Bisphenol A Induces Reactive Oxygen Species Production and Apoptosis-Related Gene Expression in Pacific Red Snapper Lutjanus peru Leukocytes.

Bisphenol A is one of the most used components of the polycarbonate plastic industry in the word. This contaminant has disrupting effect in cells in in vitro and in vivo in fish. This study evaluated for the first time the cytotoxicity, oxidative stress and apoptosis induced by bisphenol A (BPA) in head-kidney and spleen leukocytes isolated from Pacific red snapper Lutjanus peru. Head-kidney and spleen leukocytes were exposed to 100, 1000 and 10,000 µg/mL of BPA at 2 and 24 h. Results showed cytotoxicity of BPA at 1000 and 10,000 µg/mL. Cell viability > 80% was observed in leukocytes exposed to 100 µg/mL for 2 h; thus, this concentration was selected for the remainder of the study. Reactive oxygen species (ROS) production, analyzed by DCF-DA and NBT assays, significantly increased in those leukocytes exposed to BPA compared to controls after 2 or 24 h. Superoxide dismutase and catalase activities increased in head-kidney leukocytes after 24 h of BPA exposure. Apoptosis was inferred from caspase (casp-1 and casp-3), granzyme A (granz-A) and perforin 1 (perf-1) gene expression, which was significantly up-regulated, at 2 h BPA exposure in head-kidney leukocytes, and from granz-A and perf-1, which were up-regulated, after 24 h BPA exposure in spleen leukocytes. Short cytoplasmic prolongations and membrane blebs, suggestive of apoptosis, were observed by scanning electron microscopy. These data suggest that BPA at 100 µg/mL induces cytotoxicity, oxidative stress, apoptosis in Pacific red snapper head-kidney and spleen leukocytes.

Redox Metabolism in Ecophysiology and Evolution.

Aerobic organisms have developed a complex system of endogenous antioxidants to manage the reactivity of oxygen and its byproducts [...].

DEHP exposure impairs human skeletal muscle cell proliferation in primary culture conditions: preliminary study.

The plasticizer di (2-ethylhexyl) phthalate (DEHP) inhibits differentiation, impairs glucose metabolism, and decreases mitochondrial function in murine muscle satellite cells; however, if these effects are translated to human cells is unknown. The goal of this study was to evaluate changes in morphology and proliferation of primary human skeletal muscle cells exposed to DEHP. Rectus abdominis muscle samples were obtained from healthy women undergoing programed cesarean surgery. Skeletal muscle cells were isolated and grown under standard primary culture conditions, generating two independent sample groups of 25 subcultures each. Cells from the first group were exposed to 1 mM DEHP for 13 days and monitored for changes in cell morphology, satellite cell frequency and total cell abundance, while the second group remained untreated (control). Differences between treated and untreated groups were compared using generalized linear mixed models (GLMM). Cell membrane and nuclear envelope boundary alterations, loss of cell volume and presence of stress bodies were observed in DEHP-treated cultures. DEHP-treated cultures also showed a significant reduction in satellite cell frequency compared to controls. Exposure to DEHP reduced human skeletal muscle cell abundance. Statistical differences were found between the GLMM slopes, suggesting that exposure to DEHP reduced growth rate. These results suggest that exposure to DEHP inhibits human skeletal muscle cell proliferation, as evidenced by reduced cell abundance, potentially compromising long-term culture viability. Therefore, DEHP induces human skeletal muscle cell deterioration potentially inducing an inhibitory effect of myogenesis by depleting satellite cells.

Dolphin leukocytes exhibit an attenuated cytokine response and increase heme oxygenase activity upon exposure to lipopolysaccharides.

