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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 355 (1975), S. 63-75 
    ISSN: 1432-2013
    Keywords: Isolated Dog Heart ; Hypoxic Coronary Dilatation ; Pharmacological Coronary Dilatation ; Adenosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary On 11 isolated dog hearts, perfused with arterial blood of a donor dog, the degree of hypoxic dilatation and the maximum coronary blood flow achieved by adenosine were compared. The maximum coronary blood flow under adenosine infusion amounted to 455 ml/min×100 g, that means an increase of about 600% of the normal flow. If coronary venouspO2 was below 5 mm Hg coronary blood flow was increased to 420 ml/min×100 g, which is 93% of the pharmacologically achieved maximum increase of the coronary blood flow. The difference between the maximum hypoxic and the maximum pharmacological dilatation is due to the method; it is caused by an increase of the extravascular component of coronary resistance under the influence of catecholamines in the case of hypoxic dilatation. It is pointed out that in order to achieve a maximum hypoxic dilatation oxygen pressure has to be below the critical value. It can be concluded that the intravascular component of coronary resistance is as low under hypoxic as under pharmacological dilatation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Coronary Collateral Blood Flow ; Coronary Embolization ; Coronary Resistance ; Myocardial Infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Myocardial infarction was produced in 21 anaesthetized dogs by ligation of the anterior descending branch of the left coronary artery and subsequent embolization with microspheres. Coronary antegrade and retrograde flow as well as coronary retrograde pressure were measured before and after embolization. Since nearly complete embolization of the terminal vascular bed of a ligated coronary artery was achieved by injecting plastic microspheres, it was possible to produce a completely ischaemic infarction area in which the microcirculatory influx via collateral vessels was also obstructed. Following embolization, retrograde flow increases by a factor of two or three. Thus, retrograde flow measured after tying a coronary artery without embolization will considerably underestimate the true collateral circulation. Collateral circulation can be important in keeping the occluded area in labile equilibrium after acute coronary occlusion, since if retrograde flow removes even a small amount of blood from the ischaemic zone, fatal ventricular fibrillation may develop. Both retrograde pressure and the microcirculation in the affected areas must be taken into account in determining collateral blood flow or resistance. It is concluded that in normal dog hearts coronary resistance proximal to the origin of the collateral vessels is comparable to that of the terminal vascular bed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 327 (1971), S. 225-233 
    ISSN: 1432-2013
    Keywords: Extravascular Resistance ; Enddiastolic Pressure ; Coronary Blood Flow ; Systolic Time ; Barbiturates ; Extravasaler Widerstand ; Enddiastolischer Druck ; Coronardurchblutung ; Systolenzeit ; Barbiturate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In Experimenten an narkotisierten Hunden wurde durch i.v. Injektionen eines Barbiturates bei gleichzeitigen Bluttransfusionen, die den arteriellen Blutdruck konstant hielten, der enddiastolische Druck im linken Ventrikel erhöht. Die Herzen wurden nach Ausschalten des Sinusknotens über das rechte Herzohr elektrisch mit 150 Impulsen in der Minute stimuliert. Die metabolische Komponente des Einflußwiderstandes wurde durch eine pharmakologische, maximale Dilatation der Coronargefäße konstant gehalten. Die Coronardurchblutung bei maximaler pharmakologischer Dilatation sinkt mit steigendem end-diastolischen Druck ab. Die extravasale Komponente des Einflußwiderstandes steigt mit zunehmendem enddiastolischen Druck während der Systole, der Diastole und des Gesamtcyclus an. Die Systolendauer nimmt mit steigendem enddiastolischen Druck zu.
