Sublethal Effects of Arsenic on Oxygen Consumption, Hematological and Gill Histopathological Indices in Chanos chanos

Background: The current study was performed aiming to evaluate possible changes in the effect on oxygen consumption, hematology and gill histopathological parameters in fish (Chanos chanos) upon exposure to sublethal concentration of the metalloid arsenic. Methods: Bioassay tests were conducted for determining the LC50 values of arsenic for 96 h. Oxygen consumption in control and arsenic-exposed fish was estimated using Winkler’s method. Red blood corpuscular (RBC) count was examined with a Neubauer counting chamber under a phase contrast microscope. Hemoglobin (Hb) was estimated following the acid hematin method. Histopathological studies were carried by processing and staining the gill tissues with hematoxylin and eosin in accordance with standard histological techniques. They were then subjected to examination under a scanning electron microscope. Results: Chanos chanos exposed to 1/10th of LC50 (24.61%) for a period of 30 days exhibited a maximum decline in the rate of respiration, followed by a decline in RBC and Hb above 45.59% and 51.60%, respectively. Significant toxic lesions encompassing fused gill lamellae, detached gill epithelium, hyperplasia and hypertrophy of respiratory epithelium became heavy handed on the 30th day. Conclusion: Information synthesized from our study serves to be useful in monitoring and managing (As) contamination in the aquatic environment.

Expression of Cytochrome c3 from Desulfovibrio vulgaris in Plant Leaves Enhances Uranium Uptake and Tolerance of Tobacco

Cytochrome c3 (uranyl reductase) from Desulfovibrio vulgaris can reduce uranium in bacterial cells and in cell-free systems. This gene was introduced in tobacco under control of the RbcS promoter, and the resulting transgenic plants accumulated uranium when grown on a uranyl ion containing medium. The uptaken uranium was detected by EM in chloroplasts. In the presence of uranyl ions in sublethal concentration, the transgenic plants grew phenotypically normal while the control plants’ development was impaired. The data on uranium oxidation state in the transgenic plants and the possible uses of uranium hyperaccumulation by plants for environmental cleanup are discussed.

Signals from predators, injured conspecifics, and pesticide modify the swimming behavior of the gregarious tadpole Rhinella dorbignyi (Anura: Bufonidae)

Tadpoles detect chemical signals released from predators and conspecifics, and those present in the environment, and adjust their behavioral responses. This study evaluated the swimming activity of Rhinella dorbignyi (Duméril and Bibron, 1941) tadpoles exposed to chemical signals, including cues from a predator fish Synbranchus marmoratus Bloch, 1975 and an injured conspecific; sublethal concentration of insecticide cypermethrin; and their combination. Swimming behavior (total distance moved, average speed, global activity, number of contacts between tadpoles) was evaluated in an individual (1) and groups of different size (3, 5, 7 and 10 tadpoles) using a video-tracking software tool. Predator exposure modified behavioral parameters, reducing encounters with predators and, therefore, mortality. Total distance moved and average speed increased in trials involving 1 tadpole and 3 interacting tadpoles exposed to injured conspecifics, whereas global activity increased in all group sizes, showing that gregarious tadpoles may be affected by alarm cues and their behavior may be disrupted. The insecticide treatments (alone and combined) increased parameters in all group sizes, causing hyperactivity due to its neurotoxic effect. The different responses observed after exposure to alarm cues and environmental signals in the different group sizes modified the normal behavior and the ecological dynamics of gregarious tadpoles.

