Endogenous 4-hydroxy-2-nonenal in microalga Chlorella kessleri acts as a bioactive indicator of pollution with common herbicides and growth regulating factor of hormesis

Enhancing the biodiesel production in the green alga Chlorella vulgaris by heavy metal stress and prediction of fuel properties from fatty acid profiles

The green microalga Chlorella vulgaris was used as a test organism during this study for evaluation of the impact of different heavy metal stress, Mn2+, Co2+, and Zn2+, on enhancing the biodiesel production. The algal cultures were grown for 13 days under heavy metal stress after which were subjected to estimation of growth, some primary metabolites, lipid, and fatty acid profiles. The maximum lipid accumulation (283.30 mg/g CDW) was recorded in the algal culture treated with 3 µM cobalt nitrate. Application of 2 mM manganese chloride; 1, 2, and 3 μM cobalt nitrate; and 0.2, 0.4, and 0.6 mM zinc sulfate caused highly significant increases in the lipid contents amounting to 183.8, 191.4, 230.6, 283.3, 176.3, 226.0, and 212.1 mg/g CDW, respectively, in comparison to control (153.4 mg/g CDW). The maximum proportion of saturated fatty acids (SFA) (64.44%) was noted in the culture treated with 6 mM MnCl2 due to the existence of palmitic acid (C16:0), stearic acid (C18:0), and pentadecylic acid (C15:0) which are represented by 53.59%, 5.96%, and 1.37%, respectively, of the total FAs. Relative increase in energy compound (REEC) showed that 1, 2, and 3 µM Co2+ lead to the highest stimulation in lipid and carbohydrate contents to 0.207, 0.352, and 0.329 × 103%, respectively. Empirical formulas were used for the assessment of biodiesel fuel properties based on FAME composition. The estimated properties met the prescribed international standard criteria.

Co-cultivation of microalgae-activated sludge for municipal wastewater treatment: Exploring the performance, microbial co-occurrence patterns, microbiota dynamics and function during the startup stage

Microalgae consortium is a promising technology for achieving low-carbon and resource utilization goals in municipal wastewater treatment. However, little is known about how the consortium affects the treatment performance in the startup stage of co-cultivation. Herein, photobioreactors were constructed with different contents of microalgae and activated sludge (AS) (wt._microalgae: wt._AS ≥ 50 %). The results showed that the concentration of microalgae increased by more than 20 % with AS, and the effluents were close or lower than Chinese discharge standards within HRT 24 h (NH₄⁺-N, TP, and COD ≤ 5.0, 0.5, and 50 mg L^-1). Furthermore, the co-occurrence pattern of microbial populations experienced inhibition-reconstruction and reconstruction-inhibition processes, respectively, and the inter-species relationship was directly related to the effluent quality. Microalgal concentration and temperature were the key factors to the microbial community profiling. The potential microorganisms in AS could promote the growth of microalgae, and the bacteria and fungi formed co-metabolism through functional complementation.

Short Overview of Some Assays for the Measurement of Antioxidant Activity of Natural Products and Their Relevance in Dermatology

Impaired systemic redox homeostasis is implicated in the onset and development of various diseases, including skin diseases. Therefore, continuous search for natural products with antioxidant bioactivities applicable in biomedicine is attractive topic of general interest. Research efforts aiming to validate antioxidant potentials of natural products has led to the development of several assays based on various test principles. Hence, understanding the advantages and limitations of various assays is important for selection of assays useful to study antioxidant and related bioactivities of natural products of biomedical interest. This review paper gives a short overview on some chemical and cellular bioassays used to estimate the antioxidant activity of chosen natural products together with a brief overview on the use of natural products with antioxidant activities as adjuvant medicinal remedies in dermatology.

