Effects of dietary phytoestrogen on global myocardial ischemia-reperfusion injury in isolated female rat hearts.

We investigated the effects of phytoestrogen on global myocardial ischemia-reperfusion injury in five groups of female rats. A high-phytoestrogen group (HPE) was ovariectomized (Ovx) and fed a diet containing soybean protein and a high-isoflavone soy extract. Another Ovx group of rats was fed the same diet as the HPE group but treated with the estrogen receptor blocker ICI-182,780 (HPE + ICI). A third group of Ovx rats was fed a diet containing soybean protein alone (low-phytoestrogen content; LPE). A fourth Ovx group was fed a diet free of phytoestrogen (Ovx). The fifth group of rats was sham ovariectomized (sham). Hearts from all rats were subjected to 30 min of global, hypothermic (4 degrees C), cardioplegic ischemia and 120 min of normothermic (37 degrees C) reperfusion with oxygenated Krebs-Henseleit buffer. Compared with either the sham or the HPE group, the Ovx and HPE + ICI groups had significantly decreased first derivative of left ventricular pressure (dP/dt), coronary flow rate (CFR), nitrite production and mitochondrial respiratory function and significantly increased Ca2+ accumulation and myocardial histological and ultrastructural injury. The CFR of the LPE group was significantly different from that of either Ovx or HPE + ICI group but the dP/dt, nitrite production, Ca2+ accumulation, and mitochondrial function were not. Our results indicate that diets containing phytoestrogen extract play a cardioprotective role in global myocardial ischemia-reperfusion in female rats.

Effect of estrogen on global myocardial ischemia-reperfusion injury in female rats.

We investigated the effects of estrogen on global myocardial ischemia-reperfusion injury in rats that were ovariectomized (Ovx), sham-operated, or ovariectomized and then given 17beta-estradiol (E(2)beta) supplementation (Ovx+E(2)beta). Hearts were excised, cannulated, perfused with and then immersed in chilled (4 degrees C) cardioplegia solution for 30 min, and then retrogradely perfused with warm (37 degrees C), oxygenated Krebs-Henseleit bicarbonate buffer for 120 min. The coronary flow rate, first derivative of left ventricular pressure, and nitrite production were all significantly lower in Ovx than in sham-operated or Ovx+E(2)beta hearts. However, coronary flow rates or nitrate production were not consistently different throughout the entire reperfusion period. Ca(2+) accumulated more in Ovx rat hearts than in sham-operated or Ovx+E(2)beta hearts, and mitochondrial respiratory function was lower in Ovx hearts than in hearts from the other two groups. Marked interstitial edema and contraction bands were seen in hematoxylin-eosin-stained sections of Ovx rat hearts but not in hearts from either of the other groups. Hematoxylin-basic fuchsin-picric acid-stained sections revealed fewer viable myocytes in hearts from the Ovx group than from the sham or Ovx+E(2)beta group. Transmission electron microscopy demonstrated more severely damaged mitochondria and ultrastructural damage to myocytes in Ovx rat hearts. Our results indicate that estrogen plays a cardioprotective role in global myocardial ischemia-reperfusion injury in female rats.

Link between heart disease, cholesterol, and Alzheimer's disease: a review.

Increased prevalence of Alzheimer's disease-like beta-amyloid deposits in the neuropil and within neurons occurs in the brains of non-demented individuals with heart disease. Heart disease is a prevalent finding in Alzheimer's disease, and may be a forerunner to the dementing disorder. In the cholesterol-fed rabbit model of human coronary heart disease there is production and accumulation of beta-amyloid in the brain. This accumulation of beta-amyloid can be reversed by removing cholesterol from the rabbits' diet. In culture cells, a cholesterol challenge has been shown to increase production of beta-amyloid, and dramatic reductions of cholesterol produced by HMG Co-A reductase inhibitors decrease production of beta-amyloid. Increased beta-amyloid production is also produced by dietary cholesterol in a number of transgenic mouse models of Alzheimer's disease. Administration of HMG Co-A reductase inhibitors may block beta-amyloid production caused by dietary cholesterol in rabbits. Clinical trials testing the benefit of HMG Co-A reductase inhibitors in the treatment of Alzheimer's disease are underway.

