Sex differences in bronchiolar epithelium response after the inhalation of lead acetate (Pb)

Genoprotective activity of the Pleurotus eryngii mushrooms following their in vitro and in vivo fermentation by fecal microbiota

Pleurotus eryngii mushrooms are commercially cultivated and widely consumed due to their organoleptic properties, and the low caloric and high nutritional value. In addition, they contain various biologically active and health-promoting compounds; very recently, their genoprotective effect in Caco-2 cells after their fermentation by the human fecal microbiota was also documented. In the current study, the effect of P. eryngii pre- and post-fermentation supernatants in micronuclei formation was evaluated in human lymphocytes. In addition, the genoprotective properties of increasing concentrations of aqueous extracts from P. eryngii mushrooms (150, 300, 600 mg/kg) against the cyclophosphamide-induced DNA damage were studied in young and elderly female and male mice in bone marrow and whole blood cells. The ability of the highest dose (600 mg/kg) to regulate the main cellular signaling pathways was also evaluated in gut and liver tissues of female animals by quantifying the mRNA expression of NrF2, Nfkβ, DNMT1, and IL-22 genes. P. eryngii post-fermentation, but not pre-fermentation, supernatants were able to protect human lymphocytes from the mitomycin C-induced DNA damage in a dose-dependent manner. Similarly, genoprotection was also observed in bone marrow cells of mice treated by gavage with P. eryngii extract. The effect was observed in all the experimental groups of mice (young and elderly, male and female) and was more potent in young female mice. Overexpression of all genes examined was observed in both tissues, mainly among the elderly animals. In conclusion, P. eryngii mushrooms were shown to maintain genome integrity through protecting cells from genotoxic insults. These beneficial effects can be attributed to their antioxidant and immunomodulatory properties, as well as their ability to regulate the cell's epigenetic mechanisms and maintain cell homeostasis.

Lead-Induced Motor Dysfunction Is Associated with Oxidative Stress, Proteome Modulation, and Neurodegeneration in Motor Cortex of Rats

Lead (Pb) is a toxic metal with great neurotoxic potential. The aim of this study was to investigate the effects of a long-term Pb intoxication on the global proteomic profile, oxidative biochemistry and neuronal density in motor cortex of adult rats, and the possible outcomes related to motor functions. For this, Wistar rats received for 55 days a dose of 50 mg/Kg of Pb acetate by intragastric gavage. Then, the motor abilities were evaluated by open field and inclined plane tests. To investigate the possible oxidative biochemistry modulation, the levels of pro-oxidant parameters as lipid peroxidation and nitrites were evaluated. The global proteomic profile was evaluated by ultraefficiency liquid chromatography system coupled with mass spectrometry (UPLC/MS) followed by bioinformatic analysis. Moreover, it was evaluated the mature neuron density by anti-NeuN immunostaining. The statistical analysis was performed through Student's t-test, considering p < 0.05. We observed oxidative stress triggering by the increase in malonaldehyde and nitrite levels in motor cortex. In the proteomic analysis, the motor cortex presented alterations in proteins associated with neural functioning, morphological organization, and neurodegenerative features. In addition, it was observed a decrease in the number of mature neurons. These findings, associated with previous evidences observed in spinal cord, cerebellum, and hippocampus under the same Pb administration protocol, corroborate with the motor deficits in the rats towards Pb. Thus, we conclude that the long-term administration to Pb in young Wistar rats triggers impairments at several organizational levels, such as biochemical and morphological, which resulted in poor motor performance.

