The effects of Crocus sativus extract on inhaled paraquat-induced lung inflammation, oxidative stress, pathological changes and tracheal responsiveness in rats.

Paraquat is a green liquid toxin that is used in agriculture and can induce multi-organ including lung injury. Various pharmacological effects of Crocus sativus (C. sativus) were indicated in previous studies. In this research, the effects of C. sativus extract and pioglitazone on inhaled paraquat-induced lung inflammation, oxidative stress, pathological changes, and tracheal responsiveness were studied in rats. Eight groups of rats (n = 7 in each) including control (Ctrl), untreated paraquat aerosol exposed group (54 mg/m3, 8 times in alternate days), paraquat treated groups with dexamethasone (0.03 mg/kg/day, Dexa) as positive control, two doses of C. sativus extract (20 and 80 mg/kg/day, CS-20 and CS-80), pioglitazone (5 and 10 mg/kg/day, Pio-5 and Pio-10), and the combination of CS-20 + Pio-5 were studied. Total and differential WBC, levels of oxidant and antioxidant biomarkers in the BALF, lung tissue cytokine levels, tracheal responsiveness (TR), and pathological changes were measured. The levels of IFN-γ, IL-10, SOD, CAT, thiol, and EC50 were reduced, but MDA level, total and differential WBC count in the BALF and lung pathological changes were increased in the paraquat group (all, p < 0.001). The levels of IFN-γ, IL-10, SOD, CAT, thiol and EC50 were increased but BALF MDA level, lung pathological changes, total and differential WBC counts were reduced in all treated groups. The effects of C. sativus high dose and combination groups on measured parameters were equal or even higher than dexamethasone (p < 0.05 to p < 0.001). The effects of the combination of CS-20 + Pio-5 on most variables were significantly higher than CS-20 and Pio-5 alone (p < 0.05 to p < 0.001). C. sativus treatment improved inhaled paraquat-induced lung injury similar to dexamethasone and showed a synergistic effect with pioglitazone, suggesting possible PPAR-γ receptor-mediated effects of the plant.

Small Molecule-Capped Gold Nanoclusters for Curing Skin Infections.

With the long-term and extensive abuse of antibiotics, bacteria can mutate into multidrug-resistant (MDR) strains, resist the existing antibiotics, and escape the danger of being killed. MDR bacteria-caused skin infections are intractable and chronic, becoming one of the most significant and global public-health issues. Thus, the development of novel antimicrobial materials is urgently needed. Non-antibiotic small molecule-modified gold nanoclusters (AuNCs) have great potential as a substitute for commercial antibiotics. Still, their narrow antibacterial spectrum hinders their wide clinical applications. Herein, we report that 4,6-diamino-2-pyrimidinethiol (DAPT)-modified AuNCs (DAPT-AuNCs) can fight against Gram-negative and Gram-positive bacterial strains as well as their MDR counterparts. By modifying DAPT-AuNCs on nanofibrous films, we develop an antibiotic film as innovative dressings for curing incised wounds, which exhibits excellent therapeutic effects on wounds infected by MDR bacteria. Compared to the narrow-spectral one, the broad-spectral antibacterial activity of the DAPT-AuNCs-modified film is more suitable for preventing and treating skin infections caused by various kinds of unknown bacteria. Moreover, the antibacterial films display excellent biocompatibility, implying the great potential for clinical applications.

RIFM fragrance ingredient safety assessment, 1-heptanethiol, CAS Registry Number 1639-09-4.

1-Heptanethiol was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data from read-across analog 1-octanethiol (CAS # 111-88-6) show that 1-heptanethiol is not expected to be genotoxic and provide a calculated MOE >100 for the reproductive toxicity endpoint. Data on read-across analog dodecanethiol (CAS # 112-55-0) provide a calculated MOE >100 for the repeated dose toxicity endpoint. Data show that there are no safety concerns for 1-heptanethiol for skin sensitization under the current declared levels of use. The phototoxicity/photoallergenicity endpoints were evaluated based on UV/Vis spectra for read-across analog methyl mercaptan (CAS # 74-93-1); 1-heptanethiol is not expected to be phototoxic/photoallergenic. The local respiratory toxicity endpoint was evaluated using the TTC for a Cramer Class I material; exposure is below the TTC (1.4 mg/day). The environmental endpoints were evaluated; 1-heptanethiol was found not to be PBT as per the IFRA Environmental Standards, and its risk quotients, based on its current volume of use in Europe and North America (i.e., PEC/PNEC), are <1.

