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Biomedical subjects

D E Robinson

Publications and source records attributed to D E Robinson.

At least 19 recordsLinked to original sources
PubMed1992

A physiologically based pharmacokinetic model for nicotine and cotinine in man.

Physiologically based pharmacokinetic (PBPK) models have been developed describing the disposition kinetics of nicotine and its major metabolite, cotinine, in man. Separate 9-compartment, flow-limited PBPK models were initially created for nicotine and cotinine. The physiological basis for compartment designation and parameter selection has been provided; chemical-specific tissue-to-blood partition coefficients and elimination rates were derived from published human and animal data. The individual models were tested through simulations of published studies of nicotine and cotinine infusions in man using similar dosing protocols to those reported. Each model adequately predicted the time course of nicotine or cotinine concentrations in the blood and urine following the administration of nicotine or cotinine. These individual models were then linked through the liver compartments to form a nicotine-cotinine model capable of predicting the metabolic production and disposition of cotinine from administered nicotine. The potential for integrating this functional PBPK model with an appropriate pharmacodynamic model for the characterization of nicotine's physiological effects is discussed.

Cotinine↗
PubMed1992

Discriminability of bursts of reproducible noise.

The ability of human listeners to discriminate pairs of bursts of reproducible noise was examined. A same-different psychophysical method was used. Bursts in a pair were identical on same trials. On different trials, bursts were identical except for tau ms of independent noise located at either the beginning, middle, or end of the pairs of bursts. As the temporal position of the tau ms of independent noise was moved from the beginning to the end of the bursts of noise, discriminability increased. For each temporal position of the independent noise, discriminability was a function of the ratio of the duration of the independent noise (tau) to the total burst duration.

Adolescent↗
PubMed1992

The mental health review board: a new concept for difficult clients.

1. The Mental Health Review Board concept is a hospital systems approach to the difficult client. Board membership varies with each case and includes representation from all areas of the hospital. 2. The Review Board deals with clients who have exhausted the system, are threatening or abusive to staff, and noncompliant with treatment recommendations. 3. The Review Board contract is the "final offer" for treatment and is without input from the client. Terms of the contract are nonegotiable. Noncompliance results in discharge and referral elsewhere.

Adult↗
PubMed1991

Pulse-echo ultrasound speed measurements: progress and prospects.

The data on the relationship of sound speed to tissue condition, and the development of methods for measurement of sound speed in vivo, are outlined. The methods developed by the authors are discussed. These include methods which use the spatial shift in images of targets viewed from different directions, time-of-flight measurements along incrementally tracked beams and echo tracking during transaxial compression of tissue. The reported sound-speed values are discussed, discrepancies noted and suggestions made on the potential clinical applications of in vivo sound-speed estimation.

Humans↗
PubMed1991

Effects of vehicle supplementation on total estradiol absorption from a transdermal estradiol delivery system.

OBJECTIVE: To evaluate the effects of vehicle supplementation on serum estradiol (E2) delivery pharmacokinetics from the Ciba-Geigy (Summit, NJ) 0.1-mg Estraderm Patch. DESIGN: Postmenopausal women were randomized to a 28-day crossover treatment protocol separated by a 14-day wash out period. SETTING: Normal human volunteers were studied in an academic research environment. PATIENTS, PARTICIPANTS: The subject pool included eight healthy postmenopausal women between 32 and 60 years of age. INTERVENTIONS: In treatment A, a 0.1-mg Estraderm Patch was worn for 7 days; in treatment B, and identical patch was worn into which 0.6 mL of ethanol was injected on day 3 of use. MAIN OUTCOME MEASURES: Serum E2 levels were measured in both groups. RESULTS: Although E2 absorption showed characteristic interpatient variability, addition of ethanol significantly extended the mean time for serum E2 levels to return to baseline, without increasing peak absorption. The mean extension was 50 hours. CONCLUSION: The addition of ethanol to the Estraderm Patch increased the duration of elevated serum E2 levels measured in menopausal women, thus potentially increasing the effective life span of the transdermal therapeutic system.

Absorption↗
PubMed1990

Effects of acute administration of diazepam and d-amphetamine on aggressive and escape responding of normal male subjects.

