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Biomedical subjects

S Redman

Publications and source records attributed to S Redman.

At least 109 records · Page 6Linked to original sources
PubMed1985

Temporal proximity and reinforcement sensitivity in multiple schedules.

Distributions of reinforcers between two components of multiple variable-interval schedules were varied over a number of conditions. Sensitivity to reinforcement, measured by the exponent of the power function relating ratios of responses in the two components to ratios of reinforcers obtained in the components, did not differ between conditions with 15-s or 60-s component durations. The failure to demonstrate the "short-component effect," where sensitivity is high for short components, was consistent with reanalysis of previous data. With 60-s components, sensitivity to reinforcement decreased systematically with time since component alternation, and was higher in the first 15-s subinterval of the 60-s component than for the component whose total duration was 15 s. Varying component duration and sampling behavior at different times since component transition may not be equivalent ways of examining the effects of average temporal distance between components.

Journal Article↗
PubMed1984

Cardiovascular responses during cuff inflation in subjects who have been sensitised to the measurement of their blood pressure.

Changes in arterial pulse transit time, interbeat interval and the interval between the ECG signal and the arrival of the ensuing pulse at a peripheral site were recorded in response to the attachment and inflation of the cuff during blood pressure measurement. Two groups of subjects were used: a control group and a blood-pressure sensitised group. Blood-pressure sensitised individuals were defined as those who reported themselves to have been diagnosed as hypertensive by a physician, since it was hypothesised that learned or emotional responses to blood-pressure measurement would be greater in this group. No cardiovascular response to the blood-pressure measurement procedure was observed in the control group, but the blood-pressure sensitised group showed an increase in interbeat and a decrease in pulse transit time during cuff inflation. Decreases in pulse transit time are thought to reflect increases in diastolic blood pressure and arterial rigidity.

Blood Pressure↗
PubMed1984

Theory and operation of a single microelectrode voltage clamp.

The theory of operation of a discontinuous single-electrode voltage clamp using an ideal microelectrode (infinite response speed) and fixed (current-passing) duty cycle has been previously described. In this paper, the theory is extended by considering a microelectrode which has a finite response speed, by allowing the duty cycle to be variable, and by considering the clamp noise. Formulate are derived for the relationships between the step response, the steady-state error, the steady-state ripple, and the stability, in terms of the cycling frequency, the duty cycle, the open loop gain, and the electrical resistance and capacitance of the microelectrode and the cell membrane. In addition, the amplification of the microelectrode noise by aliasing is analysed, the error due to incomplete decay of the microelectrode voltage is described, and the accuracy of averaging the peak current measurement is established. To achieve the fastest dynamic response and the smallest steady-state error, the cycling period should be made as small as possible, and the open-loop gain should be as large as possible, consistent with stability. Incomplete decay of the microelectrode voltage destabilizes the clamp, and can introduce a significant clamp error. The choice of duty cycle is a compromise between reducing the noise and the step response time while avoiding design problems in the current output circuit. The output noise is amplified by aliasing. It can be minimized for a given output filter cutoff frequency by keeping the cycling frequency as high as possible, and by the use of an anti-aliasing filter whose cutoff frequency must be set for each microelectrode.

Animals↗
PubMed1983

Psychological stress and arterial pulse transit time.

Progress in isolating the psychological factors contributing to the development of arterial hypertension has been retarded by the absence of suitable, non-invasive and continuous measures of significant aspects of cardiovascular activity. Pulse transit time may help to resolve this problem since it reflects changes in arterial elasticity and diastolic blood pressure. A method of recording pulse transit time is described. Significant decreases in pulse transit time were observed in response to a cold pressor test, a video game, a reaction-time task and problem solving, regardless of site of measurement or method of pulse transduction.

Adolescent↗
PubMed1983

A shielded microelectrode suitable for single-electrode voltage clamping of neurones in the CNS.

The fabrication of a shielded microelectrode is described which has a time constant of about 3 microseconds, regardless of its depth in neural tissue. The shield is insulated from surrounding tissue with an insulation resistance which exceeds 1000 M omega, and the insulation will withstand +/- 15 V. Because of its narrow profile, the electrode is suitable for in vivo intracellular recordings from motoneurones and other large neurones of the CNS. The small time constant and the high breakdown resistance of the electrode make it suitable for use with single-electrode voltage clamp circuitry to voltage clamp motoneurone somata using switching rates in excess of 30 kHz.

Animals↗
PubMed1983

The time course of synaptic potentials evoked in cat spinal motoneurones at identified group Ia synapses.