RIFM fragrance ingredient safety assessment, 2-mercaptopropionic acid, CAS Registry Number 79-42-5.

The existing information supports the use of this material as described in this safety assessment. 2-Mercaptopropionic acid was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data show that 2-mercaptopropionic acid is not genotoxic. The repeated dose, reproductive, and local respiratory toxicity endpoints were evaluated using the Threshold of Toxicological Concern (TTC) for a Cramer Class I material, and the exposure to 2-mercaptopropionic acid is below the TTC (0.03 mg/kg/day, 0.03 mg/kg/day, and 1.4 mg/day, respectively). The skin sensitization endpoint was completed using the Dermal Sensitization Threshold (DST) for reactive materials (64 µg/cm2); exposure is below the DST. The phototoxicity/photoallergenicity endpoints were evaluated based on ultraviolet (UV) spectra; 2-mercaptopropionic acid is not expected to be phototoxic/photoallergenic. For the hazard assessment based on the screening data, 2-mercaptopropionic acid is not persistent, bioaccumulative, and toxic (PBT) as per the International Fragrance Association (IFRA) Environmental Standards. For the risk assessment, 2-mercaptopropionic acid was not able to be risk screened as there were no reported volumes of use for either North America or Europe in the 2015 IFRA Survey.

Intramuscular cobinamide as an antidote to methyl mercaptan poisoning.

BACKGROUND: Methyl mercaptan occurs naturally in the environment and is found in a variety of occupational settings, including the oil, paper, plastics, and pesticides industries. It is a toxic gas and deaths from methyl mercaptan exposure have occurred. The Department of Homeland Security considers it a high threat chemical agent that could be used by terrorists. Unfortunately, no specific treatment exists for methyl mercaptan poisoning. METHODS: We conducted a randomized trial in 12 swine comparing no treatment to intramuscular injection of the vitamin B12 analog cobinamide (2.0 mL, 12.5 mg/kg) following acute inhalation of methyl mercaptan gas. Physiological and laboratory parameters were similar in the control and cobinamide-treated groups at baseline and at the time of treatment. RESULTS: All six cobinamide-treated animals survived, whereas only one of six control animals lived (17% survival) (p = 0.0043). The cobinamide-treated animals returned to a normal breathing pattern by 3.8 ± 1.1 min after treatment (mean ± SD), while all but one animal in the control group had intermittent gasping, never regaining a normal breathing pattern. Blood pressure and arterial oxygen saturation returned to baseline values within 15 minutes of cobinamide-treatment. Plasma lactate concentration increased progressively until death (10.93 ± 6.02 mmol [mean ± SD]) in control animals, and decreased toward baseline (3.79 ± 2.93 mmol [mean ± SD]) by the end of the experiment in cobinamide-treated animals. CONCLUSION: We conclude that intramuscular administration of cobinamide improves survival and clinical outcomes in a large animal model of acute, high dose methyl mercaptan poisoning.

Dietary Thiols: A Potential Supporting Strategy against Oxidative Stress in Heart Failure and Muscular Damage during Sports Activity.

Moderate exercise combined with proper nutrition are considered protective factors against cardiovascular disease and musculoskeletal disorders. However, physical activity is known not only to have positive effects. In fact, the achievement of a good performance requires a very high oxygen consumption, which leads to the formation of oxygen free radicals, responsible for premature cell aging and diseases such as heart failure and muscle injury. In this scenario, a primary role is played by antioxidants, in particular by natural antioxidants that can be taken through the diet. Natural antioxidants are molecules capable of counteracting oxygen free radicals without causing cellular cytotoxicity. In recent years, therefore, research has conducted numerous studies on the identification of natural micronutrients, in order to prevent or mitigate oxidative stress induced by physical activity by helping to support conventional drug therapies against heart failure and muscle damage. The aim of this review is to have an overview of how controlled physical activity and a diet rich in antioxidants can represent a "natural cure" to prevent imbalances caused by free oxygen radicals in diseases such as heart failure and muscle damage. In particular, we will focus on sulfur-containing compounds that have the ability to protect the body from oxidative stress. We will mainly focus on six natural antioxidants: glutathione, taurine, lipoic acid, sulforaphane, garlic and methylsulfonylmethane.

