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Biomedical subjects

J O Deeley

Publications and source records attributed to J O Deeley.

11 recordsLinked to original sources
PubMed1995

Determination of radiation-induced damage in lymphocytes using the micronucleus and microgel electrophoresis 'Comet' assays.

DNA damage assays may be useful as rapid predictors of normal tissue radiosensitivity in clinical samples. We measured in vitro radiation-induced (2 Gy) damage to lymphocytes from cancer patients and normal healthy donors using both the micronucleus and microgel electrophoresis (Comet) assays simultaneously. For damage assessment, there was a good correlation (P < 0.001) between the mean comet lengths and the fraction of cells with comets. There was no correlation with initial damage, determined as the proportion of cells within a sample that formed comets, in comparison with the mean frequency of micronuclei per binucleate cell. However, there appeared to be an association between the determination of repair proficiency in the Comet assay and the mean frequency of micronuclei per binucleate cell in lymphocytes from cancer patients.

DNA↗
PubMed1989

Nuclear lysate sedimentation measurements of peripheral blood lymphocytes from radiotherapy patients.

When isolated nuclei of human lymphocytes are challenged with 2 M NaCl a histone-free-DNA-protein (HF-DNA) complex is released. In a linear sucrose gradient (pH 8.0) the sedimentation distance of HF-DNA is reduced when immediately isolated from cells irradiated in vitro. At low doses, if irradiated cells are incubated at 37 degrees C the sedimentation behaviour approaches that of unirradiated cells (i.e. repair). In the present study such repair was usually complete within 1 h. The radiation damage to lymphocytes from a healthy donor group and three patient groups consisting of new patients (before radiotherapy), well patients (2 to 6 years post-radiotherapy) and patients with complications attributed to radiotherapy was similar. The lymphocytes from most healthy donors and new patients demonstrated complete repair of radiation damage following an incubation of 1 h at 37 degrees C. However, 2/29 (6.9 per cent) healthy donors and 2/25 (8 per cent) new patients demonstrated poor repair. Of those patients now attending with 'bowel complications' attributed to radiotherapy 7/16 (44 per cent) demonstrated poor repair. In contrast, all those (11/11) described as 'well and complication-free' showed good repair.

Adult↗
PubMed1984

A video image correlation technique for the measurement of electrophoretic mobility.

The electrophoretic movement of blood cells has been examined with a video image correlator using the signal from a 625 line monochrome television camera attached to the optical arrangement. The diffraction pattern of a cell produces a characteristic signal which can be detected and registered in any television scan line to form the data of the first image frame. Under the influence of an electric field, cells moved across the television field of view and after a short interval appeared on different scan lines. The detection and registering process was repeated, and a cross-correlation function between the first and second image frame was computed. This function was stored in an output buffer which was continuously updated as fresh functions were integrated with the existing contents. The mean electrophoretic mobility of a suspension of particles can be calculated from the peak position of the integrated correlation function. Using a triangle deconvolution procedure, the relative contributions of subpopulations of lymphocytes prepared from peripheral blood samples were examined.

Blood Cells↗
PubMed1983

Interfacial instability and membrane internalization in human erythrocytes heated in the presence of serum albumin.

The dynamics of morphological change, when human erythrocytes are heated through the spectrin denaturation temperature in the presence of bovine serum albumin, has been studied using differential interference contrast optics and a television video analysis system. Most washed (control) cells developed a wavy disturbance, with an average of 6.6 +/- 0.4 (2 S.E.) waves per cell rim, when heated. The average number of waves per cell rim decreased and the percentage of heated cells showing morphological changes in the dimple region increased with increasing serum albumin concentration, reaching 100% at 1.0 g/l. The change in the dimple region of cells heated in the presence of serum albumin involved the growth of a regular wavy disturbance around the cell dimple rim. The development of the wavy disturbance on the dimple, which resulted in the internalization of membrane, has been examined as an example of an interfacial instability on a biological membrane. Scanning and transmission electron micrographs confirm membrane internalization.

Erythrocyte Membrane↗
PubMed1983

Tetracaine modifies the fragmentation mode of heated human erythrocytes and can induce heated cell fusion.

