Segmental variation in the activity and function of the equine longissimus dorsi muscle during walk and trot

2007 ◽  
Vol 4 (2) ◽  
pp. 95-103 ◽  
Author(s):  
James M Wakeling ◽  
Pattama Ritruechai ◽  
Sarah Dalton ◽  
Kathryn Nankervis
Keyword(s):  
Axial Rotation ◽  
Longissimus Dorsi ◽  
Bending Moments ◽  
Longissimus Dorsi Muscle ◽  
Exact Function ◽  
Flexion Extension ◽  
Limit Motion ◽  
Segmental Variation ◽  
And Function

AbstractMuscle function depends in part on the interplay between its activity and its length within the stretch-shortening cycle. The longissimus dorsi is a large epaxial muscle running along the thoracic and lumbar regions of the equine back. Due to its anatomical positioning, the longissimus dorsi has the capability of contributing to many functions: developing bending moments in the dorsoventral and lateral (coupled to axial rotation) directions and also providing stiffness to limit motion in these directions. We hypothesize that the exact function of the longissimus dorsi will vary along the back and between gaits as the relation between activity and motion of the back changes. Electromyograms (EMG) were recorded at walk (inclined and level) and trot (on the level) on a treadmill from the longissimus dorsi at muscle segments T14, T16, T18 and L2. Back motion was additionally measured using a fibre-optic goniometer. Co-contractions of the muscle between its left and right sides were quantified using correlation analysis. A greater dominance of unilateral activity was found at more cranial segments and for level walking, suggesting a greater role of the longissimus dorsi in developing lateral bending moments. Timing of the EMG varied between muscle segments relative to the gait cycle, the locomotor condition tested and the flexion–extension cycle of the back. This supports the hypothesis that the function of the longissimus dorsi changes along the back and between gaits.

scholarly journals Nbr1 Is a Novel Inhibitor of Ligand-Mediated Receptor Tyrosine Kinase Degradation

2010 ◽  
Vol 30 (24) ◽  
pp. 5672-5685 ◽  
Author(s):  
Faraz K. Mardakheh ◽  
Giulio Auciello ◽  
Tim R. Dafforn ◽  
Joshua Z. Rappoport ◽  
John K. Heath
Keyword(s):  
Tyrosine Kinases ◽  
Protein Localization ◽  
Negative Regulator ◽  
Receptor Internalization ◽  
C Terminus ◽  
Late Endosomes ◽  
Exact Function ◽  
Α Helix ◽  
And Function

ABSTRACT Neighbor of BRCA1 (Nbr1) is a highly conserved multidomain scaffold protein with proposed roles in endocytic trafficking and selective autophagy. However, the exact function of Nbr1 in these contexts has not been studied in detail. Here we investigated the role of Nbr1 in the trafficking of receptor tyrosine kinases (RTKs). We report that ectopic Nbr1 expression inhibits the ligand-mediated lysosomal degradation of RTKs, and this is probably done via the inhibition of receptor internalization. Conversely, the depletion of endogenous NBR1 enhances RTK degradation. Analyses of truncation mutations demonstrated that the C terminus of Nbr1 is essential but not sufficient for this activity. Moreover, the C terminus of Nbr1 is essential but not sufficient for the localization of the protein to late endosomes. We demonstrate that the C terminus of Nbr1 contains a novel membrane-interacting amphipathic α-helix, which is essential for the late endocytic localization of the protein but not for its effect on RTK degradation. Finally, autophagic and late endocytic localizations of Nbr1 are independent of one another, suggesting that the roles of Nbr1 in each context might be distinct. Our results define Nbr1 as a negative regulator of ligand-mediated RTK degradation and reveal the interplay between its various regions for protein localization and function.

Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization

2010 ◽  
Vol 12 (2) ◽  
pp. 183-189 ◽  
Author(s):  
Hakan Bozkuş ◽  
Mehmet Şenoğlu ◽  
Seungwon Baek ◽  
Anna G. U. Sawa ◽  
Ali Fahir Özer ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Stress Shielding ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Bending Moments ◽  
Axial Loads ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Lumbar Stabilization

Object It is unclear how the biomechanics of dynamic posterior lumbar stabilization systems and traditional rigid pedicle screw-rod systems differ. This study examined the biomechanical response of a hinged-dynamic pedicle screw compared with a standard rigid screw used in a 1-level pedicle screw-rod construct. Methods Unembalmed human cadaveric L3–S1 segments were tested intact, after L4–5 discectomy, after rigid pedicle screw-rod fixation, and after dynamic pedicle screw-rod fixation. Specimens were loaded using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording motion optoelectronically. Specimens were then loaded in physiological flexion-extension while applying 400 N of compression. Moment and force across instrumentation were recorded from pairs of strain gauges mounted on the interconnecting rods. Results The hinged-dynamic screws allowed an average of 160% greater range of motion during flexion, extension, lateral bending, and axial rotation than standard rigid screws (p < 0.03) but 30% less motion than normal. When using standard screws, bending moments and axial loads on the rods were greater than the bending moments and axial loads on the rods when using dynamic screws during most loading modes (p < 0.05). The axis of rotation shifted significantly posteriorly more than 10 mm from its normal position with both devices. Conclusions In a 1-level pedicle screw-rod construct, hinged-dynamic screws allowed a quantity of motion that was substantially closer to normal motion than that allowed by rigid pedicle screws. Both systems altered kinematics similarly. Less load was borne by the hinged screw construct, indicating that the hinged-dynamic screws allow less stress shielding than standard rigid screws.

Novel posterior artificial atlanto-odontoid joint for atlantoaxial instability: a biomechanical study

2018 ◽  
Vol 28 (5) ◽  
pp. 459-466 ◽  
Author(s):  
Kai Shen ◽  
Zhongliang Deng ◽  
Junsong Yang ◽  
Chao Liu ◽  
Ranxi Zhang
Keyword(s):  
Axial Rotation ◽  
Biomechanical Study ◽  
Atlantoaxial Instability ◽  
Intact Group ◽  
Flexion Extension ◽  
Fracture Nonunion ◽  
The Mean ◽  
The Stability ◽  
Ligament Disruption ◽  
And Function

OBJECTIVEAtlantoaxial instability is usually corrected by anterior and/or posterior C1–2 fusion. However, fusion can lead to considerable loss of movement at the C1–2 level, which can adversely impact a patient’s quality of life. In this study, the authors investigated the stability and function of a novel posterior artificial atlanto-odontoid joint (NPAAJ) by using cadaveric cervical spines.METHODSThe Oc–C7 regions from 10 cadaveric spines were used for anteroposterior (AP) translation and range of motion (ROM) tests while intact and after destabilization, NPAAJ implantation, and double-rod fixation.RESULTSThe mean AP C1–2 translational distances in the intact, destabilization, and double-rod groups were 6.53 ± 1.07 mm, 11.54 ± 1.59 mm, and 3.24 ± 0.99 mm, respectively, and the AP translational distance in the NPAAJ group was significantly different from that in the intact group (p < 0.05). The AP translational distance in the NPAAJ group was not significantly different from that in the double-rod group (p = 0.24). The mean flexion, extension, and axial rotation ROM values of the NPAAJ group were 9.87° ± 0.91°, 8.75° ± 0.99°, and 61.93° ± 2.93°, respectively, and these were lower than the corresponding values in the intact group (p < 0.05). The mean lateral bending ROM in the NPAAJ group (9.26° ± 0.86°) was not significantly different from that in the intact group (p = 0.23), and the flexion, extension, and rotation ranges in the NPAAJ group were 79.5%, 85.2%, and 82.3%, respectively, of those in the intact group.CONCLUSIONSUse of NPAAJ for correction of atlantoaxial instability disorders caused by congenital odontoid dysplasia, odontoid fracture nonunion, and C-1 transverse ligament disruption (IA, IB, and IIB) may restore the stability and preserve most of the ROM of C1–2. Additionally, the NPAAJ may prevent soft tissue from embedding within the joint. However, additional studies should be performed before the NPAAJ is used clinically.

scholarly journals Exploring the Regulatory Role of Circular RNAs in Neurodegenerative Disorders

