The value of case reports in diagnostic radiography.

OBJECTIVE: - This paper sought to explore the value of case reports in diagnostic radiography with regards to current usage, relevance to evidence-based radiography, and educational benefits. KEY FINDINGS: Case reports are short accounts of novel pathologies, trauma or treatment with a critical review of relevant literature. Examples within diagnostic radiography include the appearances of COVID-19 alongside examination-level scenarios involving image artefacts, equipment failure and patient incidents in radiology. With greatest risk of bias and lowest generalisability, they are considered as low-quality evidence with generally poor citation rates. Despite this, there are examples of significant discoveries or developments initiated with case reports with important patient care implications. Furthermore, they offer educational development for both reader and author alike. Whereas the former learns about an unusual clinical scenario, the latter develops scholarly writing skills, reflective practice and may generate further, more complex, research. Radiography-specific case reports could capture the diverse imaging skills and technological expertise currently under-represented in traditional case reports. Potential avenues for cases are broad and may include any imaging modality where patient care or safety of other persons may illicit a teaching point. This encapsulates all stages of the imaging process, before, during and after patient interaction. CONCLUSION: Despite being low-quality evidence, case reports contribute to evidence-based radiography, add to the knowledge base, and foster a research culture. However, this is contingent upon rigorous peer-review and adherence to ethical treatment of patient data. IMPLICATIONS FOR PRACTICE: With the drive to increase research engagement and output at all levels in radiography (student to consultant), case reports may act as a realistic grass-root activity for a burdened workforce with limited time and resources.

Review of petroleum toxicity and identifying common endpoints for future research on diluted bitumen toxicity in marine mammals.

Large volumes of conventional crude oil continue to be shipped by sea from production to consumption areas across the globe. In addition, unconventional petroleum products also transverse pelagic habitats; for example, diluted bitumen from Canada's oilsands which is shipped along the Pacific coast to the United States and Asia. Therefore, there is a continuing need to assess the toxicological consequences of chronic and catastrophic petroleum spillage on marine wildlife. Peer-reviewed literature on the toxicity of unconventional petroleum such as diluted bitumen exists for teleost fish, but not for fauna such as marine mammals. In order to inform research needs for unconventional petroleum toxicity we conducted a comprehensive literature review of conventional petroleum toxicity on marine mammals. The common endpoints observed in conventional crude oil exposures and oil spills include hematological injury, modulation of immune function and organ weight, genotoxicity, eye irritation, neurotoxicity, lung disease, adrenal dysfunction, metabolic and clinical abnormalities related to oiling of the pelage, behavioural impacts, decreased reproductive success, mortality, and population-level declines. Based on our findings and the body of literature we accessed, our recommendations for future research include: 1) improved baseline data on PAH and metals exposure in marine mammals, 2) improved pre- and post-spill data on marine mammal populations, 3) the use of surrogate mammalian models for petroleum toxicity testing, and 4) the need for empirical data on the toxicity of unconventional petroleum to marine mammals.

The Glaucous-Winged Gull (Larus glaucescens) as an Indicator of Chemical Contaminants in the Canadian Pacific Marine Environment: Evidence from Stable Isotopes.

The Glaucous-winged gull (Larus glaucescens) has been selected by Environment Canada as a marine indicator species for long-term monitoring of persistent contaminants in the Canadian Pacific. However, the indicator value of this species depends on its trophic level and proportion of marine prey in its diet. Eggs, used as the monitoring medium, are produced entirely from maternal resources and knowledge of adult diet before and during egg production is critical to interpreting contaminant levels. Due to a lack of recent and reliable dietary ecology work, we examined the diet of breeding Glaucous-winged gulls through carbon (δ13C) and nitrogen (δ15N) stable isotope analysis at three colonies on the Pacific coast. Near-shore marine prey, occupying a high trophic level (δ15N), composed a predominant component of all Glaucous-winged gull diet. Adult diet composition from colonies in the Salish Sea was more varied than the west coast of Vancouver Island, reflecting the opportunistic foraging nature of this species in areas where the abundance of marine prey is known to fluctuate. Compared with incubating adults, pre-laying adults had a significantly lower trophic level that may reflect the need to consume marine invertebrates to acquire specific nutrients necessary for egg production. Interannual variation in both trophic level and prey source (δ13C) in egg and chick tissues indicates the need to pair ongoing contaminant monitoring with stable isotope analysis. The predominantly marine diet and relatively high trophic level of this gull supports its use as an indicator of marine pollution on the Pacific coast.

