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Holmium-laser synovectomy was carried out to remove allergically inflamed synovial membranes in rabbit knee joints. The healing process was then investigated at different periods. Left knee joints of 12 rabbits were exposed to Ho:YAG-laser radiation at a wavelength of 2.1 microns, pulse energy of 600 mJ, pulse length of 1 ms, and repetition rate of 3 Hz. Twelve others were treated conventionally and 12 served as controls. After 1 day, 1 week, and 1 and 3 months, respectively, 3 animals from each group were sacrificed and the synovialis grossly and microscopically examined. Coagulation necrosis, inflammation, and edema resulted following laser therapy. After 1 week, the synovial layer consisted of a scarlike formation of fibers and within 1 month, its surface appeared smooth. The mechanical abrasion caused hemorrhage and necrosis. Fibrosis developed in the capsular layers, and after 3 months, the surface appeared coarse and villous. Based on these preliminary findings, holmium-laser synovectomy may offer an alternative method to existing therapeutic techniques.

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The diurnal variation in the appearance of cell death in the rat retina during postnatal development was investigated. The frequency and the morphology of the necrotic cells and the mitotic figures were studied by light and electron microscopy at various stages of ontogenesis and at specified times during each day. Preliminary results show that there is a varying exponential behaviour of mean necrosis-densities at certain periods each day. This chronobiological pattern and the general problems of physiological cellular decay in the developing retina are discussed.

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