Publications by authors named "William Siu"

17 Publications

  • Page 1 of 1

Association between shift work and cognitive performance on the Trail Making Test in emergency department health officers.

Emerg Med Australas 2021 Mar 11. Epub 2021 Mar 11.

Faculty of Medicine, The University of New South Wales, Sydney, New South Wales, Australia.

Objective: Shift work has been proposed to disturb alertness and decrease cognitive efficiency. However, studies so far have had varied findings. The aim of the present study was to compare cognitive function following shifts at different times of the day in an Australian ED context.

Methods: A prospective, self-controlled observational study was conducted on medical and nursing staff at a tertiary referral centre and regional hospital ED. Participants were required to complete the Trail Making Test (TMT), a neurocognitive test consisting of two parts (TMT-A and TMT-B), at baseline (at the start of the day) and at the end of their shift (day, evening or night). Related samples Wilcoxon signed-rank tests were used to compare post-shift TMT performance to baseline in medical and nursing staff.

Results: Over a 5-month period, 140 ED staff were recruited including 109 doctors and 31 nurses. After a night shift, medical staff (n = 85) and nursing staff (n = 29) took longer to complete the TMT-B by 3.4 s (P < 0.001) and 7.1 s (P = 0.01), respectively, compared to baseline. Post-evening shift, medical staff (n = 59) took longer to complete the TMT-A by 0.3 s (P = 0.02).

Conclusions: Night shift work was associated with a longer TMT time. This may indicate a decrease in cognitive performance, in particular, visual attention, processing speed, task switching and executive function and may implicate the quality of care for patients and worker safety.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1742-6723.13753DOI Listing
March 2021

Functional MRI evaluation of the effect of carotid artery stenting: a case study demonstrating cognitive improvement.

Acta Radiol Open 2021 Feb 10;10(2):2058460120988822. Epub 2021 Feb 10.

Health Sciences and Innovation, Surrey Memorial Hospital, Fraser Health Authority, British Columbia, Canada.

Background: The narrowing of the carotid arteries with plaque formation represents a major risk factor for ischemic stroke and cognitive impairments. Carotid angioplasty and stenting is a standard clinical treatment to reduce stroke risk. The cognitive effect of carotid angioplasty and stenting remains largely unknown.

Purpose: This study aims to provide direct evidence of possible effects of carotid angioplasty and stenting on cognition, using task-phase functional magnetic resonance imaging.

Material And Methods: This study received harmonized institutional ethics board approval (Grant number REB ID =H18-02495/FHREB 2018-058). Two patients had MRI scans pre-carotid angioplasty and stenting and two-month post-carotid angioplasty and stenting. Case 1 had severe (>95%) flow-limiting stenosis in the right carotid artery. Case 2 had 70% non-flow limiting stenosis in the left carotid artery. At each scan, patients completed two functional magnetic resonance imaging sessions while performing a working memory task. Accuracy, reaction time, and brain activation were analyzed for each patient for possible pre-post carotid angioplasty and stenting changes.

Results: Case 1 showed increased activation in the right (treated-side) frontal and temporal lobes post-carotid angioplasty and stenting; associated with improvements in accuracy (from 58% to 74%) and task completion rate (from 17% to 72%). Case 2 completed the tasks pre- and post-carotid angioplasty and stenting with >90% accuracy, while decreased functional magnetic resonance imaging activation in the contralateral (untreated) hemisphere and mildly increased activation in the left (treated -side) anterior circulation territory were observed post-carotid angioplasty and stenting.

Conclusion: These cases provided the first task-phase functional magnetic resonance imaging data demonstrating that carotid angioplasty and stenting improved cognitive function in the re-perfused vascular territory. The finding supports the role of carotid angioplasty and stenting in improving cognitive performance beyond reducing stroke risk.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/2058460120988822DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7878956PMC
February 2021

A fast and fully-automated deep-learning approach for accurate hemorrhage segmentation and volume quantification in non-contrast whole-head CT.

Sci Rep 2020 11 9;10(1):19389. Epub 2020 Nov 9.

Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.