Major correlates of mercury in small fish and common loons (Gavia immer) across four large study areas in Canada.

We investigated mercury (Hg) concentrations in small fish (mainly yellow perch, Perca flavescens; ∼60% of fish collected) and in blood of common loons (Gavia immer) that prey upon them during the breeding season on lakes in 4 large, widely separated study areas in Canada (>13 lakes per study area; total number of lakes = 93). Although surface sediments from lakes near a base metal smelter in Flin Flon, Manitoba had the highest Hg concentrations, perch and other small fish and blood of common loon chicks sampled from these same lakes had low Hg concentrations similar to those from uncontaminated reference lakes. Multiple regression modeling with AIC analysis indicated that lake pH was by far the most important single factor influencing perch Hg concentrations in lakes across the four study areas (R(2) = 0.29). The best model was a three-variable model (pH + alkalinity + sediment Se; Wi = 0.61, R(2) = 0.85). A single-variable model (fish Hg) best explained among-lake variability in loon chick blood Hg (Wi = 0.17; R(2) = 0.53). From a toxicological risk perspective, all lakes posing a potential Hg health risk for perch and possibly other small pelagic fish species (where mean fish muscle Hg concentrations exceeded 2.4 µg/g dry wt.), and for breeding common loons (where mean fish muscle Hg concentrations exceeded 0.8 µg/g dry wt., and loon chick blood Hg exceeded 1.4 µg/g dry wt.) had pH < 6.7 and were located in eastern Canada.

Validation of an egg-injection method for embryotoxicity studies in a small, model songbird, the zebra finch (Taeniopygia guttata).

Female birds deposit or 'excrete' lipophilic contaminants to their eggs during egg formation. Concentrations of xenobiotics in bird eggs can therefore accurately indicate levels of contamination in the environment and sampling of bird eggs is commonly used as a bio-monitoring tool. It is widely assumed that maternally transferred contaminants cause adverse effects on embryos but there has been relatively little experimental work confirming direct developmental effects (cf. behaviorally-mediated effects). We validated the use of egg injection for studies of in ovo exposure to xenobiotics for a small songbird model species, the zebra finch (Taeniopygia guttata), where egg weight averages only 1 g. We investigated a) the effect of puncturing eggs with or without vehicle (DMSO) injection on egg fate (embryo development), chick hatching success and subsequent growth to 90 days (sexual maturity), and b) effects of two vehicle solutions (DMSO and safflower oil) on embryo and chick growth. PBDE-99 and -47 were measured in in ovo PBDE-treated eggs, chicks and adults to investigate relationships between putative injection amounts and the time course of metabolism (debromination) of PBDE-99 during early development. We successfully injected a small volume (5 µL) of vehicle into eggs, at incubation day 0, with no effects on egg or embryo fate and with hatchability similar to that for non-manipulated eggs in our captive-breeding colony (43% vs. 48%). We did find some evidence for an inhibitory effect of DMSO vehicle on post-hatching chick growth, in male chicks only. This method can be used to treat eggs in a dose-dependent, and ecologically-relevant, manner with PBDE-99, based on chemical analysis of eggs, hatchling and adults.

Ecological factors differentially affect mercury levels in two species of sympatric marine birds of the North Pacific.

In 2003 and 2004, we measured mercury concentrations and δ¹5N and δ¹³C values in the whole blood of adults of two species of seabirds, Cassin's auklet (Ptychoramphus aleuticus) and rhinoceros auklet (Cerorhinca monocerata), during their prelaying, incubation, and provisioning periods. We also collected whole blood from the offspring of both seabirds. Among prey items, δ¹5N values were higher in fish than in crustaceans, while δ¹³C did not vary systematically between prey types. Mercury concentrations in prey showed little relationship with either stable isotope. In the zooplanktivorous Cassin's auklet, year, reproductive stage, and δ¹5N and δ¹³C stable isotope values explained only 14% of the variation in mercury concentrations in adult blood, and none of these variables had a statistically significant effect. In contrast, these same variables explained 41% of the variation in mercury levels in the more piscivorous rhinoceros auklet, and all but δ¹5N values had statistically significant effects. Mercury concentrations in adult rhinoceros auklets were higher in 2003 than in 2004; higher prior to laying than during the incubation or provisioning periods; and increased with δ¹³C values--but in just one of two years. In both species, mercury concentrations were substantially higher in adults than in nestlings. Our results accord with previous studies in showing that mercury concentrations can vary among years, species and age classes, while the marked variation with reproductive stage is noteworthy because it is so rarely considered. Our results may help to explain the disparate conclusions of previous studies: while many factors influence mercury concentrations in marine predators, they apparently do so in a manner that defies easy characterization. We believe that there is a need for more studies that consider a range of physiological, ecological and behavioral factors that might affect mercury burdens in marine predators.

