Changes in egg composition of American kestrels exposed to dietary polychlorinated biphenyls

Changes in the quality of eggs of birds exposed to polychlorinated biphenyls (PCBs) have been described, but have never been directly attributed to PCBs. Polychlorinated biphenyl residues in eggs have been associated with reduced reproductive success and embryonic deformities in wild birds. Egg size and composition, specifically the amount of albumen, yolk, and water in an egg, also influence the growth and viability of embryos and hatchlings, and consequently the reproductive success of birds. To deter mine whether PCB exposure of adult birds affected the size and composition of their eggs, 25 pairs of captive American kestrels (Falco sparverius) were fed a mixture of PCB-spiked (1248:1254:1260) food to give an approximate exposure of 7 mg/kg body weight/d, beginning 1 mo prior to pairing, and continuing throughout the courtship, egg-laying, and incubation periods. This dietary level in the adult female kestrels resulted in mean total PCB residues in the eggs of 34.1 microg/g wet weight (geometric mean), which is environmentally relevant. PCB residues in eggs increased with the time of female exposure to the contaminated diet and laying date. Variation in egg size within PCB clutches was significantly greater than within control clutches, although absolute egg mass and volume did not differ markedly by treatment. Only infertile eggs and only one egg per clutch were used for egg composition analysis. Yolks in the PCB-contaminated eggs were heavier, with less wet and dry albumen relative to control eggs. Water content and eggshell thickness were not significantly affected by PCB exposure. These results suggest that eggs from the PCB treatment have relatively more lipid and less protein available for embryonic development. Changes in egg composition were not associated with egg size, lay date, ambient temperature, humidity, or precipitation, which are factors known to affect these variables in bird eggs. The PCB-induced changes in egg composition described here provide insight into possible mechanisms contributing to reduced reproductive performance in wild birds exposed to PCBs.     

Hepatic EROD activity is not a useful biomarker of polychlorinated biphenyl exposure in the adult herring gull (Larus argentatus)

Liver concentrations of polychlorinated biphenyls (PCBs) and chicken embryo hepatocyte (CEH) bioassay-derived 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQs) were measured in livers of adult herring gulls (Larus argentatus) collected from several locations on the Great Lakes and two reference sites. Total PCB concentrations (sum of 42 congeners) and TCDD-EQ concentrations were compared with hepatic ethoxyresorufin-O-deethylase (EROD) activity, methoxyresorufin-O-deethylase (MROD) activity and immunodetectable cytochrome P4501A (CYP1A) protein concentration. EROD and MROD activity were not significantly correlated with total PCB concentration or TCDD-EQ concentration in liver tissue. CYP1A protein concentration was significantly correlated with total PCB concentration, but the linear relationship had little predictive power. We conclude that EROD is not a useful biomarker of PCB exposure in the adult herring gull.     

CHANGES IN EGG COMPOSITION OF AMERICAN KESTRELS EXPOSED TO DIETARY POLYCHLORINATED BIPHENYLS

Changes in the quality of eggs of birds exposed to polychlorinated biphenyls (PCBs) have been described, but have never been directly attributed to PCBs. Polychlorinated biphenyl residues in eggs have been associated with reduced reproductive success and embryonic deformities in wild birds. Egg size and composition, specifically the amount of albumen, yolk, and water in an egg, also influence the growth and viability of embryos and hatchlings, and consequently the reproductive success of birds. To deter mine whether PCB exposure of adult birds affected the size and composition of their eggs, 25 pairs of captive American kestrels (Falco sparverius) were fed a mixture of PCB-spiked (1248:1254:1260) food to give an approximate exposure of 7 mg/kg body weight/d, beginning 1 mo prior to pairing, and continuing throughout the courtship, egg-laying, and incubation periods. This dietary level in the adult female kestrels resulted in mean total PCB residues in the eggs of 34.1 µg/g wet weight (geometric mean), which is environmentally relevant. PCB residues in eggs increased with the time of female exposure to the contaminated diet and laying date. Variation in egg size within PCB clutches was significantly greater than within control clutches, although absolute egg mass and volume did not differ markedly by treatment. Only infertile eggs and only one egg per clutch were used for egg composition analysis. Yolks in the PCB-contaminated eggs were heavier, with less wet and dry albumen relative to control eggs. Water content and eggshell thickness were not significantly affected by PCB exposure. These results suggest that eggs from the PCB treatment have relatively more lipid and less protein available for embryonic development. Changes in egg composition were not associated with egg size, lay date, ambient temperature, humidity, or precipitation, which are factors known to affect these variables in bird eggs. The PCB-induced changes in egg composition described here provide insight into possible mechanisms contributing to reduced reproductive performance in wild birds exposed to PCBs.     

