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Slowly adapting mechanoreceptors in the borders of the human fingernail encode fingertip forces. J Neurosci 2009; 29:9370-9. [PMID: 19625527 DOI: 10.1523/jneurosci.0143-09.2009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
There are clusters of slowly adapting (SA) mechanoreceptors in the skin folds bordering the nail. These "SA-IInail" afferents, which constitute nearly one fifth of the tactile afferents innervating the fingertip, possess the general discharge characteristics of slowly adapting type II (SA-II) tactile afferents located elsewhere in the glabrous skin of the human hand. Little is known about the signals in the SA-IInail afferents when the fingertips interact with objects. Here we show that SA-IInail afferents reliably respond to fingertip forces comparable to those arising in everyday manipulations. Using a flat stimulus surface, we applied forces to the finger pad while recording impulse activity in 17 SA-IInail afferents. Ramp-and-hold forces (amplitude 4 N, rate 10 N/s) were applied normal to the skin, and at 10, 20, or 30 degrees from the normal in eight radial directions with reference to the primary site of contact (25 force directions in total). All afferents responded to the force stimuli, and the responsiveness of all but one afferents was broadly tuned to a preferred direction of force. The preferred directions among afferents were distributed all around the angular space, suggesting that the population of SA-IInail afferents could encode force direction. We conclude that signals in the population of SA-IInail afferents terminating in the nail walls contain vectorial information about fingertip forces. The particular tactile features of contacted surfaces would less influence force-related signals in SA-IInail afferents than force-related signals present in afferents terminating in the volar skin areas that directly contact objects.
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Pua YH, Bryant AL, Steele JR, Newton RU, Wrigley TV. Isokinetic Dynamometry in Anterior Cruciate Ligament Injury and Reconstruction. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 2008. [DOI: 10.47102/annals-acadmedsg.v37n4p330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The use of isokinetic dynamometry has often been criticised based on the face-validity argument that isokinetic movements poorly resemble the everyday multi-segmented, dynamic activities of human movements. In the anterior cruciate ligament (ACL) reconstruction or deficiency population where muscle deficits are ubiquitous, this review paper has made a case for using isokinetic dynamometry to isolate and quantify these deficits in a safe and controlled manner. More importantly, the usefulness of isokinetic dynamometry, as applied in individuals with ACL reconstruction or deficiency, is attested by its established known-group and convergent validity. Known-group validity is demonstrated by the extent to which a given isokinetic measure is able to identify individuals who could and could not resume pre-morbid athletic or strenuous activities with minimal functional limitations following an ACL injury. Convergent validity is demonstrated by the extent to which a given isokinetic measure closely associates with self-report measures of knee function in individuals with ACL reconstruction. A basic understanding of the measurement properties of isokinetic dynamometry will guide the clinicians in providing reasoned interventions and advancing the clinical care of their clients.
Key words: Biomechanics, Knee, Validity
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Héroux ME, Tremblay F. Weight Discrimination After Anterior Cruciate Ligament Injury: A Pilot Study. Arch Phys Med Rehabil 2005; 86:1362-8. [PMID: 16003665 DOI: 10.1016/j.apmr.2004.11.045] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE To determine whether the ability to discriminate weights remained accurate after anterior cruciate ligament (ACL) injury. DESIGN Descriptive case series. SETTING Outpatient physical therapy. PARTICIPANTS Convenience sample of 10 participants with unilateral ACL injuries (age, 27.1+/-8.2 y) and 8 healthy controls (age, 22.6+/-2.8 y). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Weber fractions, expressed as percentage differences from the standard weight (3.00 kg) that could be reliably detected (75% correct level), were derived from each leg to provide an index of proprioceptive acuity for weight discrimination. Subjective ratings of knee function (Activities of Daily Living Scale of the Knee Outcome Survey) and measurements of quadriceps strength (peak isometric torque). RESULTS The ACL group exhibited a reduced acuity to detect differences in weight on the injured, as compared with the uninjured, side as reflected in the increase in Weber fractions (mean, 6.7%+/-2.3% vs 4.8%+/-1.1%, respectively; P = .043). No such difference in acuity between legs was detected in healthy controls (mean right and left, 5.4%+/-1.4% vs 5.7%+/-1.3%, respectively, P = .99). CONCLUSIONS Proprioceptive acuity for weight discrimination was significantly reduced after an ACL injury, possibly reflecting deficits in the ability to properly calibrate force signals generated while muscles are actively contracting, as a result of a loss in ligamentous sensory innervation.
