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PubMed1998

Effects of Ca2+ and epinephrine on Ca2+ recirculation fraction and total Ca2+ handling in canine left ventricles.

We investigated the effects of intracoronary Ca2+ and epinephrine on the intracellular Ca2+ recirculation fraction (RF) and total Ca2+ handling in the left ventricle (LV) of the excised cross-circulated canine heart preparation. We analyzed LV postextrasystolic potentiation (PESP) following a spontaneous extrasystole that occurred sporadically under constant atrial pacing. All PESPs decayed in alternans and none decayed monotonically. We extracted an exponential decay component from the alternans PESP, determined its beat constant (taue), and calculated RF = exp(-1/taue). Increased intracoronary Ca2+ slightly increased taue and RF, but epinephrine did not change them, although both agents enhanced LV contractility 2-3 times. Neither Ca2+ nor epinephrine affected the sinusoidal decay of the alternans PESP. These results indicate that RF via the sarcoplasmic reticulum was slightly augmented by Ca2+, but not by epinephrine. We combined these RF data with LV Ca2+ handling O2 consumption data and obtained 40-110 micromol/kg as the total amount of Ca2+ handled in one cardiac cycle in the control and enhanced contractile states. These results indicate that this new LV-level approach seems to better the understanding of the Ca2+ mass dynamics responsible for the mechanoenergetics enhanced by inotropic interventions.

Animals↗
PubMed1998

Linear O2 use-pressure-volume area relation from curved end-systolic pressure-volume relation of the blood-perfused rat left ventricle.

We measured rat left ventricular pressure, volume, and oxygen consumption ( = arteriovenous oxygen content differencexcoronary flow) to establish a new evaluation of its mechanoenergetics in the whole heart preparation by using the cross-circulation method. We obtained a curved end-systolic pressure-volume relation in contrast to a linear end-systolic pressure-volume relation in dogs, rabbits, and humans. However, we obtained a linear oxygen consumption per beat (VO2)-systolic pressure-volume area (PVA, a measure of left ventricular total mechanical energy per beat) relation as in other species. Thus PVA can be a good index for assessing rat left ventricular mechanoenergetics. The VO2 intercept and slope of the linear VO2-PVA relation correspond to those in other species. Intracoronary calcium elevated the curved end-systolic pressure-volume relation and significantly increased PVA at 0.15 ml/g of left ventricular end-diastolic volume (PVA0.15) by 50%. Calcium also significantly increased the VO2 intercept of the VO2-PVA relation by 30% without a change in its slope. We conclude that the rat left ventricular end-systolic pressure-volume relation is curved, but the VO2-PVA relation is linear, and that the VO2 intercept is mainly composed of PVA-independent VO2, presumably VO2 for Ca2+ handling in the excitation-contraction coupling and basal metabolism. Therefore we propose PVA at an appropriate left ventricular volume and the VO2 intercept as good rat left ventricular mechanoenergetic indexes despite the nonlinearity of the end-systolic pressure-volume relation.

Animals↗
PubMed2000

Mechanoenergetics characterizing oxygen wasting effect of caffeine in canine left ventricle.

Caffeine causes a considerable O(2) waste for positive inotropism in myocardium by complex pharmacological mechanisms. However, no quantitative study has yet characterized the mechanoenergetics of caffeine, particularly its O(2) cost of contractility in the E(max)-PVA-VO(2) framework. Here, E(max) is an index of ventricular contractility, PVA is a measure of total mechanical energy generated by ventricular contraction, and VO(2) is O(2) consumption of ventricular contraction. The E(max)-PVA-VO(2) framework proved to be powerful in cardiac mechanoenergetics. We therefore studied the effects of intracoronary caffeine at concentrations lower than 1 mmol/l on left ventricular (LV) E(max) and VO(2) for excitation-contraction (E-C) coupling in the excised cross-circulated canine heart. We enhanced LV E(max) by intracoronary infusion of caffeine after beta-blockade with propranolol and compared this effect with that of calcium. We obtained the relation between LV VO(2) and PVA with E(max) as a parameter. We then calculated the VO(2) for the E-C coupling by subtracting VO(2) under KCl arrest from the PVA-independent (or zero-PVA) VO(2) and the O(2) cost of E(max) as the slope of the E-C coupling VO(2)-E(max) relation. We found that this cost was 40% greater on average for caffeine than for calcium. This result, for the first time, characterized integratively cardiac mechanoenergetics of the O(2) wasting effect of the complex inotropic mechanisms of intracoronary caffeine at concentrations lower than 1 mmol/l in a beating whole heart.

