MECHANISMS OF RESISTANCE TO HALOGENATED AND NON-HALOGENATED AHR LIGANDS IN CHRONICALLY CONTAMINATED KILLIFISH POPULATIONS

Chronically contaminated killifish from Newark Bay (NB) NJ, and New Bedford Harbor (NBH) MA, have developed resistance to halogenated aromatic hydrocarbons that bind to and activate the aryl hydrocarbon receptor (AHR). To study the mechanisms of resistance, adult killifish were exposed to halogenated and non-halogenated AHR ligands and enzymatic and toxicological endpoints were measured in adult and embryonic fish. The chlorinated and non-chlorinated AHR ligands 3,34,4-tetrachlorobiphenyl (PCB77) and benzo-a-pyrene (B[a]P) induced cytochrome P450 1A (CYP1A) in reference site, but not in NB killifish. Expression of CYP3A (not part of the AHR gene battery) was inducible only in Flax Pond killifish. Basal expression of the phase II enzyme glutathione-s-transferase (GST) was higher in NB killifish. These results suggest that NB killifish are resistant to CYP1A induction by chlorinated and non-chlorinated AHR ligands. Higher basal GST activity observed in NB killifish could be protective against toxicity caused by contaminants found in this site. Activation of AHR and induction of CYP1A, by AHR ligands has been associated with the toxic effects caused by these chemicals. To determine the association between resistance to CYP1A induction and the toxicity caused by AHR ligands, CYP1A activity, developmental deformities and reactive oxygen species (ROS) production were measured in reference site and contaminated (NB and NBH) killifish embryos exposed to AHR ligands. 3,34,45-pentachlorobiphenyl (PCB126) and 3-methylcholantherene (3-MC) induced CYP1A, and ROS production in reference site embryos. NB and NBH embryos were resistant to PCB126 induction of CYP1A, but responded to 3-MC. Killifish embryos from NB and NBH were resistant to PCB126 induced deformities. PCB126 and 3-MC did not increase ROS production in NB or NBH killifish embryos. Alpha-naphthoflavone (ANF) (an AHR/CYP1A inhibitor) blocked PCB126 mediated deformities and CYP1A induction in reference site embryos, but increased ROS production. The P450 inhibitor, piperonyl butoxide (PBO) was able to block PCB126 mediated induction of CYP1A activity and ROS production. These results suggest that PCB126 induced deformities are dependent on activation of AHR and CYP1A induction. In chronically contaminated killifish populations, loss of sensitivity to coplanar PCBs and PAHs could be through reduced expression of AHR, or altered DNA sequence or methylation status of the CYP1A gene promoter. Hepatic AHR expression, measured by photoaffinity labeling, was lower in NB killifish than reference site animals, suggesting that NB killifish express less AHR protein. DNA sequence analysis did not reveal considerable differences between contaminated and reference site populations, however additional DNA fragments were observed in some promoters but not in others. The methylation of the CYP1A promoters was studied using methylation sensitive restriction enzymes and no differences were detected between reference site and NB killifish. Treatment with the DNA methyltransferase inhibitor AzaC did not restore CYP1A induction by PCB126 in NB killifish. These studies suggest that resistance to activation of AHR and induction of xenobiotic activating enzymes (CYP1A and CYP3A) in combination with increased expression of conjugating enzymes (GST) protects chronically contaminated killifish against these chemicals

The effect of downsizing on affective organisational commitment: a contextual proximity perspective

Two assumptions constrain the literature on the effects of downsizing: that all survivors are affected to a similar extent and that the effect of layoffs can be extended to all workforce reductions. Furthermore, there is inconclusive evidence on the long-term effects of downsizing. I address these issues with two empirical studies on a multinational pharmaceutical company analysing the differential effect of four downsizing methods on affective commitment depending on the contextual proximity of employees. Study 1 shows decreasing levels of affective commitment among employees exposed to layoffs and closure of units (lower commitment corresponds to greater exposure) but the opposite was observed in voluntary redundancies and divestment. Study 2 indicates that downsizing has long-term negative effects which are worse for those exposed a second time

