Exposure Impacts of Environmentally Relevant Concentrations of a Glufosinate Ammonium Herbicide Formulation on Larval Development and Thyroid Histology of Xenopus laevis.

Thyroid hormones play critical roles in body growth and development as well as reproduction. They also influence the activities of a wider variety of tissues and biological functions, such as osmoregulation, metabolism, and especially metamorphosis in organisms, such as frogs. These complex activities of thyroid hormones are prone to disruption by agricultural pesticides, often leading to modulation of growth and the reproductive system in particular. These substances include Glufosinate ammonium, Glyphosates, Imazapyr, Penoxsulam, and Diquat dibromide among other herbicides. In this study, the standardized Xenopus Metamorphosis Assay protocol was used to assess the potential thyroid-modulatory properties of the Glufosinate ammonium Basta formulation, at relevant environmental concentrations (0.05 mg/L, 0.15 mg/L, and 0.25 mg/L) for 21 days. The results showed that this formulation only reduced the hind-limb length among the morphological endpoints. Histological evaluation showed that the mean thyroid gland area and the mean thyroidal follicle epithelium height were significantly increased following 0.15 and 0.25 mg/L exposures. The present study confirmed that this Basta formulation interacts with the thyroid axis and therefore potentially pose health hazard to amphibian in particular and potentially metamorphic aquatic vertebrates. Furthermore, the result is a signal of inherent potential thyroid disrupting activities that must be further investigated and characterised in some of the aquatic herbicide formulations to safeguard the aquatic biodiversity.

Investigating (anti)estrogenic activities within South African wastewater and receiving surface waters: Implication for reliable monitoring.

Natural and synthetic steroid hormones and many persistent organic pollutants are of concern for their endocrine-disrupting activities observed in receiving surface waters. Apart from the demonstrated presence of estrogen- and estrogen-mimicking compounds in surface waters, antagonistic (anti-estrogenic) responses originating from wastewater effluent have been reported but are less known. Estrogenicity and anti-estrogenicity were assessed using recombinant yeast estrogen receptor binding assays (YES/YAES) at ten South African wastewater treatment works (WWTWs) and receiving rivers in two separate sampling campaigns during the summer- and winter periods in the area. Four WWTWs were then further investigated to show daily variation in estrogenic endocrine-disrupting activities during the treatment process. Although estrogenicity was notably reduced at most of the WWTWs, some treated effluent and river water samples were shown to be above effect-based trigger values posing an endocrine-disrupting risk for aquatic life and potential health risks for humans. Furthermore, estrogenicity recorded in samples collected upstream from some WWTW discharge points also exceeded some calculated risk trigger values, which highlights the impact of alternative pollution sources contributing towards endocrine disrupting contaminants (EDCs) in the environment. The YAES further showed variable anti-estrogenic activities in treated wastewater. The current study highlights a variety of factors that may affect bioassay outcomes and conclusions drawn from the results for risk decision-making. For example, mismatches were found between estrogenic and anti-estrogenic activity, which suggests a potential masking effect in WWTW effluents and highlights the complexity of environmental samples containing chemical mixtures having variable endocrine-disrupting modes of action. Although the recombinant yeast assay is not without its limitations to show endocrine-disrupting modulation in test water systems, it serves as a cost-effective tier-1 scoping assay for further risk characterisation and intervention.

Mortality, teratogenicity and growth inhibition of three glyphosate formulations using Frog Embryo Teratogenesis Assay-Xenopus.

Ample evidence around the world exists suggesting a link between exposure to glyphosate, toxicity and perturbed physiological functions in non-target organisms. Although glyphosate formulations are widely used for weed and alien plant management, their ecotoxicological information remain scanty. Using the 96-hour Frog Embryo Teratogenesis Assay-Xenopus protocol, embryotoxicity and teratogenicity of three glyphosate-based formulations were assessed. Embryos of Xenopus laevis were exposed to Roundup, Kilo Max and Enviro Glyphosate at concentration of 0.3-1.3, 130-280 and 320-560 mg acid equivalent (a.e.)/L respectively. The results showed Roundup to be more toxic than the other formulations with a 96-hour LC50 of 1.05 mg a.e/L. compared with 207 mg a.e./L, and 466 mg a.e./L for Kilo Max and Enviro Glyphosate respectively. Although, both Roundup and Kilo Max formulations show inhibition on growth of the embryo-larva (P Ë‚ .05), the minimum concentration inhibiting growth ratios of the three formulations was >0.30 baseline, indicating no significant growth inhibiting effect in the formulations. For teratogenicity, Roundup and Enviro Glyphosate formulations exhibited increasing teratogenic traces, with the teratogenic index at 1.7 and 1.6 respectively. Kilo Max formulation shows low teratogenicity with the teratogenic index at 1.4. Characteristic malformation induced by these formulations included generalized edema, cardiac and abdominal edema, improper gut formation and axial malformations. This study confirms that these formulations could be a potential physiological and ecological health disruptor, particularly concerning teratogenicity and growth disruption. Further studies to characterize the contributions of their surfactants will be invaluable.

