Measurement of various respiratory dynamics parameters following acute inhalational exposure to soman vapor in conscious rats

Abstract

Respiratory dynamics were investigated in head-out plethysmography chambers following inhalational exposure to soman in untreated, non-anesthetized rats. A multipass saturator cell was used to generate 520, 560 and 600?mg?×?min/m³ of soman vapor in a customized inhalational exposure system. Various respiratory dynamic parameters were collected from male Sprague-Dawley rats (300--350?g) during (20?min) and 24?h (10?min) after inhalational exposure. Signs of CWNA-induced cholinergic crisis were observed in all soman-exposed animals. Percentage body weight loss and lung edema were observed in all soman-exposed animals, with significant increases in both at 24?h following exposure to 600?mg?×?min/m³. Exposure to soman resulted in increases in respiratory frequency (RF) in animals exposed to 560 and 600?mg?×?min/m³ with significant increases following exposure to 560?mg?×?min/m³ at 24?h. No significant alterations in inspiratory time (IT) or expiratory time (ET) were observed in soman-exposed animals 24?h post-exposure. Prominent increases in tidal volume (TV) and minute volume (MV) were observed at 24?h post-exposure in animals exposed to 600?mg?×?min/m³. Peak inspiratory (PIF) and expiratory flow (PEF) followed similar patterns and increased 24?h post-exposure to 600?mg?×?min/m³ of soman. Results demonstrate that inhalational exposure to 600?mg?×?min/m³ soman produces notable alterations in various respiratory dynamic parameters at 24?h. The following multitude of physiological changes in respiratory dynamics highlights the need to develop countermeasures that protect against respiratory toxicity and lung injury.     

Vapor inhalation exposure to soman in conscious untreated rats: preliminary assessment of neurotoxicity

Neurological toxicity and brain injury following vapor inhalation exposure to the chemical warfare nerve agent (CWNA) soman (GD) were examined in untreated non-anesthetized rats. In this study, male Sprague-Dawley rats (300–350?g) were exposed to 600?mg?×?min/m³ of soman or vehicle in a customized head-out inhalation system for 7?min. Convulsant animals were observed for clinical signs and various regions of the brain (dorsolateral thalamus, basolateral amygdala, piriform cortex, and lateral cortex) were collected for pathological observations 24?h post-exposure. Signs of CWNA-induced cholinergic crises including salivation, lacrimation, increased urination and defecation, and tremors were observed in all soman-exposed animals. Soman-exposed animals at 24?h post-exposure lost 11% of their body weight in comparison to 2% in vehicle-exposed animals. Whole blood acetylcholinesterase (AChE) activity was significantly inhibited in all soman-exposed groups in comparison to controls. Brain injury was confirmed by the neurological assessment of hematoxylin-eosin (H&E) staining and microscopy in the piriform cortex, dorsolateral thalamus, basolateral amygdala, and lateral cortex. Severe damage including prominent lesions, edematous, congested, and/or hemorrhagic tissues was observed in the piriform cortex, dorsolateral thalamus, and lateral cortex in soman-exposed animals 24?h post-exposure, while only minimal damage was observed in the basolateral amygdala. These results indicate that inhalation exposure to soman vapor causes neurological toxicity and brain injury in untreated unanesthetized rats. This study demonstrates the ability of the described soman vapor inhalation exposure model to cause neurological damage 24?h post-exposure in rats.     

Assessment of inhaled acute ammonia-induced lung injury in rats

This study examined acute toxicity and lung injury following inhalation exposure to ammonia. Male Sprague-Dawley rats (300–350?g) were exposed to 9000, 20?000, 23?000, 26?000, 30?000 or 35?000?ppm of ammonia for 20?min in a custom head-out exposure system. The exposure atmosphere, which attained steady state within 3?min for all ammonia concentrations, was monitored and verified using a Fourier transform infrared spectroscopy (FTIR) gas analyzer. Animals exposed to ammonia resulted in dose-dependent increases in observed signs of intoxication, including increased chewing and licking, ocular irritation, salivation, lacrimation, oronasal secretion and labored breathing. The LCt₅₀ of ammonia within this head-out inhalation exposure model was determined by probit analysis to be 23?672?ppm (16?489?mg/m³) for the 20?min exposure in male rats. Exposure to 20?000 or 23?000?ppm of ammonia resulted in significant body weight loss 24-h post-exposure. Lung edema increased in all ammonia-exposed animal groups and was significant following exposure to 9000?ppm. Bronchoalveolar fluid (BALF) protein concentrations significantly increased following exposure to 20?000 or 23?000?ppm of ammonia in comparison to controls. BAL cell (BALC) death and total cell counts increased in animals exposed to 20?000 or 23?000?ppm of ammonia in comparison to controls. Differential cell counts of white blood cells, neutrophils and platelets from blood and BALF were significantly increased following exposure to 23?000?ppm of ammonia. The following studies describe the validation of a head-out inhalation exposure model for the determination of acute ammonia-induced toxicity; this model will be used for the development and evaluation of potential therapies that provide protection against respiratory and systemic toxicological effects.     

