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Purpose: To extend the investigations of bystander effect induction in fish of the same species as the irradiated fish, to bystander effect induction between fish species and between trophic levels. Materials and methods: To inves...
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Purpose: To extend the investigations of bystander effect induction in fish of the same species as the irradiated fish, to bystander effect induction between fish species and between trophic levels. Materials and methods: To investigate interspecies bystander effect induction, zebrafish and medaka were irradiated with a 0.5 Gy X-ray dose and then swum with non-irradiated fish of the same and opposite species. To investigate trophic level bystander effect induction, CA blackworms were irradiated with the same X-ray dose and then fed to non-irradiated rainbow trout. Results: Reductions in clonogenic survival of the HPV-G (non-transformed human keratinocytes, immortalized with the human papilloma virus) reporter cell line, treated with tissue explant media, revealed that zebrafish and medaka induced a pro-apoptotic bystander effect in the other species and that, in trout, the normally anti-apoptotic effect caused by the consumption of non-irradiated blackworms was significantly reduced or lost if the blackworms had been irradiated. Conclusions: These results are the first to show that a radiation- induced bystander effect can transcend taxonomic group and trophic level in fish. This provides further evidence that bystander signals are widespread and conserved and may be transmitted through an ecosystem, as well as between individuals of the same species.
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This study examined the bystander effect in cyberbullying. Using self-reported data from 257 Czech respondents who had witnessed a cyberbullying attack, we tested whether provided help decreased with increased number of other byst...
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This study examined the bystander effect in cyberbullying. Using self-reported data from 257 Czech respondents who had witnessed a cyberbullying attack, we tested whether provided help decreased with increased number of other bystanders. We controlled for several individual and contextual factors, including empathy, social self-efficacy, empathic response to victimization, and relationship to the victim. Results showed that participants tend to help the victims more in incidents with only one or two other bystanders. We also found that, as in the "offline" realm, bystander effect is not linear: no significant differences were found between incidents with a moderate number (3-10) and a larger number of total bystanders. Our findings, thus, provide support for the presence of the bystander effect in cyberbullying. (C) 2015 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.
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The purpose of this study was to investigate the experiential, psychological, and situational factors influencing behavioral reactions of bystanders witnessing cyberbullying. It also investigated whether the 'bystander effect' is ...
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The purpose of this study was to investigate the experiential, psychological, and situational factors influencing behavioral reactions of bystanders witnessing cyberbullying. It also investigated whether the 'bystander effect' is valid in cyberbullying situations. In addition, a moderation effect of the presence of other bystanders was examined between various influencing factors and bystander's defending tendency. A total of 1058 middle and high school students in metropolitan areas participated in the study, and the experiences of 331 students who have witnessed cyberbullying were analyzed. First, four types of bystanders were found: outsiders were the majority (n = 201, 60.7%), followed by defenders (n = 101, 30.5%), reinforcers (n = 18, 5.4%), and assistants (n = 11, 3.3%). Second, bystanders demonstrated more defending behaviors in the absence of other bystanders, thereby validating the 'bystander effect' in cyberbullying situations. Third, low moral disengagement, low anti-social conformity, high perceived control of the situation and bad relationship with bullies were identified as significant predictors of a bystander's defending tendency. Finally, the presence of other bystanders moderated the effect between moral disengagement and the bystander's defending tendency in relation to bullies. The implications of these results for the effective prevention and intervention of cyberbullying are discussed. (C) 2017 Elsevier Ltd. All rights reserved.
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The purpose of this study was to measure survival fraction of A549 lung carcinoma cells irradiated with charged particles of various LET and to determine mechanisms responsible for enhanced cell killing in the low-dose region. A54...
