scholarly journals The Mechanical Components of the Dynein Motor

2010 ◽  
Vol 10 ◽  
pp. 857-864 ◽  
Author(s):  
Peter Höök
Keyword(s):  
Motor Activity ◽  
Molecular Mechanism ◽  
Motor Proteins ◽  
The Other ◽  
Structural Components ◽  
Complex Interplay ◽  
Unique Role ◽  
Dynein Motor ◽  
Slow Progress ◽  
Mechanical Components

Unlike our understanding of the other two classes of cytoskeletal motor proteins, the myosins and kinesins, we have only recently begun to comprehend the molecular mechanism for how dynein produces force and movement. The slow progress has been attributed, in part, to the enormous size of the dynein force-producing head, but also to the complex interplay between its structural components, each of which has a unique role in regulating dynein motor activity. The integrated and highly coordinated mechanism by which these structures work together in powering the dynein machinery is discussed in this review.

Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL

1990 ◽  
Vol 48 (1) ◽  
pp. 258-259
Author(s):  
J.L. Carrascosa ◽  
G. Abella ◽  
S. Marco ◽  
M. Muyal ◽  
J.M. Carazo
Keyword(s):  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Series Method ◽  
Three Dimensional Reconstruction ◽  
Structural Components ◽  
E Coli ◽  
Dimensional Reconstruction ◽  
Morphogenetic Factors ◽  
Tilt Series

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.

Neural Patterns Associated with Ventilatory Movements in Dragonfly Larvae

1970 ◽  
Vol 52 (1) ◽  
pp. 167-175
Author(s):  
P. J. MILL
Keyword(s):  
Control System ◽  
Motor Activity ◽  
Action Potentials ◽  
Motor Units ◽  
The Other ◽  
Ventilatory Control ◽  
Expiratory Phase ◽  
Segmental Nerve ◽  
Ventral Muscle ◽  
Stimulation Of

1. Rhythmic bursts of motor activity associated with the expiratory phase of ventilation have been recorded from the second lateral segmental nerves of posterior abdominal ganglia in Aeshna and Anax larvae. 2. In Aeshna the rhythmic expiratory bursts contain one, or sometimes two, motor units; whereas in Anax there are almost invariably three units. In both animals only one unit is associated with action potentials in the respiratory dorso-ventral muscle. 3. Motor activity synchronized with the expiratory bursts in the second nerves has been recorded from the other lateral nerves and from the last unpaired nerve. In addition the fifth lateral nerves carry inspiratory bursts. 4. It has been confirmed that stimulation of a first segmental nerve can re-set the ventilatory rhythm by initiating an expiratory burst in the second nerves. The original frequency is immediately resumed on cessation of stimulation. 5. The nature of the ventilatory control system in dragonfly larvae is discussed in relation to other rhythmic systems in the arthropods.

scholarly journals TUBA1A mutations identified in lissencephaly patients dominantly disrupt neuronal migration and impair dynein activity

2018 ◽  
Vol 28 (8) ◽  
pp. 1227-1243 ◽  
Author(s):  
Jayne Aiken ◽  
Jeffrey K Moore ◽  
Emily A Bates
Keyword(s):  
Motor Activity ◽  
Neuronal Migration ◽  
Ectopic Expression ◽  
Missense Mutations ◽  
Microtubule Cytoskeleton ◽  
Tubulin Genes ◽  
Dynein Motor ◽  
Brain Malformations ◽  
Developing Mouse Brain ◽  
And Migration

Abstract The microtubule cytoskeleton supports diverse cellular morphogenesis and migration processes during brain development. Mutations in tubulin genes are associated with severe human brain malformations known as ‘tubulinopathies’; however, it is not understood how molecular-level changes in microtubule subunits lead to brain malformations. In this study, we demonstrate that missense mutations affecting arginine at position 402 (R402) of TUBA1A α-tubulin selectively impair dynein motor activity and severely and dominantly disrupt cortical neuronal migration. TUBA1A is the most commonly affected tubulin gene in tubulinopathy patients, and mutations altering R402 account for 30% of all reported TUBA1A mutations. We show for the first time that ectopic expression of TUBA1A-R402C and TUBA1A-R402H patient alleles is sufficient to dominantly disrupt cortical neuronal migration in the developing mouse brain, strongly supporting a causal role in the pathology of brain malformation. To isolate the precise molecular impact of R402 mutations, we generated analogous R402C and R402H mutations in budding yeast α-tubulin, which exhibit a simplified microtubule cytoskeleton. We find that R402 mutant tubulins assemble into microtubules that support normal kinesin motor activity but fail to support the activity of dynein motors. Importantly, the level of dynein impairment scales with the expression level of the mutant in the cell, suggesting a ‘poisoning’ mechanism in which R402 mutant α-tubulin acts dominantly by populating microtubules with defective binding sites for dynein. Based on our results, we propose a new model for the molecular pathology of tubulinopathies that may also extend to other tubulin-related neuropathies.

