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At least 1,621 records · Page 90Linked to original sources
PubMed1995

Light and electron microscopy of the human hepato-duodenal ligament: a morpho-functional study.

The morpho-functional relationships between the hepato-duodenal ligament and the superior part of the duodenum are analysed. Twenty-four specimens were removed during necropsies of adults and prepared according to various mesoscopic, microscopic, and ultramicroscopical methods, i.e., whole-mounts, membrane preparations, thick and thin histological sections, and polarized light, scanning, and transmission electron microscopy were employed. The hepato-duodenal ligament is formed by longitudinally elongated, type I collagen fiber bundles which are interlinked by more delicate bundles of type III collagen fibers. Longitudinally disposed elastic fibers are the principal component of the elastic fiber system of the ligament. These are in continuity with the elaunin and oxytalan fibers which are intermingled with the muscle cells of the vessels and duodenal wall, and fat cells of the ligament. Part of the muscle bundles of the external, longitudinal, muscle layer of the duodenum is anchored in the adventitial and subserosal collagen and elastic fiber framework of the organ while part inserts directly into the fibrous framework of the ligament. The fibrous system of the ligament is continuous with that of the subserosa and adventitia of the duodenum.

Cadaver↗
PubMed1986

Mesencephalic trigeminal sensory neurons of cat: axon pathways and structure of mechanoreceptive endings in periodontal ligament.

We injected 3H-proline into cat brainstem in order to label the entire mesencephalic trigeminal nucleus (Mes-V) for autoradiographic analysis of the size and pathways of Mes-V sensory axons and for microscopic study of Mes-V receptor structure in dental tissue. Labeled sensory axons were found in the trigeminal motor and sensory tracts and roots; approximately equal numbers of axons were found in both roots. The sensory root and all three divisions of the trigeminal nerve contained larger Mes-V axons than the motor root. Labeled Mes-V axons were found at the ganglion in the dorsomedial (infratrochlear) branch of the ophthalmic nerve but not in the ventrolateral branch. The mean diameter of Mes-V axons in periodontal ligament was 4.0 +/- 1.9 micron compared to 7.3 +/- 2.1 micron in maxillary and mandibular nerve, suggesting axonal arborization prior to innervation of ligament. Mes-V receptors in dental tissue were confined to ipsilateral periodontal ligament close to the root apex, with greater innervation on the posterior side. Receptor incidence was moderate for most teeth; however, maxillary first and second incisors and maxillary and mandibular canines had focal areas with remarkably dense innervation. No labeled axons were found in pulp of any ipsilateral teeth, and none was found in any contralateral dental tissue. EM-autoradiography demonstrated that Mes-V axons form unencapsulated Ruffini-like mechanoreceptors in periodontal ligament. The preterminal axons were small and myelinated. Neighboring bundles of unmyelinated axons and rare encapsulated endings were not labeled. The labeled mechanoreceptors branched to varying degrees among the ligament fibers; they contained numerous mitochondria and glycogen particles, as well as some vesicles and rare multivesicular bodies. They were surrounded by special Schwann cells that formed one or several layers around the ending. The endings were exposed to the basal lamina at numerous sites and occasionally extended fingers beyond the lamellar Schwann cells to contact ligament collagen.

Animals↗
PubMed1995

Biological response to ligament wear particles.

In ligament replacement cases where the artificial ligament has worn and partially or totally ruptured, the released wear particles have been associated with a chronic synovitis that inhibits integration of the ligament and contributes to the ultimate failure of the device. In this study, the biological response to ligament wear particles from nine different artificial ligaments was quantitatively evaluated in vivo. Wear particles, the majority of which were < 7 microns, were generated in vitro. These particles were injected into rabbit knee joints, and the biological response as well as the systemic migration of the particles were evaluated histologically after 4 weeks. The extent of the inflammatory reaction to the ligament wear particles was found to be significantly (p < 0.05) influenced by the type of material implanted. No particles were found in the regional lymph nodes or in the spleen, liver, kidney, or lung.

