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D J Anderson

Publications and source records attributed to D J Anderson.

At least 451 records · Page 25Linked to original sources
PubMed1978

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PubMed1977

A clinicopathologic study of prosthetic valve endocarditis in 22 patients: morphologic basis for diagnosis and therapy.

Although endocarditis is a frequently lethal complication of prosthetic valve replacement, there is little pathological information on which to base diagnosis and treatment. We have studied the clinical and pathological features of 22 patients with prosthetic valve endocarditis seen at The Johns Hopkins Hospital over the past 17 years. Five patients developed endocarditis within two months of operation and 17 between two and 48 months (average 12) after operation. Patients dying early had a more fulminant course and their endocarditis was less often recognized during life. Late deaths, tending to present with fever and bacteremia unmasked by postoperative problems, were more readily recognized. Mitral and aortic prosthetic endocarditis generally led to a different type of prosthetic valve dysfunction: nine of 14 aortic valve prostheses with endocarditis developed incompetence and one other stenosis; five of seven patients with mitral valve prostheses developed stenosis and one, a homograft, developed incompetence. Prosthetic valve dysfunction led to death in 10 patients (45 per cent) and embolic events in five (23 per cent), including four cerebrovascular accidents. Ring infection, often believed to be universally present, and a contraindication to surgery, was found only in 50 per cent of these patients. In four patients (18 per cent) the endocarditis was sterilized by antibiotics but death occurred from valve dysfunction or emboli. These findings suggest that early surgical intervention combined with antibiotics has a chance of providing effective therapy for prosthetic valve endocarditis.

Adolescent↗
PubMed1976

Transfer characteristics of first and second order lateral canal vestibular neurons in gerbil.

Discharge patterns of first and second order vestibular neurons responding to angular acceleration in the plane of the lateral canals were studied in gerbil. The resting discharge activity of each cell was used to characterize the neuron by measureing the coefficient of variation and coefficient of skewness of the interspike interval distributions. Sinusoidal angular oscillations ranging in frequency from 0.0125 to 5.0 Hz were delivered by a velocity controlled rate-table. A PDP-12 minicomputer system was used on-line to display period and post-stimulus histograms of discriminated single unit activity. Off-line Fourier analysis of the period histograms was used to determine the phase of cell response to sinusoidal accelerations, while the average level and amplitude were determined by a least squares fitting algorithm applied over the fraction of the stimulus period where the cell discharged. First order neurons were found to have high discharge rates (average = 61.7 imp./sec) and bidirectional responses to rotation, and were of two groups called regular and irregular according to their resting discharge patterns. Second order neurons, located mainly in the medial and lateral vestibular nuclei, had low or even zero resting discharge rates (average = 17.8) resulting in more uni-directional responses and were of a single population. For frequencies less than 10 Hz, the Bode plots of the regular first order neurons are similar to that of a first order system with a time constant of about 2 sec as predicted by the torsion pendulum theory for cupula movement. The irregular first order neurons show an increasing gain above 0.5 Hz and a large phase lead relative to angular velocity above 1.0 Hz suggestive of a fractional power transfer function. The second order neurons show the phase and gain characteristics of the regular first order neurons being in phase with angular velocity above 1.0 Hz.

Anesthesia↗
PubMed1976

Single unit responses recorded from the first order neuron of the pigeon auditory system.

Intracochlear recordings from the first order neurons in the eighth nerve of the pigeon were made with microelectrodes. The basic response characteristics of the single units were similar to those recorded from mammalian first order auditory neurons with the following exceptions: units responding solely to 'sweep frequencies' were found and one unit was found for which the rate of discharge decreased with increased intensity. Suppression of spontaneous activity during tonal stimulation was found within the response curve of the unit and for frequencies beyond the boundaries of the response curve. In addition, suppression of spontaneous activity was found after the termination of the tone. The amount of suppression and the recovery process varied considerably from unit to unit. The controlling variables were intensity and duration of the stimulus.

Acoustic Stimulation↗