Properties of blood, porphyrins, and exposure to legacy and emerging persistent organic pollutants in surf scoters (Melanitta perspicillata) overwintering on the south coast of British Columbia, Canada.

The surf scoter (Melanitta perspicillata) is a little-studied species of North American sea duck. Estimates suggest it has experienced a precipitous decline in breeding numbers over the latter half of the past century. To investigate the potential role of contaminant uptake and toxicity in the population decline, this study undertook to measure blood chemistry, porphyrin concentrations, EROD, and organic contaminants in mature surf scoters wintering in the Strait of Georgia, BC, Canada. Hepatic organochlorine pesticide, polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran, polychlorinated biphenyl (PCB), polybrominated diphenyl ether, and nonylphenol concentrations were relatively low; for example, SigmaTEQs (toxic equivalents) for PCBs, dioxins, and furans combined ranged from 4.7 ng/kg wet weight in reference-site (Baynes Sound) birds to 11.4 ng/kg wet weight in birds from Vancouver Harbour. Nonetheless, elevated EROD activity indicated that birds in Howe Sound were responding to an Ah-receptor-mediated stressor, which was also affecting hematocrit values and possibly vitamin A status. In addition, a low proportion of lymphocytes in individuals across locations in early spring samples was associated with poor body condition. The apparent loss of fitness just prior to the onset of northerly migrations to breeding grounds is of particular concern. Compromised health of mature birds at this point in the season might impact negatively on the productivity and survival of some individuals, particularly those overwintering in Howe Sound.

Relationships among mercury, selenium, and neurochemical parameters in common loons (Gavia immer) and bald eagles (Haliaeetus leucocephalus).

Fish-eating birds can be exposed to levels of dietary methylmercury (MeHg) known or suspected to adversely affect normal behavior and reproduction, but little is known regarding Hg's subtle effects on the avian brain. In the current study, we explored relationships among Hg, Se, and neurochemical receptors and enzymes in two fish-eating birds--common loons (Gavia immer) and bald eagles (Haliaeetus leucocephalus). In liver, both species demonstrated a wide range of total Hg (THg) concentrations, substantial demethylation of MeHg, and a co-accumulation of Hg and Se. In liver, there were molar excesses of Se over Hg up to about 50-60 microg/g THg, above which there was an approximate 1:1 molar ratio of Hg:Se in both species. However, in brain, bald eagles displayed a greater apparent ability to demethylate MeHg than common loons. There were molar excesses of Se over Hg in brains of bald eagles across the full range of THg concentrations, whereas common loons often had extreme molar excesses of Hg in their brains, with a higher proportion of THg remaining as MeHg compared with eagles. There were significant positive correlations between brain THg and muscarinic cholinergic receptor concentrations in both species studied; whereas significant negative correlations were observed between N-methyl-D-aspartic acid (NMDA) receptor levels and brain Hg concentration. There were no significant correlations between brain Se and neurochemical receptors or enzymes (cholinesterase and monoamine oxidase) in either species. Our findings suggest that there are significant differences between common loons and bald eagles with respect to cerebral metabolism and toxicodynamics of MeHg and Se. These interspecies differences may influence relative susceptibility to MeHg toxicity; however, neurochemical responses to Hg in both species were similar.

Butyltins, trace metals and morphological variables in surf scoter (Melanitta perspicillata) wintering on the south coast of British Columbia, Canada.

