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Biomedical subjects

R Taylor

Publications and source records attributed to R Taylor.

At least 307 records · Page 17Linked to original sources
PubMed1996

Investigating paediatric airways by non-bronchoscopic lavage: normal cellular data.

BACKGROUND: Bronchoscopic bronchoalveolar lavage in children to investigate bronchial disorders such as asthma has both ethical and procedural difficulties. OBJECTIVE: The aim of this study was to establish a standardized non-bronchoscopic method to perform bronchoalveolar lavage in children attending for elective surgery to obtain normal cellular data. METHODS: Bronchoalveolar lavage was performed on normal children (n = 55) by infusing saline (20 mL) through an 8 FG suction catheter passed after endotracheal intubation. Oxygen saturation, heart and respiratory rate were monitored during the bronchoalveolar lavage procedure. Cellular analysis and total protein estimation of the lavage fluid were performed. Epithelial lining fluid volume was calculated (n = 15) using the urea dilution method. RESULTS: The procedure was well tolerated by all children. Total cell count and differential cell count for children (macrophages 70.8 +/- 2.3%, lymphocytes 3.8 +/- 0.6%, neutrophils 5.7 +/- 1.0%, eosinophils 0.14 +/- 0.03%, epithelial cells 19.6 +/- 2.1%, mast cells 0.21 +/- 0.02%) were similar to those reported for adults. Age and sex comparisons revealed no differences between groups. The mean total protein recovered in the cell free supernatant was 49.72 +/- 4.29 mg/L and epithelial lining fluid volume was 0.82 +/- 0.11% of return lavageate. CONCLUSION: This method allows bronchoalveolar lavage to be performed safely and quickly on children attending for routine elective surgery. Using this method and taking the 'window of opportunity' of elective surgery, the presence or absence of airway inflammation could be studied in children with various patterns of asthma during relatively asymptomatic periods.

Adolescent↗
PubMed1995

Sequential molecular genetic changes in lung cancer development.

Epithelial tumours develop through a sequence of pre-invasive lesions of increasing disarray driven by underlying somatic genetic changes. We have studied the occurrence of the two most common somatic genetic changes associated with lung cancer in a series of premalignant bronchial lesions representing different stages in lung tumorigenesis. We present evidence that allele loss on chromosome 3 precedes damage to the p53 gene. Damage to chromosome 3 itself appears to be sequential in that the pattern of allele loss seen in dysplasia is often much more discrete than in invasive tumours. This implies that preneoplastic lesions may be a useful source of material for deletion mapping studies aimed at localising the position of tumour suppressor genes. We illustrate this by the comparison of an interstitial deletion described in this study with a homozygous deletion we have described previously, which has resulted in a better definition of the localisation of a tumour suppressor gene believed to be involved in lung cancer development.

Base Sequence↗
PubMed1995

Dosimetric evaluation of the conformation of the multileaf collimator to irregularly shaped fields.

