Projections of the revolutionary nation: French expeditions in the Pacific, 1791-1803

Revolutionary France's two Pacific expeditions, under the command of Jean-Antoine Bruny d'Entrecasteaux (1792-94) and Nicolas Baudin (1801-1804), demonstrate the importance of scientific inquiry to the newly sovereign nation. France's scientific community adapted to the changed circumstances of revolutionary upheaval by describing its work in terms of national priorities. Individuals on board the expeditions, both naval and scientific personnel, behaved as scientific citizens, intent on composing an encyclopedic body of knowledge about the Pacific. Disputes over whose science mattered more and how credit should be assigned through publication, however, broke down the consensus that science should be a national project.

Citizens and scientists: toward a gendered history of scientific practice in post-revolutionary France

Because the French Revolution failed to produce a widely acceptable definition of citizenship, the limits of manhood suffrage in the early nineteenth century were uncertain. Social practices, in particular scientific activity, served as claims to the status of citizen. By engaging in scientific pastimes, bourgeois Frenchmen asserted that they possessed the rationality and autonomy that liberal theorists associated both with manliness and with civic capacity. However, bourgeois science was never a stable signifier of masculinity or of competence. As professional science emerged, the bourgeois amateur increasingly became the feminised object of satire rather than the sober and meritorious citizen-scientist.

Activin expression by cultured human retinal pigment epithelial cells

PURPOSE

To determine whether human retinal pigment epithelial (hRPE) cells produce activin, a growth factor in the transforming growth factor beta family, and to characterize growth regulatory effects of activin on retinal pigment epithelium.

METHODS

mRNA expression was examined using polymerase chain reaction with primers specific for the beta A and beta B chains of activin and by slot blot analysis with a probe specific for the beta A chain. Protein localization was determined immunocytochemically using antibodies specific for the beta A chain of activin and intact activin A. The effect of activin A on DNA synthesis was studied by measuring (3H) thymidine incorporation after cells were exposed to recombinant human activin A (rhA). Growth regulatory effects of rhA on hRPE cells were examined with cell growth assays.

RESULTS

beta A mRNA was expressed constitutively in 8/8 cells lines tested. beta B mRNA was not expressed in any of the six cell lines tested but was expressed in human ovarian granulosa cell controls. Positive immunostaining was observed for both the beta A chain and intact activin A. (3H) thymidine incorporation was inhibited 44% (P < 0.025), 45% (P < 0.025), and 44% (P < 0.015) when RPE cells were exposed to 100 ng/ml rhA and grown in serum-free medium, medium with 0.5% serum, and 1% serum, respectively. Cell growth was inhibited 33.2% (P = 0.0001) after RPE cells were exposed to 100 ng/ml rhA for 8 days.

CONCLUSIONS

These results suggest that activin A can act as an autocrine-paracrine growth regulator in RPE cells and may help control cellular growth in ocular development and proliferative eye disease.

Role of protease inhibition in myocardial preservation in prolonged hypothermic cardioplegia followed by reperfusion. Effect of aprotinin in an experimental model

The effects of aprotinin on canine myocardium subjected to cardioplegia and global ischemia for 4 hours and then reperfused for 1 hour were investigated. Lysosomal and mitochondrial enzymes and cyclic nucleotides (adenosine cyclic monophosphate and guanosine cyclic monophosphate) were measured in coronary sinus blood. Aprotinin was given intravenously before cardiopulmonary bypass at total doses of 10 X 10(3) kallikrein units per kilogram (group A, six dogs) and 20 X 10(3) KU/kg (group B, six dogs). In group A, three dogs survived but with poor cardiac function; all dogs in group B survived and had better cardiac function. Lysosomal (N-acetyl-beta-D-glucosaminidase) and mitochondrial (aspartate aminotransferase) enzymes in coronary sinus blood at 60 minutes of reperfusion were significantly (p less than 0.05) lower in group B than in group A. In both groups, guanosine cyclic monophosphate was significantly (p less than 0.01) lower during reperfusion than before cardiopulmonary bypass; however, the values were significantly (p less than 0.05) higher in group B than in group A. Serum adenosine cyclic monophosphate was lower during reperfusion than before bypass in both groups, but it recovered during reperfusion in group B. Myocardial adenosine triphosphate was well preserved in both groups but creatine phosphate was decreased (p less than 0.01) in group A. These results suggest that aprotinin at a dose of 20 X 10(3) KU/kg may be effective in preserving myocardial viability and function after prolonged cardioplegia.

