William H. Gutstein

The central nervous system and atherogenesis: endothelial injury

Although it has been widely acknowledged that endothelial injury is an important contributing factor to the pathogenesis of atherosclerosis, and may even represent an initiating event, morphologic documentation of its occurrence both in humans and animals has been difficult to obtain. However, electrical stimulation of the lateral hypothalamus in conscious, unrestrained animals on normal diets induces severe endothelial damage with cell loss and denudation in both aortas and coronary arteries. Continued stimulation results in intimal lesions with features of atherosclerotic plaques. The mechanism by which stimulation leads to endothelial injury is discussed and involves the induction of vasospasm. These observations are considered in the light of recent clinical and epidemiological studies, in which the role of neuropsychological and behavioral responses to psychosocial stimuli have been considered important risk factors for the development of atherosclerosis.

Effects of alcohol on isoproterenol-induced ventricular fibrillation in adult rats

To determine whether the pattern of alcohol consumption, intake, and withdrawal modulates the incidence of malignant ventricular arrhythmias and sudden cardiac death due to β-adrenergic stimulation in a species susceptible to administration of isoproterenol alone, a regimen was formulated in which both continuous and interrupted alcohol ingestion was obtained. After alcohol treatment of fully mature, adult rats for 7 weeks, a single subcutaneous injection of 150 μ/kg of isoproterenol was given to control (non-alcohol-treated), alcoholic (continuous consumption), and alcohol withdrawal (interrupted) rats. The incidences of malignant ventricular arrhythmias and related deaths were compared. The results revealed that arrhythmias and arrhythmic deaths were highest in the “alcohol withdrawal group,” 92% and 54%, respectively. As judged from baseline studies, withdrawal of alcohol produced a 16% decrease in serum K+ concentration compared with controls, whereas continuous alcohol ingestion resulted in a 20% elevation in magnesium concentration. These electrolyte changes were further affected by isoproterenol and may have contributed to the differential response to β-adrenergic stimulation as a result of the pattern of alcohol intake.

Association of increased plasma lipid levels with brain stimulation

Abstract Twenty-four fasting animals were given a total meal of 1 ml. of cream by intubation and stimulated in the hypothalamic region. Pre- and post-stimulation blood specimens were analyzed for triglycerides, cholesterol and phospholipids. An equal number of control animals were sham operated, fed and identically treated except for stimulation. In the stimulated animals significant increases were observed in plasma levels of triglyceride, cholesterol and phospholipids within seventy-five minutes after the test meal was administered and 15 minutes following stimulation. The experiment was repeated with an equal number of animals treated identically except for omission of the test meal. No significant differences were observed between stimulated and nonstimulated animals in any of the variables examined, except triglycerides, when feeding was omitted. Gastric Motility was not altered by hypothalamic stimulation. The association between rapid increases in plasma lipid levels, especially in the cholesterol and phospholipid moieties, and hypothalamic stimulation after lipid feeding, is discussed in terms of a possible neural influence on liver function.

Mechanism of plasma lipid increases following brain stimulation

Abstract Ten fasting animals were given a total meal of 1 ml of cream by intubation and stimulated in the hypothalamic region. Pre- and post-stimulation blood specimens were analyzed for total cholesterol, phospholipids and alkaline phosphatase. An equal number of control animals were sham operated, fed and identically treated except for stimulation. In the stimulated animals significant increases were observed in plasma levels of total cholesterol, phospholipids and alkaline phosphatase within 60 minutes after the test meal was administered and 30 minutes following stimulation. These increases were accompanied by electron microscopic evidence of biliary canalicular dilatation. The experiment was repeated with ten animals in which the common bile duct was ligated without subjecting the animals to brain stimulation. Similar changes were observed in the concentration and activity of the variables examined and in the structure of the bile canaliculi, when compared with control animals. In a third experiment the patency of the common bile duct in ten animals was maintained by introduction of a rigid canulla and stimulation was subsequently carried out. No increases in plasma levels of total cholesterol, phospholipids and alkaline phosphatase were observed, and no changes were present in anatomical structure of the bile canaliculi, when compared with animals treated identically except for the presence of the canulla in the common bile duct. From these experiments in may be concluded that the mechanism of plasma lipid increases following stimulation in the lateral hypothalamic region depends upon the patency of the extrahepatic biliary system and the maintenance of a free flow of bile from the liver into the duodenum.

Vasospasm, vascular injury, and atherogenesis: A perspective

It is generally believed that injury of the vessel wall is an important condition for the development of atherosclerosis. The nature of this injury and its relationship to lesion origin, however, are not clearly understood. Based on early work by the author and a selective review of the literature, evidence is presented to show how a common cardiovascular event, vasospasm, may be one of the factors responsible for this tissue damage, because it produces a substantial arteriopathy in the very vessel in which it occurs.

