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23 results on '"Lam, Michael H.W."'

19. Polybrominated Diphenyl Ethers (PBDEs) Alter Larval Settlement of Marine Intertidal Organisms across Three Phyla via Reducing Bacterial Abundance on the Biofilms

Author

Chiu, Jill Man Ying, Po, Beverly H.K., Chan, Christine Y.S., Lam, Michael H.W., Qian, Peiyuan, Wu, Rudolf Shiu Sun, Chiu, Jill Man Ying, Po, Beverly H.K., Chan, Christine Y.S., Lam, Michael H.W., Qian, Peiyuan, and Wu, Rudolf Shiu Sun

Abstract

Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants over the last three decades, and are now ubiquitous in the marine environment. While the harmful effects of PBDEs on the abnormal development and reproductive impairment in mammals and fish are well documented, the effects on marine invertebrates remain virtually unknown. Using three model intertidal species accross three phyla, including the polychaete Hydroides elegans (Phylum Annelida), the gastropod Crepidula onyx (Phylum Mollusca), and the barnacle Balanus amphitrite (Phylum Arthopoda), this study demonstrated that (a) chronic exposure to BDE-47 (at spiking concentrations up to 1000 ng L-1) throughout the entire larval stage did not affect settlement, development or growth of all three species per se, despite bioaccumulation was dearly evident (measured body burden ranging from approximately 7000 to 13 000 ng BDE-47 g(-1) lipid), and (b) BDE-47, at measured concentrations of 15 and 113 ng g(-1) lipid, reduced the bacterial abundance in biofilms and resulted in a concomitant change in larval settlement pattern of all the model intertidal species across three phyla.

Published
2012

23. Effects of PCBs and MeSO2–PCBs on adrenocortical steroidogenesis in H295R human adrenocortical carcinoma cells

Author

Xu, Yan, Yu, Richard M.K., Zhang, Xiaowei, Murphy, Margaret B., Giesy, John P., Lam, Michael H.W., Lam, Paul K.S., Wu, Rudolf S.S., and Yu, Hongxia

Subjects
*ADRENOCORTICAL hormones, *STEROIDS, *POLYCHLORINATED biphenyls, *BIPHENYL compounds, *BIOCHEMISTRY
Abstract

Abstract: Some endocrine disrupting chemicals (EDCs) in the environment have been shown to exert their biological effects through interference with steroidogenesis. In this study, the potential effects of four selected polychlorinated biphenyl (PCB) congeners (PCB101, PCB110, PCB126 and PCB149) as well as several of their environmentally-relevant methylsulfonyl-(MeSO2–) PCB metabolites (3′-MeSO2–CB101, 4′-MeSO2–CB101, 4′-MeSO2–CB110, 3′-MeSO2–CB149 and 4′-MeSO2–CB149) on adrenocortical steroidogenesis were evaluated by in vitro bioassay based on the human adrenocortical carcinoma H295R cell line. The PCBs included in the study represented different structures and potential mechanisms of action. Cells were exposed for 48h to 10μM of each PCB congener in the presence or absence of 20% (w/w) of their corresponding MeSO2–PCB metabolite(s). After the chemical treatments, changes in mRNA expression of 11 steroidogenic genes (CYP11A, CYP11B1, CYP11B2, CYP17, CYP19, CYP21, 3β-HSD1, 3β-HSD2, 17β-HSD1, StAR and HMGR) were quantified using molecular beacon-based real-time RT-PCR. Genes coding for enzymes involved in the later or final steps of steroid production (CYP11B1, CYP11B2, CYP19, 3β-HSD1, 3β-HSD2 and 17β-HSD1) were up-regulated to various extents by most PCBs. The greatest transcriptional activations (2.8–29.9-fold) were elicited by PCB110 on CYP11B1, CYP11B2, 3β-HSD2 and CYP19, and PCB149 on CYP11B1, 3β-HSD1 and 17β-HSD1. Increased expression of these steroidogenic genes might ultimately lead to a change in hormonal balance through excessive production of steroid hormones including aldosterone, cortisol and estradiol. In addition, co-treatment with 3′- and 4′-MeSO2–PCB149 resulted in a significant decrease in PCB149-induced 3β-HSD1 and 17β-HSD1 expression. This result indicates that some PCB congeners and their MeSO2-metabolites may affect steroidogenesis via different mechanisms. Overall, these findings suggest that PCBs and PCB metabolites can affect regulation of adrenocortical steroidogenesis. [Copyright &y& Elsevier]

Published
2006
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