Role of two-dimensional echocardiography in the prediction of in-hospital complications after acute myocardial infarction

To evaluate prospectively the prognostic value of two-dimensional echocardiography after acute myocardial infarction, two-dimensional echocardiography was performed on 61 consecutive patients who were admitted to the hospital with this condition. A left ventricular wall motion score index was derived from analysis of regional wall motion; an index of 2.0 or more within 12 hours of admission identified patients at high risk for pump failure, malignant ventricular arrhythmia or death. These complications occurred in 24 of 27 patients with an initial wall motion score index of 2.0 or more, but in only 6 of 34 with an initial index of less than 2.0 (p less than 0.0005). Of the 47 patients who were in Killip class I on admission, complications developed in 11 (79%) of the 14 with an initial index of 2.0 or more, but in only 6 (18%) of the 33 with an initial index of less than 2.0. After acute myocardial infarction, early determination of the wall motion score index by two-dimensional echocardiography is useful for identifying patients at high risk for complications and is especially valuable in the subset of patients who initially seem to be in stable condition as judged from clinical variables.

Cardiovascular hemodynamics of bicycle and handgrip exercise in normal subjects before and after administration of propranolol

Radionuclide angiography was used to study the effects of supine and upright bicycle exercise and handgrip exercise in 17 (12 well-trained) normal subjects before (control) and immediately after the administration of propranolol (160 mg/day for 4 days). Cardiac hemodynamic values were related to position in that control left ventricular volumes and the cardiac index were greater in the supine position than in the upright at rest but resting left ventricular ejection fraction was similar in both positions. The pressure volume index was greater in the upright position than in the supine. At maximal exercise before treatment, however, similar cardiovascular hemodynamic measurements were recorded in both positions. Propranolol increased left ventricular end-diastolic volume at rest and at maximal exercise. Left ventricular end-systolic volume, however, was substantially greater only in the upright position both at rest and at maximal exercise when compared with control values. Heart rate, systolic arterial pressure, cardiac index, and pressure volume index were decreased at rest and maximal exercise after treatment with propranolol. Ejection fraction was decreased in the upright position after propranolol administration but was unchanged in the supine position. Handgrip exercise primarily increased heart rate and arterial pressure and did not affect cardiac volume, and this response was unaffected by propranolol.

Reentrant tachycardia associated with atrial synchronous pacing. Report of a case with intact ventriculoatrial conduction

Reentrant tachycardia occurred after implantation of an atrial synchronous ventricular-inhibited pacemaker in a patient with bradycardia caused by second-degree (Mobitz II) atrioventricular block. Despite the presence of antegrade atrioventricular block, intact ventriculoatrial conduction was present at a cycle length that exceeded the atrial refractory period of the pacemaker. Consequently, a reentrant or "endless-loop" tachycardia occurred. Application of a magnet terminated the tachycardia. Because the episodes were frequent and could not be prevented by medication, the pacemaker was reprogrammed to a ventricular-inhibited mode. All candidates for atrial synchronous pacing should undergo an appropriate electrophysiologic study preoperatively.

