Predicting abundance-body size relationships in functional and taxonomic subsets of food webs.

Abundance-body size relationships are widely observed macroecological patterns in complete food webs and in taxonomically or functionally defined subsets of those webs. Observed abundance-body size relationships have frequently been compared with predictions based on the energetic equivalence hypothesis and, more recently, with predictions based on energy availability to different body size classes. Here, we consider the ways in which working with taxonomically or functionally defined subsets of food webs affected the relationship between the predicted and observed scaling of biomass and body mass in sediment dwelling benthic invertebrate communities at three sites in the North Sea. At each site, the energy available to body size classes in the "whole" community (community defined as all animals of 0.03125-32.0 g shell-free wet weight) and in three subsets was predicted from estimates of trophic level based on nitrogen stable isotope analysis. The observed and predicted scalings of biomass and body size were not significantly different for the whole community, and reflected an increase in energy availability with body size. However, the results for subsets showed that energy availability could increase or decrease with body size, and that individuals in the subsets were likely to be competing with individuals outside the subsets for energy. We conclude that the study of abundance-body mass relationships in functionally or taxonomically defined subsets of food webs is unlikely to provide an adequate test of the energetic equivalence hypothesis or other relationships between energy availability and scaling. To consistently and reliably interpret the results of these tests, it is necessary to know about energy availability as a function of body size both within and outside the subset considered.

Large-scale, low-amplitude bedforms (chevrons) in the selima sand sheet, egypt.

Landsat images of the Selima sand sheet in southwestern Egypt display alternating light and dark chevron-shaped patterns that occur downwind from low scarps and major dune fields. Images acquired between 1972 and 1988 indicate that these features move as discrete bedforms at a rate of up to 500 meters per year. Extremely long-wavelength (130 to 1200 meters), low-amplitude (10 to 30 centimeters) bedforms were measured in the field; the light chevrons seen in the orbital data may be thin accumulations of active sand sheet deposits in the lee of these bedforms. Dark chevrons contain an admixture of coarse-granule lag deposits that are continually winnowed by aeolian erosion on the windward sides of the large bedforms. Sediment transport budgets derived from orbital and field analyses suggest net movement of up to 83,000 cubic meters per year for a single light chevron; such measurements can be used as a check on similar calculations from dunes and other smaller scale features to determine sand transport budgets for large areas of the eastern Sahara.

Use of tumor colony assay in clinical oncology.

We have evaluated the usefulness of the tumor colony assay in predicting chemotherapeutic drug response in our cancer patient population. We found that a wide variety of human tumors will produce clonal growth in this in vitro assay. Low growth rates in many of the common human tumors, however, severely restrict the utility of this assay in a large number of cancer patients. A retrospective analysis using the assay to predict anticancer drug response revealed a true-positive predictive rate of 63% and a true-negative predictive rate of 96%. We conclude that if growth stimulants can be developed to enhance clonal growth without altering the predictability of the assay, the tumor colony assay could prove to be extremely useful in selecting appropriate chemotherapy for individual cancer patients.

Total, dialyzable, and nondialyzable postabsorptive hydroxyproline. Values in patients with cancer.

The postabsorptive urinary total (T), dialyzable (D), and nondialyzable (ND) hydroxyproline (HYPRO) tests were evaluated to determine whether the patterns of excretion varied according to the predominance of osteoblastic v osteolytic bone involvement in 58 patients with neoplastic disease. In patients with osteolytic lesions from multiple myeloma, elevated T and D levels with normal ND HYPRO values were observed, along with elevated D/ND ratios. In prostate cancer, the T, D, and ND values were all elevated and the D/ND ratio was normal. Patients with Hodgkin's disease had elevated T, D, and ND HYPRO levels, and the D/ND ratio was in the range of patients with prostate cancer. The data suggest that these collagen markers may be useful in the long-term evaluation of these neoplasms in patients.