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Blood flow in the circumflex branch of the left coronary artery of the intact dog
Department
of Reviews
and Abstracts
ZZZZZ Selected
Abstracts
Bronk, D. W., Ferguson, L. K., Margaria, R., and Solandt, D. Y.: The Activity the Cardiac Sympathetic Centers. Am. J. Physiol. 117: 237, 1936.
of
The activity of the cardiac sympathetic center s has been invsstigated by recordthe action potentials in the cardiac nerves from the stellate ganglia of the cat. There is a fairly continuous discharge of impulses which exert a ‘I tonic” augmentor and accelerator influence upon the heart. This discharge is, however, largely modified by changes in the chemical composition of the blood and by afferent impulses. The principal pathways of the impuhes from the cord to the stellate’ ganglion are the third and fourth and to a lesser extent the second and fifth thoracic rami. !l!he impulse frequency from the individual sympathetic motor nerve cells seldom exceeds ten or fifteen a second, and is usually considerably less. This contrasts with the much higher frequency of discharge from somatic motor nerve cells. ‘l!he potential pulses in the postganglionic nerves are of considerable magnitude because of the grouping of impulses which results from the innervation of many postganglionie fibers by a single preganglionic fiber. There are also much larger potential waves caused by the synchronous activity in very many nerve fibers. It is shown that this is due to the coordinated and This activity rhythmic discharge from large numbers of nerve cells in the centers. is b’ilaterally synchronous. The grouped activity is of four types. The volleys may come at irregular intervals or at other times periodically with frequencies varying from 5 to 20 sec. but unrelated to any other obvious rhythm of the organism. Or, on the other hand, the bursts of impulses may be synchronous with the pulse or the respiratory cycle. The latter two forms of rhythmic cellular activity are largely due to afferent impulses from the vissera: bursts of impulses from the blood vessels initiated by the systolic rise in pressure or the impulses from distention receptors in the lungs. An example of the marked effect of such afferent impulses upon the activity of the sympathetic centers is found in the observation that it is possible to drive those centers by repetitive stimulation of the central ends of the carotid sinus or aortic nerves, thus causing the motor nerve cells to discharge periodically with the frequency of the afferent impulses. This can be done within a limited range of stim.ulus frequencies. The characteristically grouped discharges from the cardiac sympathetic centers cause periodic variations in heart rate only if the bursts of efferent impulses are This is due to the inertia of the &ector mechanism. separated by some seconds. ing
AUTHOR. Essex, Hiram E., Herrick, J. F., Baldes, Edward J., and Mann, Flow in the Circumflex Branch of the Left Coronary Artery Am.
J. Physiol.
117:
271,
Frank C.: Blood of the Intact Dog.
1936.
E:y the use of the thermostromuhr of Rein, experiments have been made on the blood flow in the circumflex branch of the left coronary artery of the intact dog. Observations have been made over periods as long as fourteen days. 119
120
THE
AMERICAN
HIZART
JOURNAL
Epinephrtie causes a transient but marked increase in coronary blood flow, amounting in some experiments to as much as four or five times the control values. The coronary blood flow is doubled by administration of nitroglycerin or amyl nitrite, but the effect is of short duration. In response to appropriate doses of thyroxin, increases in coronary fiow as great as 244 per cent above the control values were observed forty-eight to ninety-six hours after injection. During the digestion of a meat meal the coronary flow was increased to a degree comparable to what has been observed in other vessels of the body. Exercise on a treadmill produced an initial rapid augmentation in coronary flow, which declined to a lower level as the exercise continued but additional work induced by changing the angle of the treadmill agtlin caused a temporary increase jn coronary flow, which declined to a lower value as the same degree of exercise continued. A significant correlation between heart weight and coronary flow or between pulse rate and coronary flow was not found.
AUTIIOR. Donal, John S., Jr., and Gamble, Physiol. 116: 495, 1936.
Clarence
J.:
The
Cardiac
Output
in Man.
Am.
J.
