Framework for gender differences in human and animal toxicology

Relationship between blood cadmium, lead, and serum thyroid measures in US adults - the National Health and Nutrition Examination Survey (NHANES) 2007-2010

Experimental studies have shown that both cadmium (Cd) and lead have potent endocrine disrupting activity. However, studies on whether these heavy metals disrupt thyroid system in humans, especially in general populations with low levels of exposure, are sparse. The study analyzed 6,231 participants aged 20 and older with measurements from 2007-2010 of the National Health and Nutrition Examination Survey (NHANES) to investigate whether whole blood Cd and lead level are associated with serum thyroid hormones measures. Our study suggests that thyroid function may be disrupted by both Cd and lead exposures in the general population and the specific roles of Cd and lead exposure on thyroid axis may differ by sex. However, the mechanisms by which these heavy metals may disrupt thyroid system function in general population needs to be further investigated.

Sex differences in urinary levels of several biological indicators of exposure: a simulation study using a compartmental-based toxicokinetic model

Toxicokinetic modeling is a useful tool to describe or predict the behavior of a chemical agent in the human or animal organism. A general model based on four compartments was developed in a previous study to quantify the effect of human variability on a wide range of biological exposure indicators. The aim of this study was to adapt this existing general toxicokinetic model to three organic solvents--methyl ethyl ketone, 1-methoxy-2-propanol, and 1,1,1,-trichloroethane--and to take into account sex differences. In a previous human volunteer study we assessed the impact of sex on different biomarkers of exposure corresponding to the three organic solvents mentioned above. Results from that study suggested that not only physiological differences between men and women but also differences due to sex hormones levels could influence the toxicokinetics of the solvents. In fact the use of hormonal contraceptive had an effect on the urinary levels of several biomarkers, suggesting that exogenous sex hormones could influence CYP2E1 enzyme activity. These experimental data were used to calibrate the toxicokinetic models developed in this study. Our results showed that it was possible to use an existing general toxicokinetic model for other compounds. In fact, most of the simulation results showed good agreement with the experimental data obtained for the studied solvents, with a percentage of model predictions that lies within the 95% confidence interval varying from 44.4 to 90%. Results pointed out that for same exposure conditions, men and women can show important differences in urinary levels of biological indicators of exposure. Moreover, when running the models by simulating industrial working conditions, these differences could be even more pronounced. A general and simple toxicokinetic model, adapted for three well-known organic solvents, allowed us to show that metabolic parameters can have an important impact on the urinary levels of the corresponding biomarkers. These observations give evidence of an interindividual variability, an aspect that should have its place in the approaches for setting limits of occupational exposure.

Selenium in brown bears (Ursus arctos) from Croatia: Relation to cadmium and mercury

Muscle (n = 111), liver (n = 111), and kidney cortex (n = 101) samples from brown bears (Ursus arctos) were collected in the 2009 and 2010 hunting seasons in Croatia and analysed for selenium (Se), cadmium (Cd), and total mercury (Hg). The aim was to assess the levels of these elements according to age, sex, and season of collection, and to investigate possible Se/Cd and Se/Hg interactions. Median Se concentrations were 0.139 μg/g in muscle, 0.409 μg/g in liver and 1.75 μg/g wet mass in kidney cortex. Median Cd and Hg were 0.0078 and 0.0018 μg/g in muscle, 1.09 and 0.031 μg/g in liver, and 16.5 and 0.206 μg/g wet mass in the renal cortex, respectively. Se/Cd molar ratios were less than 1 in the kidney cortex, and close to or above 1 in liver and muscle, respectively. Toxic Cd and Hg correlated with Se in all of the studied tissues. Sex differences were found for all three elements (except Se in liver), with females having higher tissue concentration than males. Only Cd showed age-dependence. Bear samples collected in fall had higher Se in muscles, and Hg in muscles and liver compared to samples collected in spring. Element concentrations in brown bear tissues were within the range of previously reported studies. Bear meat is considered a rich source of Se, safe for consumption with regard to its Cd and Hg content. According to the molar ratio and correlation results, we assume that Se binding is not the primary detoxification pathway for Cd and Hg in brown bears.

Effects of complex organohalogen contaminant mixtures on thyroid homeostasis in hooded seal (Cystophora cristata) mother-pup pairs

