J Clem - Academia.edu (original) (raw)
Papers by J Clem
Women and Birth, 2021
BACKGROUND Identifying common factors that influence job satisfaction for midwives working in div... more BACKGROUND Identifying common factors that influence job satisfaction for midwives working in diverse work settings is challenging. Applying a work design model developed in organisational behaviour to the midwifery context may help identify key antecedents of midwives job satisfaction. AIM To investigate three job characteristics - decision-making autonomy, empowerment, and professional recognition as antecedents of job satisfaction in New Zealand (NZ) midwives. METHODS Latent multiple regressions were performed on data from Lead Maternity Carer (LMC) midwives n = 327, employed midwives n = 255, and midwives working in 'mixed-roles' n = 123. FINDINGS We found that professional recognition is positively linked to job satisfaction for midwives in all three work settings. At the same time, decision-making autonomy and empowerment were shown to influence job satisfaction for midwives working as LMCs only. DISCUSSION Our main finding suggests that the esteem generated from being acknowledged as an expert and valuable contributor by maternity health colleagues is satisfying across all work contexts. Professional recognition encompasses the social dimension of midwifery work and influences midwives job satisfaction. Decision-making autonomy and empowerment are task and relational job characteristics that may not be similarly experienced by all midwives to noticeably influence job satisfaction. CONCLUSION Given that job satisfaction contributes to recruitment, retention, and sustainability, our findings show that drivers of job satisfaction differ by midwifery work context. We present evidence to support tailored efforts to bolster midwives job satisfaction, especially where resources are limited.
The alleged estrogen receptor (ER)-mediated activities of eight phthalate esters (i.e., di-2-ethy... more The alleged estrogen receptor (ER)-mediated activities of eight phthalate esters (i.e., di-2-ethyl hexyl, di-n-butyl (DBPE), butyl benzyl (BBPE), di-hexyl (DHPE), diisoheptyl, di-n-octyl, diiso-nonyl, diiso-decyl) were investigated in several in vitro bioassays. Results from recombinant receptor/reporter gene assays consisting of MCF-7 human breast cancer cells transiently transfected with the Ga14-human estrogen receptor construct, Ga14-HEGO, and the Ga14-regulated luciferase reporter gene, 17m5-G-Luc, have shown that 10 {micro}M of DBPE, BBPE, or DHPE exhibited 36, 42, and 20% activity, respectively, when compared to the 100% response induced by the standard, 1 nM 17{beta}-estradiol (E2). However, these increases, while statistically significant, are not sufficient to conclude that DBPE, BBPE, or DHPE are estrogenic. No significant increase in luciferase activity was observed with the five remaining phthalate esters. In preliminary studies, only BBPE was found to (1) induce lucife...
Women and Birth, 2021
Introduction: This research aimed to identify what supports and what hinders job autonomy for mid... more Introduction: This research aimed to identify what supports and what hinders job autonomy for midwives in New Zealand. Methods: Registered midwives participated in an open-ended, online survey in 2019. Anonymised participants were asked to describe an incident when they felt they were using their professional judgement and/or initiative to make decisions and the resultant actions. The data was analysed thematically. Findings: The participants identified that autonomy is embedded within midwifery practice in New Zealand. Self-employed midwives who provide continuity of care as Lead Maternity Carers, identified they practice autonomously 'all the time'. The relationship with women and their family, and informed decision making, motivated the midwife to advocate for the womanregardless of the midwife's work setting. Midwifery expertise, skills, and knowledge were intrinsic to autonomy. Collegial relationships could support or hinder the midwives' autonomy while a negative hospital work culture could hinder job autonomy. Discussion: Midwives identified that autonomous practice is embedded in their day to day work. It strengthens and is strengthened by their relationships with the woman/whanau and when their body of knowledge is acknowledged by their colleagues. Job autonomy was described when midwifery decisions were challenged by health professionals in hospital settings and these challenges could be viewed as obstructing job autonomy. Conclusion: The high job autonomy that New Zealand midwives enjoy is supported by their expertise, the women and colleagues that understand and respect their scope of practice. When their autonomy is hindered by institutional culture and professional differences provision of woman-centred care can suffer.
New Zealand College of Midwives Journal, 2020
Background: Following the receipt of a pregnancy test result, a woman's access to timely and appr... more Background: Following the receipt of a pregnancy test result, a woman's access to timely and appropriate information is essential for enabling her to make informed decisions. Individually tailored information can be hard to find, which can constrain decision-making, leading to delayed engagement with maternity services. Carefully designed eHealth interventions could speedily deliver targeted information but women at most risk of adverse birth outcomes may experience significant barriers to accessing digitally delivered information. Aim: To investigate how women find information about what to do next when they have a positive or negative pregnancy test. Method: Professional networks were used to recruit women from ethnic and socio-demographic groups associated with delayed engagement in antenatal care. Informed by participatory design, we sought to understand how these women access reproductive health information following a pregnancy test; and then we explored their perspectives about which eHealth tool they would find most helpful. We collected qualitative and quantitative data from three focus groups and two individual interviews. Qualitative data were analysed interpretively using thematic analysis, and quantitative data were analysed descriptively. Findings: Women accessed reproductive information following pregnancy from doctors, school nurses, midwives, the internet and, for some, family and friends. Barriers to access included financial challenges, degree of information literacy and the feeling of being judged by others. Participants expressed a clear preference for reproductive information which was free, instant, private and personalised to them. The most preferred eHealth tool was a free 0800 number and the least popular were the QR code and free text options. Conclusions: Despite the rapid uptake of eHealth health tools to access health information in general, following a pregnancy test, study participants indicated they valued free, confidential and personal interactions with a health professional to supplement any electronic information they used or accessed. These methods did not eclipse the importance to many participants of embodied, faceto-face contact with a desired health professional, specifically a midwife.
Reflective Practice, 2020
A Practice Development Tool (PDT) was developed to assist midwifery students to reflect in a way ... more A Practice Development Tool (PDT) was developed to assist midwifery students to reflect in a way that would contribute to the development of their practice. A survey was undertaken to explore midwifery students' experience of using this tool across the three years of their undergraduate programme. While a simplified model using reflection to develop practice was helpful, this was alongside the significant contribution of the relationship with the educator who supported them in practice and provided feedback on their use of the tool. The students indicated that they became better at reflecting, identifying their strengths and areas for improvement, and their ability to plan for change within the midwifery programme. The need to provide scaffolding of the elements within the tool, and subsequently to improve the education on the use of the tool at each year, was highlighted for future development.