Aerosolized scopolamine protects against microinstillation inhalation toxicity to sarin in guinea pigs

Sarin is a volatile nerve agent that has been used in the Tokyo subway attack. Inhalation is predicted to be the major route of exposure if sarin is used in war or terrorism. Currently available treatments are limited for effective postexposure protection against sarin under mass casualty scenario. Nasal drug delivery is a potential treatment option for mass casualty under field conditions. We evaluated the efficacy of endotracheal administration of muscarinic antagonist scopolamine, a secretion blocker which effectively crosses the blood-brain barrier for protection against sarin inhalation toxicity. Age and weight matched male Hartley guinea pigs were exposed to 677.4?mg/m³ or 846.5?mg/?m³ (1.2?×?LCt₅₀) sarin by microinstillation inhalation exposure for 4?min. One minute later, the animals exposed to 846.5?mg/?m³ sarin were treated with endotracheally aerosolized scopolamine (0.25?mg/kg) and allowed to recover for 24?h for efficacy evaluation. The results showed that treatment with scopolamine increased the survival rate from 20% to 100% observed in untreated sarin-exposed animals. Behavioral symptoms of nerve agent toxicity including, convulsions and muscular tremors were reduced in sarin-exposed animals treated with scopolamine. Sarin-induced body weight loss, decreased blood O₂ saturation and pulse rate were returned to basal levels in scopolamine-treated animals. Increased bronchoalveolar lavage (BAL) cell death due to sarin exposure was returned to normal levels after treatment with scopolamine. Taken together, these data indicate that postexposure treatment with aerosolized scopolamine prevents respiratory toxicity and protects against lethal inhalation exposure to sarin in guinea pigs.     

Acute respiratory toxicity following inhalation exposure to soman in guinea pigs

Respiratory toxicity and lung injury following inhalation exposure to chemical warfare nerve agent soman was examined in guinea pigs without therapeutics to improve survival. A microinstillation inhalation exposure technique that aerosolizes the agent in the trachea was used to administer soman to anesthetized age and weight matched male guinea pigs. Animals were exposed to 280, 561, 841, and 1121 mg/m³ concentrations of soman for 4 min. Survival data showed that all saline controls and animals exposed to 280 and 561 mg/m³ soman survived, while animals exposed to 841, and 1121 mg/m³ resulted in 38% and 13% survival, respectively. The microinstillation inhalation exposure LCt₅₀ for soman determined by probit analysis was 827.2 mg/m³. A majority of the animals that died at 1121 mg/m³ developed seizures and died within 15-30 min post-exposure. There was a dose-dependent decrease in pulse rate and blood oxygen saturation of animals exposed to soman at 5-6.5 min post-exposure. Body weight loss increased with the dose of soman exposure. Bronchoalveolar lavage (BAL) fluid and blood acetylcholinesterase and butyrylcholinesterase activity was inhibited dose-dependently in soman treated groups at 24 h. BAL cells showed a dose-dependent increase in cell death and total cell counts following soman exposure. Edema by wet/dry weight ratio of the accessory lung lobe and trachea was increased slightly in soman exposed animals. An increase in total bronchoalveolar lavage fluid protein was observed in soman exposed animals at all doses. Differential cell counts of BAL and blood showed an increase in total lymphocyte counts and percentage of neutrophils. These results indicate that microinstillation inhalation exposure to soman causes respiratory toxicity and acute lung injury in guinea pigs.     

