Sympathetic or reflex footpad swelling occurred in rats when several crystals known to be pathogenic in human joints or soft tissues were injected into the opposite footpad. Monosodium urate (MSU), calcium pyrophosphate dihydrate (CaPPD), hydroxyapatite, calcium oxalate (CaOx), and xanthine (X) suspension induced varying degrees of such reflex of sympathetic swelling. In the second cycle of crystal-induced swelling, the foot that had been the initial or primary site of inflammation reacted with greater reflex swelling, when compared to the first cycle. Similarly, reflex increases in temperature occurred when CaPPD was injected. These reflex increases in swelling and temperature may relate to signs and symptoms of patients with reflex neurovascular dystrophy or shoulder--hand syndrome.
In 120 patients with rheumatic disorders concomitant assays of serum and synovial fluid were done for acute phase reactants, immunoglobulins and the neuropeptide beta-endorphin. One-third of the patients with rheumatoid disease demonstrated synovial fluid levels of endorphin to be several-fold higher than serum levels, while in two-thirds the opposite results were found. These changes are discussed as adaptive or defense mechanisms. The synovial membrane is postulated to synthesize beta-endorphin.
A new method is presented for measuring swelling or rat paw edema in inflammation induced by carrageenin injection. This technique is compared to other widely used ones. A spring-loaded dial indicator produces results that are accurate, precise and reproducible. It is recommended for investigators seeking the advantages of a noninvasive, low cost, rapid method quantifying the swelling of inflammation.
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