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To explore relationships between erection hardness and other outcomes in men with erectile dysfunction (ED). Pooled analyses were conducted on 27 randomized, double-blind, placebocontrolled trials and six open-label trials from the worldwide sildenafil database. Outcomes included erection hardness graded subjectively, hardness and sexual satisfaction questions from the International Index of Erectile Function, general and sexually-specific emotional well-being from the self-esteem and relationship questionnaire, and the erectile dysfunction inventory of treatment satisfaction. Hardness outcomes improved (with a possible dose-response relationship for the achievement of fully hard and rigid erections) and correlated positively with the other outcomes. Sildenafil 100 mg produced optimal erection hardness (fully hard and rigid erections) in a substantial proportion of men with ED. Because optimal erection hardness correlated positively with some emotional well-being and satisfaction outcomes, sildenafil 100 mg may be the most appropriate dosage for treatment of ED for most men.

Studies on the effect of X-irradiation on antibody formation in vivo have clearly established that X-irradiation is much more inhibitory to antibody formation when given before as opposed to after antigen (1-3). This seems to imply that cells which are actually synthesizing antibody are more radioresistant than cells which have the potential to respond to antigenic stimulation. However, this difference might be only apparent in view of the complexity of factors involved in studying the effect of irradiation in the intact animal. Many antigens are known to produce nonspecific stimulation of the reticuloendothelial system (RES) and might thereby protect against the effect of irradiation given subsequently (4). A high level of circulating antibody during the productive phase might mask a depression of the rate of antibody synthesis (5). It is known that at a certain stage of the immune response X-irradiation can actually enhance the amount of antibody produced (6). Such an enhancement may be due to an increased population of antibody-forming cells and may prevent precise evaluation of a possible simultaneous inhibitory effect on individual antibodyforming cells.Another interesting phenomenon is the progressive decrease in the capacity to respond to antigen over the first 6-48 hr after X-irradiation. This has been consistently observed for the primary response (1) and in a few cases also for the secondary (7-9). This suggests that cells which have suffered irradiation