Many lipid-soluble and phenolic compounds present in the complex mixture of orgaohalogen contaminants (OHCs) that arctic wildlife is exposed to have the ability to interfere with the thyroid hormone (TH) system. The aim of this study was to identify compounds that might interfere with thyroid homeostasis in 14 nursing hooded seal (Cystophora cristata) mothers and their pups (1-4d old) sampled in the West Ice in March 2008. Multivariate modelling was used to assess the potential effects of measured plasma levels of OHCs on circulating TH levels of the measured free (F) and total (T) levels of triidothyrine (T3) and thyroxine (T4). Biological factors were important in all models (e.g. age and sex). In both mothers and pups, TT3:FT3 ratios were associated with α- and β-hexachlorocyclohexane (HCH), ortho-PCBs, chlordanes and DDTs. The similarities between the modelled TT3:FT3 responses to OHC levels in hooded seal mothers and pups most probably reflects similar exposure patterns, but could also indicate interconnected TH responses. There were some differences in the modelled TH responses of mothers and pups. Most importantly, the negative relationships between many OH-PCBs (particularly 3'-OH-CB138) and TT3:FT3 ratio and the positive relationships between TT4:FT4 ratios and polybrominated diphenyl ether [PBDE]-99, -100 and 4-OH-CB107 in pups, which was not found in mothers. Although statistical associations are not evidence per se of biological cause-effect relationships, the results suggest that thyroid homeostasis is affected in hooded seals, and that the inclusion of the fullest possible OHC mixture is important when assessing TH related effects in wildlife.

Modification of neurobehavioral effects of mercury by genetic polymorphisms of metallothionein in children

Mercury (Hg) is neurotoxic, and children may be particularly susceptible to this effect. A current major challenge is the identification of children who may be uniquely susceptible to Hg toxicity because of genetic disposition. We examined the hypothesis that genetic variants of metallothionein (MT) that are reported to affect Hg toxicokinetics in adults would modify the neurotoxic effects of Hg in children. Five hundred seven children, 8-12 years of age at baseline, participated in a clinical trial to evaluate the neurobehavioral effects of Hg from dental amalgam tooth fillings. Subjects were evaluated at baseline and at 7 subsequent annual intervals for neurobehavioral performance and urinary Hg levels. Following the completion of the clinical trial, we performed genotyping assays for variants of MT isoforms MT1M (rs2270837) and MT2A (rs10636) on biological samples provided by 330 of the trial participants. Regression modeling strategies were employed to evaluate associations between allelic status, Hg exposure, and neurobehavioral test outcomes. Among girls, few significant interactions or independent main effects for Hg exposure and either of the MT gene variants were observed. In contrast, among boys, numerous significant interaction effects between variants of MT1M and MT2A, alone and combined, with Hg exposure were observed spanning multiple domains of neurobehavioral function. All dose-response associations between Hg exposure and test performance were restricted to boys and were in the direction of impaired performance. These findings suggest increased susceptibility to the adverse neurobehavioral effects of Hg among children with relatively common genetic variants of MT, and may have important public health implications for future strategies aimed at protecting children and adolescents from the potential health risks associated with Hg exposure. We note that because urinary Hg reflects a composite exposure index that cannot be attributed to a specific source, these findings do not support an association between Hg in dental amalgams specifically and the adverse neurobehavioral outcomes observed.

Grape Seed Procyanidin Extract Improves Insulin Production but Enhances Bax Protein Expression in Cafeteria-Treated Male Rats

In a previous study, the administration of a grape seed procyanidin extract (GSPE) in female Wistar rats improved insulin resistance, reduced insulin production, and modulated apoptosis biomarkers in the pancreas. Considering that pharmacokinetic and pharmacodynamic parameters in females are different from these parameters in males, the aim of the present study was to evaluate the effects of GSPE on male Wistar cafeteria-induced obese rats. The results have confirmed that the cafeteria model is a robust model mimicking a prediabetic state, as these rats display insulin resistance, increased insulin synthesis and secretion, and increased apoptosis in the pancreas. In addition, GSPE treatment (25 mg/kg of GSPE for 21 days) in male rats improves insulin resistance and counteracts the cafeteria-induced effects on insulin synthesis. However, the administration of the extract enhances the cafeteria-induced increase in Bax protein levels, suggesting increased apoptosis. This result contradicts previous results from cafeteria-fed female rats, in which GSPE seemed to counteract the increased apoptosis induced by the cafeteria diet.

Toxicogenomic analysis suggests chemical-induced sexual dimorphism in the expression of metabolic genes in zebrafish liver

Differential gene expression in two sexes is widespread throughout the animal kingdom, giving rise to sex-dimorphic gene activities and sex-dependent adaptability to environmental cues, diets, growth and development as well as susceptibility to diseases. Here, we present a study using a toxicogenomic approach to investigate metabolic genes that show sex-dimorphic expression in the zebrafish liver triggered by several chemicals. Our analysis revealed that, besides the known genes for xenobiotic metabolism, many functionally diverse metabolic genes, such as ELOVL fatty acid elongase, DNA-directed RNA polymerase, and hydroxysteroid dehydrogenase, were also sex-dimorphic in their response to chemical treatments. Moreover, sex-dimorphic responses were also observed at the pathway level. Pathways belonging to xenobiotic metabolism, lipid metabolism, and nucleotide metabolism were enriched with sex-dimorphically expressed genes. We also observed temporal differences of the sex-dimorphic responses, suggesting that both genes and pathways are differently correlated during different periods of chemical perturbation. The ubiquity of sex-dimorphic activities at different biological hierarchies indicate the importance and the need of considering the sex factor in many areas of biological researches, especially in toxicology and pathology.

