Michael M. Lyons

Evidence for Cardiomyopathy in Familial Diabetes Mellitus

Recent epidemiologic studies have suggested that cardiac disease in common in diabetics and may often have a noncoronary basis. To examine the status of the left ventricle, 17 adult-onset diabetics of familial type without hypertension or obesity underwent hemodynamic study and were compared to 9 controls of similar age. Of the 17, 12 subjects had no significant occlusive lesions by coronary angiography. From this group eight without heart failure had a modest, but significant, elevation of left ventricular end-diastolic pressure. End-diastolic and stroke volumes were reduced, but ejection fraction and mean rate of fiber shortening were within normal limits. The left ventricular end-diastolic pressure/volume ratio was significantly higher than controls. Afterload increments effected a significant increase of filling pressure compared to normals without a stroke volume response, consistent with a preclinical cardiomyopathy. Four patients with prior heart failure had similar but more extensive abnormalities. None had local dyskinesia by angiography, and lactate production was not observed during pacing-induced tachycardia. Left ventricular biopsy in two patients without ventricular decompensation showed interstitial collagen deposition with relatively normal muscle cells. These findings suggest a myopathic process without ischemia. Postmortem studies were performed in 11 uncomplicated diabetics. Nine were without significant obstructive disease of the proximal coronary arteries, and the majority succumbed with cardiac failure. On left ventricular sections, none had evident luminal narrowing of the intramural vessels. All nine exhibited periodic acid-Schiff-positive material in the interstitium. Collagen accumulation was present in perivascular loci, between myofibers, or as replacement fibrosis. Multiple samples of left ventricle and septum revealed enhanced triglyceride and cholesterol concentrations, as compared to controls. Thus, a diffuse extravascular abnormality may be a basis for cardiomyopathic features in diabetes.

Altered Myocardial Function and Metabolism in Chronic Diabetes Mellitus without Ischemia in Dogs

Myocardial disease in diabetes mellitus is usually attributed to coronary atherosclerosis. To examine the influence of uncomplicated diabetes on the left ventricle, a mild noninsulin-requiring diabetes was produced in male mongrel dogs after three intravenous doses of alloxan were administered at monthly intervals. There was a persistent decline in glucose tolerance and a reduced insulin content in the pancreas of each alloxan-diabetic dog at the termination of the experiment. The dogs were anesthetized for hemodynamic and metabolic studies after approximately 11 months. Left ventricular end-diastolic volume and cardiac output were measured by the indicator-dilution method. An increase in afterload with moderate aortic pressure elevations elicited a significant rise in end-diastolic volume and stroke volume in normal control dogs. In diabetes, despite a similar end-diastolic pressure response, the end-diastolic volume and the stroke volume responses were significantly less than those in control dogs. During acute volume expansion of the ventricle with saline, the end-diastolic pressure increment in diabetic dogs was twice that in control dogs. These responses were attributed to an increased stiffness of the left ventricle that was apparently due to accumulation of glycoprotein (measured by periodic acid-Schiff staining) in the interstitium. Since similar abnormalities were observed in dogs with diabetes occurring spontaneously and were absent when the pancreatic effects of alloxan were inhibited in a separate group of dogs, the pathogenetic role of alloxan via a direct action on myocardium was excluded. Analysis of lipids in the left ventricle revealed elevated triglyceride and cholesterol concentrations despite normal plasma levels. During infusion of 14C-1-oleic acid, cardiac oxidation appeared to be normal, but fatty acid incorporation, which was predominantly into phospholipid in the control dogs, was diverted to triglyceride in the diabetic dogs. Since an aberration of de novo synthesis was not found during studies with 14C-acetate, triglyceride accumulation was attributed to altered intracellular metabolism, perhaps related to glycerol phosphate acyl transferase activity. The basis for cholesterol accumulation was less clear, since neither 14C-acetate nor 14C-oleate incorporation into sterol was enhanced. Myocardial ischemia was excluded on the basis of patency of coronary arteries and normal coronary blood flow, myocardial cation content, and mitochondrial morphology. Thus, it was concluded that chronic diabetes mellitus can alter myocardial composition and function independent of vascular effects.

