Página 22 dos resultados de 45945 itens digitais encontrados em 0.054 segundos

‣ Prion potency in stem cells biology

Lopes, Marilene Hohmuth; Santos, Tiago G.
Fonte: LANDES BIOSCIENCE; AUSTIN Publicador: LANDES BIOSCIENCE; AUSTIN
Tipo: Artigo de Revista Científica
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Prion protein (PrP) can be considered a pivotal molecule because it interacts with several partners to perform a diverse range of critical biological functions that might differ in embryonic and adult cells. In recent years, there have been major advances in elucidating the putative role of PrP in the basic biology of stem cells in many different systems. Here, we review the evidence indicating that PrP is a key molecule involved in driving different aspects of the potency of embryonic and tissue-specific stem cells in self-perpetuation and differentiation in many cell types. It has been shown that PrP is involved in stem cell self-renewal, controlling pluripotency gene expression, proliferation and neural and cardiomyocyte differentiation. PrP also has essential roles in distinct processes that regulate tissue-specific stem cell biology in nervous and hematopoietic systems and during muscle regeneration. Results from our own investigations have shown that PrP is able to modulate self-renewal and proliferation in neural stem cells, processes that are enhanced by PrP interactions with stress inducible protein 1 (STI1). Thus, the available data reveal the influence of PrP in acting upon the maintenance of pluripotent status or the differentiation of stem cells from the early embryogenesis through adulthood.

‣ 42nd Annual Meeting of the American Society for Cell Biology, San Francisco, California, USA, 14–18 December 2002

Kenny, Paraic A; Rizki, Aylin
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
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The Annual Meeting of the American Society for Cell Biology (ASCB) is a diverse conference covering all topics in cell biology. While all of the basic biology presented at this meeting may potentially contribute to breast cancer research, there were a significant number of presentations and posters directly pertinent to this field. Here we have summarized the research that is of greatest immediate relevance to breast cancer, with particular emphasis on mammary gland development and tumorigenesis in vivo, three-dimensional in vitro models of mammary morphogenesis, alterations of signal transduction pathways in breast cancer, and global studies in expression profiling and drug screening.

‣ MicroRNAs from the Planarian Schmidtea mediterranea: A model system for stem cell biology

Palakodeti, Dasaradhi; Smielewska, Magda; Graveley, Brenton R.
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em /09/2006 Português
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MicroRNAs (miRNAs) are ∼22-nt RNA molecules that typically bind to the 3′ untranslated regions of target mRNAs and function to either induce mRNA degradation or repress translation. miRNAs have been shown to play important roles in the function of stem cells and cell lineage decisions in a variety of organisms, including humans. Planarians are bilaterally symmetric metazoans that have the unique ability to completely regenerate lost tissues or organs. This regenerative capacity is facilitated by a population of stem cells known as neoblasts. Planarians are therefore an excellent model system for studying many aspects of stem cell biology. Here we report the cloning and initial characterization of 71 miRNAs from the planarian Schmidtea mediterranea. While several of the S. mediterranea miRNAs are members of miRNA families identified in other species, we also identified a number of planarian-specific miRNAs. This work lays the foundation for functional studies aimed at addressing the role of these miRNAs in regeneration, cell lineage decisions, and basic stem cell biology.

‣ Th1/Th2 Cytokines: An Easy Model to Study Gene Expression in Immune Cells

Morán, José M.; González-Polo, Rosa A.; Soler, Germán; Fuentes, José M.
Fonte: American Society for Cell Biology Publicador: American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em //2006 Português
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This report describes a laboratory exercise that was incorporated into a Cell Biology and Molecular Biology advanced course. The exercise was made for a class size with eight students and was designed to reinforce the understanding of basic molecular biology techniques. Students used the techniques of reverse transcription and arginase activity measurement as well as nitric oxide determination to discover whether two specific genes were expressed by cytokine-stimulated dendritic cells. The experiment served as the basis for discussing the importance of differential gene expression inside the eukaryotic cell and the importance of cytokines in the immune system.

