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J M Ibarz

Publications and source records attributed to J M Ibarz.

11 recordsLinked to original sources
PubMed1997

Effects of the gliotoxin fluorocitrate on spreading depression and glial membrane potential in rat brain in situ.

DC extracellular potential shifts (deltaVo) associated with spreading depression (SD) reflect massive cell depolarization, but their cellular generators remain obscure. We have recently reported that the glial specific metabolic poison fluorocitrate (FC) delivered by microdialysis in situ caused a rapid impairment of glial function followed some hours later by loss of neuronal electrogenic activity and neuron death. We have used the time windows for selective decay of cell types so created to study the relative participation of glia and neurons in SD, and we report a detailed analysis of the effects of FC on evoked SD waves and glial membrane potential (Vm). Extracellular potential (Vo), interstitial potassium concentration ([K+]o), evoked potentials, and transmembrane glial potentials were monitored in the CA1 area before, during, and after administration of FC with or without elevated K+ concentration in the dialysate. SD waves propagated faster and lasted longer during FC treatment. DeltaVo in stratum pyramidale, which normally are much shorter and of smaller amplitude than those in stratum radiatum, expanded during FC treatment to match those in stratum radiatum. The coalescing SD waves that develop late during prolonged high-K+ dialysis and are typically limited to stratum radiatum, also expanded into stratum pyramidale under the influence of FC. SD provoked in neocortex normally does not spread to the CA1, but during FC treatment it readily reached CA1 via entorhinal cortex. Once neuronal function began to deteriorate, SD waves became smaller and slower, and eventually failed to enter the region around the FC source. Slow, moderately negative deltaVo that mirrored [K+]o increments could still be recorded well after neuronal function and SD-associated Vo had disappeared. Glial cell Vm gradually depolarized during FC administration, beginning much before depression of neuronal antidromic action potentials. Calculations based on the results predict a large decrease in glial potassium content during FC treatment. The results are compatible with neurons being the major generator of the deltaVo associated with SD. We conclude that energy shortage in glial cells makes brain tissue more susceptible to SD and therefore it may increase the risk of neuron damage.

Animals↗
PubMed1997

[Quality of life after radical prostatectomy].

OBJECTIVE: To evaluate the quality of life of our prostatectomized patients relative to the following factors: continence, mictional quality, sexual potency and psychological repercussion. MATERIAL AND METHODS: The study includes a series of 204 patients undergoing radical prostatectomy between June 1986 and October 1996, where a personal questionnaire was administered to 112 of them. The questionnaire consisted of 25 questions dealing with various aspects related to their quality of life. RESULTS: The overall rating on continence shows the following results: total continence 59.8%, minimal incontinence grade I 17.8%, moderate incontinence grade II 13.3% and total incontinence grade III 8%. Only 2.6% retains sexual potency after surgery. 29.3% of impotent patients consulted for their dysfunction. 91% declared to be satisfied with the results of the surgical procedure. CONCLUSIONS: In our experience, continence (total + grade I incontinence) is acceptable for 77.6%, the level of mictional satisfaction being very high. There is a high index of impotence after surgery. However, most patients appear to be impervious to this fact. Overall, quality of life of our patients has not changed significantly as a result of the intervention.

Aged↗
PubMed1994

Rectification properties and Ca2+ permeability of glutamate receptor channels in hippocampal cells.

Excitatory amino acids exert a depolarizing action on central nervous system cells through an increase in cationic conductances. Non-NMDA receptors have been considered to be selectively permeable to Na+ and K+, while Ca2+ influx has been thought to occur through the NMDA receptor subtype. Recently, however, the expression of cloned non-NMDA receptor subunits has shown that alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are permeable to Ca2+ whenever the receptor lacks a particular subunit (edited GluR-B). The behaviour of recombinant glutamate receptor channels predicts that Ca2+ would only permeate through receptors that show strong inward rectification and vice versa, i.e. AMPA receptors with linear current-voltage relationships would be impermeable to Ca2+. Using the whole-cell configuration of the patch-clamp technique, we have studied the Ca2+ permeability and the rectifying properties of AMPA receptors, when activated by kainate, in hippocampal neurons kept in culture or acutely dissociated from differentiated hippocampus. Cells were classified according to whether they showed outward rectifying (type I), inward rectifying (type II) or almost linear (type III) current-voltage relationships for kainate-activated responses. AMPA receptors of type I cells (52.2%) were mostly Ca(2+)-impermeable (PCa/PCs = 0.1), while type II cells (6.5%) expressed Ca(2+)-permeable receptors (PCa/PCs = 0.9). Type III cells (41.3%) showed responses with low but not negligible Ca2+ permeability (PCa/PCs = 0.18). The degree of Ca2+ permeability and inward rectification were well correlated in cultured cells, i.e. more inward rectification corresponded to higher Ca2+ permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1994

Role of neuronal synchronizing mechanisms in the propagation of spreading depression in the in vivo hippocampus.

