scholarly journals The Many Faces of Mitochondrial Autophagy: Making Sense of Contrasting Observations in Recent Research

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Alexander I. May ◽  
Rodney J. Devenish ◽  
Mark Prescott
Keyword(s):  
Budding Yeast ◽  
Eukaryotic Cell ◽  
Current Understanding ◽  
Eukaryotic Cells ◽  
Experimental Conditions ◽  
Life And Death ◽  
Function Mechanism ◽  
Making Sense ◽  
Autophagic Degradation ◽  
The Many

Research into the selective autophagic degradation of mitochondria—mitophagy—has intensified in recent years, yielding significant insights into the function, mechanism, and regulation of this process in the eukaryotic cell. However, while some molecular players in budding yeast, such as Atg32p, Uth1p, and Aup1p, have been identified, studies further interrogating the mechanistic and regulatory features of mitophagy have yielded inconsistent and sometimes conflicting results. In this review, we focus on the current understanding of mitophagy mechanism, induction, and regulation in yeast, and suggest that differences in experimental conditions used in the various studies of mitophagy may contribute to the observed discrepancies. Consideration and understanding of these differences may help place the mechanism and regulation of mitophagy in context, and further indicate the intricate role that this essential process plays in the life and death of eukaryotic cells.

scholarly journals Origin of the Eukaryotic Cell

2017 ◽  
Vol 01 (02) ◽  
pp. 108-120 ◽  
Author(s):  
Nick Lane
Keyword(s):  
Protein Synthesis ◽  
Host Cell ◽  
Genome Size ◽  
Energy Savings ◽  
Nuclear Genome ◽  
Eukaryotic Cell ◽  
Eukaryotic Cells ◽  
Bacterial Genomes ◽  
Complex Cells ◽  
Life On Earth

All complex life on Earth is composed of ‘eukaryotic’ cells. Eukaryotes arose just once in 4 billion years, via an endosymbiosis — bacteria entered a simple host cell, evolving into mitochondria, the ‘powerhouses’ of complex cells. Mitochondria lost most of their genes, retaining only those needed for respiration, giving eukaryotes ‘multi-bacterial’ power without the costs of maintaining thousands of complete bacterial genomes. These energy savings supported a substantial expansion in nuclear genome size, and far more protein synthesis from each gene.

Wittgenstein’s philosophy and action research

2003 ◽  
Vol 8 (3) ◽  
pp. 295-301 ◽  
Author(s):  
John Shotter
Keyword(s):  
Action Research ◽  
Social Isolation ◽  
Scientific Method ◽  
Gain Control ◽  
Participatory Culture ◽  
Ordinary People ◽  
Making Sense ◽  
The Social ◽  
Professional Research ◽  
The Many

Three themes seem to be common to both Greenwood’s and Gustavsen’s accounts: One is the social isolation of professional [research] elites from the concerns of ordinary people, which connects with another: the privileging of theory over practice. Both of these are connected, however, with a third: the great, unresolved struggle of ordinary people to gain control over their own lives, to escape from schemes imposed on them by powerful elites, and to build a genuinely participatory culture. An understanding of Wittgenstein’s later philosophy, and the recognition of its striking differences from any previous philosophical works, can make some important contributions to all these issues. Wittgenstein’s aim is not, by the use of reason and argument, to establish any foundational principles to do with the nature of knowledge, perception, the structure of our world, scientific method, etc. Instead, he is concerned to inquire into the actual ways available to us of possibly making sense in the many different practical activities we share in our everyday lives together: “We are not seeking to discover anything entirely new, only what is already in plain view.”

scholarly journals Computational modelling of mitotic exit in budding yeast: the role of separase and Cdc14 endocycles

2011 ◽  
Vol 8 (61) ◽  
pp. 1128-1141 ◽  
Author(s):  
P. K. Vinod ◽  
Paula Freire ◽  
Ahmed Rattani ◽  
Andrea Ciliberto ◽  
Frank Uhlmann ◽  
...  
Keyword(s):  
Regulatory Networks ◽  
Budding Yeast ◽  
Cell Cycle Control ◽  
Computational Modelling ◽  
Eukaryotic Cell ◽  
Mitotic Exit ◽  
Intuitive Reasoning ◽  
Systematic Analysis ◽  
Systems View