Comparison of sarin and cyclosarin toxicity by subcutaneous,intravenous and inhalation exposure in Gottingen minipigs

Abstract

Sexually mature male and female Gottingen minipigs were exposed to various concentrations of GB and GF vapor via whole-body inhalation exposures or to liquid GB or GF via intravenous or subcutaneous injections. Vapor inhalation exposures were for 10, 60 or 180?min. Maximum likelihood estimation was used to calculate the median effect levels for severe effects (ECT₅₀ and ED₅₀) and lethality (LCT₅₀ and LD₅₀). Ordinal regression was used to model the concentration?×?time profile of the agent toxicity. Contrary to that predicted by Haber’s rule, LCT₅₀ values increased as the duration of the exposures increased for both nerve agents. The toxic load exponents (n) were calculated to be 1.38 and 1.28 for GB and GF vapor exposures, respectively. LCT₅₀ values for 10-, 60- and 180-min exposures to vapor GB in male minipigs were 73, 106 and 182?mg?min/m³, respectively. LCT₅₀ values for 10-, 60?- and 180-min exposures to vapor GB in female minipigs were 87, 127 and 174?mg?min/m³, respectively. LCT₅₀ values for 10-, 60- and 180-min exposures to vapor GF in male minipigs were 218, 287 and 403?mg?min/m³, respectively. LCT₅₀ values for 10-, 60- and 180-min exposures in female minipigs were 183, 282 and 365?mg?min/m³, respectively. For GB vapor exposures, there was a tenuous gender difference which did not exist for vapor GF exposures. Surprisingly, GF was 2–3 times less potent than GB via the inhalation route of exposure regardless of exposure duration. Additionally GF was found to be less potent than GB by intravenous and subcutaneous routes.     

Lung damage following whole body,but not intramuscular,exposure to median lethality dose of sarin: findings in rats and guinea pigs

Objective: Sarin is an irreversible organophosphate cholinesterase inhibitor and a highly toxic, volatile warfare agent. Rats and guinea pigs exposed to sarin display cholinergic excitotoxicity which includes hyper-salivation, respiratory distress, tremors, seizures, and death. Here we focused on the characterization of the airways injury induced by direct exposure of the lungs to sarin vapor and compared it to that induced by the intramuscularly route.

Materials and methods: Rats were exposed to sarin either in vapor (～1LCT50, 34.2?±?0.8?µg/l/min, 10?min) or by i.m. (～1LD50, 80?µg/kg), and lung injury was evaluated by broncho-alveolar lavage (BAL).

Results and discussion: BAL analysis revealed route-dependent effects in rats: vapor exposed animals showed elevation of inflammatory cytokines, protein, and neutrophil cells. These elevations were seen at 24?h and were still significantly higher compared to control values at 1?week following vapor exposure. These elevations were not detected in rats exposed to sarin i.m. Histological evaluation of the brains revealed typical changes following sarin poisoning independent of the route of administration. The airways damage following vapor exposure in rats was also compared to that induced in guinea pigs. The latter showed increased eosinophilia and histamine levels that constitutes an anaphylactic response not seen in rats.

Conclusions: These data clearly point out the importance of using the appropriate route of administration in studying the deleterious effects of volatile nerve agents, as well as the selection of the appropriate animal species. Since airways form major target organs for the development of injury following inhalation toxicity, they should be included in any comprehensive evaluation of countermeasures efficacy.     

Treatment with endotracheal therapeutics after sarin microinstillation inhalation exposure increases blood cholinesterase levels in guinea pigs

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in the blood and tissues of animals that are treated with a number of endotracheally aerosolized therapeutics for protection against inhalation toxicity to sarin. Therapeutics included, aerosolized atropine methyl bromide (AMB), scopolamine or combination of AMB with salbutamol, sphingosine 1-phosphate, keratinocyte growth factor, adenosine A1 receptor antisense oligonucleotide (EPI2010), 2,3-diacetyloxybenzoic acid (2,3 DABA), oxycyte, and survanta. Guinea pigs exposed to 677.4?mg/m³ or 846.5?mg/m³ (1.2 LCt₅₀) sarin for 4?min using a microinstillation inhalation exposure technique and treated 1?min later with the aerosolized therapeutics. Treatment with all therapeutics significantly increased the survival rate with no convulsions throughout the 24?h study period. Blood AChE activity determined using acetylthiocholine as substrate showed 20% activity remaining in sarin-exposed animals compare to controls. In aerosolized AMB and scopolamine-treated animals the remaining AChE activity was significantly higher (45–60%) compared to sarin-exposed animals (p?<?0.05). Similarly, treatment with all the combination therapeutics resulted in significant increase in blood AChE activity in comparison to sarin-exposed animals although the increases varied between treatments (p?<?0.05). BChE activity was increased after treatment with aerosolized therapeutics but was lesser in magnitude compared to AChE activity changes. Various tissues showed elevated AChE activity after therapeutic treatment of sarin-exposed animals. Increased AChE and BChE activities in animals treated with nasal therapeutics suggest that enhanced breathing and reduced respiratory toxicity/lung injury possibly contribute to rapid normalization of chemical warfare nerve agent inhibited cholinesterases.     

