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Biomedical subjects

M Simpson

Publications and source records attributed to M Simpson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Body composition analysis in liver cirrhosis. The measurement of body fat by dual energy X-ray absorptiometry in comparison to skinfold anthropometry, bioelectrical impedance and total body potassium.

In this cross-sectional study of methods to determine total body fat in patients with abnormal body composition secondary to chronic liver disease, we have demonstrated that TBFDXA by four-site skinfold anthropometry was highly correlated to TBFDXA, with small SEE and no bias in patients with ascites, but a small and significant bias in patients without ascites. TBFBIA showed no bias but a weaker correlation with a large SEE. In the presence of fluid retention the correlation coefficient decreased. TBFTBK showed a highly significant bias, and the correlation was not as good as SFA, and decreased in the presence of fluid retention.

Absorptiometry, Photon↗
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

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

Tryptophan perturbation in the L intermediate of bacteriorhodopsin: fourier transform infrared analysis with indole-15N shift.

In the photoreaction of bacteriorhodopsin, the L intermediate shows an intense band at 3486 cm-1 which is unaffected by 2H2O (Maeda, A., Sasaki, J., Shichida, Y., & Yoshizawa, T. (1992) Biochemistry 31, 462-467]. This band is shifted to 3477 cm-1 by [indole-15N]tryptophan substitution and therefore is assigned to the N-H stretching vibration of the indole of tryptophan. Free indole in carbon tetrachloride shows its N-H stretching vibration at 3491 cm-1 [Fuson, N., Josien, M.-L., Powell, R. L., & Utterback, E. (1952) J. Chem. Phys. 20, 145-152]. Thus, it is suggested that at least one tryptophan residue in the L intermediate is not hydrogen bonded.

Bacteriorhodopsins↗
PubMed1992

Relationship between bond strength and microleakage measured in the same Class I restorations.

Microleakage measurements were made by use of a pressurized fluid method in Class I restorations prepared in extracted human teeth just prior to measuring the tensile bond strengths of the same restorations. The restorative materials included dentin bonding systems that are applied to smear layers as well as those which remove the smear layer. A light-cured glass-ionomer cement was also included. The results demonstrated that there was an inverse relationship between dentin bond strength and microleakage in some materials and that the bond strengths made to three-dimensional Class I cavities were much lower than those made to flat dentin surfaces. Measurement of microleakage by fluid filtration had no apparent effect on bond strength.

Adhesives↗
PubMed1992

In vitro permeability of furcation dentin in permanent teeth.

Extracted unerupted permanent third molars with the occlusal half of the crown and apical half of the roots removed were cemented to Plexiglas blocks. Using a positive pressure system in which the movement of fluid across the dental tubules could be measured, the permeability of furcation dentin was measured before and after alteration of the furcation thickness. Subsequently, measurements of reduction in thickness of cementum and dentin were performed. Furcation dentin permeability was found to increase as the cementum and dentin thickness was reduced and the smear layer removed. The permeability values obtained for the furcation dentin were similar to those found in radicular dentin in general, indicating that root dentin has a low permeability and that it has good barrier properties. The data would suggest that any bone resorption seen under the furcation region of permanent molars is more likely to be due to the presence of accessory canals than due to permeation directly through furcation hard tissues.

Adolescent↗
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

Comparative pharmacokinetics of zidovudine in healthy volunteers and in patients with AIDS with and without hepatic disease.

To understand whether disease caused by the human immunodeficiency virus (HIV) affects zidovudine disposition, we compared the drug's pharmacokinetics in six healthy volunteers; six persons with the acquired immunodeficiency syndrome (AIDS) and no evidence of gastrointestinal (nausea, vomiting, diarrhea), renal (elevated blood urea nitrogen, serum creatinine), or hepatic (elevated liver function tests) disease; and three patients with AIDS and hepatic disease. After a single oral dose of zidovudine, serial blood samples were analyzed for drug concentration by radioimmunoassay. A one-compartment oral absorption model was fit to the concentration-time data. The absorption rate constant (4.05 vs 2.11 hr-1) and time to maximum concentration (0.61 vs 1.03 hr) were significantly different in healthy volunteers versus patients with AIDS without hepatic disease. Differences in half-life, oral clearance, and area under the curve were not statistically significant. In the three patients with AIDS plus hepatic disease, clearance was reduced an average of 63%, and area under the curve was increased by a factor of 2.3. These comparative pharmacokinetic data do not support profound differences between zidovudine's disposition in healthy volunteers and individuals with AIDS; however, the differences and trends that were observed may represent an effect of HIV disease. Although the presence of hepatic disease clearly indicates a need to modify individual dosages, these pharmacokinetic data may have more generalized implications for zidovudine dosing as the relationships between drug concentration and therapeutic or toxic effects are clarified.

Absorption↗
PubMed1991

Working towards dependency scoring in critical care.

