scholarly journals Transformations in Flagellar Structure ofRhodobacter sphaeroides and Possible Relationship to Changes in Swimming Speed

1999 ◽  
Vol 181 (16) ◽  
pp. 4825-4833 ◽  
Author(s):  
Judith P. Armitage ◽  
Thomas P. Pitta ◽  
Margot A.-S. Vigeant ◽  
Helen L. Packer ◽  
Roseanne M. Ford
Keyword(s):  
Swimming Speed ◽  
Three Dimensional ◽  
Photosynthetic Bacterium ◽  
High Amplitude ◽  
Three Dimensions ◽  
Helical Conformation ◽  
Free Swimming ◽  
Swimming Pattern ◽  
Dic Microscopy

ABSTRACT Rhodobacter sphaeroides is a photosynthetic bacterium which swims by rotating a single flagellum in one direction, periodically stopping, and reorienting during these stops. Free-swimming R. sphaeroides was examined by both differential interference contrast (DIC) microscopy, which allows the flagella of swimming cells to be seen in vivo, and tracking microscopy, which tracks swimming patterns in three dimensions. DIC microscopy showed that when rotation stopped, the helical flagellum relaxed into a high-amplitude, short-wavelength coiled form, confirming previous observations. However, DIC microscopy also revealed that the coiled filament could rotate slowly, reorienting the cell before a transition back to the functional helix. The time taken to reform a functional helix depended on the rate of rotation of the helix and the length of the filament. In addition to these coiled and helical forms, a third conformation was observed: a rapidly rotating, apparently straight form. This form took shape from the cell body out and was seen to form directly from flagella that were initially in either the coiled or the helical conformation. This form was always significantly longer than the coiled or helical form from which it was derived. The resolution of DIC microscopy made it impossible to identify whether this form was genuinely in a straight conformation or was a low-amplitude, long-wavelength helix. Examination of the three-dimensional swimming pattern showed that R. sphaeroides changed speed while swimming, sometimes doubling the swimming speed between stops. The rate of acceleration out of stops was also variable. The transformations in waveform are assumed to be torsionally driven and may be related to the changes in speed measured in free-swimming cells. The roles of and mechanisms that may be involved in the transformations of filament conformations and changes in swimming speed are discussed.

scholarly journals Budding yeast chromatin is dispersed in a crowded nucleoplasm in vivo

2016 ◽  
Vol 27 (21) ◽  
pp. 3357-3368 ◽  
Author(s):  
Chen Chen ◽  
Hong Hwa Lim ◽  
Jian Shi ◽  
Sachiko Tamura ◽  
Kazuhiro Maeshima ◽  
...  
Keyword(s):  
Budding Yeast ◽  
Three Dimensional ◽  
Chromatin Organization ◽  
Three Dimensions ◽  
Yeast Saccharomyces Cerevisiae ◽  
Nuclear Structures ◽  
Three Dimensional Models ◽  
Electron Cryotomography ◽  
Fundamental Units

Chromatin organization has an important role in the regulation of eukaryotic systems. Although recent studies have refined the three-dimensional models of chromatin organization with high resolution at the genome sequence level, little is known about how the most fundamental units of chromatin—nucleosomes—are positioned in three dimensions in vivo. Here we use electron cryotomography to study chromatin organization in the budding yeast Saccharomyces cerevisiae. Direct visualization of yeast nuclear densities shows no evidence of 30-nm fibers. Aside from preribosomes and spindle microtubules, few nuclear structures are larger than a tetranucleosome. Yeast chromatin does not form compact structures in interphase or mitosis and is consistent with being in an “open” configuration that is conducive to high levels of transcription. From our study and those of others, we propose that yeast can regulate its transcription using local nucleosome–nucleosome associations.

scholarly journals In vivo three-dimensional mandibular kinematics and functional point trajectories during temporomandibular activities using 3d fluoroscopy

2020 ◽  
pp. 20190464
Author(s):  
Chien-Chih Chen ◽  
Cheng-Chung Lin ◽  
Hong-Po Hsieh ◽  
Yang-Chieh Fu ◽  
Yunn-Jy Chen ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Mouth Opening ◽  
Three Dimensions ◽  
Forward Movement ◽  
Joint Activities ◽  
End Point ◽  
3D Fluoroscopy ◽  
Point Trajectories ◽  
Functional Point