It is known that human erythrocytes in saline fragment by development of an unstable surface wave on the cell rim when cells are heated through the denaturation temperature of the structural protein, spectrin. Here the influence of tetracaine on the fragmentation process has been recorded and analysed by video microscopy of cells heated in rectangular glass microcapillaries. The number of waves per cell rim decreases with increasing tetracaine concentration until, at 0.5 mM tetracaine, wave growth on the cell rim is suppressed on most cells and the cells internalize membrane at the cell dimple. The rate constant for the change in the number of waves per cell with increasing tetracaine concentration is 9.6 mM-1 at a heating rate of 0.5 K/s. 50% of heated cells internalize membrane at 0.14 mM tetracaine. When cells are heated rapidly in suspension in test tubes the presence of tetracaine reduces the temperature for 50% haemolysis from 66 degrees C for washed control cells to 60.5 degrees C for cells in 2 mMs tetracaine. Cells heat in microcapillaries in tetracaine concentrations of 3 mM and higher begin to swell before the spectrin denaturation temperature is reached. Cell fusion was observed at and above the spectrin denaturation temperature in cells heated in 3 and 4 mM tetracaine. It was also noted that the morphology of erythrocytes maintained in 3.6 mM tetracaine for times up to 30 min at 37 degrees C or 20 degrees C was strongly dependent on temperature and time.

Cell Fusion↗
PubMed1980

Effects of ionic strength, serum protein and surface charge of membrane movements and vesicle production in heated erythrocytes.

Morphological changes and fragmentation of human erythrocytes heated at various rates through the spectrin inactivation temperature have been examined by cinephotomicroscopy. Most cells heated in 0.20 ionic strength buffered saline developed a wavy disturbance along the cell rim when heated. Vesicles developed from the crests of the growing waves within 0.3 s of the initiation of a wave when the heating rate was 1 degree C/s. At an ionic strength of 0.02, only 48% of the cells developed a wave outline. The average number of waves per cell was half that at 0.2 ionic strength. When the cell surface charge was reduced by neuraminidase treatment, only 12% of the cells fragmented. Bovine serum albumin or homologous plasma also reduced fragmentation. The dependence of the wave growth on ionic strength and surface charge was broadly consistent with theoretical predictions for the growth of a displacement instability on a low interfacial tension interface. Attention has been paid to the importance of bending energy in the development of the wave. Where wave development was suppressed, the morphological changes due to heating appeared to involve membrane internalization in the region of the cell dimple.

Erythrocyte Membrane↗
PubMed1979

Instability development in heated human erthrocytes.

Heated human erythrocytes gradually lose their form-maintaining structure as the temperature is increased to 50 degrees C and can behave in some respects as a viscous fluid. We have developed a technique for heating and stressing these cells that is novel, simple and quantitatively precise. We have applied this technique to heated human erythrocytes and have measured instability development in cells. We have employed instability growth theory to calculate a value for an effective surface tension which, in contrast to other methods of membrane surface tension measurement sought to minimize the effects of membrane supporting structural elements. The value obtained for the surface tension of the heated erythrocyte membrane was 0.9 . 10(-6) N/m with a range of variation from 0.4 . 10(-6)N/m to 1.4 . 10(-6) N/m. The methods described may be useful for determining fundamental physical parameters such as internal viscosity and interfacial tension in other systems.

Erythrocytes↗
PubMed1979

The influence of temperature and incubation time on deformability of human erythrocytes.

Human erythrocytes have been heated and stressed in a novel and controlled manner using rectangular microcapillaries. Heated cells attached to the capillary wall were stressed by liquid flow. Under particular conditions of stress, temperature and incubation time the body of the cell could be pulled in the flow, retaining a connection with the glass by means of a narrow process or tether. The tethers appear as: regularly beaded, irregularly beaded or without beads depending upon the incubation conditions. We have outlined the incubation regimes necessary to achieve these different responses in the temperature range 48--55 degrees C. The cells become less deformable as the incubation is continued beyond an optimum time. The behaviour of the tether is compared with that of a viscoelastic liquid. Circular dichroism studies of ghost membranes show that the denaturation of membrane proteins is partially reversible when incubation times are similar to those required to bring about a loss of deformability.

Circular Dichroism↗
PubMed1978

Vesicle production of heated and stressed erythrocytes.

Human erythrocytes develop vesicles by budding when heated to temperatures close to the thermal transition for spectrin. Regularly spaced strings of vesicles also develop if cells heated to 51--54 degrees C are pulled into unstable shapes by flow of liquid between cover slips. These strings of vesicles develop when cells which had attached to the glass are restrained in the flow by a long membrane-bound tether which maintains a connection with the attachment site on the glass. Breakup into regularly spaced vesicles suggests the breakup of a liquid-like cylinder by growth of Rayleigh instabilities. The ratio of length:diameter of the fragments of cylinder on which each disturbance grew ranged from 2.2 to 5.4 to 1 with a peak of 3.2, as measured from scanning electron micrographs. The upper limit of the range is slightly less than the ratio for the disturbance most likely to grow if surface tension and viscosity alone controlled the vesicle formation. Similar vesicle formation when the form-maintaining structures were weakened has been reported in other systems.

Erythrocyte Membrane↗