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Biomedical subjects

D Kennedy

Publications and source records attributed to D Kennedy.

At least 181 records · Page 10Linked to original sources
PubMed1978

Physical diagnosis courses--a question of emphasis.

The ability of 12 students to examine hospitalized patients at the end of a course in physical diagnosis was measured through the use of video tapes of patient examinations and audit of written summaries. The results indicate the course in physical diagnosis underemphasized the most important aspect of the patient examination, the patient interview. The errors most often committed by students performing physical examinations and taking histories from patients suggest that increased observation of students by preceptors would be profitable in improving the course. Course evaluation through video taping of actual student examinations proved highly instructive and useful in developing a more effective program.

Clinical Competence↗
PubMed1976

Effects of external pressure loading on human skin blood flow measured by 133Xe clearance.

Forearm skin blood flow was measured during external pressure loading in normal human subjects using 133Xe washout from intracutaneous injection sites. Pressures ranging between 5 and 150 mmHg were applied through a 3-cm-diameter disc placed over the site of flow determination. The pressure was maintained constant by a servo-controlled loading mechanism. Flow decreased with pressures from 5 to 10 and 30 to 150 mmHg, but remained constant with pressures from 10 to 30 mmHg. Reactive hyperemia occurred following removal of pressures of 90 mmHg or greater, but did not occur following removal of lower pressures. The pressure-flow curve for parasacral skin of paraplegic subjects closely paralleled the pressure-flow curve of normal skin at pressures tested: 5-15 mmHg. These data are interpreted to demonstrate autoregulation of skin blood flow. Autoregulation in parasacral skin of paraplegic subjects suggests a peripheral mechanism. The occurrence of hyperemia at pressures which exceed the ability of skin to autoregulate suggests that both autoregulation and post occlusion hyperemia may have the same mechanism.

Adult↗
PubMed1976

Integration of directional mechanosensory input by crayfish interneurons.

1. Interneurons activated by mechanosensory hairs on the crayfish telson respond selectively to directional displacements of the medium; the directions of maximum sensitivity lie 180 degrees apart in approximately the rostrocaudal plane, corresponding to the directional sensitivities of the two populations of primary afferent neurons. We have examined the basis for this selectivity by intracellular recording in the interneurons, correlating subthreshold potentials with activity evoked in identified afferents by bending single hairs or by producing nearfield displacements of the medium. 2. Interneurons can usually be caused to discharge by a brief train of impulses in single sensory axons. Unitary EPEPs are associated with arriving affterent spikes in the fourth (sensory) root; each primary interneuron receives convergence from several sensory axons, all sensitive to the same direction of movement. Since each afferent axon is drawn from a pair innervating a single sensory structure, this remarkable specificity of connection is unlikely to depend on an anatomical mode of address. 3. Higher order interneurons receive from directionally sensitive lower order interneurons of the same class, as well as from primary afferents of that class. The responses of such cells may show much more decrement during a train of displacement stimuli than do those of lower order cells. Directionality does not appear to be enhanced. 4. During the "null phase" some interneurons appear to be actively inhibited: bending of single hairs 180 degrees away from the effective direction may produce membrane hyperpolarization and slow spontaneous discharges, and shocks to afferent roots produce mixtures of monosynaptic EPSPs and polysynaptic IPSPs.

Animals↗
PubMed1975

Comparative strategies in the investigation of neural networks.

Comparative studies on nervous systems, though infrequently undertaken for the purpose of comparison, have yielded some important generalities about the formats of nervous networks, and about the cell biology of certain neural types. In the first category, it is clear that convergent evolutionary processes arrived at very similar networks to accomplish reciprocal and lateral inhibition, and load-compensation in "resistance reflexes." A newer general network format is described, command-derived inhibition, in which the central nervous elements controlling a rapid movement deliver presynaptic inhibition to the terminals of sensory neurons that carry reafferent excitation from the movement. It is argued that such circuits occur in several groups of animals, and that they include as a special class the efferent inhibitory neurons innervating acoustico-lateralis receptors in vertebrates. The properties of circuit elements that now seem to constitute useful generalizations include size principle (the inverse relationship between size and excitability in a variety of neurons), and the late differentiation of sensory neurons, failure to decussate, and their inability to mediate inhibition. Many other generalities have emerged, only to fall; one conclusion from such searches is that many supposedly "basic" properties of cell types or neural circuits are in fact not phylogenetically conservative, however much the physiologist may expect them to be.

Action Potentials↗
PubMed1974

Presynaptic inhibition: primary afferent depolarization in crayfish neurons.

Inhibition of transmission between tactile sensory neurons and interneurons in the crayfish was investigated by intracellular recording int the presynaptic processes. Inhibition is correlated with a depolarization of the presynaptic process, as in the mammalian spinal cord; the depolarization is accompanied by a conductance increase, and is mediated by interneurons that can be excited by a variety of routes.

Animals↗