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Biomedical subjects

L E Olson

Publications and source records attributed to L E Olson.

At least 37 records · Page 2Linked to original sources
PubMed1989

Epithelium- and mucosa-dependent relaxation and contraction of normal equine trachealis muscle in vitro.

Strips of trachealis muscle were dissected from the mid-cervical portion of the trachea from horses that were free of respiratory tract disease. The epithelium and mucosa were removed from one group of tissues and were left intact in a second group of tissues. Each tissue was suspended in a bath filled with Krebs-bicarbonate solution that was aerated with 5% CO2 in oxygen and maintained at 37 degrees C. Isometric tension was continuously recorded. The contractile response to square-wave electrical stimulations increased as frequency (3, 5, 10, 15, 20, 25, and 30 Hz), voltage (10, 15, 18, and 25 V), and pulse duration (0.2, 0.5, 1.0, 1.5, and 2.0 ms) increased in tissues with the epithelium and mucosa intact. A stimulus of 18 V, 20 Hz, and 0.5 ms induced maximal contraction. Atropine (10(-6) M) abolished the response to 18 V and 0.5 ms at all frequencies. The increase in active isometric tension was concentration dependent when acetylcholine (10(-9) to 10(-4) M) was added to the baths in 0.5-logarithmic increments. Tissues that were contracted in response to acetylcholine (10(-5) M) had a concentration-dependent decrease in active isometric tension when isoproterenol was added to the baths in 0.5-logarithmic increments (10(-9) to 10(-4) M). The contraction and relaxation curves were qualitatively similar, but quantitatively different in tissues with and without the epithelium and mucosa. Removing the epithelium and mucosa increased the contractile response to acetylcholine at bath concentrations of 3.1 x 10(-7) M and 10(-6) M. The presence of epithelium and mucosa enhanced the magnitude of isoproterenol-induced relaxations.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1989

Response of equine airway smooth muscle to acetylcholine and electrical stimulation in vitro.

Smooth muscle strips from the midcervical portion of the trachea and bronchial smooth muscle strips from third-generation airways of horses were placed in tissue baths, and isometric contractile force was measured. Active force was measured in response to electrical stimulation and exogenous acetylcholine. Square-wave electrical stimuli were applied at various voltages (10, 12, 15, 18, 20, 25 V), frequencies (3, 5, 10, 15, 20, 25, 30 Hz), and pulse durations (0.2, 0.5, 1.0, 1.5, 2.0 ms). Isometric contractile force increased as voltage, frequency, and pulse duration increased. Maximal contractile response to electrical stimulation was obtained at 18 V, 25 Hz, and 0.5 ms. Atropine (10(-6)M) or tetrodotoxin (3 x 10(-6)M) blocked the contraction, indicating that the contractile response was attributable to the release of neurotransmitter from cholinergic nerves. Cumulative concentration-response curves to acetylcholine (10(-9)M through 10(-4)M) were determined. Isometric contractile force increased as acetylcholine concentration increased. There was a significant (P less than 0.05) difference in the 50% effective dose for acetylcholine in tracheal smooth muscle and bronchial smooth muscle. The mean (+/- SD) contractile response to maximal electrical stimulus was 89% (+/- 7.4%) of that in response to 10(-4)M acetylcholine in tracheal smooth muscle and was 68% (+/- 10.4%) of the response to 10(-4)M acetylcholine in bronchial smooth muscle.

Acetylcholine↗
PubMed1988

Innervation of crab-eating monkey trachealis muscle determined in vitro.

