Galectin-3 (Gal-3) is the only chimeric protein in the galectin family. Gal-3 structure comprises unusual tandem repeats of proline and glycine-rich short stretches bound to a ...carbohydrate-recognition domain (CRD). The present review summarizes Gal-3 functions in the extracellular and intracellular space, its regulation and its internalization and secretion, with a focus on the current knowledge of Gal-3 role in central nervous system (CNS) health and disease, particularly oligodendrocyte (OLG) differentiation, myelination and remyelination in experimental models of multiple sclerosis (MS). During myelination, microglia-expressed Gal-3 promotes OLG differentiation by binding glycoconjugates present only on the cell surface of OLG precursor cells (OPC). During remyelination, microglia-expressed Gal-3 favors an M2 microglial phenotype, hence fostering myelin debris phagocytosis through TREM-2b phagocytic receptor and OLG differentiation. Gal-3 is necessary for myelin integrity and function, as evidenced by myelin ultrastructural and behavioral studies from
mice. Mechanistically, Gal-3 enhances actin assembly and reduces Erk 1/2 activation, leading to early OLG branching. Gal-3 later induces Akt activation and increases MBP expression, promoting gelsolin release and actin disassembly and thus regulating OLG final differentiation. Altogether, findings indicate that Gal-3 mediates the glial crosstalk driving OLG differentiation and (re)myelination and may be regarded as a target in the design of future therapies for a variety of demyelinating diseases.
Multiple sclerosis (MS) is one of the most common causes of progressive disability affecting young people with very few therapeutic options available for its progressive forms. Its pathophysiology ...involves demyelination and neurodegeneration apparently driven by microglial activation, which is physiologically dependent on colony‐stimulating factor‐1 receptor (CSF‐1R) signaling. In the present work, we used microglial modulation through oral administration of brain‐penetrant CSF‐1R inhibitor BLZ945 in acute and chronic cuprizone (CPZ)‐induced demyelination to evaluate preventive and therapeutic effects on de/remyelination and neurodegeneration. Our results show that BLZ945 induced a significant reduction in the number of microglia. Preventive BLZ945 treatment attenuated demyelination in the acute CPZ model, mainly in cortex and external capsule. In contrast, BLZ945 treatment in the acute CPZ model failed to protect myelin or foster remyelination in myelin‐rich areas, which may respond to a loss in microglial phagocytic capacity and the consequent impairment in oligodendroglial differentiation. Preventive and therapeutic BLZ945 treatment promoted remyelination and neuroprotection in the chronic model. These results could be potentially transferred to the treatment of progressive forms of MS.
Main Points
• CSF‐1R inhibitor BLZ945 reduces the number of microglial cells.
• BLZ945 reduces myelin damage in acute CPZ‐induced demyelination mainly in myelin poor areas.
• BLZ945 promotes remyelination and neuroprotection in chronic CPZ‐induced demyelination.
A Late Pleistocene–Holocene loess–paleosol sequence in central Argentina was studied to obtain a weathering insight and to probe geochemical tools as paleoclimatic proxies. Three paleosols and a ...buried soil interlayered with loess mantles compose Corralito I sequence (32°00′7″ S, 64°11′08″ W, 469 m a.s.l). Several weathering indices (CIA, CIA-K, and LWI) and elemental ratios (∑Bases/Al
2
O
3,
Rb/Sr, CaO/TiO
2
, Na
2
O/TiO
2
) were calculated. An incipient weathering degree throughout the sequence was detected, denoting that the parent material (i.e., loess mantles) has not been substantially modified by pedogenesis. Although a statistically significant correlation between magnetic susceptibility and several weathering indices was identified, the weathering intensity was not strong enough to produce a decrease in the magnetic signal of the paleosols, which is, in part, inherited from the detrital fraction. Paleoprecipitation indices, calculated using geochemical data, suggest slightly wetter conditions during paleosol formation when compared to loess. Paleosols were formed during humid conditions (paleosols II and II during MIS 5e, and paleosol I during MIS 3) with sedimentation pause and soil development, whereas loess layers were deposited during more arid conditions.
Mineral aerosols profoundly impact global climate. Modeling of the dust cycle is the main tool used to gauge this effect. However, the scarcity of in situ modern dust flux measurements is the main ...reason why validation of existing models is hampered. We present the first long-term (14-year) record of dust flux in the Pampas, southern South America, home to the largest loess deposit in the Southern Hemisphere. Measured 14-year mean deposition (40 g m−2 year−1) and horizontal (362 g m−2 year−1) fluxes imply that current models underestimate the power of the central Pampas as a dust sink. Based on cross-spectral analysis, both wet and, to a lesser extent, dry deposition are found to play significant roles in atmospheric dust extraction. Dust is sourced regionally from the South American Arid Diagonal and from the shores of Mar Chiquita lake (~260 km), which we find to be the main contributor of dust particles >30 µm. Cross-spectral and satellite image analyses show that surface wind speed and precipitation at the Puna-Altiplano Plateau are controlling factors for horizontal dust flux in the Pampas. El Niño Southern Oscillation probably plays a role in controlling interannual horizontal dust flux periodicities. Finally, preliminary comparisons between modern vertical dust fluxes and loess accumulation rates point to the Pampas as a more powerful dust sink during the last deglaciation and Antarctic Cold Reversal (18–12.5 ka).
