Histopathological findings in Gonads of Xenopus laevis from Central Chile (original) (raw)
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2008
A number of man-made chemicals has been shown to mimic endogenous hormones and to induce alterations of reproductive physiology in wild populations. Of particular importance are compounds that mimic estrogens and androgens (and their antagonists), because of their central role in reproductive function. In this study, male and female adult South African clawed toads (Xenopus laevis) were exposed to ethinylestradiol (EE2), tamoxifen (TAM), methyldihydrotestosterone (MDHT) and flutamide (FLU) as (anti)estrogenic and (anti)androgenic model compounds, respectively, at a concentration of 10 − 8 M, and to water from the river Lambro (LAM), a contaminated watercourse from Northern Italy. Potential disrupting effects on reproduction were studied by histological analyses of gonads. The strongest adverse effects were observed in EE2 and LAM exposed males, e.g. tubule mean diameter reduction, spermatogenic nest breakdown and interlobular wall thickening. In both groups, the occurrence of small oocytes within the seminiferous tubules was observed. In TAM and MDHT exposed females slight oocyte atresia and occurrence of spermatogenic nests were observed. In contrast to previous studies addressing the alteration of molecular biomarkers in the same experimental setup, histological analyses of gonads were very sensitive and indicated an adverse effect of water from Lambro River on reproductive physiology of X. laevis.
Xenopus laevis as a Bioindicator of Endocrine Disruptors in the Region of Central Chile
Archives of Environmental Contamination and Toxicology, 2019
One of the direct causes of biodiversity loss is environmental pollution resulting from the use of chemicals. Different kinds of chemicals, such as persistent organic pollutants and some heavy metals, can be endocrine disruptors, which act at low doses over a long period of time and have a negative effect on the reproductive and thyroid system in vertebrates worldwide. Research on the effects of endocrine disruptors and the use of bioindicators in neotropical ecosystems where pressure on biodiversity is high is scarce. In Chile, although endocrine disruptors have been detected at different concentrations in the environments of some ecosystems, few studies have been performed on their biological effects in the field. In this work, Xenopus laevis (African clawed frog), an introduced species, is used as a bioindicator for the presence of endocrine disruptors in aquatic systems with different degrees of contamination in a Mediterranean zone in central Chile. For the first time for Chile, alterations are described that can be linked to exposure to endocrine disruptors, such as vitellogenin induction, decreased testosterone in male frogs, and histological changes in gonads. Dioxin-like and oestrogenic activity was detected in sediments at locations where it seem to be related to alterations found in the frogs. In addition, an analysis of land use/ cover use revealed that urban soil was the best model to explain the variations in frog health indicators. This study points to the usefulness of an invasive species as a bioindicator for the presence of endocrine-disruptive chemicals. Human activity is responsible for the loss of natural habitat observed worldwide, which affects not only biodiversity but also human well-being (Millennium Ecosystem Assessment
Gonadal Histopathology of Fish from La Pólvora Urban Lagoon in the Grijalva Basin, Mexico
Revista Internacional de Contaminación Ambiental
Studies on environmental pollution in Mexican freshwater ecosystems by means of fish histopathology are extremely scarce. In that view, this research analyzed the gonad histopathology of four teleost fish species from a hyper-eutrophicated fragmented urban lagoon, in order to determine possible harmful effects of water pollutants on their reproductive fitness. Gonads were processed by histological conventional techniques. The gonadal alterations detected in both, the clupeid Dorosoma petenense and the cichlid Thorichthys meeki expose the need to clarify the connection of these alterations to the presence of specific pollutants. Palabras clave: contaminación acuática, toxicología reproductiva, ovario, testículo, ictiofauna RESUMEN El diagnóstico ambiental de los ecosistemas dulceacuícolas a través de la histopatología de los peces ha sido poco abordado en México. Con base en lo anterior se realizó un análisis histopatológico de las gónadas de cuatro especies de teleósteos provenientes de una laguna urbana hipertrófica y fragmentada, con la finalidad de identificar posibles alteraciones reproductivas inducidas por contaminantes presentes en el agua. Las gónadas se procesaron con técnicas histológicas de rutina. Las alteraciones histopatológicas detectadas en las gónadas de Dorosoma petenense y Thorichthys meeki exponen la necesidad de establecer una conexión directa entre estas alteraciones con la presencia de contaminantes específicos. SHORT COMMUNICATION
