1,720,961 research outputs found
The Efficiency of In Vitro Differentiation of Primate iPSCs into Cardiomyocytes Depending on Their Cell Seeding Density and Cell Line Specificity
No full textA thorough characterization of induced pluripotent stem cells (iPSCs) used with in vitro models or therapeutics is essential. Even iPSCs derived from a single donor can exhibit variability within and between cell lines, which can lead to heterogeneity in results and hinder the promising future of cell replacement therapies. In this study, the cell seeding density of human and rhesus monkey iPSCs was tested to maximize the cell line-specific yield of the generated cardiomyocytes. We found that, despite using the same iPSC generation and differentiation protocols, the cell seeding density for the cell line-specific best differentiation efficiency could differ by a factor of four for the four cell lines used here. In addition, the cell lines showed differences in the range of cell seeding densities that they could tolerate without the severe loss of differentiation efficiency. Overall, our data show that the cell seeding density is a critical parameter for the differentiation inefficiency of primate iPSCs to cardiomyocytes and that iPSCs generated with the same episomal approach still exhibit considerable heterogeneity. Therefore, individual characterization of iPSC lines is required, and functional comparability with in vivo processes must be ensured to warrant the translatability of in vitro research with iPSCs
Transgene-Free Cynomolgus Monkey iPSCs Generated under Chemically Defined Conditions
No full textNon-human primates (NHPs) are pivotal animal models for translating novel cell replacement therapies into clinical applications, including validating the safety and efficacy of induced pluripotent stem cell (iPSC)-derived products. Preclinical development and the testing of cell-based therapies ideally comprise xenogeneic (human stem cells into NHPs) and allogenic (NHP stem cells into NHPs) transplantation studies. For the allogeneic approach, it is necessary to generate NHP-iPSCs with generally equivalent quality to the human counterparts that will be used later on in patients. Here, we report the generation and characterization of transgene- and feeder-free cynomolgus monkey (Macaca fascicularis) iPSCs (Cyno-iPSCs). These novel cell lines have been generated according to a previously developed protocol for the generation of rhesus macaque, baboon, and human iPSC lines. Beyond their generation, we demonstrate the potential of the novel Cyno-iPSCs to differentiate into two clinically relevant cell types, i.e., cardiomyocytes and neurons. Overall, we provide a resource of novel iPSCs from the most frequently used NHP species in the regulatory testing of biologics and classical pharmaceutics to expand our panel of iPSC lines from NHP species with high relevance in preclinical testing and translational research
Generation of marmoset primordial germ cell–like cells under chemically defined conditions
No full textPrimordial germ cells (PGCs) are the embryonic precursors of sperm and oocytes, which transmit genetic/epigenetic information across generations. Mouse PGC and subsequent gamete development can be fully reconstituted in vitro, opening up new avenues for germ cell studies in biomedical research. However, PGCs show molecular differences between rodents and humans. Therefore, to establish an in vitro system that is closely related to humans, we studied PGC development in vivo and in vitro in the common marmoset monkey
Callithrix jacchus
(
cj
). Gonadal cjPGCs at embryonic day 74 express SOX17, AP2Ɣ, BLIMP1, NANOG, and OCT4A, which is reminiscent of human PGCs. We established transgene-free induced pluripotent stem cell (cjiPSC) lines from foetal and postnatal fibroblasts. These cjiPSCs, cultured in defined and feeder-free conditions, can be differentiated into precursors of mesendoderm and subsequently into cjPGC-like cells (cjPGCLCs) with a transcriptome similar to human PGCs/PGCLCs. Our results not only pave the way for studying PGC development in a non-human primate in vitro under experimentally controlled conditions, but also provide the opportunity to derive functional marmoset gametes in future studies.Alexander von Humboldt-Stiftung http://dx.doi.org/10.13039/100005156German Centre for Cardiovascular Research 100010447Klaus Tschira Stiftung http://dx.doi.org/10.13039/501100007316International Max Planck Research School for Genome ScienceInternational Max Planck Research School for Molecular Biolog
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Hegel’s Concept of Action between Deflationary Approaches and The Science of Logic
