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Biomedical subjects

M Taylor

Publications and source records attributed to M Taylor.

At least 37 records · Page 2Linked to original sources
PubMed2005

Characterisation of deep arterio-venous anastomoses within monochorionic placentae by vascular casting.

OBJECTIVE: To characterise arterio-venous anastomoses (AVA) in monochorionic (MC) placentae and determine (i) whether shared cotyledons lie beneath the co-termination of an artery from one twin and a vein to the contralateral twin and (ii) whether all AVA can be detected by visual inspection of the chorionic plate. METHODS: Vascular casts were made of 15 MC placentae. The number of typical AVAs suspected visually before digestion was compared with the number of AVAs identified after acid digestion. RESULTS: Thirty-three of 67 (49%) suspected typical AVAs were confirmed as typical after casting. There were five false positives and no false negatives. The remainder were classified as atypical AVAs, found in > or =90% of MC placentae. Type I (small vascular connections between two apparently normal cotyledons not seen before casting) and Type II (shared cotyledons arising within larger apparently normal cotyledons) atypical AVAs were found in 53% and 73% of placentae, respectively. CONCLUSIONS: Only half the shared cotyledons in MC placentae are characterised by co-termination of an artery and vein on the chorionic plate. We report the existence of deep anastomoses beneath the chorionic plate that cannot be visualised by chorionic plate inspection. These findings have implications for laser treatment of twin-twin transfusion syndrome.

Adult↗
PubMed2005

Evaluation by respirometry of the degradability of retort water using a shale ash and overburden packed column.

Oil shale processing produces an aqueous wastewater stream known as retort water. The fate of the organic content of retort water from the Stuart oil shale project (Gladstone, Queensland) is examined in a proposed packed bed treatment system consisting of a 1:1 mixture of residual shale from the retorting process and mining overburden. The retort water had a neutral pH and an average unfiltered TOC of 2,900 mg 1(-1). The inorganic composition of the retort water was dominated by NH4+. Only 40% of the total organic carbon (TOC) in the retort water was identifiable, and this was dominated by carboxylic acids. In addition to monitoring influent and effluent TOC concentrations, CO2 evolution was monitored on line by continuous measurements of headspace concentrations and air flow rates. The column was run for 64 days before it blocked and was dismantled for analysis. Over 98% of the TOC was removed from the retort water. Respirometry measurements were confounded by CO2 production from inorganic sources. Based on predictions with the chemical equilibrium package PHREEQE, approximately 15% of the total CO2 production arose from the reaction of NH4+ with carbonates. The balance of the CO2 production accounted for at least 80% of the carbon removed from the retort water. Direct measurements of solid organic carbon showed that approximately 20% of the influent carbon was held-up in the top 20cm of the column. Less than 20% of this held-up carbon was present as either biomass or as adsorbed species. Therefore, the column was ultimately blocked by either extracellular polymeric substances or by a sludge that had precipitated out of the retort water.

Biodegradation, Environmental↗
PubMed2005

Beating the barriers: recruitment of people with intellectual disability to participate in research.

BACKGROUND: The health status of people with intellectual disability (ID) is poor, yet very little research has been done on their health needs. There are several barriers to performing this research. The aim of our research was to examine the significant barriers encountered in recruiting adults with ID to participate in research. METHODS: Our project was a randomized controlled trial aiming to improve health advocacy of people with ID. We approached many organizations to recruit participants and kept records of our results. Recruitment was very low for the first 4 months. Then we adopted two new recruitment strategies--in-service telephone recruitment and meetings with prospective participants. We then monitored the subsequent recruitment rates. We also questioned participants about the difficulties they encountered when considering recruitment. RESULTS: Initial recruitment of participants yielded less than one-third of the expected number. Additional strategies implemented were partially successful. Significant barriers to recruitment included several sectoral issues and the challenges arising from the research process. CONCLUSIONS: While this population is a difficult one to reach for research, attempts to do so should not be abandoned, because the potential health benefits for this underserved group far outweigh the recruitment barriers experienced.

Adult↗
PubMed2005

Colorectal cancer audit: a comparative study before and after establishing a specialty colorectal surgery unit.

OBJECTIVE: A prospective audit was kept for colorectal cancer after the establishment of a special-interest colorectal unit at a Melbourne metropolitan teaching hospital. METHODS: These data were compared with data collected retrospectively on surgical management of colorectal cancer by general surgeons in the hospital. RESULTS: The groups were well matched with respect to age, sex, pathological staging and elective vs urgent surgery. Differences were found in postoperative length of stay (9 vs 12 days, P = 0.01) in favour of the colorectal special interest group. Differences were found in the permanent stoma rate with regard to rectal cancer with the colorectal special interest group having a lower permanent stoma rate. CONCLUSION: Specialisation improved the results of treatment.