Endocrine effects of environmental pollution on Xenopus laevis and Rana temporaria
Environmental Research, 2003
To determine the capacity of sewage treatment work effluents to disrupt the endocrine system under semifield conditions, two amphibian species, Xenopus laevis and Rana temporaria, were exposed to the effluent of a regional sewage treatment plant in South Bavaria during larval development until completion of metamorphosis. Exposure was carried out in river water (Wu¨rm) as a reference, and a 1:12-mixture sewage effluent representing the real situation on the spot, and in a higher concentration of sewage using a 1:2 mixture. An accidental impact of industrial wastewater into the reference and dilution medium, Wu¨rm, which was caused by a spate in the respective area during the sensitive period of sex differentiation of amphibian larvae, is assumed to be responsible for the relatively high percentage of females observed by histological analysis in all treatment groups. All of these values were higher than those determined in controls exposed to artificial tap water in laboratory experiments conducted in a comparable study design. Sex ratios between species, revealed by the semifield study with decreasing portions of females from control to 1:12 to 1:2, were strongly correlated. Determination of biomarker-mRNA-levels in Xenopus liver using semiquantitative RT-PCR at the end of the experimental phase, when exposure regime has turned into the initially expected situation with the highest load of potential estrogens in the effluent, followed by 1:2 and 1:12 mixture, resulted in a significant increase of Vitellogenin-mRNA in female juveniles exposed to the highest portion of sewage, whereas expression of both androgen and estrogen receptor-mRNA showed no clear differences. The results concerning the induction of estrogenic biomarkers are in accordance with our findings for estrogen receptor binding of sample extracts from the Wu¨rm and sewage taken in parallel at the end of the experiment, when sewage extracts possessed a much higher ability to displace [ 3 H]estradiol from the estrogen receptor than the ones extracted from the mixtures.
Environmental Research, 2010
The purpose of the study was to compare wildlife in the proximity and away from the sources of known industrial pollution. Macroscopic, focal, gritty areas that appeared white were observed in the testes of all 24 South African eland (Tragelaphus oryx) culled in the Rietvlei Nature Reserve (RNR; n=17) between 2001 and 2003 and Suikerbosrand Nature Reserve (SNR; n=7) in 2004. Histopathological evaluation of testes showed multiple intratubular dystrophic calcifications, focal areas of sperm stasis, and interstitial chronic cell infiltrates with fibrosis. Spermatogenesis was generally impaired; a few atypical germ cells were also encountered. Sertoli cell vacuolization and sloughing of the seminiferous epithelium were evident. Adenomatous changes of the rete testis, reflective of possible chronic estrogenic exposure, were found. In testes collected from three reference eland in 2007 from the Molopo Nature Reserve (MNR) in the Kalahari/Kgalagadi Desert, except for one focal area of sperm stasis and another with microcalcification, the seminiferous epithelium as well as collecting/rete tubules were normal. Analyses of fat tissue for environmental pollutants showed that 11 out of 17 RNR eland contained a detectable estrogenic chemical pnonylphenol (mean ± SD: 184.8 ± 24.6 µg/kg fat); no organochlorine chemicals or polychlorinated biphenyls were detected. Of the 7 SNR eland, 5 had detectable octylphenol residues (50.2 ± 30.9 µg/kg fat), 3 had detectable p-nonylphenol (137.8 ± 77.9 µg/kg fat), 3 had o-p'-DDT (114.9 ± 31.1 µg/kg fat), 3 had p-p'-DDT (127.3 ± 49.9 µg/kg(79.5 ± 30.4 µg/kg fat) and 5 contained o-p'-DDE (27.7 ± 9.9 µg/kg fat). One eland from the MNR contained one 70.6 µg o-p'-DDT/kg fat and another p-p'-DDE 61.3 µg/kg fat. Therefore, in eland with testicular abnormalities, significant amounts of various estrogenic chemicals were bioaccumulated in fat samples. It therefore seems likely that the lesions found in RNR and SNR were associated with the relatively high body-burden of environmental pollutants (phenols), although the possibility of systemic infections cannot be ruled out. No testicular 3 abnormalities were found in reference eland. These findings are the first indication of mammalian wildlife being affected by environmental pollution of endocrine disrupting chemicals in South Africa.
