Effects In Tadpoles Research Articles

Bioconcentration, oxidative stress and molecular mechanism of the toxic effect of acetamiprid exposure on Xenopus laevis tadpoles

Acetamiprid is a neonicotinoid commonly detected in aquatic ecosystems, with residual concentrations of up to 0.41 mg/L in surface water, posing a threat to the health of nontarget aquatic organisms. However, studies on the potential toxicity and underlying mechanisms of action of acetamiprid on nontarget aquatic organisms are limited. This study investigated the acute and short-term toxicity of acetamiprid to Xenopus laevis tadpoles. A 96-h acute toxicity test determined the LC50 of acetamiprid to be 32.1 mg/L. After 28 days of exposure to 1/10 and 1/100 LC50 concentrations, tadpole samples were collected for bioconcentration elimination analysis, biochemical analyses, transcriptomics, and metabolomics studies to comprehensively evaluate the toxic effects of acetamiprid and its underlying mechanisms. The results, indicating bioconcentration factors (BCFs) < 1, suggest that acetamiprid has a low bioconcentration in tadpoles. Additionally, oxidative stress was observed in treated Xenopus laevis tadpoles. Transcriptomic and nontargeted metabolomic analyses identified 979 differentially expressed genes (DEGs) and 95 differentially metabolites in the 0.321 mg/L group. The integrated analysis revealed that disruption of purine and amino acid metabolic pathways potentially accounts for acetamiprid-induced toxic effects in tadpoles. The disruptive effects of acetamiprid on valine, leucine and isoleucine biosynthesis; and aminoacyl-tRNA biosynthesis metabolic pathways in tadpoles were validated through targeted metabolomics analysis. These findings are crucial for assessing the risk of acetamiprid to nontarget aquatic organisms.

Chronic effects of lead on metamorphosis, development of thyroid gland, and skeletal ossification in Bufo gargarizans

We examined the Pb2+ exposure on tadpoles of Bufo gargarizans from Gosner stage 26–42. Mortality, growth and development, time to metamorphosis, size, and skeletal ossification at metamorphic climax of Bufo gargarizans were examined. Also, histological characteristics of thyroid glands in tadpoles at Gosner stage 33, 38, and 42 as well as transcript levels of thyroid hormone-related genes in the hind-limb, tail, and liver of tadpoles at metamorphic climax were examined. Pb2+ exposure induced mortality in a concentration-dependent manner in Bufo gargarizans larvae. The significant increase in growth and development, percent metamorphosis, size at metamorphic climax, and skeletal ossification were observed at 50 μg Pb2+ L−1; however, exposure to 1000 μg Pb2+ L−1 resulted in the opposite effects in tadpoles. In addition, histological alterations of thyroid gland, such as follicular cell hyperplasia and colloid depletion could be found in 50–1000 μg Pb2+ L−1 treatments. Furthermore, Pb2+ exposure at 1000 μg L−1 resulted in significantly decreased transcript levels of Dio2, TRα and TRβ, and increased transcript levels of Dio3. In contrast, 50 μg Pb2+ L−1 significantly upregulated the mRNA levels of Dio2, TRα, and TRβ, but it reduced the Dio3 expression. These results suggested that Pb2+ might disrupt TH homeostasis in tadpoles by histological alterations of thyroid gland and disturb the transcript levels of Dio2, Dio3, TRα, and TRβ, leading to altered growth and development, as well as percent metamorphosis and skeletal ossification. Further studies are needed to elucidate the underlying mechanisms of low-dose stimulation and high-dose inhibition effects.

Assessing Genotoxicity and Mutagenicity of Three Common Amphibian Species Inhabiting Agroecosystem Environment.

Amphibians are constantly exposed to pollutants and the stress of agricultural activities. We selected three anuran amphibian species Dendropsophus minutus, Boana albopunctata, and Physalaemus cuvieri, totaling 309 individuals. We collected tadpoles in 15 permanent ponds: 5 soybean crops, 3 corn crops, and 7 nonagricultural lands. Our study provides the first comparative data on the genotoxicity and mutagenicity of three common amphibian anurans. Dendropsophus minutus was the most vulnerable species compared with B. albopunctata and P. cuvieri for comet assay and micronuclei test. However, the more significant amount of DNA damage seen in D. minutus does not mean that their populations are threatened once such species adapt well to anthropogenic disturbances. Despite, P. cuvieri was less sensitive than the other two species; the DNA damage was significantly higher in soybean crops. Physalaemus cuvieri is a leptodactylidae species that deposit their eggs in foam nests, which are essential to protect eggs from dehydration. Moreover, the foam reduces the contact of eggs with water; thus, P. cuvieri eggs could be less exposed to contaminants present in pounds, compared with D. minutus and B. albopunctata, which deposit their eggs directly in the water. Therefore, this study was sufficiently sensitive to detect genotoxic and mutagenic effects in tadpoles exposed to agroecosystems. We strongly suggest D. minutus in future biomonitoring studies that involve the comparison of anthropized versus not anthropized environments. Overall, we recommend the comet assay and micronucleus test as effective methods for the detection of genotoxic damage in amphibian anurans to the environmental disturbance, especially in agricultural sites.

