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Chemosphere Aug 2024Ciprofloxacin (CIP) and levofloxacin (LEV) are broad-spectrum antibiotics with potent antibacterial activity. Although many studies have shown that antibiotics can lead...
Ciprofloxacin (CIP) and levofloxacin (LEV) are broad-spectrum antibiotics with potent antibacterial activity. Although many studies have shown that antibiotics can lead to gut microbiota disruption, the effects of CIP and LEV on gut microbial colonization at the embryonic stage remain poorly characterized. Here, we evaluated the response of Bufo gargarizans embryos in terms of gut microbiota colonization, growth and developmental stages to CIP and LEV exposure. Embryos treated with 100 μg/L CIP and LEV exhibited significantly reduced diversity and richness of the gut microbiota, as well as altered community structure. Both CIP and LEV treatments resulted in an increase in the pathogenic bacteria Bosea and Aeromonas, and they appeared to be more resistant to CIP than LEV. Additionally, CIP exposure caused reduced total length and delayed the development in B. gargarizans embryos, while LEV increased the total length and promoted embryonic development. The present study revealed the adverse effects of CIP and LEV exposure on host gut microbiota, growth and development during the embryonic stage, and contributed new perspectives to the evaluation of early aquatic ecological risk under CIP and LEV exposure.
Topics: Ciprofloxacin; Gastrointestinal Microbiome; Animals; Levofloxacin; Anti-Bacterial Agents; Bufonidae; Water Pollutants, Chemical; Embryo, Nonmammalian; Bacteria
PubMed: 38871193
DOI: 10.1016/j.chemosphere.2024.142587 -
PeerJ 2024Amphibians are experiencing declines globally, with emerging infectious diseases as one of the main causes. Haematological parameters present a useful method for...
Amphibians are experiencing declines globally, with emerging infectious diseases as one of the main causes. Haematological parameters present a useful method for determining the health status of animals and the effects of particular diseases, but the interpretation of differential cell counts relies on knowing the normal ranges for the species and factors that can affect these counts. However, there is very little data on either normal haematological parameters or guides for blood cell types for free-ranging frog species across the world. This study aims to 1) create a visual guide for three different Australian frog species: , , and , 2) determine the proportions of erythrocytes to leukocytes and 3) differential leukocytes within blood smears from these three species and 4) assess the association between parasites and differential counts. We collected blood samples from free-ranging frogs and analysed blood smears. We also looked for ectoparasites and tested for the fungal disease chytridiomycosis. Overall, we found that the differentials of erythrocytes to leukocytes were not affected by species, but the proportions of different leukocytes did vary across species. For example, while lymphocytes were the most common type of leukocyte across the three species, eosinophils were relatively common in but rarely present in the other two species. We noted chytridiomycosis infection as well as ectoparasites present in some individuals but found no effect of parasites on blood parameters. Our results add baseline haematological parameters for three Australian frog species and provide an example of how different frog species can vary in their differential blood cell counts. More information is needed on frog haematological data before these parameters can be used to determine the health status of wild or captive frogs.
Topics: Animals; Anura; Australia; Reference Values; Erythrocytes; Blood Cell Count; Hematologic Tests; Species Specificity; Leukocyte Count; Male
PubMed: 38860213
DOI: 10.7717/peerj.17406 -
Methods in Molecular Biology (Clifton,... 2024Ion channels comprise one of the largest targets for drug development and treatment and have been a subject of enduring fascination since first discovered in the 1950s....
Ion channels comprise one of the largest targets for drug development and treatment and have been a subject of enduring fascination since first discovered in the 1950s. Over the past decades, thousands of publications have explored the cellular biology and molecular physiology of these proteins, and many channel structures have been determined since the late 1990s. Trying to connect the dots between ion channel function and structure, voltage clamp fluorometry (VCF) emerges as a powerful tool because it allows monitoring of the conformational rearrangements underlying the different functional states of the channel. This technique represents an elegant harmonization of molecular biology, electrophysiology, and fluorescence. In the following chapter, we will provide a concise guide to performing VCF on Xenopus laevis oocytes using the two-electrode voltage clamp (TEVC) modality. This is the most widely used configuration on Xenopus oocytes for its relative simplicity and demonstrated success in a number of different ion channels utilizing a variety of attached labels.