From 1998 to 2001 we examined spatial and temporal variation in uptake of contaminants by surf scoters (Melanitta perspicillata) in the Georgia Basin region of the Pacific coast of Canada. Samples were collected during late fall and early spring at industrialized and reference locations, carcasses examined, and tissues collected for histology, biomarkers, and contaminant analyses. Scoters from both Vancouver and Victoria harbours had significantly higher hepatic concentrations of summation operatorbutyltins than birds from a reference site. In adult male surf scoters, hepatic summation operatorbutyltins increased over the winter at two sites (p=0.02, n=26), while mercury increased (p=0.03, n=15) and selenium decreased at one site (p=0.001, n=15). Body condition decreased over the winter at both the treatment site, Howe Sound (p<0.0001, n=12), and the reference site, Baynes Sound (p=0.02, n=15). Multiple regression analysis using Akaike's Information Criteria (AIC(C)) showed an association between hepatic butyltin concentrations and overall body condition (p=0.06, r=-0.237).

Vitamin A and contaminant concentrations in surf scoters (Melanitta perspicillata) wintering on the Pacific coast of British Columbia, Canada.

Surf scoters are part of a community of sea ducks on the western coast of North America that have shown signs of long-term, unexplained declines in breeding bird numbers. Substantial numbers of scoters winter in the major harbours on the west coast, after breeding in the west-central northern boreal forest. To address the potential for contaminants to impact the health and survival of those birds, we investigated the condition and contamination of surf scoters during the winters of 1998-2001 at four foraging locations in the Strait of Georgia region of the Pacific coast of Canada. Vitamin A status was evaluated in liver and plasma samples collected from adults and juveniles, as part of a larger assessment of tissue contamination, body condition and biomarker responses. Individuals collected from a relatively contaminated site, Howe Sound, showed consistently low hepatic concentrations of retinol and retinyl palmitate forms of vitamin A, and gender-specific associations of retinyl palmitate with hepatic EROD activity. The relationship of hepatic retinol to retinyl palmitate was not constant across geographic locations, and a clear, linear relationship between the two forms of vitamin A was only evident in birds from the relatively uncontaminated site. This study also identified strong positive relationships between vitamin A and tissue burdens of cadmium and zinc. The positive association between hepatic retinyl palmitate and renal cadmium is similar to one observed in laboratory rats, in which a mechanism of interference with the controlled release of retinol from the liver was suggested.

Regulation of acetyl-CoA carboxylase.

Acetyl-CoA carboxylase (ACC) catalyses the formation of malonyl-CoA, an essential substrate for fatty acid synthesis in lipogenic tissues and a key regulatory molecule in muscle, brain and other tissues. ACC contributes importantly to the overall control of energy metabolism and has provided an important model to explore mechanisms of enzyme control and hormone action. Mammalian ACCs are multifunctional dimeric proteins (530-560 kDa) with the potential to further polymerize and engage in multiprotein complexes. The enzymatic properties of ACC are complex, especially considering the two active sites, essential catalytic biotin, the three-substrate reaction and effects of allosteric ligands. The expression of the two major isoforms and splice variants of mammalian ACC is tissue-specific and responsive to hormones and nutritional status. Key regulatory elements and cognate transcription factors are still being defined. ACC specific activity is also rapidly modulated, being increased in response to insulin and decreased following exposure of cells to catabolic hormones or environmental stress. The acute control of ACC activity is the product of integrated changes in substrate supply, allosteric ligands, the phosphorylation of multiple serine residues and interactions with other proteins. This review traces the path and implications of studies initiated with Dick Denton in Bristol in the late 1970s, through to current proteomic and other approaches that have been consistently challenging and immensely rewarding.

Chlorinated hydrocarbon contaminants and stable isotope ratios in pelagic seabirds from the North Pacific Ocean.