scholarly journals Developing virtual worlds: The interplay of design, communities and rationality

First Monday ◽  
2010 ◽  
Author(s):  
F. Ted Tschang ◽  
Jordi Comas
Keyword(s):  
Business Model ◽  
Virtual Worlds ◽  
The Other ◽  
User Generated Content ◽  
Complex Interplay ◽  
Emergent Community ◽  
To Come

This paper examines the evolution of virtual worlds from the developer's perspective. What are the motivations of developers? What are the specific challenges of the governance of user-generated content? User-created virtual worlds may be characterized according to their degree of design or emergence. On one end is the 'the designer as god' perspective and on the other is the unforeseeable and perpetually emergent 'user creativity.' Utilizing a theoretically derived sample of virtual worlds, we illustrate how governance is more complex as designers contend with three major issues. In general, across all three worlds, developers had to come to grips with the limits of their ability to design virtual worlds for premeditated outcomes. Secondly, communities forming within worlds, as opposed to atomized users, are central to the (creative) building, usage and governance of virtual worlds. Developers have a range of choices for how to interact with communities ranging from arm's length monitoring to engagement. Thirdly, developers have to manage instrumentally rational aspects of their business which can lead to tensions with the design and community goals, and, ultimately, lead to the failure of a world's business model. A fuller accounting of governance will have to accommodate the complex interplay between purposeful design, emergent community, and the logic of the marketplace.

scholarly journals The conception of substitution of the equals sign plays a unique role in students' algebra performance

2019 ◽  
Vol 5 (1) ◽  
pp. 24-37 ◽  
Author(s):  
Emine Simsek ◽  
Iro Xenidou-Dervou ◽  
Ilyas Karadeniz ◽  
Ian Jones
Keyword(s):  
Secondary School ◽  
Secondary School Students ◽  
The Other ◽  
School Students ◽  
Unique Role ◽  
School Year ◽  
Equals Sign ◽  
Definition Of ◽  
Unique Predictor ◽  
Algebra Learning

Students’ conceptions of the equals sign are related to algebraic success. Research has identified two common conceptions held by children: operational and relational. The latter has been widely operationalised in terms of the sameness of the values on each side of the equals sign, but it has been recently argued that the substitution component of relational equivalence should also be operationalised (Jones, Inglis, Gilmore, & Dowens, 2012, https://doi.org/10.1016/j.jecp.2012.05.003). In this study, we investigated whether students’ endorsement of the substitution definition of the equals sign is a unique predictor of their algebra performance independent of the other two definitions (operational and sameness). Secondary school students were asked to rate the ‘cleverness’ of operational, sameness, and substitution definitions of the equals sign and completed an algebra test. Our findings demonstrate that endorsement of substitution plays a unique role in explaining secondary school students’ algebra performance above and beyond school year and the other definitions. These findings contribute new insights into how students’ algebra learning relates to their conceptions of the equals sign.

The role of the WTO in achieving equity and efficiency in international markets for agricultural products

2005 ◽  
Vol 4 (2) ◽  
pp. 229-247 ◽  
Author(s):  
DONALD MACLAREN
Keyword(s):  
International Markets ◽  
Agricultural Products ◽  
Differential Treatment ◽  
The Other ◽  
Doha Round ◽  
Equity And Efficiency ◽  
Slow Progress ◽  
The One ◽  
Fundamental Objective

The fundamental objective of the negotiations on agriculture that are taking place in the Doha Round is to establish a new set of rules, which will correct current distortions and prevent future distortions in international markets for agricultural products while taking into account non-trade concerns and special and differential treatment. A summary of the chronology of the very slow progress to date in the negotiations is provided. This rate of progress is explained through considering the weights the different groups of governments are giving to removing trade distortions, on the one hand, and to non-trade concerns and special and differential treatment, on the other. Some results from the economic theory of distortions and welfare are used to explain the conditions under which the twin pursuits of non-trade concerns domestically and fairness internationally are compatible. These results are contrasted with the realities of the current negotiations on the agriculture component of the ‘July 2004 package’.

