Novel Apoplastic Antifreeze Proteins of Deschampsia antarctica as Enhancer of Common Cell Freezing Media for Cryobanking of Genetic Resources, a Preliminary Study.

Antifreeze proteins (AFPs) are natural biomolecules found in cold-adapted organisms that lower the freezing point of water, allowing survival in icy conditions. These proteins have the potential to improve cryopreservation techniques by enhancing the quality of genetic material postthaw. Deschampsia antarctica, a freezing-tolerant plant, possesses AFPs and is a promising candidate for cryopreservation applications. In this study, we investigated the cryoprotective properties of AFPs from D. antarctica extracts on Atlantic salmon spermatozoa. Apoplastic extracts were used to determine ice recrystallization inhibition (IRI), thermal hysteresis (TH) activities and ice crystal morphology. Spermatozoa were cryopreserved using a standard cryoprotectant medium (C+) and three alternative media supplemented with apoplastic extracts. Flow cytometry was employed to measure plasma membrane integrity (PMI) and mitochondrial membrane potential (MMP) postthaw. Results showed that a low concentration of AFPs (0.05 mg/mL) provided significant IRI activity. Apoplastic extracts from D. antarctica demonstrated a cryoprotective effect on salmon spermatozoa, with PMI comparable to the standard medium. Moreover, samples treated with apoplastic extracts exhibited a higher percentage of cells with high MMP. These findings represent the first and preliminary report that suggests that AFPs derived from apoplastic extracts of D. antarctica have the potential to serve as cryoprotectants and could allow the development of novel freezing media.

Chronic Toxicity of Iron to Aquatic Organisms under Variable pH, Hardness, and Dissolved Organic Carbon Conditions.

A series of chronic toxicity tests was conducted exposing three aquatic species to iron (Fe) in laboratory freshwaters. The test organisms included the green algae Raphidocelis subcapitata, the cladoceran Ceriodaphnia dubia, and the fathead minnow Pimephales promelas. They were exposed to Fe (as Fe (III) sulfate) in waters under varying pH (5.9-8.5), hardness (10.3-255 mg/L CaCO3 ), and dissolved organic carbon (DOC; 0.3-10.9 mg/L) conditions. Measured total Fe was used for calculations of biological effect concentrations because dissolved Fe was only a fraction of nominal and did not consistently increase as total Fe increased. This was indicative of the high concentrations of Fe required to elicit a biological response and that Fe species that did not pass through a 0.20- or 0.45-µm filter (dissolved fraction) contributed to Fe toxicity. The concentrations frequently exceeded the solubility limits of Fe(III) under circumneutral pH conditions relevant to most natural surface waters. Chronic toxicity endpoints (10% effect concentrations [EC10s]) ranged from 442 to 9607 µg total Fe/L for R. subcapitata growth, from 383 to 15 947 µg total Fe/L for C. dubia reproduction, and from 192 to 58,308 µg total Fe/L for P. promelas growth. Toxicity to R. subcapitata was variably influenced by all three water quality parameters, but especially DOC. Toxicity to C. dubia was influenced by DOC, less so by hardness, but not by pH. Toxicity to P. promelas was variable, but greatest under low hardness, low pH, and low DOC conditions. These data were used to develop an Fe-specific, bioavailability-based multiple linear regression model as part of a companion publication. Environ Toxicol Chem 2023;42:1371-1385. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A methodology to design, develop, and evaluate machine learning models for predicting dropout in school systems: the case of Chile.