Exposure of the alga Pseudokirchneriella subcapitata to environmentally relevant concentrations of the herbicide metolachlor: Impact on the redox homeostasis

This study investigated the effect of the herbicide metolachlor (MET) on the redox homeostasis of the freshwater green alga Pseudokirchneriella subcapitata. At low MET concentrations (≤40 μg L^-1), no effects on algal cells were detected. The exposure of P. subcapitata to 45-235 μg L^-1 MET induced a significant increase of reactive oxygen species (ROS). The intracellular levels of ROS were particularly increased at high (115 and 235 μg L^-1) but environmentally relevant MET concentrations. The exposure of algal cells to 115 and 235 μg L^-1 MET originated a decrease in the levels of antioxidants molecules (reduced glutathione and carotenoids) as well as a reduction of the activity of scavenging enzymes (superoxide dismutase and catalase). These results suggest that antioxidant (non-enzymatic and enzymatic) defenses were affected by the excess of MET. As consequence of this imbalance (ROS overproduction and decline of the antioxidant system), ROS inflicted oxidative injury with lipid peroxidation and damage of cell membrane integrity. The results provide further insights about the toxic modes of action of MET on a non-target organism and emphasize the relevance of toxicological studies in the assessment of the impact of herbicides in freshwater environments.

Isolation of Four Microalgal Strains From the Lake Massaciuccoli: Screening of Common Pollutants Tolerance Pattern and Perspectives for Their Use in Biotechnological Applications

Aquatic ecosystems represent one of the largest reservoirs of phytoplankton accounting for most of the primary production of the Earth. The Lake Massaciuccoli located in Tuscany (Italy) is one of the largest swamps that in ancient times entirely covered the Versilia coastal plain. Despite its peculiar features, especially the eutrophic characteristics, its native microalgal consortia have never been explored up to now. In this work, we isolated and described four autochthonous microalgal strains from different sites in the lake (FB, Idr, CL_Sc, and CL_Ch); the four microalgal strains were identified within the Chlorella sorokiniana clade. We exposed them to ten of the most common or emerging environmental contaminants in order to describe their preliminary response to the tested substances: five metals (As, Fe, Ni, Cu, and Zn), two herbicides (Metolachlor and Sethoxydim), two antibiotics (Ciprofloxacin and Benzylpenicillin) and a non-steroidal anti-inflammatory drug (Ibuprofen). Physiological response of the strains highlighted intraspecific differences; strain CL_Sc was the most tolerant in presence of metals while strain Idr was the most sensitive. All strains were sensitive to sethoxydim and tolerant to metolachlor at all the tested concentrations. Strains FB and Idr were the most sensitive in presence of Ibuprofen while strain CL_Ch was the most sensitive to the highest Benzylpenicillin concentration. Resistance pattern of strain Idr somehow reflects both the phylogenetic and the geographic "isolation" from all other three strains. Finally, optical microscope observation confirmed some differences also in the microalgae morphological aspect. Overall, all the strains showed interesting responses in presence of high concentrations of the tested substances, representing putative interesting candidates for water remediation in wastewater treatment plants.

Phytoextraction of diuron, hexazinone, and sulfometuron-methyl from the soil by green manure species

The herbicides diuron, hexazinone, and sulfometuron-methyl present a potential risk of environmental contamination and are widely used for weed control in sugarcane cultivation. Our objectives were to measure the tolerance of Canavalia ensiformes (L.) DC., Stilizobium aterrimum L., Raphanus sativus L., Crotalaria spectabilis Röth, Lupinus albus L., and Pennisetum glaucum (L.) R. Br. To the herbicides diuron, hexazinone, and sulfometuron-methyl to assess the capacity of these species to extract and accumulate the herbicides in their tissues. Before sowing the green manure species, the soils were individually contaminated with the three ¹⁴C-radiolabeled herbicides. ¹⁴C-diuron and ¹⁴C-sulfometuron-methyl showed higher values remaining in the soil (>90%) for all species of green manure compared to hexazinone (<80%). The green manure species analyzed showed greater potential to remedy soils contaminated with hexazinone than the other herbicides. C. ensiformes showed high phytoextraction of hexazinone when compared to the other species, removing 11.2% of the pollutant from the soil, followed by L. albus (8.6%), S. aterrimum (7.3%), R. sativus (4.8%), C. spectabilis (2.5%), and P. glaucum (1.1%). The results indicate that the phytoextraction of diuron, hexazinone and sulfometuron-methyl is dependent on the species of green manure and can be an important tool for the decontamination of areas polluted by these herbicides.

