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Biomedical subjects

M R Fedde

Publications and source records attributed to M R Fedde.

At least 73 records · Page 4Linked to original sources
PubMed1983

Routes of blood supply to the head of the Pekin duck.

The principal routes of blood flow to the head in birds are the common carotid arteries and their branches. However, additional routes exist, and these were identified in White Pekin ducks. Metallic mercury was infused into the ischiatic artery of euthanized ducks with occluded brachiocephalic arteries during direct fluoroscopic visualization. In 7 of 10 birds, mercury reached the head through anastosmoses between the dorsal intercostal rami of the aorta and the descending vertebral arteries. In one bird, an anastomotsis was also present between the external iliac artery and the pectoral trunk. In 3 birds, no connections between the aorta and branches to the head could be demonstrated. It is likely that a small blood flow can reach the head through these anatomotses but it probably constitutes an insignificant fraction of the total.

Angiography↗
PubMed1982

Intrapulmonary CO2 receptors and control of breathing in ducks: effects of prolonged circulation time to carotid bodies and brain.

The role of intrapulmonary chemoreceptors in the breath-to-breath control of spontaneous breathing was studied in anesthetized ducks by stimulating these receptors with changes in mixed venous CO2 loads during prolonged circulation time to the carotid bodies and brain by vascular loops placed in both brachiocephalic arteries. Blood equilibrated with gas mixtures of high (85% CO2-15% O2) or low CO2 (air) was infused into the right ventricle at 100 ml . min-1, while simultaneously withdrawing blood from the entrance of the right atrium at the same rate. A variety of cardiopulmonary and blood gas variables were measured. Infusing blood of high PCO2 increased both respiratory frequency and tidal volume long before the altered blood could have reached the carotid bodies or brain. The increase in ventilation was not enough to prevent a rise in PaCO2. Infusing blood of low PCO2 decreased both respiratory frequency and tidal volume. Again, the changes in respiration occurred before the infused blood had reached the carotid bodies or the brain. Infusion of blood similar in PCO2 to mixed venous blood did not significantly alter ventilation or arterial blood gases. The rapidity of the ventilation response to a change in mixed venous CO2 load led us to conclude that the intrapulmonary chemoreceptors can detect changes in mixed venous CO2 loads and that they initiate a ventilatory change appropriate to minimize alterations in PaCO2. These receptors, thus, can control breathing on a breath-to-breath basis in birds.

Animals↗
PubMed1982

A method for localizing intrapulmonary chemoreceptors in the parabronchial mantle of the duck.

1. A method is presented for estimating the location of avian intrapulmonary chemoreceptors within the parabronchial mantle. 2. By determining the discharge frequency of a receptor at known receptor site Pco2's in a nonventilated but perfused lung, the receptor discharge could be calibrated to indicate the receptor site Pco2 during both ventilation and perfusion. 3. The relation among receptor site Pco2, mixed venous Pco2 and inspired Pco2 may be compared with calculated Pco2 profiles along the contact between air capillaries and blood capillaries and the receptor location may be determined as the relative distance between the luminal and peripheral ends of the air capillaries. 4. Of four receptors at the caudal end of a parabronchus, two were located at the terminal end of the air capillary and two along the peripheral half of the air capillary.

Animals↗
PubMed1980

Functional localization of avian intrapulmonary CO2 receptors within the parabronchial mantle.

To determine the location of avian intrapulmonary CO2 receptors, we changed the CO2 stimulus at different regions within the parabronchial mantle and measured the resulting changes in breathing pattern. Three procedures were used to vary the CO2 stimulus: (1) reverse the direction of pulmonary perfusion; (2) stop pulmonary ventilation while maintaining perfusion; and (3) stop pulmonary perfusion while maintaining ventilation. Right and left lungs of adult, anesthetized White Leghorn type chickens were independently, unidirectionally ventilated. The right lung was used to maintain the bird while the left pulmonary artery and vein were cannulated and connected to an extracorporeal gas exchanger, thereby isolating this lung's perfusion. The innervation to both lungs remained intact. When left pulmonary perfusion was reversed, the bird's breathing pattern remained unchanged. The change in breathing pattern that resulted from stopping left pulmonary ventilation was the same during forward perfusion (pulmonary artery to pulmonary vein) as during backward perfusion (pulmonary vein to pulmonary artery). The change in breathing pattern that resulted from stopping forward perfusion was the same as that resulting from stopping backward perfusion. The results indicate that CO2 receptors are not concentrated on the peripheral side of the parabronchial mantle, where venous blood would influence tham, or on the luminal side of the mantle, where arterialized blood would influence them. The CO2 receptors are either distributed symmetrically between the peripheral and luminal sides of the mantle or located in the epithelial lining of the parabronchial lumen.

Animals↗
PubMed1980

Control of respiration in the chicken: effects of venous CO2 loading.

