Ethylene oxide neuropathy in rats. Exposure to 250 ppm

In Wistar rats subjected to a 6-h exposure to ethylene oxide at the concentration of 250 parts per million once, 5 times a week for 9 months, histopathologic studies of myelinated fibers of the proximal sural, distal sural and peroneal nerves and of the fasciculus gracilis at the 5th thoracic and 3rd cervical segments of the spinal cord were performed to observe whether ethylene oxide of such a concentration would lead to degeneration of primary sensory neurons. Throughout the study, no definite abnormality of the gait or posture was observed in both control and test rats. Qualitative histologic studies disclosed preferential distal axonal degeneration of myelinated fibers in both sural nerves and gracile fascicles in the test rats, although the extent of the distribution and the severity of the degenerative findings were variable. Such findings are consistent with mild axonal degeneration found among patients suffering from ethylene oxide toxicity. Therefore, in rats, exposure to 250 ppm ethylene oxide produces central-peripheral distal axonal degeneration of primary sensory neurons.     

Residual ethylene oxide in hollow fiber hemodialysis units is neurotoxic in vitro

Ethylene oxide gas is used to sterilize plastic medical equipment including capillary flow dialysis membranes. To test whether ethylene oxide retained in the dialyzers might be neurotoxic, tissue culture medium was incubated in the blood compartment of dialyzers. Embryonic rat dorsal root ganglion neurons were then incubated in this medium for up to 5 days. During the first 24 hours axonal growth was normal. During the next 24-hour period varicosities appeared on axons, and after 4 days neuron cell bodies died. The pattern of degeneration was identical to that observed when cultures were exposed to an atmosphere containing 1 ppm ethylene oxide gas. Culture medium introduced into dialyzers after routine prerinsing still caused degeneration, which was not completely abolished even by a 10-liter rinse. When medium was exposed to identical dialyzers sterilized by gamma irradiation, no changes were seen in culture. Identical morphological changes were produced by using dialysis patient serum in the culture medium in place of the usual calf bovine serum. Such changes were never seen with control human serum. Since ethylene oxide is toxic to the human peripheral nervous system, it is proposed that ethylene oxide in dialyzers may contribute to the progressive neuropathy observed in patients on long-term hemodialysis.     

Evidence of neurologic dysfunction related to long-term ethylene oxide exposure

Eight hospital workers with chronic ethylene oxide exposure were age-sex matched with eight nonexposed controls with no significant differences in educational backgrounds and vocabulary scores. The exposed group performed more poorly on all eight measures of cognition, memory, attention, and coordination, with 71.3% less accuracy on the Hand-Eye Coordination Test. There was a dose-response relationship between exposure and the following: Continuous Performance Test and sural velocity. These findings suggest that neurologic dysfunction may result from long-term low-dose exposure to ethylene oxide, and that these effects may occur at exposure levels common in hospital sterilizer operations.     

Nitric oxide synthase expression and enzymatic activity in multiple sclerosis

We used post-mortem magnetic resonance imaging (MRI) guidance to obtain paired biopsies from the brains of four patients with clinical definite multiple sclerosis (MS). Samples were analyzed for the immunoreactivity (IR) of the three nitric oxide (NO) synthase isoforms [inducible, neuronal and endothelial nitric oxide synthase (NOS)], and enzymatic NO synthase activity. MRI guided biopsies documented more active plaques than macroscopic examination, and histological examination revealed further lesions. Inducible NOS (iNOS) was the dominant IR isoform, while reactive astrocytes were the dominant iNOS expressing cells in active lesions. NOS IR expressing cells were widely distributed in plaques, in white and gray matter that appeared normal macroscopically, and on MR. Endothelial NOS (eNOS) was highly expressed in intraparenchymal vascular endothelial cells of MS patients. A control group matched for age and sex showed no such changes. Our data support the hypothesis that NO is a pathogenic factor in MS, and that NOS IR is strongly expressed in brain regions appearing normal by MRI.     