    Notes: Summary In experiments on anaesthetized dogs the enddiastolic pressure was gradually raised by intravenous application of a barbiturate and simultaneous arterial blood transfusion, which kept the arterial blood pressure constant. After elimination of the sinus node the heart rate was kept constant at 150 beats per minute by electrical stimulation of the right auricle. The metabolically regulated component of coronary resistance was kept constant by a maximal pharmacological dilatation. The coronary blood flow decreases with increasing enddiastolic pressure. The extravascular component of the inflow resistance increases with increasing enddistaolic pressure during systole, diastole, and the whole cycle. The duration of systole becomes longer with increasing diastolic pressure.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 328 (1971), S. 170-175 
    ISSN: 1432-2013
    Keywords: Coronary Blood Flow ; Carbonic Acid Concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 9 dogs the heart rate was kept constant by electrical stimulation of the right auricle after elimination of the sinus node. Hypercapnia was induced by increasing inspiratory carbonic acid concentration at constant oxygen concentration. The mean arterial carbonic acid partial pressure increased from 40.5 to 70.5 mm Hg. The mean pH decreased from 7.30–7.14. Under these conditions the coronary flow did not change. Systolic and diastolic aortic pressure, left ventricular pressure, and the maximal rate of pressure rise in the left ventricle remained unchanged. Alterations of coronary blood flow caused by increased carbonic acid concentrations as described by other authors can be explained by a change of hemodynamic conditions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 349 (1974), S. 369-376 
    ISSN: 1432-2013
    Keywords: Intraventricular Volume ; Heart Volume ; Ultrasonic Heart Catheter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A method for the measurement of intraventricular volume by means of an ultrasound echo technique (intraventricular catheter) is described. From two diameters measured and a correction factor the volume is calculated. The correction factor was derived from measurements on excised non beating hearts. In experiments on beating hearts of 6 anesthetized dogs stroke volume was measured simultaneously with the ultrasonic catheter and the dye dilution technique. Under normal physiological conditions there was a good agreement between the two methods. The difference of 4.0±1.7% (N=24) was not significant. When the hearts were enlarged or made smaller, large deviations occurred which were consistent in their direction, while the scattering remained almost as small as under basic conditions. Only further work can show whether the method can be developed to a reliable procedure for routine measurement of stroke volume under a variety of conditions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 323 (1971), S. 241-249 
    ISSN: 1432-2013
    Keywords: Coronary Blood Flow ; Extravascular Resistance ; Heart Rate ; Systolic Time ; Coronardurchblutung ; extravasaler Widerstand ; Herzfrequenz ; Systolenzeit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei elektrischer Reizung des Herzens (rechtes Herzohr) nach Ausschaltung des Sinusknotens finden sich in dem untersuchten Frequenzbereich von 60–220 Schlägen in der Minute normale Systolen- und Diastolenzeiten. Wird durch eine maximale pharmakologische Coronardilatation die intravasale Komponente des Coronarwiderstandes konstant gehalten, so läßt sich mit steigender Frequenz in allen Experimenten eine Zunahme der extravasalen Komponente des Coronarwiderstandes nachweisen. Diese Zunahme wird durch die relative Zunahme der Systolenzeit auf Kosten der Diastolenzeit hervorgerufen. Die Zunahme der extravasalen Komponente der Coronarwiderstandes ist relativ gering, weil eine Abnahme des systolischen Einstromwiderstandes die Wirkung der Systolenverlängerung vermindert. Die extravasale Komponente des diastolischen Einstromwiderstandes ist frequenzunabhängig.
