Browsing by Author "ITURRIAGA, R"
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- ItemAXONAL MICROTUBULES - COMPARATIVE ANATOMY IN VERTEBRATES, INCLUDING MAN(1991) VERGARA, J; SERRA, M; SAITUA, F; ITURRIAGA, R; ALVAREZ, JThe microtubular density was assessed with the electron microscope in 3-mu-m myelinated fibers, myelin excluded, of 11 species from the following classes: Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. The average for all species was 20.6 microtubules/mu-m2. Dispersion of values was restricted as shown by a coefficient of variation of 15.8. The microtubular content of nonmedullated axons was assessed in trout, lizard, finch, and man. In the four species, the number of microtubules increased with the cross sectional area of the axon. In trout, lizard and finch, the microtubular density decreased from over 100 microtubules/mu-m2 in fibers smaller than 0.1-mu-m2 to about 30 in 1-mu-m2 fibers; in axons of equal size, the packing of microtubules of nonmedullated was similar between them, and with reported values for peripheral axons of cat and rat. In man, the microtubular density of nonmedullated fibers exhibited only a mild decrease with the axonal size. In the finch, myelinated and nonmedullated axons overlapped in the range 0.23-0.60-mu-m2 and both groups exhibited similar microtubular densities. We conclude that the packing of microtubules of the vertebrate peripheral axon is a feature largely conserved during evolution.
- ItemCAROTID-BODY CHEMORECEPTOR EXCITATION PRODUCED BY CAROTID OCCLUSION(1986) ALCAYAGA, J; ITURRIAGA, R; ZAPATA, PThe 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.
- ItemCOMPARISON OF THE SUBCELLULAR-DISTRIBUTION OF ALVEOLAR SURFACTANT IN 2 MAMMALIAN-SPECIES OF SIMILAR BODY-WEIGHT - CAT AND RABBIT(1992) OYARZUN, MJ; MORGADO, E; DUSSAUBAT, N; LATHROP, ME; ITURRIAGA, R; LARRAIN, C; ZAPATA, P1. 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.
- ItemCONFREG - A BASIC PROGRAM FOR CALCULATING AND PLOTTING CONFIDENCE-REGIONS BASED ON CORRELATIONAL ANALYSES(1989) ITURRIAGA, R; ALCAYAGA, J; ZAPATA, PMany 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.
- ItemFLOW-DEPENDENT CHEMOSENSORY ACTIVITY IN THE CAROTID-BODY SUPERFUSED INVITRO(1988) ALCAYAGA, J; ITURRIAGA, R; ZAPATA, PThe 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.degree. 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.
- ItemMICROTUBULE DENSITY AND SIZE OF AXONS IN EARLY DIABETES - IMPLICATIONS FOR NERVE-CELL HOMEOSTASIS(1985) ITURRIAGA, RThe density of microtubles and the axonal caliber were studied in myelinated axons from sural nerves of young male alloxan-diabetic and age-matched rats, at 0, 15, 30 and 60 days after diabetes induction. The longitudinal growth of axons was normal in diabetic rats, but, in contrast, the radial growth of axons was impaired. The axonal area was 20% less than normal in diabetic rats at the 60th day. Microtubule density was assessed in 3-.mu.m-diameter axons. No differences in microtubule density (range: 25.0-28.0 mictrotubules/.mu.m2) were found between or within diabetic and control groups. The subnormal axonal size in diabetic rats entailed a reduced content of microtubules in a nerve trunk because the relation between axonal size and mictrotuble density remained normal. Apparently mictrotubule density was independent of axonal length, and of age, weight or diabetic conditions of rats and was related only to the axonal size. These findings have implications in nerve cell homeostatis.