A. Effect of exercise on muscle blood blow in normal and sympathectomized limbs. B. Collateral circulation before and after sympathectomy

Fundamentals about onset and progressive disease character of type 2 diabetes mellitus

ResearchGate is a world wide web for scientists and researchers to share papers, ask and answer questions, and find collaborators. As one of the more than 15 million members, the author uploads research output and reads and responds to some of the questions raised, which are related to type 2 diabetes. In that way, he noticed a serious gap of knowledge of this disease among medical professionals over recent decades. The main aim of the current study is to remedy this situation through providing a comprehensive review on recent developments in biochemistry and molecular biology, which can be helpful for the scientific understanding of the molecular nature of type 2 diabetes. To fill up the shortcomings in the curricula of medical education, and to familiarize the medical community with a new concept of the onset of type 2 diabetes, items are discussed like: Insulin resistance, glucose effectiveness, insulin sensitivity, cell membranes, membrane flexibility, unsaturation index (UI; number of carbon-carbon double bonds per 100 acyl chains of membrane phospholipids), slow-down principle, effects of temperature acclimation on phospholipid membrane composition, free fatty acids, energy transport, onset of type 2 diabetes, metformin, and exercise. Based on the reviewed data, a new model is presented with proposed steps in the development of type 2 diabetes, a disease arising as a result of a hypothetical hereditary anomaly, which causes hyperthermia in and around the mitochondria. Hyperthermia is counterbalanced by the slow-down principle, which lowers the amount of carbon-carbon double bonds of membrane phospholipid acyl chains. The accompanying reduction in the UI lowers membrane flexibility, promotes a redistribution of the lateral pressure in cell membranes, and thereby reduces the glucose transporter protein pore diameter of the transmembrane glucose transport channel of all Class I GLUT proteins. These events will set up a reduction in transmembrane glucose transport. So, a new blood glucose regulation system, effective in type 2 diabetes and its prediabetic phase, is based on variations in the acyl composition of phospholipids and operates independent of changes in insulin and glucose concentration. UI assessment is currently arising as a promising analytical technology for a membrane flexibility analysis. An increase in mitochondrial heat production plays a pivotal role in the existence of this regulation system.

Thoracic sympathectomy: a review of current indications

BACKGROUND

Thoracic sympathetic ablation was introduced over a century ago. While some of the early indications have become obsolete, new ones have emerged. Sympathetic ablation is being still performed for some odd indications thus prompting the present study, which reviews the evidence base for current practice.

METHODS

The literature was reviewed using the PubMed/Medline Database, and pertinent articles regarding the indications for thoracic sympathectomy were retrieved and evaluated. Old, historical articles were also reviewed as required.

RESULTS AND CONCLUSIONS

Currently, thoracic sympathetic ablation is indicated mainly for primary hyperhidrosis, especially affecting the palm, and to a lesser degree, axilla and face, and for facial blushing. Despite modern pharmaceutical, endovascular and surgical treatments, sympathetic ablation has still a place in the treatment of very selected cases of angina, arrhythmias and cardiomyopathy. Thoracic sympathetic ablation is indicated in several painful conditions: the early stages of complex regional pain syndrome, erythromelalgia, and some pancreatic and other painful abdominal pathologies. Although ischaemia was historically the major indication for sympathetic ablation, its use has declined to a few selected cases of thromboangiitis obliterans (Buerger's disease), microemboli, primary Raynaud's phenomenon and Raynaud's phenomenon secondary to collagen diseases, paraneoplastic syndrome, frostbite and vibration syndrome. Thoracic sympathetic ablation for hypertension is obsolete, and direct endovascular renal sympathectomy still requires adequate clinical trials. There are rare publications of sympathetic ablation for primary phobias, but there is no scientific basis to support sympathetic surgery for any psychiatric indication.

