Assessing the Combined Effects of Host and Parasite Exposure to Forever Chemicals in an Amphibian-Echinostome System.

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants of growing concern due to their potential negative effects on wildlife and human health. Per- and polyfluoroalkyl substances have been shown to alter immune function in various taxa, which could influence the outcomes of host-parasite interactions. To date, studies have focused on the effects of PFAS on host susceptibility to parasites, but no studies have addressed the effects of PFAS on parasites. To address this knowledge gap, we independently manipulated exposure of larval northern leopard frogs (Rana pipiens) and parasites (flatworms) via their snail intermediate host to environmentally relevant PFAS concentrations and then conducted trials to assess host susceptibility to infection, parasite infectivity, and parasite longevity after emergence from the host. We found that PFAS exposure to only the host led to no significant change in parasite load, whereas exposure of parasites to a 10-µg/L mixture of PFAS led to a significant reduction in parasite load in hosts that were not exposed to PFAS. We found that when both host and parasite were exposed to PFAS there was no difference in parasite load. In addition, we found significant differences in parasite longevity post emergence following exposure to PFAS. Although some PFAS-exposed parasites had greater longevity, this did not necessarily translate into increased infection success, possibly because of impaired movement of the parasite. Our results indicate that exposure to PFAS can potentially impact host-parasite interactions. Environ Toxicol Chem 2024;43:1537-1546. © 2024 SETAC.

The effects of two short-chain perfluoroalkyl carboxylic acids (PFCAs) on northern leopard frog (Rana pipiens) tadpole development.

Short-chain perfluoroalkyl carboxylic acids (PFCAs) have been detected in the environment globally. The presence and persistence of these compounds in the environment may lead to chronic wildlife exposure. We used northern leopard frog (Rana pipiens) tadpoles to investigate the chronic toxicity and the bioconcentration of two short-chain PFCAs, perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA). We exposed Gosner stage 25 tadpoles to PFBA and PFHxA (as individual chemicals) at nominal concentrations of 0.1, 1, 10, 100, and 1000 µg/L for 43-46 days. Tadpoles exposed to 0.1 to 100 µg/L of PFBA and PFHxA had significantly higher mean snout-to-vent lengths, mean masses, and scaled mass indexes than control tadpoles. These results indicate that exposure to short-chain PFCAs influences tadpole growth. Further investigation into the mechanism(s) causing the observed changes in tadpole growth is warranted. We observed a significantly higher proportion of males in the PFBA 1 µg/L treatment group, however further histological analyses are required to confirm visual sex identification before making concrete conclusions on the effects of PFCAs on amphibian sex ratios. PFBA concentrations in tissues were higher than PFHxA concentrations; a pattern that contrasts with previously published studies using fish, suggesting potential differences between taxa in PFBA and PFHxA bioconcentration. Bioconcentration factors were <10 L/kg wet weight, indicating low bioconcentration potential in tadpoles. Our results suggest that PFBA and PFHxA may have effects at environmentally-relevant concentrations (0.1-10 µg/L) and further investigation is required before these compounds can be deemed a "safe" alternative to their long-chain counterparts.

Efecto del plomo y del arsénico en condiciones de laboratorio sobre la rana africana de uñas (Xenopus laevis) y la rana leopardo (Lithobates berlandieri) / Effect of lead and arsenic under laboratory conditions on African clawed frog (Xenopus laevis) and leopard frog (Lithobates berlandieri)

Actualmente, existe una creciente preocupación ya que algunas especies de anfibios han mostrado un declive en sus poblaciones por causa de diversos factores, entre ellos los metales pesados; por esta razón, es importante realizar estudios sobre esta problemática ambiental. El objetivo de este estudio fue determinar la cantidad del plomo y arsénico que se concentra en los tejidos de la rana Africana de uñas (Xenopus laevis) en etapa juvenil y de la rana Leopardo (Lithobates berlandieri) en etapa larvaria y en el agua después de 16 semanas expuestas a placas de plomo y arseniato de sodio, con la finalidad de determinar si esta acumulación de metales provoca eventualmente anomalías morfológicas en su desarrollo. Los individuos fueron puestos en contacto con placas de plomo, arseniato de sodio, agua de la red de abastecimiento de agua de consumo público (grupos experimentales) y con agua potable (grupo control). Los organismos fueron inspeccionados de manera externa para identificar anomalías macroscópicas, además de realizarles análisis morfométricos. Los análisis espectroquímicos (espectrofotometría de absorción atómica, con la técnica de horno de grafito) mostraron que hay un proceso de bioconcentración y bioacumulación de metales cuando los organismos están en contacto con estos metales y con agua de la red de abastecimiento público, la cual está contaminada también, pues se detectaron cantidades altas de metales en los tejidos de las larvas. Respecto a la morfometría hubo diferencias significativas en algunas estructuras entre el grupo control y los grupos experimentales en X. laevis. En L. berlandieri fueron detectadas anomalías macroscópicas como curvatura de la cola, problemas de pigmentación, protuberancias en el abdomen e inadecuada posición de los intestinos en aquellos individuos que estuvieron en contacto con estos metales pesados. (AU)

