The Structure of Polyunsaturated Lipid Bilayers Important for Rhodopsin Function: A Neutron Diffraction Study

The structure of oriented 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine bilayers with perdeuterated stearoyl- or docosahexaenoyl hydrocarbon chains was investigated by neutron diffraction. Experiments were conducted at two different relative humidities, 66 and 86%. At both humidities we observed that the polyunsaturated docosahexaenoyl chain has a preference to reside near the lipid water interface. That leaves voids in the bilayer center that are occupied by saturated stearoyl chain segments. This uneven distribution of saturated- and polyunsaturated chain densities is likely to result in membrane elastic stress that modulates function of integral receptor proteins like rhodopsin.     

Simultaneous binding of Guidance Cues NET1 and RGM blocks extracellular NEO1 signaling

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ERP Modulation during Observation of Abstract Paintings by Franz Kline

The aim of this study was to test the involvement of sensorimotor cortical circuits during the beholding of the static consequences of hand gestures devoid of any meaning.In order to verify this hypothesis we performed an EEG experiment presenting to participants images of abstract works of art with marked traces of brushstrokes. The EEG data were analyzed by using Event Related Potentials (ERPs). We aimed to demonstrate a direct involvement of sensorimotor cortical circuits during the beholding of these selected works of abstract art. The stimuli consisted of three different abstract black and white paintings by Franz Kline. Results verified our experimental hypothesis showing the activation of premotor and motor cortical areas during stimuli observation. In addition, abstract works of art observation elicited the activation of reward-related orbitofrontal areas, and cognitive categorization-related prefrontal areas. The cortical sensorimotor activation is a fundamental neurophysiological demonstration of the direct involvement of the cortical motor system in perception of static meaningless images belonging to abstract art. These results support the role of embodied simulation of artist’s gestures in the perception of works of art.     

Matching catalytic activity to developmental function: tolloid-related processes Sog in order to help specify the posterior crossvein in the Drosophila wing

The Drosophila tolloid (tld) and tolloid related (tlr) gene products belong to a family of developmentally important proteases that includes Bone Morphogenetic Protein 1 (Bmp1). Tld is required early in Drosophila development for proper patterning of dorsal embryonic structures, whereas Tlr is required later during larval and pupal stages of development. The major function of Tld is to augment the activity of Decapentaplegic (Dpp) and Screw (Scw), two members of the Bmp subgroup of the Tgf beta superfamily, by cleaving the Bmp inhibitor Short gastrulation (Sog). In this study, we provide evidence that Tlr also contributes to Sog processing. Tlr cleaves Sog in vitro in a Bmp-dependent manner at the same three major sites as does Tld. However, Tlr shows different site selection preferences and cleaves Sog with slower kinetics. To test whether these differences are important in vivo, we investigated the role of Tlr and Tld during development of the posterior crossvein (PCV) in the pupal wing. We show that tlr mutants lack the PCV as a result of too little Bmp signaling. This is probably caused by excess Sog activity, as the phenotype can be suppressed by lowering Sog levels. However, Tld cannot substitute for Tlr in the PCV; in fact, misexpressed Tld can cause loss of the PCV. Reducing levels of Sog can also cause loss of the PCV, indicating that Sog has not only an inhibitory but also a positive effect on signaling in the PCV. We propose that the specific catalytic properties of Tlr and Tld have evolved to achieve the proper balance between the inhibitory and positive activities of Sog in the PCV and early embryo, respectively. We further suggest that, as in the embryo, the positive effect of Sog upon Bmp signaling probably stems from its role in a ligand transport process.     

