Effects of environment on morphology of rat cerebral cortex and hippocampus.

Cortical depth differences were found between male rats exposed to enriched or impoverished environmental conditions for successively shorter times, i.e., for 15 days (from 25 to 40 days of age), for seven days (25 to 32 days of age), and for four days (26 to 30 or 60 to 64 days of age). If the experiments began at weaning (at 25 days of age), the cortical depth changes were caused primarily by impoverishment. If the animals were young adults (60 days of age), upon entering their respective conditions, the cortical changes were induced by enrichment. No cortical depth differences were found between enriched and impoverished rats after one day of differential experience, from 60 to 61 days of age. In every age group and for every duration, except for the one day group, the dorsal-medial segment of the occipital cortex responded to the environmental conditions. No significant hippocampal depth differences were noted between enriched and impoverished animals.     

Effects of root-feeding nematodes on aboveground net primary production in a North American grassland

The impact of nematode consumption on aboveground net primary production (ANPP) was addressed by treating two areas of mixed-grass prairie with the nematicide carbofuran. Monthly assessments of shoot biomass and nematode populations were made from each treated and control site for two growing seasons. Seasonal mean density of root-feeding nematodes was reduced approximately 82% by carbofuran. ANPP was significantly greater in the treated plots for both seasons in Site 1 but only for the second year in Site 2. Increases in ANPP averaged 51% in Site 1 and 26% in Site 2. It was estimated that root-feeding nematodes reduced ANPP by 16 times more than they consumed.     

Interaction of fibronectin with C1q and collagen. Effects of ionic strength and denaturation of the collagenous component

By attaching native collagen and C1q to Sepharose, it was possible to test the binding of fibronectin (Fn) to the native and heat-denatured forms of these proteins without complications due to aggregation, precipitation, or fibril formation. Binding to the native proteins occurred only at low (sub-physiological) ionic strength whereas binding to the denatured proteins occurred even in 1 M NaCl. Thus both of these proteins possess one or more strong sites which are masked in the native state and become exposed during thermal denaturation. Fn did not bind to albumin-Sepharose or IgG-Sepharose either before or after heat-denaturation. C1q bound readily to native IgG-Sepharose but did not mediate the binding of Fn. Nor did Fn inhibit the reconstitution of C1 on antibody-coated erythrocytes. The fluorescence polarization of fluorescein-labeled collagen in 1 M NaCl displayed a downward transition at 38-40 degrees C consistent with unfolding of the triple helix. In the presence of Fn, the same material displayed an upward transition at slightly lower temperature suggesting that gross unfolding is not required to expose the strong binding site(s).     

Fungal modification of pterocarpan phytoalexins from Melilotus alba and Trifolium pratense

Medicarpin (3-hydroxy-9-methoxypterocarpan), an isoflavonoid phytoalexin characteristic of sweetclover (Melilotus alba), is metabolised by three fungi, Botrytis cinerea, Colletotrichum lindemuthianum (race β) and C. coffeanum (isolates CCA and CCP) to afford products with decreased antifungal activity. Peterocarpan phytoalexins from red clover (Trifolium pratense) are similarly modified. A fourth organism, Helminthosporium carbonum apparently lacks this ability. Fungal-mediated tranformation principally involves hydroxylation, methylation and demethylation although ring fission has also been noted.