Biomedical subjects
Publications and source records attributed to R Walden.
Our study of the developing small intestine presents a detailed report of the catalytic isozymic and kinetic properties of lactate dehydrogenase. These results allow for a better understanding of the properties of this intestinal enzyme during devlopment as well as relating these properties to the changing metabolic roles of this tissue during development.
Attempts to noninvasively estimate the significance of carotid arterial stenoses have resulted in a recent technological explosion. Ocular pulse wave timing [oculoplethysmography (OPG) pulse delay] has been strongly promulgated but also criticized on theoretical grounds and for lack of physiologic validation. Audiofrequency analysis of carotid bruits (carotid phonoangiography CPA) has been combined with OPG allegedly to improve accuracy. To evaluate these methods in a controlled model, we studied the effects of graded unilateral stenoses in the canine carotid artery on physiological parameters and associated OPG and CPA recordings. Arterial compliance was calculated from simultaneous diameter and pressure recordings distal to the stenosis. OPG time delay correlated directly with reductions in flow and pressure and with increasing arterial compliance (P less than 0.01). Thus, the delay is caused at least partially by a decreased pulse wave velocity, resulting from the increased compliance distal to stenoses associated with a significant pressure gradient. OPG is most discriminating for stenoses of higher grades. Because bruits arise from flow disturbances that occur even with moderate degrees of stenosis, CPA provides diagnostic information before profound flow reduction occurs. This study illustrates the value of complementary methods for analyzing complex hemodynamic phenomena and provides evidence to support use of the pulse delay concept to diagnose arterial disease.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Although thrombotic occlusion of small vessels in thrombocytosis is allegedly well recognized, it has been reported only rarely. We treated 4 patients with primary thrombocytosis in whom ischemic toe lesions with normal peripheral pulses were the presenting and only symptoms. The symptoms preceded diagnosis by 5 years, 3 years, 1 year, and 1 month respectively. Treatment of the hematologic disorder resulted in disappearance of the toe lesions. Thrombocytosis should be routinely searched for in patients with ischemic toes and normal peripheral pulses.
Explore the source record for details and available documents.
Congenital membranous obstruction of the inferior vena cava is a rare phenomenon resulting from failure of anastomosis between the right subcardinal vein and the liver. A case is reported in which the presenting symtpom was bleeding from esophageal varices. Cirrhosis was present and other signs of vena caval obstruction were minimal. The diagnosis was made only after an ineffective mesenterico-caval shunt had been performed. Venacavography or pressure measurements in the inferior vena cava are mandatory before attempting a porta-systemic shunt operation.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Ten patients with pregangrenous and gangrenous changes of the toes in the presence of normal peripheral pulses are described. In the absence of diabetes this is an uncommon condition and is only rarely reported upon in the literature. Four patients had non occlusive arteriosclerotic changes in large arteries; three suffered from thrombocytosis and one from polycythemia vera; one patient had a monoclonal gamopathy and one was exposed to cold three months before the onset of gangrene. None of these patients smoked regularly. Severe pain usually preceded the gangrene. The process did not progress proximally in any patients, and in those who underwent toe amputations the healing was uneventful. Vasodilators and low-molecular dextran were not effective. Lumbar sympathectomy was performed in three patients, also with no effect on the course of the disease. Treatment of hematological disorders gave relief in three patients. Proximal arteriosclerotic changes should be corrected if possible to eliminate a source of emboli. In two patients anti-platelet aggregation agents provided relief. Toe amputation should be conservative and performed when definite demarcation appears between necrotic and viable tissue. This condition has a benign prognosis.
Phantom sweating is a sensation in which the patient feels that sweat is about to burst out of skin pores, but in which sweating never actually occurs. In a series of 100 patients undergoing bilateral upper dorsal sympathectomy for palmar hyperihidrosis, 82 patients were specifically questioned and 48 (59%) reported phantom sweating. Phantom sweating started soon after the operation, was triggered by the same stimuli that caused hyperhidrosis preoperatively, lasted for a few seconds, and tended to diminish with time. In an average follow-up of 18 months, the phenomenon disappeared in 11 patients (23%). Phantom sweating is probably a symptom of residual sympathetic activity.
Bioavailability of capsule and tablet formulations of tolamolol were compared by measuring plasma concentration of tolamolol and reduction in maximum exercise heart rate over a period of twelve hours in eight healthy subjects in a two-way cross-over study. Tolamolol was absorbed more rapidly from capsules than from tablets; this did not result in any significant difference in the reduction in maximum exercise heart rate between the two formulations. There was no significant difference between area under curve of reduction in exercise tachycardia and area under-curve of plasma concentration of tolamolol for the two formulations. Reduction in maximum exercise heart rate was related to logarithm of plasma concentration of tolamolol between two and twelve hours after both formulations.
Explore the source record for details and available documents.
Pharmacokinetic and physiological variables were measured in six healthy subjects after intravenous and oral administration of tolamolol. 2. After intravenous injection of tolamolol (20 mg), there was a biphasic decline both in plasma concentration and attenuation of maximum exercise tachycardia. First and second phase half-lives of plasma concentration were 7 min and 2.5 h respectively. WReduction of maximum exercise tachycardia declined from 32 beats/min at 2 h to 19 beats/min at 8 hours. Clearance of tolamolol from blood ranged from 0.8-1.41 min-1. 3. After the oral administration of tolamolol (100 mg), the average volume of distribution was 220.1 and plasma concentration half-life 1.8 hours. After ten eight-hourly doses of 100 mg there was no accumulation of tolamolol and the half-life of plasma clearance was unchanged. 4. Hydroxytolamolol was detected in plasma in two of six subjects after oral tolamolol. 5. There was a significant positive correlation between reduction in maximum exercise heart rate and logarithm of plasma concentration of tolamolol after both oral and intravenous administration.
Explore the source record for details and available documents.