Kinetic studies of C1 and C2 Criegee intermediates with SO2 using laser flash photolysis coupled with photoionization mass spectrometry and time resolved UV absorption spectroscopy.

Recent, direct studies have shown that several reactions of stabilized Criegee intermediates (SCI) are significantly faster than indicated by earlier indirect measurements. The reaction of SCI with SO2 may contribute to atmospheric sulfate production, but there are uncertainties in the mechanism of the reaction of the C1 Criegee intermediate, CH2OO, with SO2. The reactions of C1, CH2OO, and C2, CH3CHOO, Criegee intermediates with SO2 have been studied by generating stabilized Criegee intermediates by laser flash photolysis (LFP) of RI2/O2 (R = CH2 or CH3CH) mixtures with the reactions being followed by photoionization mass spectrometry (PIMS). PIMS has been used to determine the rate coefficient for the reaction of CH3CHI with O2, k = (8.6 ± 2.2) × 10-12 cm3 molecule-1 s-1 at 295 K and 2 Torr (He). The yield of the C2 Criegee intermediate under these conditions is 0.86 ± 0.11. All errors in the abstract are a combination of statistical at the 1σ level and an estimated systematic contribution. For the CH2OO + SO2 reaction, additional LFP experiments were performed monitoring CH2OO by time-resolved broadband UV absorption spectroscopy (TRUVAS). The following rate coefficients have been determined at room temperature ((295 ± 2) K):CH2OO + SO2: k = (3.74 ± 0.43) × 10-11 cm3 molecule-1 s-1 (LFP/PIMS),k = (3.87 ± 0.45) × 10-11 cm3 molecule-1 s-1 (LFP/TRUVAS)CH3CHOO + SO2: k = (1.7 ± 0.3) × 10-11 cm3 molecule-1 s-1 (LFP/PIMS)LFP/PIMS also allows for the direction observation of CH3CHO production from the reaction of CH3CHOO with SO2, suggesting that SO3 is the co-product. For the reaction of CH2OO with SO2 there is no evidence of any variation in reaction mechanism with [SO2] as had been suggested in an earlier publication (Chhantyal-Pun et al., Phys. Chem. Chem. Phys., 2015, 17, 3617). A mean value of k = (3.76 ± 0.14) × 10-11 cm3 molecule-1 s-1 for the CH2OO + SO2 reaction is recommended from this and previous studies. The atmospheric implications of the results are briefly discussed.

Plating of open pediatric tibia fractures.

This study is a single center retrospective chart and radiographic review of patients with open tibia fractures under the age of 16 years of age over past 10 years. The purpose of this study is to investigate the treatment of open pediatric tibia fractures with plating in regards to time to ambulation, time to union, and deformity in comparison to other treatment options. We found that plating open pediatric tibia fractures is a safe treatment option that can lead to excellent results with low risk of complications.

Hemophilic pseudotumor.

Bleeding diatheses are a hallmark of hemophilia. Hemophilic pseudotumor results from multiple episodes of hemorrhage into bones or soft tissue spaces. It is uncommon and is seen in severe cases of hemophilia only 1-2% of the time. Complications and symptoms arise due to pain and/or compression of surrounding structures. Pathologic fractures can be associated with intraosseous lesions and can result from bone destruction or resorption due to the chronic pressure of an osseous hemorrhage. Radiographs may demonstrate expansile lesions of the bones or increased soft tissue density that may be associated with extra osseous lesions. Bleeding may also occur within the joint space. These intra-articular hemorrhages can, over time, result in hemophilic arthropathy. The following case report demonstrates both an expansile lesion of a metacarpal as well as hemophilic knee arthropathy in an 11 year old.

Subchronic inhalation of triethylamine vapor in Fischer-344 rats: organ system toxicity.