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Affiliation(s)
- Martin E Héroux
- School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa, Ontario, Canada
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Lu Y, Chen C, Kallakuri S, Patwardhan A, Cavanaugh JM. Development of an in vivo method to investigate biomechanical and neurophysiological properties of spine facet joint capsules. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2005; 14:565-72. [PMID: 15690211 PMCID: PMC3489229 DOI: 10.1007/s00586-004-0835-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2004] [Revised: 08/10/2004] [Accepted: 09/28/2004] [Indexed: 10/25/2022]
Abstract
Facet joint capsules (FJC) may experience large mechanical deformation under spine motion. There has been no previous quantitative study of the relationship between capsular strain and sensory nerve activation in spine FJC in vivo. Space limitation in the cervical spine makes such a study difficult, as the facet joint must be loaded while simultaneously monitoring nerve discharge from nerve roots immediately adjacent to the loaded tissue. A new methodology was developed to investigate biomechanical and neurophysiological properties of spine facet joint capsules in vivo. The method incorporated a custom-fabricated testing frame for facet joint loading, a stereoimaging system, and a template-matching technique to obtain single afferent response. It was tested by loading goat C5-C6 FJC in vivo with simultaneous nerve root recordings and 3D strain tracking of the capsules. Preliminary data showed that 18 of 23 afferents (78.3%) were found to be mechanosensitive to tensile stretch, and five were not responsive, even under tensile load as high as 27.5 N. Mechanosensitive afferents in goat capsules had tensile strain thresholds of 0.119+/-0.080. Neural responses of all mechanosensitive units showed statistically significant correlations (all P<<0.05) with both capsular load (r(2)=0.744+/-0.109) and local strain (r(2)=0.868+/-0.088). This method enables the investigation of the correlation between tissue load, deformation and neural responses of mechanoreceptors in spine facet joint capsules, and can be adapted to investigate tissue loading and neural response of other soft tissues.
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Affiliation(s)
- Ying Lu
- Bioengineering Center, Wayne State University, Detroit, MI 48202, USA.
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Grigg P, Robichaud DR, Del Prete Z. Properties of mouse cutaneous rapidly adapting afferents: relationship to skin viscoelasticity. J Neurophysiol 2004; 92:1236-40. [PMID: 15028748 DOI: 10.1152/jn.01033.2003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
When skin is stretched, stimuli experienced by a cutaneous mechanoreceptor neuron are transmitted to the nerve ending through the skin. In these experiments, we tested the hypothesis that the viscoelastic response of the skin influences the dynamic response of cutaneous rapidly adapting (RA) neurons. Cutaneous RA afferent neurons were recorded in 3 species of mice (Tsk, Pallid, and C57BL6) whose skin has different viscoelastic properties. Isolated samples of skin and nerve were stimulated mechanically with a dynamic stretch stimulus, which followed a pseudo Gaussian waveform with a bandwidth of 0-60 Hz. The mechanical response of the skin was measured as were responses of single RA cutaneous mechanoreceptor neurons. For each neuron, the strength of association between spike responses and the dynamic and static components of stimuli were determined with multiple logistic regression analysis. The viscoelastic material properties of each skin sample were determined indirectly, by creating a nonlinear (Wiener-Volterra) model of the stress-strain relationship, and using the model to predict the complex compliance (i.e., the viscoelastic material properties). The dynamic sensitivity of RA mechanoreceptor neurons in mouse hairy skin was weakly related to the viscoelastic properties of the skin. Loss modulus and phase angle were lower (indicating a decreased viscous component of response) in Tsk and Pallid than in C57BL6 mice. However, RA mechanoreceptor neurons in Tsk and Pallid skin did not differ from those in C57 skin with regard to their sensitivity to the rate of change of stress or to the rate of change of incremental strain energy. They did have a decreased sensitivity to the rate of change of tensile strain. Thus the skin samples with lower dynamic mechanical response contained neurons with a somewhat lower sensitivity to dynamic stimuli.
