Fibroblast growth factors (FGFs) induce the proliferation and differentiation of cells of mesodermal and neuroectodermal origin. Using in situ hybridization, messenger ribonucleic acid encoding acidic FGF, basic FGF and FGF receptor 1 (FGFR1) were localized in the middle ear mucosa of experimental animals with acute and chronic immune-mediated otitis media with effusion (OME). Basic FGF-labeled cells were seen in the subepithelial connective tissue layer (SE) preferentially near the epithelial basement membrane. Acidic FGF-labeled cells were seen in the SE, preferentially near blood vessels and occasionally in the cellular middle ear effusion (CE). FGFR1-labeled cells were seen in the SE and in the CE. The distribution of labeled cells in the middle ear suggests that basic FGF is produced by fibroblasts, acidic FGF is produced by leukocytes, and FGFR1 is produced by both fibroblasts and leukocytes. A role is proposed for these peptides in the proliferation and maintenance of the middle ear submucosa during otitis media.

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To enable direct testing of a range of potential toxins or pathogens that might be involved in grass sickness, equine thoracic sympathetic chain ganglion cell lines were established from primary cell cultures by retroviral-mediated transduction of the temperature-sensitive mutant of the establishment oncogene encoding SV40 large T antigen. Morphological and behavioral features, temperature dependence, and immunocytochemical characteristics of the cell lines were investigated. The majority of cells were noradrenergic neurons in which dopamine-beta-hydroxylase, the enzyme that catalyzes norepinephrine synthesis, and neuropeptide Y coexisted. Cells treated with plasma from grass sickness cases that had previously been shown to induce autonomic nervous system damage when injected into normal horses showed significantly decreased mitochondrial function after 1 day. After 3 days exposure most cells showed severe degeneration in contrast to those treated with normal plasma. Liver and lung cell lines were also susceptible to plasma, suggesting that the toxin is not specifically neurotoxic.