Analytical and Bioanalytical Chemistry, 2008
Xenopus laevis has been introduced as a model to study effects of endocrine-active compounds (EAC) on development and sexual differentiation. However, variable and inconsistent data have raised questions about the reliability of the test methods applied. The current study was conducted in two laboratories to develop, refine, and standardize procedures and protocols. Larvae were exposed in flow-through systems to 17β-estradiol (E2), at concentrations from 0.2 to 6.0 μg E2 L −1 in Experiment 1A, and 0.015 to 2.0 μg E2 L −1 in Experiment 1B. In both studies survival (92%, 99%) and percentage of animals that completed metamorphosis (97%, 99%) indicated reproducible biological performance. Furthermore, minor variations in husbandry led to significant differences in snout-to-vent length, weight, and gonad size. In Experiment 1A, almost complete feminization occurred in all E2 treatment groups whereas a concentration response was observed in Experiment 1B resulting in an EC 50 of 0.12 μg E2 L −1. The final verified protocol is suitable for determining effects of EAC on development and sexual differentiation in X. laevis.
2009
The African clawed frog (Xenopus laevis) has been identified as an appropriate sentinel for testing endocrine activity of existing chemicals in North America and Europe. Some reports suggest that the herbicide, atrazine (CAS Number [1912-24-9]) causes ovarian follicles to form in the testes of this frog. X. laevis collected from North East (NE) sites in South Africa had testicular ovarian follicles, irrespective of exposure to atrazine, while frogs from Southwest Western (SW) Cape region sites had none. Phylogenetic analysis of mitochondrial and nuclear genes indicates that frogs from the SW Cape are evolutionarily divergent from those from NE South Africa and the rest of sub-Saharan Africa. These findings provide a possible explanation for why conflicting results have been reported concerning the impact of atrazine on amphibian sexual differentiation and highlight the importance of understanding taxonomic status of the experimental animal. Even in common laboratory animals, there is a need for their correct taxonomic characterization before their use in tests for endocrine disruption.
Reproductive dysgenesis in wildlife: a comparative view
International Journal of Andrology, 2006
Abnormal reproductive development in males has been linked to environmental contaminant exposure in a wide variety of vertebrates. These include humans, rodent models, and a large number of comparative wildlife species. In human males, abnormal reproductive development can manifest as a suite of symptoms, described collectively as testicular dysgenesis syndrome (TDS). TDS is also described as demasculinization or feminization of the male phenotype. The suite includes cryptorchidism, in situ germ cell carcinoma of the testis and overt testicular cancer, reduced semen quality, and hypospadias. In this paper, we review examples of TDS among comparative species. Wildlife exposed to environmental contaminants are susceptible to some of the same developmental abnormalities and subsequent symptoms as those seen in human males with TDS. There are additional end points, which are also discussed. In some cases, the symptoms are more severe than those normally seen in humans with TDS (i.e. oocytes developing within the testis) because some non-mammalian species exhibit greater innate reproductive plasticity, and are thus more easily feminized. Based on our review, we present an approach regarding the ontogeny of TDS. Namely, we suggest that male susceptibility to the androgynizing influences of environmental contaminants originates in the sexually undifferentiated embryo, which, in almost all species, including humans, consists of bipotential reproductive tissues. These tissues can develop as either male or female and their ultimate direction depends on the environment in which they develop.
Aquatic Toxicology, 2009
The African clawed frog (Xenopus laevis) has been identified as an appropriate sentinel for testing endocrine activity of existing chemicals in North America and Europe. Some reports suggest that the herbicide, atrazine (CAS Number [1912-24-9]) causes ovarian follicles to form in the testes of this frog. X. laevis collected from North East (NE) sites in South Africa had testicular ovarian follicles, irrespective of exposure to atrazine, while frogs from Southwest Western (SW) Cape region sites had none. Phylogenetic analysis of mitochondrial and nuclear genes indicates that frogs from the SW Cape are evolutionarily divergent from those from NE South Africa and the rest of sub-Saharan Africa. These findings provide a possible explanation for why conflicting results have been reported concerning the impact of atrazine on amphibian sexual differentiation and highlight the importance of understanding taxonomic status of the experimental animal. Even in common laboratory animals, there is a need for their correct taxonomic characterization before their use in tests for endocrine disruption.
