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P Zapata

Publications and source records attributed to P Zapata.

At least 19 recordsLinked to original sources
PubMed1996

Dissociation of hypoxia-induced chemosensory responses and catecholamine efflux in cat carotid body superfused in vitro.

1. To examine the correlation between chemosensory response and dopamine release induced by hypoxic stimulation, we studied carotid bodies excised from anaesthetized cats. 2. The carotid bodies with their carotid (sinus) nerves were superfused in vitro with modified Tyrode solution (pH 7.40, at 37.5 degrees C) equilibrated with 20 or 100% O2. The PO2 of the superfusing channel was monitored polarographically. The frequency of chemosensory discharges (fx) was recorded from the whole carotid nerve. Catecholamine (CA) efflux-mostly consisting of dopamine-was measured by high-speed chronoamperometry, through Nafion-coated carbon electrodes placed on the carotid body tissue. Chemosensory stimulation was induced by intrastream injections of NaCN, by superfusion with 100% N2-equilibrated saline (lowering PO2 to 25-40 Torr) or by flow interruption. 3. Low doses of NaCN increased fx, but had no measurable effect on CA efflux, while larger doses produced fast increases in fx, preceding delayed and prolonged increases in CA efflux. Repeated injections of NaCN, still increasing fx, gave reduced CA effluxes. 4. Switching to hypoxic superfusion for 6-8 min produced large and fast fx increases, but delayed and prolonged augmentations of CA efflux. 5. Administration of three to four boluses of dopamine (7-15 micrograms; augmenting CA concentration by up to 35 microM) initially decreased fx, after which hypoxic stimulation resulted in enhanced and faster CA effluxes, without changing the speed and intensity of chemosensory responses. 6. Flow interruptions induced fast increases in fx and delayed increases in CA efflux. Repeated flow interruptions produced similar increases in fx but progressively attenuated CA effluxes. 7. Our results suggest that CA efflux is not essential for hypoxia-induced chemosensory excitation in the cat carotid body. They also suggest the presence of two pools of releasable CAs in the carotid body, one of slow turnover and release, and another of recently incorporated dopamine and fast release, both pools being rapidly depleted by repeated stimulation of the carotid body.

Animals↗
PubMed1994

Effects of dopaminergic blockade upon carotid chemosensory activity and its hypoxia-induced excitation.

The effects of domperidone, antagonist of D2 receptors, on arterial chemoreceptor activity were studied in spontaneously breathing and pentobarbitone anesthetized cats, in which recordings of chemosensory impulse activity were obtained simultaneously from both cut carotid (sinus) nerves. Intravenous injections of domperidone 50 micrograms/kg produced a maintained increase in the basal frequency of chemosensory discharges, after which hyperoxic tests (breathing 100% O2 for 30 s) evoked larger falls in the rate of chemosensory impulses. Chemosensory responses evoked by hypoxic hypoxia (100% N2 tests) and by cytotoxic hypoxia (i.v. injections of NaCN) reached higher impulse rates after domperidone treatment. The effects of domperidone reveal that a resting release of dopamine from glomus cells maintains a low level of basal chemosensory activity under normoxic conditions. Domperidone turns off such restraining dopaminergic control and enhances the transient chemosensory responses to hypoxic stimuli. Present data support a modulatory role for dopamine within the chemoreceptor process, but not its participation as excitatory transmitter between glomus cells and sensory nerve endings.

Animals↗
PubMed1994

Phrenic nerve activity during artificial ventilation at different body temperatures and its relationships with carotid chemosensory activity.

While the chemoreceptor discharges of carotid bodies in vitro are highly dependent on temperature, these chemoreceptors in situ contribute only moderately to the ventilatory adjustment to changing body temperature (Tb), probably because of the concomitant and reverse changes in natural chemoreceptor stimuli in closed-loop preparations. Accordingly, we studied the frequency of carotid chemosensory discharge (fx) and the phrenic integrated electroneurogram (IENGph) in pentobarbitone anesthetized cats, paralyzed with alcuronium and artificially ventilated, at three steady-state levels of Tb (35.5, 37.5 and 40.2 degrees C), modifying the frequency and volume of the ventilator to maintain PETCO2 within normal range. While fx increases along with Tb when PETCO2 is allowed to fluctuate freely, its mean basal value was not consistently different at the three Tb's studied under controlled conditions. The amplitude of IENGph was reduced and the frequency of phrenic inspiratory cycles was increased as Tb was raised from 35.5 to 37.5 degrees C and then to 40.2 degrees C. Brief 100% O2 inhalations and i.v. injections of dopamine produced minimal depressions of IENGph amplitude in hypothermia, but pronounced although similar depressions in normothermia and hyperthermia. i.v. injections of NaCN augmented fx and IENGph in dose related manner, and the relationships between both variables showed larger changes in IENGph at the hypothermic and normothermic conditions when expressed in absolute terms, but not when expressed in relative terms. Thus, the chemosensory input is not consistently modified by thermal levels under controlled ventilatory conditions, but the chemosensory drive of the ventilatory output is less pronounced in hypothermia. The chemosensory input is similarly affected by varying degrees of cytotoxic hypoxia at different Tb's, but the ventilatory output is less vigorously increased in hyperthermia, pointing to a decreased reflex gain in that condition.