Objectives: To measure in vivo three-dimensional kinematics of the mandible and associated end-point trajectories and to quantify their relationships during temporomandibular joint activities using 3D fluoroscopy. Methods: A novel fluoroscopy-based 3D measurement method was used to measure motions of the mandible and the associated end points (i.e. incisors and lateral poles of both condyles) during open close, lateral gliding and protrusion-retraction movements in healthy young individuals. The contributions of each of the rotational and translational components of the mandible to the end-point trajectories were quantified through experiment-based computer simulations. Results: The mandibular rotation was found to account for 91% of the maximal mouth-opening-capacity and 73% of the maximal lateral incisor movement, while the condylar translation contributed to 99% of the anterior protrusion distance. Incisor trajectories were nearly vertical within the first 60% of the maximal opening during the open-close movement. Conclusions: Similar condylar downward rotation paths but with bilaterally asymmetrical ranges were used to perform basic mandibular movements of different targeted TI trajectories in three dimensions, that is, open-close, lateral-gliding and protrusion-retraction. Mandibular rotations contributed to the majority of the principal displacement components of the incisor, that is, vertical during open-close and towards the working-side-during lateral-gliding, while mandibular translation contributed mainly to the forward movement of the incisor during protrusion-retraction. Owing to the anatomical constraints, the freedom of mandibular translation is limited and mainly in the anteroposterior direction, which is considered helpful for the control and stability of the TMJ during oral activities.

scholarly journals Mesenchymal stem cell spheroids: potential cell materials for cell therapy

STEMedicine ◽  
2020 ◽  
Vol 2 (5) ◽  
pp. e67
Author(s):  
Zhongjuan Xu ◽  
Xingzhi Liu ◽  
Yu Wei ◽  
Zhe Zhao ◽  
Junjun Cao ◽  
...  
Keyword(s):  
Regenerative Medicine ◽  
Tissue Injury ◽  
Three Dimensional ◽  
3D Culture ◽  
Research Field ◽  
Three Dimensions ◽  
Spheroid Formation ◽  
Culture Methods ◽  
Differentiation Potential

Mesenchymal stromal/stem cells (MSCs) have been applied in clinical trials with an increasing number in recent years. MSCs showed their great potentials in regenerative medicine for their extensive sources, multilineage differentiation potential, low immunogenicity and self-renewal ability. However, the clinical application of MSCs still confronts many challenges including the requirement of large quantity of cells, low survival ability in vivo and the loss of main original characteristics due to two-dimensional (2D) culture although it is beneficial to cells fast expansion. Three-dimensional (3D) culture artificially creates an environment that permits cells to grow or interact with their surroundings in all three dimensions. Therefore, 3D culture was widely regarded as a more preferable and closer physiological microenvironment for cells growth. Recently, many different 3D spheroid culture methods have been developed to optimize MSCs biological characteristics to meet the demand of regenerative medicine. In this review, we comprehensively discussed the merits and demerits of different spheroid formation methods, expounded the mechanisms of spheroid formation and its microenvironment, and illustrated their optimized biological functions and the pre-clinical applications in various tissue injury and regeneration. In the end, we prospected the trends of this research field and proposed the key problems needed to be solved in the future.

scholarly journals Geometric constraints alter cell arrangements within curved epithelial tissues

2017 ◽  
Vol 28 (25) ◽  
pp. 3582-3594 ◽  
Author(s):  
Jean-Francois Rupprecht ◽  
Kok Haur Ong ◽  
Jianmin Yin ◽  
Anqi Huang ◽  
Huy-Hong-Quan Dinh ◽  
...  
Keyword(s):  
Cell Morphology ◽  
Three Dimensional ◽  
Quantitative Information ◽  
Geometric Constraints ◽  
Three Dimensions ◽  
Drosophila Embryo ◽  
Anterior Pole ◽  
Epithelial Tissues ◽  
Early Drosophila Embryo

Organ and tissue formation are complex three-dimensional processes involving cell division, growth, migration, and rearrangement, all of which occur within physically constrained regions. However, analyzing such processes in three dimensions in vivo is challenging. Here, we focus on the process of cellularization in the anterior pole of the early Drosophila embryo to explore how cells compete for space under geometric constraints. Using microfluidics combined with fluorescence microscopy, we extract quantitative information on the three-dimensional epithelial cell morphology. We observed a cellular membrane rearrangement in which cells exchange neighbors along the apical-basal axis. Such apical-to-basal neighbor exchanges were observed more frequently in the anterior pole than in the embryo trunk. Furthermore, cells within the anterior pole skewed toward the trunk along their long axis relative to the embryo surface, with maximum skew on the ventral side. We constructed a vertex model for cells in a curved environment. We could reproduce the observed cellular skew in both wild-type embryos and embryos with distorted morphology. Further, such modeling showed that cell rearrangements were more likely in ellipsoidal, compared with cylindrical, geometry. Overall, we demonstrate that geometric constraints can influence three-dimensional cell morphology and packing within epithelial tissues.

scholarly journals Biosensor-Expressing Spheroid Cultures for Imaging of Drug-Induced Effects in Three Dimensions