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Affiliation(s)
- P Grigg
- Department of Physiology S4-245, University of Massachusetts Medical School, 55 Lake Avenue, Worcester, MA 01655, USA.
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Khalsa PS, Ge W. Encoding of tensile stress and strain during stretch by muscle mechano-nociceptors. Muscle Nerve 2004; 30:216-24. [PMID: 15266638 DOI: 10.1002/mus.20096] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Groups III and IV muscle mechano-nociceptors (MNs) can be stimulated during noxious stretch, as may occur during hyperextension of a joint. However, the mechanical state (characterized by stress and strain) encoded by MNs during stretch has not previously been determined. The current study used an ex vivo gracilis muscle-nerve preparation in a rat model to apply either a uniform uniaxial or pseudo-shear-loading paradigm. Single mechanically sensitive group III or IV MNs were mechanically stimulated while plane stress and strain were measured at the location of the MN's receptive field. Linear regression was used to evaluate the relationships between neural response and mechanical stress and strain. The mean neural response (threshold, 47.2 kPa; sensitivity, 0.05 Hz/kPa) was highly correlated to tensile stress, tensile strain, and in-plane compressive strain but was significantly and substantially less correlated with shear strain. Although the overall stress and strain relationship was nonlinear, it was reasonably linear (r2 = 0.92) for levels suprathreshold for MNs. Hence, at tensile loads sufficient to stimulate MNs, the muscle was acting as a pseudo-elastic tissue. Thus, muscle MNs encode noxious stretch differently than compression and exhibit different encoding of stretch than cutaneous MNs.
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Affiliation(s)
- Partap S Khalsa
- Department of Biomedical Engineering, State University of New York, HSC T18-031, Stony Brook, New York 11794-8181, USA.
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Khalsa PS, Ge W, Uddin MZ, Hadjiargyrou M. Integrin α2β1 affects mechano-transduction in slowly and rapidly adapting cutaneous mechanoreceptors in rat hairy skin. Neuroscience 2004; 129:447-59. [PMID: 15501602 DOI: 10.1016/j.neuroscience.2004.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2004] [Indexed: 10/26/2022]
Abstract
The role of a transmembrane protein, integrin alpha2beta1, to modulate the neural responses of cutaneous mechanoreceptors to mechanical indentation was examined using an isolated skin-nerve preparation in a rat model. Skin and its intact innervation were harvested from the medial thigh of the hindlimb and placed in a dish containing synthetic interstitial fluid. Using a standard teased nerve preparation, the neural responses of single slowly or rapidly adapting mechanoreceptors (SA or RA, respectively) were identified and the afferents categorized according to standard protocols (i.e. response to constant stimuli). The most sensitive spot of a mechanoreceptor's receptive field was identified and then stimulated using controlled compressive stress (constant or dynamic loads between threshold and saturation load for SAs and RAs, respectively). Loads were applied before, during, and after passive diffusion into the skin of a function-blocking anti-integrin alpha2 monoclonal antibody (FBmAb) or one of two types of control antibodies (immunoglobulin G or a FBmAb conjugated with a secondary antibody). The sensitivities of both SA and RA mechanoreceptors were profoundly reduced in the presence of the FBmAb, while not changing the waveforms of their action potentials or their adaptation properties. Both control antibodies had no significant effect on mechanoreceptors' sensitivities. Following removal of the FBmAb, the effects in some neurons were partially reversible. Taken together, the data from this study support the hypothesis that integrin alpha2beta1 plays a significant role in modulating mechanoreceptive response to compressive indentation.