Animals↗
PubMed1994

A report on the evolution of this journal and an analysis of its present state and perspectives.

This journal appeared as Archivos de Biología y Medicina Experimentales between 1964 and 1992, its name being changed into Biological Research in 1992. This is a report on the past and present of the journal, analyzing the problems of a scientific journal published in English but produced in Latin America, those that its contributors must deal with in the preparation of the manuscripts, those involved in the evaluation procedures and editing of material for the press, and those about coverage by indexing services and the international recognition of the journal quality.

Chile↗
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↗
PubMed1992

Comparison of the subcellular distribution of alveolar surfactant in two mammalian species of similar body weight: cat and rabbit.

1. We studied the total amount and subcellular distribution of alveolar surfactant, extracted through bronchoalveolar lavage of anesthetized cats and rabbits. This was correlated to several morphometric and ventilatory variables of these animals. 2. Lung weight was significantly larger in the cat while respiratory frequency and minute ventilation were significantly larger in the rabbit. No significant differences were observed in tidal volume, total lung capacity, P(a)O2, P(a)CO2 and pH(a). 3. While both species had similar protein contents in the bronchoalveolar lavage, rabbits had larger phospholipid contents, mostly distributed in the lighter, more active subfractions. 4. With regard to the estimated values obtained from allometric equations derived for mammals, the rabbit presented a lung weight of nearly one-third of the estimated one, an exceedingly larger minute ventilation (by nearly 60%) and a respiratory frequency twice the calculated one. 5. We suggest that the different distribution of alveolar surfactant in these species may be explained by disparities in their ventilatory demands, the rabbit having a higher respiratory frequency and a larger minute ventilation, performed by a mass of lung tissue lower than that corresponding to its body mass.

Animals↗
PubMed1991

Effects of body temperature on chemosensory activity of the cat carotid body in situ.

The effects of changes in body core temperature (TB) upon the frequency of chemosensory discharges (fx) from one carotid nerve were studied in pentobarbitone anesthetized cats. Raising TB from 35 to 40 degrees C increased fx in some cats, an effect more commonly seen after contralateral carotid neurotomy. In other animals, the simultaneously increased alveolar ventilation counteracted the above effect. A multiple correlation analysis of global data showed predicted increases in fx in response to raising TB at different CO2 levels.

Analysis of Variance↗
PubMed1991

Thermal effects on ventilation in cats: participation of carotid body chemoreceptors.

In pentobarbitone anesthetized cats, raising body temperature from 37 to 40 degrees C by external heat increased respiratory frequency, tidal volume, frequency of spontaneous gasps and mean inspiratory flow. It reduced end-tidal CO2 pressure, together with inspiratory and expiratory durations. After bilateral section of the carotid nerves, raising body temperature still induced hyperventilation, but the increase in gasp frequency was less pronounced and no significant change in tidal volume was observed. In comparison to steady ventilatory values in the intact condition, significant reductions in tidal volume at 38 degrees C and in gasp frequency at 37, 39 and 40 degrees C were observed after bilateral carotid neurotomy. Brief hyperoxic tests induced transient decreases in tidal volume and increases in end-tidal CO2 pressure which were significantly larger at 40 degrees C than at 37 degrees C. These changes disappeared after bilateral carotid neurotomy. Anesthetic block of both carotid nerves produced transient reductions in tidal volume at any given temperature. We conclude that carotid body afferents contribute to the hyperventilation evoked by hyperthermia. After their interruption, such contribution is replaceable from other thermal afferents.

Animals↗
PubMed1991

Factors affecting distribution of alveolar surfactant during resting ventilation.