Animals↗
PubMed2000

Logistic time constant of isometric relaxation force curve of ferret ventricular papillary muscle: reliable index of lusitropism.

We have found that a logistic function fits the left ventricular isovolumic relaxation pressure curve in the canine excised, cross-circulated heart more precisely than a monoexponential function. On this basis, we have proposed a logistic time constant (tau(L)) as a better index of ventricular isovolumic lusitropism than the conventional monoexponential time constant (tau(E)). We hypothesize in the present study that this tau(L) would also be a better index of myocardial isometric lusitropism than the conventional tau(E). We tested this hypothesis by analyzing the isometric relaxation force curve of 114 twitches of eight ferret isolated right ventricular papillary muscles. The muscle length was changed between 82 and 100% L(max) and extracellular Ca(2+) concentrations ([Ca(2+)](o)) between 0.2 and 8 mmol/l. We found that the logistic function always fitted the isometric relaxation force curve much more precisely than the monoexponential function at any muscle length and [Ca(2+)](o) level. We also found that tau(L) was independent of the choice of the end of isometric relaxation but tau(E) was considerably dependent on it as in ventricular relaxation. These results validated our present hypothesis. We conclude that tau(L) is a more reliable, though still empirical, index of lusitropism than conventional tau(E) in the myocardium as in the ventricle.

Animals↗
PubMed2001

New calculation of internal Ca(2+) recirculation fraction from alternans decay of postextrasystolic potentiation.

In our previous studies, we calculated the internal Ca(2+) recirculation fraction (RF) after obtaining the beat decay constant (tau(e)) of the monoexponential component in the postextrasystolic potentiation (PESP) of the alternans decay by curve fitting. However, this method sometimes suffers from the sensitive variation of tau(e) with small noises in the measured contractilities of the 5th and 6th postextrasystolic (PES) beats in the tail of the exponential component. We now succeeded in preventing this problem by a new method to calculate RF without obtaining tau(e). The equation for the calculation in the new method expresses an alternans decay of PESP as a recurrence formula of PESP. It can calculate RF directly from the contractilities of the 1st through the 4th PES beats without any fitting procedure. To evaluate the reliability of the new method, we calculated RF from the alternans decay of PESP of the left ventricle (LV) of the canine excised cross-circulated heart preparation by both the original fitting and the new method. Although there was no significant difference in the mean value of the obtained RF between these two methods, the variance of RF was smaller with the new method than with the original method. Thus the new method proved useful and more reliable than the original fitting method.

Animals↗
PubMed2001

No dependency of a new index for oxygen cost of left ventricular contractility on heart rates in the blood-perfused excised rat heart.

