Growth-associated protein 43 (GAP-43) plays a central role in the formation of presynaptic terminals, synaptic plasticity, and axonal growth and regeneration. During development, GAP-43 is found in ...axonal extensions of most neurons. In contrast, in the mature brain, its expression is restricted to a few presynaptic terminals and scattered axonal growth cones. Urokinase-type plasminogen activator (uPA) is a serine proteinase that, upon binding to its receptor (uPAR), catalyzes the conversion of plasminogen into plasmin and activates signaling pathways that promote cell migration, proliferation, and survival. In the developing brain, uPA induces neuritogenesis and neuronal migration. In contrast, the expression and function of uPA in the mature brain are poorly understood. However, recent evidence reveals that different forms of injury induce release of uPA and expression of uPAR in neurons and that uPA/uPAR binding triggers axonal growth and synapse formation. Here we show that binding of uPA to uPAR induces not only the mobilization of GAP-43 from the axonal shaft to the presynaptic terminal but also its activation in the axonal bouton by PKC-induced calcium-dependent phosphorylation at Ser-41 (pGAP-43). We found that this effect requires open presynaptic N-methyl-d-aspartate receptors but not plasmin generation. Furthermore, our work reveals that, following its activation by uPA/uPAR binding, pGAP-43 colocalizes with presynaptic vesicles and triggers their mobilization to the synaptic release site. Together, these data reveal a novel role of uPA as an activator of the synaptic vesicle cycle in cerebral cortical neurons via its ability to induce presynaptic recruitment and activation of GAP-43.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The brain produces two brain-derived neurotrophic factor (BDNF) transcripts, with either short or long 3′ untranslated regions (3′ UTRs). The physiological significance of the two forms of mRNAs ...encoding the same protein is unknown. Here, we show that the short and long 3′ UTR BDNF mRNAs are involved in different cellular functions. The short 3′ UTR mRNAs are restricted to somata, whereas the long 3′ UTR mRNAs are also localized in dendrites. In a mouse mutant where the long 3′ UTR is truncated, dendritic targeting of BDNF mRNAs is impaired. There is little BDNF in hippocampal dendrites despite normal levels of total BDNF protein. This mutant exhibits deficits in pruning and enlargement of dendritic spines, as well as selective impairment in long-term potentiation in dendrites, but not somata, of hippocampal neurons. These results provide insights into local and dendritic actions of BDNF and reveal a mechanism for differential regulation of subcellular functions of proteins.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Yeelimite, Ca4Al6O12SO4, is outstanding as an aluminate sodalite, being the framework of these type of materials flexible and dependent on ion sizes and anion ordering/disordering. On the other hand, ...yeelimite is also important from an applied perspective as it is the most important phase in calcium sulfoaluminate cements. However, its crystal structure is not well studied. Here, we characterize the room temperature crystal structure of stoichiometric yeelimite through joint Rietveld refinement using neutron and X-ray powder diffraction data coupled with chemical soft-constraints. Our structural study shows that yeelimite has a lower symmetry than that of the previously reported tetragonal system, which we establish to likely be the acentric orthorhombic space group Pcc2, with a √2a × √2a × a superstructure based on the cubic sodalite structure. Final unit cell values were a = 13.0356(7) Å, b = 13.0350(7) Å, and c = 9.1677(2) Å. We determine several structures using density functional theory calculations, with the lowest energy structure being Pcc2 in agreement with our experimental result. Yeelimite undergoes a reversible phase transition to a higher-symmetry phase which has been characterized to occur at 470 °C by thermodiffractometry. The higher-symmetry phase is likely cubic or pseudocubic possessing an incommensurate superstructure, as suggested by our theoretical calculations which show a phase transition from an orthorhombic to a tetragonal structure. Our theoretical study also predicts a pressure-induced phase transition to a cubic structure of space group I 43m. Finally, we show that our reported crystal structure of yeelimite enables better mineralogical phase analysis of commercial calcium sulfoaluminate cements, as shown by RF values for this phase, 6.9% and 4.8% for the previously published orthorhombic structure and for the one reported in this study, respectively.