One of the main disadvantages of dependency scoring in the intensive care unit, is that popular scoring systems such as the Intensive Care Register (ICR) fail to take into account many of the most important factors that contribute to patient dependency. Factors such as counselling of patients and their families, setting up for certain procedures and dealing with an agitated patient, for example, all contribute to the overall dependency of the patients; and ultimately influence the level of nursing support required. It is with these thoughts in mind that a system of dependency scoring has been developed for the intensive care unit (ICU). The system outlined here is designed to be used in conjunction with the ICR, thus providing a more accurate and realistic measure of dependency; while still maintaining a vital link to a well established system.

Consciousness↗
PubMed1991

Measurement of dentin permeability and wetness by use of the Periotron device.

The ability of the Periotron device to measure changes in dentin permeability and wetness was evaluated by use of extracted human teeth in vitro. Pulpal pressures were varied from zero to 40 cm H2O for simulation of different pulpal tissue pressures. Non-physiologic pulpal pressures of 703 cm H2O were used for comparison of dentin permeability measurements made with the Periotron device with those made using micropipettes. Measurements made with the Periotron device correlated well with methods used previously for measurement of dentin permeability. The shear bond strength of Scotchbond 2/Silux was measured 24 h after being bonded to dentin held at zero pulpal pressure. There was an inverse correlation between the shear bond strengths of Scotchbond 2/Silux and Periotron values, suggesting that increased wetness decreases the bond strength of that system. The Periotron device offers a new, simple, convenient measure of dentin surface wetness which may be useful in dentin bonding studies.

Adhesiveness↗
PubMed1990

Human immunodeficiency virus type 1 detected in all seropositive symptomatic and asymptomatic individuals.

Between February 1987 and October 1988, peripheral mononuclear blood cells (PBMC) from 409 adult individuals antibody positive by Western (immuno-)blot for human immunodeficiency virus type 1 (HIV-1) (56 acquired immunodeficiency syndrome [AIDS] patients, 88 patients with AIDS-related complex, and 265 asymptomatic individuals) were consecutively cultured for HIV-1 or tested for the presence of HIV-1 DNA sequences by a polymerase chain reaction assay (PCR). We isolated HIV-1 or detected HIV-1 DNA sequences from the PBMC of all 409 HIV-1 antibody-positive individuals. None of 131 healthy HIV-1 antibody-negative individuals were HIV-1 culture positive, nor were HIV-1 DNA sequences detected by PCR in the blood specimens of 43 seronegative individuals. In addition, HIV-1 PCR and HIV-1 culture were compared in testing the PBMC of 59 HIV-1 antibody-positive and 20 HIV-1 antibody-negative hemophiliacs. Both methods were found to have sensitivities and specificities of at least 97 and 100%, respectively. In contrast, the sensitivities of serum HIV-1 antigen testing in AIDS patients and asymptomatic seropositive patients were 42 and 17%, respectively. Our ability to directly demonstrate HIV-1 infection in all HIV-1 antibody-positive individuals provides definitive support that HIV-1 antibody positivity is associated with present HIV-1 infection. Moreover, the sensitivities and specificities of PCR and culture for the detection of HIV-1 appear to be equivalent, and both methods are superior to testing for HIV-1 antigen in serum for the direct detection of HIV-1.

AIDS-Related Complex↗
PubMed1990

Intertrochanteric femoral fractures. Mechanical failure after internal fixation.

In a prospective study we assessed the causes of mechanical failure in a series of 230 intertrochanteric femoral fractures which had been internally fixed with either a sliding hip screw or a Küntscher Y-nail. The overall rate of mechanical failure was 16.5%; cutting-out of the implant from the femoral head was the cause in three-quarters of the instances. Implants placed posteriorly in the femoral head cut out more often (27%) than those placed centrally (7%). The cut-out rate was also determined by the quality of the fracture reduction, but age, walking ability and bone density (assessed by the Singh grade and metacarpal indices) had no significant influence. We conclude that these fractures should be reduced as accurately as possible and it is imperative that the implant is placed centrally within the femoral head.

Aged↗
PubMed1990

Immunoassays and nucleic acid detection with a biosensor based on surface plasmon resonance.

A technique based on surface plasmon resonance is described which can be used to detect changes of refractive index that occur when one partner of a molecular binding pair diffuses from solution to bind the other partner which is immobilised on a silver surface. Results for the molecular binding pairs; protein-antibody, hapten-antibody and DNA-DNA are described. Instrumentation necessary for implementation of the technique is detailed. Immunoassay of proteins and haptens is possible in less than one minute with a sensitivity of 10(-9) mol/l. Hybridisation of 10 fmoles of a 97 base target sequence on the 1 mm2 area of detection to an immobilised oligonucleotide probe can be detected in less than five minutes. Advantages of the technique include the ability to record the kinetics of binding reactions in "real time" and the lack of labels in this simple assay format. Methods of improving the sensitivity are discussed.

Animals↗
PubMed1989

Malignant fibrous histiocytoma in a cat.

A large proliferative soft tissue mass found on the forelimb of an adult cat was identified as a malignant fibrous histiocytoma through cytologic and histologic examinations. This is a rare tumor of mesenchymal cell origin, which has been previously reported in cats, dogs, horses, and human beings. In this cat metastasis to the local lymph node was found.

Animals↗