Relationship between left ventricular morphology and postoperative cardiac function following valve replacement for mitral stenosis

The left ventricular myocardium excised from 14 patients who had mitral stenosis and who underwent mitral valve replacement was examined, and myocardial fibrosis was quantitated in relation to cardiac function. Conventional mitral valve replacement was performed with cold potassium-induced cardioplegia associated with systemic hypothermia (28 degrees C rectal temperature) and topical cooling. All 14 patients had perivascular fibrosis; the amounts ranged from 16% to 54% of the whole tissue excised. The mean left ventricular end-diastolic volume index (LVEDVI) determined by M-mode echocardiography increased significantly (p less than 0.001) from 66.9 +/- 4.6 ml/m2 preoperatively to 79.0 +/- 2.9 ml/m2 postoperatively. The difference between preoperative and postoperative LVEDVIs was significantly correlated (p less than 0.01) to the percentage of myocardial fibrosis (r = 0.72), in that the index increased postoperatively when myocardial fibrosis was more than 35% and decreased when fibrosis was less than 35%. After mitral valve replacement, the mean ejection fraction increased when fibrosis was less than 35% of whole tissue (+0.12 +/- 0.04) and decreased when fibrosis was greater than 35% (-0.02 +/- 0.02, p less than 0.01). No measured preoperative hemodynamic parameters were predictive of prognosis. These data suggest that the degree of myocardial fibrosis is related to left ventricular performance after mitral valve replacement.

Five-year experience with temporary pacemaker therapy in the coronary care unit

The clinical course of 1,022 consecutive patients who received a temporary transvenous pacemaker in the coronary care unit during a 5-year period between January 1976 and January 1981 was reviewed. The route of pacemaker insertion was identified in 942 patients (92.2%) and included antecubital vein cutdown in 606 patients (59.3%), subclavian venipuncture in 177 patients (17.3%), right internal jugular venipuncture in 111 patients (10.9%), and femoral venipuncture in 48 patients (4.7%). Pacemaker-related complications occurred in 140 instances (13.7% morbidity), without associated mortality. The most common complication was the development of a new pericardial rub (54 patients, 5.3%). The right internal jugular approach was associated with the lowest complication rate. On the basis of these findings, it is our practice to insert temporary pacemakers via the right internal jugular or subclavian route.

Detection of intracellular anoxia and its relationship to onset of hemodynamic dysfunction and ST-segment elevation in the intact dog heart

The temporal relationships among onset of cellular anoxia after coronary artery occlusion, contractile dysfunction, and electrocardiographic ischemia were studied in dogs with an intact circulation. Nicotinamide adenine dinucleotide (NADH) fluorescence was used to detect intracellular anoxia, using a fiber-optic method. Paired NADH concentrations from ischemic (394 +/- 10 mumol/g) and normoxic (285 +/- 11 mumol/g) regions of the heart were obtained, and the differences (delta[NADH]) were correlated with compensated fluorescence (r = 0.76, P less than 0.01). Onset of fluorescence occurred 1 to 2 sec after coronary artery occlusion, followed by hemodynamic (5 sec) and electrocardiographic (13 sec) changes. These data indicate that intracellular anoxia, with alterations in redox potential, is not synchronous with the onset of contractile failure and provide indirect support for intracellular acidosis as the likely mediator of contractile failure.

Preservation of oxidative phosphorylation by lidocaine in ischemic and reperfused myocardium

The effect of lidocaine (2 mg/kg bolus, 0.04 mg/kg per min infusion) on ischemic and reperfused myocardial respiration was assessed in 32 dogs, using indices of mitochondrial respiration (ADP:O ratio, state 3 and state 4 respiration, and respiratory control index). Heart rate, left ventricular (LV) pressure, LV dp/dt, cardiac index, epicardial ST segment, and regional myocardial blood flow, using 9 +/- 1 micron radiospheres, were measured after 40 min of constriction of the anterior descending coronary artery (N = 16) and after 20 min of reperfusion (N = 16). Results showed that lidocaine increased state 3 respiration and respiratory control in reperfused myocardium (P less than 0.05) with both glutamate and succinate-rotenone as substrate. It is concluded that lidocaine improves postischemic mitochondrial oxidative phosphorylation independent of altered hemodynamics or change in myocardial blood flow.

