An EM Algorithm for Fitting a 4-Parameter Logistic Model to Binary Dose-Response Data

Evaluation of Recovery Methods for Fragaria vesca L. Oil: Characteristics, Stability and Bioactive Potential

Wild strawberry (Fragaria vesca L.) seed oil (WSO) recovered by two methods-cold pressing (CP) and extraction with supercritical carbon dioxide (SCO₂E)-taking into account the different extraction times, was characterized for its composition and quality. The cytotoxicity assessment of WSOs was also carried out using the normal human dermal fibroblast (NHDF) cell line. Tocopherol and total polyphenol contents were significantly higher in WSO recovered by SCO₂E, up to 1901.0 and 58.5 mg/kg, respectively, in comparison with CP oil. In CP oil, the highest content of carotenoids and squalene was determined (123.8 and 31.4 mg/kg, respectively). Phytosterol summed up to 5396 mg/kg in WSO collected in 30 min of SCO₂E. Moreover, the highest oxidative stability was found for this oil. All studied WSOs were non-cytotoxic in lactate dehydrogenase (LDH) leaching and sulforhodamine B (SRB) assays; however, oils collected by SCO₂E in 15 and 30 min were found to be cytotoxic in the tetrazolium salt (MTT) test, with the CC₅₀ at a concentration of 3.4 and 5.5%, respectively. In conclusion, the composition of WSO indicates that, depending on the method of its recovery, seeds can have different bio-potencies and various applications.

TiO2 Nanomaterials Non-Controlled Contamination Could Be Hazardous for Normal Cells Located in the Field of Radiotherapy

Among nanomaterials (NMs), titanium dioxide (TiO₂) is one of the most manufactured NMs and can be found in many consumers' products such as skin care products, textiles and food (as E171 additive). Moreover, due to its most attractive property, a photoactivation upon non-ionizing UVA radiation, TiO₂ NMs is widely used as a decontaminating agent. Uncontrolled contaminations by TiO₂ NMs during their production (professional exposure) or by using products (consumer exposure) are rather frequent. So far, TiO₂ NMs cytotoxicity is still a matter of controversy depending on biological models, types of TiO₂ NMs, suspension preparation and biological endpoints. TiO₂ NMs photoactivation has been widely described for UV light radiation exposure, it could lead to reactive oxygen species production, known to be both cyto- and genotoxic on human cells. After higher photon energy exposition, such as X-rays used for radiotherapy and for medical imaging, TiO₂ NMs photoactivation still occurs. Importantly, the question of its hazard in the case of body contamination of persons receiving radiotherapy was never addressed, knowing that healthy tissues surrounding the tumor are indeed exposed. The present work focuses on the analysis of human normal bronchiolar cell response after co-exposition TiO₂ NMs (with different coatings) and ionizing radiation. Our results show a clear synergistic effect, in terms of cell viability, cell death and oxidative stress, between TiO₂ NMS and radiation.

A method to evaluate factors influencing the microbial reduction in domestic dishwashers

AIMS

To develop a method that is able to determine the microbial reduction in different dishwasher cleaning cycles and differentiate between different program parameters used.

METHODS AND RESULTS

Stainless steel biomonitors were contaminated with Micrococcus luteus or Entereococcus faecium and cleaned in a specially programmed household dishwasher with different cleaning temperatures and durations. No detergent, bleach-free detergent or detergent containing activated oxygen bleach was used. The logarithmic reduction (LR) was determined. The microbial reduction depended on the cleaning temperature, the duration of the cleaning cycles and the detergent type used. LR increased with higher temperatures, longer cleaning cycles and use of detergent.

CONCLUSIONS

The factors cleaning cycle temperature, cleaning cycle duration, final rinsing temperature and the use of detergent all contributed to the reduction of test-strains in dishwasher cycles. A combination of longer dishwashing cycles and increased temperatures resulted in LR_max of the microbial load.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cycles in domestic appliances are very diverse; therefore a standardized method to determine their ability to reduce the microbial load is of great use. The method described here is able to demonstrate the reductions achieved by dishwashing cycles with different parameters and might help to find the necessary balance between energy saving and an acceptable level of hygiene.

Comparisons of outlier tests for potency bioassays

Potency bioassays are used to measure biological activity. Consequently, potency is considered a critical quality attribute in manufacturing. Relative potency is measured by comparing the concentration-response curves of a manufactured test batch with that of a reference standard. If the curve shapes are deemed similar, the test batch is said to exhibit constant relative potency with the reference standard, a critical requirement for calibrating the potency of the final drug product. Outliers in bioassay potency data may result in the false acceptance/rejection of a bad/good sample and, if accepted, may yield a biased relative potency estimate. To avoid these issues, the USP<1032> recommends the screening of bioassay data for outliers prior to performing a relative potency analysis. In a recently published work, the effects of one or more outliers, outlier size, and outlier type on similarity testing and estimation of relative potency were thoroughly examined, confirming the USP<1032> outlier guidance. As a follow-up, several outlier detection methods, including those proposed by the USP<1010>, are evaluated and compared in this work through computer simulation. Two novel outlier detection methods are also proposed. The effects of outlier removal on similarity testing and estimation of relative potency were evaluated, resulting in recommendations for best practice.

An algorithm for computing profile likelihood based pointwise confidence intervals for nonlinear dose-response models

This study was inspired by the need to estimate pointwise confidence intervals (CIs) for a nonlinear dose-response model from a dose-finding clinical trial. Profile likelihood based CI for a nonlinear dose response model is often recommended. However, it is still not commonly used in dose-finding studies because it cannot generally be calculated explicitly. Most previous research has mainly focused on the performance of the profile likelihood based CI method compared with other common approaches. However, there are still no reports on computing profile likelihood based pointwise CIs for an entire dose-response curve. Based on a previous dose-finding trial with binary-response data, this present study proposed to calculate profile likelihood based pointwise CIs by using the bisection method with proper calculation order for doses in the curve plus crude search when the expected response is close to a boundary. The convergence could be improved by applying appropriate starting values for the optimization procedure with straightforward programming techniques. The algorithm worked well in most cases based on the simulation study and it can be applied more generally to other dose-response models, and other type of data like normally distributed response. It would indeed be great to be able to use profile likelihood approaches more routinely when constructing pointwise CIs for nonlinear dose-response models.

Optimal designs based on the maximum quasi-likelihood estimator

We use optimal design theory and construct locally optimal designs based on the maximum quasi-likelihood estimator (MqLE), which is derived under less stringent conditions than those required for the MLE method. We show that the proposed locally optimal designs are asymptotically as efficient as those based on the MLE when the error distribution is from an exponential family, and they perform just as well or better than optimal designs based on any other asymptotically linear unbiased estimators such as the least square estimator (LSE). In addition, we show current algorithms for finding optimal designs can be directly used to find optimal designs based on the MqLE. As an illustrative application, we construct a variety of locally optimal designs based on the MqLE for the 4-parameter logistic (4PL) model and study their robustness properties to misspecifications in the model using asymptotic relative efficiency. The results suggest that optimal designs based on the MqLE can be easily generated and they are quite robust to mis-specification in the probability distribution of the responses.