Adaptive capacity in ecosystems.

Understanding the adaptive capacity of ecosystems to cope with change is crucial to management. However, unclear and often confusing definitions of adaptive capacity make application of this concept difficult. In this paper, we revisit definitions of adaptive capacity and operationalize the concept. We define adaptive capacity as the latent potential of an ecosystem to alter resilience in response to change. We present testable hypotheses to evaluate complementary attributes of adaptive capacity that may help further clarify the components and relevance of the concept. Adaptive sampling, inference and modeling can reduce key uncertainties incrementally over time and increase learning about adaptive capacity. Such improvements are needed because uncertainty about global change and its effect on the capacity of ecosystems to adapt to social and ecological change is high.

Morphological factors influencing transepithelial conductance in a rabbit model of ileitis.

BACKGROUND & AIMS: Infection of rabbits with coccidia (Eimeria magna) causes chronic ileal inflammation and diarrhea. Inflamed ileum also shows decreased transmural conductance. The aim of this study was to characterize morphological factors known to affect paracellular permeability that may alter transmural conductance in inflamed ileum. METHODS: Ileal mucosa was mounted in Ussing chambers for study of [3H]mannitol and [3H]inulin fluxes. Light and electron microscopy were used for morphometric studies. Alterations in the zonula occludens of epithelial cells were evaluated in freeze-fracture replicas. RESULTS: Inflamed ileum showed diminished paracellular fluxes. Inoculated rabbits showed marked lymphoplasmocytic infiltration and villus blunting in ileum. Villus linear junctional density was unaffected. However, total villus apical surface area per square centimeter of tissue was reduced in inflamed ileum, causing a diminished total villus linear junctional pathway per square centimeter of apical surface. Villus zonula occludens strand number was reduced in inflamed ileum, whereas the frequency of both villus and crypt lateral surface extrajunctional strands increased. CONCLUSIONS: Chronic inflammation exerts a profound effect on ileal paracellular permeability. Morphological data suggest that this effect may be caused in part by alterations in inflamed ileal mucosal structure and tight junctional organization and density, particularly on villi.

Left atrial leiomyosarcoma: manifestation as unexplained pulmonary vascular disease.

Primary, left-sided cardiac tumors are a rare cause of unexplained pulmonary hypertension. We describe herein two patients with leiomyosarcoma of the left atrium, who were initially seen with symptoms suggestive of primary pulmonary hypertension, venoocclusive disease, or multiple, small thromboemboli. Postmortem examination showed extension of the leiomyosarcoma into the pulmonary veins, which resulted in pulmonary venous hypertension. Although unusual, the occurrence of left-sided cardiac neoplasms should be included in the differential diagnosis of patients who are initially seen with unexplained pulmonary hypertension. An open lung biopsy should be considered and may indicate a venous origin for the hypertension.