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Biomedical subjects

D H Johnson

Publications and source records attributed to D H Johnson.

At least 343 records · Page 19Linked to original sources
PubMed1978

The relationship of post-stimulus time and interval histograms to the timing characteristics of spike trains.

PST (post-stimulus time) and interval histograms computed from recorded spike trains are related to an average timing characteristics of the spike train. The exact nature of this relationship varies with recording parameters, interfering signals, the histogram bin width, and the duration of the measurement interval. This work describes the conditions under which a PST histogram can serve as an unbiased estimate of the ensemble average of a spike train's intensity and an interval histogram can serve as an unbiased estimate of the probability density function of the interspike intervals. Simulation studies are used to confirm the validity of the theoretical results. As an example of an application, these results are used to analyze recordings of singleunit activity in the eight cranial nerve.

Action Potentials↗
PubMed1978

The effect of an alexidine mouthwash on plaque and gingivitis.

A clinical study was conducted on the effects of an alexidine or placebo oral rinse on plaque and gingivitis. Forty-two male subjects rinsed for 54 days while continuing toothbrushing. This was followed by 4 days of mouthrinsing only. The alexidine mouthrinse significantly reduced the plaque index when used in conjunction with toothbrushing and also when brushing was discontinued. The gingivitis results were inconclusive.

Adult↗
PubMed1976

Analysis of discharges recorded simultaneously from pairs of auditory nerve fibers.

Spike trains were recorded simultaneously from pairs of auditory nerve fibres in anesthetized cats. Tests for correlation between spike trains were developed for spontaneous activity and for discharge patterns resulting from single-tone stimuli. The application of these tests to the recordings indicates that the responses of auditory nerve fibers to a tone and to silence can be described as statistically independent point processes. This result implies that the initiation of spikes in these fibers is governed by localized processes specific for each fiber.

Acoustic Stimulation↗
PubMed1975

Bacterial endocarditis in children under 2 years of age.

The risk of bacterial endocarditis in infants with bacterial sepsis was assessed by review of clinical and autopsy records (1930 to 1972). There were 12 cases of bacterial endocarditis among 847 patients (1.4%) dying with bacterial sepis; a single survivor was noted during the entire period. Of the 12 autopsy patients, six had underlying congenital heart disease (CHD). Among 61 patients with bacterial sepsis associated with CHD, six acquired bacterial endocarditis (10%), whereas in 786 infants with sepsis but without underlying heart disease, only six developed bacterial endocarditis (0.8%) (P less than .01). There is a high mortality in infants with bacterial endocarditis, and an increased risk of it in infants with sepsis and CHD.

Age Factors↗
PubMed1975

Temporal bone radiography: a screening survey approach.

For preliminary evaluation of the temporal bone, a combination of conventional radiographs and hypocycloidal tomography in the frontal projection is advocated. If significant abnormalities are detected in this screening survey, a more in-depth study can then be pursued.

Humans↗
PubMed1975

A forty-year review of bacterial endocarditis in infancy and childhood.

A retrospective review of 149 episodes of bacterial endocarditis (BE) in 141 patients under 25 years of age, at The Children's Hospital Medical Center from 1933 through June of 1972, demonstrates increasing survival and a distinct change in the frequency of underlying congenital heart disease and rheumatic heart disease (RHD). Certain forms of congenital heart disease such as tetralogy of Fallot, small ventricular septal defect, and aortic stenosis are at particular risk for BE. Following BE, patients with ventricular septal defect and tetralogy of Fallot have less morbidity and higher survival rates than children with aortic outflow lesions. over the entire time period, alpha Streptococcus is the most common pathogen and Staphylococcus aureus, second most frequent organism. Surgical correction in patients with congenital heart disease may offer the best form of prevention.

Adolescent↗
PubMed1975

Fitting Richards' Curve to data of diverse origins.

Published techniques for fitting data to nonlinear growth curves are briefly reviewed; most techniques require knowledge of the shape of the curve. A flexible growth curve developed by Richards (1959) is discussed as an alternative when the shape is unknown. The shape of this curve is governed by a specific parameter, which can be estimated from the data. We describe in detail the fitting of a diverse set of longitudinal and cross-sectional data to Richards' growth curve for the purpose of determining the age of red fox (Vulpes vulpes) pups on the basis of right hind foot length. The fitted curve is found suitable for pups less than approximately 80 days old. The curve is extrapolated to pre-natal growth and shown to be appropriate only for about 10 days prior to birth.

Age Factors↗
PubMedDate not supplied

Bilateral suppurative thrombophlebitis due to Staphylococcus aureus.

Suppurative thrombophlebitis is an infection of the wall of a superficial vein, usually is associated with intravenous catheter placement, and accounts for about 10% of all nosocomial infections. Suppurative thrombophlebitis occurs most commonly in patients with burns, patients with cancer, and persons receiving steroids. Skin flora organisms (e.g., Staphylococcus aureus and to a lesser extent Enterobacteriaceae) are the most common pathogens. Suppurative thrombophlebitis should be suspected when a patient having phlebitis presents with a temperature of 102 degrees F or higher. The diagnosis of suppurative thrombophlebitis is usually straightforward and made by demonstration of pus coming from the wound of the removed intravenous device or by aspiration of pus percutaneously from the involved vein. Treatment of superficial suppurative thrombophlebitis consists of venotomy of the affected vessel and systemic antimicrobial therapy. We present a case of S. aureus bilateral suppurative thrombophlebitis, which is most unusual.

Arm↗
PubMedDate not supplied

Information-theoretic analysis of neural coding.

We describe an approach to analyzing single- and multiunit (ensemble) discharge patterns based on information-theoretic distance measures and on empirical theories derived from work in universal signal processing. In this approach, we quantify the difference between response patterns, whether time-varying or not, using information-theoretic distance measures. We apply these techniques to single- and multiple-unit processing of sound amplitude and sound location. These examples illustrate that neurons can simultaneously represent at least two kinds of information with different levels of fidelity. The fidelity can persist through a transient and a subsequent steady-state response, indicating that it is possible for an evolving neural code to represent information with constant fidelity.

Information Theory↗