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R Varas

Publications and source records attributed to R Varas.

17 recordsLinked to original sources
PubMed2000

Acetylcholine sensitivity in sensory neurons dissociated from the cat petrosal ganglion.

The petrosal ganglia contain the somata of the sensory fibers of the glossopharyngeal nerves, innervating structures of the tongue, pharynx, carotid sinus and carotid body. Petrosal ganglia were excised from adult cats and their neurons were dissociated and kept in tissue culture for 7-12 days. Intracellular recordings were obtained through conventional microelectrodes. In response to depolarizing pulses, most cells (41/60) presented a 'hump' in the falling phase of their action potentials (H-type), while the remaining neurons lack such hump (F-type). The two types of cells had no differences in resting membrane potential or action potential amplitude. Acetylcholine (ACh) applied locally elicited responses in nearly two thirds of both H-type and F-type neurons tested. Most H-type neurons (17/19) responded with a slow long lasting depolarization, while the remaining (2) did so by generating spikes. In contrast, half of F-type neurons (6/12) responded with one or more spikes and the other half only with a slow depolarization. These results indicate that ACh receptors are present in the soma of many petrosal ganglion neurons subjected to tissue culture, thus supporting the idea that - under normal conditions - their peripheral sensory processes may be excited by ACh.

Acetylcholine↗
PubMed1999

Responses to hypoxia of petrosal ganglia in vitro.

NaCN is a classical stimulus used to elicit discharges from carotid body chemoreceptors. The effect is assumed to be mediated by glomus (type I) cells, which release an excitatory transmitter for the excitation of carotid nerve endings. Since the sensory perikarya of the glossopharyngeal nerve (from which the carotid nerve branches) are located in the petrosal ganglion, we tested whether application of this drug to the petrosal ganglion superfused in vitro elicits antidromic discharges in the carotid nerve. NaCN did indeed cause an intense and prolonged burst of nerve impulses in the carotid nerve, while provoking a less intense and much briefer burst of discharges in the glossopharyngeal branch. Carotid nerve responses to NaCN were reduced and shortened by prior or following application of dopamine to the ganglion. Sodium azide applied to the petrosal ganglion evoked a less intense and much briefer burst of impulses in the carotid nerve. Ganglionar application of 2,4-dinitrophenol did not induce discharges in the carotid nerve. Switching the superfusion of the ganglion from a normoxic to a hypoxic solution did not evoke discharges in the carotid nerve. Therefore, the perikarya of carotid nerve neurons are sensitive to NaCN, but are not excited by reducing the pO(2) of the superfusing solution.

2,4-Dinitrophenol↗
PubMed1999

Dopamine modulates carotid nerve responses induced by acetylcholine on the cat petrosal ganglion in vitro.

We have recently reported that application of acetylcholine (ACh) or nicotine to the petrosal ganglion-the sensory ganglion of the glossopharyngeal nerve-elicits a burst of discharges in the carotid nerve branch, innervating the carotid body and sinus, but not in the glossopharyngeal branch, innervating the tongue and pharynx. Thus, the perikarya of sensory neurons for the carotid bifurcation exhibit selective cholinosensitivity. Since dopamine (DA) modulates carotid nerve chemosensory activity, we searched for the presence of DA sensitivity at the perikarya of these neurons in the cat petrosal ganglion superfused in vitro. Applications of DA in doses of up to 5 mg to the ganglion did not modify the rate of spontaneous discharges in the carotid nerve. However, if DA was applied 30 s before ACh injections, ACh-evoked reactions were modified: low doses of DA enhanced the subsequent responses to ACh, while high doses of DA depressed the responses to ACh. This depressant effect of DA on ACh responses was partially antagonized by adding spiroperone to the superfusate. Our results show that the response to ACh of petrosal ganglion neurons projecting through the carotid nerve is modulated by DA acting on D(2) receptors located in the somata of these neurons. Thus, dopaminergic modulation of cholinosensitivity could be shared also by the membranes of peripheral endings and perikarya of primary sensory neurons involved in arterial chemoreception.