2019 ◽  
Vol 20 (21) ◽  
pp. 5477 ◽  
Author(s):  
Eleonora D’Ambra ◽  
Davide Capauto ◽  
Mariangela Morlando
Keyword(s):  
Nervous System ◽  
Neuronal Development ◽  
Circular Rnas ◽  
Pathological Conditions ◽  
Exact Function ◽  
Modulation Of Gene Expression ◽  
Development And Aging ◽  
And Function ◽  
Regulatory Functions

Circular RNAs (circRNAs) are a distinctive class of regulatory non-coding RNAs characterised by the presence of covalently closed ends. They are evolutionary conserved molecules, and although detected in different tissues, circRNAs resulted specifically enriched in the nervous system. Recent studies have shown that circRNAs are dynamically modulated during neuronal development and aging, that circRNAs are enriched at synaptic levels and resulted modulated after synaptic plasticity induction. This has suggested that circRNAs might play an important role in neuronal specification and activity. Despite the exact function of circRNAs is still poorly understood, emerging evidence indicates that circRNAs have important regulatory functions that might extensively contribute to the dynamic modulation of gene expression that supports neuronal pathways. More interestingly, deregulation of circRNAs expression has been linked with various pathological conditions. In this review, we describe current advances in the field of circRNA biogenesis and function in the nervous system both in physiological and in pathological conditions, and we specifically lay out their association with neurodegenerative diseases. Furthermore, we discuss the opportunity to exploit circRNAs for innovative therapeutic approaches and, due to their high stability, to use circRNAs as suitable biomarkers for diagnosis and disease progression.

scholarly journals The Spinebot—A Robotic Device to Intraoperatively Quantify Spinal Stiffness

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Philippe Büchler ◽  
Jonas Räber ◽  
Benjamin Voumard ◽  
Steve Berger ◽  
Brett Bell ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Three Dimensional ◽  
Axial Rotation ◽  
Flexion Extension ◽  
Torque Load ◽  
The Moment ◽  
Reference Measurements ◽  
Spine Function ◽  
And Function

Abstract Degenerative spine problems and spinal deformities have high socio-economic impacts. Current surgical treatment is based on bony fusion that can reduce mobility and function. Precise descriptions of the biomechanics of normal, deformed, and degenerated spinal segments under in vivo conditions are needed to develop new approaches that preserve spine function. This study developed a system that intraoperatively measures the three-dimensional segmental stiffness of patient's spine. SpineBot, a parallel kinematic robot, was developed to transmit loads to adjacent vertebrae. A force/torque load cell mounted on the SpineBot measured the moment applied to the spinal segment and calculated segmental stiffnesses. The accuracy of SpineBot was characterized ex vivo by comparing its stiffness measurement of five ovine specimens to measurements obtained with a reference spinal testing system. The SpineBot can apply torques up to 10 N·m along all anatomical axes with a total range of motion of about 11.5 deg ± 0.5 deg in lateral bending, 4.5 deg ± 0.3 deg in flexion/extension, and 2.6 deg ± 0.5 deg in axial rotation. SpineBot's measurements are noisier than the reference system, but the correlation between SpineBot and reference measurements was high (R2 &gt; 0.8). In conclusion, SpineBot's accuracy is comparable to that of current reference systems but can take intraoperative measurements. SpineBot can improve our understanding of spinal biomechanics in patients who have the pathology of interest, and take these measurements in the natural physiological environment, giving us information essential to developing new “nonfusion” products.

scholarly journals Biomechanical effects of a novel posteriorly placed sacroiliac joint fusion device integrated with traditional lumbopelvic long-construct instrumentation

2021 ◽  
pp. 1-10
Author(s):  
Bernardo de Andrada Pereira ◽  
Jennifer N. Lehrman ◽  
Anna G. U. Sawa ◽  
Derek P. Lindsey ◽  
Scott A. Yerby ◽  
...  
Keyword(s):  
Statistical Significance ◽  
Axial Rotation ◽  
High Rate ◽  
Joint Motion ◽  
Bending Moments ◽  
Lateral Bending ◽  
Fusion Device ◽  
Joint Fusion ◽  
Flexion Extension ◽  
Si Joint

