A Comparative Analysis of Acyl‐Homoserine Lactone Synthase Assays

Quorum sensing is cell‐to‐cell communication that allows bacteria to coordinate attacks on their hosts by inducing virulent gene expression, biofilm production, and other cellular functions, including antibiotic resistance. AHL synthase enzymes synthesize N‐acyl‐l ‐homoserine lactones, commonly referred to as autoinducers, to facilitate quorum sensing in Gram‐negative bacteria. Studying the synthases, however, has proven to be a difficult road. Two assays, including a radiolabeled assay and a colorimetric (DCPIP) assay are well‐documented in literature to study AHL synthases. In this paper, we describe additional methods that include an HPLC‐based, C?S bond cleavage and coupled assays to investigate this class of enzymes. In addition, we compare and contrast each assay for both acyl‐CoA‐ and acyl‐ACP‐utilizing synthases. The expanded toolkit described in this study should facilitate mechanistic studies on quorum sensing signal synthases and expedite discovery of antivirulent compounds.     

Physicochemical changes during strawberry development in the field compared with those that occur in harvested fruit during storage

‘Chandler’, ‘Oso Grande’ and ‘Sweet Charlie’ strawberry cultivars were harvested at four stages of color development ranging from color break to full red and stored in the dark for 8 days at 1 °C. Changes in the physical and chemical characteristics of fruit during storage were compared with those occurring during development in the field. Strawberry fruit harvested at the three‐quarters colored and full red stages continued their development and ripening during storage. However, fruit harvested at the color break and half‐colored stages did not develop like those ripened in the field. Strawberries harvested at the three‐quarters colored stage developed the same pH, acidity, soluble solids, ascorbic acid and total phenolics content during storage as the at‐harvest levels present in strawberries harvested at the full red stage. In addition, three‐quarters colored strawberries were as firm and red after storage as the full red stage fruit were at the time of harvest. Thus, strawberries harvested at the three‐quarters colored stage can be stored for a longer period than strawberries harvested full red while retaining better color and firmness. Copyright © 2005 Society of Chemical Industry     

Performance assessment of the anticipatory approach to optimal experimental design for model discrimination

The problem of model discrimination arises when several models are proposed to describe one and the same process, a situation encountered in many research fields. To identify the best model from the set of rival models, it may be necessary to collect new information about the process, and thus additional experiments have to be performed. Several approaches have been described in literature to design optimal discriminatory experiments. The anticipatory approach is one of them and is very appealing from a conceptual point of view because the expected information content of the newly designed experiment is considered, even before the experiment is performed (anticipatory design). In this paper, the performance of this approach is evaluated by comparing it with the performance of other, established approaches to optimal experimental design for model discrimination. To conduct this comparison four performance measures were defined: (1) whether the most appropriate model could be identified, (2) the number of additional experiments that have to be designed and performed to achieve model discrimination, (3) the quality of the parameter estimates of the model that is eventually identified as the most appropriate one, and (4) the rate at which the inadequate models are identified. The results clearly indicate that the anticipatory approach has its benefits and may be the preferred approach in many applications in (bio)chemical engineering and in-silico biology.     

Scheduling operating rooms: achievements,challenges and pitfalls

In hospitals, the operating room (OR) is a particularly expensive facility and thus efficient scheduling is imperative. This can be greatly supported by using advanced methods that are discussed in the academic literature. In order to help researchers and practitioners to select new relevant articles, we classify the recent OR planning and scheduling literature into tables regarding patient type, used performance measures, decisions made, OR up- and downstream facilities, uncertainty, research methodology and testing phase. Based on these classifications, we identify trends and promising topics. Additionally, we recognize three common pitfalls that hamper the adoption of research results by stakeholders: the lack of a clear choice of authors on whether to target researchers (contributing advanced methods) or practitioners (providing managerial insights), the use of ill-fitted performance measures in models and the failure to understandably report on the hospital setting and method-related assumptions. We provide specific guidelines that help to avoid these pitfalls. First, we show how to build up an article based on the choice of the target group (i.e., researchers or practitioners). Making a clear distinction between target groups impacts the problem setting, the research task, the reported findings, and the conclusions. Second, we discuss points that need to be considered by researchers when deciding on the used performance measures. Third, we list the assumptions that need to be included in articles in order to enable readers to decide whether the presented research is relevant to them.     

The wartime kitchen: Food advice and cooking tips in Belgium during the First World War

This article addresses a special aspect of daily life in occupied Belgium during the First World War. It examines and compares the nutritional advice and the cooking tips which were given by private and public organizations, physicians, nutritional experts, and home economic teachers. Furthermore, the article compares these recommendations with actual practices, through the personal testimonies of diaries and wartime memories. This analysis results in three main conclusions. Firstly, it is clear that during the war, the diet (and the advice given on food) had to be adjusted on a regular basis, depending on the availability of foodstuffs. As the war progressed, fewer animal products were consumed; more expensive calories were gradually substituted by cheaper ones. The import of American foodstuffs and the search for ersatz products became increasingly important, especially during the “hunger winter” of 1916–1917. Secondly, this article underlines the influential role of experts in promoting the latest nutritional science (such as the concept of calories) in light of the war situation. It demonstrates that at the beginning of the war, experts such as agronomists and physicians published relatively technical brochures, written in a language that was very far removed from the general population. From 1916 onwards, female authors especially published cookery booklets in an easily understandable language in which they presented recipes and menus that were nutritious, cheap, and easy to prepare. Thirdly, it emphasizes the importance of women in shaping and defining the eating experience during the war. Housewives were most especially faced with the daily price increases and with the limited supply of both familiar and unfamiliar foodstuffs; hence it was they to whom the food recommendations within these wartime cookery booklets were primarily aimed.     

Rapid and long-lasting suppression of the ATF-2 transcription factor is a common response to neuronal injury

To determine if intestinal stromal cells secrete diffusible factors such as insulin-like growth factors (IGFs) capable of regulating epithelial cell growth in vitro, stromal cells were isolated by enzymatic digestion of rat intestine. Incorporation of [3H]thymidine into DNA and [14C]leucine into protein of IEC-6 cells, a model intestinal epithelial cell line, was significantly increased (two- to threefold) when the IEC-6 cells were co-cultured with stromal cells, relative to IEC-6 cells grown alone. Medium conditioned by stromal cells stimulated DNA synthesis of IEC-6 cells in a dose-dependent manner. Analysis of the conditioned medium revealed that intestinal stromal cells secreted IGF-I, but little IGF-II, in addition to an M(r) 32,000 IGF-binding protein (IGFBP-2) and an IGFBP having M(r) approximately 24,000. We conclude that rat intestinal stromal cells secrete one or more diffusible factors, which may include IGF-I and IGFBPs, capable of stimulating proliferation of IEC-6 cells in vitro.