Complement localization and mediation of ischemic injury in baboon myocardium.

We sought to determine whether the third component of complement (C3) is localized in ischemic baboon myocardium after coronary artery ligation. Furthermore, we assessed the effects of prior C3 depletion on myocardial necrosis. We studied seven control baboons (group I) and seven C3-depleted (group II) baboons that were killed 24 h after ligation of the anterior descending coronary artery. Multiple tissue samples were obtained from infarct, intermediate, and normal myocardial sites as defined by serial unipolar epicardial ECG mapping. In group I baboons, myocardial creatine kinase content from infarct sites was reduced as compared with normal sites (12.6+/-0.92 [SE] vs. 24.4+/-0.75 IU/mg protein, P < 0.001). The intermediate sites from group I contained more creatine kinase (19.0+/-1.25 IU/mg protein) than infarct sites (P < 0.001), but less (P < 0.025) than normal sites. In group II, intermediate sites showed no significant reduction in creatine kinase from normal sites and there was significantly less creatine kinase depletion in infarct sites when compared with group I animals (33.7+/-4.6 and 51.4+/-1.8% depletion, respectively, P < 0.001). In all seven group I baboons, uniform C3 localization was observed in infarct sites by direct immunofluorescence but appeared in mosaic patterns in intermediate sites. C3 was not demonstrated in any normal sites, nor in any site from group II baboons. Additional studies on baboons killed at earlier times after ligation indicated that C3 was localized focally on swollen myocytes in infarct sites as early as 4 h after coronary ligation. These results strongly implicate the active participation of the complement system of inflammatory proteins in the pathogenesis of myocardial tissue injury following coronary occlusion.

Lovastatin induces apoptosis by inhibiting mitotic and post-mitotic events in cultured mesangial cells.

Lovastatin, an inhibitor of protein prenylation, was reported to inhibit DNA synthesis and induce apoptosis in cultured cells. This report describes the morphological consequences of lovastatin treatment. Lovastatin (50 microM) induced mesangial cell rounding and disassembly of actin stress fibers within 24 to 48 h. After 48 to 72 h of lovastatin treatment, the cells detached from the substratum and underwent apoptotic cell death as evidenced by condensed nuclear chromatin, nuclear fragmentation, cell blebbing and decrease in cell size. Time lapse cinematography revealed that lovastatin caused cell rounding by either inhibiting cytokinesis or cell spreading following cytokinesis. Lovastatin-induced cell rounding, detachment, and apoptosis were dependent upon cell proliferation. These effects were prevented by serum deprivation to inhibit cell proliferation or by plating cells at densities which resulted in contact inhibition of cell growth. Lovastatin-induced mesangial cell rounding and apoptosis were also prevented by the inclusion of the isoprenoids all-trans-farnesol or all-trans-geranylgeraniol in the incubation medium. These results indicate that the effects of lovastatin were mediated by inhibition of protein isoprenylation because exogenous all-trans-geranylgeraniol can be used only in protein prenylation. The small GTP-binding protein RhoA, which may be important for cell spreading and cytokinesis, accumulated in the cytosol following treatment with lovastatin, suggestive of its inactivation. This effect was also prevented by the inclusion of either farnesol or geranylgeraniol in the incubation medium. Thus, lovastatin-induced apoptosis in mesangial cells occurs by interfering with prenylation dependent mitotic and post-mitotic events.

Analysis of myocardial response to significant weight loss in obese rats.

We evaluated cardiac response to weight loss induced by a very-low-energy (VLE) diet similar to commercially available protein-sparing diets. Such diets have been implicated in sudden death, and whether organ and tissue responses to them are untoward is not known. Rapid weight loss was induced in rats with weights ranging from obese to normal, and cardiac mass and myocardial histomorphometry were assessed. Over 3 wk body weight dropped from 544 +/- 12 to 417 +/- 21 g (P < 0.001). Heart weight was less in the VLE group than in obese controls (1246 +/- 115 vs 1625 +/- 179 mg, P < 0.001), as were the weights of the left ventricle (805 +/- 81 vs 1061 +/- 134 mg, P < 0.001) and right ventricle (198 +/- 27 vs 265 +/- 40 mg, P < 0.002). Reduction in heart weight was commensurate with loss of body weight (r = 0.89). Myocyte cross-sectional area was reduced in the VLE group (452.6 +/- 108.6 to 331.8 +/- 41.5 microns 2, P < 0.05), with no structural abnormalities. We conclude that weight loss in the weight range studied is accompanied by proportional reduction in cardiac mass and myocyte size. Myocardial regression is not accompanied by myocyte dropout or edema, and likely represents a simple adaptation to reduced body size.

