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1
Joly, Aurélia, und Raphaël Rousset. „Tissue Adaptation to Environmental Cues by Symmetric and Asymmetric Division Modes of Intestinal Stem Cells“. International Journal of Molecular Sciences 21, Nr. 17 (02.09.2020): 6362. http://dx.doi.org/10.3390/ijms21176362.
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Tissues must adapt to the different external stimuli so that organisms can survive in their environments. The intestine is a vital organ involved in food processing and absorption, as well as in innate immune response. Its adaptation to environmental cues such as diet and biotic/abiotic stress involves regulation of the proliferative rate and a switch of division mode (asymmetric versus symmetric) of intestinal stem cells (ISC). In this review, we outline the current comprehension of the physiological and molecular mechanisms implicated in stem cell division modes in the adult Drosophila midgut. We present the signaling pathways and polarity cues that control the mitotic spindle orientation, which is the terminal determinant ensuring execution of the division mode. We review these events during gut homeostasis, as well as during its response to nutrient availability, bacterial infection, chemical damage, and aging. JNK signaling acts as a central player, being involved in each of these conditions as a direct regulator of spindle orientation. The studies of the mechanisms regulating ISC divisions allow a better understanding of how adult stem cells integrate different signals to control tissue plasticity, and of how various diseases, notably cancers, arise from their alterations.
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Kim, K. M., T. Ishigami, D. Hata, K. Yamaoka, M. Mayumi und H. Mikawa. „Regulation of cell division of mature B cells by ionomycin and phorbol ester.“ Journal of Immunology 148, Nr. 6 (15.03.1992): 1797–803. http://dx.doi.org/10.4049/jimmunol.148.6.1797.
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Abstract The growth of a human B lymphoma cell line B104, an experimental model for mature B cells, was inhibited by ionomycin but not 12-O-tetradecanoylphorbol-13-acetate (TPA). Ionomycin inhibited B104 cells from entering into the M phase of the cell cycle without affecting DNA synthesis. The inhibition of cell division of B104 cells by ionomycin occurred within 24 h after stimulation. Because such a mode of action resembles that of anti-IgM antibodies, signals transduced by Ca2+ may be responsible for the inhibition of cell division of B104 cells by anti-IgM antibodies. Indeed, EGTA suppressed the inhibition of cell division of B104 cells caused not only by ionomycin, but also by anti-IgM antibody. Although TPA itself did not have any ability to promote the growth of B104 cells, it could cancel the inhibition of cell division of B104 cells by ionomycin and increase the proportion of B104 cells entering into the M phase of the cell cycle. Staphylococcus aureus Cowan I causes the greatest proliferation of normal human peripheral blood B cells during the period from 48 to 72 h after stimulation. When ionomycin was added to S. aureus Cowan I-stimulated peripheral blood B cells at 48 h of culture, it inhibited cell division during this period without affecting DNA synthesis. In the presence of TPA, this activity of ionomycin was suppressed, and the proportion of M-phase cells increased. These results suggest that cell division of mature B cells is regulated by the signals mediated by Ca2+ and protein kinase C in a mode quite different from that of regulation of DNA synthesis.
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Fischer, Jan, und Simon Guy. „Re-interpreting Regulations: Architects as Intermediaries for Low-carbon Buildings“. Urban Studies 46, Nr. 12 (16.10.2009): 2577–94. http://dx.doi.org/10.1177/0042098009344228.
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Regulations are highly influential in shaping urban places and architectural form. This paper investigates the impact of changing regulation on the working practices of architects. First, it outlines how the building regulations have grown in scope and complexity, especially with regard to energy regulations. Secondly, the relationship of regulation and design is explored, showing a shift from a dialectic of constraint and autonomy to one of interpretation of pathways. This is partly linked to performance-based regulation and weak state enforcement. Thirdly, the response of architects to this emerging mode of design is identified. The division of labour in the design process changes, with the architect focusing increasingly on intermediation. Finally, opportunities and threats to architects and their role are examined.
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Lei, Jinzhi, Simon A. Levin und Qing Nie. „Mathematical model of adult stem cell regeneration with cross-talk between genetic and epigenetic regulation“. Proceedings of the National Academy of Sciences 111, Nr. 10 (05.02.2014): E880—E887. http://dx.doi.org/10.1073/pnas.1324267111.
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Adult stem cells, which exist throughout the body, multiply by cell division to replenish dying cells or to promote regeneration to repair damaged tissues. To perform these functions during the lifetime of organs or tissues, stem cells need to maintain their populations in a faithful distribution of their epigenetic states, which are susceptible to stochastic fluctuations during each cell division, unexpected injury, and potential genetic mutations that occur during many cell divisions. However, it remains unclear how the three processes of differentiation, proliferation, and apoptosis in regulating stem cells collectively manage these challenging tasks. Here, without considering molecular details, we propose a genetic optimal control model for adult stem cell regeneration that includes the three fundamental processes, along with cell division and adaptation based on differential fitnesses of phenotypes. In the model, stem cells with a distribution of epigenetic states are required to maximize expected performance after each cell division. We show that heterogeneous proliferation that depends on the epigenetic states of stem cells can improve the maintenance of stem cell distributions to create balanced populations. A control strategy during each cell division leads to a feedback mechanism involving heterogeneous proliferation that can accelerate regeneration with less fluctuation in the stem cell population. When mutation is allowed, apoptosis evolves to maximize the performance during homeostasis after multiple cell divisions. The overall results highlight the importance of cross-talk between genetic and epigenetic regulation and the performance objectives during homeostasis in shaping a desirable heterogeneous distribution of stem cells in epigenetic states.
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Han, Dongchu, und Mianfang Liu. „How Does the Digital Economy Empower Green Development? From the Perspective of the Division of Labor in New Classical Economics“. Sustainability 14, Nr. 23 (26.11.2022): 15740. http://dx.doi.org/10.3390/su142315740.
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The rise of the digital economy provides an alternative path for global green development. On the basis of analyzing the connotations of green development, digital economy and division of labor, this paper studies the theoretical mechanisms of the digital economy empowering green development; this is based on the division of labor thought of as the new classical economics. From the research results, it can be seen that the digital economy, through technological change, is conducive to the improvement of transaction efficiency and the evolution of the division of labor model. Under the dual role of the government’s green system and the market regulation mechanism, it promotes the transaction from the “black division of labor” mode to the “green division of labor” mode, thereby empowering green development. The impact of the digital economy on the level of green development is not single linear. This paper creatively analyzes the theoretical mechanisms of the digital economy empowering green development, from the perspective of the division of labor. These research results have good theoretical value and practical significance for promoting the sustainable development of the global economy.
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Ali Azam Khan, Md, und Mohammad Ali Choudhury. „Efficient Voltage Regulation with Modified Hybrid SEPIC DC-DC-Converter“. MATEC Web of Conferences 160 (2018): 02004. http://dx.doi.org/10.1051/matecconf/201816002004.
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Switch mode dc-dc converters are attractive for their small size, ease of control and efficient power conversion. Output voltage is regulated by duty cycle control of semiconductor switch of switch mode dc-dc converters. The voltage gain and efficiency of practical switching regulators deviate from ideal values at extreme duty cycles. Also, desired gain /attenuation is not achievable at high/low duty cycles. In applications where high gain or high attenuation of voltage is desired with acceptable energy conversion efficiency, hybrid dc-dc switching converters are used. Hybrid dc-dc converters are combination of voltage multiplier/division circuit with appropriate SMPS circuits. By incorporating voltage multiplier/division cell with conventional SEPIC converters, desired voltage gain (either very low or very high) may be achieved at acceptable energy conversion efficiency. In the present work with an aim to attain very high voltage gain by conventional SEPIC topologies, a new voltage multiplier cell consisting of multiple inductors and diodes is proposed.
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Sakai, Satoshi, Nobumichi Ohoka, Kikuo Onozaki, Masatoshi Kitagawa, Makoto Nakanishi und Hidetoshi Hayashi. „Dual Mode of Regulation of Cell Division Cycle 25 A Protein by TRB3“. Biological & Pharmaceutical Bulletin 33, Nr. 7 (2010): 1112–16. http://dx.doi.org/10.1248/bpb.33.1112.
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Bhargava, Pushpa M., und Sushil A. Chandani. „Regulation of cell division and malignant transformation“. Bioscience Reports 8, Nr. 6 (01.12.1988): 519–29. http://dx.doi.org/10.1007/bf01117330.
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The problem of regulation of cell division is essentially a problem of understanding regulation of transition from the resting state of a cell to the dividing state and vice versa. In malignancy the ability to revert back to a normal resting state is impaired. A model is presented which attempts to explain the control of the above transitions through control of uptake of essential nutrients by a transport-inhibitory protein. Experimental evidence in favour of the model is given.