Protective effect of lidocaine during regional myocardial ischemia: an altered pathophysiologic response assessed by NADH fluorescence

Studies were undertaken to determine the effects of lidocaine on ischemic myocardium, which was induced by coronary artery constriction in open-chested dogs. A real-time epicardial fluorescent technique to detect in vivo-reduced nicotinamide adenine dinucleotide (NADH) during 60 seconds of ischemia was used. Blood flow of ischemic myocardium was measured by using radioactive microspheres of 9 +/- 1 micrometers (mean +/- SE) and was compared with that of normal myocardium, shown by injection of alpha-zurine blue dye. Lidocaine effectively reduced peak NADH fluorescence by 18.6%, from 93.9 +/- 7.2 to 76.4 +/-4.1 mV (p less than 0.005). Lidocaine delayed the onset of fluorescence (2.2 +/- 0.2 versus 1.3 +/- 0.1 s p less than 0.002) and facilitated the recovery from ischemia (38.4 +/- 2.9 versus 54.8 +/- 2.9 s p less than 0.001). Increase in NADH concentration during ischemia correlated (r=0.76, p less than 0.006) with ischemic fluorescence. These findings were independent of altered hemodynamics or change in myocardial blood flow. Results indicate that lidocaine provides myocardial cellular protection during transient ischemia; there is an altered NADH fluorescent response to coronary artery occlusion.

Beneficial effects of multidose coronary artery washout during elective cardiac arrest and cardiopulmonary bypass: biochemical and hemodynamic evaluation

Coronary artery washout with buffered saline (pH 7.4) during 60 and 120 minutes of elective cardiac arrest was studied in dogs during moderate hypothermic cardiopulmonary bypass. Compared with results in a group undergoing simple ischemic arrest, significantly greater myocardial adenosine triphosphate concentrations were present at 90 and 120 minutes of cardiac arrest in the coronary artery washout group. After 60 minutes of aortic cross-clamping and 60 minutes of reperfusion, left ventricular function was significantly superior in the coronary artery washout group. Coronary artery washout during the period of aortic cross-clamping preserves dynamic myocardial performance during reperfusion and is an important principle of myocardial protection during elective cardiac arrest.

Lidocaine-induced reduction in size of experimental myocardial infarction

In anesthetized open chest dogs, the effects of therapeutic doses of lidocaine on myocardial cell respiration, creatine kinase depletion, left ventricular stroke work and cardiac necrosis were assessed. The dogs were subjected to 40 minutes of occlusion of the left anterior descending coronary artery, followed by 5 hours of reperfusion. Group I (12 dogs) had infusion of saline solution; group II (8 dogs) had infusion of 0.2 mg/kg per min of lidocaine (serum level 16.8 +/- 1.4 microgram/ml); group III (5 dogs) had infusion of 0.04 mg/kg per min or lidocaine (serum level 3.6 micrograms/ml). Ischemic regional myocardial blood flow (measured by 9 micrometer spheres of strontium-85) was 6.34 +/- 1.62 ml/100 mg per min in group I, 1.48 +/- 0.59 in group II (p < 0.05) and 1.32 +/- 0.50 in group III (p < 0.05). Oxygen consumed during conversion of adenosine diphosphate to adenosine triphosphate in mitochondria from control and lidocaine-treated ischemic tissue was depressed (p < 0.05) and correlated (r = 0.63) with creatine kinase depletion. Left ventricular stroke work was not significantly different among the three groups. Infarct size (in percent of left ventricular weight) was 12.6 +/- 2.0 for group I, 4.8 +/- 1.2 for group II (p < 0.01) and 4.8 +/- 2.5 for group III (p < 0.05). The data suggest that the reduction of myocardial infarct size by lidocaine was not dependent on enhanced myocardial blood flow and was independent of left ventricular stroke work.