This project aimed to develop and evaluate a fast and fully-automated deep-learning method applying convolutional neural networks with deep supervision (CNN-DS) for accurate hematoma segmentation and volume quantification in computed tomography (CT) scans. Non-contrast whole-head CT scans of 55 patients with hemorrhagic stroke were used. Individual scans were standardized to 64 axial slices of 128 × 128 voxels. Each voxel was annotated independently by experienced raters, generating a binary label of hematoma versus normal brain tissue based on majority voting. The dataset was split randomly into training (n = 45) and testing (n = 10) subsets. A CNN-DS model was built applying the training data and examined using the testing data. Performance of the CNN-DS solution was compared with three previously established methods. The CNN-DS achieved a Dice coefficient score of 0.84 ± 0.06 and recall of 0.83 ± 0.07, higher than patch-wise U-Net (< 0.76). CNN-DS average running time of 0.74 ± 0.07 s was faster than PItcHPERFeCT (> 1412 s) and slice-based U-Net (> 12 s). Comparable interrater agreement rates were observed between "method-human" vs. "human-human" (Cohen's kappa coefficients > 0.82). The fully automated CNN-DS approach demonstrated expert-level accuracy in fast segmentation and quantification of hematoma, substantially improving over previous methods. Further research is warranted to test the CNN-DS solution as a software tool in clinical settings for effective stroke management.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-76459-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7652921PMC
November 2020

Haemodialysis for lithium poisoning: Translating EXTRIP recommendations into practical guidelines.

Br J Clin Pharmacol 2020 05 11;86(5):999-1006. Epub 2020 Feb 11.

Department of Emergency Medicine & Clinical Toxicology, Prince of Wales Hospital, Sydney, Australia.

Objectives: This study aimed to determine the impact on practice of applying the Extracorporeal Treatments in Poisoning (EXTRIP) Workgroup criteria to lithium toxicity.

Method: We retrospectively examined the medical records of patients from three hospitals who presented with chronic or acute on chronic lithium poisoning with a lithium concentration ≥1.3 mmol/L (2008-2018). We determined which criteria were met by patients and their subsequent course. We developed and validated a method to predict if lithium concentration would be >1mmol/L at 36 hours.

Results: There were 111 acute on chronic and 250 chronic lithium toxic patients. Nine patients (2.5%) were treated with haemodialysis. Six chronic patients had neurological sequelae. The "estimated lithium concentration at 36 hours > 1 mmol/L" criterion required pharmacokinetic calculations. A simple nomogram was developed using Estimated Glomerular Filtration Rate (eGFR) and lithium concentration. For chronic toxicity, the nomogram would have correctly predicted lithium concentration >1.4 mmol/L at 36 hours in all except two patients. If EXTRIP criteria were followed, dialysis would have been instituted for 211 patients (58%). However, only 51 patients with chronic toxicity fulfilled both a concentration and a clinical criterion. Late neurological sequelae were observed in five out of six patients who fulfilled a concentration and a clinical criterion on admission, with the sixth meeting these criteria shortly after admission.

Conclusions: The EXTRIP criteria are too broad, but minor modifications allow haemodialysis to be targeted to those most at risk of sequelae. Most acute on chronic poisonings do not need haemodialysis, but it might shorten hospital stay in those with very high concentrations. The nomogram accurately predicts the fall in lithium concentration for chronic poisoning.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/bcp.14212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7163377PMC
May 2020

Seasonal and temperature effect on serum lithium concentrations.

Aust N Z J Psychiatry 2020 03 29;54(3):282-287. Epub 2019 Nov 29.

Department of Emergency Medicine & Clinical Toxicology, Prince of Wales Hospital, Sydney, NSW, Australia.

Background: Lithium remains the gold standard treatment for bipolar disorder. However, it has a very narrow therapeutic index (0.6-0.8 mmol/L). It has been suggested that high environmental temperature can lead to dehydration, elevated plasma lithium concentration and then lithium toxicity.

Objectives: We aimed to investigate the effect of seasonal and short-term changes in temperature on serum lithium concentrations in Sydney, Australia.

Methods: We retrospectively analysed data from all patients who had serum lithium concentrations taken from the Prince of Wales and Sutherland Hospitals between 2008 and 2018. Temperature data came from the Bureau of Meteorology. We examined correlations between lithium concentrations and the preceding 5 days maximum temperatures, month and season. We also performed a longitudinal analysis of the effect of temperature and seasons within selected patients who had repeated levels.

Results: A total of 11,912 serum lithium concentrations from 2493 patients were analysed. There was no significant association between higher lithium concentration and preceding higher temperatures ( = -0.008,  = 0.399). There was also no important seasonal or monthly variation, across all patients or in the smaller cohort with longitudinal data ( = 123,  = 0.008, 95% confidence interval: [-0.04, 0.06]).