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Tie, Warwick. „The ‘Correction’ of Community Crime Control: A Legal-Pluralist Interpretation“. Australian & New Zealand Journal of Criminology 29, Nr. 3 (Dezember 1996): 282–98. http://dx.doi.org/10.1177/000486589602900306.
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The New Zealand Corrections Division has historically used the voluntary social work sector as a means of regulating criminality ‘at a distance’. Shifts in the modes through which the Division has related to the voluntary sector are analyzed here using Santos' form of legal-pluralist theory. That theory suggests that innovative forms of legal regulation are created when divergent modes of law interpenetrate one another. These new modes of legal power then attempt to regulate sociality by constructing the subjectivity of those with which they interact. This article suggests that the Corrections Division is itself characterised by dual forms of subjectivity, namely communitarian and proceduralist. The tension between these has become evident as the Division has sought to inculcate a proceduralist subjectivity within the voluntary sector, so as to construct voluntary sector agencies as self-regulating subjects. The tension exists between the Division's need to use the voluntary sector as a means by which it can regulate criminality, and to construct and respect that sector as an autonomous entity. Moreover, the imposition of a proceduralist subjectivity, because it is an imposition, has the potential to diminish the ability of those agencies to control crime and/or to critique its social construction.
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Palani, Saravanan, Darius V. Köster, Tomoyuki Hatano, Anton Kamnev, Taishi Kanamaru, Holly R. Brooker, Juan Ramon Hernandez-Fernaud et al. „Phosphoregulation of tropomyosin is crucial for actin cable turnover and division site placement“. Journal of Cell Biology 218, Nr. 11 (09.10.2019): 3548–59. http://dx.doi.org/10.1083/jcb.201809089.
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Tropomyosin is a coiled-coil actin binding protein key to the stability of actin filaments. In muscle cells, tropomyosin is subject to calcium regulation, but its regulation in nonmuscle cells is not understood. Here, we provide evidence that the fission yeast tropomyosin, Cdc8, is regulated by phosphorylation of a serine residue. Failure of phosphorylation leads to an increased number and stability of actin cables and causes misplacement of the division site in certain genetic backgrounds. Phosphorylation of Cdc8 weakens its interaction with actin filaments. Furthermore, we show through in vitro reconstitution that phosphorylation-mediated release of Cdc8 from actin filaments facilitates access of the actin-severing protein Adf1 and subsequent filament disassembly. These studies establish that phosphorylation may be a key mode of regulation of nonmuscle tropomyosins, which in fission yeast controls actin filament stability and division site placement.
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Merk, Daniel J., Pengcheng Zhou, Samuel M. Cohen, Maria F. Pazyra-Murphy, Grace H. Hwang, Kristina J. Rehm, Jose Alfaro et al. „The Eya1 Phosphatase Mediates Shh-Driven Symmetric Cell Division of Cerebellar Granule Cell Precursors“. Developmental Neuroscience 42, Nr. 5-6 (2020): 170–86. http://dx.doi.org/10.1159/000512976.
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During neural development, stem and precursor cells can divide either symmetrically or asymmetrically. The transition between symmetric and asymmetric cell divisions is a major determinant of precursor cell expansion and neural differentiation, but the underlying mechanisms that regulate this transition are not well understood. Here, we identify the Sonic hedgehog (Shh) pathway as a critical determinant regulating the mode of division of cerebellar granule cell precursors (GCPs). Using partial gain and loss of function mutations within the Shh pathway, we show that pathway activation determines spindle orientation of GCPs, and that mitotic spindle orientation correlates with the mode of division. Mechanistically, we show that the phosphatase Eya1 is essential for implementing Shh-dependent GCP spindle orientation. We identify atypical protein kinase C (aPKC) as a direct target of Eya1 activity and show that Eya1 dephosphorylates a critical threonine (T410) in the activation loop. Thus, Eya1 inactivates aPKC, resulting in reduced phosphorylation of Numb and other components that regulate the mode of division. This Eya1-dependent cascade is critical in linking spindle orientation, cell cycle exit and terminal differentiation. Together these findings demonstrate that a Shh-Eya1 regulatory axis selectively promotes symmetric cell divisions during cerebellar development by coordinating spindle orientation and cell fate determinants.
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Chouchane, Malek, und Claudia Petritsch. „STEM-01. INVESTIGATING ASPM FUNCTION IN REGULATION OF CELL DIVISION MODE OF OLIGODENDROCYTE PROGENITOR CELLS“. Neuro-Oncology 19, suppl_6 (November 2017): vi226. http://dx.doi.org/10.1093/neuonc/nox168.919.
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Clark, Natalie M., Adam P. Fisher, Barbara Berckmans, Lisa Van den Broeck, Emily C. Nelson, Thomas T. Nguyen, Estefano Bustillo-Avendaño et al. „Protein complex stoichiometry and expression dynamics of transcription factors modulate stem cell division“. Proceedings of the National Academy of Sciences 117, Nr. 26 (15.06.2020): 15332–42. http://dx.doi.org/10.1073/pnas.2002166117.
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Stem cells divide and differentiate to form all of the specialized cell types in a multicellular organism. In theArabidopsisroot, stem cells are maintained in an undifferentiated state by a less mitotically active population of cells called the quiescent center (QC). Determining how the QC regulates the surrounding stem cell initials, or what makes the QC fundamentally different from the actively dividing initials, is important for understanding how stem cell divisions are maintained. Here we gained insight into the differences between the QC and the cortex endodermis initials (CEI) by studying the mobile transcription factor SHORTROOT (SHR) and its binding partner SCARECROW (SCR). We constructed an ordinary differential equation model of SHR and SCR in the QC and CEI which incorporated the stoichiometry of the SHR-SCR complex as well as upstream transcriptional regulation of SHR and SCR. Our model prediction, coupled with experimental validation, showed that high levels of the SHR-SCR complex are associated with more CEI division but less QC division. Furthermore, our model prediction allowed us to propose the putative upstream SHR regulators SEUSS and WUSCHEL-RELATED HOMEOBOX 5 and to experimentally validate their roles in QC and CEI division. In addition, our model established the timing of QC and CEI division and suggests that SHR repression of QC division depends on formation of the SHR homodimer. Thus, our results support that SHR-SCR protein complex stoichiometry and regulation of SHR transcription modulate the division timing of two different specialized cell types in the root stem cell niche.
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Adamus, Rafał. „Podział spółki przez wyodrębnienie“. Prawo w Działaniu 52 (2022): 123–42. http://dx.doi.org/10.32041/pwd.5206.
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This study concerns the introduction of a new type of division into the domestic legal order – the so-called division by separation, as part of the wider problem of cross-border mobility of companies, regulated in Directive 2017/1132 as amended by Directive 2019/2121. The current legal regulation of the Code of Commercial Companies does not know the structure of division by separation, which is used to build corporate vertical relations. All division modes known to Polish commercial law are horizontal divisions. Meanwhile, as a result of the implementation of the directive in the cross-border dimension, it will be possible to make a cross-border division by separation also with the participation of Polish companies (i.e. companies subject to the Polish Commercial Companies Code). Failure to supplement the provisions of the Commercial Companies Code with the division by separation available to interested companies – under national procedures, without a cross-border element – would lead to the phenomenon of reverse discrimination. Reverse discrimination is a legal phenomenon that is unfavorable both economically and socially. Due to the principle of numerus clausus of transformation procedures and due to their regulation mostly by mandatory norms (iuris cogentis), it would not be possible to apply such a procedure without an explicit normative basis. Division by separation may become an interesting instrument for building vertical holding structures (and, in effect, even multi-stage), an alternative to a simple contribution in kind to a daughter company. Therefore, the study presents in detail the essence of the division by separation.
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Wyatt, Tom P. J., Andrew R. Harris, Maxine Lam, Qian Cheng, Julien Bellis, Andrea Dimitracopoulos, Alexandre J. Kabla, Guillaume T. Charras und Buzz Baum. „Emergence of homeostatic epithelial packing and stress dissipation through divisions oriented along the long cell axis“. Proceedings of the National Academy of Sciences 112, Nr. 18 (23.04.2015): 5726–31. http://dx.doi.org/10.1073/pnas.1420585112.