Animals↗
PubMed2005

Analysis of mesenchymal stem cells grown on a three-dimensional HYAFF 11-based prototype ligament scaffold.

Ligaments are complex structures that maintain the mechanical stability of the joint. Healing of injured ligaments involves the interactions of different cell types, local cellular environment, and the use of devices. To gain new information on the complex interactions between mesenchymal stem cells (MSCs) and a specific hyaluronan-based prototype scaffold (HYAFF, useful for ligament tissue engineering, short time-course experiments were performed to analyze the proliferation, vitality, and phenotype of MSCs grown on the scaffold. MSC proliferation was analyzed using the MTT test, during the early time points (2, 4, 6, days). Viability was assessed using calcein/acetyloxymethylester immunofluorescence dye and confocal microscopy analysis. Hyaluronic acid receptor (CD44), typical matrix ligament proteins (collagen type I, type III, laminin, fibronectin, actin), and chondrogenic/osteogenic markers (collagen type II and bone sialoprotein) were evaluated by immunohistochemistry. Our data demonstrated that MSC growth and viability were cell density-dependent. MSCs completely wrapped the fibers of the scaffold, expressed CD44, collagen type I, type III, laminin, fibronectin, and actin, and were negative to collagen type II and bone sialoprotein. These data demonstrate that MSCs survive well in the hyaluronan-based prototype ligament scaffold, as assessed after 2 days from seeding, and express CD44, a receptor important for scaffold interaction, and proteins responsible for the functional characteristics of the ligaments.

Animals↗
PubMed1993

Effects of bone-seeking hormones on DNA synthesis, cyclic AMP level, and alkaline phosphatase activity in cultured cells from human posterior longitudinal ligament of the spine.

In a study of the osteogenesis capability of the human posterior longitudinal ligament of the spine, ligament cells were isolated and cultured. The effect of bone-seeking hormones, such as parathyroid hormone (PTH), calcitonin (CT), prostaglandin E2 (PGE2), and 1,25-dihydroxycholecalciferol [1,25-(OH)2D3], on the ligament cells was investigated with respect to DNA synthesis, adenosine-3',5'-cyclic monophosphate (cAMP) levels, alkaline phosphatase (ALP) activity, and acid phosphatase (ACP) activity. Cell lines obtained from nonossified sites in patients with ossification of the posterior longitudinal ligament of the spine (OPLL) were found to have several different phenotypic characteristics for osteoblasts: high ALP activity, PTH- and PGE2-stimulated increases in cAMP, and responses to both CT and 1,25-(OH)2D3. It is clear that proliferation and differentiation in such ligament cells are controlled by various types of bone-seeking hormones, and it was suggested that many cells with osteoblast-like characteristics are present. These results are considered important with respect to the etiology of OPLL, and an experimental system using cultured ligament cells appears to be useful in research on OPLL.

Acid Phosphatase↗
PubMed1987

In-vitro ligament tension pattern in the flexed knee in passive loading.

Tensions generated in selected bands of the four major ligaments of the flexed knee (40-90 degrees) have been measured in vitro when the tibia is subjected to passive anterior translation and axial rotation with and without a compressive preload. The measurements were made in 30 fresh-frozen specimens using the buckle transducer attached to the anteromedial band of the anterior cruciate ligament [ACL (am)], the posterior fibres of the posterior cruciate ligament [PCL (pf)], the superficial fibres of the medial collateral ligament [MCL (sf)], and in the total lateral collateral ligament (LCL). Particular attention was placed on the evaluation of the performance of the transducer specific to such measurements in order to minimize the errors associated with the use of this transducer. The results indicate that, among the measured ligaments, substantial tension (greater than 20 N) is generated only in the ACL (am) in tibial anterior translation up to 5 mm. The tension pattern generated in response to tibial axial rotation, however, is complex and exhibits considerable variation between specimens. In general, both the MCL (sf) and LCL are tensed at all tested flexion angles, with the tension in external rotation being significantly greater than in internal rotation. At 40 degrees of flexion, the ACL (am) bears tension mainly in internal rotation, while at 90 degrees of flexion the PCL (pf) is tensed in both senses of rotation. The response of the LCL shows marked variation among specimens; very small tension (less than 15 N) is generated in internal rotation in 48% of the specimens, and in either sense of rotation in 20% of the specimens. The tension in the ACL (am) in internal rotation is invariably greater in those specimens in which LCL tension is negligible. This correlation between increased ACL (am) function and inadequate LCL restraint appears significant in terms of ACL injury and repair.

