Convergence in foraging strategies by two morphologically and phylogenetically distinct nocturnal aerial insectivores

We used measurements of morphological parameters of common nighthawks ( Chordeiles minor ) and big brown bats ( Eptesicus fuscus )to derive predictions about foraging behaviour based on the animals foraging at the same site. We tested the predictions using data from direct observation, radio telemetry and diet analysis and found a high degree of convergence in behaviour by these two species.     

Effects of inspiratory resistance loading on lung fluid balance in awake sheep

Because pulmonary edema has been associated clinically with airway obstruction, we sought to determine whether decreased intrathoracic pressure, created by selective inspiratory obstruction, would affect lung fluid balance. We reasoned that if decreased intrathoracic pressure caused an increase in the transvascular hydrostatic pressure gradient, then lung lymph flow would increase and the lymph-to-plasma protein concentration ratio (L/P) would decrease. We performed experiments in six awake sheep with chronic lung lymph cannulas. After a base-line period, we added an inspiratory load (20 cmH2O) and allowed normal expiration at atmospheric pressure. Inspiratory loading was associated with a 12-cmH2O decrease in mean central airway pressure. Mean left atrial pressure fell 11 cmH2O, and mean pulmonary arterial pressure was unchanged; calculated microvascular pressure decreased 8 cmH2O. The changes that occurred in lung lymph were characteristic of those seen after other causes of increased transvascular hydrostatic gradient, such as increased intravascular pressure. Lung lymph flow increased twice base line, and L/P decreased. We conclude that inspiratory loading is associated with an increase in the pulmonary transvascular hydrostatic gradient, possibly by causing a greater fall in interstitial perimicrovascular pressure than in microvascular pressure.     

Thromboxane A2 and prostacyclin do not modulate pulmonary hemodynamics during exercise in sheep

The purpose of this study was to determine the role of thromboxane and prostacyclin in modulating pulmonary hemodynamics during maximal cardiopulmonary stress in the healthy lung. We studied 11 yearling sheep in paired studies during progressive maximal treadmill exercise with and without meclofenamate (n = 5), ibuprofen (n = 6), or UK38485 (n = 2). We also studied five sheep during hypoxia and hypoxic exercise, and six sheep during prolonged steady-state treadmill exercise for 45-60 min with and without drug treatment. We measured the metabolites of thromboxane A2 (thromboxane B2, TxB2) and prostacyclin (6-ketoprostaglandin F1 alpha, 6-keto-PGF1 alpha) in blood plasma and lung lymph in each protocol. We found that progressive exercise significantly reduced pulmonary vascular resistance but that cyclooxygenase or thromboxane synthesis blockade did not alter the change. Plasma TxB2 rose minimally but significantly during maximal exercise, but 6-keto-PGF1 alpha did not change. During continuous hypoxia, exercise reduced pulmonary vascular resistance nearly to base-line levels, but the degree of reduction was also unchanged by drug treatment. There were also no significant changes in lymph or plasma TxB2 or 6-keto-PGF1 alpha during 45-60 min of continuous moderate exercise. We conclude that neither TxB2 nor prostacyclin modulate pulmonary hemodynamics in the normal lung during maximal exercise, prolonged moderate exercise, or exercise-induced reductions in vascular resistance during hypoxia.     

Increased vasoreactivity and chronic pulmonary hypertension following thoracic irradiation in sheep

Six chronically catheterized sheep were exposed to 1,500-rad whole-lung irradiation and followed for a four-week period. Pulmonary arterial, left atrial and systemic arterial pressures, cardiac output, arterial blood gases, and pH were measured at base line and biweekly following radiation. Pulmonary vasoreactivity to 12% O2, 100% O2, and an analogue of prostaglandin H2 (PGH2-A) was also assessed. Five nonirradiated sheep served as controls. By the 2nd wk following irradiation, pulmonary vascular resistance had doubled. Final pulmonary arterial pressure was increased 50% over the base-line value (base line = 14 +/- 1 cm H2O; final 22 +/- 2; mean +/- SE; P less than 0.05). Arterial PO2 was decreased to approximately 70 Torr throughout the study. In addition, pulmonary vasoreactivity to PGH2-A, but not to breathing 12 or 100% O2, was significantly increased above base line in the irradiated animals (P less than 0.05). Morphometric techniques applied to the lungs in which the pulmonary arterial circulation was distended with barium gelatin mixture, showed extension of muscle into the distal intra-acinar arteries, and a reduction in both the external diameter and the number of barium-filled peripheral arteries in the irradiated animals. Thus thoracic irradiation results in functional and structural changes of chronic pulmonary hypertension and increased pulmonary vasoreactivity to PGH2-A. The structural changes in the peripheral pulmonary arterial bed may contribute to the increased pulmonary vascular reactivity following thoracic irradiation.     