Long-Term Lead Exposure Since Adolescence Causes Proteomic and Morphological Alterations in the Cerebellum Associated with Motor Deficits in Adult Rats

Lead (Pb) is an environmental contaminant that presents a high risk for human health. We aimed to investigate the possible alterations triggered by the exposure to Pb acetate for a long period in motor performance and the possible relationship with biochemical, proteomic and morphological alterations in the cerebellum of rats. Male Wistar rats were exposed for 55 days, at 50 mg/Kg of Pb acetate, and the control animals received distilled water. Open field (OF) and rotarod tests; biochemistry parameters (MDA and nitrite); staining/immunostaining of Purkinje cells (PC), mature neurons (MN), myelin sheath (MS) and synaptic vesicles (SYN) and proteomic profile were analyzed. Pb deposition on the cerebellum area and this study drove to exploratory and locomotion deficits and a decrease in the number of PC, MN, SYN and MS staining/immunostaining. The levels of MDA and nitrite remained unchanged. The proteomic profile showed alterations in proteins responsible for neurotransmitters release, as well as receptor function and second messengers signaling, and also proteins involved in the process of apoptosis. Thus, we conclude that the long-term exposure to low Pb dose promoted locomotion and histological tracings, associated with alterations in the process of cell signaling, as well as death by apoptosis.

Microanatomy, lipid peroxidation and antioxidant system of the visual cortex of rats following withdrawal from prolonged lead nitrate administration

Exposure to lead (Pb) has been shown to alter the function of central nervous system and affect cholinergic neurons of the visual cortex in animal models. This study sought to investigate the withdrawal symptoms and oxidative stress on the visual cortex after lead exposure. A total of 20 healthy male Wistar rats were randomly divided into two groups (n=10): group A, control, received 10 ml/kg of distilled water for 30 days orally; group B, lead treated group, received 10 mg/kg of lead nitrate solution for 30 days orally. Group B was divided into two subgroups, group B1 serves as non-recovery while B2 serves as recovery (withdrawal). Five rats from each group were sacrificed under ether anesthesia 24 hours after the last oral administration of lead, while the remaining 5 rats (withdrawal subgroup) were sacrificed 30 days after the last oral administration of lead. The visual cortex was grossed from the brain tissue and processed for histology. Blood/serum samples were obtained and markers of oxidative stress (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPX]), and lipid peroxidation (malondialdehyde [MDA]) were analyzed. Lead-exposed rats display a significant reduction in the SOD, CAT, and GPX level as well as increased in MDA level. However, following a recovery period, a non-significant improvement was seen in the histoarchitecture of the visual cortex.

The effect of environmental lead exposure on human health and the contribution of inflammatory mechanisms, a review

Lead (Pb) pollution has been considered as a major threat for human health due to induction of inflammatory cascades in various tissues. The aim of present review is to summarize the literature on the effects of lead exposure on respiratory, neurologic, digestive, cardiovascular and urinary disorders and the role of inflammation as an underlying mechanism for these effects. Various databases such as ISI Web of Knowledge, Medline, PubMed, Scopus, Google Scholar and Iran Medex, were searched from 1970 to November 2017 to gather the required articles using appropriate keywords such as lead, respiratory disorders, neurologic disorders, digestive disorders, cardiovascular disorders, urinary disorders and inflammation. Disorders of various body systems and the role of inflammation due to lead exposure has been proven by various studies. These studies indicate that lead exposure may cause respiratory, neurologic, digestive, cardiovascular and urinary diseases. The results were also indicated the increased inflammatory cells and mediators due to lead exposure including cytokines and chemokines due to lead exposure which suggested to be the cause various organ disorders.

