Light and electron microscopic localization of parathyroid hormone (PTH) in human and bovine parathyroid tissue has been achieved using an indirect peroxidase labeled antibody method. Granular deposition of the reaction product was found throughout the chief cell cytoplasm. There was no nuclear staining. At the ultrastructural level, parathyroid hormone localized by this method appeared to be largely confined to the secretory granules in the cytoplasm of cells. Mitochondria and nuclei were free of reaction product. Aggregated sacs of granular endoplasmic reticulum were minimally reactive, and Golgi apparatuses did not show reaction product.

Brown recluse spider (loxosceles reclusa) venom has been demonstrated by a ferritin-labeled antibody technique to attach to human erythrocyte cell membranes. The number of individual attachment sites per cell is proportional to the concentration of the venom used to sensitize the erythrocytes. Structural changes in the red cell membrane are associated with the venom attachment. These sites may be related to the red cell hemolysis which sometimes occurs in the human as a result of the spider bite.