Humans↗
PubMed1989

Prevention of ligament and meniscus atrophy by active joint motion in a non-weight-bearing model.

This study describes the effect of active joint motion on the maintenance of ligament and meniscus mass in a non-weight-bearing model of disuse. Denervation and fixation models of immobilization have shown that resorption of isotope and atrophy of mass occurred for hard tissue (bone) and soft tissues (ligament, tendon, or meniscus). A unilateral ankle disarticulation model of disuse that maintains active knee motion without weight bearing was studied for 8 weeks in dogs that were chronically prelabeled with three different isotopes. The effects of non-weight-bearing without denervation or fixation were analyzed for the resorption of isotopes, and net atrophy of bone mass (femur or tibia) and soft-tissue mass (collateral or cruciate ligaments, menisci). A large and similar loss of all three isotopes, as well as collagen and calcium mass occurred for whole femur and tibia; this indicated that mass loss was equivalent to bone resorption and suggests little replacement with new bone. No loss of isotope or mass per whole tissue occurred for the collateral and cruciate ligaments or menisci. The strength of the femur-anterior cruciate ligament-tibia complex was analyzed by a tensile failure test when a fast rate of deformation was applied; the results did not differ qualitatively or quantitatively between control and experimental limbs. The absence of weight bearing for 8 weeks resulted in marked bone atrophy without resorption or atrophy of soft tissues, or decrease of the mechanical strength for the femur-ligament-tibia complex.

Animals↗
PubMed1994

Effects of different levels of direct current on early ligament healing in a rat model.

Electrical stimulation has been shown to enhance the repair of biological tissues such as bone and tendon. The objective of this study was to determine whether low level direct current enhances the early healing of injured medial collateral ligaments. Eighty-seven rats were divided into three groups on the basis of the level of current delivered. All underwent transection of the medial collateral ligament bilaterally. The experimental medial collateral ligaments received current (which varied by group), while the contralateral medial collateral ligaments (the controls), with identical electrodes, received no current. After 12 days, each ligament was tested biomechanically with use of a hydraulic materials testing machine. Group 1 (8.6 +/- 5.9 microA) showed statistically significant improvements in maximum rupture force, energy absorbed, stiffness, and laxity. The groups that had received lower levels of current did not show significant improvements. In this study, stimulation of 1-20 microA was the most effective level of direct current for the enhancement of early healing of the medial collateral ligament.

Animals↗
PubMed1995

Changes of cytoskeletal architecture and incorporation of 3H-proline in contracted anterior cruciate ligament.

Changes of cytoskeletal architecture and incorporation of 3H-proline were investigated in contracted anterior cruciate ligaments with use of a model of contracture. In control ligaments, fibroblasts were shown by immunofluorescence microscopy to contain actin, vimentin, and myosin in their cytoplasm. Cytoskeletons were visualized by electron microscopy as a mesh network of microfilaments among cell organelles. In contracted anterior cruciate ligaments, fibroblasts were spindle-shaped and their cytoplasm could not be observed clearly in sections stained with hematoxylin and eosin. Actin staining was distributed irregularly and extensively, whereas vimentin and myosin staining was not scattered so extensively. When compared electromyographically, the actin staining appeared in cytoplasmic pseudopods of the fibroblasts. It was thought that these cytoplasmic pseudopods contained mainly actin and little or no other cytoskeletal elements such as vimentin and myosin. In autoradiographs, contracted anterior cruciate ligaments were shown, with use of 3H-proline, to experience a decrease in the number of labeled cells. On the basis of these findings of cytoskeletal rearrangement and of decreased incorporation of 3H-proline, we hypothesized that fibroblasts of the anterior cruciate ligament had the capacity to change their character during knee immobilization and to play a role in ligament contracture.