Conclusion: There were no clinically important differences in serum lithium concentration related to seasons, months or temperatures, which suggests that patients on lithium are able to adequately maintain hydration during hot weather in Sydney.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/0004867419889160DOI Listing
March 2020

MRI-based evaluation of structural degeneration in the ageing brain: Pathophysiology and assessment.

Ageing Res Rev 2019 01 22;49:67-82. Epub 2018 Nov 22.

ImageTech Laboratory, Health Sciences and Innovation, Surrey Memorial Hospital, Surrey, British Columbia, Canada; Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; Health Sciences and Innovation, Surrey Memorial Hospital, Surrey, British Columbia, Canada. Electronic address:

Advances in MRI technology have significantly contributed to our ability to understand the process of brain ageing, allowing us to track and assess changes that occur during normal ageing and neurological conditions. This paper focuses on reviewing structural changes of the ageing brain that are commonly seen using MRI, summarizing the pathophysiology, prevalence, and neuroanatomical distribution of changes including atrophy, lacunes, white matter lesions, and dilated perivascular spaces. We also review the clinically accessible methodology for assessing these MRI-based changes, covering visual rating scales, as well computer-aided and fully automated methods. Subsequently, we consider novel assessment methods designed to evaluate changes across the whole brain, and finally discuss new directions in this field of research.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.arr.2018.11.004DOI Listing
January 2019

Automation of CT-based haemorrhagic stroke assessment for improved clinical outcomes: study protocol and design.

BMJ Open 2018 04 19;8(4):e020260. Epub 2018 Apr 19.

Health Sciences and Innovation, Fraser Health Authority, Surrey, British Columbia, Canada.

Introduction: Haemorrhagic stroke is of significant healthcare concern due to its association with high mortality and lasting impact on the survivors' quality of life. Treatment decisions and clinical outcomes depend strongly on the size, spread and location of the haematoma. Non-contrast CT (NCCT) is the primary neuroimaging modality for haematoma assessment in haemorrhagic stroke diagnosis. Current procedures do not allow convenient NCCT-based haemorrhage volume calculation in clinical settings, while research-based approaches are yet to be tested for clinical utility; there is a demonstrated need for developing effective solutions. The project under review investigates the development of an automatic NCCT-based haematoma computation tool in support of accurate quantification of haematoma volumes.

Methods And Analysis: Several existing research methods for haematoma volume estimation are studied. Selected methods are tested using NCCT images of patients diagnosed with acute haemorrhagic stroke. For inter-rater and intrarater reliability evaluation, different raters will analyse haemorrhage volumes independently. The efficiency with respect to time of haematoma volume assessments will be examined to compare with the results from routine clinical evaluations and planimetry assessment that are known to be more accurate. The project will target the development of an enhanced solution by adapting existing methods and integrating machine learning algorithms. NCCT-based information of brain haemorrhage (eg, size, volume, location) and other relevant information (eg, age, sex, risk factor, comorbidities) will be used in relation to clinical outcomes with future project development. Validity and reliability of the solution will be examined for potential clinical utility.

Ethics And Dissemination: The project including procedures for deidentification of NCCT data has been ethically approved. The study involves secondary use of existing data and does not require new consent of participation. The team consists of clinical neuroimaging scientists, computing scientists and clinical professionals in neurology and neuroradiology and includes patient representatives. Research outputs will be disseminated following knowledge translation plans towards improving stroke patient care. Significant findings will be published in scientific journals. Anticipated deliverables include computer solutions for improved clinical assessment of haematoma using NCCT.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/bmjopen-2017-020260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5914893PMC
April 2018

MRI assessment of whole-brain structural changes in aging.

Clin Interv Aging 2017 9;12:1251-1270. Epub 2017 Aug 9.

Health Sciences and Innovation, ImageTech Laboratory, Fraser Health Authority, Surrey, BC, Canada.

Purpose: One of the central features of brain aging is the accumulation of multiple age-related structural changes, which occur heterogeneously in individuals and can have immediate or potential clinical consequences. Each of these deficits can coexist and interact, producing both independent and additive impacts on brain health. Many of the changes can be visualized using MRI. To collectively assess whole-brain structural changes, the MRI-based Brain Atrophy and Lesion Index (BALI) has been developed. In this study, we validate this whole-brain health assessment approach using several clinical MRI examinations.