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Affiliation(s)
- P S Khalsa
- Department of Biomedical Engineering, State University of New York, HSC T18-031, Stony Brook, NY 11794-8181, USA.
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Del Prete Z, Baker SP, Grigg P. Stretch responses of cutaneous RA afferent neurons in mouse hairy skin. J Neurophysiol 2003; 89:1649-59. [PMID: 12612035 DOI: 10.1152/jn.00909.2002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rapidly adapting (RA), stretch-sensitive neurons were recorded in vitro, using an isolated preparation of skin and nerve from mouse hindlimb. The skin was stretched uniaxially using a pseudo-Gaussian noise stimulus. Loads and displacements were recorded as were spike responses of single RA afferent neurons. The goal was to determine what components of the mechanical stimulus were associated with spike responses. The association between stimuli and spike responses was measured using multiple logistic regression. Spike responses were strongly associated with the rate of change of stress and weakly associated with the rate of change of strain and with stress. There was no association between spike responses and strain. There were significant memory effects associated with each variable, and memory effects differed for each variable. The maximal effect of the rate of change of stress was observed 8-12 ms prior to a spike.
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Affiliation(s)
- Zaccaria Del Prete
- Department of Mechanical Engineering, University of Rome La Sapienza, 00184 Rome, Italy
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Ge W, Khalsa PS. Encoding of compressive stress during indentation by group III and IV muscle mechano-nociceptors in rat gracilis muscle. J Neurophysiol 2003; 89:785-92. [PMID: 12574456 DOI: 10.1152/jn.00624.2002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanical state encoded by group III and IV muscle afferents, putative mechano-nociceptors, during indentation was examined using an isolated muscle-nerve preparation in a rat model. Gracilis muscle and its intact innervation were surgically removed from the medial thigh of the rat hindlimb and placed in a dish containing rodent synthetic interstitial fluid. The tendons of the muscle were coupled to an apparatus that could stretch and apply compression to the muscle. Using a standard teased-nerve preparation, the neural responses of single mechanically sensitive group III or IV afferents were identified. Afferents were classified as mechano-nociceptors on the basis of their graded response to noxious levels of compressive stress (or strain) as well as, in some cases, their polymodal response to noxious thermal stimuli. Mechano-nociceptors (n = 13) were stimulated using controlled compressive stress (10-30 kPa) or strain (40-80%) while simultaneously measuring displacement and force by compressing the muscle between a flat cylinder and a hard platform. Linear regression was used to evaluate the relationships between neural response and mechanical stress, force, strain, and displacement. The mean neural response (threshold: 1.1 +/- 0.4 kPa; sensitivity: 0.5 +/- 0.1 Hz/kPa; means +/- SE) was significantly and substantially more highly correlated with compressive stress than force, strain, or displacement. The data from this study support the hypothesis that muscle nociceptors stimulated by indentation encode compressive stress rather than force, strain, or displacement.
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Affiliation(s)
- Weiqing Ge
- Department of Biomedical Engineering, State University of New York, Stony Brook, New York 117941-8181, USA
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Ge W, Khalsa PS. Encoding of compressive stress during indentation by slowly adapting type I mechanoreceptors in rat hairy skin. J Neurophysiol 2002; 87:1686-93. [PMID: 11929890 DOI: 10.1152/jn.00414.2001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanical state encoded by slowly adapting type 1 mechanoreceptors (SAI) during indentation was examined using an isolated preparation in a rat model. Skin and its intact innervation were harvested from the medial thigh of the rat hindlimb and placed in a dish, with the corium side down, containing synthetic interstitial fluid. The margins of the skin were coupled to an apparatus that could stretch and apply compression to the skin. Using a standard teased nerve preparation, the neural responses of single SAIs were identified. SAIs were stimulated, using controlled compressive stress while simultaneously measuring displacement, by compressing the skin between indenters (flat cylinders) of different diameters and a hard platform. SAIs were subcategorized according to whether their neural response saturated above or below 10 kPa compressive stress (SAI-H or SAI-L, respectively). Linear regression was used to evaluate the relationships between neuron response and stress and force and displacement. For all SAIs, the mean neural response was significantly and substantially more highly correlated with compressive stress than force or displacement. For the SAI-L subcategory, the mean correlation coefficient was significantly and substantially greater for stress than for force but not significantly different for displacement. The data from this study support the hypothesis that SAI mechanoreceptors stimulated by indentation encode compressive stress rather than force, displacement, or strain.