‣ Visualization of Polarized Membrane Type 1 Matrix Metalloproteinase Activity in Live Cells by Fluorescence Resonance Energy Transfer Imaging*S⃞

Ouyang, Mingxing; Lu, Shaoying; Li, Xiao-Yan; Xu, Jing; Seong, Jihye; Giepmans, Ben N. G.; Shyy, John Y.-J.; Weiss, Stephen J.; Wang, Yingxiao
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em 20/06/2008 Português
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Membrane type 1 matrix metalloproteinase (MT1-MMP) plays a critical role in cancer cell biology by proteolytically remodeling the extracellular matrix. Utilizing fluorescence resonance energy transfer (FRET) imaging, we have developed a novel biosensor, with its sensing element anchoring at the extracellular surface of cell membrane, to visualize MT1-MMP activity dynamically in live cells with subcellular resolution. Epidermal growth factor (EGF) induced significant FRET changes in cancer cells expressing MT1-MMP, but not in MT1-MMP-deficient cells. EGF-induced FRET changes in MT1-MMP-deficient cells could be restored after reconstituting with wild-type MT1-MMP, but not MMP-2, MMP-9, or inactive MT1-MMP mutants. Deletion of the transmembrane domain in the biosensor or treatment with tissue inhibitor of metalloproteinase-2, a cell-impermeable MT1-MMP inhibitor, abolished the EGF-induced FRET response, indicating that MT1-MMP acts at the cell surface to generate FRET changes. In response to EGF, active MT1-MMP was directed to the leading edge of migrating cells along micropatterned fibronectin stripes, in tandem with the local accumulation of the EGF receptor, via a process dependent upon an intact cytoskeletal network. Hence...

‣ Investigative Cases and Student Outcomes in an Upper-Division Cell and Molecular Biology Laboratory Course at a Minority-serving Institution

Knight, Jonathan D.; Fulop, Rebecca M.; Márquez-Magaña, Leticia; Tanner, Kimberly D.
Fonte: American Society for Cell Biology Publicador: American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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Active-learning strategies are increasingly being integrated into college-level science courses to make material more accessible to all students and to improve learning outcomes. One active-learning pedagogy, case-based learning (CBL), was developed as a way to both enhance engagement in the material and to accommodate diverse learning styles. Yet, adoption of CBL approaches in undergraduate biology courses has been piecemeal, in part because of the perceived investment of time required. Furthermore, few CBL lesson plans have been developed specifically for upper-division laboratory courses. Here, we describe four cases that we developed and implemented for a senior cell and molecular biology laboratory course at San Francisco State University, a minority-serving institution. To evaluate the effectiveness of these modules, we used both written and verbal assessments to gauge learning outcomes and attitudinal responses of students over two semesters. Students responded positively to the new approach and seemed to meet the learning goals for the course. Most said they would take a course using CBL again. These case modules are readily adaptable to a variety of classroom settings.

‣ Identification of the Small Protein Rich in Arginine and Glycine (SRAG): A NEWLY IDENTIFIED NUCLEOLAR PROTEIN THAT CAN REGULATE CELL PROLIFERATION*S⃞

Zullo, Alfred J.; Michaud, Monia; Zhang, Weiping; Grusby, Michael J.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em 01/05/2009 Português
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The characterization of new proteins will aid in our explanation of normal biology and disease. Toward that goal, we describe the initial characterization of the small protein rich in arginine and glycine (SRAG). Human and mouse SRAG are 248/249-amino acid arginine- and glycine-rich proteins that are widely expressed in tissues and cell lines. Two SRAG isoforms, SRAG-5 and SRAG-3, which are truncations of full-length SRAG, were also identified. Although all SRAG proteins reside in the nucleus, they were also found within the nucleolus. Localization within the nucleolus was regulated by the N terminus of the protein. Our initial studies indicated that SRAG can interact with RNA. Full-length SRAG protein levels were highest in resting cells and were reduced in proliferating cells. The reduction in SRAG protein that occurs in proliferating cells was mapped with inhibitors to the G2/M phase of the cell cycle. As expected, the overexpression of SRAG reduced the percentage of cells in the G2/M phase and increased cell death. In sum, we have identified a new and intriguing member of the nucleolar proteome.

