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Biomedical subjects

S P Stewart

Publications and source records attributed to S P Stewart.

At least 19 recordsLinked to original sources
PubMed1999

Regional bone mineral density after orthotopic liver transplantation.

OBJECTIVES: Although there is a fall in lumbar spine bone mineral density (BMD) after liver transplantation, little is known about femoral neck or total body BMD. Therefore we determined: (a) the proportion of patients with preexisting hepatic osteopenia before transplantation and (b) the effects of transplantation on global and regional BMD. DESIGN: Retrospective analysis of BMD measurements of patients before and up to 2 years after liver transplantation. METHODS: BMD was assessed by dual energy X-ray absorptiometry in 56 patients, before and at regular intervals after liver transplantation, for up to 24 months, to measure total body, lumbar spine (L2-L4) and femoral neck BMDs. RESULTS: Pre-transplant, 23% of patients had osteoporosis (a negative Z score > 2). Paired data before and after transplantation revealed no change in total body BMD. However, there was a fall in lumbar spine BMD (1.04+/-0.03 to 1.02+/-0.03 g/cm2; P < 0.04) at 1 month after transplantation. The reduction in lumbar spine BMD was seen up to 12 months, BMD at 18-24 months being similar to pre-transplant values. Femoral neck BMD also fell (0.96+/-0.06 to 0.83+/-0.04 g/cm2; P < 0.03), but only after 6-9 months, thereafter remaining below pre-transplant values until the end of the follow-up period. CONCLUSIONS: Although osteopenia is common in patients with liver disease, total bone density does not fall after transplantation. Nonetheless regional lumbar spine and femoral neck bone density does fall after transplantation with a risk period for femoral neck fracture which may extend for up to 2 years.

Absorptiometry, Photon↗
PubMed1998

Comparison of in-vivo body composition using two Lunar dual-energy X-ray absorptiometers.

OBJECTIVE: To compare in-vivo composition analysis between two dual energy X-ray absorptiometers, a DPX and a DPX/L, from the same manufacturer (LUNAR), pre(Study A) and post(Study B) hardware changes on both absorptiometers. DESIGN: Comparison of (1) quality assurance (QA) data: air-counts low (38 keV), air-counts high (70 keV), air-counts ratio, percent spillover, R-delrin; and (2) total body compartments: total body tissue (TBTISS), total body fat (TBF), percent total body fat (%TBF), total body lean (TBLEAN), total body bone mineral content (TBBMC) and total body bone mineral density (TBBMD), between the two absorptiometers. SETTING: Centre for Bone and Body Composition Research, University of Leeds. SUBJECTS: Study A, 14 normal subjects and Study B, a different cohort of 19 normal subjects, were scanned on both machines on the same day. RESULTS: In Study A, large significant differences were observed in the QA parameters between the two machines. The DPX, air-counts low and air-counts high, being 25% and 22% lower than the DPX/L. The Bland Altman method of analysis indicated that the DPX was significantly higher for TBTISS (0.3 kg), %TBF (2%) and TBF ( 1.4 kg) and correspondingly lower for TBLEAN (-1.0 kg). No significant difference was observed in TBBMC. After the hardware changes (Study B) a marked reduction in the differences in QA air-counts was observed. The DPX air-counts low was now 1% higher and air-counts high 8% lower than the DPX/L. The DPX had now only small significant negative differences for %TBF (-0.6%) and TBF (-0.4 kg) and a small significant positive difference for TBLEAN (0.4 kg), compared to the DPX/L. TBBMC difference although slightly increased, was still non-significant. CONCLUSIONS: The closer agreement observed in the QA parameters after the hardware changes was associated with a reduction in the mean differences, 95%CI of the mean differences and limits of agreement of the comparison of body composition analysis from the Lunar machines using the Bland-Altman method. The study indicates that the QA limits set for bone mineral analysis may require more stringent limits for body composition.

Absorptiometry, Photon↗
PubMed1998

Effects of orthotopic liver transplantation on body composition.