Failure of interventions to maintain mitochondrial function in ischemic myocardium

The purpose of this study was to investigate whether pyruvate (2.5 mmol/kg), the combination of glucose (3.9 mmol/kg) and insulin (0.13 unit/kg) with potassium (9.27 meq/kg), or sodium dichloroacetate (120 mg/kg) infused for 15 minutes before and 20 minutes after ligation of the left anterior descending coronary arterv in anesthetized dogs restricted the depression in mitochondrial respiratory function induced by ischemia. Myocardial blood flow after ligation in the three groups was o.2 ml/min per gram or less in ischemic subendocardium and was similar to that in saline-infused controls that had also undergone coronary artery ligation. The depressions induced in mitochondrial respiratory control index and state 3 respiration by ischemia in the subendocardium and subepicardium of the three treatment groups, when compared with corresponding nonischemic tissue, were not significantly improved from the control values. It was concluded that these three interventions fail to preserve mitochondrial respiration in ischemic myocardium.

Effect of betamethasone on mitochondrial oxidative phosphorylation in ischemic canine myocardium

Hemodynamics and myocardial blood flow were studied in 14 anesthetized open-chest dogs that were subjected to coronary artery occlusion followed by reperfusion. In six dogs, betamethasone was given intravenously 30 minutes before occlusion. During reperfusion, a significant increase in myocardial blood flow in nonischemic tissue was observed in the betamethasone group as compared with control (P less than 0.05). Also, the increase in myocardial blood flow in steroid-treated nonischemic tissues during reperfusion was significantly greater (P less than 0.05) than that measured in ischemic tissues in the same group. However, betamethasone failed to protect mitochondrial respiration from ischemic damage. Respiratory control indices in ischemic tissues were significantly depressed, compared with those in nonischemic tissues, even in betamethasone-treated dogs, and the degree of depression was the same in the ischemic tissues of control and treated dogs. These data suggest that betamethasone was not effective in preserving mitochondrial function in ischemia but that it increased myocardial blood flow in nonischemic tissue.

Effect of magnesium in cardioplegic solution upon hypothermic ischemic myocardial mitochondria

Twelve anesthetized mongrel dogs were subjected to systemic hypothermia and potassium-induced cardioplegia for 60 minutes with or without magnesium-1-aspartate. The effect of magnesium was assessed by indices of mitochondrial oxidative phosphorylation. Cardiac arrest was induced by potassium (20 mEq per liter) (6 dogs) or potassium (20 mEq per liter)- magnesium (8 mM per liter). The heart was reperfused for ten minutes following arrest. Dogs were supported by standard cardiopulmonary bypass with hypothermia at 20 degrees C of myocardial temperature. Mitochondria were isolated from the endocardium, the epicardium of the left ventricle and the ventricular septum. ADP: 0 ratio and state 3 respiration were well maintained in both groups following 60 minutes of ischemic arrest and 10 minutes of reperfusion. Magnesium suppressed the non-phosphorylated oxygen consumption of mitochondria, therefore, respiratory control index was signficantly enhanced in the group of potassium-magnesium-1-aspartate cardioplegia. These data suggest that magnesium protects functional capacity of mitochondrial phosphorylation in the myocardium from ischemia.

Myocardial respiration and edema following hypothermic cardioplegia and anoxic arrest

