PubMed Health⌕ Search

Biomedical subjects

P Tothill

Publications and source records attributed to P Tothill.

At least 37 records · Page 2Linked to original sources
PubMed1994

Comparisons between Hologic, Lunar and Norland dual-energy X-ray absorptiometers and other techniques used for whole-body soft tissue measurements.

OBJECTIVES: Assessment of the precision and accuracy of dual-energy X-ray absorptiometers (DXA) from three manufacturers, used for measuring soft-tissue composition, and comparability with each other and other techniques. DESIGN: Measurements of an anthropomorphic model of variable composition and thickness. 11 volunteers measured with each instrument and by underwater weighing (UWW) and three brands of bioelectric impedance analysis (BIA) apparatus. RESULTS: New software, introduced by each manufacturer during the course of the investigation, led to changes in measured fat proportion. The precision of determination of fat proportion by DXA in the (small) model was 3-4% (coefficient of variation), with little difference between brands. In vivo precision was 2-3%. In the model, measurements of % fat differed from the nominal values, but variation with thickness was small. There were significant mean differences of total fat proportion in the volunteers between pairs of DXA instruments of 2.6-6.3% fat. The SDs of the differences were 1.8-2.9% fat. Regional differences were greater, with trunk % fat being particularly underestimated by Hologic relative to Lunar and Norland. Compared with UWW, mean % fat was the same for Hologic, but higher for Lunar and Norland. SDs of 4% demonstrated inadequate agreement. The differences varied with proportion of bone in lean tissue, questioning the assumption of constant density of lean tissue in UWW. There were no mean differences of % fat between the BIA instruments and DXA and UWW, but SDs of 3-6% suggest that BIA using these instruments does not offer an acceptable accuracy in estimating fat proportion. CONCLUSIONS: UWW has limitations as a reference method. DXA is a useful technique, but its limitations, particularly regarding assumptions about fat distribution, must be borne in mind. The differences of fat proportion recorded by the three DXA instruments are such as to preclude interchangeability in measurements of individual subjects or in clinical trials.

Absorptiometry, Photon↗
PubMed1992

Long-term studies of cisplatin-induced reductions in porcine renal functional reserve.

Mature Large White female pigs aged approx. 10 months received single intravenous doses of 1.5, 2, or 2.5 mg/kg cisplatin. The glomerular filtration rate (GFR) and the effective renal plasma flow (ERPF) in individual kidneys were measured prior to and at 4-week intervals for up to 24 weeks after cisplatin administration by renography using [99mTc]-diethylenetriamminepentaacetic acid (DTPA) and iodohippurate sodium I 131, respectively. The left kidney of each cisplatin-treated pig and that of three age-matched control pigs was then removed, and GFR and ERPF values were measured in the remaining kidney at 4-week intervals for a further 24 weeks after unilateral nephrectomy (UN). Pigs treated with cisplatin showed no significant reduction in GFR or ERPF for up to 24 weeks after drug infusion. As measured using inductively coupled plasma mass spectrometry, the mean renal platinum concentration in the left kidney removed at UN was 77.5 +/- 9.1 ng/g kidney per mg/kg cisplatin. Histological evaluation of these kidneys revealed narrow interconnecting rays of interstitial fibrosis in the deep cortex and medulla; in these areas, glomeruli exhibited thickened Bowman's capsules and occasionally shrunken sclerotic capillaries. In cisplatin-treated pigs, UN was associated with a marked reduction in the ability of the remaining kidney to increase its function in terms of GFR and, to a lesser extent, of ERPF. The increase seen in GFR following UN in the cisplatin-treated pigs was only ca. 50%-70% of that seen in age-matched UN controls. Histologically, these kidneys revealed resolution of the peritubular fibrosis observed at UN; occasional sclerotic glomeruli were also evident. Platinum remained detectable in these kidneys, the mean levels being 18.8 +/- 4.9 ng/g kidney per mg/kg cisplatin. These findings confirm previous observations and illustrate the need for caution in considering further treatment of patients who have previously received cisplatin along with a second potentially nephrotoxic agent.

Animals↗
PubMed1992

The long-term retention of platinum in human tissues following the administration of cisplatin or carboplatin for cancer chemotherapy.

Mass spectrometry has been used to study the distribution and retention of platinum in the tissues of patients following the administration of cisplatin or carboplatin. Blood platinum was measured up to 2 years and renal excretion up to 5 years after treatment. Platinum concentrations in plasma and red cells fell according to a power function, approximately as the inverse square of the time after administration. The concentration in the urine fell more slowly. Necropsy samples were used to examine the distribution of platinum in various human organs up to 17 months after treatment. The highest concentrations were found in the liver, which retained approximately 2% of the dose. Although the results were scattered between patients, there was little loss of platinum after about 1 month. The prolonged retention of platinum may be relevant to long-term toxicity.

Adolescent↗
PubMed1992

Errors due to non-uniform distribution of fat in dual X-ray absorptiometry of the lumbar spine.