Sex Differences in Human and Animal Toxicology

Sex, the states of being female or male, potentially interacts with all xenobiotic exposures, both inadvertent and deliberate, and influences their toxicokinetics (TK), toxicodynamics, and outcomes. Sex differences occur in behavior, exposure, anatomy, physiology, biochemistry, and genetics, accounting for female-male differences in responses to environmental chemicals, diet, and pharmaceuticals, including adverse drug reactions (ADRs). Often viewed as an annoying confounder, researchers have studied only one sex, adjusted for sex, or ignored it. Occupational epidemiology, the basis for understanding many toxic effects in humans, usually excluded women. Likewise, Food and Drug Administration rules excluded women of childbearing age from drug studies for many years. Aside from sex-specific organs, sex differences and sex × age interactions occur for a wide range of disease states as well as hormone-influenced conditions and drug distribution. Women have more ADRs than men; the classic sex hormone paradigm (gonadectomy and replacement) reveals significant interaction of sex and TK including absorption, distribution, metabolisms, and elimination. Studies should be designed to detect sex differences, describe the mechanisms, and interpret these in a broad social, clinical, and evolutionary context with phenomena that do not differ. Sex matters, but how much of a difference is needed to matter remains challenging.

Inhaled lead affects lung pathology and inflammation in sensitized and control guinea pigs

The association between lead exposure and respiratory diseases including asthma is controversial. Some studies indicate that exposure to environmental lead pollution may cause asthma; however, there is not sufficient data in this regard. The effect of lead on lung pathological findings and serum inflammatory mediators in sensitized and non-sensitized guinea pigs exposed to inhaled lead was examined. Eleven animal groups including control, sensitized, three groups of non sensitized animals, three groups during sensitization, and three groups after sensitization exposed to aerosol of three lead concentrations (n = 6 for each group) were studied. Serum inflammatory mediators levels and lung pathological changes were evaluated. All pathological changes and serum ET-1, EPO, NO levels were significantly higher in the sensitized and non sensitized animals exposed to lead than control group (p < 0.05 to p < 0.001). There was no significant difference between non sensitized groups exposed to high lead concentration and sensitized group. Serum inflammatory mediators levels and pathological findings in sensitized groups exposed to lead both during and after sensitization were significantly higher than sensitized non exposed group (p < 0.05 to p < 0.001). The data of exposed animals to high lead concentration were significantly higher than those of medium and low concentrations; those of medium concentration were also higher than low concentration (p < 0.05 to p < 0.001). In summary, the present study indicates that exposure to inhaled lead is able to induce respiratory changes similar to asthma. In addition, the results indicated that exposure to environmental lead is able to aggravate asthma severity both during development of asthma or after its manifestation.

Long-term ultrastructural indices of lead intoxication in pulmonary tissue of the rat

In the present research long-term pulmonary toxicity of lead was investigated in rats treated by intraperitoneal administration of lead acetate for three consecutive days (25 mg/kg per day). Five weeks after treatment average lead content in the whole blood was 0.41 μg/dL ± 0.05, in the lung homogenates it measured 3.35 μg/g ± 0.54, as compared to the control values of 0.13 ± 0.07 μg/dL and 1.03 μg/g ± 0.59, respectively. X-ray microanalysis of lung specimens displayed lead localized mainly within type II pneumocytes and macrophages. At the ultrastructural level the effects of lead toxicity were found in lung capillaries, interstitium, epithelial cells, and alveolar lining. Alveolar septa showed intense fibrosis, consisting of collagen, elastin, and fibroblasts. Thinned alveolar septa had emphysematous tissue with some revealing signs of angiogenesis. Type II pneumocytes contained lamellar bodies with features of laminar destruction. Fragments of the surfactant layer were often detached from the alveolar epithelium. These findings indicate that 5 weeks after exposure, lead provokes reconstruction of the alveolar septa including fibrosis and emphysematous changes in the lung tissue.

Inhaled lead exposure affects tracheal responsiveness and lung inflammation in guinea pigs during sensitization