AIMS/BACKGROUND: The effects of orthotopic liver transplantation on body composition are unclear. We aimed to assess changes in body composition after transplantation using dual energy x-ray absorptiometry and total body potassium. METHODS: Dual energy x-ray absorptiometry and total body potassium counting to assess muscle mass were performed in 55 patients before and up to 24 months after liver transplantation and the results expressed as paired data before and at time intervals after transplantation. RESULTS: The results showed that total body weight fell by 3.6 +/- 1.3 kg (p < 0.02) at 1 month, with a maximal fall in lean tissue mass at 2-5 months of 4.8 +/- 1.2 kg (p < 0.003). Thereafter, no change in lean tissue mass was recorded, although there were increases at 12 and 24 months of total body weight (11.5 +/- 2.4 kg, 7.8 +/- 3.1 kg; p < 0.03, respectively) and fat mass (12.9 +/- 2.2 and 10.5 +/- 2.7 kg; p < 0.003). A fall in total body potassium was seen at 1 month (118 +/- 12 mmol; p < 0.003) and 2-5 months (176 +/- 9.9 mmol; p < 0.03), which mirrored the fall in lean mass. CONCLUSIONS: After liver transplantation there is an initial fall in body weight due to a loss of lean mass. Lean mass does not recover after transplantation, although there is an increase in fat mass that leads to the observed increase in total body weight.

Absorptiometry, Photon↗
PubMed1996

Limiting multiple pregnancy in in vitro fertilization/embryo transfer (IVF-ET) cycles.

PURPOSE: Our purpose was to assess how the number of embryos transferred can be adjusted to limit multiple gestations. METHODS: A retrospective analysis of 535 consecutive embryo transfers for the years 1991-1993 was conducted. RESULTS: Fewer than three embryos were associated with a low pregnancy rate. Pregnancy rates were highest in women less than 35 when four or more embryos were transferred. With four or more embryos, multiple gestation pregnancy correlated with the number of high-quality embryos transferred. The risk of triplets and quadruplets was greatest for women less than 40. CONCLUSIONS: Multiple-embryo transfer carries a risk of plural gestation. The risk of multiple pregnancy cannot be eliminated without decreasing the pregnancy rate. The risk of high-order multiple pregnancy was best correlated with the number of good-quality embryos transferred. While all are at risk, patients younger than 40 were at highest risk.

Adult↗
PubMed1996

Spatial distribution of femoral bone mineral in dual energy X-ray absorptiometry images: a possible technique to improve discrimination between normal and osteoporotic patients.

The measurement of bone mineral density (BMD) using dual energy X-ray absorptiometry (DXA) provides an indicator of subsequent risk of hip fracture, but because of the significant overlap of measurements obtained from osteoporotic and control groups its predictive power is limited. The radiographic technique of Singh grading for the assessment of femoral osteoporosis utilizes information about the distribution of trabecular bundles, but the morphological information available in the DXA image has not previously been analysed. In this study of DXA images from 64 individuals (32 controls and 32 classified as osteoporotic) a subjective grading technique analogous to Singh grading is proposed, and quantitative measurements are made of image features corresponding to two of the categories. Discrimination was assessed using receiver operating characteristic (ROC) curves: the best discrimination was by spinal BMD (Az = 0.85 +/- 0.05) a performance equalled by one of the new parameters; the subjective grading method (Az = 0.79 +/- 0.07) performed as well as measurements of BMD in the femur. These results suggest that although the alternative measures do not improve on the discrimination possible using spinal BMD, morphological information from the hip itself may in the future have a place in the assessment of bone quality.

Absorptiometry, Photon↗
PubMed1994

Comparison of changes in bone mineral in idiopathic and secondary osteoporosis following therapy with cyclical disodium etidronate and high dose calcium supplementation.

