scholarly journals The ventral disc is a flexible microtubule organelle that depends on domed ultrastructure for functional attachment of Giardia lamblia

2017 ◽  
Author(s):  
Christopher Nosala ◽  
Scott C. Dawson
Keyword(s):  
Giardia Lamblia ◽  
Conformational Dynamics ◽  
Three Dimensional ◽  
Dynamic Structure ◽  
Hydrodynamic Flow ◽  
Bare Area ◽  
Second Stage ◽  
Dynamic Movement ◽  
Ventral Disc ◽  
Disc Formation

AbstractThe parasite Giardia lamblia interacts with its host by directly attaching the lumen of the small intestine. Attachment is mediated by a cytoskeletal structure termed the ventral disc and proceeds in four distinct stages: skimming, seal formation, cell body contacts, and bare area contacts. The precise mechanism of disc-mediated attachment is unclear and attachment models rely heavily on whether or not the ventral disc is a dynamic structure. We sought to investigate the second stage of attachment in which a seal is formed beneath the ventral disc. Three-dimensional, live imaging of Giardia expressing specific ventral disc markers to the lateral crest, ventral groove, and disc body indicate dynamic movement in all of these regions. We observe seal formation by the lateral crest and determine that movement of the ventral groove region aids lateral crest seal formation. We also report the discovery of a new protein that is necessary for ventral disc formation and functional attachment (DAP_7268). Lastly, we observed that attachment largely depends on ventral disc ultrastructure as flattened discs display hindered attachment proficiency whether or not they retain the ability to form a seal. We propose a synthesized mechanism for attachment that includes flagellar hydrodynamic flow to help generate suction as well as disc conformational dynamics to aid in both hydrodynamic flow and the maintenance of negative pressure.

scholarly journals A 3D hydrodynamic flow-focusing device for cell sorting

2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Xiaofei Yuan ◽  
Andrew Glidle ◽  
Hitoshi Furusho ◽  
Huabing Yin
Keyword(s):  
Cell Sorting ◽  
Control Strategies ◽  
Three Dimensional ◽  
Hydrodynamic Flow ◽  
Proof Of Concept ◽  
Flow Focusing ◽  
Hydrodynamic Focusing ◽  
Cell Handling ◽  
Fluid Flow Control ◽  
High Degree

AbstractOptical-based microfluidic cell sorting has become increasingly attractive for applications in life and environmental sciences due to its ability of sophisticated cell handling in flow. The majority of these microfluidic cell sorting devices employ two-dimensional fluid flow control strategies, which lack the ability to manipulate the position of cells arbitrarily for precise optical detection, therefore resulting in reduced sorting accuracy and purity. Although three-dimensional (3D) hydrodynamic devices have better flow-focusing characteristics, most lack the flexibility to arbitrarily position the sample flow in each direction. Thus, there have been very few studies using 3D hydrodynamic flow focusing for sorting. Herein, we designed a 3D hydrodynamic focusing sorting platform based on independent sheath flow-focusing and pressure-actuated switching. This design offers many advantages in terms of reliable acquisition of weak Raman signals due to the ability to precisely control the speed and position of samples in 3D. With a proof-of-concept demonstration, we show this 3D hydrodynamic focusing-based sorting device has the potential to reach a high degree of accuracy for Raman activated sorting.

scholarly journals Special Issue: Application of Extracellular Matrix in Regenerative Medicine

2021 ◽  
Vol 11 (7) ◽  
pp. 3262
Author(s):  
Neill J. Turner
Keyword(s):  
Extracellular Matrix ◽  
Regenerative Medicine ◽  
Wound Repair ◽  
Three Dimensional ◽  
Dynamic Structure ◽  
Scaffold Material ◽  
Special Issue ◽  
Organ Regeneration ◽  
Scaffold Materials ◽  
The Many

The present Special Issue comprises a collection of articles addressing the many ways in which extracellular matrix (ECM), or its components parts, can be used in regenerative medicine applications. ECM is a dynamic structure, composed of a three-dimensional architecture of fibrous proteins, proteoglycans, and glycosaminoglycans, synthesized by the resident cells. Consequently, ECM can be considered as nature’s ideal biologic scaffold material. The articles in this Special Issue cover a range of topics from the use of ECM components to manufacture scaffold materials, understanding how changes in ECM composition can lead to the development of disease, and how decellularization techniques can be used to develop tissue-derived ECM scaffolds for whole organ regeneration and wound repair. This editorial briefly summarizes the most interesting aspects of these articles.

scholarly journals The Core and Holoenzyme Forms of RNA Polymerase from Mycobacterium smegmatis