New Zealand College of Midwives Journal, 2019
Background: Strong evidence supports the premise that many low-risk women and babies experience p... more Background: Strong evidence supports the premise that many low-risk women and babies experience perinatal outcomes, in a free-standing, midwifery-led, primary level maternity unit (PMU) similar to, or better than, those of an obstetric-led tertiary level maternity hospital (TMH). Aim: The aim of this study was to identify whether place of birth affected measurable maternal and neonatal outcomes in a low-risk cohort within one New Zealand District Health Board. Method: We gathered the birth records of a retrospective cohort of low-risk women (n=4,207), who had birthed within two distinct environments, including one TMH and three PMUs. Comparison was made of three maternal outcomes: emergency caesarean section, acute postpartum admission to theatre/high dependency unit/intensive care unit (<12hr post birth) and postpartum haemorrhage (PPH; >500ml). Neonatal outcomes analysed were 5-min Apgar score <7 and acute neonatal admission to neonatal intensive care unit (NICU; <12hr post birth). Findings: Logistic regression of data revealed statistically significant associations between place of birth and the five perinatal outcomes. Low-risk women giving birth in one of the three PMUs had fewer emergency caesarean sections (OR 0.25, 95% CI, 0.157-0.339), PPHs (OR 0.692, 95% CI, 0.534-0.898), and acute postpartum admissions to theatre (OR 0.201, 95% CI, 0.102-0.398) than women giving birth in the TMH. Babies born to women at a PMU were less likely to experience a 5-min Apgar <7 (OR 0.313, 95% CI, 0.124-0.791) or acute neonatal admission to NICU (OR 0.492, 95% CI, 0.324-0.747) compared to babies of women of similar risk status, born in the TMH. Conclusion: Low-risk women birthing in PMUs in South Auckland, New Zealand, experienced a significant reduction in morbidity for themselves and their babies.
New Zealand College of Midwives Journal, 2018
Background: Birth is a socially constructed experience for Pasifika living in New Zealand that is... more Background: Birth is a socially constructed experience for Pasifika living in New Zealand that is shaped by their community and maternity provider's influences. Pasifika women in the Counties Manukau region predominantly choose to birth in a tertiary facility despite there being primary facilities available. Aim: This study asked Pasifika women about their choices for place of birth within the Counties Manukau District Health Board region. Method: Six healthy, low risk Pasifika women, who had given birth in the Counties Manukau District Health Board region, participated in this study. All women were interviewed individually and conversations were analysed using thematic analysis, followed by a hermeneutic interpretation. Findings: The women shared a culture of "we birth at Middlemore [Hospital] and that is where you have babies". Their data surprised us as researchers. Those who had been transferred postnatally to primary units tended to still prefer Middlemore. We use the word "prejudice" in recognising that we thought (backed by research evidence) that they would be more likely to have a normal birth in a primary unit, and would prefer that experience. They told us that Middlemore Hospital was close to home; it was a place they knew; and it was where they preferred to give birth. The Pasifika women's understanding of choice of birthplace was influenced by their community and, perhaps, by their midwife. While they seemed to have minimal understanding of why they would choose to birth at a primary birthing unit, there was a sense that even if they had this knowledge, they would not have changed their minds. They had a trust of, and familiarity with, Middlemore Hospital that held firm. They had their prejudice; we had ours. Recognising these different views offers a different space for conversation. Conclusion: It is important that any new or redesigned birthing unit be planned in collaboration with Pasifika women if it is intended for their use. Further, it is important that midwives take the time to listen to Pasifika women, and those from other cultures, to understand their point of view.
Chinook salmon from lakes Ontario and Huron, and Coho salmon from lakes Ontario and Erie were cap... more Chinook salmon from lakes Ontario and Huron, and Coho salmon from lakes Ontario and Erie were captured during their fall spawning migration. Subsamples of extracted pooled muscle, liver and egg tissue were used to measure congener specific PCBs, chlorinated dioxins and furans as well as bioassay derived 2,3,7,8-TCDD toxic equivalent concentration (TEC). The cell culture bioassays used to measure TECs were rat hepatoma (H411E) and rainbow trout hepatocyte (RTL-W1) continuous cell lines as well as chicken embryo hepatocyte primary culture (CEH). Although excellent correlations were found between all 3 cell culture bioassays, CEH was found to be 10 times and 30 times more sensitive than H411E and RTL-W1 respectively. Lake Ontario TECs were found to be higher than either Lake Huron or Lake Erie samples for both species of Salmon, and Chinook salmon was elevated over Coho Salmon. Chemical data indicates that the more toxic coplanar PCBs are selectively concentrated in eggs as compared to liver and muscle. Bioassay derived TECs are discussed with regard to chemical contribution of the PCB and dioxin/furan congeners based on an additive model.
The RTL-WL rainbow trout liver and H4IIE rat hepatoma cell lines were exposed to organic solvent ... more The RTL-WL rainbow trout liver and H4IIE rat hepatoma cell lines were exposed to organic solvent extracts from livers of lake trout collected from two Lake Superior sites (Jackfish Bay -- a pulp mill site and Black Bay -- a reference site) and one Lake Ontario site (Eastern Basin -- a PCB-contaminated site). These two bioassays measure the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent concentrations (TECs) of the residues as indicated by their relative ability to induce 7-ethoxyresorufin-o-deethylase (EROD) activity. This estimates the burden of compounds that could act through the Ah receptor and are potentially toxic, Subsamples of liver were also analyzed for hepatic EROD activity. For Jackfish Bay extracts, the H4IIE mean TEC was found to be significantly higher than that derived using RTL-WL, indicating a more potent contaminant mixture to this mammalian model. No such difference was seen between mean TECs derived for Lake Ontario extracts. The reference site, Black Bay, had TECs significantly lower than those from the other two sites. A significant positive correlation between TECs derived with H4IIE vs. RTL-WL was seen for Jackfish Bay, but not Lake Ontario. Lake Ontario extracts had a significantly higher mean TEC than the mean TEC from Jackfish Bay regardless more » of the cell line used. Hepatic EROD activities of liver subsamples from Jackfish Bay were found to be significantly higher than subsamples from Black Bay, while Lake Ontario subsamples were variable. No significant correlation was found between hepatic EROD activity and TEC values. The RTL-WL cell line bioassay was found to have excellent utility for rapid TEC determination and should be generally suitable for estimating the toxic potency of environmental samples. « less
The Science of the total environment, Jan 15, 2005
Ambient particulate matter (PM(10)) in urban centres varies depending on emission sources, geogra... more Ambient particulate matter (PM(10)) in urban centres varies depending on emission sources, geography, demography, and meteorology. Hence physical (PM(10), wind speed, rainfall, temperature), chemical (polycyclic aromatic hydrocarbons, PAH), and toxicological (Ames Test, H4IIE EROD Assay) analyses were done on daily PM(10) (approximately 1640 m(3)/day) collected from three New Zealand urban sites where winter emissions were predominantly due to domestic home heating. Daily PM(10) levels ranged between 9.7 and 20.8 in summer and between 21.8 and 61.0 microg/m(3) in winter. Daily PAH concentrations were 0.5, 0.45, and 1.5 ng/m(3) in summer and 52.1, 128.9, and 5.8 ng/m(3) in winter at sites Christchurch, Alexandra and Dunedin, respectively. During winter, 74% of PM(10) extracts from all three sites showed significant mutagenicity in the Ames Test (TA 98, -S9), whereas approximately 25% of the daily PM(10) was mutagenic in summer. Benzo[a]pyrene and BaP carcinogenic equivalence concentr...