Errors in spinal dual X-ray absorptiometry (DXA) were studied by analysing X-ray CT scans taken for diagnostic purposes on 20 patients representing a wide range of fat content. The mean difference between the fat thickness over the vertebral bodies and that over a background area in antero-posterior (AP) scanning was 6.7 +/- 8.1 mm for men and 13.4 +/- 4.7 mm for women. For lateral scanning the mean fat thickness difference was only 4 mm for both sexes, but the dispersion was greater, with a standard deviation of 15 mm. To relate these differences to errors in bone mineral, measurements were made of the bone mineral equivalence of fat-equivalent materials on DXA machines from three manufacturers. 10 mm of adipose tissue was equivalent to -0.043 g/cm2 of hydroxyapatite. For AP scanning a non-uniform fat distribution leads to a mean overestimate of 0.029 g/cm2 for men and 0.057 g/cm2 for women. The error exceeded 0.1 g/cm2 in 10% of slices. For lateral scanning the error exceeded 0.1 g/cm2 (about 15% of normal) in a quarter of slices.

Absorptiometry, Photon↗
PubMed1989

An introduction to body composition models used in nutritional studies.

Chemical analysis of cadavers has led to the definition of 'reference' man but diseases may result in significant changes in body composition. By measuring body composition in patient groups the nature of disease progression can be followed and management regimens evaluated. Various techniques are available which attempt to measure body composition in vivo. Several models of body composition have evolved with the introduction of new measurement techniques. A description of these models is presented. The limitations of the models and the techniques adopted for their measurement are discussed.

Body Composition↗
PubMed1989

Evaluation of oral cisapride and metoclopramide in diabetic autonomic neuropathy: an eight-week double-blind crossover study.

Nineteen diabetic patients with autonomic neuropathy were enrolled in a double-blind crossover study of cisapride, metoclopramide and placebo. Symptoms were evaluated from diary cards and from assessments undertaken at the end of each eight week treatment period. Measurements of oesophageal transit, gastric emptying and whole gut transit were made before treatment began and at the end of each treatment period. Three patients dropped out early in the study, and the results from 16 patients were analysed. The severity of autonomic neuropathy, judged from cardiovascular reflex tests, correlated with delayed oesophageal transit and prolonged gastric emptying, but abnormal oesophageal transit and gastric emptying were often unrelated to the presence of upper gastrointestinal symptoms. Neither cisapride nor metoclopramide had a statistically significant effect on oesophageal transit, gastric emptying or whole-gut transit, nor was any significant effect on symptoms identified, although a trend towards reduced nausea and vomiting with metoclopramide and reduced epigastric fullness and diarrhoea with cisapride was suggested. Upper gastrointestinal symptoms correlate poorly with objective abnormalities of gastrointestinal motor function in diabetes. In consequence, the symptomatic benefit to be expected from correction of these motor abnormalities remains uncertain.

Adult↗
PubMed1987

Measurement of hand bone mineral content using single-photon absorptiometry.

A single photon absorption imaging technique has been developed to assess the bone mass of the hand, especially in patients with rheumatoid arthritis or bronchial asthma. A modified rectilinear scanner images the hand by transmission scanning in a water bath with a 7.4 GBq 125I source. A microcomputer is used to calculate the bone mineral distribution, and the total bone mineral content (BMC) of the hand is determined from that distribution. The precision (coefficient of variation) of the measurement is 1.9%. A control population of 20 men and 58 women has been studied to determine normal variations in hand bone mineral content with age, sex, body size, hand volume and years since menopause. The normal men are found to have an average hand BMC of 25.1 g with a coefficient of variation (CV) of 22%, which is reduced to 12% by normalising for body size using span. The normal women had an average hand BMC of 18.0 g +/- 15%. The CV is reduced to 13% by normalising for span and years post-menopause.

Adult↗
PubMed1987

Bone blood flow measured with microspheres: the problem of non-entrapment.

Radioactive microspheres were injected into the tibial nutrient arteries of dogs. The validity of their use to measure bone blood flow was tested by examining their concentration in femoral venous blood. Non-entrapment in the tibia was considerable in two animals following rather prolonged alternate periods of perfusion and ischaemia. When such treatment was minimised, non-entrapment was small, showing that in this respect microspheres provide a valid means of measuring bone blood flow.

Animals↗
PubMed1987

The pattern of distribution of blood flow in dog limb bones measured using microspheres.

The distribution of blood flow to segments of the leg bones of anaesthetised dogs was studied using radioactive microspheres injected into the heart or the tibial nutrient artery. Following central injection, repeated measurements after an interval showed no change of pattern of distribution. The effects of ligation of the tibial nutrient artery during this interval suggested that 30% of the blood flow to the tibia is normally via this vessel, which predominantly supplies the diaphysis. This deduction differed from that derived from the injection of microspheres during perfusion through a tibial nutrient artery cannula, when half the flow reached the epiphyses. This proportion decreased and the flow to the diaphyseal marrow increased after alternate periods of perfusion and ischaemia, demonstrating the labile nature of bone blood flow distribution.

Animals↗
PubMed1987

Prediction of fracture healing in the tibia by quantitative radionuclide imaging.

The uptake of 99mTc-MDP was studied in 73 patients after a tibial fracture. The image obtained five minutes after injection during a period between one and four weeks after fracture was found to be related to the incidence of non-union after six months. A ratio of 1.3 between the uptake at the fracture site and at normal bone adjacent to it predicted non-union in an individual patient with a sensitivity of about 70% and a specificity of 90%.

Adolescent↗