Effect of 3,4,3',4'-tetrachlorobiphenyl on the reworking behavior of Lumbriculus variegatus exposed to contaminated sediment

The reworking response (bioturbation) of the oligochaete Lumbriculus variegatus was measured by following the burial rate and spread of a 137Cs marker layer translating worm activity into a biological burial rate (Wb) and a biological diffusion rate constant (Db) for surficial sediment mixing. Reworking was measured at 10 and 22 degrees C in two sediments: a reference site sediment dosed with 3,4,3',4'-tetrachlorobiphenyl (TCBP) and a field-collected sediment from a polychlorinated biphenyl (PCB)-contaminated site in Dicks Creek (DCC, Middletown, OH, USA). The body residue associated with response to TCBP also was determined. Reduction in the temperature from 22 to 10 degrees C reduced both Wb and Db by a factor of approximately two. The internal TCBP concentration to reduce the Wb by 50% was 96 nmol/g (95% CI 45-225 nmol/g) and 124 nmol/g (40-547 nmol/g) (28 and 36 microg/g) wet weight at 22 and 10 degrees C, respectively, and was independent of temperature. The Wb for the DCC sediment was lower than observed for the highest TCBP treatment. The internal body residue for total PCB for worms exposed to DCC sediment was 20-fold lower than TCBP in worms exposed to the lowest TCBP treatment on a molar basis. Comparing body residues of total PCB to TCBP assumes that the PCB congeners act additively on a molar basis. The DCC site contained a higher proportion of coarse material and a lower organic carbon concentration. The difference in sediment characteristics was assumed to be responsible for differences in the Wb.     

Comparing behavioral and chronic endpoints to evaluate the response of Lumbriculus variegatus to 3,4,3',4'-tetrachlorobiphenyl sediment exposures

The response of Lumbriculus variegatus to 3,4,3',4'-tetrachlorobiphenyl (TCBP) was examined with feeding behavior and changes in carbon assimilation by using stable carbon isotopes at 22 and 10 degrees C. The classical measure of feeding behavior determined on a subset of sediment for which the biological burial rate was determined in a companion study allowed direct method comparison. This comparison helped address relationships between biological burial rate, feeding rate, and bioaccumulation. The change in stable isotope composition reflects the total metabolic activity by measuring carbon assimilation rate and was compared to feeding rate, biological burial rate (as determined in the companion study), and reproduction. Decreasing the temperature from 22 to 10 degrees C resulted in a twofold reduction in feeding rate and carbon assimilation. The fractional decline in feeding rate relative to the control mimicked the decline in the biological burial rate with increasing TCBP concentration that was found in the companion study. The bioaccumulation factor declined with increasing TCBP sediment concentration, tracking the feeding rate decline. Stable isotope measures showed differences in metabolic rates between the exposure temperatures but did not distinguish a metabolic rate change at 22 degrees C among TCBP treatments. Likewise, reproduction declined from 22 to 10 degrees C, with no reproduction at 10 degrees C. Like the stable isotope measure, no dose response was found among TCBP treatments at 22 degrees C. The reduction in carbon assimilation rate tracked the reduction in reproduction with lower temperature.     

Investigating the role of desorption on the bioavailability of sediment-associated 3,4,3',4'-tetrachlorobiphenyl in benthic invertebrates

Only a fraction of all sediment-associated hydrophobic organic contaminants are bioavailable, and a simple Tenax extraction procedure may estimate this fraction. Bioavailability is assumed to coincide with the rapidly and, possibly, slowly desorbing sediment-associated contaminant. River sediment was spiked with radiolabeled (14C) and nonradiolabeled (12C) 3,4,3',4'-tetrachlorobiphenyl (TCBP), and desorption kinetics using Tenax extraction were obtained at 10 degrees C and 22 degrees C. Bioaccumulation was measured in Lumbriculus variegatus, Chironomus tentans, and Hyalella azteca. Desorption of TCBP was triphasic at 22 degrees C and slowed at 10 degrees C to show only biphasic kinetics. The rapidly desorbing fractions decreased with increasing TCBP sediment concentration. The biota sediment accumulation factors, biota accumulation factors, and sediment clearance coefficients (ks) also decreased with increasing sediment TCBP concentration. The rapidly plus slowly desorbing fractions and the total TCBP desorbed when 99.9% of the rapidly desorbing fraction had desorbed were used to estimate bioavailable TCBP. These Tenax-based fractions did not explain the decreasing bioavailability with increasing TCBP load. Several factors, such as animal behavior and TCBP water solubility limitations, were evaluated to explain the concentration effect, but the most likely cause was severe diffusion limitations in whole sediment that were not predicted by the fully mixed Tenax extraction. Therefore, desorbing fractions determined by Tenax extraction overestimated the bioavailable fractions in sediments.     