Association between PCBs and lower embryonic weight in black-crowned night herons in San Francisco Bay

Reproductive problems, including congenital malformations, reduced hatching success, and decreased survival of hatchlings, have been observed in colonial-nesting water birds at the San Francisco Bay National Wildlife Refuge (SFBNWR). Twenty-four black-crowned night heron (Nycticorax nycticorax) eggs were collected from SFBNWR in 1983. Twelve of these were collected from separate nests when late-stage embryos were pipping, and an additional egg was randomly collected from each nest for organochlorine analysis. Overt anomalies and skeletal defects were not apparent. Embryonic weights (with partially absorbed yolk sacs removed) were 15% lower (p less than 0.05) in SFBNWR embryos compared to control embryos from the Patuxent Wildlife Research Center (PWRC). Crown-rump length and femur length were shorter for SFBNWR embryos. The geometric mean polychlorinated biphenyl (PCB) concentration in SFBNWR eggs was 4.1 ppm wet weight, with a range of 0.8-52.0 ppm. A negative correlation (r = -0.61; p less than 0.05) existed between embryonic weight and log-transformed PCB residues in whole eggs collected from the same nest at SFBNWR, suggesting a possible impact of PCBs on embryonic growth. A correlation with embryonic weight did not occur for DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene] residues. Liver microsomal aryl hydrocarbon hydroxylase activity was neither significantly elevated nor correlated with PCB, DDE, or PCB plus DDE log-transformed residues. It is unknown whether the apparent association between PCBs and lower weight is persistent through hatching.     

Developmental stage dependent toxicity of aminoguanidine on chick embryos

Aminoguanidine (AG) sulfate was injected into the thin albumen of fertile eggs on the different days of incubation. The lethality of AG sulfate on the developing chick embryos became lower when the treatment was done at later developmental stage. When AG was injected on the 5th day of incubation, the frequency of retardation of development of the body and liver, aplasia of gallbladder and enlarged spleen was highest without high mortality compared with the other experiments. Embryos with liver damage could not hatch. 14C-AG hydrochloride injected on the 5th day of incubation easily distributed into the embryo through the yolk from the thin albumen of the injection site, but when injected on the 9th day, the agent transferred very little into the yolk and embryo. The change of transport in the eggs with development may elucidate the difference of lethality of AG. Additionally, it was confirmed using thin layer chromatography that a large part of the radioactivity in the embryo might be an unknown metabolite of AG and the substance was accumulated with extremely high concentration in the liver at 24-48 hr after the injection of AG on the 5th day of incubation. This is probably the main cause of the peculier abnormalities in the liver of chick embryos.     

Physiologically based modeling of the accumulation in plasma and tissue lipids of a mixture of PCB congeners in female Sprague-Dawley rats

This study aimed to develop a physiologically based model for simulating the concentrations of polychlorinated biphenyls (PCBs) in tissue and plasma lipids of rats exposed to PCB mixtures. The model was based on the assumption that the neutral lipid fraction is the only critical determinant of the tissue distribution of PCBs, and that the solubility/retention in other tissue components is negligible. The volumes of the model compartments reflected the volumes of neutral lipids, whereas the flow rates corresponded to those of the neutral lipids in blood. Since the equilibrium ratio of PCB concentrations in neutral lipids of tissues and plasma equals 1, the present modeling approach does not require the use of tissue:blood partition coefficients. Metabolism rates were derived from the best visual fit of the model to the PCB concentrations in hepatic lipids determined on d 41 and 90 in rats exposed to a mixture containing 5, 50, or 500 microg PCBs (118, 138, 153, 170, 180 and 187) per kilogram body weight according to various protocols: (a) every-day dosing, (b) once-a-week dosing, (c) consecutive dosing for 13 d with no further treatment, and (d) 13 irregularly spaced doses. The resulting model consistently simulated the concentrations of PCBs in adipose tissue and plasma lipids of rats exposed according to the four described protocols. The physiologically based pharmacokinetic (PBPK) model developed in this study should be useful as a basis for interpretating blood or plasma lipid concentration data on PCBs collected during biomonitoring studies.     

