Spontaneous lesions in the sternums of growing rats

Pathologic examination of sternums from young growing rats revealed a number of skeletal lesions involving both cartilage and bone elements. Degeneration or aseptic necrosis of the intersternebral cartilage was a frequent finding in most rats that were examined either at 130 or 180 days of age. Thickening of the sternal cortices and trabeculae containing prominent cement lines were less frequently occurring lesions in these sternums. These changes were absent in rats of 70 days of age. The etiology of the lesions is not understood, although several factors may be incriminated.     

Midpoints versus endpoints: The sacrifices and benefits

On May 25–26, 2000 in Brighton (England), the third in a series of international workshops was held under the umbrella of UNEP addressing issues in Life Cycle Impact Assessment (LCIA). The workshop provided a forum for experts to discuss midpoint vs. endpoint modeling. Midpoints are considered to be links in the cause-effect chain (environmental mechanism) of an impact category, prior to the endpoints, at which characterization factors or indicators can be derived to reflect the relative importance of emissions or extractions. Common examples of midpoint characterization factors include ozone depletion potentials, global warming potentials, and photochemical ozone (smog) creation potentials. Recently, however, some methodologies have adopted characterization factors at an endpoint level in the cause-effect chain for all categories of impact (e.g., human health impacts in terms of disability adjusted life years for carcinogenicity, climate change, ozone depletion, photochemical ozone creation; or impacts in terms of changes in biodiversity, etc.). The topics addressed at this workshop included the implications of midpoint versus endpoint indicators with respect to uncertainty (parameter, model and scenario), transparency and the ability to subsequently resolve trade-offs across impact categories using weighting techniques. The workshop closed with a consensus that both midpoint and endpoint methodologies provide useful information to the decision maker, prompting the call for tools that include both in a consistent framework.