Experimental temporomandibular joint disc perforation in the rabbit: a gross morphologic, biochemical, and ultrastructural analysis.

This study evaluates the progression of osteoarthritis (OA) in the adult New Zealand white rabbit temporomandibular joint following unilateral disc perforation. Thirty-seven animals were divided into five groups: control (n = 8), 6-week sham (n = 5), and experimental 6-, 12-, and 24-weeks (n = 8 each). Quantitative data was examined with two-way analysis of variance, and followed by Scheffe pair-wise comparisons. Transmission electron microscopy, acid phosphatase [AcP] activity, uronic acid content, and gross morphologic analysis indicated that disc perforation induced remodeling activity and degenerative changes in the condylar cartilage and bone as early as 6 weeks postoperatively. AcP activity of homogenized cartilage samples was significantly increased in experimental joints versus the side that did not undergo surgery at 6 and 12 weeks (P < .05). Uronic acid content was significantly greater in experimental joints versus the side that did not undergo surgery at 6 weeks (P < .05). Heightened cellular activity was present in the deep zone of osteoarthritic fibrocartilage of the 6- and 12-week experimental groups. Degenerating chondrocytes appeared to contain greater proportions of intracytoplasmic filaments and lysosome-like bodies. Disc perforation provided the impetus for degenerative or remodeling changes in the condylar cartilage of experimental joints, and is consistent with secondary OA. These dynamic events were most significant in the deep zone of articular fibrocartilage.

Mechanisms of neutrophil damage to human alveolar extracellular matrix: the role of serine and metalloproteases.

Many syndromes of lung injury are associated with accumulation of neutrophils within the pulmonary parenchyma. These neutrophils have the capacity to produce lung injury by products including proteases and reactive oxygen species (ROS). We examined the ability of activated neutrophils to solubilize human alveolar extracellular matrix (ECM), and by use of scavengers and inhibitors, evaluated the role of ROS and proteases in this process. Supernatants of phorbol myristate acetate-activated neutrophils routinely solubilized 10.2% +/- 0.8% (n = 30) of collagen in human alveolar ECM, as measured by hydroxyproline release. Scavengers of ROS had no significant effect on ECM solubilization. Inhibitors of metalloproteases partially inhibited ECM solubilization (38.5% +/- 4.6% inhibition by ethylenediaminetetraacetic acid [n = 6], and 37.0% +/- 14.7% by 1,10-phenanthroline [n = 6]; p less than 0.05). Inhibitors of the neutrophil serine proteases, elastase and cathepsin G, markedly inhibited ECM solubilization (100.9% +/- 3.7% by alpha 1-protease inhibitor [alpha 1-PI] [n = 6] and 81.9% +/- 0.1% by soybean trypsin inhibitor [n = 6]; p less than 0.01). Since alpha 1-PI completely inhibited solubilization, metalloprotease activity appeared to be related to serine protease activity. This finding was confirmed by the observation that addition of a metalloenzyme activator, p-aminophenylmercuric acetate, in the presence of alpha 1-PI, restored solubilization to the same level as that inhibited by metal chelators. We conclude that human neutrophil metalloproteases and serine proteases directly solubilize human alveolar ECM. Furthermore, neutrophil serine proteases activate latent metalloproteases. However, ROS were not demonstrated to play a major role in ECM solubilization in our system.

Neural elements in the human temporomandibular articular disc.

The purpose of this study was to determine the presence and describe the location of neural elements in the articular disc of the human temporomandibular joint. Six articular discs were obtained from three adult human subjects at autopsy. Four discs were cut into segments of known anterior-posterior orientation. The remaining two were processed intact. All tissues were stained in bulk with gold chloride, and frozen, sectioned on a sliding microtome at 70 to 100 microns, mounted on slides, dehydrated, and coverslipped. Nerve fibers were seen penetrating the discs from the pericapsular connective tissue. Structures resembling Ruffini endings, Pacinian corpuscles, and Golgi tendon organs were identified in the pericapsular connective tissue and within the disc. The population density of neural elements was the greatest at the periphery of the disc and progressively decreased towards the center, which was essentially devoid of them. The concentration of neural elements appeared to be greater at the anterior and posterior margins of the disc, with the greatest concentration being posteriorly. These findings support the theory that afferent nerves may arise from neural elements within the disc.

Neural elements in human cervical intervertebral discs.

This study attempted to characterize neural elements within the human cervical intervertebral disc. Cervical intervertebral discs were obtained from four adult human subjects at autopsy. Discs were stained in bulk with gold chloride, sectioned, and viewed with the light microscope. Nerve fibers appeared to enter the disc in the posterolateral direction and course both parallel and perpendicular to the bundles of the anulus fibrosus. Nerves were seen throughout the anulus but were most numerous in the middle third of the disc. Receptors resembling Pacinian corpuscles and Golgi tendon organs were seen in the posterolateral region of the upper third of the disc. These results provide further evidence that human cervical intervertebral discs are supplied with both nerve fibers and mechanoreceptors.

Anatomical demonstration of the nerve-supply to the flexor tendon.

