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Preconditioning may find ready applicability in humans facing scheduled global cardiac ischemiareperfusion (IR) during bypass or transplantation, where such a maneuver is feasible before arrest. Our objective was to delineate and exploit the endogenous preconditioning mechanism triggered by transient ischemia (TI) and thereby attenuate myocardial postischemic mechanical dysfunction by clinically acceptable means. Preconditioning by 2 minutes of TI followed by 10 minutes of normal perfusion protected isolated rat left ventricle function assessed after 20 minutes of global, 37°C ischemia and 40 minutes of reperfusion. Final recovery of developed pressure (DP) was improved (91.5±l.9%o of equilibration DP versus unconditioned IR control, 57.4+2.4%, P<.01) and was accompanied by increased contractility (±dP/dt). Norepinephrine release increased after TI, and reserpine pretreatment abolished TI preconditioning. This suggests that endogenous norepinephrine mediates functional preconditioning in rat. Brief pretreatment (2 minutes) with exogenous norepinephrine reproduced the protection (89.1+1.4%) of postischemic function. Functional protection persisted after the hemodynamic effects had resolved. Norepinephrine-induced preconditioning was simulated by phenylephrine and blocked by al-adrenergic receptor antagonist. TI preconditioning was similarly lost after selective ovl-adrenergic receptor blockade. We conclude that transient ischemic preconditioning is mediated by the sympathetic neurotransmitter release and at,-adrenergic receptor stimulation. Although the postreceptor mechanism remains unclear, functional protection after IR does not seem related to the magnitude of ATP depletion and elevation of resting pressure during ischemia. Rather, the endogenous mechanisms facilitate both recovery of mechanical function and ATP repletion during reperfusion. (Circ Res. 1993;73:656-670.) KEY WoRDs * adaptation * preconditioning mechanism * myocardial function * norepinephrine * cl-adrenergic receptors * ATP * rat heart T he high rate of energy turnover in myocardial tissue renders the heart very susceptible to ischemia.' Although perfusion must be restored to preserve myocardial function and viability, reperfusion can itself be deleterious.12 Yet, the 150 000 cardiopulmonary bypass and 1000 heart transplantation operations performed annually necessitate extended periods of myocardial ischemia with subsequent reperfusion. Although myocardial dysfunction becomes progressively irreversible with extended ischemia, brief periods of myocardial ischemia trigger an adaptive response that protects the heart against sustained ischemia and reperfusion.2-4 This "preconditioning" phenomenon suggests that transient ischemia (TI) induces intrinsic changes within the myocardium, thereby enhancing its resistance to subsequent ischemia-reperfusion (IR) injury. These protective changes appear effective against a range of post-IR pathophysiology, including stunning, arrhythmias, and infarction. If this preconditioning effect

Many species are threatened with extinction and efforts are underway worldwide to restore imperilled species to their native ranges. Restoration requires knowledge of species' historical diversity and distribution. For some species, many populations were extirpated or individuals moved beyond their native range before native diversity and distribution were documented, resulting in a lack of accurate information for establishing restoration goals. Moreover, traditional taxonomic assessments often failed to accurately capture phylogenetic diversity. We illustrate a general approach for estimating regional native diversity and distribution for cutthroat trout in the Southern Rocky Mountains. We assembled a large archive of historical records documenting human-mediated change in the distribution of cutthroat trout (Oncorhynchus clarkii) and combined these data with phylogenetic analysis of 19th century samples from museums collected prior to trout stocking activities and contemporary DNA samples. Our study of the trout in the Southern Rocky Mountains uncovered six divergent lineages, two of which went extinct, probably in the early 20th century. A third lineage, previously declared extinct, was discovered surviving in a single stream outside of its native range. Comparison of the historical and modern distributions with stocking records revealed that the current distribution of trout largely reflects intensive stocking early in the late 19th and early 20th century from two phylogenetically and geographically distinct sources. Our documentation of recent extinctions, undescribed lineages, errors in taxonomy and dramatic range changes induced by human movement of fish underscores the importance of the historical record when developing and implementing conservation plans for threatened and endangered species.

Pacific trout Oncorhynchus spp. in western North America are strongly valued in ecological, socioeconomic, and cultural views, and have been the subject of substantial research and conservation efforts. Despite this, the understanding of their evolutionary histories, overall diversity, and challenges to their conservation is incomplete. We review the state of knowledge on these important issues, focusing on Pacific trout in the genus Oncorhynchus. Although most research on salmonid fishes emphasizes Pacific salmon, we focus on Pacific trout because they share a common evolutionary history, and many taxa in western North America have not been formally described, particularly in the southern extent of their ranges. Research in recent decades has led to the revision of many hypotheses concerning the origin and diversification of Pacific trout throughout their range. Although there has been significant success at addressing past threats to Pacific trout, contemporary and future threats represented by nonnative species, land and water use activities, and climate change pose challenges and uncertainties. Ultimately, conservation of Pacific trout depends on how well these issues are understood and addressed, and on solutions that allow these species to coexist with a growing scope of human influences. Conservación de la diversidad de truchas nativas del Pacífico en el oeste de NorteaméricaLa trucha del Pacífico Oncorhynchus spp. en el oeste de Norteamérica tiene un alto valor desde el punto de vista ecológi-co, socioeconómico y cultural, y ha sido objeto de importantes esfuerzos de conservación e investigación. A pesar de ello, el conocimiento que se tiene sobre su historia evolutiva, diversidad general y retos de conservación sigue siendo incompleto. Se hace una revisión del estado del conocimiento sobre estos puntos, con énfasis en la trucha del Pacífico dentro del género Oncorhynchus. Si bien la mayor parte de los estudios hechos sobre salmónidos se enfocan al salmón del Pací-fico, aquí nos enfocamos en la trucha del Pacífico ya que ambos groupos de especies comparten una historia evolutiva en común sobre todo en lo que se refiere al extremo sur de sus rangos de distribución. En investigaciones llevadas a cabo en décadas recientes, se han revisado varias hipótesis relativas al origen y diversificación de la trucha del Pacífico a lo largo de su rango de distribución. Aunque se han logrado identificar adecuadamente las amenazas pasadas que enfrentó la trucha del Pacífico, las amenazas actuales y futuras que representan especies no nativas, actividades de uso de tierra y agua y el cambio climático se consideran importantes retos e incertidumbres. Al final, la conservación de la trucha del Pacífico depende de qué tan bien se comprendan y abordan estos temas, y de las soluciones que les permitan a estas especies coexistir con una gama creciente de influencias humanas. Conservation de la diversité de la truite du Pacifique indigène dans l'ouest de l'Amérique du NordLes truites du Pacifique ou Oncorhynchus spp. dans l'ouest...

Guard honeybees stand at the entrance of colonies and facilitate the exclusion of nonnestmates from the colony. In this study, we examined the hypothesis that genetic variability among individuals in colonies might explain variability in guarding activity. To do this, we cross-fostered honey bees between colonies with high-defensive responses and colonies with low-defensive responses in alarm pheromone tests. Individuals from high-defensive colonies were more likely to guard in their own colonies (controls) than cross-fostered bees from low-defensive colonies. Cross-fostered high-defensive bees also were more like to guard in low-defense colonies. These results support the hypothesis that interindividual differences in guarding behavior are at least partially under genetic control. A positive correlation between number of guards and response to alarm pheromone demonstrates a link between behaviorally separated components of the overall defensive response.