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Biomedical subjects

T Mark

Publications and source records attributed to T Mark.

At least 19 recordsLinked to original sources
PubMed2006

Multiple-trait multiple-country genetic evaluations for udder health traits.

International genetic bull evaluations of somatic cell counts (SCC) from 8 different Holstein populations and clinical mastitis from 3 of these populations were inferred simultaneously using a multiple-trait-multiple-country evaluation (MT-MACE) model. This model considered effective independent weighting factors and multivariately deregressed national genetic evaluations for countries with multiple-trait national models. Predictions of genetic merit from MT-MACE and their reliabilities were compared with the corresponding results from 2 separate single-trait-multiple-country evaluations (ST-MACE) for different groups of bulls. The assumed heritabilities for clinical mastitis (h(2) = 0.02 to 0.05) were substantially lower than the heritabilities for SCC (h(2) = 0.08 to 0.27). The predictive ability of MT-MACE was essentially equal to or better than the predictive ability of ST-MACE for all country-trait combinations, but both methods yielded effectively unbiased and consistent consecutive predictions (correlation > 0.93). Both sets of predictions also agreed well with future national genetic evaluations for bulls receiving additional daughter information (correlation > 0.96), except for evaluations for which within-country correlations were utilized internationally, but not nationally (correlation = 0.86 to 0.97). The reliabilities for MT-MACE were essentially equal to or higher than reliabilities for ST-MACE, depending on the trait and group of bulls in question. Reliabilities increased most for young bulls, and for clinical mastitis in countries that did not use the within-country correlations with SCC in the national evaluation (up to a 23% increase in average reliability).

Animals↗
PubMed2005

Identifying competencies for Australian health professionals working in international health.

A profile of the roles performed by Australian health professionals working in international health was constructed to identify the core competencies they require, and the implications for education and training of international health practitioners. The methods used included: literature review and document analysis of available training and education; an analysis of competencies required in job descriptions for international health positions; and consultations with key informants. The international health roles identified were classified in four main groups: Program Directors, Program Managers, Team Leaders and Health Specialists. Thirteen 'core' competencies were identified from the job analysis and key informant/group interviews. Contributing to international health development in resource poor countries requires high level cultural, interpersonal and teamwork competencies. Technical expertise in health disciplines is required, with flexibility to adapt to new situations. International health professionals need to combine public health competencies with high level personal maturity to respond to emerging challenges.

Australia↗
PubMed2005

Prior (co)variances can improve multiple-trait across-country evaluations of weakly linked bull populations.

National genetic evaluation results for fore udder attachment from 9 Ayrshire populations were used to assess the impact of different uses of prior genetic correlations in multiple-trait across-country evaluations (MACE) on predicted international genetic merit. These Ayrshire populations were poorly connected; that is, 2% of the bulls had evaluations in 2 or more countries. Genetic correlations from the Holstein populations in the same countries were used as prior information to improve inferences of location parameters and international genetic merits. Fully Bayesian analyses using Gibbs sampling and computationally less demanding traditional MACE assuming a weighted average of prior and estimated Ayrshire genetic correlations were compared for 3 different prior degrees of belief and for different groups of bulls. Posterior means of genetic correlations estimated by Gibbs sampling were on average higher (+0.2) than those estimated by REML. Posterior heritabilities differed up to 0.2 units from those assumed in national genetic evaluations. Predicted genetic merit and international sire rankings of bulls with daughter information in the country of interest were not affected substantially by method of analysis and even less by varying prior degree of belief. Method of analysis had a larger impact on predicted genetic merit for bulls without daughter information in the country of interest. Here the average correlation between predicted genetic merit in different analyses ranged from 0.62 to 0.99. The predictive ability for young and randomly chosen bulls favored Bayesian MACE. The prior degree of belief did not have much impact on sire rankings and predictive ability, but intermediate prior degree of belief tended to perform best. All MACE analyses yielded nearly unbiased predictions. Traditional MACE assuming a simple weighted average of prior and estimated Ayrshire genetic correlations has been implemented by Interbull for routine international genetic evaluations.

Analysis of Variance↗
PubMed2005

Short communication: Difficulties in estimating across-country genetic correlations for weakly linked bull populations.

Genetic correlations across 9 weakly linked bull populations were estimated with various models, methods, and data sets. Estimates of the same genetic correlation differed noticeably depending on estimation strategy (up to 1.03 units) for country-pairs with no or few direct genetic links. Differences in estimated genetic correlations decreased with an increasing number of genetic ties between countries, and, essentially, no differences were found between estimated genetic correlations based on 61 common bulls, regardless of the estimation strategy used.