Male and female F-344 rats were exposed at 0, 25, or 247 ppm triethylamine (TEA) vapor, 6 hr per day, 5 days per week for up to 28 weeks in order to characterize the subchronic organ system toxicity. Rats were weighed biweekly and scheduled sacrifices were performed following about 30, 60, and 120 days of exposure. No statistically significant treatment-related effects on organ weights, hematology, clinical chemistry, or electrocardiographic indices were observed. Body weight gain was not affected by TEA treatment. No physiologic or pathologic evidence of cardiotoxicity was seen in rats exposed to either TEA concentration for up to 28 weeks. No gross or histopathologic lesions attributable to TEA exposure were noted in any of the organs examined, including the nasal passages. This latter finding is in marked contrast to previously reported findings from this laboratory in which squamous metaplasia, suppurative rhinitis, and lymphoid hyperplasia were found in the respiratory epithelium of F-344 rats exposed to the structurally related chemical, diethylamine, under the same conditions as this study (Lynch et al., 1986).

Establishing aerosol exposure concentrations for inhalation toxicity studies.

Criteria for the selection of aerosol concentrations to be used in inhalation studies assessing the toxicity and carcinogenicity of chemical substances were discussed by the authors in a meeting sponsored by the National Toxicology Program. Concepts in the design of aerosol inhalation studies emerged from that meeting and are being communicated through this publication. Inhalation studies assessing the toxicity and carcinogenicity of aerosols have often used maximum exposure levels on the basis of technological feasibility. Evidence has now accumulated that the amount of pulmonary burden of deposited particles impacts on particle clearance above some as yet not well-defined exposure concentration. The sequelae are such that lung clearance decreases with increased particulate burden to the point of approaching complete cessation. This paper focuses on the major determinants in establishing maximal aerosol concentrations for use in inhalation toxicity studies with special emphasis on experimental design features to assess lung retention. The subject matter of this paper is a rapidly developing area in terms of knowledge. Accordingly, the contents of this article are intended as guidelines and not as absolute rules for the conduct and interpretation of inhalation exposure studies.

Sister chromatid exchange in chronic ethylene oxide-exposed primates: unexpected effects of in vitro culture duration, incubation temperature, and serum supplementation.

Ethylene oxide (EtO), a potent monofunctional DNA alkylating agent, has been shown to induce sister chromatid exchanges (SCE) in the peripheral blood lymphocytes of animals and workers exposed to it in vivo. We have previously reported that elevations of SCE persist for 6 years after cessation of EtO exposure in cynomolgus monkeys chronically exposed to EtO; the elevation in mean SCE was entirely attributable to a subpopulation of high SCE frequency cells (HFCs). We now report that the detection of persistent HFCs is dependent on the conditions of cell growth, and that EtO exposure increases the replication indices of lymphocytes from the exposed animals when these cells are examined at early cytogenetic harvest times. Culture of lymphocytes in differing serum supplements, changes in cytogenetic harvest times, and alterations in in vitro incubation temperature all markedly affected mean SCE frequency by influencing the detection of HFCs. The frequency of EtO-induced HFCs was independent of 5-bromodeoxyuridine concentration, used for differential staining of sister chromatids. These observations indicate that the detection of persistent alkylation-induced chromosomal changes, observed long after cessation of in vivo chronic exposure of these animals, is highly dependent upon factors affecting cell growth.

Persistently elevated sister chromatid exchanges in ethylene oxide-exposed primates: the role of a subpopulation of high frequency cells.

Ethylene oxide (EtO) is a potent DNA-alkylating agent which has been shown to induce sister chromatid exchanges (SCE) in the peripheral blood lymphocytes of exposed workers. To study further the persistence of EtO-induced SCE, we have examined lymphocytes from a group of cynomolgus monkeys exposed to EtO in control, 50-ppm, and 100-ppm concentrations for 7 h/day, 5 days/week over the years 1979-1981. The data collected in 1987 were compared with those generated immediately prior to the cessation of exposure in 1981. EtO-induced SCE persisted at levels significantly above those of the nonexposed controls. Comparison of the distributions of SCE between 1979 and 1987 shows that, although mean SCE decreased from 1981 to 1987, the mean SCE in the top 10% of the distribution has not diminished over time. Consequently, the increased level of SCE is entirely attributable to a subpopulation of cells with high frequencies of SCE. These findings suggest that long-lived lymphocytes may inefficiently repair EtO-induced lesions which produce SCE. The results also have important implications for the proper use of SCE analytical techniques in the epidemiological study of cytogenetic damage after chronic exposure to DNA-alkylating agents.

