PubMed Health⌕ Search

Biomedical subjects

Simon J Walsh

Publications and source records attributed to Simon J Walsh.

At least 19 recordsLinked to original sources
PubMed2006

Population data from sub-populations of the Northern Territory of Australia for 15 autosomal short tandem repeat (STR) loci.

It is a requirement that forensic DNA profiling evidence be accompanied by an estimation of its weight, in order that the court can assign an appropriate probative value to the evidence during legal proceedings. There are various models by which this estimation can be made, but each relies on approximations of the allele frequencies in the relevant population. It is also important to assess relevant population genetic features of the available data. This report provides allele frequencies and estimates of common population genetic parameters for the major sub-populations of the Northern Territory of Australia genotyped at 15 autosomal short tandem repeat (STR) loci.

Australia↗
PubMed2006

How reliable is the sub-population model in DNA testimony?

The performance of the sub-population model first proposed by Balding and Nichols [D.J. Balding, R.A. Nichols, DNA profile match probability calculation: how to allow for population stratification, relatedness, database selection and single bands. Forensic Sci. Int. 64 (1994) 125-140] is examined using a simulation approach. This work extends the investigations of Curran et al. [J.M. Curran, J.S. Buckleton, and C.M. Triggs, What is the magnitude of the sub-population effect? Forensic Sci. Int. 135 (2003) 1-8]. In particular the effect of underestimating the coancestry coefficient, theta, and the effect of departures from the modelling assumptions were investigated. The model tends to give strongly conservative estimates if the estimate for the coancestry coefficient is accurate. If this coefficient is underestimated then a larger fraction of cases give non-conservative estimates. Departures from the modelling assumption that the sub-population is in Hardy-Weinberg and linkage equilibria appear to have very little effect.

Consanguinity↗
PubMed2006

Novel rectangular biphasic and monophasic waveforms delivered by a radiofrequency-powered defibrillator compared with conventional capacitor-based waveforms in transvenous cardioversion of atrial fibrillation.

AIMS: To investigate the feasibility and efficacy of novel low-tilt biphasic waveforms in transvenous cardioversion of atrial fibrillation (AF), delivered by a radiofrequency-powered defibrillator. METHODS AND RESULTS: The investigation was performed in three phases in an animal model of AF: a feasibility and efficacy study (in 10 adult Large White Landrace swine), comparison with low-tilt monophasic and standard capacitor-based waveforms, and an assessment of sequential shocks delivered over several pathways (in 15 adult Suffolk sheep). Defibrillation electrodes were positioned transvenously under fluoroscopic control in the high lateral right atrium and distal coronary sinus. When multiple defibrillation pathways were tested, a third electrode was also attached to the lower interatrial septum. The electrodes were then connected to a radiofrequency (RF)-powered defibrillator or a standard defibrillator. After confirmation of successful induction of sustained AF, defibrillation was attempted. Percentage success was calculated from the effects of all shocks delivered to all the animals within each set of experiments. Of the low-tilt (RF) biphasic waveforms delivered during internal atrial cardioversion, 100% success was achieved with a 6/6 ms 100/-50 V waveform (1.45+/-0.01 J). This waveform was similar in efficacy to low-tilt (RF) monophasic waveforms (88 vs. 92% success, 1.58+/-0.01 vs. 2.67+/-0.03 J; P=NS; delivered energy 41% lower) and superior to equivalent voltage standard monophasic (50% success, 0.67+/-0.00 J; P<0.001) and biphasic waveforms (72% success, 0.69+/-0.00 J; P=0.03). Sequential shocks delivered over dual pathways did not improve the efficacy of low-tilt biphasic waveforms. CONCLUSION: A low-tilt biphasic waveform from a RF-powered defibrillator (6/6 ms 100/-50 V) is more efficacious than standard monophasic or biphasic waveforms (equivalent voltage) and is similar in efficacy to low-tilt monophasic waveforms.

Animals↗
PubMed2006

Clopidogrel in the treatment of ischaemic heart disease.