The effects of 1 and 2 hours of hypothermic anoxic arrest and cardioplegia induced by Mg-lidocaine, K-Mg, or K on left ventricular mitochondrial respiratory function, blood flow, and edema were studied in 41 mongrel dogs. Mitochondrial respiration was assessed by the indices of oxidative phosphorylation. Myocardial temperature recorded in ventricular septum was kept at 20 degrees C during ischemic arrest and 10 minutes of reperfusion. Cardioplegic solutions did not influence noncoronary blood flow during cross-clamping of the aorta. Mitochondrial respiratory function remained at control levels after 1 hour of ischemia induced by hypothermic anoxic arrest or by Mg-lidocaine or K-Mg hypothermic cardioplegia. Mitochondrial state 3 respiration after 2 hours of anoxic arrest was significantly higher in Mg-lidocaine cardioplegia than in anoxic arrest (p less than 0.05), but myocardial edema was equivalent in both groups. Mg in the cardioplegic solution suppressed mitochondrial nonphosphorylating oxygen consumption. These data suggest that mitochondrial function after 1 hour of ischemic arrest at 20 degrees C and 10 minutes of reperfusion is not significantly depressed, but at 2 hours of ischemic arrest, mitochondrial respiration is significantly impaired. However, hypothermic Mg-lidocaine cardioplegia appears to be more effective in sustaining myocardial respiration than does simple hypothermic anoxic arrest when the anoxic period is extended to 2 hours.

Quantitative evaluation of myocardial ultrastructure following hypothermic anoxic arrest

Thirty-six anesthetized mongrel dogs were subjected to systemic hypothermia and anoxic cardiac arrest while on cardiopulmonary bypass. Myocardial fine structure in the left ventricle was evaluated by quantitative analysis in the subepicardial, mid-myocardial, and subendocardial layers. The specimens were obtained by a transmural myocardial biopsy method. Graded hypothermia was employed at 36 degrees, 30 degrees, 28 degrees, 25 degrees, and 22 degrees C. The aorta was cross-clamped for 30 minutes at 36 degrees, 30 degrees, 28 degrees, and 25 degrees C. or for 45 minutes at 25 degrees and 22 degrees C. Observations indicated that pathological changes of the myocardial fine structure were significant after anoxic arrest in the normothermic group. Lesions were most extensive in the subendocardial layer after normothermic anoxic arrest, whereas hypothermia below 30 degrees C. preserved the myocardium throughout all layers without difference in pathological changes in the fine structure among the layers. Mitochondria and glycogen granules in the mid-myocardial layer and the subendocardial layer were best preserved with hypothermia at 25 degrees and 22 degrees C. after 30 minutes or 45 minutes of anoxic arrest, and dogs in these groups had a survival rate of 100 percent. Quantitative analysis of ultrastructural changes induced in these experiments suggest that a safe duration of anoxic arrest at 22 degrees to 25 degrees C. is between 30 and 45 minutes.

Myocardial ultrastructural changes after experimental ventricular fibrillation and anoxic arrest

A transmural myocardial biopsy method was used to study changed in ultrastructure after induced ventricular fibrillation or anoxic arrest in the canine heart. Interstitial edema, mitochondrial derangement, contraction bands, and swelling of capillary endothelium were more extensive in subendocardial than in subepicardial layer after anoxic arrest. Significant numbers of contraction bands were also seen in the myocardium after induced ventricular fibrillation. These changes appeared to be reversible at least in part in the group with induced ventricular fibrillation but generally not in the anoxic arrest animals. After anoxic arrest, preservation of the endocardial layer was significantly poorer than that of the epicardium; after ventricular fibrillation, there appeared to be no such difference. Myocardial mitochondria and glycogen granules were intact and more numerous after ventricular fibrillation than after anoxic arrest. The lesser damage after ventricular fibrillation than after anoxic arrest suggest that the myocardium may be affected less by the no-reflow phenomenon after normal coronary circulation is restored in ventricular fibrillation.

Intra-aortic balloon assist: initial Mayo Clinic experience and current concepts

The initial experience with intra-aortic balloon assist (IABA) at the Mayo Clinic has been with 34 desperately ill individuals; 17 survived hospitalization. Hemodynamic improvement associated with institution of IABA can be documented. An unacceptably high complication rate (26%) has resulted in extensive modification in the technique of employing IABA. Concepts of patient selection and applications of IABA have evolved from this initial experience and from a review of the literature and have resulted in less reluctant use of this cardiac-assist modality.

