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Biomedical subjects

D E Donald

Publications and source records attributed to D E Donald.

At least 37 records · Page 2Linked to original sources
PubMed1977

Blood reservoir function of dog spleen, liver, and intestine.

The reflex decrease in blood volume of the spleen, the liver, and the intestine of vagotomized dogs was measured by plethysmographic techniques during bilateral carotid occlusion and moderate and severe hemorrhage. The volume of blood mobilized from each organ during carotid occlusion and moderate hemorrhage was from 6 to 30% of their respective blood volumes and from 55 to 81% during severe hemorrhage. In each experimental situation the spleen exhibited the greatest ability to release blood and the intestine, the least. During moderate hemorrhage (9 ml/kg) the spleen yielded a volume equal to 35% of the blood lost, the liver 14% and the intestine 7%. Comparable figures for severe hemorrhage were 26, 13, and 5%, respectively. This order of ranking the component regions of the splanchnic circulation with regard to function as a blood reservoir may be specific for the dog.

Animals↗
PubMed1977

Collection of urine from each kidney in the rabbit without ureteral cannulation.

Collection of urine in rabbits by conventional methods such as catheterization of ureters or bladder with polyethylene tubing or Foley cannulas is hampered by the occurrence of hematuria or obstruction of urine flow, or both. These problems were solved by placing in the bladder a stainless steel device with a horizontal round disk attached to an eliptic vertical septum. The vertical septum divides the bladder into two compartments in such a way as to allow the collection of urine from each kidney. Studies show that this intrabladder devide can be satisfactorily used in acute experiments in anesthetized or conscious rabbits for periods up to 5-6 h.

Animals↗
PubMed1977

Anodal block of medullated cardiopulmonary vagal afferents in cats.

In anesthetized cats examination was made of the conditions under which the application of DC current to a mixed nerve permits determination of whether a reflex response is mediated by medullated or nonmedullated afferents. The following precautions should be observed. The nerve must be stripped of its sheath and bleeding avoided. The anode should be 6 mm distant from the cathode. The temperature of the mineral oil surrounding the nerve should be 30-32 degrees C to avoid activation of nonmedullated fibers during the block. The major limitation is a time- and frequency-dependent block of nonmedullated fibers which makes the technique suitable only for differentiating between medullated fibers and nonmedullated fibers with low frequency traffic. Observing these criteria, anodal block of the cervical vagus in sino-aortic denervated cats resulted in a mean rise in aortic pressure of 8 Torr; subsequent cold block caused a further mean rise of 30 Torr. Thus 80% of the total increase in aortic pressure could be ascribed to interruption of vagal C-fiber activity.

Afferent Pathways↗
PubMed1977

Change in liver blood flow and blood content in dogs during direct and reflex alteration of hepatic sympathetic nerve activity.

A mean decrease of 60% in liver blood volume was recorded by a plethysmographic technique during electrical stimulation of the hepatic nerves in anesthetized, vagotomized dogs. A decrease in pressure in the vascularly isolated carotid sinus to 40 mm Hg, from a mean control of 144 mm Hg, decreased liver blood volume by a mean of 16%; arterial blood pressure increased by a mean of 77 mm Hg. Carotid sinus hypotension was accompanied by respective mean increases of 16% and 1.4% in hepatic arterial and portal venous blood flows, and of 45% and 22% in arterial and portal resistances. Increase in sinus pressure to 240 mm Hg increased liver blood volume by a mean of 20%; arterial blood pressure decreased by 90 mm Hg. Sinus hypertension was accompanied by respective mean decreased of 10% and 1.5% in hepatic arterial and portal venous blood flows, and of 44% and 18% in arterial and portal resistances. Interruption of afferent vagal traffic from cardiopulmonary receptors was maximally effective in decreasing liver blood volume at a carotid sinus pressure of 40 mm Hg and was ineffective at carotid sinus pressures greater than 160 mm Hg. Combined withdrawal of carotid and cardiopulmonary vasomotor inhibition decreased liver blood volume by 42%; of this 37% was due to the cardiopulmonary and 63% to the carotid baroreflex. The study showed the canine liver to function as a blood reservoir by active mobilization of a portion of its blood volume.

Animals↗
PubMed1977

Behavior of cardiac receptors with nonmyelinated vagal afferents during spontaneous respiration in cats.

