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Biomedical subjects

M R Fedde

Publications and source records attributed to M R Fedde.

108 records · Page 6Linked to original sources
PubMed1970

Intrapulmonary receptor response to changes in airway-gas composition in Gallus domesticus.

1. A unidirectional, artificial ventilating system was used to observe respiratory and neural responses to changes in CO(2) concentration in pulmonary airways of the chicken.2. Sectioning any of the three pulmonary branches of the vagus slowed the respiratory response to sudden removal of CO(2) from unidirectional ventilating gas stream.3. The impulse frequency of CO(2)-sensitive units was inversely related to the CO(2) content in the ventilating gas stream.4. Abrupt elimination of CO(2) from the ventilatory gas stream caused a transient burst of activity from CO(2)-sensitive receptors, which quickly adapted to a constant discharge frequency. Fifty percent of the units responded within 0.35 sec after CO(2)-free gas reached the lungs. The neural response to abrupt re-addition of CO(2) to the gas stream was less rapid.5. Acetylcholine or NaCN injected into the pulmonary artery had no apparent effect on the discharge of CO(2)-sensitive receptors. Veratridine temporarily reduced discharge and occasionally produced short, rapid bursts of activity.6. Hypoxia and hyperoxia (5% and 80% O(2)) produced no significant change in the discharge of CO(2)-sensitive receptors.7. Carbon dioxide-sensitive units in spontaneously breathing chickens were silenced by adding 10% CO(2) to the inspired gas; the units responded vigorously to inflation of the respiratory system with a gas containing no CO(2) but remained silent during inflation with gas containing 15% CO(2). Units insensitive to CO(2), which increased their impulse frequency during inflation regardless of the CO(2) content of the inflating gas, also were observed.

Acetylcholine↗
PubMed1969

Electrical properties and acetylcholine sensitivity of singly and multiply innervated avian muscle fibers.

Membrane constants and distribution of acetylcholine (ACh) receptors were determined for multiply innervated fibers of the anterior latissimus dorsi (ALD) and singly innervated fibers of the posterior latissimus dorsi (PLD) muscles of 3-6 month old chickens. The values of the various membrane constants were: length constant, 1.78 mm (mean) in ALD, 0.68 mm in PLD; time constant, 35 msec in ALD, 3.7 msec in PLD; transverse membrane resistance, 4388 ohm cm(2) in ALD, 561 ohm cm(2) in PLD; and membrane capacitance, 8.2 microF/cm(2) in ALD, 7.0 microF/cm(2) in PLD. Peaks of ACh sensitivity occurred at intervals of ca. 740 micro on ALD fibers with a low sensitivity remaining between peaks. Only one peak of ACh sensitivity was detected on PLD fibers. The maximum ACh sensitivity found was 5 +/- 4 mv/ncoul for fibers of the ALD and 77 +/- 60 mv/ncoul for fibers of the PLD. The distance over which this sensitivity fell to 0.1 was ca. 225 micro in the ALD and 140 micro in the PLD. The membranes of these two muscle fiber types differ widely regarding some electrical properties and the disposition of ACh-sensitive receptor sites.

Acetylcholine↗
PubMed1968

Receptors sensitive to carbon dioxide in lungs of chicken.

Receptors responsive to the removal of carbon dioxide from ventilatory gas were demonstrated in the lungs of the chicken. Apnea was induced in 0.64 second after rapid lowering of respired carbon dioxide in the absence of blood flow through the lungs. Afferent impulses from the receptors are conducted centrally in the vagi.

Animals↗
PubMedDate not supplied

Blood viscosity in chronically hypoxic rats: an effect independent of packed cell volume.

We compared apparent blood viscosity, measured with a cone-plate viscometer, in normoxic and chronically hypoxic rats. All comparisons were made at equal packed cell volume (PCV) and shear rate conditions. Apparent viscosity of whole blood from the hypoxic rats was significantly lower than that from normoxic littermates and was similar to that of young rats. Apparent viscosity of red cells from hypoxic rats suspended in phosphate buffered saline remained lower than that from the normoxic rats. When blood cells from the hypoxic rats were suspended in plasma from normoxic rats, apparent viscosity was lower than when blood cells from normoxic animals were suspended in plasma from hypoxic rats. The lower viscosity of the blood from hypoxic rats appears to be associated with characteristics present in newly generated red cells. The reduced apparent viscosity of blood in hypoxic rats may partially compensate for the increase in PCV, at least during the early stages of hypoxia.

Aging↗