Biomedical subjects

S Meairs

Publications and source records attributed to S Meairs.

24 records · Page 2Linked to original sources

PubMed1995

[Aspirin dosage for prevention of cerebral infarct: arguments for low dosage].

Acetylsalicylic acid (ASS) is one of the best examined substances used in secondary prevention after TIA and stroke. Since different strategies and measurement variables were used in numerous randomised, double-blind, placebo-controlled studies (one end-variable, such as non-fatal stroke, myocardium infarction and vascular mortality, or combined end-variables, such as TIA, stroke and death), meta-analysis was necessary to prove that ASS resulted in about 22% reduction of secondary stroke. There is disagreement over the optimal dosage to prevent a stroke: earlier studies considered > or = 975 mg ASS per day, sometimes in combination with other substances, while more recently, lower dosages of about 300 mg per day or even as low as < or = 100 mg per day have been proposed. Higher and lower dosages were effective compared with placebo but with no significant difference in risk reduction, despite the trend towards a transient but insignificant reduction of secondary events for the high dosage. All available studies demonstrated a strictly dose-related gastro-intestinal hemorrhagic bleeding complication rate. Since no data are available from a direct comparison in a large sample size trial to prove the superiority of low-dose ASS (< or = 300 mg per day) over high dosages (> or = 975 mg per day) in secondary prevention of stroke, we believe that the lowest dosage of < or = 100 mg per day should be recommended for safety reasons.

Aspirin↗

PubMed1994

Pathophysiologic assessment of data from a stroke data bank.

Stroke data banks have been instrumental in helping us to clarify stroke etiology and in the investigation of clinical-topographic correlations. For these purposes they have relied upon results from noninvasive vascular and cardiac methods, including extra- and transcranial Doppler sonography and echocardiography, as well as from procedures such as cranial computed tomography and magnetic resonance imaging. Conventional database concepts have also been used to assess pathophysiologic aspects of stroke. Although such applications have made important contributions in this multidiscipline area of investigation, they are limited by a lack of explicit representation of pathophysiologic knowledge for data interpretation. Recent results from artificial intelligence research suggest exciting new frontiers for medical database design with concepts stemming from second generation expert systems. We propose an extended concept for stroke data banks to include a knowledge-based system which incorporates current patient data, heuristic knowledge relating clinical features to functional impairment, and pathophysiologic models of neurological disease.

Cerebrovascular Disorders↗

PubMed1991

MRI of transient osteoporosis of the hip.

Among the available imaging techniques such as conventional radiography, radionuclide bone scan, and computed tomography (CT), magnetic resonance imaging (MRI) has made significant contributions to the diagnosis of acute hip joint disease in adults by enabling early differentiation between such conditions as idiopathic avascular femoral head necrosis, septic coxitis, degenerative disease, and tumors. In this study we investigated the use of MRI for evaluation of patients with transient osteoporosis (TO). MRI with T1- and T2-weighted sequences in coronal, transverse, and sagittal sections was performed in 12 patients with retrospectively confirmed TO, both at the onset of the disease and later as follow-up procedure. MRI revealed three typical stages of TO: a diffuse stage, a focal stage, and a residual stage. Characteristic symptoms of TO are hip pain and a need for protective splinting of the hip joint. Conventional radiographs show demineralization of the hip joint without joint space narrowing. Clinical, radiologic, and MRI findings normalize within 6-10 months, indicating that TO has a good prognosis with complete restoration of bone density.

Female↗

PubMed1990

Magnetic resonance imaging of the craniocervical junction in rheumatoid arthritis: value, limitations, indications.

The cervical spine is the second most common location for manifestation of rheumatoid arthritis (RA). Symptoms are typically related to involvement of the craniocervical junction. Unfortunately, conventional radiographic examination is often unable to demonstrate that RA is the cause of such symptoms. Magnetic resonance imaging (MRI) provides an unique opportunity to visualize nerves, connective tissue, and bone in all planes without the use of contrast agents. These features suggest that MRI could provide important information related to RA of the cervical spine. The possibilities and limitations of MRI were therefore evaluated in 60 patients with cervical RA. The main objective of this study was to correlate symptoms and clinical findings with MRI results to establish indications for this imaging procedure.

Arthritis, Rheumatoid↗

PubMed1988

Beta-2-microglobulin adsorption and release in-vitro: influence of membrane material, osmolality and heparin.

We studied the effects of cuprammonium rayon (CR), polyacrylonitrile (PAN), polysulfone (PS), changes in osmolality, and heparin dosage on beta-2-microglobulin (b2M) handling in an in-vitro model that excluded convective transport and minimized diffusive transport. Both PAN and PS exhibited high adsorption capacity for b2M. Osmolality changes had no effect on b2M adsorption or release. CR membrane adsorption was minimal but increased slightly when higher heparin doses were used. In experiments with CR and high heparin doses (4 U/ml) b2M release occurred during the first 15 minutes of in-vitro dialysis, but this increase was inhibited by removing the leukocytes from the blood, indicating that b2M is released from leukocytes.

Acrylic Resins↗

PubMed1984

Morphologic investigation of coronary arteries subjected to hypertension by experimental supravalvular aortic stenosis in dogs.

A sustained and gradual development of hypertension in coronary arteries of 16 foxhounds was induced by afterload stress with supravalvular aortic stenosis. Dogs were perfusion fixed after 4 months and 1 year of stenosis for morphologic analysis of coronary arteries with scanning electron microscopy, transmission electron microscopy, and light microscopy. Mean prestenotic pressures and SD standard deviations in millimeters of mercury for perfusion-fixed foxhounds after 4 months were systolic 141 +/- 14, mean arterial 101 +/- 8, and diastolic 81 +/- 7, and after 1 year systolic 182 +/- 31, mean arterial 128 +/- 22, and diastolic 101 +/- 16. Scanning electron microscopy results of coronary arteries subjected to 4 months of hypertension show little change from normal coronary arteries. Only isolated cases of desquamating endothelial cells were seen directly proximal to ostia of coronary arteries. Transmission electron microscopy showed no ultrastructural changes in this banding group. In four of six foxhounds subjected to 1 year of hypertension, scanning electron microscopy observations of coronary arteries revealed one to five areas of endothelial denudation, typically oriented parallel to the longitudinal axis of the artery, a few cell diameters wide and 100 to 300 microns in length. These lesions were often seen to form narrow channels between two or more branching points, either in a continuous or in series fashion. Platelets, lymphocytes, granulocytes, and monocytes adhered to the subendothelial surface. Occasional denudations were oriented transversely to the longitudinal axis. Denudations were restricted to arteries greater than 1.2 mm in diameter. In the vicinity of denudation lesions, lymphocytes and monocytes adhered to endothelium showing alterations in cell size and shape. Transmission electron and light microscopy of this banding group showed breaks and duplication of the internal elastic lamina and smooth muscle proliferation in the intima. Focal areas of intimal inflammatory reactions, sometimes superimposed upon intimal proliferative changes, were noted in those areas exhibiting luminal cell adherence to endothelium. The results indicate that the morphologic equivalent of hypertension varies depending on the manner in which it is experimentally produced. The findings of intimal proliferation and late endothelial denudation give support to the response-to-injury hypothesis for the pathogenesis of atherosclerosis and suggest a mechanism for the role of hypertension as a risk factor.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