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J Alcayaga

Publications and source records attributed to J Alcayaga.

29 records · Page 2Linked to original sources
PubMed1996

The petrosal ganglion of the adult cat: neuronal count, sectional area, and their respective distributions.

The petrosal ganglion contains most of the perikarya of sensory neurons of the glossopharyngeal nerve. We studied the number and size of neuronal somata in 4 petrosal ganglia from adult cats. Ganglia were serially sectioned in length at 8 microns, sections drawn through a projection microscope, and those neuronal profiles presenting nuclei and nucleoli on each section were counted and their areas measured. The number of neurons ranged from 2311 to 3429 (2908 +/- 271; mean +/- SEM). Neurons were symmetrically distributed around the longitudinal axes of most ganglia, with a skewed distribution in only one ganglion. The sectional area of most neurons (> 98%) ranged between 250 and 1725 microns 2, with median values of 667-963 microns 2. Area distributions were significantly different, but differences never exceeded 8.2% in related area bins. The ganglion presenting a skewed count distribution and the highest median area departed from the rest, with differences surpassing 25%. We conclude that the neuronal population of the petrosal ganglion of the cat is regular both with respect to the number and the size of its constituents, with departures from this pattern probably reflecting individual variations.

Adult↗
PubMed1993

Thermal dependence of chemosensory activity in the carotid body superfused in vitro.

We studied the relationship between chemosensory activity and temperature in carotid bodies excised from pentobarbitone-anesthetized cats, and superfused in vitro at flows between 0.4 and 2.0 ml/min with modified Tyrode's solution buffered with HEPES at pH 7.43. The basal frequencies of chemosensory discharges were recorded from the entire carotid nerve at different steady thermal conditions. For preparations superfused with saline equilibrated with 100% O2, thermally dependent increases in frequency were observed, with significant differences between all nearby thermal stages separated by 0.5 degrees C steps between 36.0 and 38.5 degrees C. The larger gains were recorded between higher temperatures at high flows, between mid temperatures at intermediate flows, and between lower temperatures at low flows. The critical temperature for the calculated maximal gain was directly correlated to superfusion flow. The basal frequencies were consistently elevated when switching to saline equilibrated with 20% O2 and no significant differences in mean ranks were recorded between 36 and 37 degrees C, as between 38 and 39 degrees C, but frequencies at 36-37 degrees C were significantly higher than those at 38-39 degrees C. Brief rises in chemosensory discharges were evoked by injections of NaCN applied to carotid bodies superfused with saline equilibrated with 100% O2. The least effective dose was lower at 40 degrees C than at 37.5 degrees or 35.0 degrees C, but the reactivity and slope were not significantly different. It is concluded that the carotid body chemoreceptors fulfill the criteria for being considered as thermosensors, and that their frequency of discharges is thermally modulated within a range close to physiological body temperature.

Animals↗
PubMed1991

The chick chorioallantoic membrane promotes survival of co-transplanted rat carotid bodies and nodose ganglia.

Carotid bodies and nodose ganglia, removed from adult rats, were co-implanted onto the chorioallantois of 6- to 12-day chick embryos. Implants were rapidly vascularized and incorporated into the chorioallantoic membrane, where they survived and grew for up to 12 days. The morphological characteristics of grafted tissues were largely preserved. Regenerating axons from nodose neurons invaded the carotid body and contacted some glomus cells through morphologically immature synapses. Thus, the chick chorioallantoic membrane may be a useful substrate to study carotid chemoreceptor-sensory neuron interactions.

Allantois↗
PubMed1990

Electrophysiological evidence for the reconstitution of chemosensory units in co-cultures of carotid body and nodose ganglion neurons.