Cetaceans exhibit physiological adaptations that allowed the transition to aquatic life, including a robust antioxidant defense system that prevents injury from repeated exposure to ischemia/reperfusion events associated with breath-hold diving. The signaling cascades that characterize ischemic inflammation in humans are well characterized. In contrast, cetaceans' molecular and biochemical mechanisms that confer tolerance to inflammatory events are poorly understood. Heme oxygenase (HO) is a cytoprotective protein with anti-inflammatory properties. HO catalyzes the first step in the oxidative degradation of heme. The inducible HO-1 isoform is regulated by various stimuli, including hypoxia, oxidant stress, and inflammatory cytokines. The objective of this study was to compare the response of HO-1 and cytokines to a proinflammatory challenge in leukocytes isolated from humans and bottlenose dolphins (Tursiops truncatus). We measured changes in HO activity, and abundance and expression of interleukin 1 beta (IL-1ß), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and heme oxygenase 1 (HMOX1) in leukocytes treated with lipopolysaccharide (LPS) for 24 and 48 h. HO activity increased (p < 0.05) in dolphin (48 h) but not human cells. TNF-α expression increased in human (24 h, 48 h), but not dolphin cells following LPS stimulation. LPS-induced cytokine expression was lower in dolphin than in human leukocytes, suggesting a blunted cytokine response in bottlenose dolphin leukocytes treated with LPS. Results suggest species-specific regulation of inflammatory cytokines in leukocytes treated with LPS, which may lead to differential responses to a pro-inflammatory challenge between marine and terrestrial mammals.

Spatial and Temporal Variability of Trace and Macro Elements in the Red Crab Pleuroncodes planipes in the Pacific Coast of the Baja California Peninsula, Mexico.

The red crab, Pleuroncodes planipes, is a decapod crustacean abundant off the Pacific coast of the Baja California Peninsula. This species is caught and used in preparing animal feed, such as flour, particularly for aquaculture. Levels of calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), nickel (Ni), phosphorus (P), and zinc (Zn) were measured in red crabs collected from three geographic zones during three cruises in different seasons. Significant differences were found in the levels of Ca, Cd, Cu, Fe, Mg, Ni, P, and Zn between the two El Niño years (cruises C1 and C3, based on a threshold of ±0.5 °C for the Oceanic Niño Index). The highest concentrations of most elements were observed in the south of the Baja California Peninsula, a highly productive area influenced by upwelling events. Our findings suggest that while environmental temperature plays a central role in the benthic or pelagic distribution of red crabs, their content and variability of trace and macro elements appear to be associated with the presence of oceanic conditions, such as upwelling and potential changes in the composition of their diet associated with the depth in which these crustaceans are collected.

Changes in Toxin Production, Morphology and Viability of Gymnodinium catenatum Associated with Allelopathy of Chattonella marina var. marina and Gymnodinium impudicum.

Allelopathy between phytoplankton organisms is promoted by substances released into the marine environment that limit the presence of the dominating species. We evaluated the allelopathic effects and response of cell-free media of Chattonella marina var. marina and Gymnodinium impudicum in the toxic dinoflagellate Gymnodinium catenatum. Additionally, single- and four-cell chains of G. catenatum isolated from media with allelochemicals were cultured to evaluate the effects of post exposure on growth and cell viability. Cell diagnosis showed growth limitation and an increase in cell volume, which reduced mobility and led to cell lysis. When G. catenatum was exposed to cell-free media of C. marina and G. impudicum, temporary cysts and an increased concentration of paralytic shellfish toxins were observed. After exposure to allelochemicals, the toxin profile of G. catenatum cells in the allelopathy experiments was composed of gonyautoxins 2/3 (GTX2/3), decarcarbamoyl (dcSTX, dcGTX2/3), and the sulfocarbamoyl toxins (B1 and C1/2). A difference in toxicity (pg STXeq cell−1) was observed between G. catenatum cells in the control and those exposed to the filtrates of C. marina var. marina and G. impudicum. Single cells of G. catenatum had a lower growth rate, whereas chain-forming cells had a higher growth rate. We suggest that a low number of G. catenatum cells can survive the allelopathic effect. We hypothesize that the survival strategy of G. catenatum is migration through the chemical cloud, encystment, and increased toxicity.

"Oxidative stress induced by phthalates in mammals: State of the art and potential biomarkers".