Natural product-based semisynthesis and biological evaluation of thiol/amino-Michael adducts of xanthatin derived from Xanthium strumarium as potential pesticidal agents.

Xanthatin, a natural sesquiterpene lactone, occurs as one of the major constituents of Xanthium plants (Compositae) and exhibits many important biological properties. To discover natural products-based pesticides, forty-nine Michael-type thiol/amino adducts of xanthatin were synthesized and characterized, while their pesticidal activities were investigated. Among them, compounds 2c, 2h, 2i, and 2t exhibited more potent antifungal activity against Botrytis cinerea (IC50 = 0.96, 0.38, 6.33, and 7.21 µg/mL, respectively) than xanthatin and the two commercial fungicides. Compounds 2t and 2u displayed broad-spectrum and excellent antifungal effects against all tested phytopathogenic fungi, while their IC50 values ranged from 7.21 to 75.88 µg/mL. Compounds 2a, 2f, 2l, 2m, 2v, 7c, 7e, 7h, 7i, and 7j showed moderate larvicidal activity against Plutella xylostella Linnaeus. Furthermore, compounds 2b, 7g, and 7h demonstrated significant ovicidal activity against P. xylostella with the LC50 values of 14.04, 10.00, and 11.95 mg/L, respectively. These findings suggest that thiol/amino appended in the C-13 position of xanthatin may improve antifungal and ovicidal activities for the derivatives. It was also noticed that the exocyclic double bond of xanthatin is crucial for its larvicidal activity. This work also provides some important hints for further design, synthesis, and structural modification of the xanthanolides sesquiterpene lactones toward development of the new environmentally friendly pesticides for sustainable agricultural production.

Cytocompatible and non-fouling zwitterionic hyaluronic acid-based hydrogels using thiol-ene "click" chemistry for cell encapsulation.

In this work, a facile click reaction strategy is employed to form hydrogels in situ with cytocompatibility, biodegradability, self-healing property and resistance to protein. The thiol-functionalized zwitterionic carboxybetaine methacrylate copolymer, which take part as a cross-linker in the "thiol-ene" click reaction with the methacrylated hyaluronic acid. The hydrogels are obtained under the physiological condition without the presence of any copper catalyst and UV light. The hydrogel consisting of zwitterionic component shows an obvious reduction in protein adsorption and cell adhesion and avoid non-targeted factor interference in the biological experiments. The hydrogels also demonstrate adjustable degradation behavior. Human mesenchymal stem cells (hMSCs) are easily encapsulated into the hydrogels and remains metabolically active, indicating the excellent biocompatibility of the hydrogels. Additionally, the result of the cytokine secretion assays (IL-6 and TNF-α) has shown that this clickable hydrogel can serve to suppress inflammatory reactions and is beneficial for in vivo applications. Based on the above results, this clickable hydrogel with excellent performance can be an amenable platform for 3D cell encapsulation.

Identification of Novel Metabolites of Vildagliptin in Rats: Thiazoline-Containing Thiol Adducts Formed via Cysteine or Glutathione Conjugation.

Vildagliptin (VG), a dipeptidyl peptidase-4 inhibitor, is used for treating type 2 diabetes. On rare occasions, VG causes liver injury as an adverse reaction. One case report suggested the involvement of immune responses in the hepatotoxicity, but the underlying mechanisms are unknown. We recently reported that VG binds covalently in vitro to l-cysteine to produce a thiazoline acid metabolite, M407, implying that the covalent binding may trigger the immune-mediated hepatotoxicity. There was no evidence, however, that such a thiazoline acid metabolite was formed in vivo. In the present study, we administered a single oral dose of VG to male Sprague-Dawley rats, and detected M407 in plasma. The sum of urinary and fecal excretions of M407 reached approximately 2% of the dose 48 hours postdosing. Using bile duct-cannulated rats, we demonstrated that M407 was secreted into bile as a glucuronide, designated as M583. Another newly identified thiazoline metabolite of VG, the cysteinylglycine conjugate M464, was detected in urine, feces, and bile. The formation of M464 was confirmed by in vitro incubation of VG with glutathione even in the absence of metabolic enzymes. A glutathione adduct against the nitrile moiety M611 was also detected in vitro but not in vivo. In summary, we found three new thiazoline-containing thiol adduct metabolites in VG-administered rats. Nonenzymatic covalent binding of VG would likely occur in humans, and it may be relevant to predicting adverse reactions.

