On the Modeling of Some Anti-inflammatory and Anti-thrombotic Drugs by AM1

Two families of autacoids from cell membrane phospholipids have been identified. The first, the icosanoids, which are formed from arachidonic acid, include prostaglandins and leukotrienes. The other includes modified phospholipids, as the platelet aggregating factor (PAF). These compounds are related to inflammatory and cardiovascular diseases. We review in this paper some of the work that has been done in our laboratories in the last few years relating to the modeling of new potential thromboxane synthase (TXS) and 5-lipoxygenase (5-LO) and cyclooxygenase (COX) inhibitors, and TXA₂ receptor antagonists derived from nitrogenated heterocycles. We include the results of the modeling of a group of proposed PAF antagonists, and compare their structures with PAF itself and with a recently proposed PAF antagonist model. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ecomorphological correlates in ten species of subtropical seagrass fishes: diet and microhabitat utilization

Synopsis Ecomorphological correlates were sought among ten species of distantly related subtropical seagrass fishes. Morphometric data associated with feeding and microhabitat utilization were compared by principal components analysis, cluster analysis, and canonical correspondence analysis to dietary data. Morphology was generally a poor predictor of diet except for a group of mid-water planktotrophic filter feeders. Separation of the species along morphological axes appears to be related more to microhabitat utilization resulting in three major groups: (1) a group of planktotrophic, mid-water fishes specialized for cruising and seeking out evasive prey characterized by a compressed fusiform body, forked caudal fin, long, closely spaced gill rakers, short to intermediate! length pectoral fin, pointed pectoral fin, large lateral eye, short head, and a terminal or subterminal mouth; (2) slow swimming, less maneuverable epibenthic fishes that pick or suck their prey off the substrate. They are united by more rounded caudal and pectoral fins, and short or no gill rakers; and (3) a group of more mobile and maneuverable epibenthic foragers characterized by a more compressed, sub-gibbose body, long, pointed pectoral fins, forked caudal fins, large lateral eyes, subterminal mouth, and greater jaw protrusibility. Cases of convergence in trophic and microhabitat utilization characters were apparent in some of the groups.     

Ferredoxin—ferredoxin NADP reductase interaction: Catalytic differences between the soluble and thylakoid-bound complex

Ferredoxin-NADP reductase (FNR) and ferredoxin form a complex when the former is membrane-bound as they do when both components are in solution, with the same dissociation constant. The rate constant of NADP photoreduction, first order with respect to the complex, is more than 20-times higher when FNR is membrane-bound than when the enzyme is in solution. The Arrhenius activation energy is identical in both conditions. These observations are interpreted in terms of ‘entropic catalysis’ of NADP reduction by the thylakoid-bound FNR.     

Changes in the surface morphology of the rabbit endometrium related to the estrous and progestational stages of the reproductive cycle

Summary Changes occurring on the surface of the uterine luminal epithelium of the rabbit during the estrous and progestational stages of the reproductive cycle were examined by scanning and transmission electron microscopy. The findings demonstrate that the uterine epithelium, or endometrium, contains two cell types: ciliated cells and nonciliated, microvillous cells. In estrous animals, ciliated cells, although not very numerous, were usually observed in small groups. However, at increasing intervals of time following mating, ciliated cells progressively disappeared from the endometrium until approximately eight to ten days post coitum, when they became scare. From several hours to four to five days following mating, extensive changes occurred on the surfaces of microvillous cells. When observed by TEM, these elements contained organelles typical of cells involved in the synthesis and secretion of glycoproteins. Furthermore, microvillous cells during this period displayed numerous apical protrusions of different sizes and shapes and containing material of varying electron density. Parallel SEM examinations of the same material confirmed the presence of these protrusions. Some of the protrusions appeared as spheroidal masses attached to the cytoplasm by means of a cytoplasmic strand. Other surface masses were clearly unattached to the cell surface and were distributed (1) on the surface of microvillous cells, (2) on the cilia of adjacent ciliated cells, and (3) on the surface of spermatozoa.Changes occurring on the luminal surface during the early postcoital period are interpreted as an expression of morphodynamic processes likely involving coupled secretion (exocytosis) and resorption (endocytosis) of luminal material. The observations presented here also demonstrate that between six and ten days post coitum, the rabbit endometrium contained increasing numbers of enlarged, nonciliated cells that probably arose by the fusion of smaller, microvillous elements.The work reported here was supported by C.N.R. contracts No. CT 760128809 and CT 77014239 (to P.M.) and NIH. Grant HD-04274 (to J.V.B.)     

Probing protein structure by solvent perturbation of nuclear magnetic resonance spectra. Nuclear magnetic resonance spectral editing and topological mapping in proteins by paramagnetic relaxation filtering.