Acetylcholine↗
PubMed1998

Selective activation of carotid nerve fibers by acetylcholine applied to the cat petrosal ganglion in vitro.

The petrosal ganglion innervates carotid body chemoreceptors through the carotid (sinus) nerve. These primary sensory neurons are activated by transmitters released from receptor (glomus) cells, acetylcholine (ACh) having been proposed as one of the transmitters involved in this process. Since the perikarya of primary sensory neurons share several properties with peripheral sensory endings, we studied the electrical responses of the carotid nerve and glossopharyngeal branch to ACh locally applied to the cat petrosal ganglion superfused in vitro. Ganglionar applications of AChCl (1 microg-1 mg) generated bursts of action potentials conducted along the carotid nerve, while only a few spikes were exceptionally recorded from the glossopharyngeal branch in response to the largest doses. Carotid nerve responses to ACh were dose-dependent, the higher doses inducing transient desensitization. Application of nicotine to the petrosal ganglion also evoked dose-dependent excitatory responses in the carotid nerve. Responses to ACh were reversibly antagonized by adding hexamethonium to the superfusate, more intense and prolonged block of ACh responses being produced by mecamylamine. Ganglionar applications of gamma-amino butyric acid and serotonin, in doses of up to 5 mg, did not induce firing of action potentials in any of the branches of the glossopharyngeal nerve. Our results indicate that petrosal ganglion neurons projecting through the carotid nerve are selectively activated by ACh acting on nicotinic ACh receptors located in the somata of these neurons. Thus, cholinosensitivity would be shared by the membranes of peripheral endings and perikarya of primary sensory neurons involved in arterial chemoreception.

Acetylcholine↗
PubMed1991

A qualitative comparison of paper flowsheets vs a computer-based clinical information system.

Demonstrating the value of computerized clinical information systems (CIS) relative to its cost has been difficult. Decreased mortality in the intensive care unit or a reduction in nursing staff have not been apparent, but CIS does lead to a significant improvement in documentation over handwritten flowsheets, both in volume and accuracy. This may have a medicolegal and quality assurance impact, as well as enhancing patient care.

Burn Units↗
PubMed1988

Suppurative thrombophlebitis: a new look at a continuing problem.

Despite knowledge of its existence and despite precautionary measures, suppurative thrombophlebitis remains a significant problem in critical care, with a reported incidence of approximately 4% and associated mortality as high as 83%. In a retrospective study, we identified additional risk factors such as emergency department or field placement of catheters and administration of potassium boluses. New guidelines for surveillance and prevention have proved successful.

Catheters, Indwelling↗
PubMedDate not supplied

Burn nurse retention. Elements of success.

With the national nursing shortage most acute in the critical care area, greater emphasis on effective recruitment and nurse retention is vital. Despite the high-stress environment of a busy burn center, nursing turnover can be reduced to acceptable levels. The greatest "satisfiers" are centered around nursing issues such as schedule flexibility, nurse/patient ratio, and the center's reputation and standards. Salary and the physical plant environment were of little importance in comparison.

Attitude of Health Personnel↗
PubMedDate not supplied

Coordinated strategies in burn prevention programs: a case study.

Smoke alarm giveaway programs can be successful, as demonstrated by the experience of the extensive 1982 Baltimore Fire Department project. In the absence of municipal government commitment for such an intensive campaign, a community program that involves many sectors can also be successful. It may, in fact, reach elements of the high-risk population who do not traditionally participate in smoke detector programs, such as renters. A decrease in "extra-alarm" fires and fire deaths can be achieved with multifaceted programs. In Dade County, with a growing population of approximately 1.7 million people that includes large migrant and illegal alien populations, fire-related deaths decreased from 26 in 1985 and 27 in 1986 to 17 in 1987. In the city of Miami, the county's inner core, fire-related deaths decreased by half from 1985 to 1987, in spite of an increase in high-risk population groups and substandard housing. Thus through extensive networking, the integrated efforts of a cross-section of the community can result in a successful safety campaign that has little overhead or political constraints. Designed as multifaceted, ongoing community-based programs, such efforts can, over time and through "persistent learning," lead to desired changes in behavior.

Accident Prevention↗