Effects of prolonged elevated microvascular pressure on lung fluid balance in sheep

Experiments were conducted in seven chronically instrumented unanesthetized sheep to estimate the osmotic reflection coefficient (sigma d) for total proteins and the solvent-drag reflection coefficients (sigma f) for six endogenous protein fractions. We measured the lymph-to-plasma ratio of total proteins (CL/CP) and six protein fractions during base-line conditions and after left atrial pressure elevations of 24-26 h per elevation. We also monitored pulmonary arterial pressure, left atrial pressure, systemic arterial pressure, and lung lymph flow at the various levels of pulmonary microvascular pressure. Our results indicate the CL/CP may require up to 24 h to reach a true steady state. It was found that sigma d is at least 0.89 for total proteins and sigma f is at least 0.84, 0.87, 0.86, 0.92, 0.95, and 0.96 for protein fractions with effective molecular radii of 36, 39.5, 44, 66, 105, and 123 A, respectively. In addition, the sigma f values for various protein fractions obtained from this investigation are compared with the predicted values of various mathematical models of the lung microcirculation.     

Ketamine-induced tongue protrusions in rats

1. The purpose of this study was to demonstrate that ketamine anesthesia (100 mg/kg) induces tongue protrusions (P) in addition to retrusions (R) and swallows (S) in adult rats. 2. These linguo-pharyngeal events occur alone or combined in various sequential patterns. 3. The SPR sequence is not the predominant pattern in all preparations suggesting profound disruption of physiological linkages by ketamine. 4. Haloperidol administration suppresses these events for 1-120 min depending on the dose (0.75-2.5 mg/kg). 5. Swallows are the least vulnerable to haloperidol. 6. This and previous findings provide further evidence that ketamine induced linguo-pharyngeal activity can serve as a model for acute or tardive dyskinesia better than stereotypies.     

Tumor necrosis factor's effects on lung mechanics, gas exchange, and airway reactivity in sheep

The macrophage- and monocyte-produced cytokine tumor necrosis factor alpha (TNF alpha) has been proposed as a major mediator of endotoxin-induced injury. To determine if TNF alpha could reproduce the effects of endotoxin on the lung, we intravenously administered 10 micrograms/kg of human recombinant TNF alpha into five chronically instrumented unanesthetized sheep on two occasions to characterize the TNF alpha response and its reproducibility. We assessed changes in lung mechanics, pulmonary and systemic hemodynamics, gas exchange, and the number and type of peripheral blood leukocytes. We also determined airway reactivity by use of aerosolized histamine before and after TNF alpha infusion. Pulmonary arterial pressure (Ppa) peaked within 30 min of initiating the TNF alpha infusion [47.7 +/- 2.2 vs. 15.9 +/- 0.4 (SE) cmH2O at base line] and then returned toward base line over 4 h. There was a brief decline in left atrial pressure after TNF alpha. Pulmonary hypertension was accompanied by leukopenia, neutropenia, and increases in the alveolar-arterial O2 difference (AaDO2). Dynamic lung compliance (Cdyn) declined after TNF alpha, reaching a nadir within 15 min of the initiation of the TNF alpha infusion [0.045 +/- 0.007 vs. 0.093 +/- 0.007 (+/- SE) l/cmH2O at base line]. Resistance to airflow across the lung (RL) increased from 1.2 +/- 0.2 cmH2O.l-1.s at base line, peaking at 5.4 +/- 1.3 cmH2O.l-1.s 30 min after the start of the TNF alpha infusion. Alterations in Cdyn and RL persisted for 4 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of granulocyte depletion on pulmonary responsiveness to aerosol histamine

The effects of granulocyte depletion with hydroxyurea on pulmonary responsiveness to aerosol histamine were studied in 10 chronically instrumented unanesthetized sheep. Sheep were studied when granulocyte counts were normal (B), after 3 days of hydroxyurea but before granulocyte counts had dropped below 700 cells/mm3 (H), and after granulocyte counts had fallen below 200 cells/mm3 (D). Hydroxyurea itself had no effect on aerosol histamine responsiveness and the results were unaffected by the order of experimentation. All 10 sheep were less responsive (P less than 0.05) to aerosol histamine when granulocyte depleted effective dose of histamine that caused a reduction to 65% of control dynamic compliance (ED65Cdyn = 23.98 +/- 4.70 mg/ml) compared with base line (ED65Cdyn = 7.06 +/- 1.86 mg/ml). Those sheep initially most responsive to aerosol histamine had the greatest attenuation in their airway responsiveness to aerosol histamine (P less than 0.05). There was a significant negative correlation between absolute granulocyte counts in peripheral blood and pulmonary responsiveness to aerosol histamine during base-line (B) condition (r = -0.74, P less than 0.05) and for the data as a whole [r = -0.69, P less than 0.05 (B + H + D)]. Circulating granulocytes and/or pulmonary inflammation may contribute to pulmonary responsiveness to bronchial challenge.