Toxicological Sciences, 1998
The estrogenic activities of eight phthalate esters (i.e., di-2-ethylhexyl, din -butyl (DBP), but... more The estrogenic activities of eight phthalate esters (i.e., di-2-ethylhexyl, din -butyl (DBP), butylbenzyl (BBP), di-hexyl (DHP), diisoheptyl, di-77-octyl, diiso-nonyl, diiso-decyl) were investigated in vitro using estrogen receptor (ER) competitive ligand-binding and mammalian-and yeast-based gene expression assays. In vivo, their effects on uterine wet weight and vaginal cell cornification using ovariectomized Sprague-Dawley rats were assessed. DBP, BBP, and DHP weakly competed with 17/3-estradiol (E2) for binding to the ER in competitive ligand-binding assays. In gene expression assays using MCF-7 cells transiently transfected with the Gal4-human estrogen receptor construct, Gal4-HEGO, and the Gal4-regulated luciferase reporter gene, 17m5-G-Luc, 10 fiM DBP, BBP, or DHP exhibited 36, 42, and 20% activity, respectively, when compared to the 100% response observed with 10 nM E2. Only BBP was found to induce luciferase activity (32%) in HeLa cells stably transfected with Gal4-HEGO and 17m5-G-Luc constructs and to impart minimal ERmediated viability to the E2-dependent recombinant yeast strain, PL3, on selective medium. No significant responses were observed with the other phthalate esters in any of the in vitro assays. In vivo, none of the eight phthalate esters reproducibly induced significant increases in uterine wet weight in immature ovariectomized Sprague-Dawley rats treated with oral doses of 20, 200, or 2000 mg/kg of phthalate ester. In addition, treatment with phthalate esters at the same doses did not affect the degree of vaginal epithelial cell cornification in mature ovariectomized rats. These results indicate that only selected phthalate esters (i.e., DBP, BBP, and DHP) exhibit weak ER-mediated activity in some in vitro assays at high concentrations but none of the eight phthalate esters elicited in vivo estrogenic responses based upon results obtained from uterotrophic and vaginal cornification assays.
Molecular and Cellular Endocrinology, 2001
Several fish proteins exhibit compromised function at temperatures outside of their normal physio... more Several fish proteins exhibit compromised function at temperatures outside of their normal physiological range. In this study, the effect of temperature on the ligand binding and the transactivation abilities of the rainbow trout estrogen receptor (rtER) and human estrogen receptor alpha (hERa) were examined. Saturation analysis and gene expression assays, using GST-ER and Gal4-ER fusion proteins consisting of the D, E and F domains of human (hERadef) and rainbow trout (rtERdef) receptors, show that GST-rtERdef E2 binding affinity and transactivation ability decrease with increasing temperature. A comparison of the amino acid sequence differences between their ligand binding pockets identified two conservative amino acid residue substitutions in rtER (M317, I496) and hERa (L349, M528). The effect of these substitutions on ligand binding and transactivation were examined by constructing reciprocal mutants, which effectively exchanged the binding pockets between rtER and hERa. The rtERdef M317L:I496M double mutant exhibited increased E2 binding affinity and transactivation ability at higher temperatures, and displayed hERa phenotypic behavior for the phytoestrogen, coumestrol. The hERadef L349M:M528I double mutant also exhibited a modest trend towards adopting the rtER phenotype. These studies demonstrate that conservative changes in residue hydrophobicity and volume can significantly affect ER ligand binding and transactivation ability in a temperature-dependent manner. The lack of a complete exchange of phenotypes between rtER and hERa indicates that factors outside of the ligand binding pocket are also involved.
Journal of Great Lakes Research, 1994
... No. 23. Clemons, IH, van den Heuvel, MR, BoIs, NC, and Dixon, DG 1993. Toxic equivalent facto... more ... No. 23. Clemons, IH, van den Heuvel, MR, BoIs, NC, and Dixon, DG 1993. Toxic equivalent factors for selected congeners of PCDDs, PCDFs and PCBs using a rainbow trout liver cell line (RTL-W1). ... Sci. 48:875-883. ___, Hufnagle, Jr., Lc, Clayton, MK, and Peter son, RE 1992. ...
Journal of Applied Toxicology, 2000
ABSTRACT Estrogen receptor (ER) transactivation assays were initially designed to study endogenou... more ABSTRACT Estrogen receptor (ER) transactivation assays were initially designed to study endogenous mechanisms of steroid hormone action, but more recently have been used to assess industrial chemicals for potential estrogenic activity. Given the diverse spectrum of physicochemical properties of these chemicals, we examined the effects of pH (a weak organic and strong inorganic acid and base), hyperosmolality (NaCl, mannitol) and two different vehicles (DMSO, Triton X-100) on responses to estradiol-17beta (E2) in an ER transactivation assay. MCF-7 human breast cancer cells were transiently transfected with a chimeric estrogen receptor (Gal4-HEG0) and a Gal4-regulated luciferase reporter gene (17m5-G-Luc), treated with E2 under various test conditions, and then assessed for ER-mediated luciferase activity. Maximal E2-induced reporter activity was observed at pH 7.8 (pre-incubation), but was markedly reduced at pH < or =7.5, or > or =8.0 (P < 0.001), even though there was no evidence of cytotoxicity. Hyperosmolality induced by addition of mannitol (> or =25 mM) resulted in significant decreases in overall assay responsiveness, whereas NaCl (> or =80 mM) decreased the sensitivity of the assay by increasing the no-observed-effect level for E2 compared to control cultures (330 mOsm). The maximal DMSO concentration that resulted in consistently high E(2)-induced reporter activity was 0.1%, whereas concentrations of Triton X-100 above 1 ppm inhibited E2-induced reporter responses and were cytotoxic above 10 ppm. These results indicate that various physicochemical factors have the potential to confound assay data if not kept within predefined operational limits.
Environmental Toxicology and Chemistry, 1998
For livers of lake trout from three Great Lakes sites, the 2,3,7,8-tetrachlorodibenzo-p-dioxin (T... more For livers of lake trout from three Great Lakes sites, the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalent concentrations (TEQs) were determined in four ways. Bioassay-derived (BD) TEQs were measured with rat (H4IIE) and rainbow trout (RTL-W1) cell lines, and ...
