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Late Pleistocene paleosol formation in a dynamic aggradational microenvironment - A case study from the Malá nad Hronom loess succession (Slovakia)
The geomorphological characteristics of the loess succession at Malá nad Hronom (Slovakia) mean that it provides a valuable opportunity for the investigation of differences in soil formation in various topographic positions. Along with the semiquantitative characterization of the paleosols (on the basis of physical properties, texture, the characteristics of peds, clay films, horizon boundaries), high-resolution field magnetic susceptibility measurements and sampling were carried out along four different sections of the profile. Samples for luminescence dating were also taken, in order to establish the chronostratigraphical position of the paleosols studied. The comparison of various proxies revealed the differences in soil formation in a dynamic aggradational microenvironment for the same paleosol horizons located in various positions along the slope. Contrary to expectation, paleosols developed in local top or slope topographical positions did not display significant differences in e.g. in their degree of development, nor the characteristics of their magnetic susceptibility curves. In the case of paleosols in positions lower down the slope, signs of quasi-permanent sediment input could be recognized as being present as early as during the formation of the soil itself. This sediment input would seem to be surpassed in the case of pedogenesis strengthened by the climate of the last interglacial (marine isotope stage - MIS 5). Pedogenesis seems to be sustained by renewed intense dust accumulation in the Late Pleistocene, in MIS 3, though compared to MIS 5, the climate of MIS 3 did not favor intense pedogenesis. Despite the general belief that loess series formed in plateau positions can preserve terrestrial records without significant erosion, in the case of the Malá nad Hronom loess this is not so. Compared to the sequence affected by erosional events in the local top position, the sequence affected by quasi-continuous sediment input in the lower slope position seems to have preserved the soil horizons intact.International Visegrad Fund (project Number 11410020). The paper was also supported by a long-term conceptual development subvention available to research organizations RVO: 68145535 from the Institute of Geonics AS CR, by the Slovak Research and Development Agency under contract No. APVV-0625-11 (project “A new synthesis of the Western Carpathians landform evolution – preparation of the database for testing of key hypotheses”. B. Bradák acknowledges the financial support of project BU235P18 (Junta de Castilla y Leon, Spain) and the European Regional Development Fund (ERD), project PID2019-108753GB-C21 / AECI / 10.13039/501100011033 of the Agencia Estatal de Investigación and project PID2019-105796GB-100 / AECI / 10.13039/501100011033 of the Agencia Estatal de Investigación
NUCLEAR TRANSLOCATION OF p90Rsk AND PHOSPHORYLATION OF CREB IS INDUCED BY IONOMYCIN IN A RAS-INDEPENDENT MANNER IN PC12 CELLS
In the present study we examined the possible role of p90Rsk in pathways leading to neuronal differentiation
of PC12 cells induced by nerve growth factor (NGF) and the calcium ionophore ionomycin. PC12-
M17 cells, expressing a dominant inhibitory Ras protein, do not undergo neuronal differentiation in
response to NGF like wild-type PC12 cells, but exhibit neurite outgrowth when treated with NGF in combination
with ionomycin. However, the blockade of Ras in these cells results in failure of activation of
mitogen-activated protein kinase (MAPK)/extracellular signal regulation kinase (ERK) (MEK) and ERK
activation as well, therefore kinases other than those of the ERK pathway might play a role in the induction
of neuronal differentiation in this case. Here we show that p90Rsk translocates to the nucleus in
response to ionomycin in both wild-type PC12 and PC12-M17 cells, and this spatial distribution is followed
by increased phosphorylation of the cAMP response element binding protein (CREB). Since
CREB is believed to be the transcription factor that can integrate Ca2+, growth factor and cAMP-induced
signals, we suggest that p90Rsk may be one of the kinases which is able to replace ERKs under certain
circumstances, thereby participating in Ras-independent neuronal differentiation induced by NGF plus
ionomycin