1. Foetal rat hemi-calvaria were incubated in organ culture with sera from patients with active rheumatoid arthritis. 2. Increased 45 Ca resorption was produced by sera from patients who were hypercalcaemic. 3. This bone-resorbing effect could be inhibited by calcitonin.

1. The uptake of a low dose of intravenously administered 99m Tc over the distal and proximal interphalangeal joints was found to be lower in normal subjects than in patients suffering from rheumatoid arthritis, osteoarthritis and psoriatic arthritis. 2. The percentage uptake of technetium over the proximal and distal diarthrodial joints was significantly decreased in patients with rheumatoid arthritis by the oral administration of aspirin (4 g/day for 7 days) and it is proposed that this method may be of value in the routine assessment of anti-inflammatory drug therapy in rheumatoid arthritis.

1. Uptake of intravenously administered radioactive technetium ( 99m Tc) was measured over the knee joints in normal human volunteers, in patients with osteoarthritis and in groups of synovectomized and unoperated patients with rheumatoid arthritis. The uptake was compared with clinical indices of inflammation (pain, tenderness swelling and stiffness), and the clearance rate of intra-articularly injected radioactive xenon ( 133 Xe). The 99m Tc uptakes were found to be unrelated to the isotope dose and the day-to-day reproducibility was acceptable. 2. The mean uptake of 99m Tc was within normal limits in osteoarthritis. Both in synovectomized and in unoperated rheumatoid arthritis 99m Tc uptake was significantly higher than in normal subjects. 3. Of the clinical indices studied significant correlation of 99m Tc uptake was found with pain and swelling in all groups of patients studied. 4. Faster clearance of 133 Xe in unoperated rheumatoid arthritis correlated well with the higher 99m Tc uptakes. 5. The results confirm that 99m Tc uptakes are raised in inflammatory arthritis but not in degenerative arthritis. The relation of 99m Tc uptake to the clinical indices of inflammation and to the 133 Xe clearance from the joint is discussed.

1. The half-life ( T ½ ) of the disappearance curve of 133 Xe from the knee joint has been used as an indirect measure of synovial perfusion. 2. The effects of intra-articularly administered isoprenaline and noradrenaline and their respective blocking agents, propranolol and phentolamine, on the T ½ values have been investigated in normal subjects and in patients with osteoarthritis and rheumatoid arthritis. 3. In normal subjects isoprenaline increased the clearance rate and this effect was blocked by propranolol. Noradrenaline decreased the clearance rate and this effect was blocked by phentolamine. 4. The injection of phentolamine in normal subjects caused an increase in synovial perfusion, suggesting the presence of a basal α-constrictor tone. 5. In the patients with osteoarthritis and rheumatoid arthritis quantitative differences were found in the responses to isoprenaline and noradrenaline and their respective blocking agents. 6. There appeared to be a qualitative difference in the case of phentolamine; it is possible that vasoconstrictor tone may be lost in inflamed joints.