Ozone enhancement of platinum asthma in a primate model.

Three groups of adult male cynomolgus monkeys (Macaca fascicularis) were exposed to either 200 micrograms/m3 ammonium hexachloroplatinate [(NH4)2PtCl6], 200 micrograms (NH4)2PtCl6 concurrently with 1 ppm ozone (O3), or to 1 ppm O3 only. The animals were exposed by inhalation for 6 h per day, 5 days per week for 12 wk. The experimental design included methacholine preexposure and Na2PtCl6 bronchoprovocation challenge evaluations, Na2PtCl6 threshold skin tests, and sera for analyses of antibodies. Two weeks after the 12-wk exposures, these same indices were reevaluated. Baseline pulmonary function was not significantly affected by the exposure regimens; however, the combination of exposure to O3 and (NH4)2PtCl6 significantly reduced the concentration of platinum (Pt) salt and methacholine necessary to increase average pulmonary flow resistance (RL) 200% (EC200 RL). Ozone or Pt exposure alone had no significant effect on these parameters. Platinum and methacholine EC200 RL values were highly correlated for both Pt-exposed groups after exposure. These data indicated that combined O3 and Pt exposure significantly increased specific (Pt) and nonspecific (methacholine) bronchial hyperreactivity more often than did exposure to either O3 or the Pt salt alone. Combined O3 plus Pt exposure also significantly increases the incidence of positive Pt skin tests when compared with the other exposure groups. Similar to the human experience, radioallergosorbent testing (RAST) for Pt-specific antibodies was not as sensitive as direct skin testing in identifying allergic persons.

Subchronic inhalation of diethylamine vapor in Fischer-344 rats: organ system toxicity.

Male and female Fischer 344 (F-344) rats were exposed at 0,25 or 250 ppm diethylamine (DEA) vapor, 6.5 hr per day, 5 days per week, for 24 weeks in order to assess cardiac and other organ system toxicity. Scheduled sacrifices were performed following 30, 60, and 120 days of exposure. During the first 2 weeks of exposure, the rats exposed at 250 ppm DEA did not gain weight. After 2 weeks, however, the rate of weight gain of these rats was greater than that of controls. Nevertheless, mean body weights for both sexes of rats exposed at 250 ppm DEA remained depressed compared to controls throughout the study. Sneezing, tearing, and reddened noses were seen in rats exposed at 250 ppm DEA. Histopathologic examinations revealed lesions of the nasal mucosa of rats exposed at 250 ppm DEA (rats exposed at 25 ppm were not evaluated). These lesions of the respiratory epithelium consisted of squamous metaplasia, suppurative rhinitis, and lymphoid hyperplasia. There were no pronounced treatment-related effects on organ weights, hematology, or clinical chemistry indices except for blood urea nitrogen which was evaluated in rats of both sexes exposed at 250 ppm DEA for 24 weeks. In contrast to the high-dose animals, no treatment-related effects were observed in rats intermittently exposed at 25 ppm DEA for up to 24 weeks. No evidence of cardiotoxicity was seen in rats exposed to either DEA concentration for up to 24 weeks.

Pulmonary effects of acute vanadium pentoxide inhalation in monkeys.

An experimental study was conducted to investigate the hypothesis that changes in pulmonary function induced by vanadium pentoxide (V2O5) inhalation would be accompanied by evidence of pulmonary inflammation. Sixteen adult, male cynomolgus monkeys were acutely exposed by whole-body inhalation of V2O5 dust at aerosol concentrations of 0.5 mg V2O5/m3 and 5.0 mg V2O5/m3, conducted at a 1-wk interval. Comprehensive pulmonary function tests were performed 1 day after each inhalation exposure to detect functional changes in the airways and pulmonary parenchyma. Pulmonary inflammation was assessed by cytologic analysis of respiratory cells recovered from the lower respiratory tract by bronchoalveolar lavage (BAL). Postexposure values for pulmonary function and BAL were compared with the baseline values determined for each monkey prior to V2O5 exposure. Acute V2O5 dust inhalation produced significant air-flow limitation in both central and peripheral airways without producing any detectable changes in parenchymal function. These functional changes were accompanied by a significant increase in the total cell counts recovered from the lungs by BAL. The increase in total cell count occurred through a dramatic increase in absolute number and relative percentage of polymorphonuclear leukocytes (PMN). These findings suggest that pulmonary inflammatory changes involving PMN may play an important role in the occurrence of air-flow limitation after acute inhalation of V2O5 dust.