Excitatory post-synaptic potentials (e.p.s.p.s) were evoked in motoneurones by impulses in single group Ia axons. After recording the e.p.s.p., the motoneurone and the group Ia axon were injected with horseradish peroxidase. The morphological details of the connexion formed by each group Ia axon with a motoneurone were subsequently reconstructed. Four Ia axon-motoneurone pairs were obtained. The electrotonic distance from the soma to each synaptic bouton in the connexion was calculated. The electrotonic lengths of those dendrites on which synaptic connexions were found were also calculated. The shape indices of each recorded e.p.s.p. and the standard cable model of the motoneurone were used to calculate the electrotonic distance from the soma to the point on the equivalent dendritic cable at which the e.p.s.p. originated. This distance was compared with the distance obtained from the reconstruction of the synaptic connexion at which the e.p.s.p. was generated. For two of the four connexions, the locations calculated by both methods agreed to within 0.1 lambda. Similar agreement could only be obtained for the other two connexions if synaptic transmission did not occur at some of the boutons in the termination. Evidence that some boutons were not involved in transmission is presented in the following paper (Redman & Walmsley, 1983).

Animals↗
PubMed1983

Amplitude fluctuations in synaptic potentials evoked in cat spinal motoneurones at identified group Ia synapses.

Excitatory post-synaptic potentials (e.p.s.p.s) were evoked in spinal motoneurones (of anaesthetized cats) by impulses in single group Ia axons. The morphological details of the Ia axon-motoneurone connexion involved in generating each e.p.s.p. were subsequently reconstructed, as described by Redman & Walmsley (1983). The fluctuation pattern of the peak amplitude of each e.p.s.p. was determined using a deconvolution method, taking into account the recording noise. Four e.p.s.p.s were analysed. One did not fluctuate in amplitude; the others fluctuated between discrete amplitudes which were separated by quantal increments. The number of increments which must be added to produce the largest peak amplitude of each e.p.s.p. was always less than, or equal to, the number of synaptic boutons in the connexion at which the e.p.s.p. was generated. The results are consistent with the hypothesis that transmission occurs in an all-or-none manner at each synaptic bouton. Different boutons in the termination of a Ia axon with a motoneurone have different probabilities of releasing transmitter, and this probability is sometimes zero at low stimulation rates. The results support the idea that the discrete amplitudes of an evoked e.p.s.p. result from intermittent transmission, in an all-or-none manner, at some or all of the boutons in the termination.

Animals↗
PubMed1983

Free-operant forgetting: Delayed stimulus control of multiple-schedule performance.

Pigeons' responses were reinforced in two components of several multiple variable-interval variable-interval schedules of food reinforcement. In one component, the key was illuminated green for 15 seconds and white for 45 seconds. In the other component, the key was illuminated red for 15 seconds and white for 45 seconds. Values for the exponent of the power functions relating response ratios to reinforcement ratios were higher in the presence of the discriminative stimuli (green or red) than in the presence of white. Sensitivity of response ratios to changes in reinforcement ratios provided an index of the extent to which responding was under delayed stimulus control by prior discriminative stimuli.

Journal Article↗
PubMed1980

The recovery of a random variable from a noisy record with application to the study of fluctuations in synaptic potentials.

Analysis of fluctuations in the amplitude of evoked synaptic potentials can be severely handicapped by the presence of spontaneous synaptic potentials and recording noise. A numerical procedure has been described whereby it is possible to remove some of the masking effects of this noise from the underlying distribution of the fluctuating synaptic potentials. it is not necessary to make an initial assumption about the type of distribution which will best describe the fluctuations. To use this technique, it is necessary to measure the histograms which approximate the probability densities of both the noise, and the noisy evoked potential. It is also necessary to assume that the statistical mechanisms generating the noise are independent of those mechanisms which cause the fluctuation in synaptic transmission, and that the noise and the evoked potentials add linearly. The statistical reliability of the technique depends upon the amount of noise present, and the sample size. Problems of resolution which arise from finite sampling and high noise levels are discussed.

Afferent Pathways↗
PubMedDate not supplied

Two sequential randomized trials of community participation to recruit women for mammographic screening.

BACKGROUND: If mammographic screening is to reduce mortality from breast cancer, it is essential that a high proportion of the target population attend for screening. In order to achieve this, effective recruitment strategies are needed. This paper reports two trials of recruitment strategies for mammographic screening involving eight communities in rural New South Wales (NSW), Australia. METHODS: Each trial involved two matched pairs of towns in the Hunter Valley region of NSW. Towns were randomly allocated to intervention, receiving either mass media promotion or community participation in Trial 1 and community participation or family physician involvement in Trial 2. RESULTS: In Trial 1, significantly higher attendance rates were observed in the two towns that received the community participation intervention compared with their matched media promotion towns (63% vs 34%, P < 0.001 and 51% vs 34%, P < 0.01). In Trial 2, a significantly higher attendance rate was observed in one town that received the family physician involvement intervention compared with its matched town which received the community participation intervention (68% vs 51%, P < 0.01). There was no significant difference in attendance in the other pair of towns (68% vs 58%, P = 0.11). CONCLUSIONS: Both community participation and family practitioner involvement are more promising strategies for the promotion of attendance at mammographic screening facilities than media promotion alone.

