Antibody synthesis in anamnestic lymphoid cells, measured by incorporation of leucine-C14 into specific antibody, was inhibited at moderate concentrations of actinomycin D. This was accompanied by marked inhibition of synthesis of RNA as measured by incorporation of H3-cytidine monophosphate. However, at low concentrations of actinomycin D, antibody synthesis was unaffected or even increased while RNA synthesis continued to be inhibited. The results obtained suggest that messenger RNA for antibody synthesis, either because it is relatively stable or present in excess, does not become a limiting factor until its synthesis is maximally inhibited. Puromycin, an inhibitor of amino acid coupling, abolished antibody synthesis in low concentration. 6-Mercaptopurine had no effect on the synthesis of antibody or RNA even at high concentration. The data obtained support the view that antibody synthesis follows pathways similar to those utilized for the formation of other types of proteins.

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Eleven patients with cryptogenic fibrosing alveolitis were evaluated for the presence of pulmonary shunting by injection of radiolabelled particles of macroaggregated albumin larger than lO 4um in diameter and by body scanning with a gamma camera. The mean shunt of 9% (SD 2%) in the patients was not significantly different from the mean shunt of 7% (2%) measured in 10 normal controls. These findings suggest that shunting is not an important part of the gas exchange abnormalities noted in such patients.Arteriovenous channels larger than normal pulmonary capillaries have been found in the lung in patients with hepatic cirrhosis and with chronic obstructive lung disease.'`3 This abnormal vasculature has been evaluated by quantitative radionuclide techniques. These enlarged vessels are believed to play a part in the genesis of hypoxaemia in these disorders. In cirrhosis a constellation of disturbances may occur, including decreased lung diffusing capacity, aggravation of hypoxaemia by exercise, and an apparent shunt like mechanism.4 The findings are similar in chronic obstructive lung disease, and the magnitude of the radionuclide shunt is correlated with the decrement in diffusing capacity.3 In chronic obstructive lung disease aggravation of hypoxaemia by exercise is correlated with loss of diffusing capacity.5 Decreased diffusing capacity and aggravation of hypoxaemia with exercise are also characteristic of pulmonary fibrosis,6 and these findings are themselves correlated in pulmonary fibrosis.7 A common underlying mechanism in the form of enlarged alveolar vessels might be present in all these disorders. We have studied patients with pulmonary fibrosis for evidence of the presence of abnormal pulmonary vasculature. MethodsMacroaggregated albumin particles tagged with 3mCi of technetium 99m were injected intravenously with the patient in the supine position. The radioactivity distributed to the brain, kidneys, and lungs was measured with a gamma camera. Acquisition of counts was begun dorsally 10 minutes after injection with Address for reprint requests: Dr Warren C Miller, Humana Pulmonary Center, 500 Medical Center Boulevard, Webster, Texas 77598, USA. Accepted 23 July 1985 sequential two minute intervals each for lungs, kidneys and brain, so that counting was completed 16 minutes after injection. The particles were measured by light microscopy, with an eye piece micrometer; the longest diameter was noted. Particles were found to be 1 1-60 gm in diameter with a typical size distribution of: 11-20 gm 54%; 21-30gm 26%; 31-40 gm 16% (they were rarely greater than 40 pm). Any particles traversing the lungs to the systemic circulation would necessarily pass through vessels larger than 10pm. The amount of radioactivity in the distribution of the systemic circulation was calculated on the assumption that at rest 32% of the cardiac output goes to brain and kidneys.8 The fractional amount of blood shunted is therefore the radioactivity in the systemic circulation divided by the sum of that radioactivity and tha...

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