Endotracheal aerosolization of atropine sulfate protects against soman-induced acute respiratory toxicity in guinea pigs

The efficacy of endotracheal aerosolization of atropine sulfate for protection against soman (GD)-induced respiratory toxicity was investigated using microinstillation technique in guinea pigs. GD (841?mg/m³, 1.3 LCt₅₀ or 1121?mg/m³, 1.7 LCt₅₀) was aerosolized endotracheally to anesthetized male guinea pigs that were treated with atropine sulfate (5.0?mg/kg) 30 s postexposure by endotracheal microinstillation. Animals exposed to 841?mg/m³ and 1121?mg/m³GD resulted in 31 and 13% while treatment with atropine sulfate resulted in 100 and 50% survival, respectively. Cholinergic symptoms and increased body weight loss were reduced in atropine-treated animals compared to GD controls. Diminished pulse rate and blood O₂ saturation in GD-exposed animals returned to normal levels after atropine treatment. Increased cell death, total cell count and protein in the bronchoalveolar fluid (BALF) in GD-exposed animals returned to normal levels following atropine treatment. GD exposure increased glutathione and superoxide dismutase levels in BALF and that were reduced in animals treated with atropine. Respiratory parameters measured by whole-body barometric plethysmography revealed that treatment with atropine sulfate resulted in normalization of respiratory frequency, tidal volume, time of expiration, time of inspiration, end expiratory pause, pseudo lung resistance (Penh) and pause at 4 and 24?h post 841?mg/m³ GD exposure. Lung histopathology showed that atropine treatment reduced bronchial epithelial subepithelial inflammation and multifocal alveolar septal edema. These results suggest that endotracheal aerosolization of atropine sulfate protects against respiratory toxicity and lung injury induced by microinstillation inhalation exposure to lethal doses of GD.     

Aerosolized delivery of oxime MMB-4 in combination with atropine sulfate protects against soman exposure in guinea pigs

We evaluated the efficacy of aerosolized acetylcholinesterase (AChE) reactivator oxime MMB-4 in combination with the anticholinergic atropine sulfate for protection against respiratory toxicity and lung injury following microinstillation inhalation exposure to nerve agent soman (GD) in guinea pigs. Anesthetized animals were exposed to GD (841?mg/m³, 1.2 LCt₅₀) and treated with endotracheally aerosolized MMB-4 (50 µmol/kg) plus atropine sulfate (0.25?mg/kg) at 30?sec post-exposure. Treatment with MMB-4 plus atropine increased survival to 100% compared to 38% in animals exposed to GD. Decreases in the pulse rate and blood O₂ saturation following exposure to GD returned to normal levels in the treatment group. The body-weight loss and lung edema was significantly reduced in the treatment group. Similarly, bronchoalveolar cell death was significantly reduced in the treatment group while GD-induced increase in total cell count was decreased consistently but was not significant. GD-induced increase in bronchoalveolar protein was diminished after treatment with MMB-4 plus atropine. Bronchoalveolar lavage AChE and BChE activity were significantly increased in animals treated with MMB-4 plus atropine at 24?h. Lung and diaphragm tissue also showed a significant increase in AChE activity in the treatment group. Treatment with MMB-4 plus atropine sulfate normalized various respiratory dynamics parameters including respiratory frequency, tidal volume, peak inspiratory and expiratory flow, time of inspiration and expiration, enhanced pause and pause post-exposure to GD. Collectively, these results suggest that aerosolization of MMB-4 plus atropine increased survival, decreased respiratory toxicity and lung injury following GD inhalation exposure.     