To determine if ventilation in unanesthetized chickens is adjusted sufficiently to prevent alterations in the partial pressure of carbon dioxide in arterial blood (PaCO2) when the CO2 content of mixed venous blood is changed, hypercapnic (PCO2 about 533 Torr) and hypocapnic (PCO2 less than 10 Torr) blood was infused into the left jugular vein of decerebrate chickens at 38 ml . min-1 for 30 sec. Ventilation and PaCO2 were assessed by determining respiratory frequency (f), tidal volume (VT), and the end-tidal CO2 fraction while serial samples of arterial blood were withdrawn from the sciatic artery. Infusion of hypercapnic blood resulted in an increase VT and minute ventilation (VE) as well as an increase in PaCO2. Infusion of hypocapnic blood resulted in a decrease in VT and VE and a small, transient decrease in PaCO2; the PaCO2 often returned to control levels before the end of the infusion period. The respiratory control system in the chicken appears to be better able to maintain a constant PaCO2 when perturbed by a reduced venous CO2 load reaching the lung than when perturbed by a reduced venous CO2 load reaching the lung than when perturbed by an increased CO2 load. These results are consistent with the hypothesis that intrapulmonary CO2 receptors, whose sensitivity to PCO2 is highest at low PCO2, are involved in the breath-to-breath control of breathing in birds.

Animals↗
PubMed1980

Arterial and mixed venous blood gas tensions in exercising ducks.

Adult White Pekin ducks were exercised at three work levels on a treadmill at speeds of .9, 1.47, and 2.16 km/hr for 20 min with a 90 min rest period following each exercise period. Blood gas and pH analyses were performed on samples simultaneously withdrawn from the brachial artery and the right ventricle (as an estimate of mixed venous blood) at predetermined intervals during the experiment. Both arterial and mixed venous PCO2 significantly decreased with the increases in the level of exercise. Arterial pH did not change significantly from resting values at any level of exercise. Mixed venous pH decreased at the onset of exercise but returned to near resting value by the end of each exercise period. These measurements indicate that ducks increase their ventilation during exercise above that required to eliminate the generated CO2. Because the increased ventilation produces a reduction in arterial PCO2, it is unlikely that peripheral or central CO2-sensitive chemoreceptors are responsible for the ventilatory drive.

Animals↗
PubMed1980

End-tidal partial pressure of CO2 as an estimate of arterial partial pressure of CO2 during various ventilatory regimens in halothane-anesthetized dogs.

The correlation between end-tidal partial pressure of CO2 (PETCO2) and arterial PCO2 (PaCO2) was studied in six halothane-anesthetized dogs maintained under four different ventilatory regimens: (A) spontaneous breathing; (B) assisted positive-pressure ventilation; (C) intermittent manual inflation; and (D) ventilator-controlled breathing. For procedures A, B, and D together, there was a strong correlation between PETCO2 and PaCO2 (r = 0.8) that was highly significant at P less than 0.0001 for PETCO2 values between 31.3 and 61 mm of Hg. In spontaneous and controlled breathing, PETCO2 is representative of PaCO2 and provides a useful noninvasive tool for monitoring the patient maintained under general anesthesia. Furthermore, data suggest that any ventilatory support of the anesthetized patient markedly improves blood gas and acid-base status compared with that of the unsupported, spontaneously breathing animal.

Anesthesia, Inhalation↗
PubMed1979

Respiratory and cardiovascular responses to exercise in the duck.

Adult White Pekin ducks were exercised for 20 min on a treadmill (3 degrees incline) at two speeds: 0.9 and 1.47 km/h. Each exercise period was followed by a 90-min rest. Heart rate and systolic and diastolic blood pressure increased significantly during each exercise period. During exercise, tidal volume decreased and respiratory frequency increased. Minute ventilation markedly increased at the onset of exercise and continued to increase throughout, whereas clavicular air sac PCO2 (PCSCO2) decreased. Both PACO2 and PVCO2 decreased as the running speed increased. pHv decreased at the onset of exercise, but returned to near resting values by the end of an exercise period. During either exercise period pHa did not significantly change from control values. PAO2 exhibited significant increases at both exercise speeds. Both arterial and mixed venous plasma [HCO3-] decreased significantly with each exercise period. Body temperature increased 1-2 degrees C during each run. Because the increased ventilation produced a reduction in PaCO2 and Pcsco2, it is unlikely that peripheral or central CO2 receptors were responsible for the ventilatory drive: that drive may result from hyperthermia or activity of certain muscle afferents.

Air Sacs↗
PubMed1979

Cardiopulmonary responses to inhaled sulfur dioxide in the chicken.