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IJS, KILJ, NUK, PNG, UL, UM
The availability of cements, including eco-cements, with tailored mechanical properties is very important for special applications in the building industry. Here we report a full study of the ...hydration of calcium sulfoaluminate eco-cements with different sulfate sources (gypsum, bassanite and anhydrite) and two water/cement ratios (0.50 and 0.65). These parameters have been chosen because they are known to strongly modify the mechanical properties of the resulting mortars and concretes. The applied multi-technique characterization includes: phase assemblage by Rietveld method, evolved heat, conductivity, rheology, compressive strength and expansion/retraction measurements. The dissolution rate of the sulfate sources is key to control the hydration reactions. Bassanite dissolves very fast and hence the initial setting time of the pastes and mortars is too short (20min) to produce homogeneous samples. Anhydrite dissolves slowly so, at 1 hydration-day, the amount of ettringite formed (20wt%) is lower than that in gypsum pastes (26wt%) (w/c=0.50), producing mortars with lower compressive strengths. After 3 hydration-days, anhydrite pastes showed slightly larger ettringite contents and hence, mortars with slightly higher compressive strengths. Ettringite content is the chief parameter to explain the strength development in these eco-cements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Sodalites are tridimensional alumino-silicate materials containing cages where loosely bonded anions are located. Ye’elimite, Ca4Al6O12SO4, is outstanding as an aluminate sodalite with a flexible ...framework accepting several type of dopants with important structural consequences. Moreover, ye’elimite is also important from an applied perspective as it is the most relevant phase in calcium sulfoaluminate cements. The crystal structure of stoichiometric ye’elimite has recently been unraveled, but the structure of dopant-containing ye’elimite, which is present in cements, is not well studied. Here, we report the pseudocubic crystal structure of doped ye’elimite, Ca3.8Na0.2Al5.6Fe0.2Si0.2O12SO4, from high-resolution synchrotron powder diffraction data. The powder pattern is indexed with a cubic cell, and a structural model is reported based on the I4̅3m space group. However, this compound displays diffraction peak narrowing on heating. Furthermore, some high-angle split peaks become a single peak on heating, and a phase transition is measured at 525 °C. Therefore, it is concluded that the crystal structure at room temperature has a lower symmetry, although it can be described as cubic. The structural study at 800 °C suggests a truly cubic structure, and we speculate that this phase transition, on heating, is likely related to the dynamical disordering of the sulfate anions. Finally it is concluded that the high temperature cubic state was not quenchable to ambient, even when the tested chemical substituents are introduced into the structure.
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IJS, KILJ, NUK, PNG, UL, UM
Belite-rich cements hold promise for reduced energy consumption and CO2 emissions, but their use is hindered by the slow hydration rates of ordinary belites. This drawback may be overcome by ...activation of belite by doping. Here, the doping mechanism of B and Na/B in belites is reported. For B-doping, three solid solutions have been tested: Ca2-x/2□x/2(SiO4)1-x(BO3)x, Ca2(SiO4)1-x(BO3)xOx/2 and Ca2-xBx(SiO4)1-x(BO4)x. The experimental results support the substitution of silicate groups by tetrahedral borate groups with the concomitant substitution of calcium by boron for charge compensation, Ca2-xBx(SiO4)1-x(BO4)x. Otherwise, the coupled Na/B-doping of belite has also been investigated and Ca2-xNax(SiO4)1-x(BO3)x series is confirmed to exist for a large range of x values. Along this series, α'H-C2S is the main phase (for x≥0.10) and is single phase for x=0.25. Finally, a new structural description for borax doping in belite has been developed for α'H-Ca1.85Na0.15(SiO4)0.85(BO3)0.15, which fits better borax activated belite cements in Rietveld mineralogical analysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Stoichiometric dicalcium silicate, Ca
2
SiO
4
, displays a well-known polymorphism with temperature. When this phase is doped by a range of elements, belite, one of the main phases of cements, is ...generated. Here, we thoroughly study the aluminum doping of dicalcium silicate. This type of study is important for cement characterization and also from a basic point of view. Ca
2
Si
1−2
x
Al
2
x
O
4−
x
x
(
x
= 0, 0.010, 0.014, 0.03) has been prepared and studied by X-ray powder diffraction and the Rietveld method. The limiting composition has been established as Ca
2
Si
0.972
Al
0.028
O
3.986
0.014
. The
27
Al MAS NMR band located close to ∼−70 ppm is ascribed to tetrahedral environments, in agreement with the proposed aliovalent Si/Al atomic substitution mechanism. Thermal analysis measurements under a wet atmosphere indirectly confirm the increase of oxygen vacancies as the amount of incorporated protons increases with the aluminium content. A thorough electrical characterization has been carried out including overall conductivity measurements under wet and dry atmospheres and conductivity as a function of the oxygen partial pressure. The samples show oxide anion conductivity with a small p-type electronic contribution under oxidizing conditions. These compounds display a very important proton contribution to the overall conductivities under humidified atmospheres.