The operating principles of complex regulatory networks are best understood with the help of mathematical modelling rather than by intuitive reasoning. Hereby, we study the dynamics of the mitotic exit (ME) control system in budding yeast by further developing the Queralt's model. A comprehensive systems view of the network regulating ME is provided based on classical experiments in the literature. In this picture, Cdc20–APC is a critical node controlling both cyclin (Clb2 and Clb5) and phosphatase (Cdc14) branches of the regulatory network. On the basis of experimental situations ranging from single to quintuple mutants, the kinetic parameters of the network are estimated. Numerical analysis of the model quantifies the dependence of ME control on the proteolytic and non-proteolytic functions of separase. We show that the requirement of the non-proteolytic function of separase for ME depends on cyclin-dependent kinase activity. The model is also used for the systematic analysis of the recently discovered Cdc14 endocycles. The significance of Cdc14 endocycles in eukaryotic cell cycle control is discussed as well.

scholarly journals Enzyme activity in the micropylar region of Melanoxylon brauna Schott seeds during germination under heat stress conditions

2020 ◽  
Vol 42 ◽  
Author(s):  
Marcone Moreira Santos ◽  
Eduardo Euclydes de Lima e Borges ◽  
Glauciana da Mata Ataíde ◽  
Raquel Maria de Oliveira Pires ◽  
Debora Kelli Rocha
Keyword(s):  
Enzyme Activity ◽  
Heat Stress ◽  
Seed Germination ◽  
Pectin Methylesterase ◽  
Stress Conditions ◽  
Southeastern Brazil ◽  
Experimental Conditions ◽  
Mannanase Activity ◽  
Ecological Importance ◽  
The Many

Abstract: Recent studies indicate that global temperatures will rise substantially in the 21st century, leading to the extinction of several plant species, as plant metabolism and germination are greatly affected by temperature. Melanoxylon brauna, a tree species native to the Atlantic Forest that occurs from northeastern to southeastern Brazil, is one of the many species threatened by global warming. Despite the economic and ecological importance of M. brauna, studies investigating the influence of heat stress on seed germination and biochemical responses are still incipient. This study aimed to evaluate enzyme activity in the micropylar region of M. brauna seeds during germination under heat stress conditions. Endo-β-mannanase, α-galactosidase, polygalacturonase, pectin methylesterase, pectin lyase, total cellulase, 1,3-β-glucosidase, and 1,4-β-glucosidase activities were determined in micropyles of seeds imbibed for 24, 48 and 72 h at 25, 35 and 45 °C. Seed germination was highest at 25 °C. Endo-β-mannanase activity was not detected under any of the experimental conditions, but imbibition temperature had a significant effect on the activity of all other enzymes.

scholarly journals Bacterial tail anchors can target to the mitochondrial outer membrane

2017 ◽  
Author(s):  
Güleycan Lutfullahoğlu Bal ◽  
Abdurrahman Keskin ◽  
Ayşe Bengisu Seferoğlu ◽  
Cory D. Dunn
Keyword(s):  
Outer Membrane ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Eukaryotic Cell ◽  
Eukaryotic Cells ◽  
Mitochondrial Outer Membrane ◽  
Bacterial Proteins ◽  
Rate Limiting Step ◽  
Protein Entry ◽  
Rate Limiting