BACKGROUND: Phthalates, plasticizers that are widely used in consumer products including toys, cosmetics, and food containers, have negative effects in liver, kidney, brain, lung and reproductive system of humans and other mammals. OBJECTIVES: To summarize, describe and discuss the available information on the effects of phthalate exposure in mammals, with emphasis on oxidative stress, and to suggest potential biomarkers of the health risks associated with phthalate exposure. METHODS: An assessment of scientific journals was performed using the PRISMA model for systematic reviews. Manuscripts reporting effects of phthalate exposure on mammalian health published in the last decade were selected according to originality, content, and association to health hazards. RESULTS AND DISCUSSION: We identified 25 peer-reviewed articles published between January 1st, 2010 and June 1st, 2021 that fit the aims and selection criteria. Phthalates induce oxidative stress and cell degenerative processes by increasing intracellular reactive species. Antioxidant cytoprotective systems decrease with time of exposure; conversely, oxidative damage markers, including thiobarbituric acid-reactive substances (TBARS), 8-hydroxy-2'-desoxyguanosine (8-OHdG) and malondialdehyde (MDA), increase. Phthalates were associated with endocrine system disfunction, metabolic disorders, infertility, nonviable pregnancy, cell degeneration, growth impairment, tumor development, and cognitive disorders. Phthalates can also aggravate health conditions such as asthma, hepatitis, diabetes, allergies, chronic liver and kidney diseases. Among humans, the more vulnerable subjects to phthalate exposure effects were children and individuals with a prior health condition. CONCLUSION: Chronic exposure to phthalates induces oxidative stress in mammals with concomitant adverse effects in reproductive, respiratory, endocrine, circulatory, and central nervous systems in both in vitro and in vivo trials. Oxidative damage markers and phthalate metabolites levels were the most common biomarkers of phthalate exposure effects. Studies in free-ranging and wild mammals are nil. Further studies on the pathways that lead to metabolic disruption are needed to identify potential treatments against phthalate-induced detrimental effects.

Fetal mercury concentrations in central California Pacific harbor seals: Associated drivers and outcomes.

Mercury (Hg) is a well-known toxicant in wildlife and humans. High total Hg concentrations ([THg]) have been reported in central California harbor seals Phoca vitulina richardii. We evaluated the effects of presence/absence of early natal coat (lanugo), year (2012 to 2017), sex, stranding location, and trophic ecology (ẟ13C and ẟ15N values) on hair [THg] along coastal central California. Also examined were [THg] effects on growth rates of pups in rehabilitation and probability of release (e.g., successful rehabilitation). The [THg] ranged from 0.46-81.98 mg kg-1 dw, and ẟ15N and ẟ13C ranged from 13.6-21.5‰, and -17.2 to -13.0‰, respectively. Stranding location, year, and presence of lanugo coat were important factors explaining variation in [THg]. Seals from Sonoma and San Mateo County had higher [THg] than other locations. Seals with full or partial lanugo coat had lower [THg]. Seals from 2016 and 2017 had higher [THg] than those from 2015. Hair [THg] exceeded lower and upper toxicological thresholds (>20 mg kg-1 by year (5.88% to 23.53%); >30 mg kg-1 (0% to 12.31%)) with a pronounced increase from 2015 to 2016. Pups in 2017 had significantly higher odds ratio of [THg] above 20 mg kg-1 than pups of 2015, and pups in 2016 had significantly higher odds ratio than those from 2013 and 2015 (similar when using 30 mg kg-1). Pups in Sonoma County had the highest odds ratio for [THg] in lanugo above 20 mg kg-1. ẟ15N values were higher in 2015-2017, particularly relative to 2014, probably associated with the El Niño event. The [THg] was not a good predictor for probability of release and mass-specific growth rates in captivity. Further investigation of temporal trends of [THg] in harbor seals is warranted given the relatively high percentage of samples exceeding threshold values, particularly in the most recent sampling years.

Morphological alterations in human skeletal muscle cells exposed to di-(2-Ethylhexyl) Phthalate (dehp) in primary cell culture conditions / Alteraciones morfológicas en células musculares esqueléticas humanas expuestas a Ftalato de di-(2-etilhexilo) (dehp) en condiciones de cultivo celular primario

SUMMARY: Di-(2-ethylhexyl) phthalate (DEHP) is among the most common plasticizer additives that humans are in contact with daily. DEHP can be released from plastic and enter the human body, whereby it is metabolized and transformed into oxidative hydrophilic molecules. Clinical follow-ups in patients exposed to this phthalate and investigations in cultures of several cell types have provided information on its effects. For example, it is associated with inhibition of diploid human cell development and morphological changes in cultured germ cells. Although skeletal muscle represents around 50 % of the human body mass, knowledge about the effects of DEHP on this tissue is poor. Cultured skeletal muscle cells were exposed to DEHP (1 mM) for 13 days with the aim of exploring and evaluating some of the potential morphological effects. Three culture development parameters and nine cell characteristics were monitored during the bioassay. At 13 days, growth area, cell viability, and concentration of total proteins were lower in DEHP exposed than in control cells. Cell width and area, as well as the diameter of the nucleus and nucleolus, were greater in exposed cells than in control cells. These are interpreted as signs of cytotoxicity and suggest potential adverse effects on the development of skeletal muscle cells from DEHP exposure, as reported for other cell types.