Neuropathology of mitral valve prolapse in man and cardiopulmonary bypass (CPB) surgery in adolescent Yorkshire pigs.

We investigated the brains of non-demented individuals with mitral valve prolapse (MVP) and found evidence of Alzheimer-like lesions. This neuropathology consisted of premature presence of beta-amyloid-containing senile plaques (SP) without increased prevalence of neurofibrillary tangles. Low levels of SP occurred in 20 to 45- year-old subjects with MVP, and much greater densities were observed in subjects between 45 and 62 years of age. We also investigated the brains of adolescent Yorkshire pigs undergoing cardiopulmonary bypass surgery and likewise found evidence of Alzheimer-like neuropathology. This took the form of intraneuronal accumulation of beta-amyloid immunoreactivity and increasing numbers of Alz-50 immunoreactive neurons with reduced recovery of cardiac efficiency after the surgery. Based on prevailing concepts in Alzheimer's disease, it is feasible to hypothesize that cognitive dysfunction occurring after cardiopulmonary bypass surgery with coronary artery grafting or valve repair/replacement is a functional sequela of AD-like neuropathology. This postulate is based on the premise that an individual seeking such surgery would have pre-existing, elevated AD-like neuropathology to start with. It is further coupled with the probability that these forms of cardiovascular surgery exacerbate the extent and progression of AD-like neuropathology.

Myocardial ischemia-reperfusion injury in estrogen receptor-alpha knockout and wild-type mice.

We investigated the function of estrogen receptor-alpha in global myocardial ischemia and reperfusion injury in male estrogen receptor-alpha knockout (ERKO) and wild-type mice. Mouse hearts were subjected to 45 min of global ischemia followed by 180 min of reperfusion. The hearts were excised, cannulated, and maintained in a chilled (4 degrees C) cardioplegia solution until warm (37 degrees C) oxygenated Krebs-Henseleit bicarbonate buffer was perfused through the coronary arteries. ERKO hearts started beating later and had a higher incidence of ventricular fibrillation and/or tachycardia than control hearts. Coronary flow rate was significantly lower in ERKO hearts during the 90- and 120-min periods of reperfusion. Ca(2+) accumulation was significantly greater following 30, 90, 120, 150, and 180 min of reperfusion in ERKO hearts. Nitrite production was significantly less in ERKO hearts following 90, 120, and 150 min of reperfusion. Myocardial reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was significantly lower in experimental ERKO hearts. Marked interstitial edema and contraction bands were seen in hematoxylin-eosin-stained sections of ischemia-reperfused ERKO hearts but not in control tissues. Hematoxylin-basic fuchsin-picric acid-stained sections from experimental ERKO hearts had fewer viable myocytes compared with controls. Transmission electron microscopy revealed swollen and fragmented mitochondria with amorphous and granular bodies, loss of matrix, and rupture of cristae in experimental ERKO hearts. This is the first demonstration that estrogen receptor-alpha plays a cardioprotective role in ischemia-reperfusion injury in males.

Thrombogenicity of polyethylene oxide-bonded Dacron sewing ring in a mechanical heart valve.