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The purpose of this study was to measure survival fraction of A549 lung carcinoma cells irradiated with charged particles of various LET and to determine mechanisms responsible for enhanced cell killing in the low-dose region. A549 cells were irradiated with a broadbeam of either 10 and 25 keV/μm protons or 100 keV/μm alpha particles and then processed for clonogenic assays and phospho-histone H3 staining. The survival fraction of unirradiated A549 cells co-cultured with irradiated cells was also evaluated. A549 cells were shown to exhibit low-dose hypersensitivity (HRS) for both protons and alpha particles. The dose threshold at which HRS occurs decreased with increasing linear energy transfer (LET), whereas αs, the initial survival curve slope, increased with increasing LET. In addition, the enhanced cell killing observed after irradiation with alpha particles was partly attributed to the bystander effect, due to the low proportion of hit cells at very low doses. Co-culture experiments suggest a gap junction-mediated bystander signal. Our results indicate that HRS is likely to be dependent on LET, and that a bystander effect and low-dose hypersensitivity may co-exist within a given cell line.
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The bystander effect, the phenomenon that the (real or imagined) presence of others inhibits helping, has often been ascribed to bystanders' apathy. In the present research, we demonstrate that the occurrence of the bystander effe...
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The bystander effect, the phenomenon that the (real or imagined) presence of others inhibits helping, has often been ascribed to bystanders' apathy. In the present research, we demonstrate that the occurrence of the bystander effect has rational roots. Three studies reveal that the presence of other bystanders does not inhibit helping when effective helping requires more than one help-giver. Mediation analyses showed that the bystander effect did not occur when many responses were needed because bystanders did not shift responsibility to others when in the presence of other bystanders. These findings suggest that the rational considerations underlying the bystander effect can mitigate the effects of the presence of other bystanders on helping behaviour when more than one help-giver is needed.
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We hypothesized that radiation-induced rescue effect (RIRE) shared similar mechanisms with ‘metabolic cooperation’, in which nutrient-deprived cancer cells prompted normal cells to provide nutrients. Our data demonstrated that X...
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We hypothesized that radiation-induced rescue effect (RIRE) shared similar mechanisms with ‘metabolic cooperation’, in which nutrient-deprived cancer cells prompted normal cells to provide nutrients. Our data demonstrated that X-ray irradiation induced autophagy in HeLa cells, which could last at least 18 h, and proved that the irradiated cells (IRCs) resorted to breaking down their own intracellular components to supply the molecules required for cell-repair enhancement (e.g. to activate the NF-κB pathway) in the absence of support from bystander unirradiated cells (UICs). Furthermore, autophagy accumulation in IRCs was significantly reduced when they were partnered with UICs, and more so with UICs with pre-induced autophagy before partnering (through starvation using Earle’s Balanced Salt Solution), which showed that the autophagy induced in UICs supported the IRCs. Our results also showed that interleukin 6 (IL-6) was secreted by bystander UICs, particularly the UICs with pre-induced autophagy, when they were cultured in the medium having previously conditioned irradiated HeLa cells. It was established that autophagy could activate the signal transducer and activator of transcription 3 (STAT3) that was required for the IL-6 production in the autophagy process. Taken together, the metabolic cooperation of RIRE was likely initiated by the bystander factors released from IRCs, which induced autophagy and activated STAT3 to produce IL-6 in bystander UICs, and was finally manifested in the activation of the NF-κB pathway in IRCs by the IL-6 secreted by the UICs.
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Although the importance of peer bystanders in bullying has been recognized, there are few studies that examine the phenomenon in relation to Latane and Darley's (1970) classic Bystander Intervention Model, which states that there ...
