Using zebrafish (Danio rerio) to study the behavioral impacts of early bisphenol F exposure reveals decreased swim speed, increased distance between fish, and increased freezing behaviors

The widespread use of endocrine disrupting chemicals (EDCs) has been a source of concern because of their various effects on the endocrine system. These effects include metabolic disorders, complications in reproductive health, hormone-related cancers, and neurodevelopmental disorders. Of particular concern is bisphenol A (BPA), a synthetic compound commonly found in consumer products such as water bottles, thermal receipt paper, and epoxy resins used in processed food packaging. Previous studies have shown that BPA can mimic estrogen through a variety of mechanisms and thus elicit an endocrine response. Some manufacturers have responded by removing BPA from their products; however, studies using a replacement compound bisphenol S have reported it to be just as, if not more, dangerous. The use of zebrafish (Danio rerio) larvae as a model organism allows for the effects of bisphenol exposure to be rapidly quantified through a simple behavioral assay. In studies involving bisphenol exposure, the use of zebrafish has demonstrated reproductive, developmental, endocrine, and behavioral effects. The study of bisphenol F, yet another endocrine disruptor that has become a replacement for BPA in consumer products, is highly important to public safety

Effects of endocrine-disrupting chemical exposure on zebrafish ovarian follicles

The process of oocyte maturation involves both nuclear and cytoplasmic events that are essential for the production of viable eggs and subsequent fertilization in sexually reproducing animals. In zebrafish, oocyte nuclear maturation (meiotic resumption) is marked by a transition from opaque to translucent ovarian follicles. This transition is called clearing and results from germinal vesicle breakdown (GVBD) and the transformation of vitellogenin into yolk proteins. Oocyte maturation can be perturbed by endocrine-disrupting chemicals (EDCs). These EDCs have been broadly shown to interfere with reproductive development. Many herbicides and pesticides used agriculturally act as EDCs. These chemicals can enter aquatic ecosystems via runoff and erosion. To evaluate the effects of EDCs on zebrafish oocyte maturation, zebrafish ovarian follicles were cultured and exposed to various concentrations of either atrazine, 2,4-D, or diazinon. Follicles were evaluated at 2, 3, and 4 hours for size and viability, but clearing was assessed only at 4 hours post-exposure. Atrazine and diazinon significantly reduced follicle clearing at the tested concentrations. No effect was observed with 2,4-D exposure. At low enough concentrations, none of the chemicals produced endocrine-disrupting effects. The results suggest that at or above environmentally relevant concentrations, some EDCs impair oocyte maturation in exposed zebrafish follicles. The results support the need to monitor EDC exposure to prevent harmful effects not only on aquatic organisms, but also on humans and wildlife that are also exposed to these contaminants

Evaluating the Effects of Bisphenols F and S with Respect to Bisphenol A on Primordial Germ Cell Migration in Zebrafish (Danio rerio) Embryos Using Immunofluorescence Microscopy

Primordial Germ Cell (PGC) migration occurs in early embryonic development and is highly conserved across taxa. PGC migration occurs within the first 24 hours post fertilization (hpf) in zebrafish, making the organism an efficient model for observing the migration pathway. Proper PGC migration is necessary for normal gonad development and, in some species, sex determination. Disruption of this process leads to defects in gonad formation and abnormal sex determination and differentiation. Studies show that endocrine-disrupting chemicals such as bisphenol A (BPA) disrupt PGC migration in zebrafish. BPA is an estrogenic compound that has been linked to a variety of human diseases, including various cancers, diabetes, reproductive disorders, obesity, and cardiovascular diseases. It is one of the most widely used synthetic compounds worldwide, as it is used to make polycarbonate plastics. Many studies provide evidence of the harmful effects of BPA on living organisms. In response, manufacturers have started to use replacements such as bisphenol F (BPF) and bisphenol S (BPS). However, due to their structural similarity, it is likely that BPF and BPS are just as harmful to organisms as BPA. In this study, we use antibody staining and immunofluorescence microscopy to confirm that BPA exposure results in abnormal PGC migration in zebrafish embryos, as previously studied, and to illustrate that BPF and BPS exposure results in similar PGC migration defects

The Early History of Sussex

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Transcription of nanos-1 in Zebrafish Embryos is not Affected by Bisphenol A: Evaluated Using Quantitative Real-Time PCR

