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Biomedical subjects

A Murray

Publications and source records attributed to A Murray.

At least 325 records · Page 18Linked to original sources
PubMed1988

The pulsed dye laser and atherosclerotic vascular disease.

The use of a pulsed dye laser to ablate atheromatous tissue obtained from post-mortem human aortic specimens is reported. Laser energy was delivered with a 600 micron quartz fibre, at a wavelength of 504 nm and a pulse length of 1 microseconds. Pulse energy was varied from 30-140 mJ, producing peak pulse powers of the order of 100 kW. With these parameters the laser ablated fatty, fibrous and calcified plaques. At this wavelength atheroma is vaporized but there is minimal damage to normal vessel wall, due to preferential absorption of the laser light. Light microscopy shows that by microsecond pulsing, thermal damage to surrounding tissues associated with continuous wave lasers is avoided. Transmission electron micrographs reveal a sharp demarcation between a laser crater and the adjacent vessel wall with little ultrastructural disruption. Scanning electron micrographs show the crater walls to be smooth. The pulsed dye laser may therefore be effective in the treatment of occlusive peripheral vascular disease without undue risk of vessel perforation.

Arteriosclerosis↗
PubMed1988

Comparison of the in vitro transforming activities of human papillomavirus types.

The association of certain human papillomavirus (HPV) types with the majority of human cervical carcinomas suggests a role for the virus in the development of this type of cancer. In this paper, we have examined the transforming properties of several HPV types where the early region genes of the virus are under the control of a strong heterologous promoter and show that major differences exist between the HPV types in their ability to transform primary rat kidney epithelial cells in conjunction with an activated ras oncogene. Those HPV types most commonly found in carcinomas--types 16, 18, 31 and 33--are capable of co-operating with ras to transform primary cells, but those types most commonly found in benign lesions--types 6 and 11--are not. We further demonstrate that the E7 gene of HPV16 by itself is sufficient to co-operate with activated ras to produce transformed cells which are tumorigenic in immunocompetent animals.

Adenocarcinoma↗
PubMed1988

Minimum energy for cardiac pacing.

Conditions for minimum energy pacing of the heart have been investigated. A total of 99 patients undergoing permanent cardiac pacing with one of three different leads were studied. Measurements of threshold voltage and current flow were made at 0.25, 0.5, 0.75, and 1.0 ms pulse durations. All measurements were made directly from the lead at implantation. There were no significant differences in threshold energy between the three leads used, and therefore all 99 leads were pooled for further analysis. There were significant differences (P less than 0.05) between the pacing energies required at the four pulse durations; the mean threshold energy at 0.25 ms was 156 nJ, at 0.5 ms 115 nJ, at 0.75 ms 110 nJ, and at 1.0 ms 102 nJ. Significant energy savings may be achieved when programming pacemakers to the optimum output for each patient by reducing pacemaker voltage - current output in preference to reducing pacing pulse duration.

Aged↗
PubMed1988

Repeatability of peripheral pulse measurements on ears, fingers and toes using photoelectric plethysmography.

Peripheral pulses have been recorded and analysed to determine the accuracy with which pulse transit times (PTTs) can be measured. Measurements of PTT between the ECG Q-wave and various peripheral sites were made in 10 normal subjects on 10 separate days. Mean values were determined for the ears (174 ms), fingers (245 ms), and toes (361 ms). The technique was sufficiently accurate to detect small changes in PTT due to changes in posture; sitting to lying, 5.2 ms. When comparing simultaneous measurements on bilateral sites only small differences in PTT were discovered, and these were not significant in the study group as a whole. However, these differences were significant in some individuals. When the subjects raised a single arm or leg, significant differences (38 ms and 49 ms respectively) were recorded between sides. The day-to-day repeatability sigma (expressed as the square root of the within-subject mean square variance) of individual PTT measurements on a subject (supine) was for ears, fingers and toes respectively 9.4, 9.2 and 12 ms. For right-left differences the repeatability was 7.2, 5.9 and 14 ms. Hence changes in PTTs, or differences between right and left sides, can be detected from single measurements with 95% confidence if they exceed approximately 20 ms in ears or fingers and 30 ms in toes.

Adult↗
PubMed1988

Reproducibility of cardiac output measurement by cross sectional and Doppler echocardiography.