A Review of Algae-Based Produced Water Treatment for Biomass and Biofuel Production

Produced water (PW), the largest waste stream generated in oil and gas industries, has the potential to be a harmless product rather than being a waste. Biological processes using microorganisms have proven useful to remediate PW contaminated by petroleum hydrocarbons, complex organic chemicals, and solvents. In particular, the bioremediation of PW using algae is an eco-friendly and low-cost approach due to algae’s ability to utilize certain pollutants as nutrient sources. Therefore, the utilization of PW as an algal growth medium has a great potential to eliminate chemicals from the PW and minimize the large volumes of freshwater needed for cultivation. Although several reviews describing the bioremediation of PW have been published, to the best of our knowledge, no review has exclusively focused on the algae-based PW treatment. Therefore, the present review is dedicated to filling this gap by portraying the many different facets of the algae cultivation in PW. Several algal species that are known to thrive in a wide range of salinity and the critical steps for their cultivation in hypersaline PW have been identified. Overall, this comprehensive review highlights the PW bioremediation using algae and brings attention to utilizing PW to grow biomass that can be processed to generate biofuels and useful bioproducts.

Multistressor negative effects on an experimental phytoplankton community. The case of glyphosate and one toxigenic cyanobacterium on Chlorophycean microalgae

Aquatic ecosystems face serious pollution issues. Discharges of toxic substances and eutrophication may lead to changes in the phytoplankton community and foster cyanobacterial blooms. Glyphosate-based herbicides are chemical stressors of microalgae that may affect the structure of phytoplankton communities, and also stimulate the synthesis of cyanotoxins by cyanobacteria. The simultaneous presence of glyphosate and toxigenic cyanobacteria increases the stress on microalgae, jointly affecting their growth and development. This study evaluated the combined effect of a toxigenic cyanobacterium and glyphosate in the development of an experimental microalgal community. We studied the effect of Microcystis aeruginosa on the population growth of the microalgae Ankistrodesmus falcatus, Chlorella vulgaris, Pseudokirchneriella subcapitata, and Scenedesmus incrassatulus. We also evaluated the combined effect of sub-inhibitory glyphosate (Faena®) concentrations on the content of macromolecules and the enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), as well as on the concentration of TBARS. These effects were evaluated through the integrated biomarker response (IBR). In individual experiments, microalgae showed lower growth rates versus M. aeruginosa. In the mixed bioassays, both M. aeruginosa and microalgae showed reduced growth. IC50 values for Faena® ranged from 1.022 to 2.702 mg L-1. In the microalgae + cyanobacteria bioassays, the herbicide lowered the growth rates of microalgae but stimulated the proliferation of M. aeruginosa. The joint action of both stressors affected growth rate and population dynamics, macromolecule content, and led to increased CAT and GPx levels. Faena® influenced growth rate and caused oxidative stress. On the other hand, the herbicide stimulated the synthesis of cyanotoxins, which further affected microalgal development. The experimental community was not only affected by the herbicide, but the mixed culture with cyanobacteria magnified the effects of chemical stress. These results illustrate the potential damage to phytoplankton expected in anthropically eutrophic water bodies that are also polluted by glyphosate.

Reproductive cycle progression arrest and modification of cell morphology (shape and biovolume) in the alga Pseudokirchneriella subcapitata exposed to metolachlor

