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Biomedical subjects

E Soto

Publications and source records attributed to E Soto.

At least 19 recordsLinked to original sources
PubMed1992

Streptomycin blocks the afferent synapse of the isolated semicircular canals of the frog.

This study aimed to define the acute electrophysiological effects of the perilymphatic perfusion of streptomycin in the sensory apparatus of the semicircular canals of the frog. The ampullary DC potential, the vestibular nerve multiunit discharge, the nerve DC potential and the unitary EPSP activity were recorded in isolated semicircular canals of the frog (Rana esculenta L). The results demonstrated that perilymphatic microperfusion of streptomycin (0.1, 0.3, 1 and 3 mM) reduced both resting and mechanically evoked afferent discharge, while the response of the hair cells remains unchanged. Intracellular recordings from single afferent axons showed that the reduction of the afferent discharge was mainly due to a reduction of the amplitude, but not the frequency, of the EPSPs. These results indicate that streptomycin, when applied in the fluid bathing the synaptic pole of the sensory cells, can act as an antagonist of the vestibular afferent transmitter at the postsynaptic level.

Afferent Pathways↗
PubMed1991

Streptomycin blocks the postsynaptic effects of excitatory amino acids on the vestibular system primary afferents.

It has been suggested that streptomycin might be an antagonist of the glutamate receptors, and that it selectively blocks quisqualic acid receptors. We studied whether streptomycin blocks the responses to excitatory amino acid agonists on the vestibular system primary afferents, and if it allows us to differentiate between kainate (KA) and quisqualate (QA) receptor mediated responses. The experiments were performed in the axolotl (Ambystoma tigrinum). Intra- and extracellular records of the electrical activity of semicircular canal afferent fibers were obtained. Drugs were applied by pressure ejection in volumes of 20 microliters in a 10 ml bath. Streptomycin (0.01-10 mM), induced a dose dependent reversible inhibition of the basal spike discharge of the afferent fibers. This coincided with a reduction in the amplitude of excitatory postsynaptic potentials (EPSP) recorded intracellularly in the afferent fibers. Streptomycin also blocked the excitatory action produced by KA and QA; increasing concentrations of streptomycin produced a rightward shift in the concentration-response curves for both KA and QA. This action persisted even in a high Mg2+ (10 mM), low Ca2+ (0.09 mM) Ringer solution, indicating its postsynaptic nature. These results show that streptomycin might be a non-selective excitatory amino acid (EAA) receptor antagonist.

Ambystoma↗
PubMed1990

Coronary artery spasm induced by anesthesia: a case report and review of the literature.

Anesthesia-induced coronary vasospasm has been reported only rarely. We report a case, without previous cardiac history, in which immediately after anesthesia induction a marked ST elevation was noted on the EKG monitor. Premature ventricular contractions as well as non-sustained ventricular tachycardia were noted. These changes resolved immediately after nitroglycerin infusion and 75 mg of lidocaine were given. A coronary angiogram revealed normal coronary arteries and left ventriculogram. Ergonovine stimulation was not performed. The patient was discharged home on calcium entry blockers and nitrates. Exercise stress test two weeks after discharge was negative for ischemia. Induction of anesthesia triggering coronary spasm has been reported rarely, and to our knowledge never in the presence of angiographically normal coronary anatomy. Coronary vasospasm with typical EKG changes--namely, ST elevation and ventricular arrhythmias--has to be included as a possible complication of general anesthesia. Recognition of this syndrome allows prompt treatment and prevention of future episodes.

Anesthesia, General↗
PubMed1990

Teaching field potentials: a microcomputer simulation of the nerve action potential in a bidimensional conductor.

A computer simulation of the extracellular field potential recording of nerve activity is presented. An experimental setup composed of an oscilloscope, a nerve, a conductive surface, and a recording electrode is graphically simulated. The user may study the influence of the position of the recording electrode and of certain nerve properties (membrane potential, velocity of conduction and action potential duration), on the action potential shape. The different waves which constitute the action potential may be analyzed and their peak values plotted as a function of the independent variable (e.g. electrode distance from the nerve). Three-dimensional plots of a set of action potentials as a function of the independent variable may also be obtained. The stimulation allows the user to study the basic factors which determine the configuration of an extracellularly recorded compound nerve action potential.