Materials And Methods: Data came from three independent studies: the Alzheimer's Disease Neuroimaging Initiative Phase II (n=950; women =47.9%; age =72.7±7.4 years); the National Alzheimer's Coordinating Center (n=722; women =55.1%; age =72.7±9.9 years); and the Tianjin Medical University General Hospital Research database on older adults (n=170; women =60.0%; age =62.9±9.3 years). The 3.0-Tesla MRI scans were evaluated using the BALI rating scheme on the basis of T1-weighted (T1WI), T2-weighted (T2WI), T2-weighted fluid-attenuated inversion recovery (T2-FLAIR), and T2*-weighted gradient-recalled echo (T2*GRE) images.

Results: Atrophy and lesion changes were commonly seen in each MRI test. The BALI scores based on different sequences were highly correlated (Spearman >0.69; <0.00001). They were associated with age (>0.29; <0.00001) and differed by cognitive status (>26.48, <0.00001). T2-FLAIR revealed a greater level of periventricular (=29.09) and deep white matter (=26.65, <0.001) lesions than others, but missed revealing certain dilated perivascular spaces that were seen in T2WI (<0.001). Microhemorrhages occurred in 15.3% of the sample examined and were detected using only T2*GRE.

Conclusion: The T1WI- and T2WI-based BALI evaluations consistently identified the burden of aging and dementia-related decline of structural brain health. Inclusion of additional MRI tests increased lesion differentiation. Further research is to integrate MRI tests for a clinical tool to aid the diagnosis and intervention of brain aging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2147/CIA.S139515DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5557118PMC
March 2018

Efinaconazole Topical Solution, 10%: Factors Contributing to Onychomycosis Success.

J Fungi (Basel) 2015 Jul 3;1(2):107-114. Epub 2015 Jul 3.

Dow Pharmaceutical Sciences, a Division of Valeant Pharmaceuticals North America LLC, Petaluma, CA 94954, USA.

To provide an adequate therapeutic effect against onychomycosis, it has been suggested that topical drugs should have two properties: drug permeability through the nail plate and into the nail bed, and retention of their antifungal activity in the disease-affected areas. Only recently has the importance of other delivery routes (such as subungual) been discussed. Efinaconazole has been shown to have a more potent antifungal activity than the most commonly used onychomycosis treatments. The low keratin affinity of efinaconazole contributes to its effective delivery through the nail plate and retention of its antifungal activity. Its unique low surface tension formulation provides good wetting properties affording drug delivery both through and under the nail. High antifungal drug concentrations have been demonstrated in the nail of onychomycosis patients, and effectiveness of efinaconazole topical solution, 10% confirmed in two large well-controlled multicenter Phase 3 clinical studies in patients with mild-to-moderate disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/jof1020107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5753103PMC
July 2015

Safety and pharmacokinetics of efinaconazole 10% solution in healthy volunteers and patients with severe onychomycosis.

J Drugs Dermatol 2013 Sep;12(9):1010-6

Objectives: To characterize the systemic exposure and pharmacokinetics of efinaconazole 10% solution and assess the potential for drug-drug interaction (DDI) in human volunteers and onychomycosis patients following topical administration.

Methods: Two single-center, open-label studies in healthy volunteers and severe onychomycosis patients. Efinaconazole 10% solution was applied topically to all 10 toenails (0.42 mL total daily dose volume); administered as single and then 7 daily doses to 10 healthy volunteers, and once daily for 28 days to 19 severe onychomycosis patients. Plasma concentrations of efinaconazole and its major metabolite H3 were determined by LC-MS-MS at multiple timepoints. Safety evaluations were carried out throughout both studies.

Results: The mean peak plasma concentrations (Cmax) of efinaconazole and H3 were 0.54 and 1.63 ng/mL, respectively, in healthy volunteers; and 0.67 and 2.36 ng/mL, respectively, in patients. Both parent drug and metabolite accumulated following repeat dosing, and reached steady state in plasma by 14 days. Efinaconazole was well tolerated in both studies; no drug-related adverse events were reported.

