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Biomedical subjects

R F Dunn

Publications and source records attributed to R F Dunn.

10 recordsLinked to original sources
PubMed1979

Horizontal ampullary nerve fiber projections to the crista angustarum in the crista ampullaris.

Individual nerve fibers were traced on consecutive serial 1-micron-thick cross-sections to determine their position of origin within the horizontal ampullary nerve trunk (HANT) and the site at which they penetrated the basilar lamina of the horizontal crista in the guitarfish, Rhinobatos productus. Of the 132 fibers successfully traced, 87.1% followed an anatomical projection pattern consistent with the dynamic response characteristics of the nerve fibers. That projection pattern was: from the peripheral HANT region to the ipsilateral slope; from the central HANT region to the crest; and from the intermediate HANT region both to the ipsilateral slope and the crest of the horizontal crista. The 12.9% of "error" fibers not following this projection pattern were also consistent with the functional neurophysiological data. The terms crista bulbus and crista angustarum were introduced to designate specific anatomical regions of the dumb-bell shaped crista ampullaris.

Animals↗
PubMed1979

Serial exercise thallium myocardial perfusion scanning and exercise electrocardiography in the diagnosis of coronary artery disease.

Serial exercise thallium-201 myocardial perfusion scanning (exercise and 4-hour redistribution) was compared to rest and exercise electrocardiography (ECG) for the detection of coronary artery disease in 125 patients with known or suspected coronary artery disease. All patients underwent coronary arteriography and 108 were found to have significant coronary artery lesions. The serial exercise thallium scan was significantly more sensitive than rest and exercise ECG in detecting coronary artery disease (94% v. 83% P less than 0.01). The sensitivity of a reversible thallium perfusion scan abnormality and a positive exercise ECG for detecting exercise induced myocardial ischaemia in coronary artery disease was similar (69% v. 63%). The exercise thallium scan complemented the exercise ECG, and the sensitivity of the combined test was significantly greater than the exercise ECG alone (84% v. 63% P less than 0.001). The specificity for coronary artery disease of the exercise ECG was 65% and that of the exercise thallium-201 myocardial perfusion scan was 82% (P = NS). Thallium-201 myocardial perfusion scanning complements the rest and exercise ECG in the non-invasive detection of coronary artery disease.

Adult↗
PubMed1979

Multivessel coronary artery spasm.

A 60-year-old patient with variant angina was shown to have myocardial ischemia in two different regions supplied by separate major coronary arteries. Neither artery had significant coronary atherosclerotic obstruction. Ventricular fibrillation was noted during ST-segment elevation in anteroseptal leads. The attacks of pain and arrhythmias disappeared during nifedipine therapy.

Angina Pectoris↗
PubMed1978

Nerve fibers of the eighth nerve and their distribution to the sensory nerves of the inner ear in the bullfrog.

The number of both myelinated and unmyelinated nerve fibers has been determined for the eighth nerve and each of its sensory branches in the bullfrog. No significant differences were found in the size distribution of the myelinated nerve fibers among the three ampullary nerves or between the saccular and lagenar nerves. Comparison of these two functional groups also showed no significant differences in the myelinated nerve fiber size distribution between the angular acceleration and otolithic receptors, collectively the equilibrium receptors. The wide variability, that was found not only among the animals but also between the right and left sides, most likely resulted in the absence of differences. Highly significant differences were noted when the myelinated nerve fiber diameter distributions to the acoustic organs were compared to those of the equilibrium organs. The most notable difference was the absence of any myelinated nerve fibers whose diameters were greater than 8 micrometer.

Animals↗
PubMed1978

Myocardial perfusion scanning with thallium--201 for the non-invasive diagnosis of coronary artery disease.

Thallium--201 myocardial perfusion scanning has been evaluated in Australia in patients with coronary artery disease. Myocardial scans reliably detect both acute myocardial infarction and the transient myocardial ischaemia of angina pectoris. The non-invasive nature, ease of study, and the ability to scan patients with conventional cameras makes thallium--201 an attractive additional diagnostic agent for patients with suspected coronary artery disease. Although thallium--201 reliably indicates perfusion defects in the myocardium, its diagnostic use at the moment should be reserved to clarify such diagnostic problems in patients with coronary artery disease which cannot be satisfactorily explained by conventional investigation.

Angina Pectoris↗
PubMed1976

Analysis of afferent responses from isolated semicircular canal of the guitarfish using rotational acceleration white-noise inputs. I. Correlation of response dynamics with receptor innervation.

The small-signal linear characteristics of afferent responses from the isolated semicircular canal were described by the use of white-noise rotational acceleration inputs. The results, based on cross-correlation analysis, showed a striking and systematic variation in linear system impulse response characteristics from afferents which innervated different regions of the receptor. Afferents from centrally located nerve bundles innervating the crest region of the crista exhibited an initial maximum response amplitude followed by a rapid decay. In contrast, afferents from extreme rostral and caudal nerve bundles innervating the crista slopes exhibited an initial rise up to a low-amplitude maximum followed by a slower decay. These results imply that the afferents innervating a single canal do not merely carry redundant information concerning current head acceleration, but could be considered an ensemble of specific classes of filters that are tuned individually to specific classes of head movements. On the basis of these considerations, a new hypothesis of matched filter detection was proposed as relevant to information processing and dynamic control in central vestibular pathways.

Animals↗
PubMed1975

Quantitative analysis of micrographs by computer graphics.

A computer-aided graphical analysis system is presented which can be used to quantify several types of information from micrographs of cross-sectioned peripheral nerves. A simple input consisting of eight points, corresponding to two diameters of each axon and two for each axon plus myelin, is used to compute statistical and numerical estimates of these diameters, the myelin thickness being expressed as a function of axon diameter, and both the spatial position and distribution of nerve fibres within the bundle. The computer programs presented and summarized here describe the procedure for digitizing the input data and the subsequent computations for editing and analysis. The general applicability of this approach for automated analyses of other anatomical areas is also presented.

Axons↗