Interaction of preservatives with contact materials during filling and storage of parenteral liquid formulations.

Silicone tubing is a frequently used material in pharmaceutical filling processes for parenteral formulations, as its characteristics like flexibility, chemical resistance and easy handling make it particularly suitable for these purposes. This study investigated the time-dependent interaction of phenol and m-cresol with silicone tubing and other broadly applied contact materials used during the filling and transport processes of parenteral formulations. Phenol losses could be observed after incubation in silicone tubing, depending on the inner diameter (ID).

Quantification of ultrasound correlation-based flow velocity mapping and edge velocity gradient measurement.

This study investigated the use of ultrasound speckle decorrelation- and correlation-based lateral speckle-tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation-based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods.

In vivo vascular wall shear rate and circumferential strain of renal disease patients.

This study measures the vascular wall shear rate at the vessel edge using decorrelation based ultrasound speckle tracking. Results for nine healthy and eight renal disease subjects are presented. Additionally, the vascular wall shear rate and circumferential strain during physiologic pressure, pressure equalization and hyperemia are compared for five healthy and three renal disease subjects.

Determining the error of dose estimates and minimum and maximum acceptable concentrations from assays with nonlinear dose-response curves.

A method is described here that uses a modified Monte-Carlo method to provide an improved estimate of the confidence bounds of concentration estimates. This method accommodates even strongly nonlinear curve models, such as the five parameter logistic model, in contrast to the common but often poor approach of linearizing the regression problem and using linear theory to obtain the confidence bounds. The method uses an interpolation technique to reduce artifacts in the precision profile due to small simulation sample sizes and proximity to horizontal asymptotes in the curve model.

The five-parameter logistic: a characterization and comparison with the four-parameter logistic.

Improvements in assay technology have reduced the amount of random variation in measured responses to the point where even slight asymmetry of the assay data can be more significant than random variation. Use of the five-parameter logistic (5PL) function to fit dose-response data easily accommodates such asymmetry. The 5PL can dramatically improve the accuracy of asymmetric assays over the use of symmetric models such as the four-parameter logistic (4PL) function.

Measuring parallelism, linearity, and relative potency in bioassay and immunoassay data.

There is often a need to determine parallelism or linearity between pairs of dose-response data sets for various biological applications. This article describes a technique based on a modification of the well-known extra-sum-of-squares principle of statistical regression. The standard extra-sum-of-squares method uses an F-distributed ratio as a statistic and an F-test based on this statistic as the parallelism test.