Plasmalemma Invaginations as Characteristic Constituents of Plasmodia of Physarum Polycephalum

1974 ◽  
Vol 16 (1) ◽  
pp. 23-37
Author(s):  
K. E. WOHLFARTH-BOTTERMANN
Keyword(s):  
Physarum Polycephalum ◽  
Close Contact ◽  
Surrounding Medium ◽  
Defined Medium ◽  
Subsequent Paper ◽  
Outer Border ◽  
Shuttle Streaming ◽  
Food Absorption ◽  
Plasmalemma Invaginations

Plasmodia of Physarum polycephalum grown on agar or filter paper and fed with rolled oats as food or with a partially defined medium were morphologically analysed in the living state and after fixation. Observation of the living plasmodium growing on agar reveals plasmalemma indentations in the outer regions of protoplasmic strands, which were studied in more detail by phase-contrast microscopy of unstained 1-µm sections. Plasmodia fixed and embedded in situ, i.e. in close contact to their substrate, exhibit an extensive system of plasmalemma invaginations as characteristic constituents throughout all regions. In plasmodial strands measuring between 40 µm and 1.5 mm in diameter and involved in shuttle streaming, the plasmalemma invaginations are found within the outer ectoplasmic wall. Rounded-up parts of this branched extracellular labyrinth limit the endoplasmic core engaged in the mass transport of protoplasm by shuttle streaming. Despite this clearcut borderline, the central endoplasmic core and the ectoplasmic cortex are connected by occasional protoplasmic bridges. The extracellular phase within the ectoplasmic regions of the strands can be interpreted either as a result of plasmalemma invaginations from the outer border of the strand, or as a consequence of pseudopodial-like processes originating from the central core and extending into the surrounding medium. The invagination system provides an extensive enlargement of the surface area within the multinucleate protoplasmic mass, probably important for food absorption, excretion processes and motility phenomena. In thick protoplasmic strands with diameters between 0.2 and 1.5 mm, there is an intimate connexion between the actomyosin fibrils and the invagination system. The fibrils are attached to the plasmalemma invaginations and/or run parallel to the invaginated plasmalemma sheets. The close relations between the invagination system and actomyosin fibrils will be described in detail in a subsequent paper.

Smart Textiles with Biosensing Capabilities

2012 ◽  
Vol 80 ◽  
pp. 129-135 ◽  
Author(s):  
Stéphanie Pasche ◽  
Bastien Schyrr ◽  
Bernard Wenger ◽  
Emmanuel Scolan ◽  
Réal Ischer ◽  
...  
Keyword(s):  
Real Time ◽  
Optical Fibers ◽  
Close Contact ◽  
Biological Fluids ◽  
Wearable Sensors ◽  
Surrounding Medium ◽  
Sol Gel ◽  
The Body ◽  
In Situ Monitoring ◽  
Easy Integration

Real-time, on-body measurement using minimally invasive biosensors opens up new perspectives for diagnosis and disease monitoring. Wearable sensors are placed in close contact with the body, performing analyses in accessible biological fluids (wound exudates, sweat). In this context, a network of biosensing optical fibers woven in textile enables the fabric to measure biological parameters in the surrounding medium. Optical fibers are attractive in view of their flexibility and easy integration for on-body monitoring. Biosensing fibers are obtained by modifying standard optical fibers with a sensitive layer specific to biomarkers. Detection is based on light absorption of the sensing fiber, placing a light source and a detector at both extremities of the fiber. Biosensing optical fibers have been developed for the in situ monitoring of wound healing, measuring pH and the activity of proteases in exudates. Other developments aim at the design of sensing patches based on functionalized, porous sol-gel layers, which can be deposited onto textiles and show optical changes in response to biomarkers. Biosensing textiles present interesting perspectives for innovative healthcare monitoring. Wearable sensors will provide access to new information from the body in real time, to support diagnosis and therapy.

