Radiation-Induced Bystander Effects in Cultured Human Stem Cells

The radiation-induced "bystander effect" (RIBE) was shown to occur in a number of experimental systems both in vitro and in vivo as a result of exposure to ionizing radiation (IR). RIBE manifests itself by intercellular communication from irradiated cells to non-irradiated cells which may cause DNA damage and eventual death in these bystander cells. It is known that human stem cells (hSC) are ultimately involved in numerous crucial biological processes such as embryologic development; maintenance of normal homeostasis; aging; and aging-related pathologies such as cancerogenesis and other diseases. However, very little is known about radiation-induced bystander effect in hSC. To mechanistically interrogate RIBE responses and to gain novel insights into RIBE specifically in hSC compartment, both medium transfer and cell co-culture bystander protocols were employed.Human bone-marrow mesenchymal stem cells (hMSC) and embryonic stem cells (hESC) were irradiated with doses 0.2 Gy, 2 Gy and 10 Gy of X-rays, allowed to recover either for 1 hr or 24 hr. Then conditioned medium was collected and transferred to non-irradiated hSC for time course studies. In addition, irradiated hMSC were labeled with a vital CMRA dye and co-cultured with non-irradiated bystander hMSC. The medium transfer data showed no evidence for RIBE either in hMSC and hESC by the criteria of induction of DNA damage and for apoptotic cell death compared to non-irradiated cells (p>0.05). A lack of robust RIBE was also demonstrated in hMSC co-cultured with irradiated cells (p>0.05).These data indicate that hSC might not be susceptible to damaging effects of RIBE signaling compared to differentiated adult human somatic cells as shown previously. This finding could have profound implications in a field of radiation biology/oncology, in evaluating radiation risk of IR exposures, and for the safety and efficacy of hSC regenerative-based therapies

Evaluating everyday explanations

People frequently rely on explanations provided by others to understand complex phenomena. A fair amount of attention has been devoted to the study of scientific explanation, and less on understanding how people evaluate naturalistic, everyday explanations. Using a corpus of diverse explanations from Reddit's "Explain Like I'm Five" and other online sources, we assessed how well a variety of explanatory criteria predict judgments of explanation quality. We find that while some criteria previously identified as explanatory virtues do predict explanation quality in naturalistic settings, other criteria, such as simplicity, do not. Notably, we find that people have a preference for complex explanations that invoke more causal mechanisms to explain an effect. We propose that this preference for complexity is driven by a desire to identify enough causes to make the effect seem inevitable

Women and men in the Australasian College of Physical Scientists and Engineers in Medicine: workforce survey

A survey was designed to determine aspirations, motivations and workplace experiences of both female and male members of the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM). The survey collected both quantitate and qualitative data, including open ended questions. This paper reports the survey's qualitative results. The research was approved by Ethics at University of South Australia and endorsed by ACPSEM. All 205 women (30% of total membership) and 440 men were invited to complete the survey online. The data for the qualitative analysis were responses to open-ended questions within the survey. 102 women and 150 men completed surveys were received, with 66 surveys analysed, before data saturation was reached. The survey revealed a number of themes that reflect concerns and opportunities identifying the direction for improving work-life balance and gender equity within the medical physics profession in Australasia. Issues around managing challenging workloads and professional development were amplified for women with children and child-rearing responsibilities, directly contributing to a reduction in work capacity and a reorientation of work-life priorities. The survey provides direction for strategies to improve work-life balance and enable equitable engagement in the profession. The first is to identify and develop role models that actively model successful work-life balance and flexibility in gender roles and in professional conduct. The second is to improve the management skills of current and emerging administrators, advocating for improved work conditions for medical physics professionals at an organisation level. Finally, efforts need to be made to establish flexible professional development and career progression opportunities amongst those that are unable to commit to large workloads, which is common for those with child-rearing responsibilities. The realisation of these strategic goals will reduce the identified barriers to full female participation in the workforce, and shift gender-based subcultures within the workplace.Eva Bezak, Roksolana Suchowerska, Elizabeth Claridge Mackonis, Heath Pillen, Anna Ralston, Annette Haworth, Natalka Suchowersk

