Harlan J. Pederson

The Function of Platelets

The main function of platelets, the maintenance of hemostasis, depends on three of their properties, the endothelial supporting function of platelets, the ability to form hemostatic plugs and to release lipoprotein material (platelet factor 3). When the number of circulating platelets is reduced the capillary endothelium becomes weakened as platelets are not available to enter the endothelial cytoplasm to support it and the capillary wall ruptures when exposed to minor trauma. The bleeding through the ruptured vessel wall is arrested by formation of a clump of platelets forming a hemostatic plug. Damage to the vessel wall initiates both the coagulation mechanisms and degradation of adenosine triphosphate. The products of each of these reactions, namely, thrombin and adenosine diphosphate bring about aggregation of platelets to form the hemostatic plug. These are the platelet functions performed following a transfusion of platelets into a thrombocytopenic recipient. The platelets remaining in the circulation and which are counted in platelet survival studies are those in excess of the immediate need of the recipient.

Ultrastructural changes associated with loss of transparency in the primary spectacle and cornea of spawning sea lamprey

Abstract Structural changes associated with loss of transparency in the nonswelling primary spectacle and cornea of the sea lamprey during spawning were studied by electronmicroscopy. Epithelial cells of the spectacle were separated by enlarged extracellular spaces, while the stroma of both the spectacle and cornea was found to be invaded by leukocytes. Collagen break-down and the presence of electron-dense amorphous and filamentous material were observed in the superficial stroma.

Cytoplasmic Activity in Type I Pulmonary Epithelial Cells Induced by Macroaggregated Albumin

After the intravenous injection of radioalbumin macroaggregate, large numbers of cytoplasmic inclusion bodies were observed in the lung tissue of rats. The inclusions were located mainly in the cytoplasm of type I alveolar lining cells, appeared 40 minutes after the injection, and lasted up to 2 days. These observations suggest that the type I alveolar lining cells participate in the clearing mechanism of the lung tissue, a function that thus far has not been attributed to this type of cell.

Intraocular Safety Evaluation of Ethylene Oxide and Sterilant Residues

AbstractMany materials and solutions used during intraocular surgery undergo ethylene oxide sterilization and consequently contain residues that could affect ocular tissues. This study was undertaken to investigate the corneal endothelial toxicity of ethylene oxide and two of its reaction products, ethylene chlorohydrin and ethylene glycol. Isolated rabbit and human corneas were mounted in a specular microscope and the endothelia perfused with a balanced salt solution containing varying concentrations of ethylene chlorohydrin (0 to 2500 ppm), ethylene glycol (0 to 10,000 ppm), and ethylene oxide (250 ppm) in combination with those residues. Some corneas were also perfused with a solution of either mannitol or urea in a balanced salt solution as osmotic controls. Measurements of corneal thickness were made throughout the perfusion period, and at selected times the corneas were fixed and prepared for scanning and transmission electron microscopy. Whole corneal oxygen consumption was also determined for corn...