Environmental Science & Technology, 1998
Polar and nonpolar fractions prepared from an organic extract of inhalable air particulate materi... more Polar and nonpolar fractions prepared from an organic extract of inhalable air particulate material collected from an urban location in downtown Toronto, Ontario, Canada, were examined for estrogen and Ah receptor-mediated activities using in vitro gene expression assays. The presence of estrogenic activity was determined using MCF-7 human breast cancer cells transiently transfected with a Gal4-human estrogen receptor chimera and a Gal4-regulated luciferase reporter gene. 2,3,7,8-Tetracholordibenzo-pdioxin (TCDD)-like activity was detected using Hepa 1c1c7 cells transiently transfected with a CYP1A1-regulated reporter gene (pGudLuc 1.1). Significant estrogenic and TCDDlike activity was detected in the crude extract and in the nonpolar fractions. Results from the analyses of nine environmentally prevalent polyaromatic hydrocarbons (PAH) indicated that PAH might be significant contributors to the observed activity. Surprisingly, three PAH, namely benzo-[a]pyrene, chrysene, and benz[a]anthracene, were found to substantially induce in vitro estrogenic and TCDD-like activities that were mediated by the estrogen and Ah receptors, respectively. Benzo[k]fluoranthene, dibenz[a,h]anthracene, and anthracene also exhibited significant in vitro TCDD-like activity. These results demonstrate the utility of in vitro gene expression assays to identify the presence of potential endocrine disruptors within complex mixtures.
Cell Biology and Toxicology, 1993
A cell line, RTL-W1, has been developed from the normal liver of an adult rainbow trout by proteo... more A cell line, RTL-W1, has been developed from the normal liver of an adult rainbow trout by proteolytic dissociation of liver fragments. RTL-W1 can be grown routinely in the basal medium, L-15, supplemented with 5% fetal bovine serum. In this medium, the cells have been passaged approximately 100 times over an 8-year period. The cells do not form colonies or grow in soft agar. The cultures are heteroploid. The cell shape was predominantly polygonal or epithelial-like, but as cultures became confluent, bipolar or fibroblast-like cells appeared. Among the prominent ultrastructural features of RTL-W1 were distended endoplasmic reticulum and desmosomes. Benzo[a]pyrene was cytotoxic to RTL-W1. Activity for the enzyme, 7-ethoxyresorufin O-deethylase (EROD), which is a measure of the cytochrome P4501A1 protein, increased dramatically in RTL-W1 upon their exposure to increasing concentrations of either beta-naphthoflavone (BNF) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). With these properties, RTL-W1 should be useful for studying the expression of the cytochrome P450 enzymes and as a tool for assessing the toxic potency of environmental contaminants.
Canadian Journal of Fisheries and Aquatic Sciences, 1994
Toxic equivalent factors (TEFs) for eight polychlorinated dibenzo-p-dioxin (PCDD) and polychlorin... more Toxic equivalent factors (TEFs) for eight polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) congeners were derived with a rainbow trout (Oncorhynchus mykiss) cell line, RTL-W1, and compared with TEFs obtained with a rat hepatoma cell line, H4IIE. Cells were exposed to a range of concentrations of the congeners which included 1,2,3,7,8-pentaCDD, 1,2,3,4,7,8-hexaCDD, 1,2,3,6,7,8-hexaCDD, 1,2,3,4,6,7,8-heptaCDD, 2,3,7,8-tetraCDF, 1,2,3,7,8-pentaCDF, 2,3,4,7,8-pentaCDF, and 1,2,3,4,7,8-hexaCDF. Ethoxyresorufin o-deethylase (EROD) activity was measured and EC50 values calculated from a dose–effect curve newly proposed for this purpose. TEFs were computed using 2,3,7,8-tetraCDD standard curves run concurrently with each assay. With the exception of 1,2,3,6,7,8-hexaCDD and 1,2,3,7,8-pentaCDF, all of the RTL-W1-derived TEFs were significantly higher (two- to eightfold higher) than the respective H4IIE TEFs. Immunoblotting analysis with the monoclonal anti-scup ...
Canadian Journal of Fisheries and Aquatic Sciences, 1996
Toxic equivalency factors (potency of a compound relative to the 2,3,7,8-tetrachlorodibenzo-p-dio... more Toxic equivalency factors (potency of a compound relative to the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) standard) for polychlorinated biphenyls (PCBs) were derived from cytochrome P4501A1 induction, measured as ethoxyresorufin o-deethylase (EROD) activity, in a rainbow trout (Oncorhynchus mykiss) liver cell line (RTL-W1) and a rat hepatoma cell line (H4IIE). In RTL-W1 under normal growth conditions, EROD activity was induced only by PCBs 77, 81, 118, and 126. In overconfluent RTL-W1 cultures, EROD induction was also detected with PCBs 105, 156, and 169. Immunoblotting with the polyclonal antibody anti-trout CYP1A1 277-294 /KLH confirmed the results of EROD induction. The RTL-W1 toxic equivalency factors were 0.023 for PCB 126, 0.0064 for PCB 81, 0.0034 for PCB 77, 0.000 16 for PCB 169, and 0.000 017 for PCB 118. Toxic equivalency factors for PCBs 105 and 156 were <0.000 03. All seven PCBs clearly induced EROD activity in H4IIE. Generally the H4IIE toxic equivalency factors were higher than the RTL-W1 toxic equivalency factors. Therefore, the toxic impact of PCBs on rainbow trout probably would be overestimated by currently proposed risk assessment toxic equivalency factors and assessed more appropriately with toxic equivalency factors derived from rainbow trout. Résumé : On a déterminé la valeur du facteur d'équivalence toxique (ou pouvoir toxique d'un composé par rapport à un étalon de 2,3,7,8-tétrachlorodibenzo-p-dioxine (TCDD)) de divers biphényles polychlorés (BPC) d'après l'induction du cytochrome P4501A1, évaluée d'après l'activité de l'éthoxyrésorufine o-déséthylase (EROD) chez une lignée de cellules hépatiques de truite arc-en-ciel (Oncorhynchus mykiss) (RTL-W1) et chez une lignée de cellules d'hépatome de rat (H4IIE). En conditions de culture normales, l'activité EROD n'a été induite que par les BPC 77, 81, 118 et 126 dans les cellules RTL-W1; toutefois, dans des cultures surconfluentes de RTL-W1, les BPC 105, 156 et 169 ont aussi induit une activité EROD. L'immunotransfert avec des anticorps polyclonaux anti-CYP1A1 277-294 /KLH de truite a confirmé ces observations. On a obtenu les facteurs d'équivalence toxique suivants dans les cellules RTL-W1 : 0,023 pour le BPC 126, 0,0064 pour le BPC 81, 0,0034 pour le BPC 77, 0,000 16 pour le BPC 169 et 0,000 017 pour le BPC 118. Le facteur d'équivalence toxique des BPC 105 et 156 était inférieur à 0,000 03. Dans les cultures de H4IIE, les sept BPC ont nettement induit une activité EROD. En général, les facteurs d'équivalence toxique mesurés dans les cellules H4IIE sont plus élevés que ceux obtenus avec les cellules RTL-W1. Par conséquent, avec les facteurs d'équivalence toxique qu'on propose actuellement d'employer dans les évaluations de risque, on surestimerait probablement l'effet toxique des BPC chez la truite arc-en-ciel; l'estimation devrait être plus juste avec des facteurs d'équivalence toxique déterminés au moyen de cellules de truite arc-en-ciel. [Traduit par la Rédaction]
Women and Birth, 2021
BACKGROUND Identifying common factors that influence job satisfaction for midwives working in div... more BACKGROUND Identifying common factors that influence job satisfaction for midwives working in diverse work settings is challenging. Applying a work design model developed in organisational behaviour to the midwifery context may help identify key antecedents of midwives job satisfaction. AIM To investigate three job characteristics - decision-making autonomy, empowerment, and professional recognition as antecedents of job satisfaction in New Zealand (NZ) midwives. METHODS Latent multiple regressions were performed on data from Lead Maternity Carer (LMC) midwives n = 327, employed midwives n = 255, and midwives working in 'mixed-roles' n = 123. FINDINGS We found that professional recognition is positively linked to job satisfaction for midwives in all three work settings. At the same time, decision-making autonomy and empowerment were shown to influence job satisfaction for midwives working as LMCs only. DISCUSSION Our main finding suggests that the esteem generated from being acknowledged as an expert and valuable contributor by maternity health colleagues is satisfying across all work contexts. Professional recognition encompasses the social dimension of midwifery work and influences midwives job satisfaction. Decision-making autonomy and empowerment are task and relational job characteristics that may not be similarly experienced by all midwives to noticeably influence job satisfaction. CONCLUSION Given that job satisfaction contributes to recruitment, retention, and sustainability, our findings show that drivers of job satisfaction differ by midwifery work context. We present evidence to support tailored efforts to bolster midwives job satisfaction, especially where resources are limited.