4-hydroxy-2',4',6'-trichlorobiphenyl and 4-hydroxy-2',3',4',5'-tetrachlorobiphenyl are estrogenic in rainbow trout

Many natural and synthetic xenobiotics are known to interact with endocrine systems of animals. Various hydroxylated metabolites of persistent polychlorinated biphenyl contaminants (hydroxy-polychlorinated biphenyls [OH-PCBs]) have been shown to have agonist or antagonist interactions with estrogen receptors (ERs). In this study, 4-hydroxy-2',4',6'-trichlorobiphenyl (OH-PCB 30) and 4-hydroxy-2',3',4',5'-tetrachlorobiphenyl (OH-PCB 61), and the natural estrogen 17 beta-estradiol (E2) and estrone (E1), were incorporated into diet and fed to juvenile rainbow trout. The production of vitellogenin (VTG), an egg yolk protein precursor in oviparous animals, was used as a marker of hepatic ER binding. All compounds induced plasma VTG in a dose-dependent manner, with maximal levels of approximately 5 mg VTG/ml plasma induced by E2, E1, and OH-PCB 30. Maximum plasma VTG of 0.048 mg/ml in the highest dose (50 mg/kg) of OH-PCB 61 was approximately 100-fold lower than natural estrogens and OH-PCB 30. At doses that induced submaximal VTG, E1 was two- to threefold less potent, and OH-PCBs were up to 500-fold less potent, than E2. Sex differences in VTG synthesis were apparent at weakly estrogenic doses, but not at maximal VTG-inducing doses. Predictions from previous receptor-binding studies underestimated the maximum estrogenic response of OH-PCB 30 in trout, which was achieved with a dose 10 times higher than E2. Differences in plasma VTG induction by OH-PCB 30 and OH-PCB 61 support in vitro predictions that the degree and position of chlorination are important for ER activation. Neither mixtures of estrogens nor OH-PCBs resulted in synergistic VTG induction.     

Lead toxicity in chicks: interactions with dietary methionine and choline

Two factorial experiments were conducted to study the effects of dietary methionine and choline on lead toxicity in chicks. Dietary variables were 0.3 or 0.63% (experiment 1) or 0.23 or 0.75% methionine (experiment 2); 0 or 1000 ppm lead (as Pb acetate X 3H2O); and 1130 or 3300 mg/kg (experiment 1) or 396 or 1266 mg/kg choline (experiment 2). In both experiments, lead depressed growth while methionine stimulated growth. Growth depression by lead was less with methionine-adequate than with methionine-inadequate diets. There were no differences in growth with the choline-marginal or choline-excess diets. In experiment 2, the methionine x lead interaction for growth was observed with choline-adequate but not with choline-inadequate diets. Lead-induced depression of growth was exacerbated by added choline when methionine-inadequate diets were fed. With methionine-adequate diets, choline level had no effect on the lead-induced depression of growth. Hepatic nonprotein sulfhydryl (NPSH) concentrations were increased by both supplemental methionine and lead with no interaction. Choline levels had no effect on NPSH. Dietary methionine significantly lowered Pb concentration of kidney and muscle but not of bone, liver or blood. Choline had no effect on organ Pb concentrations. Methionine, either dietary or in the dosing solution, had no effect on in situ intestinal absorption or 203PbCl2. These results suggest that lead lowers the chick's choline requirement and that the methyl moiety of methionine does not participate directly in lead detoxication. The amelioration of Pb toxicity by methionine appears to be related to increased excretion of Pb.     