We have reported the linear relation of myocardial oxygen consumption per beat (VO(2)) and systolic pressure-volume area (PVA) in the left ventricle of the cross-circulated rat heart. The VO(2) intercept (PVA-independent VO(2)) is primarily composed of VO(2) for Ca(2+) handling in excitation-contraction coupling and basal metabolism. Recently, we proposed a new index for oxygen cost of contractility obtainable as a slope of a linear relation between PVA-independent VO(2) and left ventricular contractility. This index indicates the Ca(2+) handling VO(2) per unit contractility change. However, a dependency of this index on heart rate has not yet been investigated. The aim of the present study was to investigate the dependency of oxygen cost of contractility on heart rate. This is a critical point to compare this cost under different heart rates. At first we found no differences of VO(2)-PVA relations at 240 and 300 beats/min (bpm). Therefore, after control VO(2)-PVA relation at 300 bpm, we gradually enhanced left ventricular contractility by Ca(2+) at a midrange left ventricular volume and obtained the gradually increased PVA-independent VO(2). At each contractility level, the pacing rate was alternately changed at 240 and 300 bpm. We obtained the two composite VO(2)-PVA relation lines and found no significant differences between the slopes of PVA-independent VO(2) and left ventricular contractility relations at 240 and 300 bpm. The present results indicated no dependency of oxygen cost of left ventricular contractility on heart rates within 240--300 bpm. Based on this fact, we concluded that even under the different pacing rates within 240--300 bpm, this oxygen cost is valid for assessing cardiac mechanoenergetics, especially the economy of total Ca(2+) handling in E-C coupling.

Animals↗
PubMed2003

Postextrasystolic contractility normally decays in alternans in canine in situ heart.

We have reported that the postextrasystolic (PES) potentiation of left ventricular (LV) contractility usually decays in alternans at heart rates above 80-100 beats/min in the canine excised, cross-circulated heart. We examined whether the PES contractility would also decay in alternans even in the canine in situ heart presumably more physiological than the excised heart. In anesthetized, ventilated, and open-chest mongrel dogs, we measured LV pressure and volume with a micromanometer and a conductance catheter cannulated into the LV and obtained LV end-systolic maximum elastance (E(max)) as the reasonably load-independent contractility index. We inserted an extrasystole followed by a compensatory pause into steady-state regular beats at heart rates above 90 beats/min and analyzed the PES decay pattern of E(max). We found that E(max) potentiated in the first PES beat decayed in alternans within 5-6 PES beats. This indicates that PES contractility also decays in alternans in the normal canine in situ heart.

Animals↗
PubMed2003

Exponential fitting of postextrasystolic potentiation may underestimate the cardiac Ca2+ recirculation fraction: a theoretical analysis.

The recirculation fraction of intramyocardial Ca(2+) (RF) has conventionally been obtained from the monotonic decay of postextrasystolic potentiation (PESP). The used assumption is that the decay is exponential. However, we have found that PESP usually decays in alternans even at spontaneous heart rates (>100 beats/min) in excised, cross-circulated canine heart preparations under normal coronary perfusion and normothermia. We have already devised a means of extracting the exponential decay component for RF calculation by subtracting the oscillatory component from the alternans PESP decay by a curve-fitting method. Using mathematics, we assessed the possible error in estimated RF when an exponential curve was naively fit to the alternans PESP decay. We obtained results showing that the exponential assumption may considerably underestimate RF even when the alternans is trivial with the oscillatory component of only 10% of the exponential component.

Algorithms↗
PubMed2004

Load independence of temperature-dependent Ca2+ recirculation fraction in canine heart.

Intramyocardial Ca(2+) recirculation fraction (RF) critically determines the economy of excitation-contraction coupling. RF is obtainable from the exponential decay of the postextrasystolic potentiation of left ventricular (LV) contractility. We have shown that RF remains unchanged despite increasing LV volume (LVV) at normothermia, but decreases with increasing temperature at a constant LVV. However, it remains unknown whether the temperature-dependent RF was not due to the simultaneously changed peak LV pressure (LVP) at a constant LVV. We hypothesized that this temperature-dependent RF would be independent of the simultaneous change in LVP. We used nine excised, cross-circulated canine hearts and allowed their LVs to contract isovolumically. During stable regular beats at 500 msec intervals, we inserted an extrasystolic beat at 360 msec interval followed by the postextrasystolic beats (PESs) at 500 msec intervals. We equalized the temperature-dependent peak LVPs of the regular beats at 36 degrees C and 38 degrees C to the peak LVP level of the stable regular beat at 33 degrees C by adjusting LVV. We fitted the same equation: nEmax = a.exp[-(i - 1)/tau(e)] + b.exp[-(i - 1)/tau(s)]cos[pi(i - 1)] + 1, used before to the normalized Emax (maximum elastance) values of PESi (i = 1-6) relative to the regular beat Emax. RF given by exp(-1/tau(e)) decreased by 19% to 38 degrees C from 33 degrees C. The temperature coefficient (Q(10)) of 1/RF was significantly greater than 1.3. The present results indicated a similar temperature dependence of RF and its Q(10) to those we observed previously without equalizing peak LVP. Thus, the temperature-dependent RF is independent of ventricular loading conditions.

