Perception of nonnative tonal contrasts by Mandarin-English and English-Mandarin sequential bilinguals

This study examined the role of acquisition order and crosslinguistic similarity in influencing transfer at the initial stage of perceptually acquiring a tonal third language (L3). Perception of tones in Yoruba and Thai was tested in adult sequential bilinguals representing three different first (L1) and second language (L2) backgrounds: L1 Mandarin-L2 English (MEBs), L1 English-L2 Mandarin (EMBs), and L1 English-L2 intonational/non-tonal (EIBs). MEBs outperformed EMBs and EIBs in discriminating L3 tonal contrasts in both languages, while EMBs showed a small advantage over EIBs on Yoruba. All groups showed better overall discrimination in Thai than Yoruba, but group differences were more robust in Yoruba. MEBs’ and EMBs’ poor discrimination of certain L3 contrasts was further reflected in the L3 tones being perceived as similar to the same Mandarin tone; however, EIBs, with no knowledge of Mandarin, showed many of the same similarity judgments. These findings thus suggest that L1 tonal experience has a particularly facilitative effect in L3 tone perception, but there is also a facilitative effect of L2 tonal experience. Further, crosslinguistic perceptual similarity between L1/L2 and L3 tones, as well as acoustic similarity between different L3 tones, play a significant role at this early stage of L3 tone acquisition.Published versio

Ex vivo differentiation of human bone marrow-derived stem cells into neuronal cell-like lineages

Adeeb Al-Zoubi,1,2 Feras Altwal,3 Farah Khalifeh,2 Jamil Hermas,4 Ziad Al-Zoubi,5 Emad Jafar,5 Mohammed El-Khateeb,6,7 1Department of Surgery, University of Illinois College of Medicine at Peoria, Peoria, IL, USA; 2Stem Cells of Arabia, Amman, Jordan; 3Department of Neuroscience, School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA; 4Stem Cell Division, Al-Yamama Company, 5Jordan Orthopedic and Spinal Center, 6National Center for Diabetes, Endocrinology and Genetics, 7Department of Pathology, Faculty of Medicine, University of Jordan, Amman, Jordan Background: Methods to obtain safe and practical populations of stem cells (SCs) at a clinical grade that are able to differentiate into neuronal cell lineages are yet to be developed. In a previous study, we showed that mouse bone marrow-derived SCs (BM-SCs) differentiated into neuronal cell-like lineages when put in a neuronal-like environment, which is a special media supplemented with the necessary growth factors needed for the differentiation of SCs into neuronal cell-like lineages. Aim: In this study, we aim to assess the potentials of adult human CD34+ and CD133+ SCs to differentiate into neuronal cell-like lineages ex vivo when placed in a neuronal-like microenvironment. Methods: The neuronal-like microenvironment was created by culturing cells in nonhematopoietic expansion media (NHEM) supplemented with growth factors that favor differentiation into neuronal cell lineages (low-affinity nerve growth factor [LNGF], mouse spinal cord extract [mSpE], or both). Cultured cells were assessed for neuronal differentiation by cell morphologies and by expression of GFAP. Results: Our results show that culturing unpurified human BM-derived mononuclear cells (hBM-MNCs) in NHEM+LNGF+mSpE did not lead to neuronal differentiation. In contrast, culturing of purified CD34+ hBM-SCs in NHEM+LNGF+mSpE favored their differentiation into astrocyte-like cells, whereas culturing of purified CD133+ hBM-SCs in the same media favored their differentiation into neuronal-like cells. Interestingly, coculturing of CD34+ and CD133+ hBM-SCs in the same media enhanced the differentiation into astrocyte-like cells and neuronal-like cells, in addition to oligodendrocyte-like cells. Conclusion: These results suggest that a mixture of purified CD34+ and CD133+ cells may enhance the differentiation into neuronal cell-like lineages and give broader neuronal cell lineages than when each of these cell types is cultured alone. This method opens the window for the utilization of specific populations of hBM-SCs to be delivered in a purified form for the potential treatment of neurodegenerative diseases in the future. Keywords: cell therapy, neurodegenerative disease, neurons, astrocyes, CD34+, CD133+, MAC

Iron(II) Complexes with Scorpiand-Like Macrocyclic Polyamines: Kinetico-Mechanistic Aspects of Complex Formation and Oxidative Dehydrogenation of Coordinated Amines

The Fe­(II) coordination chemistry of a pyridinophane <i>tren</i>-derived scorpiand type ligand containing a pyridine ring in the pendant arm is explored by potentiometry, X-ray, NMR, and kinetics methods. Equilibrium studies in water show the formation of a stable [FeL]²⁺ complex that converts to monoprotonated and monohydroxylated species when the pH is changed. A [Fe­(H_–2L)]²⁺ complex containing an hexacoordinated dehydrogenated ligand has been isolated, and its crystal structure shows the formation of an imine bond involving the aliphatic nitrogen of the pendant arm. This complex is low spin Fe­(II) both in the solid state and in solution, as revealed by the Fe–N bond lengths and by the NMR spectra, respectively. The formation rate of [Fe­(H_–2L)]²⁺ in aqueous solutions containing Fe²⁺ and L (1:1 molar ratio) is strongly dependent on the pH, the process being completed in times that range from months in acid solutions to hours in basic conditions. However, detailed kinetic studies show that those differences are caused, at least in part, by the effect of pH on the rate of formation of the unoxidized [FeL]²⁺ complex. In this sense, the protonation of the donor atoms in the pendant arm of the scorpiand ligand leads to the formation of protonated species resistant to oxidative dehydrogenation. Complementary studies in acetonitrile solution indicate that the initial stage in the oxidative dehydrogenation process is the oxidation of the starting complex to form a [FeL]³⁺ complex, which then undergoes disproportionation into [Fe­(H_–2L)]²⁺ and [FeL]²⁺. Experiments starting with Fe­(III) have allowed us to determine that disproportionation occurs with first order kinetics both in water and acetonitrile solutions. However, whereas a significant acceleration is observed in water when the pH is increased, no effect of the addition of acid or base on the rate of disproportionation is observed in acetonitrile. Oxidative dehydrogenation of the Fe­(II) complex formed in experiments starting with an Fe­(III) salt is slower than that occurring when an Fe­(II) salt is used, an observation that can be explained in terms of the formation of two different Fe­(III) complexes, one of them with a structure unable to evolve directly toward the product of oxidative dehydrogenation