Electron transfer mechanism of aromatic 'nucleophilic' substitution

Mechanistic implications of the ready formation of aryl iodides from aryldiazonium salt solutions and the iodide ion (in contrast with the general need for cuprous or other catalysts with other halides) have been studied. The reaction between benzenediazonium fluoroborate and potassium iodide in methanol at 0�C has been investigated. A new mechanism involving initial one-electron transfer from the iodide anion to the benzenediazonium cation, resulting in the formation of radical intermediates by heterolytic cleavage of a bond, has been proposed in order to account for the products, viz. iodobenzene, benzene, biphenyl, iodine, anisole, and formaldehyde, and the effect of photochemical catalysis.

Experimental myocardial infarction. X. Efficacy of glucagon in acute and healing phase in intact conscious dogs: effects on hemodynamics and myocardial oxygen consumption

This study was designed to test the efficacy of glucagon in the treatment of hemodynamic abnormalities of acute and healing experimental canine myocardial infarction. Myocardial infarction was produced in intact, conscious dogs by gradual inflation of a balloon cuff device implanted around the left anterior descending coronary artery 1 to 2 weeks prior to the study. Hemodynamic and metabolic effects of 50 µg/kg of glucagon were assessed serially in the control state, 1 hour after myocardial infarction and again 1 week later. In the control state glucagon improved cardiac performance and increased myocardial oxygen consumption. One hour after acute myocardial infarction glucagon improved cardiac performance and reduced the degree of left ventricular failure, without any increase in myocardial oxygen consumption. Similar effects of glucagon were noted in the healing phase of myocardial infarction. It is postulated that in this animal model in the presence of heart failure due to myocardial infarction there are reciprocal changes in the factors that increase myocardial oxygen consumption (glucagon-induced inotropy) and decrease oxygen consumption (fall in ventricular end-diastolic volume and wall stress), resulting in no net change in oxygen requirement.

Disturbed patterns of behaviour in morphine tolerant and abstinent rats

1. Eating, drinking and spontaneous motor activity were studied in rats receiving large daily doses of morphine. These forms of behaviour were largely suppressed when the rats were made abstinent and were restored when morphine was given again.2. Compensation for depressions of behaviour during abstinence did not seem sufficient to account for all the stimulant effects of morphine in tolerant rats. Morphine also had slight stimulant actions in non-tolerant rats.3. In tolerant rats, the repeated pairing of the effects of morphine with the re-emergence of behaviour such as eating and drinking may intensify the rewarding value of the drug.

Experimental myocardial infarction. 8. Chronotropic augmentation of cardiac function in left ventricular failure of acute and healing stages in intact conscious dogs

The hemodynamic effects of tachycardia induced by atrial pacing were investigated in left ventricular failure of acute and healing experimental myocardial infarction in 20 intact, conscious dogs. Myocardial infarction was produced by gradual inflation of a balloon cuff device implanted around the left anterior descending coronary artery 10-15 days prior to the study. 1 hr after acute myocardial infarction, atrial pacing at a rate of 180 beats/min decreased left ventricular end-diastolic pressure from 19 to 8 mm Hg and left atrial pressure from 17 to 12 mm Hg, without change in cardiac output. In the healing phase of myocardial infarction 1 wk later, atrial pacing decreased left ventricular end-diastolic pressure from 17 to 9 mm Hg and increased the cardiac output by 37%. This was accompanied by evidence of peripheral vasodilation. In two dogs with healing anterior wall myocardial infarction, left ventricular failure was enhanced by partial occlusion of the circumflex coronary artery. Both the dogs developed pulmonary edema. Pacing improved left ventricular performance and relieved pulmonary edema in both animals. In six animals propranolol was given after acute infarction, and left ventricular function deteriorated further. However the pacing-induced augmentation of cardiac function was unaltered and, hence, is not mediated by sympathetics.The results show that the spontaneous heart rate in left ventricular failure of experimental canine myocardial infarction may be less than optimal and that maximal cardiac function may be achieved at higher heart rates.

Renal failure after radiological contrast media

Over a 12-month period four patients developed acute renal failure after undergoing radiological investigations using contrast media. Though the incidence of serious complications is low, the possibility of adverse side effects must be weighed against the usefulness of the information provided by these techniques.

Experimental myocardial infarction. IV. Reduction of left ventricular compliance in the healing phase

Compliance of the infarcted left ventricle was studied in dogs 3-5 days after occlusion of the left anterior descending coronary artery. Compliance was assessed from postmortem pressure-volume curves and from pressure-length measurements (mercury-in-silastic segment length gauges) made both in vivo and postmortem. Postmortem pressure-volume curves showed reduced compliance compared to sham-operated animals. Postmortem pressure-length curves of infarcted and adjacent normal myocardium indicated that the diminished total compliance could be attributed to an increase in stiffness of the infarcted area. This was confirmed by in vivo end-diastolic pressure-length changes produced by transient aortic occlusion. The infarcted area was akinetic, showing neither contraction nor aneurysmal bulging. In addition, anesthetized dogs with infarcts, when compared with sham-operated animals, had similar left ventricular end-diastolic volumes (indicator dilution method), but higher left ventricular end-diastolic pressures. Taken with previous observations, which show that systolic aneurysmal bulging is uniformly present at the onset of ischemia, these results indicate that stiffening of the ischemic myocardium occurs during the first 5 days after infarction, and show that elevation of left ventricular filling pressure does not necessarily signify ventricular dilatation. The results also suggest a mechanism whereby ventricular performance may improve during recovery from acute myocardial infarction.

Effects of fear on exploratory behaviour in rats

It has been suggested that mild fear may evoke rather than inhibit exploratory responses in rats. The relationship between conditioned fear and exploratory behaviour was analysed in three experiments and there was no evidence that mild fear increased exploration. Conditioned fear was found to be under relatively precise stimulus control and its magnitude was related to the intensities and durations of the unconditioned stimulus, inescapable electric shock.

Hemodynamic effects of pneumonia. II. Expansion of plasma volume

Previous work has demonstrated that approximately one-third of patients with pneumonia have a hypodynamic circulatory response. This response is characterized by an abnormally wide arteriovenous oxygen difference, a low cardiac output, increased peripheral resistance, and an increased hematocrit. This state was found to abate in convalescence. In an attempt to elucidate the pathogenesis of this hypodynamic state, nine additional patients were studied hemodynamically during the acute phase of pneumonia before and during acute expansion of blood volume by low molecular weight dextran (seven patients) or normal saline (two patients). Five patients were restudied before and during acute blood volume expansion in convalescence. Three patients with pneumonia had a normal arteriovenous oxygen difference (< 5.5 vol%), and six patients were hypodynamic in that their arteriovenous oxygen differences were greater than 5.5 vol%. With expansion of blood volume in the acute phase of pneumonia, all patients showed an increase in cardiac output, a decrease in arteriovenous oxygen difference, and a decrease in peripheral vascular resistance; however, the percentage change in the hypodynamic patients was not as great as occurred in the patients with normal hemodynamics nor as great as occurred when restudied in convalescence. Likewise, all patients had a normal or near normal hemodynamic profile in convalescence. In addition, ventricular function in the acute phase of pneumonia was depressed. The findings suggest that the hypodynamic state associated with acute pneumonia is due to depressed myocardial contractility to which relative hypovolemia may contribute.