Adenocarcinoma of retinal pigment epithelium arising from a juxtapapillary histoplasmosis scar.

A 66-year-old woman underwent a transocular fine-needle aspiration biopsy for an enlarging mass arising from a juxtapapillary histoplasmosis scar in the left eye. The cytologic study revealed pigmented malignant cells, suggesting that the lesion was either a malignant choroidal melanoma or an adenocarcinoma of the retinal pigment epithelium. The eye was enucleated and histopathologic studies revealed findings suggestive of an adenocarcinoma of the retinal pigment epithelium. Immunohistochemical stains were positive for cytokeratin and were negative for melanoma-specific antigen, supporting an epithelial origin of the neoplasm. It is possible that the tumor developed as a neoplastic transformation of a reactive proliferation of the retinal pigment epithelium in a histoplasmosis scar. The possible association between a chorioretinal scar and the development of a tumor of the pigment epithelium is discussed herein.

Airway epithelial cells are the site of expression of a mammalian antimicrobial peptide gene.

We previously reported the isolation and characterization of a broad-spectrum antimicrobial peptide from the bovine tracheal mucosa, which we called tracheal antimicrobial peptide (TAP). We now show the TAP gene is expressed throughout the adult conducting airway, from nasal to bronchiolar tissue, but not in tissues other than airway mucosa, as determined by Northern blot analysis. In situ hybridization of airway sections localizes TAP mRNA to columnar cells of the pseudostratified epithelium. We report the structural organization of the TAP gene and show that TAP is a member of a large family of related sequences with high nucleotide identity in the 5' exon. The data support the hypothesis that antimicrobial peptides contribute to host defense of the respiratory tract.

Dantrolene prevents the malignant hyperthermic syndrome by reducing free intracellular calcium concentration in skeletal muscle of susceptible swine.

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle triggered when susceptible subjects are exposed to volatile anesthetic agents and/or depolarizing muscle relaxants. We have used Ca2+ selective microelectrodes to measure in vivo the intracellular free [Ca2+] in skeletal muscle of MH susceptible swine before and after the administration of dantrolene. We have investigated the effectiveness of this muscle relaxant in preventing clinical MH and the relationship between the resting intracellular free [Ca2+] and the probability of inducing the MH syndrome. The resting intracellular free [Ca2+] was 0.41 +/- 0.01 microM (M +/- SEM), which agrees with our previous measurements in susceptible swine. The administration of 0.5, 1, 2, 2.5 and 3 mg/Kg Dantrolene, reduced the intracellular free [Ca2+] to 0.31, 0.21, 0.09, 0.08, 0.08 microM respectively. The 0.5 mg/Kg dose induced a moderate decrease of [Ca2+]i and failed to prevent the MH syndrome after exposure to halothane (2%). The 1 mg/Kg dose produced a further reduction in [Ca2+]i and was sufficient to prevent the clinical syndrome in 2 out of 3 animals. The 2.5 mg/Kg dose was uniformly protective in all animals. These results suggest that the mechanism by which dantrolene protects susceptible animals exposed to triggering agents is by reducing the intracellular free [Ca2+] in skeletal muscle.