Plasmonic Colloidosome-Based Single Cell Detector: A Strategy for Individual Cell Secretion Sensing.

Phenotyping single cells based on molecules that they secrete or consume is a key bottleneck in many biotechnology applications. Here, we demonstrate a new approach for detecting secretions from individual single cells, namely, plasmonic colloidosome-based single cell detector (PCSD). This strategy uses colloidosomes to encapsulate single cells and aid molecular detection. Colloidosomes are constructed by emulsifying lactate probe and hydrophobic ligand dual-functionalized silver nanoparticles on an immiscible liquid-liquid interface. The established colloidosome-based platform exhibits negligible surface-enhanced Raman scattering (SERS) background interference, ultrasensitive SERS response, and excellent signal reproducibility in response to acidification of the medium inside the colloidosomes. Taking lactate as a model molecule, the acidification induced by single cells confined in the colloidosomes is detected. The approach shows promising applicability in single cell analysis based on extracellular metabolites production or consumption.

In vitro compatibility testing of thiol-ene/acrylate-based shape memory polymers for use in implantable neural interfaces.

Shape memory polymers (SMPs) based on thiol-ene/acrylate formulations are an emerging class of materials with potential applications as structural and/or dielectric coatings for implantable neural interfaces. Here, we report in vitro compatibility studies of three novel thiol-ene/acrylate-based SMP formulations. In vivo cytotoxicity assays were carried out in accordance with International Organization for Standards (ISO) protocol 10993-5, using NCTC clone 929 fibroblasts as well as embryonic cortical cultures. All three SMP formulations passed standardized cytotoxicity assays (>70% normalized cell viability) using both cell types. Functional neurotoxicity assays were carried out using primary cortical networks cultured on substrate-integrated microelectrode arrays (MEAs). We observed significant reduction in cortical network activity in the case of positive control material, but no significant alterations in activity following incubation with SMP material extracts, indicating functional cytocompatibility. Finally, we assessed cell reactivity at the tissue-material interface by performing an in vitro glial scarring assay. Through immunostaining, we observed similar astrocyte-associated (GFAP) mean intensity ratios near nonsoftening SMP-coated and uncoated stainless steel microwires (1.10 ± 0.06 vs. 1.19 ± 0.10), suggesting similar glial cell reactivity. However, we observed decreased mean intensity ratios in the presence of fully softening SMP-coated microwires (1.02 ± 0.04) suggesting reduced glial cell reactivity. Overall, these results indicate that the thiol-ene/acrylate SMP formulations presented here are neither cytotoxic nor neurotoxic, and suggest that fully softening SMP may reduce foreign body response in terms of glial cell reactivity. These findings support further consideration of this class of materials as backbone or insulating materials for implantable neural stimulating/recording devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2891-2898, 2018.

Protective effects of taurine against inflammation, apoptosis, and oxidative stress in brain injury.

The protective effect of taurine against inflammation, apoptosis and oxidative stress in traumatic brain injury was investigated in the present study. Taurine is a non­proteogenic and essential amino acid in animals. It plays a critical nutritional role in brain cell growth, differentiation, and development. Taurine is involved in regeneration and neuroprotection in the injured nervous system, and is an effective antioxidant against lead­, cadmium­, and exercise­induced oxidative stress. Astrocytes and neuron cells were co­cultured and cells were treated with different concentrations of taurine (100, 200 and 300 mg/l) for 72 h, and the levels of reactive oxygen species, malondialdehyde, reduced glutathione, glutathione peroxidase, superoxide dismutase, catalase, acetylcholinesterase, tumor necrosis factor­α, interleukin­6, caspase­3, p53, B­cell lymphoma 2 and Bcl­2­associated X protein were determined. These inflammatory, apoptotic, and oxidative stress markers were substantially increased in injured cells, and returned to normal levels following taurine supplementation. Thus, taurine supplementation may be effective against oxidative stress, apoptosis, and inflammation in injured brain cells.