RESUMEN: Diariamente los seres humanos tenemos contacto con aditivos plastificantes, el di-(2-etilhexil) ftalato (DEHP) se encuentra entre los más comunes. El DEHP puede liberarse del plástico e ingresar al cuerpo humano, donde es metabolizado y transformando en moléculas hidrofílicas oxidativas. Seguimientos en pacientes expuestos a este ftalato e investigaciones en cultivos de varios tipos celulares han aportado información sobre sus efectos. El DEHP es asociado con la inhibición del desarrollo de células humanas diploides y cambios morfológicos en células germinales en cultivo. Sin embargo, aún es poco lo que se sabe sobre los efectos en el músculo esquelético, a pesar de que este tejido representa alrededor del 50 % de la masa corporal del humano. Para explorar y evaluar algunos efectos morfológicos en células de músculo esquelético, cultivos primarios fueron expuestos a DEHP (1 mM) durante 13 días. Se dio seguimiento a tres parámetros de desarrollo del cultivo y nueve características celulares. Al término de 13 días de exposición, los valores del área de crecimiento, viabilidad celular y concentración de proteínas totales fueron inferiores con respecto a los cultivos control. Se observaron cambios morfométricos en las células expuestas. Particularmente, el ancho y área celular, así como los diámetros del núcleo y nucleolos, fueron mayores a los registros en las células control. Estos resultados se interpretan como signos de citotoxicidad y sugieren efectos potencialmente adversos en el desarrollo de las células del músculo esquelético ante una exposición al DEHP, como se ha registrado para otros tipos celulares.

Morphometric characteristics of human skeletal muscle cells in primary culture / Características morfométricas de células musculares esqueléticas humanas en cultivo primario

SUMMARY: The study of cell morphology has contributed to the innovation of clinical techniques and biomedical research. Primary cell culture techniques are well standardized; however, knowledge about morphometric parameters under cell culture conditions is scarce. Variations in morphology can affect cell physiology and responses. The aim of this study was to use morphometric tools to describe the growth and development of skeletal muscle cells under standard cell culture conditions. A photographic database was generated, and morphometric data was obtained for nine cell characteristics (n = 559 cells). Four muscular cell shapes (spherical, irregular outline, triangular and spindle/fusiform) were characterized with wide ranges in variation. The maximum cell length (110-262 µm), width (35-66 µm), area (2,642 - 9,480 µm2), projection lengths (45 - 127 µm), and nucleus diameter (28 ± 11 µm) were obtained by day 23 of culture. A single centrally positioned nucleus was observed in each cell; nucleoli diameter (5 ± 2 µm) and number (1 - 5) varied. In general, cyclic changes in cell sizes were identified during culture, whereas cell length, width, and area increased in spurts. These results suggest that morphometric parameters can be used to monitor skeletal muscle cell development under standard culture conditions.

RESUMEN: A partir de células madre musculares, surgen los mioblastos que se dividen y fusionan entre sí para formar a los miocitos. Estas células ya diferenciadas son precursoras de miocitos que maduran en fibras musculares y posteriormente forman los músculos. La implementación de cultivos celulares de mioblastos ha permitido obtener conocimiento detallado del tejido muscular. Particularmente, algunas de las aportaciones morfológicas fueron el punto de partida de técnicas clínicas, terapias o investigaciones biomédicas. Sin embargo, los estudios morfométricos en condiciones de cultivo celular son escasos. Por lo cual, realizamos seguimientos fotográficos a cultivos desarrollados bajo condiciones estándar, registramos datos para nueve características celulares y aplicamos técnicas morfométricas para analizar estas células (n = 559). Se caracterizaron cuatro formas celulares adoptadas por los mioblastos (esférica, irregular, triangular y huso) y se registraron intervalos amplios de variación en los caracteres. Hacia el día 23 de cultivo se presentaron los valores máximos en la longitud (110-262 µm), el ancho (35-66 µm) y el área celular (2,642-9,480 µm2), así como en el tamaño máximo de las proyecciones celulares (45-127 µm) y el diámetro del núcleo (28±11 µm). El núcleo se observó como único y en posición central; los nucleolos variaron poco en diámetro (5±2 µm), aunque no en número (1 a 5). En términos generales, se identificaron cambios cíclicos en la talla de las células durante los cultivos, esto es, períodos intercalados de incremento y decremento en el largo, ancho y área celular. Debido a que estas características reflejaron los cambios generales sufridos por los mioblastos durante el cultivo, se proponen para monitorear sus etapas de desarrollo en cultivo.