A physiologically based toxicokinetic model for dietary uptake of hydrophobic organic compounds by fish: I. Feeding studies with 2,2',5,5'-tetrachlorobiphenyl.

A physiologically based toxicokinetic (PBTK) model was developed to describe dietary uptake of hydrophobic organic compounds by fish. The gastrointestinal (GI) tract was modeled using four compartments corresponding to the stomach, pyloric ceca, upper intestine, and lower intestine, and the lumenal volume of each compartment was allowed to change in time as a function of bulk flow down the GI tract and (for the pyloric ceca and upper intestine) nutrient uptake. The model was developed using data from rainbow trout that were fed a single meal of 60-day-old fathead minnows contaminated with [UL-(14)C] 2,2',5,5'-tetrachlorobiphenyl ([(14)C] PCB 52). Chemical partitioning coefficients for the gut contents and tissues were adjusted to account for changes in chemical affinity associated with uptake of dietary lipid. Permeability constants for the absorbing gut segments were then fitted by modeling to measured [(14)C] PCB 52 concentrations in gut contents and tissues. The model accurately describes observed patterns of gastric evacuation and bulk flow of digesta, the concentration time course for [(14)C] PCB 52 in contents and tissues of the GI tract, and [(14)C] PCB 52 distribution to other major tissues. Most of the [(14)C] PCB 52 was taken up in the pyloric ceca and upper intestine during the period of peak lipid absorption. It is concluded, however, that a kinetic limitation acting along the entire length of the GI tract resulted in a chemical disequilibrium between feces and tissues of the lower intestine.     

Relationship between PCB accumulation and reproductive output in conditioned oysters Crassostrea virginica fed a contaminated algal diet

Because of their resistance to environmental degradation, polychlorinated biphenyls (PCBs) are among the most widespread environmental contaminants. PCBs have high bioaccumulation potential and may affect a number of biological/physiological processes including disruption of the endocrine system function, lipid metabolism and reproduction. The objective of this study was to test whether conditioning sexually immature oysters with PCB-contaminated algal diets affects their subsequent reproductive success. Sexually immature oysters were conditioned in individual containers and fed daily with 0.7 g algal paste containing 0, 0.35 or 3.5 microg PCBs for up to 76 days. The impact of sediment load on PCB accumulation in oysters was also tested by exposure of a subset of oysters to clay particles. Oysters in different treatments were sampled 56 days after conditioning with PCB-contaminated algal diets to determine uptake and distribution of PCBs in gonad, digestive gland, mantle, gill and muscle, and the presence of gametes. Tissues from oysters exposed to PCBs alone for 56 days were also analyzed for lipid and fatty acid composition. Following 61 and 76 days of PCB exposure, remaining oysters from all treatments were induced to spawn via thermal stimulation. Non-spawned oysters were stripped to determine if sexual products were present. Oysters exposed to PCBs alone and PCBs plus clay particles showed similar trends in PCB accumulation, but concentrations were generally lower in the latter. PCB accumulation in oysters increased with an increase in algal-associated PCB concentrations, varied with organ types and was correlated with lipid content. The highest PCB concentration was in the gonad and the lowest in gill and muscle. PCB-153, -138/158, -118, -90/101 and -149 were the dominant congeners in all tissue compartments, except the muscle where PCB-28/31 was the dominant congener pair. PCB exposure appeared to impair both lipid metabolism and reproductive success. Although PCB exposure produced only slight changes in the lipid class composition in the oysters, decreases in phospholipids were observed in gonad, muscle and mantle of oysters exposed to 3.5 microg PCBs daily for 56 days. After 56 days of conditioning with PCB-sorbed algal paste, no well-developed mature eggs were observed in any of the oysters examined for the presence of sexual products. No significant difference was noted in reproductive success (production of spawned females and males) between sediment-treated and non-treated groups after 76 days of PCB exposure compared to controls, PCB-exposed oysters produced fewer spawned females, but no dose-dependent relationship was observed.     