Total and differential white blood cells (WBC), and cytokines, levels in serum were examined in guinea pigs exposed to inhaled lead acetate. Different groups of guinea pigs including: control (group C), sensitized group (group S), and exposed animals to aerosol of three lead concentrations during sensitization (n = 6 for each group) were studied. Total and differential WBC counts of lung lavage, serum cytokine (IFNγ and IL-4), levels and tracheal responsiveness to methacholine and ovalbumin were measured. All measured values were significantly increased except for IFNγ/IL-4 ratio which was significantly decreased in nonexposed sensitized and those exposed to all lead concentrations compared to control group (p < 0.05 to p < 0.001). Most measured values in animals exposed to higher lead concentration were also significantly higher than group S except for tracheal responsiveness to methacholine and lymphocyte count. Lead concentration significantly increased in lung tissues of animals exposed to all three lead concentrations (p < 0.001 for all cases). These results showed that lead exposure during sensitization can induce greater increase in tracheal responsiveness, total WBC, eosinophil, neutrophil, and basophil counts as well as serum level of IL-4. It can also cause a decrease in lymphocyte count, IFNγ level, and IFNγ/IL-4 ratio especially in its high concentration. Therefore inhaled lead exposure may cause increased severity of asthma during development of the disease.

The effect of lead exposure on tracheal responsiveness to methacholine and ovalbumin, total and differential white blood cells count, and serum levels of immunoglobulin E, histamine, and cytokines in guinea pigs

The effect of exposure to inhaled lead acetate in guinea pigs was evaluated. The present study comprised of five groups of guinea pigs including control (C), sensitized to ovalbumin (OA; S) and three groups exposed to 0.1, 0.2, and 0.4 M inhaled lead (Pb; n = 6 for each group). Tracheal responsiveness to methacholine and OA, total and differential white blood cells (WBCs) count in lung lavage, serum levels of cytokines (interferon γ (IFN-γ) and interleukin 4 (IL-4)), histamines, and immunoglobulin E (IgE), and Pb concentration in lung were measured. Tracheal responsiveness to methacholine, OA, total and differential WBC types as well as IL-4, IFN-γ, histamine, and IgE were significantly increased but IFN-γ/IL-4 were significantly decreased in sensitized animals as well as those exposed to high Pb concentrations when compared with the control group (from p < 0.05 to p < 0.001). In addition, there was not a significant difference in most measured values between animals exposed to high Pb concentration and group S. The Pb concentration in lung tissues of animals exposed to all three Pb concentrations was significantly higher than that of group C (p < 0.001 for all cases).These results showed that inhaled lead acetate exposure can induce lung inflammatory changes similar to sensitized animals. Therefore, exposure to environmental Pb pollution may cause asthma-like changes.

Tracheal responsiveness to methacholine and ovalbumin; and lung inflammation in guinea pigs exposed to inhaled lead after sensitization

The association between lead exposure and asthma is controversial. The effect of inhaled lead acetate on lung inflammation, tracheal responsiveness and immune components in guinea pigs after sensitization was examined in this study. Five groups of guinea pigs were randomly allocated to control (group C), sensitized (group S), and three test groups exposed to inhaled lead concentrations 0.1, 0.2 and 0.4M Pb after sensitization (n=6 for each group). The measured variables included tracheal responsiveness to methacholine and ovalbumin (OA); total and differential white blood cells (WBC) counts of lung lavage; serum cytokine levels (IFN-γ and IL-4); and lead concentration in lung tissue. Tracheal responsiveness to methacholine and OA; total and differential WBC counts; IL-4 and IFN-γ were significantly increased in sensitized animals compared to control group (p<0.05 to p<0.001). However, the ratio of IFN-γ/IL-4 were significantly decreased in group S (p<0.05). In addition, all measured parameters in animals exposed to highest lead concentration and most of them in animals exposed to medium lead concentration were significantly higher than group S, except for the IFN-γ and IFN-γ/IL-4 ratio, which were significantly decreased (p<0.05 to p<0.001). The lead concentration in lung tissues of all test animals was significantly higher than that of group C (p<0.001 for all groups). These results showed that lead acetate exposure can cause further increase in tracheal responsiveness to methacholine and OA, total and differential WBC count and IL-4, IFN-γ and IFN-γ/IL-4 ratio. Therefore, environmental exposure to lead may aggravate the severity of asthma.