BACKGROUND AND AIM OF THE STUDY: The aim of the study was to evaluate the effect of binding hydrophilic polyethylene oxide (PEO) onto Dacron fibers in the sewing ring of a mechanical heart valve (MHV), in terms of thrombogenicity of the prosthesis. METHODS: The study was performed in blinded fashion. Six Yorkshire-cross pigs (bodyweight 35-45 kg) were implanted with MHVs, in the mitral annulus, with the PEO-treated sewing ring. An additional five pigs implanted with identical MHVs, but with untreated sewing rings, served as controls. PEO of chain-length 10,000 Da was grafted to Dacron fibers using gamma irradiation. PEO-bonded Dacron fibers (diameter 100 microns) were used to weave the sewing ring, which was then assembled on a titanium stent (OD 25 mm). Autologous platelets were labeled with 111In-tropolone and injected intravenously (850-1250 microCi per injection) into the pigs on removal from cardiopulmonary bypass (CPB). At 20-24 h after surgery, platelet thrombi adherent to MHV components, and shed emboli trapped in the brain, lung, heart, kidneys and other organs/connective tissues were imaged using a gamma camera. The animals were killed and the amounts of thrombi adherent to MHV components and organ-trapped emboli quantified using an ionization chamber and gamma counter. RESULTS: There was no statistically significant difference in the adhesion of 111In-labeled platelets to either control sewing rings (0.08 +/- 0.06% dose) or PEO-treated rings (0.19 +/- 0.21% dose). The thrombogenicity of MHV components in both animal groups was in the ascending order: Dacron ring > Teflon pledgets > polypropylene sutures > titanium housing > pyrolytic carbon. The number of platelet-emboli trapped in the organs was not significantly different between the two groups. CONCLUSIONS: Simple modifications may not reduce platelet thrombosis or wound-healing of the sewing ring in the acute phase, at which time several complex processes are activating and inactivating platelets and coagulant factors during CPB and implantation of MHVs.

Quantitation of adsorption and conjugation of plasma proteins by residual glutaraldehyde in fixed collagenous tissue with radioiodinated plasma proteins.

Residual glutaraldehyde (GA) in collagenous cardiovascular tissue prostheses after multiple saline rinses remains in the prostheses and accounts for adsorption and conjugation of a variety of plasma proteins. This may account for later beneficial or adverse effects. Human serum albumin (SA), gamma globulin (GG), and fibrinogen (FB) were iodinated with 125I using the iodogen-transfer technique. Bovine pericardium (PC) was fixed with 0.5% GA for 24 hr and rinsed to remove excess GA. Fresh and GA-fixed PC (FRPC, GAPC: 1 x 1 cm2), in triplicate, were incubated with 0.5-1.0 microCi of tracers in human, porcine, or bovine blood (2 ml) for a period of 0.5, 1, 2, and 3 hr and washed (5x) with saline. Maximum adsorbed proteins per unit weight of collagen (pmol/mg of PC, mean +/- SD) at 3 hr on FRPC and GAPC were quantified with a gamma counter. Fixed PC absorbed significantly more plasma proteins from blood than fresh PC. These conjugated plasma proteins are tightly bound to fixed PC. The adsorbed and conjugated plasma proteins for GAPC and FRPC have the same sequence: SA > GG > FB vs SA > GG > FB. Protein conjugation may affect the remodeling of collagenous cardiovascular tissue prostheses post implantation.

Successful prosthetic mitral valve implantation in pigs.

Clotting mechanisms, the coagulation cascade, platelet function, and platelet-leukocyte-endothelial cell interactions are all very similar in humans and pigs. Because of these similarities, the authors concluded that the pig would be an ideal model for the study of thromboembolism resulting from prosthetic heart valves. To date, they have successfully recovered a total of 11 pigs (52.9 +/- 8.1 kg), 3 with bioprosthetic valves and 8 with mechanical valves, all in the mitral position (25 mm od). The normal presence of high numbers of pulmonary endothelial macrophages and other unique aspects of porcine cardiovascular and pulmonary function dictate somewhat different surgical protocols than those normally used for human patients and ruminant species. Some of these special procedures include 1) crystalloid prime without the use of plasma volume expanders, especially those with a starch base; 2) pharmacologic protection against arrhythmias (lidocaine, 4 mg/kg); 3) special attention to adequate hypothermic cardioprotection during the time of cross-clamp; 4) the use of shock doses of corticosteroid (prednisolone sodium succinate, 0.5 mg/kg) before removal of the aortic cross-clamp; and 5) positive inotropic support (dopamine, 0.008 mg/kg) while weaning from cardiopulmonary bypass. Gamma camera images of 111In tagged autologous platelets 24 hours after surgery show most thrombi located on the sewing ring with fewer on the pledgets and anchor sutures. The latter observations were confirmed by quantification of platelet deposition using a gamma counter.

Development of a minimally invasive technique for coronary revascularization in a porcine model.