A dissection of four unembalmed human fingers demonstrated a branch from the digital nerve which enters the flexor tendon sheath at the same place as the transverse branch of the digital artery. We conclude that this branch supplies the nerve fibres found within the vinculum.

Neuroreceptors in the tissues of the knee joint.

Four types of receptors have been described in the articular tissues of the knee joint in humans and animals. The first three types are encapsulated; the fourth is unencapsulated: type I, Ruffini endings; type II, Pacinian corpuscles; type III, Golgi tendon organs; and type IV, free nerve endings. Ruffini endings, Pacinian corpuscles, and free nerve endings are most prevalent in the fibrous joint capsule; Golgi tendon organs are most common in the collateral and cruciate ligaments and the menisci. In the anterior and posterior cruciate ligaments (ACL, PCL), receptors are concentrated at the tibial and femoral attachments of the ligaments. In the menisci, neural elements penetrate the horns and the outer and middle thirds of the body. Ruffini mechanoreceptors are believed to contribute mainly to maintenance of muscle tone, Pacinian corpuscles and Golgi tendon organs are stimulated during movement, and free nerve endings are nociceptors. Thus, receptors of the knee joint are able to produce a discriminating afferent inflow to the central nervous system (CNS), thereby contributing to the protection and function of the joint through the musculature.

Fluorescent light decreases autoimmunity and improves immunity in B/W mice.

Fluorescent light emitted from cool white tubular fluorescent lamps covered with standard acrylic lids decreased autoimmunity and enhanced immunity in the New Zealand Black/New Zealand White F1 hybrid female (B/W) mouse model of systemic lupus erythematosus (SLE). Thirty-three weeks of daily cool white fluorescent light exposure significantly decreased anti-ds DNA antibody levels and spleen size, and increased lymphocyte responsiveness to lipopolysaccharide (LPS) in B/W mice depilated to enhance light penetration. Depilation alone had no significant effect. The immunomodulatory potential of fluorescent light in B/W mice has not been previously appreciated, and may have important implications in SLE.

Effects of soft contacts of differing thickness on corneal wound healing in rabbits.

This study was undertaken to determine the effects of thin (60 microns) and thick (240 microns) soft contact lenses of equal water content (70%) and power on nonlesioned and lesioned rabbit corneas. In one group of animals, corneas were not lesioned. Thin lenses were placed on left corneas and thick lenses on right corneas. In a second group, lesions were made in both corneas. Left corneas were covered with thin lenses and right corneas with thick lenses. Post-treatment times were 8 hr and 24 hr. At sacrifice, one-half of the cornea was fixed in 4% buffered glutaraldehyde for SEM study. The other half was cut into segments, fixed in a buffered glutaraldehyde-ruthenium red (RR) solution post-osmicated in osmium containing RR and prepared for TEM. At both 8 hr and 24 hr SEM showed cell migration in lesioned corneas covered with thin lenses but not in lesioned corneas covered with thick lenses. At 8 hr, TEM of nonlesioned and lesioned corneas showed no changes in the thickness of the corneal epithelium or the RR staining of the surface. At 24 hr, in nonlesioned corneas covered with thick lenses, the RR staining of microvilli and the height of the corneal epithelium were less than in nonlesioned corneas covered with thin lenses. In lesioned corneas covered with thick lenses, the thickness of the cornea was markedly reduced, the RR staining of microvilli was less and basal cells were more compressed than in lesioned corneas covered with thin lenses. The results of this study indicate that the thickness of a soft contact lens is important in treating corneal trauma.

Mechano-receptors in the flexor tendons of the hand.

Flexor tendons of the hand obtained fresh at autopsy were studied histologically for free nerves and mechano-receptors. In addition to free nerves, Ruffini endings, Pacinian corpuscles and Golgi tendon organs were found throughout the tendons. Golgi tendon organs and Pacinian corpuscles were subjectively in greater numbers than Ruffini endings. The predominance of these two mechano-receptors indicates that position sense and kinetic activities of the fingers are well-served, as evidenced in hand movements.

Mechanoreceptors in articular tissues.

The morphology, distribution, and function of mechanoreceptors in joint capsules, ligaments, knee-joint menisci, and articular disks of the temporomandibular joints of animals, including humans, have been reviewed. In addition to free nerve endings, three types of joint receptors are present in most animal joints: 1) a Ruffini-like receptor situated in the capsule, 2) a Golgi tendon organ situated in a ligament; and 3) the encapsulated Pacinian-like corpuscle. In the anterior cruciate ligament, nerve fibers enter from the subsynovial connective tissue and terminate in receptors. Most of the receptors are found in the distal portion of the ligament. In the meniscus, nerves penetrate the outer and middle one-third of the body and the horns from the perimeniscal tissue, with a greater concentration at the horns. In the temporomandibular articular disk, the mechanoreceptor density is greatest at the periphery and progressively decreases toward the center. If a joint has an intra-articular structure, mechanoreceptors undoubtedly are present within it. The concentration of mechanoreceptors appears greater in areas related to the extremes of movement and probably represents the first line of defense in sensing these extremes. These afferent discharges elicit support from discharging mechanoreceptors located in the joint capsule and subsequently from those in the surrounding muscles. This total afferent output alerts the central nervous system of impending injury, which can then be averted through reflex mechanisms.