Short-term inhalation study of graphene oxide nanoplates

Graphene oxides possess unique physicochemical properties with important potential applications in electronics, pharmaceuticals, and medicine. However, the toxicity following inhalation exposure to graphene oxide has not yet been clarified. Therefore, this study conducted a short-term graphene oxide inhalation toxicity analysis using a nose-only inhalation exposure system and male Sprague–Dawley rats. A total of four groups (15 rats per group) were exposed: (1) control (fresh air), (2) low concentration (0.76?±?0.16?mg/m³), (3) moderate concentration (2.60?±?0.19?mg/m³), and (4) high concentration (9.78?±?0.29?mg/m³). The rats were exposed to graphene oxide for 6?h/day for 5 days, followed by recovery for 1, 3, and 21 days. No significant body or organ weight changes were noted after the short-term exposure or during the recovery period. Similarly, no significant systemic effects of toxicological importance were noted in the hematological assays, bronchoalveolar lavage fluid (BAL) inflammatory markers, BAL fluid cytokines, or blood biochemical assays following the graphene oxide exposure or during the post-exposure observation period. Moreover, no significant differences were observed in the BAL cell differentials, such as lymphocytes, macrophages, or polymorphonuclear cells. Graphene oxide-ingested alveolar macrophages as a spontaneous clearance reaction were observed in the lungs of all the concentration groups from post 1?day to post 21 days. Histopathological examination of the liver and kidneys did not reveal any significant test-article-relevant histopathological lesions. Importantly, similar to previously reported graphene inhalation data, this short-term nose-only inhalation study found only minimal or unnoticeable graphene oxide toxicity in the lungs and other organs.     

Acute toxicity of some nerve agents and pesticides in rats

Objectives: Highly toxic organophosphorus compounds (V- and G-nerve agents) were originally synthesized for warfare or as agricultural pesticides. Data on their acute toxicity are rare and patchy. Therefore, there is a need for integrated summary comparing acute toxicity of organophosphates using different administration routes in the same animal model with the same methodology. Based on original data, a summary of in vivo acute toxicity of selected V- and G-nerve agents (tabun, sarin, soman, VX, Russian VX) and organophosphates paraoxon (POX) and diisopropyl fluorophosphate (DFP) in rats has been investigated. Materials and methods: Male Wistar rats were exposed to organophosphates in several administration routes (i.m., i.p., p.o, s.c., p.c.). The acute toxicity was evaluated by the assessment of median lethal dose (LD₅₀, mg?kg^?1) 2, 4, and 24 hours post exposure. Results: V-agents were the most toxic presented with LD₅₀ ranged from 0.0082?mg?kg^?1 (VX, i.m.) to 1.402?mg?kg^?1 (Russian VX, p.o.), followed by G-agents (LD₅₀?=?0.069?mg?kg^?1/soman, i.m./ – 117.9?mg?kg^?1/sarin, p.c./), organophosphate POX and DFP (LD₅₀?=?0.321?mg?kg^?1/POX, i.m./ – 420?mg?kg^?1/DFP, p.c./). Generally, i.m. administration was the most toxic throughout all tested agents and ways of administration (LD₅₀?=?0.0082?mg?kg^?1/VX/ – 1.399?mg?kg^?1/DFP/) whereas p.c. way was responsible for lowest acute toxicity (LD₅₀?=?0.085?mg?kg^?1/VX/ – 420?mg?kg^?1/DFP/). Conclusion: The acute toxicity of selected organophosphorus compounds is summarized throughout this study. Although the data assessed in rats are rather illustrative prediction for human, it presents a valuable contribution, indicating the toxic potential and harmfulness of organophosphates.     

Effects of inhaled aerosolized carfentanil on real-time physiological responses in mice: a preliminary evaluation of naloxone