2018 ◽  
Vol 201 (4) ◽  
Author(s):  
Tomáš Kouba ◽  
Jiří Pospíšil ◽  
Jarmila Hnilicová ◽  
Hana Šanderová ◽  
Ivan Barvík ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Rna Polymerase ◽  
Conformational Changes ◽  
Mycobacterium Smegmatis ◽  
Drug Target ◽  
Conformational Dynamics ◽  
Three Dimensional ◽  
Cryo Electron Microscopy ◽  
Bacterial Rna ◽  
High Degree

ABSTRACT Bacterial RNA polymerase (RNAP) is essential for gene expression and as such is a valid drug target. Hence, it is imperative to know its structure and dynamics. Here, we present two as-yet-unreported forms of Mycobacterium smegmatis RNAP: core and holoenzyme containing σA but no other factors. Each form was detected by cryo-electron microscopy in two major conformations. Comparisons of these structures with known structures of other RNAPs reveal a high degree of conformational flexibility of the mycobacterial enzyme and confirm that region 1.1 of σA is directed into the primary channel of RNAP. Taken together, we describe the conformational changes of unrestrained mycobacterial RNAP. IMPORTANCE We describe here three-dimensional structures of core and holoenzyme forms of mycobacterial RNA polymerase (RNAP) solved by cryo-electron microscopy. These structures fill the thus-far-empty spots in the gallery of the pivotal forms of mycobacterial RNAP and illuminate the extent of conformational dynamics of this enzyme. The presented findings may facilitate future designs of antimycobacterial drugs targeting RNAP.

scholarly journals DNA Polymerase: Structural Homology, Conformational Dynamics, and the Effects of Carcinogenic DNA Adducts

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
Richard G. Federley ◽  
Louis J. Romano
Keyword(s):  
Dna Replication ◽  
Dna Polymerase ◽  
Dna Adducts ◽  
Structural Changes ◽  
Dna Polymerases ◽  
Conformational Dynamics ◽  
Three Dimensional ◽  
Structural Homology ◽  
Human Right ◽  
Selection Of

DNA replication is vital for an organism to proliferate and lying at the heart of this process is the enzyme DNA polymerase. Most DNA polymerases have a similar three dimensional fold, akin to a human right hand, despite differences in sequence homology. This structural homology would predict a relatively unvarying mechanism for DNA synthesis yet various polymerases exhibit markedly different properties on similar substrates, indicative of each type of polymerase being prescribed to a specific role in DNA replication. Several key conformational steps, discrete states, and structural moieties have been identified that contribute to the array of properties the polymerases exhibit. The ability of carcinogenic adducts to interfere with conformational processes by directly interacting with the protein explicates the mutagenic consequences these adducts impose. Recent studies have identified novel states that have been hypothesised to test the fit of the nascent base pair, and have also shown the enzyme to possess a lively quality by continually sampling various conformations. This review focuses on the homologous structural changes that take place in various DNA polymerases, both replicative and those involved in adduct bypass, the role these changes play in selection of a correct substrate, and how the presence of bulky carcinogenic adducts affects these changes.

Static and dynamic postural control in long-term microgravity: evidence of a dual adaptation

2001 ◽  
Vol 90 (1) ◽  
pp. 205-215 ◽  
Author(s):  
Guido Baroni ◽  
Alessandra Pedrocchi ◽  
Giancarlo Ferrigno ◽  
Jean Massion ◽  
Antonio Pedotti
Keyword(s):  
Postural Control ◽  
Time Course ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Principal Component ◽  
Movement Analysis ◽  
Trunk Flexion ◽  
Dynamic Movement ◽  
Static Body

The adaptation of dynamic movement-posture coordination during forward trunk bending was investigated in long-term weightlessness. Three-dimensional movement analysis was carried out in two astronauts during a 4-mo microgravity exposure. The principal component analysis was applied to joint-angle kinematics for the assessment of angular synergies. The anteroposterior center of mass (CM) displacement accompanying trunk flexion was also quantified. The results reveal that subjects kept typically terrestrial strategies of movement-posture coordination. The temporary disruption of joint-angular synergies observed at subjects' first in-flight session was promptly recovered when repetitive sessions in flight were analyzed. The CM anteroposterior shift was consistently <3–4 cm, suggesting that subjects could dynamically control the CM position throughout the whole flight. This is in contrast to the observed profound microgravity-induced disruption of the quasi-static body orientation and initial CM positioning. Although this study was based on only two subjects, evidence is provided that static and dynamic postural control might be under two separate mechanisms, adapting with their specific time course to the constraints of microgravity.

scholarly journals Two-Stage Discrete Mechanical Modelin Three-Dimensional Space for Garment Simulation