Metolachlor (MET) is an herbicide widely used and frequently found (at μg L^-1) in aquatic systems. This work aimed to study the modes of action of MET on the green microalga Pseudokirchneriella subcapitata. Algae exposed to 115 or 235 μg L^-1 MET, for 48 or 72 h, presented a reduction of metabolic activity, chlorophyll a and b content and photosynthetic efficiency. The exposure to 115 or 235 μg L^-1 MET also induced growth yield reduction, mean cell biovolume increase and alteration of the typical algae shape (cells lunate or helically twisted) to "French croissant"-type; at these MET concentrations, algal population was mainly composed by multinucleated cells (≥ 4 nuclei), which suggest that MET impairs the normal progression of the reproductive cycle but did not hinder nuclear division. The accumulation of multinucleated cells seems to be the consequence of the incapacity of the parent cell to release the autospores. In conclusion, MET disrupts the physiology of P. subcapitata cells; the disturbance of the progression of the reproductive cycle should be in the origin of growth slowdown (or even its arrest), increase of mean cell biovolume and modification of algal shape. This work contributed to elucidate, in a systematically and integrated way, the toxic mechanism of MET on the non-target organism, the alga P. subcapitata.

Physiological and enzymatic responses of Chlorella vulgaris exposed to produced water and its potential for bioremediation

In South America, Colombia is known as an important oil-producing country. However, the environmental impact of crude oil industry has not been studied deeply and few studies have been carried out for evaluating responses of algae and its adaptation under specific conditions. Enzymatic and physiological effects in Chlorella vulgaris and its potential for bioremediation after exposure to produced water (PW) were assessed using different PW concentrations (0, 25, 50, 75 and 100%) and crude oil. Variables such as cell density, growth rate (μ), percentage of growth inhibition (% I), chlorophyll a and b and cell diameter were evaluated during 5 days. Furthermore, enzymatic biomarkers such as superoxide dismutase (SOD) and catalase (CAT) were also measured. Results showed that the treatment with 100% PW had the highest cell density and μ; similarly, 25% PW treatment had a similar behaviour, being these two treatments with the highest growth. A dose-dependent response was seen for chlorophyll a and b and cell diameter, showing significant differences between treatments and the control. Different levels of SOD and CAT were observed in algae exposed to PW. At 24 h, an increase in SOD and CAT activity was observed, probably due to effects caused by xenobiotics. After 72 h, a decrease in the activity of both enzymes was observed. The results evidenced that C. vulgaris can adapt easily to PW, showing an increase on its growth and stabilisation in its antioxidant activity. Additionally, cell diameter results and decrease of hydrocarbons and phenols show the potential of these algae to degrade xenobiotics from PW.

Interaction between 1,2-benzisothiazol-3(2H)-one and microalgae: Growth inhibition and detoxification mechanism

Isothiazolinones, such as 1,2-benzisothiazol-3(2H)-one (BIT), are widely used as biocides for bacterial growth control in many domestic and industrial processes. Despite their advantages as biocides, they are highly toxic and pose a potential risk to the environment. This study investigated the inhibition process and detoxification mechanism involved in microalgal survival and growth recovery after BIT poisoning. BIT could seriously inhibit the growth of Scenedesmus sp. LX1, Chlorella sp. HQ, and Chlamydomonas reinhardtii with half maximal effective concentrations at 72 h (72h-EC₅₀) of 1.70, 0.41, and 1.16 mg/L, respectively. The primary inhibition mechanism was the BIT-induced damage to microalgal photosynthetic systems. However, the inhibited strains could recover when their growth was not completely inhibited. The influence of this inhibiting effect on subsequent algal regrowth was negligible or weak. BIT consumption was the primary reason for their recovery. Notably, algae did not die even if their growth was completely inhibited. If the BIT concentration did not exceed a certain high level, then the inhibited algae could recover their growth relatively well. Microalgal generation of reduced glutathione (GSH) and the oxygen radical scavenging enzymes, superoxide dismutase (SOD) and catalase (CAT), played a key role in detoxification against BIT poisoning.