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Cell division plays an important role in animal tissue morphogenesis, which depends, critically, on the orientation of divisions. In isolated adherent cells, the orientation of mitotic spindles is sensitive to interphase cell shape and the direction of extrinsic mechanical forces. In epithelia, the relative importance of these two factors is challenging to assess. To do this, we used suspended monolayers devoid of ECM, where divisions become oriented following a stretch, allowing the regulation and function of epithelial division orientation in stress relaxation to be characterized. Using this system, we found that divisions align better with the long, interphase cell axis than with the monolayer stress axis. Nevertheless, because the application of stretch induces a global realignment of interphase long axes along the direction of extension, this is sufficient to bias the orientation of divisions in the direction of stretch. Each division redistributes the mother cell mass along the axis of division. Thus, the global bias in division orientation enables cells to act collectively to redistribute mass along the axis of stretch, helping to return the monolayer to its resting state. Further, this behavior could be quantitatively reproduced using a model designed to assess the impact of autonomous changes in mitotic cell mechanics within a stretched monolayer. In summary, the propensity of cells to divide along their long axis preserves epithelial homeostasis by facilitating both stress relaxation and isotropic growth without the need for cells to read or transduce mechanical signals.
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Shalapyonok, Alexi, Robert J. Olson und Ludmila S. Shalapyonok. „Ultradian Growth inProchlorococcus spp“. Applied and Environmental Microbiology 64, Nr. 3 (01.03.1998): 1066–69. http://dx.doi.org/10.1128/aem.64.3.1066-1069.1998.
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ABSTRACT Species of the widespread marine prokaryoteProchlorococcus exhibited ultradian growth (faster than 1 division per day) both in situ and in culture, even though cell division is strictly phased to the light-dark cycle. Under optimal conditions a second DNA replication and cell division closely followed, but did not overlap with, the first division. The timing of cell cycle events was not affected by light intensity or duration, suggesting control by a light-triggered timer or circadian clock rather than by completion of a light-dependent assimilation phase. This mode of ultradian growth has not been observed previously and poses new questions about the regulation of cellular rhythms in prokaryotes. In addition, it implies that conclusions regarding the lack of nutrient limitation of Prochlorococcus in the open ocean, which were based on the appearance that cells were growing at their maximal rate, need to be reconsidered.
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Banwarth-Kuhn, Mikahl, Kevin Rodriguez, Christian Michael, Calvin-Khang Ta, Alexander Plong, Eric Bourgain-Chang, Ali Nematbakhsh et al. „Combined computational modeling and experimental analysis integrating chemical and mechanical signals suggests possible mechanism of shoot meristem maintenance“. PLOS Computational Biology 18, Nr. 6 (21.06.2022): e1010199. http://dx.doi.org/10.1371/journal.pcbi.1010199.
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Stem cell maintenance in multilayered shoot apical meristems (SAMs) of plants requires strict regulation of cell growth and division. Exactly how the complex milieu of chemical and mechanical signals interact in the central region of the SAM to regulate cell division plane orientation is not well understood. In this paper, simulations using a newly developed multiscale computational model are combined with experimental studies to suggest and test three hypothesized mechanisms for the regulation of cell division plane orientation and the direction of anisotropic cell expansion in the corpus. Simulations predict that in the Apical corpus, WUSCHEL and cytokinin regulate the direction of anisotropic cell expansion, and cells divide according to tensile stress on the cell wall. In the Basal corpus, model simulations suggest dual roles for WUSCHEL and cytokinin in regulating both the direction of anisotropic cell expansion and cell division plane orientation. Simulation results are followed by a detailed analysis of changes in cell characteristics upon manipulation of WUSCHEL and cytokinin in experiments that support model predictions. Moreover, simulations predict that this layer-specific mechanism maintains both the experimentally observed shape and structure of the SAM as well as the distribution of WUSCHEL in the tissue. This provides an additional link between the roles of WUSCHEL, cytokinin, and mechanical stress in regulating SAM growth and proper stem cell maintenance in the SAM.
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Curtis, Natalie L., Gian Filippo Ruda, Paul Brennan und Victor M. Bolanos-Garcia. „Deregulation of Chromosome Segregation and Cancer“. Annual Review of Cancer Biology 4, Nr. 1 (09.03.2020): 257–78. http://dx.doi.org/10.1146/annurev-cancerbio-030419-033541.
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The mitotic spindle assembly checkpoint (SAC) is an intricate cell signaling system that ensures the high fidelity and timely segregation of chromosomes during cell division. Mistakes in this process can lead to the loss, gain, or rearrangement of the genetic material. Gross chromosomal aberrations are usually lethal but can cause birth and development defects as well as cancer. Despite advances in the identification of SAC protein components, important details of the interactions underpinning chromosome segregation regulation remain to be established. This review discusses the current understanding of the function, structure, mode of regulation, and dynamics of the assembly and disassembly of SAC subcomplexes, which ultimately safeguard the accurate transmission of a stable genome to descendants. We also discuss how diverse oncoviruses take control of human cell division by exploiting the SAC and the potential of this signaling circuitry as a pool of drug targets to develop effective cancer therapies.
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Firmansyah, Ade Arif, Yhannu Setyawan und Malicia Evendia. „RESPONSIVE LAW MODEL FOR REALIZING FOOD SOVEREIGNTY REGENCY“. Constitutional Law Society 1, Nr. 1 (02.04.2022): 41–49. http://dx.doi.org/10.36448/cls.v1i1.14.
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Data from the Ministry of Agrarian and Spatial Planning/National Land Agency in 2018 showed that the raw area of rice fields in Indonesia was only 7.1 million hectares (ha) or down compared to 2013 which was still 7.75 million hectares. This will of course have a negative impact onthe achievement of national food sovereignty vsi, coupled with the condition of regional agricultural regulations which are still sectoral and not comprehensive. By using a doctrinal approach, this paper aims todevelop a responsive legal model to create a food-sovereign district. The results of the study indicate that a responsive legal model to empower farmers and create food sovereignty districts is needed because so far regional regulations in the agricultural sector are still partial so that they have not fully supported the realization of the condition of food sovereignty. The targets to be realized, the scope of regulation, the scope, and direction of the regulation model of a responsive law-based food sovereignty district will contain three major parts, namely: the Agricultural Land Protection Division, the Farmer Protection and Empowerment Division, and the Irrigation Network Section, so that the realization of a sovereign district is realized. food can be achieved comprehensively.
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Xu, Yan, Peng Hu, Fengyang Zhang und Tao Zhou. „Distributed Generation Cluster Division Method Considering Frequency Regulation Response Speed“. Applied Sciences 14, Nr. 6 (13.03.2024): 2432. http://dx.doi.org/10.3390/app14062432.
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With the large-scale integration of distributed generation (DG), it is difficult to realize distribution network planning and operation under specific requirements using the traditional cluster division method based on a single criterion. To reduce the complexity of frequency regulation control strategies, this paper proposes a cluster division method that synthesizes structural and functional indexes. First, the ability of DG within a cluster to provide flexibility to the system is analyzed. Then, a cluster response speed model is proposed to cope with the frequency regulation of demand flexibility on shorter time scales. Based on the above analysis, this paper proposes a distributed generation cluster (DGC) frequency regulation response speed index. The combined electrical distance based on the impedance–power reserve (I–PR) is defined by considering the power reserve of each node of the system. The I–PR is weighted to the structural indexes to improve the division. Meanwhile, in order to enhance the convergence speed of the algorithm for the division process, an adaptive genetic algorithm (GA) based on the encoding method of the weighted network adjacency matrix is used. Finally, distributed generation cluster division is performed on two systems to verify the validity of the proposed indexes in this paper.
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Yang, Rong, Minglei Wang, Jia Wang, Xingxu Huang, Ru Yang und Wei-Qiang Gao. „Cell Division Mode Change Mediates the Regulation of Cerebellar Granule Neurogenesis Controlled by the Sonic Hedgehog Signaling“. Stem Cell Reports 5, Nr. 5 (November 2015): 816–28. http://dx.doi.org/10.1016/j.stemcr.2015.09.019.
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Darmawan, Ericka, Karunia Galih Permadani und Alfi Anjani. „The STAD learning model: Cognitive learning and self-regulation effects“. JPBIO (Jurnal Pendidikan Biologi) 8, Nr. 2 (30.11.2023): 186–95. http://dx.doi.org/10.31932/jpbio.v8i2.2398.