OBJECTIVE: Our clinical practice has been to offer treatment with cyclical disodium etidronate and high dose calcium supplements (1500-1600 mg/day) to all female patients with osteoporosis who are unable or unwilling to take hormone replacement therapy (HRT), and male osteoporotics. In a retrospective study we compared the effect of this treatment on measures of bone mineral over a 12-month period in women with post-menopausal and secondary osteoporosis. We also assessed its effects in 10 male osteoporotics. DESIGN: A retrospective analysis of 83 consecutive patients with osteoporosis who completed 12 months of treatment with disodium etidronate and calcium and who had a dual energy X-ray absorptiometry (DEXA) scan at baseline and following 12 months of therapy. PATIENTS: The study included 73 women (45 post-menopausal and 28 secondary osteoporotics) and 10 men with established osteoporosis as shown by spinal and femoral bone mineral densities (BMD) > 2 standard deviations (SD) below young normals, and radiological evidence of osteoporosis. MEASUREMENTS: Each patient had routine biochemistry at baseline, an X-ray of thoracic and lumbar spine and a DEXA scan of lumbar spine (L2-L4) and femoral neck. The DEXA scan was repeated following 12 months of therapy. RESULTS: There was no difference between increase in spinal BMD in the post-menopausal (5.7%) versus secondary osteoporotic group (6.7%). There was a significant increase in spinal BMD at 12 months in the 10 male osteoporotics (9.0%, P < 0.01). No overall change in femoral neck BMD was noted. CONCLUSIONS: Cyclical disodium etidronate given with high dose calcium supplements is equally effective in increasing spinal bone mineral density in post-menopausal and secondary osteoporosis. It also results in a significant rise in spinal bone mineral density in male osteoporotics. Whether this produces a reduction in fracture rates is unknown.

Bone Density↗
PubMed1993

The mutator mut7-1 of Saccharomyces cerevisiae.

The mut7-1 mutant of Saccharomyces cerevisiae is a cell-division-cycle mutant, exhibiting temperature-sensitive lethality and enhancement of mutator activity with increases in temperature. The base-sequence alterations in mutants arising in a mut7-1 background differed from the control by there being a higher transversion/transition ratio and by the much increased production of multi-base deletions. The deletions were, in every instance, associated with repeated oligonucleotide sequences (3-8 bases in length), where one of the two sequences was removed during the deletion process. The mutant mut7-1 failed to complement with cdc2, the temperature-sensitive mutant of the locus which encodes DNA polymerase III (delta).

Base Sequence↗
PubMed1993

Bone mineralisation, body fat and anthropometric measurement in mothers delivering preterm.

Twenty mothers of preterm babies who had survived to 1 year old, were matched for age and parity of the mother and time of birth of the baby, with 20 mothers delivering fullterm. Bone mineral, body composition and anthropometric measurements were obtained for each mother and analysed using paired t-tests. The only significant difference (P < 0.01) between the groups was a lower fat-free mass in the preterm mothers calculated from skinfold thickness measurements.

Adipose Tissue↗
PubMed1993

Estimation of body composition from bioelectrical impedance of body segments: comparison with dual-energy X-ray absorptiometry.

In twenty-eight healthy subjects, ten men and eighteen women, with a range in body mass index (BMI) of 17.9-31.6 kg/m2 and an age range 20-60 years, body composition was estimated by dual-energy X-ray absorptiometry (DEXA), skinfold anthropometry (SFA) and bioelectrical impedance analysis (BIA) of the 'whole body' and body segments. In thirteen subjects muscle mass was also estimated by 24 h urinary creatinine excretion. The relationship between fat-free mass (FFM) determined by DEXA and the impedance index of each body segment (calculated as length2/impedance (Z)) was analysed. The strongest correlation was between FFM (DEXA) and height2/'whole-body' Z (ZW) (r 0.97 for the combined sexes, standard error of estimate (SEE) 2.72 kg). Separate prediction equations were found to be necessary for males and females when estimating FFM from BIA measurement of the arm (for men, r 0.93, SEE 1.98 kg; for women, r 0.75, SEE 2.87 kg). Muscle mass derived from 24 h creatinine excretion showed weak correlation with FFM (DEXA) (r 0.57, P = 0.03) and no correlation with FFM (SFA). FFM (SFA) correlated well with both FFM (DEXA) (r 0.96, SEE = 3.12 kg) and with height2/ZW (r 0.92, SEE 4.52 kg). Measurement of the impedance of the arm offers a simple method of assessing the composition of the whole body in normal individuals, and it appears comparable with other methods of assessment.

Absorptiometry, Photon↗
PubMed1993

Primary generalized osteoarthritis and bone mass.

The association of OA with increased bone mass is controversial. This study measured BMD at the hip and spine and total body bone mineral (TBBM) by dual energy X-ray absorptiometry, and BMD at the distal forearm by single photon absorptiometry in 20 post-menopausal women with primary generalized OA. The data were compared with those from 89 normal controls. Osteoarthritic women had significantly increased BMD at the spine (P < 0.001), distal forearm (P < 0.05) and increased TBBM (P < 0.01), but no difference was seen at the femoral neck. These differences were not explained by obesity. The influence of mobility is discussed.