‣ New developments in mast cell biology

Kalesnikoff, Janet; Galli, Stephen J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/2008 Português
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Mast cells can function as effector and immunoregulatory cells in IgE-associated allergic disorders, as well as in certain innate and adaptive immune responses. This review will focus on exciting new developments in the field of mast cell biology published within the last year. It will highlight advances in the understanding of FcεRI-mediated signaling and mast cell activation events, as well as in the use of genetic models to study mast cell function in vivo. Finally, we will discuss newly identified roles of mast cells or individual mast cell products, such as proteases and IL-10, in host defense, cardiovascular disease and tumor biology, and in settings in which mast cells have anti-inflammatory or immunosuppressive functions.

‣ Cell biology of retroviral RNA packaging

Jouvenet, Nolwenn; Lainé, Sébastien; Vivares, Lucie Pessel; Mougel, Marylène
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
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Generation of infectious retroviral particles rely on the targeting of all structural components to the correct cellular sites at the correct time. Gag, the main structural protein, orchestrates the assembly process and the mechanisms that trigger its targeting to assembly sites are well described. Gag is also responsible for the packaging of the viral genome and the molecular details of the Gag/RNA interaction are well characterized. Until recently, much less was understood about the cell biology of retrovirus RNA packaging. However, novel biochemical and live-cell microscopic approaches have identified where in the cell the initial events of genome recognition by Gag occur. These recent developments have shed light on the role played by the viral genome during virion assembly. Other central issues of the cell biology of RNA packaging, such as how the Gag-RNA complex traffics through the cytoplasm toward assembly sites, await characterization.

‣ The emerging functions of the p53-miRNA network in stem cell biology

Lin, Chao-Po; Choi, Yong Jin; Hicks, Geoffrey G.; He, Lin
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em 01/06/2012 Português
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The p53 pathway plays an essential role in tumor suppression, regulating multiple cellular processes coordinately to maintain genome integrity in both somatic cells and stem cells. Despite decades of research dedicated to p53 function in differentiated somatic cells, we are just starting to understand the complexity of the p53 pathway in the biology of pluripotent stem cells and tissue stem cells. Recent studies have demonstrated that p53 suppresses proliferation, promotes differentiation of embryonic stem (ES) cells and constitutes an important barrier to somatic reprogramming. In addition, emerging evidence reveals the role of the p53 network in the self-renewal, proliferation and genomic integrity of adult stem cells. Interestingly, non-coding RNAs, and microRNAs in particular, are integral components of the p53 network, regulating multiple p53-controlled biological processes to modulate the self-renewal and differentiation potential of a variety of stem cells. Thus, elucidation of the p53-miRNA axis in stem cell biology may generate profound insights into the mechanistic overlap between malignant transformation and stem cell biology.

‣ Tracking Single Cells in Live Animals Using a Photoconvertible Near-Infrared Cell Membrane Label

Carlson, Alicia L.; Fujisaki, Joji; Wu, Juwell; Runnels, Judith M.; Turcotte, Raphaël; Celso, Cristina Lo; Scadden, David T.; Strom, Terry B.; Lin, Charles P.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
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We describe a novel photoconversion technique to track individual cells in vivo using a commercial lipophilic membrane dye, DiR. We show that DiR exhibits a permanent fluorescence emission shift (photoconversion) after light exposure and does not reacquire the original color over time. Ratiometric imaging can be used to distinguish photoconverted from non-converted cells with high sensitivity. Combining the use of this photoconvertible dye with intravital microscopy, we tracked the division of individual hematopoietic stem/progenitor cells within the calvarium bone marrow of live mice. We also studied the peripheral differentiation of individual T cells by tracking the gain or loss of FoxP3-GFP expression, a marker of the immune suppressive function of CD4+ T cells. With the near-infrared photoconvertible membrane dye, the entire visible spectral range is available for simultaneous use with other fluorescent proteins to monitor gene expression or to trace cell lineage commitment in vivo with high spatial and temporal resolution.