Clopidogrel is an effective antiplatelet agent that has undergone rigorous assessment in the setting of ischaemic heart disease over the last decade. There is extensive evidence for the use of this drug in patients undergoing percutaneous coronary intervention, in those with stable ischaemic heart disease and also in those with acute coronary syndromes. This article examines the use of clopidogrel in patients with ischaemic heart disease.

Adolescent↗
PubMed2005

The role of biphasic shocks for transthoracic cardioversion of atrial fibrillation.

The modern generation of transthoracic defibrillators now employ impedance compensated biphasic waveforms. These new devices are superior to those with monophasic waveforms and practice is currently switching to biphasic defibrillators for the treatment of both ventricular and atrial fibrillation. However, there is no universal guideline for the use of biphasic defibrillators in direct current cardioversion of atrial fibrillation. This article reviews the use of biphasic defibrillation waveforms for transthoracic cardioversion of atrial fibrillation.

Journal Article↗
PubMed2005

The contribution of forensic science to crime analysis and investigation: forensic intelligence.

The debate in forensic science concentrates on issues such as standardisation, accreditation and de-contextualisation, in a legal and economical context, in order to ensure the scientific objectivity and efficiency that must guide the process of collecting, analysing, interpreting and reporting forensic evidence. At the same time, it is recognised that forensic case data is still poorly integrated into the investigation and the crime analysis process, despite evidence of its great potential in various situations and studies. A change of attitude is needed in order to accept an extended role for forensic science that goes beyond the production of evidence for the court. To stimulate and guide this development, a long-term intensive modelling activity of the investigative and crime analysis process that crosses the boundaries of different disciplines has been initiated. A framework that fully integrates forensic case data shows through examples the capital accumulated that may be put to use systematically.

Crime↗
PubMed2005

Impedance compensated biphasic waveforms for transthoracic cardioversion of atrial fibrillation: a multi-centre comparison of antero-apical and antero-posterior pad positions.

AIMS: To compare the success rate for transthoracic direct current cardioversion (DCC) of atrial fibrillation (AF) with antero-posterior (AP) and antero-apical (AA) electrode positions using an impedance compensated biphasic (ICB) waveform. METHODS AND RESULTS: Three-hundred and seven patients [mean age 66 (SD+/-13), 195 male] with AF were recruited in three centres. Patients were randomized to an AA (n=150) or AP (n=144) pad position. Thirteen patients with implanted pacemakers were defaulted to the AP pad position. Cardioversion was performed using an ICB waveform with a 70, 100, 150, and 200 J energy selection protocol. If the fourth shock was unsuccessful, the pads were crossed over to the alternative position for a final 200 J shock. Shock 1 was successful in 54/150 (36%) AA and 45/144 (31%) AP patients, whereas success was achieved by shock 2 in 99/150 (66%) AA and 74/144 (51%) AP, by shock 3 in 123/150 (82%) AA and 109/144 (76%) AP, and by shock 4 in 143/150 (95%) AA and 127/144 (88%) AP and after cross-over in 144/150 (96%) AA and 135/144 (94%) AP. Overall success rate was higher than expected at 95%. Pad position was not associated significantly with success. There was a trend towards an improved outcome with the AA configuration (P=0.05). CONCLUSION: The influence of pad position for DCC of AF may be less pertinent with ICB waveforms than with monophasic waveforms.

Aged↗
PubMed2005

Percutaneous coronary intervention and 1 year survival in patients treated with fibrinolytic therapy for acute ST-elevation myocardial infarction.