BACKGROUND: This porcine model was designed to develop a minimally invasive method for internal mammary artery (IMA) grafting using an anterior mediastinal approach and without routine use of cardiopulmonary bypass. METHODS: Assessment was made of IMA mobilization through a small parasternal incision, the feasibility of coronary artery grafting with cardiopulmonary bypass using this approach, and conditions for off-pump bypass grafting. RESULTS: In group 1, 6 pigs underwent IMA mobilization through a 5-cm horizontal midparasternal incision. Of the 2 group 2 pigs, 1 underwent IMA grafting to the left anterior descending coronary artery and the other, bilateral IMA grafting to the left anterior descending and right coronary arteries using femoral-vessel cardiopulmonary bypass. In group 3, 4 of 10 pigs had successful off-pump grafting during retrograde regional coronary venous perfusion of arterial blood. Retrograde coronary venous perfusion could not be established in the other 6 pigs, and attempts at off-pump grafting failed. CONCLUSIONS: The study demonstrates that coronary artery grafting with the IMA by this minimally invasive off-pump method is feasible, although it draws attention to areas of concern and potential methods of correction. The model provides a realistic and important learning platform for the surgical issues involved with this minimally invasive technique.

Effects of donor position on harvested lung quality.

Potential lung donors are frequently maintained in one position for prolonged periods of time prior to harvest. This study was designed to determine if the effects of gravity induced by maintaining an animal model in the supine position for 24 hr would have adverse effects on the harvested lung. Group 1 pigs were anesthetized, instrumented, mechanically ventilated, and the lungs harvested within 90 min. Group 2 pigs were anesthetized, instrumented, and mechanically ventilated in an identical manner then maintained in the same dorsal-spinal recumbency position for 24 hrs. Hemodynamic and respiratory parameters were stable and not statistically different between the two groups for the baseline and 1 hr time period measurements. There were no significant differences between the two groups for shunt fractions, wet/dry ratios, blood flow distribution, or flush solution distribution. We conclude that in anesthetized pigs there is no evidence that routine repositioning protocols improve blood flow distribution, shunting, or dependent edema.

Minimally invasive coronary artery bypass grafting: a new method using an anterior mediastinotomy.

The benefit of internal mammary artery (IMA) grafting as a long-lasting intervention for coronary artery disease is well recognized. However, largely because they are less invasive, catheter based alternatives are frequently chosen, particularly to treat single or double vessel disease. To retain the advantages of the IMA graft, and to offset the invasiveness of conventional coronary artery bypass grafting, we developed a new minimally invasive method using an anterior mediastinotomy for treating left anterior descending (LAD) or right coronary artery disease, or both. Feasibility studies using 16 pigs and a human cadaver led to approval by the Institutional Review Board for use of this procedure to treat six patients (four men, two women; mean age, 63.8 +/- 13.6 [SD] yrs) who granted informed consent. Pedicle dissection of the IMA, using video assisted thoracoscopy if necessary, was made through a 2- to 3-inch horizontal anterior mediastinotomy. The underlying LAD artery was grafted during femoral vessel cardiopulmonary bypass, with cooling to 30 degrees C, induced ventricular fibrillation, and left ventricular venting if required. Transesophageal echocardiography performed after bypass showed that two patients maintained normal wall motion and four had improvement from the original impairment. One patient suffered a recurrence of angina 4 weeks after the procedure; recatheterization showed an acutely angled IMA, subsequently corrected by balloon angioplasty. The results of follow-up dobutamine echocardiographic stress tests were negative in all patients. With this minimally invasive approach, the procedure should provide the benefits of IMA grafting with shorter hospital stay, more rapid recovery, and less overall cost.

Preincubation of endotoxin with monoclonal anti-lipid A (E5), but not in vivo treatment, inhibits circulatory dysfunction.