The simultaneous values of oxygen tension and of carbon dioxide tension in the lungs were computed for hypothetieai experiments of the type used in the triple extrapolation method of Redfield, Bock, and Meakins (1922) for estimating the cardiac output in man. When each computed value of carbon dioxide tension was plotted as a function of the computed oxygen tension, the points were found to lie on curves and not on straight lines as is assumed in the triple extrapolation method. The plotting of analyses of successive samples taken during continuous rebreathing gave curves with the same characteristics as those calculated from theoretical considerations. Pairs of such curves were constructed from experiments on ten subjects. When these were extrapolated by the linear procedure of the triple extrapolation method the venous tensions found were different from those indicated by the convergence of the curves. Because of the tensions in the rebreathed mixtures chosen for these experiments, these differences were greater for carb’on dioxide than for oxygen. Cardiac outputs of these subjects determined at the same time by the ethyl iodide method agreed more closely with a curved than with a linear extrapolation. Xt is concluded from these results that when gases are rebreathed or held in the lungs, variations in carbon dioxide and in oxygen tensions canuot be assumed to be directly proportional to each other. In consequence, the triple extrapolation method for the estimation of blood flow which Redfield, Bock, and Mea,kins have based on such an assumption cannot be expected to give reliable results. In eleven rebreathing experiments, return to the lungs of blood abnormally low in oxygen content was evident at an average time of 24.5 sec., after the beginning of rebreathing. Recirculation of blood high in carbon dioxide was less readily detectable and was not evident until a later time.
AUTHOR. Pfuhl, Wilhelm: The Function. Deutsches
Lapse Arch.
of Cardiac Contraction as Affected f. klin. Med. 247: 179, 1936:
by
Intrathoracic
The author states that the emptying of the heart by contraction of the muscle is a relatively simple phenomenon compared with the refilling of the heart during diastole. No original experiments are brought to bear on the subject. Older work is frequently cited, and the paper takes the form of a thorough discussion of the possible factors involved. The eonchrsions are, however, interesting. He believes that a considerable portion of the energy for filling the ventrmles is derived from
of Reviews
and Abstracts
ZZZZZ Selected
Abstracts
Bronk, D. W., Ferguson, L. K., Margaria, R., and Solandt, D. Y.: The Activity the Cardiac Sympathetic Centers. Am. J. Physiol. 117: 237, 1936.
of
The activity of the cardiac sympathetic center s has been invsstigated by recordthe action potentials in the cardiac nerves from the stellate ganglia of the cat. There is a fairly continuous discharge of impulses which exert a ‘I tonic” augmentor and accelerator influence upon the heart. This discharge is, however, largely modified by changes in the chemical composition of the blood and by afferent impulses. The principal pathways of the impuhes from the cord to the stellate’ ganglion are the third and fourth and to a lesser extent the second and fifth thoracic rami. !l!he impulse frequency from the individual sympathetic motor nerve cells seldom exceeds ten or fifteen a second, and is usually considerably less. This contrasts with the much higher frequency of discharge from somatic motor nerve cells. ‘l!he potential pulses in the postganglionic nerves are of considerable magnitude because of the grouping of impulses which results from the innervation of many postganglionie fibers by a single preganglionic fiber. There are also much larger potential waves caused by the synchronous activity in very many nerve fibers. It is shown that this is due to the coordinated and This activity rhythmic discharge from large numbers of nerve cells in the centers. is b’ilaterally synchronous. The grouped activity is of four types. The volleys may come at irregular intervals or at other times periodically with frequencies varying from 5 to 20 sec. but unrelated to any other obvious rhythm of the organism. Or, on the other hand, the bursts of impulses may be synchronous with the pulse or the respiratory cycle. The latter two forms of rhythmic cellular activity are largely due to afferent impulses from the vissera: bursts of impulses from the blood vessels initiated by the systolic rise in pressure or the impulses from distention receptors in the lungs. An example of the marked effect of such afferent impulses upon the activity of the sympathetic centers is found in the observation that it is possible to drive those centers by repetitive stimulation of the central ends of the carotid sinus or aortic nerves, thus causing the motor nerve cells to discharge periodically with the frequency of the afferent impulses. This can be done within a limited range of stim.ulus frequencies. The characteristically grouped discharges from the cardiac sympathetic centers cause periodic variations in heart rate only if the bursts of efferent impulses are This is due to the inertia of the &ector mechanism. separated by some seconds. ing
AUTHOR. Essex, Hiram E., Herrick, J. F., Baldes, Edward J., and Mann, Flow in the Circumflex Branch of the Left Coronary Artery Am.