The alleged estrogen receptor (ER)-mediated activities of eight phthalate esters (i.e., di-2-ethy... more The alleged estrogen receptor (ER)-mediated activities of eight phthalate esters (i.e., di-2-ethyl hexyl, di-n-butyl (DBPE), butyl benzyl (BBPE), di-hexyl (DHPE), diisoheptyl, di-n-octyl, diiso-nonyl, diiso-decyl) were investigated in several in vitro bioassays. Results from recombinant receptor/reporter gene assays consisting of MCF-7 human breast cancer cells transiently transfected with the Ga14-human estrogen receptor construct, Ga14-HEGO, and the Ga14-regulated luciferase reporter gene, 17m5-G-Luc, have shown that 10 {micro}M of DBPE, BBPE, or DHPE exhibited 36, 42, and 20% activity, respectively, when compared to the 100% response induced by the standard, 1 nM 17{beta}-estradiol (E2). However, these increases, while statistically significant, are not sufficient to conclude that DBPE, BBPE, or DHPE are estrogenic. No significant increase in luciferase activity was observed with the five remaining phthalate esters. In preliminary studies, only BBPE was found to (1) induce lucife...
Women and Birth, 2021
Introduction: This research aimed to identify what supports and what hinders job autonomy for mid... more Introduction: This research aimed to identify what supports and what hinders job autonomy for midwives in New Zealand. Methods: Registered midwives participated in an open-ended, online survey in 2019. Anonymised participants were asked to describe an incident when they felt they were using their professional judgement and/or initiative to make decisions and the resultant actions. The data was analysed thematically. Findings: The participants identified that autonomy is embedded within midwifery practice in New Zealand. Self-employed midwives who provide continuity of care as Lead Maternity Carers, identified they practice autonomously 'all the time'. The relationship with women and their family, and informed decision making, motivated the midwife to advocate for the womanregardless of the midwife's work setting. Midwifery expertise, skills, and knowledge were intrinsic to autonomy. Collegial relationships could support or hinder the midwives' autonomy while a negative hospital work culture could hinder job autonomy. Discussion: Midwives identified that autonomous practice is embedded in their day to day work. It strengthens and is strengthened by their relationships with the woman/whanau and when their body of knowledge is acknowledged by their colleagues. Job autonomy was described when midwifery decisions were challenged by health professionals in hospital settings and these challenges could be viewed as obstructing job autonomy. Conclusion: The high job autonomy that New Zealand midwives enjoy is supported by their expertise, the women and colleagues that understand and respect their scope of practice. When their autonomy is hindered by institutional culture and professional differences provision of woman-centred care can suffer.
New Zealand College of Midwives Journal, 2020
Background: Following the receipt of a pregnancy test result, a woman's access to timely and appr... more Background: Following the receipt of a pregnancy test result, a woman's access to timely and appropriate information is essential for enabling her to make informed decisions. Individually tailored information can be hard to find, which can constrain decision-making, leading to delayed engagement with maternity services. Carefully designed eHealth interventions could speedily deliver targeted information but women at most risk of adverse birth outcomes may experience significant barriers to accessing digitally delivered information. Aim: To investigate how women find information about what to do next when they have a positive or negative pregnancy test. Method: Professional networks were used to recruit women from ethnic and socio-demographic groups associated with delayed engagement in antenatal care. Informed by participatory design, we sought to understand how these women access reproductive health information following a pregnancy test; and then we explored their perspectives about which eHealth tool they would find most helpful. We collected qualitative and quantitative data from three focus groups and two individual interviews. Qualitative data were analysed interpretively using thematic analysis, and quantitative data were analysed descriptively. Findings: Women accessed reproductive information following pregnancy from doctors, school nurses, midwives, the internet and, for some, family and friends. Barriers to access included financial challenges, degree of information literacy and the feeling of being judged by others. Participants expressed a clear preference for reproductive information which was free, instant, private and personalised to them. The most preferred eHealth tool was a free 0800 number and the least popular were the QR code and free text options. Conclusions: Despite the rapid uptake of eHealth health tools to access health information in general, following a pregnancy test, study participants indicated they valued free, confidential and personal interactions with a health professional to supplement any electronic information they used or accessed. These methods did not eclipse the importance to many participants of embodied, faceto-face contact with a desired health professional, specifically a midwife.
Reflective Practice, 2020
A Practice Development Tool (PDT) was developed to assist midwifery students to reflect in a way ... more A Practice Development Tool (PDT) was developed to assist midwifery students to reflect in a way that would contribute to the development of their practice. A survey was undertaken to explore midwifery students' experience of using this tool across the three years of their undergraduate programme. While a simplified model using reflection to develop practice was helpful, this was alongside the significant contribution of the relationship with the educator who supported them in practice and provided feedback on their use of the tool. The students indicated that they became better at reflecting, identifying their strengths and areas for improvement, and their ability to plan for change within the midwifery programme. The need to provide scaffolding of the elements within the tool, and subsequently to improve the education on the use of the tool at each year, was highlighted for future development.