Thyroid Hormone Acts Locally to Increase Neurogenesis, Neuronal Differentiation, and Dendritic Arbor Elaboration in the Tadpole Visual System.

Thyroid hormone (TH) is a critical regulator of perinatal brain development in vertebrates. Abnormal TH signaling in early pregnancy is associated with significant cognitive deficits in humans; however, it is difficult to probe the function of TH in early brain development in mammals because of the inaccessibility of the fetal brain in the uterine environment and the challenge of disambiguating maternal versus fetal contributions of TH. The external development of tadpoles allows manipulation and direct observation of the molecular and cellular mechanisms underlying TH's effects on brain development in ways not possible in mammals. We find that endogenous TH locally regulates neurogenesis at developmental stages relevant to circuit assembly by affecting neural progenitor cell proliferation and differentiation and by acting on neurons to enhance dendritic arbor elaboration.

Grazing on toxic cyanobacterial blooms by tadpoles of edible frog Rana grylio

SUMMARYTadpoles of Rana grylio were raised as edible frogs in fishponds of Guanqiao in Wuhan City, Hubei, China, during cyanobacterial blooms from June to October. The dominant cyanobacterial species was Microcystis, which was found to be lethally toxic by intraperitoneal (i.p.) mouse bioassay. Little is known about the effect of tadpoles on toxic cyanobacterial blooms. To evaluate the potential of the tadpoles to graze on cyanobacterial blooms, the tadpoles were fed on Microcystis collected from the field in the laboratory. The Microcystis cells decreased from 1.19 × 107 cells mL−1 to 3.23 × 106 cells mL−1, with a sharp reduction of 73% of the initial Microcystis population observed in the first 24 h after introduction of the tadpoles. The ponds containing tadpoles had a markedly lower density of Microcystis than those lacking tadpoles. Tadpoles exposed to either cultured Microcystis aeruginosa (NIES–90, 2.768 µg microcystins mg–1 dw–1) cells or lysed M. aeruginosa cells grew well, however, indicating that they were unaffected by Microcystis toxins. We found a significant increase in tadpole body weight after feeding on either field Microcystis or cultured M. aeruginosa. The mean increase in individual body weight was 20 mg day−1 when fed on Microcystis from the pond, and 7 mg day−1 when fed on M. aeruginosa from culture. Our study strongly suggested that there is a direct trophic relationship between R. grylio tadpoles and toxic Microcystis blooms and they possess the potential to graze on toxic Microcystis. The results imply that R. grylio tadpoles may play an important ecological role in reducing toxic cyanobacterial blooms caused by Microcystis.

Isovaleric, Methylmalonic, and Propionic Acid Decrease Anesthetic EC50 in Tadpoles, Modulate Glycine Receptor Function, and Interact with the Lipid 1,2-Dipalmitoyl-Sn-Glycero-3-Phosphocholine

Elevated concentrations of isovaleric (IVA), methylmalonic (MMA), and propionic acid are associated with impaired consciousness in genetic diseases (organic acidemias). We conjectured that part of the central nervous system depression observed in these disorders was due to anesthetic effects of these metabolites. We tested three hypotheses. First, that these metabolites would have anesthetic-sparing effects, possibly being anesthetics by themselves. Second, that these compounds would modulate glycine and gamma-aminobutyric acid (GABA(A)) receptor function, increasing chloride currents through these channels as potent clinical inhaled anesthetics do. Third, that these compounds would affect physical properties of lipids. Anesthetic EC(50)s were measured in Xenopus laevis tadpoles. Glycine and GABA(A) receptors were expressed in Xenopus laevis oocytes and studied using two-electrode voltage clamping. Pressure-area isotherms of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers were measured with and without added organic acids. IVA acid was an anesthetic in tadpoles, whereas MMA and propionic acid decreased isoflurane's EC(50) by half. All three organic acids concentration-dependently increased current through alpha(1) glycine receptors. There were minimal effects on alpha(1)beta(2)gamma(2s) GABA(A) receptors. The organic acids increased total lateral pressure (surface pressure) of DPPC monolayers, including at mean molecular areas typical of bilayers. IVA, MMA, and propionic acid have anesthetic effects in tadpoles, positively modulate glycine receptor function and affect physical properties of DPPC monolayers.

