This study was undertaken to develop a technique for the preparation of sheets of endothelial cells and to investigate the effects of bacterial endotoxin on large numbers of cells from continuous sheets of vascular endothelium. Rabbits were divided into one control and two experimental groups. The experimental animals received intracardially an LD50 dose of Escherichia coli endotoxin. 1 and 24 hr postinjection, the vessels of the animals were perfused with glutaraldehyde in Millonig's buffer with methylene blue as a marker. Pieces of mesentery containing arteries were postfixed in buffered glutaraldehyde, dehydrated, and placed in acetone (to remove fat deposits). The surrounding connective tissue was stripped from the mesenteric arteries, and segments of the vessels were slit longitudinally, flattened out, and firmly affixed to a sheet of cork with fine mounting pins. A 3% solution of Formvar in ethylene dichloride was pipetted onto the luminal surfaces of the vessels. The endothelial cells were impregnated with and adhered to the Formvar and, after soaking overnight in 10 N NaOH, could be stripped from the vessel walls as monolayers. Sheets of Formvar-impregnated cells were temporarily mounted on glass slides in aqueous methylene blue and examined by phase and bright-field microscopy. Methylene blue stained the nuclei a deep blue and the cytoplasm faintly, but cell outlines were indistinct. Endothelial sheets from control rabbits had smooth, elliptical nuclei oriented parallel to the longitudinal axis of the cells and irregularly distributed over a smooth background with faint longitudinal striations. Essentially every cell in endothelial sheets from endotoxin-injected animals appeared to be severely damaged. Cell sheets from 24 hr posttreatment animals exhibited the same type of, but more extensive, damage than that observed in 1 hr posttreatment animals. The most prominent features of the damaged endothelium were distorted nuclei, apparent nuclear vacuolization, and missing nuclei. Unstained platelets and plaques were present on the surfaces of the specimens from the experimental animals only. Stained and unstained red blood cells were also dispersed over the luminal surfaces of the endotoxin-treated vessels.

Administration of air under the skin produced a pouch wall that closely resembled a synovium in that the inner lining was made up of macrophages and fibroblasts. Administration of 1% carrageenan directly into the 7-day-old air pouch produced an inflammation characterized by an increased number of mast cells in pouch fluid as well as an increase in wall vascularity. A punch biopsy weight of the pouch wall did not reveal an increase in 1% carrageenan-treated animals. However, a 10% Aloe vera treatment of carrageenan-inflamed synovial pouches reduced the vascularity 50% and the number of mast cells in synovial fluid 48%. The pouch wall punch biopsy weight was increased by A. vera, which was verified by histologic examination of the inner synovial lining. Aloe vera stimulated the synovial-like membrane, as evidenced by an increased number of fibroblasts, suggesting that A. vera stimulated fibroblasts for growth and repair of the synovial model. The synovial air pouch can be used to study simultaneously the acute anti-inflammatory and fibroblast stimulating activities of A. vera.

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