Coronary artery spasm in the rat induced by hypothalamic stimulation

Anesthetized rats were sterotaxically implanted with electrodes and electrically stimulated in the lateral hypothalamus. During elevation of the S-T segment on simultaneous precordial electrocardiograms, the heart was perfused with glutaraldehyde-paraformaldehyde fixative and the major coronary arteries prepared for morphometry of luminal dimensions. A similar procedure was performed in a second group receiving intravenous arginine vasopressin (AVP) in place of hypothalamic stimulation. Elevation of the S-T segment was present in these animals as well. Control animals were implanted, not stimulated and otherwise treated in the same way. Morphometry showed that reductions of mean luminal diameter and cross-sectional area of statistical significance occurred in the two experimental groups compared to controls, suggesting that coronary spasm was the cause of the elevated S-T segments. Pooled plasma from separate groups of implanted control and hypothalamically-stimulated animals revealed substantial elevation of AVP levels in the latter raising the possibility that the neuroendocrine was involved in eliciting coronary artery spasm.

Endothelial injury. Association with elevations of serum bile acid and cholesterol concentration in biliary-obstructed rats.

An association between atherosclerosis, biliary obstruction and hyperlipidemia has been reported in the literature. In previous study from this laboratory, ultrastructural evidence of coronary artery endothelial damage was obtained in rats following ligation-induced biliary obstruction. In the present investigation, serum bile acids, total cholesterol and alkaline phosphatase levels were studied in association with similarly induced biliary obstruction and related to electron-microscopic observations of coronary artery endothelium. The results disclosed marked elevation of all serum parameters in as short a time as 24 hr following ligation compared with shamoperated controls. Animals exhibiting increases of serum bile acids and cholesterol also revealed severe configurational changes of endothelial cells which manifesed as buckling, detachment from the underlying internal elastic lamina, and vacuole formation. The role of elevated circulating bile acids and hypercholesterolemia as possible factors in producing arterial injury through membrane interaction is discussed. These observations suggest that biliary obstruction, even of short duration, may act as a potentially atherogenic mechanism in the experimental animal.

Proliferation of arterial smooth muscle cells incubated in serum from brain-stimulated rats

Platelet deficient serum prepared from rats subjected to acute electrical stimulation of the lateral hypothalamus demonstrated mitogenic activity when added to incubating media supporting growth of homologous arterial smooth muscle cells in vitro. This activity did not appear to be related to the presence of platelet-derived growth factor, hyperlipidemic lipoproteins or increased amounts of insulin. Plasma arginine vasopressin concentration was elevated in these animals, but further investigation is required to determine if this elevation is causally related. Since hypothalamic stimulation is also associated with severe endothelial injury in vivo, the mitogenic activity of the blood of such animals could induce proliferation of SMC which have migrated into the arterial intima. Such features have been observed in chronically stimulated animals and may be of relevance for the role of neural factors in atherogenesis.

Effect of hypothalamic stimulation on the endothelial morphology of the aorta in the conscious squirrel monkey

The role of neurogenic factors in the development of atherosclerosis has not previously been studied in detail. In recent years evidence has accumulated to implicate endothelial injury as a primary stimulus for the proliferation of myo-intimal cells resulting in the formation of the early morphologic lesion. In the present investigation, the effect on aortic endothelial morphology of repetitive electrical stimulation of the lateral hypothalamus in the conscious, unrestrained squirrel monkey, maintained on a cholesterol-free low-fat diet, has been studied. Stimulation was performed with a self-powered, miniaturized electronic stimulator connected to indwelling electrodes. Implanted nonstimulated animals served as controls. Endothelial injury in the form of cell degeneration, denudation, with plasma insudation and partial junctional separation were observed electron-microscopically in stimulated animals compared with controls. These alterations were found to be independent of hypercholesterolemia and/or hypertension. Possible pathways for the induction of injury in this neurogenic model are: (1) direct, through neural circuits from the brain to the vessel wall, and (2) indirect, by elaboration of angiopathic substances inside or outside of the CNS, released into the circulation and transported to the vessel wall where they exert their effects. Reversibility of the endothelial injury progression to established lesions and mechanisms involved remain to be determined in further investigations.

Serum Cholesterol Responses to Hypothalamic Stimulation and Fatty Acid Administration in the Rat

Summary Responses of serum cholesterol concentration to electric stimulation of the lateral hypothalamus were determined in fasted rats given stearic, oleic or linoleic acid by direct duodenal instillation. Greatest percentage increase occurred in the saturated, with intermediate and zero responses in the mono- and diunsaturated fatty acid groups respectively, suggesting that the double bond number of the carbon chain influenced the response.