School dropout is a structural problem which permanently penalizes students and society in areas such as low qualification jobs, higher poverty levels and lower life expectancy, lower pensions, and higher economic burden for governments. Given these high consequences and the surge of the problem due to COVID-19 pandemic, in this paper we propose a methodology to design, develop, and evaluate a machine learning model for predicting dropout in school systems. In this methodology, we introduce necessary steps to develop a robust model to estimate the individual risk of each student to drop out of school. As advancement from previous research, this proposal focuses on analyzing individual trajectories of students, incorporating the student situation at school, family, among other levels, changes, and accumulation of events to predict dropout. Following the methodology, we create a model for the Chilean case based on data available mostly through administrative data from the educational system, and according to known factors associated with school dropout. Our results are better than those from previous research with a relevant sample size, with a predictive capability 20% higher for the actual dropout cases. Also, in contrast to previous work, the including non-individual dimensions results in a substantive contribution to the prediction of leaving school. We also illustrate applications of the model for Chilean case to support public policy decision making such as profiling schools for qualitative studies of pedagogic practices, profiling students' dropout trajectories and simulating scenarios.

Effect of exogenous lipids on cryotolerance of Atlantic salmon (Salmo salar) spermatozoa.

The development of semen cryopreservation strategies is necessary to improve the semen storage technologies of species of great commercial interest for aquaculture. Recent studies demonstrate that lipids play an important role in the fertility and cryotolerance of fish gametes. This study investigated the effect of exogenous lipids in the freezing medium on the post-thaw functional parameters of Salmo salar spermatozoa. Semen samples (n = 12) were incubated in standard extender supplemented with different concentrations of oleic acid (OA, C18:1n9), linoleic acid (LA, C18:2n6), arachidonic acid (ARA, C20:4n6) and cholesterol-loaded cyclodextrin (CLC). Post-thaw motility, membrane integrity, mitochondrial membrane potential (ΔΨm), superoxide anion (O2•-) and fertility rates were analyzed. The results revealed that the semen incubated with 0.003 mmol/L OA increased the motility (~7%) and ΔΨm (~2%) (P < 0.05), but membrane integrity and fertility were not increased. The addition of 0.003 mmol/L LA increased the motility (~4%) and all LA extenders increased the ΔΨm (P < 0.05); however, LA increased the O2•- levels and decreased the membrane integrity and fertility (P < 0.05). Semen incubated with ARA improved sperm motility (~5%), membrane integrity (~10.5%) and fertility rates (~11%) (P < 0.05). The maximum improvement in post-thaw sperm functionality was observed by adding 0.003 mmol/L ARA. In contrast, sperm quality parameters and fertility were decreased by the CLC addition (P < 0.05). This study showed that ARA could be considered as an additive for semen cryopreservation and could be relevant in the reproductive process and reproductive management of Salmo salar.

Copper alloys' metal migration and bioaccessibility in saliva and gastric fluid.

The oral bioaccessibility of copper alloys and pure metals was assessed using in vitro methods with synthetic saliva and gastric fluid. The metal-specific migration rates from polished alloy surfaces are higher in gastric (pH 1.5) than in saliva fluid (pH 7.2). In both media, migrations are higher for lead than for other metals. The bioaccessible metal concentrations in massive copper alloys, after 2 h in gastric fluid, was only <0.01%-0.18%, consistent with the low surface reactivity of copper alloys (defined as 1 mm spheres). The average metal-specific migrations of cobalt, copper, nickel and lead from most of the tested copper alloys in gastric media are comparable to the ones from their pure metals. The data further show that the bioaccessibility of metals in massive copper alloys primarily depends on the bioelution medium, the exposed surface area and the composition of the alloy. The tested copper alloys show only limited evidence for influence of alloy surface microstructure. This is contrary to findings for other alloys such as stainless steel. Additional investigations on other copper alloys could allow to further refine these conclusions. These findings are useful for establishing the hazard and risk profile of copper alloys following oral exposure.

Bioavailability Assessment of Metals in Freshwater Environments: A Historical Review.