To detect what initiates spreading depression (SD), the early prodromal events were investigated in hippocampal CA1 of urethane-anesthetized rats. SD was provoked by microdialysis or focal microinjection of high-K+ solution. Extracellular DC potentials and extracellular potassium concentration ([K+]o) were recorded, and spontaneous and evoked potentials analyzed for current source-density (CSD). In the front of an approaching SD wave, several seconds before the onset of the typical sustained negative potential shift (delta Vo) and the increased [K+]o, fast electrical activity was detected. This consisted initially of small rhythmic (60-70 Hz) sawtooth wavelets, which then gave way to a shower of population spikes (PSs) of identical frequency. Prodromal wavelets and PSs were synchronized over considerable distances in the tissue. Sawtooth wavelets were identified as pacemakers of the prodromal PS burst. Simultaneous recording at three depths revealed that the spontaneous prodromal PSs occurred exactly in phase in dendrites and somata whereas synaptically transmitted PSs arose first in the proximal dendrites and were conducted from there into the soma membrane. During a spike burst, stratum (st.) pyramidale served as current sink, while in the proximal sublayer of st. radiatum spike-sinks gave way to spike sources that grew larger as the sinks in st. pyramidale began to subside. Blocking synaptic transmission did not abolish the prodromal spike burst, yet repetitive orthodromic activation inhibited it without altering the subsequent SD waveform. Complex changes in cell excitability were detected even before fast spontaneous activities. We concluded that, in the initial evolution of SD, changes in neuron function precede the regenerating depolarization by several seconds. We propose that the opening of normally closed electric junctions among neurons can best explain the long-distance synchronization and the flow current that occurs in the leading edge of a propagating wave of SD.

Animals↗
PubMed1986

Spectral estimation of temporal series at unequal intervals.

Many biological variables present rhythmic oscillations at different frequencies. Most common techniques, which statistically characterize temporal series and permit the study of these rhythms, require equidistant sampling. However, it is not always possible to register at regular intervals many of the variables under study, either because of the nature of the phenomenon which generates them or because of the difficulty in obtaining the samples. This paper proposes a method for spectral estimation by means of fitting to the cosine functions of sampled variables using a nonuniform point process.

Animals↗
PubMed1985

Cortical visual evoked potentials during the sleep-wakefulness cycle in the freely moving cat. A dynamic study.

The dynamic features of visual evoked potentials, elicited by a light emitting diode chronically implanted in the frontal sinus of the freely moving cat, were studied during sleep stages by means of calculation of the power spectra of the EEG prior to the stimulus and the poststimulus EEG which contain the single evoked potential. The statistical analysis between mean frequencies from both EEG prior to the stimulus and single evoked potential, within each sleep stage, showed that the main changes occurred during slow sleep, with a significant increase in the percentage of the alpha band. These results are interpreted as a partial desynchronization evoked by the visual stimulation during the synchronized phase of sleep.

Animals↗
PubMed1984

Cortical visual evoked potentials during the sleep wakefulness cycle of the freely moving cat. Characterization and statistical comparisons.

Visual evoked potentials (VEPs) were obtained during the stages of wakefulness (W), slow sleep (SS) and paradoxical sleep (PS) by means of a light-emitting diode chronically implanted in the frontal sinus of the freely moving cat. Statistical analysis of the variables: latencies, latency intervals and amplitudes, between each of the mentioned stages shows that, for the first components, variations occurred only in the first interval of latency during SS vs. W. Lengthening of VEP latencies and increase of VEP amplitudes were observed for all secondary components in the comparisons between both SS and W, and SS and PS. PS-VEPs vs. W-VEPs showed shortening of latencies and decrease of amplitudes of all secondary components of the former case. The results confirm that in the freely moving cat, the secondary VEP response is more intensely affected by sleep than the primary VEP response, but indicate that there are different mechanisms in the generation of the VEP during SS and PS.

Animals↗
PubMed1983

[Statistical analysis of the parameters defining the cortical visual evoked potentials in the phases of the sleep-wake cycle].

Visual evoked potential parameters (latencies, intervals of latencies and amplitudes) obtained by photic stimulation using a light-emitting diode implanted in the frontal sinus of cats were studied by statistical methods (analysis of variance) during the stages of wakefulness, slow sleep and paradoxical sleep. The results show: a) greater intraindividual homogeneity in all cases with special emphasis on the latencies; b) the greatest homogeneity of responses was found during slow sleep and paradoxical sleep stages; c) in relation to the influences exerted by the sleep-wakefulness cycle on the visual evoked potentials, the parameters most affected were those closely related to the secondary complex. We conclude, that latency, due to its great homogeneity, is the most useful parameter in this kind of experiments and secondly, that it is the secondary complex of the visual evoked potentials that is affected by the endogenous conditions of the subject (in our case the sleep-wakefulness cycle stage).

Activity Cycles↗