Influenza virus infection in mice after exposure to coal dust and diesel engine emissions.

Influenza virus infection initiated after aerosol exposure of CD-1, white Swiss mice for durations of 1, 3, and 6 months to respirable particulates maintained at 2 mg/m3 of either coal dust (CD), diesel engine emissions (DEE), a combination of both (CD/DEE), or to filtered air (control) was studied. The course of infection in mice previously exposed for 1 month to various particulates did not differ appreciably among the four animal groups with respect to mortality, virus growth in lungs, interferon levels, or hemagglutinin antibody response. In mice exposed for 3 and 6 months to different particulates, the mortality response was similar among all animal groups. However, the percentage of animals showing lung consolidation was significantly higher in the 3-month groups exposed to DEE (96.5%) and CD/DEE (97%) than in the control (61.2%); in the 6-month groups, the percentages were twice that of the control for both DEE- and CD/DEE-exposed animals. Complementing these observations of both 3- and 6-month-exposed animals was the higher virus growth levels attained in the DEE and CD/DEE animals with concomitant depressed interferon levels which were the inverse of findings noted in the control group. Hemagglutinin-antibody levels in particulate-exposed animals, especially at the 6-month interval, were fourfold less than the control. Histopathologic examination of lungs revealed no qualitative differences in the inflammatory response at any one specified time interval of exposure to influenza virus among the control and particulate-exposed animal groups. However, there were differences in severity of reaction in relation to the particulate component of the exposures. Focal macular collections of pigment-laden macrophages were seen only in DEE and CD/DEE but not in CD animals after 3- and 6-month exposures. The findings of this study indicated that the severity of influenza virus infection is more pronounced in mice exposed to diesel engine emissions than in control animals and it is not appreciably accentuated by coal dust.

Effects of a two-year inhalation exposure of rats to coal dust and/or diesel exhaust on tension responses of isolated airway smooth muscle.

This study was performed to determine whether chronic inhalation exposure of rats to levels of coal dust (CD) and/or diesel exhaust (DE) similar to those experienced by underground miners affects the pharmacologic characteristics of the animal's airway smooth muscle. Animals were exposed for 2 yr to CD alone (2 mg/m3 of respirable particulates), DE alone (2 mg/m3 of respirable particulates), or CD and DE (CD + DE) in combination (1 mg/m3 CD plus 1 mg/m3 DE). Concentration-response relationships for tension changes induced with acetylcholine, 5-hydroxytryptamine, potassium chloride, and isoproterenol were assessed in vitro on isolated preparations of rat airway smooth muscle (trachealis). Compared with control animals, the maximal contractile responses to acetylcholine of tissues from CD-, DE-, and CD + DE-exposed animals were significantly increased; the effects of CD and DE exposure were additive. The CD + DE exposure, but not the individual treatments, resulted in a significant increase in the maximal relaxation response elicited by isoproterenol; this interaction may have resulted from the addition of, or the synergism between, the nonsignificant effects of CD and DE alone. No treatment altered the sensitivity (EC50 values) of the muscles to the agonists used. The results indicate that chronic exposure to CD, DE, and CD + DE produces differential modifications in the behavior of rat airway smooth muscle. These findings may have some bearing on humans exposed to these substances.

Pulmonary responsiveness to methacholine and disodium hexachloroplatinate (Na2PtCl6) aerosols in cynomolgus monkeys (Macaca fascicularis).