Ethylene oxide-induced polyneuropathy. A clinical and electrophysiologic study

Occupational exposure to ethylene oxide (ETO) was manifested as a subacute polyneuropathy, with bilateral footdrop and denervation potentials on electromyography as the principal abnormalities in three young adults whom we examined. To our knowledge, this is the second report of neurotoxic effects caused by long-term ETO exposure in humans and brings the number of patients described with symptomatic polyneuropathy to five.     

A radiological evaluation of allografts (ethylene oxide sterilized cadaver bone) and autografts in anterior cervical fusion

Serial roentgenograms of 40 patients who had 70 cervical intervertebral spaces grafted with ethylene oxide sterilized cadaver bone and 28 patients who received 44 iliac crest auto grafts for anterior cervical spine fusion, were studied. The radiological evaluation was made on the basis of settlement of intervertebral spaces, fusion rate, delayed union, non-union, graft collapse and extrusion of the graft. Indigenous methodologies were designed for the assessment of settlement of grafted intervertebral spaces in percentage. Disc space settlement was more common in autografts (93% cases) than in allografts (80% cases). The average percentage of settlement of intervertebral disc space (S%) was 22 in autografts and 28 in allografts during the first four months. By the end of eight months, allograft disc spaces settle more. No significant difference was noted in fusion rate at the end of one year viz. allografts (90% cases) and autografts (93% cases). Autograft and allograft (ethylene oxide sterilized cadaver bone) are equally useful in anterior cervical spine fusions.     

On ethylene oxide neurotoxicity: report of two cases of peripheral neuropathy

Two cases of clinically and electromyographically proven ethylene oxide neuropathy occurred among 12 workers at the Lecco Hospital Sterilization Center. Cessation of exposure to the gas, which had lasted for two years, was followed by swift remission of the symptoms and complete normalisation of the EMG record at follow-up six months later. The paucity of published data on the subject may well mean that the real risk of ethylene oxide toxicity is being underrated.

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Sommario Vengono descritti due casi di neuropatia da ossido di etilene, con sintomatologia clinica ed alterazione dei parametri elettrografici investigati, insorti in un gruppo di dodici lavoratori addetti al Centro di Sterilizzazione dell'Ospedale di Lecco. L'allontanamento dalla esposizione al gas (che datava da due anni) ha determinato una pronta remissione dei sintomi ed una normalizzazione completa del quadro elettrografico, ad un controllo eseguito sei mesi dopo. Si sottolinea la scarsità dei dati della letteratura al riguardo (sette casi in tutto, compresi quelli da noi descritti), possibile espressione, a nostro avviso, di una sottovalutazione del reale pericolo di neurotossicità dell'ossido di etilene.

     

Dystrophinopathy muscle biopsies in the genetic testing ERA: One center's data

Introduction: Comprehensive genetic testing for dystrophinopathy can detect ～95% of pathogenic variants in the dystrophin gene (DMD) and is often the preferred diagnostic approach. Methods: We reviewed pathology reports for muscle biopsies evaluated at the University of Iowa with a pathological diagnosis of dystrophinopathy based on dystrophic histopathology and abnormal immunofluorescence staining: reduced to absent dystrophin, expression of utrophin, and loss of neuronal nitric oxide synthase. Results: The percentage of muscle biopsies with dystrophinopathy has been stable since 1997. Among 2,298 biopsies evaluated between 2011 and 2016, 72 (3.1%) had pathologic features of dystrophinopathy. Median age at biopsy was 8 years (range, 0.66–84). Half had undergone DMD genetic testing prior to biopsy. Clinical phenotypes recorded on requisitions were typical of muscular dystrophy for 57 (79%) biopsies. Discussion: Muscle biopsy continues to play an important role in the diagnosis of dystrophinopathy, particularly in patients with later symptom onset, comorbidities, or normal DMD genetic testing results. Muscle Nerve 58 : 148–152, 2018     

Parkinsonism secondary to ethylene oxide exposure: case report]