In situ preparation of the nuclear matrix of Physarum polycephalum: ultrastructural and biochemical analysis of different matrix isolation procedures

1988 ◽  
Vol 90 (4) ◽  
pp. 621-628 ◽  
Author(s):  
W. Waitz ◽  
P. Loidl
Keyword(s):  
Nuclear Matrix ◽  
Physarum Polycephalum ◽  
Matrix Isolation ◽  
Protein Composition ◽  
Biochemical Properties ◽  
Agarose Beads ◽  
In Situ Preparation ◽  
The Matrix ◽  
Important Approach

A novel method for in situ preparation of nuclear matrix from whole plasmodia of Physarum polycephalum without isolation of nuclei is presented. Plasmodia are encapsulated in agarose beads and after solubilization of the cytoplasm the nuclear matrix is prepared. With this quick and easy technique nuclear matrix can be reproducibly prepared with perfect recovery. We compared the ultrastructural and biochemical properties of the matrix after three different matrix isolation procedures: preparation with high salt, ammonium sulphate and lithium diiodosalicylic acid. The results show that the ultrastructure and protein composition of the three types of matrix are very similar or even identical. We conclude that many of the conflicting results on nuclear matrix in the literature are due to perturbations of nuclear integrity during the isolation of nuclei. For this reason the new in situ method is an important approach in the standardization of nuclear matrix isolation.

Observations on the Performance of Vibration-Isolated Railway Track

1997 ◽  
Author(s):  
Hugh E. M. Hunt
Keyword(s):  
Travelling Waves ◽  
Surrounding Medium ◽  
Railway Track ◽  
Relative Speed ◽  
Tunnel Wall ◽  
Infinite Beam ◽  
Slab Track ◽  
Torsional Response ◽  
Made In

Abstract Vibration generated by underground railways is difficult to control because of the very limited space available in a tunnel. A popular approach is to use ‘floating slab track’ whereby the rails are fixed to a large concrete foundation separated from the tunnel wall by a resilient material. This paper investigates some of the vibration characteristics of floating slab track from measurements made in situ. These measurements are compared with the theoretical response of an infinite beam on an elastic foundation taking into account the torsional response of the beam. The transmission of vibration through the tunnel wall and into the surrounding medium is discussed with reference to the relative speed of travelling waves and the coincidence frequencies.

Skeletal development and formation of osteoclast-like cells from in situ progenitors in fetal mouse metatarsals cultured in chemically defined medium

1991 ◽  
Vol 12 (3) ◽  
pp. 141-155 ◽  
Author(s):  
Cedric Minkin ◽  
Steven St. James ◽  
Hong-hui Tao ◽  
Xiao-hui Yu ◽  
Shirwin Pockwinse ◽  
...  
Keyword(s):  
Skeletal Development ◽  
Defined Medium ◽  
Chemically Defined Medium ◽  
Fetal Mouse

A small-scale numerical study of fault slip mechanisms using DEM

2020 ◽  
Author(s):  
Nathalie Casas ◽  
Guilhem Mollon ◽  
Ali Daouadji
Keyword(s):  
Numerical Study ◽  
Surrounding Medium ◽  
Computational Cost ◽  
Static Friction ◽  
Discrete Element Modelling ◽  
Small Scale ◽  
In Situ Experiments ◽  
Fault Gouges ◽  
Fault Network

<p>How do earthquakes start? What are the parameters influencing fault evolutions? What are the local parameters controlling the seismic or aseismic character of slip?</p><p>To predict the dynamic behaviour of faults, it is important to understand slip mechanisms and their source. Lab or in-situ experiments can be very helpful, but tribological experience has shown that it is complicated to install local sensors inside a mechanical contact, and that they could disturb the behaviour of the sheared medium. Even with technical improvements on lab tools, some interesting data regarding gouge kinematics and rheology remains very difficult or impossible to obtain. Numerical modelling seems to be another way of understanding physics of earthquakes.</p><p>Fault zone usually present a granular gouge, coming from the wear material of previous slips. That is why, in this study, we present a numerical model to observe the evolution and behaviours of fault gouges. We chose to focus on physics of contacts inside a granular gouge at a millimetre-scale, studying contact interactions and friction coefficient between the different bodies. In order to get access to this kind of information, we implement a 2D granular fault gouge with Discrete Element Modelling in the software MELODY (Mollon, 2016). The gouge model involves two rough surfaces representing the rock walls separated by the granular gouge.</p><p>One of the interests of this code is its ability to represent realistic non-circular grain shapes with a Fourier-Voronoï method (Mollon et al., 2012). As most of the simulations reported in the literature use circular (2D)/spherical (3D) grains, we wanted to analyse numerically the contribution of angular grains. We confirm that they lead to higher friction coefficients and different global behaviours (Mair et al., 2002), (Guo et al., 2004).</p><p>In a first model, we investigate dry contacts to spotlight the influence of inter-particular cohesion and small particles on slip behaviour and static friction. A second model is carried out to observe aseismic and seismic slips occurring within the gouge. As stability depends on the interplay between the peak of static friction and the stiffness of the surrounding medium, the model includes the stiffness of the loading apparatus on the rock walls.</p><p>The work presented here focuses on millimetre-scale phenomena, but the employed model cannot be extended to the scale of the entire fault network, for computational cost reasons. It is expected, however, that it will lead to a better understanding of local behaviours that may be injected as simplified interface laws in larger-scale simulations.</p>