Positive indirect effect of tadpoles on a detritivore through nutrient regeneration

In aquatic food webs consumers can affect other members of the web by releasing nutrients as a result of their feeding activity. There is increasing evidence of these positive effects on primary producers, but such nutrient regeneration can also affect detritivores, by favoring the activities of detritus-associated microbes. We examined the effects of nutrient regeneration by tadpoles on leaf-eating detritivores under laboratory conditions. We fed four species of tadpoles three different food items (leaf litter, algae, and sludgeworms). We then conditioned terrestrial dead leaves with water from reared tadpoles (treatments) or food items alone (controls), and compared the C:N ratios of the conditioned leaves and the growth of the isopod Asellus hilgendorfii fed on the conditioned leaves. Tadpole feeding activity reduced the C:N ratio of conditioned leaves, and the effect was greatest when tadpoles were fed algae. Isopod growth rates were often higher when they were fed the litter conditioned with water from reared tadpoles. Thus, nutrient regeneration by tadpoles had a positive indirect effect on detritivores by enhancing leaf quality. Tadpoles often occur in nutrient-limited habitats where leaf litter is the major energy source, and their facilitative effects on leaf-eating detritivores may be of great significance in food webs by enhancing litter decomposition.

Chargino Production in Different Supergravity Models and the Effect of the Tadpoles

If the lightest chargino is discovered at LEP2, the measurement of its mass and cross-section together with the mass of the lightest neutralino, enables the determination of the parameters that define the theory and the entire supersymmetric and Higgs spectrum. Within this context, we: (i) study the effect of the one-loop tadpoles in the minimization condition of the Higgs potential, by comparing the RGE-improved Higgs potential approximation with the calculation of the minimum including the effect of the one-loop tadpoles, and (ii) compare the prediction of two different supergravity models, namely, the model based on B=2m0 and motivated by the solution of the μ-problem, and the minimal supergravity model, based on A=B-m0.

The effect of tadpoles on algal growth in temporary, rain‐filled rock pools

SUMMARY. Small, temporary, rain‐filled rock pools in Malawi, Central Africa, are colonized by algae, insect larvae and tadpoles. Algal growth in these pools is largely controlled by nutrient supply, flushing rate and the presence of tadpoles. Dissolved nitrogen and phosphorus concentrations were usually high following filling but subsequently declined. Nitrogen supply may limit algal growth at times. The flushing rate of the pools is an over‐riding factor in determining the population size of floating algae. Experiments and field observations showed that tadpoles apparently, paradoxically, promoted the growth of the epineustic and phytoplanktonic algae on which they grazed. The explanation of this paradox probably has in the transfer, by the tadpoles, of nutrients from the sediments to the overlying water. This nutrient enrichment stimulates the growth of the epineuston and phytoplankton.

Lethal effects in tadpoles of Xenopus laevis (Daudin) after irradiation with high-energy electrons.

SINCE 1957 in our department, an increasing number of patients—up to now about 1,200—have been treated with high-energy electrons, using a 31-MeV BBC betatron. Some observations which we made during this period, are the same as reported also elsewhere1–4; but at other points we made divergent observations.

Source of the Pigmentary Hormone of Amphibian Hypophysis

There has been some confusion as to the rôle of the different lobes of the hypophysis in the secretion of the hormone that causes the well known pigmentary effects in tadpoles consisting of a darkening in the presence of an excess of the hormone and the assumption of a very pale color in its absence. The various methods of experimentation have been largely responsible for this diversity of view. P. E. and I. B. Smith caused these pigment changes by making repeated intraperitoneal injections of saline extracts of crushed beef glands, securing positive results with pars anterior, pars nervosa and pars intermedia, the last named being the most pronounced. This method would not preclude the possibility of the fainter color changes caused by pars anterior and pars nervosa material being due to the presence of secretion diffused from the pars intermedia. In the work of the writer for several years the method of transplantation has been used. Care is taken to use only unmixed material of the pars intermedia sliced off at some distance from its surface of intimate union with the pars nervosa. Transplants of the latter never cause pigmentary effects when taken with similar precautions against contamination with pars intermedia substance. In all cases the region of junction between these two portions is discarded. While there is a slight transitory pigmentary effect produced by pars anterior or pars nervosa transplantation, they do not persist, while on the other hand pars intermedia of an adult frog transplanted into normal or hypophysectomized tadpoles becomes functional and causes most intense expansion of the superficial melanophores with deposition of pigment granules in the epidermal cells. This forms a dense mass closely applied to the side of the nucleus directed toward the surface of the body.