Safety Evaluation of a Prototypical Diazirine-Based Covalent Crosslinker and Molecular Adhesive.

bis-Diazirine reagents are increasingly being used as polymer crosslinkers, adhesives, and photopatterning agents in the materials sciences literature, but little effort has been made thus far to document their chemical safety profile. Here, we describe the results of a detailed toxicity assessment of a representative bis-diazirine. Safety was evaluated by a series of in vitro assays, which found the product to be non-mutagenic in bacterial tester strains TA98 and TA100, non-corrosive and non-irritating to skin, and requiring no classification for eye irritation or serious damage. While in vitro tests do not capture the integrated whole animal system, and thus cannot completely rule out the possibility of adverse responses, the results of this study suggest a desirable safety profile for bis-diazirine reagents and provide a solid foundation upon which to add in vivo assessment of safety risk and dose-response studies.

Toxicity studies of trimethylsilyldiazomethane administered by nose-only inhalation to Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice.

Trimethylsilyldiazomethane (TMSD) is a methylating reagent widely used in organic chemistry. TMSD is structurally related to the compound diazomethane, which is a known lethal respiratory toxicant in humans and in animal models. TMSD is less reactive (with lower explosive potential) than diazomethane and is considered a safer, less toxic alternative. Few toxicity data are available to support this claim, however, and TMSD is readily available commercially from chemical suppliers. Concern over the inhalation toxicity of TMSD originates from reports of the death of two chemists resulting from lung injury and acute respiratory distress syndrome following exposure to TMSD in the workplace. Other concerns include the known inhalation toxicity of diazomethane and the absence of inhalation toxicity data for TMSD. The National Toxicology Program (NTP) conducted this study to evaluate the acute inhalation toxicity of TMSD in vivo.(Abstract Abridged).

Delayed respiratory fatality from trimethylsilyldiazomethane: what do workers need to know about potentially hazardous exposures?

The Occupational Medicine Forum is prepared by the ACOEM Occupational and Environmental Medical Practice Committee and does not necessarily represent an official ACOEM position. The Forum is intended for health professionals and is not intended to provide medical or legal advice, including illness prevention, diagnosis or treatment, or regulatory compliance. Such advice should be obtained directly from a physician and/or attorney.

Lysosomal protease inhibitors induce meganeurites and tangle-like structures in entorhinohippocampal regions vulnerable to Alzheimer's disease.

Lysosomal protease inhibitors induce signs of human brain aging in rat hippocampal slices. The present studies tested if they (1) also cause neurofibrillary tangles and (2) reproduce regional patterns of pathology found in Alzheimer's disease (AD). Slices of hippocampus plus retrohippocampal cortex were prepared from rats at postnatal days 6-7 and maintained for 2-5 weeks. In agreement with earlier studies, 6- to 12-day infusions of selective (ZPAD) or generalized (chloroquine) inhibitors of lysosomal proteases generated meganeurites of the type found in aged human cortex. Surveys and quantitative analyses established that the meganeurites developed almost exclusively in AD vulnerable regions. Antibodies against the phosphorylated tau protein in neurofibrillary tangles labeled thick filaments running through neurons in the superficial layers of entorhinal cortex in 6-day ZPAD-treated slices. The general appearance of the stained structures resembled that of early stage tangles. More mature tangle-like profiles were found at a number of sites after longer incubations; these were threefold more frequent in the superficial (AD vulnerable) than in the deep layers of the entorhinal cortex. Immunoblots indicated that essentially all phosphorylated tau labeling in the slices involved approximately 29-kDa fragments of the native isoforms. These findings establish that lysosomal dysfunction triggers the parallel formation of meganeurites and tangles with the regional distribution of both effects reflecting that for AD vulnerability.

In vitro embryotoxicity of the cysteine proteinase inhibitors benzyloxycarbonyl-phenylalanine-alanine-diazomethane (Z-Phe-Ala-CHN2) and benzyloxycarbonyl-phenylalanine-phenylalanine-diazomethane (Z-Phe-Phe-CHN2).

This study makes use of whole embryo culture to investigate the potential embryotoxicity of benzyloxycarbonyl-phenylalanine-alanine-diazomethane (Z-Phe-Ala-CHN2) and benzyloxycarbonyl-phenylalanine-phenylalanine-diazomethane (Z-Phe-Phe-CHN2), two low molecular weight, active site-directed and irreversible inhibitors of the lysosomal cysteine proteinases. Peptidyl diazomethanes are the most specific inhibitors available for lysosomal cysteine proteinases and can be hypothesized to interrupt visceral yolk sac (VYS)-mediated nutrition during early organogenesis. When added directly to the culture medium of gestational day 10-11 rat conceptuses, both compounds inhibited lysosomal cysteine proteinase activity in the VYS in a concentration-dependent fashion that correlated with the degree of embryotoxicity observed. Z-Phe-Ala-CHN2 and Z-Phe-Phe-CHN2 were also found to increase the protein content of the VYS, even though all other conceptual growth parameters decreased. This effect was dependent on the serum content of the culture medium and the exposure time. Histological examination of Z-Phe-Ala-CHN2-treated conceptuses revealed a dramatic increase in the size and number of vacuoles in the VYS endoderm epithelium, suggestive of inhibition of VYS proteolysis. At the same time, excessive cell death was observed throughout the neuroepithelium and in specific regions of the mesenchyme of the corresponding embryos. This cell death manifested morphological characteristics of apoptosis and could be detected by supravital staining with Nile Blue Sulphate. These findings provide additional evidence in support of the hypothesis that lysosomal cysteine proteinases play a critical role in VYS-mediated histiotrophic nutrition and suggest that peptidyl diazomethanes may be useful in further characterization of these enzymes. The possible direct effects of these inhibitors on embryonic cells and the relationships between interruption of VYS-mediated nutritional processes and embryonic cell death are discussed.