Stoichiometric dicalcium silicate, Ca
2
SiO
4
, displays a well-known polymorphism with temperature.
Here we explore the role of semaphorin 3A and 3F (Sema3A, Sema3F) in the formation of the mesotelencephalic pathway. We show that Sema3A and 3F are expressed in the ventral mesencephalon (VM) of ...E13.5 rat embryos; the receptors Neuropilin 1 and Neuropilin 2, and co-receptors L1CAM, NrCAM, and Plexins A1 and A3 but not A4 are expressed by VM dopaminergic neurons; these neurons bind Sema3A and 3F
in vitro which induces collapse of their growth cones and elicits, with different potencies, a repulsive response; and this response is absent in axons from Nrp1 and Nrp2 null embryos. Despite these
in vitro effects, only very mild anatomical defects were detected in the organization of the mesotelencephalic pathway in embryonic and adult
Nrp1 or
Nrp2 null mice. However, the dopaminergic meso-habenular pathway and catecholaminergic neurons in the parafascicular and paraventricular nuclei of the thalamus were significantly affected in
Nrp2 null mice. These data are consistent with a model whereby Sema3A and 3F, in combination with other guidance molecules, contributes to the navigation of DA axons to their final synaptic targets.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Background & Aims: The isolation and culture of primary enteric neurons is a difficult process and yields a small number of neurons. We developed fetal and postnatal enteric neuronal cell lines using ...H-2Kb -tsA58 transgenic mice (immortomice) that have a temperature-sensitive mutation of the SV40 large tumor antigen gene under the control of an interferon γ–inducible H-2Kb promoter element. Methods: Enteric neuronal precursors were isolated from the intestines of E13-mouse fetuses and second day postnatal mice using magnetic immunoselection with a p75NTR antibody. The cells were maintained at the permissive temperature, 33°C, and interferon-γ for 24 or 48 hours, and then transferred to 39°C in the presence of glial cell line–derived neurotrophic factor for 7 days for further differentiation. Neuronal markers were assessed by reverse-transcription polymerase chain reaction, Western blot, and immunocytochemistry. Neuronal function was assessed by transplanting these cells into the colons of Piebald or nNOS−/− mice. Results: Expression analysis of cells showed the presence of neuronal markers peripherin, PGP9.5, HuD, tau, synaptic marker synaptophysin, characteristic receptors of enteric neurons, Ret, and 5-hydroxytryptamine–receptor subtypes at 33°C and 39°C. Nestin, S-100β, and α-smooth muscle actin were expressed minimally at 39°C. Glial cell line–derived neurotrophic factor resulted in increased phosphorylation of Akt in these cells, similar to primary enteric neurons. Transplantation of cells into the piebald or nNOS−/− mice colon improved colonic motility. Conclusions: We have developed novel enteric neuronal cell lines that have neuronal characteristics similar to primary enteric neurons. These cells can help us in understanding newer therapeutic options for Hirschsprung's disease.
AimA decrease in proteinuria has been considered protective from renal damage in lupus nephritis (LN), but a cut-off point has yet to be established. The aim of this study was to identify the ...predictors of renal damage in patients with LN and to determine the best cut-off point for a decrease in proteinuria.MethodsWe included patients with LN defined clinically or histologically. Possible predictors of renal damage at the time of LN diagnosis were examined: proteinuria, low complement, anti-double-stranded DNA antibodies, red cell casts, creatinine level, hypertension, renal activity (assessed by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)), prednisone dose, immunosuppressive drugs and antimalarial use. Sociodemographic variables were included at baseline. Proteinuria was assessed at baseline and at 12 months, to determine if early response (proteinuria <0.8 g/day within 12 months since LN diagnosis) is protective of renal damage occurrence. Renal damage was defined as an increase of one or more points in the renal domain of The Systemic Lupus International Collaborating Clinics (SLICC)/American College of Rheumatology (ACR) Damage Index (SDI). Cox regression models using a backward selection method were performed.ResultsFive hundred and two patients with systemic lupus erythematosus patients were included; 120 patients (23.9%) accrued renal damage during their follow-up. Early response to treatment (HR=0.58), antimalarial use (HR=0.54) and a high SES (HR=0.25) were protective of renal damage occurrence, whereas male gender (HR=1.83), hypertension (HR=1.86) and the renal component of the SLEDAI (HR=2.02) were risk factors for its occurrence.ConclusionsEarly response, antimalarial use and high SES were protective of renal damage, while male gender, hypertension and higher renal activity were risk factors for its occurrence in patients with LN.
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