Relationship of cervical and abdominal vagal activity to lower esophageal sphincter function

The purpose of this study was to compare the effects of electrical stimulation of the abdominal and cervical portions of the vagus on lower esophageal sphincter (LES) pressure in the anesthetized opossum. Unilateral or bilateral abdominal vagotomy gave no significant change in basal LES pressure or in the sphincteric response to swallowing. Electrical stimulation of the peripheral end of the sectioned cervical vagus gave a frequency-related decrease in LES pressure with a maximum reduction of 93.5 +/- 2.5% at 10 HZ, 10 V. Stimulation of the central end of the cervical vagus increased LES pressure, with a maximum response of 34.0 +/- 1.9 mm Hg. Neither peripheral nor central stimulation of the sectioned abdominal vagus had significant effect on LES pressure (P greater than 0.05). Additionally, LES relaxation in response to swallowing or cervical vagal stimulation was intact after bilateral abdominal vagotomy. These studies suggest that whereas the cervical portion of the vagus mediates inhibitory and excitatory changes in LES pressure, the abdominal vagus has no demonstrable role in the control of LES function.     

A method for accurately determining lattice parameters using electron diffraction in a commercial electron microscope

In this paper an electron diffraction method is discussed by which the lattice constants of polycrystalline thin films can be accurately determined (0.1%). The method involves the sequential examination of a standard material and the unknown material mounted on separate grids. The error which can arise through the possible difference in height of the two grids can be corrected by means of height and tilting adjustments. The analytical approach of the dependence of the camera constant on the ring diameter as given in literature appears to be insufficient. An experimental correction factor for this dependence is introduced. The accuracy of this method, and the influence of relevant sources of error, are discussed and explained in terms of some experimental results.     

Comparison of rest/exercise ECG, thallium-201 scans and radionuclide angiography in patients with suspected coronary artery disease

The results of rest and exercise ECG, 201Tl myocardial perfusion imaging and equilibrium radionuclide angiography were analyzed in 71 consecutive patients referred for diagnosis or evaluation of coronary artery disease (CAD). In 45 patients the diagnosis was established either by catheterization or typical history. In this group the overall sensitivity for rest/exercise ECG was 66%, for 201Tl scans 74%, for both combined 79% and for the ejection fraction response to exercise determined by radionuclide angiography 97%. If only the exercise response was considered, the corresponding sensitivity values were 58% (ECG), 50% (201Tl scans), 71% (ECG + 201Tl) and 97% (radionuclide angiography). The specificity for coronary artery disease was determined to be 71% for ECG, 86% for 201Tl scans and 42% for radionuclide angiography. All patients with false-positive results by radionuclide angiography had cardiomyopathies, thus this test has a high specificity for left ventricular dysfunction rather than for CAD alone. Criteria developed from the analysis of the test results in the 45 patients with definite diagnoses were then applied to the evaluation of 26 additional patients with atypical chest pain. A diagnosis could be made in all but 5 of them and radionuclide angiography was again the single most reliable test. Based on this study a new approach for the noninvasive evaluation of patients with suspected coronary artery disease is proposed.     

Analysis of fiber types in the pigeon's metapatagialis muscle. II. Effects of denervation

The pigeon's metapatagialis muscle consists of three slips, two twitch and one tonic, and these slips are distinguishable at the gross anatomical level. Comparative studies of denervation are facilitated because the two fiber types are under the same mechanical forces, can be denervated as one muscle, and can be distinguished after denervation. Both fiber types atrophied after denervation, with the twitch fibers having a more variable response. Pathological alterations observed by light microscopy suggested that the twitch fibers were more affected by denervation than the tonus fibers. Ultrastructurally, both fiber types showed the same changes, with the twitch fibers again being more consistently altered. Proliferation of the transverse tubular system and sarcoplasmic reticulum were more marked in the tonus than twitch fibers, and the sarcoplasmic reticulum proliferated prior to the transverse tubules. Filament and fibril degeneration, peripheral and central degeneration, lysosomes and their derivatives, and satellite cell proliferation were common to both fiber types. Contracture knots were common to the denervated fibers, and were suggested to be characteristic of degenerating fibers. Degenerating motor end plates were observed, and most neurons in the fibers were naked, lacking myelin sheaths. The results are discussed in relation to the function of the neuron in maintaining the muscle, and the possibility of denervation inducing a transformation of tonic to twitch fibers.