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Affiliation(s)
- Weiqing Ge
- Department of Biomedical Engineering, State University of New York, Stony Brook, New York 11794-8181, USA
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Hiemstra LA, Webber S, MacDonald PB, Kriellaars DJ. Knee strength deficits after hamstring tendon and patellar tendon anterior cruciate ligament reconstruction. Med Sci Sports Exerc 2000; 32:1472-9. [PMID: 10949014 DOI: 10.1097/00005768-200008000-00016] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The purpose of this study was to examine the strength of the knee flexors and knee extensors after two surgical techniques of ACL reconstruction and compare them to an age and activity level matched control group. METHODS Twenty-four subjects who had undergone ACL reconstruction greater than 1 yr previously were placed into one of two groups according to autograft donor site: patellar tendon (BPB; N = 8) and hamstring (H; N = 16), and compared with an active, control group (N = 30). Knee flexor and extensor strength was evaluated using isovelocity dynamometry (5 speeds, eccentric and concentric, 5-95 degrees ROM). Strength maps were used to graphically analyze strength over a broad operational domain of the neuromuscular system. Average strength maps were determined for each autograft group and compared with controls. A difference map (control minus graft group) and confidence (t-test) maps were used to quantitatively identify strength deficits. RESULTS The combined ACL group (N = 24) revealed a global 25.5% extensor strength deficit, with eccentric regional (angle and velocity matched) deficits up to 50% of control. Strength deficits covered over 86% of the sampled strength map area (P < 0.01). These knee extensor strength deficits are greater than previously reported. In addition, the BPB group demonstrated a concentric, low velocity, knee extensor strength deficit at 60-95 degrees that was not observed in the H group. Significant graft site dependent, regional knee flexor deficits of up to 50% of control were observed for the H group. CONCLUSIONS Strength deficits localized to specific contraction types and ranges of motion were demonstrated between the ACL and control groups that were dependent upon autograft donor site. Postoperative rehabilitation protocols specific to these deficits should be devised.
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Affiliation(s)
- L A Hiemstra
- School of Medical Rehabilitation, Section of Orthopaedic Surgery, University of Manitoba, Winnipeg, Canada
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Cooper B, Oberdorfer M, Rumpf D, Malakhova O, Rudman R, Mariotti A. Trauma modifies strength and composition of retrodiscal tissues of the goat temporomandibular joint. Oral Dis 1999; 5:329-36. [PMID: 10561723 DOI: 10.1111/j.1601-0825.1999.tb00099.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Temporomandibular pain is often accompanied by pathologic changes to joint retrodiscal tissues. The substantial representation of females in this condition has encouraged hypotheses which link genetic or hormonally induced abnormalities in tissue composition (type III collagen, type I collagen, type III/type I ratio) to the development of temporomandibular disorders. As this condition is often associated with a history of orofacial trauma, we investigated the functional impact of retrodiscal trauma on the composition and biomechanics of retrodiscal tissues. DESIGN AND METHODS Retrodiscal tissue of female goats received trauma or sham trauma. Following a healing period of 30 days, the tissues were pulled to failure on an extensometer. OUTCOME MEASURES Assessments were made of tissue biomechanical properties (failure force, elastic stiffness, strain distribution). Tissue fragments were assayed for collagens I and III. RESULTS Thirty days after surgical section of retrodiscal tissues, the tissue had reformed, but the composition and biomechanics were substantially changed. Healed tissue manifested less than half the strength of normal tissue (P = 0.02). In addition, the development of tissue strain shifted from a relatively even distribution to a confined region near the retrodiscal-discal attachment zone. It appeared that a large increase in the expression of type III collagen (179.6%; P = 0.038) and the ratio of type III/type I collagen (180.9%; P = 0.011) accounted for these functional changes. CONCLUSIONS We suggest that shifts in collagen expression following injury create shifts in strain development which focus tissue stresses near the interface of the disc and retrodiscal tissue, and that this shift dramatically weakens the tissue and increases the probability of re-injury, inflammation and pain.