This study examined the real-time exposure–response effects of aerosolized carfentanil (CRF) on opioid-induced toxicity, respiratory dynamics and cardiac function in mice. Unrestrained, conscious male CD-1 mice (25–30?g) were exposed to 0.4 or 4.0?mg/m³ of aerosolized CRF for 15?min (Ct?=?6 or 60?mg?min/m³) in a whole-body plethysmograph chamber. Minute volume (MV), core body temperature (T_c), mean arterial blood pressure (MAP) and heart rate (HR) were evaluated in animals exposed to CRF or sterile H₂O. Loss of consciousness and Straub tail were observed in before 1?min following initiation of exposure to 6 or 60?mg?min/m³ of CRF. Clinical signs of opioid-induced toxicity were observed in a dose-dependent manner. Exposure to 6 or 60?mg?min/m³ of CRF resulted in significant decrease in MV as compared to the controls. MAP, HR and T_c decreased 24?h in animals exposed to either 6 or 60?mg?min/m³ of CRF as compared to the controls. Post-exposure administration of naloxone (NX, 0.05?mg/kg, i.m.) did not increase the MV of animals exposed to CRF to control levels within 24?h, but decreased clinical signs of opioid-induced toxicity and the duration of respiratory depression. This is the first study to evaluate real-time respiratory dynamics and cardiac function during exposure and up to 24?h post-exposure to CRF. The evaluation of toxicological signs and respiratory dynamics following exposure to CRF will be useful in the development of therapeutic strategies to counteract the ongoing threat of abuse and overuse of opioids and their synthetic variants.     

Comparative evaluation of antidotal efficacy of 2-PAM and HNK-102 oximes during inhalation of sarin vapor in Swiss albino mice

Abstract

Efficacy of two oximes treatments evaluated during inhalation of sarin vapor (LCt₅₀, 755.9?mg/min/m³) in simulated real scenario in vivo. Majority of mice either became moribund or died within 1–2?min during exposure to multifold-lethal concentrations of sarin vapor. Protection indices were determined by exposing to sarin vapor in two sessions, 1?min exposure followed by treatments with or without HNK-102 (56.56?mg/kg, im) or 2-PAM (30?mg/kg, im) and atropine (10?mg/kg, ip), and again exposed for remaining 14?min. Protection offered by HNK-102 was found to be four folds higher compared to 2-PAM in the same toxic environment. Secondly, sub-lethal concentration of sarin vapor (0.8?×?LCt₅₀ or 605?mg/min/m³), 24?h post investigations revealed that the oximes could not reactivate brain and serum acetylcholinesterase (AChE) activity. The treatments prevented increase in protein concentration (p?<?.05) and macrophages infiltration compared to sarin alone group in broncho-alveolar lavage fluid. Lung histopathology showed intense peribronchial infiltration and edema with desquamating epithelial lining and mild to moderate alveolar septal infiltration in sarin and atropine groups, respectively. Noticeable peeling-off observed in epithelial lining and sporadic mild infiltration of epithelial cells at bronchiolar region in 2-PAM and HNK-102 groups, respectively. The oximes failed to reactivate AChE activity; however, the mice survived up to 6.0?×?LCt₅₀, proved involvement of non-AChE targets in sarin toxicity. Atropine alone treatment was found to be either ineffective or increased the toxicity. HNK-102, exhibited better survivability with lung protection, can be considered as a better replacement for 2-PAM to treat sarin inhalation induced poisoning.     

Thirteen-week study of toxicity of fiber-like multi-walled carbon nanotubes with whole-body inhalation exposure in rats

Abstract

Cancer development due to fiber-like straight type of multi-walled carbon nanotubes (MWCNTs) has raised concerns for human safety because of its shape similar to asbestos. To set concentrations of MWCNT for a rat carcinogenicity study, we conducted a 13-week whole body inhalation study. F344 male and female rats, 6-week-old at the commencement of the study, were exposed by whole-body inhalation to MWCNT at concentrations of 0, 0.2, 1 and 5?mg/m³ with a generation and exposure system utilizing the cyclone sieve method. Measured concentrations in the exposure chambers were 0.20?±?0.02, 1.01?±?0.11 and 5.02?±?0.25?mg/m³ for 13 weeks. The MMAD (GSD) of MWCNT were 1.4–1.6?μm (2.3–3.0), and mean width and length were 94.1–98.0?nm and 5.53–6.19?μm, respectively, for each target concentration. Lung weights were increased 1.2-fold with 1?mg/m³ and 1.3-fold with 5?mg/m³ in both sexes compared to the controls. In the bronchoalveolar lavage fluid (BALF) analyses, inflammatory parameters were increased concentration-dependently in both sexes from 0.2?mg/m³. Granulomatous changes in the lung were induced at 1 and 5?mg/m³ in females and even at 0.2?mg/m³ in males. Focal fibrosis of the alveolar wall was observed in both sexes at 1?mg/m³ or higher. Inflammatory infiltration in the visceral pleural and subpleural areas was induced only at 5?mg/m³. In conclusion, we determined 0.2?mg/m³ as the low-observed-adverse-effect level (LOAEL) for respiratory tract toxicity in the present inhalation exposure study of rats.     

