-
Microscopy Research and Technique Jun 2024Unlike mammals, species such as fish and amphibians can regenerate damaged spinal cords, offering insights into potential therapeutic targets. This study investigates...
Unlike mammals, species such as fish and amphibians can regenerate damaged spinal cords, offering insights into potential therapeutic targets. This study investigates the structural features of the molly fish spinal cord through light and electron microscopy. The most notable characteristic was the presence of Mauthner cells (M-cells), which exhibited large cell bodies and processes, as well as synaptic connections with astrocytes. These astrocytic connections contained synaptic vesicles, suggesting electrical transmission at the M-cell endings. Astrocytes, which were labeled with glial fibrillary acidic protein (GFAP), contained cytoplasmic glycogen granules, potentially serving as an emergency fuel source. Two types of oligodendrocytes were identified: a small, dark cell and a larger, lighter cell, both of which reacted strongly with oligodendrocyte transcription factor 2 (Olig2). The dark oligodendrocyte resembled human oligodendrocyte precursors, while the light oligodendrocyte was similar to mature human oligodendrocytes. Additionally, proliferative neurons in the substantia grisea centralis expressed myostatin, Nrf2, and Sox9. Collectively, these findings suggest that the molly fish spinal cord has advanced structural features conducive to spinal cord regeneration and could serve as an excellent model for studying central nervous system regeneration. Further studies on the functional aspects of the molly fish spinal cord are recommended. RESEARCH HIGHLIGHTS: Mauthner cells (M-cell), with their typical large cell body and processes, were the most characteristic feature in Molly fish spinal cord, where it presented synaptic connections with astrocytes and their ends contained synaptic vesicles indicating an electrical transmission in the M-cells endings. Two types of oligodendrocytes could be recognized; both reacted intensely with Oligodendrocyte transcription factor 2 (Olig2). The proliferative neurons of the substantia grisea centralis expressed myostatin, Nrf2, and Sox9. The findings of this study suggest that molly fish possess highly developed structural features conducive to spinal cord regeneration. Consequently, they could be deemed an exemplary model for investigating central nervous system regeneration.
PubMed: 38923674
DOI: 10.1002/jemt.24633 -
Molecular Ecology Jun 2024A common goal in evolutionary biology is to discern the mechanisms that produce the astounding diversity of morphologies seen across the tree of life. Aposematic...
A common goal in evolutionary biology is to discern the mechanisms that produce the astounding diversity of morphologies seen across the tree of life. Aposematic species, those with a conspicuous phenotype coupled with some form of defence, are excellent models to understand the link between vivid colour pattern variations, the natural selection shaping it, and the underlying genetic mechanisms underpinning this variation. Mimicry systems in which species share a conspicuous phenotype can provide an even better model for understanding the mechanisms of colour production in aposematic species, especially if comimics have divergent evolutionary histories. Here we investigate the genetic mechanisms by which mimicry is produced in poison frogs. We assembled a 6.02-Gbp genome with a contig N50 of 310 Kbp, a scaffold N50 of 390 Kbp and 85% of expected tetrapod genes. We leveraged this genome to conduct gene expression analyses throughout development of four colour morphs of Ranitomeya imitator and two colour morphs from both R. fantastica and R. variabilis which R. imitator mimics. We identified a large number of pigmentation and patterning genes differentially expressed throughout development, many of them related to melanophores/melanin, iridophore development and guanine synthesis. We also identify the pteridine synthesis pathway (including genes such as qdpr and xdh) as a key driver of the variation in colour between morphs of these species, and identify several plausible candidates for colouration in vertebrates (e.g. cd36, ep-cadherin and perlwapin). Finally, we hypothesise that keratin genes (e.g. krt8) are important for producing different structural colours within these frogs.
PubMed: 38923007
DOI: 10.1111/mec.17438 -
Brazilian Journal of Biology = Revista... 2024Many anuran amphibians deposit their eggs in foam nests, biostructures that help protect the eggs and tadpoles from predators. Currently, there are no other...