Normal males participated in sessions providing two operant response options and were administered either diazepam (study I and II) or d-amphetamine (study II). The acute effects of diazepam on human aggressive responding, which ostensibly subtracted points from another person, were determined in study I. Study II was conducted to determine the extent to which social context and response consequence influenced diazepam (study I) and d-amphetamine (previous research) effects on aggressive responding. In study II, the other response option was escape responding which protected the subject's counter from point losses. Aggressive and escape responding were engendered by subtracting points from the subject's counter, and maintained by initiation of intervals free of point loss. Point subtractions were attributed to the other person (study I) or to a machine (study II). Responding to accumulate points exchangeable for money was available in both studies. Acute diazepam administration decreased aggressive responding in most subjects (study I), slightly increased escape responding (study II), and decreased responding to accumulate points. In study II, d-amphetamine increased both escape responding and responding to accumulate points. The effects of d-amphetamine and diazepam were altered by the instructed source of point loss.

Aggression↗
PubMed1989

A sonographic technique to reduce beam distortion by curved interfaces.

Ultrasonic beams are distorted during propagation between two media with different velocities if the traversed interface is curved within the ultrasonic beamwidth. The distorting effects of various interfaces on a beam generated by a multi-element transducer are analyzed and a technique to reduce these by controlling the time delays to the individual elements is presented.

Equipment Design↗
PubMed1989

Ultrasound in diagnosis--an Australian perspective.

The paper is a personal perspective of the development of diagnostic ultrasound in Australia, outlining some of the contributions from the Ultrasonics Institute. The present status of current technology and applications are briefly described, with some comments on the potential and directions for further development of ultrasonic techniques.

Australia↗
PubMed1988

Ultrasonic characterization of splenic tissue in myelofibrosis: further evidence for reversal of fibrosis with chemotherapy.

Fibrosis in patients with myelofibrosis (MF) is seen not only in the bone marrow but also around the metaplastic foci in the spleen and liver. Following our observation of reversal of bone marrow fibrosis in MF patients treated with chemotherapy, we undertook ultrasonic splenic tissue characterization studies using sound speed measurements to assess the effect of such therapy on the splenic fibrosis. Single studies in 19 patients showed overlapping ranges among the three sub-groups classified according to the grade of bone marrow fibrosis, but the mean values in these sub-groups showed a trend towards decreasing sound speed with increasing marrow fibrosis. Sequential studies in 9 of these patients showed increased splenic sound speed with decreasing marrow fibrosis in 8 patients following treatment, with a reversal of this pattern seen in 1 patient 1-2 years post-treatment. These results suggest simultaneous reversal of fibrosis in the bone marrow and the spleen in MF patients receiving effective chemotherapy.

Bone Marrow↗
PubMed1987

An approach to digital signal processing for ultrasonics research.

The increasingly sophisticated techniques for the extraction of information from ultrasonic data entail a corresponding increase in complexity of the software used. An interactive signal and image processing package, called TWODIMSY, has been developed at the Ultrasonics Institute to allow non-programmers an entry to digital signal processing, and to simplify the task of staff involved in programming. We present an outline of the design considerations which shaped TWODIMSY, and a brief history of its ancestors. A detailed description of the package is given, including the type of computational facilities provided and the approach taken to solve the problems of data storage, operator interface and documentation.

Humans↗
PubMed1987

Clinical sound speed measurement in liver and spleen in vivo.

The paper describes an implementation of clinical sound speed measurement using either a commercial water path scanner or a specially developed dual transducer real time scanner, each interfaced to a general purpose minicomputer for off-line analysis. It describes the examination technique to obtain suitable in vivo clinical data from the liver and the spleen. It develops signal processing methods to achieve clinical confidence in individual measurements. Forty-five liver patients and 46 spleen patients were examined. Sound speed was found to correlate closely with fibrosis content in both the liver and the spleen with an increase in fibrosis resulting in a decrease in sound speed. Sound speed in various pathological conditions are discussed. Clinical results of sequential examinations on patients under treatment are presented and successful monitoring of the disease status is demonstrated. The potential clinical role of sound speed measurement is suggested.

Acoustics↗
PubMed1987

Evaluation of ultrasonic attenuation in diffuse diseases of spleen and liver.

Ultrasonic attenuation has been measured using frequency domain signal processing in clinical trials of patients with liver and spleen diseases. By comparing the variance encountered in local measurements and in measurements at a number of adjoining sites, the need for averaging over large volumes of tissue to avoid the effects of large fluctuations is established. In spleens of patients with myelofibrosis, no correlation between fibrosis and attenuation was found. However it was found that variations in splenic volume were accompanied by inverse changes in attenuation, most likely due to blood pooling. A correlation was found between splenic blood flow per unit organ volume and attenuation. In cirrhotic livers, attenuation was significantly increased with fatty infiltration, but only slightly increased in livers containing minimal fat. These findings tend to reduce the probability of finding successful clinical applications for attenuation slope measurements.