Strips of smooth muscle from the cervical tracheae of six adult male crab-eating monkeys (Macaca fascicularis) were studied in jacketed 25 ml organ baths filled with Krebs-bicarbonate solution maintained at 37 degrees C and gassed with 5% CO2 in oxygen. Isometric tissue tension increased in response to electrical field stimulation (18 V, 25 Hz, 0.5 msec), norepinephrine in the presence of propranolol, acetylcholine and histamine. Atropine abolished the contractile response to electrical stimulation. Tissues that were contracted with acetylcholine or pretreated with atropine then contracted with histamine relaxed when stimulated electrically. The relaxation was unaffected by propranolol but was abolished by tetrodotoxin. Isoproterenol relaxed tissues that were contracted with histamine, but failed to relax histamine-contracted tissues that had been pretreated with propranolol. Norepinephrine did not change isometric tension in untreated tissues or tissues pretreated with phentolamine. These results demonstrate the presence of excitatory and inhibitory nerves and noninnervated beta-adrenergic receptors in macaque trachealis. The excitatory nerves appear to be cholinergic. The inhibitory response to electrical stimulation is not mediated through muscarinic cholinergic or beta-adrenergic receptors. The inhibitory response to electrical field stimulation was likely mediated through nonadrenergic noncholinergic nerves.

Acetylcholine↗
PubMed1988

Pleural liquid pressure measured with rib capsules in anesthetized ponies.

Pleural liquid pressure was measured at end expiration in 11 spontaneously breathing anesthetized ponies in the prone and supine positions. A liquid-filled capsule was implanted into a rib to measure pleural liquid pressure with minimal distortion of the pleural space (Wiener-Kronish et al., J. Appl. Physiol. 59: 597-602, 1985). Capsule position relative to lung height was measured from thoracic radiographs taken in each position. In each body position, pleural liquid pressure was most negative in the superior lung regions and least negative in the inferior lung regions. In the supine position, the magnitude of the vertical gradient in pleural liquid pressure was 0.67 cmH2O/cm ht and was not significantly different from 1 cmH2O/cm ht. In the inferior lung regions (less than 50% lung ht), pleural liquid pressure averaged -1.3 cmH2O, indicating a low transpulmonary pressure over the region of the chest where most of the lung mass is located. When animals were in the prone position, the magnitude of the vertical gradient in pleural liquid pressure was 0.14 cmH2O/cm ht and was not statistically different from 0 cmH2O/cm ht. In each body position, mean transpulmonary pressure, measured postmortem, was similar to the estimated magnitude of pleural liquid pressure at 50% lung ht. This suggests that pleural liquid pressure is closely related to pleural surface pressure. These results are consistent with the poor ventilation distribution and reduced lung volumes measured in anesthetized horses in the supine position compared with values measured in horses in the prone position.

Animals↗
PubMed1987

Effect of variable parenchymal expansion on gas mixing.

Using implanted radiopaque markers, Hubmayr et al. (J. Appl. Physiol. 54: 1048-1056, 1983) and Olson et al. (J. Appl. Physiol. 57: 1710-1714, 1984) detected a variability in the volume changes of regions defined by the markers in intact and excised dog lungs, respectively. In dogs lying prone and in excised lobes, there is virtually no large-scale spatial organization of the variability. We interpret these data as evidence of an intrinsic heterogeneity of parenchymal expansion. The effect of variability of parenchymal expansion on gas mixing is calculated. From a statistical model, we infer that the variability of volume changes observed by Olson et al. is a result of an underlying variability with a larger magnitude at a smaller scale and that the variability at the smaller scale is large enough to explain the inefficiency of mixing observed in single-breath oxygen tests on excised dog lobes.

Animals↗
PubMed1987

Small airway pressure-diameter relationships during nonhomogeneous lung lobe inflation.