New Zealand College of Midwives Journal, 2019
Background: Strong evidence supports the premise that many low-risk women and babies experience p... more Background: Strong evidence supports the premise that many low-risk women and babies experience perinatal outcomes, in a free-standing, midwifery-led, primary level maternity unit (PMU) similar to, or better than, those of an obstetric-led tertiary level maternity hospital (TMH). Aim: The aim of this study was to identify whether place of birth affected measurable maternal and neonatal outcomes in a low-risk cohort within one New Zealand District Health Board. Method: We gathered the birth records of a retrospective cohort of low-risk women (n=4,207), who had birthed within two distinct environments, including one TMH and three PMUs. Comparison was made of three maternal outcomes: emergency caesarean section, acute postpartum admission to theatre/high dependency unit/intensive care unit (<12hr post birth) and postpartum haemorrhage (PPH; >500ml). Neonatal outcomes analysed were 5-min Apgar score <7 and acute neonatal admission to neonatal intensive care unit (NICU; <12hr post birth). Findings: Logistic regression of data revealed statistically significant associations between place of birth and the five perinatal outcomes. Low-risk women giving birth in one of the three PMUs had fewer emergency caesarean sections (OR 0.25, 95% CI, 0.157-0.339), PPHs (OR 0.692, 95% CI, 0.534-0.898), and acute postpartum admissions to theatre (OR 0.201, 95% CI, 0.102-0.398) than women giving birth in the TMH. Babies born to women at a PMU were less likely to experience a 5-min Apgar <7 (OR 0.313, 95% CI, 0.124-0.791) or acute neonatal admission to NICU (OR 0.492, 95% CI, 0.324-0.747) compared to babies of women of similar risk status, born in the TMH. Conclusion: Low-risk women birthing in PMUs in South Auckland, New Zealand, experienced a significant reduction in morbidity for themselves and their babies.
New Zealand College of Midwives Journal, 2018
Background: Birth is a socially constructed experience for Pasifika living in New Zealand that is... more Background: Birth is a socially constructed experience for Pasifika living in New Zealand that is shaped by their community and maternity provider's influences. Pasifika women in the Counties Manukau region predominantly choose to birth in a tertiary facility despite there being primary facilities available. Aim: This study asked Pasifika women about their choices for place of birth within the Counties Manukau District Health Board region. Method: Six healthy, low risk Pasifika women, who had given birth in the Counties Manukau District Health Board region, participated in this study. All women were interviewed individually and conversations were analysed using thematic analysis, followed by a hermeneutic interpretation. Findings: The women shared a culture of "we birth at Middlemore [Hospital] and that is where you have babies". Their data surprised us as researchers. Those who had been transferred postnatally to primary units tended to still prefer Middlemore. We use the word "prejudice" in recognising that we thought (backed by research evidence) that they would be more likely to have a normal birth in a primary unit, and would prefer that experience. They told us that Middlemore Hospital was close to home; it was a place they knew; and it was where they preferred to give birth. The Pasifika women's understanding of choice of birthplace was influenced by their community and, perhaps, by their midwife. While they seemed to have minimal understanding of why they would choose to birth at a primary birthing unit, there was a sense that even if they had this knowledge, they would not have changed their minds. They had a trust of, and familiarity with, Middlemore Hospital that held firm. They had their prejudice; we had ours. Recognising these different views offers a different space for conversation. Conclusion: It is important that any new or redesigned birthing unit be planned in collaboration with Pasifika women if it is intended for their use. Further, it is important that midwives take the time to listen to Pasifika women, and those from other cultures, to understand their point of view.
Chinook salmon from lakes Ontario and Huron, and Coho salmon from lakes Ontario and Erie were cap... more Chinook salmon from lakes Ontario and Huron, and Coho salmon from lakes Ontario and Erie were captured during their fall spawning migration. Subsamples of extracted pooled muscle, liver and egg tissue were used to measure congener specific PCBs, chlorinated dioxins and furans as well as bioassay derived 2,3,7,8-TCDD toxic equivalent concentration (TEC). The cell culture bioassays used to measure TECs were rat hepatoma (H411E) and rainbow trout hepatocyte (RTL-W1) continuous cell lines as well as chicken embryo hepatocyte primary culture (CEH). Although excellent correlations were found between all 3 cell culture bioassays, CEH was found to be 10 times and 30 times more sensitive than H411E and RTL-W1 respectively. Lake Ontario TECs were found to be higher than either Lake Huron or Lake Erie samples for both species of Salmon, and Chinook salmon was elevated over Coho Salmon. Chemical data indicates that the more toxic coplanar PCBs are selectively concentrated in eggs as compared to liver and muscle. Bioassay derived TECs are discussed with regard to chemical contribution of the PCB and dioxin/furan congeners based on an additive model.
The RTL-WL rainbow trout liver and H4IIE rat hepatoma cell lines were exposed to organic solvent ... more The RTL-WL rainbow trout liver and H4IIE rat hepatoma cell lines were exposed to organic solvent extracts from livers of lake trout collected from two Lake Superior sites (Jackfish Bay -- a pulp mill site and Black Bay -- a reference site) and one Lake Ontario site (Eastern Basin -- a PCB-contaminated site). These two bioassays measure the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent concentrations (TECs) of the residues as indicated by their relative ability to induce 7-ethoxyresorufin-o-deethylase (EROD) activity. This estimates the burden of compounds that could act through the Ah receptor and are potentially toxic, Subsamples of liver were also analyzed for hepatic EROD activity. For Jackfish Bay extracts, the H4IIE mean TEC was found to be significantly higher than that derived using RTL-WL, indicating a more potent contaminant mixture to this mammalian model. No such difference was seen between mean TECs derived for Lake Ontario extracts. The reference site, Black Bay, had TECs significantly lower than those from the other two sites. A significant positive correlation between TECs derived with H4IIE vs. RTL-WL was seen for Jackfish Bay, but not Lake Ontario. Lake Ontario extracts had a significantly higher mean TEC than the mean TEC from Jackfish Bay regardless more » of the cell line used. Hepatic EROD activities of liver subsamples from Jackfish Bay were found to be significantly higher than subsamples from Black Bay, while Lake Ontario subsamples were variable. No significant correlation was found between hepatic EROD activity and TEC values. The RTL-WL cell line bioassay was found to have excellent utility for rapid TEC determination and should be generally suitable for estimating the toxic potency of environmental samples. « less
The Science of the total environment, Jan 15, 2005
Ambient particulate matter (PM(10)) in urban centres varies depending on emission sources, geogra... more Ambient particulate matter (PM(10)) in urban centres varies depending on emission sources, geography, demography, and meteorology. Hence physical (PM(10), wind speed, rainfall, temperature), chemical (polycyclic aromatic hydrocarbons, PAH), and toxicological (Ames Test, H4IIE EROD Assay) analyses were done on daily PM(10) (approximately 1640 m(3)/day) collected from three New Zealand urban sites where winter emissions were predominantly due to domestic home heating. Daily PM(10) levels ranged between 9.7 and 20.8 in summer and between 21.8 and 61.0 microg/m(3) in winter. Daily PAH concentrations were 0.5, 0.45, and 1.5 ng/m(3) in summer and 52.1, 128.9, and 5.8 ng/m(3) in winter at sites Christchurch, Alexandra and Dunedin, respectively. During winter, 74% of PM(10) extracts from all three sites showed significant mutagenicity in the Ames Test (TA 98, -S9), whereas approximately 25% of the daily PM(10) was mutagenic in summer. Benzo[a]pyrene and BaP carcinogenic equivalence concentr...