The content of elements in rainwater and its relation to the frequency of hospitalization for gastric and duodenal peptic ulcers in Opole Voivodship, Poland, during 2000-2002

The relationship between chemical elements in rainwater and the frequency of hospitalizations for gastric and duodenal peptic ulcers was studied on the population of the province (Voivodship) of Opole, Poland, during the years 2000-2002. There is a high positive correlation between hospitalized cases of gastric peptic ulcers with chromium in rainwater (r = 0.71), cadmium (r = 0.63), and lead (r = 0.70). Mild positive correlations were found with zinc (r = 0.55), copper (r = 0.56), iron (r = 0.57), chloride (r = 0.60), and sulfate (r = 0.52). These correlations were higher on men, suggesting that there are gender correlations involved. In duodenal peptic ulcers, we observed a high positive correlation between chromium in rainwater and hospitalized cases (r = 0.61) and mild positive correlations with lead (r = 0.57), copper (r = 0.52), and cadmium (r = 0.51). Significant gender differences were not found. These positive correlations may be due to the biological activity of the elements, such as their cytotoxic activity, enhanced local adrenergic stimulation on mucosal vasculature, ion channel (mainly calcium channels) remodeling, and, for example promoting infection by Helicobacter pylori.

Gender and manganese exposure interactions on mouse striatal neuron morphology

Gender differences in sensitivity and toxicokinetics of multiple metals have been identified in humans. A recent study suggested that young girls performed worse on intellectual exams than young boys exposed to manganese (Mn) in the environment. Animal studies have shown that Mn exposure causes differential effects on behavior in male compared to female mice. We hypothesized that in response to Mn exposure striatal Mn accumulation and/or striatal medium spiny neuron (MSN) morphology show gender-dependent effects. We evaluated the contribution of gender to neuropathology by examining striatal MSN morphology in male and female mice exposed to Mn. We found that gender played a significant role in alterations of striatal MSN morphology in mice exposed to Mn. Gender-dependent changes were strongest when striatal Mn levels were elevated 24h following the final Mn exposure. Nevertheless, gender-dependent alterations in neuron morphology were still present 3 weeks after the final Mn exposure. Gender differences in neuron morphology were not due to differential striatal Mn accumulation between genders. We conclude that although gender does not affect striatal Mn accumulation, MSN morphology is differentially sensitive to elevated Mn levels.

Lead exposure in female workers who are pregnant or of childbearing age

In adults, high-level lead exposure often occurs in the lead-related industries. Acute lead poisoning has become rare, but chronic exposure to low-level lead remains a public health issue. With recent advances in our understanding of lead toxicity at low-levels, researchers have shifted their focus to studying lead at concentrations below those currently recommended as 'acceptable' in worker protection. As gender plays an important role in the storage, biokinetics, and toxicity of lead, it seems inappropriate to extrapolate findings of lead exposure in men to women. Women's bones release lead more slowly to the bloodstream, so blood levels remain increased for a long time after cessation of high exposure, reflecting the endogenous source of the lead. Particularly in pregnant women, bone lead release could influence health in pregnancy and be extremely harmful to the rapidly growing and developing fetus. Accordingly, female workers of childbearing age should avoid excessive lead exposure. However, because studies of pregnant workers encounter many difficulties and inconveniences, sufficient research has not been conducted in this area. As an alternative, a group of non-occupationally exposed women, matched as well as possible for anthropometric and reproductive variables and with almost the same levels of blood lead, could be recruited for survey.

