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Biomedical subjects

M D Ward

Publications and source records attributed to M D Ward.

5 recordsLinked to original sources
PubMed1991

Piezoelectric cell growth sensor.

We have developed a reusable piezoelectric sensor that enables rapid characterization of cell viability and response to cell-affecting agents. This is accomplished via a novel polymer transduction principle that involves reaction of a pH-sensitive amphoteric polymer with metabolically generated acid. Subsequent adhesion of the protonated polymer to the transducer surface causes a decrease in the sensor resonant frequency corresponding to the cell metabolic rate. This disclosure provides the first example of a piezoelectric sensor capable of detecting metabolic responses of viable cells. The sensor provides real-time measurement of cell metabolism and division rates, and antibiotic sensitivity. This technology provides the basis for an advanced piezoelectric sensor that does not require immobilized biological receptors and can be miniaturized without compromising signal-to-noise factors.

Anti-Bacterial Agents↗
PubMed1975

Neostigmine methylsulfate. Does it have a chronic effect as well as a transient one?

Three groups of 200-gm rats were injected subcutaneously with neostigmine methylsulfate (1 mg/kg/day) for 7, 30, and 100 days. Electrophysiological changes were assessed in vitro, using microelectrode techniques to examine diaphragm muscles of treated and untreated animals. Miniature end-plate potential (MEPP) amplitude decreased in neostigmine-treated preparations. Guanidine hydrochloride enhances transmitter release and increases MEPP frequency in control preparations. Neostigmine-treated animals examined between 6 to 72 hours after discontinuation of neostigmine therapy showed impaired response to the facilitating influence of guanidine. Recovery of response to guanidine was inversely related to length of treatment with neostigmine. Results of electron-microscopic examination of motor end-plates in treated animals revealed ultrastructural changes, including simplified end-plates, and, occasionally, multiple, separate, junctional regions. Therefore, the chronic administration of cholinesterase inhibitors in man may have a deleterious effect, as well as a transient beneficial one.

Animals↗
PubMedDate not supplied

Morphology of cell-substratum adhesion. Influence of receptor heterogeneity and nonspecific forces.

Many cell types modulate growth, differentiation, and motility through changes in cell substrate adhesion, including regulation of focal contact formation. Clustering of cell surface adhesion receptors is an essential early step in the development of focal contacts, and thus may influence cell physiology. In this paper, we present a theoretical framework to examine how cell surface chemistry affects receptor clustering. Our one-dimensional tape-peeling model couples the equations of mechanical equilibrium for a cell membrane with kinetic receptor-ligand binding relations. We considered two distinct model scenarios: Adhesion mediated by multiple receptor-ligand interactions of different length and specific binding of a single receptor type occurs in the presence of van der Waals attraction and nonspecific repulsion. In each case, nonuniform (wave-like) membrane morphologies are observed in certain parameter ranges that support the clustering of adhesion receptors. The formation of these morphologies is described in terms of a balance of membrane stresses; when cell-surface potential as a function of separation distance is symmetric between two potential energy minima, nonuniform morphologies are obtained. Increases in the chemical binding energy between receptor and ligand (e.g., increases in ligand density) or decreases in the membrane rigidity result in smaller wavelengths for nonuniform interfaces. Additionally, we show wave-like geometries appear only when the mechanical compliance of receptor-ligand bonds is within an intermediate range, and examine how the mobility of "repellers"--glycocalyx molecules that exert a nonspecific repulsive force--influences membrane morphology. We find fully mobile repellers always redistribute to prevent nonuniform morphologies.

Animals↗
PubMedDate not supplied

Fluoroscopic technique for double-contrast knee arthrography.

The fluoroscopic double-contrast technique of arthrography of the knee is useful in documenting the extent of suspected injury to the knee. It is of particular value in demonstrating small and large lesions involving the menisci, cruciate ligaments, patellar cartilages, as well as the articular cartilages of the femoral condyles and tibial plateaus. This examination is instrumental in the diagnosis of the patient with an atypical history of injury and unusual physical findings. A simple restraint device allows the fluoroscopist complete control over the stress applied to the knee while positioning the patient for filming. Fluoroscopic spot radiographs of excellent contrast and sharp detail can be obtained of each of the various structures, applying the stress needed. When the radiologic technologist takes a little time to become more knowledgeable about the anatomy of the knee jount, and the rationale for the various views, the knee arthrographic examination is easily understood.

Cartilage, Articular↗