Acute Disease↗
PubMed2005

Atypical anti-psychotics in the real world--a naturalistic comparative outcome study.

BACKGROUND: There are few real life independent comparative studies of atypical antipsychotics. We prospectively examined five commonly used atypical antipychotics in the UK, without support from the pharmaceutical industry. METHOD: Prospective naturalistic systematic clinical evaluation. Patients being newly prescribed atypical anti-psychotics over a one year period were assessed by psychiatrists at initiation and after six months treatment using five outcome measures: clinical global impression; positive and negative psychotic symptoms; drug related side effects; and quality of life. RESULTS: 373 patients participated in total. Olanzapine and risperidone produced statistically significant reductions in all ratings at six months. Amisulpride, clozapine, and quetiapine were also studied. There was limited variance between the different drugs, although some sample sizes were small. CONCLUSION: Atypical anti-psychotics were found to be clinically effective, and produced similar outcomes. Routine monitoring of outcomes in psychiatry is feasible.

Adolescent↗
PubMed2005

Effect of bone material properties on the initial stability of a cementless hip stem: a finite element study.

In previous finite element studies of cementless hip stems reported in the literature, the effect of bone quality on the initial micromotion and interface bone strain has been rarely reported. In this study, the effect of varying cortical and cancellous bone modulus on initial stem micromotion and interface bone strain was examined and the potential consequence of these changes on bone ingrowth and implant migration was reported. A finite element (FE) model of a total hip replacement (THR) was created and the Young's moduli of cortical and cancellous bone were systematically varied to study the relative effect of the quality of both types of bone on the initial stability of a cementless THR. It was found that the initial micromotion and interface bone strain in a THR was significantly affected by the overall stiffness of the femur. In other words, both the reduction of the modulus of cortical and cancellous bone caused an increase in the initial micromotion and interface bone strain. This suggests that for FE studies to be truly predictive, a range of bone quality must be examined to study the performance envelope of a particular stem and to allow comparison with clinical results.

Arthroplasty, Replacement, Hip↗
PubMed2005

Effect of hip stem taper on cement stresses.

The aim of this study was to use finite element models to investigate the effect of the design of the taper of polished, collarless, total hip replacement femoral components on stresses in the cement mantle surrounding the component. A single-taper prosthesis, double-taper prosthesis, and triple-taper prosthesis were compared. Peak stresses and stress distributions in the cement mantle were found to be a function of taper design, although the differences between designs were minor. Using a probability of failure technique based on the initial cement stress distribution, a triple-taper prosthesis was predicted to cause less cement mantle damage (0.15% of the volume of the cement mantle failing after 20 million loading cycles) than a double-taper prosthesis (0.74%) or a single-taper prosthesis (1.50%). Further research is required to confirm this finding.

Bone Cements↗
PubMed2004

Quantitation of circulating DNA in the serum of breast cancer patients by real-time PCR.

The purpose of this study was to quantify the level of serum DNA in different groups of primary breast cancer patients and in healthy controls using real-time quantitative PCR in order to determine whether such measurements have diagnostic or prognostic value. A total of 96 serum samples of patients with primary breast cancer before surgery (with positive or negative lymph nodes and with high or low relapse-free survival) as well as 24 healthy controls were analysed. DNA concentrations in the serum of the patients differed significantly from the concentration of serum DNA in the controls (medians were 221 and 63 ng x ml(-1), respectively, P<0.001 M-W test). However, no statistically significant difference was observed between the patient groups (P=0.87, M-W test). The serum DNA levels were elevated independently of the size of primary tumour or lymph node metastases. The overall survival of patients with serum DNA concentrations >221 ng x ml(-1) was better than patients with serum DNA concentration <or=221 ng ml(-1) (Kaplan-Meier, P=0.028).

Adult↗
PubMed2004

Mathematical modelling of skeletal repair.

Tissue engineering offers significant promise as a viable alternative to current clinical strategies for replacement of damaged tissue as a consequence of disease or trauma. Since mathematical modelling is a valuable tool in the analysis of complex systems, appropriate use of mathematical models has tremendous potential for advancing the understanding of the physical processes involved in such tissue reconstruction. In this review, the potential benefits, and limitations, of theoretical modelling in tissue engineering applications are examined with specific emphasis on tissue engineering of bone. A central tissue engineering approach is the in vivo implantation of a biomimetic scaffold seeded with an appropriate population of stem or progenitor cells. This review will therefore consider the theory behind a number of key factors affecting the success of such a strategy including: stem cell or progenitor population expansion and differentiation ex vivo; cell adhesion and migration, and the effective design of scaffolds; and delivery of nutrient to avascular structures. The focus will be on current work in this area, as well as on highlighting limitations and suggesting possible directions for future work to advance health-care for all.

