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Biomedical subjects

H Burgess

Publications and source records attributed to H Burgess.

6 recordsLinked to original sources
PubMed2006

Monitoring interfacial bioelectrochemistry using a FRET switch.

Generation of functionally active biomolecular monolayers is important in both analytical science and biophysical analyses. Our ability to monitor the redox-active state of immobilized proteins or enzymes at a molecular level, from which stochastic and surface-induced variations would be apparent, is impeded by comparatively slow electron-transfer kinetics and associated signal:noise difficulties. We demonstrate herein that by covalently tethering an appropriate dye to the copper protein azurin a highly oxidation-state-sensitive FRET process can be established which enables redox switching to be optically monitored at protein levels down to the zeptomolar limit. The surface-potential-induced cycling of emission enables the redox potential of clusters of a few hundred molecules to be determined.

Azurin↗
PubMed2001

A week of simulated night work delays salivary melatonin onset.

In most studies, the magnitude and rate of adaptation to various night work schedules is assessed using core body temperature as the marker of circadian phase. The aim of the current study was to assess adaptation to a simulated night work schedule using salivary dim light melatonin onset (DLMO) as an alternative circadian phase marker. It was hypothesised that the night work schedule would result in a phase delay, manifest in relatively later DLMO, but that this delay would be somewhat inhibited by exposure to natural light. Participants worked seven consecutive simulated 8-hour night shifts (23:00-07:00 h). By night 7, there was a mean cumulative phase delay of 5.5 hours, equivalent to an average delay of 0.8 hours per day. This indicates that partial circadian adaptation occurred in response to the simulated night work schedule. The radioimmunoassay used in the current study provides a sensitive assessment of melatonin concentration in saliva that can be used to determine DLMO, and thus provides an alternative phase marker to core body temperature, at least in laboratory studies.

Adaptation, Physiological↗
PubMed2001

The effects of bright light and nighttime melatonin administration on cardiac activity.

Although melatonin has an important physiological role in the facilitation of sleep, its precise mechanism of action is not clear. To investigate the potential contribution of melatonin to influence cardiac autonomic activity in the evening, 16 young healthy subjects participated in a repeated measures design where cardiac autonomic activity, heart rate and blood pressure were examined during three experimental conditions. An initial baseline condition involved dim light exposure (< 10 lux), permitting the normal nocturnal rise in endogenous melatonin. In other sessions, subjects were exposed to bright light (> 3000 lux) to suppress melatonin secretion and administered a placebo or melatonin (5 mg) capsule at the estimated time of increase in endogenous melatonin (wake time + 14 hours). Heart rate, pre-ejection period (a measure of cardiac sympathetic activity) and respiratory sinus arrhythmia (a measure of parasympathetic activity) were not significantly altered in response to the three melatonin levels. While melatonin had no effect on diastolic blood pressure, systolic blood pressure was maximally decreased by 6 +/- 1.93 mmHg (mean +/- SEM, p < 0.005) 150 minutes after exogenous melatonin. The results indicate that melatonin does not directly modulate cardiac autonomic activity, but may rather act directly on the cardiovascular system.

Adolescent↗
PubMed1972

A note on some reinforcing properties of university lectures.

Contingency management systems in university courses have sometimes assigned the role of reinforcing stimulus to lectures and demonstrations. Attending a lecture was made contingent upon having previously finished certain course assignments. The present paper investigated some variables that control student attendance at lectures. Attendance remained high throughout each course at those class meetings where quizzes contributing to course grades were given or where impending quizzes were discussed. Attendance at lectures over the reading assignments or over material unrelated to course quizzes rapidly declined. When students were given course credit for attending these lectures, or when the lectures included information for future quizzes, attendance increased. When attending these lectures was made contingent upon having completed certain assignments the prior week, no increase in assignment completion was noted and the attendance at the lectures decreased even further. All lectures were given during one class meeting each week. Attendance at the other class meetings during the week remained stable.

Journal Article↗