Organochlorine pesticides, polychlorinated biphenyls (PCBs), and stable isotopes of nitrogen (delta15N) and carbon (delta13C) were determined in livers of eight seabird species (Diomedea immutabilis, D. nigripes, Fulmarus glacialis, Puffinus bulleri, P. carneipes, P. griseus, P. tenuirostris, and Fratercula corniculata) collected opportunistically from an experimental fishery in the North Pacific Ocean. Concentrations of P, P'-DDE were found in all samples but were highly variable among species, ranging over >2 orders of magnitude from 1.23 mg/kg (wet weight) in D. nigripes to 0.008 mg/kg in P. tenuirostris, whereas total PCBs ranged from 1.14 to 0.020 mg/kg in those same two species. Residues of hexachlorobenzene, trans-nonachlor, photo-mirex, mirex, beta-hexachlorocyclohexane, oxychlordane, and heptachlor expoxide were quantified at lower concentrations in all samples. There were significant positive regressions of lipid-normalized concentrations of DDE (r2 = 0.526), total PCBs (r2 = 0.566), CB-153 (r2 = 0.565), and mirex (r2 = 0.586) on the hepatic delta15N signature, indicating that trophic level accounted for approximately 50% of the variability in those contaminants among species. In some species, e.g., P. bulleri, concentrations were lower than expected based on delta15N, which was attributed to a dietary switch before sampling and therefore lack of concordance in the time scales integrated by hepatic chlorinated hydrocarbon concentrations compared with delta15N.

Effects of azinphos-methyl on cholinergic responses and general health in zebra finches (Taeniopygia guttata) after previous treatment with p,p'-DDE.

Although organochlorine (OC) pesticides were replaced with organophosphates (OPs) in the early 1970s, they continue to persist in orchard environments today. Extensive research has been conducted to determine the effects of currently used OPs on cholinesterase (ChE) activity; however, although OCs continue to be prevalent in areas of previous use, few studies have looked at the toxicity of a combination of residual OC compounds with currently used OP pesticides. The focus of our study was to determine the effects of azinphos-methyl (a common OP used in apple orchards today) on ChE activity and general health in zebra finches (Taeniopygia guttata) previously exposed to p,p'-DDE (a commonly detected metabolite of DDT). The main results of our study were as follows: (1) azinphos-methyl alone caused a dose-dependent inhibition of plasma and brain ChE activity; (2) p,p'-DDE in combination with azinphos-methyl did not change azinphos-methyl inhibition of ChE activity; and (3) there were suggestions of immunostimulation in birds dosed 1 year previously to p,p'-DDE and of anemia when p,p'-DDE was combined with azinphos-methyl; however, there was no dose-response for these parameters in birds subsequently dosed with p,p'-DDE.

Assessing breeding potential of peregrine falcons based on chlorinated hydrocarbon concentrations in prey.

Peregrine falcons (Falco peregrinus) now breed successfully in most areas of North America from which they were previously extirpated. The loss during the mid-part of the last century of many of the world's peregrine populations was largely a consequence of impaired reproduction caused by the effects of DDE on eggshell quality and embryo hatchability. Population recovery has been attributed to re-introduction efforts, coupled with regulatory restrictions on the use of organochlorine pesticides. Peregrines have not returned to breed in some areas, such as the Okanagan Valley of British Columbia. That region has been extensively planted in fruit orchards which were treated annually with DDT during the early 1950s to the 1970s. Ongoing contamination of avian species, including potential peregrine prey, inhabiting orchards has been documented. In response to an initiative to release peregrines around the city of Kelowna in the Okanagan Valley, we collected potential peregrine prey species and analyzed whole bodies for chlorinated hydrocarbon residues. We used a simple bioaccumulation model to predict concentrations of DDE in peregrine eggs using concentrations in prey and estimates of dietary makeup as input. Peregrines would be expected to breed successfully only if they fed on a diet primarily of doves. Feeding on as little as 10% of other species such as starlings, robins, gulls and magpies would produce DDE concentrations in peregrine eggs greater than the threshold of 15 mg/kg. We also estimated the critical concentration of DDE in total prey to be about 0.5 mg/kg, one half of the previous most conservative criterion for peregrine prey. Concentrations of dieldrin and PCBs in peregrine prey are less than suggested critical levels.

Mercury in fish from the Pinchi Lake Region, British Columbia, Canada.

