Search PubMed⌕ Search

Biomedical subjects

A K Dixon

Publications and source records attributed to A K Dixon.

At least 19 recordsLinked to original sources
PubMed2003

Serotonin receptor mRNA expression in rat dorsal root ganglion neurons.

In the present study, we have used in situ hybridization to examine the distribution of serotonin (5-HT) receptors in rat dorsal root ganglion (DRG) neurons. Within DRG neurons, mRNAs for 5-HT1B, 5-HT1D, 5-HT2A, 5-HT2B, 5-HT3B and 5-HT4 receptors were readily detected in small (<25 microm), medium (25-45 microm) and large (>45 microm) diameter neurons. In contrast mRNAs for 5-HT1A, 5-HT1E, 5-HT2C, 5-HT5A, 5-HT5B, 5-HT6 and 5-HT7 receptors were undetectable in these neurons. The present study provides an insight into the molecular profile of 5-HT receptor subtypes in neurons responsible for modulating sensory information.

Animals↗
PubMed2003

Lumbar lordosis: study of patients with and without low back pain.

We used magnetic resonance imaging (MRI) to assess lumbar lordosis in 27 patients with low back pain and 19 patients and 10 volunteers with no known back pain. Our study aimed to investigate whether lordosis changes with age and is reduced in those with low back pain. Although our results confirm known observations that lumbar lordosis is more prominent in women (P < 0.01) and those with a higher body mass index (P < 0.04), we were unable to demonstrate any significant variation in lordosis with age. Nor could we demonstrate any difference in the degree of lordosis among women with or without back pain. Men with low back pain tended to have a less prominent lordosis, but this difference did not reach statistical significance. Therefore, a 'reduced lumbar lordosis' should be regarded as a very weak clinical sign.

Adult↗
PubMed2002

Evaluation of CT in identifying colorectal carcinoma in the frail and disabled patient.

Frail and physically or mentally disabled patients frequently have difficulty in tolerating formal colonic investigations. The aims of this study were to evaluate the accuracy of minimal-preparation CT in identifying colorectal carcinoma in this population and to determine the clinical indications and radiological signs with the highest yield for tumour. The CT technique involved helical acquisition (10-mm collimation, 1.5 pitch) following 2 days of preparation with oral contrast medium only. The outcome of 4 years of experience was retrospectively reviewed. The gold standards were pathological and cancer registration records, together with colonoscopy and barium enema when undertaken, with a minimum of 15 months follow-up. One thousand seventy-seven CT studies in 1031 patients (median age 80 years) were evaluated. CT correctly identified 83 of the 98 colorectal carcinomas in this group but missed 15 cases; sensitivity and specificity (with 95% confidence interval) 85% (78-92%) and 91% (90-93%), respectively. Multivariate analysis identified: (a) a palpable abdominal mass and anaemia to be the strongest clinical indications, particularly in combination (p<0.0025); and (b) lesion width and blurring of the serosal margin of lesions to be associated with tumours (p<0.0001). Computed tomography has a valuable role in the investigation of frail and otherwise disabled patients with symptoms suspicious for a colonic neoplasm. Although interpretation can be difficult, the technique is able to exclude malignancy with good accuracy.

Aged↗
PubMed2002

Improving risk assessment: hip geometry, bone mineral distribution and bone strength in hip fracture cases and controls. The EPOS study. European Prospective Osteoporosis Study.

Hip geometry and bone mineral density (BMD) have previously been shown to relate independently to hip fracture risk. Our objective was to determine by how much hip geometric data improved the identification of hip fracture. Lunar pencil beam scans of the proximal femur were obtained. Geometric and densitometric values from 800 female controls aged 60 years or more (from population samples which were participants in the European Prospective Osteoporosis Study, EPOS) were compared with data from 68 female hip fracture patients aged over 60 years who were scanned within 4 weeks of a contralateral hip fracture. We used Lunar DPX 'beta' versions of hip strength analysis (HSA) and hip axis length (HAL) applied to DPX(L) data. Compressive stress (Cstress), calculated by the HSA software to occur as a result of a typical fall on the greater trochanter, HAL, body mass index (BMI: weight/(height)2) and age were considered alongside femoral neck BMD (FN-BMD, g/cm2) as potential predictors of fracture. Logistic regression was used to generate predictors of fracture initially from FN-BMD. Next age, Cstress (as the most discriminating HSA-derived parameter), HAL and BMI were added to the model as potentially independent predictors. It was not necessary to include both HAL and Cstress in the logistic models, so the entire data set was examined without excluding the subjects missing HAL measurements. Cstress combined with age and BMI provided significantly better prediction of fracture than FN-BMD used alone as is current practice, judged by comparing areas under receiver operating characteristic (ROC) curves (p<0.001, deLong's test). At a specificity of 80%, sensitivity in identification was improved from 66% to 81%. Identifying women at high risk of hip fracture is thus likely to be substantially enhanced by combining bone density with age, simple anthropometry and data on the structural geometry of the hip. HSA might prove to be a valuable enhancement of DXA densitometry in clinical practice and its use could justify a more proactive approach to identifying women at high risk of hip fracture in the community.