The electrophysiological characteristics of nodose ganglion sensory neurons, cultured alone or co-cultured with carotid body tissue, were compared. Some properties of the neurons and their response to acid (a carotid body 'natural' stimulus) changed in the presence of this tissue. (a) The evoked action potential after-hyperpolarization was smaller and longer whereas spike amplitude and duration, and the passive membrane properties remained unaltered. (b) Spontaneously occurring action potentials happened more frequently (16% vs 3%). (c) Acid solutions induced appreciable depolarization, an increased discharge, or both, only in a population of co-cultured neurons. These changes probably arose because of synaptic and/or trophic interactions between neurons and glomus cells.

Action Potentials↗
PubMed1989

Fast activity and oscillatory potential of carp retina in the frequency domain.

There are two kinds of fast activity in the ERG: fast retinal potentials (FRP), an irregular series of spiky wavelets and oscillatory potentials (OP), a rhythmic sequence of events. Corneal ERG from nine intact young carps, evoked by extended pulses of diffuse white light under mesopic adaptation, displayed two different groups of wavelets related to ON and OFF, respectively. Stimulation and recording conditions were established to permit separate Fourier analysis of both groups of wavelets. Power distributions of normalized ON spectra showed both a wide dispersion and a high inter-subject variability. All normalized OFF spectra showed, instead, components within a narrow band from 52 to 56 Hz, most of them maximum relative power peaks. It is concluded that FRP originating in highly labile sources dominate ON fast activity, while the predominant OFF fast activity are OP originating in a stable discrete source.

Animals↗
PubMed1989

CONFREG: a BASIC program for calculating and plotting confidence regions based on correlational analyses.

Many observations encountered in biological and medical research are randomly distributed in bivariate scales, and thus not susceptible to simple regression analyses. Since such data are depicted by ellipses in scatter diagrams, a computer program to calculate the confidence regions for the means or the total data of bivariate samples was written in BASIC for correlational analyses. The program, based on the principal axes algorithm, plots the calculated confidence regions as an elliptic area, using the fitted equations for its major and minor axes. The program displays the sample parameters required to perform comparisons between different groups of experimental conditions.

Animals↗
PubMed1988

Flow-dependent chemosensory activity in the carotid body superfused in vitro.

The relationship between carotid body chemoreceptor activity and flow was studied in preparations superfused in vitro. The carotid bodies were excised from pentobarbitone-anesthetized cats and superfused with modified Tyrode's solution, buffered with HEPES-NaOH to pH 7.41. The bath temperature was kept constant at 37.7 degrees C. The frequency of chemosensory discharges from the entire carotid nerve was determined during steady-state superfusion with 100% or 20% O2-equilibrated saline at flow rates between 0.15 and 2.95 ml/min, and during 5 min flow interruptions. The peak frequency evoked by flow interruptions was maximal and independent of previous superfusion flows, but the half-excitation time of chemosensory responses to flow interruption was minimal when preceded by superfusion with 100% O2-equilibrated saline at 0.7 ml/min. In steady-state conditions, mean chemosensory activity was higher at lower rates of flow, and, at constant flow, higher under 20% O2 than under 100% O2. To allow comparisons of all data, basal frequencies at given basal flows were referred to their own maximal frequencies evoked by flow interruptions. The best fitting for the relation between basal chemosensory activity and superfusion flow was provided by inverse sigmoid (logistic decay) curves: r = -0.90 and -0.84, at 100% and 20% O2 levels, respectively. The maximal gains were at about 0.78 and 0.86 ml/min, respectively. It is concluded that the chemosensory discharge frequency recorded from carotid bodies superfused in vitro is determined by the superfusion flow, when all other natural chemoreceptor stimuli are held constant.

Animals↗
PubMed1988

Contribution of carotid body chemoreceptors and carotid sinus baroreceptors to the ventilatory and circulatory reflexes produced by common carotid occlusion.