The presence of primordial germ cells (PGCs) is crucial for proper gonad formation in zebrafish (Danio rerio). The many aspects of PGC migration that allow these cells to reach the proper location at the gonadal ridge include receptors, ligands, germ plasm components, and internal maintenance of PGCs. Any one of these factors could be affected by endocrine-disrupting chemicals (EDCs), which have been shown to alter the directed migration of these cells during early embryonic development. Based on recent research wherein the EDC bisphenol A (BPA) inhibited normal PGC migration, we have used the same dose of BPA to determine the impact of BPA on a gene central to proper germ cell migration. Zebrafish embryos were exposed to BPA, and the levels of the target gene nanos-1 were analyzed using quantitative real-time PCR (q-PCR). The target gene nanos-1 is a critically important germplasm component that allows for survival and proper migration of PGCs. The q-PCR results showed that BPA did not affect the transcription level of nanos-1 in zebrafish embryos

Corporate Citizenship and Community Stakeholders

Stipulating that work on corporate citizenship is intended to add to the conversation around the role of business in society, it is reasonable to assume that scholars adopting (and adapting) the language of corporate citizenship find something there that allows for better description, analysis and synthesis of this role. Though what \u27better\u27 may mean here remains an open question, a sensible place to begin considering the question is to compare and contrast corporate citizenship with more established ways of conceiving business\u27s role in society such as, in the case of this chapter, stakeholder theory

Stakeholders

This landmark book takes a retrospective look at the most important and influential works in the study of stakeholders since Freeman’s 1984 publication, Strategic Management: A Stakeholder Approach. 2009 marked the 25th anniversary of this watershed in organizational scholarship, so now is an excellent time for Phillips and Freeman to revisit this topical and exciting subject. From the tremendous upsurge in the literature, the editors have carefully selected ground-breaking works on topics including corporate governance, stakeholder-agency theory, management models, ethical theory and stakeholder orientation. This invaluable volume will shape the thinking of scholars and academics for the next 25 years.https://scholarship.richmond.edu/bookshelf/1048/thumbnail.jp

Cluster growth in the dynamical Erdös-Rényi process with forest fires

We investigate the growth of clusters within the forest fire model of Ráth and Tóth [EJP, vol 14, paper no 45]. The model is a continuous-time Markov process, similar to the dynamical Erdős-Rényi random graph but with the addition of so-called fires. A vertex may catch fire at any moment and, when it does so, causes all edges within its connected cluster to burn, meaning that they instantaneously disappear. Each burned edge may later reappear. We give a precise description of the process CtCt of the size of the cluster of a tagged vertex, in the limit as the number of vertices in the model tends to infinity. We show that CtCt is an explosive branching process with a time-inhomogeneous offspring distribution and instantaneous return to 1 on each explosion. Additionally, we show that the characteristic curves used to analyse the Smoluchowski-type coagulation equations associated to the model have a probabilistic interpretation in terms of the process CtCt

What Stakeholder Theory Is Not

The term stakeholder is a powerful one. this is due, to a significant degree, to its conceptual breadth. The term means many different things to many different people and hence evokes praise or scorn for a wide variety of scholars and practitioners of myriad academic disciplines and backgrounds. Such breadth of interpretation, though one of stakeholder theory\u27s greatest strengths, is also one of its most prominent theoretical liabilities as a topic of reasoned discourse. Much of the power of stakeholder theory is a direct result of the fact that, when used unreflectively, its managerial prescriptions and implications are nearly limitless. When discussed in its instrumental variation (i.e., that managers should attend to stakeholders as a means to achieving other organizational goals such as profit or shareholder wealth maximization) stakeholder theory stands virtually unopposed. The goal of the current paper is like that of a controlled burn that clears away some of the underbrush of misinterpretation in the hope of denying easy fuel to the critical conflagration that would attempt to raze the theory. The aim is to attempt to narrow its technical meaning for greater facility of use in management and organizational studies. By elaborating a number of common misinterpretations of the theory, we hope to render a stronger and more convincing stakeholder theory as a starting place for future research

Stakeholder Theory and Marketing: Moving from a Firm-Centric to a Societal Perspective

This essay is inspired by the ideas and research examined in the special section on “Stakeholder Marketing” of the Journal of Public Policy & Marketing in 2010. The authors argue that stakeholder marketing is slowly coalescing with the broader thinking that has occurred in the stakeholder management and ethics literature streams during the past quarter century. However, the predominant view of stakeholders that many marketers advocate is still primarily pragmatic and company centric. The position advanced herein is that stronger forms of stakeholder marketing that reflect more normative, macro/societal, and network-focused orientations are necessary. The authors briefly explain and justify these characteristics in the context of the growing “prosociety” and “proenvironment” perspectives—orientations that are also in keeping with the public policy focus of this journal. Under the “hard form” of stakeholder theory, which the authors endorse, marketing managers must realize that serving stakeholders sometimes requires sacrificing maximum profits to mitigate outcomes that would inflict major damage on other stakeholders, especially society