Gender differences in chemical carcinogenesis in National Toxicology Program 2-year bioassays

Differences in cancer incidences between men and women are often explained by either differences in environmental exposures or by influences of sex hormones. However, there are few studies on intrinsic gender differences in susceptibility to chemical carcinogens. We have analyzed the National Toxicology Program (NTP) database for sex differences in rat responses to chemical carcinogens. We found that the odds that male rat bioassays were assigned a higher level of evidence than female rat bioassays was 1.69 (p < .001). Of 278 carcinogenic chemicals in the database, 201 (72%) exhibited statistical gender differences (p ≤ .05) in at least one nonreproductive organ. One hundred thirty of these 201 chemicals induced gender-specific tumors in male rats and 59 in female rats. Sixty-eight chemicals induced tumors in males but no tumors in females. Less than one third (i.e., 19 chemicals) induced tumors in females but not males. Male-specific tumors included pancreatic and skin tumors, and female-specific tumors included lung tumors. For some tumor sites, these differences in gender susceptibility can be associated with literature data on sex hormone receptor expression. In conclusion, gender-specific tumors were common. The male dominance is in line with recent human data, and the male susceptibility to carcinogens should be further studied.

Effects of obesity and sex on antimicrobial pharmacokinetics and acute kidney injury: validation of a preclinical model

Obese patients may be at a greater risk for acute kidney injury (AKI) with the use of certain antimicrobial agents that are dosed by weight. Current preclinical models of AKI utilize the male rat within a narrow weight range that limits extrapolation of the generated results. We evaluated the pharmacokinetics and AKI potential of gentamicin in 14-week-old diet-induced obesity-prone (n = 40) and obesity-resistant (n = 40) rats of both sexes. Single daily doses of gentamicin (12.5, 18.75, or 25 mg/kg of body weight) or saline (control) were administered intraperitoneally for 14 doses. Blood samples were collected after doses 1, 7, and 14, assayed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and analyzed using a nonparametric population pharmacokinetic approach for gentamicin. Urine was collected after doses 1, 3, and 5 and assayed for kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) and normalized to creatinine (Cr) values. Histology was performed on all animals, and the degree of proximal tubular injury was graded. The mean (minimum, maximum) weight of the rats was 330 (136, 580) g. NGAL/Cr predicted AKI better than did KIM-1/Cr and was detectable in male rats after dose 1 and in obesity-prone female rats after dose 5. Proximal tubular injury by histology was significantly higher in male than in female rats. A significant relationship between the gentamicin area under the curve from zero to 24 hours (AUC(0-24)) estimates and the maximum NGAL/Cr ratio was observed. This preclinical model has the potential to aid with dose extrapolation for body size and improve assessment of the toxicology potential of antimicrobials in development.

The relation between human exposure to mercury and thyroid hormone status

The aim of this study was to investigate total mercury (THg) and methylmercury (MeHg) exposure of 75 mother-child pairs in relation to their thyroid hormone status (thyroid-stimulating hormone (TSH), triiodothyronine (T3), free triiodothyronine (fT3), thyroxine (T4), and free thyroxine (fT4)). THg and MeHg in blood samples were measured by atomic absorption spectrometry and gas chromatography-inductively coupled plasma-mass spectrometry, respectively. The median THg and MeHg levels in maternal blood, cord blood, and blood of 6-month-old children were 0.50, 0.53, and 0.32 and 0.22, 0.32, and 0.08 μg/L, respectively. There were significant correlations between paired maternal-cord blood levels for THg and MeHg, with a greater transplacental transport of MeHg compared with THg (mean cord/maternal blood ratio, 1.80 vs. 1.24). The maternal blood THg was found to be a better predictor of TSH levels in children than their current THg exposure. There was a positive correlation between maternal THg and children's TSH. T3 and fT3 levels in children were negatively related to cord blood THg in the majority (Caucasian) subgroup, whereas these associations were positive in the Roma subgroup. Mothers with dental amalgam fillings had significantly lower T4 and fT4 levels. Moreover, fT4 in the mothers of boys negatively correlated with maternal THg levels. MeHg exposure lowered T3 levels in the mothers of girls. Our results suggest that low-level exposure to Hg can affect thyroid hormone status during prenatal and early postnatal exposure depending on the form of Hg, gender, ethnicity, lifestyle, or socioeconomic status (dental amalgam fillings).