J. Physiol.
117:
271,
Frank C.: Blood of the Intact Dog.
1936.
E:y the use of the thermostromuhr of Rein, experiments have been made on the blood flow in the circumflex branch of the left coronary artery of the intact dog. Observations have been made over periods as long as fourteen days. 119
120
THE
AMERICAN
HIZART
JOURNAL
Epinephrtie causes a transient but marked increase in coronary blood flow, amounting in some experiments to as much as four or five times the control values. The coronary blood flow is doubled by administration of nitroglycerin or amyl nitrite, but the effect is of short duration. In response to appropriate doses of thyroxin, increases in coronary fiow as great as 244 per cent above the control values were observed forty-eight to ninety-six hours after injection. During the digestion of a meat meal the coronary flow was increased to a degree comparable to what has been observed in other vessels of the body. Exercise on a treadmill produced an initial rapid augmentation in coronary flow, which declined to a lower level as the exercise continued but additional work induced by changing the angle of the treadmill agtlin caused a temporary increase jn coronary flow, which declined to a lower value as the same degree of exercise continued. A significant correlation between heart weight and coronary flow or between pulse rate and coronary flow was not found.
AUTIIOR. Donal, John S., Jr., and Gamble, Physiol. 116: 495, 1936.
Clarence
J.:
The
Cardiac
Output
in Man.
Am.
J.
The simultaneous values of oxygen tension and of carbon dioxide tension in the lungs were computed for hypothetieai experiments of the type used in the triple extrapolation method of Redfield, Bock, and Meakins (1922) for estimating the cardiac output in man. When each computed value of carbon dioxide tension was plotted as a function of the computed oxygen tension, the points were found to lie on curves and not on straight lines as is assumed in the triple extrapolation method. The plotting of analyses of successive samples taken during continuous rebreathing gave curves with the same characteristics as those calculated from theoretical considerations. Pairs of such curves were constructed from experiments on ten subjects. When these were extrapolated by the linear procedure of the triple extrapolation method the venous tensions found were different from those indicated by the convergence of the curves. Because of the tensions in the rebreathed mixtures chosen for these experiments, these differences were greater for carb’on dioxide than for oxygen. Cardiac outputs of these subjects determined at the same time by the ethyl iodide method agreed more closely with a curved than with a linear extrapolation. Xt is concluded from these results that when gases are rebreathed or held in the lungs, variations in carbon dioxide and in oxygen tensions canuot be assumed to be directly proportional to each other. In consequence, the triple extrapolation method for the estimation of blood flow which Redfield, Bock, and Mea,kins have based on such an assumption cannot be expected to give reliable results. In eleven rebreathing experiments, return to the lungs of blood abnormally low in oxygen content was evident at an average time of 24.5 sec., after the beginning of rebreathing. Recirculation of blood high in carbon dioxide was less readily detectable and was not evident until a later time.
AUTHOR. Pfuhl, Wilhelm: The Function. Deutsches
Lapse Arch.
of Cardiac Contraction as Affected f. klin. Med. 247: 179, 1936:
by
Intrathoracic
The author states that the emptying of the heart by contraction of the muscle is a relatively simple phenomenon compared with the refilling of the heart during diastole. No original experiments are brought to bear on the subject. Older work is frequently cited, and the paper takes the form of a thorough discussion of the possible factors involved. The eonchrsions are, however, interesting. He believes that a considerable portion of the energy for filling the ventrmles is derived from