Effects of furazolidone, PCB77, PCB126, Aroclor 1248, paraquat and p,p'-DDE on transketolase activity in embryonal chicken brain

The effect of in ovo exposure to PCBs, DDE and paraquat on transketolase activity was measured in 19-day-old chicken embryos. Furazolidone was used as a positive control for decreased activity of the enzyme. The potency of contaminants to interact with transketolase was also tested in an in vitro system, using control brain 7000xg supernatants containing the enzyme. No effects were found on transketolase activity after in ovo or in vitro exposure to PCB126, Aroclor, DDE or paraquat. PCB77 decreased transketolase activity in vitro, but only at concentrations that, extrapolated to in ovo exposure, would be lethal to the embryo. Furazolidone decreased transketolase activity both in ovo and in vitro. For this contaminant, thiamine residues were analysed in the yolk sacs, but no differences were found between exposed and non-exposed eggs. Transketolase is dependent on thiamine pyrophosphate as a cofactor, and therefore, the decreased enzyme activity could be the result of an interaction between furazolidone and thiamine metabolism. Since thiamine residues were not affected by furazolidone and transketolase inhibition in vitro was similar to the inhibition after in ovo exposure, it was concluded that furazolidone interacted with transketolase on the enzymatic level rather than by a depletion of thiamine.     

Toxicity and distribution of 2-methyl-4-chlorophenoxyacetic acid (MCPA) in developing chick embryos

The toxicity of the herbicide Erbitox E30, a commercial formulation of 2-methyl-4-chlorophenoxyacetic acid (MCPA) containing 28% MCPA as sodium-potassium salt and 72% of unknown ingredients, was tested on chick embryos. Sterile aqueous solutions of MCPA were injected into the air chamber at doses of 0, 1.5, 3.0, 6.0, 9.0, or 10.5 mg/egg on day 0 or on day 4 of incubation. The mortality rate for the embryos treated on day 0 of incubation was high in the first 5 days, low from 5-12 days and again increased by 15 days. The 15-day LD50 was 4.4 mg/egg (95% C.I. 3.7-5.3 mg/egg). HPLC analysis of albumen and yolk showed that concentrations of MCPA in the albumen were detectable at 5 min, highest at 7 days and markedly diminished by 14 days of incubation; a significantly lower concentration of MCPA was found in the yolk throughout the incubation period, except at 14 days when the yolk concentration was 4 times higher than the albumen concentration. At 15 days of incubation, MCPA was evenly distributed in the tissues of the embryo. MCPA was more toxic to 4-day embryos; concentrations above 6.0 mg/egg were lethal to all embryos within the first week of incubation. The 15-day LD50 for treatment on day 4 of incubation was 2.8 mg/egg (95% C.I. 2.5-3.2 mg/egg). The liver was affected by treatment with MCPA, being green in treated embryos. However, histological examination revealed few changes in the liver parenchyma.     

Effects of PCB 126 on thymocyte surface marker expression and immune organ development in chicken embryos