Analysis of Variance↗
PubMed2004

Determination of a unique solution to parallel proton transfer reactions using the genetic algorithm.

Kinetic analysis of the dynamics as measured in multiequilibria systems is readily attained by curve-fitting methodologies, a treatment that can accurately retrace the shape of the measured signal. Still, these reconstructions are not related to the detailed mechanism of the process. In this study we subjected multiple proton transfer reactions to rigorous kinetic analysis, which consists of solving a set of coupled-nonlinear differential rate equations. The manual analysis of such systems can be biased by the operator; thus the analysis calls for impartial corroboration. What is more, there is no assurance that such a complex system has a unique solution. In this study, we used the Genetic Algorithm to investigate whether the solution of the system will converge into a single global minimum in the multidimensional parameter space. The experimental system consisted of proton transfer between four proton-binding sites with seven independent adjustable parameters. The results of the search indicate that the solution is unique and all adjustable parameters converge into a single minimum in the multidimensional parameter space, thus corroborating the accuracy of the manual analysis.

Algorithms↗
PubMed2004

Applied genetic evaluations for production and functional traits in dairy cattle.

The objective of this study was to review the current status of genetic evaluation systems for production and functional traits as practiced in different Interbull member countries and to discuss that status in relation to research results and potential improvements. Thirty-one countries provided information. Substantial variation was evident for number of traits considered per country, trait definition, genetic evaluation procedure within trait, effects included, and how these were treated in genetic evaluation models. All countries lacked genetic evaluations for one or more economically important traits. Improvement in the genetic evaluation models, especially for many functional traits, could be achieved by closing the gaps between research and practice. More detailed and up to date information about national genetic evaluation systems for traits in different countries is available at www.interbull.org. Female fertility and workability traits were considered in many countries and could be next in line for international genetic evaluations.

Animals↗
PubMed2003

[Kinematic analysis before and after bicondylar resurfacing knee arthroplasty].

Knee joint motion appears as a hinge movement around the flexion-extension axis. Corresponding to the rolling-sliding mechanism and alternative models of knee joint kinematics, an instant center pathway must be expected. The current photogrammetric investigation aimed to analyze these pathways when assessed in the sagittal plane in patients with preoperative varus or valgus deformity. A total of 40 patients either with varus or valgus deformity (20 in each group) were examined before and 6 months after implantation of PFC-SIGMA prostheses. Apart from the influence of knee joint deformity, a so-called soft tissue ratio was investigated. Therefore, the relation of thigh and femur as well as lower limb and tibia diameters was calculated and combined in one value. The investigation unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Results showed the following characteristics: small values of soft tissue ratio were represented by round or oval courses of the pathway whereas increasing ratios led to triangular and slightly increased dimensions of the courses. Varus deformity was primarily combined with an increase of the pathway's dimension and in contrast, valgus deformity showed decreased pathways. In each case, dimensions normalized after prosthesis implantation. The instant center pathway of knee joint motion showed for both patient groups characteristic phenomena. They were clearly associated with constitutional and clinical features of each patient.

Aged↗
PubMed2003

[Photogrammetry of knee joint kinematics after hinge arthroplasty].

Hinge prostheses are the oldest total knee arthroplasties based on the easiest model of knee joint kinematics. The complex knee joint movement is simplified by a hinge rotating around the flexion-extension axis. Nevertheless, different studies showed that in unscathed joints an instant center pathway in the sagittal plane must be expected. The objective of the current photogrammetric investigation was the assessment of these pathways after hinge arthroplasty. Moreover, they were compared with reference pathways from healthy participants. A total of 20 patients were examined on average 12.1 years after implantation of St. Georg hinge prostheses. Apart from this, 50 test persons with unscathed knee joints were investigated. The examination unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Patients with hinge prostheses showed small pathways almost comparable to dots. Apart from this, courses of the pathways depended on the extent of soft tissue in the knee joint area. Small values were associated with round or oval courses,whereas increasing soft tissue led to triangular and slightly increased dimensions of the courses. Pathways of the reference participants confirmed this observation and additionally showed clearly greater dimensions of the pathways. The instant center pathway of unscathed knee joints showed a dependence of the course on the extent of soft tissue. The same observation was made in patients with hinge prostheses. Moreover,the latter were characterized by very small, almost fixed pathways. These results confirm the neglect of additional movement components in hinge prostheses.

Adult↗
PubMed2002

International genetic evaluations of Holstein sires for milk somatic cell and clinical mastitis.