Circulating levels of persistent organic pollutants (POPs) among elderly men and women from Sweden: results from the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS)

Persistent Organic Pollutants (POPs) are a huge group of chemicals that have been linked to various adverse health effects in humans. Large epidemiological studies investigating gender differences in levels of POPs in the elderly are limited and the results from these are not always consistent. The present study was undertaken to examine the background levels of a broad range of POPs in human plasma samples among elderly men and women from Sweden and to assess the influence of gender. Levels of 23 POPs were determined in plasma samples collected during 2001-2004 from 1016 (50.2% women) 70year-old participants from the population-based Prospective Study of the Vasculature in Uppsala Seniors (PIVUS). Measurements were performed using high resolution gas chromatography with high resolution mass spectrometry (HRGC-HRMS) and the POPs studied were 16 polychlorinated biphenyls (PCBs), five organochlorine (OC) pesticides, one dioxin, and one brominated flame retardant. The concentrations of the selected POPs were found similar, or comparable, to other studies of non-occupationally exposed populations from Sweden and Europe. Differences in levels of POPs between men and women were assessed by using Wilcoxon rank-sum (Mann-Whitney) test. Significant (p<0.0001) gender differences in levels of specific POPs were observed and a number of POP concentrations were found to differ between men and women. More specifically, levels of HCB, OCDD, and PCB congeners #74, #105, and #118 were found to be higher in women, while the rest of the majority of POPs were higher in men.

Sex-related differences in renal toxicodynamics in rodents

INTRODUCTION

An issue yet to be addressed, in the investigation of the xenobiotic toxicity, is a detailed characterization of the sex differences in toxicological responses. The 'sex issue' is particularly significant in nephrotoxicology as the kidney is a relevant target organ for xenobiotics and few studies have approached this subject in the past. There is a strong need to improve our understanding regarding the influence of sex in toxicology, given their increased requirement to establish the limits of exposure to chemicals in the environment and at work.

AREAS COVERED

In this review, the authors provide the reader with the current knowledge of sex differences in kidney toxicity for rats and mice. To make the review easier to consult, these studies have been organized according to the class of xenobiotic.

EXPERT OPINION

From the analysis of the present knowledge emerges a dramatic need for information on sex differences in xenobiotics toxicity. Although animals are reasonably good predictors of adverse renal effects in patients, there is need to identify alternative methods (e.g. in vitro/ex vivo) to better study sex differences in organ toxicity.

Modification of neurobehavioral effects of mercury by a genetic polymorphism of coproporphyrinogen oxidase in children

Mercury (Hg) is neurotoxic, and children may be particularly susceptible to this effect. A current major challenge is the identification of children who may be uniquely susceptible to Hg toxicity because of genetic disposition. We examined the hypothesis that CPOX4, a genetic variant of the heme pathway enzyme coproporphyrinogen oxidase (CPOX) that affects susceptibility to mercury toxicity in adults, also modifies the neurotoxic effects of Hg in children. Five hundred seven children, 8-12 years of age at baseline, participated in a clinical trial to evaluate the neurobehavioral effects of Hg from dental amalgam tooth fillings in children. Subjects were evaluated at baseline and at 7 subsequent annual intervals for neurobehavioral performance and urinary mercury levels. Following the completion of the clinical trial, genotyping assays for CPOX4 allelic status were performed on biological samples provided by 330 of the trial participants. Regression modeling strategies were employed to evaluate associations between CPOX4 status, Hg exposure, and neurobehavioral test outcomes. Among girls, few significant CPOX4-Hg interactions or independent main effects for Hg or CPOX4 were observed. In contrast, among boys, numerous significant interaction effects between CPOX4 and Hg were observed spanning all 5 domains of neurobehavioral performance. All underlying dose-response associations between Hg exposure and test performance were restricted to boys with the CPOX4 variant, and all of these associations were in the expected direction where increased exposure to Hg decreased performance. These findings are the first to demonstrate genetic susceptibility to the adverse neurobehavioral effects of Hg exposure in children. The paucity of responses among same-age girls with comparable Hg exposure provides evidence of sexual dimorphism in genetic susceptibility to the adverse neurobehavioral effects of Hg in children and adolescents.

Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears

The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complex mixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 East Greenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) was analyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model, most important variables with a negative influence on cortisol levels were particularly BDE-99, but also CB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence on cortisol were CB-66/95, α-HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p'-DDD. Although statistical modeling does not necessarily fully explain biological cause-effect relationships, relationships indicate that (1) the hypothalamic-pituitary-adrenal (HPA) axis in East Greenland polar bears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisol may be linked with the hypothalamus-pituitary-thyroid (HPT) axis.

Sex-gender research sensitivity and healthcare disparities

Authors Nieuwenhoven and Klinge (Journal of Women's Health 2010;19:1-6) argue that despite advances, sex and gender are not well treated in the biomedical literature. Many studies in which males and females are represented do not address the similarities or differences between sexes, sometimes adjusting for (thereby obscuring) sex differences and sometimes ignoring sex altogether. Women continue to be underrepresented in randomized drug trials, excluded from some by potential reproductive effects, and perhaps frightened from others by IRB-required warnings. Although recognized, sex disparities in treatment, for example, for acute cardiac syndrome, persist. As electronic abstracts become a prime means of communicating research results, they must adequately and accurately represent a study's findings.