Hepatic response to a very-low-energy diet and refeeding in rats.

Hepatic effects of very-low-energy diets (VLEDs) and refeeding were studied in dietary obese rats. Rats weighing 490-530 g (ages 72-119 d) were randomly assigned to control (C) and VLED groups. Control animals consumed a complete diet ad libitum whereas VLED animals consumed 20% of the energy intake of C animals for 7, 14, or 21 d, and some VLED animals were refed the C diet for 7 d. Hepatic weights, lipid, DNA, and total protein decreased in VLED animals. Observed hepatocytic lipid was high in C and progressively decreased in VLED rats. Hepatocytes from VLED rats lost cytoplasmic organelles, contained myelin figures, and became smaller. Decreased protein-DNA ratios and lipids in these same animals is consistent with atrophy. Other biochemical findings included reductions in blood urea nitrogen, albumin, triglycerides, total protein, and glucose, all of which are synthesized or metabolized by the liver. These observations suggest that attenuation of hepatic function is likely.

Does lower systemic temperature enhance cardioplegic myocardial protection?

This study was performed to determine if systemic temperature affects the rate of cooling and rewarming of the myocardium between infusions of cold potassium cardioplegic solution and if it alters the degree of myocardial protection. Twenty-one dogs underwent cardiopulmonary bypass and 3 hours of ischemic arrest produced by infusing 0 degrees to 4 degrees C potassium cardioplegic solution every 20 minutes. The animals were perfused at different systemic temperatures--Group A, 23 degrees C; Group B, 30 degrees, C; and Group C, 37 degrees C. Myocardial temperature decreased to 11 degrees C in Groups A and B as compared with 13 degrees C in Group C immediately after infusion of the potassium cardioplegic solution (p < 0.0007). Myocardial temperature increased to 19 degrees, 21 degrees, and 26 degrees C in Groups A, B, and C (p < 0.000005) 20 minutes after infusion. Myocardial adenosine triphosphate (ATP) concentration significantly decreased, from 6.69 to 3.56 mumoles/gm (p < 0.0003) in Group B and from 4.99 to 2.80 (p < 0.005) in Group C at the end of 3 hours of cardioplegic arrest. Myocardial glycogen levels also significantly decreased, from 1.156 to 446 mg% (p < 0.003) in Group B and from 811 to 439 mg% (p < 0.04) in Group C. Myocardial ATP and glycogen did not decrease significantly in Group A during the period of arrest. Myocardial lactate values increased more in Groups B and C during the arrest period than in Group A. 12.6 versus 6.5 mumoles/gm (p < 0.03). Moderate systemic hypothermia, therefore, appears to enhance the myocardial protection of potassium cardioplegia.

Effects of aortic balloon pumping during cardiopulmonary bypass on myocardial perfusion, metabolism, and contractility.

This study was undertaken to determine if the production of pulsatile flow by the intra-aortic balloon pump during cardiopulmonary bypass has any beneficial effect on coronary flow, regional myocardial flow, myocardial metabolism, and left ventricular function. Thirty-six conditioned dogs were subjected to one hour of total normothermic cardiopulmonary bypass. They were divided into the following five groups: (1) controls, beating heart and femoral inflow; (2) balloon, beating heart, and femoral inflow; (3) balloon, beating heart, and aortic inflow; (4) control, fibrillating heart and femoral inflow; and (5) balloon, fibrillating heart, and femoral inflow. Total coronary flow, left ventricular flow, coronary sinus flow, and the endocardial-to-epicardial flow ratio increased in group 3. This increase in flow may have been in part due to increased resistance to flow in the descending aorta by the balloon. No differences in flow were noted in the other groups, all of which were perfused via the femoral artery. No significant differences in myocardial metabolism or left ventricular contractility could be demonstrated between balloon-treated and control groups in these normal hearts.

Effects of ventricular fibrillation on coronary blood flow and myocardial metabolism.

Ventricular fibrillation is frequently induced during cardiac surgery to quiet the operative field. The reported effects of fibrillation on the myocardium vary considerably. In an attempt to better define these effects, we subjected 28 dogs to one hour of total normothermic bypass. Myocardial blood flow, lactate, adenosine triphosphate (ATP), oxygen consumption, and left ventricular fibrillation was induced in 5 dogs and continuous electrical fibrillation in 7 dogs. These groups were compared to two respective control groups with beating hearts of 8 animals each. Coronary sinus flow, total coronary blood flow, left ventricular flow, myocardial oxygen consumption, and myocardial tissue lactate increased significantly in the fibrillating hearts. Left ventricular dp/dt decreased with fibrillation, but not significantly. It is concluded that the metabolic demands of ventricular fibrillation exceed the increase in coronary blood flow, when compared to demands of the beating heart, and that decreased left ventricular performance may result.