‣ The Major Histocompatibility Complex (MHC) and the proteasome-ubiquitin pathway in T cell development; MHC and the proteasome-ubiquitin pathway in T cell development

Vugmeyster, Yulia, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 100 leaves; 12393782 bytes; 12393538 bytes; application/pdf; application/pdf
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The essential role of classical MHC molecules in T cell development as well as the proteasome role in antigen processing for MHC-mediated antigen presentation to T cells is well established. However, the contribution of nonclassical MHC molecules, the signals evoked by the MHC-TCR interactions, the signaling role of the proteasome-mediated proteolysis, and the regulation of the proteasome-ubiquitin proteolysis remain to be clarified. Here we address these more subtle but essential aspects of T cell development. We obtained mice deficient for MHC molecules encoded by the H-2K and H-2D genes. KbDb -/- mice have greatly reduced numbers of mature CD8+ T cells, indicating that selection of CD8+ T cells can not be compensated for by [beta]2m-associated molecules other than classical H-2K and D locus products. Spleen cells from KbDb -/- mice generate strong CD8+ MHC class I-specific responses after in vivo priming. Thus, a minor population of CD8+ T cells arises in the complete absence of classical MHC class I molecules. KbDb -/- animals also have self-tolerant natural killer (NK) cells that retain their cytotoxic potential. We utilize a fetal thymic organ culture (FTOC) system with a panel of proteasome inhibitors to implicate the proteasome in thymocyte apoptosis and negative selection. We find that proteasome inhibitors do not completely block but rather delay both dexamethasone- and antigen-triggered thymocyte apoptosis. We also show that proteasome activity is increased in apoptotic thymocytes...

‣ Molecular-genetic analysis of cell cycle diversification in early zebrafish embryos

Dalle Nogare, Damian Edward
Fonte: Universidade Rice Publicador: Universidade Rice
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Modulation of basic cell-cycle parameters during development is necessary to ensure spatio-temporal diversity of cell cycle behaviour and impose specific cell cycle constraints during developmental processes. We have used the zebrafish, Danio rerio, to examine the molecular-genetic control of cell cycle diversification in early vertebrate embryos. We have cloned genes encoding four crucial regulators of cell cycle progression including two members of the cdc25 gene family and two of the wee gene family. Together, these genes modify the activity of the Cdk1 protein, a central component of the cell cycle regulatory mechanism. We show that these genes are dynamically expressed during early development, and that the action of one, cdc25a, is rate limiting for cell cycle progression in the early embryo. To further understand how the developmental program imposes constraints on cell cycle behaviour, we have investigated the mechanisms underlying acquisition of cell-cycle diversity at the first cell cycle transition, the midblastula transition (MBT). In zebrafish, and many other organisms, development begins with a rapid and synchronous cell division program with no gap phases between successive rounds of DNA synthesis and mitosis. This early cell cycle program is terminated at the MBT (cycle 10) when zygotic transcription is initiated and gap phases are first observed...