Cajal-type cells from human mammary gland stroma: phenotype characteristics in cell culture

We report here the in vitro isolation of Cajal-like interstitial cells from human inactive mammary-gland stroma. Primary cell cultures examined in phase-contrast microscopy or after vital methylene-blue staining revealed a cell population with characteristic morphological phenotype: fusiform, triangular or polygonal cell body and the corresponding (very) long, slender, moniliform cytoplasmic processes. Giemsa staining pointed out the typical knobbed aspect of cell prolongations. Immunofluorescence (IF) showed, like in situ immunohistochemistry, that Cajal-type cells in vitro (primary cultures), expressed c-kit/CD117 and vimentin. In conclusion, the images presented here reinforce our previous hypothesis that human mammary glands have a distinct population of Cajal-like cells in non-epithelial tissue compartments.     

Regulation of intracellular Ca2+ release in corpus cavernosum smooth muscle: synergism between nitric oxide and cGMP

Tonic contraction of corpus cavernosum smooth muscle cells (SMCs) maintains the flaccid state of the penis, and relaxation is initiated by nitric oxide (NO), leading to erection. Our aim was to investigate the effect of NO on the smooth muscle cellular response to adrenergic stimulation in corpus cavernosum. Fura-2 fluorescence was used to record intracellular Ca²⁺ concentration ([Ca²⁺]_i) from freshly isolated SMCs from rat and human. Phenylephrine (PE) transiently elevated [Ca²⁺]_i in the presence and absence of extracellular Ca²⁺, indicating release from intracellular stores. Whereas the NO donor S-nitroso-N-acetylpenicillamine (SNAP) with sildenafil citrate (SIL) caused no change in basal [Ca²⁺]_i, the PE-induced rise of [Ca²⁺]_i was reversibly inhibited by 27 ± 7% (n = 21, P < 0.005) in rat and by 55 ± 15% (n = 9, P < 0.01) in human SMCs. SNAP and SIL also reduced the contractile response to PE. To investigate the mechanism, we applied mediators alone or in combination. The soluble guanylyl cyclase inhibitor ODQ reduced the effect of SNAP and SIL. SIL, cGMP analogs, and NO donors without SIL did not reduce the PE-induced rise of [Ca²⁺]_i. However, the combination of 8-bromo-cGMP with SNAP reduced the Ca²⁺ peak by 42 ± 9% (n = 22, P < 0.01). Our results demonstrate that NO and cGMP act synergistically to reduce Ca²⁺ release from intracellular stores. Reduction of intracellular Ca²⁺ release may contribute to relaxation of the corpus cavernosum, leading to erection. calcium stores; nitric oxide; sildenafil citrate; inositol 1,4,5-trisphosphate receptor     

Regulation of dynamin-2 assembly-disassembly and function through the SH3A domain of intersectin-1s

Intersectin-1s (ITSN-1s), a five Src homology 3 (SH3) domain-containing protein, is critically required for caveolae and clathrin-mediated endocytosis (CME), due to its interactions with dynamin (dyn). Of the five SH3A-E domains, SH3A is unique because of its high affinity for dyn and potent inhibition of CME. However, the molecular mechanism by which SH3A integrates in the overall function of ITSN-1s to regulate the endocytic process is not understood. Using biochemical and functional approaches as well as high-resolution electron microscopy, we show that SH3A exogenously expressed in human lung endothelial cells caused abnormal endocytic structures, distorted caveolae clusters, frequent staining-dense rings around the caveolar necks and 60% inhibition of caveolae internalization. In vitro studies further revealed that SH3A, similar to full-length ITSN-1s stimulates dyn2 oligomerization and guanosine triphosphatase (GTP)ase activity, effects not detected when other SH3 domains of ITSN-1s were used as controls. Strikingly, in the presence of SH3A, dyn2-dyn2 interactions are stabilized and despite continuous GTP hydrolysis, dyn2 oligomers cannot disassemble. SH3A may hold up caveolae release from the plasma membrane and formation of free-transport vesicles, by prolonging the lifetime of assembled dyn2. Altogether, our results indicate that ITSN-1s, via its SH3A has the unique ability to regulate dyn2 assembly-disassembly and function during endocytosis.