Mechanism of divergent growth factor effects in mesenchymal stem cell differentiation

Closely related signals often lead to very different cellular outcomes. We found that the differentiation of human mesenchymal stem cells into bone-forming cells is stimulated by epidermal growth factor (EGF) but not platelet-derived growth factor (PDGF). We used mass spectrometry-based proteomics to comprehensively compare proteins that were tyrosine phosphorylated in response to EGF and PDGF and their associated partners. More than 90% of these signaling proteins were used by both ligands, whereas the phosphatidylinositol 3-kinase (PI3K) pathway was exclusively activated by PDGF, implicating it as a possible control point. Indeed, chemical inhibition of PI3K in PDGF-stimulated cells removed the differential effect of the two growth factors, bestowing full differentiation effect onto PDGF. Thus, quantitative proteomics can directly compare entire signaling networks and discover critical differences capable of changing cell fate.     

SILVER-INDUCED CHANGES IN THE NUTRIENT AND TRACE ELEMENT UPTAKE BY WHEAT AND AMOUNT OF THE RHIZOSPHERE PROTEINS

The information on biogeochemistry of silver (Ag) is scarce and mechanisms of Ag uptake by plants are still unclear. We studied the impact of silver sulfate (Ag₂SO₄) and silver nitrate (AgNO₃) on biomass of wheat seedlings, the rhizosphere proteins and uptake of nutrients and trace elements. Most part of Ag was accumulated in roots. Concentrations of Ag in leaves remained the same as in control plants. Both treatments (Ag₂SO₄ and AgNO₃) affected biomass of the seedlings. Plant biomass was decreased more after treatment with AgNO₃. Both Ag₂SO₄ and AgNO₃ reduced leaf concentrations of sodium and barium and root concentrations of calcium. Over time (three days), protein concentration in the rhizosphere of control plants and plants treated with AgNO₃ increased, whereas treatment with Ag₂SO₄ reduced concentration of the rhizosphere proteins. In soil treated with Ag₂SO₄ only low-molecular-weight proteins were found. In the control soil and in soil treated with AgNO₃ we also observed polydisperse fraction.     

Atypical Reactive Center Kunitz-Type Inhibitor from the Sea Anemone Heteractis crispa

The primary structure of a new Kunitz-type protease inhibitor InhVJ from the sea anemone Heteractis crispa (Radianthus macrodactylus) was determined by protein sequencing and cDNA cloning. InhVJ amino acid sequence was shown to share high sequence identity (up to 98%) with the other known Kunitz-type sea anemones sequences. It was determined that the P1 Thr at the reactive site resulted in a decrease of the K(i) of InhVJ to trypsin and α-chymotrypsin (7.38 × 10(-8) M and 9.93 × 10(-7) M, respectively). By structure modeling the functional importance of amino acids at the reactive site as well as at the weak contact site were determined. The significant role of Glu45 for the orientation and stabilization of the InhVJ-trypsin complex was elucidated. We can suggest that there has been an adaptive evolution of the P1 residue at the inhibitor reactive site providing specialization or functional diversification of the paralogs. The appearance of a key so-called P1 Thr residue instead of Lys might lead to refinement of inhibitor specificity in the direction of subfamilies of serine proteases. The absence of Kv channel and TRPV1-receptor modulation activity was confirmed by electrophysiological screening tests.     

An outbreak of tuberculosis by Mycobacterium bovis in coatis (Nasua nasua)

Mycobacterium tuberculosis complex, which includes Mycobacterium bovis, infrequently causes severe or lethal disease in captive wildlife populations. A dead coati from a wildlife triage center showing pulmonary lesions compatible with tuberculosis had raised suspicion of a potential disease caused by mycobacteria species and was further investigated. Four native coatis (Nasua nasua) with suspected mycobacterial infection were sedated, and bronchoalveolar lavages and tuberculin skin tests (TSTs) were performed. All animals tested positive upon TST. Mycobacterial culturing, Ziehl-Neelsen staining, and genetic testing were performed on postmortem samples and the etiologic agent was identified as M. bovis. Molecular genetic identification using a polymerase chain reaction panel was crucial to achieving a definitive diagnosis.     