Many metals (aluminum, cadmium, cobalt, copper, nickel, lead, zinc) are widely studied environmental contaminants because of their ubiquity, potential toxicity to aquatic life, and tendency for toxicity to vary widely as a function of water chemistry. The interactions between metal and water chemistry influence metal "bioavailability," an index of the rate and extent to which the metal reaches the site of toxic action. The implications of metal bioavailability for ecological risk assessment are large, with as much as a 100-fold variability across a range of water chemistries in surface waters. Beginning as early as the 1930s, considerable research effort was expended toward documenting and understanding metal bioavailability as a function of total and dissolved metal, water hardness, natural organic matter, pH, and other water characteristics. The understanding of these factors and improvements in both analytical and computational chemistry led to the development of modeling approaches intended to describe and predict the relationship between water chemistry and metal toxicity, including the free ion activity model, the gill surface interaction model, the biotic ligand model, and additional derivatives and regression models that arose from similar knowledge. The arc of these scientific advances can also be traced through the evolution of the US Environmental Protection Agency's ambient water quality criteria over the last 50 yr, from guidance in the "Green Book" (1968) to metal-specific criteria produced in the last decade. Through time, water quality criteria in many jurisdictions have incorporated increasingly sophisticated means of addressing metal bioavailability. The present review discusses the history of scientific understanding of metal bioavailability and the development and application of models to incorporate this knowledge into regulatory practice. Environ Toxicol Chem 2019;39:48-59. © 2019 SETAC.

Effects of cryopreservation on cAMP-dependent protein kinase and AMP-activated protein kinase in Atlantic salmon (Salmo salar) spermatozoa: Relation with post-thaw motility.

Sperm motility in fish with external fertilization is critical for reproductive efficiency in aquaculture, especially in salmonids. Gamete preservation techniques, such as cryopreservation, however, reduce sperm motility and fertilizing capacity. Very few studies have addressed cryodamage from energetic and cell signalling approaches. In this study, cAMP-dependent protein kinase (PKA) and AMP-activated kinase (AMPK) activities were quantified in fresh and cryopreserved spermatozoa of Atlantic salmon (Salmo salar); and the relation with motility was analysed. Results indicate there was a decrease in membrane integrity and motility in post-thawed spermatozoa compared to fresh samples, however, there was about 30% of cells with intact plasma membrane but incapable of motility. The PKA and AMPK activities were less after cryopreservation, indicating that loss of motility may be related to alteration of these key enzymes. Furthermore, PKA and AMPK activities were positively correlated with each other and with motility; and inhibition decreased motility, indicating there is a functional relationship between PKA and AMPK. The PKA inhibition also decreased AMPK activity, but results from protein-protein docking analyses indicated AMPK activation directly by PKA is unlikely, thus an indirect mechanism may exist. There have been no previous reports of these kinase actions in fish spermatozoa, making these findings worthy of assessment when there are future studies being planned, and may serve as base knowledge for optimization of cryopreservation procedures and development of biotechnologies to improve reproduction efficiency in the aquaculture industry.

Sperm morphology and ultrastructure of Patagonian blenny (Eleginops maclovinus).

In this study, the morphology and ultrastructure of Eleginops maclovinus spermatozoa were characterized through scanning and electron microscopy. Findings revealed that E. maclovinus spermatozoa can be differentiated into three major parts: a spherical head without acrosome (typical for externally fertilizing teleost), a midpiece containing 2-5 spherical mitochondria, and a long flagellum. The mean length of the spermatozoa was 40.08 ± 2.30 µm, with flagella accounting for 38.38 ± 2.08 µm. The head was 1.31 ± 0.17 µm long, and 1.63 ± 0.01 µm wide. The midpiece was 0.39 ± 0.05 µm in length and 0.95 ± 0.12 µm in width. It was located below the nucleus and contained 2 to 5 spherical mitochondria. The mitochondria were separated from the axoneme by a cytoplasmic canal. There was no evidence of the flagellum membrane forming sidefins, and the axoneme was composed of the typical 9 + 2 microtubular doublet structure enclosed by cell membrane. The present study reveals that E. maclovinus sperm can be categorized as a primitive type. This study is the first to provide comprehensive details on the ultrastructure of spermatozoa in E. maclovinus.

Determination of Bioavailable Aluminum in Natural Waters in the Presence of Suspended Solids.