AIMS: To assess the predictors of 1 year mortality in patients treated with fibrinolytic therapy for ST-segment elevation myocardial infarction (STEMI) and to determine whether a strategy of early percutaneous coronary intervention (PCI) improves outcome. METHODS AND RESULTS: Consecutive patients (n = 474) admitted to our unit (1998-2001) with STEMI were treated with fibrinolytic therapy. For each patient, age, gender, admission via mobile coronary care unit (MCCU), infarct location, initial systolic blood pressure and Killip class, prior history of ischaemic heart disease, hypertension, diabetes mellitus, smoking status, family history, hyperlipidaemia, and in-hospital PCI (n = 154) were recorded. Mortality at 1 year was obtained from medical records (n = 473). Binary logistic regression analysis was performed to determine independent predictors of 1 year mortality. Mortality in the non-PCI group was 21 vs. 7% in the PCI group. Independent predictors of 1 year mortality were age (risk ratio 1.12, 95% CI 1.08-1.15, P < 0.0001), initial SBP < or = 80 mmHg (risk ratio 4.34, 95% CI 1.68-11.2, P = 0.002), initial Killip class > or = 3 (risk ratio 2.97, 95% CI 1.42-6.2, P = 0.004), and lack of in-hospital PCI (risk ratio 0.39, 95% CI 0.19-0.81, P = 0.012). Although the PCI group were younger (P = 0.007), more likely to be admitted via the MCCU (P = 0.008), with a shorter pain to needle time (P = 0.04), multivariable analysis adjusted for these differences. CONCLUSION: In-hospital PCI in patients treated with fibrinolytic therapy for STEMI is associated with a substantial reduction in 1 year mortality.

Aged↗
PubMed2004

Legal perceptions of forensic DNA profiling part I: a review of the legal literature.

A forensic biologist is usually involved in the criminal justice system process somewhere between the police and the legal system, interacting in a practical context regularly and extensively with both. Forensic DNA research and development commonly involves initiatives that encroach into the neighbouring domains of the law enforcement or legal agencies. Despite this level of association, establishing meaningful cross-disciplinary communication and understanding within the justice system remains a challenge. As an example, there is an abundance of literature relating to forensic DNA profiling in legal and criminological periodicals. Such journals are perhaps outside the regular reading of forensic scientists and much of the legal discussion appears to go unnoticed. This situation is understandable; however, it is also undesirable particularly as forensic DNA developments are intertwined with significant changes in legislation and contentious issues of privacy, civil liberty and social justice. This paper attempts to address this shortcoming directly by summarising - from the viewpoint of a forensic scientist - some of the discussion in the legal literature. In particular the review focuses on discussion raising ideological and ethical concerns. Awareness of these views is of relevance to forensic science. It assists us to accurately place DNA evidence into context and to develop its role in achieving the broader criminal justice system objectives. Understanding the discussion also provides a way to enter the debate and communicate at an appropriate level the true potential of DNA to the legal community.

Crime↗
PubMed2004

Efficacy of distinct energy delivery protocols comparing two biphasic defibrillators for cardiac arrest.

Limited data have been published on the use of external defibrillators that deliver impedance compensated biphasic (ICB) waveforms in patients. We compared 2 ICB defibrillators, the Heartstream XL (150-150-150 J protocol) and Heartsine Samaritan (100-150-200 J protocol) in 78 consecutive patients in cardiac arrest. The performance of the 2 devices over the first 2 shocks was statistically equivalent. By the third shock, the Heartsine Samaritan had significantly better performance in removing ventricular fibrillation (p = 0.029). Energy selection for ICB waveforms requires further validation.

Aged↗
PubMed2004

Prehospital 80-LAD mapping: does it add significantly to the diagnosis of acute coronary syndromes?