Actins↗
PubMed1995

Rabbit medial collateral ligament scar weakness is associated with decreased collagen pyridinoline crosslink density.

This study was carried out to quantify the potential associations between material strength and both collagen concentration and pyridinoline collagen crosslink density in the healing medial collateral ligament of the rabbit and to compare these parameters with those of normal ligaments. The right hindlimbs of 24 skeletally mature (12-month-old) New Zealand White rabbits were subjected to a standardized 4 mm midsubstance "gap" injury to the medial collateral ligament. The animals were killed in groups of six at postoperative intervals of 3, 6, 14, or 40 weeks, and the femur-medial collateral ligament-tibia complexes were mechanically tested in tension to failure. Subsequent to mechanical testing, the failure sites of the ligaments were assessed for concentrations of hydroxyproline and hydroxylysyl pyridinoline. Nine additional rabbits served as age-matched normal controls. In healing ligaments, normal collagen concentrations were reached in less than 14 weeks, but the hydroxylysyl pyridinoline crosslink densities remained low and were only 45% of the control values after 40 weeks of healing. Similarly, mechanical values remained much less than the controls. Linear regression analysis of data on scar tissue alone showed a moderately strong positive correlation between hydroxyproline concentration and material strength (r2 = 0.51, p = 0.0001) but no correlation between crosslink density and strength of scar tissue. A similar pattern of correlation was obtained between the elastic modulus of the scar tissue and the biochemical variables, but the r2 values were lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1995

Biomechanical analysis of the ankle anterior drawer test for anterior talofibular ligament injuries.

The effect of sectioning the anterior talofibular ligament on the load-displacement behavior of the ankle was evaluated in vitro during the anterior drawer test using the flexibility approach. Controlled forces were applied across the ankle joint in the anterior-posterior direction, and the resulting displacements were measured at four flexion angles (10 degrees of dorsiflexion, neutral, and 10 degrees and 20 degrees of plantar flexion). The anterior talofibular ligament then was sectioned, and the anterior-posterior loadings were repeated at the four flexion angles. Two parameters were developed to describe the nonlinear load-displacement response of the ankle joint: neutral zone laxity (joint displacement between +/- 2.5 N) and flexibility (a measure of the nonlinear load-displacement response of the ankle between 10 and 50 N of anterior drawer loading). After sectioning the anterior talofibular ligament, significant increases in neutral zone laxity were observed at all angles of ankle flexion. The largest increases in neutral zone laxity were found with the ankle in 10 degrees of plantar flexion (76.3% increase) and 20 degrees of plantar flexion (89.7% increase). After sectioning the ligament, a significant increase (19.3%) in flexibility of the ankle was observed at 10 degrees of dorsiflexion, but no change in flexibility was observed with the ankle in the neutral and plantar flexed positions. These findings indicate that anterior drawer testing of the anterior talofibular ligament-deficient ankle between 10 degrees and 20 degrees of plantar flexion results in the largest increase in neutral zone laxity compared with the normal ankle with intact ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1996

Responses of mechanoreceptor neurons in the cat knee joint capsule before and after anterior cruciate ligament transection.

It is known that afferent neurons play a protective role in knees made unstable by transection of the anterior cruciate ligament. However, it is not known whether cutting the anterior cruciate ligament has an effect on the response of the sensory neurons that innervate the joint. In this study, the responsiveness (activation threshold and position sensitivity) of single, mechanically sensitive afferent neurons from the cat knee was evaluated by a series of extension, internal, and external rotations. The anterior cruciate ligament then was cut and the same procedure was repeated. Transection of the ligament increased joint laxity for all types of rotation. The responsiveness of the neurons was not changed significantly by cutting the ligament (p > 0.05). Therefore, capsule afferents continue to behave normally in joints in which the anterior cruciate ligament has been transected.

Animals↗
PubMed1996

Intraoperative force-setting did not improve the mechanical properties of an augmented bone-tendon-bone anterior cruciate ligament graft in a goat model.