S-metolachlor promotes oxidative stress in green microalga Parachlorella kessleri - A potential environmental and health risk for higher organisms

The estimation of the toxic influences of herbicide products on non-target aquatic organisms is essential for evaluation of environmental contamination. We assessed the effects of the herbicide S-metolachlor (S-MET) on unicellular green microalga Parachlorella kessleri during 4-72 in vitro exposure to concentrations in the range 2-200μg/L. The results have shown that S-MET had a significant effect on algae, even in doses 10 and 20 times lower than the EC50 values obtained for P. kessleri (EC50-72h=1090μg/L). It generates reactive oxygen species in algae, decreases their growth and photosynthetic pigment concentration, changes their ultrastructure and alters the cellular antioxidant defence capacities. The levels of protein adducts with the reactive aldehyde 4-hydroxy-2-nonenal (HNE), the end-product of lipid peroxidation, were significantly elevated in S-MET treated cells revealing the insufficient effectiveness of P. kessleri antioxidant mechanisms and persistent lipid peroxidation. Since algae are fundamental aquatic food component, the damaged algal cells, still capable of dividing while having persistently increased content of HNE upon S-MET contamination could represent an important environmental toxic factor that might further affect higher organisms in the food chain.

Ecotoxicological and biochemical mixture effects of an herbicide and a metal at the marine primary producer diatom Thalassiosira weissflogii and the primary consumer copepod Acartia tonsa

Mixture effects of chemicals and their potential synergistic interactions are of great concern to the public and regulatory authorities worldwide. Intensive agricultural activities are leading to discharges of chemical mixtures to nearby estuarine and marine waters with possible adverse effects on the aquatic communities and for the trophic food web interlinking these communities. Further information about the impacts of these stressors on aquatic organisms is needed. This study addresses ecotoxicological and biochemical effects of single and mixtures of the metal copper and the herbicide Primextra® Gold TZ on the marine diatom Thalassiosira weissflogii and on the estuarine calanoid copepod Acartia tonsa by determining growth rate and survival, respectively, and changes on fatty acid(FA) profiles in both species. Mixture effects on diatom species revealed that copper and Primextra® acted most likely additively with respect to the concentration addition (CA) and independent action (IA) models with model deviation ratios (MDR), 0.752 and 1.063, respectively. For the copepod species, copper and Primextra® were most likely non-interactive with respect to the CA model (MDR = 1.521) but acted most likely synergistically with respect to the IA model (MDR = 2.026). A significant decline in the absolute FA concentration was observed for copepod species after mixture exposure including a considerable decrease of essential FAs that cannot be synthesized de novo by these grazers. We concluded that the mixture effects are more hazardous for primary consumer than for primary producer species in terms of both abundance and biomass quality, suggesting a potential for harmful effects for higher trophic levels and thus a decrease in energy flow through the ecosystem.

Acrolein-Induced Oxidative Stress and Cell Death Exhibiting Features of Apoptosis in the Yeast Saccharomyces cerevisiae Deficient in SOD1

The yeast Saccharomyces cerevisiae is a useful eukaryotic model to study the toxicity of acrolein, an important environmental toxin and endogenous product of lipid peroxidation. The study was aimed at elucidation of the cytotoxic effect of acrolein on the yeast deficient in SOD1, Cu, Zn-superoxide dismutase which is hypersensitive to aldehydes. Acrolein generated within the cell from its precursor allyl alcohol caused growth arrest and cell death of the yeast cells. The growth inhibition involved an increase in production of reactive oxygen species and high level of protein carbonylation. DNA condensation and fragmentation, exposition of phosphatidylserine at the cell surface as well as decreased dynamic of actin microfilaments and mitochondria disintegration point to the induction of apoptotic-type cell death besides necrotic cell death.

Nutrient removal by Chlorella vulgaris F1068 under cetyltrimethyl ammonium bromide induced hormesis

