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The blocking of trigger points in the calf by the local injection of an anesthetic agent was performed in 15 patients with intermittent claudication. Reactive and exercise hyperemia, work load and duration of exercise were recorded before and after infiltration of the trigger points. Reactive hyperemia does not change, but the exercise tolerance of the leg significantly improves after local blocking of the trigger areas and the exercise hyperemia increases because of the higher work load. The pain pattern of intermittent claudication can be activated by the summation of abnormal input from muscles, due to contraction in the presence of anoxia, with activity from trigger points. Local infiltration of trigger areas blocks theirir activity. The vicious cycle of pain is interrupted and the exercise tolerance of the leg is increased, without improving blood circulation.

Biological systems often need to operate in complex environments where conditions can rapidly change. This is possible due to their inherent ability to sense changes and adapt by adjusting their behavior in response. Here, we detail recent advances in the creation of synthetic genetic parts and circuits whose behaviors can be dynamically tuned through a variety of intra- and extra-cellular signals. We show how this capability lays the foundation for implementing control engineering schemes in living cells and allows for the creation of biological systems that are able to self-adapt, ensuring their functionality is maintained in the face of varying environmental and physiological conditions. We end by discussing some of the broader implications of this technology for the safe deployment of synthetic biology.

No abstract

Blood flow in the calf was measured during postexercise hyperemia in normal subjects and in PAD patients by means of a foot ergometer that gives direct reading of the work performed. In normals, first and peak flow increased with the rise of work load up to 100 KGM. The duration of hyperemia increased with a work load of 30 to 200 KGM. In PAD patients, first flow did not coincide with peak flow. Peak flow was lower and delayed, and the duration of hyperemia was more prolonged than in normal subjects. In patients with intermittent claudication, first flow, peak flow, and work load were higher than in patients with rest pain or impending gangrene. Exercise hyperemia appears as a useful test for screening normal limbs from those with arterial obstruction. Since in PAD patients exercise is interrupted when muscular pain appears, it is evident that the earlier the arrest of work and the appearance of pain, the greater is the involvement in the arterial tree of the leg. Therefore the exercise hyperemia test can be used also as a means of evaluating the different stages of PAD.