Ethylene oxide is a gas widely used in the production of industrial chemicals. It is also used to sterilize heat-sensitive medical supplies. Previous reports of acute and chronic exposure have described neurotoxic effects like peripheral neuropathy and cognitive impairment. We describe a pure parkinsonian syndrome following acute ethylene oxide intoxication. A 39-years-old male was referred to our Movement Disorders Clinic for evaluation of a parkinsonian syndrome. He was acutely exposed to ethylene oxide four years before and remained comatose for three days, and gradually regained consciousness. At that time he showed a global parkinsonian syndrome including bradykinesia, rigidity and rest tremor, with a severe motor disability; no other neurological disorders were found. The symptomatology was partially controlled with biperidene and levodopa plus carbidopa. Two years later he developed L-dopa induced dyskinesias. Four years after the intoxication he was evaluated at our clinic. General examination showed no abnormalities. Neurologic examination revealed a normal mental status. Motor evaluation disclosed moderate bradykinesia, rigidity and rest tremor, shuffling gait, poor facial mimic, stooped posture, and his speech was low and monotonous; deep tendon reflexes were brisk. The Hoehn-Yahr disability score was degree IV. Routine laboratory and radiological exams showed results within normal limits. The CSF examination was normal. Brain computed tomography and magnetic ressonance were normal. A trial with bromocriptine and levodopa plus carbidopa did not improve dyskinesia, and he was put on a schedule including amantadine and biperidene with improvement to grade III in Hoehn-Yahr scale. In the present case there was a clear relation between the acute exogenous intoxication and irreversible parkinsonism.(ABSTRACT TRUNCATED AT 250 WORDS)     

ANCA相关性血管炎存在血管内皮细胞血栓调节蛋白以及内皮源性一氧化氮合酶弥漫性丢失

目的 探索ANCA相关性血管炎(antineutrophil cytoplasmic antibody-associated vasculitis,AAV)微小动脉和静脉的血管内皮细胞膜结合性血栓调节蛋白(thrombomodulin,TM)、内皮源性一氧化氮合酶(endothelial-nitric oxide synthase,eNOS)的表达规律.方法 12例经过临床、血清免疫学检查证实的AAV患者,2例Wegerner肉芽肿、5例显微镜下多血管炎和5例Churg-Strause综合征.Birmingham血管炎活动评分提示疾病处于活动期.均进行腓肠神经活检标本的常规组织学染色以及以抗CD68、CD3、CD20、血栓调节蛋白(thrombomodulin,TM)、eNOS以及第八因子(von Willebrand factor,vWF)抗体为第一抗体的免疫组织化学染色,以正常血管为对照.结果 12例患者的腓肠神经病理检查发现9例活动性血管炎,可见大量CD68阳性单核细胞和CD3阳性淋巴细胞浸润.和对照组相比,所有患者微小动脉和毛细血管内皮细胞eNOS和TM减低或消失,包括无炎细胞浸润血管,其中eNOS的下降程度较TM更明显.Churg-Strause综合征的血管内皮细胞eNOS和TM下降最显著.结论 AAV外周血管存在血管内皮细胞TM和eNOS弥漫性下降,两者下降程度在AAV不同亚型之间存在差异.     

Ethylene oxide neurotoxicity: report of four cases and review of the literature.

Four workers were exposed to ethylene oxide gas. Acute encephalopathy occurred in one, and peripheral neuropathy in three, two of whom were symptomatic. Nerve conduction velocity studies were abnormal in three, including the asymptomatic patient. Decreasing the amount of exposure resulted in relief of symptoms. The abnormal nerve conduction studies did not change in two patients who continued to work at a lower level of exposure, whereas the conduction abnormalities improved in the patient who was removed from exposure.     

Neurological and emotional sequelae of exposure to ethylene oxide

Subjects were 66 traumatic brain-injured (TBI) versus 22 neurotoxic-injured individuals (due to ethylene oxide - ETO). Among significant findings were higher cognitive functioning for the TBI group for FSIQ, VIQ and PIQ; elevated scores on MMPI scales 1, 2, 3 and 8 for both groups, and elevated anxiety scores on the MAACL for the ETO group relative to the TBI group. Results indicate a more severe impact of ETO exposure in the areas of intellectual functioning and anxiety.     