scholarly journals Microbial Community Succession during Lactate Amendment and Electron Acceptor Limitation Reveals a Predominance of Metal-Reducing Pelosinus spp.

2012 ◽  
Vol 78 (7) ◽  
pp. 2082-2091 ◽  
Author(s):  
Jennifer J. Mosher ◽  
Tommy J. Phelps ◽  
Mircea Podar ◽  
Richard A. Hurt ◽  
James H. Campbell ◽  
...  
Keyword(s):  
Electron Acceptor ◽  
Defined Medium ◽  
Flow Reactors ◽  
Content Type ◽  
Low Levels ◽  
Individual Variables ◽  
Continuous Flow Reactors ◽  
New Strategies

ABSTRACTThe determination of the success ofin situbioremediation strategies is complex. By using controlled laboratory conditions, the influence of individual variables, such as U(VI), Cr(VI), and electron donors and acceptors on community structure, dynamics, and the metal-reducing potential can be studied. Triplicate anaerobic, continuous-flow reactors were inoculated with Cr(VI)-contaminated groundwater from the Hanford, WA, 100-H area, amended with lactate, and incubated for 95 days to obtain stable, enriched communities. The reactors were kept anaerobic with N2gas (9 ml/min) flushing the headspace and were fed a defined medium amended with 30 mM lactate and 0.05 mM sulfate with a 48-h generation time. The resultant diversity decreased from 63 genera within 12 phyla to 11 bacterial genera (from 3 phyla) and 2 archaeal genera (from 1 phylum). Final communities were dominated byPelosinusspp. and to a lesser degree,Acetobacteriumspp., with low levels of other organisms, including methanogens. Four new strains ofPelosinuswere isolated, with 3 strains being capable of Cr(VI) reduction while one also reduced U(VI). Under limited sulfate, it appeared that the sulfate reducers, includingDesulfovibriospp., were outcompeted. These results suggest that during times of electron acceptor limitationin situ, organisms such asPelosinusspp. may outcompete the more-well-studied organisms while maintaining overall metal reduction rates and extents. Finally, lab-scale simulations can test new strategies on a smaller scale while facilitating community member isolation, so that a deeper understanding of community metabolism can be revealed.

scholarly journals THE CHANGING PATTERN OF BIREFRINGENCE IN PLASMODIA OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM

1965 ◽  
Vol 25 (2) ◽  
pp. 361-374 ◽  
Author(s):  
Hiromichi Nakajima ◽  
Robert D. Allen
Keyword(s):  
Physarum Polycephalum ◽  
Cytoplasmic Streaming ◽  
Channel Wall ◽  
Polarized Light ◽  
Orthogonal Arrays ◽  
Slime Mold ◽  
Wall Material ◽  
Shuttle Streaming ◽  
Oriented Parallel ◽  
Birefringent Fibrils