Aged↗
PubMed1993

Variation in lumbar spine and femoral neck bone mineral measured by dual energy X-ray absorption: a study of 329 normal women.

Reference ranges used in dual energy X-ray absorptiometry (DXA) have previously used piecewise linear fits to the whole data set for spine or femur bone mineral density (BMD) as a function of age. In a study of 329 Caucasian normal women we present a refinement to the normal range by fitting straight lines between quinquennial mean values of BMD for each site measured (lumbar spine, femoral neck and Ward's triangle). From the age of 40 years onwards the premenopausal women demonstrated minimal loss of BMD whereas postmenopausal women showed a rapid loss amounting to 27% in the lumbar spine, 27% in the femoral neck and 38% in the Ward's triangle region in the age range under examination. Comparison of quinquennial means for pre and postmenopausal women in age bands 45-49 years and 50-54 years shows that at these ages postmenopausal BMD is significantly lower than premenopausal BMD (P < 0.05). This finding suggests that separate normal ranges should be used for pre and postmenopausal women. As reduction in the production of oestrogen is a major factor in postmenopausal bone loss and oestrogen function is related to years since menopause (YSM), a more logical way of displaying postmenopausal normal BMD ranges would be in terms of YSM rather than chronological age. Such data are given in this paper.

Absorptiometry, Photon↗
PubMed1992

Bone ultrasonic attenuation in women: reproducibility, normal variation and comparison with photon absorptiometry.

The reproducibility of two methods of measuring broadband ultrasonic attenuation (BUA) in the calcaneus have been studied. An improvement in reproducibility in vivo from 9.6% to 2.8% between old and new techniques has been observed. Measurements of the calcaneus using BUA were correlated with measurements of bone mineral density measured by dual energy x-ray absorptiometry in the lumbar spine, femur and total body and bone mineral content in the distal and proximal forearm measured by single photon absorptiometry. For the older BUA technique the correlation coefficients ranged between r = 0.27 and r = 0.34. For the newer BUA technique the correlation coefficients ranged between r = 0.49 and r = 0.62 and were all significant (P less than 0.001).

Absorptiometry, Photon↗
PubMed1992

Comparison of measures of body composition in a trial of low dose growth hormone replacement therapy.

OBJECTIVE: We assessed the effects of the administration of low dose growth hormone in growth hormone deficient adults on body composition and physical performance. We compared the validity of different measures of body composition in GH treated adults. DESIGN: An uncontrolled longitudinal study of eight patients with GH deficiency who were treated with 4 units of biosynthetic growth hormone (Norditropin), three times a week. Subjects were studied for 8 weeks. PATIENTS: Eight patients with acquired growth hormone deficiency as defined by < 5 mU/l GH following standard provocative investigations in whom other hormone replacement was optimized. MEASUREMENTS: IGF-I was measured on day 1 and after 4 and 8 weeks of treatment with recombinant human growth hormone. Body composition was estimated by dual energy X-ray absorptiometry, bioelectrical impedance, skinfold anthropometry, total body potassium measurement and by computerized tomography of a representative cross-sectional area of thigh on day 1 and following 8 weeks of treatment. Exercise capacity was measured on an electromechanical bicycle and palmar grip strength was measured using a Jamar dynamometer on day 1 and after 8 weeks. RESULTS: IGF-I increased significantly. Exercise capacity and maximum heart rate achieved on the electromechanical bicycle increased significantly. Grip strength did not change. There was a significant increase in fat-free mass and a decline in fat mass as shown by dual energy X-ray absorptiometry and bioelectrical impedance. However, this was not confirmed by other methods. No side-effects were noted. CONCLUSIONS: This study shows that a low dose of biosynthetic growth hormone can elevate IGF-I levels and have a pronounced physical impact in the growth hormone deficient adult without the side-effects seen at higher dosage schedules. Over a 2 month period the increase in fat-free mass may be due to an increase in total body water; however, the decline in fat mass is a genuine effect.

Absorptiometry, Photon↗
PubMed1988

The master patient index: split patient records.

Systems integrators have overlooked the potential for corrupting the medical-record database through the creation of multiple (split) records for the individual patient. This article introduces a computer software technology that has been used at the University of California, San Francisco (UCSF) Medical Center to identify split patient records.

California↗