PURPOSE: The goal of this study was to evaluate the dosimetric characteristics of geometric MLC prescription strategies and compare them to those of conventional shielding block. METHODS AND MATERIALS: Circular fields, square fields, and 12 irregular fields for patients with cancer of the head and neck, lung, and pelvis were included in this study. All fields were shaped using the MLC and conventional blocks. A geometric criterion was defined as the amount of area discrepancy between the MLC and the prescription outline. The "least area discrepancy" (LAD) of the MLC conformation was searched by selecting the collimator angle, meanwhile keeping a preselected position along the width of the leaf into the prescribed field. Five LAD conventions were studied. These included the LAD-0, LAD-1/3, LAD-1/2, and LAD-2/3 that inserted the leaves at the 0, 1/3, 1/2, and 2/3 of the leaf end into the prescription field, respectively. In addition, the LAD optimization was applied to the transecting (TRN) approach for leaf conformation that prescribed an equal area of overblocking and underblocking under each leaf. Film dosimetry was performed in a 20 cm polystyrene phantom at 10 cm depth 100 cm from source to axis distance (SAD) for both 6 and 18 MV photons with each of the above MLC conformations and conventional blocks. The field penumbra width, defined as the mean of the separation between the 20% and 80% isodose lines along the normal of the prescription field edge, was calculated using both the MLC and conventional block film dosimetry and compared. In a similar way, the d20 is defined as the mean separation between the 20% isodose line and the prescription field edge, and the d80 is defined as the mean separation between the 80% isodose line and the prescription field edge. RESULTS: The field penumbra width for all MLC conventions was approximately 2 mm larger than that of the conventional block. However, there was a larger variation of the separation distribution in the penumbra region of the irregular fields for the MLC, which had a standard deviation of 1 mm (a factor of 5 larger than the conventional block). The dosimetry for the circular fields showed that the LAD-TRN, LAD-1/2, and LAD-1/3 approximated the conventional blocking well in terms of d20 and d80; however, no single convention produced the best conformation for both measures. The dosimetric result of the patient treatment fields was similar for all sites. The LAD-1/3, LAD-1/2, and LAD-TRN strategies conformed to within 1 to 1.5 mm of the d80 of the conventional block for both 6 MV and 18 MV, respectively. The LAD-1/2 and LAD-TRN conformations were virtually identical, although it is proven analytically that the LAD-1/2 convention has the least overall area discrepancy of all conventions. CONCLUSIONS: The five MLC conformation conventions resulted in similar dosimetric penumbrae for all field shapes studied. The LAD-1/3, LAD-TRN, and LAD-1/2 produced the more favorable approximation to conventional block. The field penumbra width, although useful for evaluating irregular field shapes, could not describe the large local variations in the penumbra along the field edge for the MLC. These local variations could be of clinical concern when they appear near vital organs. However, the variation in a local region can potentially be reduced by minimizing the jaggedness of the leaf steps in that local region. The dosimetric results were useful as guidelines for the clinicians in the evaluation and adjustment of MLC leaf positions.

Head and Neck Neoplasms↗
PubMed1995

A multileaf collimator field prescription preparation system for conventional radiotherapy.

PURPOSE: The purpose of this work is to develop a prescription preparation system for efficient field shaping using a multileaf collimator that can be used in community settings as well as research institutions. The efficiency advantage of the computer-controlled multileaf collimator, over cerrobend blocks, to shape radiation fields has been shown in conformal treatments, which typically require complete volumetric computerized tomographic data for three-dimensional radiation treatment planning--a utility not readily available to the general community. As a result, most patients today are treated with conventional radiation therapy. Therefore, we believe that it is very important to fully use the same efficiency advantage of multileaf collimator as a block replacement in conventional practice. METHODS AND MATERIAL: The multileaf collimator prescription preparation system developed by us acquires prescription images from different sources, including film scanner and radiation treatment planning systems. The multileaf collimator angle and leaf positions are set from the desired field contour defined on the prescription image, by minimizing the area discrepancies. Interactive graphical tools include manual adjustment of collimator angle and leaf positions, and definition of portions of the field edges that require maximal conformation. Data files of the final leaf positions are transferred to the multileaf collimator controller via a dedicated communication link. RESULTS: We have implemented the field prescription preparation system and a network model for integrating the multileaf collimator and other radiotherapy modalities for routine treatments. For routine plan evaluation, isodose contours measured with film in solid water phantom at prescription depth are overlaid on the prescription image. Preliminary study indicates that the efficiency advantage of the MLC over cerrobend blocks in conformal therapy also holds true for conventional treatments. CONCLUSION: Our model of computer-controlled prescription, evaluation, and treatment using multileaf collimators can be effectively implemented in both community settings and research institutions. The resultant increase in treatment efficiency and accuracy is now available for conventional radiotherapy.

Equipment Design↗
PubMed1995

Adenosine effects upon insulin action on lipolysis and glucose transport in human adipocytes.