The pressure-diameter behavior of airways within a collaterally ventilating segment of lung was evaluated radiographically in 12 excised dog lung lobes. The results were compared with the pressure-diameter behavior of airways in a lung region adjacent to the collaterally ventilating segment. Airways in each lung region were dusted with powdered tantalum, and airway diameters were measured during homogeneous and nonhomogeneous lobe inflation. Intrasegmental and extrasegmental airways behaved similarly during homogeneous lobe inflation; airway diameter increased as alveolar pressure increased. The lobe was inflated nonhomogeneously by raising pressure in the collaterally ventilating segment (Ps) while maintaining pressure at the lobar bronchus (Pao) constant at 5, 10, or 15 cmH2O. Increasing Ps at constant Pao reciprocally affected intrasegmental and extrasegmental airways. When Pao was low, intrasegmental airways were expanded, and extrasegmental airways were compressed when Ps was raised. When Pao was high, airway diameter was unaffected by increasing Ps presumably because the airways were already maximally expanded. A comparison of diameters during homogenous and nonhomogenous lobe inflation suggests a very small interdependence effect from the parenchyma surrounding the collaterally ventilating segment. These results demonstrate the combined effects of parenchymal properties and airway pressure-diameter relationships in determining the effect of local lung distortion on airway function.

Animals↗
PubMed1986

Effect of flow direction on collateral ventilation in excised dog lung lobes.

We determined the effect of flow direction on the relationship between driving pressure and gas flow through a collaterally ventilating lung segment in excised cranial and caudal dog lung lobes. He, N2, and SF6 were passed through the lung segment distal to a catheter wedged in a peripheral airway. Gases were pushed through the segment by raising segment pressure (Ps) relative to airway opening pressure (Pao) and pulled from the segment by ventilating the lobe with the test gas, then lowering Ps relative to Pao. Driving pressures (Ps - Pao) between 0.25 and 2 cmH2O were evaluated at Pao values of 5, 10, and 15 cmH2O. Results were similar in cranial and caudal lobes. Flow increased as Ps - Pao increased and was greatest at Pao = 15 cmH2O for the least-dense gas (He). Although flow direction was not a significant first-order effect, there was significant interaction between volume, driving pressure, and flow direction. Dimensional analysis suggested that, although flow direction had no effect at Pao = 10 and 15 cmH2O, at Pao = 5 cmH2O, raising Ps relative to Pao increased the characteristic dimension of the flow pathways, and reducing Ps relative to Pao reduced the dimension. These data suggest that at large lobe volumes, airways (including collateral pathways) within the segment are maximally dilated and the stiffness of the parenchyma prevents any significant distortion when Ps is altered. At low lobe volumes, these pathways are affected by changes in transmural pressure due to the increased airway and parenchymal compliance.

Analysis of Variance↗
PubMed1985

Cutaneous lymphoid hyperplasia: results of radiation therapy.

Four cases of cutaneous lymphoid hyperplasia (CLH) were treated with radiation therapy. Sixteen separate areas of the skin were irradiated. Only two received more than 18 Gy (1,800 rad). Follow-up ranged from eight months to seven years. No infield recurrences were observed, and cosmetic results were excellent. The authors suggest that radiation therapy can be highly effective in the treatment of CLH.

Adult↗
PubMed1985

Distortion of submerged dog lung lobes.

The conically shaped caudal lobes of dog lungs were submerged, tip downward in saline, and the lateral surfaces of the lobes were thereby exposed to a hydrostatic gradient in transpulmonary pressure. The force that was required to balance the buoyancy was applied through a clip attached to the tip of the lobe. The locations of metal markers implanted in the parenchyma and attached to the surface were tracked, and regional volume and the horizontal and vertical components of strain were obtained as functions of vertical position. An engineering analysis of the deformation is qualitatively consistent with the data, but the predicted strains are larger than the observed strains. From the experimental and analytical results, we conclude that, for this deformation, the regional volume-local transpulmonary pressure curve closely follows the pressure-volume curve because negative horizontal strains nearly balance the positive vertical strain caused by the buoyancy force.

Animals↗
PubMed1985

Effect of transpulmonary and driving pressures on collateral gas flow in dog lungs.