Analyses of natural waters frequently show elevated levels of total aluminum (Al) attributable to acid extraction of Al from the total suspended solids (TSS) minerals. Hence, there is a need for an analytical method that measures only bioavailable Al. Natural waters high in TSS were collected to study the chronic effects of Al on Ceriodaphnia dubia. In the collected waters TSS ranged from 30 to 411 mg/L; total Al concentrations ranged from 2.0 to 44.8 mg/L. The TSS in natural waters inhibited reproduction of C. dubia up to 40% in comparison to the same filtered waters. This inhibition did not correlate with the concentration of TSS or total Al; it was attributed to nutritional deficiency and was prevented by increasing the food supply. To demonstrate that toxicity can be measured in natural waters, samples with elevated TSS were spiked with soluble Al, and survival and reproduction were measured in chronic studies performed at pH 6.3 and 8.0. To properly characterize the Al concentrations in the toxicity studies, a method was needed that could discriminate bioavailable Al from mineral forms of Al. An extraction method at pH 4 for bioavailable Al was developed and evaluated using C. dubia chronic toxicity studies in the presence of TSS. It is concluded that the proposed method is better able to discriminate chronic toxicity effects attributable to bioavailable Al from mineralized nontoxic forms of Al compared with existing methods using total or total recoverable Al (i.e., extraction at pH ≤ 1.5). We propose that this new method be used when assessing the potential for Al in natural surface waters to cause toxicity. Environ Toxicol Chem 2019;38:1668-1681. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Modeling the Fate of Metal Concentrates in Surface Water.

Metals present in concentrates are in a solid form and are not bioavailable, but they can dissolve or potentially transform to more soluble forms. Transformation/dissolution laboratory protocols have been developed to assess the importance of dissolution of sparingly soluble metal substances in the context of hazard classification; however, these tests represent worst-case scenarios for metal bioavailability because attenuation mechanisms such as complexation, sorption, and transport to the sediment are not considered. A unit world model (UWM) for metals in lakes, tableau input coupled kinetics equilibrium transport (TICKET)-UWM, has been developed that considers key processes affecting metal transport, fate, and toxicity including complexation by aqueous inorganic and ligands, partitioning to dissolved organic carbon (DOC) and particulate organic carbon (POC), precipitation, and transport of dissolved metals and solids between the water column and sediment. The TICKET-UWM model was used to assess the fate of a metal concentrate and dissolved metal ions released from the concentrate following an instantaneous input to a generalized lake. Concentrate dissolution rates in the water column were parameterized using results from batch transformation/dissolution tests for 2 specific concentrates containing lead (Pb), copper (Cu), and cobalt (Co). The TICKET-UWM results for a generalized lake environment showed that water column concentrations of metals in the lake environment after 28 d were several orders of magnitude lower than the 28-d concentration from the transformation/dissolution tests because Pb, Cu, and Co partitioned to POC in the water column and were subsequently removed due to settling. Resuspension of sediment served to increase total metal in the water column, but the resulting concentrations were still much lower than the 28-d concentrations from the transformation/dissolution tests. Information from TICKET-UWM could be used to refine the environmental hazard profiles of metals. Environ Toxicol Chem 2019;38:1256-1272. © 2019 SETAC.

Changes in Atlantic salmon (Salmo salar) sperm morphology and membrane lipid composition related to cold storage and cryopreservation.