Polyneuropathy caused by ethylene oxide. Report of a case with clinical, electrophysiological and histopathological studies]

A man who worked as an operator in a factory of sterilization of heat-sensitive materials has been exposed to ethylene oxide for seven years. He developed a mild sensori-motor polyneuropathy. The electromyography and nerve condition studies showed an axonal degenerative type of neuropathy. The sural nerve biopsy revealed mild loss of myelinated fibers, some fibers with axonal degeneration, some clusters of regeneration and few rows of myelin ovoids in the teased nerve fiber preparation. This is the first report of ethylene-oxide polyneuropathy in Brazil.     

Neurotoxicants and the cytoskeleton

Exposure to occupational and environmental toxicants can result in distal axonopathies through reaction with various components of the axonal cytoskeleton. The solvents n-hexane and methyl n-butyl ketone are metabolized to the beta-diketone, 2,5-hexanedione, which covalently cross-links neurofilaments, resulting in large paranodal axonal swellings filled with neurofilaments. Carbon disulfide exposure leads to an identical axonopathy, achieving neurofilament cross-linking through a parallel series of reactions. Acrylamide and ethylene oxide, on the other hand, adduct proteins but do not lead to cross-linking. These toxicants appear to affect the function of microtubule-associated proteins, such as kinesin, and result in the impaired transport of synaptic vesicles.     

Ethylene oxide polyneuropathy: clinical follow-up study with morphometric and electron microscopic findings in a sural nerve biopsy

Summary A case is reported of ethylene oxide polyneuropathy after 5 months of exposure. There was symmetrical distal weakness of both lower extremities and transitory reduced nerve conduction velocities with increased latencies. Sural nerve biopsy revealed nerve fibre degeneration of the Wallerian type, associated with reduction of axonal cross-sectional areas and some degree of nerve fibre regeneration that could be confirmed morphometrically. In addition, there was conspicuous paranodal vesicular disintegration of individual myelin lamellae. Unusual cisternae with introverted hemidesmosomes were noted in endoneurial fibroblasts.Support from the Deutsche Forschungsgemeinschaft (Schr 195/5-5)     

Magnetic resonance for evaluation of toxic encephalopathies: implications from animal experiments

Examinations of brain of rats intoxicated with hexachlorophene or acrylamide with ultrahigh-field (4.7 T) proton magnetic resonance (MR) showed alterations consistent with clinical pictures in humans and morphological findings in experimental animals. On the other hand, conventional biochemical analyses have revealed that ethylene oxide, methyl bromide, and acrylamide inhibit creatine kinase (CK; an enzyme catalyzing the reaction: ATP+creatine<-->ADP+phosphocreatine) activities in the brain of animals. Thus, 31P MR combined with magnetization transfer may be utilized to monitor living humans (or animals) intoxicated with these chemicals by determining CK activities in the target organ.     

Activities of mitochondrial complexes correlate with nNOS amount in muscle from ALS patients

The pathogenesis of amyotrophic lateral sclerosis (ALS) is poorly understood. Increased levels of free radicals derived from nitric oxide (NO), the product of nitric oxide synthase (NOS), may damage mitochondrial function leading to motor neurone death. Previous studies demonstrated a specific impairment of mitochondrial function in skeletal muscle of ALS patients. In order to verify a pathogenetic relationship between neuronal NOS (nNOS) and mitochondrial function, we studied nNOS expression by Western blot and mitochondrial enzyme activity by spectrophotometric assays in muscle biopsies of 16 sporadic ALS patients and 16 controls subjects. We observed a reduced activity of respiratory chain complexes with mitochondrial encoded subunits and a lower nNOS amount in ALS muscles. There was a direct correlation between levels of nNOS and values of mitochondrial enzymes function. In ALS muscles we found normal levels of manganese superoxide dismutase (SOD2) that is assumed as related to mitochondrial DNA abnormalities. Our data suggest a beneficial role for NO to mitochondrial function and lead to the hypothesis of a common oxidative damage in motor neurones and skeletal muscle in sporadic ALS patients.     