The dose response effect of a new adenosine analogue, GR79236 (N-[1S trans-2-hydroxycyclopentyl] adenosine) upon insulin sensitivity was examined in human adipocytes. The influence of adenosine upon insulin sensitivity for suppression of lipolysis and stimulation of glucose transport was examined. Removal of adenosine by use of adenosine deaminase stimulated lipolysis to the same extent as did 10(-9) M noradrenaline. GR79236 brought about dose dependent inhibition of lipolysis with half-maximal effect at 11.3 +/- 7.8 x 10(-9) M. When lipolysis was stimulated by noradrenaline alone the subsequent inhibition of lipolysis brought about by GR79236 was significantly greater than that of insulin. To examine adenosine effects on the insulin signalling pathway separately from those on lipolysis, the insulin sensitivity of glucose transport was examined. Removal of adenosine brought about a small but significant increase in the concentration of insulin required for half-maximal stimulation of glucose transport. Adenosine agonists offer promise as new agents for the modulation of metabolism in diabetes and other states of insulin resistance.

3-O-Methylglucose↗
PubMed1995

Radiotherapy in the treatment of low-grade astrocytomas. II. The physical and cognitive sequelae.

The purpose of the present study was to define the late effects, both physical and psychological, of treating low-grade astrocytomas with radiotherapy. Fifty patients, half of whom received radiotherapy, underwent an assessment of neurological and neuropsychological function. There was no difference in neurological function between the two groups. The radiotherapy recipients, including those with cerebellar tumours, performed significantly worse on measures of intelligence and information processing. In addition, there was a greater incidence of special education needs in the irradiated group. We conclude that children with low-grade astrocytomas who receive radiotherapy have no greater neurological deficit but that the use of radiotherapy carries a penalty in terms of long-term cognitive function and confirmed the findings of many previous reports that supratentorial irradiation is detrimental. More surprisingly, it has been demonstrated that local field irradiation to the posterior fossa can also produce significant cognitive impairment.

Adolescent↗
PubMed1995

Estimating rates of chronic fatigue syndrome from a community-based sample: a pilot study.

Most of the Chronic Fatigue Syndrome (CFS) epidemiological studies have relied on physicians who refer patients having at least six months of chronic fatigue and other symptoms. However, there are a number of potential problems when using this method to derive prevalence statistics. For example, some individuals with CFS might not have the economic resources to access medical care. Other individuals with CFS might be reluctant to use medical personnel, particularly if they have encountered physicians skeptical of the authenticity of their illness. In addition, physicians that are skeptical of the existence of CFS might not identify cases. In the present pilot study, a random community sample (N = 1,031) was interviewed by telephone in order to identify and comprehensively evaluate individuals with symptoms of CFS and those who self-report having CFS. Different definitions of CFS were employed, and higher rates (0.2%) of CFS were found than in previous studies. Methodological benefits in using more rigorous epidemiological methods when estimating CFS prevalence rates are discussed.

Adolescent↗
PubMed1995

The effects of caring on health: a community-based longitudinal study.

This paper begins with a critical review of studies which have examined the effects of caring on health. Most are shown to suffer from defects in sampling and design, so that the evidence for detrimental effects is suggestive rather than conclusive. The substantive part of the paper then utilizes data on a cohort of 55-year-olds to compare the health of carers with the health of non-carers and to examine changes in caring and health over a 3-year period. The comparison yields no systematic evidence of the deleterious effects of caring on health; indeed, if there is a tendency in the accumulated data, it is in the opposite direction i.e. that carers report better health and functioning than non-carers. It is suggested that part of the explanation relates to selection and self-selection and the longitudinal data reveals high volatility in caring status, even over a short time period. The paper goes on to examine sub-groups of carers considered to be at greater risk. There is no evidence that their health is compromised but the authors acknowledge weaknesses in the data and argue for a specially designed study. The paper concludes with a discussion of the findings and their implications for research, policy and practice.