Absorptiometry, Photon↗
PubMed2002

Body computed tomography in critically ill patients.

The aim of the study was to assess the effectiveness of computed tomography in the management of critically ill patients. We performed a prospective study over a 4-month period. The requesting clinician was asked to document their clinical diagnosis and confidence thereof on a visual analogue scale. They were also asked about their management plan if computed tomography had not been available. After imaging, any change in the management plan was assessed. During the study period, 16 computed tomograms were performed on 14 patients. There were 21 possible clinical diagnoses: of these eight were confirmed, and 13 were refuted. Seven new diagnoses were established. Computed tomography did not help in the management of two patients and it led to more confusion in the management of one patient. The management of seven patients was altered after computed tomography and in six the management depended solely on computed tomography findings.

Confidence Intervals↗
PubMed2002

Caecal carcinomas in the elderly: useful signs in minimal preparation CT.

OBJECTIVE: Frail, elderly and immobile patients frequently have difficulty in tolerating formal colonic investigations. Caecal tumours may account for up to 35% of colonic tumours. Barium enema and colonoscopy have limitations in assessing this region. The aims of this study were to evaluate the accuracy of a minimal preparation CT technique (merely with prolonged oral contrast medium) in identifying caecal carcinomas and to determine helpful radiological signs. MATERIALS AND METHODS: The CT technique involved helical acquisition following 2 days of preparation with oral contrast medium. The outcome of 4 years' experience (1995-1998) was reviewed. The gold-standards were pathological and cancer registration records, together with colonoscopy and barium enema where available, with a minimum of 15 months' follow-up. RESULTS: CT correctly identified 27 of 30 caecal carcinomas, and missed three, in a total of 1077 CT studies in 1031 patients (median age 80 years). There were also 21 false-positive cases in which CT incorrectly raised the possibility of a caecal tumour. The sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were 90%, 98%, 99% and 56%, respectively. Serosal margin blurring, tumour length, presence of abnormal peri-colic fat and terminal ileal wall thickening were identified as useful radiological signs. CONCLUSIONS: Minimal preparation CT is able to identify caecal carcinomas with fair accuracy. Such evaluation may become important given the increasing population age and evidence of a 'proximal shift' in the site of colonic tumours in the elderly.

Aged↗
PubMed2002

Histopathological correlates of abnormal pericolic fat on CT in the assessment of colorectal carcinoma.

The aim of this study was to assess the pathological significance of abnormal pericolic fat shown by CT in the context of colorectal carcinoma. CT and histopathological findings of 63 resected colorectal carcinomas were retrospectively reviewed. CT examinations were assessed by two observers for the presence or absence of abnormal pericolic fat (typically linear or nodular opacities) at tumour sites. Specimens were reviewed histopathologically for depth of tumour invasion, extramuscular tissue reaction, and number and largest size of tumour-involved and tumour-free lymph nodes. The sensitivity, specificity, positive predictive value and negative predictive value of pericolic fat in identifying extension of tumour infiltration beyond the muscle coat were 79% (42/53), 33% (2/6), 91% (42/46) and 15% (2/13), respectively. Despite these indicators of efficacy, the association between the presence of pericolic fat abnormality on CT and extramuscular extension of tumour (infiltration and/or nodal disease) or tissue reaction alone or in combination did not reach statistical significance (p>0.3 in all cases). Abnormal ("misty" or "mucky") pericolic fat in the assessment of colorectal cancer on CT is not a precise indicator of extramuscular extension of tumour, as it cannot clearly distinguish between tumour infiltration and tissue reaction beyond the muscle coat, or pericolic nodal involvement. However, it is a very helpful CT sign that may draw attention to the presence and site of a potential colonic abnormality.

Adipose Tissue↗
PubMed2002

Supportive cushions produce no practical reduction in lumbar lordosis.

It is common practice to place a pillow or bolster under the knees of patients undergoing lumbar spine CT or MRI. The use of such supportive cushions leads to gentle hip flexion that is thought to ease pain and "reduce lumbar lordosis". It is also thought to facilitate axial imaging through the discs. Observations in seven subjects who underwent lumbar spine MRI with and without such hip flexion showed no appreciable change in the degree of lordosis. As the use of such devices does not produce a practical reduction of lumbar lordosis, the decision to employ them should be made entirely with respect to patient comfort.

Beds↗
PubMed2002

Superficial collateral veins on abdominal CT: findings in cirrhosis and systemic venous obstruction.

Inspection of the superficial veins of the abdominal wall has long been a routine part of the physical examination. To date, radiologists have given such veins rather scant attention, even though they are elegantly demonstrated by CT. We have performed a study of 21 patients with cirrhosis, 7 patients with caval obstruction and 28 normal control counterparts in order to determine whether superficial veins were more numerous in these two clinical conditions. The 7 patients with caval obstruction included 4 with superior and 3 with inferior vena cava obstructions. Electronic data from the CT examinations of these 28 cases and 28 controls were analysed on a viewing console. Superficial veins were significantly more numerous in patients with cirrhosis (mean maximum=5, p<0.01) and caval obstruction (mean maximum=9.1, p<0.01) than in the normal controls (mean maximum=2.1). The combination of too many superficial veins and a large superior mesenteric vein is a pointer towards cirrhosis. The presence of excessive superficial veins is yet another clue to the presence of underlying disease when analysing abdominal CT.

