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Biomedical subjects

D C Lloyd

Publications and source records attributed to D C Lloyd.

At least 37 records · Page 2Linked to original sources
PubMed1999

Easy biodosimetry for high-dose radiation exposures using drug-induced, prematurely condensed chromosomes.

PURPOSE: To propose a practical method of biodosimetry for high-dose estimation. MATERIALS AND METHODS: Okadaic acid in the range 100 nM to 500 nM was given for 1-6 h to cultured lymphocytes that had been exposed in the range of 0 Gy to 40 Gy. The frequency of the cells with prematurely condensed chromosomes (PCC) was compared with that of metaphases accumulated by 0.05 microg/ml colcemid. The dose-response relationship of the yield of prematurely condensed ring chromosomes (PCC rings) in the irradiated lymphocytes was examined. RESULTS: The 0.05 microg/ml colcemid collected few metaphases when lymphocytes were irradiated to over 10 Gy. However, 500 nM okadaic acid produced a substantial number of analysable PCC in lymphocytes that had been exposed in the range of 0 Gy to 40 Gy. After 1 h of treatment, the 500 nM okadaic acid gave the most suitable chromosome morphology for the analysis. PCC rings were narrow, which facilitated their detection in Giemsa-stained preparations. The yield of PCC rings increased dose-dependently up to 20 Gy. CONCLUSION: PCC rings are a more suitable indicator than dicentrics at high doses over 10 Gy. This technique requires no particular equipment or exceptional skill. After a serious radiation accident, it can be easily performed in a short time in most medical facilities to obtain dose information to assist physicians.

Azure Stains↗
PubMed1999

Chromosomal analysis of peripheral lymphocytes of patients before and after radiation synovectomy with samarium-153 particulate hydroxyapatite.

OBJECTIVE: Radiation synovectomy may be indicated for the treatment of chronic synovitis. A number of factors may affect its current use, including availability, limited evidence for its efficacy compared to intra-articular glucocorticoid, and concerns regarding the potential long-term effects of radiation exposure, particularly in younger patients. Specific chromosome-type abnormalities in peripheral lymphocytes can be useful indicators of whole-body radiation exposure. The frequency of these aberrations has been shown to increase in patients who have had radiation synovectomy using yttrium-90 by up to five times compared to baseline levels. Samarium-153 particulate hydroxyapatite (Sm-153 PHYP) is a new radiopharmaceutical currently on trial which appears to have less extra-articular leakage than yttrium-90 compounds. The aim of this study was to identify any increase in specific chromosome-type abnormalities, using published criteria, in patients following Sm-153 PHYP synovectomy of the knee. The 10 patients (five men, five women) in whom the analyses were performed had a mean age of 47 yr (range 28-70 yr). RESULTS: There was no increase in scored chromosome-type abnormalities after Sm-153 PHYP synovectomy. CONCLUSION: This study further supports the relative safety of Sm-153 PHYP compared to other radiopharmaceuticals.

Adult↗
PubMed1998

Sonographic appearances of meniscal cysts.

PURPOSE: This study was conducted to define the sonographic appearances of cysts of the tibial menisci. METHODS: Thirteen cases of meniscal cyst, proven by magnetic resonance imaging (MRI), were assessed using high-resolution sonography, and results of the 2 imaging modalities were correlated. RESULTS: Seven meniscal cysts were lateral to the joint line, and 6 were located medially. MRI showed all 13 cysts to be associated with a tear of the adjoining meniscus. On sonograms, cyst size varied from 9 to 56 mm. Echotexture varied from uniformly hypoechoic or hypoechoic with echogenic septa to heterogeneously hyperechoic. Septated cysts were demonstrated by MRI and sonography. CONCLUSIONS: Because of their diverse echo patterns, meniscal cysts may be easily mistaken for soft-tissue tumors, ganglions, or other lesions, which may result in surgery being inappropriately recommended. This is particularly true in the case of echogenic cysts. The cardinal sonographic characteristic of a meniscal cyst is its continuity with the meniscus, not its echotexture.

Adult↗
PubMed1998

Magnetic resonance imaging of acute intraosseous disc herniation.