A Kinetic-Based Model of Radiation-Induced Intercellular Signalling

It is now widely accepted that intercellular communication can cause significant variations in cellular responses to genotoxic stress. The radiation-induced bystander effect is a prime example of this effect, where cells shielded from radiation exposure see a significant reduction in survival when cultured with irradiated cells. However, there is a lack of robust, quantitative models of this effect which are widely applicable. In this work, we present a novel mathematical model of radiation-induced intercellular signalling which incorporates signal production and response kinetics together with the effects of direct irradiation, and test it against published data sets, including modulated field exposures. This model suggests that these so-called "bystander" effects play a significant role in determining cellular survival, even in directly irradiated populations, meaning that the inclusion of intercellular communication may be essential to produce robust models of radio-biological outcomes in clinically relevant in vivo situations

Are Heuristics Knowledge–Enhancing? Abduction, Models, and Fictions in Science

In my opinion, it is only in the framework of a study concerning abductive inference that we can correctly and usefully grasp the cognitive status of heuristics. To this aim, it is useful to see heuristics in the perspective of the so-called In my opinion, it is only in the framework of a study concerning abductive inference that we can correctly and usefully grasp the cognitive status of heuristics. To this aim, it is useful to see heuristics in the perspective of the so-called fill-up and cutdown problems, which characterize abductive cognition. Abduction is a procedure in which something that lacks classical explanatory epistemic virtue can be accepted because it has virtue of another kind: [9] contend (GW-Model) that abduction presents an ignorance-preserving or (ignorance-mitigating) character. The question is: are abductive heuristic strategies always ignorance preserving? To better reframe the cognitive status of heuristics I will take advantage of my eco-cognitive model (EC-model) of abduction. I contend that, through abductive heuristics, knowledge can be enhanced, even when abduction is not considered an inference to the best explanation in the classical sense of the expression, that is an inference necessarily characterized by an empirical evaluation phase, or inductive phase, as Peirce called it. Hintikka maintains, implicity agreeing with the perspective on abduction as ignorance-preserving, that the true justification of a rule of abductive inference is a strategic one, but this strategic justification does not warrant any specific step of the whole process. I argue, taking advantage of a distinction between static and dynamic aspects of scientific inquiry, that this does mean that every abductive guess heuristically reached is damned to be ignorance-preserving if evidentially inert. When Hintikka contends that the abductive steps which lead to intermediate models cannot have “warrants” at the level of strategic justification, and also at the level of non strategic justification, in my perspective we can relieve ourselves of this burden fill-up and cutdown problems, which characterize abductive cognition. Abduction is a procedure in which something that lacks classical explanatory epistemic virtue can be accepted because it has virtue of another kind: [9] contend (GW-Model) that abduction presents an ignorance-preserving or (ignorance-mitigating) character. The question is: are abductive heuristic strategies always ignorance preserving? To better reframe the cognitive status of heuristics I will take advantage of my eco-cognitive model (EC-model) of abduction. I contend that, through abductive heuristics, knowledge can be enhanced, even when abduction is not considered an inference to the best explanation in the classical sense of the expression, that is an inference necessarily characterized by an empirical evaluation phase, or inductive phase, as Peirce called it. Hintikka maintains, implicity agreeing with the perspective on abduction as ignorance-preserving, that the true justification of a rule of abductive inference is a strategic one, but this strategic justification does not warrant any specific step of the whole process. I argue, taking advantage of a distinction between static and dynamic aspects of scientific inquiry, that this does mean that every abductive guess heuristically reached is damned to be ignorance-preserving if evidentially inert. When Hintikka contends that the abductive steps which lead to intermediate models cannot have “warrants” at the level of strategic justification, and also at the level of non strategic justification, in my perspective we can relieve ourselves of this burde