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The learning approach at MAN Temanggung is predominantly teacher-centered, neglecting the individual learning needs of students. Consequently, the cognitive learning outcomes of students remain subpar. Furthermore, self-regulation, a crucial psychological factor that impacts student learning outcomes, is not adequately addressed. This study aims to determine the effect of the Student Teams Achievement Division (STAD) learning model on students' cognitive learning outcomes and self-regulation on excretion system material at MAN Temanggung. The STAD learning model based on differentiated learning is applied to the experimental class. The applied differentiation learning is product differentiation. Data was collected using a pretest and post-test to measure cognitive learning outcomes and a questionnaire to measure self-regulation abilities. The results showed a significance value of 0.000 <0.005, meaning that the STAD learning model based on differentiation learning affects cognitive learning outcomes and students' self-regulation. Thus, the Student Teams Achievement Division (STAD) learning model based on differentiation learning significantly affects cognitive learning outcomes and students' self-regulation.
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Kovács, Zsuzsa, und Csaba Kálmán. „The role of self-regulation and perceived self-efficacy in adaptation to home-office work during the pandemic“. Journal of Adult Learning, Knowledge and Innovation 4, Nr. 2 (01.02.2022): 88–98. http://dx.doi.org/10.1556/2059.2021.00048.
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Abstract As a consequence of the unprecedented labor market circumstances that the prolonged Covid-19 pandemic brought about, organizations have faced challenges never seen before. One such challenge was the sudden ubiquity of working from home, which resulted in an intensive learning experience for employees and employers alike. While there is an increasing body of research on working from home in general, the perceived effectiveness of this mode of working is still under-researched. This niche provided the inspiration for us to investigate what factors might influence employees' self-efficacy in working from home arrangements. We conducted a mixed-methods case study by collecting both qualitative and quantitative data from 24 employees of a division of the Hungarian subsidiary of a chemical and consumer goods multinational. The purpose of our investigation was to gain a deeper understanding of perceived self-efficacy and self-regulation during the learning processes that the participants experienced under the new circumstances. Results suggest that the perceived high level of work-efficiency among the employees of the examined division was based on the firmly controlled work-division, trusting managers, as well as supportive and clear communication, which created space for autonomy in the adaptation process. The findings also revealed that self-reflection acted as a predictor of perceived work self-efficacy.
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Weber, Hans, Ute Heim, Sabine Golombek, Ljudmilla Borisjuk und Ulrich Wobus. „Assimilate uptake and the regulation of seed development“. Seed Science Research 8, Nr. 3 (September 1998): 331–46. http://dx.doi.org/10.1017/s0960258500004268.
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AbstractSeed development is a series of events involving cell division, followed by cell differentiation and storage activity In legume cotyledons, cell differentiation starts in certain regions and gradually spreads to other parts, thereby building up developmental gradients The entire process appears to be subject to metabolic control The high hexose state of the premature legume embryo as controlled by seed coat-specific invertases favours cell division Differentiation is initiated when hexose decreases and sucrose increases Seed development occurs in a close interaction with seed metabolism and transport processes Movement of photoassimilates from the sieve tubes to the unloading region of the maternal seed tissue is symplasmic and controlled by plasmodesmal passage Sucrose uptake into Vicia faba cotyledons is mediated by a H+-sucrose symporter located in the outer epidermis which generates transfer cells Formation of the sucrose uptake system is induced during the early to mid-cotyledon stage by tissue contact with the maternal seed coat and is controlled by carbohydrate availability In contrast, a hexose transporter gene is also expressed in epidermal cells covering younger, mitotically active regions of the cotyledons The sucrose uptake system apparently generates the high sucrose state immediately preceding the storage phase Sucrose specifically induces storage-associated differentiation processes indicating a specific sucrose-dependent signalling pathway operating in maturing cotyledons Moreover, the mode of sucrose uptake — apoplasmic movement into the epidermal cells with subsequent symplasmic transfer to the storage parenchyma cells — appears to control coordinated cotyledon development Unlike sucrose, amino acid transport into legume cotyledons is passive during early development but at later stages when large amounts of storage proteins are synthesized an additional active uptake system is established to ensure a sufficient supply
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Wang, Yicheng. „A Brief analysis of the Division of Labor Between College Counselors and Class Teachers“. International Journal of Education and Humanities 7, Nr. 2 (28.02.2023): 9–12. http://dx.doi.org/10.54097/ijeh.v7i2.5251.
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Homeroom teachers and counselors, as the main educators and organizers of college students' classes, play a crucial role in the collective construction of college students' classes and the generation of college talents. All colleges and universities have introduced relevant policies and regulations for the ideological and political education of college students and daily student management, and most colleges and universities have implemented the dual-track student management mode of counselor + class teacher. This paper will take Jiujiang University as an example to investigate the division of labor mode of counselor + class teacher in each secondary college, and combine the number of students, major Settings, and teacher conditions. The paper analyzes the scientificity and rationality of the division of labor mode between counselors and class teachers and puts forward some suggestions for improving the division of labor mode between different classes of counselors and class teachers.
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Michie, Katherine A., Leigh G. Monahan, Peter L. Beech und Elizabeth J. Harry. „Trapping of a Spiral-Like Intermediate of the Bacterial Cytokinetic Protein FtsZ“. Journal of Bacteriology 188, Nr. 5 (01.03.2006): 1680–90. http://dx.doi.org/10.1128/jb.188.5.1680-1690.2006.
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ABSTRACT The earliest stage in bacterial cell division is the formation of a ring, composed of the tubulin-like protein FtsZ, at the division site. Tight spatial and temporal regulation of Z-ring formation is required to ensure that division occurs precisely at midcell between two replicated chromosomes. However, the mechanism of Z-ring formation and its regulation in vivo remain unresolved. Here we identify the defect of an interesting temperature-sensitive ftsZ mutant (ts1) of Bacillus subtilis. At the nonpermissive temperature, the mutant protein, FtsZ(Ts1), assembles into spiral-like structures between chromosomes. When shifted back down to the permissive temperature, functional Z rings form and division resumes. Our observations support a model in which Z-ring formation at the division site arises from reorganization of a long cytoskeletal spiral form of FtsZ and suggest that the FtsZ(Ts1) protein is captured as a shorter spiral-forming intermediate that is unable to complete this reorganization step. The ts1 mutant is likely to be very valuable in revealing how FtsZ assembles into a ring and how this occurs precisely at the division site.
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Zhao, Jing, Zhihua Zhang, Hongdan Zhou, Zengfu Bai und Kun Sun. „The Study on Sea Buckthorn (Genus Hippophae L.) Fruit Reveals Cell Division and Cell Expansion to Promote Morphogenesis“. Plants 12, Nr. 5 (22.02.2023): 1005. http://dx.doi.org/10.3390/plants12051005.
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Due to its unique flavor and high antioxidant content, the sea buckthorn (genus Hippophae L.) fruit is increasingly favored by consumers. Developing from the perianth tube, the sea buckthorn fruit varies greatly among species in both size and shape. However, the cellular regulation mechanism of sea buckthorn fruit morphogenesis remains unclear. This study presents the growth and development patterns, morphological changes, and cytological observations of the fruits of three Hippophae species (H. rhamnoides ssp. sinensis, H. neurocarpa, and H. goniocarpa). The fruits were monitored every 10–30 days after anthesis (DAA) for six periods in their natural population on the eastern margin of the Qinghai-Tibet Plateau in China. The results showed that the fruits of H. rhamnoides ssp. sinensis and H. goniocarpa grew in a sigmoid mode, while H. neurocarpa grew in an exponential mode under the complex regulation of cell division and cell expansion. In addition, cellular observations showed that the mesocarp cells of H. rhamnoides ssp. sinensis and H. goniocarpa were larger in the area with prolonged cell expansion activity, while H. neurocarpa had a higher cell division rate. Elongation and proliferation of the mesocarp cells were found to be essential factors affecting the formation of fruit morphology. Finally, we established a preliminary cellular scenario for fruit morphogenesis in the three species of sea buckthorn. Fruit development could be divided into a cell division phase and a cell expansion phase with an overlap between 10 and 30 DAA. In particular, the two phases in H. neurocarpa showed an additional overlap between 40 and 80 DAA. The description of the sea buckthorn fruit’s transformation and its temporal order may provide a theoretical basis to explore the growth mechanism of fruits and regulate their size through certain cultivation techniques.
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Anderson, Hilary, und Vernon French. „Cell division during intercalary regeneration in the cockroach leg“. Development 90, Nr. 1 (01.12.1985): 57–78. http://dx.doi.org/10.1242/dev.90.1.57.
