Urinary 5-hydroxyindole acetate concentration in pregnancy induced hypertension.
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Female↗
Biomedical subjects
P Maynard
Publications and source records attributed to P Maynard.
Biosensors.
This review introduces biosensors as analytical devices that respond selectively to analytes in appropriate samples and convert their concentrations into electrical signals via a combination of a biological recognition system and a suitable transducer. The last decade has seen dramatic advances in the design of sensor configurations, the marriage of biological systems with modern monolithic silicon and optical technologies, the development of effective electron-exchange systems and the introduction of direct immunosensors.
Animals↗
Effect of age on behavioral responses and tissue levels of apomorphine in the rat.
Rats of several ages between 2 and 24 months were tested for stereotyped behavioral responses to R(-)apomorphine-HCl (APO), a potent and selective dopamine agonist. Between 2 and 24 months, the ED50 for apomorphine decreased 2.5-fold (0.14-0.06 mg/kg, i.p.), as assessed by a microcomputer-assisted technique. Not only were older rats more sensitive to apomorphine, but the duration of the behavioral effects increased with age and showed a greater change at doses which were greater than the ED50. When levels of apomorphine in brain were assayed by liquid chromatography and electrochemical detection, there was a progressive increase in peak levels of the agent in the tissue as well as a delay in its elimination from brain, with increasing age. Moreover, there was a highly significant correlation between increased behavioral effect and the level of apomorphine in brain with increasing age (r greater than 0.8). These results indicate that increased levels in brain or decreased elimination of apomorphine may be an important factor contributing to a marked increase in behavioral sensitivity to apomorphine with age in the rat.
Aging↗
Measurement of lung volume by multiple indicator dilution. Differences in apparent volumes of distribution of oxygen, nitrogen and argon.
A variant of a rebreathing/indicator-dilution technique was used to measure lung volume. Two or three indicators, which should have essentially the same pulmonary volume of distribution, were used. Gas compositions were measured by respiratory mass spectrometry and an extrapolation was used to allow for oxygen consumption. Carbon dioxide output, for which the extrapolation did not allow, caused considerable discrepancies between the apparent volumes of distribution of the three indicators: oxygen, nitrogen and argon. The discrepancies varied with the change in concentration imposed between the control and rebreathing periods. An iterative arithmetical correction is described, with its limitations. The approach offers a method of lung volume measurement which seems more applicable to anaesthesia than existing methods.
Argon↗
Measurement of lung volume by multiple indicator dilution. Testing a modelled hypothesis with on-line computation.
Respiratory mass spectrometry and on-line computation were used to estimate lung volume in normal subjects by a rebreathing technique, using oxygen, nitrogen and argon as indicators. The computation had previously been tested in a numerical model. In real normal lungs, it performed well enough for practical purposes, despite recognizable oversimplifications in the modelling assumptions. The differences in estimate to be expected from different composition changes between control and rebreathing were less than 100 ml, and those from different indicators within a composition change were less than 50 ml. The use of two indicators in lung volume measurement allows a correction for volume changes attributable to carbon dioxide and nitrous oxide, and a third indicator provides a degree of quality control.
Humans↗
Pulse polarography and intravascular oxygen electrodes.
The membranes covering standard polarographic in vivo PO2 electrodes were modified with a view to altering their response times. Their performance was examined under constant and pulsed polarization. Pulse polarization diminished the under-reading of the PO2 signal which occurred at low flow rates. The stability of the electrode signal was greatly improved by integrating the electrode current over the pulse period. The combination of thin membranes and pulsed polarography will provide a PO2 electrode with a fast time response without under-reading the true in vivo PO2.
Electrodes↗
Oestrogen receptors and prognosis in early breast cancer.
In a study of the role of oestrogen-receptor analysis in early breast cancer the oestrogen-receptor content of the tumour was estimated in 286 patients undergoing mastectomy. These patients were followed for up to 39 months, and the recurrence of disease was noted in relation to the presence or absence of oestrogen receptor.Recurrence-rates were significantly higher in patients whose tumours did not contain receptors than in those whose tumours did. This same relationship was seen when women with and without axillary metastases were considered separately. The highest rates of recurrence were in women with axillary lymph-node involvement whose tumours lacked oestrogen receptors. Women without axillary-node involvement whose tumours lacked oestrogen receptors showed the same high rate of recurrence as all women with axillary-node involvement. The oestrogen-receptor content of a primary breast cancer appears to be an independent guide to early recurrence of the disease.
Breast Neoplasms↗
Continuous measurement of blood gases in vivo by mass spectrometry.
Continuous analysis of oxygen and carbon dioxide tension in the blood phase, over periods of 4-5 h, was carried out in the pulmonary artery (93 determinations in six anesthetized dogs) and in the aorta (29 determinations in four anaesthetized dogs). Silastic-covered stainless steel catheters attached to a mass spectrometer were used. The mass spectrometer signals were linearly related to the blood-gas tensions measured by conventional analysis. The mass spectrometer signals were calibrated in vivo by exposing the animals to high and low oxygen and carbon dioxide tension. With such in vivo calibration the slopes of the straight line regressions for mass spectrometer PO2 or PCO2 on PO2 or PCO2 by conventional analysis were comprised between 0.944 and 1.031 while the standard error of the slopes were between 0.019 and 0.031. Deliberate reductions of cardiac output had little effect on the mass spectrometer readings.
Animals↗
The Bain system: gas flows in small subjects.
Rabbits weighing 2-4 kg were ventilated using a Bain type co-axial circuit. Acceptable blood-gas tensions were achieved with a tidal volume of 10 ml kg-1, a frequency of 40 b.p.m., and a fresh gas flow of 3 litre min-1. This technique may be applicable to neonatal anaesthesia.
Animals↗
A microelectronic conductimetric biosensor.
The fabrication and operation of a microelectronic conductimetric biosensor is described. The device monitors the change in solution conductance occasioned by the catalytic action of enzymes immobilised over a planar conductance cell comprising serpentined and interdigitated metal conductor tracks. The output of the instrument was linear over a 3 min period on addition of urea to a sample cell overlaid with immobilised urease. The responses to any given urea concentration were reproducible to within approximately +/- 1%. The device responds to urea present in serum samples.
Electrochemistry↗