Sex and gender in adverse drug events, addiction, and placebo

Sex-gender-based differences in response to pharmaceutical treatments are still under evaluation but evidence already exists regarding the impact of sex-gender-related differences on drug safety profile, drug abuse/addiction, and placebo effects. For a number of drugs it is well recognized that a sex-gender dimorphic profile in terms of drug adverse effects exists and appears to be more frequent and severe in women than in men. However, it is not well known whether this is due to pharmacodynamic or pharmacokinetic differences. Indeed the optimization of therapy requires that attention is paid to single sex-gender. Numerous pharmacokinetic, pharmacodynamic, and sociocultural differences between women and men in drug abuse have been described. Here we focus on sex-gender differences in alcoholism and nicotine addiction. The relevance of sex and gender differences in addiction appear to be relevant. Specific programs aimed to address addicted women's specific needs (child care, pregnancy, housing, and violence and others) are recommended. Finally, this article discusses the possible effect of sex-gender on placebo response in the light of the more significant recent literature evidencing that studies are urgently required in order to better understand the role of sex-gender on placebo mechanism and its impact on randomized clinical trials outcomes.

Prenatal epoxiconazole exposure effects on rat postnatal development

Although some studies have pointed out to embryo/fetal toxicity, knowledge about the potential toxicity of the fungicide epoxiconazole is still limited. Once the results of these previous studies have raised some concern, this study studied the effects of epoxiconazole maternal exposure on the physical endpoints in the development of rat pups. To accomplish that, the effects of epoxiconazole (50.0, 100.0, and 150.0  mg/kg) were examined when rats were exposed at two different developmental stages: during the first 6 days of pregnancy or in the organogenesis period (6-15 days). After parturition, pups were tested for growth and maturational milestones. Maternal exposure to the fungicide, independently of phase, resulted in significantly early mean time to vaginal opening and delayed time to testes descent in pups. Weight gain rate in pups and their mothers was not affected for the tested exposure period. The findings of this study emphasize that epoxiconazole maternal exposure may lead to alterations in developmental patterns in nursing pups, consistent with the known influence of epoxiconazole on steroid hormone synthesis.

δ-Aminolevulinic acid dehydratase single nucleotide polymorphism 2 and peptide transporter 2*2 haplotype may differentially mediate lead exposure in male children

Child low-level lead (Pb) exposure is an unresolved public health problem and an unaddressed child health disparity. Particularly in cases of low-level exposure, source removal can be impossible to accomplish, and the only practical strategy for reducing risk may be primary prevention. Genetic biomarkers of increased neurotoxic risk could help to identify small subgroups of children for early intervention. Previous studies have suggested that, by way of a distinct mechanism, δ-aminolevulinic acid dehydratase single nucleotide polymorphism 2 (ALAD(2)) and/or peptide transporter 2*2 haplotype (hPEPT2*2) increase Pb blood burden in children. Studies have not yet examined whether sex mediates the effects of genotype on blood Pb burden. Also, previous studies have not included blood iron (Fe) level in their analyses. Blood and cheek cell samples were obtained from 306 minority children, ages 5.1 to 12.9 years. (208)Pb and (56)Fe levels were determined with inductively coupled plasma-mass spectrometry. General linear model analyses were used to examine differences in Pb blood burden by genotype and sex while controlling for blood Fe level. The sample geometric mean Pb level was 2.75 μg/dl. Pb blood burden was differentially higher in ALAD(2) heterozygous boys and hPEPT2*2 homozygous boys. These results suggest that the effect of ALAD(2) and hPEPT2*2 on Pb blood burden may be sexually dimorphic. ALAD(2) and hPEPT2*2 may be novel biomarkers of health and mental health risks in male children exposed to low levels of Pb.

Disruptive effects of persistent organohalogen contaminants on thyroid function in white whales (Delphinapterus leucas) from Svalbard

We analysed levels of 56 organohalogen contaminants (OHCs) including brominated flame retardants, polychlorinated biphenyls (PCBs), and organochlorine pesticides in the blubber of white (beluga) whales (Delphinapterus leucas) from Svalbard, Norway (N=12; 6 adults [5 males and 1 female] and 6 subadults [4 males and 2 females]) collected in 1996-2001. We also measured circulating levels of thyroid hormones (THs) and thyroid stimulating hormone (TSH) in the whales. The results confirm that OHC levels in these white whales are among the highest levels recorded in wildlife from Svalbard, and at the high end of the range when compared to white whales from the North American Arctic. A projection to latent structure (PLS) model (subadults and adult males grouped together) revealed that known or suspected thyroid disruptive contaminants (polybrominated diphenylether [PBDE]-28, -47, -99, -100, and -154, hexachlorobenzene [HCB], and PCB-105) were negatively correlated with circulating levels of total thyroxin (TT4), free T4 (FT4) and free triiodothyronine (FT3). Most of these negative relationships were also confirmed using partial correlations controlling for length (and thus age) of the whales. The positive correlations of TT4, FT4 and FT3 with hexabromocyclododecane (HBCD), α-hexachlorocyclohexane (α-HCH), chlorinated bornanes CHB-40 and CHB-62 revealed by the PLS model were not confirmed by partial correlations. TH levels in the present study appeared to be somewhat lower than levels measured in beluga whales from the Canadian Arctic. However, we were not able to determine if this was caused by different levels of OHCs, or differences in biological factors (e.g. age, sex, moulting status, and season) and analytical methods between the studies. Although the sample sizes were low and statistical models cannot depict the biological cause-effect relationships, this study suggests negative influences of specific OHCs, particularly PBDEs, on thyroid hormone levels in white whales. The impact this might have on individual and population health is unknown.