Investigating Transcriptomic Induction of Resistance and/or Virulence in Listeria monocytogenes Cells Surviving Sublethal Antimicrobial Exposure

The potential transcriptomic induction of resistance and/or virulence in two L. monocytogenes strains belonging to the most frequent listeriosis-associated serovars (i.e., 1/2a and 4b), following their sublethal antimicrobial exposure, was studied through qPCR determination of the relative expression of 10 selected related genes (i.e., groEL, hly, iap, inlA, inlB, lisK, mdrD, mdrL, prfA, and sigB). To induce sublethal stress, three common antimicrobials (i.e., benzalkonium chloride, thymol, and ampicillin) were individually applied for 2 h at 37 °C against stationary phase cells of each strain, each at a sublethal concentration. In general, the expression of most of the studied genes remained either stable or was significantly downregulated following the antimicrobial exposure, with some strain-specific differences to be yet recorded. Thymol provoked downregulation of most of the studied genes, significantly limiting the expression of 6/10 and 4/10 genes in the strains of ser. 1/2a and ser. 4b, respectively, including those coding for the master regulators of stress response and virulence (SigB and PrfA, respectively), in both strains. At the same time, the two genes coding for the invasion internalin proteins (InlA and InlB), with crucial role in the onset of L. monocytogenes pathogenesis, were both importantly upregulated in ser. 4b strain. The results obtained increase our knowledge of the stress physiology of L. monocytogenes under certain sublethal antimicrobial conditions that could be encountered within the food chain and in clinical settings, and may assist in better and more effective mitigation strategies.

Evaluation of Behavioral Changes and Tissue Damages in Common Carp (Cyprinus carpio) after Exposure to the Herbicide Glyphosate

Pesticides can induce changes in behavior and reduce the survival chance of aquatic organisms. In this study, the toxic effects of glyphosate suspension (Glyphosate Aria 41% SL, Tehran Iran) on behavior and tissues of common carp (Cyprinus carpio) were assessed. For this purpose, a 96 h LC50 of glyphosate suspension (68.788 mL·L−1) was used in the toxicity test. All individuals were divided into control and treatment groups with four replicates. Exposure operations were performed under two conditions: increasing concentration of suspension from 0 to 68.788 mL·L−1; then, decreasing to the first level. The swimming pattern was recorded by digital cameras during the test and tissue samples were collected at the end of the test. There were significant differences between the swimming pattern of treated individuals and control ones during both steps. The sublethal concentration of glyphosate led to hypertrophy, hyperplasia and hyperemia in the gill of fish. However, changes were obvious only after sampling. The exposed fish also displayed clinical signs such as darkening of the skin and increasing movement of the operculum. Moreover, glyphosate suspension affected swimming patterns of fish suggest that the swimming behavior test can indicate the potential toxicity of environmental pollutants and be used as a noninvasive, useful method for managing environmental changes and assessing fish health conditions by video monitoring.

Surface charge-dependent mitochondrial response to similar intracellular nanoparticle contents at sublethal dosages

Background Considering the inevitability for humans to be frequently exposed to nanoparticles (NPs), understanding the biosafety of NPs is important for rational usage. As an important part of the innate immune system, macrophages are widely distributed in vital tissues and are also a dominant cell type that engulfs particles. Mitochondria are one of the most sensitive organelles when macrophages are exposed to NPs. However, previous studies have mainly reported the mitochondrial response upon high-dose NP treatment. Herein, with gold nanoparticles (AuNPs) as a model, we investigated the mitochondrial alterations induced by NPs at a sublethal concentration. Results At a similar internal exposure dose, different AuNPs showed distinct degrees of effects on mitochondrial alterations, including reduced tubular mitochondria, damaged mitochondria, increased reactive oxygen species, and decreased adenosine triphosphate. Cluster analysis, two-way ANOVA, and multiple linear regression suggested that the surface properties of AuNPs were the dominant determinants of the mitochondrial response. Based on the correlation analysis, the mitochondrial response was increased with the change in zeta potential from negative to positive. The alterations in mitochondrial respiratory chain proteins indicated that complex V was an indicator of the mitochondrial response to low-dose NPs. Conclusion Our current study suggests potential hazards of modified AuNPs on mitochondria even under sublethal dose, indicates the possibility of surface modification in biocompatibility improvement, and provides a new way to better evaluation of nanomaterials biosafety.