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In a series of grafting operations on cockroach legs, epidermal cells from different positions or from the same position on the circumference of the femur were placed together. Where cells from different positions were confronted, new cuticular structures corresponding to the positions which would normally have lain between them were formed during the following moults. At the control junctions, where cells from the same positions were placed together, no new structures were formed. Grafted legs were examined histologically at various times after the operation. The events following grafting fell into four phases: wound healing — when epidermal cells migrated over the wound to re-establish epidermal continuity and cells adjacent to the wound divided to compensate for cell emigration; intercalation — when cell divisions took place at the host-graft borders where there was a positional discrepancy; proliferation — when the general growth of the epidermis occurred by widespread cell division; cuticle secretion — when apolysis occurred, cell division ceased, and cuticle secretion began. The results show that intercalary regeneration is associated with local cell division at the graft-host borders, and that these divisions are not confined to the normal proliferative phase of the moult cycle, but begin much earlier in the cycle, as soon as wound healing is complete. These results support epimorphic models (such as the Polar Coordinate Model) of pattern regulation, where change of positional value is tied to cell division, but they do not discount the possibility of a limited initial morphallactic phase.
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Voß, Yannik, Severina Klaus, Julien Guizetti und Markus Ganter. „Plasmodium schizogony, a chronology of the parasite’s cell cycle in the blood stage“. PLOS Pathogens 19, Nr. 3 (02.03.2023): e1011157. http://dx.doi.org/10.1371/journal.ppat.1011157.
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Malaria remains a significant threat to global health, and despite concerted efforts to curb the disease, malaria-related morbidity and mortality increased in recent years. Malaria is caused by unicellular eukaryotes of the genus Plasmodium, and all clinical manifestations occur during asexual proliferation of the parasite inside host erythrocytes. In the blood stage, Plasmodium proliferates through an unusual cell cycle mode called schizogony. Contrary to most studied eukaryotes, which divide by binary fission, the parasite undergoes several rounds of DNA replication and nuclear division that are not directly followed by cytokinesis, resulting in multinucleated cells. Moreover, despite sharing a common cytoplasm, these nuclei multiply asynchronously. Schizogony challenges our current models of cell cycle regulation and, at the same time, offers targets for therapeutic interventions. Over the recent years, the adaptation of advanced molecular and cell biological techniques have given us deeper insight how DNA replication, nuclear division, and cytokinesis are coordinated. Here, we review our current understanding of the chronological events that characterize the unusual cell division cycle of P. falciparum in the clinically relevant blood stage of infection.
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Luo, Zhiling, und Qi Yao. „Multi-Model-Based Predictive Control for Divisional Regulation in the Direct Air-Cooling Condenser“. Energies 15, Nr. 13 (30.06.2022): 4803. http://dx.doi.org/10.3390/en15134803.
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Flow distortions caused by ambient wind can have complex negative effects on the performance of direct air-cooling condensers, which use air as their cooling medium. A control-oriented model of the direct air-cooling condenser model, considering fan volumetric effectiveness and plume recirculation rate, was developed, and its linearization model was derived. The influences of fan volumetric effectiveness and plume recirculation rate on backpressure were analyzed, and the optimal backpressure was calculated. To improve both the transient performance and steady-state energy saving of the condenser, a multi-model-based predictive control strategy was proposed to divisionally adjust the fan array. Four division schemes of the direct air-cooling fan array constituted the local models, and in each division scheme, axial fans were divided into three groups according to the wind direction: windward fans, leeward fans, and other fans. The simulation results showed that the turbine backpressure can be increased by 15 kPa under the influence of plume recirculation and the reduction of the fan volumetric efficiency. The fan division adjustment strategy can achieve satisfactory control performance with switching rules.
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Bizyaev, Anton. „REGULATION OF PUBLIC TRANSPORT IN ISRAEL“. Eastern Analytics, Nr. 3 (2020): 28–40. http://dx.doi.org/10.31696/2227-5568-2020-03-028-040.
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At the end of the 20th century massive wave of transport reforms produced a large variety of transport organization forms. Evolution of the regulator has played a key role in these changes. This paper studies the structure of transport regulation in Israel. I describe the structure of the regulator, division of authority between national and regional levels, operators’ involvement in transport planning (STO model), and competition. Then I discuss potential problems highlighted in the literature on Israeli transport regulation. The paper shows that the structure of the regulator combines government authorities with private company providing the expertise to the government in the field of reforms. This is a result of liberal reforms in Israel at the end of the 20th which included among its goals solving the issue of regulatory capture in Israeli transport sector. However, the division of authority has not been changed. Regional authorities still play a minor role in transportation policy compared to national regulator which might hinder the ability of the government to adapt and quickly respond to changes in the transportation market. Lastly, STO model has shown that almost all decisions in transport planning are made by government and not by transport companies. This distinguishes Israel from European practic delegating the ability to make decisions on tactical (and sometimes even strategic) level to transit operators.
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Huang, Rongsheng, und Jinzhi Lei. „Dynamics of gene expression with positive feedback to histone modifications at bivalent domains“. International Journal of Modern Physics B 32, Nr. 07 (05.03.2018): 1850075. http://dx.doi.org/10.1142/s0217979218500753.
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Experiments have shown that in embryonic stem cells, the promoters of many lineage-control genes contain “bivalent domains”, within which the nucleosomes possess both active (H3K4me3) and repressive (H3K27me3) marks. Such bivalent modifications play important roles in maintaining pluripotency in embryonic stem cells. Here, to investigate gene expression dynamics when there are regulations in bivalent histone modifications and random partition in cell divisions, we study how positive feedback to histone methylation/demethylation controls the transition dynamics of the histone modification patterns along with cell cycles. We constructed a computational model that includes dynamics of histone marks, three-stage chromatin state transitions, transcription and translation, feedbacks from protein product to enzymes to regulate the addition and removal of histone marks, and the inheritance of nucleosome state between cell cycles. The model reveals how dynamics of both nucleosome state transition and gene expression are dependent on the enzyme activities and feedback regulations. Results show that the combination of stochastic histone modification at each cell division and the deterministic feedback regulation work together to adjust the dynamics of chromatin state transition in stem cell regenerations.
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Olesnicky, Eugenia, und Ethan Wright. „Drosophila as a Model for Assessing the Function of RNA-Binding Proteins during Neurogenesis and Neurological Disease“. Journal of Developmental Biology 6, Nr. 3 (18.08.2018): 21. http://dx.doi.org/10.3390/jdb6030021.
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An outstanding question in developmental neurobiology is how RNA processing events contribute to the regulation of neurogenesis. RNA processing events are increasingly recognized as playing fundamental roles in regulating multiple developmental events during neurogenesis, from the asymmetric divisions of neural stem cells, to the generation of complex and diverse neurite morphologies. Indeed, both asymmetric cell division and neurite morphogenesis are often achieved by mechanisms that generate asymmetric protein distributions, including post-transcriptional gene regulatory mechanisms such as the transport of translationally silent messenger RNAs (mRNAs) and local translation of mRNAs within neurites. Additionally, defects in RNA splicing have emerged as a common theme in many neurodegenerative disorders, highlighting the importance of RNA processing in maintaining neuronal circuitry. RNA-binding proteins (RBPs) play an integral role in splicing and post-transcriptional gene regulation, and mutations in RBPs have been linked with multiple neurological disorders including autism, dementia, amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), Fragile X syndrome (FXS), and X-linked intellectual disability disorder. Despite their widespread nature and roles in neurological disease, the molecular mechanisms and networks of regulated target RNAs have been defined for only a small number of specific RBPs. This review aims to highlight recent studies in Drosophila that have advanced our knowledge of how RBP dysfunction contributes to neurological disease.
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Guo, Quan, Jun Hong, Jing Rong, Haiyan Ma, Mengnan Lv und Mengyang Wu. „Impact of Environmental Regulations on High-Quality Development of Energy: From the Perspective of Provincial Differences“. Sustainability 14, Nr. 18 (18.09.2022): 11712. http://dx.doi.org/10.3390/su141811712.
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Environmental regulation plays an important role in the green development of energy, and there are different classifications of environmental regulations in academic circles. This paper attempts to divide environmental regulation into “pure” formal environmental regulations and informal environmental regulations. By selecting the official statistical data samples of 30 provinces, autonomous regions and municipalities in China from 2005 to 2020, and by referring to the Malmquist productivity index method and the mediation effect model, we explore pure environmental regulations. By analyzing the influence mechanism of “pure” formal environmental regulations and informal environmental regulation on energy green development, it is concluded that: (1) Informal environmental regulations have direct and indirect roles in promoting the energy green development index. (2) There is a “U-shaped” relationship between “pure” formal environmental regulations and green energy development. Based on the above conclusions, relevant suggestions are put forward. At the same time, through this division of environmental regulations, on the one hand, it provides a basis for the government to accurately formulate environmental policies, and on the other hand, it provides strong support for the government to scientifically implement environmental policies.
