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Biomedical subjects

W M Clark

Publications and source records attributed to W M Clark.

96 records · Page 6Linked to original sources
PubMedDate not supplied

Local thrombolytic therapy for cerebrovascular disease: current Oregon Health Sciences University experience (July 1991 through April 1995).

PURPOSE: This report details experience with local intraarterial or intradural sinus thrombolytic therapy for cerebrovascular thromboembolic occlusions in 40 patients. PATIENTS AND METHODS: Between July 1991 and April 1995, intracranial local thrombolytic therapy with urokinase was used to treat 40 patients with occlusive vascular disease. Twenty-six patients had acute occlusions of the central retinal artery, middle cerebral artery, basilar artery, or combined internal carotid and middle cerebral arteries. Three patients had embolic complications related to cerebral vascular embolization procedures. Five patients were undergoing intracranial angioplasty procedures for occlusive atheromatous disease. Six patients had dural sinus thrombosis. RESULTS: Local intraarterial thrombolytic therapy for acute thromboembolic arterial occlusions resulted in excellent restoration of perfusion in 18 patients, partial restoration of flow in four patients, and no effect in five patients. Fourteen of these patients had excellent clinical outcomes, seven made moderate improvements, and six died. In the two patients with central retinal arterial occlusions, no angiographic or clinical response to thrombolytic therapy could be ascertained. There was no angiographic improvement response from thrombolytic therapy in five patients with primary intracranial atheromatous stenosis, and one patient may have had an embolic complication related to this therapy. Three of six patients with dural sinus thrombosis had clearing of the thrombus and an excellent clinical result. The remaining three with extensive dural thrombosis did not have clearing of the thrombus; one patient became blind, and two patients died. Among the 40 patients treated, significant cerebral hemorrhage occurred after therapy in four. CONCLUSION: Local thrombolytic therapy for thromboembolic occlusive cerebrovascular disease is useful in restoring perfusion of acutely occluded vessels. Further experience is needed to fully identify the most appropriate patients for therapy, dose of thrombolytic agent, timing and length of therapy, and risk factors for hemorrhage.

Adolescent↗
PubMedDate not supplied

Partitioning of vancomycin using poly(ethylene glycol)-coupled ligands in aqueous two-phase systems.

Affinity partitioning describes a process in which a biospecific ligand is used to manipulate the partitioning behavior of a biomolecule by coupling a ligand to one of the phase-forming polymers. It combines the high selectivity of affinity chromatography with the scalability of aqueous two-phase extractions. Fundamental studies have been made on the factors affecting affinity partitioning of the antibiotic vancomycin using a series of polymer-ligands composed of the D-Ala-D-Ala peptide coupled to poly(ethylene glycol) in methoxypoly(ethylene glycol)/dextran aqueous two-phase systems. The effects of varying the ligand molecular weight, the ligand binding interaction, the number of binding sites, the tie-line length, and the aggregation of vancomycin have been measured. A modification of the Flanagan and Barondes model for affinity partitioning has been suggested to explain the results. The modified model accounts for the changes in the surface properties of the biomaterial on complex formation.

Amino Acid Sequence↗
PubMedDate not supplied

beta-Lactamase recovery from E. coli cell lysate via two-phase electrophoresis.

beta-Lactamase was recovered from Escherichia coli cell lysate by a novel cell debris removal method using two-phase electrophoresis. The cells were harvested by centrifugation after fermentation, resuspended in a low ionic strength electrophoresis buffer, lysed, and combined with a poly(ethylene glycol)/dextran aqueous two-phase system in the same buffer. The cell lysate was subjected to a 40 V/cm electric field oriented perpendicular to the phase interface for 90 min. Experiments were conducted both with and without a nucleic acid precipitation step using poly(ethylene imine) (PEI). For PEI-treated lysate at pH 5, the positively charged beta-lactamase was directed to the upper phase, while negatively charged contaminants (including cell debris, nucleic acid/PEI precipitates, and negatively charged proteins) were directed to the lower phase with the applied field. beta-Lactamase yield in the upper phase was 81%, while cell debris and nucleic acids partitioned almost exclusively to the lower phase. For untreated lysate, beta-lactamase did not move in the electric field due to strong interaction with nucleic acids in solution.

Buffers↗
PubMedDate not supplied

Noninvasive screening of extracranial carotid disease: duplex sonography with angiographic correlation.

Initial experience with a pulsed Doppler device coupled to a high resolution real-time sonographic scanner for noninvasive evaluation of extracranial carotid disease is reported. The primary objective was to evaluate patients with asymptomatic cervical bruits and/or equivocal histories of transient cerebral ischemia to determine which of them required further study with angiography. An assessment of the degree of extracranial carotid stenosis as well as the severity of atheromatous plaque formation was made and subsequently compared with the findings at angiography. During a 455 day period, a total of 501 patients were examined. In 150 arteries with complete angiography, correlation disclosed the noninvasive duplex technique to be 92% accurate in predicting which arteries would be significantly diseased. It is proposed that careful sonographic investigation of the extracranial carotid system is a safe and useful screening test for certain patients at risk for cerebrovascular accident.

Angiography↗