Animals↗
PubMed2004

Muscle LIM protein promotes expression of the acetylcholine receptor gamma-subunit gene cooperatively with the myogenin-E12 complex.

Muscle LIM protein (MLP, also referred to as CRP3) is a muscle-specific LIM-only protein, which consists of two LIM motifs. MLP functions as a positive regulator during myogenesis. Here we report that MLP serves as a cofactor regulating the expression of the nicotinic acetylcholine receptor (AChR) gamma-subunit gene in skeletal muscle cells. We found that MLP promoted the expression of the AChR gamma-subunit gene in C2C12 myotubes, but not in C2C12 myoblasts or NIH3T3 fibroblasts. Furthermore, we showed that MLP interacted with myogenin in vivo and enhanced the binding ability of the myogenin-E12 heterodimer to the E boxes in the AChR gamma-subunit gene promoter. Together, these results suggest that MLP promotes the specific expression of the AChR gamma-subunit gene cooperatively with the myogenin-E12 complex during myogenesis.

Animals↗
PubMed2004

A combined RSA and FE study of the implanted proximal tibia: correlation of the post-operative mechanical environment with implant migration.

There is strong evidence to suggest that inducible displacements, migration and implant loosening are closely related to the initial mechanical environment of the implanted tibia. If this is true, then it should be possible to predict the likelihood of implant migration using patient-specific finite element models. Finite element models of the proximal implanted tibiae were analysed based on pre-operative quantitative computed tomography data of four patients entered into a radiographic migration study. These four patients were also part of an radiostereometric analysis (RSA) study. A variety of load cases were analysed and the risk of bone failure determined for a 2 mm layer of bone immediately beneath the tibial tray. The results were compared with the RSA data measured 1 year post-operatively for each patient. For each patient, an appropriate load case was selected based on patient weight and on the varus-valgus migrations observed in the migration study. The two patients with press-fit implants were predicted to have the highest risk of failure and were found to migrate the most. The two patients with bonded implants (one HA coated and one cemented) were found to have a low risk of failure and these implants migrated the least. This study suggests that the degree of implant migration is dependent on the initial mechanical environment and can be determined using patient-specific finite element analysis.

Aged↗
PubMed2004

Three-dimensional finite element modelling of the human ACL: simulation of passive knee flexion with a stressed and stress-free ACL.

In this study, a three-dimensional finite element model of the human anterior cruciate ligament (ACL) was developed and simulations of passive knee flexion were performed. The geometrical model of the ACL was built from experimental measurements performed on a cadaveric knee specimen which was also subjected to kinematics tests. These experiments were used to enforce the particular boundary conditions used in the numerical model. A previously developed transversely isotropic hyperelastic material model was implemented and the ability to pre-stress the ligament was also included. The model exhibited the key characteristics of connective soft tissues: anisotropy, nonlinear behaviour, large strains, very high compliance for compressive or bending loading along the collagen fibres and incompressibility. Simulations of passive knee flexion were performed, with and without pre-stressing the ACL. The resultant force generated by the ACL was monitored and the results compared to existing experimental data. The stress distribution within the ligament was also assessed. When the ACL was pre-stressed, there was a good correlation between the predicted and experimental resultant forces reported in the literature over the entire flexion-extension range. The stress distribution in the pre-stressed and stress-free ACL were similar, although the magnitudes in the pre-stressed ACL were higher, particularly at low flexion angles.

Anterior Cruciate Ligament↗
PubMed2004

Derivation of rate of arterio-arterial anastomotic transfusion between monochorionic twin fetuses by Doppler waveform analysis.

We aimed to determine rates of interfetal transfusion along arterio-arterial (AA) anastomoses in monochorionic twins in vivo from analysis of Doppler waveform patterns. Twenty-one monochorionic twin pregnancies in which an AA anastomosis was identified antenatally underwent serial Doppler velocimetry. Unidirectional AA anastomotic flow rates increased with increasing gestational age (log y = 8 x 10(-9)x - 5 x 10(-8); p = 0.0002). The mean net rate of flow through an AA anastomosis at 28 weeks gestation was 7.6 x 10(-8) l/s (SD = 4.9 x 10(-8) l/s). This flow was significantly related to the distribution of arterio-venous (AV) anastomoses (p = 0.009) and birthweight discordancy (p = 0.006). We derived estimates of flow along individual AV anastomoses by assuming that net AA countertransfusion is shared equally among uncompensated AV anastomoses, and speculate that the median AV flow rate at 28 weeks is in the order of 6 x 10(-8) l/s. In conclusion, this study demonstrates that flow rates along AA anastomoses can be quantified antenatally. These are the first estimates of flow rates in vivo along placental anastomoses. Although AA net flows are modest, chronic unbalanced counterflow of this magnitude in the absence of compensatory superficial anastomoses could lead to significant haemodynamic compromise.