Toxicological Sciences, 1998
The estrogenic activities of eight phthalate esters (i.e., di-2-ethylhexyl, din -butyl (DBP), but... more The estrogenic activities of eight phthalate esters (i.e., di-2-ethylhexyl, din -butyl (DBP), butylbenzyl (BBP), di-hexyl (DHP), diisoheptyl, di-77-octyl, diiso-nonyl, diiso-decyl) were investigated in vitro using estrogen receptor (ER) competitive ligand-binding and mammalian-and yeast-based gene expression assays. In vivo, their effects on uterine wet weight and vaginal cell cornification using ovariectomized Sprague-Dawley rats were assessed. DBP, BBP, and DHP weakly competed with 17/3-estradiol (E2) for binding to the ER in competitive ligand-binding assays. In gene expression assays using MCF-7 cells transiently transfected with the Gal4-human estrogen receptor construct, Gal4-HEGO, and the Gal4-regulated luciferase reporter gene, 17m5-G-Luc, 10 fiM DBP, BBP, or DHP exhibited 36, 42, and 20% activity, respectively, when compared to the 100% response observed with 10 nM E2. Only BBP was found to induce luciferase activity (32%) in HeLa cells stably transfected with Gal4-HEGO and 17m5-G-Luc constructs and to impart minimal ERmediated viability to the E2-dependent recombinant yeast strain, PL3, on selective medium. No significant responses were observed with the other phthalate esters in any of the in vitro assays. In vivo, none of the eight phthalate esters reproducibly induced significant increases in uterine wet weight in immature ovariectomized Sprague-Dawley rats treated with oral doses of 20, 200, or 2000 mg/kg of phthalate ester. In addition, treatment with phthalate esters at the same doses did not affect the degree of vaginal epithelial cell cornification in mature ovariectomized rats. These results indicate that only selected phthalate esters (i.e., DBP, BBP, and DHP) exhibit weak ER-mediated activity in some in vitro assays at high concentrations but none of the eight phthalate esters elicited in vivo estrogenic responses based upon results obtained from uterotrophic and vaginal cornification assays.
Molecular and Cellular Endocrinology, 2001
Several fish proteins exhibit compromised function at temperatures outside of their normal physio... more Several fish proteins exhibit compromised function at temperatures outside of their normal physiological range. In this study, the effect of temperature on the ligand binding and the transactivation abilities of the rainbow trout estrogen receptor (rtER) and human estrogen receptor alpha (hERa) were examined. Saturation analysis and gene expression assays, using GST-ER and Gal4-ER fusion proteins consisting of the D, E and F domains of human (hERadef) and rainbow trout (rtERdef) receptors, show that GST-rtERdef E2 binding affinity and transactivation ability decrease with increasing temperature. A comparison of the amino acid sequence differences between their ligand binding pockets identified two conservative amino acid residue substitutions in rtER (M317, I496) and hERa (L349, M528). The effect of these substitutions on ligand binding and transactivation were examined by constructing reciprocal mutants, which effectively exchanged the binding pockets between rtER and hERa. The rtERdef M317L:I496M double mutant exhibited increased E2 binding affinity and transactivation ability at higher temperatures, and displayed hERa phenotypic behavior for the phytoestrogen, coumestrol. The hERadef L349M:M528I double mutant also exhibited a modest trend towards adopting the rtER phenotype. These studies demonstrate that conservative changes in residue hydrophobicity and volume can significantly affect ER ligand binding and transactivation ability in a temperature-dependent manner. The lack of a complete exchange of phenotypes between rtER and hERa indicates that factors outside of the ligand binding pocket are also involved.
Journal of Great Lakes Research, 1994
... No. 23. Clemons, IH, van den Heuvel, MR, BoIs, NC, and Dixon, DG 1993. Toxic equivalent facto... more ... No. 23. Clemons, IH, van den Heuvel, MR, BoIs, NC, and Dixon, DG 1993. Toxic equivalent factors for selected congeners of PCDDs, PCDFs and PCBs using a rainbow trout liver cell line (RTL-W1). ... Sci. 48:875-883. ___, Hufnagle, Jr., Lc, Clayton, MK, and Peter son, RE 1992. ...
Journal of Applied Toxicology, 2000
ABSTRACT Estrogen receptor (ER) transactivation assays were initially designed to study endogenou... more ABSTRACT Estrogen receptor (ER) transactivation assays were initially designed to study endogenous mechanisms of steroid hormone action, but more recently have been used to assess industrial chemicals for potential estrogenic activity. Given the diverse spectrum of physicochemical properties of these chemicals, we examined the effects of pH (a weak organic and strong inorganic acid and base), hyperosmolality (NaCl, mannitol) and two different vehicles (DMSO, Triton X-100) on responses to estradiol-17beta (E2) in an ER transactivation assay. MCF-7 human breast cancer cells were transiently transfected with a chimeric estrogen receptor (Gal4-HEG0) and a Gal4-regulated luciferase reporter gene (17m5-G-Luc), treated with E2 under various test conditions, and then assessed for ER-mediated luciferase activity. Maximal E2-induced reporter activity was observed at pH 7.8 (pre-incubation), but was markedly reduced at pH < or =7.5, or > or =8.0 (P < 0.001), even though there was no evidence of cytotoxicity. Hyperosmolality induced by addition of mannitol (> or =25 mM) resulted in significant decreases in overall assay responsiveness, whereas NaCl (> or =80 mM) decreased the sensitivity of the assay by increasing the no-observed-effect level for E2 compared to control cultures (330 mOsm). The maximal DMSO concentration that resulted in consistently high E(2)-induced reporter activity was 0.1%, whereas concentrations of Triton X-100 above 1 ppm inhibited E2-induced reporter responses and were cytotoxic above 10 ppm. These results indicate that various physicochemical factors have the potential to confound assay data if not kept within predefined operational limits.
Environmental Toxicology and Chemistry, 1998
For livers of lake trout from three Great Lakes sites, the 2,3,7,8-tetrachlorodibenzo-p-dioxin (T... more For livers of lake trout from three Great Lakes sites, the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalent concentrations (TEQs) were determined in four ways. Bioassay-derived (BD) TEQs were measured with rat (H4IIE) and rainbow trout (RTL-W1) cell lines, and ...