Animals↗
PubMed1990

[Experience of carotid endarterectomy].

The clinical course of 45 patients treated by carotid endarterectomy over the past 5 years is described with emphasis on the following three points: 1) Diagnostic methods, namely digital subtraction angiography (DSA) and B-mode Doppler imaging technique; 2) surgical procedure using an improved shunt tube and surgical instruments; and 3) monitoring before and during surgery. All operations were conducted using a shunt. Morbidity and mortality rates were both 0%. Postoperative transient hemiparesis lasting for 6 hours was recognized in only four cases. The total percentage of correct diagnoses using intravenous DSA compared with conventional angiography was approximately 80%. The accuracy of the non-invasive B-mode Doppler technique in measuring the degree of constriction compared with conventional angiography was 84%. The shunt was made of silicone tubing and was based on a tube 30 cm in length and 3.5 mm in diameter which was a T-shaped loop. Different sized bulbs were fixed to each end of the tube to prevent extravascular deviation. Modified bulldog clamps and Sugita clips were used for fixation in the vessel. Regional cerebral blood flow (rCBF) measurement and electroencephalography (EEG) under contralateral Matas procedure were conducted before surgery, and cross circulation during short-term occlusion of the common carotid artery was evaluated. The emergence or increase of delta waves in EEG during occlusion was observed in six cases. The rCBF of the affected middle cerebral artery territory in these patients was lower than that in patients with no increase of delta waves. Furthermore, the mean stump pressure during surgery in cases with preoperative EEG changes was 40 mmHg and that in cases without changes was 63 mmHg; these values were significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Artery Thrombosis↗
PubMed1998

Pulmonary vasoconstriction during lidocaine administration are modulated by endothelium-derived relaxing factor.

We examined the role of endothelium-derived relaxing factor (EDRF) in lidocaine-induced pulmonary vasoconstriction in experiments using the nitric oxide synthase inhibitor NG-nitro-L-arginine (L-NNA) and EDRF precursor L-arginine in a canine cross-circulation model. The left lower lobe of one dog lung was perfused with venous blood from another dog at a constant rate of flow. Pretreatment of ibuprofen was performed to exclude the effects of vasoactive prostanoids. L-NNA significantly inhibited acetylcholine- and bradykinin-induced pulmonary vasodilation without affecting the vasodilatory responses to isoproterenol in pulmonary vessels preconstricted with thromboxane analogue U46619 or prostaglandin F2 alpha. Pulmonary vasoconstriction by 40 micrograms.ml-1 lidocaine infusion after pretreatment with L-NNA was significantly greater than that before pretreatment with L-NNA, and was reversed to the level present without L-NNA treatment by additional administration of L-arginine. We conclude that lidocaine-induced pulmonary vasoconstriction is modulated by the EDRF/NO pathway in dog lung.

Anesthetics, Local↗
PubMed1993

Extracorporeal support with a cadaver liver as a bridge to transplantation.