Effect of dietary vitamin C on ascites in broiler chicks

A total of 480 day-old broiler chicks were divided randomly into 4 equal groups, each of 4 replicates, and reared for two weeks. To their rations, which contained sodium chloride at 2.5% ascorbic acid was added at the rate of 0, 150, 300 and 450 mg/kg for groups 1, 2, 3 and 4 respectively. Incidences of ascites cases were 20.8, 10.8, 7.5 and 7.5% for the groups 1, 2, 3 and 4 respectively. When vitamin C was added to their rations body weights were increased significantly, but feed consumption remained unchanged. There were no significant differences in water consumption or body moisture. The total serum protein was significantly increased. The packed cell volume was only increased in the chicks that had received 450 mg vitamin C/kg of feed and there were no significant differences in the ascorbic acid content of the plasma. It was concluded that the addition of vitamin C to the chicks' rations reduces the incidence of ascites caused by toxic dietary levels of sodium chloride.     

Toxicokinetics of 2,2',4,4'- and 3,3',4,4'-tetrachlorobiphenyl congeners in the house cricket.

Recently, investigators have reported bioaccumulation of polychlorinated biphenyls (PCBs) in insects collected at hazardous waste sites. Little is known about differences in bioaccumulation of particular PCB congeners in insects. The authors report on the toxicokinetics of a non-coplanar ortho substituted congener, 2,2',4,4'-tetrachlorobiphenyl (PCB-47) and a coplanar non-ortho substituted PCB, 3,3',4,4'-tetrachlorobiphenyl (PCB-77) in topically treated house crickets. Penetration and excretion were more rapid for PCB-47 than for PCB-77. PCB-47 demonstrated a high affinity for abdomen, gut, and gonads, whereas, PCB-77 had a greater affinity for the head and thorax. Sex differences were observed in excretion and distribution. Females had an increased excretion of PCBs and increased accumulation in gut and gonads compared to males. Differences in lipophilicity can explain differences in distribution between sexes and of compounds within sexes. However, to explain the observed difference in penetration, it is necessary to invoke explanations based on stearic factors associated with coplanarity of the molecules. Differences in excretion are likely related to sex differences in mixed-function oxidase activities. These toxicokinetic data suggest that the more toxic coplanar congener, PCB-77, is likely to be more persistent in crickets compared to PCB-47, despite its lower lipophilicity.     

Decreased resistance and immune response to Escherichia coli infection in chicks with low or high intakes of vitamin A

The effects of vitamin A excess of insufficiency on resistance to Escherichia coli infection and subsequent anti-E. coli immune response were examined in chicks. Chicks receiving depleted (0 microgram/kg), sufficient (0.85 mg/kg) or excess (1000 mg/kg) levels of vitamin A in their feed were inoculated by a subcutaneous injection of pathogenic E. coli (1 x 10(9) and 2 x 10(9) cfu per chick). Susceptibility to E. coli was determined by mortality, morbidity and immune responses (antibody production and T lymphocyte proliferation). Excess of insufficient vitamin A led to increased susceptibility of chicks of E. coli infection; this was accompanied by depressed immune responses. Chicks receiving excess vitamin A were more sensitive to E. coli than vitamin A-depleted chicks. This was reflected in higher mortality and morbidity rates and in severely depressed immune responses. In contrast to chicks receiving excess vitamin A, T lymphocyte responses (though not antibody responses) of vitamin A-depleted chicks achieved levels similar to those of vitamin A-sufficient birds with a lag period of 6 to 10 d. Therefore, reduction in resistance to E. coli infection, resulting from vitamin A excess or deficiency, probably was compounded by a delayed immune response.     

缺碘区居民膳食结构及其对碘缺乏病的影响

目的了解重庆市缺碘区居民膳食结构和对碘缺乏病知识的掌握情况,以及膳食因素对碘缺乏病的影响,为制定该病综合防治措施及进行膳食指导、健康教育提供依据。方法采用整群随机抽样方法,对当地居民进行24h膳食回顾法调查其膳食摄入情况,并采用问卷表了解居民对碘缺乏病相关知识的知晓情况。结果云阳壁山两县居民能量摄入量分别为2066.47kcal,2256.89kcal;蛋白质65.47g,70.30g;核黄素0.74mg,1.32mg;硫胺素0.89mg,1.21mg;碘56.07μg,70.30μg,以上营养素摄入量两县的差异有统计学意义,三大营养素供能比适当,对人体缺碘主要危害的回答正确率云阳璧山分别为22.7%,26.1%(χ2=23.76,P﹤0.001)。结论两县都存在不同程度蛋白质能量营养不良以及一些与其代谢有关的维生素缺乏,且对碘缺乏病相关知识知晓情况较差,不利于碘缺乏病防治,应对两地居民的科学膳食指导和营养健康教育并尽快出台相关的营养改善政策。     

Carcinoma of the colon--association with low dietary vitamin A in females: preliminary communication.