2019 ◽  
Vol 19 (1) ◽  
pp. 26-35 ◽  
Author(s):  
Xuan Luo ◽  
Gaoming Jiang ◽  
Honglian Cong
Keyword(s):  
Mechanical Model ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Mathematical Expression ◽  
Two Stage ◽  
Second Stage ◽  
Simulation Speed ◽  
Optimal Value ◽  
Variable Distance ◽  
Stage Process

Abstract This paper focuses on the better performance between the garment simulation result and the simulation speed. For simplicity and clarity, a notation “PART” is defined to indicate the areas between the garment and the human body satisfying some constraints. The discrete mechanical model can be achieved by the two-stage process. In the first stage, the garment can be divided into several PARTs constrained by the distance. In the second stage, the mechanical model of each PART is formulated with a mathematical expression. Thus, the mechanical model of the garment can be obtained. Through changing the constrained distance, the simulation result and the simulation speed can be observed. From the variable distance, a desired value can be chosen for an optimal value. The results of simulations and experiments demonstrate that the better performance can be achieved at a higher speed by saving runtime with the acceptable simulation results and the efficiency of the proposed scheme can be verified as well.

scholarly journals The Giardia Median Body Protein Is a Ventral Disc Protein That Is Critical for Maintaining a Domed Disc Conformation during Attachment

2012 ◽  
Vol 11 (3) ◽  
pp. 292-301 ◽  
Author(s):  
David J. Woessner ◽  
Scott C. Dawson
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Shear Forces ◽  
Bare Area ◽  
Body Protein ◽  
Content Type ◽  
Intestinal Epithelia ◽  
Normal Forces ◽  
Membrane Contacts ◽  
Ventral Disc

ABSTRACTGiardiahas unique microtubule structures, including the ventral disc, the primary organelle of attachment to the host, and the median body, a structure of undefined function. During attachment, the ventral disc has a domed conformation and enablesGiardiato attach to the host intestinal epithelia within seconds. The mechanism of attachment via the ventral disc and the overall structure, function, and assembly of the ventral disc are not well understood. Our recent proteomic analysis of the ventral disc indicated that the median body protein (MBP), previously reported to localize exclusively to the median body, was primarily localized to the ventral disc. Using high-resolution light and electron microscopy, we confirm that the median body protein localizes primarily to the overlap zone of the ventral disc. The MBP also occasionally localized to the median body during prophase. To define the contribution of MBP to the ventral disc structure, we depleted MBP using an anti-MBP morpholino. We found that the ventral disc was no longer able to form properly and that the disc structure often had an aberrant nondomed or flattened horseshoe conformation. The ability of attached anti-MBP morpholino-treated trophozoites to withstand shear forces and normal forces was significantly decreased. Most notably, the plasma membrane contacts with the surface, including those of the bare area, were defective after the anti-MBP knockdown. To our knowledge, this is the first ventral disc protein whose depletion directly alters ventral disc structure, confirming that the domed ventral disc conformation is important for robust attachment.

Intercalation of pentane into the stage 2 to 4 cesium graphitides: Relation between cesium density in the intercalated layers and the stage of the parent binary

1993 ◽  
Vol 8 (9) ◽  
pp. 2288-2298 ◽  
Author(s):  
H. Pillière ◽  
M. Goldmann ◽  
F. Béguin
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Structural Transformations ◽  
Layer Model ◽  
Simultaneous Formation ◽  
Ternary Compounds ◽  
Second Stage ◽  
The Third ◽  
Cesium Ions ◽  
Third Stage

Isotherms (at 300 K and 328 K) and isobars (in the range 300 to 400 K) of n-pentane intercalation in CsC24 and CsC36 were established. With CsC24, three plateaus were identified at 0.52, 0.7, and 1.0 n-pentane/24 C, whereas only two plateaus at 0.8 and 0.97 n-pentane/36 C were found with CsC36. The progress of the reaction between n-pentane and CsC24, CsC36, and CsC56 (stage 2 to 4) was monitored by real-time neutron diffraction. The intercalation of n-pentane in CsC24 results in the simultaneous formation of a second stage ternary and a first stage binary “CsC8”, whereas, from the third stage CsC36 or the fourth stage CsC56, only pure second stage or third stage ternary compounds are formed, respectively. Owing to the formation of binary domains rich in alkali metal (CsC8) or to stage lowering produced by the ternarization, the in-plane cesium density is smaller in the ternary layer than in the starting binary. The electrostatic repulsion between the cesium ions, provoked by the sorption of n-pentane, is believed to be at the origin of the increased coverage. During the intercalation or de-intercalation processes, three-dimensional segregation occurs in each grain. A pleated layer model with canted fronts is presented. It accounts for the various phases present within each grain and for the structural transformations caused by pressure variations. At room temperature, the ternary layer seems to be disordered. The order-disorder transition appearing either by decreasing the temperature or by increasing the n-pentane pressure is correlated to a hindered motion of the intercalated molecules.

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