Ceramide From Sphingomyelin Hydrolysis Induces Neuronal Differentiation, Whereas De Novo Ceramide Synthesis And Sphingomyelin Hydrolysis Initiate Apoptosis After NGF Withdrawal In PC12 Cells

Background: Ceramide, important for both neuronal differentiation and dedifferentiation, resides in several membranes, is synthesized in the endoplasmic reticulum, mitochondrial, and nuclear membranes, and can be further processed into glycosphingolipids or sphingomyelin. Ceramide may also be generated by hydrolysis of sphingomyelin by neutral or acidic sphingomyelinases in lysosomes and other membranes. Here we asked whether the differing functions of ceramide derived from different origins. Methods: We added NGF to PC12 cells and to TrkA cells. These latter overexpress NGF receptors and are partially activated to differentiate, whereas NGF is required for PC12 cells to differentiate. We differentiated synthesis from hydrolysis by the use of appropriate inhibitors. Results: When NGF is added, the kinetics and amounts of ceramide and sphingomyelin indicate that the ceramide comes primarily from hydrolysis but, when hydrolysis is inhibited, can also come from neosynthesis. When NGF is removed, the ceramide comes from both neosynthesis and hydrolysis. Conclusion: We conclude that the function of ceramide depends heavily on its intracellular location, and that further understanding of its function will depend on resolving its location during changes of cell status.

Kraft (Force)

The lexeme Kraft (force) is a foundational concept for Goethe that expresses the dynamism essential to his thought. Its tendency to move between operations of particularity and generality, polarity and intensification, differentiation and dedifferentiation, potentiality and actuality, norm and deviation, rationality and irrationality, and cognition and creativity together lend it a characteristic mobility, multiplicity, and diffusion. The discursive tensions and blendings of the concept during the seventeenth and eighteenth centuries—which extend between the obscure aesthetic construction of force in Karl Philipp Moritz and Johann Gottfried Herder and its scientific construction in Kant and Newton as the condition of possibility of knowledge—also manifest themselves in Goethe’s concept. As a grounding and ungrounding at one and the same time, Kraft thus serves as a material condition for the genesis of knowledge, on the one hand, and a metaphysical index of something absolutely unconditioned (das Unbedingte), on the other. When Goethe conceptualizes force as unconditioned, rather than as a condition of this or that individual being, he configures it in a number of ways. These include force as movement in processes of transformation and becoming, as potential, as a capacity for trans-discursive drift or blending, and as a non-discursive resistance to integration into normative, cognitive, and representational modes of thought. Certain scenes in Goethe's literary works—including most prominently, Die Wahlverwandtschaften (1809; The Elective Affinities), Wilhelm Meisters Wanderjahre (1821/29; Wilhelm Meister's Journeyman Years), Pandora (1807/08), and Faust(1808/32)—can be read as thought experiments that offer ontological conceptions of force in order to explore its informing oppositions of movement and metamorphosis, potentiality and actuality, as well as trans-discursivity and non-discursivity.

Author Correction: Alternating Differentiation and Dedifferentiation between Mature Osteoblasts and Osteocytes

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Whole Organism Model to Study Molecular Mechanisms of Differentiation and Dedifferentiation

Cancer recurrence has remained a significant challenge, despite advances in therapeutic approaches. In part, this is due to our incomplete understanding of the biology of cancer stem cells and the underlying molecular mechanisms. The phenomenon of differentiation and dedifferentiation (phenotypic switching) is not only unique to stem cells but it is also observed in several other organisms, as well as evolutionary-related microbes. Here, we propose the use of a primitive eukaryotic unicellular organism, Acanthamoeba castellanii, as a model to study the molecular mechanisms of cellular differentiation and dedifferentiation.

P3503Transcriptome changes in atrial myocytes during the transition from a proliferative into a contractile phenotype and vice versa