Many anuran amphibians deposit their eggs in foam nests, biostructures that help protect the eggs and tadpoles from predators. Currently, there are no other identification and description studies of the cultivable microbiota role in the nests of the Leptodactylid frogs such as Physalaemus cuvieri, Leptodactylus vastus and Adenomera hylaedactyla. This study aimed to isolate and identify the culturable bacteria from these three anuran species' nests, as well as to prospect enzymes produced by this microbiota. Foam nests samples and environmental samples were diluted and viable cell count was determined. Bacterial morphotypes from foam nest samples were isolated through spread plate technique. Isolates' DNAs were extracted followed by rRNA 16S gene amplification and Sanger sequencing. To evaluate their enzymatic potential, the isolates were cultured in ATGE medium supplemented with starch (0.1% w/v), gelatin (3% w/v) and skimmed milk (1% w/v), to verify amylase and protease activity. A total of 183 bacterial morphotypes were isolated, comprising 33 bacterial genera. Proteobacteria phylum was the most abundant in all the three nests (79%). The genera Pseudomonas and Aeromonas were the most abundant taxon in P. cuvieri and L. vastus. In A. Hylaedactyla, were Enterobacter and Bacillus. Regarding enzymatic activities, 130 isolates displayed protease activity and 45 isolates were positive for amylase activity. Our results provide unprecedented information concerning culturable bacterial microbiota of the foam nests of the Leptodactylid frogs, as well as their potential for biomolecules of biotechnological interest.
Topics: Animals; Anura; Bacteria; RNA, Ribosomal, 16S; Nesting Behavior; Microbiota; DNA, Bacterial
PubMed: 38922194
DOI: 10.1590/1519-6984.280884 -
Toxins Jun 2024Studies on the interaction sites of peptide toxins and ion channels typically involve site-directed mutations in toxins. However, natural mutant toxins exist among them,... (Comparative Study)
Comparative Study
Studies on the interaction sites of peptide toxins and ion channels typically involve site-directed mutations in toxins. However, natural mutant toxins exist among them, offering insights into how the evolutionary process has conserved crucial sequences for activities and molecular target selection. In this study, we present a comparative investigation using electrophysiological approaches and computational analysis between two alpha toxins from evolutionarily close scorpion species of the genus , namely, Tst3 and Ts3 from and , respectively. These toxins exhibit three natural substitutions near the C-terminal region, which is directly involved in the interaction between alpha toxins and Nav channels. Additionally, we characterized the activity of the Tst3 toxin on Nav1.1-Nav1.7 channels. The three natural changes between the toxins did not alter sensitivity to Nav1.4, maintaining similar intensities regarding their ability to alter opening probabilities, delay fast inactivation, and induce persistent currents. Computational analysis demonstrated a preference for the down conformation of VSD4 and a shift in the conformational equilibrium towards this state. This illustrates that the sequence of these toxins retained the necessary information, even with alterations in the interaction site region. Through electrophysiological and computational analyses, screening of the Tst3 toxin on sodium isoform revealed its classification as a classic α-NaTx with a broad spectrum of activity. It effectively delays fast inactivation across all tested isoforms. Structural analysis of molecular energetics at the interface of the VSD4-Tst3 complex further confirmed this effect.
Topics: Scorpion Venoms; Animals; Scorpions; Brazil; Humans; Xenopus laevis; Ion Channel Gating; Amino Acid Sequence; Animals, Poisonous
PubMed: 38922152
DOI: 10.3390/toxins16060257 -
MedComm Jul 2024Overexposure to ultraviolet light (UV) has become a major dermatological problem since the intensity of ultraviolet radiation is increasing. As an adaption to outside...
Overexposure to ultraviolet light (UV) has become a major dermatological problem since the intensity of ultraviolet radiation is increasing. As an adaption to outside environments, amphibians gained an excellent peptide-based defense system in their naked skin from secular evolution. Here, we first determined the adaptation and resistance of the dark-spotted frogs ) to constant ultraviolet B (UVB) exposure. Subsequently, peptidomics of frog skin identified a series of novel peptides in response to UVB. These UV-induced frog skin peptides (UIFSPs) conferred significant protection against UVB-induced death and senescence in skin cells. Moreover, the protective effects of UIFSPs were boosted by coupling with the transcription trans-activating (TAT) protein transduction domain. In vivo, TAT-conjugated UIFSPs mitigated skin photodamage and accelerated wound healing. Transcriptomic profiling revealed that multiple pathways were modulated by TAT-conjugated UIFSPs, including small GTPase/Ras signaling and MAPK signaling. Importantly, pharmacological activation of MAPK kinases counteracted UIFSP-induced decrease in cell death after UVB exposure. Taken together, our findings provide evidence for the potential preventive and therapeutic significance of UIFSPs in UV-induced skin damage by antagonizing MAPK signaling pathways. In addition, these results suggest a practicable alternative in which potential therapeutic agents can be mined from organisms with a fascinating ability to adapt.
PubMed: 38919335
DOI: 10.1002/mco2.625 -
Microbiology Spectrum Jun 2024The coccidian parasite is the causative agent for foodborne outbreaks of cyclosporiasis disease and multiple annual fresh produce recalls. The aim of this study was to...