ABSTRACTDuring the generation and evolution of the eukaryotic cell, a proteobacterial endosymbiont was refashioned into the mitochondrion, an organelle that appears to have been present in the ancestor of all present-day eukaryotes. Mitochondria harbor proteomes derived from coding information located both inside and outside the organelle, and the rate-limiting step toward the formation of eukaryotic cells may have been development of an import apparatus allowing protein entry to mitochondria. Currently, a widely conserved translocon allows proteins to pass from the cytosol into mitochondria, but how proteins encoded outside of mitochondria were first directed to these organelles at the dawn of eukaryogenesis is not clear. Because several proteins targeted by a carboxyl-terminal tail anchor (TA) appear to have the ability to insert spontaneously into the mitochondrial outer membrane (OM), it is possible that self-inserting, tail-anchored polypeptides obtained from bacteria might have formed the first gate allowing proteins to access mitochondria from the cytosol. Here, we tested whether bacterial TAs are capable of targeting to mitochondria. In a survey of proteins encoded by the proteobacterium Escherichia coli, predicted TA sequences were directed to specific subcellular locations within the yeast Saccharomyces cerevisiae. Importantly, TAs obtained from DUF883 family members ElaB and YqjD were abundantly localized to and inserted at the mitochondrial OM. Our results support the notion that eukaryotic cells are able to utilize membrane-targeting signals present in bacterial proteins obtained by lateral gene transfer, and our findings make plausible a model in which mitochondrial protein translocation was first driven by tail-anchored proteins.

The stability of pendent liquid drops. Part 2. Axial symmetry

1974 ◽  
Vol 63 (3) ◽  
pp. 487-508 ◽  
Author(s):  
E. Pitts
Keyword(s):  
Surface Tension ◽  
Energy Change ◽  
Maximum Volume ◽  
Experimental Conditions ◽  
Liquid Drops ◽  
Stable Equilibria ◽  
Equilibrium Shapes ◽  
The Stability ◽  
The Many ◽  
Horizontal Support

In a drop of liquid which hangs below a horizontal support or a t the end of a tube, the forces due to surface tension, pressure and gravity are in equilibrium. Amongst the many possible equilibrium shapes of the drop, only those which are stable occur naturally. The calculus of variations has been used to determine theoretically the stable equilibria, by calculating the energy change when the liquid in equilibrium experiences axially symmetrical perturbations under physically realistic constraints. If the energy change can be made negative, the drop is unstable. With this criterion, stable equilibria have been identified through which the naturally growing drops evolve until they reach a maximum volume, when they become unstable. These results are illustrated by calculations relating to typical experimental conditions.

Fission yeast Pds5 is required for accurate chromosome segregation and for survival after DNA damage or metaphase arrest

2002 ◽  
Vol 115 (3) ◽  
pp. 587-598 ◽  
Author(s):  
Shao-Win Wang ◽  
Rebecca L. Read ◽  
Chris J. Norbury
Keyword(s):  
Dna Damage ◽  
Fission Yeast ◽  
Sister Chromatid ◽  
Budding Yeast ◽  
Eukaryotic Cell ◽  
Sister Chromatid Cohesion ◽  
Chromosome Loss ◽  
Dependent Manner ◽  
Yeast Saccharomyces Cerevisiae ◽  
Chromatid Cohesion

Sister chromatid cohesion, which is established during the S phase of the eukaryotic cell cycle and persists until the onset of anaphase, is essential for the maintenance of genomic integrity. Cohesion requires the multi-protein complex cohesin, as well as a number of accessory proteins including Pds5/BIMD/Spo76. In the budding yeast Saccharomyces cerevisiae Pds5 is an essential protein that localises to chromosomes in a cohesin-dependent manner. Here we describe the characterisation in the fission yeast Schizosaccharomyces pombe of pds5+, a novel,non-essential orthologue of S. cerevisiae PDS5. The S. pombePds5 protein was localised to punctate nuclear foci in a manner that was dependent on the Rad21 cohesin component. This, together with additional genetic evidence, points towards an involvement of S. pombe Pds5 in sister chromatid cohesion. S. pombe pds5 mutants were hypersensitive to DNA damage and to mitotic metaphase delay, but this sensitivity was apparently not due to precocious loss of sister chromatid cohesion. These cells also suffered increased spontaneous chromosome loss and meiotic defects and their viability was dependent on the spindle checkpoint protein Bub1. Thus, while S. pombe Pds5 has an important cohesin-related role, this differs significantly from that of the equivalent budding yeast protein.

scholarly journals A Case Study of Enhanced Sulfidization Flotation of Lead Oxide Ore: Influence of Depressants