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Affiliation(s)
- B Cooper
- Department of Oral and Maxillofacial Surgery and Diagnostic Sciences, University of Florida, Gainesville FL 32610, USA
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Prete ZD, Grigg P. Responses of rapidly adapting afferent neurons to dynamic stretch of rat hairy skin. J Neurophysiol 1998; 80:745-54. [PMID: 9705465 DOI: 10.1152/jn.1998.80.2.745] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Twenty-four rapidly adapting (RA) cutaneous afferents were recorded from a preparation of isolated, innervated hairy skin from the rat hindlimb for the purpose of identifying the mechanical variables associated with the initiation of afferent discharge. Neurons were studied while the skin was stretched dynamically along a single direction with the use of a linear actuator and a feedback controller. Input signals were load- or displacement-controlled stretches that followed either periodic or pseudorandom Gaussian noise control signals. When the tissue was actuated, loads and displacements were measured along the direction of stretch and neuronal responses were recorded. All RA afferents were activated by dynamic stretching. None had a sustained response to static stretch. Cross-correlation products, calculated between neuronal responses and either stress- or strain-related variables observed at the time of the spike, revealed a strong relationship between neuronal responses and tensile stress. Neuronal responses were observed at rates of change of stress between +1,000 and -800 kPa/s. Neuronal responses were poorly related to skin strain. Two loading conditions were used along the direction transverse to the stretch. In one condition the sides were unconstrained, so that on axial loading there was zero stress and negative strain along the transverse axis. In the other condition the sides were constrained so that when the tissue was loaded axially there was zero strain and positive stress along the transverse axis. In these two conditions the same level of axial stress was associated with two levels of axial strain. The neuronal responses were determined by the stress and not the strain. Neuronal responses were observed at stresses >5 kPa. It appears that RA afferents make little contribution to signaling limb movements or position in rat hindlimb on the basis of the behavior of rat hindlimb skin, as observed when the limb is rotated.
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Affiliation(s)
- Z D Prete
- Department of Mechanical and Aeronautical Engineering, University of Rome la Sapienza, 00184 Rome, Italy
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Khalsa PS, LaMotte RH, Grigg P. Tensile and compressive responses of nociceptors in rat hairy skin. J Neurophysiol 1997; 78:492-505. [PMID: 9242296 DOI: 10.1152/jn.1997.78.1.492] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Mechanically sensitive nociceptor afferents were studied in a preparation of isolated skin from rat leg. Each neuron was studied while the skin was subjected to tensile and compressive loading. The experiment was designed to create highly uniform states of stress in both tension and compression. Tensile loads were applied by pulling on the edges of the sample. Applied loads were used to determine the tensile stresses. Surface displacements were used to determine tensile strains. Compressive loads were applied by indenting the surface of the skin with flat indenter tips applied under force control. The skin was supported by a flat, hard substrate. Compressive stresses were determined from the applied loads and tip geometry. Compressive strains were determined from skin thickness and tip excursions. All nociceptors were activated by both tensile and compressive loading. There was no interaction between the responses to compressive and tensile stimuli (i.e., the responses were simply additive). Responses of nociceptors were better related to tensile and compressive stresses than to strains. Nociceptors responded better to tensile loading than to compressive loading. Response thresholds were lower and sensitivities were higher for tensile stress than for compressive stress. The response to compression was better related to compressive stress than to other stimulus parameters (i.e., load/circumference or simply load). Indentations of intact skin over a soft substrate such as muscle would be expected to cause widespread activation of nociceptors because of tensile stresses.