Lung cancer and environmental chemical exposure: a review of our current state of knowledge with reference to the role of hormones and hormone receptors as an increased risk factor for developing lung cancer in man

Lung cancer is a dominant cause of cancer mortality. The etiology of lung cancer is mainly related to cigarette smoking, airborne genotoxic carcinogens, and arsenic, but its sex-specific incidence suggests that other mechanisms, such as hormones, may also be involved in the process of carcinogenesis. A number of agents commonly present in the living environment can have dual biological effects: not only are they genotoxic / carcinogenic, but they are also hormonally active as xenoestrogens. This dualism may explain sex-specific differences reported in both types and incidence of lung cancer. In a novel approach to investigate the complexity of lung cancer, etiology, including systems biology, will be used as a tool for a simultaneous interpretation of measurable environmental and biological parameters. Using this approach, the etiology of human lung cancer can be more thoroughly investigated using the available data from oncology and environmental health. The information gained could be applied in the introduction of preventive measures, in personalized medicine, and in more relevant legislation, which should be adjusted to reflect the current knowledge on the complex environmental interactions underlying this life-threatening disease.

Frequency of hospitalization for angina pectoris, stroke, and peripheral venous thrombosis and its relationship to elements in rainwater in Opole Voivodship, Poland, during 2000-2002

The content of elements in rainwater is an indirect indicator of its occurrence in air dust. This is sometimes referred to as rain fallout and is investigated in applied environmental pollution monitoring schemes. The annual content of elements in rainwater may be recognized as good index for assessing influence of those environmental factors on human body. The possible relationship between the concentrations of selected elements in rainwater and the frequency of hospitalization by reason of angina pectoris, stroke, and peripheral venous thrombosis was investigated in the Opole Voivodship (Poland) area during the period 2000-2002. There is a relatively high or partly significant correlation between frequency of hospitalization by reason of these conditions and content of lead, cadmium, chromium, zinc, and chloride in rainwater. Significant gender-dependent differences were observed only in peripheral venous thrombosis, where important correlations with lead, cadmium, and chromium were found only in men.

Gender differences in correlations between the content of elements in rain water and the frequency of hospitalization for arterial hypertension, chronic obstructive pulmonary disease, and psoriasis in Opole Voivodship, Poland, during 2000-2002

The aim of this work is to show and give a plausible explanation to gender-dependent differences in correlations between the content of selected elements in rainwater and the frequency of hospitalization by reason of arterial hypertension, chronic obstructive pulmonary disease (COPD), and psoriasis in the area of Opolskie Voivodeship, Poland, during the period 2000-2002. The elements analyzed were sodium, potassium, calcium, magnesium, manganese, iron, total phosphorus, total nitrogen, ammonium nitrogen, zinc, copper, lead, cadmium, nickel, chromium, chloride, nitrate, and sulfate. Hospitalization due to arterial hypertension was more frequent in women, whereas those for COPD and psoriasis were more frequent in men. In the case of women hospitalized for arterial hypertension, the correlations were low, except for zinc (r = 0.47) and for cadmium (r = 0.43). In men hospitalized for COPD, all of the correlation coefficients were higher than 0.4, except for phosphorus. The coefficients for nickel, ammonia nitrogen, and total nitrogen ranged from 0.5 to 0.6 and the remaining elements from 0.6 to 0.7. In women, the correlation was limited to five elements where the coefficient was r > 0.4 for chloride, calcium, nitrate, phosphorus, and chromium. In cases of hospitalization for psoriasis, the correlation in men was between 0.4 and 0.5 for chloride, phosphorus, copper, lead, and total nitrogen and greater than 5 for sulfate, potassium, calcium, iron, manganese, nitrate, and ammonium nitrogen. The correlation in women was between 0.48 and 0.5 for ammonium nitrogen and phosphorus.