Schmorl's nodes, the result of previous intraosseous disc herniation (IODH), are a common incidental finding on plain radiographs, computed tomography (CT) and magnetic resonance imaging (MRI). Acute IODH can, however, cause severe back pain, and the radiological features may also lead to inappropriate suspicion of malignancy or infection. We present eight cases of acute IODH in order to illustrate how the correct diagnosis can be made by MRI. In six cases isotope bone scintigraphy had been performed, demonstrating focal increased activity at the site of IODH. MRI can reinforce the concern about serious underlying pathology by the demonstration of marrow oedema, which may be localized around the disc herniation or extensive, extending throughout the vertebral body and into the pedicles. The key to the correct diagnosis is the recognition of the endplate defect and disc herniation. In three cases the diagnosis may have been possible from plain radiographs in which disc calcification visible on previous radiographs had migrated into an intraosseous location.

Acute Disease↗
PubMed1998

Accidental intake of tritiated water: a cytogenetic follow-up case on translocation stability and dose reconstruction.

PURPOSE: To examine by fluorescence in situ hybridization (FISH) chromosomal translocations in a person who, 11 years previously, had accidentally incorporated tritiated water. To compare the resultant estimate of radiation dose with contemporary dosimetry made by urine analysis and dicentric chromosome scoring. MATERIALS AND METHODS: Blood lymphocytes were shared by two laboratories each performing the FISH analysis using different chromosome probe combinations. Doses were calculated by reference to an in vitro calibration curve produced in one of the laboratories. RESULTS: Good agreement in translocation yields was found by the two laboratories. Comparing the yields with the dicentric frequency obtained shortly after the accident and with a translocation frequency measured 6 years post exposure showed good agreement between all measurements. This indicates essentially perfect stability for translocations over an 11 year period in this individual. CONCLUSIONS: Dose reconstruction based on FISH-measured translocations showed good agreement with the dose estimated from initial dicentric measurements and from measurements of tritium in urine. Because of the extensive initial dosimetry performed on this individual, who received a uniform whole-body irradiation, the case serves as an excellent test for the use of FISH-measured translocations for retrospective biodosimetry.

Chromosomes, Human↗
PubMed1998

Risks from ionising radiation: deterministic effects.

This paper is a shortened version of an NRPB document that reviewed the deterministic effects on human health likely to arise from serious overexposure to ionising radiation. Little new primary information on deterministic effects has become available in recent years. However, advances in techniques for data analysis have been made, particularly in describing the sigmoid dose-effect relationships, effects of dose rate and radiation quality. These are presented in a form suitable for use in modelling the consequences to populations of serious radiological incidents.

Dose-Response Relationship, Radiation↗
PubMed1997

Chromosome aberrations in Syrian hamsters following very low radiation doses in vivo.

This paper addresses a report of a large increase (approximately 6- to 11-fold) in chromosome aberrations in lymphocytes of persons in Salzburg attributed to their exposure to fallout from the Chernobyl cloud. Their additional exposure, approximately 0.3 mGy in 1 year, comprised about a 30% increase in their normal background radiation dose. The report has attracted considerable attention because, if correct, it seriously challenges assumptions of linearity in the low-dose response for chromosomal damage and, by implication, the linear, no-threshold hypothesis for risk of induced cancer. An experiment has been carried out with Syrian hamsters treated with caesium-137 to produce a range of doses comparable with those calculated for the persons in Salzburg. No significant elevation in lymphocyte aberration yields was found in the hamsters, thus arguing against the conclusions of the Salzburg study.

Animals↗
PubMed1997

Chromosomal analysis to assess radiation dose.

This brief account of dosimetry based on cytogenetic assays reviews the sensitivity of the method and the speed with which a dose estimate can be obtained. The usefulness of chromosome studies to physicians is also discussed. Medical uses include confirming triage category for highly irradiated subjects and providing evidence for nonuniform exposure or other reasons for the presence of surviving functional stem cells. Such information can assist in medical management decisions, especially regarding transplantation of marrow or stem cells and treatment with growth factors. For subjects exposed to zero or low doses, cytogenetic studies can provide useful information for assisting physicians in counseling.

Bone Marrow Transplantation↗
PubMed1997

The changing relationship between prescribing and unemployment at family health service authority level in England, 1983-92.

STUDY OBJECTIVE: To investigate the relationship between unemployment and prescribing costs over time. DESIGN: This was a longitudinal study. SETTING: All 90 family health service authorities in England, 1983-92. PARTICIPANTS: All general practices in England. MAIN RESULTS: The strength of the relationship varied over the period, falling to a very low value during the last two years of the decade. CONCLUSION: Unemployment rates are not suitable as a proxy for the determination of prescribing costs.

Adolescent↗
PubMed1997

Magnetic resonance imaging of the lumbar spine: direct access for general practitioners.