Irreversible sorption of humic substances causes a decrease in wettability of clay surfaces as measured by a sessile drop contact angle method

Purpose

The objective of the study was to obtain quantitative assessments of the hydrophobic impact of irreversible sorption of humic substances (HSs) onto clay mineral surfaces using a sessile drop contact angle method.

Materials and methods

Two clays (kaolin and montmorillonite) were modified with four humic materials: (1) sod podzolic soil, (2) chernozem, (3) peat, and (4) coal (leonardite). The humic materials were characterized using elemental analysis, size exclusion chromatography, and ¹³C NMR spectroscopy. Both clay samples were saturated with Ca²⁺ prior to modification with HS using a sorption isotherm technique. Contact angles (CAs) of the obtained HS-clay complexes were determined using a static sessile drop method after drying the obtained HS-clay complexes in the form of a thin film.

Results and discussion

HS modification rendered both clays under study—kaolin and montmorillonite—more hydrophobic. In case of Ca-kaolin, the CA values increased from 27° (Ca-kaolin) up to 31°–32° (all HS-kaolin complexes) with no significant difference among the HS types used for modification. In the case of Ca-montmorillonite, the CA values increased from 41° (Ca-montmorillonite) up to 51°–83° with the following ascending trend for the humic types investigated: chernozem HS < coal HS < peat HS < sod-podzolic HS. This trend is in reverse to the degree of aromaticity of the HS, expressed as the content of aromatic carbon, and it is directly proportional to the molecular weight of each HS.

Conclusions

Application of a sessile drop method showed increased surface hydrophobicity of HS-modified clays. Much more substantial hydrophobization was observed for montmorillonite as compared to kaolin, which was explained by the differences in the sorption mechanism.

     

Assessment of soil erosion rate trends in two agricultural regions of European Russia for the last 60 years

Purpose

Forest–steppe and the southern forest ecotones of European Russia (ER) are the most productive agricultural areas in Russia. Both climate and land use changes have occurred within the ER during last 30 years. These changes can lead to changes in the timing, magnitude, and spatial distribution of soil erosion rates on cultivated lands. The objective of this research was to assess the trends in soil erosion rates since the 1960s for two agricultural regions of ER.

Materials and methods

Rates of soil erosion were estimated for two time windows (1963–1986 and 1986–2015) within the two agricultural regions. Both regions are characterized by a high proportion of cropland (>?60%), and within each region, one river basin and one 1st–3rd-order agricultural catchment were selected for a detailed assessment of soil erosion rates. Erosion models and visual interpretation of satellite images were used for the evaluation of the erosion rates for the river basins. Sediment budget assessments, ¹³⁷Cs dating, geomorphologic mapping, and erosion models were used for the evaluation of the sediment redistribution for the two time windows in agricultural catchments.

Results and discussion

At the river basin scale, the mean annual erosion rate did not change in the western part of forest–steppe ecotone; however, there was a weak negative trend in the mean annual erosion rate for the eastern part of the southern forest ecotone. A large negative trend in the erosion rate was found for both small agricultural catchments. In all cases, the reduction in the erosion rates was mainly associated with a decrease of surface runoff during snowmelt, as a result of an increase in both the air and soil temperatures during winter season. The soil loss reduction during snowmelt was counteracted by an equal increase in rainfall erosion due to increase of rainfall intensity in western part of forest–steppe ecotone.

Conclusions

Reduction of surface runoff during spring snowmelt was the main reason the erosion rates declined on cultivated lands within the forest–steppe and southern forest ecotones of ER. Evaluation of ephemeral gully erosion rate was not incorporated into State Hydrological Institute erosion model used for the evaluation of the soil losses during snowmelt. This has led to an underestimation of the total soil losses for the 1963–1986 time window for all study sites.