Fatty Liver↗
PubMed1986

Effects of d-amphetamine on human aggressive behavior.

Male research subjects were administered placebo and three doses of d-amphetamine (5, 10 and 20 mg/70 kg) in a laboratory situation which provided both aggressive and non-aggressive response options. The non-aggressive response was button pressing maintained by presentation of points exchangeable for money at the end of the session. The aggressive response was button pressing on a separate manipulanda which ostensibly subtracted points from a fictitious partner. Aggressive responding was elicited by subtracting points from the research subjects which was attributed to the fictitious partner. d-Amphetamine increased both aggressive and non-aggressive responding, particularly at 5 and 10 mg/70 kg. At the highest dose (20 mg/70 kg), aggressive responding decreased to levels similar to those observed during placebo sessions, while monetary reinforced responding remained elevated.

Adolescent↗
PubMed1986

Quantitative sonography.

The review presents a perspective on ultrasonic techniques which place numerical values on properties of tissue or physiological function. Two distinct approaches to tissue characterisation are identified and the various techniques employed are reviewed. The range of Doppler techniques currently in use or under development are described. The potential roles of the various techniques are discussed, using clinical results from the Ultrasonics Institute as a basis. Attenuation measurements show a considerable spread in results, but sound speed appears to correlate closely with the degree of fibrosis in liver and spleen. Other methods have been found useful in specialised areas. The use of pulsed Doppler with a resolution cell sufficiently large to encompass the entire vessel, in conjunction with B-mode imaging to determine geometry, permits volumetric flow measurements to be made in deep vessels and reveals previously inaccessible physiological data. The use of analysis techniques to provide quantitative information in the physiological state or function of tissue promises to add a new dimension to diagnostic ultrasound.

Doppler Effect↗
PubMed1986

Models of auditory masking: a molecular psychophysical approach.

Gilkey et al. [J. Acoust. Soc. Am. 78, 1207-1219 (1985)] measured hit proportions and false alarm proportions for detecting a 500-Hz tone at each of four starting phase angles in each of 25 reproducible noise samples. In the present paper, their results are modeled by fitting the general form of the electrical analog model of Jeffress [J. Acoust. Soc. Am. 48, 480-488 (1967)] to the diotic data. The best-fitting configurations of this model do not correspond to energy detectors or to envelope detectors. A detector composed of a 50-Hz-wide single-tuned filter, followed by a half-wave rectifier and an integrator with an integration time of 100 to 200 ms fits the data of all four subjects relatively well. Linear combinations of the outputs of several detectors that differ in center frequency or integration window provide even better fits to the data. These linear combinations assign negative weights to some frequencies or to some time intervals, suggesting that a subject's decision is based on a comparison of information in different spectral or temporal portions of the stimulus.

Acoustic Stimulation↗
PubMed1985

Effects of masker waveform and signal-to-masker phase relation on diotic and dichotic masking by reproducible noise.

The proportions of hits and false alarms were estimated for the detection of a 500-Hz sinusoidal signal in each of 25, reproducible samples of wideband, white, Gaussian noise. The effects of signal phase were investigated under diotic (MoSo) and dichotic (MoS pi) conditions and compared to the predictions of two major models of binaural hearing. Averaging the data over samples obscured important across-sample and across-subject differences in performance. The proportions of hits and false alarms for individual noise samples presented under the MoSo condition were highly correlated with those for the same noise samples under the dichotic MoS pi condition, suggesting that the cues determining performance under these conditions are related. Signal-to-masker phase had a large effect on the proportion of hits under the MoSo condition, but only a small effect under the MoS pi condition. The Vector model predicts a large effect of signal phase under the MoS pi condition, and is, therefore, imcompatible with this aspect of the data. The expected value of the decision variable of the EC model is independent of signal phase. However, when the variance of the decision variable is also considered, the EC model does predict changes in the proportion of hits with the phase of the signal, comparable to those observed here. Further, it was shown that, if minor changes in the form of the EC model's decision variable or in the distribution of the internal noise parameters are assumed, the expected value of the decision variable also changes with the phase of the signal.

Acoustic Stimulation↗