A study on the analytical sensitivity of 6 BSE tests used by the Canadian BSE reference laboratory

Bovine spongiform encephalopathy (BSE) surveillance programs have been employed in numerous countries to monitor BSE prevalence and to protect animal and human health. Since 1999, the European Commission (EC) authorized the evaluation and approval of 20 molecular based tests for the rapid detection of the pathological prion protein (PrP^sc) in BSE infection. The diagnostic sensitivity, convenience, and speed of these tests have made molecular diagnostics the preferred method for BSE surveillance. The aim of this study was to determine the analytical sensitivity of 4 commercially available BSE rapid-test kits, including the Prionics®-Check WESTERN, the Prionics® Check-PrioSTRIP™, the BioRad® TeSeE™ ELISA, and the IDEXX® HerdChek™ EIA. Performances of these tests were then compared to 2 confirmatory tests, including the BioRad® TeSeE™ Western Blot and the modified Scrapie Associated Fibrils (SAF)/OIE Immunoblot. One 50% w/v homogenate was made from experimentally generated C-type BSE brain tissues in ddH₂O. Homogenates were diluted through a background of BSE-negative brainstem homogenate. Masses of both positive and negative tissues in each dilution were calculated to maintain the appropriate tissue amounts for each test platform. Specific concentrated homogenization buffer was added accordingly to maintain the correct buffer condition for each test. ELISA-based tests were evaluated using their respective software/detection platforms. Blot-protocols were evaluated by manual measurements of blot signal density. Detection limitations were determined by fitted curves intersecting the manufacturers'' positive/negative criteria. The confirmatory SAF Immunoblot displayed the highest analytical sensitivity, followed by the IDEXX® HerdChek™ EIA, Bio-Rad® TeSeE™ Western Blot, the Bio-Rad® TeSeE™ ELISA, Prionics®-Check PrioSTRIP™, and Prionics®-Check WESTERN™, respectively. Although the tests performed at different levels of sensitivity, the most sensitive and least sensitive of the rapid tests were separated by 2 logs in analytical sensitivity, meeting European performance requirements. All rapid tests appear suitable for targeted BSE surveillance programs, as implemented in Canada.     

On the meaning of the distance-to-target weighting method and normalisation in Life Cycle Impact assessment

Distance-to-target weighting methods are widely used in life cycle impact assessment. The methods rank impacts as being more important the further away society’s activities are from achieving the desired targets for the pollutants. However, we feel that the scientific bases of the distance-to-target methods still need more clarification. This article illustrates how multiattribute value theory (MAVT) can be applied to interpret the impact category weights as well as the aggregation rule and normalisation used in the distant-to-target methods. Our comparison revealed that under certain conditions two of the three commonly used impact assessment methods (Ecoindicator 95, ET-method) applying distance-to-target weighting are consistent with the impact assessment framework derived from MAVT. This consistency holds for non-zero targets with equal importance and linear damage functions passing through the origin. We show that the MAVT framework offers a foundation for the methodological development in life cycle impact assessment.     

The lower muscular balance of the face used to lift labial commissures

One of the weak points in face lifts is their failure to fully correct the ptosis of the labial commissures. This article illustrates a new technique to optimize this commissural repositioning in face lifts by using the muscular balances of the lower half of the face. There is, in effect, a third type of muscular balance, which acts on the commissural modiolus and is created by the opposing forces of the levator muscles (notably the zygomaticus major and the levator anguli oris) and the depressor muscles (principally the depressor anguli oris). Rarely a purely cutaneous problem, labial commissural ptosis is more a part of mediofacial ptosis affecting the entire soft tissue. I have used the malar subperiosteal face lift technique, the only approach that allows the centrofacial features to be lifted as a whole block, since late 1996 and have treated a series of more than 30 patients affected with mediofacial ptoses involving the malar eminences, the nasolabial folds, and the labial commissures. Retensioning the levator muscles was combined with wholesale subperiosteal release of the depressor muscles, notably the depressor anguli oris. Patient follow-up has lasted between 6 and 20 months. In all instances, this use of the lower facial muscular balances allowed optimal repositioning of the labial commissure. In particularly outstanding cases, unilateral release of the depressor muscles was used to correct facial asymmetry at the level of the lip commissures and thereby restore harmony and alignment. In 10 of our cases, this slackening of the depressor muscles was also used in conjunction with a peripheral face lift; the resulting heightening of the commissures was, in these cases, perhaps less spectacular, but it invariably contributed to the rejuvenation of the face.     

An examination of some statistical tests used in the analysis of mark-recapture data

Summary Some statistical tests used in mark-recapture analysis are examined. It is shown that the tests presently available are insensitive and are not adequate under certain conditions. The most important of these is that a population stratified with respect to probability of capture may not, by present tests, be distinguished from a homogenous population.     

An assessment of methods used for measuring the recovery of mammalian cells from freezing and thawing

Traditional methods of determining cell viability (vital dye staining and plating efficiency) as a measure of recovery from freeze-thaw cycles were found particularly unsuitable for human diploid cell lines. A modified plating efficiency method (RI) and a method using the release of radiochromate from injured or dead cells were compared and assessed for their suitability as measurements of cell recovery from freezing and thawing.     

An assessment of methods for measuring volumes of planktonic bacteria, with particular reference to television image analysis

Several methods for measuring volumes of planktonic bacteria were compared. The eyepiece micrometer grossly overestimated cell width (47–65%) and hence volume (73%). Shrinkage occurred with scanning electron microscopy, so volumes were underestimated by about 77%. All the other methods gave similar results (mean volume = 0.133 µm³). The optimum technique was to filter acridine orange stained bacteria through polycarbonate membrane filters (0.2 µm) which were photographed with epifluorescence microscopy using Kodak Tri-X pan film. We recommend that volumes are estimated from individual area and perimeter measurements of at least 200 bacteria with a Quantimet 800 or Q10 image analyzer.     

