Escherichia coli O89 lipopolysaccharide (LPS) was treated with different doses of gamma irradiation (5, 10, 15, and 20 Mrad). Various biological activities such as lethal effect, decrease in arterial blood pressure in dogs, and interaction with the complement system were determined for the parent and irradiated preparations. Irradiation of LPS significantly and in a dose-dependent manner decreased its lethal and blood pressure-depressing effects along with its ability to activate the complement system. In contrast, radio-detoxified LPS fixed more strongly the isolated human C1 than did the parent LPS. The possible connection between the toxicity of endotoxin and endotoxin-induced complement activation is discussed.
The authors have studied the local blood flow regulation of the heart under the influence of the stimulation of the carotid sinus nerve in segmental myocardial ischaemia. The experiments were carried out on 38 dogs. By ligating the mid-portion of the left anterior descending coronary artery, a small artificial infarction has been produced. Circulatory examinations were made after 24 hours following the coronary ligation. In 18 dogs the circulatory investigations were done during the electrical stimulation of the carotid sinus nerve while 20 dogs were used as control. The local nutritive blood flow of the heart was measured by the administration of 86 rubidium in the intact zone, in the ischaemia (necrotic) zone and at the border zone of the heart. According to the experimental data, under the influence of the carotid sinus nerve stimulation the blood flow of the intact zone does not change considerably while the necrotic and border zones increases to a great extent. Reflex redistribution of the myocardial blood flow probably plays a decisive role in the antianginal effect of carotid sinus nerve stimulation.
Infusion of noradrenaline (1.0 mug/kg/min body weight, i.v.) brings about an increase of the diastolic wall stiffness in the ischaemic canine heart. Similar effect is not elicitable in the normal heart.
Introduction: Cardiomyocytes respond to stress with the expression of various heat shock proteins (HSPs). Expression of mitochondrial HSP60 is known to be induced by various stress factors, including ischaemia and reperfusion. The aim of the study was to investigate the induction of HSP60 in human myocardium during cardiac surgery. Method: From eight patients undergoing elective coronary artery bypass grafting or valve replacement, samples of right atrium were harvested before and after extracorporeal circulation (ECC). Two patients had atrial fibrillation and six were in sinus rhythm. The myocardial samples were excised and immediately immersed in liquid nitrogen. The HSP60 protein level was determined using sodium dodecyl sulphate-polyacryl-amide gel electrophoresis, Western blot, and subsequent ECL technique. The amount of HSP60 protein was quantified by optical densitometry, according to the immunoreactive bands of actin. Results: In all samples HSP60 was detected before and after ECC. We could not find any difference in HSP60 expression before and during cardiac surgery. There was no correlation with duration of cardiopulmonary bypass or reperfusion time. Conclusion: We could not demonstrate a cytoprotective upregulation of HSP60 after an obligatory period of ischaemia, cardioplegic arrest and reperfusion. This might reflect effective cardioprotection during ECC.
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