Background iAM-1 cells are conditionally immortalized neonatal rat atrial myocytes allowing toggling between proliferative and contractile phenotypes by a single-component change in culture medium composition. In the absence of proliferation stimuli, the cells synchronously differentiate into functional cardiomyocytes. Following re-expression of the immortalization factor, the fully differentiated iAM-1 cells dedifferentiate and start to proliferate again. Purpose The aim of our study was to investigate the changes in gene expression profile in iAM-1 cells during one round of cardiac differentiation and dedifferentiation in order to identify potential (new) regulators of atrial myocyte differentiation and proliferation. Methods RNA sequencing was performed on iAM-1 cells at 9 time points during one cycle of cardiomyogenic differentiation and dedifferentiation (20 million 150-bp paired-end reads per sample, 4 samples per time point). The resulting sequence data were analysed by EdgeR. Hierarchical clustering and principle component analysis were performed in R. GO category enrichment was determined using DAVID. Results Approximately 13,000 genes were extracted from the RNA sequencing analysis. In general, dynamic changes in mRNA levels during the transition from a proliferative into a contractile phenotype opposed those that occurred when differentiated iAM-1 were re-exposed to proliferation stimuli. These inverse trends were most evident for genes involved in cell cycle progression, DNA replication, sarcomere formation and cardiac contraction. Moreover, the RNA-SEQ data allowed us to make a distinction between genes contributing to the early and late phases of cardiomyogenic differentiation and dedifferentiation and to identify similarities and differences in the transcriptional programs underlying the cardiomyogenic differentiation of iAM-1 cells versus those of embryonic stem cells and induced pluripotent stem cells. The transcriptome analysis also unveiled several genes with potentially important and previously unrecognized roles in cardiomyocyte differentiation and proliferation. iAM-1 differentiation and dedifferention Conclusions Due to their ability to homogenously and synchronously differentiate and dedifferentiate, iAM-1 cells offer unique new insights into the transcriptional regulation of cardiomyocyte differentiation and proliferation.

Alternating Differentiation and Dedifferentiation between Mature Osteoblasts and Osteocytes

Osteocytes are terminally differentiated osteoblasts embedded in the bone matrix. Evidence indicates that cells in the mesenchymal lineage possess plasticity. However, whether or not osteocytes have the capacity to dedifferentiate back into osteoblasts is unclear. This study aimed to clarify the dedifferentiation potential of osteocytes. Mouse calvarial osteoblasts were isolated and maintained in normal two-dimensional (2D) or collagen gel three-dimensional (3D) cultures. In 2D cultures, osteoblasts exhibited a typical fibroblast-like shape with high Alpl and minimal Sost, Fgf23, and Dmp1 expression and osteoblasts formed mineralised nodules. When these osteoblasts were transferred into 3D cultures, they showed a stellate shape with diminished cytoplasm and numerous long processes and expression of Alpl decreased while Sost, Fgf23, and Dmp1 were significantly increased. These cells were in cell cycle arrest and showed suppressed mineralisation, indicating that they were osteocytes. When these osteocytes were recovered from 3D cultures and cultured two-dimensionally again, they regained adequate cytoplasm and lost the long processes, resulting in a fibroblast-like shape. These cells showed high Alpl and low Sost, Fgf23, and Dmp1 expression with a high mineralisation capability, indicating that they were osteoblasts. This report shows that osteocytes possess the capacity to dedifferentiate back into mature osteoblasts without gene manipulation.

Evaluation of responses embryogenic Cycas revoluta thumb., from callus culture obtained in vitro

Processes cell differentiation and dedifferentiation are included in the development of biotechnology protocols to promote somatic embryogenesis as an alternative to the in vitro propagation of plants, somatic embryos may be an excellent strategy for both propagation and conservation of fossil species such as cycads. They were evaluated in vitro with different strategies, morphogenic responses associated with obtaining somatic embryos of C. revolute. calli of megagametophytes, subsequently subcultured in four combinations of basic salts of Murashige and Skoog (1962) MS, with the addition of benzyladenine (BA), and 2, dichlorophenoxyacetic (2,4-D) were used, and kinetin (K), and picloram. In the results, It was possible to characterize potentially embryogenic callus, evaluating the levels of both cellular differentiation, necrosis, texture and color; and increases mass or weight considered to start differentiation or proembryogenic or globular type. Calli were subcultured in a medium containing MS salts, incorporating abscisic acid (ABA) in 0, 0.38, 1.13, 3.78 and 5.67 uM doses influenced both the production and maturation of somatic embryos. Embryonic structures, presented a pink coloration characteristic strongly associated towards maturity. The effect of combinations of BA, Kin, 2,4-D, GA3 and ANA influenced the development and germination of mature somatic embryos. And the combination of 1.36 mM 2,4-D+4.44 uM BA promoted the appearance of calluses with a compact texture, characteristic related to their embryogenic potential. The purpose of this research in Cycas sp was to contribute to the study of the in vitro morphogenic responses of this group of plants. And somatic embryogenesis, will allow the obtaining and multiplication as well as its preservation of Cycas sp. Gender that is evolutionary very important