Nasal passages of Göttingen minipigs from the neonatal period to young adult.

Histopathological examination of the nasal passages requires a standardized approach for recording lesion distribution patterns. Nasal diagrams provide guidance to map the lesions. Information on lesions exists for rodents, dogs, and monkeys, which all have been used in inhalation studies. Recently, minipigs have garnered interest as an inhalation model because minipigs resemble humans in many features of anatomy, physiology, and biochemistry and may be a good alternative to monkeys and dogs. The present work explored the microanatomy and histology of the nasal passages of Göttingen minipigs from postnatal day 1 until 6 months of age. Six nasal levels were selected, which allow examination of the squamous, transitional (nonciliated) and ciliated respiratory, and olfactory epithelia; the nasopharynx; and relevant structures such as the vomeronasal organ, olfactory bulb, and nasal/nasopharynx-associated lymphoid tissue.

Potentially increased sensitivity of pregnant and lactating female rats to immunotoxic agents.

Characteristic susceptibility to environmental and pharmaceutical exposure may occur during periods in life of marked histophysiological changes of the immune system. Perinatal development is such a period; pregnancy followed by lactation is potentially another one. Here, we explored the influence of pregnancy and lactation on the model immunotoxic compound di-n-octyltin dichloride (DOTC) in rats using clinical and histopathological parameters. Female rats were exposed to 0, 3, 10, or 30 mg DOTC/kg feed during pregnancy and up to 20 (at weaning) or 56 days after delivery. Age-matched nonmated females were exposed during the same time periods. DOTC at the level of 10 and 30 mg/kg decreased thymus weight and affected thymus morphology in the lactating rats. In addition, DOTC decreased the numbers of neutrophils in the lactating rats. These effects were no longer apparent at day 56 despite continuous exposure to DOTC. This explorative study indicates that the innate and adaptive immune system may be especially sensitive to immunotoxicants during pregnancy and lactation.

Hyperplasia of the lymphoepithelium of NALT in rats but not in mice upon 28-day exposure to 15 ppm formaldehyde vapor.

To investigate if local lymphoid tissues are a target of FA, nasopharynx-associated lymphoid tissues (NALT) and upper-respiratory tract-draining lymph nodes were examined in a 28-day inhalation study with FA vapor in Fischer-344 rats and B6C3F1 mice. Paraffin-embedded tissues were sectioned and stained with H&E or stained immunohistochemically for cell proliferation (BrdU incorporation). Light microscopy revealed simple hyperplasia of NALT lymphoepithelium of rats exposed to 15 ppm and an increased proliferation rate of the epithelial cells. Principal component (discriminant) analysis of rat NALT and lymph nodes data did not reveal other effects or effects at lower exposure levels. Mice tissues were not affected. It was concluded that hyperplasia of the lymphoepithelium of NALT of rats exposed to 15 ppm was the only distinct effect of FA vapor on local lymphoid tissues (NALT and lymph nodes) of Fischer-344 rats and B3C3F1 mice.