Exposure to mixtures of organohalogen contaminants and associative interactions with thyroid hormones in East Greenland polar bears (Ursus maritimus)

We investigated the multivariate relationships between adipose tissue residue levels of 48 individual organohalogen contaminants (OHCs) and circulating thyroid hormone (TH) levels in polar bears (Ursus maritimus) from East Greenland (1999-2001, n=62), using projection to latent structure (PLS) regression for four groupings of polar bears; subadults (SubA), adult females with cubs (AdF_N), adult females without cubs (AdF_S) and adult males (AdM). In the resulting significant PLS models for SubA, AdF_N and AdF_S, some OHCs were especially important in explaining variations in circulating TH levels: polybrominated diphenylether (PBDE)-99, PBDE-100, PBDE-153, polychlorinated biphenyl (PCB)-52, PCB-118, cis-nonachlor, trans-nonachlor, trichlorobenzene (TCB) and pentachlorobenzene (QCB), and both negative and positive relationships with THs were found. In addition, the models revealed that DDTs had a positive influence on total 3,5,3'-triiodothyronine (TT3) in AdF_S, and that a group of 17 higher chlorinated ortho-PCBs had a positive influence on total 3,5,3',5'-tetraiodothyronine (thyroxine, TT4) in AdF_N. TH levels in AdM seemed less influenced by OHCs because of non-significant PLS models. TH levels were also influenced by biological factors such as age, sex, body size, lipid content of adipose tissue and sampling date. When controlling for biological variables, the major relationships from the PLS models for SubA, AdF_N and AdF_S were found significant in partial correlations. The most important OHCs that influenced TH levels in the significant PLS models may potentially act through similar mechanisms on the hypothalamic-pituitary-thyroid (HPT) axis, suggesting that both combined effects by dose and response addition and perhaps synergistic potentiation may be a possibility in these polar bears. Statistical associations are not evidence per se of biological cause-effect relationships. Still, the results of the present study indicate that OHCs may affect circulating TH levels in East Greenland polar bears, adding to the "weight of evidence" suggesting that OHCs might interfere with thyroid homeostasis in polar bears.

Sex and circadian modulatory effects on rat liver as assessed by transcriptome analyses

The present study was designed to fully uncover sex and circadian modulatory effects on rat liver. Hepatic transcriptome analyses were performed at 4 hr intervals of a day-night cycle using young adult male and female rats. Sexually dimorphic genes, which were identified by a cross-sex comparison of time series data, included representative sex-predominant genes such as male- or female-predominant cytochrome P450 subfamilies (Cyp2c11, Cyp2c12, Cyp2c13, and Cyp3a2), sulfotransferases, and glutathione S-transferase Yc2. The identified sexually dimorphic genes were over-represented in the metabolism of retinols, xenobiotics, linoleic acids, or androgen and estrogen, or bile acid biosynthesis. Furthermore, transcription factor targets modeling suggested that transcription factors SP1, hepatocyte nuclear factor 4-alpha (HNF4-alpha), and signal transducer and activator of transcription 5b (STAT5b) serve as core nodes in the regulatory networks. On the other hand, Fourier transform analyses extracted universal circadian-regulated genes in both sexes. The circadian-regulated genes included clock or clock-controlled genes such as aryl hydrocarbon receptor nuclear translocator-like (Arntl), period homolog 2 (Per2), and D site albumin promoter binding protein (Dbp). The extracted cyclic genes were over-represented in major tissue activities, e.g. the urea cycle and the metabolism of amino acids, fatty acids, or glucose, indicating that the major liver functions are under circadian control. The transcription factor targets modeling suggested that transcription factors SP1, HNF4-alpha, and c-Myc proto-oncogene protein (c-MYC) serve as major hubs in the circadian-regulatory gene networks. Interestingly, transcription factors SP1 and HNF4-alpha are likely to orchestrate not only sexually dimorphic, but also circadian-regulated genes even though each criterion was rather mutually exclusive. This suggests the cross-talk between those regulations. Sexual dimorphism is likely to interact with circadian rhythmicity via overlapping gene regulatory networks on rat liver.

Clinical Experience with Linezolid at a Large Academic Medical Center: A Case Series and Review of the Literature

Purpose

The objectives of this study were to evaluate current patterns of use, microbiologic cure rates, and hematologic toxicities, including identification of risk factors, associated with linezolid utilization at our institution.