Previous studies have shown that chicken (Gallus domesticus) embryos are sensitive to the immunotoxic effects of Ah receptor agonists. These chemicals cause atrophy of the thymus gland and bursa of Fabricius, the sites of T- and B-lymphocyte maturation, respectively. The objectives of this study were (1) to evaluate the effects of 3,3,4,4',5-pentachlorobiphenyl (PCB 126) on thymocyte phenotypes (CD4-CD8-, CD4+CD8+, CD4+CD8-, CD4-CD8+, TCRalphabeta+, and TCRgammadelta) in chicken embryos, and (2) to compare phenotype alterations with masses and cellularity of lymphoid organs. To simulate exposure in wild avian embryos, chicken eggs were injected with PCB 126 (sunflower oil carrier) into the air cell before incubation. Doses ranged from 0.051 to 0.8 ng/g egg with carrier-injected and noninjected control groups. The thymus and bursa were removed, weighed, and homogenized on d 20 of egg incubation (1 d before hatch). Thymocyte phenotypes were quantified by flow cytometry using monoclonal antibodies for CD4, CD8, TCRalphabeta (Vbeta1), and TCRgammadelta. Right thymus mass declined with dose, decreasing significantly between 0.32 and 0.8 ng/g to a size 28% lower than controls. Live lymphoid cell numbers in the right thymus dropped markedly (21% lower than controls) between 0.051 and 0.13 ng/g, with a further decrease (35% lower than controls) at higher doses. There was no significant change in the percentage of thymocytes expressing TCRalphabeta. The total number of TCRalphabeta+ thymocytes decreased with dose as a function of the declines in TCRalphabeta+ percentages and total thymocyte numbers. The percentages of all other measured phenotypes were unaltered by PCB 126. The total number of CD4+CD8+ cells, and to a lesser degree CD4-CD8+ cells, decreased in a dose-dependent manner following the pattern of total live thymocytes. The number of viable lymphoid cells in the bursa decreased to 45% lower than controls at 0.13 ng/g and fell to 76% lower than controls at 0.8 ng/g. Lymphoid atrophy occurred at doses that were 8- to 12-fold lower with full-term incubation as compared to exposure only during later stages of incubation, and the lymphoid atrophy was associated with decreased TCRalphabeta+ thymocytes at higher doses. These immunological effects were observed at concentrations of PCB 126 comparable to those found in Great Lakes herring gull eggs, after correcting for interspecies differences in sensitivity to PCB 126.     

Aflatoxin deposition and clearance in the eggs of laying hens

Hens fed a diet containing 3310 μg of AFB₁ and 1680 μg of AFB₂ per kg feed for 28 days showed a significant decrease in egg production and egg weights by wk 3 and 4 of feeding, respectively. Transfer of aflatoxins to the eggs occurred rapidly, reaching maximum levels after 4–5 days, and remained relatively constant throughout aflatoxin feeding. The mean values for combined residue levels in eggs were less than 0.5 μg/kg. Levels of AFB₂, AFM₁ and AFM₂ were similar in yolk and albumen while levels of B₁ and B_2a were higher in the yolk. Upon removal of the aflatoxin-containing diet, residues in eggs decreased rapidly. Clearance of aflatoxin residues from the albumen occurred faster than from the yolk. Thus, no residues were detected in the albumen and in the yolk after 5 and 7 days of withdrawal, respectively. No aflatoxin residues could be recovered from whole eggs after feeding the aflatoxin-free diet for 4 days.     

Biological effects of marine PCB contamination on black guillemot nestlings at Saglek,Labrador: liver biomarkers

Black guillemots (Cepphus grylle) in Saglek Bay, Labrador have elevated polychlorinated biphenyl (PCB) concentrations due to marine sediment contamination around a former military site. We measured liver biomarkers and PCB concentrations in 31 nestlings from three PCB-exposure groups: Reference group (range: 15–46 ng/g liver, wet wt.), moderately exposed Islands group (24–150 ng/g), and highly exposed Beach group (170–6200 ng/g). Biomarker responses were dose-dependent and in some cases sex-dependent. Livers of female Beach nestlings were enlarged 36% relative to Reference females. In both sexes, Beach nestlings had liver ethoxyresorufin-O-deethylase (EROD) activities elevated 79% and liver retinol concentrations reduced 47%. Retinyl palmitate concentrations were reduced 50% but only among female nestlings. Island nestlings also exhibited EROD induction (57%) and reductions in retinol and retinyl palmitate concentrations (28 and 58%, respectively). Liver lipid content increased with PCBs in both sexes, and correlated with liver mass in males. Malic enzyme activity and porphyrin concentrations showed little association with PCBs. Although similar associations between liver biomarkers and organochlorine exposure in fish-eating birds are well documented, typically exposures involve multiple contaminants and there is uncertainty about specific PCB effects. Our findings indicate that liver biomarkers respond to relatively low PCB exposures (73 ng/g liver) in guillemots.     

