Tetrabromobisphenol A Disturbs Brain Development in Both Thyroid Hormone-Dependent and -Independent Manners in Xenopus laevis

Although tetrabromobisphenol A (TBBPA) has been well proven to disturb TH signaling in both in vitro and in vivo assays, it is still unclear whether TBBPA can affect brain development due to TH signaling disruption. Here, we employed the T3-induced Xenopus metamorphosis assay (TIXMA) and the spontaneous metamorphosis assay to address this issue. In the TIXMA, 5–500 nmol/L TBBPA affected T3-induced TH-response gene expression and T3-induced brain development (brain morphological changes, cell proliferation, and neurodifferentiation) at premetamorphic stages in a complicated biphasic concentration-response manner. Notably, 500 nmol/L TBBPA treatment alone exerted a stimulatory effect on tadpole growth and brain development at these stages, in parallel with a lack of TH signaling activation, suggesting the involvement of other signaling pathways. As expected, at the metamorphic climax, we observed inhibitory effects of 50–500 nmol/L TBBPA on metamorphic development and brain development, which was in agreement with the antagonistic effects of higher concentrations on T3-induced brain development at premetamorphic stages. Taken together, all results demonstrate that TBBPA can disturb TH signaling and subsequently interfere with TH-dependent brain development in Xenopus; meanwhile, other signaling pathways besides TH signaling could be involved in this process. Our study improves the understanding of the effects of TBBPA on vertebrate brain development.

Whin Sill contact metamorphism in the Cow Green reservoir boreholes, Northern England: evidence for an Upper Teesdale source for the Whin Sill magma

Contact metamorphism of Carboniferous rocks by the Whin Sill in Upper Teesdale is documented utilizing boreholes drilled in the 1960s ground investigation for the Cow Green reservoir. Hedenbergite, prehnite and datolite are recorded for the first time, and the first analyses for seven contact minerals are presented. Pure limestones are recrystallized into saccharoidal marbles with average calcite grain sizes increasing from <0.1 mm at >20 m from the contact, up to 0.5 mm within 5 m from the contact. Grossular is the most abundant mineral, and along with epidote is recorded over 20 m from the sill contact; all other minerals are restricted to < c. 10 m from the contact. This substantial contact metamorphism around Cow Green is unique in comparison with other boreholes across the Alston Block that have penetrated even thicker leaves of the sill, and for which no contact metamorphic mineral development has been reported. The currently favoured model has the magma sourced from dykes on the southern and northern borders of the Alston Block, but the evidence in support is circumstantial. The contrast in the metamorphic development is definitive evidence that the heat flow linked to the Whin Sill intrusion in the Upper Teesdale area lasted much longer than other areas across the Block, giving strong support to the magma being sourced in this area, rather than from the dykes.Supplementary material: X-ray fluorescence whole rock Sr (ppm) analyses of limestone beds in boreholes 17, 18, 21, 22, 35, 39, 40 and 41 in Table S1, and Electron MicroProbe Analysis of garnet, feldspar, epidote, idocrase, prehnite, pyroxene and chlorite in Table S2 are available at: https://doi.org/10.6084/m9.figshare.c.5077640

Metamorphosis in Crustaceans

Many crustaceans undergo considerable morphological and ecological changes throughout ontogeny. Especially drastic and rapid cases are generally addressed as metamorphosis, which cannot be easily differentiated from nonmetamorphic development; a comparative view is necessary. Evolutionary changes lead to a more metamorphic development either by changing the speed of the developmental process or the morphological difference between earlier and later stages. Five cases of evolutionary changes are differentiated: (1) Skipping stages: An ancestrally gradual developmental pattern becomes more metamorphic as the morphological changes of several molts occur in a single molt; the intermediate stage is skipped. (2) Peramorphosis: A developmental pattern becomes more metamorphic by increasing the morphological difference between early and late stages by “adding” new morphologies to the later part of individual development. (3) Delay and acceleration, single step: A single larval stage becomes delayed in development, more resembling the earlier stage, but differing more strongly from the next stage; hence, this later molt becomes more metamorphic. (4) Delay and acceleration, globally: Several larval stages are delayed in development and hence increase the morphological difference to the later larval stages; this stronger difference is bridged by a single, more metamorphic molt. (5) Caenogenesis: new structures evolve in earlier stages, increasing the difference to later stages; these structures become reduced usually in a single molt, making it more metamorphic. For all cases, examples are presented. Furthermore, terminological issues are discussed, as well as costs and benefits of metamorphic development, followed by a short comparison to insects.

Modulation of Metamorphic and Regenerative Events by Cold Atmospheric Pressure Plasma Exposure in Tadpoles, Xenopus laevis

Atmospheric pressure plasma has found wide clinical applications including wound healing, tissue regeneration, sterilization, and cancer treatment. Here, we have investigated its effect on developmental processes like metamorphosis and tail regeneration in tadpoles. Plasma exposure hastens the process of tail regeneration but delays metamorphic development. The observed differences in these two developmental processes following plasma exposure are indicative of physiological costs associated with developmental plasticity for their survival. Ultrastructural changes in epidermis and mitochondria in response to the stress of tail amputation and plasma exposure show characteristics of cellular hypoxia and oxidative stress. Mitochondria show morphological changes such as swelling with wide and fewer cristae and seem to undergo processes such as fission and fusion. Complex interactions between calcium, peroxisomes, mitochondria and their pore transition pathways are responsible for changes in mitochondrial structure and function, suggesting the subcellular site of action of plasma in this system.