Monoclonal antibodies (mAb) directed against the toxic lipid A portion of lipopolysaccharide (LPS) have been shown to bind lipid A in vitro, but clinical trials of such mAbs have yielded mixed results. In 53 rats instrumented for macrocirculatory and cremaster muscle microcirculatory measurements, we examined whether E5, a murine-derived anti-lipid A mAb, could inhibit LPS-induced circulatory dysfunction when incubated with LPS in vitro or given separately in vivo prior to LPS administration. Compared with Control rats (Group I), rats infused with 10 mg/kg Escherichia coli LPS (Group II) displayed marked decreases in arterial pressure and cardiac output and marked decreases in erythrocyte velocity in second, third, and fourth order skeletal muscle arterioles. Infusion of 2 mg/kg E5 90 min prior to LPS infusion (Group III) did not improve cardiovascular performance. In contrast, incubation of LPS with either 2 mg/kg (Group IV) or 10 mg/kg (Group V) E5 prior to infusion significantly attenuated LPS-induced changes in both macrocirculatory and microcirculatory function. Further investigation of the disparity between the in vitro and in vivo neutralizing capacity of anti-lipid A mAbs may aid interpretation of the variable clinical results achieved with these preparations.

Effects of internal mammary artery pedicle coronary artery bypass grafting on aortic valve leaflet positioning.

Approximately 50% of all patients who require replacement of the aortic valve (AVR) also require coronary artery bypass grafting (CABG) for concomitant coronary artery disease. Internal mammary artery (IMA) pedicle grafts are being used with increasing frequency for this purpose. Since the ostia of the IMA are considerably downstream from the sinus of Valsalva we hypothesized the CABG would change the local coronary flow dynamics and possibly alter the timing of both natural and prosthetic valve opening and closing dynamics. Both IMA'S were dissected as pedicle grafts in five pigs and the animals were put on cardiopulmonary bypass. Anastomotic sites were the proximal 1/3 of the left anterior descending and proximal 1/5 of the right coronary arteries. Aortic root, left ventricular and right ventricular pressures were measured and flowmeter transducers were placed on the aortic root, the left main coronary artery, the right coronary artery, the left IMA and the right IMA for measuring flows. Echocardiographic images of the aortic valve, in the longitudinal view, were recorded with a simultaneous ECG. Time points were defined during each cardiac cycle based upon characteristic points in the native coronary hemodynamics. These were identified at 8, 14 and 22% of the cycle (valve opening) and 38, 45 and 55% of the cycle (valve closing). Calculations were made based upon each cycle being initiated with the ECG R wave peak. Significant alterations in flow patterns were identified and quantitated between native coronary and IMA grafts. Only minor changes in valve positioning were identified. These differences in natural valve leaflet position occurred at 22% and 45% of the cycle.

Increased density of cortical apolipoprotein E immunoreactive neurons in rabbit brain after dietary administration of cholesterol.

Rabbits were fed 2% cholesterol diet for 4, 6 and 8 weeks or control diet for 6 weeks. Frontal cortex and hippocampal formation were stained with apolipoprotein E (Apo-E) antibody using standard immunocytochemical methods. The number of neurons expressing the Apo-E epitope and the intensity of Apo-E immunoreactivity increased with increasing time on the cholesterol diet. Because Apo-E chaperones cholesterol in the brain, the data may suggest that elevated circulating levels of cholesterol eventually cause increased cerebral levels.

Coronary vascular and myocardial effects of substance P in hypercholesterolemic rabbits.

Age-matched male New Zealand white rabbits (n = 16) were allocated to two groups: group 1 (n = 8) received a standard rabbit diet; group 2 (n = 8) received a 2% cholesterol-enriched diet. After 8 weeks of prescribed diet, hearts were excised and placed on a constant perfusion pressure Langendorff-type apparatus. Coronary flow, left ventricular pressure, and isovolumic dP/dt were continuously measured. Baseline recordings were made and then a single 5 nmol bolus dose of substance P was delivered into the coronary perfusate. Mean serum cholesterol levels in group 1 were 53 +/- 17 (SEM) mg.dl-1, in group 2 1438 +/- 143 mg.dl-1. In group 1, the injection of substance P caused mean coronary flow to increase 39 +/- 6%, mean coronary vascular resistance to decrease 28 +/- 3%, and mean dP/dt to increase 11 +/- 4%. In group 2, coronary flow increased 57 +/- 13%, coronary vascular resistance decreased 33 +/- 5%, and dP/dt increased 17 +/- 4%. Within groups, values changed significantly from baseline but these changes were not significantly different between groups. The duration of coronary flow response was 113 +/- 20 s in group 1 and 63 +/- 8 s in group 2. Substance P is a potent dilator of coronary resistance vessels and has positive inotropic effects in the rabbit. High levels of cholesterol exposure do not alter the magnitude of substance P-induced vasodilation, but the duration of the response is shortened.