Selected cardiopulmonary variables were measured in anesthetized, male, White Leghorn type chickens before, during, and after 60 min exposure to various inhaled SO2 concentrations ranging from 0 to 5000 ppm. In one series of experiments, birds breathed through their nostrils and mouth; in a second series they breathed through a tracheal cannula. Exposure to 5000 ppm SO2 rapidly caused death in all birds with cannulated tracheae and in 4 of 5 birds with an intact respiratory system; one bird in each series of experiments died when exposed to 1000 ppm. Inhaling 100 ppm SO2 did not alter heart rate, blood pressure, tidal volume, respiratory frequency, or arterial blood gases and pH. Airway resistance was decreased by inhaling 500 ppm SO2 and was initially decreased but later greatly increased by inhaling 1000 ppm. Respiratory frequency and minute volume were decreased and PaCO2 was increased by inhaling 1000 ppm. The cardiopulmonary responses to inhaling 5000 ppm were generally augmentations of those responses which occurred when 1000 ppm was inhaled. The SO2 could not be detected in caudal thoracic or abdominal air sac gas at any concentration inhaled but vascular congestion and areas of brown discoloration appeared in the lungs of all birds that inhaled 5000 ppm and some that inhaled 1000 ppm. Mucous secretion in the trachea increased in some birds that inhaled 500 ppm SO2 and in most that inhaled higher concentrations. Chickens appear to have more tolerance for inhaled SO2 than most mammals but the pollutant gas at high concentrations detrimetally affects the cardiopulmonary system.

Airway Resistance↗
PubMed1978

Ventilatory response to CO2 in birds. I. Measurements in the unanesthetized duck.

Ventilation and blood gases were measured in unanesthetized ducks at various levels of inspired CO2 partial pressure (PICO2). Ventilation was markedly augmented with increasing PICO2, whereas arterial and mixed venous PCO2 stayed essentially constant up to a PICO2 of about 20 torr and changed only slightly between that and the highest level tested (34 torr). After carbonic anhydrase had been blocked, blood PCO2 was elevated at all levels of PICO2 but the ventilatory response to increases in PICO2 were attenuated. The response to CO2 in the normal bird (before administration of acetazolamide) shows similarities to that in mammals. Qualitative differences between both classes of vertebrates after blockade of carbonic anhydrase may, however, suggest differences in their systems that control ventilation.

Acetazolamide↗
PubMed1978

Ventilation response to CO2 in birds. II. Contribution by intrapulmonary CO2 receptors.

The CO2 sensitivity of intrapulmonary CO2 receptors (IPC) in the duck was studied, before (Control) and after blockade of carbonic anhydrase by Diamox, by recording single unit afferent activity in the vagus nerve. During Control, IPC activity decreased with increasing airway CO2 concentration. After Diamox administration, the discharge from IPC was higher at all levels of airway PCO2, and the receptors' CO2 sensitivity was markedly attenuated. Comparing these results with measurements on ventilation and blood gases of the duck under similar experimental conditions (Powell et al., 1978b) suggests that IPC play a role in the adjustment of ventilation to altered concentrations of inspired CO2; IPC may thus be a significant component in the control of breathing under physiological conditions.

Acetazolamide↗
PubMed1978

Are avian intrapulmonary CO2 receptors chemically modulated mechanoreceptors or chemoreceptors?

Openings of paleopulmonic parabronchi in paralyzed, unidirectionally ventilated geese were photographed through small holes in the birds' mediodorsal secondary bronchi during single-unit recording from intrapulmonary CO2 receptors. Changes in the discharge frequency of the receptors as fractional CO2 concentration of ventilating gas was alternated between 0 and 0.05 were compared with the changes in cross-sectional areas of randomly selected parabronchial lumina. Intrapulmonary CO2 receptors, similar to those found in other avian species, are also present in geese. Changes in intrapulmonary CO2 concentration greatly influenced the discharge of these receptors but did not induce movement of parabronchial smooth muscle in this region of the lung. If most of the receptors are located in the paleopulmonic parabronchi, as currently appears to be the case, we must conclude that changes in receptor discharge in response to changes in intrapulmonary CO2 concentration do not result from mechanical distortion of the receptors induced by smooth muscle contraction; intrapulmonary CO2 receptors appear to be true chemoreceptors.

Action Potentials↗
PubMed1978

Hydrogen sulfide: effects on avian respiratory control and intrapulmonary CO2 receptors.

The respiratory response to acute inhalation of hydrogen sulfide (H2S) and the response of pulmonary CO2 receptors to this gas were studied in male White Leghorn chickens. Inhaling low concentrations of H2S (0.05%) for 30 min had no effect on ventilation, but respiratory frequency and tidal volume became irregular and variable in birds that inhaled 0.2% and 0.3% H2S for that period. All birds that inhaled 0.4% H2S died within 15 min. H2S, presented in the gas stream of unidirectionally ventilated birds, caused an increase in the discharge frequency of intrapulmonary CO2 receptors and an increase in the amplitude of sternal movements. Because an increase in the discharge of these receptors normally inhibits the central respiratory neurons and may lead to apnea, it is clear that H2S also has actions that increase the output from these central neurons. The possibility that H2S affects the intrapulmonary CO2 receptors by inhibiting carbonic anhydrase in them is discussed.

Animals↗
PubMed1978

Biogenic amine-containing cells in the chicken lung.

Formaldehyde induced fluorescence was used to identify biogenic amine-containing cells in the adult chicken lung. Such cells, found in the parabronchial region, are sparsely distributed. There are at least two types of biogenic amine-containing cells in the lung: one type probably contains serotonin and the other a catecholamine. These cells might function as either a humoral or hormonal regulator of pulmonary ventilation and perfusion or as a receptor involved in control of breathing.

Animals↗