Perspectivas latinoamericanas sobre el rol de los profesionales de la comunicación organizacional y las relaciones públicas

The paper presents evidences of the consolidation of organizational communication as a profession in Latin America, and proposes a review of empirical research published on scientific databases about the role of the organizational communication and public relations professional in the region. Different traditions existing in the region and the debate on the name of the professional field, in which the denominations of ‘organizational communication’ and ‘public relations’ prevail, are highlighted. Then, the outstanding consolidation process of that profession in Brazil, achieved by the fact that both market and academia bolstered it, as well as by its early institutionalization, is analyzed. As a result of the review, a classification of the lines of thought on the aforementioned profession that have been most widely disseminated in scientific journals is proposed, and the main researchers and the most empirical research on for each line are shown. It is found that, unlike in European and North American scholarly publishing, in which the performance study of the professional role predominates, in Latin America the concern about the situation of the professional role stands out. Three schools of thought stand out in empirical studies: Research on the profession’s political and social role with studies on its contribution to development and social change; research framed in a strategic view of the profession; and a series of empirical studies that conclude on the influence of the social environment in the practice of the profession in Latin America.O artigo apresenta as evidências da consolidação da profissão na América Latina e propõe uma revisão das pesquisas empíricas publicadas em bases científicas sobre o papel do profissional da comunicação organizacional e as relações públicas na região. São apontadas diferentes tradições presentes na região e o debate sobre o nome do campo profissional, no qual prevalecem as denominações de “comunicação organizacional” e “relações públicas”. Em seguida, analisa-se o destacado processo de consolidação da profissão no Brasil, alcançado pelo impulso do mercado e da academia, bem como pela institucionalização precoce da profissão. Como resultado da revisão, propõe-se uma classificação das linhas de pensamento sobre a profissão que mais tem se difundido em publicações científicas e, para cada uma, são registados os principais pesquisadores e as pesquisas empíricas mais destacadas. Observa-se que, diferentemente da publicação científica da América do Norte e da Europa — onde predomina o estudo do desempenho do papel do profissional —, na América Latina se destaca a preocupação sobre a situação do papel do profissional. Em particular, três correntes de pensamento se sobressaem nos estudos empíricos: as pesquisas sobre a função política e social da profissão com os estudos sobre a colaboração da profissão para o desenvolvimento e para a mudança social; as pesquisas enquadradas em uma perspectiva estratégica da profissão, e uma série de estudos empíricos que concluem sobre a influência do entorno social no exercício da profissão na América Latina.El artículo presenta las evidencias de la consolidación de la profesión en América Latina y propone una revisión de las investigaciones empíricas publicadas en bases científicas sobre el rol del profesional de la comunicación organizacional y las relaciones públicas en la región. Se señalan diferentes tradiciones presentes en la región y el debate sobre el nombre del campo profesional, en el que prevalecen las denominaciones de comunicación organizacional y relaciones públicas. Luego, se analiza el destacado proceso de consolidación de la profesión en Brasil, logrado por el impulso del mercado y la academia, así como por la institucionalización temprana de la profesión. Como resultado de la revisión se propone una clasificación de las líneas de pensamiento sobre la profesión que más se han difundido en publicaciones científicas y, para cada una, se registran los principales investigadores y las investigaciones empíricas más destacadas. Se observa que, a diferencia de la publicación científica de Norte América y Europa, donde predomina el estudio del desempeño del rol profesional, en América Latina se destaca la preocupación sobre la situación del rol del profesional. En particular tres corrientes de pensamiento sobresalen en los estudios empíricos: las investigaciones sobre la función política y social de la profesión con los estudios sobre el aporte de la profesión al desarrollo y el cambio social, las investigaciones enmarcadas en una perspectiva estratégica de la profesión, y una serie de estudios empíricos que concluyen sobre la influencia del entorno social en el ejercicio de la profesión en América Latina.https://revistas.udem.edu.co/index.php/anagramas/article/view/241