Instantaneous changes in arterial compliance reduce energetic load on left ventricle during systole.

We tested the hypothesis that arterial compliance changes during each cardiac cycle, and that these instantaneous changes are beneficial for energy conservation. Using an adaptive identification procedure, we were able to obtain an instantaneous impulse-response representation of the arterial system. By assuming a three-element windkessel model, we obtained the instantaneous compliance. The arterial compliance remained relatively constant during diastole but increased during systole. The calculated time trajectory was compared with an optimal compliance calculation based on minimum ventricular ejection energy criteria. The two compliance trajectories followed similar paths. We conclude that increases in arterial compliance during systole reduce the energy demands on the left ventricle.

Skeletal muscle microcirculatory response to rat alpha-calcitonin gene-related peptide.

We used in vivo video microscopy to determine the effect of increasing doses of rat alpha-calcitonin gene-related peptide (rCGRP) on rat cremaster muscle arterioles in the presence or absence of the nitric oxide synthase inhibitor N-omega-nitro-L-arginine (L-NNA). Male Sprague-Dawley rats (118-148 g) were anaesthetized with pentobarbital, and neurovascularly intact cremaster muscles were imaged. Changes in the diameter, erythrocyte velocity and volume flow in second-(A2), third-(A3), and fourth-(A4) order arterioles were determined. To produce uniform arteriolar tone, the cremaster preparation was challenged with norepinephrine (NE: 10(-7) M). L-NNA (10(-4) M), which was shown to inhibit acetylcholine-(ACh: 10(-6) M) induced arteriolar dilations, was added to 16 of the preparations. Preparations were then challenged by adding cumulative log concentrations of rCGRP (10(-12)-10-7) M; n = 16) or an equivalent volume of vehicle (n = 19) to the bath. Following rCGRP challenge, arterioles were maximally dilated with 10(-5) M nitroprusside (NP). rCGRP caused significant dose-dependent increases in erythrocyte velocity and volume flow in A2 arterioles, and in diameter, velocity, and volume flow in A3 and A4 arterioles, by 10(-8) M, when compared with vehicle-treated controls. L-NNA had no significant effect on rCGRP-induced responses. These data indicate that rCGRP causes dose-dependent dilation of skeletal muscle resistance arterioles at a concentration similar to that observed in larger vessels. This dilation does not appear to be dependent on the vascular production of nitric oxide from L-arginine.

Early endotoxic shock results in enhanced vasodilator responses to nitroglycerin but unaltered responses to neuropeptides calcitonin gene-related peptide and substance P.

To determine the role that vasoactive neuropeptides, calcitonin gene-related peptide, and substance P play in tissue-blood flow regulation during early septic shock, we examined the responsiveness of arteries removed from pigs 3 h after administration of Escherichia coli lipopolysaccharide or saline vehicle. The carotid, cranial mesenteric, and left anterior descending coronary arteries were excised, and rings were cut from each vessel. Constrictor responses were obtained to cumulative doses of norepinephrine or potassium chloride. Rings were reconstricted and challenged with acetylcholine, substance P, calcitonin gene-related peptide, and nitroglycerin. Lipopolysaccharide significantly increased the cranial mesenteric artery's response to high concentrations of norepinephrine and the response to nitroglycerin in all vessels. This enhancement of responses to nitroglycerin suggests augmented smooth-muscle responsiveness to an exogenous source of nitric oxide, possibly associated with early depression of basal endothelial function. Depression of agonist-induced nitric oxide release may mask such enhancement with endothelial-dependent dilators and may enhance the response to adrenergic constrictors in some vascular beds.