Topics: Animals; Patch-Clamp Techniques; Fluorometry; Xenopus laevis; Oocytes; Ion Channels; Ion Channel Gating
PubMed: 38856899
DOI: 10.1007/978-1-0716-3818-7_8 -
Journal of Thermal Biology May 2024When amphibians thermoregulate, they face a fundamental trade-off between the ability to maintain activity and an increased rate of dehydration at higher temperatures....
When amphibians thermoregulate, they face a fundamental trade-off between the ability to maintain activity and an increased rate of dehydration at higher temperatures. Canopy coverage affects both the thermal and hydric conditions of the environment and can therefore influence amphibian thermoregulation. Frogs require proper conditions to thermoregulate to successfully grow, survive, and reproduce. But while we know how canopy and environmental variables typically affect operative temperature, less is known about effects on amphibian water loss rates. In this study, we measure the effect of canopy coverage on the conditions available for thermoregulation at a breeding pond of the California red-legged frog, Rana draytonii. We use agar frog models to estimate the thermal and hydric capacities frogs would experience in locations with different canopy coverage and microhabitats. At each site, we deployed models under four microhabitat treatments: wet/sun, wet/shade, dry/sun, and dry/shade. We modeled how environmental variables affected operative temperature and evaporative water loss from agar frogs. We found positive effects of air temperature, the sun treatment, and reduced canopy cover on operative temperature, and negative direct or indirect effects of these variables on evaporative water loss, consistent with the hypothesized trade-off between thermoregulatory behavior to increase temperature and the increased desiccation risk due to higher water loss. Additionally, our results indicate that the availability of wet microhabitats can allow frogs to reduce water loss, potentially mitigating the risk of desiccation when thermoregulating to achieve higher operative temperatures. Our findings suggest, that with access to proper microhabitats, amphibians can mitigate the fundamental trade-off and receive benefits of thermoregulating at high temperatures.
Topics: Animals; Body Temperature Regulation; Ecosystem; Ranidae; Water Loss, Insensible; Temperature; Models, Biological
PubMed: 38852487
DOI: 10.1016/j.jtherbio.2024.103864 -
The Science of the Total Environment Sep 2024Bile acids (BAs) are amphipathic steroid acids whose production and diversity depend on both host and microbial metabolism. Nitrate (NO) is a widespread pollutant in...
Bile acids (BAs) are amphipathic steroid acids whose production and diversity depend on both host and microbial metabolism. Nitrate (NO) is a widespread pollutant in aquatic ecosystems, which can cause rapid changes in microbial community structure and function. However, the effect of gut microbiota reshaped by nitrate‑nitrogen (NO-N) on BAs profiles remains unclarified. To test this, intestinal targeted BAs metabolomics and fecal metagenomic sequencing were performed on Bufo gargarizans tadpoles treated with different concentrations of NO-N. NO-N exposure induced a reduction in the abundance of microbiota with bile acid-inducible enzymes (BAIs) and/or hydroxysteroid dehydrogenases (HSDHs), thus inhibiting the conversion of primary BAs to secondary BAs. Inhibition of BAs biotransformation decreased protective hydrophilic BAs (UDCA) and increased toxic hydrophobic BAs (CA and CDCA), which may contribute to intestinal histopathological damage. Moreover, we found that NO-N treatment increased microbial virulence factors and decreased Glycoside hydrolases, further highlighting the deleterious risk of NO-N. Overall, this study shed light on the complex interactions of NO-N, gut microbiota, and BAs, and emphasized the hazardous effects of NO-N pollution on the health of amphibians.
Topics: Animals; Gastrointestinal Microbiome; Larva; Nitrates; Water Pollutants, Chemical; Bile Acids and Salts; Bufonidae; Intestines
PubMed: 38851338
DOI: 10.1016/j.scitotenv.2024.173795 -
Environmental Toxicology and Chemistry Jul 2024Amphibians are the most threatened vertebrate class globally. Multiple factors have been implicated in their global decline, and it has been hypothesized that...