The Paraná River basin is one of the largest hydrological systems in South America. The present study focuses on the mineralogical and chemical composition of the suspended sediments exported by the ...Paraná River to the Atlantic Ocean, with the aim of analyzing their provenance, the chemical weathering signature and the likelihood of sedimentary recycling. The particulate matter of the Middle Paraná River and its main tributaries (i.e., the Paraguay and the Upper Paraná rivers) is mostly composed of quartz, plagioclase, K-feldspar, and clays, such as illite and kaolinite. Different geochemical approaches indicate that the suspended sediments transported by the Paraná River preserve the chemical signature of its sources and its composition is not significantly modified during transport. These sediments are mainly supplied by acidic arc sources located in the Andean headwaters of the Bermejo and Pilcomayo rivers (and transported by the Paraguay River); and by tholeiitic basalts outcropping in the headwaters of the Upper Paraná River. The incomplete mixing of both main tributaries produces a transverse geochemical asymmetry in the particulate material of the Middle Paraná River, which was detected ~32km downflow the confluence. The suspended load transported by the Paraguay River (which includes the contributions from the Bermejo and Pilcomayo rivers) indicates incipiently to moderately weathering, whereas the particulate matter exported by the Upper Paraná River reveals a higher degree of chemical alteration. This is the result of the different lithology and climatic regimes that prevail in the headwaters of both tributaries. The weathering signature of the Middle Paraná River's suspended load resembles that of the Paraguay River, which in turns supplies most of the particulate matter through the Bermejo River. This work also shows that the suspended load exported by the Paraná River basin has a mixed origin, where the chemical signatures from young materials derived from undifferentiated volcanic rocks, and from recycled materials affected by intracrustal differentiation can be distinguished.
•The suspended load carried by the Paraná R. is mainly supplied by acidic arc sources.•The Paraná R. suspended sediments preserve the chemical signature of the sources.•The particulate load exported by the Paraná R. shows incipient to moderate weathering.•Geochemical signals of sedimentary recycling were identified in the Paraná R. basin.
•A transverse chemical and isotopic asymmetry is observed in the Middle Paraná River.•The asymmetry is due to the incomplete mixing of the Upper Paraná and Paraguay rivers.•Groundwater inputs ...represent between 0.5% and 6% of the total river discharge.
The Paraná River basin is one of the largest hydrological systems in South America (∼2.6×106km2). Downflow the confluence of tributaries, most large rivers exhibit transverse and longitudinal inhomogeneities that can be detected for tens or even hundreds of kilometers. Concordantly, a noticeable cross-sectional chemical asymmetry in the dissolved load was distinguished in the Middle Paraná River, after the confluence of its main tributaries (i.e., the Paraguay and Upper Paraná rivers). Water chemistry and isotopic signature in three cross-sections along the Middle Paraná River, as well as from main and minor tributaries, and some deep (∼105mbs) and shallow boreholes (∼15mbs) located near both river banks, were analyzed in order to define the extent of mixing and identify possible contributions from groundwater discharges. Downflow the confluence of the Upper Paraná and Paraguay rivers a chemical and isotopic asymmetry was observed, mainly through the values of EC, major ions (Ca2+, Na+, Mg2+, Cl− and SO42−), some trace elements (Fe, U, Th, Ba, Sr, As and REE) and stable isotopes (δ18O and δ2H). Toward its western margin, higher elemental concentrations which resembled that of the Paraguay River were measured, whereas at the eastern border, waters were more diluted and preserved the chemical signature of the Upper Paraná River. This variability remained detectable at least until ∼225km downflow the confluence, where differences between western and eastern margins were less evident. At ∼580km downflow the confluence, a slight inversion in the transverse chemical asymmetry was observed. This trend switch can be the result of the input of solutes from minor tributaries that reach the main channel from the East and/or may be due to higher groundwater discharges from the East bank. A mass balance model was applied, as a first approach, to estimate the groundwater inflow using the geochemical tracer 222Rn. The results indicate that groundwater contributions represent between ∼0.5% and 6% of the total water inputs to the Middle Paraná River under baseflow conditions. This implies that the chemical asymmetry in the Middle Parana River is mostly due to the incomplete mixing of the main tributaries. Though the influence of groundwater is not a determining factor in the chemical variability of the river, it may partially explain the higher concentrations of some trace elements found in the eastern margin ∼580km downflow the confluence.