Analysis of the diluents used for rubella virus hemagglutination and hemagglutination-inhibition tests

[This corrects the article on p. 222 in vol. 18.].     

An assessment of a tow net used to sample coarse fish fry in rivers

The design and use of a tow net for sampling coarse fish fry in rivers are described, and its performance over a year is discussed with regard to species selectivity and size selectivity. The extent to which it can be used to provide data on the comparative abundance of the fry and their mean lengths and associated variances are described.     

Sex-specific reliability and multidimensional stability of responses to tests assessing neuromuscular function

The objective of this study was to estimate sex-specific effects in the test–retest cross-reliability of peripheral and central changes in nonlinear and linear measures of a surface electromyography signal during a brief (5 second) and sustained (2 minute) isometric maximal voluntary contraction, combined with superimposed electrical stimulation involving the ankle plantar flexors over five identical trials. In this study, we repeated the testing protocol used in our previous study of 10 women (age 20.9, SD = 0.3 years) (Bernecke et al., 2015) in a group of 10 men (age 21.2, SD = 0.4 years). Despite the central (sex effect; p < 0.05, η_p² > 0.71, SP > 70%) and peripheral fatigability (sex effect; p < 0.01, η_p² > 0.8, SP > 90%) during sustained isometric maximal voluntary contraction, and lower reliability for central activation ratio during brief (intraclass correlation coefficient [ICC] = 0.95 for men and ICC = 0.82 for women) and sustained maximal voluntary contraction (ICC > 0.82 for men and ICC > 0.66 for women) over ankle plantar flexors expressed in women more than in men, all the ICCs of all indices measured by tests assessing neuromuscular function across the five identical test–retest trials were found as meaningful (correlation significance of p < 0.05 was reached) and no significant differences were found between trials for any of the measured variables. In conclusion, the present study demonstrated greater central and peripheral fatigue for female participants following sustained (2 minute) isometric maximal voluntary contraction of the plantar flexor muscles for all repeated trials and indicated an acceptable agreement between measurements of the characteristic variables made using the three different devices (dynamometry, electrical stimulation, and surface electromyography) over time for both sexes.     

Between-session reliability of four hop tests and the agility T-test

The purposes of this study were firstly to investigate whether learning affects were present in the administration of 4 hop tests and the Agility T-test and secondly to assess the between-session reliability of these tests. Twenty-two recreational athletes (11 women: age 22.3 ± 3.7 years, height 167.7 ± 6.2 cm, weight 59.2 ± 6.9 kg and 11 men: age 22.8 ± 3.1 years, height 179.8 ± 4 cm, weight 79.6 ± 10 kg) took part in the study. The subjects performed 6 repetitions of each hop test and 4 repetitions of the Agility T-test once a week over a period of 3 weeks. Distances were normalized to leg length and presented as a percentage value for the single, triple and crossover hop. Results showed that there were significant differences in scores between genders and that learning affects were present in all tests. Intraclass correlation coefficients ranged from 0.76 to 0.92 for the hop tests and 0.82 to 0.96 for the Agility T-test. The results indicated that the hop and Agility T-tests are reliable tests for use with subjects in a clinical or team sport environment. The error measurement statistics presented could be of help to practitioners to determine whether changes in individuals' scores in the hop and Agility T-tests are because of a true change in performance or measurement error. Of most importance was the fact that all subjects achieved at least 90% limb symmetry index on all 4 hop tests. Therefore, we recommend that a minimum limb symmetry value of 90%, rather than previously recommended 85%, should be adopted during rehabilitation and conditioning.     

An assessment of methanolysis and other factors used in the analysis of carbohydrate-containing materials

The stability of monosaccharides in methanolic hydrochloric acid of different strengths and at different temperatures was determined. They are generally stable for 24h in methanolic 1m- and 2m-hydrochloric acid at both 85 degrees C and 100 degrees C, but undergo considerable destruction in methanolic 4m- and 6m-hydrochloric acid at 100 degrees C. Analysis of glycopeptides and oligosaccharides of known composition showed that release of carbohydrate was complete within 3h in methanolic 1m-hydrochloric acid at 85 degrees C. Removal of methanolic hydrochloric acid by rotary evaporation resulted in considerable losses of monosaccharides, which could be prevented by prior neutralization. Methanolysis caused extensive de-N-acetylation of acetamidohexoses, so that a re-N-acetylation step is necessary in the analytical procedure. The addition of acetic anhydride for this purpose also prevented loss of internal standard by adsorption on the insoluble silver salts used in neutralization. Several trimethylsilylating agents were studied and suitable conditions are recommended. The effects on the analytical system of water and some common organic and inorganic contaminants are assessed.     

评估蛋白质相互作用可信度的生物信息学方法

随着基因组规模的高通量实验鉴定技术和计算预测方法的发展,出现了大量蛋白质相互作用数据,但大规模蛋白质相互作用数据中的较高比例的假阳性影响了相互作用数据的质量。生物信息学方法能够从已有的数据和知识出发,通过计算方法系统评估大规模蛋白质相互作用的可信度。本文从过程模型设计、数据集构建、特征选择与综合属性抽取、一些算法使用、实例概述等方面介绍了生物信息学方法评估蛋白质相互作用可信度的研究特点与进展。