Hyperreactivity of the airways is a common finding in human asthma, and responsiveness to inhaled methacholine aerosols is routinely used for assessing airway irritability. Workers in precious metal refineries demonstrate pulmonary signs suggestive of asthma, presumably related to exposure to soluble platinum salts. In these workers, evidence of physiologic dysfunction precedes immunologic evidence (skin test) of disease, suggesting an initial pharmacologic mechanism. With a primate animal model for the screening of occupational asthmogens, 24 Cynomolgus monkeys were evaluated for their comparative pulmonary responsiveness to inhaled aerosols of methacholine and sodium hexachloroplatinate (Na2PtCl6). Average pulmonary flow resistance (RL), dynamic compliance (CLdyn), maximum expiratory flow volume (MEFV), and respiratory frequency changes were evaluated after bronchoprovocation challenge. Both agents produced dose-dependent increases in RL, dose-dependent decreases in CLdyn and MEFV, and no effect on respiratory rates. Analyses of the correlation between concentration effects of the two agents showed no association between cholinergic airway irritability status and Na2PtCl6-induced bronchoconstriction. Na2PtCl6 bronchoprovocation produced significantly greater flow impairment at lower lung volumes when compared to methacholine concentrations with equipotent effects on RL and CLdyn. These compounds have differential effects on peripheral airway function. The lack of respiratory rate change seen on bronchoprovocation with these compounds, in comparison to the rapid shallow breathing in anesthetized monkeys following irritant or histamine challenge, indicates that neither aerosol stimulated pulmonary irritant receptors.

Fibrogenic potential of intratracheally instilled quartz, ferric oxide, fibrous glass, and hydrated alumina in hamsters.

As a first step in the development of an animal model for determining the role of pulmonary fibrosis in the etiology and pathogenesis of lung cancer, the fibrogenic potential of quartz, quartz and ferric oxide administered together, fibrous glass, and hydrated alumina were studied by multiple intratracheal instillation in groups of male Lak:LVG Syrian golden hamsters. Dose-related decreases in survival were evident for the groups instilled with the two highest doses of quartz or quartz and ferric oxide. Instillation of quartz or quartz and ferric oxide induced the greatest pulmonary fibrosis in response to the materials tested. However, the dense fibrous tissue present in the lungs in classical human silicosis and in experimental silicosis of rats was not observed in this study. The results of this study indicate that the Syrian golden hamster is not a suitable species for studying the role of quartz-induced pulmonary fibrosis in pulmonary carcinogenesis.

Subchronic inhalation toxicity of isobutyl nitrite in BALB/c mice. I. Systemic toxicity.

The effects of subchronic inhalation exposure to isobutyl nitrite (IBN) on body weight, selected organ weights, hematology, and gross pathology and histopathology of BALB/c mice were evaluated. Mice of both sexes were exposed at 0, 20, 50, or 300 ppm IBN for 6.5 h/d, 5 d/wk for up to 18 wk. Most changes in measured indices occurred in mice exposed at 300 ppm IBN and included decreased thymus weight (females); decreased liver weight (males); decreased white blood cell counts (males); mild focal hyperplasia and vacuolization of the epithelium lining bronchi and bronchioles of the lungs (males and females). Organ weight and hematologic changes, however, were not accompanied by any observed histologic changes. In addition, elevated methemoglobin concentrations were detected in mice of both sexes exposed at 50 and 300 ppm IBN. Body weights were not adversely affected by exposure. These data suggest that mild tissue injury, restricted to the lung, and methemoglobinemia are the major toxic effects observed following exposures of mice to IBN at concentrations up to 300 ppm for 18 wk. No treatment-related effects were noted in mice exposed at 20 or 50 ppm IBN, except for slight elevations in methemoglobin concentrations in mice exposed at 50 ppm.

Sister-chromatid exchanges and chromosome aberrations in lymphocytes from monkeys exposed to ethylene oxide and propylene oxide by inhalation.

