Search PubMed⌕ Search

Biomedical subjects

J F Malone

Publications and source records attributed to J F Malone.

At least 37 records · Page 2Linked to original sources
PubMed1994

Sources of variance in ocular microtremor.

This study presents a preliminary investigation of the sources of variance in the measurement of ocular microtremor frequency in a normal population. When the results from both experienced and relatively inexperienced operators are pooled, factors that contribute significantly to the total variance include the measurement procedure (p < 0.001), day-to-day variations within subjects (p < 0.001), and inter-subject differences (p < 0.01). Operator experience plays a role in determining the measurement precision: the intra-subject coefficient of variation is about 5% for a very experienced operator, and about 14% for a relatively inexperienced operator.

Adult↗
PubMed1993

Observing the brachial artery through a pressure cuff.

A technique is described which enables ultrasonic imaging of the brachial artery whilst pressure is applied via a pressure cuff. This involves a new instrument--a sphygmomanometer, which uses water as opposed to air as the pressure medium, in order to permit ultrasonic imaging through the cuff. The technique was found to be acceptable in the clinical setting, and gave a measurement of the systolic blood pressure which correlated with the conventional cuff measurement in eleven elderly subjects (r = 0.89, p < 0.001). The technique should have an important role to play in studying the origin of differences which occur between direct and indirect blood pressure measurements.

Blood Pressure Determination↗
PubMed1993

Measurement of arterial closing pressure.

It has been suggested that certain artifacts in blood pressure measurement by auscultation stem from stiffness of the tissues underneath the pressure cuff, resulting in a component of cuff pressure being required to overcome resistance to brachial artery collapse. This paper describes a technique for measuring the pressure required to collapse a segment of the brachial artery which has been isolated from central arterial pressure. This measurement is termed the arterial closing pressure. In a study of eleven elderly subjects, the artery collapsed spontaneously (zero closing pressure) after being isolated from central pressure in seven subjects. The remaining four required external pressures ranging from 4.6 to 10.7 kPa (35 to 81 mmHg) in order to collapse the artery. Thus arterial closing pressure may frequently be a significant fraction of arterial blood pressure in the elderly population, and may contribute to error in the measurement of blood pressure by auscultation. Arterial closing pressure may be a useful tool for investigating the origin of differences between indirect and direct blood pressure measurements, and also in the investigation of spontaneous arterial closure.

Aged↗
PubMed1988

Evaluation of the processing functions of a digital subtraction angiography image processor.

A large number of imaging systems for digital subtraction angiography (DSA) are now commercially available. Numerous evaluations of the performance of these systems have been reported in the literature. However systematic evaluations of the processing functions of DSA image processors have not been widely reported. Such an evaluation for one commercial system is presented in this paper. Functions evaluated include linear transformation, logarithmic transformation, integration, subtraction and temporal filtration. The observations indicate that image processing results are frequently achieved by indirect routes which compromise the fidelity of the image data.

Angiography↗
PubMed1987

Experimental examination of videodensitometry of large opacifications in digital subtraction angiography.

With the recent introduction of digital radiography the possibility of extracting clinically useful quantitative indices of function has emerged. In digital subtraction angiography (DSA), videodensitometric analysis has been widely applied. An experimental investigation of the usefulness of logarithmically transformed pixel values in DSA images for quantitative densitometry is performed. Dependence on image uniformity, transmittance, scattered radiation and video offset voltages is examined. Results indicate independence of both uniformity and transmittance and dependence on both scattered radiation and offset voltages. The possible use of lead absorbers to derive corrections for contributions from scattered radiation and similar aberrations in each image used for subtraction is also examined. Observations indicate that such corrections can allow accurate videodensitometry.

Angiography↗
PubMed1984

Digital fluoroscopy with a conventional fluoroscopic room and a nuclear medicine computer system.

The potential of a commercially-available nuclear medicine computer, with a digital video interface, supplied by its manufacturers, for digital fluoroscopy is described. In the absence of universally accepted standards against which the performance of digital fluoroscopy systems may be judged, the parameters included in the description of this system included linearity, uniformity, signal-to-noise ratio, matrix size at given frame rates and study sizes. In addition some examples of clinical studies involving subtraction are presented.

Cerebral Angiography↗
PubMed1984

Maintenance of differentiated sheep thyroid cells in primary culture for three months.

A method is described which permits culture of primary thyroid cells without subculture for at least 100 days. Cultures are maintained without medium changes for the entire period, and concentrated glucose is added to replenish energy supplies at carefully defined intervals. The cells retain morphological and functional differentiation shown by light and electron microscopy, PAS positive histochemistry, iodine uptake and T4 production for at least 100 days. After this time fairly sudden death of the cultures occurs. Possible mechanisms for the effect are postulated. The technique should make it possible to study long-term effects of drugs/radiation on differentiated cultures without the need for continuous subculture.

Animals↗
PubMed1983

Kinetics of technetium 99m labelled macroaggregated albumin in humans.