Full text linkThe research in this paper attempts to outline the connection between Hegel’s concept of action and the contemporary philosophy of action. Hegel’s concept of action has some features in common with the ideas of analytical philosophers, and might open unexpected integration of these different philosophical traditions, which would contribute to the development of both of them. A brief overview of ways to comprehend Hegel’s concept of action (from Taylor to Brandom) shows that the cause of ambiguous understandings of this concept lies in the complexity of Hegel’s approach. The following article highlights the tension between “deflationary” interpretations and the complexity of Hegel´s original approach. Further, by revisiting the Section “Teleology” in Hegel’s Science of Logic, the article illustrates how deflationary interpretations of human action can be improved, so that they are topical for both contemporary practical philosophy and the philosophy of action, beyond the unnecessary split between analytical vs. continental philosophy. Such concepts as “purpose” and “mediation” become crucial, as they have sociological and normative extensions in Hegel’s Philosophy of Right, as discussed in the last Section of this article
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Characterization of testosterone and androgen receptor action in human and rhesus macaque heart muscle cells
Full text linkAndrogens are sex steroid hormones that influence various processes in reproductive tissues and peripheral organs. Their lipophilic nature enables free diffusion through the plasma membrane. In the cytoplasm, testosterone (T) binds to its receptor, the androgen receptor (AR), and the complex then translocates to the nucleus for activation or inhibition of gene expression. Although the effects of androgens are studied greatly in healthy and diseased reproductive tissues, little is known about their cellular and molecular action in the cardiovascular system. Clinical research reported the impact of high and low T levels on the human heart and vasculature, but the data are currently conflicting. Additionally, most of the molecular and cellular processes triggered by androgens in heart muscle cells were researched using rodents. These models vastly contributed to our understanding of biological processes, though are partially limited due to differences in heart physiology to humans. This work focused on studying the impact of male physiological (25 nM) and supraphysiological (100 nM) concentrations of T on primate cardiomyocytes (CMs) of human and rhesus macaque origin. For the first time, AR was detected in CM nuclei of male rhesus macaque tissue. Notably, no signal was detected in female heart cells. For further in vitro studies we used an induced pluripotent stem cell (iPSC) model. AR was detected in human and rhesus macaque iPSCs and was induced and translocated by T. A directed cardiac differentiation protocol was optimized and used to generate CMs from male and female human and rhesus macaque cell lines. Non-treated cells showed cytoplasmic AR staining while T-treated cells displayed mostly nuclear signals. T treatment induced AR abundance in male rhesus iPSCs and iPSC-CMs. Interestingly, we detected an AR-V7 isoform with no T-binding capabilities in human iPSC-CMs and human left ventricular tissue. Since T may also exhibit AR-independent action, we generated a clonal AR knock-out (KO) human male iPSC line to investigate AR-independent effects. Further analysis of the AR KO cell line showed fewer CMs generated after differentiation, a higher proliferation rate, and a more disorganized contractile apparatus compared with wild-type (WT) cells. The analysis of differentially expressed genes in KO and WT cells further highlighted a more immature state of KO CMs. While 24 hours of T treatment resulted in a decrease in Ca2+ current density, 48 hours of exposure did not result in significant changes between treated and non- treated groups of WT cells. Overall, the data has shown a more drastic effect of the AR KO itself than T treatment. That is why we hypothesized T conversion to other androgens. LC- MS/MS analysis demonstrated low levels of T in cell culture media 48 hours after T addition confirming our assumption. Moreover, androstenedione, a weaker androgen than T, was detected in human samples, but almost none in rhesus. In conclusion, this work demonstrates relevant effects of the T / AR system on proliferation, cytoskeleton organization, electrophysiological parameters, and gene expression of primate CMs.2024-04-0
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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