Amphibians are the most threatened vertebrate class globally. Multiple factors have been implicated in their global decline, and it has been hypothesized that interactions between stressors may be a major cause. Increased ultraviolet (UV) radiation, as a result of ozone depletion, has been identified as one such stressor. Exposure to UV radiation has been shown to have detrimental effects on amphibians and can exacerbate the effects of other stressors, such as chemical pollutants. Chemical pollution has likewise been recognized as a major factor contributing to amphibian declines, particularly, endocrine-disrupting chemicals. In this regard, 17β-trenbolone is a potent anabolic steroid used in the agricultural industry to increase muscle mass in cattle and has been repeatedly detected in the environment where amphibians live and breed. At high concentrations, 17β-trenbolone has been shown to impact amphibian survival and gonadal development. In the present study, we investigated the effects of environmentally realistic UV radiation and 17β-trenbolone exposure, both in isolation and in combination, on the morphology and behavior of tadpoles (Limnodynastes tasmaniensis). We found that neither stressor in isolation affected tadpoles, nor did we find any interactive effects. The results from our 17β-trenbolone treatment are consistent with recent research suggesting that, at environmentally realistic concentrations, tadpoles may be less vulnerable to this pollutant compared to other vertebrate classes. The absence of UV radiation-induced effects found in the present study could be due to species-specific variation in susceptibility, as well as the dosage utilized. We suggest that future research should incorporate long-term studies with multiple stressors to accurately identify the threats to, and subsequent consequences for, amphibians under natural conditions. Environ Toxicol Chem 2024;43:1615-1626. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
Topics: Animals; Ultraviolet Rays; Larva; Water Pollutants, Chemical; Trenbolone Acetate; Anura; Behavior, Animal
PubMed: 38837484
DOI: 10.1002/etc.5895 -
Revista Brasileira de Parasitologia... 2024The aim of this study was to record Centrorhynchus sp. associated with the exotic species Aquarana catesbeiana (bullfrog) in southern Brazil and to present a checklist...
The aim of this study was to record Centrorhynchus sp. associated with the exotic species Aquarana catesbeiana (bullfrog) in southern Brazil and to present a checklist of vertebrate hosts in South America. Twenty-nine adults and juveniles of A. catesbeiana were collected in Capão do Leão, state of Rio Grande do Sul, Brazil, between October 2019 and December 2020. We found 275 specimens of Centrorhynchus sp. cystacanths in the stomach musculature and coelomic cavity of 55.1% of hosts (16). There was no significant differences in the prevalence and mean intensity of infection with cystacanths when compared males and females of A. catesbeiana. The prevalence was significantly higher in adults than in juveniles. The checklist presents 106 species of vertebrate hosts and 14 taxa of Centrorhynchus recorded in nine South American countries. Avian were the main definitive hosts of Centrorhynchus spp. and snakes Dipsadidae, anurans Hylidae and Leptodactylidae the main paratenic hosts in South America. This is the first record of Centrorhynchus cystacanths in A. catesbeiana in the South America. The study provides tools to help understand the parasitic relationships between species of Centrorhynchus and A. catesbeiana and other hosts in areas where bullfrog have been introduced.
Topics: Animals; Anura; Female; Male; Checklist; Brazil; Acanthocephala; South America; Prevalence; Helminthiasis, Animal; Vertebrates; Birds; Snakes
PubMed: 38836808
DOI: 10.1590/S1984-29612024024 -
Frontiers in Cellular and Infection... 2024The rabies virus enters the nervous system by interacting with several molecular targets on host cells to modify behavior and trigger receptor-mediated endocytosis of...