Abdominal Muscles↗
PubMed2002

Appendicitis: spectrum of appearances on helical CT.

Acute appendicitis has extremely varied clinical presentations. A delayed or missed diagnosis may result in severe adverse consequences. Helical CT is evolving as an important diagnostic aid, but the CT signs can be varied and can easily be overlooked by the unwary. This pictorial review illustrates the spectrum of radiological signs and appearances of appendicitis on helical CT.

Acute Disease↗
PubMed2002

Single cell expression analysis--pharmacogenomic potential.

A fundamental challenge in biology is to correlate physiology with gene expression in specific cell types. This can only be achieved by understanding gene expression at the level of the single cell because, in many systems, each cell has the capacity to express a unique set of genes. Therefore, each cell can be considered to be functionally distinct. A clearer understanding of gene expression differences at such a discrete level provides an opportunity to develop drugs with more targeted pharmacologies or with decreased side effects.

Animals↗
PubMed2002

The UK national study of magnetic resonance imaging as a method of screening for breast cancer (MARIBS).

The UK national study of magnetic resonance imaging as a method of screening for breast cancer (MARIBS) is in progress. The study design, accrual to date, and related research projects are described. Revised accrual rates and expected recruitment are given. 15 cancers have been detected to date, from a total of 1236 screening measurements. This event rate and the tumour grades reported are compared with recent reports from other studies in women at high risk of breast cancer.

Adult↗
PubMed2001

Streptozocin-induced neuropathy is associated with altered expression of voltage-gated calcium channel subunit mRNAs in rat dorsal root ganglion neurones.

Voltage-gated calcium channels (VGCCs) within sensory neurones are believed to perform an important role in neuropathic pain. In the present study we examine the changes in VGCC mRNA which occur following streptozocin- (STZ) induced diabetic neuropathy using in situ hybridization. STZ caused a significant increase in alpha(2)delta(1), alpha(2)delta(2), and alpha(2)delta(3) mRNA levels in all neuronal cell types. Similarly, mRNA levels of alpha(1F), alpha(1I), and alpha(1S) were increased in all cell types studied whilst alpha(1A) and alpha(1G) mRNAs were specifically upregulated in medium and large diameter neurones. In conclusion, we demonstrate that the induction of diabetic neuropathy is associated with dramatic changes in the expression of VGCCs.

Animals↗
PubMed2001

Expression of voltage-gated calcium channel subunits in rat dorsal root ganglion neurons.

In the present study, we have used in situ hybridisation to examine the distribution of calcium channel subunits in rat dorsal root ganglion (DRG) neurons. Within DRG neurons, the calcium channel alpha subunit mRNAs alpha(1A), alpha(1B), alpha(1C), alpha(1D), alpha(1E), alpha(1I) and alpha(1S) were readily detected in small (<25 microm), medium (25-45 microm) and large (>45 microm) diameter neurons. alpha(1F) was present at very low levels in these neurons whilst alpha(1G) was virtually undetectable. The calcium channel auxiliary subunits alpha(2)delta(1) and alpha(2)delta(2) showed a complementary pattern of distribution to that of alpha(2)delta(3) in DRG neurons. alpha(2)delta(1) and alpha(2)delta(2) transcripts were expressed predominantly in small c-type sensory neurons and were present at lower levels in large Abeta-type sensory neurons. In contrast, alpha(2)delta(3) mRNA was present in high quantities in the large-diameter cells but was expressed at lower levels in small-diameter neurons of the DRG. The present study provides an insight into the molecular profile of calcium channel alpha(1) and alpha(2)delta subunits in the neurons responsible for transmitting sensory information.

Animals↗
PubMed2001

Requests for body computed tomography: increasing workload, increasing indications and increasing age.

Increasing numbers of increasingly elderly patients were being examined in our Body CT department. At the same time, some of our clinical colleagues perceived that their patients might be discriminated against on the basis of their age when allocating CT time. We therefore studied the population trends in our department over a 10-year period. The ages of patients attending the Body CT department were collected from the hospital's computer information system from 1995 to 2000 and from handwritten logbooks for the months of September 1988 and 1998. Comparison was made with population trends within the hospital and local demographic data. There has been an average increase of 11% per annum in the number of examinations performed in the Body CT unit. The average age of patients examined increased from 52.7 years in 1988 to 58.9 years in 1998. The largest increase occurred in the over 75-year population (18% rise per annum). Hospital and local demographic population profiles changed little during the same period. We are performing increasing numbers of body CT examinations on increasingly elderly patients. This is probably due to an increased willingness to investigate and treat elderly patients, rather than changes in the local population. There is no evidence of a general discriminatory policy on the basis of age.

Adolescent↗