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 95
Author(s):  
Haiyun Xie ◽  
Rui Sun ◽  
Jizong Wu ◽  
Dongxia Feng ◽  
Likun Gao
Keyword(s):  
Lead Oxide ◽  
Open Circuit ◽  
Bench Test ◽  
Infrared Spectrometry ◽  
Experimental Conditions ◽  
Function Mechanism ◽  
Lead Metal ◽  
Special Value ◽  
Flotation Method

The refractory lead oxide ore has become an important source of lead metal with the continuous depletion of lead sulfide minerals. Lead oxide ore is of poor floatability and there are few cases to concentrate it successfully. In this study, the sulfidization-xanthate flotation method is applied for the beneficiation of lead oxide ore in Yunnan Province (China) with sodium hexametaphosphate and carboxymethyl cellulose as depressant. Chemical analysis and phase analysis was performed to explore the physicochemical property of raw ore, which provides a research basis for process design and operational control. The main influencing factors during the process, including grinding fineness, reagent types, and dosage, etc., have been studied through flotation tests. Zeta potential measurements and Fourier transfer-infrared spectrometry (FTIR) analysis were conducted to reveal the function mechanism of the reagents. Based on the determined experimental conditions, open circuit tests and closed circuit tests with one stage rougher, three-stage scavenger, and two-stage cleaner flotation, were carried out with the run-of-mine ore with a lead grade of 4.57%. Through close circuit bench test, the lead concentrate with a lead grade of 64.08% and recovery of 92.30% was obtained. This study is of special value, as it provides referencing significance for economically exploiting lead oxide ore.

scholarly journals Current perspectives on the evolution of birds

2008 ◽  
Vol 77 (2) ◽  
pp. 109-116 ◽  
Author(s):  
Per G.P. Ericson
Keyword(s):  
Evolutionary History ◽  
Genetic Data ◽  
Morphological Characters ◽  
Current Understanding ◽  
Sources Of Information ◽  
Theropod Dinosaurs ◽  
History Of ◽  
Evolution Of Birds ◽  
The Many ◽  
Rapid Radiations

The paper summarizes the current understanding of the evolution and diversification of birds. New insights into this field have mainly come from two fundamentally different, but complementary sources of information: the many newly discovered Mesozoic bird fossils and the wealth of genetic analyses of living birds at various taxonomic levels. The birds have evolved from theropod dinosaurs from which they can be defined by but a few morphological characters. The early evolutionary history of the group is characterized by the extinctions of many major clades by the end of the Cretaceous, and by several periods of rapid radiations and speciation. Recent years have seen a growing consensus about the higher-level relationships among living birds, at least as can be deduced from genetic data.

scholarly journals APC/C: current understanding and future perspectives

F1000Research ◽  
2019 ◽  
Vol 8 ◽  
pp. 725 ◽  
Author(s):  
Hiroyuki Yamano
Keyword(s):  
Cell Cycle ◽  
Molecular Mechanisms ◽  
Current Understanding ◽  
Historical Background ◽  
Cell Cycle Regulators ◽  
Anaphase Promoting Complex ◽  
Electron Microscopy Analysis ◽  
Cellular Machinery ◽  
The Many ◽  
Ubiquitin Conjugating Enzymes

The separation of sister chromatids at anaphase, which is regulated by an E3 ubiquitin ligase called the anaphase-promoting complex/cyclosome (APC/C), is arguably the most important irrevocable event during the cell cycle. The APC/C and cyclin-dependent kinase 1 (Cdk1) are just two of the many significant cell cycle regulators and exert control through ubiquitylation and phosphorylation, respectively. The temporal and spatial regulation of the APC/C is achieved by multiple mechanisms, including phosphorylation, interaction with the structurally related co-activators Cdc20 and Cdh1, loading of distinct E2 ubiquitin-conjugating enzymes, binding with inhibitors and differential affinities for various substrates. Since the discovery of APC/C 25 years ago, intensive studies have uncovered many aspects of APC/C regulation, but we are still far from a full understanding of this important cellular machinery. Recent high-resolution cryogenic electron microscopy analysis and reconstitution of the APC/C have greatly advanced our understanding of molecular mechanisms underpinning the enzymatic properties of APC/C. In this review, we will examine the historical background and current understanding of APC/C regulation.

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