Effects of PCB 126 on primary immune organ development in chicken embryos

This experiment evaluated the immunotoxic effects of developmental exposure to a planar polychlorinated biphenyl (3,3',4,4',5-pentachlorobiphenyl; PCB 126) in chicken embryos. Previous investigations on the immunotoxic effects of PCBs and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in developing avian embryos were undertaken with embryos exposed only during the latter stages of incubation. To simulate exposure in embryos in the wild, chicken eggs were injected with PCB 126 (sunflower oil carrier) into the air cell before initiation of incubation. It was hypothesized that exposure to PCB 126 during the complete incubation period would decrease immune organ masses and lymphocyte numbers. Doses of PCB 126 ranged from 0.051 to 0.80 ng/g egg. Control groups consisted of carrier-injected and noninjected eggs. The thymus and bursa of Fabricius were removed and weighed on d 20 of incubation (1 d before hatch). The immune organs were homogenized, and viable lymphoid cells were counted using the trypan blue exclusion method. Probit analysis estimated the LD20 to be 0.21 ng/g and the LD50 to be 1.01 ng/g. Thymus mass dropped sharply between 0.13 and 0.32 ng/g, and lymphoid cell numbers in the thymus fell sharply between 0.051 and 0.13 ng/g. Bursa mass began to decrease at the lowest dose of 0.051 ng/g and reached a minimum at 0.32 ng/g. The number of viable cells decreased slightly at 0.051 ng/g and reached a minimum at the 0.13- and 0.32-ng/g doses. In general, lymphoid cell numbers were more sensitive to PCB 126 than organ masses, and the bursa tended to be more sensitive than the thymus. Doses necessary to reduce the number of viable lymphoid cells in the thymus and bursa were at least one order of magnitude lower with full-term incubation as compared to exposure only during later stages of incubation.     

EFFECTS OF PCB 126 ON PRIMARY IMMUNE ORGAN DEVELOPMENT IN CHICKEN EMBRYOS

This experiment evaluated the immunotoxic effects of developmental exposure to a planar polychlorinated biphenyl (3,3',4,4',5-pentachlorobiphenyl; PCB 126) in chicken embryos. Previous investigations on the immunotoxic effects of PCBs and 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) in developing avian embryos were undertaken with embryos exposed only during the latter stages of incubation. To simulate exposure in embryos in the wild, chicken eggs were injected with PCB 126 (sunflower oil carrier) into the air cell before initiation of incubation. It was hypothesized that exposure to PCB 126 during the complete incubation period would decrease immune organ masses and lymphocyte numbers. Doses of PCB 126 ranged from 0.051 to 0.80 ng/ g egg. Control groups consisted of carrier-injected and noninjected eggs. The thymus and bursa of Fabricius were removed and weighed on d 20 of incubation (1 d before hatch). The immune organs were homogenized, and viable lymphoid cells were counted using the trypan blue exclusion method. Probit analysis estimated the LD20 to be 0.21 ng/g and the LD50 to be 1.01 ng/ g. Thymus mass dropped sharply between 0.13 and 0.32 ng/g, and lymphoid cell numbers in the thymus fell sharply between 0.051 and 0.13 ng/ g. Bursa mass began to decrease at the lowest dose of 0.051 ng/g and reached a minimum at 0.32 ng/g. The number of viable cells decreased slightly at 0.051 ng/g and reached a minimum at the 0.13- and 0.32-ng/g doses. In general, lymphoid cell numbers were more sensitive to PCB 126 than organ masses, and the bursa tended to be more sensitive than the thymus. Doses necessary to reduce the number of viable lymphoid cells in the thymus and bursa were at least one order of magnitude lower with full-term incubation as compared to exposure only during later stages of incubation.     

