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| 2. |
- Igamberdiev, A U, et al.
(author)
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Decarboxylation of glycine contributes to carbon isotope fractionation in photosynthetic organisms
- 2001
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In: Photosynthesis Research. - 0166-8595 .- 1573-5079. ; 67:3, s. 177-184
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Journal article (peer-reviewed)abstract
- Carbon isotope effects were investigated for the reaction catalyzed by the glycine decarboxylase complex (GDC; EC 2.1.2.10). Mitochondria isolated from leaves of pea (Pisum sativum L.) and spinach (Spinacia oleracea L.) were incubated with glycine, and the CO2 evolved was analyzed for the carbon isotope ratio (delta C-13). Within the range of parameters tested (temperature, pH, combination of cofactors NAD(+), ADP, pyridoxal 5-phosphate), carbon isotope shifts of CO2 relative to the C-1-carboxyl carbon of glycine varied from +14 parts per thousand to -7 parts per thousand. The maximum effect of cofactors was observed for NAD(+), the removal of which resulted in a strong C-12 enrichment of the CO2 evolved. This indicates the possibility of isotope effects with both positive and negative signs in the GDC reaction. The measurement of delta C-13 in the leaves of the GDC-deficient barley ( Hordeum vulgare L.) mutant (LaPr 87/30) plants indicated that photorespiratory carbon isotope fractionation, opposite in sign when compared to the carbon isotope effect during CO2 photoassimilation, takes place in vivo. Thus the key reaction of photorespiration catalyzed by GDC, together with the key reaction of CO2 fixation catalyzed by ribulose-1,5-bisphosphate carboxylase, both contribute to carbon isotope fractionation in photosynthesis.
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| 3. |
- Annibaldi, S. V., et al.
(author)
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Dust-acoustic dispersion relation in three-dimensional complex plasmas under microgravity
- 2007
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 9
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Journal article (peer-reviewed)abstract
- A series of dedicated experiments with the Plasma Kristal Experiment ( PKE)-Nefedov ( Nefedov et al 2003 New J. Phys. 5 33) set-up were performed on board the International Space Station to measure the dispersion relation ( DR) for the longitudinal dust-acoustic ( DA) waves in quasi-isotropic three-dimensional ( 3D) complex plasmas. The waves were excited by applying ac electric modulation of variable frequency to the radio frequency ( rf) electrodes. The amplitude of excitation was varied with frequency to ensure a 'sufficiently linear' regime of the dust density perturbations. The DR was obtained by measuring the induced density perturbations, revealing fairly good agreement with a simple multispecies theory of DA waves.
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| 4. |
- Ratynskaia, Svetlana V., et al.
(author)
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Superdiffusion and viscoelastic vortex flows in a two-dimensional complex plasma
- 2006
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96:10
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Journal article (peer-reviewed)abstract
- Viscoelastic vortical fluid motion in a strongly coupled particle system has been observed experimentally. Optical tracking of particle motion in a complex plasma monolayer reveals high grain mobility and large scale vortex flows coexistent with partial preservation of the global hexagonal lattice structure. The transport of particles is superdiffusive and ascribed to Levy statistics on short time scales and to memory effects on the longer scales influenced by cooperative motion. At these longer time scales, the transport is governed by vortex flows covering a wide spectrum of temporal and spatial scales.
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| 5. |
- Lopez-Posadas, R., et al.
(author)
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Inhibiting PGGT1B Disrupts Function of RHOA, Resulting in T-cell Expression of Integrin alpha 4 beta 7 and Development of Colitis in Mice
- 2019
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In: Gastroenterology. - : Elsevier BV. - 0016-5085. ; 157:5, s. 1293-1309
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Journal article (peer-reviewed)abstract
- BACKGROUND & AIMS: It is not clear how regulation of T-cell function is altered during development of inflammatory bowel diseases (IBD). We studied the mechanisms by which geranylgeranyltransferase-mediated prenylation controls T-cell localization to the intestine and chronic inflammation. METHODS: We generated mice with T-cell-specific disruption of the geranylgeranyltransferase type I, beta subunit gene (Pggt1b), called Pggt1b(Delta CD4) mice, or the ras homolog family member A gene (Rhoa), called Rhoa(Delta CD4) mice. We also studied mice with knockout of CDC42 or RAC1 and wild-type mice (controls). Intestinal tissues were analyzed by histology, multiphoton and confocal microscopy, and real-time polymerase chain reaction. Activation of CDC42, RAC1, and RHOA were measured with G-LISA, cell fractionation, and immunoblots. T cells and lamina propria mononuclear cells from mice were analyzed by flow cytometry or transferred to Rag1(-/-) mice. Mice were given injections of antibodies against integrin alpha4beta7 or gavaged with the RORC antagonist GSK805. We obtained peripheral blood and intestinal tissue samples from patients with and without IBD and analyzed them by flow cytometry. RESULTS: Pggt1b(Delta CD4) mice developed spontaneous colitis, characterized by thickening of the intestinal wall, edema, fibrosis, accumulation of T cells in the colon, and increased expression of inflammatory cytokines. Compared with control CD4+ T cells, PGGT1B-deficient CD4+ T cells expressed significantly higher levels of integrin alpha4beta7, which regulates their localization to the intestine. Inflammation induced by transfer of PGGT1B-deficient CD4+ T cells to Rag1(-/-) mice was blocked by injection of an antibody against integrin alpha4beta7. Lamina propria of Pggt1b(Delta CD4) mice had increased numbers of CD4+ T cells that expressed RORC and higher levels of cytokines produced by T-helper 17 cells (granulocyte-macrophage colony-stimulating factor, interleukin [IL]17A, IL17F, IL22, and tumor necrosis factor [TNF]). The RORC inverse agonist GSK805, but not antibodies against IL17A or IL17F, prevented colitis in Pggt1b(Delta CD4) mice. PGGT1B-deficient CD4+ T cells had decreased activation of RHOA. RhoA(Delta CD4) mice had a similar phenotype to Pggt1b(Delta CD4) mice, including development of colitis, increased numbers of CD4+ T cells in colon, increased expression of integrin alpha4beta7 by CD4+ T cells, and increased levels of IL17A and other inflammatory cytokines in lamina propria. T cells isolated from intestinal tissues from patients with IBD had significantly lower levels of PGGT1B than tissues from individuals without IBD. CONCLUSION: Loss of PGGT1B from T cells in mice impairs RHOA function, increasing CD4+ T-cell expression of integrin alpha4beta7 and localization to colon, resulting in increased expression of inflammatory cytokines and colitis. T cells isolated from gut tissues from patients with IBD have lower levels of PGGT1B than tissues from patients without IBD.
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| 7. |
- Ratynskaia, Svetlana V., et al.
(author)
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Transport in strongly coupled two-dimensional complex plasmas : Role of the interaction potential
- 2007
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In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 14:1
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Journal article (peer-reviewed)abstract
- Observations of particle motion in a complex plasma monolayer in rf discharge have revealed anomalous dependence on neutral gas pressure; an immobile system at high gas pressures, then, decreasing the pressure, a state with viscoelastic vortical fluid motions and, hence, dramatically enhanced transport, followed again by an ordered state. While the inhibited transport at higher pressures can be attributed to dissipation on neutrals, the transition of the system back to an ordered state at lower pressures has been explained by an increase of the dust-dust viscous dissipation due to significant modifications of the interaction potential between the particles.
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