Brain tumors in F344 rats associated with chronic inhalation exposure to ethylene oxide

Groups of F344 rats of each sex were exposed to either ethylene oxide (ETO) vapor (concentrations of 100, 33 or 10 ppm) or to room air for 6 hours daily, 5 days per week, for up to 2 years. Three representative sections of the brain from each rat were evaluated. Twenty-three primary brain tumors were found, two of which were in control animals. Increased numbers of brain tumors were seen in 100 ppm and 33 ppm ETO exposed male and female rats. Significant trend analyses were found for both males and females, indicating that, under the conditions of this study, ETO exposure above 10 ppm was related to the development of these brain tumors.     

Role of nitric oxide as mediator of nerve injury in inflammatory neuropathies

Different lines of evidence suggest that nitric oxide (NO) plays a key role in the pathogenesis of inflammatory neuropathies; however, it is still unclear which structures in the peripheral nerve are the primary targets of NO-mediated nerve injury. To address this issue, we determined the expression of NO metabolites in sural nerve biopsies and in cerebrospinal fluid from patients with inflammatory neuropathies and studied the pathologic effects of NO in an in vitro model of myelinated Schwann cell-neuron cocultures. In cerebrospinal fluid samples, nitrite levels remained unaltered; however, nitrotyrosine, a marker for peroxynitrite formation, could be identified in nerve biopsies from patients with inflammatory neuropathies. In an in vitro model of Schwann cell neuron cocultures, high concentrations of NO induced robust demyelination, which was the result of NO-mediated axonal injury, whereas Schwann cell viability remained unaffected. These findings suggest that in contrast to Schwann cells, sensory neurons are the primary target of NO-mediated cytotoxicity and the loss of myelin is the result of selective damage to axons rather than a direct harmful effect to Schwann cells. Our findings imply that NO contributes to the pathologic changes seen in the inflamed peripheral nervous system, which is characterized by the features of axonal injury and subsequent myelin degradation, previously described as Wallerian-like degeneration.     

Increased mucosal nitric oxide production in ulcerative colitis is mediated in part by the enteroglial-derived S100B protein

Abstract  In the central nervous system glial-derived S100B protein has been associated with inflammation via nitric oxide (NO) production. As the role of enteroglial cells in inflammatory bowel disease has been poorly investigated in humans, we evaluated the association of S100B and NO production in ulcerative colitis (UC). S100B mRNA and protein expression, inducible NO synthase (iNOS) expression, and NO production were evaluated in rectal biopsies from 30 controls and 35 UC patients. To verify the correlation between S100B and NO production, biopsies were exposed to S100B, in the presence or absence of specific receptor for advanced glycation end-products (RAGE) blocking antibody, to measure iNOS expression and nitrite production. S100B and iNOS expression were evaluated after incubation of biopsies with lipopolysaccharides (LPS) + interferon-gamma (IFN-γ) in the presence of anti-RAGE or anti-S100B antibodies or budesonide. S100B mRNA and protein expression, iNOS expression and NO production were significantly higher in the rectal mucosa of patients compared to that of controls. Exogenous S100B induced a significant increase in both iNOS expression and NO production in controls and UC patients; this increase was inhibited by specific anti-RAGE blocking antibody. Incubation with LPS + IFN-γ induced a significant increase in S100B mRNA and protein expression, together with increased iNOS expression and NO production. LPS + IFN-γ-induced S100B up-regulation was not affected by budesonide, while iNOS expression and NO production were significantly inhibited by both specific anti-RAGE and anti-S100B blocking antibodies. Enteroglial-derived S100B up-regulation in UC participates in NO production, involving RAGE in a steroid insensitive pathway.