Microvillar bleb formation in primate hepatocytes irradiated with 32-meV protons.

Eight rhesus monkeys (Macaca mulatta) were whole-body irradiated with 6000 rads of 32-MeV protons. Animals were killed at several time intervals after exposure. Tissue blocks were fixed in glutaraldehyde, post-osmicated, and then embedded in Maraglas-D.E.R. 732 resin. Observation of ultrathin sections by electron microscopy revealed balloon-like enlargements of distal portions of hepatocytic microvilli (blebs) which were less dense than the proximal portion of microvilli. The blebs ranged widely in size; some were contained within the space of Disse, whereas many protruded into the sinusoidal lumen. In a few micrographs the sinusoidal lumen as filled with bleb-like structures. Such bleb formation suggests a possible mechanistic explanation for hepatic congestion following high levels of irradiation.

Comparison of roller pump versus pressurized bag administration of potassium cardioplegic solution.

We sought to determine the relative efficacy of administering cardioplegia by the pressurized bag versus roller pump technique. Fourteen dogs were placed on cardiopulmonary bypass at 30 degrees C and subjected to 2 hours of cardioplegic arrest. Group 1 (7 dogs) was administered cardioplegic solution from a plastic bag under pressure into the ascending aorta every 20 minutes for the 2-hour period, and Group 2 (7 dogs) was given cardioplegia by means of a roller pump. Myocardial temperature decreased in Group 1 to 13.4 degrees C following administration of the cardioplegic solution, and to 13.1 degrees C in Group 2 (not significant). These temperatures were reached in 3.0 minutes in Group 1 and 1.9 minutes in Group 2 (p less than 0.03). Aortic root pressures during cardioplegic infusion were 31 +/- 2 mm Hg in Group 1 versus 46 +/- 2 mm Hg in Group 2 (p less than 0.01). No significant differences between groups were noted in myocardial distribution of cardioplegia, myocardial blood flow or metabolism, or left ventricular hemodynamics. We conclude that both methods of administering cardioplegia lowered myocardial temperature adequately and protected the myocardium for a period of 2 hours in these normal hearts. The roller pump method facilitated faster cooling and produced significantly higher aortic perfusion pressures, however, which may be important in hearts with coronary stenosis.

Effects of varied cardioplegic perfusion pressure on myocardial preservation with critical coronary stenosis.

Inadequate delivery of cardioplegic solution distal to coronary artery stenosis may result in increased injury during ischemic arrest. This study was performed to determine the effects of cardioplegic perfusion pressure on cardioplegia delivery and myocardial preservation in hearts with critical coronary artery stenosis. Twenty dogs underwent 90 minutes of cold potassium cardioplegic arrest with partial occlusion of the circumflex coronary artery. Group 1 received cardioplegia at 50 mm Hg pressure, Group 2 at 90 mm Hg pressure, and Group 3 at 130 mm Hg pressure. It was found that cooling rates were 5.4 degrees, 9.1 degrees, and 18.2 degrees C per minute in the nonischemic area (p = 0.004) and 2.0 degrees, 4.5 degrees, and 7.9 degrees C in the ischemic area (p = 0.008) in Groups 1, 2, and 3, respectively. Total of cardioplegic solution flows were 86, 188, and 262 ml per minute per 100 gm in Groups 1, 2, and 3, respectively (p = 0.001). However, flow did not differ significantly between groups in the ischemic area. Rate of rise of left ventricular (LV) pressure decreased significantly in Groups 1 and 2 but not in Group 3 (p = 0.002). Other measured variables did not differ significantly between groups, although LV function curves showed less deterioration in the high-pressure groups. It is concluded that higher cardioplegic perfusion pressure resulted in more rapid cooling in normal and ischemic areas and slightly better preservation of ventricular function as measured by some indexes. However, preservation was generally good for each of the pressures for up to 90 minutes of ischemia when the septum was consistently cooled to 10 degrees C.

Unsuspected amyloidosis and cardiac arrest following mitral valve replacement.

We performed an autopsy on a 58-year-old female with previously unsuspected cardiac amyloidosis. One day prior to expiration the patient underwent a mitral valve replacement with a Bjork-Shiley prosthesis for mitral valve regurgitation. The valvular defect along with the massive myocardial amyloidosis which created a restrictive cardiomyopathy, were the etiology of the patient's poor cardiac output and subsequent demise.