UNLABELLED
The coccidian parasite is the causative agent for foodborne outbreaks of cyclosporiasis disease and multiple annual fresh produce recalls. The aim of this study was to identify potential cross-reacting species for the 18S rRNA and MIT1C gene target real-time quantitative polymerase chain reaction (qPCR) assays. The environmental samples evaluated were irrigation pond water, produce wash water, and wastewater treatment sludge from a previous study with qPCR detections of by the 18S rRNA gene target qPCR. From these samples, longer regions of the 18S rRNA gene and the mitochondrial cytochrome c oxidase subunit III gene () were sequenced. Of 65 irrigation pond water samples with positive test results using the 18S rRNA gene qPCR assay, none had MIT1C qPCR assay detections or sequences that clustered with based on sequencing of the and 18S rRNA gene. Sequences from these samples clustered around coccidia sequences found in bird, fish, reptile, and amphibian hosts. Of 26 sludge samples showing detections by either qPCR assay, 14 (54%) could be confirmed as containing by sequencing of and 18S rRNA gene regions. In three of the remaining sludge samples, sequenced reads clustered with coccidia from rodents. This study demonstrated that caution should be taken when interpreting qPCR detection data in environmental samples and sequencing steps will likely be needed for confirmation.
IMPORTANCE
Fresh produce is a leading transmission source in cyclosporiasis outbreaks. It is therefore essential to understand the role that produce-growing environments play in the spread of this disease. To accomplish this, sensitive and specific tests for environmental and irrigation waters must be developed. Potential cross-reactions of real-time quantitative polymerase chain reaction (qPCR) assays have been identified, hindering the ability to accurately identify this parasite in the environment. Amplicon sequencing of the cox3 and 18S rRNA genes revealed that all irrigation pond water and two sludge samples that initially detected by qPCR were most likely cross-reactions with related coccidian organisms shed from birds, fish, reptiles, amphibians, and rodents. These results support that a single testing method for environmental samples is likely not adequate for sensitive and specific detection of .
PubMed: 38916361
DOI: 10.1128/spectrum.00906-24 -
The Journal of Experimental Biology Oct 2024Amphibians are a classical object for physiological studies, and they are of great value for developmental studies owing to their transition from an aquatic larval form...
Amphibians are a classical object for physiological studies, and they are of great value for developmental studies owing to their transition from an aquatic larval form to an adult form with a terrestrial lifestyle. Axolotls (Ambystoma mexicanum) are of special interest for such studies because of their neoteny and facultative pedomorphosis, as in these animals, metamorphosis can be induced and fully controlled in laboratory conditions. It has been suggested that their metamorphosis, associated with gross anatomical changes in the heart, also involves physiological and electrical remodeling of the myocardium. We used whole-cell patch clamp to investigate possible changes caused by metamorphosis in electrical activity and major ionic currents in cardiomyocytes isolated from paedomorphic and metamorphic axolotls. T4-induced metamorphosis caused shortening of atrial and ventricular action potentials (APs), with no changes in resting membrane potential or maximum velocity of AP upstroke, favoring higher heart rate possible in metamorphic animals. Potential-dependent potassium currents in axolotl myocardium were represented by delayed rectifier currents IKr and IKs, and upregulation of IKs caused by metamorphosis probably underlies AP shortening. Metamorphosis was associated with downregulation of inward rectifier current IK1, probably serving to increase the excitability of myocardium in metamorphic animals. Metamorphosis also led to a slight increase in fast sodium current INa with no changes in its steady-state kinetics and to a significant upregulation of ICa in both atrial and ventricular cells, indicating stronger Ca2+ influx for higher cardiac contractility in metamorphic salamanders. Taken together, these changes serve to increase cardiac reserve in metamorphic animals.
Topics: Animals; Metamorphosis, Biological; Ambystoma mexicanum; Myocytes, Cardiac; Action Potentials; Patch-Clamp Techniques; Heart; Myocardium
PubMed: 38916053
DOI: 10.1242/jeb.247712 -
PeerJ 2024The Jambato Harlequin toad (), a formerly abundant species in the Andes of Ecuador, faced a dramatic population decline in the 1980s, with its last recorded sighting in...