The content of elements in rainwater and its relation to the frequency of hospitalization for arterial hypertension, chronic obstructive pulmonary disease, and psoriasis in Opole Voivodship, Poland during 2000-2002

The content of chemical elements in rainwater is a suitable indirect indicator of its presence in airborne dust, sometimes referred to as rain fallout. Rainwater is considered a suitable monitor for environmental or natural pollution. The yearly content of chemical elements in rainwater may be considered as a good indicator for determining the influence of these environmental factors on the human body. We decided to investigate the relationship between chemical elements in rainwater and the frequency of hospitalizations for arterial hypertension, chronic obstructive pulmonary disease, and psoriasis. There is a mild correlation between zinc and cadmium and cases of arterial hypertension. For obstructive pulmonary disease, there is a strong correlation with the content of potassium, calcium, iron, manganese, lead and nickel, and with chloride, sulfide, total nitrogen, and nitrites. There is also a mild correlation with magnesium, zinc, copper, cadmium and chromium, and with ammonium nitrogen. In cases of hospitalization for psoriasis, a correlation was revealed with such elements as potassium, ammonium nitrogen, and phosphorus.

Framework for gender differences in human and animal toxicology

Differences in exposure, anatomy, physiology, biochemistry, and behavior between males and females are a dominant theme in biology, transcending the plant and animal kingdoms. Yet differences due to sex and gender have not received adequate attention in human or animal toxicology nor always in epidemiology. Generalizations are often made about species' responses to xenobiotics, without data or consideration of female/male differences. Despite the leading role that pharmacology and drug development play in elucidating toxicokinetics, gender studies are relatively recent. Phenomenologic or clinical observations of sex differences often go unexplored, but pharmaceutical companies recognize the importance of enhanced understanding of toxicokinetics and toxicodynamics and emphasize the value of translational or integrational research--bringing laboratory findings to bedside applications and bedside questions to laboratory study. However, for many years Food and Drug Administration guidelines specifically precluded participation of females in many drug studies. Many occupational epidemiology studies, on which much of our understanding of toxic effects is based, begin by excluding women and minorities. Sex differentiation begins in the embryo under genetic and hormonal control. Changes affecting exposure, susceptibility, risk, and health continue throughout life. This paper provides a framework for analyzing the level(s) at which gender differences arise. The framework addresses exposure, toxicokinetics, toxicodynamics, and modulating influences. Men and women differ in many aspects of vulnerability to xenobiotics and other stressors, beginning with their opportunities for exposure. Toxicokinetic differences mainly involve metabolism, with few differences in absorption yet demonstrated. In addition, lifestyle, psychosocial, and hormonal factors modify the kinetics and responsiveness. Some phenomena fit the Classic Sex Hormone Paradigm in which castration (with and without hormone replacement) and administration of the opposite sex hormone demonstrate the primary regulatory role of sex hormones. Many phenomena, however, differ between males and females without showing a clear-cut relationship with the sex hormones. Since every cell both has a sex chromosome (X or Y) and is exposed to hormones, elegant techniques are just beginning to tease apart genetic from hormonal influences. Wherever possible, studies should use balanced gender and gender x age designs and should analyze data by sex and interactions, rather than simply adjusting for (discarding) gender. Power should be adequate, or lack of power (if inevitable) should be clearly stated.

Lead and immune function

The heavy metal lead is a widely deposited environmental toxicant known to impact numerous physiological systems, including the reproductive, neurological, hepatic, renal, and immune systems. Studies illustrating the capacity of lead to impair immune function and/or host resistance to disease date back to at least the 1960s. However, it has only been in recent years that lead has been recognized among a new category of immunotoxicants-those that dramatically shift immune functional capacity while producing only modest changes to immune cell populations and lymphoid organs. These relatively noncytotoxic immunomodulating chemicals and drugs represent the immunotoxic hazards most difficult to identify and problematic for risk assessment using historic approaches. As a result, such environmental factors are also among the most likely to contribute to chronic immune-related disease at relevant exposure levels. This review considers the animal and human evidence that lead exposure can produce a stark shift in immune functional capacity with a skewing predicted to elevate the risk of atopic and certain autoimmune diseases. At the same time, host defenses against infectious agents and cancer may be reduced. Age-based exposure studies also suggest that levels of blood lead previously thought to be safe, that is, below 10 microg/dl, may be associated with later life immune alterations.