The variability of Doppler echocardiographic estimation of cardiac output at the aortic orifice was investigated in eight healthy subjects. Cross sectional echocardiograms of the aortic orifice and aortic Doppler velocities were recorded and measured by four echocardiographers. Between subject variability was significantly larger than within subject variability for all variables. Variability owing to different echocardiographers and different measurement times was small compared with total variability. Coefficients of variation for aortic annular diameter, aortic velocity integral, and heart rate were 4.1%, 6.4%, and 5.0% respectively. The coefficient of variation for cardiac output was 8.8% and the 95% confidence interval for measurement of cardiac output by the Doppler method was 4.45 to 6.35 l/min. One echocardiographer reanalysed all the recordings and the results showed that recording the echocardiograms introduces a significantly larger source of error than measuring them. Thus serial measurements of cardiac output by the Doppler method can be performed with acceptable reproducibility; this indicates that the technique can be accurately applied in clinical practice.

Adult↗
PubMed1988

Sequence of epicardial repolarisation and configuration of the T wave.

Epicardial activation and repolarisation sequences were investigated in patients with upright or inverted T waves in left ventricular leads of the surface electrocardiogram. Fifteen patients were studied: 10 were undergoing coronary artery bypass grafting (upright T waves) and five aortic valve replacement (four patients with T inversion). Monophasic action potentials were recorded intraoperatively from eight to 10 left ventricular sites in each patient. In patients with upright T waves there was an inverse relation between the duration of the monophasic action potential and the activation time (mean slope -1.44). As a consequence, activation and repolarisation proceeded in opposite directions. Dispersion of repolarisation time (14 ms) was less than dispersion of activation time (23 ms). In patients with T wave inversion caused by aortic stenosis there was no relation between the duration of action potential and activation time; the repolarisation sequence resembled the activation sequence, and the dispersion of repolarisation time was greater than the dispersion of activation time (31 and 26 ms respectively). These results show that there are epicardial repolarisation gradients in man and that these are related to the configuration of the T wave. In patients with upright T waves an inverse relation between the duration of the action potential and the activation time reduces the dispersion of the repolarisation time. When the T wave was inverted this relation was no longer found and the dispersion of repolarisation increased.

Action Potentials↗
PubMed1987

Human papillomavirus type 16 DNA cooperates with activated ras in transforming primary cells.

The close association of human papillomavirus type 16 DNA with a majority of cervical carcinomas implies some role for the virus in this type of cancer. To define the transforming properties of HPV-16 DNA in vitro we have now performed transfection experiments on baby rat kidney cells using HPV-16 DNA in conjunction with an activated ras gene. We have demonstrated that a 6.6-kb DNA fragment, containing the early genes of HPV-16 under the control of Moloney murine leukaemia virus long terminal repeats (MoMuLV-LTRs), cooperates with EJ-ras in transforming these cells. Both DNAs are required and neither alone is effective. The cooperating activity appears to reside in a protein or proteins derived from the E6/E7 region of the HPV-16 genome.

Animals↗
PubMed1987

Respiratory effects of quazepam and pentobarbital.

Quazepam is a new benzodiazepine that may provide good hypnotic action with negligible effect on motor coordination or respiration. Sleep laboratory studies on human volunteers have shown quazepam 15 mg to be an effective hypnotic dose, with the 30-mg dose being optimal. At these doses, there was no deterioration of motor performance, and the drug, when given nightly for two weeks, continued to exert hypnotic effects without serious adverse effects. Therefore, this study was designed to compare the respiratory effects of quazepam 15 and 30 mg to those of pentobarbital 50 and 150 mg and to placebo. Five adult male volunteers received each dose at separate times. A double-blind technique was employed for controlled rebreathing studies, to a ventilation of 40 L/min or a PETCO2 of 8%. Respiratory curves were compared with controls. The mean displacement curve at the 20-liter intercept showed a depressant effect for pentobarbital 150 mg at two hours and a stimulant effect for quazepam 15 mg at two hours but a slight depression effect for quazepam 30 mg at three hours compared with placebo. The slope of the respiratory curve was not affected.

Anti-Anxiety Agents↗
PubMed1987

Clinical comparison of one in vitro and three in-line blood gas PO2 sensors during cardiopulmonary bypass.