The effect of changing segment pressure (Ps) and airway opening pressure (Pao) on flow through a collaterally ventilating lung segment was evaluated in intact and excised dog lungs. He, N2, and SF6 were passed through the lung segment distal to a catheter wedged in a peripheral airway at driving pressures (Ps - Pao) between 0.25 and 2 cm H2O. Eight excised caudal lobes were studied at Pao = 5, 10, and 15 cm H2O. Flow was directly related to Ps - Pao and Pao and inversely related to the density of the gas. A dimensionless plot of the driving pressure normalized to a reference dynamic pressure as a function of Reynolds number (Re) indicated that flow through the segment behaved as if it were laminar at Re less than 100 and that increasing Pao increased the dimension of the pathways conducting flow as shown previously. Small changes in Ps had no effect on pathway geometry or on the pattern of flow through the segment at Pao = 10 and 15 cmH2O. At Pao = 5 cm H2O increasing segment pressure appeared to increase the dimensions of the flow pathways slightly. Similar changes in Ps - Pao had no consistent effect on flow pattern or pathway geometry in six anesthetized, paralyzed, vagotomized dogs at functional residual capacity or after widely opening the chest (Pao = 5 cm H2O). These results suggest that, at large lobe volumes, airways (including collateral pathways) are maximally dilated and therefore relatively insensitive to small changes in segment pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1984

Regional interdependence in calf lungs.

We measured K, an index of interdependence in sublobar segments of both intact and excised calf lungs. In excised and intact lungs, segment volume was held constant while the lung was inflated. K in excised lungs was of small magnitude but was greater in caudal than in cranial and middle lobes. When isolated segments in a variety of regions and with a variety of shapes were studied, K was positively correlated with the interface area between the segment and the remainder of the lung, was negatively correlated with the pleural surface area of the segment, but was not correlated with segment volume. In a given region of lung, however, small segments had a greater interdependence than large segments. In intact lungs of anesthetized calves, K was an order of magnitude greater than in excised lungs, confirming that the chest wall is the major determinant of interdependence. There were no lobar differences in K in intact lungs.

Anesthesia, General↗
PubMed1984

Regional differences in expansion in excised dog lung lobes.

The position of small metallic markers embedded within the lung parenchyma and glued to the pleural surface of four excised right caudal dog lobes were determined during stepwise deflation from an airway opening pressure of 25 cmH2O in air-filled suspended lobes and 8 cmH2O in saline-filled lobes submerged in saline. Changes in the volumes of tetrahedrons formed by four noncoplanar markers were taken as regional lung volume changes at the centroids of the tetrahedron. In both air- and saline-filled lobes at all volumes below total lobe capacity (TLC) there was considerable variability in regional volume. The variability occurred at the first step below TLC and increased with deflation. Regions behaved consistently; regions that were proportionally larger or smaller than the overall lobe at any step tended to be larger or smaller, respectively, at all steps. There was a significant correlation between the regional behavior of the air- and saline-filled lobes. The variability of regional volume did not follow any clear topographical orientation. These results indicate there is considerable variability of lung compliance within small regions. This heterogeneity of regional parenchymal properties may be the anatomical basis of the nonuniformity of regional ventilation known to occur in intact animals and excised lobes within small regions at the same vertical height.

Air↗
PubMed1983

Topographical distribution of regional lung volume in anesthetized dogs.

The distribution of regional lung volume during static deflation from total lung capacity to functional residual capacity was determined from the positions of intraparenchymal metallic markers ascertained by a biplane video roentgenographic technique in supine and prone anesthetized dogs. Regional lung volumes were linearly related to overall lung volume so that regional volume could be characterized by a ventilation index (VI), which is the ventilation per alveolus relative to the ventilation of the overall lung. For the supine position, there were vertical and cephalocaudal gradients in VI in both the upper and lower lobes. Mean VI was greater in the lower lobe than in the upper lobe, but VI was less than would be predicted from extrapolation of the upper lobe relationship. For the prone position, there was no consistent gradient in VI in any direction. The magnitude of the gradients in VI and the effects of body position suggest that, in the recumbent dog, the thoracic cavity shape is a more important determinant of regional lung volume than is the effect of gravity on the lung itself.

