NAM-based Prediction of Point-of-contact Toxicity in the Lung: A Case Example With 1,3-dichloropropene

Time, cost, ethical, and regulatory considerations surrounding in vivo testing methods render them insufficient to meet existing and future chemical safety testing demands. There is a need for the development of in vitro and in silico alternatives to replace traditional in vivo methods for inhalation toxicity assessment. Exposures of differentiated airway epithelial cultures to gases or aerosols at the air-liquid interface (ALI) can assess tissue responses and in vitro to in vivo extrapolation can align in vitro exposure levels with in-life exposures expected to give similar tissue exposures. Because the airway epithelium varies along its length, with various regions composed of different cell types, we have introduced a known toxic vapor to five human-derived, differentiated, in vitro airway epithelial cell culture models-MucilAir of nasal, tracheal, or bronchial origin, SmallAir, and EpiAlveolar-representing five regions of the airway epithelium-nasal, tracheal, bronchial, bronchiolar, and alveolar. We have monitored toxicity in these cultures 24hours after acute exposure using an assay for transepithelial conductance (for epithelial barrier integrity) and the lactate dehydrogenase (LDH) release assay (for cytotoxicity). Our vapor of choice in these experiments was 1,3-dichloropropene (1,3-DCP). Finally, we have developed an airway dosimetry model for 1,3-DCP vapor to predict in vivo external exposure scenarios that would produce toxic local tissue concentrations as determined by in vitro experiments. Measured in vitro points of departure (PoDs) for all tested cell culture models were similar. Calculated rat equivalent inhaled concentrations varied by model according to position of the modeled tissue within the airway, with nasal respiratory tissue being the most proximal and most sensitive tissue, and alveolar epithelium being the most distal and least sensitive tissue. These predictions are qualitatively in accordance with empirically determined in vivo PoDs. The predicted PoD concentrations were close to, but slightly higher than, PoDs determined by in vivo subchronic studies.

Seizure-associated brain injury in term newborns with perinatal asphyxia

BACKGROUND

There is controversy over whether seizures, the most common manifestation of neonatal brain injury, may themselves damage the developing brain.

OBJECTIVE

To determine if neonatal seizures are independently associated with brain injury in newborns with perinatal asphyxia.

METHODS

Ninety term neonates were studied with MRI and single-voxel (1)H-MRS on median day of life 6 (range 1 to 13 days). The severity of MR abnormality in the (1)H-MRS regions of interest was scored using a validated scale. Seizure severity was scored based on seizure frequency and duration, EEG findings, and anticonvulsant administration. Multivariable linear regression tested the independent association of seizure severity with impaired cerebral metabolism measured by lactate/choline and compromised neuronal integrity measured by N-acetylaspartate/choline in both regions.

RESULTS

Clinical seizures occurred in 33 of 90 infants (37%). Seizure severity was associated with increased lactate/choline in both the intervascular boundary zone (p < 0.001) and the basal nuclei (p = 0.011) when controlling for potential confounders of MRI abnormalities and amount of resuscitation at birth. Each increase in seizure score was independently associated with a 21% increase in lactate/choline in the intervascular boundary zone (95% CI, 5.1-38.2%) and a 15% increase in the basal nuclei (95% CI, 0.1-31.7%). Seizure severity was independently associated with diminished N-acetylaspartate/choline in the intervascular boundary zone (p = 0.034).

CONCLUSION

The severity of seizures in human newborns with perinatal asphyxia is independently associated with brain injury and is not limited to structural damage detectable by MRI.

Trisomy 21 with 47,+18 lymphocyte cell line: double mitotic nondisjunction

A patient with Down's syndrome was found to have 47,XX,+18/47,XX,+21 mosaicism. Chromosome 18 trisomy was found only in 18% of lymphocytes and not in skin fibroblasts. A likely interpretation is double nondisjunction in a single lymphocyte precursor of a trisomy 21 embryo. A brief review of other cases of mitotic multiple nondisjunction and double aneuploid mosiacism is presented.