It has been hypothesized that load affects the mechanical properties of an anterior cruciate ligament graft while it remodels. The goal of this study was to use an existing goat model to evaluate the effect of intraoperative set force on the postoperative mechanical properties of an autograft that had been augmented with a synthetic segment. The following questions were addressed. Do augmented autografts set with a high force intraoperatively have improved structural and material graft properties and lower anterior-posterior knee laxity at 3 months after surgery, compared with autografts set with a low intraoperative force? How do the structural and material properties of these implanted autografts compare with the mechanical properties of an intact anterior cruciate ligament or an unimplanted control autograft? The anterior cruciate ligament was reconstructed in seven goats with use of a composite graft consisting of a bone-patellar tendon-bone autograft and a synthetic augmentation device. A force-setting technique was used intraoperatively to establish the load-sharing between the autograft and augmentation segments such that the autograft carried either a high (16.5 N in four animals) or low (1.5 N in three animals) level of force, while the total force in the composite graft remained constant. Tensile testing was performed at 3 months after surgery to determine the material and structural properties of the autograft, the intact anterior cruciate ligament from the normal contralateral knee, and a control bone-patellar tendon-bone graft of similar size that was harvested from the contralateral knee at the time of necropsy and had never been implanted in the joint. The structural and material properties of the autografts initially set to high or low loads at surgery were not significantly different after 3 months of implantation. The strength and stiffness of the implanted tendons were an average of 24 and 20% of the strength and stiffness of the normal anterior cruciate ligament and 31 and 62% of the control tendons, respectively. Intraoperative set force in an augmented anterior cruciate ligament graft at the levels chosen in this study did not significantly affect weakening of the autograft at 3 months.

Animals↗
PubMed1998

Effect of combined axial compressive and anterior tibial loads on in situ forces in the anterior cruciate ligament: a porcine study.

This study investigated the impact of a combination of axial compressive and anterior-posterior tibial loads on the in situ forces in the anterior cruciate ligament. An axial compressive load is believed to contribute to increased stability of the knee joint; however, its effect on in situ forces in the anterior cruciate ligament has not been clearly defined, to our knowledge. It was hypothesized that the application of an axial compressive load, when combined with an anterior tibial load, would result in larger in situ forces in the anterior cruciate ligament than those caused by an isolated anterior tibial load. With use of a porcine knee model, the results confirmed this hypothesis; the addition of a 200 N axial compressive load to a 100 N anterior tibial load increased knee stability by reducing anterior-posterior tibial translation and internal-external tibial rotation and also caused a significant increase in in situ forces in the anterior cruciate ligament (p < 0.05). Specifically, there was a 34% increase in the in situ force at 30 degrees of flexion, a 68% increase at 60 degrees of flexion, and an 84% increase at 90 degrees of flexion compared with those for an isolated anterior tibial load of 100 N. Additionally, there was a statistically significant increase of the in situ forces in the anterior cruciate ligament at 60 and 90 degrees as compared with those at 30 degrees. These results suggest that axial compressive loads on the knee may play a role in injury of the anterior cruciate ligament when the knee is flexed.

Animals↗
PubMed1999

Estrogen level alters the failure load of the rabbit anterior cruciate ligament.

We hypothesized that increasing the level of circulating serum estrogen would decrease the load at failure for the rabbit anterior cruciate ligament. We developed an animal model in which hormonal manipulations could be correlated with load at failure for the anterior cruciate ligament. Sixteen New Zealand White ovariectomized rabbits were matched and divided into two groups. The eight rabbits that were not treated with the estrogen supplement (Group O) and the eight that were treated with the supplement (Group E) were housed for 30 days. Serum estrogen levels were measured. The knees were stripped of all soft tissue, and the load at failure for the anterior cruciate ligament was measured in a materials testing machine with a displacement rate of 0.5 mm/sec. The load at failure for all 16 specimens in Group E (446 +/- 54 N) (mean +/- SD) was significantly reduced (p = 0.02) compared with that for the nine specimens in Group O (503 +/- 48 N). It is recognized that an increased number of anterior cruciate ligament injuries occurs in female athletes. Although the mechanism responsible for failure of the anterior cruciate ligament in women is yet to be defined, this experiment suggests that estrogen may alter ligament strength.