Extracorporeal liver perfusion (ECLP) has been used for detoxifying blood in patients in class IV hepatic encephalopathy. Palliation of the moribund patient utilizing extracorporeal devices with cross-circulation of a cadaver liver has been documented for over three decades. Common problems associated with this procedure which appear in the literature include cadaver liver distention, increased resistance to blood flow, and limited time of extracorporeal support due to cadaver liver failure. This report summarizes the experiences of the perfusion team in utilizing an extracorporeal circuit with an otherwise nontransplantable cadaveric liver, to support the decompensating hepatic patient as a bridge to transplantation. Between January and July 1992, three patients were supported for hepatic failure with ECLP. Two patients were placed on ECLP with a modified circuit containing two positive displacement pumps and one centrifugal pump. The third patient was placed on ECLP with a circuit that contained two centrifugal pumps and one positive displacement pump. Patient age ranged from 6 to 38 years and length of support ranged from 24 to 72 hours. In all three patients, a centrifugal pump was placed in the suprahepatic inferior vena cava line to facilitate cadaver liver drainage and decompression. Intensive monitoring of both patient and cadaver liver hemodynamics, hepatic function, and hematological status was performed. All three patients were successfully weaned from ECLP. Two patients received successful orthotopic liver transplantation. The third died of complications unrelated to ECLP after support was discontinued.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1970

Cerebral release of gastric acid inhibitor.

1. Gastric juice collected during electro-anesthesia and limbic system stimulation in monkeys contains a substance which, when injected into other monkeys, produces reduction in basal gastric acid secretion. 2. Cross-circulation experiments indicate that a factor producing reduction in acid secretion is also present in blood during electroanesthesia.

Animals↗
PubMedDate not supplied

Thymus: primary site of lymphopoiesis.

The thymus of the leopard frog is the primary, if not the sole, source of progenitor lymphocytic cells that normally colonize the spleen. Following embryonal parabiosis, a high level of cell chimerism exists in the thymus glands of each member of the parabiotic pair. Evidently, there can be an appreciable amount of cross-circulation of thymic cells between thymus glands.

Animals↗
PubMed2001

[Pre- and postnatal diagnosis of omphalo-xiphopagus conjoined twins].

We report a case with successful surgical separation of female omphalo-xiphopagus conjoined twins. Ultrasonographic examination at 20 weeks of gestation showed twins joined at the abdomen from the xiphoid process to the umbilicus. Conjoined structures included liver. Karyotype was normal. The parents refused interruption of the pregnancy. Plain films, US and MRI confirmed findings at prenatal ultrasound examination. There was no cross circulation into the livers and the gastrointestinal tract was not conjoined. In our observation, postnatal MRI did not offer additional information.

Female↗
PubMed2002

[An ideal liver support system and xenotransplantation].

Currently, the rapid increase in the number of candidates for orthotopic liver transplantation has resulted in a shortage of donor organs and, especially for fulminant hepatic failure, an urgent need for transplantations. Thus the need for a liver support system as a "bridge" before liver transplantation is also urgent, as is the need for treatment of reversible acute liver disease. Various liver support systems have been proposed, for example, cross-circulation systems, extracorporeal liver support systems, hemodialysis, and hemadsorption, but these are not considered to function sufficiently. Demetriou's system, Sussman's system, and Gerlach's system have reached clinical trials. The ideal liver support system should have significant metabolic capacity, the ability to be used in continuous treatment, simplicity of use, biocompatibility, ready availability, consistency, economy, and safety from viral infection, but no system meets all of these criteria.

Animals↗
PubMedDate not supplied

Heart preservation: analysis of cardioprotective infusate characteristics. Membrane stabilization, calcium antagonism, and protease inhibition on myocardial viability: a biochemical, ultrastructural, functional study.