Effects of in ovo exposure to PCBs 126 and 77 on mortality, deformities and post-hatch immune function in chickens

In laboratory experiments, planar PCBs produce immune organ atrophy in chicken embryos. To study the immunotoxic effects of PCBs in birds, the coplanar congeners 3,3',4,4',5-pentachlorobiphenyl (PCB 126) and 3,3',4,4'-tetrachlorobiphenyl (PCB 77) were injected into the air cell of fertile white leghorn chicken eggs before incubation at doses of 0.25 and 0.5 ng/g egg PCB 126 and 0.64 ng/g egg PCB 77. Mortality and deformities were assessed during incubation of the eggs, and immune function was analyzed post-hatch using phytohemagglutinin (PHA) skin test for T-cell mediated immunity, antibody titers to sheep red blood cells (SRBC), mitogenesis of peripheral blood lymphocytes, and immune organ mass and cellularity. Exposure to 0.25 ng/g PCB 126 elevated mortality (61% and 69%) and deformities (31% and 32%), three or more times higher than controls. Two-fold suppression of antibody titers was observed in 28 day old chicks exposed to PCB 126 or PCB 77. No consistent alterations in PHA skin response or lymphocyte proliferation were observed. In 14 day old chicks in experiment two, PCB 126 decreased thymus and bursa cellularity by 33% and 35%, respectively. Immune organ atrophy was transient, recovering to control levels by 42 days of age. These experiments demonstrate that PCB 126 and 77 suppress antibody responses in juvenile chickens following an in ovo PCB exposure. Results reinforce the need for measuring multiple immune endpoints to detect immunotoxicity.     

Gonadal feminization and halogenated environmental contaminants in common terns (Sterna hirundo): evidence that ovotestes in male embryos do not persist to the prefledgling stage

Common terns (Sterna hirundo) and roseate terns (Sterna dougallii) breed on Bird Island, Massachusetts, USA, near a Superfund site highly contaminated with polychlorinated biphenyls (PCBs). Observations of skewed sex ratios and female–female pairings among endangered roseate terns (Nisbet and Hatch (1999) Ibis 141, 307) suggested the possibility of contaminant-related endocrine disruption in these birds and prompted investigation of common terns as a surrogate species. In 1993 and 1994, 60–90% of pipping male common tern embryos sampled exhibited ovarian cortical tissue in their testes (ovotestes) (Nisbet et al. (1996) Bull. Environ. Contam. Toxicol. 57, 895; Hart et al. (1998) Mar. Environ. Res. 46, 174). To examine the possible impact of ovotestes on the reproductive capabilities of common terns, we examined gonadal histology in common tern prefledglings (approximately 21 days old) collected from Bird Island in 1995. As a measure of embryonic contaminant exposure, contaminants were measured in a subset of eggs collected from the same nests as the prefledglings. Concentrations of total PCBs in these eggs ranged from 14.4 to 546 µg/g lipid. No evidence of ovotesticular development was observed in any of the 19 male prefledglings examined. Some gonadal irregularities were observed, including small nodules of testicular tissue within the epithelial capsule of the testes, but these were judged not likely to affect testicular function. There was no relationship between any observed irregularities and levels of contaminants present in the matched eggs. The results suggest that the ovotestes that occur in 60–90% of pipping common tern embryos from this site become fully regressed by approximately 21 days posthatch. Our data from this and previous studies are consistent with the idea that ovotestes occur naturally in some individual common terns at hatching, although the frequency of occurrence may be enhanced by exposure to chlorinated organic contaminants such as PCBs. In either case, we suggest that the presence of ovotestes in common tern embryos from PCB-contaminated sites such as Bird Island does not lead to permanent alterations in gonadal histology that would be expected to impair reproductive function.     

Feeding Ecology and the Concentration of Organochlorines in Glaucous Gulls

We investigated the blood concentrations of organochlorines (OCs) and the diet of glaucous gulls Larus hyperboreus breeding in two neighbouring areas at Bear Island in the Barents Sea, north-eastern Atlantic. One area was situated on the edge of the large seabird cliff, about 100–150 m above sea level. The second area was about 1–2 km from the seabird cliff, and 10–50 m above sea level. In both 1997 and 1998 there were significant differences between the breeding areas for five OCs (HCB, HCH, Oxychlordan, DDE and PCB) measured, with the birds breeding on the cliff having higher levels. These differences were accompanied by a difference in diet between the areas. Birds in the former area had at least four times higher intake of guillemot Uria spp. eggs, while the birds near sea level seemed to have a much higher intake of fish. This study demonstrates the importance of feeding ecology for the distribution of OCs within populations. The results have important implications for the establishment of monitoring programs for OC contamination of the glaucous gull in the Arctic.