An evaluation of the endocrine disruptive potential of crude oil water accommodated fractions and crude oil contaminated surface water to freshwater organisms using in vitro and in vivo approaches.

Knowledge regarding the potential impacts of crude oil on endocrine signaling in freshwater aquatic vertebrates is limited. The expression of selected genes as biomarkers for altered endocrine signaling was studied in African clawed frog, Xenopus laevis, tadpoles and juvenile Mozambique tilapia, Oreochromis mossambicus, exposed to weathered bunker and unweathered refinery crude oil water accommodated fractions (WAFs). In addition, the expression of the aforementioned genes was quantified in X. laevis tadpoles exposed to surface water collected from the proximity of an underground oil bunker. The (anti)estrogenicity and (anti)androgenicity of crude oil, crude oil WAFs, and surface water were furthermore evaluated using recombinant yeast. Thyroid hormone receptor beta expression was significantly down-regulated in X. laevis in response to both oil WAF types, whereas a further thyroid linked gene, type 2 deiodinase, was up-regulated in O. mossambicus exposed to a high concentration of bunker oil WAF. In addition, both WAFs altered the expression of the adipogenesis-linked peroxisome proliferator-activated receptor gamma in X. laevis. The crude oil and WAFs exhibited antiestrogenic and antiandrogenic activity in vitro. However, O. mossambicus androgen receptor 2 was the only gene, representing the reproductive system, significantly affected by WAF exposure. Estrogenicity, antiestrogenicity, and antiandrogenicity were detected in surface water samples; however, no significant changes were observed in the expression of any of the genes evaluated in X. laevis exposed to surface water. The responses varied among the 2 model organisms used, as well as among the 2 types of crude oil. Nonetheless, the data provide evidence that crude oil pollution may lead to adverse health effects in freshwater fish and amphibians as a result of altered endocrine signaling. Environ Toxicol Chem 2017;36:1330-1342. © 2016 SETAC.

Characterization of evolutionary trend in squamate estrogen receptor sensitivity.

Steroid hormones are a key regulator of reproductive biology in vertebrates, and are largely regulated via nuclear receptor families. Estrogen signaling is regulated by two estrogen receptor (ER) subtypes alpha and beta in the nucleus. In order to understand the role of estrogen in vertebrates, these ER from various species have been isolated and were functionally analyzed using luciferase reporter gene assays. Interestingly, species difference in estrogen sensitivity has been noted in the past, and it was reported that snake ER displayed highest estrogen sensitivity. Here, we isolated additional ER from three lizards: chameleon (Bradypodion pumilum), skink (Plestiodon finitimus), and gecko (Gekko japonicus). We have performed functional characterization of these ERs using reporter gene assay system, and found high estrogen sensitivity in all three species. Furthermore, comparison with results from other tetrapod ER revealed a seemingly uniform gradual pattern of ligand sensitivity evolution. In silico 3D homology modeling of the ligand-binding domain revealed structural variation at three sites, helix 2, and juncture between helices 8 and 9, and caudal region of helix 10/11. Docking simulations indicated that predicted ligand-receptor interaction also correlated with the reporter assay results, and overall squamates displayed highest stabilized interactions. The assay system and homology modeling system provides tool for in-depth comparative analysis of estrogen function, and provides insight toward the evolution of ER among vertebrates.

Reuteran and levan as carbohydrate sinks in transgenic sugarcane.

The present study reports the effect of high molecular weight bacterial fructan (levan) and glucan (reuteran) on growth and carbohydrate partitioning in transgenic sugarcane plants. These biopolymers are products of bacterial glycosyltransferases, enzymes that catalyze the polymerization of glucose or fructose residues from sucrose. Constructs, targeted to different subcellular compartments (cell wall and cytosol) and driven by the Cauliflower mosaic virus-35S: maize-ubiquitin promoter, were introduced into sugarcane by biolistic transformation. Polysaccharide accumulation severely affected growth of callus suspension cultures. Regeneration of embryonic callus tissue into plants proved problematic for cell wall-targeted lines. When targeted to the cytosol, only plants with relative low levels of biopolymer accumulation survived. In internodal stalk tissue that accumulate reuteran (max 0.03 mg/g FW), sucrose content (ca 60 mg/g FW) was not affected, while starch content (<0.4 mg/g FW) was increased up to four times. Total carbohydrate content was not significantly altered. On the other hand, starch and sucrose levels were significantly reduced in plants accumulating levan (max 0.01 mg/g FW). Heterologous expression resulted in a reduction in total carbohydrate assimilation rather than a simple diversion by competition for substrate.

Lizard epidermal gland secretions. II. Chemical characterization of the generation gland secretion of the sungazer, Cordylus giganteus.