The rabies virus enters the nervous system by interacting with several molecular targets on host cells to modify behavior and trigger receptor-mediated endocytosis of the virion by poorly understood mechanisms. The rabies virus glycoprotein (RVG) interacts with the muscle acetylcholine receptor and the neuronal α4β2 subtype of the nicotinic acetylcholine receptor (nAChR) family by the putative neurotoxin-like motif. Given that the neurotoxin-like motif is highly homologous to the α7 nAChR subtype selective snake toxin α-bungarotoxin (αBTX), other nAChR subtypes are likely involved. The purpose of this study is to determine the activity of the RVG neurotoxin-like motif on nAChR subtypes that are expressed in brain regions involved in rabid animal behavior. nAChRs were expressed in oocytes, and two-electrode voltage clamp electrophysiology was used to collect concentration-response data to measure the functional effects. The RVG peptide preferentially and completely inhibits α7 nAChR ACh-induced currents by a competitive antagonist mechanism. Tested heteromeric nAChRs are also inhibited, but to a lesser extent than the α7 subtype. Residues of the RVG peptide with high sequence homology to αBTX and other neurotoxins were substituted with alanine. Altered RVG neurotoxin-like peptides showed that residues phenylalanine 192, arginine 196, and arginine 199 are important determinants of RVG peptide apparent potency on α7 nAChRs, while serine 195 is not. The evaluation of the rabies ectodomain reaffirmed the observations made with the RVG peptide, illustrating a significant inhibitory impact on α7 nAChR with potency in the nanomolar range. In a mammalian cell culture model of neurons, we confirm that the RVG peptide binds preferentially to cells expressing the α7 nAChR. Defining the activity of the RVG peptide on nAChRs expands our understanding of basic mechanisms in host-pathogen interactions that result in neurological disorders.
Topics: alpha7 Nicotinic Acetylcholine Receptor; Animals; Rabies virus; Humans; Xenopus laevis; Glycoproteins; Oocytes; Viral Proteins; Viral Envelope Proteins; Host-Pathogen Interactions; Protein Binding; Rabies; Acetylcholine; Neurotoxins
PubMed: 38836054
DOI: 10.3389/fcimb.2024.1394713 -
The Journal of General Physiology Jul 2024Voltage-gated ion channels are responsible for the electrical excitability of neurons and cardiomyocytes. Thus, they are obvious targets for pharmaceuticals aimed to...
Voltage-gated ion channels are responsible for the electrical excitability of neurons and cardiomyocytes. Thus, they are obvious targets for pharmaceuticals aimed to modulate excitability. Compounds activating voltage-gated potassium (KV) channels are expected to reduce excitability. To search for new KV-channel activators, we performed a high-throughput screen of 10,000 compounds on a specially designed Shaker KV channel. Here, we report on a large family of channel-activating compounds with a carboxyl (COOH) group as the common motif. The most potent COOH activators are lipophilic (4 < LogP <7) and are suggested to bind at the interface between the lipid bilayer and the channel's positively charged voltage sensor. The negatively charged form of the COOH-group compounds is suggested to open the channel by electrostatically pulling the voltage sensor to an activated state. Several of the COOH-group compounds also activate the therapeutically important KV7.2/7.3 channel and can thus potentially be developed into antiseizure drugs. The COOH-group compounds identified in this study are suggested to act via the same site and mechanism of action as previously studied COOH-group compounds, such as polyunsaturated fatty acids and resin acids, but distinct from sites for several other types of potassium channel-activating compounds.
Topics: Animals; Ion Channel Gating; Shaker Superfamily of Potassium Channels; KCNQ2 Potassium Channel; Potassium Channels, Voltage-Gated; KCNQ3 Potassium Channel; Humans; Xenopus laevis
PubMed: 38832889
DOI: 10.1085/jgp.202313516 -
Disease Models & Mechanisms May 2024Recent progress in human disease genetics is leading to rapid advances in understanding pathobiological mechanisms. However, the sheer number of risk-conveying genetic... (Review)
Review
Recent progress in human disease genetics is leading to rapid advances in understanding pathobiological mechanisms. However, the sheer number of risk-conveying genetic variants being identified demands in vivo model systems that are amenable to functional analyses at scale. Here we provide a practical guide for using the diploid frog species Xenopus tropicalis to study many genes and variants to uncover conserved mechanisms of pathobiology relevant to human disease. We discuss key considerations in modelling human genetic disorders: genetic architecture, conservation, phenotyping strategy and rigour, as well as more complex topics, such as penetrance, expressivity, sex differences and current challenges in the field. As the patient-driven gene discovery field expands significantly, the cost-effective, rapid and higher throughput nature of Xenopus make it an essential member of the model organism armamentarium for understanding gene function in development and in relation to disease.
Topics: Animals; Xenopus; Humans; Disease Models, Animal; Genetic Diseases, Inborn; Phenotype
PubMed: 38832520
DOI: 10.1242/dmm.050754