Propineb induced notochord deformity, craniofacial malformation, and osteoporosis in zebrafish through dysregulated reactive oxygen species generation.

Dithiocarbamate (DTC) fungicides are contaminants that are ubiquitous in the environment. Exposure to DTC fungicides has been associated with a variety of teratogenic developmental effects. Propineb, a member of DTCs, was evaluated for the toxicological effects on notochord and craniofacial development, osteogenesis in zebrafish model. Embryos at 6 hours post-fertilization (hpf) were exposed to propineb at dosages of 1 and 4 µM. Morphological parameters were evaluated at exposure times of 24, 48, 72, and 120 hpf after propineb exposure. The survival and hatching rates as well as body length decreased at 1 and 4 µmol/L groups. Besides, transgenic zebrafish exposed to propineb showed abnormal vacuole biogenesis in notochord cells at the early stage of development. The expression of collagen type 2 alpha 1a (col2a1a), sonic hedgehog (shh), and heat shock protein family B member 11 (hspb11) measured by quantitative PCR and in situ hybridization experiment of col8a1a gene have consolidated the proposal process. Besides, Alcian blue, calcein, and alizarin red staining profiles displayed craniofacial malformations and osteoporosis were induced following propineb exposure. PPB exposure induced the changes in oxidative stress and reactive oxygen species inhibitor alleviated the deformities of PPB. Collectively, our data suggested that propineb exposure triggered bone abnormalities in different phenotypes of zebrafish. Therefore, propineb is a potential toxicant of high priority concern for aquatic organisms.

Diflovidazin damages the hematopoietic stem cells to zebrafish embryos via the TLR4/ NF-κB/ p53 pathway.

Exposure to environmental contaminants frequently induces the occurrence of blood diseases, but the underlying molecular mechanisms are scarcely known. The toxicity of Diflovidazin (DFD), a widely used mite-remover, to the blood system of non-target organisms requires urgent elucidation. To investigate the deleterious effects of DFD (2, 2.5, and 3 mg/L) on the development and survive of hematopoietic stem cells (HSCs), the zebrafish model was used in this study. DFD exposure reduced the number of HSCs and their subtypes, including macrophages, neutrophils, thymus T-cells, erythrocytes, and platelets. The significant changes in the abnormal apoptosis and differentiation of HSCs were the major reasons for the reduction in blood cells. Using small-molecule antagonists and p53 morpholino revealed that the NF-κB/p53 pathway was responsible for the apoptosis of HSCs upon DFD exposure. The restoration results attributed to the TLR4 inhibitor and molecular docking showed that the TLR4 protein, which was upstream of NF-κB signaling, played a vital role in DFD toxicology. This study elucidates the role and molecular mechanism of DFD in damaging zebrafish HSCs. It provides a theoretical basis for the occurrence of various blood diseases in zebrafish and other organisms.

Disproportional erosion of the middle-lower Yangtze River following the operation of the Three Gorges Dam.

The operation of the Three Gorges Dam (TGD) modifies downstream flow and sediment regimes, triggering disproportional fluvial responses at different distances downstream. However, our understanding of the downstream geomorphic changes in the middle-lower Yangtze River remains incomplete due to the complexity of the river responses across temporal and spatial scales. Here, we leverage data on discharge, suspended sediment concentration (SSC), riverbed grain size, cross-sectional profiles and high-resolution channel bathymetric maps at different locations downstream of the TGD to investigate geomorphic responses. The results show that the magnitude of fluvial erosion decreases downstream, with the Yichang-Luoshan Reach (the first ~500 km downstream) experiencing the most severe erosion in 2003-2020 (~9.05 × 104 t/km/yr). Local changes in riverbed morphology include channel bar erosion, channel incision (~0.43 m/yr in CS1 near the dam site over 2002-2019), riverbank retreat and bed material coarsening (an increase in D50 from 0.175 to 43.1 mm at Yichang station from 2002 to 2017). Such marked erosion is caused by the sharply reduced SSC in the dominant discharge range (10,000-30,000 m3/s) and the extended duration of this dominant discharge range. The sediment erosive magnitude in the Luoshan-Datong Reach is relatively small (3.85 × 104 t/km/yr) in 2002-2020. The Luoshan-Hukou Reach (~500-1000 km downstream) exhibits moderate channel incision, minor bed material coarsening and moderate mid-channel bar lateral erosion. The Hukou-Datong Reach (below 1000 km downstream) experienced minor geomorphic change without significant evidence of bed material coarsening. The relatively small impact of the TGD on the lower reach from Luoshan to Datong can be mainly attributed to the progressive SSC recovery along the river induced by upstream channel erosion providing sediment replenishment. These findings have significant implications for estimating geomorphic changes in response to upstream damming and thus could inform better river management and ecological assessment in other similar alluvial rivers.

Simulating the impact of piers on hydrodynamics and pollutant transport: A case study in the Middle Yangtze River.

It is known that channel engineering, including the construction of piers, will change the river hydrodynamic characteristics, which is a significant factor affecting the transport process of pollutants. With this regard, this study uses the well-validated and tested hydrodynamic module and transport module of MIKE 21 to simulate the hydrodynamics and water quality under various pier densities in the Wuhan reach. Hydrodynamic changes around the piers show spatial differences, which are similar under different discharges. The range and amplitude of hydrodynamic spatial variations increase with the increase in pier density. However, there is a critical value of 1.25 to 2.5 units/km. When the pier density is less than this critical value, this type of cumulative effect is the most significant. Additionally, greater changes can be found in chemical oxygen demand concentrations, which also show spatial and temporal variations. The area with high chemical oxygen demand concentration upstream and downstream from the engineering area exhibits the distribution characteristics of "decrease in the downstream area and increase in the upstream area" and "increase in downstream the area and decrease in the upstream area" respectively. In the reach section of the engineering area, the area with high chemical oxygen demand concentration increases in the front area near the piers and decreases near the shoreline. Furthermore, the concentration shows attenuation actions with a longer residence time owing to the buffering effect of pier groups. These results have significant implications on shoreline planning and utilization. Moreover, they provide scientific guidelines for water management.