In silico Characterization of the Heme Oxygenase 1 From Bottlenose Dolphin (Tursiops truncatus): Evidence of Changes in the Active Site and Purifying Selection.

Cetacea is a clade well-adapted to the aquatic lifestyle, with diverse adaptations and physiological responses, as well as a robust antioxidant defense system. Serious injuries caused by boats and fishing nets are common in bottlenose dolphins (Tursiops truncatus); however, these animals do not show signs of serious infections. Evidence suggests an adaptive response to tissue damage and associated infections in cetaceans. Heme oxygenase (HO) is a cytoprotective protein that participates in the anti-inflammatory response. HO catalyzes the first step in the oxidative degradation of the heme group. Various stimuli, including inflammatory mediators, regulate the inducible HO-1 isoform. This study aims to characterize HO-1 of the bottlenose dolphin in silico and compare its structure to the terrestrial mammal protein. Upstream HO-1 sequence of the bottlenose dolphin was obtained from NCBI and Ensemble databases, and the gene structure was determined using bioinformatics tools. Five exons and four introns were identified, and proximal regulatory elements were detected in the upstream region. The presence of 10 α-helices, three 310 helices, the heme group lodged between the proximal and distal helices, and a histidine-25 in the proximal helix serving as a ligand to the heme group were inferred for T. truncatus. Amino acid sequence alignment suggests HO-1 is a conserved protein. The HO-1 "fingerprint" and histidine-25 appear to be fully conserved among all species analyzed. Evidence of positive selection within an α-helix configuration without changes in protein configuration and evidence of purifying selection were found, indicating evolutionary conservation of the coding sequence structure.

Cell Death and Metabolic Stress in Gymnodinium catenatum Induced by Allelopathy.

Allelopathy between phytoplankton species can promote cellular stress and programmed cell death (PCD). The raphidophyte Chattonella marina var. marina, and the dinoflagellates Margalefidinium polykrikoides and Gymnodinium impudicum have allelopathic effects on Gymnodinium catenatum; however, the physiological mechanisms are unknown. We evaluated whether the allelopathic effect promotes cellular stress and activates PCD in G. catenatum. Cultures of G. catenatum were exposed to cell-free media of C. marina var. marina, M. polykrikoides and G. impudicum. The mortality, superoxide radical (O2●-) production, thiobarbituric acid reactive substances (TBARS) levels, superoxide dismutase (SOD) activity, protein content, and caspase-3 activity were quantified. Mortality (between 57 and 79%) was registered in G. catenatum after exposure to cell-free media of the three species. The maximal O2●- production occurred with C. marina var. marina cell-free media. The highest TBARS levels and SOD activity in G. catenatum were recorded with cell-free media from G. impudicum. The highest protein content was recorded with cell-free media from M. polykrikoides. All cell-free media caused an increase in the activity of caspase-3. These results indicate that the allelopathic effect in G. catenatum promotes cell stress and caspase-3 activation, as a signal for the induction of programmed cell death.

Influence of sex and maturity state on trace elements content in liver and muscle of the Sciaenidae Totoaba macdonaldi.