Novel amides of 1,1-bis-(carboxymethylthio)-1-arylethanes: Synthesis, characterization, acetylcholinesterase, butyrylcholinesterase, and carbonic anhydrase inhibitory properties.

The thiolation reaction was carried out in a benzene solution at 80°C and p-substituted ketones and mercaptoacetic acid in a molar ratio (1:4) of in the presence of a catalytic amount of toluene sulfonic acids. The enzyme inhibition activities of the novel amides of 1,1-bis-(carboxymethylthio)-1-arylethanes derivatives were investigated. These novel amides of 1,1-bis-(carboxymethylthio)-1-arylethanes derivatives showed good inhibitory action against acetylcholinesterase (AChE) butyrylcholinesterase (BChE), and human carbonic anhydrase I and II isoforms (hCA I and II). AChE inhibitors, interacting with the enzyme as their primary target, are applied as relevant drugs and toxins. Many clinically established drugs are carbonic anhydrase inhibitors, and it is highly anticipated that many more will eventually find their way into the market. The novel synthesized compounds inhibited AChE and BChE with Ki values in the range of 0.64-1.47 nM and 9.11-48.12 nM, respectively. On the other hand, hCA I and II were effectively inhibited by these compounds, with Ki values between 63.27-132.34 and of 29.63-127.31 nM, respectively.

Evaluation of dermal adhesive formulations for topical application.

Topical delivery is one of the main challenges in the pharmaceutical technology. This study aimed to synthesize a potential adhesive polymeric excipient stable enough for pronounced skin adhesiveness to pave the skin delivery pathway. Polyacrylic acid an anionic well established polymer in the pharmaceutical field was chemically modified with sulfhydryl moieties and in a second step, this sulfhydryl bearing polymer was prone to a preactivation process. During this process, mercaptonicotinic acid was covalently bound to the sulfhydryl groups of polyacrylic acid. The obtained polymeric conjugates were characterized with respect to viscosity measurements, and evaluated in terms of skin adhesive properties with the help of tensile strength assay as well as bond strength assay. Findings exhibited promising potential of newly synthesized preactivated polyacrylic acid in terms of adhesive properties. Preactivated polyacrylic acid revealed a 15.39-fold improved adhesion compared to unmodified polymeric excipient. Therefore, the herein designed preactivated polyacrylic acid shows interesting features for skin application such as scar and wound management.

Quantifying engineered nanomaterial toxicity: comparison of common cytotoxicity and gene expression measurements.

BACKGROUND: When evaluating the toxicity of engineered nanomaterials (ENMS) it is important to use multiple bioassays based on different mechanisms of action. In this regard we evaluated the use of gene expression and common cytotoxicity measurements using as test materials, two selected nanoparticles with known differences in toxicity, 5 nm mercaptoundecanoic acid (MUA)-capped InP and CdSe quantum dots (QDs). We tested the effects of these QDs at concentrations ranging from 0.5 to 160 µg/mL on cultured normal human bronchial epithelial (NHBE) cells using four common cytotoxicity assays: the dichlorofluorescein assay for reactive oxygen species (ROS), the lactate dehydrogenase assay for membrane viability (LDH), the mitochondrial dehydrogenase assay for mitochondrial function, and the Comet assay for DNA strand breaks. RESULTS: The cytotoxicity assays showed similar trends when exposed to nanoparticles for 24 h at 80 µg/mL with a threefold increase in ROS with exposure to CdSe QDs compared to an insignificant change in ROS levels after exposure to InP QDs, a twofold increase in the LDH necrosis assay in NHBE cells with exposure to CdSe QDs compared to a 50% decrease for InP QDs, a 60% decrease in the mitochondrial function assay upon exposure to CdSe QDs compared to a minimal increase in the case of InP and significant DNA strand breaks after exposure to CdSe QDs compared to no significant DNA strand breaks with InP. High-throughput quantitative real-time polymerase chain reaction (qRT-PCR) data for cells exposed for 6 h at a concentration of 80 µg/mL were consistent with the cytotoxicity assays showing major differences in DNA damage, DNA repair and mitochondrial function gene regulatory responses to the CdSe and InP QDs. The BRCA2, CYP1A1, CYP1B1, CDK1, SFN and VEGFA genes were observed to be upregulated specifically from increased CdSe exposure and suggests their possible utility as biomarkers for toxicity. CONCLUSIONS: This study can serve as a model for comparing traditional cytotoxicity assays and gene expression measurements and to determine candidate biomarkers for assessing the biocompatibility of ENMs.