The cold storage and cryopreservation of semen decrease sperm quality. Morphological and biochemical analyses of spermatozoa provide valuable information for the optimization of storage protocols to obtain a sufficient number of spermatozoa for in vitro fertilization. The aim of this study was to evaluate the morphology and lipid composition of Atlantic salmon (Salmo salar) spermatozoa after storage at 4 °C and cryopreservation. Semen samples were obtained by stripping. One aliquot was stored at 4 °C for 7 days, and another aliquot was cryopreserved. The morphology and ultrastructure were analysed using electron microscopy. The lipid composition was analysed by gas chromatography and a commercial kit. After cold storage, the mitochondrion was the most affected component; however, plasma membrane rupture and detachment of the flagellum were also observed. Morphological abnormalities were greater in cryopreserved spermatozoa. The head and mid-piece were dehydrated, sperm membranes were vesiculated, and alterations of mitochondria were observed. After cold storage and cryopreservation, there were less polyunsaturated and omega-3 fatty acids. Furthermore, there was an increase in saturated fatty acids and decrease in cholesterol concentration after cryopreservation (P < 0.05). Based on the results, cryopreservation drastically damaged sperm membranes; the cryogenic damage was associated with membrane lipid composition alterations. The sperm membranes were affected less by cold storage but there was also a decrease of some lipids; therefore, there is a need for improvement in cold storage processes to decrease structural damage of spermatozoa so that semen cryopreservation can be effectively used in the salmon industry.

[Recomendaciones sobre la utilización de las fórmulas infantiles con proteína aislada de soya en la alimentación del lactante. Documento de posición basado en la evidencia].

BACKGROUND: Soy infant formulas (SIF) have long been used as an alternative for infants with special nutritional requirements. However, the medical indications for their use, their allergenicity, safety and efficacy are still controversial. OBJECTIVE: To present recommendations for the use of SIF based on the existing literature. METHODS: We consulted systematic reviews and clinical practice guides, through validated search algorithms, and systems such as Appraisal of Guidelines for REsearch and Evaluation (AGREE)II and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). For the elaboration of the clinical recommendations, the most important topics were analyzed and discussed by the responsible researchers and the group of experts in the development of a position paper. The quality of the evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. RESULTS: Several reports with variable quality of evidence were found. They support SIF's efficacy in the management of cow's milk allergy and infant's digestive tolerance, as well as its low cross allergy compared to cow's milk and other formulas. We also found other studies that indicate the safety of SIFs on different nutritional, immune and developmental parameters. There is also evidence that demonstrates that SIFs have important advantages in terms of cost-benefit, palatability and effects on the intestinal microbiota, compared to other formulas. CONCLUSIONS: Although evidence to recommend its use in functional digestive disorders is limited, SIFs have an adequate safety profile and are still a valid option for infant feeding.

ANTECEDENTES: Las fórmulas a base de proteína de soya (FBPS) se han utilizado desde hace tiempo como una alternativa para lactantes con requerimientos nutricionales especiales. Sin embargo, las indicaciones médicas para su uso, su alergenicidad, seguridad y eficacia aún son controvertidas. OBJETIVO: Presentar recomendaciones del uso de FBPS basadas en la literatura existente. MÉTODOS: Se realizó la consulta de revisiones sistemáticas y guías de práctica clínica, por medio de algoritmos de búsqueda validados, y sistemas como AGREE (Appraisal of Guidelines for REsearch and Evaluation) II y PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Para la elaboración de las recomendaciones clínicas se analizaron y discutieron los tópicos de mayor importancia, por parte de los investigadores responsables y el grupo de expertos del desarrollo de un documento de posición. Se evaluó la calidad de la evidencia utilizando el sistema GRADE (Grading of Recommendations, Assessment, Development and Evaluation). RESULTADOS: Se encontraron distintos reportes con calidad de evidencia variable que sustentan la eficacia de las FBPS en el manejo de la alergia a la proteína de la leche de vaca y en la tolerancia digestiva del lactante, así como su baja alergia cruzada en comparación a la leche de vaca y otras fórmulas. También se encontraron otros estudios que indican la seguridad de las FBPS sobre distintos parámetros nutricionales, inmunitarios y de desarrollo. Existe además evidencia que demuestra que las FBPS tienen ventajas importantes en cuestión de costo-beneficio, palatabilidad y efectos sobre la microbiota intestinal, en comparación con otras fórmulas. CONCLUSIONES: Aunque existe evidencia limitada para recomendar su utilización en los trastornos digestivos funcionales, las FBPS tienen un perfil de seguridad adecuado y continúan siendo una opción válida para la alimentación del lactante.