Adult↗
PubMedDate not supplied

Disordered eating and unhealthy weight reduction practices among adolescent females.

BACKGROUND: Dissatisfaction with body weight and the use of unhealthy weight reduction practices have been reported among adolescent females. There is a need for methodologically rigorous studies using large representative samples of adolescent females to accurately assess the prevalence of these behaviors and attitudes. METHODS: Eight hundred sixty-nine Australian school girls ages 14-16 years were administered a self-report questionnaire to determine the prevalence of disordered eating behaviors, unhealthy dieting practices, and distorted body image. Anthropometric (height and weight) data were collected on each of these adolescent females. RESULTS: The prevalences of disordered eating, unhealthy dieting, and distorted body image were 33, 57, and 12%, respectively. Over one-third (36%) of the total sample had used at least one "extreme" dieting method in the past month, i.e., "crash" dieting, fasting, slimming tablets, diuretics, laxatives, and/or cigarettes to lose weight. Of the total sample, 77% wanted to lose weight and 51% had tried to lose weight in the past month. Motivating factors for disordered eating and unhealthy dieting behaviors were peer pressure, media pressure, and the perception that extreme dieting strategies were harmless. CONCLUSION: The prevalence of disordered eating and dieting behaviors among adolescent females shown by this study suggests the need for preventive programs encouraging appropriate eating and dieting behaviors.

Adolescent↗
PubMedDate not supplied

The accuracy of self-report of smoking status in pregnant women.

Little is known about the accuracy of usual-care providers' detection of pregnant smokers. This study explored the proportion of pregnant women misclassified as nonsmokers by midwives in a public antenatal clinic. A sample of 204 women whom midwives classified as nonsmokers were asked to complete a self-administered questionnaire and to provide a urine specimen for cotinine analysis. Results indicate that midwives failed to detect a significant proportion of smokers. The conservative estimate of the proportion of midwife-identified nonsmokers who could be reclassified as smokers on the basis of the questionnaire and urinalysis procedures was 7.4% (95% CI 3.8-10.9%), the medium estimate was 8.8% (95% CI 4.9-12.7%) and the worst-case estimate was 15.2% (95% CI 10.3-20.1%). To increase the coverage achieved by smoking-cessation programs, antenatal clinics should consider incorporating biochemical measurements into routine screening procedures. Future studies examining smoking status in pregnancy should detail the methods used to classify subjects and document response rates in relation to each self-report and biochemical measurement.

Confidence Intervals↗
PubMedDate not supplied

The hippocampus, long-term potentiation and memory.

1. The induction of long-term potentiation (LTP) at excitatory synapses on CA1 pyramidal neurons occurs partly through an increase in the quantal AMPA current. It is also accompanied by an increase in the number of active sites. Any presynaptic modification, requiring the presence of a retrograde messenger, remains uncertain. 2. There are no definitive data that establish a causal link between LTP and the formation of memories. Pharmacological blockage of NMDA and mGLU receptors and genetic mutants with proteins deleted that are thought to be involved in LTP induction or maintenance or in the formation of memories have all linked deficits in LTP with impairments to behavioural learning, but these links are not necessarily causal. The development of tissue- and time-specific lesion of gene expression for multiple gene products may overcome the present limitations of gene deletion experiments and provide more revealing insights into the relationship between LTP and memory.

Animals↗
PubMedDate not supplied

Patient-provider interactions and patient outcomes.

Research shows that a number of provider interactional skills are empirically related to patient adherence, making interaction skills a necessary and important part of clinical competence. These skills fall into three broad categories: techniques to elicit and modify patients' health and treatment beliefs, to aid recall of information, and to aid adherence. Specific skills in each category are discussed. Research further shows that health care providers can be taught effective communication skills, and that one of the most effective teaching techniques is audio or video feedback in which the provider's interaction with a patient is judged by tutor and peers using explicit, empirically based criteria.

Attitude to Health↗
PubMedDate not supplied

The relative effectiveness of educational and behavioral instruction programs for patients with NIDDM: a randomized trial.

In this randomized trial patients with non-insulin-dependent diabetes were allocated to one of four programs: a minimal instruction program (n = 59), and education program of individual visits (n = 57), an education program incorporating a group education course (n = 66), and a behavioral program (n = 59). Individual and group education programs had higher attrition rates than the behavioral and minimal programs. The four programs, which involved different amounts of patient contact time, delivery format, and instructional strategies, all produced reductions in HbA1 and BMI, with no significant differences between the programs. There were no differences between groups over three time periods in total cholesterol, HDL cholesterol, systolic blood pressure, or proportion of patients consulting an ophthalmologist. The behavioral program produced a greater reduction in diastolic blood pressure over 12 months than the education programs and a greater reduction in the cholesterol risk ratio over 3 months than the other programs. The behavioral program patients were more likely to have visited a podiatrist after 6 months and reported higher satisfaction.

Adolescent↗