Currently, there is growing concern as some amphibian species have shown a decline in their populations due to various factors, including heavy metals; for this reason, it is important to carry out studies on this environmental problem. The objective of this study was to determine the amount of lead and arsenic concentrated in the tissues of the African clawed frog (Xenopus laevis) in the juvenile stage and the Leopard frog (Lithobates berlandieri) in the larval stage and in the water after 16 weeks exposed to lead plates and sodium arsenate, in order to determine if this accumulation of metals eventually causes morphological abnormalities in their development. The individuals were placed in contact with lead plates, sodium arsenate, water from the public water supply network (experimental groups) and with drinking water (control group). The organisms were externally inspected to identify macroscopic anomalies, in addition to performing morphometric analysis. The spectrochemical analyzes (atomic absorption spectrophotometry, with the graphite furnace technique) showed that there is a process of bioconcentration and bioaccumulation of metals when the organisms are in contact with these metals and with water from the public supply network, which is also contaminated, since high amounts of metals were detected in the tissues of the larvae. Regarding morphometry, there were significant differences in some structures between the control group and the experimental groups in X. laevis. In L. berlandieri, macroscopic abnormalities such as curvature of the tail, pigmentation problems, protuberances in the abdomen and inappropriate position of the intestines were detected in those individuals that were in contact with these heavy metals. (AU)

Some current challenges in research on air pollution and health / Desafíos actuales de la investigación sobre contaminación del aire y salud

This commentary addresses some of the diverse questions of current interest with regard to the health effects of air pollution, including exposure-response relationships, toxicity of inhaled particles and risks to health, multipollutant mixtures, traffic-related pollution, accountability research, and issues with susceptibility and vulnerability. It considers the challenges posed to researchers as they attempt to provide useful evidence for policy-makers relevant to these issues. This commentary accompanies papers giving the results from the ESCALA project, a multi-city study in Latin America that has an overall goal of providing policy-relevant results. While progress has been made in improving air quality, driven by epidemiological evidence that air pollution is adversely affecting public health, the research questions have become more subtle and challenging as levels of air pollution dropped. More research is still needed, but also novel methods and approaches to address these new questions.

Este comentario aborda algunos de los temas de interés actual en relación con los efectos de la contaminación del aire sobre la salud, tales como las relaciones exposición-respuesta, la toxicidad y riesgos para la salud de las partículas inhaladas, las mezclas de contaminantes múltiples, la contaminación relacionada con el tráfico, la investigación sobre responsabilidad, y los problemas de susceptibilidad y vulnerabilidad. Considera los retos que se presentan a los investigadores que intentan proporcionar evidencia para los responsables políticos en estas cuestiones. Este texto acompaña otros trabajos con resultados del proyecto ESCALA, un estudio en varias ciudades de América Latina que tiene como objetivo general proporcionar resultados relevantes para la política pública. Aunque ha habido avances para mejorar la calidad del aire, gracias a la evidencia epidemiológica de que la contaminación aérea está afectando negativamente a la salud pública, las preguntas de investigación se han vuelto más sutiles y difíciles a medida que los niveles de contaminación se reducen. Se necesita más investigación, pero también nuevos métodos y enfoques capaces de enfrentar estas preguntas.

The internal horizontal cell of the frog: spatial summation

En la Rana pipiens se estudiaron las propiedades del campo receptivo de las células horizontales internas (CHI). Se determinó la constante de espacio de cada célula usando puntos luminosos de diferentes tamaños o moviendo una abertura luminosa rectangular a lo largo de la retina. Con el primer método, la constante varió entre 100 - 500 um y con el segundo, entre 100 - 720 um. Se describió un rango de valores similar en el Xenopus, aunque sus SHI son más grandes que las de la Rana. Aparentemente, el acoplamiento entre las CHI es más eficiente en la retina de la Rana que en aquellá del Xenopus. El amplio rango de los valores sugiere que entre las células de la misma retina hay una variación importante en la eficiencia del acoplamiento (AU)

The internal horizontal cell of the frog: spatial summation

En la Rana pipiens se estudiaron las propiedades del campo receptivo de las células horizontales internas (CHI). Se determinó la constante de espacio de cada célula usando puntos luminosos de diferentes tamaños o moviendo una abertura luminosa rectangular a lo largo de la retina. Con el primer método, la constante varió entre 100 - 500 um y con el segundo, entre 100 - 720 um. Se describió un rango de valores similar en el Xenopus, aunque sus SHI son más grandes que las de la Rana. Aparentemente, el acoplamiento entre las CHI es más eficiente en la retina de la Rana que en aquellá del Xenopus. El amplio rango de los valores sugiere que entre las células de la misma retina hay una variación importante en la eficiencia del acoplamiento

Structure-activity relationship of reversible cholinesterase inhibitors: activation, channel blockade and stereospeceficity of the nicotinic acetylcholine receptor-ion channel complex

We have shown that alt cholinesterase (ChE) inhibitors, in addition to their well-known anti-ChE activity, have multiple effects on the nicotinic acetylcholine receptor-ion channel (AChR) macromolecule resulting from interactions with the agonist recognition site and with sites located at the ion channel component. Activation, competitive antagonism and different types of noncompetitive blockade occurring at similar concentration ranges and contributing in different proportions result in complex and somewhat unpredictable alterations inn AChR function. The question is now raised as to how each effect of these compounds contributes to their antidotal property against organophosphorus (OP) poisoning, and what set of actions makes one reversible ChE inhibitor a better antidote. Many lines of evidence support the importance of direct interactions with various sites on the AChR: 1) morphological and toxicological studies with (+) physostigmine showed that anti-ChE activity is not essential to protect animals against toxicity by irreversible ChE inhibitors; 2) (-) physostigmine is far more effective against OP poisoning; 3) open channel blockers such as mecamylamine with no significant anti-ChE activity enhance the protective action of (-) physostigmine; 4) neostigmine, pyridostigmine, (-) physostigmine and (+) physostigmine showed qualitatively and quantitatively distinct toxicity and damage to endplate morphology and function. In prophylaxis and during the very early phase of OP poisoning, carbamates, especially (-) physostigmine combined with mecamylamine and atropine, could protect almost 100% of the animals exposed to multiple lethal doses of OPs...