At the Cardiff Royal Infirmary we have offered general practitioners (GPs) direct access for magnetic resonance imaging (MRI) of the lumbar spine for sciatica or suspected spinal claudication since January 1993. We compared referrals for MRI from GPs and hospital outpatient doctors, and assessed GP patient management following the scan report. No difference in the diagnostic rates for disc herniation and spinal stenosis were found. GP direct access shortens investigation time, potentially reduces waiting lists, and allows GPs to make more informed management decisions.

Adult↗
PubMed1995

Specific therapeutic group age-sex related prescribing units (STAR-PUs): weightings for analysing general practices' prescribing in England.

OBJECTIVES: To derive cost comparators for prescribing by English general practitioners in eight specific therapeutic groups, based on age-sex related weightings, and to confirm, from a new dataset, earlier age-sex weightings for overall prescribing (ASTRO-PUs). DESIGN: Calculations based on one year's prescribing data from selected practices using AAH Meditel software, held on MediPlus by Intercontinental Medical Statistics (IMS, UK and Ireland), and research practices using VAMP software, held on the General Practice Research Database. SETTING: 112 English practices with 739,672 patients and 510 British practices with 3,126,570 patients. MAIN OUTCOME MEASURES: Cost based weightings for 18 age-sex groups and for temporary residents for eight leading specific therapeutic groups and for prescribing overall. RESULTS: The two datasets were similar in age distribution and in the way that prescription numbers were distributed by age-sex band in each therapeutic group. The cost based weightings for specific therapeutic groups showed great variation in the use of these groups for patients in different age-sex groups. When these weightings were applied to the prescribing of practices in two family health services authorities they differed in their power to predict prescribing costs: for cardiovascular and gastrointestinal drugs predictive power was particularly high; for drugs for infections it was particularly low, since these are widely used at all ages and for both sexes. Cost based weightings for overall prescribing derived from the IMS data were similar to those of the ASTRO-PU system even though they were derived by different methods from different datasets. CONCLUSIONS: The weightings (STAR-PUs) offer a sound basis for cost comparisons at the therapeutic group level. Cost-based weightings for overall prescribing derived from the IMS data were reassuringly similar to those of the existing ASTRO-PU system.

Adolescent↗
PubMed1995

Allocating census data to general practice populations: implications for study of prescribing variation at practice level.

OBJECTIVES: To assign census data to general practice populations and to test accuracy of different procedures for estimating the proportion of patients aged over 64. DESIGN: Patients' postcodes from patient register of one family health services authority and the directory linking postcodes to census enumeration districts were used to locate patients in their census area of residence. With different levels of census geography and four different allocation procedures, proportion of patients aged over 64 in each area was used to predict proportion of patients aged over 64 in each general practice. Predicted figures were compared with real figures from each practice register to assess accuracy of allocation methods. SETTING: Data from 1991 census and from 73 practices administered by one family health services authority. MAIN OUTCOME MEASURES: Actual and predicted proportions of patients aged over 64 in general practice populations. RESULTS: Correlations between actual and predicted proportions of patients aged over 64 were significant for all four allocation procedures--values of 0.66, 0.7, 0.84, and 0.84 were achieved (P < 0.0005). Predicted ranges of proportions of patients aged over 64, however, were well short of those that actually existed, and significant differences existed between predicted percentages and actual figures for all four methods. CONCLUSION: Although predicted values correlated with actual values, the failure of the allocation procedures to correctly predict values, especially at the extremes, casts doubt on the validity of similar techniques for allocating census variables to general practice populations.

Age Factors↗
PubMed1995

Low income scheme index: a new deprivation scale based on prescribing in general practice.

OBJECTIVES: To describe and validate a new deprivation index, based on the percentage of prescribed items exempt from the prescription charge under the low income scheme, at both family health services authority and practice level. DESIGN: Comparison of the index with three other deprivation indices and correlation of index values with the use of drugs given for conditions with known social class gradients. SETTING: All 90 family health services authorities and 7619/9289 practices in England. RESULTS: The ranking of family health services authorities on the new index correlated highly with rankings on the other indices. Values in relation to the use of drugs given for conditions with known social class gradients were in the predicted direction at both family health services authority level and practice level; correlation was highly significant at the authority level, but less significant at practice level. CONCLUSIONS: The new index provides a good measure of deprivation at family health services authority level, and at practice level the results are sufficiently encouraging to warrant further research. It provides the best available instrument for relating deprivation to the use of drugs in any population that can be defined by prescribing data, but an attempt to use it in determining allocation of resources would at this stage be premature.

Drug Costs↗