‣ The role of E2F·pocket protein repressive complexes in cell cycle control and differentiation

Landsberg, Rebecca L. (Rebecca Lynn), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 277 leaves; 10513562 bytes; 18640317 bytes; application/pdf; application/pdf
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The pocket protein family is comprised of pRB (the protein product of the retinoblastoma susceptibility gene), p107, and p130. This family regulates the GI/S transition by interacting with their major downstream target, the E2F transcription factor. E2F is a heterodimeric protein composed of one DP subunit and one E2F subunit. The E2F family can be subdivided into three categories based upon structural and functional homology: E2F6; the 'activating E2Fs' (1-3); and 'the repressive E2Fs' (4-5). The focus of this study is E2F4 and E2F5, the members of the repressive E2F subgroup. The repressive E2Fs function by occupying E2F responsive promoters during Go and recruiting in the pocket proteins. As cells begin cycling, E2F4 and E2F5 are replaced at promoters by members of the activating E2Fs subgroup. Loss of either E2F4 or E2F5 does not result in cell cycle defects but instead lead to the abnormal development of specific tissues. The lack of a cell cycle phenotype in single mutants could be due to compensation by the other repressive E2F. In order to determine the role that E2F4·pocket protein repressive complexes play in regulating cell cycle control, differentiation, and development, mice lacking E2F4 and two members of the pocket protein family...

‣ Using Osteoclast Differentiation as a Model for Gene Discovery in an Undergraduate Cell Biology Laboratory

Birnbaum, Mark J.; Picco, Jenna; Clements, Meghan; Witwicka, Hanna; Yang, Meiheng; Hoey, Margaret T.; Odgren, Paul R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/2010 Português
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A key goal of molecular/cell biology/biotechnology is to identify essential genes in virtually every physiological process to uncover basic mechanisms of cell function and to establish potential targets of drug therapy combating human disease. The current article describes a semester-long, project-oriented molecular/cellular/biotechnology laboratory providing students, within a framework of bone cell biology, with a modern approach to gene discovery. Students are introduced to the topics of bone cells, bone synthesis, bone resorption, and osteoporosis. They then review the theory of microchip gene arrays, and study microchip array data generated during the differentiation of bone-resorbing osteoclasts in vitro. The class selects genes whose expression increases during osteoclastogenesis, and researches them in small groups using web-based bioinformatics tools. Students then go to a biotechnology company website to find and order siRNAs designed to “knockdown” expression of the gene of interest. Students then learn to transfect these siRNAs into osteoclasts, stimulate the cells to differentiate, assay osteoclast differentiation in vitro, and measure specific gene expression using real-time PCR and immunoblotting. Specific siRNA knockdown resulting in a decrease in osteoclastogenesis is indicative of a gene's physiological relevance. The results are analyzed statistically...

‣ Students' Studying and Approaches to Learning in Introductory Biology

Tomanek, Debra; Montplaisir, Lisa
Fonte: American Society for Cell Biology Publicador: American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em //2004 Português
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This exploratory study was conducted in an introductory biology course to determine 1) how students used the large lecture environment to create their own learning tasks during studying and 2) whether meaningful learning resulted from the students' efforts. Academic task research from the K–12 education literature and student approaches to learning research from the postsecondary education literature provided the theoretical framework for the mixed methods study. The subject topic was cell division. Findings showed that students 1) valued lectures to develop what they believed to be their own understanding of the topic; 2) deliberately created and engaged in learning tasks for themselves only in preparation for the unit exam; 3) used course resources, cognitive operations, and study strategies that were compatible with surface and strategic, rather than deep, approaches to learning; 4) successfully demonstrated competence in answering familiar test questions aligned with their surface and strategic approaches to studying and learning; and 5) demonstrated limited meaningful understanding of the significance of cell division processes. Implications for introductory biology education are discussed.