Caregivers↗
PubMed1995

Clinical comparison of Provisc and Healon in cataract surgery.

This prospective, randomized, multicenter clinical trial compared the safety and efficacy of the Provisc and Healon viscoelastics. Sixty-one eyes of 61 patients had an extracapsular cataract extraction with implantation of a posterior chamber intraocular lens with the aid of Provisc (n = 32) or Healon (n = 29). Mean changes in preoperative versus postoperative corneal thickness and intraocular pressure and the incidence and magnitude of postoperative corneal edema and iritis were not significantly different between the two groups. Observed complications were considered consequences of the surgery and unrelated to viscoelastic use. No adverse medical events occurred. These results indicate Provisc and Healon are clinically equivalent in terms of safety and efficacy when used as surgical aids.

Cataract Extraction↗
PubMed1995

Australian trends in mortality by socioeconomic status using NSW small area data, 1970-89.

This ecological study examines trends in socioeconomic differentials in mortality in New South Wales, Australia, over a 20-year period (1970-89). The proportion unskilled was used as the indicator of socioeconomic status and its selection justified. Using census data aggregated by Local Government Area, the relationship between mortality and socioeconomic status was examined using quintiles based on the proportion unskilled in the population. Local Government Areas were also sorted into quintiles using mortality rates (0-74 years) to describe change in mortality differentials over time. Socioeconomic differentials were more evident in the relatively homogeneous Local Government Areas within the Sydney Statistical Division than in the remaining NSW Statistical Divisions which are more heterogeneous and predominantly rural. Although there has been an overall decline in mortality for males and females, and for high and low status groups, over this period the relative socioeconomic differentials have not declined. For the most recent period (1985-89) there appears to be some widening of differentials for males. The NSW state trends are generally similar to those reported for Britain and for other industrialised countries, suggesting that this is a common trend and that policies to reduce inequalities have not been effective.

Adolescent↗
PubMed1995

Lack of effect of vitamin E administration on basal nitric oxide function in male smokers and non-smokers.

1. The antioxidant properties of vitamin E (alpha-tocopherol) have been proposed to account for a possible protective effect in coronary artery disease. Coronary risk factors are associated with depressed endothelium-derived nitric oxide responses, and some evidence suggests increased quenching of the vasodilator effect of nitric oxide by oxygen free radicals. This study examined the possibility that vitamin E supplementation would improve basal function of the nitric oxide dilator system in long-term smokers and non-smokers. 2. Nine healthy male life-long non-smoking subjects and eight smokers (36 +/- 6 cigarettes per day, > 7 years) were given 1000 i.u. of vitamin E per day for a 4-week period, while five additional non-smokers received placebo. Forearm blood flow responses to intra-arterial infusion of noradrenaline (60, 120 and 240 rho mol/min) and the competitive inhibitor of nitric oxide synthesis, NG-monomethyl-L-arginine (1, 2 and 4 mumol/min) were measured before and after therapy. 3. No changes were evident in the constrictor responses to noradrenaline or NG-monomethyl-L-arginine in any group. These results indicate that vitamin E supplementation does not influence basal activity of the nitric oxide-dilator system in vivo.

Adult↗
PubMed1995

Hepatocyte growth factor gene expression after massive small bowel resection: lack of stimulation in lung and liver.

Both hepatic and renal regeneration are associated with rapid increases in hepatocyte growth factor (HGF)mRNA levels, not only in the regenerating tissue, but also in the lung. In this study, changes in the levels of HGF mRNA in the terminal ileum and also in distal organs in the rat following massive small bowel resection (MSBR) have been investigated with a sensitive S1 nuclease assay. HGF mRNA levels are low in the ileum and increase only transiently post-MSBR. In contrast to the other models of regeneration, no increase in HGF mRNA levels is observed in the lung nor in kidney and liver post-MSBR. This suggests that the ileum does not release "injurin", the putative humoral mediator of the response of the lung observed after hepatectomy or nephrectomy.

Animals↗