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To investigate the mechanisms of restenosis and detect useful interventions to prevent it, reliable quantitative measurements must be evaluated. Coronary arteries of domestic and minipigs (n = 18) were mechanically injured by balloon overstretching and killed at different intervals (2 to 25 weeks) after quantitative angiographic analysis. Morphometric measurements evaluated intimal hyperplasia at 0.59 +/- 0.42 mm without relation to artery size or balloon/artery ratio. Intimal hyperplasia, expressed as the ratio of neointimal area to total wall area (A), is directly related to the injury, assessed by the ratio of internal elastic lamina (IEL) fracture length to IEL circumference (B), r = 0.84, p = 0.002. Restenosis injury index, defined as A/B, provides a useful tool for the quantitative assessment of future angioplasty-related restenosis interventions.

An adenosine cyclic 3',5'-monophosphate (cAMP) dependent protein kinase has recently been shown to exist in Dictyostelium discoideum and to be developmentally regulated. In this report we have followed the chromatographic behavior of both the holoenzyme and its subunits. A cAMP-dependent holoenzyme could be obtained from the 100000 g soluble fraction after passage through DE-52 cellulose (pH 7.5) and Sephacryl S300. Under conditions of low pH the holoenzyme could be further purified by flat-bed electrofocusing (pI = 6.8). Application of the holoenzyme to electrofocusing at high pH resulted in dissociation of the holoenzyme into a cAMP binding component (pI = 6.1) and a cAMP-independent catalytic activity (pI = 7.4). Dissociation of the holoenzyme into subunits also occurred during histone affinity chromatography and gel filtration chromatography (S300) in the presence of a dissociating buffer. Although the subunit structure was clearly evident during chromatography, the holoenzyme could not be dissociated by simple addition of cAMP to the extract. The catalytic subunit could be purified further by CM-Sephadex, DE-52 cellulose (pH 8.5), histone affinity, and hydrophobic chromatography. The regulatory subunit was further purified by DE-52 cellulose (pH 8.5) and cAMP affinity chromatography. Proof that the cAMP binding activity and the cAMP-independent catalytic activity were in fact the regulatory and catalytic subunits was shown by reconstitution of the cAMP-dependent holoenzyme from the purified subunits. By using these separation procedures, one can obtain from extracts of Dictyostelium the subunits that are free of each other as well as free of any endogenous protein substrates.

It has been known for 20 years that during cellular differentiation of Dictyostelium discoideum, glycogen is degraded to provide the glucose precursors that are required for the synthesis of the end-products of development. Because this pathway provided a distinct developmentally regulated event, a number of laboratories have investigated the regulation of the first step in glycogen degradation, glycogen phosphorylase. Of particular interest was the possible regulation of this enzyme by cAMP. Cyclic AMP is know to act as a signal in this organism for both chemotaxis and cell differentiation. The phosphorylase activity was found to increase during development and, therefore, it has been used in many studies as a marker for late stage development. However, only one form of the phosphorylase was found, and therefore it was concluded that cAMP was not involved in regulation of this key step in the developmental pathway. Here we report the discovery of a second form of the enzyme. This form is completely dependent on AMP for activity and is found only in the undifferentiated stage. This second form contains several of the properties of the nonphosphorylated enzyme that occurs in systems that are regulated by cAMP. This result and the recent discovery of a cAMP-dependent protein kinase has rekindled the possibility that at least one of the effects of cAMP in this organism occurs via a cAMP-dependent cascade of phosphorylation; that is, the activation of glycogen phosphorylase and subsequent production of the precursors for the end-products of development.