‣ Across and beyond the cell are peptide strings

Radulescu, Razvan Tudor
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/11/2007 Português
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Until presently, most approaches for understanding physiological or pathological phenomena have been based on the assumption that these processes start from individual cells, a concept introduced primarily by Virchow in the 19th century. Yet, it has also been increasingly recognized that this perception is insufficient, at least when it comes to grasping the mechanisms underlying largely incurable diseases such as metastatic cancer or rheumatoid arthritis. Despite this insight, even recently founded disciplines such as systems biology are still locked in this century-old mind-set of cellular building blocks and thus predictably of limited usefulness. Other studies conducted over the past years, however, suggest that there is something more fundamental to life and its various conditions than the cell: peptide strings. Here, I review the origin and nature of these sub- and trans-cellular elements as well as their potential to provide the long-sought answers hitherto inaccessible to cell biology.; Comment: 6 pages, 2 figures

‣ Neuroglobin protects nerve cells from apoptosis by inhibiting the intrinsic pathway of cell death

Raychaudhuri, Subhadip; Skommer, Joanna; Henty, Kristen; Birch, Nigel; Brittain, Thomas
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/07/2010 Português
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In the past few years, overwhelming evidence has accrued that a high level of expression of the protein neuroglobin protects neurons in vitro, in animal models, and in humans, against cell death associated with hypoxic and amyloid insult. However, until now, the exact mechanism of neuroglobin's protective action has not been determined. Using cell biology and biochemical approaches we demonstrate that neuroglobin inhibits the intrinsic pathway of apoptosis in vitro and intervenes in activation of pro-caspase 9 by interaction with cytochrome c. Using systems level information of the apoptotic signalling reactions we have developed a quantitative model of neuroglobin inhibition of apoptosis, which simulates neuroglobin blocking of apoptosome formation at a single cell level. Furthermore, this model allows us to explore the effect of neuroglobin in conditions not easily accessible to experimental study. We found that the protection of neurons by neuroglobin is very concentration sensitive. The impact of neuroglobin may arise from both its binding to cytochrome c and its subsequent redox reaction, although the binding alone is sufficient to block pro-caspase 9 activation. These data provides an explanation the action of neuroglobin in the protection of nerve cells from unwanted apoptosis.; Comment: 11 pages

‣ Characterizing the Relationship Between Cell-Cycle Progression and a Transcriptional Oscillator

Bristow, Sara Lynn
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2013 Português
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The cell division cycle is the process in which the entirety of a cell's contents is duplicated completely and then equally segregated into two identical daughter cells. The order of the steps in the cell cycle must be followed with fidelity to guarantee two viable cells. Understanding the regulatory mechanisms that control cell-cycle events remains to be a fundamental question in cell biology. In this dissertation, I explore the mechanisms that coordinate and regulate cell-cycle progression in the budding yeast, Saccharomyces cerevisiae.

Cell-cycle events have been shown to be triggered by oscillations in the activity of cyclin dependent kinases (CDKs) when bound to cyclins. However, several studies have shown that some cell-cycle events, such as periodic transcription, can continue in the absence of CDK activity. How are periodic transcription and other cell-cycle events coupled to each other during a wild-type cell cycle? Currently, two models of cell-cycle regulation have been proposed. One model hypothesizes that oscillations in CDK activity controls the timing of cell-cycle events, including periodic transcription. The second model proposes that a transcription factor (TF) network oscillator controls the timing of cell-cycle events...

‣ On Asymmetry in Biology and Nature

I. C. Baianu
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
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Symmetry has attracted a substantial amount of effort because considerable simplifications are possible in the mathematical and physical treatment of phenomena and natural systems that possess a certain degree of symmetry. Among physical and chemical systems the most widely known are those related to crystals and fluids. Whereas crystals have a lattice structure and a symmetry caused by ‘perfect’ order which can be classified by mathematical symmetry groups, most fluids have an average isotropic, highly-disordered ‘structure’ that is often considered to be random.Asymmetry is widely encountered in Biology and ecological systems- from amino acids to trees forests, and tribes, from physiological processes to anatomy- one often finds asymmetry to be present , although symmetries are also encountered whenever nature affords it. An important case is that of cell biomembranes that possess a marked structural and functional asymmetry which is essential to the survival of cells and microorganisms. Asymmetry both in time and selection ‘criteria’ plays a key role in the evolution of organisms and species.