The effects evoked by 1 min occlusions of the common carotids were studied in 16 spontaneously breathing pentobarbitone anesthetized cats. Unilateral occlusions induced increases in systemic arterial pressure (to 111.5% of basal), but no changes in ventilation. Bilateral occlusions provoked larger increases in systemic arterial pressure (to 137.5% of basal) and mild tachycardia, associated with pulmonary and alveolar hyperventilation. Breath-by-breath minute volume augmented (to an averaged maximum of 144.7% of basal), the increase in tidal volume being more important than that of respiratory frequency. The maximal changes occurred shortly after occlusion and they were inversely but not linearly related to the minimal levels of intrasinusal pressure attained. Changes were subsequently attenuated during each occlusion, depending on the partial restoration of intrasinusal pressure. After barosensory denervation of the carotid sinuses, the cardiovascular responses to bilateral occlusions were reduced, but the respiratory ones were not affected. During 100% O2 breathing in cats with intact innervation or carotid barodenervation, the respiratory responses to bilateral occlusions were much reduced and delayed, or even absent. That the above circulatory and respiratory effects of carotid occlusions were of reflex nature was demonstrated by their elimination after bilateral section of the carotid (sinus) nerves. Results indicate that while barosensory withdrawal during carotid occlusion is mostly responsible for reflex hypertension and bradycardia, chemosensory excitation induced by this maneuver is the major cause of reflex hyperventilation.

Animals↗
PubMed1986

Nerve branching and terminal arborizations in the carotid body of the cat. A light microscopic study following anterograde injury filling of carotid nerve axons with horseradish peroxidase.

The terminal arborizations of carotid nerve axons within the carotid body of the cat were densely filled with horseradish peroxidase and studied under the light microscope. Two types of terminal arborizations were found in contact with glomus (type I) cells. The axons differed principally in the wealth of terminal swellings. The largest and most numerous type of arborization consisted of one to several clusters of terminals of variable size and shape arising from a single fiber and distributed in a rather ellipsoidal domain of about 9,000 microns 3 for each cluster. Thus, these arborizations might be in close relation with 20-60 glomus cells. The second type of arborization had substantially fewer terminal swellings, occupying a smaller volume and probably contacted significantly less glomus cells. Both kinds of axons had small rounded and large calyciform endings. The larger arborizations were derived consistently from larger fibers than those which produced the smaller arborizations. The results suggest that the carotid nerve axons generate two types of arborizations within the carotid body. Thus, glomus cells potentially can contact two classes of afferent fibers. The functional significance of a dual chemoreceptor innervation of the carotid body is discussed.

Animals↗
PubMed1986

Carotid body chemoreceptor excitation produced by carotid occlusion.

The effects of common carotid artery occlusions on the afferent activity recorded from the carotid (sinus) nerve were studied in 20 pentobarbitone anesthetized cats. Ipsilateral occlusions lowered intrasinusal pressure down to 15-100 torr, depending on previous pressures, and resulted in silencing of carotid barosensory impulses. For cats breathing room air and with mean systemic arterial pressure below 125 torr, chemosensory excitation was induced whenever these occlusions lasted 5 sec or longer and it persisted during 10 min occlusions. The chemosensory excitation had a delay of about 4 sec and the maximal frequency of discharges was attained at nearly 30 sec, followed by a maintained submaximal level of about 80-90% of the peak frequency. For ipsilateral occlusions performed under 100% O2 inhalation, the delay of the excitation was increased to ca. 20 sec and the maximal frequency attained only 30-40% of that obtained for the same animal when breathing room air. Bilateral occlusions caused deeper falls in intrasinusal pressure and stronger chemoreceptor excitation. When arterial pressure was above 130 torr, ipsilateral occlusions only produced transient increases in chemosensory discharges or suppression of their ventilatory fluctuations. Chemical stimuli further increased chemosensory frequency during occlusions, indicating that blood flow through carotid body was not arrested. It is concluded that occlusions of the common carotid may induce an increased frequency of carotid chemosensory discharges. This increment is dependent on systemic arterial pressure, ventilatory conditions and duration of the occlusion. It is suggested that the increased carotid chemosensory activity may interact with the withdrawal of barosensory discharges to elicit the reflex changes observed during carotid occlusions.

Animals↗