2013 ◽  
Vol 18 (6) ◽  
pp. 736-743 ◽  
Author(s):  
Rainer Wittig ◽  
Verena Richter ◽  
Stephanie Wittig-Blaich ◽  
Petra Weber ◽  
Wolfgang S. L. Strauss ◽  
...  
Keyword(s):  
Cell Cultures ◽  
Fluorescent Protein ◽  
Temporal Dynamics ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Structured Illumination ◽  
Three Dimensional Model ◽  
Structured Illumination Microscopy ◽  
Drug Induced

In the past, the majority of antitumor compound-screening approaches had been performed in two-dimensional (2D) cell cultures. Although easy to standardize, this method provides results of limited significance because cells are surrounded by an artificial microenvironment, are not exposed to hypoxia gradients, and lack cell-cell contacts. These nonphysiological conditions directly affect relevant parameters such as the resistance to anticancer drugs. Multicellular tumor spheroids more closely resemble the in vivo situation in avascularized tumors. To monitor cellular reactions within this three-dimensional model system, we stably transfected a spheroid-forming glioblastoma cell line with Grx1-roGFP2, a green fluorescent protein (GFP)–based glutathione-specific redox sensor that detects alterations in the glutathione redox potential. Functionality and temporal dynamics of the sensor were verified with redox-active substances in 2D cell culture. Based on structured illumination microscopy using nonphototoxic light doses, ratio imaging was then applied to monitor the response of the glutathione system to exogenous hydrogen peroxide in optical sections of a tumor spheroid. Our approach provides a proof of concept for biosensor-based imaging in 3D cell cultures.

scholarly journals SELF-REGULATION OF GROWTH IN THREE DIMENSIONS

1973 ◽  
Vol 138 (4) ◽  
pp. 745-753 ◽  
Author(s):  
Judah Folkman ◽  
Mark Hochberg
Keyword(s):  
Surface Area ◽  
Self Regulation ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Cell Populations ◽  
Simple Diffusion ◽  
The Face

Multi-cell spheroids were grown in soft agar. When each spheroid was cultured in a large volume of medium, frequently renewed, all spheroids eventually reached a dormant phase at a diameter of approximately 3–4 mm and a population of approximately 106 cells. In the dormant spheroid, newly generated cells at the periphery balanced those lost by necrosis in the center. We propose that this dormant phase is due to a gradual reduction in the ratio of surface area to volume: a size is achieved beyond which there is insufficient surface area for the spheroid to eliminate catabolites and absorb nutrients. Thus, in the face of unlimited space and of new medium, three-dimensional cell populations become self-regulating. This phenomenon contrasts with standard tissue culture in which cell populations, living on a flat plane in two dimensions, will not stop growing in the face of unlimited space and new medium because the ratio of surface area to volume remains constant. These experiments provide a mechanism for our observations in vivo: before vascularization, solid tumors live by simple diffusion as three-dimensional spheroids or ellipsoids. They become dormant at a diameter of only a few millimeters; once vascularized, they are released from this dormant phase and begin exponential growth. Thus, tumor dormancy resulting from absence of angiogenesis in vivo, may operate by the same mechanism responsible for dormancy of spheroids in vitro.

The three-dimensional hydrodynamics of tadpole locomotion.

1997 ◽  
Vol 200 (22) ◽  
pp. 2807-2819 ◽  
Author(s):  
H Liu ◽  
R Wassersug ◽  
K Kawachi
Keyword(s):  
Unsteady Flow ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Small Region ◽  
High Amplitude ◽  
Three Dimensions ◽  
Cfd Model ◽  
Hind Limbs ◽  
Lower Amplitude ◽  
Low Efficiency

Tadpoles are unusual among vertebrates in having a globose body with a laterally compressed tail abruptly appended to it. Compared with most teleost fishes, tadpoles swim awkwardly, with waves of relatively high amplitude at both the snout and tail tip. In the present study, we analyze tadpole propulsion using a three-dimensional (3D) computational fluid dynamic (CFD) model of undulatory locomotion that simulates viscous and unsteady flow around an oscillating body of arbitrary 3D geometry. We first confirm results from a previous two-dimensional (2D) study, which suggested that the characteristic shape of tadpoles was closely matched to their unusual kinematics. Specifically, our 3D results reveal that the shape and kinematics of tadpoles collectively produce a small 'dead water' zone between the head-body and tail during swimming precisely where tadpoles can and do grow hind limbs--without those limbs obstructing flow. We next use our CFD model to show that 3D hydrodynamic effects (cross flows) are largely constrained to a small region along the edge of the tail fin. Although this 3D study confirms most of the results of the 2D study, it shows that propulsive (Froude) efficiency for tadpoles is overall lower than predicted from a 2D analysis. This low efficiency is not, however, a result of the high-amplitude undulations of the tadpole. This was demonstrated by forcing our 'virtual' tadpole to swim with fish-like kinematics, i.e. with lower-amplitude propulsive waves. That particular simulation yielded a much lower Froude efficiency, confirming that the large-amplitude lateral oscillations of the tadpole do, indeed, provide positive thrust. This, we believe, is the first time that the unsteady flow generated by an undulating vertebrate has been realistically modelled in three dimensions. Our study demonstrates the feasibility of using 3D CFD methods to model the locomotion of other undulatory organisms.