Partial anomalous pulmonary venous connection (intact atrial septum) associated with mitral regurgitation

The association of partial anomalous pulmonary venous connection with intact atrial septum and isolated severe nonrheumatic mitral regurgitation is rare, this combination of lesions having been reported on only one other occasion. Two such cases have been presented, with each patient having experienced an episode resembling subacute bacterial endocarditis. At operation, however, the mitral valve had a congenital cleft in one case and was normal in the other. One patient underwent mitral valvuloplasty and the second patient had mitral valve replacement. The diagnosis of associated partial anaomalous pulmonary venous connection was established at cardiac catheterization, and successful surgical correction was achieved in each case by diversion of the anamolaous pulmonary venous drainage to the left atrium via a pericardial tunnel through a surgically created atrial septal defect.

The role of Ca++ ions in the hypertrophied myocardium [proceedings]

Pressure-hypertrophied right ventricular myocardium (RVH) demonstrates paradoxically increased oxygen consumption (MVO2) related to increased in vitro energy-linked mitochondrial calcium flux. The present experiments were designed to measure mitochondrial Ca++ retention in intact RVH and relate changes in mitochondrial Ca++ metabolism to altered RVH contractile behavior and relaxation. Sixteen cats were pulmonary artery banded and their hearts plus paired controls were perfused with 45Ca Krebs-Henseleit at 30 degrees C, 120 beats/min for 10 min. At Lmax papillary muscles showed reduced active tension, a slower contraction rate, a reduced relaxation rate, a greater time to peak tension and a greater relaxation time. Retained 45Ca of mitochondria was increased from 16.75 + .96nM/mg protein in controls to 20.82 +/- .98 in RVH, (p less than 0.005). This increase in mitochondrial 45Ca retention correlated (r equal to 0.93), (P less than 0.001) with the decreased rate of papillary muscle relaxation. These data show an increased 45Ca retention of mitochondria in pressure-induced RVH and relate this biochemical abnormality to a decreased myocardial relaxation in this state.

[The calcium metabolism of myocardial mitochondria and sarcoplasmic reticulum in experimental potassium deficiency (author's transl)]

Mechanical Parameters of the whole, Langendorff-perfused cat heart and of isolated right ventricular papillary muscles are depressed in chronic potassium deficiency. 45Ca binding of sarcoplasmic reticulum (SR) was found to be diminished and correlated with a reduced contractility of the perfused hearts. 45Ca uptake of sarcoplasmic reticulum isolated from potassium deficient hearts was also reduced. The mitrochondrial 45Ca binding and endogenous Ca concentration were increased and there was a positive correlation between these two parameters. The data suggest that a reduced SR Ca binding plays a role in the depression of myocardial contractility in chronic potassium deficiency. Increased mitochondrial 45Ca binding in the presence of reduced 45Ca binding and uptake of sarcoplasmic reticulum suggests the possibility that mitochondria are an additional myocardial calcium pool in chronic potassium deficiency.

Mechanisms for the abnormal energetics of pressure-induced hypertrophy of cat myocardium

Depressed myocardial contractility with paradoxically increased oxygen consumption has been demonstrated in previous studies of pressure overload hypertrophy. To determine whether altered mitochondrial respiration participates in the abnormal energetics of this muscle, right ventricular hypertrophy (RVH) was produced in 12 cats by pulmonary artery banding. A polarographic muscle bath was used to study eight control and eight RVH papillary muscles, and the respiration of mitochondria isolated from these right ventricles was characterized. RVH muscles demonstrated depressed force-velocity and length-tension curves. The myocardial oxygen consumption per gram of peak active tension was increased from 0.65 ± 0.05 nliters/mg beat -1 (control) to 1.10±0.07 nliters/mg beat -1 (RVH) ( P <0.001). Abnormal mitochondrial respiration was shown by an increase in the rate of state 4 oxygen consumption from 12.5±0.8 natoms/mg min -1 (control) to 19.9±0.8 natoms/mg min -1 (RVH) ( P < 0.001). The altered oxygen cost of active isometric tension in the RVH muscles was linearly correlated with the altered rate of mitochondrial state 4 oxygen consumption ( r = 0.91). Ruthenium red, a compound that blocks mitochondrial calcium uptake, reduced the rate of RVH state 4 oxygen consumption to the control level. The present study suggests a mechanism for the abnormal myocardial oxygen consumption in pressure overload hypertrophy and relates it to nonphosphorylating mitochondrial respiration linked to calcium transport.