Journal of Biology and Life Science, 2013
The present work aimed to study some aspect of the reproductive biology of the P. javanicus with emphasis on histopathology abnormalities of gonads and intersex problems. Fish samples of Puntius javanicus (local name:tawes) were collected from Mas River on the Surabaya downtown whereas highly pollution. Fishes were identified for morphological abnormality and gonad organs were evaluated. Histological preparation was done to observe the gonad condition. This report reveals that 20% male P. javanicus were found to be feminized on July 19, 2012 collection from that river. Some histological samples indicated the presence of testis-ova in fish gonad, which indicated the occurrence of intersex of this species. The above finding suggests that greater attention needs to be given to xenobiotic pollutants and endocrine disrupting chemicals problems.
Aquatic Toxicology, 2005
The ultrastructure of testicular cells of adult male African clawed frogs (Xenopus laevis) exposed to either estradiol (0.1 g/L) or 2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine (atrazine; 10 or 100 g/L) was examined by electron microscopy and compared to plasma concentrations of the steroid hormones, testosterone (T) and estradiol (E2), testicular aromatase activity and gonad growth expressed as the gonado-somatic index (GSI). Exposure to E2 caused significant changes both at the sub-cellular and biochemical levels. Exposure to E2 resulted in significantly fewer sperm cells, inhibition of meiotic division of germ cells, more lipid droplets that are storage compartments for the sex steroid hormone precursor cholesterol, and lesser plasma T concentrations. Although not statistically significant, frogs exposed to E2 had slightly smaller GSI values. These results may be indicative of an inhibition of gonad growth and disrupted germ cell development by E2. Concentrations of E2 in plasma were greater in frogs exposed to E2 in water. Exposure to neither concentration of atrazine caused effects on germ cell development, testicular aromatase activity or plasma hormone concentrations. These results suggest that atrazine does not affect testicular
2022
The morphology and maturation process of gonads of 70 Burmeister´s porpoises, with body lengths ranging 135-183 cm (n= 34 females) and 64.5-182 cm (n= 36 males) were described. Samples were collected in six ports of central and northern Peru in 1987-1999. In the field, females were classified as immature, mature (resting, lactating, pregnant) and males as immature, pubescent and mature based on, respectively, the presence of ovarian corpora and the relative quantity of semen in cut epididymides. The ovaries of P. spinipinnis are ovoid or bean-shaped and flattened, with corpora modifying surface appearance. In the laboratory, ovaries were examined macro-and microscopically, measured, weighed and sliced in 1-3 mm sections. The number of corpora ovarica (lutea, albicantia, atretica) found in each ovary as well as their macroscopic and microscopic characteristics were documented in some detail. The follicles, their oocytes and nucleus were measured. Follicular development in P. spinipinnis is predominantly left-sided, but occurs in both ovaries in 16.3% of females, mainly in those with numerous corpora. Macroscopically, several corpora atretica with luteinization had characteristics similar to those of corpora albicantia, making microscopic determination essential. Inconclusive evidence of recent ovulation was found in January. Two of three immature females showed good follicular development in March and April. The body length at 50% sexual maturity in females was estimated at 152.7 cm. There was no evidence of reproductive senescence. The testes of P. spinipinnis are elongated and cylindrical. Of the 36 males examined macroscopically, 7 were immature, 5 pubescent and 24 mature. The histological analysis determining the presence and abundance of Sertoli cells, spermatogonia, spermatocytes, spermatids and spermatozoa, the relative amount of interstitial tissue, the elongation and mean diameter of the seminiferous tubules and the relative size of the lumen allowed to confidently determine sexual maturity status. The field evaluation of maturity based on the presence of sperm in the epididymides is a useful but, in 8.3% of cases, not exact method. For males the body length at 50% sexual maturity was estimated at 157 cm. No histological evidence of male reproductive seasonality was found. Spermatogenesis was perceptible year-round and tubule diameters had non-specific variations for each month.