Digital artery deformation on movement of the proximal interphalangeal joint

2018 ◽  
Vol 44 (2) ◽  
pp. 187-195
Author(s):  
Susumu Saito ◽  
Ryoma Bise ◽  
Aya Yoshikawa ◽  
Hiroyuki Sekiguchi ◽  
Itaru Tsuge ◽  
...  
Keyword(s):  
Index Finger ◽  
Three Dimensional ◽  
Proximal Interphalangeal Joint ◽  
Interphalangeal Joint ◽  
Three Dimensions ◽  
Morphological Data ◽  
Photoacoustic Tomography ◽  
Digital Artery ◽  
Specific Mechanism

This study aimed to characterize in vivo human digital arteries in three-dimensions using photoacoustic tomography in order to understand the specific mechanism underlying arterial deformation associated with movement of the proximal interphalangeal joint. Three-dimensional morphological data were obtained on the radialis indicis artery (radial artery of the index finger) at different angles of the joint. The association between increased curvature of the deformation and the anatomical region was assessed. Characteristic morphological deformations in areas of major deformation were determined. The deformation of the artery was characterized by three consecutive curves in juxta-articular regions, which were particularly noticeable when the joint was flexed at an angle of ≥ 60°. The change in the curvature of the deformation during 30°–90° of flexion was lower in middle-aged individuals than in young individuals. Better understanding of the mechanism underlying deformation of the digital arteries may contribute to advancements in flap procedures and rehabilitation strategies after digital artery repair.

Cryoelectron Microscopy of Red Cell Skeletons Reveals that Spectrin has a Helical Conformation

1997 ◽  
Vol 3 (S2) ◽  
pp. 333-334
Author(s):  
Li Yang ◽  
Robert Josephs
Keyword(s):  
Three Dimensional ◽  
Helical Conformation ◽  
Cryoelectron Microscopy ◽  
Red Cell ◽  
Electron Micrograph ◽  
Cross Link ◽  
Sinusoidal Shape ◽  
Cell Skeleton ◽  
Membrane Skeletons

In vivo the red blood cell reversibly and rapidly deforms as it passes through the small capillaries. Although the physiochemical basis of the red cell's deformability is unknown, it is regarded as being a property of the membrane protein spectrin. We have used cryoelectron microscopy to study the structure of spectrin in membrane skeletons to determine how its molecular structure confers elastic properties on the cell membrane. Cryomicroscopy has the virtue of minimally perturbing easily deformable structures such as spectrin.Figure 1 is an electron micrograph of a portion of a frozen-hydrated red cell skeleton. The spectrin molecules are indicated by the arrow heads. They cross link the skeletal network by interacting with short rod like segments F-actin (indicated by the arrows) containing about 13 actin molecules. In such micrographs the spectrin appears to have a sinusoidal shape whereas in negatively stained preparations spectrin appears to be straight.We have used the procedure of Margalef in order to determine the three dimensional trajectory of the spectrin molecule.

scholarly journals Visualizing biointerfaces in three dimensions: electron tomography of the bone–hydroxyapatite interface

2010 ◽  
Vol 7 (51) ◽  
pp. 1497-1501 ◽  
Author(s):  
K. Grandfield ◽  
E. A. McNally ◽  
A. Palmquist ◽  
G. A. Botton ◽  
P. Thomsen ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Collagen Matrix ◽  
Human Bone ◽  
Three Dimensions ◽  
X Rays ◽  
Positive Interaction ◽  
Implant Surface

A positive interaction between human bone tissue and synthetics is crucial for the success of bone-regenerative materials. A greater understanding of the mechanisms governing bone-bonding is often gained via visualization of the bone–implant interface. Interfaces to bone have long been imaged with light, X-rays and electrons. Most of these techniques, however, only provide low-resolution or two-dimensional information. With the advances in modern day transmission electron microscopy, including new hardware and increased software computational speeds, the high-resolution visualization and analysis of three-dimensional structures is possible via electron tomography. We report, for the first time, a three-dimensional reconstruction of the interface between human bone and a hydroxyapatite implant using Z-contrast electron tomography. Viewing this structure in three dimensions enabled us to observe the nanometre differences in the orientation of hydroxyapatite crystals precipitated on the implant surface in vivo versus those in the collagen matrix of bone. Insight into the morphology of biointerfaces is considerably enhanced with three-dimensional techniques. In this regard, electron tomography may revolutionize the approach to high-resolution biointerface characterization.

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