Water, surface sediments, and <40 cm rainbow trout (Oncorhynchus mykiss) and northern pikeminnow (Ptychocheilus oregonensis) were collected from Pinchi Lake, British Columbia, and from several nearby reference lakes. Hg concentrations in sediment samples from Pinchi L. were highly elevated compared to sediments from reference lakes, especially in sites adjacent to and downstream of a former Hg mine. In both fish species examined, Hg concentration was positively related to age and/or fork length. In northern pikeminnow, Hg concentrations were also positively related to trophic level (deltaN). Hg concentrations in both fish species were highest in Pinchi L., and were higher in pikeminnow than in rainbow trout of similar size. Average Hg concentrations in small rainbow trout from all lakes, including Pinchi L., were lower than dietary levels reported to cause reproductive impairment in common loons (Gavia immer); however, Hg levels in small pikeminnow from Pinchi L. were sufficiently high to be of concern. The risk for Hg toxicity in the study area is greatest for animals that consume larger piscivorous fish such as larger northern pikeminnow or lake trout, which are known from previous studies to contain higher Hg concentrations.

Reproductive success and chlorinated hydrocarbon contamination of resident great blue herons (Ardea herodias) from coastal British Columbia, Canada, 1977 to 2000.

Over the period 1977-2000, eggs of Pacific great blue heron (Ardea herodias fannini) were collected from 23 colonies along the southern coast of British Columbia, Canada, and analyzed for persistent organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs). Concentrations of OC pesticides in eggs declined sharply in the late 1970s, after which there were minimal changes. The sums of PCB congeners were not reduced appreciably during the 1980s and 1990s, but Aroclor 1260 concentrations suggested a sharp decline in PCB contamination of eggs in the late 1970s, similar to that shown for OC pesticides. Eggs collected along or near the Fraser River delta showed higher levels of most pesticides compared to other monitored colonies. Although the delta lands support a long-standing agricultural economy, the primary factors influencing OC levels in the delta colonies were thought to be driven by estuarine processes. We suggest two possible influencing factors were: 1) a greater rate of bioaccumulation in the estuary due to the deposition of particulates collected over a vast area encompassed by the Fraser River watershed; or 2) a higher rate of biomagnification in the estuary due to species differences at lower trophic levels of the heron food chain. Eggs from urban colonies contained higher levels of PCBs. The congener pattern was not clearly different from that observed in less contaminated eggs from rural and pulp mill-influenced colonies, except that colonies in Vancouver had greater proportions of PCB-66, suggesting a local source of Aroclor 1242. Productivity in the coastal heron colonies was highly variable over the period of study, with 71% of recorded colony-wide reproductive failures occurring in colonies near pulp mills. However, the predominant factors influencing reproductive success were probably disturbance by humans and bald eagles, combined with loss and degradation of nesting habitat, and not sublethal toxicity.

Mercury residues in livers of bald eagles (Haliaeetus leucocephalus) found dead or dying in British Columbia, Canada (1987-1994).

Postmortem examinations were conducted on 82 bald eagles (Haliaeetus leucocephalus) found dead or dying in British Columbia, Canada, from 1987 to 1994. As part of the examination, livers were analyzed for total mercury (Hg) content, as well as methylmercury (meHg) and selenium (Se) in selected individuals. In total, 67 eagles were classed as having low Hg exposure [total Hg liver residues ranging from 0.5 to 17.2 mg/kg dry weight (dw)]. Fourteen eagles were moderately exposed (liver residues ranging from 19.2 to 36.8 mg/kg Hg dw). One eagle was judged to have died of Hg poisoning, with a total liver Hg content of 130.3 mg/kg dw, of which approximately 77% was meHg. The poisoned eagle and most of the exposed eagles were found in locations where effluent from pulp and paper processing plants is discharged along the British Columbia coast. In total, 6% of eagles examined died as a result of acute metal toxicosis (one from Hg poisoning, four from lead poisoning), in comparison to 72% dying from trauma (electrocution, vehicle/power line collision, eagle attack, trap, gunshot, drowning, and asphyxiation) and 11% from disease. The cause of death was undetermined in the remaining 11% of eagles.

Metal and metallothionein concentrations in Scoter (Melanitta spp.) from the Pacific northwest of Canada, 1989-1994.