    Notes: Summary When the heart is stimulated artificially by way of the right auricle after elimination of the sinus node, systolic and diastolic times are normal in the studied range of 60–220 beats per minute. When the intravascular component of coronary resistance is kept constant by way of a pharmacological maximal dilatation, an increase of extravascular resistance can be observed in all experiments with increased heart rate. This increase is caused by the relative increase of systolic time and the decrease of diastolic time. The increase of resistance is relatively small, because the decrease of systolic inflow resistance counterbalances the effect of lengthening of systole. The extravascular component of diastolic inflow resistance is independent of heart rate.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2013
    Keywords: Coronary Blood Flow ; Extravascular Resistance ; dp/dt max ; Systolic Time ; Isoproterenol ; Coronardurchblutung ; extravasaler Widerstand ; dp/dt max ; Systolenzeit ; Isoproterenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In Experimenten an narkotisierten Hunden wurde durch intracoronare Isoproterenolinfusionen die maximale Druckanstiegsgeschwindigkeit im linken Ventrikel (dp/dt max) vergrößert. Dabei wurde nach Ausschaltung des Sinusknotens die Herzfrequenz durch elektrische Reizung des rechten Herzohres konstant gehalten. Die intravasale (metabolisch regulierte) Komponente des Einflußwiderstandes wurde durch eine maximale pharmakologische Dilatation konstant gehalten. Die extravasale Komponente des Einflußwiderstandes steigt mit zunehmendemdp/dt max an, und zwar während der Systole. Der diastolische Einflußwiderstand bleibt konstant. Da gleichzeitig die Diastole auf Kosten der Systole länger wird, ist der Widerstandsanstieg während des ganzen Herzcyclus relativ gering.
    Notes: Summary In experiments on anaesthetized dogs the maximal rate of intraventricular pressure rise (dp/dt max) was enhanced by intracoronary infusions of isoproterenol. Heart rate was kept constant by electrical stimulation of the auricle afterelimination of the sinus node. The intravascular component (metabolically regulated) of coronary resistance was kept constant by a maximal pharmacological dilatation. The extravascular component of the inflow resistance increases with increasingdp/dt max but only during systole. The diastolic resistance remains unchanged. Since in addition the systole becomes shorter and the diastole longer, the rise of resistance during the whole cycle is relatively small.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 56 (1978), S. 247-251 
    ISSN: 1432-1440
    Keywords: Cephradine ; Cephalothin ; Brain Tissue Concentration ; Serum Concentration ; Furosemide ; Drug Interference ; Cephradin ; Cephalotin ; Hirngewebekonzentration ; Serumkonzentration ; Furosemid ; Wechselseitige Beeinflussung von Arnzeimitteln
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei insgesamt 16 Patienten mit hirnchirurgischen Eingriffen wurden Serum- und Hirngewebekonzentrationen von Cephradin und Cephalotin nach i.v.-Gabe von je 4 g bestimmt. 6 der 11 Patienten, die Cephradin erhielten, wurden zusätzlich oral mit 2mal tgl. 40 mg Furosemid behandelt. 5 Patienten erhielten Cephalotin i.v. Cephradin fällt im Serum zwischen der 60. und 100. Minute nach Infusion von 104,9 mcg/ml auf 56,7 mcg/ml ab und im Gewebe von 13,02 auf 8,37 mcg/g im Durchschnitt. Bei zusätzlicher Furosemid-Gabe liegen die Serumwerte von Cephradin signifikant höher und im Hirngewebe signifikant niedriger (p〈0,01). Die Cephalotinkonzentrationen waren auch ohne zusätzliche Furosemidgabe in der 60. und 70. Minute mit 32,3 mcg/ml im Serum deutlich niedriger, im Hirngeweb waren sie mit 0,55 mcg/g extrem niedrig, so daß auf die Prüfung einer Beeinflussung durch Furosemid verzichtet wurde. Im Liquor cerebrospinalis waren zu keinem Zeitpunkt nennenswerte Konzentrationen von Cephradin oder Cephalotin nachweisbar. Die durch die zusätzliche Furosemidmedikation bedingten, teilweise erheblichen Konzentrationsunterschiede von Cephradin im Serum und im Hirngewebe zeigen, daß einer Mehrfachmedikation besonderes Augenmerk gewidmet werden muß.
