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A structural event during the evolution of a myocardial infarction (MI) is left ventricular (LV) remodeling. The mechanisms that contribute to early changes in LV myocardial remodeling in the post-MI period remain poorly understood. Matrix metalloproteinases (MMPs) contribute to tissue remodeling in several disease states. Whether and to what degree MMP activation occurs within the myocardial interstitium after acute MI remains to be determined. Adult pigs (n = 15) were instrumented to measure regional myocardial function and interstitial MMP levels within regions served by the circumflex and left anterior descending arteries. Regional function was measured by sonomicrometry, and interstitial MMP levels were determined by selective microdialysis and zymography as well as by MMP interstitial fluorogenic activity. Measurements were performed at baseline and sequentially for up to 3 h after ligation of the obtuse marginals of the circumflex artery. Regional fractional shortening fell by over 50% in the MI region but remained unchanged in the remote region after coronary occlusion. Release of soluble MMPs, as revealed by zymographic activity of myocardial interstitial samples, increased by 2 h post-MI. The increased zymographic activity after MI was consistent with MMP-9. Myocardial interstitial MMP fluorogenic activity became detectable within the ischemic region as early as 10 min after coronary occlusion and significantly increased after 1 h post-MI. MMP fluorogenic activity remained unchanged from baseline values in the remote region. The present study demonstrated that myocardial MMP activation can occur within the MI region in the absence of reperfusion. These unique results suggest that MMP release and activation occurs within the ischemic myocardial interstitium in the early post-MI period.

Emlen's (1995) paper "An evolutionary theory of the family" reviewed existing ideas about the nature of family systems and the reasons why they have evolved in certain animal species. His theorizing led him to propose 15 predictions about how family systems function, based on favorable evidence from various species, mostly birds. While he suggested that these predictions can be applied to the human case, he himself did not attempt to do so. We consider the applicability of Emlen's 15 predictions to the study of human family systems, and find that several aspects of the life history and ecology of Homo sapiens require that they be modified. These considerations include: (1) the importance of intragroup solidarity in the context of intergroup competition: unlike in many other species where dispersal constraints arise from food or breeding site shortages, the primary pressure driving human sociality seems to be competition from other human groups; (2) the complex nature of exchange and reciprocity in human society: reciprocal altruism in particular is integral to human social interaction and leads to a particularly high degree of non-nepotistic helping behavior; and (3) the implications of menopause and the existence of potentially dominant, postreproductive helpers: helpers of this sort have little incentive to disperse or to encourage offspring to disperse, thus greatly increasing family stability.

Although avian parents appear to exhibit a variety of feeding strategies in nature, there currently exist no models or theories that account for this range of diversity. Here we present the results of a computer simulation designed to model inter-dependent parental decisions, where investment is meted out in small doses, and must be distributed over time to maximize return on investment at the end of the parentalcare period. With this technique we show that the success of various simple, observed, parental rules of thumb varies with environmental resource level, and that increasing the complexity of parental decision rules does not necessarily result in increased ¢tness.

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