The arterial baroreflex resets with orthostasis

The arterial baroreflexes, located in the carotid sinus and along the arch of the aorta, are essential for the rapid short term autonomic regulation of blood pressure. In the past, they were believed to be inactivated during exercise because blood pressure, heart rate, and sympathetic activity were radically changed from their resting functional relationships with blood pressure. However, it was discovered that all relationships between carotid sinus pressure and either HR or sympathetic vasoconstriction maintained their curvilinear sigmoidal shape but were reset or shifted so as to best defend BP during exercise. To determine whether resetting also occurs during orthostasis, we examined the arterial baroreflexes measured supine and upright tilt. We studied the relationships between systolic BP and HR (the cardiovagal baroreflex), mean BP, and ventilation (the ventilatory baroreflex) and diastolic BP and sympathetic nerve activity (the sympathetic baroreflex). We accomplished these measurements by using the modified Oxford method in which BP was rapidly varied with bolus injections of sodium nitroprusside followed 1 min later by bolus injections of phenylephrine. Both the cardiovagal and ventilatory baroreflexes were “reset” with no change in gain or response range. In contrast, the sympathetic baroreflex was augmented as well as shifted causing an increase in peripheral resistance that improved the subjects’ defense against hypotension. This contrasts with findings during exercise in which peripheral resistance in active skeletal muscle is not increased. This difference is likely selective for exercising muscle and may represent the actions of functional sympatholysis by which exercise metabolites interfere with adrenergic vasoconstriction.

Effect of intra-arterially induced alpha-receptor blockade upon resistance in collateral arteries in patients with occlusion of the superficial femoral artery

The effect of intra-arterially phentolamine inducing alpha-receptor blockade upon the resistance in collateral arteries bypassing an occlusion of the femoral artery was studied in five patients. The patients were placed on a tilt table and the measurements were performed with the patients in supine position and titled 40 degrees (head-up). Arterial blood pressure was measured directly in the brachial-common femoral-and popliteal artery. Relative blood flow was calculated as the relative change in arterio-venous oxygen saturation. Head-up tilt caused a decrease in blood flow of about 35% corresponding to an increase in total vascular resistance of 38%. Resistance in collateral arteries increased by 45%. In supine position alpha-receptor blockade reduced collateral resistance by 17%. However, the title-induced constriction of the collateral arteries was blocked by 87%. The results indicate that the constriction of the collateral arteries bypassing an occlusion of the superficial femoral artery is mainly mediated via sympathetic adrenergic vasoconstrictor fibres.

Marihuana and the cardiovascular system

The actions of marihuana on the cardiovascular system in man are the most consistent physiological effects produced by acue administration. Significant tachycardia and conjunctival injection are well established effects. When the subject is upright, marihuana produces a fall in blood pressure; however, either no significant effect or a slight increase in blood pressure occurs when the subject is supine. Marihuana has been reported to increase limb blood flow and produce no significant effect on electrocardiogram of normal subjects. It, however, interferes with the integrity of peripheral vascular reflex responses. Although the detailed mechanism of action has not been elucidated, there is evidence that marihuana produces both sympathetci nervous system stimulation and parasympathetic nervous system blockade. No data are available that indicate the acute administration of marihuana presents a significant hazard to the cardiovascular system of normal subjects.

Measurement of Blood Flow in the Femoral Artery in Man at Rest and during Exercise by Local Thermodilution

A new method is described for measuring blood flow in the femoral artery in man, based on local thermodilution. The method makes it possible to take 3 or 4 measurements per minute at rest and during muscular exercise of the investigated limb. The average blood flow in eight subjects at rest was 635.9±223.1 ml./min., or 6.0±2.3 ml./100 ml. limb volume/min.

Changes during graded and increased work loads were also measured in 5-minute periods (150, 200, and 250 Kg./min.). The rate of flow rise was faster at the start of a given period than in the latter half of the same period. After the end of the work load, the rate of return of blood flow to the baseline fell off rapidly with time, but by 30 minutes later baseline values had still not been attained.