Eighty-six surf ( Melanitta perspicillata) and nine white winged (M. fusca) scoters were collected from 1989-1994 at 11 locations in British Columbia and the Yukon. Their kidney and liver tissues were analyzed for cadmium (Cd), copper (Cu), zinc (Zn), and metallothionein (MT) concentrations. Individual kidney Cd values ranged from 2.4 microg/g dry weight (DW) in birds from northern Vancouver Island to 390.2 microg/g (DW) in birds from the Queen Charlotte Islands, which is in the range of values potentially associated with kidney damage. Birds from the Queen Charlotte Islands also had high kidney Zn concentrations, which were significantly higher than values in birds from Naniamo and Westham Island on the south coast of BC. Cd values were significantly (p < 0.001) correlated with both Zn and MT concentrations in kidney tissue (r = 0.66 and 0.62, respectively). Male surf scoters had significantly higher kidney Cd and Zn levels than females, with mean Cd values of 47.3 and 19.7 microg/g DW (p < 0.002) for males and females, respectively. Mean Zn values were 120.8 and 108.0 microg/g DW (p < 0.05) for males and females, respectively. However, no sex differences were observed for either Cu or MT concentrations in kidney tissue. Individual MT values ranged from 2.7 to 416.8 microg/g wet weight (WW). Individual kidney Cu values ranged from 15.1 to 48.4 microg/g DW for both sexes. Kidney and liver Cd concentrations were significantly correlated (r = 0.90, p < 0.05) with kidney levels almost always higher than liver values. Although Cd accumulation by the Skidegate scoters was high, comparable tissue Cd values have been documented in other seabirds collected from the same general area, indicating elevated Cd concentrations in marine food chains around the Queen Charlotte Islands (Haida Gwaii) region of the Pacific coast.

The effect of cure rate on the mechanical properties of dental resins.

OBJECTIVE: This study investigates the effect of cure rate on the mechanical properties of a common dimethacrylate dental resin formulation (75/25 wt% bis-GMA/TEGDMA). METHODS: The polymerization rate and final conversion of the exact specimens subsequently used for mechanical testing were monitored by near-infrared (near-IR) spectroscopy. The glass transition temperature (T(g)) and modulus, as a function of temperature, were determined by dynamic mechanical analysis (DMA). Iniferter initiating systems were used to create partially cured networks that did not contain any trapped radicals. By the elimination of trapped radicals from the system, the formed networks can be characterized as a function of both temperature and double bond conversion without inducing additional thermal cure during testing. RESULTS: Copolymer specimens were cured with UV and visible light initiating systems, UV light intensities that varied by over four orders of magnitude, and cure temperatures that differed by 60 degrees C. Even though the polymerization rates for these resins were vastly different, similar T(g) and modulus were measured for specimens cured to the same final double bond conversion. SIGNIFICANCE: This study shows that highly cross-linked dimethacrylate systems, such as bis-GMA/TEGDMA, exhibit similar network structure and properties as a function of double bond conversion, regardless of the method or rate of cure.

Assessment of biological effects of chlorinated hydrocarbons in osprey chicks.

Osprey (Pandion haliaetus) eggs were collected during 1995 and 1996 at seven sites along the Fraser and Columbia River systems of British Columbia, Canada, and Washington and Oregon, USA. Fifty-four eggs were placed into a laboratory incubator. Thirty-eight of the hatched chicks were sacrificed within 24 h. Hatching success did not differ among sites and therefore between treatment and reference areas. Residual yolk sacs of eggs collected downstream of the large bleached-kraft pulp mill at Castlegar contained greater mean concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 2,930 ng/kg lipid) compared with reference sites such as the Nechako River, an upper tributary of the Fraser system (33.7 ng/kg). Total polychlorinated biphenyls (PCBs) in yolk sacs were also higher at Castlegar and in samples from the Columbia River downstream of Portland, Oregon, compared with those from the Nechako River. Concentrations of measured chemicals, including TCDD toxic equivalents (TEQs), total PCBs, p,p'-dichlorodiphenylethylene (p,p'-DDE), and other organochlorines were not different in eggs that failed to hatch compared with calculated whole-egg values for hatched eggs. There were significant biochemical responses; a hepatic cytochrome P4501A (CYP1A) cross-reactive protein was detected in all samples tested and correlated positively with ethoxyresorufin o-deethylase (EROD) activity and yolk sac concentrations of TEQs and total PCBs. Tissue concentrations of vitamin A compounds varied among sites and correlated positively with yolk sac concentrations of TEQs and PCBs. Morphological, histological, and other physiological parameters, including chick growth, edema, deformities, and hepatic and renal porphyrin concentrations, neither varied among sites nor showed concentration-related effects.