Evaluation of the antidysrhythmic effects of delta- and kappa-opioid receptor agonists and antagonists on calcium chloride-, adrenaline- and ischemia/reperfusion-induced arrhythmias in rats.

This study was undertaken to evaluate the involvement of delta- and kappa-opioid receptors in both ischemia- and reperfusion-induced arrhythmias, and to elucidate some of the plausible mechanisms conferring antidysrhythmic effects on opioid delta- and kappa-receptor agonists and antagonists. Different models of arrhythmia (calcium chloride [CaCl(2)]-, adrenaline-, and ischemia/reperfusion-induced arrhythmias) were employed. The following opioid agonists, antagonists and blockers were used in the study: [D-Ala(2), D-Leu(5)]enkephalin (DADLE), a selective delta-receptor agonist; trans-3,4-Dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide (U-50488H), a selective kappa-receptor agonist; Naltriben Methanesul-fonate (NTB), a selective delta(2)-antagonist with kappa-receptor agonist-like activity; natrindole, a non-selective delta(1)- and delta(2)-receptor antagonist; nor-binaltorphimine dehydrochloride (nor-BNI), a selective kappa-receptor antagonist; chelerythrine, a selective protein kinase C inhibitor, and glibenclamide, a selective blocker of ATP-sensitive K channel. Although results of the morphometric, enzymatic, hemodynamic, electrocardiographic and pharmacodynamic studies undertaken suggest that both opioid delta(1)- and kappa-receptors are involved in the phenomenon of ischemic heart preconditioning (IPC), the antidysrhythmic effects of the opioids seem to be mediated mainly via kappa-receptors. The antidysrhythmic effect of U50488H was found to be a consequence of its beta-blocking activity (which is comparable to that of propranolol, a Class II antiarrhythmic drug) and its ability to prolong myocardial action potential (QT-interval prolongation, which is comparable to that of amiodarone, a Class III antiarrhythmic drug). The antidysrrhythmic effects of the opioid compounds examined were almost completely abolished by glibenclamide or chelerythrine pretreatment. No calcium-channel blocking activity was observed in this investigation. The present observations suggested that opioid receptors displaying well known analgesic properties may have the potential to protect the myocardium during cardiac ischemia at the early stages of myocardial infarction (when early arrhythmias are the most common causes of death).

Variations of the posterior interosseous nerve.

The posterior interosseous nerves of 58 cadaver forearms of black South Africans were dissected to study their order of branching. In 43 specimens (74%), the most common order of branching was: extensor carpi radialis brevis; supinator; extensor digitorum; extensor carpi ulnaris; extensor digiti minimi; abductor pollicis longus; extensor pollicis brevis; extensor pollicis longus and extensor indicis. In 15 specimens (26%) different variations of the nerve were observed, some of which are reported for the first time. The knowledge of these variations could be useful during operations in the vicinity of the nerve, and when repairing a nerve injury or forecasting the location of a compressive lesion.

Chronic aluminum intoxication in rats: dose-dependent morphological changes.

The objective of the study was to evaluate the chronic cytotoxic effect of very low nontoxic aluminum (Al) in the drinking water of rats. The control group (10 rats) received deionized water, whereas the two experimental groups (10 rats each) received Al in a dose of 5 mg and 20 mg/kg bw/day, respectively. Al was applied in their drinking water during the 6-month duration of the study. Light and electron microscopy (EM) was performed on several body tissues (i.e., kidney, liver muscle, brain). The results showed distinct dose-dependent changes in kidney and brain. In tubulo-interstitial part of the kidney many proximal tubules were hyperdilated. Their cells were swollen and the microvilli were largely lost. Atrophy of some tubules, surrounded by focal areas of interstitial fibrosis was also observed. Some of the glomeruli were undergoing partial sclerosis and in many focal mesangial hypercellularity was found. No distinct morphological changes in other peripheral tissues were observed. In brain, most pronounced changes were observed in hippocampus: they include spongioform changes in pyramidal layer, nuclear deformity and presence of vaculoes in the nuclei. Neurofibrillary degeneration, similar to neurofibrillary tangles in Alzheimer's disease, was also observed. It can thus be concluded that despite very low gastrointestinal absorption (less than 1%), Al in drinking water might accumulate in the long term in vital organs such as kidney and brain, with distinct cytotoxic and neurotoxic effects.

Variations of the pubic vascular anastomoses in black South Africans.

Variations of the arterial and venous pubic anastomoses (APA, VPA) were studied. Forty-four percent of the APA were replaced by an obturator artery arising from the inferior epigastric and 25% by an obturator artery arising from the external iliac. Seven percent of the VPA were replaced by a single obturator vein, 37% by the superior companion of a double obturator vein, and 2% by a double obturator vein. Black South African subjects exhibit a higher incidence of variations of the pubic anastomoses than North American, European and Japanese populations.

Fine structure of the fibrous layer of the mandibular condylar cartilage of the Chacma baboon (Papio ursinus) using postfixation in osmium-potassium ferrocyanide.

The aim of this study was to use a fixation technique not previously used to elucidate the fine structure of the fibrous layer of the mandibular condylar cartilage. The sample was obtained from four one-year-old Chacma baboons (Papio ursinus). Blocks of tissue were prepared according to the method of Farnum and Wilsman (1983) and examined by transmission electron microscopy. This study revealed the presence of superficially situated fibroblast-like cells and deeply placed chondrocyte-like cells. The matrix consisted of Type 1 collagen fibres which were arranged either loosely near the articular surface or in tightly packed bundles deep to the surface. Elastic fibres were also present. A variety of matrix vesicles resembling cell debris, as well as interfibrillar electron dense granular material thought to be fibronectin, were also identified. This technique reveals more structural details than the conventional fixation technique.