Few studies have been done to establish the ventilatory factors affecting alveolar surfactant under resting conditions. Experiments in which ventilatory variables were recorded for 4 h were performed in 12 adult cats breathing spontaneously under pentobarbital sodium anesthesia. After the animals were killed and bronchoalveolar lavages (BALs) were performed, the resulting fluid was subjected to differential centrifugation and determinations of proteins, phospholipids (PL), and disaturated phosphatidylcholine (DSPC). Pellet P1+2 was obtained by two centrifugations at 140 g; the supernatant was centrifuged at 1,000 g to obtain pellet P3 and subsequently at 60,000 g to obtain P4. Pellets P3 and P4 had the higher contents of PL and DSPC. Bivariate and multivariate correlational analyses indicate that 1) total PL in BAL was not related to any of the ventilatory variables studied, 2) PL in P3 and P4 fractions was directly correlated to the physiological range of variations in the frequency of large spontaneous gasps (fL), and 3) PL in P1+2 fraction was inversely related to fL. Cats subjected to bilateral section of carotid nerves, although presenting reduced chemosensory drive and ventilatory chemoreflexes, did not exhibit significant differences in resting ventilatory variables nor in alveolar surfactant components. Present results indicate that the total content of alveolar surfactant is not modified by ventilatory variations within physiological range but that the spontaneous occurrence of large gasps increases the proportion of more active forms of alveolar surfactant. This may mediate the role of augmented breaths in keeping lung compliance and preventing atelectasis under resting ventilatory conditions.

Animals↗
PubMed1990

Functional recovery of the ventilatory chemoreflexes after partial chronic denervation of the nucleus tractus solitarius.

In pentobarbitone-anesthetized cats breathing spontaneously, we studied whether excision of one petrosal ganglion would modify the reflex efficacy of the remaining carotid and aortic chemoafferences in ventilatory control. Resting ventilation was not affected shortly after the ganglionectomy, but decreased sensitivities and reactivities for changes in tidal volume and respiratory frequency were revealed by dose-response curves for ventilatory chemoreflexes evoked by NaCN i.v. After 2 weeks of ganglionectomy, basal tidal volume was increased, being slightly reduced by contralateral carotid neurotomy, but persisting above control after section of all buffer nerves. The ventilatory chemosensory drive--tested by breathing 100% O2--was unmodified with respect to the acute condition, but the tonic ventilatory influence exerted by the right carotid nerve was diminished. Dose-response curves for reflex changes in tidal volume exhibited increased sensitivity, while those for changes in respiratory frequency showed increased reactivity. Thus, partial chemosensory denervation of the nucleus tractus solitarius triggers a slowly developing increase in the reflex efficacy of the remaining chemosensory inputs. The recovery of sensitivity for reflex changes in tidal volume required the presence of contralateral carotid afferents, while the increased reactivity in respiratory frequency needed the integrity of aortic afferents. The results also suggest an enhanced contribution of central structures other than chemosensory inputs in respiratory control after partial deafferentation.

Animals↗
PubMed1990

Disappearance of opioidergic tone on LH secretion in underfed prepubertal sheep.

A study was conducted to determine whether an opioid tonus inhibitory of LH secretion is present in underfed prepubertal sheep. Ten Suffolk ewe lambs were subjected to food restriction during 60 days. During this period they were allowed to pasture only 2 hours per day while control ewe lambs were allowed for 10 hours. Body weight and plasma blood levels of glucose, urea and total proteins were measured weekly. At the end of this period, an intravenous injection of Naloxone (NAL, 1.5 mg/kg BW) was given to control and underfed animals followed 60 min later by an intravenous injection of LHRH to test the pituitary responsiveness. Underfed animals did not show an increase in plasma LH while control animals presented a rise from 0.28 +/- 0.08 to 2.02 +/- 0.6 ng/ml after the NAL stimulus (P less than 0.05). The response to LHRH was similar in both group of animals. Basal plasma levels of insulin were lower in underfed ewe lambs than in control animals (P less than 0.05). Underfed animals were placed on plain feeding with a schedule similar to control lambs for 30 days and the same experiment was repeated. During this occasion, NAL increased plasma LH concentration in both group of lambs. Levels of plasma insulin were not different in both groups. The lack of effect of NAL on LH secretion in food restricted ewe lambs suggests that the opioid modulation of LH secretion is absent by underfeeding in female prepubertal sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

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↗