Cooling the central ear artery of the rabbit: Myogenic and adrenergic responses

Experiments were designed to determine the effects of acute cooling (from 37-24°C) on responses to alpha-1 and alpha-2 adrenergic activation in the central ear artery of the rabbit. Rings were suspended in physiological salt solution for recording of isometric force. Cooling quiescent vessels resulted in an increase in force. This myogenic response was sensitive to depletion of either intra- or extracellular calcium, as well as treatment with the calcium antagonists verapamil and diltiazem. Cooling did not significantly alter contractile responses to norepinephrine in ear arteries under control conditions or under alpha-2 adrenergic blockade (rauwolscine). Cooling arteries under alpha-1 adrenergic blockade (prazosin) caused augmentations which were not significantly different in magnitude from the myogenic responses to cooling exhibited by the same rings when unstimulated. The alpha-1 adrenergic agonist phenylephrine caused concentration-dependent contractions which were not altered by cooling. The alpha-2 adrenergic agonist UK 14,304 evoked only weak contractions; cooling rings exposed to UK 14,304 caused further increases in tension but no more so than when quiescent. A similar pattern was seen to hold for contractions elicited by electrical stimulation. Thus, in the central ear artery of the rabbit cooling appears to have very little effect on adrenergically induced contractions but does cause the development of myogenic tone.link_to_subscribed_fulltex

Cooling and alpha adrenergic responses in the saphenous vein of the rabbit

Experiments were designed to determine the effects of cooling on alpha-1 and alpha-2 adrenergic responses in a cutaneous vein of the rabbit. Rings of saphenous vein were suspended in physiological salt solution for the recording of isometric force. Cooling (from 37-24°C) caused no significant increase in force in quiescent rings. Similarly, the same degree of cooling had no significant effect on the response to exogenous norepinephrine (10-9-10-5 M), whether under control conditions or in the presence of either the alpha-1 adrenergic antagonist prazosin (3 x 10-7 M) or the alpha-2 adrenergic antagonist rauwolscine (10-7 M). Contractions evoked by the alpha-1 adrenergic agonist phenylephrine were reduced, but those induced by the alpha-2 adrenergic agonist UK 14,304 (10-9-10-5 M) were unaffected by the same degree of cooling. Cooling augmented the response elicited by electrical field stimulation of the sympathetic nerves, although only under conditions of alpha-1 or combined alpha-1 and alpha-2 adrenergic blockade. Data obtained with the sympathomimetic tyramine suggest that both alpha-1 and alpha-2 adrenoceptors are innervated in this blood vessel. Together, the present data suggest that the effects of acute cooling on the saphenous vein of the rabbit, unlike that of the dog, are not mediated by changes in the affinity of postjunctional alpha-2 adrenoceptors.link_to_subscribed_fulltex

Ammonium ions cause relaxation of isolated canine arteries

Experiments were designed to determine the mechanism of action underlying relaxation of vascular smooth muscle induced by ammonium ions. In particular, the possibility that these ions might be an endothelium-derived relaxing factor was examined. Rings of large canine femoral, mesenteric and coronary arteries and of small arteries from the gracilis muscle were suspended in organ chambers for the recording of isometric force. Membrane potential was recorded with intracellular microelectrodes in smooth muscle cells from the mesenteric artery. Ammonium ions induced relaxations which were independent of the presence of the endothelium. The relaxations were not prevented by adrenergic, serotonergic, muscarinic and histaminic blockers, by scavengers of oxygen-derived radicals or by inhibitors of soluble guanylate cyclase. The relaxations were prevented by a decrease in extracellular calcium concentration and by inhibition of the Na+/K+ pump. The results are compatible with the hypothesis that the relaxation induced by ammonium ions is related to changes in intracellular pH and, at high concentration of these ions, possibly to activation of the Na+/K+ pump. Ammonium ions are neither the endothelium-derived relaxing factor which activates guanylate cyclase nor the factor that induces endothelium-derived hyperpolarization. Inasmuch as relatively low concentrations of the ion induce relaxation of small arteries of skeletal muscle, they could contribute to exercise hyperemia.link_to_subscribed_fulltex

Duke Surgery Research Central: an open-source Web application for the improvement of compliance with research regulation

<p>Abstract</p> <p>Background</p> <p>Although regulatory compliance in academic research is enforced by law to ensure high quality and safety to participants, its implementation is frequently hindered by cost and logistical barriers. In order to decrease these barriers, we have developed a Web-based application, Duke Surgery Research Central (DSRC), to monitor and streamline the regulatory research process.</p> <p>Results</p> <p>The main objective of DSRC is to streamline regulatory research processes. The application was built using a combination of paper prototyping for system requirements and Java as the primary language for the application, in conjunction with the Model-View-Controller design model. The researcher interface was designed for simplicity so that it could be used by individuals with different computer literacy levels. Analogously, the administrator interface was designed with functionality as its primary goal. DSRC facilitates the exchange of regulatory documents between researchers and research administrators, allowing for tasks to be tracked and documents to be stored in a Web environment accessible from an Intranet. Usability was evaluated using formal usability tests and field observations. Formal usability results demonstrated that DSRC presented good speed, was easy to learn and use, had a functionality that was easily understandable, and a navigation that was intuitive. Additional features implemented upon request by initial users included: extensive variable categorization (in contrast with data capture using free text), searching capabilities to improve how research administrators could search an extensive number of researcher names, warning messages before critical tasks were performed (such as deleting a task), and confirmatory e-mails for critical tasks (such as completing a regulatory task).</p> <p>Conclusion</p> <p>The current version of DSRC was shown to have excellent overall usability properties in handling research regulatory issues. It is hoped that its release as an open-source application will promote improved and streamlined regulatory processes for individual academic centers as well as larger research networks.</p