Thirty-three canine hearts were isolated after initial cardioplegia and preserved for 6 hours in 4 degrees C saline solution with intermittent infusion of cardioprotective solution every hour. Reperfusion was observed for 2 hours under normothermic cross-circulation. Hearts were divided into five groups depending on the agent(s) added to the K(+)-Mg2+ cardioplegic solution (K(+)-Mg(2+)-CP) infused. Control hearts (n = 6) received K(+)-Mg(2+)-CP solution alone; group I (n = 7) received lidocaine, 200 mg/L, added to the K(+)-Mg(2+)-CP solution; group II (n = 7) received betamethasone (250 mg/L) added to the formula for group I; group III (n = 6) received diltiazem (200 micrograms/L) added to the formula for group II; group IV (n = 7) received aprotinin (150 KIU/L) added to the formula of group III. Coronary sinus MB fraction of creatine kinase level was significantly decreased at 60 and 120 minutes of reperfusion in group II, as was mitochondrial aspartate aminotransferase level at 2 hours of reperfusion. Lysosomal enzyme release decreased in group IV. Myocardial adenosine triphosphate levels and total adenine nucleotides showed no significant difference among the groups at the end of reperfusion; however, myocardial adenosine diphosphate and adenosine monophosphate levels during reperfusion increased significantly in group I, and myocardial adenosine diphosphate and adenosine monophosphate levels at the end of reperfusion in groups I and IV were significantly higher than those of the control. Calcium overload, which was lowest in group II, was not completely prevented during reperfusion in any group. Left ventricular end-systolic pressure volume relationship in group II showed the "best" functional recovery. In addition, the ultrastructure of the left ventricular myocardium was well preserved in all groups. These results suggest that membrane stabilization with lidocaine and betamethasone affords beneficial effects on myocardial biochemical and functional viability. Diltiazem appears to be less effective in preventing calcium overload during ischemia-reperfusion, and protease inhibition with aprotinin (150 KIU/ml) seems to be highly effective in suppressing lysosomal enzyme activation-release and maintaining myocardial adenosine diphosphate and adenosine monophosphate levels.

Adenine Nucleotides↗
PubMed1992

Myocardial oxygen consumption of fibrillating ventricle in hypothermia. Successful account by new mechanical indexes--equivalent pressure-volume area and equivalent heart rate.

We studied the effects of cardiac hypothermia on myocardial oxygen consumption of a fibrillating ventricle and evaluated whether myocardial oxygen consumption of a fibrillating ventricle in hypothermia can be accounted for by new mechanical indexes: equivalent pressure-volume area and equivalent heart rate in the isolated cross-circulated canine heart preparation. Equivalent pressure-volume area is the area that is surrounded by a horizontal pressure-volume line at the pressure of a fibrillating ventricle and the end-systolic and end-diastolic pressure-volume relations in the beating state in the pressure-volume diagram. Equivalent pressure-volume area is an analog of the pressure-volume area of a beating heart and has been proposed to be a measure of the total mechanical energy of a fibrillating ventricle. Equivalent heart rate was calculated from myocardial oxygen consumption per minute in both beating and fibrillating states under unloaded conditions as an estimate of the frequency of contractions of individual myocytes on the assumption that individual myocytes during ventricular fibrillation have the same contractility as that in the beating state. We estimated myocardial oxygen consumption per minute of the fibrillating ventricle at various ventricular volumes as a function of both equivalent pressure-volume area and equivalent heart rate. The myocardial oxygen consumption-equivalent pressure-volume area relation during ventricular fibrillation in hypothermia was highly linear, with a correlation coefficient of 0.90 (mean). The relation between estimated and directly measured myocardial oxygen consumption values of a fibrillating ventricle in hypothermia was highly linear (r = 0.98), and the regression line (y = 0.80x + 0.48) was close to the identity line in the working range. Therefore we conclude that equivalent pressure-volume area is the primary determinant of myocardial oxygen consumption during ventricular fibrillation in hypothermia, and myocardial oxygen consumption of a fibrillating ventricle in hypothermia can be accounted for by the combination of equivalent pressure-volume area and equivalent heart rate as in normothermia.

Animals↗