Soluble spin labels, which "bleach" the surface proton resonances of a protein to n.m.r. measurements, can provide useful information about protein conformation and dynamics. The use of the soluble nitroxide, TEMPOL, has been explored to show the correlation of the paramagnetic perturbations of protein two-dimensional n.m.r. data with proton exposure to the free radical in hen egg-white lysozyme. The results demonstrate that the nitroxide approaches the protein randomly, and that the extent of the observed paramagnetic effects reflects the native folding pattern of the protein. A correlation of spectral simplification with the known tertiary structure establishes the feasibility of new strategies for topological mapping of surface and buried protons of the protein. Application to the elucidation of protein structure and to the study of dynamical processes is discussed.     

Solution conformation of salmon calcitonin in sodium dodecyl sulfate micelles as determined by two-dimensional NMR and distance geometry calculations

The 32 amino acid hormone salmon calcitonin was studied at pH 3.7 and 7.4 by two-dimensional NMR in sodium dodecyl sulfate (SDS) micelles at 310 K. The spectrum was fully assigned, and the secondary structure was obtained from nuclear Overhauser enhancement spectroscopy (NOESY), 3JHN alpha coupling constants, and slowly exchanging amide data. Three-dimensional structures consistent with NMR data were generated by using distance geometry calculations. A set of 260 interproton distances, derived from NOESY, and hydrogen-bond constraints, obtained from analysis of the amide exchange, were used. From the initial random conformations, 13 distance geometry structures with minimal violations were selected for further refinement with restrained energy minimization. In SDS, at both pHs, the main conformational feature of the hormone is an alpha-helix from Thr6 through Tyr22, thus including the amphipathic 8-22 segment and two residues of the Cys1-Cys7 N-terminal loop. The C-terminal decapeptide forms a loop folded back toward the helix. The biological significance of this conformation is discussed.     

Conformational preferences of [Leu5]enkephalin in biomimetic media. Investigation by 1H NMR

The conformation of [Leu5]enkephalin has been studied by 1H-NMR spectroscopy in media more like the actual environment in which the agonist-receptor interaction takes place than water, i.e. in three cryoprotective mixtures (dimethylformamide/water, methanol/water and ethylene glycol/water), in aqueous SDS and in two neat solvents, dimethylformamide and acetonitrile, whose dielectric constants (36.7 and 37.5) are intermediate between that of water and that of the lipid phase. In all cases examined, contrary to the studies in water or dimethylsulfoxide, we were able to detect numerous nuclear Overhauser effects, indicating that the media employed favour well-defined structures and/or reduce the internal motions of the peptide. Data from both organic solvents and cryoprotective mixtures suggest a 4----1 beta turn as the most probable structure of [Leu5]enkephalin in solution, whereas in SDS/H2O micelles the structural picture appears completely different, suggesting the presence of a 5----2 beta turn. The existence of two different preferred conformations of enkephalins may possibly be related to their ability to be effective towards both mu and delta opioid receptors.     

Effects of dietary fats on the fluidity of human high-density lipoprotein: influence of the overall composition and phospholipid fatty acids

The present study was undertaken to analyze whether the changes induced by dietary manipulations in the chemical composition of HDL, particularly in total phospholipids, phosphatidylcholine and sphingomyelin fatty acid composition, modified their fluidity. 12 healthy women, aged 26-49 years were studied. They consumed, over periods of 5 weeks, various isocaloric diets, each containing 30% of the calories as fat. 15.6% of the total calories were provided successively by olive oil, soybean oil, corn oil, and milk fats. The HDL fluorescence anisotropy was measured with 1,6-diphenyl-1,3,5-hexatriene (DPH) by fluorescence polarization. The HDL from the monounsaturated diet, olive oil, were the most fluid particles. The HDL fluorescence anisotropy was positively correlated with their free cholesterol percentage and negatively correlated with their triacylglycerol content and their triacylglycerol/phospholipid ratio. Moreover, the HDL fluorescence anisotropy was negatively correlated with the percentage of oleic acid in their total phospholipids and particularly in the phosphatidylcholine. These results suggest that the percentages of triacylglycerol and oleic acid in phospholipids of HDL have a fluidifying effect on these lipoproteins.     

Development of the ovarian surface and associated germ cells in the human fetus

Summary The ovarian surface and associated germ cells have been studied in human fetuses from 12 weeks of age until near term, using light, TEM and SEM techniques. The surface epithelium and related cords proliferate extensively, especially at midterm. The cords in the ovarian cortex appear to be linked with ingrowths from the surface epithelium, and both structures have a common basal lamina. Germ cells are always interspersed among the somatic cells of the surface epithelium and associated cords. These results indicate that both the proliferating cords and surface epithelium may contribute to the formation of early follicles. Furthermore, the occurrence, of elements having some of the features of primitive steroidogenic cells in the regions of cordsurface epithelium continuity, suggests that both structures (surface epithelium and cords) contribute somatic cells, which in addition to becoming granulosa cells, might also contribute to the provision of primitive interstitial cells.Gonocytes tend to migrate through the developing ovarian tissue towards the surface where they become extruded into the peritoneal cavity. This phenomenon might contribute to the reduction in the number of germ cells at birth and parallels the atretic processes within the ovary.