Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography

The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.     

Lithium acetate gastrointestinal diffusion system. Part 1: Lithium acetate single-unit gastrointestinal diffusion system: preparation and release rate studies

The gastrointestinal diffusion system (GDS), containing lithium acetate (1), releases the drug by a controlled source of diffusion energy. The unit can possibly be used for all soluble drugs in which solubility is independent from the pH of the gastrointestinal contents as is the case with 1. The one-compartment unit is obtained by tabletting the drug and coating the tablets with a membrane of cellulose acetate to which soluble porofores-gum arabic, sodium chloride, 1-are added. When the pore-creating substance is dissolved out of the coating, there remains a porous film, which controls the rate of release of the drug. The release characteristics depend on membrane composition and mass. The systems reported here provided for zero-order drug delivery in vitro.     

Paediatric dacryocystorhinostomy

Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease.     

The effect of sulphinpyrazone and alpha-tocopherol on platelet activation and function in haemodialysed patients

In 30 patients on chronic haemodialysis treatment the platelet activity and function were studied before and during antiplatelet therapy with alpha-tocopherol and sulphinpyrazone. In both kinds of treatment a significant decrease of ADP-induced and spontaneous aggregation was observed. Sulphinpyrazone exerts an inhibitory effect not only on platelet aggregation but also on platelet factor 3 and provokes a significant prolongation of the bleeding time.     

Myocardial stiffness and reparative fibrosis following coronary embolisation in the rat

The structural nature of fibrillar collagen involved in the replacement fibrosis which accompanies discrete areas of cell necrosis remains uncertain, as does its influence on the diastolic and systolic stiffness of the intact myocardium. This study, using 15 micron diameter microsphere embolisation of the rat myocardium, was undertaken to address these issues. Collagen volume fraction (trichrome), fibrillar collagens (picrosirius-polarisation technique), and the stress-strain relations of the intact myocardium (isolated hearts) were determined 30 d after the infusion of microspheres into the left ventricle. Significant differences from controls included: (a) the presence of hypertension secondary to renovascular embolisation; (b) a greater volume fraction of collagen that included not only a meshwork of short, taut appearing, thick and thin collagen fibres, interposed between muscle in areas of cell loss, but also a perivascular fibrosis involving intramyocardial coronary arteries; (c) elevated active stiffness, and (d) a more exponential diastolic stress-strain relation with increased stiffness at strains of 5% or more. These findings suggest that the replacement fibrosis accompanying myocyte necrosis has distinguishing morphological features involving fibrillar collagen and which because of its structure, alignment, and location relative to muscle leads to enhanced myocardial stiffness, including a more exponential rise in the diastolic stress-strain relation. The perivascular accumulation of collagen suggests that additional factors other than microsphere induced necrosis were responsible for this reactive fibrosis.