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Heard, Kathryn A. „Theorizing Employment Division v. Smith: The Affective Politics of the Legal Regulation of Religion“. Law, Culture and the Humanities 16, Nr. 1 (24.11.2016): 53–69. http://dx.doi.org/10.1177/1743872116678213.
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This commentary interrogates, first, Justice Antonin Scalia’s assertion in Employment Division v. Smith that the law must uphold the belief-action distinction in order to preserve democratic norms and, second, the affect that this distinction had on Alfred Smith’s relationship with his faith. I argue that as Smith responded to the law’s repeated requests for justification as to why his religious convictions ought to exempt him from the criminal regulation of peyote, he experienced a profound sense of legal, political, and spiritual disempowerment – a disempowerment compounded by the erasure of the complexities of his faith in both the decision and aftermath of Smith. By way of making this argument, I bring Scalia, Smith, and Smith into sustained conversation with an unlikely interlocutor: Jürgen Habermas. As one of the leading legal and political theorists of religion in the late modern moment, Habermas articulates a vision of democratic life that at once venerates public religious expression and insulates law- and policy-making institutions from faith-based influence. Habermas’s vision is often characterized by contemporary political theorists and legal academics as the ideal to which all religiously plural democracies should aspire, but when his argument is considered alongside the experiences of Smith before the Court, a powerful disjuncture between theory and practice emerges. For although Habermas encourages religious individuals to adopt an epistemic stance of public reason and to engage in cooperative acts of translation in order to settle collaboratively the appropriate limits of religion as well as the law, I argue that, when applied to Smith, these methods of discursive engagement work to not only underscore the absolute primacy of the law over religion, but also to undercut Smith’s own understanding of his faith. I ultimately suggest that this mode of inquiry – that is to say, infusing theory with nuances gleamed from the everyday legal lives of ordinary individuals – generates new pathways through which to ameliorate latent social and political harms.
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McTavish, Christina, Wesley Bérubé-Janzen, Xu Wang, Matthew Maitland, Louisa Salemi, David Hess und Caroline Schild-Poulter. „Regulation of c-Raf Stability through the CTLH Complex“. International Journal of Molecular Sciences 20, Nr. 4 (21.02.2019): 934. http://dx.doi.org/10.3390/ijms20040934.
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c-Raf is a central component of the extracellular signal-regulated kinase (ERK) pathway which is implicated in the development of many cancer types. RanBPM (Ran-Binding Protein M) was previously shown to inhibit c-Raf expression, but how this is achieved remains unclear. RanBPM is part of a recently identified E3 ubiquitin ligase complex, the CTLH (C-terminal to LisH) complex. Here, we show that the CTLH complex regulates c-Raf expression through a control of its degradation. Several domains of RanBPM were found necessary to regulate c-Raf levels, but only the C-terminal CRA (CT11-RanBPM) domain showed direct interaction with c-Raf. c-Raf ubiquitination and degradation is promoted by the CTLH complex. Furthermore, A-Raf and B-Raf protein levels are also regulated by the CTLH complex, indicating a common regulation of Raf family members. Finally, depletion of CTLH subunits RMND5A (required for meiotic nuclear division 5A) and RanBPM resulted in enhanced proliferation and loss of RanBPM promoted tumour growth in a mouse model. This study uncovers a new mode of control of c-Raf expression through regulation of its degradation by the CTLH complex. These findings also uncover a novel target of the CTLH complex, and suggest that the CTLH complex has activities that suppress cell transformation and tumour formation.
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Salpeter, Seth J., Agnes Klochendler, Noa Weinberg-Corem, Shay Porat, Zvi Granot, A. M. James Shapiro, Mark A. Magnuson et al. „Glucose Regulates Cyclin D2 Expression in Quiescent and Replicating Pancreatic β-Cells Through Glycolysis and Calcium Channels“. Endocrinology 152, Nr. 7 (26.04.2011): 2589–98. http://dx.doi.org/10.1210/en.2010-1372.
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Understanding the molecular triggers of pancreatic β-cell proliferation may facilitate the development of regenerative therapies for diabetes. Genetic studies have demonstrated an important role for cyclin D2 in β-cell proliferation and mass homeostasis, but its specific function in β-cell division and mechanism of regulation remain unclear. Here, we report that cyclin D2 is present at high levels in the nucleus of quiescent β-cells in vivo. The major regulator of cyclin D2 expression is glucose, acting via glycolysis and calcium channels in the β-cell to control cyclin D2 mRNA levels. Furthermore, cyclin D2 mRNA is down-regulated during S-G2-M phases of each β-cell division, via a mechanism that is also affected by glucose metabolism. Thus, glucose metabolism maintains high levels of nuclear cyclin D2 in quiescent β-cells and modulates the down-regulation of cyclin D2 in replicating β-cells. These data challenge the standard model for regulation of cyclin D2 during the cell division cycle and suggest cyclin D2 as a molecular link between glucose levels and β-cell replication.
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Zhao, Jingyao, Xufeng Chen, Guangrong Song, Jiali Zhang, Haifeng Liu und Xiaolong Liu. „Uhrf1 controls the self-renewal versus differentiation of hematopoietic stem cells by epigenetically regulating the cell-division modes“. Proceedings of the National Academy of Sciences 114, Nr. 2 (12.12.2016): E142—E151. http://dx.doi.org/10.1073/pnas.1612967114.
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Hematopoietic stem cells (HSCs) are able to both self-renew and differentiate. However, how individual HSC makes the decision between self-renewal and differentiation remains largely unknown. Here we report that ablation of the key epigenetic regulator Uhrf1 in the hematopoietic system depletes the HSC pool, leading to hematopoietic failure and lethality. Uhrf1-deficient HSCs display normal survival and proliferation, yet undergo erythroid-biased differentiation at the expense of self-renewal capacity. Notably, Uhrf1 is required for the establishment of DNA methylation patterns of erythroid-specific genes during HSC division. The expression of these genes is enhanced in the absence of Uhrf1, which disrupts the HSC-division modes by promoting the symmetric differentiation and suppressing the symmetric self-renewal. Moreover, overexpression of one of the up-regulated genes, Gata1, in HSCs is sufficient to phenocopy Uhrf1-deficient HSCs, which show impaired HSC symmetric self-renewal and increased differentiation commitment. Taken together, our findings suggest that Uhrf1 controls the self-renewal versus differentiation of HSC through epigenetically regulating the cell-division modes, thus providing unique insights into the relationship among Uhrf1-mediated DNA methylation, cell-division mode, and HSC fate decision.
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Marvan Muzher und Hussein Muzher. „Development of normative-legislative provision of state-banking partnership in Ukraine“. Middle European Scientific Bulletin 2 (05.07.2020): 4–7. http://dx.doi.org/10.47494/mesb.2020.2.11.
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The analysis of the legal framework for regulating the development of public-private (state-banking) partnership in Ukraine is carried out. Attention is drawn to the fact that the problem of inconsistency of the relevant laws and regulations on the regulation of public-private partnership, which often contain different rules on the same issues in this field, and the mechanism of implementation of such projects, is quite problematic and of the highest priority for state regulation. is not unambiguous and unified.
The priority plan of changes is outlined, which takes the following form: amending the legislation on public-private partnership for the purpose of its uniform application and interpretation; introduction of a unified procedure for all types of state-bank partnership agreements; development of an authorized state body responsible for the development of state-banking partnership in Ukraine; strengthening the functions of local self-government bodies in the sphere of state-banking partnership; a clear division of functions between the relevant public authorities regarding the implementation of state-bank partnership projects; introduction of a single model contract of public-private partnership.
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Bertaux, François, Samuel Marguerat und Vahid Shahrezaei. „Division rate, cell size and proteome allocation: impact on gene expression noise and implications for the dynamics of genetic circuits“. Royal Society Open Science 5, Nr. 3 (März 2018): 172234. http://dx.doi.org/10.1098/rsos.172234.
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The cell division rate, size and gene expression programmes change in response to external conditions. These global changes impact on average concentrations of biomolecule and their variability or noise. Gene expression is inherently stochastic, and noise levels of individual proteins depend on synthesis and degradation rates as well as on cell-cycle dynamics. We have modelled stochastic gene expression inside growing and dividing cells to study the effect of division rates on noise in mRNA and protein expression. We use assumptions and parameters relevant to Escherichia coli , for which abundant quantitative data are available. We find that coupling of transcription, but not translation rates to the rate of cell division can result in protein concentration and noise homeostasis across conditions. Interestingly, we find that the increased cell size at fast division rates, observed in E. coli and other unicellular organisms, buffers noise levels even for proteins with decreased expression at faster growth. We then investigate the functional importance of these regulations using gene regulatory networks that exhibit bi-stability and oscillations. We find that network topology affects robustness to changes in division rate in complex and unexpected ways. In particular, a simple model of persistence, based on global physiological feedback, predicts increased proportion of persister cells at slow division rates. Altogether, our study reveals how cell size regulation in response to cell division rate could help controlling gene expression noise. It also highlights that understanding circuits' robustness across growth conditions is key for the effective design of synthetic biological systems.
