PubMed Health⌕ Search

Biomedical subjects

H M Morgan

Publications and source records attributed to H M Morgan.

14 recordsLinked to original sources
PubMed2001

Human breast-cancer cells stimulate the fusion, migration and resorptive activity of osteoclasts in bone explants.

A central event in bone resorption is the recruitment of osteoclasts to future resorption sites. Breast-cancer cells invariably metastasise to the skeleton and induce extensive bone destruction by osteoclasts. However, our understanding of the mechanisms by which cancer cells interact with osteoclasts remains unclear. Consequently, we compared the effects of conditioned medium (CM) from 2 human breast-cancer cell lines, MB-MDA-231 and MCF-7, with those of a normal human breast epithelial cell line, HME, on osteoclastic fusion, resorptive activity and migration from the periosteum to the developing marrow cavity of fetal mouse metatarsals in culture. Osteoclastic resorptive activity was assessed by pre-labelling 17-day-old fetal metatarsal explants with 45Ca, whilst fusion and migration were monitored by histomorphometry and osteoclasts were identified by their tartrate-resistant acid phosphatase activity. CM from TPA-stimulated breast-cancer cell lines produced a significant increase in osteoclastic resorptive activity, whilst the normal breast cell line produced a minimal increase. The breast-cancer cell lines also stimulated osteoclastic fusion and migration in the metatarsal explants, but the normal breast cell line was without effect. The stimulatory effect of CM from MDA-MB-231 cells on osteoclastic fusion, but not migration, was partially inhibited by preventing prostaglandin and leukotriene synthesis by cells within the bone explants. In contrast, a synthetic matrix metalloproteinase (MMP) inhibitor, but not a cysteine proteinase inhibitor, prevented the migration of osteoclasts to the calcified centre of the metatarsal explants in response to CM from MDA-MB-231 cells. MDA-MB-231 cells also induced an increase in the expression of MMP-9 by migrating osteoclasts. Fractionation of the TPA-stimulated breast cancer cell CM established that the resorptive activity was associated with factors of m.w. >3 kDa. We determined by immuno-assay that human breast-cancer cells secrete parathyroid hormone-related protein (PTH-rP), tumour necrosis factor-alpha (TNF-alpha) and interleukins (ILs) 6 and 11. Neutralizing experiments with human antibodies to these cytokines established that PTH-rP and TNF-alpha production by MDA-MB-231 cells were responsible for mediating their effects on osteoclastic migration and ultimately bone resorption in the metatarsal explants.

Animals↗
PubMed1999

In vivo dosimetry using diodes as a quality control tool--experience of 2 years and 2000 patients.

This paper reports the use of diodes as a quality control tool on more than 95% of patients undergoing megavoltage radiotherapy during the past 2 years. The paper describes a simple method for using the diodes, a number of possible pitfalls and a quality issue raised by the measurements. In general, the results have been reassuring with very few patients falling outside a +/- 5% action level.

Breast Neoplasms↗
PubMed1999

Gamma-ray scattering for mandibular bone density measurement.

There has been considerable interest in the measurement of bone density in the mandible, either to study bone resorption following tooth loss or to determine the relationship between mandibular and skeletal bone mineral density. Measurements mostly have been made on dental radiographs but more significant correlations between mandibular and skeletal bone density have been obtained when more sophisticated techniques have been used, such as quantitative CT and dual energy X-ray absorptiometry. The present work investigates the feasibility of using gamma-ray scattering measurements to estimate mandibular bone density. Using a phantom to simulate the jaw, an 241Am source and a hyperpure germanium detector it is shown that bone density may be measured with a precision of about 1%.

Absorptiometry, Photon↗
PubMed1997

Gamma-ray scattering for fat fraction measurement.

The work reported examines the potential of using gamma-ray photon backscatter information to measure in vivo the percentage of fat in specific tissue volumes. 241Am gamma rays are used as the source and the backscatter detected with a hyperpure germanium detector, with ethanol (approximately 80% fat, 20% muscle) and water (muscle) being used as tissue substitutes. Two measurement techniques are examined; the measurement of the ratio of coherent scatter to Compton scatter and the measurement of the Compton scatter profile. Both are shown to be sensitive to the composition difference between ethanol and water. For the coherent-Compton scatter ratio, the measured difference between water and ethanol is 1.85:1, close to the value calculated (about 2:1). A similar difference in the coherent-Compton ratios between muscle and fat is calculated (2.2:1). The FWHM of the Compton profile has also been shown to vary with tissue composition with a difference of 0.10 keV (5%) between the ethanol and water profile widths.

Adipose Tissue↗
PubMed1995

Dose rates and energy spectra in the maze of a linear accelerator treatment room.