Environmental Science & Technology, 1998
Polar and nonpolar fractions prepared from an organic extract of inhalable air particulate materi... more Polar and nonpolar fractions prepared from an organic extract of inhalable air particulate material collected from an urban location in downtown Toronto, Ontario, Canada, were examined for estrogen and Ah receptor-mediated activities using in vitro gene expression assays. The presence of estrogenic activity was determined using MCF-7 human breast cancer cells transiently transfected with a Gal4-human estrogen receptor chimera and a Gal4-regulated luciferase reporter gene. 2,3,7,8-Tetracholordibenzo-pdioxin (TCDD)-like activity was detected using Hepa 1c1c7 cells transiently transfected with a CYP1A1-regulated reporter gene (pGudLuc 1.1). Significant estrogenic and TCDDlike activity was detected in the crude extract and in the nonpolar fractions. Results from the analyses of nine environmentally prevalent polyaromatic hydrocarbons (PAH) indicated that PAH might be significant contributors to the observed activity. Surprisingly, three PAH, namely benzo-[a]pyrene, chrysene, and benz[a]anthracene, were found to substantially induce in vitro estrogenic and TCDD-like activities that were mediated by the estrogen and Ah receptors, respectively. Benzo[k]fluoranthene, dibenz[a,h]anthracene, and anthracene also exhibited significant in vitro TCDD-like activity. These results demonstrate the utility of in vitro gene expression assays to identify the presence of potential endocrine disruptors within complex mixtures.
Cell Biology and Toxicology, 1993
A cell line, RTL-W1, has been developed from the normal liver of an adult rainbow trout by proteo... more A cell line, RTL-W1, has been developed from the normal liver of an adult rainbow trout by proteolytic dissociation of liver fragments. RTL-W1 can be grown routinely in the basal medium, L-15, supplemented with 5% fetal bovine serum. In this medium, the cells have been passaged approximately 100 times over an 8-year period. The cells do not form colonies or grow in soft agar. The cultures are heteroploid. The cell shape was predominantly polygonal or epithelial-like, but as cultures became confluent, bipolar or fibroblast-like cells appeared. Among the prominent ultrastructural features of RTL-W1 were distended endoplasmic reticulum and desmosomes. Benzo[a]pyrene was cytotoxic to RTL-W1. Activity for the enzyme, 7-ethoxyresorufin O-deethylase (EROD), which is a measure of the cytochrome P4501A1 protein, increased dramatically in RTL-W1 upon their exposure to increasing concentrations of either beta-naphthoflavone (BNF) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). With these properties, RTL-W1 should be useful for studying the expression of the cytochrome P450 enzymes and as a tool for assessing the toxic potency of environmental contaminants.
Canadian Journal of Fisheries and Aquatic Sciences, 1994
Toxic equivalent factors (TEFs) for eight polychlorinated dibenzo-p-dioxin (PCDD) and polychlorin... more Toxic equivalent factors (TEFs) for eight polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) congeners were derived with a rainbow trout (Oncorhynchus mykiss) cell line, RTL-W1, and compared with TEFs obtained with a rat hepatoma cell line, H4IIE. Cells were exposed to a range of concentrations of the congeners which included 1,2,3,7,8-pentaCDD, 1,2,3,4,7,8-hexaCDD, 1,2,3,6,7,8-hexaCDD, 1,2,3,4,6,7,8-heptaCDD, 2,3,7,8-tetraCDF, 1,2,3,7,8-pentaCDF, 2,3,4,7,8-pentaCDF, and 1,2,3,4,7,8-hexaCDF. Ethoxyresorufin o-deethylase (EROD) activity was measured and EC50 values calculated from a dose–effect curve newly proposed for this purpose. TEFs were computed using 2,3,7,8-tetraCDD standard curves run concurrently with each assay. With the exception of 1,2,3,6,7,8-hexaCDD and 1,2,3,7,8-pentaCDF, all of the RTL-W1-derived TEFs were significantly higher (two- to eightfold higher) than the respective H4IIE TEFs. Immunoblotting analysis with the monoclonal anti-scup ...
Canadian Journal of Fisheries and Aquatic Sciences, 1996
Toxic equivalency factors (potency of a compound relative to the 2,3,7,8-tetrachlorodibenzo-p-dio... more Toxic equivalency factors (potency of a compound relative to the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) standard) for polychlorinated biphenyls (PCBs) were derived from cytochrome P4501A1 induction, measured as ethoxyresorufin o-deethylase (EROD) activity, in a rainbow trout (Oncorhynchus mykiss) liver cell line (RTL-W1) and a rat hepatoma cell line (H4IIE). In RTL-W1 under normal growth conditions, EROD activity was induced only by PCBs 77, 81, 118, and 126. In overconfluent RTL-W1 cultures, EROD induction was also detected with PCBs 105, 156, and 169. Immunoblotting with the polyclonal antibody anti-trout CYP1A1 277-294 /KLH confirmed the results of EROD induction. The RTL-W1 toxic equivalency factors were 0.023 for PCB 126, 0.0064 for PCB 81, 0.0034 for PCB 77, 0.000 16 for PCB 169, and 0.000 017 for PCB 118. Toxic equivalency factors for PCBs 105 and 156 were <0.000 03. All seven PCBs clearly induced EROD activity in H4IIE. Generally the H4IIE toxic equivalency factors were higher than the RTL-W1 toxic equivalency factors. Therefore, the toxic impact of PCBs on rainbow trout probably would be overestimated by currently proposed risk assessment toxic equivalency factors and assessed more appropriately with toxic equivalency factors derived from rainbow trout. Résumé : On a déterminé la valeur du facteur d'équivalence toxique (ou pouvoir toxique d'un composé par rapport à un étalon de 2,3,7,8-tétrachlorodibenzo-p-dioxine (TCDD)) de divers biphényles polychlorés (BPC) d'après l'induction du cytochrome P4501A1, évaluée d'après l'activité de l'éthoxyrésorufine o-déséthylase (EROD) chez une lignée de cellules hépatiques de truite arc-en-ciel (Oncorhynchus mykiss) (RTL-W1) et chez une lignée de cellules d'hépatome de rat (H4IIE). En conditions de culture normales, l'activité EROD n'a été induite que par les BPC 77, 81, 118 et 126 dans les cellules RTL-W1; toutefois, dans des cultures surconfluentes de RTL-W1, les BPC 105, 156 et 169 ont aussi induit une activité EROD. L'immunotransfert avec des anticorps polyclonaux anti-CYP1A1 277-294 /KLH de truite a confirmé ces observations. On a obtenu les facteurs d'équivalence toxique suivants dans les cellules RTL-W1 : 0,023 pour le BPC 126, 0,0064 pour le BPC 81, 0,0034 pour le BPC 77, 0,000 16 pour le BPC 169 et 0,000 017 pour le BPC 118. Le facteur d'équivalence toxique des BPC 105 et 156 était inférieur à 0,000 03. Dans les cultures de H4IIE, les sept BPC ont nettement induit une activité EROD. En général, les facteurs d'équivalence toxique mesurés dans les cellules H4IIE sont plus élevés que ceux obtenus avec les cellules RTL-W1. Par conséquent, avec les facteurs d'équivalence toxique qu'on propose actuellement d'employer dans les évaluations de risque, on surestimerait probablement l'effet toxique des BPC chez la truite arc-en-ciel; l'estimation devrait être plus juste avec des facteurs d'équivalence toxique déterminés au moyen de cellules de truite arc-en-ciel. [Traduit par la Rédaction]