scholarly journals Inputs from Sequentially Developed Parallel Fibers Are Required for Cerebellar Organization

Cell Reports ◽  
2019 ◽  
Vol 28 (11) ◽  
pp. 2939-2954.e5 ◽  
Author(s):  
Heeyoun Park ◽  
Taegon Kim ◽  
Jinhyun Kim ◽  
Yukio Yamamoto ◽  
Keiko Tanaka-Yamamoto
Keyword(s):  
Parallel Fibers

scholarly journals Contact interactions in complex fibrous metamaterials

2021 ◽  
Author(s):  
Mario Spagnuolo ◽  
Antonio M. Cazzani
Keyword(s):  
Strain Energy ◽  
Point Of View ◽  
The Other ◽  
Contact Interactions ◽  
Coupling Term ◽  
Dissipation Potential ◽  
Parallel Fibers ◽  
Mathematical Point

AbstractIn this work, an extension of the strain energy for fibrous metamaterials composed of two families of parallel fibers lying on parallel planes and joined by connective elements is proposed. The suggested extension concerns the possibility that the constituent fibers come into contact and eventually scroll one with respect to the other with consequent dissipation due to friction. The fibers interact with each other in at least three different ways: indirectly, through microstructural connections that could allow a relative sliding between the two families of fibers; directly, as the fibers of a family can touch each other and can scroll introducing dissipation. From a mathematical point of view, these effects are modeled first by introducing two placement fields for the two fiber families and adding a coupling term to the strain energy and secondly by adding two other terms that take into account the interdistance between the parallel fibers and the Rayleigh dissipation potential (to account for friction).

scholarly journals Fractographical Analysis and Biomechanical Considerations of a Tooth Restored With Intracanal Fiber Post: Report of the Fracture and Importance of the Fiber Arrangements

2016 ◽  
Vol 41 (5) ◽  
pp. E149-E158 ◽  
Author(s):  
VF Wandscher ◽  
CD Bergoli ◽  
IF Limberger ◽  
TP Cenci ◽  
P Baldissara ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Glass Fiber ◽  
Shear Stresses ◽  
Fiber Post ◽  
Element Analysis ◽  
Parallel Fibers ◽  
Tooth Structure ◽  
Anterior Teeth ◽  
Compressive Stresses

SUMMARY Objective: This article aims to present a fractographic analysis of an anterior tooth restored with a glass fiber post with parallel fiber arrangement, taking into account force vectors, finite element analysis, and scanning electron microscopy (SEM). Methods: A patient presented at the Faculty of Dentistry (Federal University of Santa Maria, Brazil) with an endodontically treated tooth (ETT), a lateral incisor that had a restorable fracture. The treatment was performed, and the fractured piece was analyzed using stereomicroscopy, SEM, and finite element analysis. Results: The absence of remaining coronal tooth structure might have been the main factor for the clinical failure. We observed different stresses actuating in an ETT restored with a fiber post as well as their relationship with the ultimate fracture. Tensile, compression, and shear stresses presented at different levels inside the restored tooth. Tensile and compressive stresses acted together and were at a maximum in the outer portions and a minimum in the inner portions. In contrast, shear stresses acted concomitantly with tensile and compressive stresses. Shear was higher in the inner portions (center of the post), and lower in the outer portions. This was confirmed by finite element analysis. The SEM analysis showed tensile and compression areas in the fiber post (exposed fibers=tensile areas=lingual surface; nonexposed fibers=compression areas=buccal surface) and shear areas inside the post (scallops and hackle lines). Stereomicroscopic analysis showed brown stains in the crown/root interface, indicating the presence of microleakage (tensile area=lingual surface). Conclusion: We concluded that glass fiber posts with parallel fibers (0°), when restoring anterior teeth, present a greater fracture potential by shear stress because parallel fibers are not mechanically resistant to support oblique occlusal loads. Factors such as the presence of remaining coronal tooth structure and occlusal stability assist in the biomechanical equilibrium of stresses that act upon anterior teeth.

