Enantioselective substrate specificity of 15-lipoxygenase 1.

15-Lipoxygenases are lipid-peroxidizing enzymes which have been implicated in the pathogenesis of various diseases, such as inflammation, atherosclerosis, and osteoporosis. Although the crystal structures for several lipoxygenase isoforms have been solved, there is little information on the substrate alignment at the active site and its impact on the catalytic mechanism. Investigating the oxygenation of specifically designed hydroxy fatty acids, we observed a pronounced enantioselectivity of 15-lipoxygenases for substrates carrying the oxygen moiety in close proximity to the site of hydrogen abstraction [16(R/S)-HETE, 17(R/S)-HETE]. To investigate the mechanistic basis for this unexpected behavior, we applied a strategy involving targeted substrate modification, site-directed mutagenesis, and structural modeling of the enzyme-substrate complex. Taken together, our data suggest that an (S)-hydroxy group in 16-HETE may form a hydrogen bridge between the substrate molecule and Gln548, which contributes to proper alignment of the fatty acid derivative at the active site of the enzyme. This interaction, which was not observed with 16(R)-HETE, 18(R)-HETE, or 18(S)-HETE, appears to be a major reason for the high degree of enantioselectivity during lipoxygenation of 16-HETE.

Lectin binding patterns in two cultured endothelial cell types derived from bovine corpus luteum.

Epithelial cells of different phenotypes derived from bovine corpus luteum have been studied intensively in our laboratory. In this study, specific lectin binding was examined for cells of type 1 and 3, which were defined as endothelial cells. In order to confirm differences in their glycocalyx at the light microscopic level, five biotinylated lectins were applied to postconfluent cultures which had been fixed with buffered paraformaldehyde or glutaraldehyde. Cells were not permeabilized with any detergent. Lectin binding was localized with a streptavidin-peroxidase complex which was visualized with two different techniques. The DAB technique detected peroxidase histochemically, while the immunogold technique used an anti-peroxidase gold complex together with silver amplification. Neither cell type 1 nor cell type 3 bound a particular lectin selectively, yet each cell type expressed a particular lectin binding pattern. With the DAB technique, diverse lectin binding patterns were seen, probably indicating either "outside" binding, i.e., a diffuse pattern, a lateral-cell-side pattern and a microvillus-like pattern, or "inside" binding, i.e., a diffuse pattern, and a granule-like pattern. With the immunogold technique, only "outside" binding was observed. In addition, the patterns of single cilia or of single circles were detected, the latter roughly representing 3-micron-sized binding sites for concanavalin A. When localizing them at the ultrastructural level, single circles corresponded with micron-sized discontinuities of the plasma membrane. Shedding vesicles were detected whose outer membrane was labelled with concanavalin A. Our results confirm the diversity of the two cell types under study. The "inside" lectin binding may be caused by way of transient plasma membrane openings and related to shedding of right-side out vesicles ("ectocytosis").

The importance of psychiatric illness in newly arrested prisoners.

One hundred ninety-nine male prisoners without prior felony convictions were evaluated through a structured personal interview administered within 24 hours of this arrest. While 46 per cent met psychiatric diagnostic criteria, only 5 per cent demonstrated a need for acute treatment for their affective disorder or organic brain syndrome. It is felt that the alcoholics (15 per cent) and drug-abusing prisoners (12 per cent) might benefit from counseling but were not in need of emergency care. The characteristics of men in each diagnostic group are discussed.

Premenstrual symptoms and depression in a university population.

The correlation between a premenstrual syndrome based on emotional symptoms and primary affective disorder was prospectively studied in 105 college freshmen. Students with premenstrual symptoms were twice as likely as controls to have a history of a serious depressive episodes and twice as likely to have a close family member with depression. Seven percent of women with premenstrual emotional symptoms and none of the controls had an affective episode during the ensuing year. The premenstrual syndrome did not interfere with academic performance and was not associated with any lowering of professional aspirations. The inconsistent results of past research on the relationship between depressive disorder and premenstrual symptoms may have been the consequence of differing definitions in different studies. The final answer on this possible association may result from using a clear definition of premenstrual symptoms based on emotional difficulties and a well defined research oriented criteria for the diagnoses of affective disorder.