Normal myocardial function and energetics in volume-overload hypertrophy in the cat

Depressed contractility with a paradoxically increased myocardial oxygen consumption has been associated with pressure-overload hypertrophy. The present experiments investigated myocardial hypertrophy induced by volume overload. Right ventricular volume overload was produced in 19 cats by surgically creating atrial septal defects (ASD); these cats were compared with 10 sham-operated control cats. The ASD cats showed an increase in the ratio of pulmonary blood flow to systemic blood flow from 1.04 ± 0.01 ( SE ) (control) to 3.30 ± 0.28 (ASD) ( P < 0.001). Hypertrophy was evidenced by a ratio of right ventricular weight to body weight of 0.59 ± 0.03 g/kg for control cats and 0.97 ± 0.03 for ASD cats ( P < 0.001). A polarographic muscle bath was used to study papillary muscles from 8 control and 8 ASD cats. ASD muscles demonstrated normal force-velocity curves, with maximal measured preload velocities of 1.32 ± 0.05 muscle lengths/sec: control velocities were 1.33 ± 0.05 muscle lengths/sec ( P > 0.9). The myocardial oxygen consumption of isotonic contractions was normal for ASD muscles. The length-tension curves were comparable, with developed tensions at Lmax of 6.20 ± 0.31 g/mm 2 for ASD muscles and 6.34 ± 0.23 g/mm 2 for control muscles ( P > 0.7). Myocardial oxygen consumption pergram of tension development at Lmax was 0.66 ± 0.06 µliters/mg beat -1 x 10 -3 in the ASD muscles and 0.65 ± 0.05 µliters/mg beat -1 x 10 -3 in the control muscles ( P > 0.8). The mitochondrial oxidative indexes from control and hypertrophied right ventricles were similar, with respiratory control indexes of 14.3 ± 0.8 for ASD hearts and 12.8 ± 1.6 for control hearts ( P > 0.1). These data demonstrate that contractility and energetics are normal in volume-overload hypertrophy, although these same factors are abnormal in pressure-overload hypertrophy. Thus, hypertrophy alone is not a common denominator for abnormal myocardial function and energetics.

Inhibition of binding of tritiated digoxin to myocardium by sodium depletion in dogs

Ten intact dogs were subjected to hemodialysis against a solution of low-sodium content to determine the influence of sodium depletion on myocardial binding of digoxin- 3 H. Serial determinations of serum sodium, potassium, chloride, bicarbonate, pH, and osmolality, of cardiac output, and of cardiac rhythm were obtained in these and in 10 control dogs dialyzed against the standard solution. A dose of digoxin- 3 H (0.05 mg/kg) was given intravenously after start of the dialysis and the animals were killed 1 hour afterward for measurement of myocardial radioactivity, potassium, and sodium. Significant depletion of serum sodium and chloride and myocardial sodium ( P < 0.001) occurred in all animals dialyzed against the low-sodium solution. No significant changes occurred in other serum electrolytes or pH; osmolality was maintained constant by a slow intravenous drip of 25% urea or mannitol. Myocardial radioactivity was reduced in sodium-depleted animals by 50% ( P < 0.001). The Na-K ratio was 0.40 in the myocardium of control animals and 0.26 in sodium-depleted animals. It was concluded that depletion of body sodium inhibits binding of digitalis glycosides to the myocardium during the first hour after injection of the dose.