Myocardial Function and Lipid Metabolism in the Chronic Alcoholic Animal

In view of the variables that obscure the pathogenesis of cardiomyopathy, a study was undertaken in mongrel dogs fed ethanol as 36% of calories for up to 22 mo. Both the experimental and control groups maintained body weight, hematocrit, plasma vitamin, and protein levels. Left ventricular function was evaluated in the intact anesthetized dog using indicator dilution for end-diastolic and stroke volume determinations. During increased afterload with angiotensin, the ethanol group exhibited a larger rise of end-diastolic pressure (P<0.01), whereas end-diastolic and stroke volume responses were significantly less than in controls. Preload increments with saline elicited a significantly higher end-diastolic pressure rise in the ethanol group (P<0.01). No hypertrophy, inflammation, or fibrosis was present and it was postulated that the enhanced diastolic stiffness was related to accumulation of Alcian Blue-positive material in the ventricular interstitium. To evaluate myocardial lipid metabolism, [1-(14)C]oleic acid was infused systemically. Plasma specific activity and myocardial lipid uptake were similar in both groups. There was a significantly increased incorporation of label into triglyceride, associated with a reduced (14)CO(2) production, considered the basis for a twofold increment of triglyceride content. In addition, diminished incorporation of [(14)C]oleic acid into phospholipid was observed accompanied by morphologic abnormalities of cardiac cell membranes. Potassium loss and sodium gain, like the lipid alteration, was more prominent in the subendocardium. Thus, chronic ethanol ingestion in this animal model is associated with abnormalities of ventricular function without evident malnutrition, analogous to the preclinical malfunction described in the human alcoholic.

Relation of microcirculatory thrombosis to thrombus in the proximal coronary artery: effect of aspirin, dipyridamole, and thrombolysis.

Abstract A study was designed to determine the distribution of platelets in the microcirculation of the myocardium following experimental platelet thrombosis in a major coronary vessel. Determination was made by means of 51 Cr-labelled platelets and histologic examination. The results suggest that thrombosis in a major coronary artery is associated, at least in the first hours following its occurrence, with the presence of platelet thrombi in the microcirculation of the ischemic area. Pretreatment with aspirin or dipyridamole minimized significantly the extent of microcirculatory thrombosis without affecting the thrombus in the proximal coronary artery. A thrombolytic agent given after thrombus formation had a similar effect upon microcirculatory thrombosis remaining also independent of its effect upon proximal coronary artery thrombosis. There was a decrease in incidence of arrhythmias and mortality rate in the group of animals pretreated with aspirin and dipyridamole.

Progression of myocardial abnormalities in experimental alcoholism

Abstract To determine those characteristics of left ventricular functional and metabolic alterations in chronic ethanolism that may be time-dependent, up to 36 percent of total daily calories as ethanol was fed to dogs for an average of 18 months (study group 1) or 52 months (study group 2). The short- and long-term study groups were fed the same diet with vitamin supplements and were compared with simultaneously studied control animals. Left ventricular function was assessed in the intact anesthetized dogs using the thermodilution method for end-diastolic volume and stroke volume determinations. During preload increments with saline solution, a significantly greater increase in end-diastolic pressure was observed in both groups receiving ethanol as compared with the control animals; this increase was associated with reduced end-diastolic and stroke volume. However, the responses were similar in the short- and long-term study groups. Increased left ventricular collagen was the apparent basis for the compliance abnormality, but neither variable differed in the groups receiving ethanol. In contrast, the first derivative of ventricular pressure (dP/dt) normalized for preload and afterload, an index of left ventricular contractility, and the velocity of the contractile element (Vce) were significantly reduced only in the long-term study group while tissue calcium was normal. When chromium-51-EDTA was used as an extracellular marker, accumulation of water and sodium in myocardial cells was observed only in the long-term study group, without a reduction of cell potassium. In view of the dilatation of sarcoplasmic reticulum observed on electron microscopy, It is postulated that distortion of the tubular membranes may limit the rate of calcium availability to contractile protein and thus diminish contractile function in chronic alcoholism.

Influence of diabetes on the myocardium and coronary arteries of rhesus monkey fed an atherogenic diet.

To examine the influence of diabetes on the progression of coronary atherosclerosis and primary myocardial alterations in the rhesus monkey, a Purina or atherogenic diet was fed to nondiabetic animals of groups 1 and 2, respectively, and also to groups 3 and 4 with alloxan diabetes. After 18 months, cardiac studies were performed, by indicator dilution in the intact anesthetized state, at similar levels of heart rate and aortic pressure. Despite comparable basal hemodynamics, preload increments with saline evoked a stroke work response that was significantly less in both diabetic groups. Left ventricular end-diastolic pressure rose from 10.1 ± 1.4 mm Hg to 20.5 ± 2.7 in group 3, and from 11.1 ± 2.1 to 24.0 ± 3.3 in group 4, which were significantly higher elevations than occurred in the controls. End-diastolic volume rose much less in diabetics. Indices of contractility as well as left heart weight were normal Hydroxyproline concentrations were 4.98 ± 0.33 g/mg dry weight in group 1, 5.16 ± 0.24 in group 2, 8.4 ± 0.35 in group 3, and 7.1 ± 0.37 in group 4. Soluble collagen was significantly diminished and the insoluble fraction enhanced in diabetics and was the apparent basis for enhanced wall stiffness. The collagen increment was most evident between myoflbers. Cardiac cell organellee by electron microscopy, tissue cation concentrations, as well as the myocardial lactate response to pacing, were within normal limits. Cholesterol content of the coronary arteries, as a measure of the early atherosclerotic process observed as lipid streaks, was similarly increased in the nondiabetic and diabetic monkeys on lipid diets, with respective plasma cholesterols of 367 ± 55 and 408 ± 62 mg/100 ml. The diabetic-Purina group had a lower but significantly elevated coronary artery cholesterol, associated with higher plasma glucose and nonsterol lipid levels. Thus, in this primate model, diabetes did not intensify either the early coronary lesions induced by moderate hypercholesterolemia, nor were the myocardial changes associated with diabetes altered by the presence of moderate hypercholesterolemia.