BACKGROUND: The fish Totoaba macdonaldi is endemic to the Upper Gulf of California. Its migratory movements involve sites with high levels of trace elements in the environment that can accumulate in tissues. In this study, lead (Pb), copper (Cu), cadmium (Cd), zinc (Zn) and iron (Fe) concentrations in male and female totoaba liver and muscle were quantified at various sexual maturity stages along the species' geographic distribution. METHODS: Generalized linear models were used to explore associations between trace element concentrations and season of the year, sex/maturity stage, and total fish length. RESULTS: No detectable Pb concentrations were recorded in liver or muscle; Cu, Cd, Zn and Fe contents in totoaba liver and muscle were typical of fish inhabiting areas with no contamination issues and are within international maximum permissible levels for human consumption. Variations in the content of Cd, Cu, Zn and Fe in liver of totoaba seem to be more related to the feeding and reproductive physiology of this species than as result of environmental exposure. Results suggest that consumption of totoaba muscle does not pose a public health risk. Furthermore, depending on the sex/maturity stage of totoaba, this fish's muscle may provide approximately 70% Cu, 60% Zn and 100% Fe of the recommended dietary reference intake.

Nutritional content of Totoaba macdonaldi (Gilbert, 1890), Antioxidants and lipid peroxidation in muscle.

BACKGROUND: Totoaba, Totoaba macdonaldi, is an endemic species of the Gulf of California, where wide variations in sea temperature throughout the year, surface salinities that gradually increase towards the north, and contamination by discharge of wastewater have been recorded. In addition to the challenges of reproduction and swimming, its characteristic biannual migration presents totoaba with changes in environmental factors that could affect oxidative stress indicators. The objective of this study was to assess spatial and seasonal changes in the oxidative stress indicators in muscle samples of totoaba. METHODS: Reactive oxygen species production, antioxidant enzyme activities and lipid peroxidation levels were quantified by spectrophotometry. RESULTS: Results suggest spatial-temporal variations of the oxidative stress indicators in muscle of totoaba that may be associated to a complex interaction between environmental and biological factors, including reproduction and nutrient availability. These results contribute to explain the appeal of totoaba as a marketable meat and suggest totoaba may provide antioxidant nutrients to consumers.

Mercury concentrations in Baja California Sur fish: Dietary exposure assessment.

Total mercury concentrations ([THg]) in muscle were determined in commercial finfish and elasmobranchs from Baja California Sur (BCS), Mexico to evaluate dietary Hg exposure for BCS communities, including the relationship of trophic ecology, length and mass with [THg] that might drive future consumption advice (e.g., recommend limited consumption of large fish for some species). The [THg] ranged from 0.06 to 528.02 µg kg-1 ww in finfish and 17.68-848.26 µg kg-1 ww in elasmobranchs. Relative to the consumption threshold set for predatory fish in Mexico, all species had a concentration below 1000 µg kg-1 ww. As expected, 16 (4.02%) and 75 (18.84%) individual fish were above advisory thresholds of 500 and 200 µg kg-1 ww, respectively. The hazard quotients (HQs) in most species were significantly <1.0, only banded guitarfish showed a significant median HQ > 1.0. Thus, the relative level of risk of high Hg exposure is low for most species.

Antioxidant response to cadmium exposure in primary skeletal muscle cells isolated from humans and elephant seals.

Cadmium (Cd) occurs naturally; however, its concentration can increase with anthropogenic activities. Excess Cd increases reactive oxygen species (ROS) production and oxidative damage, which can lead to pathological conditions. Marine mammals accumulate Cd in the liver and the kidney; yet, there are no reports of Cd-associated tissue damage in whales, seals or dolphins. Response to Cd exposure (0-5.0 µM CdCl2 for 1-12 h) was analyzed and compared in primary skeletal muscle cells isolated from northern elephant seals (Mirounga angustirostris) and humans (Homo sapiens). Antioxidant enzyme activities (glutathione S-transferase, glutathione reductase, glutathione peroxidase), glutathione concentration, and protein carbonyl levels (an indicator of oxidative damage) were quantified. Glutathione levels were higher in northern elephant seal than in human cells. Protein carbonyl content in cells exposed to Cd was lower and had a smaller variability range in elephant seals than in humans. Generalized linear models (GLIM) identified Cd exposure and antioxidant defenses as significant contributors to protein carbonyl variability in human but not in elephant seal cells. These results suggest that the previously observed differences in circulating and tissue glutathione levels between marine and terrestrial mammals are maintained under cell culture conditions and that northern elephant seal and human muscle cells respond differently to Cd exposure. The results also suggest that the observed differences could potentially be associated with the protective mechanisms that allow northern elephant seals to tolerate extreme conditions that result in increased ROS generation (e.g. diving, sleep apnea, fasting) with no oxidative damage.