Arteries↗
PubMed2004

Application of an interface failure model to predict fatigue crack growth in an implanted metallic femoral stem.

A novel computational modelling technique has been developed for the prediction of crack growth in load bearing orthopaedic alloys subjected to fatigue loading. Elastic-plastic fracture mechanics has been used to define a three-dimensional fracture model, which explicitly models the opening, sliding and tearing process. This model consists of 3D nonlinear spring elements implemented in conjunction with a brittle material failure function, which is defined by the fracture energy for each nonlinear spring element. Thus, the fracture energy criterion is implicit in the brittle material failure function to search for crack initiation and crack development automatically. A degradation function is employed to reduce interfacial fracture properties corresponding to the number of cycles; thus fatigue lifetime can be predicted. Unlike other failure modelling methods, this model predicts the failure load, crack path and residual stiffness directly without assuming any pre-flaw condition. As an example, fatigue of a cobalt based alloy (CoCrMo) femoral stem is simulated. Experimental fatigue data was obtained from four point bending tests. The finite element model simulated a fully embedded implant with a constant point load. Comparison between the model and mechanical test results showed good agreement in fatigue crack growth rate.

Femur↗
PubMed2004

Fatigue characterization of a polymer foam to use as a cancellous bone analog material in the assessment of orthopaedic devices.

Analog materials are used as a substitute to cancellous bone for in vitro biomechanical tests due to their uniformity, consistency in properties and availability. To date, only the static material properties of these materials have been assessed, although they are often used in fatigue tests. Cancellous bone exhibits complex material behavior when subjected to fatigue loads, including modulus degradation, accumulation of permanent strain and increasing hysteresis. Analog materials should exhibit similar fatigue behavior to cancellous bone if they are to be used in cyclic loading tests. In our study, a polymer foam (commercial name HEREX C70.55) has been studied for its static and fatigue behavior and compared with that of cancellous bone. In compression, the foam exhibited qualitatively similar mechanical behavior, but the degree of modulus degradation and accumulation of permanent strain was lower than expected for cancellous bone. In general, the tensile properties of the foam were greater than found in compression, the opposite to the mechanical behavior of cancellous bone. The methodology employed here could form the basis of selecting suitable analog materials for cancellous bone in the future.

Biomechanical Phenomena↗
PubMed2004

Investigating the mental abilities of rural Zulu primary school children in South Africa.

INTRODUCTION: Maximising the full potential of health and educational interventions in South African schools requires assessment of the current level of mental abilities of the school children as measured by cognitive and scholastic tests and the identification of any barriers to improved performance. OBJECTIVES: This study reports on the application and interpretation of a selected battery of mental ability tests among Zulu school children and the methodological and analytical issues that need to be addressed. DESIGN: The test scores of 806 primary school children from a rural community are presented, based on four tests: Raven's Coloured Progressive Matrices (CPM), an Auditory Verbal Learning Test (AVLT), the Symbol Digit Modalities Test (SDMT) and Young's Group Mathematics Test (GMT). RESULTS: Significant gender differences were found in the test scores, and the mean scores of Zulu children in this study were lower than those reported in other studies. The results of this selected test battery provide data for the further development of appropriate test instruments for South African conditions. CONCLUSION: These results can contribute towards the development of a test battery for South African children that can be used to assess and improve their school performance.

Child↗
PubMed2004

Colloquium report: improving the health of school age children in an era of HIV/AIDS in Durban, South Africa.

Increased morbidity and mortality due to the HIV/AIDS epidemic in South Africa necessitates the examination of policies for the protection and support of school age children. At a colloquium held in Durban participants from government and non-government health and education sectors briefed delegates on key policies and programmes for promoting the health and mental health of school age children. Researchers gave evaluative accounts of the impacts of these measures and presented an overview of South African children's health and mental health needs. In the discussions that followed four critical issues emerged: intersectoral collaboration, accountability, retraining middle management, and a more comprehensive strategy to support pupils and teachers infected and affected by HIV/AIDS.

Acquired Immunodeficiency Syndrome↗