Activity of Purkinje cells, parallel fibers, and climbing fibers in the developing rabbit cerebellum

1971 ◽  
Vol 4 (4) ◽  
pp. 375-390 ◽  
Author(s):  
N. Delhaye-Bouchaud
Keyword(s):  
Purkinje Cells ◽  
Climbing Fibers ◽  
Parallel Fibers

Scattering Characteristics of Fibrous Media Containing Closely Spaced Parallel Fibers

1996 ◽  
Vol 10 (1) ◽  
pp. 192-192
Author(s):  
Siu-Chun Lee ◽  
Jan A. Grzesik
Keyword(s):  
Fibrous Media ◽  
Parallel Fibers

Oral Implants: The Paradigm Shift in Restorative Dentistry

2019 ◽  
Vol 98 (12) ◽  
pp. 1287-1293 ◽  
Author(s):  
N.P. Lang
Keyword(s):  
Paradigm Shift ◽  
Clinical Performance ◽  
Titanium Implants ◽  
Restorative Dentistry ◽  
Maintenance Care ◽  
Parallel Fibers ◽  
Infectious Process ◽  
Oral Implants ◽  
Woven Bone ◽  
Natural Teeth

The discovery of the phenomenon “osseointegration,” or functional ankylosis, has led to the development of oral implants with high clinical performance. Consequently, the placement of titanium implants has changed the paradigms of restorative dentistry. Implants are used to prevent placing reconstructions anchored on natural teeth when these are vital and intact. Furthermore, implants are suitable to improve subjective chewing function and to replace missing and strategically important abutments. The osseointegration process is characterized by a predictable sequence of healing events that encompass the formation of woven bone, parallel fibers, and lamellar bone and result in fully functional bone that will remodel throughout life. While the osseointegration facilitates the use of implants as prosthetic abutments, it has to be kept in mind that the peri-implant soft tissue may be subject to biological complications. This, in turn, may result in an infectious process that will jeopardize the osseointegration. Consequently, the monitoring of the peri-implant tissues is an important aspect, and early intervention in situations with peri-implant mucositis is mandatory for the prevention of peri-implantitis. Hence, it is evident that oral implants need lifelong maintenance care if their longevity is to be assured.

Cbln1 induces structural changes of parallel fibers at defined sites by interactions with glutamate receptor delta 2

2010 ◽  
Vol 68 ◽  
pp. e335
Author(s):  
Aya Ito-Ishida ◽  
Eriko Miura ◽  
Keiko Matsuda ◽  
Michisuke Yuzaki ◽  
Shigeo Okabe
Keyword(s):  
Glutamate Receptor ◽  
Structural Changes ◽  
Parallel Fibers

scholarly journals Molecular Layer Inhibitory Interneurons Provide Feedforward and Lateral Inhibition in the Dorsal Cochlear Nucleus

2010 ◽  
Vol 104 (5) ◽  
pp. 2462-2473 ◽  
Author(s):  
Michael T. Roberts ◽  
Laurence O. Trussell
Keyword(s):  
Brain Stem ◽  
Lateral Inhibition ◽  
Cochlear Nucleus ◽  
Molecular Layer ◽  
Dorsal Cochlear Nucleus ◽  
Inhibitory Input ◽  
Auditory Information ◽  
Parallel Fibers ◽  
Sensory Inputs ◽  
Cartwheel Cells

In the outer layers of the dorsal cochlear nucleus, a cerebellum-like structure in the auditory brain stem, multimodal sensory inputs drive parallel fibers to excite both principal (fusiform) cells and inhibitory cartwheel cells. Cartwheel cells, in turn, inhibit fusiform cells and other cartwheel cells. At the microcircuit level, it is unknown how these circuit components interact to modulate the activity of fusiform cells and thereby shape the processing of auditory information. Using a variety of approaches in mouse brain stem slices, we investigated the synaptic connectivity and synaptic strength among parallel fibers, cartwheel cells, and fusiform cells. In paired recordings of spontaneous and evoked activity, we found little overlap in parallel fiber input to neighboring neurons, and activation of multiple parallel fibers was required to evoke or alter action potential firing in cartwheel and fusiform cells. Thus neighboring neurons likely respond best to distinct subsets of sensory inputs. In contrast, there was significant overlap in inhibitory input to neighboring neurons. In recordings from synaptically coupled pairs, cartwheel cells had a high probability of synapsing onto nearby fusiform cells or other nearby cartwheel cells. Moreover, single cartwheel cells strongly inhibited spontaneous firing in single fusiform cells. These synaptic relationships suggest that the set of parallel fibers activated by a particular sensory stimulus determines whether cartwheel cells provide feedforward or lateral inhibition to their postsynaptic targets.