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Fedorov, Aleksey V., und Anna V. Lifanchuk. „Mechanisms of regulation of the number of cells in the cell chain of diatoms“. Issues of modern algology (Вопросы современной альгологии), Nr. 1(19) (2019): 8–22. http://dx.doi.org/10.33624/2311-0147-2019-1(19)-8-22.
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We proposed hypothesis that describes the mechanism of formation and disintegration of cell chains, according to which the number of cells in a chain is determined by the difference in the rates of cell division and the separation of chains into individual cells, and the maximum number of cells in the chain is achieved at the highest division rate. Experiments showed that the addition of phosphorus stimulates the formation of longer chains. We developed a simple mathematical model of the dynamics of the number of cells in cell chains.
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Torii, Kotaro, Akane Kubota, Takashi Araki und Motomu Endo. „Time-Series Single-Cell RNA-Seq Data Reveal Auxin Fluctuation during Endocycle“. Plant and Cell Physiology 61, Nr. 2 (16.12.2019): 243–54. http://dx.doi.org/10.1093/pcp/pcz228.
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Abstract Appropriate cell cycle regulation is crucial for achieving coordinated development and cell differentiation in multicellular organisms. In Arabidopsis, endoreduplication is often observed in terminally differentiated cells and several reports have shown its molecular mechanisms. Auxin is a key factor for the mode transition from mitotic cell cycle to endocycle; however, it remains unclear if and how auxin maintains the endocycle mode. In this study, we reanalyzed root single-cell transcriptome data and reconstructed cell cycle trajectories of the mitotic cell cycle and endocycle. With progression of the endocycle, genes involved in auxin synthesis, influx and efflux were induced at the specific cell phase, suggesting that auxin concentration fluctuated dynamically. Such induction of auxin-related genes was not observed in the mitotic cell cycle, suggesting that the auxin fluctuation plays some roles in maintaining the endocycle stage. In addition, the expression level of CYCB1;1, which is required for cell division in the M phase, coincided with the expected amount of auxin and cell division. Our analysis also provided a set of genes expressed in specific phases of the cell cycle. Taking these findings together, reconstruction of single-cell transcriptome data enables us to identify properties of the cell cycle more accurately.
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Lisina, Nataly, Aleksandra Ushakova, Svetlana Ivanova und Alexander Prosekov. „Regulation of Interaction between Hunters and Land Users: A Comparative Legal Study“. Laws 12, Nr. 1 (30.01.2023): 14. http://dx.doi.org/10.3390/laws12010014.
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Hunting is a complex type of nature management. In its process, objects of the animal world and the earth are used. Obviously, the relationship between hunters and other land users should be clearly regulated by legislation. The purpose of this work was to identify common and specific problems for different systems of interaction between hunters and land owners and to assess the possibility of spreading the existing experience of solving problems faced by the hunting sector to different countries. Three main models of the relationship between hunters and land users (direct interaction, cooperation, and division of rights) are considered. Each of the models performs its tasks and has its own degree of efficiency. The interaction organization model adopted in a country depends on the specifics of the conditions in which the hunting farm develops including economic, property, legal, social, and state aspects. It is established that the availability of hunting is best ensured within the framework of the cooperation model, the observation of the rights of owners—within the direct interaction model, the convenience of management within large territories of wild animal habitats—within the division of rights model. At the same time, it is incorrect to single out the best model by all criteria or to designate a model that is universally suitable for different conditions. In the hunting farms of Russia, the described problems of interactions are not related to the potential of the division of rights model as such, but to a lack of understanding that this particular model requires increased attention of the state. The proposals aimed at improving the practice of developing and applying models of relationships between hunters and land users are represented.
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Akberdin, Ilya R., Konstantin N. Kozlov, Fedor V. Kazantsev, Stanislav I. Fadeev, Vitaly A. Likhoshvai und Tamara M. Khlebodarova. „Impact of Negative Feedbacks on De Novo Pyrimidines Biosynthesis in Escherichia coli“. International Journal of Molecular Sciences 24, Nr. 5 (02.03.2023): 4806. http://dx.doi.org/10.3390/ijms24054806.
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Earlier studies aimed at investigating the metabolism of endogenous nucleoside triphosphates in synchronous cultures of E. coli cells revealed an auto-oscillatory mode of functioning of the pyrimidine and purine nucleotide biosynthesis system, which the authors associated with the dynamics of cell division. Theoretically, this system has an intrinsic oscillatory potential, since the dynamics of its functioning are controlled through feedback mechanisms. The question of whether the nucleotide biosynthesis system has its own oscillatory circuit is still open. To address this issue, an integral mathematical model of pyrimidine biosynthesis was developed, taking into account all experimentally verified negative feedback in the regulation of enzymatic reactions, the data of which were obtained under in vitro conditions. Analysis of the dynamic modes of the model functioning has shown that in the pyrimidine biosynthesis system, both the steady-state and oscillatory functioning modes can be realized under certain sets of kinetic parameters that fit in the physiological boundaries of the investigated metabolic system. It has been demonstrated that the occurrence of the oscillatory nature of metabolite synthesis depended on the ratio of two parameters: the Hill coefficient, hUMP1—the nonlinearity of the UMP effect on the activity of carbamoyl-phosphate synthetase, and the parameter r characterizing the contribution of the noncompetitive mechanism of UTP inhibition to the regulation of the enzymatic reaction of UMP phosphorylation. Thus, it has been theoretically shown that the E. coli pyrimidine biosynthesis system possesses its own oscillatory circuit whose oscillatory potential depends to a significant degree on the mechanism of regulation of UMP kinase activity.
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Li, Hojun, Anirudh Natarajan, Jideofor Ezike, M. Inmaculada Barrasa, Huan Yang, Clement Ma, Styliani Markoulaki und Harvey Lodish. „Single Cell Resolution of Glucocorticoid Effects on Erythroid Progenitor Cells“. Blood 132, Supplement 1 (29.11.2018): 751. http://dx.doi.org/10.1182/blood-2018-99-112445.
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Abstract To generate the billions of new erythrocytes required on a daily basis, erythroid progenitor cells must exponentially increase in number before undergoing terminal differentiation. A limited number of cell divisions occur during erythropoietin (EPO)-regulated erythroid terminal differentiation, but the principal regulation of erythroid transit-amplification occurs earlier in erythropoiesis between the burst forming unit-erythroid (BFU-E) and colony forming unit-erythroid (CFU-E) stages of development. The importance of this EPO-independent early erythropoietic process is highlighted in Diamond-Blackfan Anemia (DBA). DBA is characterized by pure red cell aplasia, loss of BFU-E and CFU-E progenitors in the bone marrow, and severe anemia despite high circulating EPO levels. The only known effective medical therapy for DBA also provides insight into the regulation of erythroid transit-amplification. In patients responsive to glucocorticoid treatment, there are increased numbers of BFU-E and CFU-E progenitors in the bone marrow, and ex vivo culture studies indicate that the synthetic glucocorticoid dexamethasone (Dex) predominantly increases proliferative capacity of BFU-Es, with minimal effect on proliferative capacity of CFU-Es. These findings led to a prevailing model that glucocorticoids increase BFU-E proliferative capacity by stimulating several rounds of self-renewal cell divisions. However, a limitation of this model is that there is no mechanistic explanation for how BFU-Es regulate the fate choice of undergoing a self-renewal cell division versus a differentiation cell division in the presence or absence of glucocorticoids. In this study, we address this question by examining progression of early erythroid progenitor development at single cell resolution, and subsequently elucidate the true mechanistic nature of glucocorticoid-induced erythroid progenitor proliferative capacity amplification. By performing single cell transcriptome profiling (scRNAseq) of primary-isolated mouse fetal liver BFU-Es, CFU-Es, and their developmental intermediates, we identify a continuum of transcriptomic states during erythroid transit-amplification when performing principle component analysis (PCA) on transcriptomes of individual cells. We show that ex vivo culture of primary-isolated BFU-Es in serum free media supplemented with stem cell factor, insulin-like growth factor 1, and EPO results in developmental progression along the transcriptome continuum when performing scRNAseq and PCA on cultured BFU-Es. The addition of Dex into this culture system does not result in self-renewal of BFU-Es at the transcriptome level, but rather still results in developmental progression, albeit to less of a degree per cell division than BFU-Es cultured without Dex. We additionally show that the continuum of transcriptome states in erythroid transit-amplification is reflective of a continuum of functional states, with developmental progression characterized by decreasing proliferative capacity and decreasing glucocorticoid-responsiveness. Lastly, through manual separation of daughter cells resulting from a BFU-E cell division, we demonstrate that BFU-E cell division is a symmetric process at the transcriptome level, both with and without the addition of Dex. Our results clarify the nature of how glucocorticoids amplify BFU-E proliferative capacity. As opposed to stimulating a finite number of BFU-E self-renewal cell divisions, glucocorticoids decrease the extent of progression through the erythroid transit-amplifying developmental continuum per cell division. Thus, a decreased rate of progression through the developmental continuum is associated with an increased number of transit-amplifying cell divisions prior to terminal differentiation. These findings are important not only for the rational development of glucocorticoid-alternatives for treating DBA, but also for all bone marrow failure syndromes characterized by progenitor cell hypoplasia. Disclosures No relevant conflicts of interest to declare.
