The Concept of Sustainable Development Revisited

The concept of sustainable development is here revised in the light of a brief historical analysis, followed by a semantic analysis of the expressions development and sustainability. The authors criticize the common use of this concept in a loose way or in wide generalizations, to conclude, based on the principles of human ecology, that it is only possible to make it operational in limited spans of time and in limited spatial units.     

Early skin responses of hibernating and nonhibernating ground squirrels to topical applications of DMBA

Summary Skin patches on hibernating and nonhibernating ground squirrels were treated with multiple topical applications of the carcinogen 7,12-dimethylbenza(a)anthracene. Nonhibernators showed blistering, peeling, drying, hair loss, increased vascularization and hyperpigmentation in proportion to DMBA concentration. The latter was apparently due to a) an increased number of dermal and epidermal melanocytes and b) the appearance of melanocytes with large coarse cytoplasmic granules. Notably, hibernators remained free of gross skin changes and were histologically similar to untreated controls. Acknowledgments. This study was supported by Biomedical Research Support Grant No. 5-SO7-RR05413-20. I wish to thank Mrs Mary Gregory for her help with the silver-methenamine borate technique, Mr Albert Geiser for the photomicrographs and Dr George B. Kemper for his contributions in general.