Using carbon and nitrogen stable isotope modelling to assess dietary mercury exposure for pregnant women in Baja California Sur, Mexico.

INTRODUCTION: Previous studies of mercury (Hg) in pregnant women in the area of La Paz, Baja California Sur (BCS), Mexico found a proportion of individuals had concentrations of total Hg ([THg]) above some thresholds of concern set by health agencies. The [THg] were associated with fish and seafood consumption as well as other factors; although it was unclear which marine diet items could potentially be contributing to the concentrations observed. METHOD: We examined [THg] and monomethylmercury concentration ([MeHg+]) in the archived hair of 70 pregnant women from BCS as well as in diet items including fish, shellfish, and staple items (rice, beans, corn, and flour). We measured stable isotopes of carbon and nitrogen and employed a Bayesian stable isotope mixing model to investigate the proportion of fish and seafood in the isotopic profiles of archived hair samples. RESULTS: Concentrations of Hg species were low in staple foods and ranged from below detection limit to 5.71 parts per billion (ppb) wet weight. In hair, geometric mean [THg] was 658 ppb and [MeHg+] was 395 ppb, which were lower than previous reports. Percent MeHg+ was positively correlated with higher δ15N values. CONCLUSIONS: The largest carbon contributors to the diet of the study participants were corn and rice, and our analysis of fish contribution to diet varyingly agreed with the self-reported fish consumption. This report highlights the ability to discriminate potential sources of Hg from a diverse diet and the limitations of dietary recall studies.

Twenty years of the 'Preparation for Oxidative Stress' (POS) theory: Ecophysiological advantages and molecular strategies.

Freezing, dehydration, salinity variations, hypoxia or anoxia are some of the environmental constraints that many organisms must frequently endure. Organisms adapted to these stressors often reduce their metabolic rates to maximize their chances of survival. However, upon recovery of environmental conditions and basal metabolic rates, cells are affected by an oxidative burst that, if uncontrolled, leads to (oxidative) cell damage and eventually death. Thus, a number of adapted organisms are able to increase their antioxidant defenses during an environmental/functional hypoxic transgression; a strategy that was interpreted in the 1990s as a "preparation for oxidative stress" (POS). Since that time, POS mechanisms have been identified in at least 83 animal species representing different phyla including Cnidaria, Nematoda, Annelida, Tardigrada, Echinodermata, Arthropoda, Mollusca and Chordata. Coinciding with the 20th anniversary of the postulation of the POS hypothesis, we compiled this review where we analyze a selection of examples of species showing POS-mechanisms and review the most recent advances in understanding the underlying molecular mechanisms behind those strategies that allow animals to survive in harsh environments.

Micronutrient content and antioxidant enzyme activities in human breast milk.

Breast milk contains micronutrients that function as cofactors of antioxidant enzymes. High concentrations of iron (Fe) and copper (Cu) can increase the production of reactive oxygen species (ROS). This study aimed to assess the relationship between the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST)) and the concentration of the micronutrients Fe, Cu and zinc (Zn) in breast milk. Breast milk samples were collected from 108 mothers (7-10 days postpartum, transitional milk). The samples were grouped into three groups according to the number of pregnancies (one, two and three or more pregnancies), also grouped according to the body mass index (BMI) suggested by the World Health Organization (WHO) in underweight, normal weight, overweight and obese. Breast milk Fe, Cu and Zn concentrations were determined by atomic absorption spectrophotometry and the activity of the antioxidant enzymes was determined by spectrophotometry. An increase in GPx, SOD and GST activities in relation to the number of pregnancies was found (p = 0.05, p = 0.04 and p < 0.01, respectively). An inverse relationship between GST activity and BMI was found (p = 0.05). A positive correlation was observed between Cu and Zn concentrations (r = 0.52, p < 0.05). A negative correlation was found between Cu concentration and catalase activity (r = -0.22, p < 0.05); Fe content was negatively correlated with GPx and GST activities (r = -0.32, r = -0.22, respectively, p < 0.05). The activities of antioxidant enzymes (GPx, SOD and GST) may be affected by the number of pregnancies and contribute to prevent oxidation of nutritional molecules in breast milk.