The Jambato Harlequin toad (), a formerly abundant species in the Andes of Ecuador, faced a dramatic population decline in the 1980s, with its last recorded sighting in 1988. The species was considered Extinct by the IUCN until 2016, when a fortuitous discovery of one Jambato by a local boy reignited hope. In this study, we present findings from an investigation conducted in the Angamarca parish, focusing on distribution, abundance, habitat preferences, ecology, disease susceptibility, and dietary habits of the species. In one year we identified 71 individuals at different stages of development in various habitats, with a significant presence in agricultural mosaic areas and locations near water sources used for crop irrigation, demonstrating the persistence of the species in a complex landscape, with considerable human intervention. The dietary analysis based on fecal samples indicated a diverse prey selection, primarily comprising arthropods such as Acari, Coleoptera, and ants. Amphibian declines have been associated with diseases and climate change; notably, our study confirmed the presence of the pathogen (), but, surprisingly, none of the infected Jambatos displayed visible signs of illness. When analyzing climatic patterns, we found that there are climatic differences between historical localities and Angamarca; the temporal analysis also exposes a generalized warming trend. Finally, in collaboration with the local community, we developed a series of management recommendations for terrestrial and aquatic environments occupied by the Jambato.
Topics: Animals; Ecuador; Bufonidae; Ecosystem; Batrachochytrium; Conservation of Natural Resources
PubMed: 38915382
DOI: 10.7717/peerj.17344 -
Chemosphere Jun 2024Carbon nanomaterials rarely exist in isolation in the natural environment, and their combined effects cannot be ignored. Multi-walled carbon nanotubes (MWCNTs) have...
Carbon nanomaterials rarely exist in isolation in the natural environment, and their combined effects cannot be ignored. Multi-walled carbon nanotubes (MWCNTs) have shown tremendous potential applications in diverse fields, including pollution remediation, biomedicine, energy, and smart agriculture. However, the combined toxicities of MWCNTs and pesticides on non-target organisms, particularly amphibians, are often overlooked. Fluxapyroxad (FLX), a significant succinate dehydrogenase inhibitor fungicide, has been extensively utilized for the protection of food and cash crops and control of fungi. This raises the possibility of coexistence of MWCNTs and FLX. The objective of this study was to explore the individual and combined toxic effects of FLX and MWCNTs on the early life stages of Xenopus laevis. Embryos were exposed to varying concentrations of FLX (0, 5, and 50 μg/L) either alone or in combination with MWCNTs (100 μg/L) for a duration of 17 days. The findings indicated that co-exposure to FLX and MWCNTs worsened the inhibition of growth, liver damage, and dysregulation of enzymatic activity in tadpoles. Liver transcriptomic analysis further revealed that the presence of MWCNTs exacerbated the disturbances in glucose and lipid metabolism caused by FLX. Additionally, the combined exposure groups exhibited amplified alterations in the composition and function of the gut microflora. Our study suggests that it is imperative to pay greater attention to the agricultural applications, management and ecological risks of MWCNTs in the future, considering MWCNTs may significantly enhance the toxicity of FLX.
PubMed: 38909862
DOI: 10.1016/j.chemosphere.2024.142685 -
Comparative Biochemistry and... Jun 2024Amphibians are suffering population declines due to a variety of factors such as increased ultraviolet radiation, climate change, habitat loss, pathogens, and pollution,...
Amphibians are suffering population declines due to a variety of factors such as increased ultraviolet radiation, climate change, habitat loss, pathogens, and pollution, or a combination of these. Such changes are associated with a reduction in the availability of water, exposing these animals to a greater risk of desiccation. In this context, understanding how dehydration can modulate the hypothalamic-pituitary-interrenal axis (HPI) and the immune response is an imperative question to predict how stressors can affect amphibian species. We investigated whether dehydration promotes long-lasting effects on toads' ability to respond to a consecutive stressor (restraint) even if the toads are allowed to rehydrate, as well as its effects on the immune function. We also tested the hypothesis that the toads showing more severe dehydration would exhibit lower responsiveness to restraint challenge, even if the animals were allowed to rehydrate. Individuals of R. ornata were dehydrated mildly and severely. Thereafter, they were submitted to a restraint stress challenge for 1 and 24 h. Our results show that dehydration increased hematocrit and CORT in R. ornata toads. The restraint induced an acute stress response in fully hydrated toads (increased CORT and neutrophil: lymphocyte ratio). Otherwise, restraint in moistened cloth bags allowed full rehydration in previously dehydrated toads and did not induce an additional increase in CORT, but those toads sustained elevated CORT up to 24 h of restraint. Also, these animals showed increased neutrophil: lymphocyte ratio and the phagocytic activity of blood cells, even when they rehydrated during restraint. These results point to a continuous activation of the HPA during dehydration and subsequent restraint, even when they recovered from the dehydration state. Also, acute stressors seem to promote immune cell redistribution and augmentation of immune cellular function in R. ornata toads.
PubMed: 38909650
DOI: 10.1016/j.cbpa.2024.111683