Methods

Utilization, clinical, microbiological, and toxicity data were collected prospectively over an 8-month period (August 1, 2006 to March 31, 2007). Binary logistic and multivariate stepwise regression analyses were performed to identify potential risk factors for linezolid-associated thrombocytopenia and anemia.

Results

A total of 116 linezolid courses (102 patients) were identified with a mean duration of therapy of 12.3 days. Appropriate infectious disease service approval and consults were found in 87.9% and 62.1% of the cases, respectively. Bloodstream, urinary tract, and respiratory tract infections accounted for 29%, 21%, and 16% of clinical indications, respectively. Vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and coagulase-negative staphylococci accounted for 43%, 24%, and 7% of clinical isolates, respectively. Overall, the microbiologic cure rate among evaluable patients was 83.8%. Development of thrombocytopenia was found in approximately 30% of linezolid-treated patients. Risk factors for linezolid-associated thrombocytopenia included female gender (OR 5.66, P = .002), serum creatinine (SCr) ≥ 2 mg/dL (OR 4.48, P = .009), intensive care unit admission (OR 3.06, P = .038), and duration of therapy ≥ 28 days (OR 3.76, P = .049).

Conclusion

Utilization patterns may suggest strategies for conserving linezolid, including improved compliance with current approval policies and clinical pathway development. Linezolid microbiological cure rates were similar to those found in the primary literature. Linezolid-associated thrombocytopenia was common and risk factors were identified. Further well-designed prospective studies are needed to confirm these findings. Hosp Pharm-2010;45(12):916-926

Multivariate models to predict human adipose tissue PCB concentrations in Southern Spain

The use of Polychlorinated biphenyls (PCBs) has been severely restricted due to their high toxicity and persistency in the environment. However, the presence of PCBs in human tissues nowadays is still been reported worldwide. Background exposure predictors of the human PCB body burden require more precise understanding. In the present study, PCB congeners 138, 153, and 180 were quantified in adult adipose tissue samples (n=387) from Granada Province (Southern Spain) and data on potential predictors of PCB concentrations were gathered by questionnaire. Chemical analysis of the selected congeners was done by gas chromatography and mass spectrometry, and multivariate analyses were performed stratifying by gender. PCB residues were quantified in 92% (PCB 153), 90% (PCB 180), and 86% (PCB 138) of the population. Geometric mean concentrations were 161.65+/-4.41 ng/g lipid for PCB 153, 111.62+/-6.27 ng/g lipid for PCB 180, and 38.41+/-8.61 ng/g lipid for PCB 138. Multivariate models explained 30-36% of the variability in PCB concentrations. Age and body mass index (BMI) predicted exposure in both males and females and were positively correlated with the concentration of the three PCB congeners. Occupation and diet predicted exposure in the males, whereas only dietary predictors were observed in the females. Further in-depth studies are required to investigate the influence of dietary habits on the bioaccumulation of PCBs and to evaluate the impact of policies aimed at reducing human exposure.

Same sex, no sex, and unaware sex in neurotoxicology

Males and females of virtually all species differ in how they respond to their environment. Because such differences exist in almost all biological realms, including disease patterns and therapeutic outcomes, they have evoked calls by various bodies to incorporate their assessment in research. Neurobehavioral indices pose special questions because, unlike outwardly visible markers, they are described by complex functional outcomes or subtle alterations in brain structure. These divergent responses arise because they are inscribed in the genome itself and then by endocrine mechanisms that govern sexual differentiation of the brain during development and operate throughout life. Other organ systems that exhibit sex differences include the liver, an important consideration for neurotoxicology because it may process many toxic chemicals differentially in males and females. Despite the scope and pervasiveness of sex differences, however, they are disregarded by much of neurotoxicology research. Males predominate in behavioral experiments, few such experiments study both sexes, some investigators fail to even describe the sex of their subjects, and in vitro studies tend to wholly ignore sex, even for model systems aimed at neurological disorders that display marked sex differences. The public is acutely aware of sex differences in behavior, as attested by its appetite for books on the topic. It closely follows debates about the proportion of women in professions that feature science and mathematics. Neurotoxicology, especially in the domain of laboratory research, will be hindered in its ability to translate its findings into human health measures if it assigns sex differences to a minor role. It must also be sensitive to how such debates are framed. Often, the differences evoking the most discussion are subtle in scope. They do not lend themselves to the typical analyses conducted by experimenters; that is, reliance on mean differences and null hypothesis testing.

Bioaccumulation of metals and effects of a landfill in small mammals Part III: Structural alterations

The leachates from the Garraf landfill located in a protected site (NE Spain) contain several potentially toxic substances such as heavy metals. Here we report the histopathological alterations produced by this pollution in wild specimens of an omnivorous species, the wood mouse, Apodemus sylvaticus, and an insectivorous species, the greater white-toothed shrew, Crocidura russula. Hepatic tissue presented the most severe alterations in both the species, namely cell cycle arrest (apoptosis and necrosis), inflammation, preneoplasic nodules, vacuolation and microsteatosis. The kidneys were altered more in the mice (presenting tubular necrosis and dilatation, inflammation, and cylinders) than in the shrews, suggesting that different metabolic pathways render shrews more tolerant to renal toxicity induced by pollutants. No pollution-related alterations were observed in lung, spleen, pancreas, gonads, oesophagus, intestine, or adrenals. We conclude that the two species could be used in conjunction as bioindicators to assess the effects of environmental pollution at different trophic levels.