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Although the importance of peer bystanders in bullying has been recognized, there are few studies that examine the phenomenon in relation to Latane and Darley's (1970) classic Bystander Intervention Model, which states that there are five stages of bystander intervention: (i) notice the event; (ii) interpret the event as an emergency that requires assistance; (iii) accept responsibility for intervening; (iv) know how to intervene or provide help; and (v) implement intervention decisions. This study examined preliminary evidence of reliability and validity of the Bystander Intervention Model in Bullying (Nickerson, Aloe, Livingston, & Feeley, 2014), and the extent to which bullying role behavior (bullying, assisting, victimization, defending, and outsider behavior) and gender predicted each step of the model with a sample of 299 middle school students. Results of a Confirmatory Factor Analysis supported a five-factor structure of the measure corresponding to the steps of the model. There was evidence of convergent validity and Cronbach alpha for each subscale exceeded .75. In addition, students who reported defending their peers were more likely to also engage in all five steps of the bystander intervention model, while victims were more likely to notice events, and outsiders were less likely to intervene. Gender differences and gender interactions were also found. Aggr. Behav. 43:281-290, 2017. (c) 2016 Wiley Periodicals, Inc.
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A spectrum of radiation-induced non-targeted effects has been reported during the last two decades since Nagasawa and Little first described a phenomenon in cultured cells that was later called the "bystander effect". These non-ta...
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A spectrum of radiation-induced non-targeted effects has been reported during the last two decades since Nagasawa and Little first described a phenomenon in cultured cells that was later called the "bystander effect". These non-targeted effects include radiotherapy-related abscopal effects, where changes in organs or tissues occur distant from the irradiated region. The spectrum of non-targeted effects continue to broaden over time and now embrace many types of exogenous and endogenous stressors that induce a systemic genotoxic response including a widely studied tumor microenvironment. Here we discuss processes and factors leading to DNA damage induction in non-targeted cells and tissues and highlight similarities in the regulation of systemic effects caused by different stressors. Crown Copyright (C) 2013 Published by Elsevier Ireland Ltd. All rights reserved.
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In this paper our current knowledge of the mechanisms underlying the induction of bystander effects by low dose low LET ionising radiation is reviewed and the question of how bystander effects may be related to observed adaptive r...
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In this paper our current knowledge of the mechanisms underlying the induction of bystander effects by low dose low LET ionising radiation is reviewed and the question of how bystander effects may be related to observed adaptive responses or other protective effects of low doses exposures is considered. Bystander effects appear to be the result of a generalised stress response in tissues or cells. The signals may be produced by all exposed cells but the response may require a quoram in order to be expressed. The major response involving low LET radiation exposure discussed in the existing literature is a death response. This has many characteristics of apoptosis but is p53 independent. While a death response might appear to be adverse, the position is argued in this paper, that it is in fact protective and removes damaged cells from the population. Since many cell populations carry damaged cells without being exposed to radiation (so called 'background damage', it is possible that low doses exposures cause removal of cells damaged by agents other than the test dose of radiation. This mechanism would lead to the production of 'U-shaped' dose response curves. In this scenario, the level of 'adaptive' or beneficial response will be related to the background damage carried by the cell population. This model may be important when attempting to predict the consequences of mixed exposures involving radiation and other environmental stressors.
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Investigation of the radiation-induced bystander effect plays an important role in the
understanding of the mechanisms of radiation response after low-dose irradiation.
Sphingomyelinase (SMase) was activated by radiation and requi...
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Investigation of the radiation-induced bystander effect plays an important role in the
understanding of the mechanisms of radiation response after low-dose irradiation.
Sphingomyelinase (SMase) was activated by radiation and required the metal element
for its activation. For further elucidation of the bystander effect, we investigated the
relationship between its induction by acid SMase and a factor secreted from the
irradiated tumor cells. In the cell culture medium transfer experiment after irradiation at
a dose of 0.1 Gy, cell death was induced in non-irradiated cells. However, when cells
received prior treatment with SMase inhibitor, cell death was not induced. When
fluctuations in the activation of SMase and metal elements were detected, both
intracellularly and extracellularly after irradiation, an increase in SMase activity and Zn
concentration occurred within the cells at 5 min and outside of the cells at 15 min after
irradiation. This increase in zinc concentration at 15 min after irradiation was
suppressed by treatment with SMase inhibitor. These results suggest that activation of
SMase, which is related to the bystander effect, is dependent on zinc.
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