UNLABELLED: Early detection of acute myocardial infarction (MI) is vital in the management of acute coronary syndromes (ACS). Hence we compared the diagnostic capability of the standard 12-lead electrocardiogram (ECG) with the 80-lead ECG body surface map (BSM) prehospital. METHODS: Consecutive patients (n = 294) presenting prehospital with ischemic type chest pain were included. All had an ECG and BSM pretreatment and a baseline and 12-hour cardiac troponin-T or I (cTnT or cTnI). Acute MI was defined as cTnT > 0.09 or cTnI > 0.1 ng/mL. Acute MI on the BSM was defined as ST elevation measured at the J-point, > or = 1 mm inferior/right ventricular/high right anterior/lateral regions, > or = 2 mm anterior region, > or = 0.5 mm posterior region. RESULTS: Acute MI occurred in 182/294 (62%) based on cTnT or I. ST elevation on the standard ECG predicted acute MI in 103 (sensitivity 57%, specificity 94%; c-statistic 0.73). The optimal model for the standard ECG included ST elevation, summed ST depression and past history of MI (c-statistic 0.82; Chi-square (Wald) 120.7, 3df). The BSM predicted acute MI in 146 (sensitivity 80%, specificity 92%; c-statistic 0.86). The optimal model for the BSM included BSM criteria for acute MI and past history of MI (c-statistic 0.91; Chi-square (Wald) 180.3, 2df). CONCLUSION: The 80-lead BSM is superior to the standard 12-lead ECG in predicting acute MI prehospital.

Angina Pectoris↗
PubMed2004

Recent advances in forensic genetics.

Like many applications of molecular diagnostics, the field of forensic biology is undergoing a phase of expansion and diversification. The growth of forensic DNA databases and adoption of sophisticated analytical methods have catalyzed this increasing role. The range of molecular markers exploited in the fight against crime is beginning to increase too, and genes implying personal or physical characteristics are emerging in the research literature. However, the operational context of forensic biology is unlike many other fields of science. Harmonizing technological breakthroughs with the requirements of law enforcement agencies and the complexities of the legal system is an added challenge and one which evokes ongoing debate. This review examines the current status of this dynamic and important application of modern genetics.

Animals↗
PubMed2003

Characterisation of variant alleles at the HumD21S11 locus implies unique Australasian genotypes and re-classification of nomenclature guidelines.

Several variant alleles of the HumD21S11 locus have only been reported in Australasian population samples. Fifteen such alleles were observed in Caucasian and Australian Aborigine sub-population databases compiled from residents of the state of Western Australia. Each variant was sequenced to authenticate the allelic designation and determine the structural conformation. Nine novel structural variants are described. The structure of the repeat region of these rare alleles combined with the STR designation brings aspects of the HumD21S11 nomenclature guidelines into question, in particular the designation of common incomplete repeats (or "0.2's"). The conformation of the sequences provides evidence in support of a genetic relationship between the Australian Aborigine and the Papuan people.

Alleles↗
PubMed2003

Evidence in support of self-declaration as a sampling method for the formation of sub-population DNA databases.

Well constructed sub-population databases are fundamental to the application of DNA-based forensic statistics. The size of such databases can affect the ability to examine adequately statistical or population genetic features, and the integrity of both the DNA profile and associated ethnicity information is also of importance. Use of short tandem repeat (STR) DNA profiling technology and the thoughtful construction of the governing legislation has seen large databases of DNA profiles collated for the four major sub-populations of New Zealand. Examination of the data illustrates the suitability of self-declaration as a means of categorizing samples on the basis of ethnicity.

Databases as Topic↗
PubMed2002

Comparison of the variables affecting the recovery of DNA from common drinking containers.

As the boundaries of forensic DNA profiling continue to expand, less obvious sources of biological evidence are being collected at crime scenes for DNA profiling. One example is the recovery of biological evidence from common drink containers, such as bottles and cans, which have been found at crime scenes. There are many variables that may have an impact on recovering a DNA profile from such exhibits. In this research, the effects of person to person variation, time, type of drink (including alcoholic and non-alcoholic beverages), and type of drink container, were assessed for their impact on the major analytical outcomes of the DNA process. The results show that the alpha-amylase activity varies from individual to individual and is reduced in the presence of some alcoholic drinks. A reasonable DNA yield was obtained from all samples, however, the concentrations exhibited significant person to person variation. The type of drink container influenced the DNA yield with cans giving a higher yield than bottles of the same drink type. To a reduced extent the presence or absence of alcohol affected the overall DNA yield and when partial or failed DNA profiles were produced they were more likely to be associated with alcoholic drinks than non-alcoholic drinks.

Beverages↗