Acute,Subchronic, and Mutagenicity Studies with Norbornene Fluoroalcohol

The object of this study was to evaluate the toxicity of norbornene fluoroalcohol (NBFOH), which is used as an intermediate in the production of fluorinated monomers and polymers. NBFOH was evaluated for acute oral, dermal, and inhalation toxicity, dermal sensitization using the Local Lymph Node Assay (LLNA), mutagenesis by the Ames assay, and subchronic toxicity in a 4-week inhalation rat study. NBFOH demonstrated slight acute toxicity in oral, dermal, and inhalation studies. Approximate lethal doses of 3400 and > 5000 mg/kg for the oral and dermal routes, respectively, and an approximate lethal concentration of 4300 mg/m³ were determined. NBFOH demonstrated moderate skin irritation, was a severe eye irritant, produced dermal sensitization, but did not cause bacterial mutagenicity either in the presence or absence of S9 activation. Male and female rats were exposed nose only to airborne NBFOH at levels of 0, 410, 1400, and 1500 mg/m³, 6 h/day, 5 days/week for 4 weeks with clinical and histopathology specimens collected 1 day after the final exposure. Due to the vapor pressure of NBFOH, the 1500 mg/m³ atmosphere was 27% aerosol and 73% vapor; the 1400 mg/m³ atmosphere was 5% aerosol and 95% vapor, and the 410 mg/m³ level was only vapor. No test substance–related mortality or clinical signs of toxicity were observed over the course of the study, and male rats demonstrated significant weight loss and decreased food consumption at 1400 mg/m³. Male rats from the 1500 mg/m³ group demonstrated an 11% increase in prothrombin time that was significantly higher than the control value. Examination of fluoride in the urine did not demonstrate a concentration–response relationship, with minimal elevations observed in male rats at all exposure levels and sporadic increases in females. Both male and female rats exposed to 1400 mg/m³ or greater had squamous metaplasia of the laryngeal mucosa and degeneration of the nasal olfactory and respiratory mucosa. Based on the above findings, NBFOH demonstrates the potential to produce allergic contact dermatitis, and subchronic inhalation studies indicate a no-observed-adverse-effect-level (NOAEL) of 410 mg/m³.     

Acute pulmonary toxicity following inhalation exposure to aerosolized VX in anesthetized rats

ABSTRACT

This study evaluated acute toxicity and pulmonary injury in rats at 3, 6 and 24?h after an inhalation exposure to aerosolized O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX). Anesthetized male Sprague-Dawley rats (250–300?g) were incubated with a glass endotracheal tube and exposed to saline or VX (171, 343 and 514?mg×min/m³ or 0.2, 0.5 and 0.8?LCt₅₀, respectively) for 10?min. VX was delivered by a small animal ventilator at a volume of 2.5?ml?×?70 breaths/minute. All VX-exposed animals experienced a significant loss in percentage body weight at 3, 6, and 24?h post-exposure. In comparison to controls, animals exposed to 514?mg×min/m³ of VX had significant increases in bronchoalveolar lavage (BAL) protein concentrations at 6 and 24?h post-exposure. Blood acetylcholinesterase (AChE) activity was inhibited dose dependently at each of the times points for all VX-exposed groups. AChE activity in lung homogenates was significantly inhibited in all VX-exposed groups at each time point. All VX-exposed animals assessed at 20 min and 3, 6 and 24?h post-exposure showed increases in lung resistance, which was prominent at 20 min and 3?h post-exposure. Histopathologic evaluation of lung tissue of the 514?mg×min/m³ VX-exposed animals at 3, 6 and 24?h indicated morphological changes, including perivascular inflammation, alveolar exudate and histiocytosis, alveolar septal inflammation and edema, alveolar epithelial necrosis, and bronchiolar inflammatory infiltrates, in comparison to controls. These results suggest that aerosolization of the highly toxic, persistent chemical warfare nerve agent VX results in acute pulmonary toxicity and lung injury in rats.     