High glacial mountain environments around the world are important water reservoirs and are extremely sensitive to the effects of climate change. Considering that climate change affects snow ...accumulation and glacial melting, it is essential to understand the runoff generation and hydrological dynamics in these type of systems. Andean glaciers have shown a retreating and thinning pattern since the start of the 21st century. Regarding this, the stable isotopic composition of waters is useful to assess the contributions from different sources (i.e., glaciers, precipitation, and tributaries' inputs) to rivers. Several Patagonian mountain rivers have Andean glaciers in their headwaters, one of which is the Manso River. In this basin, over the last 30 years, the Ventisquero Negro Glacier (Manso Glacier's regenerated tongue) experienced a rapid thinning and recession that generated a proglacial lake, called Manso proglacial Lake. In this study, topographic effects upon the stable isotopic composition of river waters (δ2H and δ18O) are recognized, particularly, the altitude effect. The stable isotope composition of the Manso River varies downstream, evolving to a composition more enriched in heavy isotopes in the lower basin, likely due to altitude effects and the progressive evaporation that mainly occurs in the lakes' surfaces that the river crosses. Results show that glacial meltwater is the major water contributor in the upper basin during early fall. In the rest of the basin the stable isotopic composition of the Manso River is mainly controlled by the lakes' isotopic signatures and is highly influenced by two tributary rivers. The concordance between isotopic models and hydrological data demonstrates that stable isotopes constitute a valuable tool to quantify the contribution of different water sources. This has the potential to be particularly useful in areas where discharge data is unavailable.
Spatial variations of the stable isotope composition are researched at a catchment scale, with particular emphasis over the role of topography and lakes. The contribution of different water sources was calculated by means of isotopic modelling.
River discharge time series in southern South America (between ∼15° and ∼50°S) show dissimilar historical trends. In the Río de la Plata drainage basin (RPDB) the record shows a runoff trend change ...from decreasing to increasing, around the mid 20th century. Independently of the seasonal variation, currently-observed discharge change in the region is mainly accounted for by increased discharge during low-flow periods. In contrast, most Patagonian rivers show a negative discharge trend, which mainly occurs in some austral summer months and is particularly significant in the Negro River. When considering the historical discharge variability in the southern part of South America, the spectral analysis produced evidence of interannual, quasi-decadal, and quasi-bidecadal periodicities. Most rivers in the region show El Niño-like interannual periodicities with the exceptions of the Bermejo and Pilcomayo rivers. In the RPDB, during the 20th century, interannual periodicity changed from the ∼2 to ∼5-year band to the ∼5 to ∼7-year band between ∼1935 and ∼1970. In Patagonia, the interannual oscillation showed maximum power ∼1930 and ∼1980 in the Colorado, whereas further south (Negro and Chubut rivers), maximum power appears ∼1950. The quasi-decadal signal is strong in the RPDB, in general, and particularly in Patagonia’s Colorado, which runs close to the so-called Arid Diagonal and bears this signal presumably due to the influence of the low-level jets (LLJs). This periodicity is conspicuously absent in other Patagonian rivers. Finally, a quasi-bidecadal signature appears to be restricted to the Bermejo and Iguaçu rivers, in the RPDB, and in Patagonia’s Colorado and Santa Cruz rivers.
Water–rock interactions are one of the main factors that control water quality in rivers worldwide. Hydro-geochemical analyses from mountain rivers of the North of the Sierra de Velasco (Argentina), ...in combination with petrological studies of the granitic rocks, suggest that A-type plutons are one of the main fluorine suppliers in surface waters that drain these granitic terrains. In the rivers of the northern sector of the study area, the dissolved F
−
is above 1.72 mg L
−1
and reach up to 3.65 mg L
−1
, while in the southern sector the values range between 0.27 and 1.05 mg L
−1
. Conversely, there are no significant differences in the major hydrochemistry of the studied rivers, since all the waters are diluted (TDS: 36–116 mg L
−1
), slightly alkaline (pH: 7.50–8.16), of bicarbonate-calcium type, and with no seasonal influence of precipitation. The elevated values of F
−
in waters spatially match the F-rich A-type strongly peraluminous granite of La Costa Pluton. Fluorine in this unit is five to ten times higher than in the S-type peraluminous granite from the southern sector, and is mainly hosted in micas and fluorapatite. The higher dissolved trace elements and REE in the northern sector, also match the different lithological sources. Therefore, the identification of A-type peraluminous granites in a catchment area could be used as a petrological indicator to predict a possible high fluoride content in river waters. Additionally, high fluoride values in surface waters could be a valuable proxy of the presence of A-type plutons in the nearby region.
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