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Chandra, Vikram, Ingrid Fetter-Pruneda, Peter R. Oxley, Amelia L. Ritger, Sean K. McKenzie, Romain Libbrecht und Daniel J. C. Kronauer. „Social regulation of insulin signaling and the evolution of eusociality in ants“. Science 361, Nr. 6400 (26.07.2018): 398–402. http://dx.doi.org/10.1126/science.aar5723.
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Queens and workers of eusocial Hymenoptera are considered homologous to the reproductive and brood care phases of an ancestral subsocial life cycle. However, the molecular mechanisms underlying the evolution of reproductive division of labor remain obscure. Using a brain transcriptomics screen, we identified a single gene,insulin-like peptide 2(ilp2), which is always up-regulated in ant reproductives, likely because they are better nourished than their nonreproductive nestmates. In clonal raider ants (Ooceraea biroi), larval signals inhibit adult reproduction by suppressingilp2, thus producing a colony reproductive cycle reminiscent of ancestral subsociality. However, increasing ILP2 peptide levels overrides larval suppression, thereby breaking the colony cycle and inducing a stable division of labor. These findings suggest a simple model for the origin of ant eusociality via nutritionally determined reproductive asymmetries potentially amplified by larval signals.
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Li, Hao, Jing Han, Linjie Chen, Ni Han, Yajing Hu, Qian Ge, Zhonghai Ren und Lina Wang. „Ectopic Expression of CsSUN in Tomato Results in Elongated Fruit Shape via Regulation of Longitudinal Cell Division“. International Journal of Molecular Sciences 23, Nr. 17 (01.09.2022): 9973. http://dx.doi.org/10.3390/ijms23179973.
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Fruit shape, an important agronomic trait of cucumber (Cucumis sativus L.), is tightly controlled by a series of genes such as CsSUN, a homologue of SlSUN that is responsible for the tomato (Solanum lycopersicum) fruit shape via the modulation of cell division. However, the direct genetic evidence about the CsSUN-mediated regulation of fruit shape is still scarce, limiting our mechanistic understanding of the biological functions of CsSUN. Here, we introduced CsSUN into the round-fruited tomato inbred line ‘SN1′ (wild type, WT) via the Agrobacterium tumefaciens-mediated method. The high and constitutive expression of CsSUN was revealed by real-time PCR in all the tested tissues of the transgenic plants, especially in the fruits and ovaries. Phenotypic analyses showed that the ectopic expression of CsSUN increased fruit length while it decreased fruit diameter, thus leading to the enhanced fruit shape index in the transgenic tomato lines relative to the WT. Additionally, the reduction in the seed size and seed-setting rate and the stimulation of seed germination were observed in the CsSUN-expressed tomato. A histological survey demonstrated that the elongated fruits were mainly derived from the significant increasing of the longitudinal cell number, which compensated for the negative effects of decreased cell area in the central columellae. These observations are different from action mode of SlSUN, thus shedding new insights into the SUN-mediated regulation of fruit shape.
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Williamson, Daniel, William Tasker-Brown, James A. H. Murray, Angharad R. Jones und Leah R. Band. „Modelling how plant cell-cycle progression leads to cell size regulation“. PLOS Computational Biology 19, Nr. 10 (20.10.2023): e1011503. http://dx.doi.org/10.1371/journal.pcbi.1011503.
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Populations of cells typically maintain a consistent size, despite cell division rarely being precisely symmetrical. Therefore, cells must possess a mechanism of “size control”, whereby the cell volume at birth affects cell-cycle progression. While size control mechanisms have been elucidated in a number of other organisms, it is not yet clear how this mechanism functions in plants. Here, we present a mathematical model of the key interactions in the plant cell cycle. Model simulations reveal that the network of interactions exhibits limit-cycle solutions, with biological switches underpinning both the G1/S and G2/M cell-cycle transitions. Embedding this network model within growing cells, we test hypotheses as to how cell-cycle progression can depend on cell size. We investigate two different mechanisms at both the G1/S and G2/M transitions: (i) differential expression of cell-cycle activator and inhibitor proteins (with synthesis of inhibitor proteins being independent of cell size), and (ii) equal inheritance of inhibitor proteins after cell division. The model demonstrates that both these mechanisms can lead to larger daughter cells progressing through the cell cycle more rapidly, and can thus contribute to cell-size control. To test how these features enable size homeostasis over multiple generations, we then simulated these mechanisms in a cell-population model with multiple rounds of cell division. These simulations suggested that integration of size-control mechanisms at both G1/S and G2/M provides long-term cell-size homeostasis. We concluded that while both size independence and equal inheritance of inhibitor proteins can reduce variations in cell size across individual cell-cycle phases, combining size-control mechanisms at both G1/S and G2/M is essential to maintain size homeostasis over multiple generations. Thus, our study reveals how features of the cell-cycle network enable cell-cycle progression to depend on cell size, and provides a mechanistic understanding of how plant cell populations maintain consistent size over generations.
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Paidhungat, Madan, und Stephen Garrett. „Cdc1 Is Required for Growth and Mn2+ Regulation in Saccharomyces cerevisiae“. Genetics 148, Nr. 4 (01.04.1998): 1777–86. http://dx.doi.org/10.1093/genetics/148.4.1777.
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Abstract Cdc1 function was initially implicated in bud formation and nuclear division because cdc1(Ts) cells arrested with a small bud, duplicated DNA, and undivided nucleus. Our studies show that Cdc1 is necessary for cell growth at several stages of the cell cycle, as well as in pheromone-treated cells. Thus, Cdc1 depletion might affect bud formation and nuclear division, as well as other cellular processes, by blocking a process involved in general cell growth. Cells depleted of intracellular Mn2+ also exhibit a cdc1-like phenotype and recent results suggested Cdc1 might be a Mn2+-dependent protein. We show that all of the conditional cdc1(Ts) alleles tested cause cells to become sensitive to Mn2+ depletion. In addition, Cdc1 overproduction alleviates the chelator sensitivity of several Mn2+ homeostasis mutants. These findings are compatible with a model in which Cdc1 regulates intracellular, and in particular cytosolic, Mn2+ levels which, in turn, are necessary for cell growth.
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Meneau, Ferdinand, Aude Dupré, Catherine Jessus und Enrico Maria Daldello. „Translational Control of Xenopus Oocyte Meiosis: Toward the Genomic Era“. Cells 9, Nr. 6 (19.06.2020): 1502. http://dx.doi.org/10.3390/cells9061502.
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The study of oocytes has made enormous contributions to the understanding of the G2/M transition. The complementarity of investigations carried out on various model organisms has led to the identification of the M-phase promoting factor (MPF) and to unravel the basis of cell cycle regulation. Thanks to the power of biochemical approaches offered by frog oocytes, this model has allowed to identify the core signaling components involved in the regulation of M-phase. A central emerging layer of regulation of cell division regards protein translation. Oocytes are a unique model to tackle this question as they accumulate large quantities of dormant mRNAs to be used during meiosis resumption and progression, as well as the cell divisions during early embryogenesis. Since these events occur in the absence of transcription, they require cascades of successive unmasking, translation, and discarding of these mRNAs, implying a fine regulation of the timing of specific translation. In the last years, the Xenopus genome has been sequenced and annotated, enabling the development of omics techniques in this model and starting its transition into the genomic era. This review has critically described how the different phases of meiosis are orchestrated by changes in gene expression. The physiological states of the oocyte have been described together with the molecular mechanisms that control the critical transitions during meiosis progression, highlighting the connection between translation control and meiosis dynamics.