Action Potentials↗
PubMed1989

Computer simulation for teaching membrane potential fundamentals.

A computer simulation of membrane potential generation is presented. It allows the user to vary the intra and extracellular concentrations of sodium, potassium and chloride ions (Na+, K+ and Cl-), and determine the membrane potential and the equilibrium potential for each ion. The permeability coefficients for the ionic species considered, and the temperature may also be changed at will. Concentration-potential curves may be obtained at any time. The user may also select a voltage clamp option, which allows him to impose a certain membrane potential value, and study the resulting driving force for each ion. The use of the program in general physiology courses has shown it to be a useful aid for teaching the principles of membrane potential generation.

Chlorides↗
PubMed1989

Computer program for statistical Mann-Whitney U nonparametric analysis of neuronal spike activity.

A program for neuronal activity analysis is described. The applied computational techniques are standard in the field of digital processing, but the program is particular in its field of application and mode of data selection. The program, written in Turbo Pascal for the IBM-PC and compatibles, statistically compares (Mann-Whitney U-test) two sets of graphically selected data, and establishes whether there are significant differences between them. Although the program was developed for spike frequency analysis, it can easily be adapted to perform statistical analysis of other kinds of data.

Action Potentials↗
PubMed1988

Actions of excitatory amino acid acid agonists and antagonists on the primary afferents of the vestibular system of the axolotl (Ambystoma mexicanum).

In order to determine the nature of the transmitter in the synapse between hair cells and primary afferent fibers, both resting and evoked spike activity of vestibular system afferents were recorded. Excitatory amino acid agonists and antagonists were applied by micro perfusion. Excitatory amino acid agonists consistently increased the firing rate of these afferents. The rank order in potencies of the agonists tested was: kainate greater than or equal to quisqualate greater than D-aspartate greater than or equal to L-glutamate greater than or equal to L-aspartate greater than N-methyl D-aspartate. Blockade of synaptic transmission with high-Mg2+ and low-Ca2+ solutions did not seem to affect the responses to the excitatory amino acid agonists indicating their postsynaptic action. Excitatory amino acid antagonists inhibit both resting and physiologically evoked activity. The rank order of inhibitory potency was: kynurenate greater than L-glutamate diethyl ester greater than D,L-2-amino-4-phosphono-butyrate greater than D-alpha-amino adipate greater than D,L-2-amino-5-phosphonovalerate. These findings suggest that an amino acid-related compound may be the transmitter at this synapse. The relative potencies of agonists and antagonists tested provide evidence that the transmitter released from the hair cells' basal pole in the axolotl vestibular system interacts with postsynaptic kainic/quisqualic type receptors.

Action Potentials↗
PubMed1987

A Turbo Pascal program for on line spike data acquisition and analysis using a standard serial port.

A Turbo Pascal program for data acquisition and analysis is presented. The program detects incoming data as TTL pulses through the serial port of an IBM-PC and compatible computers and displays the instantaneous frequency plot and the interval histogram on-line. Novel features of this Pascal program are: no special hardware requirements and on-line analysis of more than one source at a time. No hardware additions to the supplied computer and easy operation make this program a valuable tool, directly useable in an IBM-PC and compatible computers.

Action Potentials↗
PubMed1987

Is GABA an afferent transmitter in the vestibular system?

This study was undertaken to determine the possible role of GABA as an afferent transmitter in the vestibular system of the axolotl. We studied the effects of GABA, muscimol, bicuculline and picrotoxin on the spontaneous spike discharge of the afferent fibers of the sacculi lagena and anterior semicircular canal. It was found that GABA and muscimol produce a very weak excitatory effect which does not mimic either the temporal course or the amplitude of the response of vestibular afferents to physiological stimuli. The GABA antagonist bicuculline has no significant effect on these fibers, and picrotoxin partially blocks the spontaneous activity in 33% of the fibers studied. These results indicate that GABA is probably not an afferent transmitter in the vestibular system as has previously been proposed.