Animals↗
PubMed2000

Characterization of hamstring reflexes during anterior cruciate ligament disruption: in vivo results from a goat model.

The existence of an anterior cruciate ligament-hamstring reflex arc, the extent to which these reflexes can protect the knee, and the extent to which they are affected by rupture of the anterior cruciate ligament remain controversial. We evaluated the temporal components of the anterior cruciate ligament-hamstring synergy by simulating an injury to the ligament in a goat model. Reflexive hamstring activation in anesthetized goats was evaluated when the anterior cruciate ligament was loaded with static subfailure, dynamic subfailure, and dynamic failure loads. Reflexive hamstring activation was not found in response to static subfailure loading but was observed in response to dynamic subfailure and failure loading. The latency of the reflex evoked by dynamic failure loading was shorter than that evoked by dynamic subfailure loading. The findings suggest that the extent to which the hamstring reflexes can protect the knee may be bounded by the ability of these muscles to generate force rapidly and the amplitude and time-course of the loads applied to the knee joint. The present data present a framework for further investigation of the contribution of anterior cruciate ligament-hamstring reflexes to the stability of the knee joint under high loads and loading rates.

Animals↗
PubMed2000

Decorin antisense gene therapy improves functional healing of early rabbit ligament scar with enhanced collagen fibrillogenesis in vivo.

Injured ligaments heal with scar tissue, which has mechanical properties inferior to those of normal ligament, potentially resulting in re-injury, joint instability, and subsequent degenerative arthritis. In ligament scars, normal large-diameter collagen fibrils have been shown to be replaced by a homogenous population of small collagen fibrils. Because collagen is a major tensile load-bearing matrix element and because the proteoglycan decorin is known to inhibit collagen fibrillogenesis, we hypothesized that the restoration of larger collagen fibrils in a rabbit ligament scar, by down-regulating the proteoglycan decorin, would improve the mechanical properties of scar. In contrast to sense and injection-treated controls, in vivo treatment of injured ligament by antisense decorin oligodeoxynucleotides led to an increased development of larger collagen fibrils in early scar and a significant improvement in both scar failure strength (83-85% improvement at 6 weeks; p < 0.01) and scar creep elongation (33-48% less irrecoverable creep; p < 0.03) under loading. This is the first report that in vivo manipulation of collagen fibrillogenesis improves tissue function during repair processes with gene therapy. These findings not only suggest the potential use of this type of approach to improve the healing of various soft tissues (skin, ligament, tendon, and so on) but also support the use of such methods to better understand specific structure-function relationships in scars.

Animals↗
PubMed2006

Nerve endings of the wrist joint: a preliminary report of the dorsal radiocarpal ligament.

As part of an investigation of the articular nerve ending populations in the wrist joint capsule associated with the anterior and posterior interosseous nerves, this study addresses the nerve ending population in the dorsal radiocarpal ligament. The ligaments were harvested from four wrists of two fresh cadavers within 12 h of death. Tissues were fixed, cryostat sectioned, and processed for fluorescence immunohistochemistry using antibody to protein gene product 9.5 (PGP 9.5), a general or pan neuronal marker, and a secondary antibody conjugated to a fluorescent tag (Alexa Fluor 488). The sections were evaluated with a confocal laser microscope and an image analyzer. Labeled nerve endings were mapped, measured, and categorized. Type I (Ruffini-like ending), Type III (Golgi-like tendon organ) and Type IV (noncorpuscular) nerve endings could be identified in all four DRC ligaments, with Types I and IV dominating. These receptors were distributed primarily over the superficial two thirds of the ligament (>80%), and near the bony attachments (>70%). The dorsal radiocarpal ligament has a rich sensory innervation from the posterior interosseous nerve terminating in nerve endings located in the superficial two-thirds of the ligaments, primarily near bony attachment sites.

Aged↗