    Notes: Summary Serum and brain tissue concentrations were determined after i.v. administration of 4 g cephradine to 11 patients of whom 6 were additionally receiving 40 mg furosemide t.i.d. peroral. Five further patients were given 4 g cephalothin i.v. All patients were undergoing a brain operation at the time of antibiotic administration. Between 60 and 100 min after dosage, cephradine decreased in the serum from 104.9 mcg/ml to 56.7 mcg/ml and in the brain tissue from 13.02 mcg/g to 8.37 mcg/g in the mean. Cephradine concentrations in serum were higher and in brain tissue lower when furosemide was given as well. These differences are statistically significant (p〈0.01). Serum concentrations of cephalothin over the same period and in the absence of furosemide were very low with 32.2 mcg/ml at 60 to 70 min, and extremely low in the brain tissue (0.55 mcg/g in the mean) so that a trial with furosemide was not performed. Neither antibiotic was detectable in the cerebrospinal fluid. The differences in serum and brain tissue concentrations of cephradine in the presence and absence of furosemide demonstrate that special care must be taken when administering more than one drug.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2013
    Keywords: Sekeletal Muscle Blood Flow ; Extravascular Support ; Skeletal Muscle Contraction ; Schlüsselwörter ; Skeletmuskeldurchblutung ; extravasculärer Gefäßwiderstand ; Skeletmuskelkontraktion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of sustained isometric and isotonic contractions on the resistance to blood flow was studied in isolated autoperfused electrically stimulated gastrocnemius muscles of anesthetized dogs. To prevent autoregulation caused by the contraction from interferring with the mechanical effects of contraction on the resistance to flow, local vasomotor tone was eliminated by dilating the vessels maximally with vasodilator drugs. Passive stretching of the muscles increased the resistance to flow in proportion to the increase of muscle length. Sustained isometric contractions increased the resistance to flow markedly in proportion to the developed tension. In some experiments powerful isometric contractions nearly completely stopped the flow through the muscle. It could be calculated that working capacity of the muscle was limited by this mechanical inhibition of flow even during weak isometric contractions. Sustained isotonic contractions increased resistance to flow not at all or insignificantly when the contraction was less than 60% of the maximum of the isotonic shortening. Isotonic contractions of more than 60% of maximal shortening increased resistance to flow markedly, but vessels were never completely occluded. That means that isometric contractions impeded flow much more than isotonic contractions. Increasing the arterial blood pressure significantly reduced the increase of resistance to flow caused by isometric or isotonic contractions. Maximum of force as well as maximum of shortening of the muscle was uninfluenced by the raised perfusion pressure, but endurance was improved by an increased blood supply to the gastrocnemius. Rhythmical isotonic and isometric tetanic contractions did not increase mean resistance to blood flow significantly. That means that the inhibition of inflow into the muscle during the contractions was compensated by a “massage effect” on the vessels. The net effect of rhythmical contraction on extravascular support, therefore, was zero.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 317 (1970), S. 336-343 
    ISSN: 1432-2013
    Keywords: Nitroglycerine ; dp/dt max ; Coronary Flow ; Nitroglycerin ; dp/dt max ; Coronardurchblutung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Intravenöse Nitroglycerininfusionen mit Stabilisierung des arteriellen Blutdruckes und intracoronare Infusionen gehen bei konstantem Aortendruck und unverändertem enddiastolischen Füllungsdruck des linken Ventrikels mit einer Steigerung der maximalen Druckanstiegsgeschwindigkeit im linken Ventrikel einher. Dies kann nicht allein durch die begleitende Frequenzerhöhung erklärt werden. Dem Nitroglycerin muß eine direkte, positiv inotrope Wirkung auf das Herz zugeschrieben werden. Der Abfall der maximalen Druckanstiegsgeschwindigkeit unter i.v. Infusionen ohne Blutdruckstabilisierung muß durch die Abnahme des enddiastolischen Füllungsdruckes des linken Ventrikels und die Senkung des Aortendruckes erklärt werden.
    Notes: Summary Nitroglycerine caused an increase indp/dt max, whether the drug was administered intravenously or directly into the coronary arteries, provided that aortic blood pressure and LVEDP were kept constant. The small changes in heart rate in our experiments cannot alone account for the increase indp/dt max. Therefore, we conclude that nitroglycerine has a direct positiv inotropic effect on the heart. The decrease ofdp/dt max from intravenous infusions without stabilization of the arterial blood pressure can be explained by reductions of LVEDP and aortic blood pressure.
    Type of Medium: Electronic Resource
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