Time filter

Source Type

Boyd A.L.,Environmental and Life science Graduate Program | Salleh A.,Environmental and Life science Graduate Program | Humber B.,Trent University | Yee J.,Environmental and Life science Graduate Program | And 4 more authors.
Cancer Prevention Research | Year: 2010

Prevention of breast cancer can be achieved with a better understanding of the factors contributing to normal breast development. Because the breast develops postnatally, alterations in the development and lifetime activity of the neuroendocrine system may set up an environment that increases cancer risk. The present study examined how two neonatal experiences over the first 3 weeks of life influence normal and malignant mammary gland development in female BALB/c mice. Following puberty, both brief (15 minutes) and prolonged (4 hours) daily maternal separations of newborn mice accelerated mammary gland development relative to nonseparated mice. Despite similar mammary gland morphologies between mice exposed to these two neonatal separation experiences, only mice exposed to prolonged maternal separation bouts showed a higher incidence and faster onset of mammary tumorigenesis following adulthood carcinogen [7,12-dimethylbenz(a)anthracene] administration. Molecular analysis of estrogen receptor α (ERα) and p53, two proteins that have been implicated in breast cancer, revealed that for mice exposed to prolonged neonatal maternal separation bouts, mammary gland ERα protein levels were upregulated in a transcription-independent manner. On the other hand, p53 expression in mammary glands of adult mice was not differentially influenced by neonatal experiences. Our findings show that chronic, moderate psychosocial stress during the neonatal period increases the expression of ERα protein and promotes mammary tumorigenesis in adulthood. ©2010 AACR.


Simmons D.B.D.,Environmental and Life science Graduate Program | Simmons D.B.D.,Environment Canada | Wallschlager D.,Trent University
Environmental Science and Technology | Year: 2011

The common green fresh water algae Chlorella vulgaris was exposed to starting concentrations of 10 μg/L selenium in the form of selenate, selenite, or selenocyanate (SeCN -) for nine days in 10% Bold's basal medium. Uptake of selenate was more pronounced than that of selenite, and there was very little uptake of selenocyanate. Upon uptake of selenate, significant quantities of selenite and selenocyanate were produced by the algae and released back into the growth medium; no selenocyanate was released after selenite uptake. Release of the reduced metabolites after selenate exposure appeared to coincide with increasing esterase activity in solution, indicating that cell death (lysis) was the primary emission pathway. This is the first observation of biotic formation of selenocyanate and its release into waters from a nonindustrial source. The potential environmental implications of this laboratory observation are discussed with respect to the fate of selenium in impacted aquatic systems, the ecotoxicology of selenium bioaccumulation, and the interpretation of environmental selenium speciation data generated, using methods incapable of positively identifying reduced inorganic selenium species, such as selenocyanate. © 2011 American Chemical Society.


Poley L.G.,Environmental and Life science Graduate Program | Pond B.A.,Ontario Ministry of Natural Resources | Schaefer J.A.,Trent University | Brown G.S.,Ontario Ministry of Natural Resources | And 2 more authors.
Journal of Biogeography | Year: 2014

Aim: An understanding of the factors that influence species distributions in heterogeneous landscapes is important when making decisions regarding conservation. Moreover, occupancy probabilities based on detection data can reveal important species-habitat relationships. Accounting for the spatial autocorrelation of detection data increases the statistical validity of occupancy models, but is not often considered. Using novel occupancy modelling that explicitly incorporates detectability and spatial autocorrelation, we assessed the influence of habitat on occupancy patterns of woodland caribou (Rangifer tarandus caribou), moose (Alces alces) and wolves (Canis lupus) across a broad biogeographical extent where fire is the dominant agent of disturbance. Location: Northern Ontario, Canada. Methods: We aerially surveyed 3851 sampling units, each covering 100 km2, for woodland caribou, moose and wolves in February-March in 2009, 2010 and 2011, and visited 1663 units more than once to estimate detectability. We used restricted spatial regression to model occupancy probabilities of each species with respect to habitat factors in two ecozones, accounting for both imperfect detection and lack of independence of sampling units. Results: Covariates influencing species detection varied among ecozones and species. Caribou occupancy was positively related to bogs and negatively related to disturbed areas, while moose occupancy showed opposite responses to these covariates. Wolf occupancy was related to high prey occupancy. Explicitly accounting for spatial autocorrelation in detection data reduced the chance of type I error in occupancy estimates compared with non-spatial models. Main conclusions: Habitat relationships and occupancy patterns support the hypothesis that caribou remain spatially segregated from moose to reduce predation risk. The broad scale of analysis indicated changes in species-habitat relationships, suggesting that limiting factors vary across biogeographical gradients. The spatial pattern in caribou occupancy allowed us to identify important areas used by caribou across the region, including the ecotone between fire-driven boreal forests and peatland complexes. The evidence for significant relationships between caribou and land cover, predators and alternate prey underscores the need for careful planning of development and infrastructure in the area. © 2013 John Wiley & Sons Ltd.


Donaldson M.E.,Environmental and Life science Graduate Program | Saville B.J.,Environmental and Life science Graduate Program | Saville B.J.,Trent University
Molecular Microbiology | Year: 2013

Summary: Ustilago maydis infection of Zea mays leads to the production of thick-walled diploid teliospores that are the dispersal agent for this pathogen. Transcriptome analyses of this model biotrophic basidiomycete fungus identified natural antisense transcripts (NATs) complementary to 247 open reading frames. The U.maydisNAT cDNAs were fully sequenced and annotated. Strand-specific RT-PCR screens confirmed expression and identified NATs preferentially expressed in the teliospore. Targeted screens revealed four U.maydisNATs that are conserved in a related fungus. Expression of NATs in haploid cells, where they are not naturally occurring, resulted in increased steady-state levels of some complementary mRNAs. The expression of one NAT, as-um02151, in haploid cells resulted in a twofold increase in complementary mRNA levels, the formation of sense-antisense double-stranded RNAs, and unchanged Um02151 protein levels. This led to a model for NAT function in the maintenance and expression of stored teliospore mRNAs. In testing this model by deletion of the regulatory region, it was determined that alteration in NAT expression resulted in decreased pathogenesis in both cob and seedling infections. This annotation and functional analysis supports multiple roles for U.maydisNATs in controlling gene expression and influencing pathogenesis. © 2013 The Authors. Molecular Microbiology published by John Wiley & Sons Ltd.


PubMed | Trent University and Environmental and Life science Graduate Program .
Type: | Journal: Journal of environmental sciences (China) | Year: 2016

Asymmetric flow-field flow fractionation-inductively-coupled plasma-mass spectrometry was used to determine whether colloidal arsenic (As) exists in soil pore water and soil extract samples at two arsenic-contaminated abandoned gold mines (Montague and Goldenville, Nova Scotia). Colloidal arsenic was found in 12 out of the 80 collected samples (=15%), and was primarily associated with iron (Fe) in the encountered colloids. The molar Fe/As ratios indicate that the colloids in some samples appeared to be discrete iron-arsenic minerals, whereas in other samples, they were more consistent with As-rich iron (oxy)hydroxides. Up to three discrete size fractions of colloidal As were encountered in the samples, with mean colloid diameters between 6 and 14nm. The pore water samples only contained one size fraction of As-bearing colloids (around 6nm diameter), while larger As-bearing colloids were only encountered in soil extracts.

Loading Environmental and Life science Graduate Program collaborators
Loading Environmental and Life science Graduate Program collaborators