International genetic evaluations for milk somatic cell and clinical mastitis have been implemented on a routine basis by Interbull. This paper examines possible genetic consequences of such evaluations. Holstein data from 12 countries were used for this purpose. Trait definitions and national genetic evaluation procedures were first summarized and showed that differences between countries existed. Estimated genetic correlations among milk somatic cell in these countries ranged from 0.47 to 0.97, with a median of 0.88. Estimated genetic correlations among clinical mastitis in three Nordic countries ranged from 0.59 to 0.83, and estimated genetic correlations between clinical mastitis in the three Nordic countries and milk somatic cell in the non-Nordic countries ranged from 0.37 to 0.78 with a median of 0.55. Bulls without daughter information in the Nordic countries had low reliabilities on the Nordic clinical mastitis scales. International genetic evaluations for milk somatic cell and clinical mastitis enable a broader selection among foreign bulls, and higher selection differentials were found when using international evaluations compared with national evaluations.

Animals↗
PubMed2002

Short communication: effect of phantom parent grouping and properties of deregression for a low heritability trait.

Properties of deregression for a low heritability trait (clinical mastitis in Sweden with heritability of 0.02) and effects of using different definitions of genetic groups in within-country deregression compared with the across-country analysis were studied. The deregression procedure was satisfactory, and the effects of different phantom parent grouping in within-country deregression compared with across-country analysis were negligible here.

Animals↗
PubMed2001

The cost of on-site versus off-site workplace urinalysis testing for illicit drug use.

Workplace drug testing has become standard business practice in America. With increasing costs, however, many corporations look for more cost-effective testing alternatives. The study compared the cost of two testing strategies: urinalysis at the work site versus testing that occurs elsewhere. Employees from seven company locations were tested for illicit drugs. Four sites conducted the initial screening test at the workplace and three sites performed testing off site. On-site testing was found to have significantly lower variable costs, and total costs were lower once a threshold of 27 employees tested was attained. On-site testing also provided immediate access to negative test results, thereby facilitating personnel decisions.

Contract Services↗
PubMed2000

Genetic interference in Trypanosoma brucei by heritable and inducible double-stranded RNA.

The use of double-stranded RNA (dsRNA) to disrupt gene expression has become a powerful method of achieving RNA interference (RNAi) in a wide variety of organisms. However, in Trypanosoma brucei this tool is restricted to transient interference, because the dsRNA is not stably maintained and its effects are diminished and eventually lost during cellular division. Here, we show that genetic interference by dsRNA can be achieved in a heritable and inducible fashion. To show this, we established stable cell lines expressing dsRNA in the form of stem-loop structures under the control of a tetracycline-inducible promoter. Targeting a-tubulin and actin mRNA resulted in potent and specific mRNA degradation as previously observed in transient interference. Surprisingly, 10-fold down regulation of actin mRNA was not fatal to trypanosomes. This type of approach could be applied to study RNAi in other organisms that are difficult to microinject or electroporate. Furthermore, to quickly probe the consequences of RNAi for a given gene we established a highly efficient in vivo T7 RNA polymerase system for expression of dsRNA. Using the alpha-tubulin test system we obtained greater than 98% transfection efficiency and the RNAi response lasted at least two to three cell generations. These new developments make it possible to initiate the molecular dissection of RNAi both biochemically and genetically.

Actins↗
PubMed2000

Risk adjustment of capitation payments to behavioral health care carve-outs: how well do existing methodologies account for psychiatric disability?

This study used 1994-1995 administrative data from a large public employer to examine the viability of commercial risk adjustment systems for setting capitation payments to competing behavioral health care "carve-outs". The ability of Hierarchical Condition Categories and Adjusted Diagnostic Groups to predict psychiatric expenditures was improved by controlling separately for psychiatric disability. However, even the best models underpredicted expenditures of patients with psychiatric disability by 15%. Relative to full capitation, "mixed" payment systems and soft capitation reduce the ability of carve-outs to earn disproportionate profits by enrolling healthy patients and avoiding sick ones, yet also diminish incentives for cost containment.

Adult↗
PubMed1981

Histologic examination of the bone marrow: aspiration or trephine?

We undertook this study to evaluate the efficacy of bone marrow aspiration as compared with trephine needle biopsy. In the 50 consecutive cases reviewed, simultaneous aspiration and biopsy yielded significant morphologic findings in either or both. A comparison was made between the morphologic findings in the aspirate and the corresponding biopsy, with quantification of these findings when feasible. The aspiration technic and method for processing used differ significantly from the so-called clot preparation currently in widespread use. For coring the marrow, a regular (adult) 11 gauge Jamshidi needle was used. More lymphoid nodules, nodular lymphoid hyperplasia, and lipid granulomas were found in the aspirate.

Biopsy, Needle↗