The ability of long-term exposures to inhaled ethylene oxide (EO) and propylene oxide (PO) to induce sister-chromatid exchanges (SCEs) and chromosome aberrations in peripheral lymphocytes of monkeys was investigated. Five groups of adult male cynomolgus monkeys were exposed at 0 (shared control), 50, or 100 ppm EO, and at 100 or 300 ppm PO (7 hr/day, 5 days/week) for 2 years. EO exposures at 50 and 100 ppm resulted in statistically significant increases in sister-chromatid exchange rates and in the incidence of chromosome aberrations in monkey lymphocytes. Both EO-exposed groups had increased numbers of SCEs/metaphase compared to controls, with the SCEs/metaphase of the EO 100 ppm group also significantly elevated versus the EO 50 ppm group. Variability of SCEs/metaphase within each monkey increased even more than the increase in total SCEs/metaphase group with increasing EO exposure. Chromatid-type aberrations were also significantly increased for both EO 50 and EO 100 ppm groups compared to controls. Statistically significant increases in the number of chromosome-type aberrations (excluding gaps) were found only in the EO 100 ppm group. Combined chromatid- and chromosome-type aberrations were increased in both EO 50 and EO 100 ppm groups. No group differences in the number of gaps were found. In lymphocytes from monkeys exposed at 100 and 300 ppm PO, there were no group differences compared to controls for any variable-chromatid or chromosome-type aberrations, gaps, or SCEs/metaphase. These results indicate that EO is a more potent clastogen than PO and demonstrate, for the first time, statistically significant effects of EO on both SCEs and chromosome aberrations in lymphocytes of nonhuman primates.

Carcinogenic and toxicologic effects of inhaled ethylene oxide and propylene oxide in F344 rats.

The chronic inhalation toxicity and carcinogenicity of ethylene oxide (EO) and propylene oxide (PO) were evaluated in a 2-year inhalation bioassay. Five groups of male weanling Fischer 344 rats, 80 per group, were exposed at 0 ppm (shared control; filtered air), 50 ppm EO, 100 ppm EO, 100 ppm PO, or 300 ppm PO (7 hr/day, 5 days/week) for 104 weeks. Body weights from rats exposed to EO and PO at all exposure concentrations were significantly reduced compared to controls. A statistically significant increase in mortality was observed in all groups of exposed rats compared to controls. Skeletal muscle atrophy in the absence of any sciatic nerve neuropathology was found in rats exposed at 100 ppm EO and 300 ppm PO. Statistically significant associations between EO exposure and an increased incidence of the following rat neoplasms were observed: mononuclear cell leukemia, peritoneal mesothelioma, and mixed cell brain glioma. Among rats exposed to PO there was a dose-dependent increase in the incidence of complex epithelial hyperplasia in the nasal passages, and two adenomas were detected in the nasal passages of rats exposed at 300 ppm PO. The incidence of adrenal pheochromocytomas was elevated in both PO exposure groups, but not in a dose-related manner. All rat groups were affected by an outbreak of Mycoplasma pulmonis infection which occurred about 16 months into the study. This infection alone and in combination with the epoxide exposures affected the survival of rats in this study, and influenced the development of the proliferative lesions in the nasal mucosa of the PO-exposed rats. No treatment-related changes in any clinical chemistry or urinalysis indices were detected. PO exposure did not increase the incidence of the three neoplasms associated with EO exposure; however, adrenal pheochromocytomas and proliferative lesions of the nasal cavity were increased in rats exposed to PO.

Toxicity evaluation of sub-chronic exposures to cyanogen in monkeys and rats.

A 6 mon (6 hr/day, 5 days/week) inhalation toxicity study was conducted with cyanogen gas using male rhesus monkeys (Macacca mulatta) and male albino rats (Charles River Strain) as experimental animals. Fifteen monkeys and 90 rats were divided into three groups of 5 monkeys and 30 rats. One group, the Controls, was not exposed to the test material; the other two groups were exposed to either 11 ppm or 25 ppm cyanogen. At the outset of exposures, there was a doubling of the rate of responding on a variable interval 2.9 min schedule of reinforcement in monkeys exposed to 25 ppm cyanogen, and increases were also seen in the monkeys receiving 11 ppm exposures; the increases were transitory as the rate returned to control levels before exposures were terminated. At the end of the 6 mon exposure, there were no effects in hematologic or clinical chemistry parameters attributable to the inhalation exposure to cyanogen. The electrocardiograms, and gross pathologic and histopathologic examinations of test animals were normal when compared with the Control animals. Total lung moisture content was significantly lower in monkeys exposed to either 11 ppm or 25 ppm cyanogen than in Control animals. Body weights were significantly lower in rats exposed to 25 ppm than in Controls. The results suggest that subchronic 25 ppm cyanogen exposures are marginally toxic, but the evidence on 11 ppm does not support a similar conclusion.