Toxicants are generally harmful to biotechnology in wastewater treatment. However, trace toxicant can induce microbial hormesis, but to date, it is still unknown how this phenomenon affects nutrient removal during municipal wastewater treatment process. Therefore, this study focused on the effects of hormesis induced by cetyltrimethyl ammonium bromide (CTAB), a representative quaternary ammonium cationic surfactant, on nutrient removal by Chlorella vulgaris F1068. Results showed that when the concentration of CTAB was less than 10 ng/L, the cellular components chlorophyll a, proteins, polysaccharides, and total lipids increased by 10.11, 58.17, 38.78, and 11.87 %, respectively, and some enzymes in nutrient metabolism of algal cells, such as glutamine synthetase (GS), acid phosphatase (ACP), H(+)-ATPase, and esterase, were also enhanced. As a result, the removal efficiencies of ammonia nitrogen (NH4 (+)) and total phosphorus (TP) increased by 14.66 and 8.51 %, respectively, compared to the control during a 7-day test period. The underlying mechanism was mainly due to an enhanced photosynthetic activity of C. vulgaris F1068 indicated by the increase in chlorophyll fluorescence parameters (the value of Fv/Fm, ΦII, Fv/Fo, and rETR increased by 12.99, 7.56, 25.59, and 8.11 %, respectively) and adenylate energy charge (AEC) (from 0.68 to 0.72). These results suggest that hormesis induced by trace toxicants could enhance the nutrient removal, which would be further considered in the design of municipal wastewater treatment processes. Graphical abstract The schematic mechanism of C. vulgaris F1068 under CTAB induced hormesis. Green arrows ( ) represent the increase and the red arrow ( ) represents the decrease.

Lipids and proteins--major targets of oxidative modifications in abiotic stressed plants

Stress factors provoke enhanced production of reactive oxygen species (ROS) in plants. ROS that escape antioxidant-mediated scavenging/detoxification react with biomolecules such as cellular lipids and proteins and cause irreversible damage to the structure of these molecules, initiate their oxidation, and subsequently inactivate key cellular functions. The lipid- and protein-oxidation products are considered as the significant oxidative stress biomarkers in stressed plants. Also, there exists an abundance of information on the abiotic stress-mediated elevations in the generation of ROS, and the modulation of lipid and protein oxidation in abiotic stressed plants. However, the available literature reflects a wide information gap on the mechanisms underlying lipid- and protein-oxidation processes, major techniques for the determination of lipid- and protein-oxidation products, and on critical cross-talks among these aspects. Based on recent reports, this article (a) introduces ROS and highlights their relationship with abiotic stress-caused consequences in crop plants, (b) examines critically the various physiological/biochemical aspects of oxidative damage to lipids (membrane lipids) and proteins in stressed crop plants, (c) summarizes the principles of current technologies used to evaluate the extent of lipid and protein oxidation, (d) synthesizes major outcomes of studies on lipid and protein oxidation in plants under abiotic stress, and finally, (e) considers a brief cross-talk on the ROS-accrued lipid and protein oxidation, pointing to the aspects unexplored so far.

Hormetic Responses of Food-Supplied Pcb 31 to Zebrafish (Danio Rerio) Growth

Hormesis is commonly defined as a beneficial or stimulatory effect caused by exposure to low doses of a chemical known to be toxic at high doses. Hormetic responses of food-supplied PCB 31 (2, 4', 5-Trichlorobiphenyl) was studied by using zebrafish (Danio rerio) growth as an end point. The results in general followed the hormesis hypothesis, PCB 31 at lower concentrations (0.042 μg/g and 0.084 μg/g) exhibited beneficial effects on the growth of zebrafish by weight and length while higher concentrations (10μg/g and 20μg/g) revealed inhibitory effects. The magnitude of stimulatory responses of zebrafish growth by weight and length at lower concentrations (0.01-0.084 μg/g) on days 14 and 21 were in the range 9.09-18.18%; 10-38.09% and 4-14.4%; 6.25-10.93%, respectively as compared to control. Growth and conditions indices also suggested that the zebrafish was healthier at lower concentrations as compared to those at higher concentrations. The results of the present study will elaborate fish toxicological evaluation regarding the hormetic model.

