Despite normal to suppressed levels of renin activity in chronic renal disease, multiple lines of evidence suggest a role for the RAS, especially its intrarenal expression, in several critical aspects of this condition. Alterations in the distribution and control of components of the renal RAS could account for localized areas of activation of this system. Renal scarring may be particularly important as a major stimulus to renin synthesis in the diseased kidney. While both intrarenal and systemic hypertension may depend in part upon actions of the RAS, other non-hemodynamic actions of the RAS may also contribute to the adaptation of residual nephrons as well as their progressive injury.

SUMMARY Two hundred and twenty nine final year medical students were assessed in paediatrics using an objective structured clinical examination (OSCE) and a traditional viva voce examination, and the results were compared with other assessments of the students made during and at the end of the

No abstract

Prior exposure to SPs does not appear to have a positive effect on subsequent performance on an SPE unless similar or identical cases are used. However, the type and site of prior exposure limited the influence of the review. In view of the increased use of SPEs in medical schools, the content of prior exposure needs to be more fully established.

No abstract

The risk of hemorrhagic complications with anticoagulation therapy in patients following intracranial surgery has prevented investigation of the potential use of heparin in the early postoperative period. The authors have evaluated the safety of anticoagulation therapy following experimental craniotomy in male Holtzman rats. The dose and schedule of heparin administration, which elevated and maintained the activated partial thromboplastin time (APTT) within the therapeutic range of 1 1/2 to 3 X control APTT, was alternating doses of 400 and 500 IU/kg injected subcutaneously every 6 hours. This schedule was initiated 2, 4, 7, 10, and 14 days after craniotomy and was continued for 72 hours thereafter. The results demonstrated that the incidence of intracerebral hemorrhage declined as the postoperative interval prior to initiation of anticoagulation increased. If anticoagulation therapy was initiated during the first 7 postoperative days, the risk of intracerebral hemorrhage was high (mean 14.7%): however, if an additional 3 to 7 days elapsed prior to initiation of anticoagulation, the incidence of intracerebral hemorrhage dropped significantly (mean 0%) (p less than 0.05). These results suggest that anticoagulation therapy can be safely initiated 10 to 14 days after craniotomy.

The feasibility of employing the rat as an experimental model for investigation of full-dose heparin anticoagulation was assessed. Striking similarities were found to exist between rats and humans regarding (1) baseline-activated partial thromboplastin time (APTT) values, and (2) dosage per kilogram of heparin required to produce an APTT value of 1 ½-3 times normal, the clinical definition of full-dose heparinization. Based upon these similarities, it appears that the rat can effectively serve as an experimental model for investigating the effects of heparin in humans.

Intraoperative ultrasound can aid the biopsy of deep intracranial lesions. It is, perhaps, less clear whether ultrasound could be useful in functional neurosurgery, where the target is not abnormal in echogenicity. As an example, we chose to investigate in a dog model the periventricular gray target, which is frequently the choice for the placement of electrodes to control intractable pain. Autopsies showed the placement of our electrodes with less than 1 mm of error in four of five brains and a 1.5-mm error in the fifth brain. The largest error was seen to occur on the video screen and was due to our failure to tighten the guide properly. The potential advantages of this technique over conventional stereotaxis include the avoidance of: ventricular catheterization, the injection of contrast agent into the ventricles, the necessity for a stereotactic frame, and multiple x-ray exposures. Also, with real time scanning the surgeon has instant visual confirmation of electrode placement and can observe quickly any significant hematoma formation.