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Biomedical subjects

P F Cranefield

Publications and source records attributed to P F Cranefield.

At least 55 records · Page 3Linked to original sources
PubMed1972

Conduction of the cardiac impulse. 3. Characteristics of very slow conduction.

The excitability of short segments (5-7 mm) of bundles of canine Purkinje fibers was depressed by exposure to 15-18 mM K(+), to 15-18 mM K(+) plus 5 x 10(-6) epinephrine or norepinephrine, to low K(+), and to low Na(+). The depressed segment was in the center chamber of a three-chamber bath; the ends of the bundle were exposed to normal Tyrode solution. Each method of depression resulted in slow and probably decremental conduction with an effective conduction velocity in the middle chamber of about 0.05 m/sec, or one-way block, or two-way block with summation of the graded responses in the depressed region. The action potential in the depressed segment (the slow response) differs from the normal action potential in its response to applied stimuli. A second active depolarization can be evoked by cathodal stimulation during much of the slow response. The response in the depressed segment is graded. The response of depressed fibers may depend on excitatory events similar to those responsible for the slow component of the cardiac action potential. It is suggested that the slow response can propagate, at least decrementally, in fibers in which the rapid, Na(+)-dependent upstroke is absent, and can cause reentrant excitation by so doing.

Action Potentials↗
PubMed1967

Retrieving the irretrievable; or the editor, the author, and the machine.

Present day programs of computerized information retrieval overvalue the importance of retrieving "facts" without either attaching a scale of importance to the material with which they deal or ordering information in any way which corresponds to the order of human thought. The limitations of classification by subject heading become especially apparent when a body of information becomes, through new insight, pertinent to a new area of thought. That body of information thereby acquires new subject headings: thus one sees that the system of retrieval by subject heading can never serve to aid fundamental discovery. The dangers of the present approach lie in their devaluation of traditional methods. Critical reviews are devalued, personal knowledge of the literature is devalued, and a false impression is created that knowledge is the same thing as retrievable information. This diminishes respect for that sort of personal organization of knowledge which alone can serve creative insight.

Abstracting and Indexing↗