Fish Physiology and Biochemistry, 2012
River damming and building of hydroelectric power plants interrupt the reproductive migration routes and change the major physicochemical parameters of water quality, with drastic consequences for populations of migratory fishes. The goal of this study was to evaluate proliferation and cell death during spermatogenesis and serum profiles of sex steroids in Prochilodus argenteus, from the São Francisco River, downstream from the Três Marias Dam. A total of 257 adult males were caught quarterly during a reproductive cycle in two sites: the first 34 km of the river after the dam (site 1) and the second 34-54 km after the dam (site 2), after the confluence with a tributary, the Abaeté River. Seasonal changes in the testicular activity associated with morphometric analyses of germ cells as well as proliferation and testicular apoptosis support a more active spermatogenesis in fish from site 2, where higher levels of sex steroids and gonadosomatic index (GSI) were also found. In site 1, fish presented low serum levels of testosterone, 17b-estradiol and 17a-hydroxyprogesterone and a low GSI during gonadal maturation. Spermatogonial proliferation (PCNA) and apoptosis (TUNEL) were more elevated in fish from site 1, but spermatocytes were mainly labelled in fish from site 2. Overall, these data demonstrate changes in testicular activity and plasma sex steroids in a neotropical teleost fish living downstream from a hydroelectric dam, supplying new data on fish reproduction in regulated rivers. Moreover, morphometric analyses associated with sex steroids profiles provide reliable tools to assess fish spermatogenesis under environmental stress conditions.
Toxics
Human pressure due to industrial and agricultural development has resulted in a biodiversity crisis. Environmental pollution is one of its drivers, including contamination of wildlife by chemicals emitted into the air, soil, and water. Chemicals released into the environment, even at low concentrations, may pose a negative effect on organisms. These chemicals might modify the synthesis, metabolism, and mode of action of hormones. This can lead to failures in reproduction, growth, and development of organisms potentially impacting their fitness. In this review, we focused on assessing the current knowledge on concentrations and possible effects of endocrine disruptor chemicals (metals, persistent organic pollutants, and others) in studies performed in South America, with findings at reproductive and thyroid levels. Our literature search revealed that most studies have focused on measuring the concentrations of compounds that act as endocrine disruptors in animals at the systemic leve...
Aquatic Toxicology, 2006
It is known that estrogen-like environmental pollutants can feminise gonadal differentiation in frogs resulting in female-biased sex-ratios at metamorphosis. The long-term effects on reproductive function in frogs following larval exposure to pollutants are less known. Amphibian test systems which allow life-cycle studies are therefore needed. The aim of the present study was to characterise long-term estrogenic effects on the reproductive system of the emerging model species Xenopus (Silurana) tropicalis following larval exposure to ethynylestradiol (EE 2 ). EE 2 is a synthetic estrogen that has been detected in sewage effluents and in surface waters. Newly hatched tadpoles (Niewkoop Faber (NF) stage 48) were exposed to the nominal EE 2 concentrations 0 (control), 1, 10, and 100 nM (with analytical chemistry support) until complete metamorphosis (NF stage 66). Effects on the reproductive organs were determined in juveniles (1 month after metamorphosis) and in 9-month-old frogs. Larval exposure to EE 2 caused female-biased phenotypic sex-ratios in both juvenile and adult frogs, which is in agreement with previous work on other frog species. Nearly all (97%) of the 63 EE 2 -exposed 9-month-old frogs had ovaries. Histological evaluation of the gonads of the 9-month-old frogs showed that they were sexually mature. Among the adult frogs with ovaries there was a dose-dependent increase in the frequency of individuals lacking oviducts. Adult frogs exposed to 100 nM EE 2 that had ovaries but no oviducts had lower levels of estrogen receptor alpha (ER␣) mRNA in the brain than control animals and those exposed to 100 nM EE 2 that had ovaries as well as oviducts. EE 2 exposure did not cause any significant changes in ER␣ mRNA levels in the ovaries of the adult frogs. The reduced level of ER␣ mRNA in the brain of individuals with ovaries lacking oviducts suggests an organizing effect of EE 2 on the central nervous system. The results show that transient early life-stage exposure to an environmental pollutant can induce effects on the reproductive organs and the central nervous system that persist into adulthood. Overall, our data suggest that X. tropicalis, which has a shorter generation time than the well-established model species Xenopus laevis, is a suitable model organism for research on developmental reproductive toxicity in anuran species.