Activity from left atrial and left ventricular receptors with nonmyelinated vagal afferents (mean conduction velocity, 1.2 m/sec) was recorded in 13 closed-chest spontaneously breathing cats anesthetized with alpha-chloralose. The anatomic position of each receptor was determined by probing the opened heart at the conclusion of the experiment. Three of eight left atrial receptors and four of five left ventricular receptors were silent under resting conditions. The mean discharge frequency under resting conditons for the six receptors displaying spontaneous activity was 1.0 +/- 0.15 impulse/sec. Thus cardiac receptors with vagal nonmyelinated afferent have a low resting discharge in spontaneously breathing cats. The frequency and pattern of discharge of atrial but not of ventricular receptors was altered during spontaneous respiration. The atrial receptors discharged with cardiac rhythmicity during end inspiration and early expiration when transmural pressure was greatest and were silent for the remainder of the respiratory cycle. Whe respiration was augmented by CO2 breathing or blood volume was increased, the rate of discharge was a linear function of atrial transmural pressure. Eleven ventricular receptors with nonmyelinated afferents (mean conduction velocity, 1.0 m/sec) were exposed to graded volume expansion and phenylephrine infusion in eight open-chest and three spontaneously breathing cats. Raising left ventricular end-diastolic pressure alone increased the frequency of discharge, and a concomitant increase in systolic pressure caused a further increase in firing.

Animals↗
PubMed1976

Interplay among carotid sinus, cardiopulmonary, and carotid body reflexes in dogs.

Interactions among vascular reflexes evoked from carotid sinuses, carotid bodies, and cardiopulmonary region were examined in anesthetized, atropinized, and respired dogs with aortic nerves cut. The carotid sinuses were perfused at 220, 150, and 40-50 mmHg; the chemoreceptors were stimulated by perfusion with hypoxic hypercapnic blood. Cardiopulmonary vasomotor inhibition was interrupted by vagal cold block. Measurements were made of arterial blood pressure and of kidney and hindlimb vascular resistance. At sinus pressures less than 170-160 mmHg, cardiopulmonary vasomotor inhibition increased with increase in blood volume. At high sinus pressure, interruption of this augmented cardiopulmonary inhibition was as ineffective in changing vascular resistance as interruption of the lesser inhibition present during normovolemia. Chemoreceptor stimulation increased the response to vagal block at intermediate but not at high or low sinus pressure. The studies demonstrate the dominant role of the carotid sinus reflex when the three systems interact and the ineffectiveness of chemoreceptor stimulation when carotid or cardiopulmonary inhibition is maximal.

Animals↗
PubMed1976

Role of heart and lung receptors with nonmedullated vagal afferents in circulatory control.

Vagal afferents from the cardiopulmonary region exert a tonic inhibition on the vasomotor center. This is demonstrated by constriction of systemic resistance and splanchnic capacitance vessels and by increased output of renin when the vagi are cut or blocked. In dogs, removal or selective denervation of organs showed that receptors in the lungs, the atria, and the ventricles each are responsible for the vasomotor inhibition. That this inhibition is due to nonmedullated vagal afferents (C fibers) was demonstrated by selective cooling of the vagi, anodal block of medullated afferents, and selective electrical stimulation of medullated and nonmedullated fibers. In the open-chest cat the discharge frequency of individual C fibers is sparse and irregular (mean, 1.4 impulses/sec) but increases to 10 or more impulses/sec with moderate increases in cardiac filling pressure and exhibits cardiac rhythmicity or is continuous throughout the cardiac cycle. The inhibition of sympathetic vasomotor outflow effected through the cardiopulmonary receptors is inversely related to that exerted by the arterial baroreceptors. The former receptors have less influence on the muscle circulation than the latter, but have an equal or greater effect on the renal circulation. In summary, receptors in the heart and lungs with nonmedullated vagal afferents are an important component of the integrated neural control of the circulation.

Action Potentials↗
PubMed1975

Effect of primary bile acids on bile lipid secretion from perfused dog liver.