The uptake and elimination of 99Tcm labelled MAA were followed by gamma camera and computer over a period of 36 hours in patients undergoing lung scanning and venography. Lungs, stomach, kidneys, GI tract, bladder and thyroid showed significant concentrations of activity at various times after the injection of radiopharmaceutical, with carefully controlled labelling efficiency. There was no indication of accumulation in the liver or spleen. Activity versus time curves were constructed. The lung curve had approximately bi-exponential form with components of effective half-lives 0.88 and 4.56 h. Areas beneath the curves gave cumulated activities for each organ and, using S values (absorbed dose per unit cumulated activity) from MIRD tables, absorbed doses from self-irradiation were calculated for each organ.

Gastric Mucosa↗
PubMed1983

An investigation of the optimum culture conditions for a differentiated culture of sheep thyroid cells.

Primary cultures of differentiated sheep thyroid were investigated to assess the effect of varying the media, sera, hormones and the initial cell number plated on the culture life span. Iodide uptake and follicular morphology were used as indices of differentiation. It was found that the effect of variations in the type of medium and the concentration and type of serum used was very small. The addition of all the hormones used - insulin, hydrocortisone and thyrotrophic hormone - had a synergistic effect on the iodide trapping ability of the culture system. A cell number of approximately 1 x 10(6) cells per 25 cm2 flask was found to be optimum for the development of differentiation in the cultures.

Animals↗
PubMed1982

Quantitative measurement of activity in small sources containing medium energy radionuclide: comparison of the gamma camera and the rectilinear scanner.

The response of a gamma camera and a rectilinear scanner to small sources containing 131I was assessed from the point of view of thier suitability for measuring the activity of a source, as opposed to their capacity to produce well-resolved images. The influence of the size of the area over which counts were integrated, and of the size and depth of hte source, were investigated for both instruments. The results indicate that both instruments are dependent on these variables, though with the particular instruments investigated the dependence of the gamma camera is much more complex and difficult to define. The conclusions indicate that with these systems quantitative activity measurements are more readily achievable with the scanner than with the camera.

Iodine Radioisotopes↗
PubMed1980

The radiobiological response of the thyroid. Part I: Sheep thyroid cells in culture as a radiobiological model.

A system for culturing sheep thyroid cells in vitro is described. The properties of the cultures may be manipulated so that they preserve in vitro the follicular architecture typical of the thyroid, or so that they undertake cellular proliferation. The cultured cells also undertake iodide metabolism. These growth and differentiation characteristics can be preserved for at least three weeks, which is sufficient time for assay of many radiobiological end-points.

Animals↗
PubMed1980

The radiobiological response of the thyroid. Part II: Response of sheep thyroid cell in vitro to single doses of X rays.

The response of sheep thyroid cells in culture to single doses of X or gamma rays is described. In the absence of cellular proliferation the cells are unusually radioresistant, showing little sign of interphase death at doses up to 9 krad. The follicular morphology characteristic of thyroid cells in vivo is also very radioresistant. Iodide trapping is reduced to 50% of the control value by doses of the order of 2 krad. When proliferation is induced the cells may be assayed for postirradiation survival using a clonogenic endpoint. The survival curves are sigmoid with a Do of 410 rad and a very low extrapolation number.

Animals↗
PubMed1980

Longterm cultures of sheep thyroid cells.

A thyroid tissue culture system has been established in which follicular morphology can be preserved for at least 30 days. The system is highly dependent on whether or not the medium supporting the cells is changed during the culture period. The high levels of TSH (40 mU/ml) normally used in thyroid culture systems enhance follicular morphology but are not a prerequisite for differentiation. In the absence of medium changes follicular morphology improves for up to 20 days after initiation of the culture. Thereafter, the cells die unless the medium is changed. If differentiation is to be preserved after 20 days the medium into which the cells are transferred must be "conditioned" by preincubation with thryoid cultures. Regular medium changes into fresh medium causes the cultures to lose their differentiated characteristics and revert to a conventional monolayer. The capacity of these cultures to trap iodide has been quantified using a new method. The method is based on comparison of the 125I--iodide retained by thyroid cells with that retained in a undifferentiated established cell line (CHO--K1). The results demonstrated that trapping can be preserved for at least 20 days in cells cultured in the presence of TSH, provided the medium is not changed; and that under appropriate conditions the cells can trap iodide even in the absence of TSH stimulation. The extent to which the above cultures proliferate is also investigated. At the relatively high innoculation of cells used in primary cultures little proliferation takes place even when the cells are stimulated by TSH. However, regular medium changed induce some growth. In the absence of medium changes the cells die after 15-20 days. Those grown in the presence of TSH live slightly longer than those grown in its absence. Subculturing thyroid cells and innoculating them at low densities in Petri dishes leads to substantial cell proliferation whether or not TSH is present. The doubling time of cells in these cultures is the order of 1 to 2 days. The population resulting from this growth exhibit both epithelial and fibroblast like morphology although the former predominates. When cells from primary thryoid cultures are reseeded at very low concentrations (approximately 10(3) cells/Petri dish) about 3-10 per cent of the population give rise to viable macroscopic clones.

Animals↗