Seventeen patients with non-metastatic carcinoma of the colon (9 male, 8 female) were compared with age- and sex-matched controls in a study examining the relationship of diet and altered cholesterol metabolism with carcinoma of the colon. Bile acid excretion in the faeces was significantly less in cancer patients (P less than 0.001), and a significantly lower intake of retinol (P less than 0.01) and vitamin A (P less than 0.05) was demonstrated in female cancer patients. There was no difference between patients and controls in hepatic cholesterol enzyme activity or in fasting plasma lipid levels.     

Age group and sex do not influence responses of vitamin K biomarkers to changes in dietary vitamin K

Inadequate vitamin K intake has been associated with abnormal soft tissue calcification. Older adults may have insufficient intakes of vitamin K and respond less to vitamin K supplementation compared with younger adults. However, little is known about the determinants that influence the response to vitamin K supplementation. Our primary objective was to assess dietary and nondietary determinants of vitamin K status in healthy younger and older adults. In a nonrandomized, nonmasked study, 21 younger (18-40 y) and 21 older (55-80 y) men and women consumed a baseline diet (200 μg phylloquinone/d) for 5 d, a phylloquinone-restricted diet (10 μg phylloquinone/d) for 28 d, and a phylloquinone-supplemented diet (500 μg phylloquinone/d) for 28 d. Changes in vitamin K status markers in response to vitamin K depletion and repletion were studied and the influences of BMI, body fat, and circulating TG were assessed by including them as covariates in the model. Despite baseline differences in measures of vitamin K status, plasma phylloquinone tended to increase (P = 0.07) and the percentage of uncarboxylated osteocalcin and uncarboxylated prothrombin both improved with phylloquinone supplementation (P < 0.007), regardless of age group or sex. Only the excretion of urinary menadione, a vitamin K metabolite, was greater among younger adults in response to depletion than in older adults (P = 0.012), regardless of sex. Adiposity measures and circulating TG did not predict response of any measures. In conclusion, poor vitamin K status can be similarly improved with vitamin K supplementation, regardless of age group or sex.     

The influence of dietary levels of vitamin A and fat on colon cancer

Rats fed diets high (24%) or low (5%) in fat were given dietary levels of vitamin A (retinyl acetate) ranging from 0.3 to 30 micrograms/g food. The lowest tumor incidence was in the group fed diets high in vitamin A and low in fat. When the diet was high in fat and low in vitamin A, tumor incidence and frequency were significantly increased over that in rats fed the high-fat diet with normal levels of vitamin A (10 micrograms/g feed). However, even with a high level of fat in the diet, raising the level of vitamin A above 10 micrograms/g feed had no further beneficial effect. Thus, although there was a significant interaction between vitamin A and fat, it is the latter that appears to require the most attention, once the vitamin A intake is adequate. These data support the view that we should set as a goal an adequate, diversified diet that is low in fat but that an excessive intake of vitamins such as vitamin A that are toxic should be avoided.     

Dermal absorption and tissue disposition of 3,3',4, 4'-tetrachlorobiphenyl (TCB) in an ex-vivo pig model: assessing the impact of dermal exposure variables

TCB is one of the dioxin-like polychlorinated biphenyls (PCBs). This research was designed to help assess the risk of occupational and environmental TCB exposure. To evaluate exposure variables' effects on dermal absorption and cutaneous disposition, 14C-TCB (40 microg/cm(2)) in acetone, methylene chloride, a water-acetone mixture, and a soil-based mixture were applied in an ex-vivo pig-skin-flap model (n = 4-5/treatment). Dermal absorption (0.11-0.66%, 8 hr) and penetration (1.14-2.48%) varied according to exposure conditions. Acetone and methylene chloride vehicles differed in absorption profiles and skin penetration patterns but were similar in absorption amounts. Adding water to the acetone did not change absorption but did alter the penetration pattern. The non-occluded soil-based mixture showed more absorption than did the liquid vehicles (p<0.05), but occlusion significantly (p<0.05) decreased that absorption (0.66-->0.29%, 8 hr) and penetration (2.48-->1.11%). In conclusion, dermal absorption data from liquid-organic or aqueousorganic mixtures may underestimate the risk of exposure to TCB-contaminated soil.