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Conclusions The role of AUXIN BINDING PROTEIN 1 (ABP1) in the auxin management in plant cells was followed using simplified model material of suspension-cultured cells of tobacco BY-2 line. ABP1 is a putative auxin receptor considered to mediate fast non-genomic responses to auxin and it can be involved in every aspect of the regulation of auxin responses, metabolism and transport. There are four major conclusions that could be made based on the results presented in this thesis: 1) Auxin binding protein 1 mediates both cell division and expansion in tobacco BY-2 cells. In standard cultivation conditions or at lower concentrations of 2,4-D in culture medium, ABP1 overexpression had no detectable impact on cell division, cell elongation or cell growth.. 5- times increased 2,4-D concentration stimulated weakly cell elongation. . Antisense suppression of ABP1 expression resulted in disturbance in both cell expansion and cell division intensity, suggesting that ABP1 is essential for the control of balance between cell division and cell elongation during the growth cycle. ABP1 is localized in endoplasmic reticulum of cells cultivated in standard medium supplemented with 1 μM 2,4-D and it appeared also at the plasma membrane following the IAA application. 2) ABP1 mediates intercellular auxin transport. Cells...

L'interaction des glycosphingolipides de la membrane plasmique avec les protéines de liaison aux glucides (lectines) est d'une importance vitale pour l'infection de la cellule hôte par divers virus et bactéries. Dans ce travail, nous avons exploré l’interaction des lectines LecA de la bactérie P. aeruginosa et de la sous-unité B de la toxine Shiga (StxB) de S. dysenteriae avec son récepteur à membrane plasmatique, le globotriaosylcéramide (Gb3). De plus, nous avons étudié l'interaction de la bactérie complète P. aeruginosa avec Gb3. Afin de déchiffrer l'interaction lectine-Gb3 en l'absence d'autres composants cellulaires, nous avons utilisé les systèmes de membrane artificielle - vésicules unilamellaires géantes (GUV) et bicouches lipidiques supportées (SLB). Nous avons observé la liaison de la lectine en utilisant différents modes de microscopie à fluorescence (confocal, TIRF, etc.). Nous examinons la liaison des deux lectines aux domaines membranaires de différents ordres et compositions. Nous avons constaté que StxB préfère des domaines membranaires plus ordonnés alors que LecA est moins préférentiel. De plus, les deux lectines induisent la réorganisation des domaines membranaires: StxB stabilise les domaines ordonnés, les réduit et induit la formation des nouveaux domaines ordonnés. D'autre part, LecA ainsi que la bactérie P. aeruginosa induisent la dissolution des domaines ordonnés. Nous pensons que ces processus de réorganisation membranaire sont cruciaux pour l’infection bactérienne. / The interaction of plasma membrane glycosphingolipids with the carbohydrate binding proteins (lectins) is of vital importance for the infection of the host cell by various viruses and bacteria. In this work, we explored the interaction of the lectins LecA from the bacterium P. aeruginosa and B subunit of Shiga toxin (StxB) from S. dysenteriae with its plasma membrane receptor globotriaosylceramide (Gb3). Moreover, we studied the interaction of the complete bacterium P. aeruginosa with Gb3. In order to decipher the lectin-Gb3 interaction in absence of other cellular components we employed the artificial membrane systems – Giant unilamellar vesicles (GUVs) and Supported lipid bilayers (SLBs). We observed the lectin binding using different modes of fluorescence microscopy (confocal, TIRF, etc…). We examine the binding of both lectins to the membrane domains of different ordere and composition. We found that StxB prefers more ordered membrane domains whereas LecA is less preferential. Moreover, both lectins induce the reorganization of the membrane domains: StxB stabilizes ordered domains, shrinks them and induces the formation of the novel ordered domains. On the other hand LecA, as well as the bacterium P. aeruginosa induce the dissolution of the ordered domains. We believe, these membrane reorganization processes are crucial for the bacterial infection.

No description available.

This study provides information on the rates of DNA synthesis, sites of DNA synthesis, and DNA content of the avian salt gland during the osmoticstressing (plasma membrane synthesis) and destressing (plasma membrane turnover) cycle, in an effort to better understand the relationship of cell turnover to the initial events in plasma membrane amplification, differentiation, and turnover. The rate of DNA synthesis increases 12-24 h after the onset of osmotic stress, is maximal at about 24 h of osmotic stress, and decreases thereafter in fully stressed and destressed glands. The maximum DNA and protein content, and the maximum protein/DNA ratio are obtained after about 3 days of stress. Autoradiograms show that at 24 h of stress 70-80% of DNA synthesis occurs in connective tissue cells and 20-30% in parenchymal cells, but by 6 days of stress, synthesis occurs about equally in these cell groups. Because destressing is characterized by a large decrease in plasma membrane and in glandular protein, but by little DNA turnover or loss, the loss of plasma membrane is likely due to some type of cell dedifferentiation rather than cell turnover.

