起NA的释放和心率明显增加,而在去甲丙咪嗪存在的情况下,酪胺的这种作用消失。结论本研究表明离体鼠心急性冬眠时,电场刺激引起的心脏NA释放明显减少,复灌后这种释放恢复至对照组水平,心脏对酪胺的NA反应证明心脏交感神经末梢功能的完整性。提示在急性心肌冬眠过程中,心脏的交感神经功能可能也经历了一个类似冬眠即神经冬眠的过程,再灌注后交感神经的功能可部分或全部恢复。     

Arteries Respond to Independent Control of Circumferential and Shear Stress in Organ Culture

Arteries respond to changes in global mechanical parameters (pressure, flow rate, and longitudinal stretching) by remodeling to restore local parameters (circumferential stress, shear stress, and axial strain) to baseline levels. Because a change in a single global parameter results in changes of multiple local parameters, the effects of individual local parameters on remodeling remain unknown. This study uses a novel approach to study remodeling in organ culture based on independent control of local mechanical parameters. The approach is illustrated by studying the short term effects of circumferential and shear stress on remodeling-related biological markers. Porcine carotid arteries were cultured for 3 days at a circumferential stress of 50 or 150 kPa or, in separate experiments, a shear stress of 0.75 or 2.25 Pa. At high circumferential stress, matrix synthesis, smooth muscle cell proliferation, and cell death are significantly greater, but matrix metalloproteinase-2 (MMP-2) and pro-MMP-2 activity are significantly less. In contrast, biological markers measured were unaffected by shear stress. Applications of the proposed approach for improved understanding of remodeling, optimizing mechanical conditioning of tissue engineered arteries, and selection of experimentally motivated growth laws are discussed.     

Some Characteristics of Digital Vasomotor Activity

Size and latency of responses to a series of tones, spontaneous fluctuations, and habituation in finger volume and pulse volume were studied in 19 healthy young soldiers by means of pneumoplethysmography. The results indicate that relationships among vasomotor measures differ from those reported for skin conductance measures. Thus, in contrast to what has been shown for skin conductance, no correlation was found between habituation and number of spontaneous fluctuations, and the variability of the first response to the tones did not differ from the variability of the following responses. Auditory stimulation did not increase the number of spontaneous fluctuations. There were highly significant correlations between spontaneous fluctuations during rest and stimulation periods. No significant correlations were obtained between pulse volume responses to an arithmetic task and responses to tone stimuli. Some differences in pattern of relationships were obtained between finger and pulse volume measures. Initial responses in finger volume were related to other response size measures, whereas this was not the case for pulse volume. Response latency increased during the auditory stimulation for pulse volume, but not for finger volume.     

Effects of Drugs and Nerve Stimulation on the Spleen and Arteries of Two Species of Dogfish,Scyliorhinus canicula and Squalus acanthias

The effects of drugs and nerve stimulation on the spleen of 2 species of dogfish have been examined by experiments with perfused spleens and isolated spleen and artery strips. Adrenaline, noradrenaline and phenylephrine, acting via alpha adrenoceptors, constrict the perfused spleen of both species, thereby releasing erythrocytes, and contract the isolated spleen and artery strips. Phentolamine competitively antagonizes the excitatory effects of adrenergic agonists. The responses of the spleen to acetylcholine are very irregular, and a rapid desensitization makes evaluation of the mode of action of this drug difficult. In the artery strips acetylcholine produces a dose-dependent contraction. Fluorescent histochemistry reveals well developed adrenergic innervation of the arteries, and a few adrenergic terminals in the spleen. Stimulation of splenic nerves produces normally splenoconstriction in Squalus, which can be blocked by phentolamine but not by atropine. The nervous control of the Scyliorhinus spleen seems to be poor or lacking. It is concluded that the dogfish spleen, and maybe also the arteries, are to a large extent controlled by circulating catecholamines and (in Squalus) also by sympathetic adrenergic fibres.     

Vasomotor nerve control of isolated arteries and veins.

In order to compare neuro-effector function in different blood vessels, frequency-response relationships were determined for the following preparations: 1)Isolated rings of the proximal saphenous, distal saphenous and ear arteries, the parietal branch of the internal iliac vein and the small saphenous vein from the rabbit, 2) spiral strips of the rabbit pulmonary artery and 3) longitudinal preparations of the rat portal vein. In each rabbit tissue only one low (less than or equal to 4 Hz) and one high (larger than or equal to 8 Hz) transmural nerve stimulation frequency was applied until steady state responses were obtained and these were expressed as a percentage of a maximum response to exogenous noradrenaline (NA) applied in each experiment. The general shape of the frequency-response curves was similar, but differences in steepness and amplitude of the maximum neurogenic response relative to exogenous NA were found. The steepness of the frequency-response relationships of the veins tended to be greater than those of the arteries. It appears that factors such as close neuro-muscular contacts, presence of terminal nerve fibres within the media and the operation of mechanisms for myogenic propagation of activity contribute to the effectiveness of neurogenic vascular control as revealed by frequency-response curves. In vivo, geometrical factors can greatly augment the hemodynamic significance of the observed differences.     

Unidirectional Fluxes in Isolated Splenic Nerve Vesicles Measured by a Millipore Filter Technique:

Isotopically labelled noradrenaline (NA) exchange was determined in an improved preparation of NA storage vesicles isolated from bovine splenic nerve trunk. A Millipore filter technique was used which permitted analyses of unidirectional fluxes. In a Mg-ATP supplemented medium at 30 and 20° C, vesicle NA is completely exchangeable with 0.5 to 3.0 μg l-NA/ml in the medium. The kinetics are compatible with a single exponential component of exchange, and the data suggest a fully saturated Mg-ATP complexing under these conditions. Reserpine in a concentration range between 2 × 10^-8 and 2 × 10^-7 M causes more pronounced inhibition of the transfer coefficient for NA influx than for efflux. However, no net loss of vesicle NA occurs because the drug inactivates a proportional amount of the readily exchangeable NA pool. Within the concentration ranges of NA and reserpine tested, virtually complete inhibition of NA exchange can be achieved and reversal of this inhibition by elevating the NA concentration in the medium can be demonstrated. The data is consistent with the suggestion that reserpine acts via transport sites in the vesicle membrane, rather than on the intravesicular NA complex per se. This membrane stabilizing concentration range of reserpine causes no obvious deleterious effects on the vesicles at the electron microscopic level.