Plasmodia of the acellular slime mold, Physarum polycephalum, reveal a complex and changing pattern of birefringence when examined with a sensitive polarizing microscope. Positively birefringent fibrils are found throughout the ectoplasmic region of the plasmodium. In the larger strands they may be oriented parallel to the strand axis, or arranged circularly or spirally along the periphery of endoplasmic channels. Some fibrils exist for only a few minutes, others for a longer period. Some, particularly the circular fibrils, undergo changes in birefringence as they undergo cyclic deformations. In the ramifying strand region and the advancing margin there is a tendency for fibrils of various sizes to become organized into mutually orthogonal arrays. In some plasmodia the channel wall material immediately adjacent to the endoplasm has been found to be birefringent. The sign of endoplasmic birefringence is negative, and its magnitude is apparently constant over the streaming cycle. The pattern of plasmodial birefringence and its changes during the shuttle streaming cycle of Physarum are considered in the light of several models designed to explain either cytoplasmic streaming alone or the entire gamut of plasmodial motions. The results of this and other recent physical studies suggest that both streaming and the various other motions of the plasmodium may very likely be explained in terms of coordinated contractions taking place in the fibrils which are rendered visible in polarized light.

scholarly journals Isolation of Key Methanogens for Global Methane Emission from Rice Paddy Fields: a Novel Isolate Affiliated with the Clone Cluster Rice Cluster I

2007 ◽  
Vol 73 (13) ◽  
pp. 4326-4331 ◽  
Author(s):  
Sanae Sakai ◽  
Hiroyuki Imachi ◽  
Yuji Sekiguchi ◽  
Akiyoshi Ohashi ◽  
Hideki Harada ◽  
...  
Keyword(s):  
Methane Emission ◽  
Methane Production ◽  
Rice Paddy ◽  
Defined Medium ◽  
Paddy Fields ◽  
Low Concentrations ◽  
In Situ Conditions ◽  
Culture Independent ◽  
Rice Paddy Fields

ABSTRACT Despite the fact that rice paddy fields (RPFs) are contributing 10 to 25% of global methane emissions, the organisms responsible for methane production in RPFs have remained uncultivated and thus uncharacterized. Here we report the isolation of a methanogen (strain SANAE) belonging to an abundant and ubiquitous group of methanogens called rice cluster I (RC-I) previously identified as an ecologically important microbial component via culture-independent analyses. To enrich the RC-I methanogens from rice paddy samples, we attempted to mimic the in situ conditions of RC-I on the basis of the idea that methanogens in such ecosystems should thrive by receiving low concentrations of substrate (H2) continuously provided by heterotrophic H2-producing bacteria. For this purpose, we developed a coculture method using an indirect substrate (propionate) in defined medium and a propionate-oxidizing, H2-producing syntroph, Syntrophobacter fumaroxidans, as the H2 supplier. By doing so, we significantly enriched the RC-I methanogens and eventually obtained a methanogen within the RC-I group in pure culture. This is the first report on the isolation of a methanogen within RC-I.

scholarly journals Periodic traction in migrating large amoeba of Physarum polycephalum

2015 ◽  
Vol 12 (106) ◽  
pp. 20150099 ◽  
Author(s):  
Jean-Paul Rieu ◽  
Hélène Delanoë-Ayari ◽  
Seiji Takagi ◽  
Yoshimi Tanaka ◽  
Toshiyuki Nakagaki
Keyword(s):  
Physarum Polycephalum ◽  
Traction Force ◽  
Cortical Layer ◽  
Force Distribution ◽  
Locomotory Activity ◽  
Multinucleated Cell ◽  
Force Microscopy ◽  
Giant Multinucleated Cell ◽  
Shuttle Streaming

The slime mould Physarum polycephalum is a giant multinucleated cell exhibiting well-known Ca 2+ -dependent actomyosin contractions of its vein network driving the so-called cytoplasmic shuttle streaming. Its actomyosin network forms both a filamentous cortical layer and large fibrils. In order to understand the role of each structure in the locomotory activity, we performed birefringence observations and traction force microscopy on excised fragments of Physarum . After several hours, these microplasmodia adopt three main morphologies: flat motile amoeba, chain types with round contractile heads connected by tubes and motile hybrid types. Each type exhibits oscillations with a period of about 1.5 min of cell area, traction forces and fibril activity (retardance) when fibrils are present. The amoeboid types show only peripheral forces while the chain types present a never-reported force pattern with contractile rings far from the cell boundary under the spherical heads. Forces are mostly transmitted where the actomyosin cortical layer anchors to the substratum, but fibrils maintain highly invaginated structures and contribute to forces by increasing the length of the anchorage line. Microplasmodia are motile only when there is an asymmetry in the shape and/or the force distribution.

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