African Journal of Herpetology, 2005
We tested the hypothesis that adult African clawed frogs (Xenopus laevis) inhabiting water bodies in maize-growing areas (MGA) of South Africa would exhibit differences in testicular structure compared to frogs from water bodies in non-maize-growing areas (NMGA) in the same locale. Adults of both sexes were collected during the autumn of 2002 in South Africa, and stereological analytical techniques were used to quantify the distribution of testicular cell types. In addition, total laryngeal mass was used as a gauge of secondary sex differences in animals from MGA and NMGA study sites. Evaluation of the total laryngeal mass revealed that there were no statistically significant differences between X. laevis of the same sex from the NMGA and MGA sites. Mean percent fractional-volume values for seminiferous tubule distribution of testicular cell types of mature X. laevis, ranged from 3-4% for spermatogonia, 26-28% for spermatocytes, 54-57% for spermatozoa, and 14-15% for other cells types. The mean percent volume for blood vessels ranged from 0.3-0.4%. These values did not differ significantly between frogs from NMGA and MGA areas. Collectively, these data demonstrated no differences in gonadal and laryngeal development in X. laevis collected in South Africa from MGA and NMGA areas and that there is little evidence for an effect of agricultural chemicals used in maize production functioning as endocrine disrupters in this species. Screening of X. laevis testes revealed a small incidence of Stage 1 testicular oocytes in adult male frogs collected from the NMGA (3%) and MGA (2%).
Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2008
In an effort to contribute to the development of Xenopus tropicalis as an amphibian model system, we carried out a detailed histological analysis of the process of gonadal sex differentiation and were able to find evidence that gonadal differentiation in X. tropicalis follows an antero-posterior gradient. Although the main reason for the presence of a gradient of sex differentiation is still unknown, this gradient enabled us to define the early events that signal ovarian and testicular differentiation and to identify the undifferentiated gonad structure. Given the various advantages of this emerging model, our work paves the way for experiments that should contribute to our understanding of the dynamics and mechanisms of gonadal sex differentiation in amphibians.
RESUMEN Estudiamos los ciclos de esteroides sexuales de machos y hembras en estado silvestre de la tortuga del Bolsón en la Reserva de la Biósfera de Mapimí (Durango). Tomamos muestras de sangre por venipunción de la yugular a intervalos bisemanales durante un período de 14 meses, determinándose los niveles circulantes de esteroides por medio de radioinmunoensayos. Los niveles hormonales mostraron tendencias estacionales. En las hembras, la testosterona tuvo un valor máximo al salir de la brumación, en asociación con el incremento en la receptividad sexual, y el nivel de estradiol aumentó después de la emergencia asociado con la maduración folicular. El nivel de estos dos esteroides se incrementó con las lluvias estacionales, cuando ocurrieron el crecimiento folicular y la vitelogénesis. La progesterona mostró niveles bajos a la emergencia, los cuales aumentaron con el incremento de la duración del dia y la temperatura, llegando al máximo antes del pico de la oviposición. La caída en los niveles de las tres hormonas estuvo asociada con la oviposición. Las hembras probablemente almacenan esperma durante parte del otoño y el invierno para usarlo en la siguiente estación reproductiva. Los machos salieron de la hibernación con bajos niveles de testosterona, pero exhibieron conductas reproductivas poco después. Junto con un incremento de la testosterona, el cortejo y la frecuencia de apareamientos se incrementaron con estímulos ambientales, prolongándose hasta principios del otoño. Los niveles de testosterona y la actividad reproductiva disminuyeron conforme se aproximaba el inicio de la hibernación. Los niveles máximos de testosterona en machos de esta especie son mayores que los conocidos para cualquier otro vertebrado. ABSTRACT This study describes sex-steroid cycles of free-living male and female Bolson tortoises at the Mapimi Biosphere Reserve in northeastern Durango, Mexico. Blood samples were taken at biweekly intervals during a 14 month period by jugular venipuncture, and plasma levels of steroids were determined using radioimmunoassays. Hormone levels showed seasonal trends. In females testosterone peaked following emergence, associated with increased sexual receptivity, and estradiol increased after emergence in association with follicular maturation. These two steroids increased with seasonal rains, when follicular enlargement and vitellogenesis occurred. Females emerged from brumation with low levels of progesterone,