Pseudemoia pagenstecheri is a viviparous Australian scincid lizard in which the maternal-embryonic placental interface is differentiated into structurally distinct regions. The chorioallantoic placenta contains an elliptical-shaped region, the placentome, characterized by hypertrophied uterine and embryonic epithelial cells supported by dense vascular networks. The remainder of the chorioallantoic placenta, the paraplacentome, is also highly vascularized but uterine and chorionic epithelia are thin. An omphaloplacenta with hypertrophied epithelia is located in the abembryonic hemisphere of the egg. There is extensive placental transport of organic and inorganic nutrients, e.g., 85-90% of neonatal calcium is received via placental transfer. Calcium uptake by extraembryonic membranes of squamates correlates with expression of the intracellular calcium binding protein, calbindin-D 28K, and plasma membrane calcium ATPase (PMCA) is a marker for active calcium transport. We estimated expression of calbindin-D 28K and PMCA in the chorioallantoic membrane in a developmental series of embryos using immunoblotting and used immunohistochemistry to define the cellular localization of calbindin-D 28K to test the hypotheses that 1) expression of calcium transporting proteins is coincident with placental transport of calcium and 2) the placenta is functionally specialized for calcium transport in regions of structural differentiation. Calbindin-D 28K and PMCA were detected at low levels in early stages of development and increased significantly prior to birth, when embryonic calcium uptake peaks. These data support the hypothesis that placental calcium secretion occurs over an extended interval of gestation, with increasing activity as embryonic demand escalates in late development. In addition, calbindin-D 28K expression is localized in chorionic epithelial cells of the placentome and in the epithelium of the omphalopleure of the omphaloplacenta, which supports the hypothesis that regional structural differentiation in the placenta reflects functional specializations for calcium transport.

Intravenous administration of ovokinin(2-7), a cleavage peptide derived from ovalbumin, dose-dependently (0.1-5 mg/kg) lowered the mean arterial pressure (MAP) that was not accompanied by a significant change in the heart rate (HR) of urethane-anesthetized rats. The hypotensive effects of ovokinin(2-7) were five orders of magnitude lower compared to that of bradykinin and were largely prevented by pretreatment with the bradykinin B2 receptor antagonist HOE140 (81.6±18.4%) and moderately affected by the B1 receptor antagonist [des-Arg10]-HOE140 (26.3±15.5%). Intracellular Ca2+ levels, as measured by Fur 2-AM, were significantly elevated in cultured aorta smooth muscle cells by ovokinin(2-7). The increases were abolished by HOE140 and unaffected by [des-Arg10]-HOE140. The elevation of intracellular Ca2+ by ovokinin(2-7) was dependent on Ca2+ entry from extracellular space as it was reduced in a Ca2+-free solution. Pretreatment of the cells with the phospholipase C inhibitor U73122 (2 μM) eliminated the Ca 2+ increase by the peptide. PA phosphohydrolase and phospholipase A2 inhibitors significantly reduced the responses as well. Our results show that ovokinin(2-7) modulates cardiovascular activity by interacting with B2 bradykinin receptors.

Historically, Australia has been important in the study of, and the development of hypotheses aimed at understanding, the evolution of viviparity in amniote vertebrates. Part of the importance of Australia in the field results from a rich fauna of skinks, including one of the broadest ranges of diversity of placental structures within one geographic region. During the last decade, we have focussed our studies on one lineage, the Eugongylus group of skinks of the subfamily Lygosominae because it contains oviparous species and some that exhibit complex placentae. Our specific objective has been to attempt to understand the fundamental steps required when viviparity, and ultimately complex placentae, evolve from oviparous ancestors. We have taken a three-prong approach: (1) detailed study of the morphology and ontogeny of the placentae of key species at the light microscope level; (2) study of changes in the uterus associated with pregnancy, or the plasma membrane transformation; and (3) measures of the net exchange of nutrients across the placenta or eggshell of key species. In turn, we have found that: (1) details of the morphology and ontogeny of placentae are more complex that originally envisaged, and that the early conclusions about a sequence in the evolution of complex placentae was naïve; (2) a plasma membrane transformation occurs in viviparous, but not oviparous lizards, and thus may be a fundamental feature of the evolution of viviparity in amniotes; and (3) species with more complex chorioallantoic placentae tend to transport more nutrients across the placenta during pregnancy than those with simpler chorioallantoic placentae but, because the correlation is not tight, the importance of the omphaloplacenta in transporting nutrients may have been overlooked. Also, the composition of yolk of highly matrotrophic species is broadly similar, but not identical, to the yolk of oviparous species. Some of the interpretation of our data within the context of our specific objective is not yet possible, pending the publication of a robust phylogeny of Eugongylus group skinks. Once such a phylogeny is available, we are in a position to propose specific hypotheses about the evolution of viviparity that can be tested using another lineage of amniotes, possibly Mabuya group skinks. © 2002 Elsevier Science Inc. All rights reserved.

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1. Abstract (EN) This thesis is collection of work focused mainly on the understanding of mast cell activation and its regulation by Orm1-like (ORMDL) proteins. ORMDL family is a group of endoplasmic reticulum (ER) membrane resident proteins that are highly conserved amongst mammalian species. ORMDL proteins can be found in diverse range of organisms from plants through fungi to animals. ORMDL proteins were first discovered in yeasts and the interest in these proteins skyrocketed after the discovery that ORMDL3 is associated with childhood onset asthma in genome wide association studies. Following research connected ORMDL3 also with allergic inflammation and inflammatory bowel disease. Since mast cells are mainly known for their role in allergy and allergen induced inflammation, we decided to investigate the role of ORMDL proteins in regulation of mast cell activation and signaling. In our first study we focused on the role of ORMDL3 in mast cell activation via the high affinity IgE receptor 1 (FcεRI). We prepared bone marrow-derived mast cells with decreased (ORMDL3-KD) or increased (ORMDL3-OE) ORMDL3 expression. We showed that ORMDL3 is a negative regulator of mast cell activation events like degranulation, cytokine release and migration, without any effect on calcium mobilization. ORMDL3 was previously...