Late Messinian rodents from Verduno (Piedmont,NW Italy): Biochronological,paleoecological and paleobiogeographic implications

The stratigraphic and paleoenvironmental context of the Verduno fossil vertebrate locality is discussed herein based on its rodent record. The Verduno section crops out in the southern part of the Tertiary Piedmont Basin (TPB), and can be included in the Messinian post-evaporitic Cassano Spinola Fm., chronologically corresponding to the so-called Lago-Mare event. Rodents are represented by a relatively rich assemblage. Murids are by far the most diverse and abundant, with at least four taxa, including the common Centralomys benericettii and Paraethomys meini, and the rare Apodemus gudrunae and Occitanomys sp. Cricetids are represented by a single species, Apocricetus cf. A. barrierei. Muscardinus aff. M. vireti appears to be the only glirid present at Verduno. The Verduno rodent assemblage shares some taxa with other Messinian post-evaporitic localities from Italy bearing continental vertebrate remains, such as Brisighella (central Italy) and Moncucco Torinese (NW Italy) (e.g., C. benericettii, P. meini) and, possibly, with Ciabòt Cagna (NW Italy). However, the general structure of these four Messinian assemblages displays substantial differences, which may reflect different palaeoenvironmental conditions.     

NPY modulates miR-30a-5p and BDNF in opposite direction in an in vitro model of Alzheimer disease: a possible role in neuroprotection?

Using in vitro models of Alzheimer’s disease (AD), we found that the toxic effects of amyloid beta 25–35 (Aβ_25–35) on the neurotrophin brain-derived neurotrophic factor (BDNF) were counteracted by pre-incubation with neuropeptide Y (NPY), a neuropeptide expressed within the central nervous system. Nonetheless, the mechanism of action of NPY on BDNF neuronal production in the presence of Aβ is not known. BDNF expression might be directly regulated by microRNA (miRs), small non-coding DNA fragments that regulate the expression of target genes. Thus, there is the possibility that miRs alterations are present in AD-affected neurons and that NPY influences miR expression. To test this hypothesis, we exposed NPY-pretreated primary rat cortical neurons to Aβ_25–35 and measured miR-30a-5p (a member of the miR-30a family involved in BDNF tuning expression) and BDNF mRNA and protein expression after 24 and 48 h. Our results demonstrated that pre-treatment with NPY decreased miR-30a-5p expression and increased BDNF mRNA and protein expression at 24 and 48 h of incubation with Aβ. Therefore, this study demonstrates that NPY modulates BDNF and its regulating microRNA miR-30a-5p in opposite direction with a mechanism that possibly contributes to the neuroprotective effect of NPY in rat cortical neurons exposed to Aβ.     

Protective effect of mitochondrial ferritin on cytosolic iron dysregulation induced by doxorubicin in HeLa cells

Doxorubicin (DOX) is an anticancer drug with cardiotoxic side effects mostly caused by iron homeostasis dysregulation. Mitochondria are involved in iron trafficking and mitochondrial ferritin (FtMt) was shown to provide protection against cellular iron imbalance. Therefore, we hypothesized that FtMt overexpression could limit DOX effects on iron homeostasis. Heart’s homogenates of DOX-treated C57BL/6 mice were analyzed for cytosolic and mitochondrial iron-related proteins’ expression and activity, revealing high cytosolic ferritin and ferritin-bound iron, low transferrin-receptor 1 and a strong hepcidin upregulation. Mitochondrial iron-related proteins (aconitase, succinate-dehydrogenase, frataxin) seemed, however, unaffected, although a partial inactivation of superoxide dismutase 2 was detected. Importantly, the ectopic expression of FtMt in human HeLa cells partially reverted DOX-induced iron imbalance. Our results, while confirming DOX effects on iron homeostasis, demonstrate that DOX affects more cytosolic than mitochondrial iron metabolism both in murine hearts and human HeLa cells and that FtMt overexpression is able to prevent most of these effects in HeLa cells.     

CDC42 switches IRSp53 from inhibition of actin growth to elongation by clustering of VASP

Filopodia explore the environment, sensing soluble and mechanical cues during directional motility and tissue morphogenesis. How filopodia are initiated and spatially restricted to specific sites on the plasma membrane is still unclear. Here, we show that the membrane deforming and curvature sensing IRSp53 (Insulin Receptor Substrate of 53 kDa) protein slows down actin filament barbed end growth. This inhibition is relieved by CDC42 and counteracted by VASP, which also binds to IRSp53. The VASP:IRSp53 interaction is regulated by activated CDC42 and promotes high‐density clustering of VASP, which is required for processive actin filament elongation. The interaction also mediates VASP recruitment to liposomes. In cells, IRSp53 and VASP accumulate at discrete foci at the leading edge, where filopodia are initiated. Genetic removal of IRSp53 impairs the formation of VASP foci, filopodia and chemotactic motility, while IRSp53 null mice display defective wound healing. Thus, IRSp53 dampens barbed end growth. CDC42 activation inhibits this activity and promotes IRSp53‐dependent recruitment and clustering of VASP to drive actin assembly. These events result in spatial restriction of VASP filament elongation for initiation of filopodia during cell migration, invasion, and tissue repair.     

The Duplex-Harpin Conformational Transition of d(CGCGCGATCGCGCG) and d(CGCGCGTACGCGCG): A Thermodynamic and Kinetic Study

Abstract

We have studied the duplex-hairpin conformational transition in two perfectly palindromic sequences, d(CGCGCGATCGCGCG)(I) and d(CGCGCGTACGCGCG)(II), by means of UV-melting, electrophoretic and T-jump experiments. Both tetradecamers exhibit biphasic thermal profiles. The lower temperature transition is concentration dependent whereas the higher temperature transition is not. The former transition has been characterized by gel electrophoresis and shows two distinct bands, whose intensity depends on temperature. This behavior is due to the occurrence of a slow premelting interconversion between the duplex and hairpin forms in both tetradecamers. The kinetics of hairpin formation from the duplex is studied by T-jump experiments. Relaxation spectra are well reproduced by a single relaxation time with rate constants characterized by a high temperature coefficient. In 10 mM NaCl, the duplex-hairpin conversion of I is characterized by an apparent activation energy of 96 ± 6 kcal/mol, a value rather close to the expected denaturation enthalpy. In 1 mM NaCl a value slightly lower has been obtained. The rate of duplex-hairpin interconversion has been found to decrease as the salt concentration is raised. These data suggest that the transformation from the duplex to the hairpin form should imply a transition state with a simultaneous breaking of most base pairs, if not total strand separation.     

dC-dG Alternating Oligonucleotides: Thermodynamic and Kinetic Aspects of the B-Z Transformation

Abstract

The alternating cytosine-guanine oligodeoxyribonucleotides (dCdG)_n, (dGdC)_n, (dCdG)_n, (dCdG)_ndC (n=3,4), (dGdC)₇ and dG(dCdG)₃ have been studied by UV and CD spectroscopy at different temperatures and NaCl concentrations. The analysis of the melting data, assuming an all-or-none model, reveals that in the B-conformation the 5′G/C3′ stacking interactions are enthalpically favoured with respect to the 5′C/G3′ one. The CD investigation of the B-Z equilibrium shows that the Z-conformation is enthalpically stabilized, while the B-conformation is entropically favoured, in the range of NaCl concentration considered (1 to 5M). The kinetic data for the B-Z transformation, obtained with a salt-jump technique for the hexamer (dCdG)₃, support a mechanism by which (he Watson-Crick hydrogen bonds are broken before the bases flip over separately and eventually stack, reforming the H-bonds, in the new helix.