Afferent Pathways↗
PubMed1986

A spike generator mechanism model simulates utricular afferents response to sinusoidal vibrations.

Using a model of spike generator mechanism (SGM) with a variable threshold we simulate the responses of utricular afferents to sinusoidal vibrations. It reproduces the phase locking characteristics (bifurcations diagrams) and the stimulus frequency firing rate relationships of different types of utricular afferents. We estimate the model parameters selecting the values which best fit the experimental results and we compare them with those from basic mechanisms involved in utricular codification.

Afferent Pathways↗
PubMed1986

Base-line data in a carcinogen-susceptible first-generation hybrid strain of Syrian golden hamsters: F1D Alexander.

Base-line data in over 600 control animals of both sexes of the first-generation hybrid BIO F1D Alexander strain of Syrian golden hamsters are presented. They involve mortality, body weights, spontaneous tumor incidence, and incidence of nonneoplastic lesions. The results confirmed previously published data on smaller numbers of animals of this hamster strain. Spontaneous tumors with an incidence of more than 2% were limited to lymphomas (less than or equal to 6%), adrenocortical carcinomas (less than 8%), adrenal adenomas (9-14% in males; 3.5% in females), islet cell adenomas (less than 6%), and follicular adenomas of the thyroid gland (3.5% in females only). This low incidence of spontaneous tumors and the high survival rate (compared to those of hamsters from other sources), together with the previously established high susceptibility to tumor induction by carcinogen administration, render the F1D Alexander hamster an excellent animal model for lifetime carcinogenesis bioassays.

Amyloidosis↗
PubMed1984

Is the Na+,K+-ATPase symmetrically distributed in the neuroepithelium of the vestibular system in the axolotl (Ambyostoma mexicanum)?

This study was undertaken to assess the localization of the Na+,K+-ATPase in the neuroepithelial cells of the macula sacculi. In vitro perilymphatic (basolateral) perfusion with ouabain produced a significant drop in the membrane potential. Endolymphatic (apical) application of ouabain had practically no effect on membrane potentials. This suggests that Na+,K+-ATPase is asymmetrically distributed in the neuroepithelial cells.

Acoustic Maculae↗
PubMed1979

Cigarette smoke inhalation studies in inbred Syrian golden hamsters.

Invasive carcinoma of the larynx was induced in 36.8% of inbred Syrian golden hamsters from strain B10 15.16, susceptible to this type of cancer when exposed to smoke from reference filter cigarettes for 59-80 weeks. Nearly half the animals (47.4%) showed laryngeal cancer, including noninvasive carcinoma and carcinoma in situ, which occurred with daily smoke exposures (twice a day for 12 min each time, for 27 sec out of each min) 7 days a week at smoke concentrations of 22%. When the smoke concentration was reduced to 11%, the number of induced lesions was reduced proprotionately. When a portion of tobacco was replaced in the cigarettes by a tobacco supplement, Cytrel (a trademark of the Celanese Corp., Charlotte, N.C.), a reduction of carcinogenesis proportionate to the Cytrel content of the cigarette took place. Smoke from cigarettes containing only Cytrel and no tobacco induced no carcinomas under the conditions used. Other dose-related changes observed were laryngeal papillomas, laryngeal epithelial hyperplasia, tracheal epithelial hyperplasia, and metaplasia and accumulation of alveolar macrophages. Tar deposition in lungs and accumulation of alveolar macrophages. Tar deposition in lungs and larynges was determined in a separate study by means of a marker, decachlorobiphenyl, added to the cigarettes. Admixture of Cytrel to cigarettes reduced tar deposition in the respiratory tract, which paralleled the decrease in the incidence of laryngeal carcinoma. However, the amounts of tar deposited in the larynx when 100% Cytrel was smoked were still significant, even though no carcinomas were observed. Thus smoke from Cytrel tobacco supplement may be less carcinogenic than equal amounts of tobacco smoke.

Animals↗