Conclusions: Efinaconazole 10% solution resulted in very low systemic exposures to efinaconazole and H3 when applied topically at maximum use conditions to healthy volunteer and onychomycosis patients' toenails. Efinaconazole is a CYP inhibitor like other azole antifungals, and its lowest ki is 91 ng/mL for CYP2C9, a >130-fold higher concentration than the mean steady state Cmax observed in patients. The Cmax/ki ratio was 0.007, well below the threshold for clinical DDI evaluation as recommended in regulatory guidances, thereby suggesting efinaconazole 10% solution has remote potential for drug-drug interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
September 2013

Mechanism of action of efinaconazole, a novel triazole antifungal agent.

Antimicrob Agents Chemother 2013 May 4;57(5):2405-9. Epub 2013 Mar 4.

Central Research Laboratories, Kaken Pharmaceutical Co, Ltd, Kyoto, Japan.

The mechanism of action of efinaconazole, a new triazole antifungal, was investigated with Trichophyton mentagrophytes and Candida albicans. Efinaconazole dose-dependently decreased ergosterol production and accumulated 4,4-dimethylsterols and 4α-methylsterols at concentrations below its MICs. Efinaconazole induced morphological and ultrastructural changes in T. mentagrophytes hyphae that became more prominent with increasing drug concentrations. In conclusion, the primary mechanism of action of efinaconazole is blockage of ergosterol biosynthesis, presumably through sterol 14α-demethylase inhibition, leading to secondary degenerative changes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AAC.02063-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3632939PMC
May 2013

Brain strain.

CJEM 2007 Sep;9(5):367, 393-4

Department of Emergency Medicine, Royal Columbian Hospital, New Westminster, British Columbia, Canada.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1017/s1481803500015311DOI Listing
September 2007

Relationships between tissue concentrations of paralytic shellfish toxins and antioxidative responses of clams, Ruditapes philippinarum.

Mar Pollut Bull 2006 May 15;52(5):572-8. Epub 2006 Mar 15.

Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.marpolbul.2006.01.009DOI Listing
May 2006

Exposure of spermatozoa to duroquinone may impair reproduction of the common carp (Cyprinus carpio) through oxidative stress.

Aquat Toxicol 2006 May 4;77(2):136-42. Epub 2006 Jan 4.

Center for Coastal Pollution and Conservation, City University of Hong Kong, Kowloon, PR China.

Toxicity of many waterborne organic contaminants to aquatic organisms is mediated through oxidative damages resulting from the production of reactive oxygen species (ROS). Using duroquinone as a model ROS inducer, we carried out in vitro and in vivo experiments to test the hypothesis that reproduction in common carp (Cyprinus carpio) can be impaired through oxidative damage of their spermatozoa. In vitro exposure of fish spermatozoa to 0, 12.5, 25, 50, 100 and 200 microM duroquinone for 2 h showed a significant increase in the level of ROS in a dose-dependant manner. Sperm motility was significantly reduced in all exposure groups, but lipid peroxidation (LPO) and DNA strand break (measured by comet assay) were only enhanced at 50 microM and above. A significant decrease in subsequent hatching rate was recorded in all the exposure groups, despite fertilization rate was not affected. In the in vivo experiment, spermatozoa were collected 24 and 72 h after fish received intra-peritoneal injections of 1.0 and 10 mg kg(-1) body weight duroquinone. DNA damage was clearly evident in spermatozoa of all treatment groups after 72 h exposure, and ROS was significantly enhanced in the high concentration group. LPO however, remained unchanged in both treatment groups. The overall results of both our in vitro and in vivo experiments demonstrated that duroquinone can induce ROS production in spermatozoa, which may impair sperm quality and subsequently reproductive success through oxidative stress.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.aquatox.2005.11.006DOI Listing
May 2006

Comparative effects of the blue green algae Nodularia spumigena and a lysed extract on detoxification and antioxidant enzymes in the green lipped mussel (Perna viridis).

Mar Pollut Bull 2005 ;51(8-12):1026-33

Department of Biotechnology and Environmental Biology, RMIT University, Melbourne, Victoria, Australia.

Nodularia spumigena periodically proliferates to cause toxic algal blooms with some aquatic animals enduring and consuming high densities of the blue green algae or toxic lysis. N. spumigena contains toxic compounds such as nodularin and lipopolysaccharides. This current work investigates physiological effects of exposure from bloom conditions of N. spumigena cells and a post-bloom lysis. Biochemical and antioxidative biomarkers were comparatively studied over an acute 3-day exposure. In general, a post-bloom N. spumigena lysis caused opposite physiological responses to bloom densities of N. spumigena. Specifically, increases in glutathione (GSH) and glutathione peroxidase (GPx) and decreases in glutathione S-transferase (GST) were observed from the N. spumigena lysis. In contrast, N. spumigena cell densities decreased GSH and increased GST and lipid peroxidation (LPO) in mussels. Findings also suggest that at different stages of a toxic bloom, exposure may result in toxic stress to specific organs in the mussel.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.marpolbul.2005.01.008DOI Listing
August 2006

Induction, adaptation and recovery of biological responses: implications for environmental monitoring.