An isolated canine liver perfusion technique featuring a second dog as the pump oxygenator was used to compare biliary lipid secretion during randomized, steady-state perfusions at two different rates of cholyl taurine or chenodeoxycholyl taurine infusions. The hepatic extraction of the trihydroxy-conjugated bile acid was considerably greater than that of the dihydroxy conjugate, possibly explained by ultrafiltration experiments which indicated that cholyl taurine was less protein bound than chenodeoxycholyl taurine. Both bile acids induced phospholipid and cholesterol secretion that was linearly proportional to bile acid secretion. However, each mole of secreted chenodeoxycholyl taurine induced a greater relative secretion of phospholipid and cholesterol than did that of cholyl taurine. Thus in the canine liver, the two primary bile acids are extracted at different rates and induce biliary secretion of different relative lipid composition.

Animals↗
PubMed1975

Similarity of blood flows using indocyanine prepared in saline or distilled water.

Directly measured blood flow pumped through a mixer circuit was compared to estimates of flow from indicator dilution curves derived from bolus injections of indocyanine green dye prepared in 0.9% saline (saline dye) and in triple-distilled water (3 D dye). At flows whose mean appearance time was 1.6 s, the mean error of estimate +/-SD of 2.3 +/- 5.1% using 3 D dye was significantly different (P less than 0.05) from that of 5.6 +/- 7.0% using saline dye. Essentially, there was no difference in estimates of blood flow with each dye solution when mean appearance time was increased to 3.8 s. Thus, the error, which was perhaps due to electrolyte in the concentrated indocyanine green dye (saline dye) and subsequent slowed rate of optical stabilization after dilution in plasma, is small and does not explain the overestimation by indocyanine dilution curves of blood flow in intact dogs.

Animals↗
PubMed1975

Demonstration that the atria, ventricles, and lungs each are responsible for a tonic inhibition of the vasomotorcenter in the dog.

To localize the areas of the cardiopulmonary region involved in tonic inhibition of the vasomotor center, anesthetized dogs were subjected to sinoaortic denervation and diaphragmatic vagotomy. Afferent vagal nerve traffic was interrupted in the neck by cooling. With the venous return taken from the venae cavae, oxygenated extracorporeally, and returned to the aorta, the heart was removed, leaving the ventilated lungs (condition 1), and the lungs and the ventricles were removed, leaving the beating atria (condition 3). With the venous return taken from the pulmonary arteries, oxygenated extracorporeally, and returned to the left atrium, the lungs were removed, leaving the intact working heart (condition 2), and the lungs were removed and the atria were denervated, leaving the working innervated ventricles (condition 4). Vagal cooling increased aortic pressure by 25 plus or minus 2 (SE) mm Hg in condition 1, by 36 plus or minus 2 mm Hg in condition 2, by 29 plus or minus 2 mm Hg in condition 3, and by 29 plus or minus 7 mm Hg in condition 4. Removing the atria in condition 3 or denervating the ventricles in condition 4 abolished the reflex response. Thus, afferent vagal nerves from the lungs and the heart tonically inhibit the vasomotor center. The inhibition exerted by the heart is caused by receptors in the atria and the ventricles.

Animals↗
PubMed1975

Role of cardiac, pulmonary, and carotid mechanoreceptors in the control of hind-limb and renal circulation in dogs.

Reflex control of hind-limb and renal resistance vessels by cardiac and pulmonary receptors was studied by interrupting afferent vagal nerve traffic when only the heart or only the lungs were in situ in anesthetized dogs with sinoaortic denervation. During normocapnia, interruption of cardiac and of pulmonary vagal traffic decreased hind-limb blood flow (constant-pressure perfusion) by 23% and 21%, respectively. Corresponding decreases in renal blood flow were 23% and 33%. Hypercapnia augmented the decreases in renal blood flow due to the vagal block. Thus, the inhibitions exerted by the heart and lung receptores on these two beds were similar during normocapnia but were greater on the renal vessels during hypercapnia. In closed-chest dogs with their aortic nerves sectioned and their carotid sinus pressure controlled, combined withdrawal of carotid and cardiopulmonary inhibition decreased hind-limb and renal blood flow by about 80% and 40%, respectively, during both normovolemia and hypervolemia. Interruption of cardiopulmonary inhibition was responsible for 17% and 31% of the decrease in hind-limb blood flow at normal and increased blood volumes, respectively; values for the decreases in renal blood flow were 50% and 65%. Thus, cardiopulmonary receptors oppose the vasoconstriction due to carotid hypotension more effectively in the kidney than they do in the hind limb.

Animals↗