scholarly journals Cholesterol sensor ORP1L contacts the ER protein VAP to control Rab7–RILP–p150Glued and late endosome positioning

2009 ◽  
Vol 185 (7) ◽  
pp. 1209-1225 ◽  
Author(s):  
Nuno Rocha ◽  
Coenraad Kuijl ◽  
Rik van der Kant ◽  
Lennert Janssen ◽  
Diane Houben ◽  
...  
Keyword(s):  
Motor Proteins ◽  
Oxysterol Binding Protein ◽  
Membrane Contact Sites ◽  
Cholesterol Levels ◽  
Dynein Motor ◽  
Late Endosomes ◽  
In Trans ◽  
Membrane Contact ◽  
Cholesterol Control ◽  
Niemann Pick

Late endosomes (LEs) have characteristic intracellular distributions determined by their interactions with various motor proteins. Motor proteins associated to the dynactin subunit p150Glued bind to LEs via the Rab7 effector Rab7-interacting lysosomal protein (RILP) in association with the oxysterol-binding protein ORP1L. We found that cholesterol levels in LEs are sensed by ORP1L and are lower in peripheral vesicles. Under low cholesterol conditions, ORP1L conformation induces the formation of endoplasmic reticulum (ER)–LE membrane contact sites. At these sites, the ER protein VAP (VAMP [vesicle-associated membrane protein]-associated ER protein) can interact in trans with the Rab7–RILP complex to remove p150Glued and associated motors. LEs then move to the microtubule plus end. Under high cholesterol conditions, as in Niemann-Pick type C disease, this process is prevented, and LEs accumulate at the microtubule minus end as the result of dynein motor activity. These data explain how the ER and cholesterol control the association of LEs with motor proteins and their positioning in cells.

Overview of Solid Waste Management of Healthcare and Related Organisations

2021 ◽  
pp. 1336-1352
Author(s):  
Isaiah Adesola Oke ◽  
Lukman Salihu ◽  
Idi Dansuleiman Mohammed ◽  
Asani M. Afolabi
Keyword(s):  
Solid Waste Management ◽  
Calorific Value ◽  
The Other ◽  
Industrialized Countries ◽  
District Health ◽  
Health Clinics ◽  
The World ◽  
Slow Progress ◽  
Basic Services ◽  
Infectious Waste

This chapter provides information on the quantities and properties of healthcare wastes in various types of facilities located in developing countries, as well as in some industrialized countries. Most of the information has been obtained from the literature, while some information has been collected by the authors and from reports available to the authors. The range of hospital waste generation varies from 0.016 to 3.23 kg/bed-day. The relatively wide variation is due to the fact that some of the facilities surveyed may include out-patient services and district health clinics; these facilities essentially provide basic services and thus the quantities of waste generated are relatively small. On the other hand, the reported amount of infectious waste varied from 0.01 to 0.65 kg/bed-day. The characteristics of the components of healthcare wastes, such as the bulk density and the calorific value, have substantial variability. It was concluded that the world has made only slow progress in proper medical in past decades, with dramatic differences among countries and regions.

scholarly journals Entropy Generation Methodology for Defect Analysis of Electronic and Mechanical Components—A Review

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 254
Author(s):  
Miao Cai ◽  
Peng Cui ◽  
Yikang Qin ◽  
Daoshuang Geng ◽  
Qiqin Wei ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Electronic Devices ◽  
Second Law Of Thermodynamics ◽  
Damage Analysis ◽  
Defect Analysis ◽  
Unique Role ◽  
Mechanical Components ◽  
Assessment Problems ◽  
The Relationship

Understanding the defect characterization of electronic and mechanical components is a crucial step in diagnosing component lifetime. Technologies for determining reliability, such as thermal modeling, cohesion modeling, statistical distribution, and entropy generation analysis, have been developed widely. Defect analysis based on the irreversibility entropy generation methodology is favorable for electronic and mechanical components because the second law of thermodynamics plays a unique role in the analysis of various damage assessment problems encountered in the engineering field. In recent years, numerical and theoretical studies involving entropy generation methodologies have been carried out to predict and diagnose the lifetime of electronic and mechanical components. This work aimed to review previous defect analysis studies that used entropy generation methodologies for electronic and mechanical components. The methodologies are classified into two categories, namely, damage analysis for electronic devices and defect diagnosis for mechanical components. Entropy generation formulations are also divided into two detailed derivations and are summarized and discussed by combining their applications. This work is expected to clarify the relationship among entropy generation methodologies, and benefit the research and development of reliable engineering components.

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