Anesthesia, General↗
PubMed1983

Pressure-flow relationships in a collaterally ventilating dog lung segment.

We evaluated the pressure (P)-flow (V) relationship in collaterally ventilating dog lung segments by passing He, N2, and SF6 through a bronchoscope (5 mm OD) wedged in a peripheral airway. Measurements were made at functional residual capacity (FRC) and two higher lung volumes, keeping segment-to-airway opening pressure constant (3 cmH2O) in five anesthetized, paralyzed, vagotomized, supine dogs. Average flows ranged from 5.0 to 8.0 ml/s for He, 4.5 to 7.5 ml/s for N2, and 3.4 to 4.7 ml/s for SF6. When these data were fitted as P = K1/3/3 mu V + K2 rho V2, density-dependent pressure losses were unimportant when He and N2 were used, suggesting laminar flow with these gases. A dimensionless plot of the total pressure drop relative to a reference dynamic pressure as a function of Reynolds number at the bronchoscope tip suggested that flow through the segment behaved as if it were laminar at Reynolds numbers less than 100. Furthermore, when the airway diameter used to compute the normalized pressure and Reynolds number was scaled as the cubic root of lung volume, curves for all three gases were superimposed, suggesting that the dimensions of intrasegmental/collateral airways scale as lung volume 1/3.

Animals↗
PubMed1982

Propranolol-vagal-alveolar CO2 interactions on collateral gas flow in dog lungs.

The mechanical properties of a collaterally ventilating lung segment were studied in 18 anesthetized paralyzed mongrel dogs artificially ventilated with room air end-tidal CO2 fraction = 5%. Nine dogs were pretreated with propranolol, and nine dogs were not. With 0, 5, or 12% CO2 in O2 flowing into the segment, steady-state resistance of segmental airways (Rss) and time for 90% pressure equilibration (T90) between the segment and airway opening after flow was discontinued were determined at functional residual capacity with the vagus nerve ipsilateral to the segment intact, sectioned, or electrically stimulated. Vagal stimulation increased Rss and T90 at all CO2 levels, whereas unilateral vagotomy had no effect. Propranolol treatment enhanced the increase in Rss caused by vagal stimulation at low but not at high CO2 levels, suggesting that high CO2 mimics the effect of propranolol on Rss. High levels of CO2 did not have the same effect as propranolol on T90, propranolol treatment reducing the increase in T90 caused by vagal stimulation at high but not at low CO2 levels. These results demonstrate that local changes in alveolar CO2 tensions modify but do not abolish the effect of vagal stimulation on collateral ventilation.

Animals↗
PubMed1980

Effect of vagal stimulation on collateral flow resistance in dog lungs.

Vagal effects on steady-state resistance of pathways within a segment of lung (Rss) were studied in open-chest dogs using a wedged catheter technique. To prevent adrenergic bronchodilation, dogs were pretreated with propranolol. Rss was determined with vagi intact or sectioned and during electrical stimulation of right and left vagi. Following determination of Rss, gas flow into the segment was arrested, segmental pressure decay recorded, and the time for 90% decay (T90) measured. Stimulation of the vagus supplying the lung with the wedged catheter (ipsilateral) increased Rss and T90 at low (2-4 cmH2O) transpulmonary pressures (Pao) and T90 at high (5-9 cmH2O) Pao. Vagal sectioning and contralateral stimulation had minimal effects. Atropine abolished vagal effects. We modeled the segment as two series compartments, one with a rapid time constant and one with a longer time constant. At both low and high Pao, vagal stimulation prolonged the slow time constant. If the fast compartment represents small airways and the slow compartment collateral pathways, collaterals may not be effective in maintaining ventilation to lung segments distal to a vagally constricted bronchus.

Animals↗