Recomendaciones sobre la utilización de las fórmulas infantiles con proteína aislada de soya en la alimentación del lactante. Documento de posición basado en la evidencia / Recommendations on the use of infant formulas with isolated soy protein in infant feeding. Evidence-Based Position Paper

Antecedentes: Las fórmulas a base de proteína de soya (FBPS) se han utilizado desde hace tiempo como una alternativa para lactantes con requerimientos nutricionales especiales. Sin embargo, las indicaciones médicas para su uso, su alergenicidad, seguridad y eficacia aún son controvertidas. Objetivo: Presentar recomendaciones del uso de FBPS basadas en la literatura existente. Métodos: Se realizó la consulta de revisiones sistemáticas y guías de práctica clínica, por medio de algoritmos de búsqueda validados, y sistemas como AGREE (Appraisal of Guidelines for REsearch and Evaluation) II y PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Para la elaboración de las recomendaciones clínicas se analizaron y discutieron los tópicos de mayor importancia, por parte de los investigadores responsables y el grupo de expertos del desarrollo de un documento de posición. Se evaluó la calidad de la evidencia utilizando el sistema GRADE (Grading of Recommendations, Assessment, Development and Evaluation). Resultados: Se encontraron distintos reportes con calidad de evidencia variable que sustentan la eficacia de las FBPS en el manejo de la alergia a la proteína de la leche de vaca y en la tolerancia digestiva del lactante, así como su baja alergia cruzada en comparación a la leche de vaca y otras fórmulas. También se encontraron otros estudios que indican la seguridad de las FBPS sobre distintos parámetros nutricionales, inmunitarios y de desarrollo. Existe además evidencia que demuestra que las FBPS tienen ventajas importantes en cuestión de costo-beneficio, palatabilidad y efectos sobre la microbiota intestinal, en comparación con otras fórmulas. Conclusiones: Aunque existe evidencia limitada para recomendar su utilización en los trastornos digestivos funcionales, las FBPS tienen un perfil de seguridad adecuado y continúan siendo una opción válida para la alimentación del lactante.

Abstract Background: Soy infant formulas (SIF) have long been used as an alternative for infants with special nutritional requirements. However, the medical indications for their use, their allergenicity, safety and efficacy are still controversial. Objective: To present recommendations for the use of SIF based on the existing literature. Methods: We consulted systematic reviews and clinical practice guides, through validated search algorithms, and systems such as Appraisal of Guidelines for REsearch and Evaluation (AGREE)II and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). For the elaboration of the clinical recommendations, the most important topics were analyzed and discussed by the responsible researchers and the group of experts in the development of a position paper. The quality of the evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. Results: Several reports with variable quality of evidence were found. They support SIF’s efficacy in the management of cow’s milk allergy and infant’s digestive tolerance, as well as its low cross allergy compared to cow’s milk and other formulas. We also found other studies that indicate the safety of SIFs on different nutritional, immune and developmental parameters. There is also evidence that demonstrates that SIFs have important advantages in terms of cost-benefit, palatability and effects on the intestinal microbiota, compared to other formulas. Conclusions: Although evidence to recommend its use in functional digestive disorders is limited, SIFs have an adequate safety profile and are still a valid option for infant feeding.

Patagonian blenny (Eleginops maclovinus) spermatozoa quality after storage at 4 ºC in Cortland medium.