OBJECTIVE S2-alar-iliac (S2AI) screw fixation effectively ensures stability and enhances fusion in long-segment constructs. Nevertheless, pelvic fixation is associated with a high rate of mechanical failure. Because of the transarticular nature of the S2AI screw, adding a second point of fixation may provide additional stability and attenuate strains. The objective of the study was to evaluate changes in stability and strain with the integration of a sacroiliac (SI) joint fusion device, implanted through a novel posterior SI approach, supplemental to posterior long-segment fusion. METHODS L1-pelvis human cadaveric specimens underwent pure moment (7.5 Nm) and compression (400 N) tests in the following conditions: 1) intact, 2) L2–S1 pedicle screw and rod fixation with L5–S1 interbody fusion, 3) added S2AI screws, and 4) added bilateral SI joint fixation (SIJF). The range of motion (ROM), rod strain, and screw bending moments (S1 and S2AI) were analyzed. RESULTS S2AI fixation decreased L2–S1 ROM in flexion-extension (p ≤ 0.04), L5–S1 ROM in flexion-extension and compression (p ≤ 0.004), and SI joint ROM during flexion-extension and lateral bending (p ≤ 0.03) compared with S1 fixation. SI joint ROM was significantly less with SIJF in place than with the intact joint, S1, and S2AI fixation in flexion-extension and lateral bending (p ≤ 0.01). The S1 screw bending moment decreased following S2AI fixation by as much as 78% in extension, but with statistical significance only in right axial rotation (p = 0.03). Extending fixation to S2AI significantly increased the rod strain at L5–S1 during flexion, axial rotation, and compression (p ≤ 0.048). SIJF was associated with a slight increase in rod strain versus S2AI fixation alone at L5–S1 during left lateral bending (p = 0.048). Compared with the S1 condition, fixation to S2AI increased the mean rod strain at L5–S1 during compression (p = 0.048). The rod strain at L5–S1 was not statistically different with SIJF compared with S2AI fixation (p ≥ 0.12). CONCLUSIONS Constructs ending with an S2AI screw versus an S1 screw tended to be more stable, with reduced SI joint motion. S2AI fixation decreased the S1 screw bending moments compared with fixation ending at S1. These benefits were paired with increased rod strain at L5–S1. Supplementation of S2AI fixation with SIJF implants provided further reductions (approximately 30%) in the sagittal plane and lateral bending SI joint motion compared with fixation ending at the S2AI position. This stability was not paired with significant changes in rod or screw strains.

Scanning electron microscopic study of collagen fibrillogenesis and extracellular compartmentalization in the chick embryo tendon

1986 ◽  
Vol 44 ◽  
pp. 208-209
Author(s):  
Grace C.H. Yang
Keyword(s):  
Chick Embryo ◽  
Extracellular Space ◽  
Fibroblast Cell ◽  
Collagen Fibrils ◽  
Electron Microscopic ◽  
Voltage Electron ◽  
Scanning Electron Microscopic Study ◽  
Microscopic Studies ◽  
And Function

The size and organization of collagen fibrils in the extracellular matrix is an important determinant of tissue structure and function. The synthesis and deposition of collagen involves multiple steps which begin within the cell and continue in the extracellular space. High-voltage electron microscopic studies of the chick embryo cornea and tendon suggested that the extracellular space is compartmentalized by the fibroblasts for the regulation of collagen fibril, bundle, and tissue specific macroaggregate formation. The purpose of this study is to gather direct evidence regarding the association of the fibroblast cell surface with newly formed collagen fibrils, and to define the role of the fibroblast in the control and the precise positioning of collagen fibrils, bundles, and macroaggregates during chick tendon development.

