Stabilized procedure for the determination of urokinase fibrinolytic potency

A stabilized procedure for the determination of urokinase (UK) fibrinolytic potency is described in which method response is dependent on urokinase concentration and independent of normal variation in assay parameters. The method is a selective stability-indicating procedure for UK active enzyme. It is suitable for evaluation of both high molecular weight as well as low molecular weight urokinase fractions and is calibrated against the World Health Organization International Reference Preparation for UK code 66/46 using a biological six-point parallel line log-log dose-response approach where sample and standard are compared under essentially identical conditions. High method stability and sensitivity are achieved through the use of appropriate levels of purified human plasminogen and human plasma (source of fibrinogen) as primary and secondary substrates, respectively. Method precision versus house reference standard (%RSD less than or equal to 2%) is suitable for research and pharmaceutical purposes. The absolute UK potency reference plane established in the calibrated procedure is equivalent to that established by other investigators in the fibrinolytic field.     

A review of the effectiveness of vaccine potency control testing

The use of potency control testing is a valuable tool for testing the actual relative strength of manufactured assembly lots of vaccine. Biological-based manufacturing methods are inherently variable and potency testing is a tool to ensure lot-to-lot consistency of commercial vaccines. A strong historical link to clinical efficacy has been established where correlation to efficacy and adequate test validation have been achieved. The link to immunogenicity and efficacy has traditionally been strongest with attenuated vaccines and toxoids. Control potency test failure does predict that a serial or batch of vaccine would most likely provide insufficient immunogenicity in typical field applications. Because of the complexity of pathogenic processes and associated immune responses, potency tests may not always directly predict the effectiveness of a vaccine. Thus, vaccines that pass control potency testing may not always provide adequate efficacy. This is particularly true of adjuvanted, inactivated vaccines. In the development of vaccine formulations and control tests for vaccines, the nature of the desired protective immune responses to the targeted pathogen (when known) should be considered. These considerations could provide better alternatives in the assays chosen as correlates of immunity and may more accurately predict efficacy and assure batch-to-batch consistency. Also, the effects of the dose and duration of antigen exposure as well as the nature of antigen presentation and generation of extrinsic cytokines could be characterised and correlated to vaccine potency as additional indicators of vaccine efficacy.     

A Bayesian nonparametric testing procedure for paired samples

We propose a Bayesian hypothesis testing procedure for comparing the distributions of paired samples. The procedure is based on a flexible model for the joint distribution of both samples. The flexibility is given by a mixture of Dirichlet processes. Our proposal uses a spike-slab prior specification for the base measure of the Dirichlet process and a particular parametrization for the kernel of the mixture in order to facilitate comparisons and posterior inference. The joint model allows us to derive the marginal distributions and test whether they differ or not. The procedure exploits the correlation between samples, relaxes the parametric assumptions, and detects possible differences throughout the entire distributions. A Monte Carlo simulation study comparing the performance of this strategy to other traditional alternatives is provided. Finally, we apply the proposed approach to spirometry data collected in the United States to investigate changes in pulmonary function in children and adolescents in response to air polluting factors.     

A multiple testing procedure for clinical trials.

A multiple testing procedure is proposed for comparing two treatments when response to treatment is both dichotomous (i.e., success or failure) and immediate. The proposed test statistic for each test is the usual (Pearson) chi-square statistic based on all data collected to that point. The maximum number (N) of tests and the number (m1 + m2) of observations collected between successive tests is fixed in advance. The overall size of the procedure is shown to be controlled with virtually the same accuracy as the single sample chi-square test based on N(m1 + m2) observations. The power is also found to be virtually the same. However, by affording the opportunity to terminate early when one treatment performs markedly better than the other, the multiple testing procedure may eliminate the ethical dilemmas that often accompany clinical trials.     

A spectrophotometric procedure for determining the activity of various rat tissue oxidases.

A continuous spectrophotometric method suitable for the determination of the activities of several peroxisomal oxidases in rat tissue homogenates is described. The assay involves the continuous spectrophotometric measurement of the reaction product, H₂O₂, by coupling it to the reduction of a chromogen, o-dianisidine, with horseradish peroxidase. Catalase interference was overcome using azide to inhibit its activity and a H₂O₂ standard curve used to quantitate oxidase activity in terms of microkatals per milliliter of enzyme.     

A novel experimental procedure based on pure shear testing of dermatome-cut samples applied to porcine skin

This paper communicates a novel and robust method for the mechanical testing of thin layers of soft biological tissues with particular application to porcine skin. The key features include the use of a surgical dermatome and the highly defined deformation kinematics achieved by pure shear testing. Thin specimens of accurate thickness were prepared using a dermatome and were subjected to different quasi-static and dynamic loading protocols. Although simple in its experimental realisation, pure shear testing provides a number of advantages over other classic uni- and biaxial testing procedures. The preparation of thin specimens of porcine dermis, the mechanical tests as well as first representative results are described and discussed in detail. The results indicate a pronounced anisotropy between the directions along and across the cleavage lines and a strain rate-dependent response.     

Replacing the NIH test for rabies vaccine potency testing: A synopsis of drivers and barriers

Approximately 70% of animal use is utilized to demonstrate quality control of vaccines. Especially rabies vaccine potency testing, using the NIH challenge test, involves objections in terms of scientific relevance, animal welfare concern and costs. Several 3R models have been proposed to refine, reduce or replace this test. Some are formally incorporated into regulatory requirements, but actual regulatory acceptance and use by industry lags behind, raising the question concerning which factors influence this process. This question is answered by a combination of literature review, interviews and a survey among 50 rabies vaccine experts. The findings are analyzed using the multilevel perspective on technology transition, which distinguishes 3 levels of factors influencing innovation acceptance. At the micro level (where 3R models are developed and validated) the dis-advantages of, and fractional experience with, 3R models, scarce data sharing and demanding validation processes exist. The meso level (existing regulatory regime) encloses the barriers of the ‘gold standard’, the lack of harmonization and the driving force of legislation stimulating 3Rs use. The macro level (the societal context) combines risk aversion and increased concern for animal welfare. Regulatory acceptance and use of 3R models requires dedicated stakeholder communication, cooperation and coordination at all three levels.     

A laboratory apparatus for the generation and biocide efficacy testing of Legionella biofilms

P.N. GREEN AND R.S. PIRRIE. 1993. The construction and operation of a laboratory biofilm generator designed to grow sessile populations of legionellas for biocide efficacy testing is described. Some examples of static biocide testing on both sessile and planktonic populations of Legionella bozemanii are discussed along with other potential applications of the apparatus.     

A GLC procedure for determining sub-nanogram levels of indol-3-yl acetic acid

Mono-, di- and tri-chloroethyl esters of indol-3-yl-acctic acid were synthesized and analysed by a gas-liquid chromatography using an electron capture     

A procedure for determining angular positional data relative to the principal axes of the human body

This paper describes a simple computational procedure for determining angular displacement-time histories of human motion from three-dimensional cine data. The method is based on algebraic transformations of coordinates and coordinate axes. Through these coordinate transformations data was acquired for a multi-axial tumbling skill to illustrate angular displacement-time data relative to the moving coordinate system described by the human body through space.