When designing an entrance maze for a linear accelerator facility, it is useful to be able to estimate both the dose rate at the entrance and, in case further shielding is necessary, the energy spectrum of the scattered photons reaching the maze entrance. This study examines the applicability of the commonly used empirical formula contained in the National Council on Radiation Protection and Measurements (NCRP) Report No. 51 for estimating the dose rates at the maze entrance in a typical treatment room, and proposes an improvement allowing for the fact that the initial scattering event occurs most often in the patient at the isocentre. The X-ray energy spectrum at the maze entrance is also measured and shown to have a lower average energy than is assumed in NCRP Report No. 51.

Algorithms↗
PubMed1994

Non-invasive quantitative EMG.

The EMG information obtained by surface recording is compared to needle derived data processed in an identical manner. Such quantitative analysis of EMG activity has been undertaken using needle electrodes and is a well recognised technique for clinical purposes (16). Results of a study comparing data collected simultaneously by surface and needle electrodes from normal healthy volunteers are presented as a preliminary to a similar study of neuropathic and myopathic patients. The EMG interference pattern during maximum voluntary contraction was analysed for turns and zero crossings as well as from frequency spectral data, and the results displayed on-line using an inexpensive novel transputer aided PC. It was found that quantitative studies of surface and needle data were directly comparable in one muscle such as tibialis anterior but very different in another, such as rectus femoris, where there were changes in signal characteristic at different depths. The variability between individuals appeared to be less marked when surface electrodes were used. Data from surface recordings also show a high degree of repeatability when collected over a period of time.

Adult↗
PubMed1992

Quality assurance of computer controlled radiotherapy treatments.

There is a need in conformal therapy, as in any radiation therapy, for adequate quality assurance of the treatment plan and the delivery of the treatment. This paper examines quality assurance of two methods of conformal treatment, on a cobalt treatment unit using computer control. Each of the two methods demonstrates a different aspect of computer controlled treatments. Following completion of each treatment plan, an additional "quality assurance plan" is prepared. This is used to assess the integrity of the treatment plan, and the precision with which the computer controls the treatment unit. A simple method, using solid state detectors in a Perspex phantom, is used to validate the dosimetry of the "quality assurance plan". Quality assurance of the computer control is performed daily prior to treatments. At each treatment, parameters identifying the start position and final position of the computer controlled couch movements and the exposure time are noted by the radiographers. Comparison of the recorded movement of the treatment couch and the exposure time with that intended during each course of treatment has demonstrated, inter alia, limitations on couch speed control at speeds of less than 10 mm per min.

Beds↗
PubMed1985

Treatment of medulloblastoma using a computer-controlled tracking cobalt unit.

Radiation therapy of the length of the spinal column presents various clinical and physical problems. The completed plan may be complicated to set up, be time-consuming and require daily variation to achieve reasonable dose homogeneity. A case of medulloblastoma is used to illustrate the steps in producing a plan for dynamic treatment using a computer-controlled tracking cobalt unit. After definition by computed tomography, the target is considered in segments in order to develop a plan which keeps the spinal cord constantly positioned at the beam isocentre. The main computer is used to develop the patient treatment file and information is transferred to a second computer which controls and monitors the safe functioning of the cobalt unit. The cranial fields are treated separately in a conventional way. Good and consistent control of the dose distribution is achieved along the entire target volume. This technique is a marked improvement over all existing methods of treating the spinal axis.

Cerebellar Neoplasms↗
PubMedDate not supplied

Gamma-ray backscatter for body composition measurement.

The purpose of this study was to examine the potential of using backscatter information to assess regional body composition at selected sites. Two measurement techniques are examined: the measurement of the ratio of coherent to Compton scatter, and the measurement of the Compton scatter profile. Two possible applications are considered: the measurement of trabecular bone mineral density, and the measurement of the average fat/muscle ratio in a tissue volume. The results presented indicate that the analysis of coherent and Compton backscattered gamma-ray spectra from an 241Am source has the potential for measuring both trabecular bone mineral density and average fat/muscle ratio in a tissue volume, with a low absorbed dose to the subject.

Adipose Tissue↗
PubMedDate not supplied

Quantitative surface EMG in the diagnosis of neuromuscular disorders.

This paper describes a non-invasive quantitative method for the diagnosis of neuromuscular disorders using surface EMG (sEMG). We found sEMG to be a reliable method that can be used to differentiate neuropathic and myopathic patients from the normal subjects. The multivariate discriminant analysis of sEMG data assisted in separating myopathic from neuropathic disorders. Nevertheless sEMG is not robust enough to replace needle EMG as a stand-alone diagnostic tool. However quantitative sEMG that is described in this paper could be adopted as a simple, rapid and non-invasive technique to be used in the out patients clinic by EMG-naive clinicians as a screening method for neuromuscular disorders, before referring the patients for detailed clinical neurophysiological examinations.

Differential Threshold↗