5-Day repeated inhalation and 28-day post-exposure study of graphene

Abstract

Graphene has recently been attracting increasing attention due to its unique electronic and chemical properties and many potential applications in such fields as semiconductors, energy storage, flexible electronics, biosensors and medical imaging. However, the toxicity of graphene in the case of human exposure has not yet been clarified. Thus, a 5-day repeated inhalation toxicity study of graphene was conducted using a nose-only inhalation system for male Sprague-Dawley rats. A total of three groups (20 rats per group) were compared: (1) control (ambient air), (2) low concentration (0.68?±?0.14?mg/m³ graphene) and (3) high concentration (3.86?±?0.94?mg/m³ graphene). The rats were exposed to graphene for 6?h/day for 5 days, followed by recovery for 1, 3, 7 or 28 days. The bioaccumulation and macrophage ingestion of the graphene were evaluated in the rat lungs. The exposure to graphene did not change the body weights or organ weights of the rats after the 5-day exposure and during the recovery period. No statistically significant difference was observed in the levels of lactate dehydrogenase, protein and albumin between the exposed and control groups. However, graphene ingestion by alveolar macrophages was observed in the exposed groups. Therefore, these results suggest that the 5-day repeated exposure to graphene only had a minimal toxic effect at the concentrations and time points used in this study.     

Organ burden and pulmonary toxicity of nano-sized copper (II) oxide particles after short-term inhalation exposure

Introduction: Increased use of nanomaterials has raised concerns about the potential for undesirable human health and environmental effects. Releases into the air may occur and, therefore, the inhalation route is of specific interest. Here we tested copper oxide nanoparticles (CuO NPs) after repeated inhalation as hazard data for this material and exposure route is currently lacking for risk assessment.

Methods: Rats were exposed nose-only to a single exposure concentration and by varying the exposure time, different dose levels were obtained (C?×?T protocol). The dose is expressed as 6?h-concentration equivalents of 0, 0.6, 2.4, 3.3, 6.3, and 13.2?mg/m³ CuO NPs, with a primary particle size of 10 9.2–14?nm and an MMAD of 1.5?μm.

Results: Twenty-four hours after a 5-d exposure, dose-dependent lung inflammation and cytotoxicity were observed. Histopathological examinations indicated alveolitis, bronchiolitis, vacuolation of the respiratory epithelium, and emphysema in the lung starting at 2.4?mg/m³. After a recovery period of 22 d, limited inflammation was still observed, but only at the highest dose of 13.2?mg/m³. The olfactory epithelium in the nose degenerated 24?h after exposure to 6.3 and 13.2?mg/m³, but this was restored after 22 d. No histopathological changes were detected in the brain, olfactory bulb, spleen, kidney and liver.

Conclusion: A 5-d, 6-h/day exposure equivalent to an aerosol of agglomerated CuO NPs resulted in a dose-dependent toxicity in rats, which almost completely resolved during a 3-week post-exposure period.     

Metabolomic changes in murine serum following inhalation exposure to gasoline and diesel engine emissions

The adverse health effects of environmental exposure to gaseous and particulate components of vehicular emissions are a major concern among urban populations. A link has been established between respiratory exposure to vehicular emissions and the development of cardiovascular disease (CVD), but the mechanisms driving this interaction remain unknown. Chronic inhalation exposure to mixed vehicle emissions has been linked to CVD in animal models. This study evaluated the temporal effects of acute exposure to mixed vehicle emissions (MVE; mixed gasoline and diesel emissions) on potentially active metabolites in the serum of exposed mice. C57Bl/6 mice were exposed to a single 6-hour exposure to filtered air (FA) or MVE (100 or 300?μg/m³) by whole body inhalation. Immediately after and 18?hours after the end of the exposure period, animals were sacrificed for serum and tissue collection. Serum was analyzed for metabolites that were differentially present between treatment groups and time points. Changes in metabolite levels suggestive of increased oxidative stress (oxidized glutathione, cysteine disulfide, taurine), lipid peroxidation (13-HODE, 9-HODE), energy metabolism (lactate, glycerate, branched chain amino acid catabolites, butrylcarnitine, fatty acids), and inflammation (DiHOME, palmitoyl ethanolamide) were observed immediately after the end of exposure in the serum of animals exposed to MVE relative to those exposed to FA. By 18?hours post exposure, serum metabolite differences between animals exposed to MVE versus those exposed to FA were less pronounced. These findings highlight complex metabolomics alterations in the circulation following inhalation exposure to a common source of combustion emissions.