During 17 cardiopulmonary bypass (CPB) operations, arterial PO2 measurements were taken at 5 min intervals using four different types of PO2 sensor; three in-line (CardioMet-1000, Polytrode, and Gas-Stat) and one blood gas analyser (IL-1302). Comparisons between sensors were made relative to the CardioMet-1000. The three in-line sensors showed close agreement. The mean and standard deviation of the difference between the Gas-Stat and the CardioMet-1000 was 0.7 +/- 4.7 kPa, and between the Polytrode and the CardioMet-1000 was -1.4 +/- 4.0 kPa. Agreement between the IL-1302 blood gas analyser and CardioMet-1000 was not as good, the difference being -7.0 +/- 8.6 kPa.

Blood Chemical Analysis↗
PubMed1987

Epicardial repolarization mapping in man.

A simple method was developed for recording epicardial monophasic action potentials intraoperatively in man. Potentials were recorded rapidly and reliably from multiple epicardial sites using a hand-held probe. The feasibility of repolarization mapping was assessed in 30 patients. It was possible to record technically adequate signals from most left ventricular and posterior right ventricular sites (success rates 72% and 61%, respectively), but it was more difficult to achieve satisfactory recordings over the free wall of the right ventricle (success rate 36%). The onset of cardiopulmonary bypass resulted in a transient rise in action potential duration of approximately 30-40 ms in the first minutes of bypass. An approximate steady state was achieved thereafter. Reproducibility of the method was assessed by mapping a small number of sites repeatedly. The 95% confidence limits for an estimate of repolarization time, based on a single potential, were +/- 21 ms. With 4 probe applications at each site, the confidence limits of the estimated site mean were reduced to +/- 8 ms. Based on this approach, statistically significant differences between sites were demonstrated in 9 of 10 patients, confirming that the method is sensitive enough to provide information on regional differences in repolarization. Intraoperative epicardial repolarization mapping has been shown to be a practical possibility. The technique holds promise as a means of assessing the role of dispersion of repolarization in arrhythmogenesis in man.

Action Potentials↗
PubMed1987

Identification of human papillomavirus type 18 E6 polypeptide in cells derived from human cervical carcinomas.

We recently reported the expression of human papillomavirus type 18 (HPV-18) E6 protein in bacteria and the production of anti-E6 polyclonal antibodies. This work has now been extended with the production of a panel of monoclonal antibodies against the HPV-18 E6 protein. These antibodies demonstrate that there is little antigenic conservation in the E6 protein between HPV-16 and HPV-18, with only one antibody recognizing a cross-reactive epitope. We have used both the monoclonal and the polyclonal antibodies to look for E6 expression in a number of HPV DNA-containing cell lines. These reagents specifically detected a 16.5K mol. wt. polypeptide in cells derived from a human cervical carcinoma.

Antibodies, Monoclonal↗
PubMed1987

The accuracy and limitations of ultrasound in the assessment of venous extension in renal carcinoma.

Ultrasound was used to assess venous extension in 28 patients with renal carcinoma, with particular reference to involvement of the inferior vena cava. The findings were correlated with surgical findings in all except two patients who had gross caval involvement and metastatic disease and in whom surgery was considered inappropriate. In 10 of the 28 patients (36%), a diagnostic ultrasound examination of the cava from the renal veins to the diaphragm was obtained. In four of these, ultrasound showed tumour involvement of the vena cava. In 12 cases (43%) only the intrahepatic part of the cava was seen, but the examination nonetheless excluded tumour involvement of the upper cava. Visualisation of the vena cava was impossible in six cases (21%), usually because of bowel gas or obesity; CT scanning provided valuable additional information in two of these cases. Inferior vena cavography confirmed the findings of the less invasive imaging procedures in 10 patients and was falsely positive once. Cavography is now seldom necessary in the assessment of renal carcinoma.

Aged↗
PubMed1987

Potassium: its relevance for arrhythmias complicating acute myocardial infarction.

Potassium plays a critical role in cellular electrophysiology. Clinically, serious cardiac rhythm disturbances are a well-recognised complication of profound hypokalaemia. Recent research has focussed on the possibility that serious ventricular arrhythmias, particularly ventricular fibrillation, might be caused by the hypokalaemia that occurs in the acute phase of myocardial infarction. Proof of this association would be a strong impetus to develop interventions that might stabilise potassium values in an attempt to produce an antiarrhythmic effect.

Arrhythmias, Cardiac↗