Role of the Cilia Membrane in Control of Microtubule Sliding

1980 ◽  
Vol 38 ◽  
pp. 612-615
Author(s):  
Edna S. Kaneshiro
Keyword(s):  
Control Mechanism ◽  
Beat Frequency ◽  
Surface Membrane ◽  
Ciliary Membrane ◽  
Ciliary Beating ◽  
Ciliary Reversal ◽  
Voltage Dependent ◽  
Reversal Mechanism ◽  
And Function

It is currently believed that ciliary beating results from microtubule sliding which is restricted in regions to cause bending. Cilia beat can be modified to bring about changes in beat frequency, cessation of beat and reversal in beat direction. In ciliated protozoans these modifications which determine swimming behavior have been shown to be related to intracellular (intraciliary) Ca2+ concentrations. The Ca2+ levels are in turn governed by the surface ciliary membrane which exhibits increased Ca2+ conductance (permeability) in response to depolarization. Mutants with altered behaviors have been isolated. Pawn mutants fail to exhibit reversal of the effective stroke of ciliary beat and therefore cannot swim backward. They lack the increased inward Ca2+ current in response to depolarizing stimuli. Both normal and pawn Paramecium made leaky to Ca2+ by Triton extrac¬tion of the surface membrane exhibit backward swimming only in reactivating solutions containing greater than IO-6 M Ca2+ Thus in pawns the ciliary reversal mechanism itself is left operational and only the control mechanism at the membrane is affected. The topographic location of voltage-dependent Ca2+ channels has been identified as a component of the ciliary mem¬brane since the inward Ca2+ conductance response is eliminated by deciliation and the return of the response occurs during cilia regeneration. Since the ciliary membrane has been impli¬cated in the control of Ca2+ levels in the cilium and therefore is the site of at least one kind of control of microtubule sliding, we have focused our attention on understanding the structure and function of the membrane.

POPDC proteins and cardiac function

2019 ◽  
Vol 47 (5) ◽  
pp. 1393-1404 ◽  
Author(s):  
Thomas Brand
Keyword(s):  
Potential Role ◽  
Striated Muscle ◽  
Short Review ◽  
Effector Proteins ◽  
Muscle Disease ◽  
Disease Genes ◽  
Protein Protein Interaction ◽  
Interaction Partners ◽  
And Function

Abstract The Popeye domain-containing gene family encodes a novel class of cAMP effector proteins in striated muscle tissue. In this short review, we first introduce the protein family and discuss their structure and function with an emphasis on their role in cyclic AMP signalling. Another focus of this review is the recently discovered role of POPDC genes as striated muscle disease genes, which have been associated with cardiac arrhythmia and muscular dystrophy. The pathological phenotypes observed in patients will be compared with phenotypes present in null and knockin mutations in zebrafish and mouse. A number of protein–protein interaction partners have been discovered and the potential role of POPDC proteins to control the subcellular localization and function of these interacting proteins will be discussed. Finally, we outline several areas, where research is urgently needed.

Role of the 807 C/T Polymorphism of the α2 Gene in Platelet GP Ia Collagen Receptor Expression and Function

1999 ◽  
Vol 81 (06) ◽  
pp. 951-956 ◽  
Author(s):  
J. Corral ◽  
R. González-Conejero ◽  
J. Rivera ◽  
F. Ortuño ◽  
P. Aparicio ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Cell Types ◽  
Receptor Expression ◽  
Case Control Studies ◽  
Platelet Surface ◽  
Vitro Analysis ◽  
And Function ◽  
In Vitro Analysis

SummaryThe variability of the platelet GP Ia/IIa density has been associated with the 807 C/T polymorphism (Phe 224) of the GP Ia gene in American Caucasian population. We have investigated the genotype and allelic frequencies of this polymorphism in Spanish Caucasians. The T allele was found in 35% of the 284 blood donors analyzed. We confirmed in 159 healthy subjects a significant association between the 807 C/T polymorphism and the platelet GP Ia density. The T allele correlated with high number of GP Ia molecules on platelet surface. In addition, we observed a similar association of this polymorphism with the expression of this protein in other blood cell types. The platelet responsiveness to collagen was determined by “in vitro” analysis of the platelet activation and aggregation response. We found no significant differences in these functional platelet parameters according to the 807 C/T genotype. Finally, results from 3 case/control studies involving 302 consecutive patients (101 with coronary heart disease, 104 with cerebrovascular disease and 97 with deep venous thrombosis) determined that the 807 C/T polymorphism of the GP Ia gene does not represent a risk factor for arterial or venous thrombosis.

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