Gender differences in the effects of organochlorines, mercury, and lead on thyroid hormone levels in lakeside communities of Quebec (Canada)

Environmental chemicals can disrupt endocrine balance and in particular thyroid hormone (TH) homeostasis. However, studies differ with respect to thyroid profile changes and gender differences are rarely examined. This study investigated the THs, triodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH), in relation to serum organochlorines (OCs), bioindicators of mercury (Hg) and blood lead (Pb) in 211 freshwater fish consumers (124 men and 87 women) from two communities in Canada. Thyroid hormones were within the normal range and the bioindicators of exposure were low compared to other reports on fish consumers. Stratified analysis showed that for women, serum T3 concentrations were negatively related to serum concentrations of PCB 138, PCB 153, the non-coplanar congeners, Arochlor 1260, and SigmaPCB, as well as p,p'-DDE. No relations were observed between T4 and any of the chemicals measured, but TSH was negatively related to blood Pb. For men, serum T4 was inversely related to PCB 138, non-ortho-substituted (dioxin-like) PCBs and SigmaPCB. A significant positive relationship was observed between serum TSH and different PCB congeners (PCB 138, PCB 180, non-coplanar congeners, mono-ortho coplanar congeners, dioxin-like PCBs), as well as SigmaPCB. Serum TSH increased with hair and blood Hg concentrations and was highest among those in the highest 50th percentile for both Hg and dioxin-like PCB congeners compared to the others. No associations were observed for T3 in men. These findings suggest that even at low concentrations, these environmental contaminants can interfere with thyroid status and effects may differ by gender.

Association between serum concentrations of persistent organic pollutants and self-reported cardiovascular disease prevalence: results from the National Health and Nutrition Examination Survey, 1999-2002

BACKGROUND

There is now increasing evidence that exposure to persistent organic pollutants (POPs) can contribute to the development of inflammatory diseases such as atherosclerosis.

OBJECTIVE

The objective of this study was to examine associations of serum concentrations of POPs with self-reported history of cardiovascular disease (CVD).

DESIGN

Cross-sectional associations of serum POPs concentrations with the prevalence of self-reported CVD were investigated in 889 adults >or= 40 years of age in the National Health and Nutrition Examination Survey, 1999-2002. We selected 21 POPs [3 polychlorinated dibenzo-p-dioxins (PCDDs), 3 polychlorinated dibenzofurans (PCDFs), 5 dioxin-like polychlorinated biphenyls (PCBs), 6 nondioxin-like PCBs, and 4 organochlorine (OC) pesticides] because they were detectable in >or= 60% of participants.

RESULTS

Dioxin-like PCBs, nondioxin-like PCBs, and OC pesticides were positively associated with the prevalence of CVD only among females. Compared with those in the lowest quartile of serum concentration, the odds ratios for CVD across increasing quartiles were 0.9, 2.0, and 5.0 for dioxin-like PCBs (p for trend < 0.01), 1.2, 1.2, and 3.8 for nondioxin-like PCBs (p for trend < 0.01), and 1.9, 1.7, and 4.0 for OC pesticides (p for trend = 0.03). PCDDs showed positive trends with the prevalence of CVD in both males and females; adjusted odds ratios were 1.4, 1.7, and 1.9 (p for trend = 0.07, males and females combined).

CONCLUSIONS

Our findings need to be carefully interpreted because of the cross-sectional design and use of self-reported CVD. Prospective studies are needed to clarify these associations.

Implications of gender differences for human health risk assessment and toxicology

This paper from The Human Health working group of SGOMSEC 16 examines a broad range of issues on gender effects in toxicology. Gender differences in toxicology begin at the gamete and embryo stage, continuing through development and maturation and into old age. Sex influences exposure, toxicokinetics, and toxicodynamics. The effects of sex have often been overlooked in both epidemiology and toxicology. In addition to the obvious modifying effects of the sex hormones and conditions affecting the male and female reproductive organs and sex roles, both genetic and hormonal effects influence many aspects of life and toxic responses. All aspects of toxicology should consider gender-balanced designs so that a more comprehensive understanding of differences and similarities can be obtained. Differential gene expression is a new frontier in toxicology. Risk assessment should account for gender and life cycle differences. The biological basis for altered sex ratios observed in several populations should be sought in animal models, and expanded to other compounds that might exert sex-selective effects. Wherever possible and feasible, toxicologic and environmental epidemiological studies should be designed and have sufficient statistical power to quantify differential gender-based exposures and outcomes.