Patagonian blenny (E. maclovinus) is a marine species recently placed in captivity and which are potentially farmable. Understanding and improving its sperm capacity to withstand short-term storage conditions is a key element of initiating an artificial propagation program for this species. The aim of this study is to evaluate the ultrastructure and quality of E. maclovinus sperm during refrigerated storage. To address this objective, scanning electron microscopy (SEM), cytofluorimetric analysis (membrane integrity; reactive oxygen species generation; mitochondrial membrane potential) and cell respiration/mitochondrial-function analysis (ATP content; oxygen consumption) could be useful for optimizing or improving management for artificial reproduction of this species. Severe damage of plasma membranes was observed by SEM at day 7 and 14 of in vitro storage. Analyses of sperm quality were conducted during the 14-day cold storage period when sperm were in diluted (with Cortland solution) and undiluted conditions. When there were diluted conditions, there was greater preservation of motile capacity (from day-7; P < 0.05), membrane integrity (from day-7; P < 0.05), mitochondrial membrane potential (from day-10; P < 0.05) and ATP stores (from day-3; P < 0.05). Oxygen consumption indicators were 18.6% ±14.7% greater in the undiluted samples from day-3, and 32.1%±2.1% of the total spermatozoa had ample amounts of superoxide anion in both undiluted and diluted semen on day-0. The use of Cortland solution extended the viability of sperm when there were longer storage times. Factors that have a greater effect on the quality of semen during storage are reactive oxygen species generation and ATP depletion. In conclusion, Patagonian blenny spermatozoa can be stored at 4 °C between 7 and 10 days using Cortland solution.

Development and application of a biotic ligand model for predicting the chronic toxicity of dissolved and precipitated aluminum to aquatic organisms.

Aluminum (Al) toxicity to aquatic organisms is strongly affected by water chemistry. Toxicity-modifying factors such as pH, dissolved organic carbon (DOC), hardness, and temperature have a large impact on the bioavailability and toxicity of Al to aquatic organisms. The importance of water chemistry on the bioavailability and toxicity of Al suggests that interactions between Al and chemical constituents in exposures to aquatic organisms can affect the form and reactivity of Al, thereby altering the extent to which it interacts with biological membranes. These types of interactions have previously been observed in the toxicity data for other metals, which have been well described by the biotic ligand model (BLM) framework. In BLM applications to other metals (including cadmium, cobalt, copper, lead, nickel, silver, and zinc), these interactions have focused on dissolved metal. A review of Al toxicity data shows that concentrations of Al that cause toxicity are frequently in excess of solubility limitations. Aluminum solubility is strongly pH dependent, with a solubility minimum near pH 6 and increasing at both lower and higher pH values. For the Al BLM, the mechanistic framework has been extended to consider toxicity resulting from a combination of dissolved and precipitated Al to recognize the solubility limitation. The resulting model can effectively predict toxicity to fish, invertebrates, and algae over a wide range of conditions. Environ Toxicol Chem 2018;37:70-79. © 2017 SETAC.

Mitochondria in teleost spermatozoa.

There is an extraordinary diversity of reproductive modes in teleost and this variability is related to the phylogenetic relationships and adaption to very different biotopes. As in all vertebrates, sperm is produced as the end product of the process of spermatogenesis, and regarding teleost the spermatozoa lack an acrosome in almost all species and motility is activated as a response to osmolarity and ion content of the aquatic medium where the sperm is released. In this context, mitochondria possess a fundamental role for fish spermatozoa motility and integrity, hence, fertilizing potential; they are the energy supplier that allows flagellar movement and their dysfunction could play a main role in structural and functional damage to the spermatozoa. The ATP production through oxidative phosphorylation provides not only energy for cell activities, which includes Na+/K+ ATPase pump, endocytosis, protein synthesis and many other cell processes; but also produces reactive oxygen species, that under mitochondrial dysfunction causes oxidative stress. The assessment of mitochondrial function (e.g. through measurement of mitochondrial membrane potential) as well as ATP content (mostly supplied by mitochondrial respiration) can be useful as quality markers of fish spermatozoa. Also quantification of ROS and antioxidant status, strongly influenced by mitochondria, are used as complementary measurements. There is much information about sperm mitochondria and their function but studies of these aspects on fish reproduction are still required for applications in aquaculture. The real role of fish sperm mitochondria under short and long term storage and in vitro manipulation is not fully understood yet. Thus future research should focus on these matters.

Effect of Fe (III) on Pseudokirchneriella subcapitata at circumneutral pH in standard laboratory tests is explained by nutrient sequestration.