In lizards, the epidermal glands of the femoral and precloacal regions are involved in the production of semiochemicals. In addition to its femoral glands, the giant girdled lizard, or sungazer, Cordylus giganteus, which is endemic to South Africa, has generation glands as an additional potential source of semiochemicals. These epidermal glands are described as glandular scales that overlay the femoral glands and are included in the normal epidermal profile located in the femoral (thigh) and anterior antebrachial (fore-leg) regions of the male sungazer. GC-MS analysis of the generation gland secretions and the trimethylsilyl derivatives of some of the steroidal constituents was employed to identify 59 constituents, including alkenes, carboxylic acids, alcohols, ketones, aldehydes, esters, amides, nitriles, and steroids. The quantitative differences of the volatile constituents of the fore- and hind-leg generation glands were compared between individuals. This is the first report on the chemical composition of generation glandular material of lizards.

Thermal benefits of melanism in cordylid lizards: a theoretical and field test.

The hypothesis that low skin reflectance (melanism) provides an advantage for thermoregulation under cold conditions has received mixed support in ectothermic vertebrates. We selected a model system, three allopatric closely related species of cordylid lizards that differ in skin reflectance, to test this hypothesis. Cordylus niger and Cordylus oelofseni are melanistic and inhabit peninsular and montane areas, respectively, whereas Cordylus cordylus is more widespread and inhabits low inland areas. By combining theoretical, experimental, and field data on these species, we demonstrate that the difference in body temperature (T(b)) between melanistic and non-melanistic lizards under ecologically relevant climate variation ranged from 0 degrees to 2 degrees C. Despite its small magnitude, however, the faster heating rate and higher T(b) of melanistic species relative to non-melanistic species conferred an advantage under cold conditions. Comparison of habitat thermal quality (d(e)) and thermal accuracy (d(b)) across species indicated that, in winter, melanism conferred the greatest advantage during small windows of thermal opportunity. This finding was most pronounced for C. oelofseni, which is most constrained by cold temperatures in its habitat. By contrast, due to their rock-dwelling habits, melanistic and non-melanistic species benefited from rock refugia in summer, giving similar levels of thermoregulatory effectiveness across species, regardless of skin reflectance. This study therefore demonstrates that skin reflectance variation across cordylids has significant effects on their thermal balance. Furthermore, studies investigating the role of varying skin reflectance in field populations and species should incorporate fine and broad temporal scales (daily, monthly, and seasonal), environmental variability, and cost-benefit trade-offs of thermoregulation.

Lizard epidermal gland secretions I: Chemical characterization of the femoral gland secretion of the sungazer, Cordylus giganteus.

The giant girdled lizard or sungazer, Cordylus giganteus, is endemic to South Africa. It has been suggested that in this species, as in other lizard species, epidermal glands in the femoral, pre-cloacal regions, and cloacal glands are the main sources of semiochemicals and that these secretions could play an important role at different levels of the social biology of the animals. To gain a better understanding of the nature of the femoral gland secretions of the sungazer, characterization of the constituents of the secretions was carried out. By using GC-MS analysis, in conjunction with auxiliary techniques, such as solventless sample introduction and trimethylsilyl derivatization, 53 relatively involatile compounds, including carboxylic acids, alcohols, ketones, esters, and steroids, were identified in the secretions of both sexes. The study showed that the secretions of male and female sungazers contain only semi-volatile chemicals.

In vitro interleukin-6 release in whole blood cultures in samples taken at rest from triathletes and professional rugby players.

The aim of this study was to investigate the endotoxin-induced interleukin-6 (IL-6) release in whole blood cultures from samples taken at rest, 24 h post-exercise, from a control group of recreationally trained individuals (C), a group of highly trained triathletes (TA) and a group of highly trained professional rugby players (RP). Fifteen RP [mean (SD): age 26 (3) years, height 1.90 (0.2) m, body mass 104.5 (12.2 kg)], 13 male TA [age 33 (5) years, height 1.78 (0.1) m, body mass 76.3 (12.6) kg] and eight recreationally active male volunteers [age 28 (6) years, height 1.80 (0.1) m, body mass 72.3 (7.3) kg] participated in the study. Plasma IL-6 concentration and in vitro IL-6 synthesis by whole blood cultures were measured in samples taken at rest. Plasma IL-6 concentration was significantly higher ( P<0.01) for the RP and TA groups than for C, as were the in vitro basal and endotoxin activated concentrations. However, after endotoxin stimulation, newly induced IL-6 concentration was significantly lower ( P<0.01) in the RP and TA than in the C group. Therefore, professional rugby players have a similar IL-6 release of whole blood cultures in vitro to that of triathletes. Specifically, mononuclear cells appear to be chronically activated to spontaneously release IL-6, but have a decreased capacity to respond to a further stimulus. Amongst possible explanations for this, the most likely is counter-regulation due to already elevated IL-6 release.