Cardiovascular effects of long-term cigarette smoking and nicotine administration☆

The nature of the cardiovascular risk in cigarette smokers has not been characterized. To compare the relative effects of long-term smoking and nicotine administration on the cardiovascular system, 18 month old beagle littermates were prepared with a permanent tracheostomy. They were classified into three groups: I, seven control dogs; II, nine dogs that smoked seven cigarettes/day; and III, eight dogs that received an equivalent amount of nicotine. After a period of up to 22 months, the animals were catheterized under anesthesia for assessment of left ventricular function and volumes by indicator-dilution technique. Heart rate, stroke volume, left ventricular end-diastolic pressure and volume and intraventricular conduction times did not differ significantly in the three groups. Left ventricular ejection fraction was 44 +/- 3 percent (mean +/- standard error of the mean) in the control group, 35 +/- 3 percent in the dogs that smoked cigarettes (P less than 0.05) and 27 +/- 3 percent in those given nicotine (P less than 0.01) despite similar values for end-diastolic variables in the three groups. The first derivative of left ventricular pressure (dP/dt) normalized for pre- and afterload was 2.4 +/- 0.2 cm/sec -1 in the control group, 1.41 +/- 0.12 in the cigarette-smoking group (P less than 0.005) and 1.34 +/-0.08 in the nicotine group (P less than 0.01). Although mean aortic pressure was significantly elevated in both the smoking (127 +/- mm Hg) and nicotine (127 +/- 10 mm Hg) groups, there was no significant correlation with the contractility indexes. Reduction of afterload to normal levels did not affect the abnormal ventricular performance. Hypertrophy, inflammation and abnormalities of cell ultrastructures were not present, and myocardial lipid and cation composition were normal. Since interstitial fibrosis was evident in both experimental groups, an alteration of elastic elements may be operative. These cardiovascular abnormalities appear to be predominantly dependent on the nicotine of cigarettes.

Ethyl alcohol as a cardiac risk factor.

Abstract The widespread use of ethyl alcohol suggests its potential importance in clinical medicine. There is no proved therapeutic effect in cardiac patients, and its role as an etiologic factor in heart disease has been disputed over the years and attributed to coexistent malnutrition. The latter factor, however, has been dissociated from ethanol use in many patients with cardiomyopathic form of heart failure. Major support for the role of ethanol as a toxic agent when used in large amounts for a prolonged period has been obtained in various species of animals, including the subhuman primate. Abnormalities include depression of ventricular function and metabolic and morphologic changes that parallel the changes in humans with preclinical malfunction of the heart. Although the mechanism of progression to heart failure or arrhythmias is not known, several factors may be associated. These include, particularly in males, the cumulative effects of ethanol alone or after intensified drinking episodes, simultaneous exposure to trace metals in excess and occasional specific nutritional deficiency or superimposed infection. The low prevalence of clinical nutritional deficiency in patients with alcoholic cardiomyopathy and the infrequency of heart disease in patients with cirrhosis or neuropathy support the view that the cardiac abnormality is not commonly dependent on malnutrition. Clinical data indicate that the cessation of alcohol intake may reverse the disease or interrupt its progression in many patients. However, the pathogenetic process may continue unabated in some patients who become abstinent.

The effects of body burdens of lead on the growing rat kidney.

The long-term sequelae of increased body burdens of lead on renal growth and development were studied in rats poisoned during the weanling stage. Thirty-two weeks after poisoning there was a significant elevation in the lead concentrations of whole blood and of kidney tissue as compared to those of controls (P < 0.05). However, the body weight, kidney weight, and renal tissue DNA and RNA concentrations were not significantly different from those of the controls. Hypertrophied renal tubular cells and intranuclear inclusions were found in the experimental group at 8 weeks after poisoning but were markedly reduced in number by 32 weeks. There was no evidence of generalized, progressive nephropathy. These results indicate that an increased body burden of lead in the growing rat does not cause alterations in renal growth or development or initiate the development of progressive interstitial nephropathy despite persistent elevations of renal tissue lead concentrations into adulthood.

Vaginal Transposition of the Ovary in Primates (Papio Cynocephalus and Macaca Arctoides)

Summary: Experimental data indicate that the time and mechanism of ovulation play a significant role in some cases of infertility and in a broad range of reproductive abnormalities. In order to establish a new experimental model for the study of these phenomena in primates, transposition of the ovary from the pelvis into the vaginal fornix was attempted in 2 species of monkeys: (a) Macaca Arctoides and (b) Papio Cynocephalus.