Monohalogenated acetamide-induced cellular stress and genotoxicity are related to electrophilic softness and thiol/thiolate reactivity.

Haloacetamides (HAMs) are cytotoxic, genotoxic, and mutagenic byproducts of drinking water disinfection. They are soft electrophilic compounds that form covalent bonds with the free thiol/thiolate in cysteine residues through an SN2 reaction mechanism. Toxicity of the monohalogenated HAMs (iodoacetamide, IAM; bromoacetamide, BAM; or chloroacetamide, CAM) varied depending on the halogen substituent. The aim of this research was to investigate how the halogen atom affects the reactivity and toxicological properties of HAMs, measured as induction of oxidative/electrophilic stress response and genotoxicity. Additionally, we wanted to determine how well in silico estimates of electrophilic softness matched thiol/thiolate reactivity and in vitro toxicological endpoints. Each of the HAMs significantly induced nuclear Rad51 accumulation and ARE signaling activity compared to a negative control. The rank order of effect was IAM>BAM>CAM for Rad51, and BAM≈IAM>CAM for ARE. In general, electrophilic softness and in chemico thiol/thiolate reactivity provided a qualitative indicator of toxicity, as the softer electrophiles IAM and BAM were more thiol/thiolate reactive and were more toxic than CAM.

Development of a two-photon fluorescent turn-on probe with far-red emission for thiophenols and its bioimaging application in living tissues.

Thiophenol is a highly toxic compound which is essential in the field of organic synthesis and drug design. However, the accumulation of thiophenols in the environment may cause serious health problems for human bodies ultimately. Therefore, it is critical to develop efficient methods for visualization of thiophenol species in biological samples. In this work, an innovative two-photon fluorescent turn-on probe FR-TP with far-red emission for thiophenols based on FR-NH2 fluorophore and 2,4-dinitrophenylsulfonyl recognition site was reported. The new probe can be used for thiophenol detection with large far-red fluorescence enhancement (about 155-fold), rapid response (completed within 100s), excellent sensitivity (DL 0.363µM), high selectivity, and lower cellular auto-fluorescence interference. Importantly, the probe FR-TP can be successfully employed to visualize thiophenols not only in the living HeLa cells but also in living liver tissues. In addition, through two-photon tissue imaging, the probe was used to monitor and investigate biological thiophenol poisoning in the animal model of thiophenol inhalation for the first time.

Validation of a Fragment-Based Profiler for Thiol Reactivity for the Prediction of Toxicity: Skin Sensitization and Tetrahymena pyriformis.

This study outlines the use of a recently developed fragment-based thiol reactivity profiler for Michael acceptors to predict toxicity toward Tetrahymena pyriformis and skin sensitization potency as determined in the Local Lymph Node Assay (LLNA). The results showed that the calculated reactivity parameter from the profiler, -log RC50(calc), was capable of predicting toxicity for both end points with excellent statistics. However, the study highlighted the importance of a well-defined applicability domain for each end point. In terms of Tetrahymena pyriformis, this domain was defined in terms of how fast or slowly a given Michael acceptor reacts with thiol leading to two separate quantitative structure-activity models. The first, for fast reacting chemicals required only -log RC50(calc) as a descriptor, while the second required the addition of a descriptor for hydrophobicity. Modeling of the LLNA required only a single descriptor, -log RC50(calc), enabling potency to be predicted. The applicability domain excluded chemicals capable of undergoing polymerization and those that were predicted to be volatile. The modeling results for both end points, using the -log RC50(calc) value from the profiler, were in keeping with previously published studies that have utilized experimentally determined measurements of reactivity. These results demonstrate that the output from the fragment-based thiol reactivity profiler can be used to develop quantitative structure-activity relationship models where reactivity toward thiol is a driver of toxicity.