Mar Pollut Bull 2005 ;51(8-12):623-34

Centre for Coastal Pollution and Conservation and Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.

A wide range of biological responses have been used to identify exposure to contaminants, monitor spatial and temporal changes in contamination levels, provide early warning of environmental deterioration and indicate occurrences of adverse ecological consequences. To be useful in environmental monitoring, a biological response must reflect the environmental stress over time in a quantitative way. We here argue that the time required for initial induction, maximum induction, adaptation and recovery of these stress responses must first be fully understood and considered before they can be used in environmental monitoring, or else erroneous conclusions (both false-negative and false-positive) may be drawn when interpreting results. In this study, data on initial induction, maximum induction, adaptation and recovery of stress responses at various biological hierarchies (i.e., molecular, biochemical, physiological, behavioral, cytological, population and community responses) upon exposure to environmentally relevant levels of contaminants (i.e., metals, oil, polycyclic aromatic hydrocarbons (PAHs), organochlorines, organophosphates, endocrine disruptors) were extracted from 922 papers in the biomarker literature and analyzed. Statistical analyses showed that: (a) many stress responses may decline with time after induction (i.e., adaptation), even if the level of stress remains constant; (b) times for maximum induction and recovery of biochemical responses are positively related; (c) there is no evidence to support the general belief that time for induction of responses at a lower biological hierarchy (i.e., molecular responses and biochemical responses) is shorter than that at higher hierarchy (i.e., physiological, cytological and behavioral responses), although longer recovery time is found for population and community responses; (d) there are significant differences in times required for induction and adaptation of biological responses caused by different types of contaminants; (e) times required for initial and maximum induction of physiological responses in fish are significantly longer than those in crustaceans; and (f) there is a paucity of data on adaptation and recovery of responses, especially those at population and community levels. The above analyses highlight: (1) the limitations and possible erroneous conclusions in the present use of biomarkers in biomonitoring programs, (2) the importance of understanding the details of temporal changes of biological responses before employing them in environmental management, and (3) the suitability of using specific animal groups as bioindicator species.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.marpolbul.2005.04.016DOI Listing
August 2006

Micronucleus induction in gill cells of green-lipped mussels (Perna viridis) exposed to mixtures of polycyclic aromatic hydrocarbons and chlorinated pesticides.

Environ Toxicol Chem 2004 May;23(5):1317-25

Center for Coastal Pollution and Conservation, Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong SAR, People's Republic of China.

Different groups of green-lipped mussels (Perna viridis) were exposed to the same net amount of a genotoxicant mixture of four polycyclic aromatic hydrocarbons ([PAHs]; anthracene, fluoranthene, pyrene, and benzo[a]pyrene) and four organochlorine pesticides ([OCs]; alpha-hexachlorocyclohexane (HCH), aldrin, dieldrin, and p,p'-DDT) for four weeks under different regimes that simulated various scenarios of fluctuating toxicant levels in the marine environment. Micronucleus (MN) formation in gill cells was studied at the end of each week. Micronucleus frequencies increased with continual addition of genotoxicants, and did not diminish significantly under conditions of either gradually decreasing concentrations or cessation of exposure for one to two weeks, suggesting that the MN response may persist over relatively long exposure periods. An almost two-fold higher mean MN frequency was recorded in a chronic exposure group than in an acute group that had received the same net nominal dose of genotoxicants, indicating that chronic exposure may lead to a greater genotoxic impact than acute exposure. The results suggested that in field studies, MN response should be monitored at multiple time points in order to elucidate the effects of potentially fluctuating toxicant levels. Finally, MN formation was positively correlated with both nominal contaminant levels and tissue levels of the genotoxicants. These findings suggest that MN responses can be a sensitive indicator of exposure to relatively low levels of genotoxicants and that MN response in mussel gill cells can be a stable biomarker of genotoxicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1897/03-225DOI Listing
May 2004