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Affiliation(s)
- P S Khalsa
- Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Loughner B, Miller J, Broumand V, Cooper B. The development of strains, forces and nociceptor activity in retrodiscal tissues of the temporomandibular joint of male and female goats. Exp Brain Res 1997; 113:311-26. [PMID: 9063717 DOI: 10.1007/bf02450329] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Chronic pain in the temporomandibular (TM) joint is predominantly manifested in women. We examined biomechanical and neural factors that could contribute to this differential representation. Relationships between jaw rotation, soft tissue strains and soft tissue forces were examined in the goat TM joint. Strains were minimal until the jaw was rotated beyond the normal range of motion (7.25 deg). There were no significant differences in rotation-strain patterns in males and females. Stress developed as strains were introduced by jaw rotation. Gender differences were observed. Males manifested higher failure loads (15.94 +/- 1.98 and 11.37 +/- 2.02 N, for males and females respectively) and higher elastic stiffness than females (5.62 +/- 1.19 N/mm and 1.64 +/- 0.31 N/mm, for males and females respectively). Recordings were made from cell bodies in the trigeminal ganglion whose distal processes innervated the retrodiscal tissue of the temporomandibular joint of the goat (n = 48). Nociceptor reactivity was characterized with respect to the capacity to transduce mandibular rotation (rotation-interval functions; n = 29). On the basis of established relationships between rotation, strain and tissue forces, rotation-interval functions were transformed into strain-interval and force-interval functions. Comparisons were made between nociceptor properties grouped by gender. No differences in properties were observed when nociceptors were characterized with respect to jaw rotation; however, gender differences were obtained when nociceptor reactivity was characterized with respect to retrodiscal strains or forces. Consistent with smaller failure loads, nociceptors of retrodiscal tissues of females manifested a smaller range (1.12 vs 4.33 N), force to average (1.51 vs 4.64 N), force to minimum (0.95 vs 2.48 N) and force to asymptotic discharge (2.07 vs 6.81 N). Consistent with lower elastic stiffness, nociceptors of female tissues manifested higher average strain (54.4% vs 41.9%) and peak strain (74.0% vs 58.1%) to asymptotic discharge relative to those sampled from male tissues. The implications of these findings for TM joint injury and chronic pain are considered.
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Affiliation(s)
- B Loughner
- Midwest Center for Head Pain Management, Upper Valley Medical Center, Troy, OH 45373, USA
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Duquette JJ, Grigg P, Hoffman AH. The effect of diabetes on the viscoelastic properties of rat knee ligaments. J Biomech Eng 1996; 118:557-64. [PMID: 8950660 DOI: 10.1115/1.2796043] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A series of experiments was performed to determine the effect of diabetes on the viscoelastic properties of knee joint ligaments. The experimental model was collateral ligaments from spontaneously diabetic, hyperglycemic (BBZDP/Wor) rats, and various controls including nondiabetic littermates, insulin treated diabetic rats, and alloxan treated rats. Material properties were measured using a dynamic, uniaxial loading paradigm. Ligaments were subjected to load controlled, sinusoidal tensile testing, using frequencies from 0.1 to 2.0 Hz. The resulting data were used to determine the storage and loss compliances of the ligaments. Storage compliance, which reflects tissue elastic properties, did not differ between groups. Loss compliance, which reflects the viscous component of the tissue response, was increased in the hyperglycemic animals. Thus, hyperglycemic diabetes affects tissue mechanical properties through the viscous rather than the elastic component of the response to dynamic loading. Rats treated with alloxan to induce diabetes did not show an increase in loss compliance.
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Affiliation(s)
- J J Duquette
- Department of Orthopedic Surgery, University of Massachusetts Medical School, Worcester 01655, USA
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