The impact of Eskoba, a glyphosate formulation, on the freshwater plankton community

This study analyzed the acute effects of a glyphosate-based herbicide (Eskoba) on the microalgae Chlorella vulgaris, the cladoceran Simocephalus vetulus, and the copepod Notodiaptomus conifer, and evaluated the recovery ability of the surviving micro-crustaceans. Survival, age of first reproduction, and fecundity were used as endpoints for S. vetulus, while survival and time to reach the adult stage were used as endpoints for N. conifer. The registered order of sensitivity was S. vetulus (48-hour effective concentration [EC50]: 21 mg/L) > C. vulgaris (72-hour EC50: 58.59 mg/ L) > N. conifer (48-hour EC50: 95 mg/L). Despite the growth of C. vulgaris stimulated after 24 hours of exposure to the commercial formulation of glyphosate Eskoba, it was inhibited after 48 hours by all the concentrations tested. In postexposure experiments, microcrustaceans reduced their life expectancy, S. vetulus decreased its fertility, and N. conifer inhibited its sexual maturity. In summary, it was demonstrated that these species lost their recovery ability.

Herbicides and plant hormesis

Herbicide hormesis is commonly observed at subtoxic doses of herbicides and other phytotoxins. The occurrence and magnitude of this phenomenon are influenced by plant growth stage and physiological status, environmental factors, the endpoint measured and the timing between treatment and endpoint measurement. The mechanism in some cases of herbicide hormesis appears to be related to the target site of the herbicide, whereas in other examples hormesis may be by overcompensation to moderate stress induced by the herbicides or a response to disturbed homeostasis. Theoretically, herbicide hormesis could be used in crop production, but this has been practical only in the case of the use of herbicides as sugar cane 'ripeners' to enhance sucrose accumulation. The many factors that can influence the occurrence, the magnitude and the dose range of hormetic increases in yield for most crops make it too unpredictable and risky as a production practice with the currently available knowledge. Herbicide hormesis can cause undesired effects in situations in which weeds are unintentionally exposed to hormetic doses (e.g. in adjacent fields, when shielded by crop vegetation). Some weeds that have evolved herbicide resistance may have hormetic responses to recommended herbicide application rates. Little is known about such effects under field conditions. A more complete understanding of herbicide hormesis is needed to exploit its potential benefits and to minimize its potential harmful effects in crop production.

Growth, bioluminescence and shoal behavior hormetic responses to inorganic and/or organic chemicals: a review

A biphasic dose response, termed hormesis, is characterized by beneficial effects of a chemical at a low dose and harmful effects at a high dose. This biphasic dose response phenomenon has the potential to strongly alter toxicology in a broad range. The present review focuses on the progress of research into hormetic responses in terms of growth (in plants, birds, algae and humans), bioluminescence, and shoal behavior as end points. The paper describes how both inorganic and organic chemicals at a low dose show stimulatory responses while at higher doses are inhibitory. The article highlights how factors such as symbiosis, density-dependent factors, time, and contrasting environmental factors (availability of nutrients, temperature, light, etc.) affect both the range and amplitude of hormetic responses. Furthermore, the possible underlying mechanisms are also discussed and we suggest that, for every end point, different hormetic mechanisms may exist. The occurrences of varying interacting receptor systems or receptor systems affecting the assessment of hormesis for each endpoint are discussed. The present review suggests that a hormetic model should be adopted for toxicological evaluations instead of the older threshold and linear non-threshold models.

Assays for the measurement of lipid peroxidation

Physical and emotional stress, metabolic alterations, carcinogenesis or inflammation are conditions that can trigger oxidative stress, which is defined as a balance shift of redox reactions towards oxidation, resulting in the increase of reactive oxygen species (ROS). ROS are continuously formed in small quantities during the normal metabolism of cell, however the overproduction of ROS is cytotoxic and damages macromolecules (DNA, proteins, sugars and lipids). Polyunsaturated fatty acids (PUFAs) that are esterified in membrane or storage lipids are subject to ROS-induced peroxidation resulting in the destruction of biomembranes. Final products of lipid peroxidation (LPO) are reactive aldehydes that are relatively stable and may diffuse far from the initial site of oxidative injury and act as second messengers or free radicals. The difference between physiological and pathological oxidative stress is often the occurrence of LPO and its final toxic products. In this chapter, two classes of methods for measurement of LPO are described. The first include assays for detection of LPO at the organismal level, while the second include molecular and cellular assays that reveal the mechanistic effects of LPO on the function, morphology and viability of the cells.