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Summary Isolated plasma membranes from mouse fibroblast lines 3T3 and its tranformant SV-3T3 contain a phosphodiesterase (oligonucleotidase, E.C. 3.1.4.19; nucleotide pyrophosphatase, E.C. 3.6.1.9) that splits capped and methylated messenger RNA obtained from both reovirus and vesicular stomatitis virus. The isolated membranes are free of demonstrable ribonuclease activity and split the mRNA to produce 7-methyl guanosine diphosphate as a product. With ATP as substrate for the phosphodiesterase enzyme, the product is AMP. Synthetic caps, AMP, ADP and ATP, but not cyclic AMP, can compete with the substratep-nitrophenyl thymidilic acid. A possible regulatory role on messenger translation is proposed.

Summary Contact-inhibited 3T3 mouse fibroblast cells, in contrast to logarithmically growing 3T3 cells and SV-3T3 transformed cells, have increased levels of plasma membranebound phosphodiesterase (oligonucleotidase, E.C. 3.1.4.19; nucleotide pryrophosphatase, E.C. 3.6.1.9) activity. The increase in enzyme, recorded as increased specific activity, is reversible, as evidenced by the return to normal values following dilution of confluent 3T2 cells and re-initiation of growth. Increased enzyme activity is induced again when the cells regain the confluent state. Transformed SV-3T3 cells can be induced to mimic the contact inhibited state, including increased plasma membrane phosphodiesterase activity, by exposure to a combination of: (i) agents that are known to induce increased intracellular cAMP levels and (ii) additions of purified 3T3 or SV-3T3 plasma membranes. Additions of either alone fails to induce the increase in membrane phosphodiesterase activity, although each alone can significantly suppress cell growth, as measured by incorporation of3H amino acids.

Functional outcome following restorative proctocolectomy depends, in part, on the volume of the pouch. This study investigates the relationship between the length of ileum and volume of saline required to distend the ileum to a set pressure, and the possibility of predicting the volume of an ileoanal pouch using these measurements. Measurements were made on the ileum of 8 mongrel dogs. There was a linear relationship between the length of ileum and volume of saline infused to produce an intraluminal pressure of 20 mmHg (r=0.94-0.99). However, the capacity of ileum varied widely from animal to animal (100 cc of saline filled 15.5 cm to 43 cm of ileum). Twenty-four pouches (15J, 9S) were constructed from segments of ileum of known capacity. The capacity of a J pouch was 1.7±0.11 times greater than the capacity of the original length of bowel and an S pouch had a capacity 2.14±0.25 times greater. These changes in capacity are similar to a theoretical calculation of change in volume of ileum after pouch construction. This technique is a simple, quick method of predicting the volume of an ileo-anal pouch which will be useful in a clinical trial to compare function of pouches of different volumes.