Distal Versus Proximal Inhibitory Shaping of Feedback Excitation in the Electrosensory Lateral Line Lobe: Implications for Sensory Filtering

1998 ◽  
Vol 80 (6) ◽  
pp. 3214-3232 ◽  
Author(s):  
Neil J. Berman ◽  
Leonard Maler
Keyword(s):  
Lateral Line ◽  
Pyramidal Cell ◽  
Stellate Cell ◽  
Molecular Layer ◽  
Pyramidal Cells ◽  
Stellate Cells ◽  
Decay Phase ◽  
Tetanic Stimulation ◽  
Parallel Fibers ◽  
Cell Inhibition

Berman, Neil J. and Leonard Maler. Distal versus proximal inhibitory shaping of feedback excitation in the electrosensory lateral line lobe: implications for sensory filtering. J. Neurophysiol. 80: 3214–3232, 1998. The inhibition controlling the indirect descending feedback (parallel fibers originating from cerebellar granule cells in the eminentia posterior pars granularis) to electrosensory lateral line lobe (ELL) pyramidal cells was studied using intracellular recording techniques in vitro. Parallel fibers (PF) contact stellate cells and dendrites of ventral molecular layer (VML) GABAergic interneurons. Stellate cells provide local input to pyramidal cell distal dendrites, whereas VML cells contact their somata and proximal dendrites. Single-pulse stimulation of PF evoked graded excitatory postsynaptic potentials (EPSPs) that were blocked by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-d-aspartate (NMDA) antagonists. The EPSPs peaked at 6.4 ± 1.8 ms (mean ± SE; n = 11) but took >50 ms to decay completely. Tetanic stimulation (100 ms, 100 Hz) produced a depolarizing wave with individual EPSPs superimposed. The absolute amplitude of the individual EPSPs decreased during the train. Spike rates, established by injected current, mostly were increased, but in some cells were decreased, by tetanic stimulation. Global application of a γ-aminobutyric acid-A (GABAA) antagonist to the recorded cell's soma and apical dendritic region increased the EPSP peak and decay phase amplitudes. Tetanic stimulation always increased current-evoked spike rates after GABAA blockade during, and for several hundred milliseconds after, the stimulus. Application of a GABAB antagonist did not have any significant effects on the PF-evoked response. This, and the lack of any long hyperpolarizing inhibitory postsynaptic potentials, suggests that VML and stellate cell inhibition does not involve GABAB receptors. Focal GABAA antagonist applications to the dorsal molecular layer (DML) and pyramidal cell layer (PCL) had contrasting effects on PF-evoked EPSPs. DML GABAA blockade significantly increased the EPSP peak amplitude but not the decay phase of the EPSP, whereas PCL GABAA-blockade significantly increased the decay phase, but not the EPSP peak, amplitude. The order of antagonist application did not affect the outcome. On the basis of the known circuitry of the ELL, we conclude that the distal inhibition originated from GABAergic molecular layer stellate cells and the proximal inhibition originated from GABAergic cells of the ventral molecular layer (VML cells). Computer modeling of distal and proximal inhibition suggests that intrinsic differences in IPSP dynamics between the distal and proximal sites may be amplified by voltage-dependent NMDA receptor and persistent sodium currents. We propose that the different time courses of stellate cell and VML cell inhibition allows them to act as low- and high-pass filters respectively on indirect descending feedback to ELL pyramidal cells.

Conduction in smooth muscles: comparative electrical properties

1960 ◽  
Vol 199 (3) ◽  
pp. 553-559 ◽  
Author(s):  
Geoffrey Burnstock ◽  
C. L. Prosser
Keyword(s):  
Smooth Muscles ◽  
Close Packing ◽  
Morphological Properties ◽  
Parallel Fibers ◽  
Low Resistance ◽  
Refractory Periods ◽  
Sucrose Gap ◽  
Low Threshold ◽  
The Individual ◽  
Long Fibers

Electrical and morphological properties were correlated in a variety of mammalian smooth muscles. In the sucrose gap electrode the gut muscles (esophagus muscularis mucosae, intestinal muscles and taenia coli) showed small slow waves (5 mv) and spikes (25–45 mv), while dog retractor penis and rat ureter gave spikes up to 110 mv. Membrane depolarization with K2SO4 was 50–72 mv in both groups of muscle; with KCl it was one-third less. Conduction velocity ranged from 15 cm/sec. for esophagus muscle to 4.1 for intestinal muscles and 1.6 cm/sec. for retractor penis. Resistance of 0.5-mm strips in the sucrose gap was approximately 1 megohm for propagating visceral muscles, 5–12 megohms for nonpropagating blood vessel muscles. Fast conduction is correlated with low resistance and high capacitance (in sucrose), brief spikes, short relative refractory periods, low threshold stimulus duration, long fibers and low interfiber spaces (close packing of cells). Conduction required many parallel fibers; it failed in strips less than about 100 µ diameter and conduction distance varied with excitability. The electrical unit is the individual fiber, but the conducting unit involves many fibers. Conduction appears to depend on relatively low resistance paths of parallel fibers which interact electrically. It also depends on excitability of individual cells which is kept high by stretch and chemical agents.

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