The complex chemistry of iron (Fe) at circumneutral pH in oxygenated waters and the poor correlation between ecotoxicity results in laboratory and natural waters have led to regulatory approaches for iron based on field studies (US Environmental Protection Agency Water Quality Criteria and European Union Water Framework Directive proposal for Fe). The results of the present study account for the observed differences between laboratory and field observations for Fe toxicity to algae (Pseudokirchneriella subcapitata). Results from standard 72-h assays with Fe at pH 6.3 and pH 8 resulted in similar toxicity values measured as algal biomass, with 50% effect concentrations (EC50) of 3.28 mg/L and 4.95 mg/L total Fe(III), respectively. At the end of the 72-h exposure, however, dissolved Fe concentrations were lower than 30 µg/L for all test concentrations, making a direct toxic effect of dissolved iron on algae unlikely. Analysis of nutrient concentrations in the artificial test media detected phosphorus depletion in a dose-dependent manner that correlated well with algal toxicity. Subsequent experiments adding excess phosphorus after Fe precipitation eliminated the toxicity. These results strongly suggest that observed Fe(III) toxicity on algae in laboratory conditions is a secondary effect of phosphorous depletion. Environ Toxicol Chem 2017;36:952-958. © 2016 SETAC.

Migration protocol to estimate metal exposure from mouthing copper and tin alloy objects.

BACKGROUND: Low blood lead levels previously thought to pose no health risks may have an adverse impact on the cognitive development of children. This concern has given rise to new regulatory restrictions upon lead metal containing products intended for child use. However few reliable experimental testing methods to estimate exposure levels from these materials are available. METHODS: The present work describes a migration test using a mimetic saliva fluid to estimate the chronic exposure of children to metals such as lead while mouthing metallic objects. The surrogate saliva medium was composed of: 150 mM NaCl, 0.16% porcine Mucin and 5 mM buffer MOPS, adjusted to pH 7.2. Alloys samples, in the form of polished metallic disc of known surface area, were subjected to an eight hours test. RESULTS: Two whitemetal alloys Sn/Pb/Sb/Cu and three brass alloys Cu/Zn/Pb were tested using the saliva migration protocol. In the case of the whitemetal alloys, first order release kinetics resulting in the release of 0.03 and 0.51 µg lead/cm2 after 8 hours of tests were observed, for lead contents of 0.05-0.07% and 5.5%, respectively. Brasses exhibited linear incremental release rates of 0.043, 0.175 and 0.243 µg lead/cm2h for lead contents of 0.1-0.2%, 1.7-2.2% and 3.1-3.5%, respectively. The linear regression analysis of lead release rates relative to Pb content in brasses yielded a slope of 0.08 µg lead/cm2h%Pb (r2 = 0.92). Lead release rates were used to estimate the mean daily mouthing exposure of a child to lead, according to age-specific estimates of mouthing time behavior. Calculated daily intakes were used as oral inputs for the IEUBK toxicokinetic model, predicting only marginal changes in blood lead levels (0.2 µg lead/dL or less) for children aged 0.5 to 1 years old exposed to either class of alloy. CONCLUSIONS: The results of this study as a whole support the use of migration data of metal ions, rather than total metal content, to estimate health risk from exposure to metals and metal alloys substances in children.

Inter-laboratory validation of bioaccessibility testing for metals.

Bioelution assays are fast, simple alternatives to in vivo testing. In this study, the intra- and inter-laboratory variability in bioaccessibility data generated by bioelution tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass alloy, and nickel sulfate hexahydrate. Standard deviations of repeatability (sr) and reproducibility (sR) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the sR:sr ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets; overall results varied more between- than within-laboratories. RSD analysis of sr showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. However, for most applications, measures of relative bioaccessibility are needed, diminishing the requirement for high inter-laboratory reproducibility in absolute metal releases. The inter-laboratory exercise suggests that the degrees of freedom within the protocol need to be addressed.