Mechanoreceptors in the human medial meniscus.

Medial menisci, obtained at autopsy, were sectioned into radial segments which were stained in bulk using a modified gold chloride method following pretreatment with Triton X-100. Segments were then sectioned on a sliding microtome at 100 microns, mounted on slides, dehydrated and coverslipped. Axons were seen penetrating from the perimeniscal tissue into the outer third of the meniscus with a heavier concentration at the horns. Neural elements were identified in the perimeniscal tissue and in the outer and middle thirds of the meniscus, but not in the inner third. The medial meniscus is capable of afferent input to the central nervous system of importance to the biomechanical function of the joint.

The use of agents which improve staining of fresh human fibrocartilage.

Comparisons of three agents were undertaken to improve the bulk staining of fresh human fibrocartilage with gold chloride for neural elements. The medial meniscus of the knee was the experimental tissue. Dimethyl sulfoxide (DMSO) increased the penetration of the stain but had a negative effect on the deposition of the gold on the tissue site. Sodium borohydride apparently reacted with tissue aldehydes decreasing the background enough to give the impression of an improved staining reaction. Triton X-100, the agent of choice, solubilized the collagen protein of the menisci sufficiently to allow penetration of the stain and, being nonionic, did not react with the gold chloride solution.

Neural anatomy of the human anterior cruciate ligament.

The histology of the anterior cruciate ligament was studied by a modified technique of the Gairns gold chloride stain for neural elements. Three morphological types of mechanoreceptors and free nerve-endings were identified: two of the slow-adapting Ruffini type and the third, a rapidly adapting Pacinian corpuscle. Rapidly adapting receptors signal motion and slow-adapting receptors subserve speed and acceleration. Free nerve-endings, which are responsible for pain, were also identified within the ligament. These neural elements comprise 1 per cent of the area of the anterior cruciate ligament.

Effects of mechanical loads on surface morphology of the condylar cartilage of the mandible in rats.

Mechanical loads on the condylar cartilage were varied by feeding either a hard diet, a soft diet, or a sequential combination of a soft diet followed by a hard diet to young male and female rats for a total period of 4 weeks, and to mature male rats for 12 weeks. Gross condylar dimensions were greatest in the hard-diet groups, intermediate in the combination soft/hard-diet groups, and smallest in the soft-diet groups. Scanning electron microscopy of the condyle revealed a smooth, nonporous articular surface in the soft-diet groups. Hard-diet condyles had a rougher, more porous articular surface while soft/hard-diet condyles were intermediate between nonporous and slightly roughened condyles. None of the condyles showed ridges or elevations on the articular surface. Sex, age and time of the diets did not significantly affect these results.

Porosity of the basement membrane overlying Peyer's patches in rats and monkeys.

The porosity of the epithelial basement membrane (basal lamina) overlying lymphoid follicles within Peyer's patches was studied in rats and monkeys by scanning electron microscopy. Basement membranes of lymphoid follicles are markedly porous, more conspicuously so than those of adjacent villus cores. The porosity increases centrifugally from the apex of the follicle to its periphery, where the basement membrane continues into the cul-de-sacs of the crypts. Such porosity may facilitate bidirectional passage of lymphocytes during an immune response. The unique structure of the basement membrane overlying lymphoid follicles suggests a biologic adaptation of this tissue boundary to a specific physiologic activity of the organism.

Mechanoreceptors in the human anterior cruciate ligament.

This study was undertaken to identify and quantitate mechanoreceptors in the human anterior cruciate ligament (ACL). Ligaments from six human subjects were obtained at autopsy, cut into cross-sectional segments 1.0-1.5 cm thick, and kept oriented as to the femoral and tibial attachments. The segments were stained in bulk by using a modified gold chloride method, frozen, and sectioned on a sliding microtome at 100 microns. The sections were floated in alcoholic gelatin, mounted on slides, dehydrated, and coverslipped. Serial sections were studied with the light microscope and receptors were photographed. Cross-sectional maps of every tenth section were made outlining the periphery of the ACL and the receptors within that section. With these maps, a computerized, morphometric analysis of the ACL was done, thus obtaining the percentage of receptors in each section and in each ACL. In addition to free nerve endings, two morphologically distinct mechanoreceptors were identified: (1) Ruffini end organs and (2) Pacinian corpuscles. Preliminary morphometric analyses show that populations of mechanoreceptors are greater at the femoral and tibial ends of the ligament and constitute approximately 2.5% of the ligament. Based on these findings the human ACL has the anatomic basis for a discriminating afferent outflow to the central nervous system.

Intramitochondrial inclusions in the kidney of the pygmy mouse.

Intramitochondrial inclusions averaging 1000 A in diameter were observed in the cells of the proximal convoluted tubules in samples of kidneys from pygmy mice, Baiomys taylori. Electron microscopic study of unstained sections and mitochondrial fractions showed that these inclusions are lipid and found at a S.G. 1.37 in a linear sucrose gradient. Renal glycogen, inorganic phosphate and plasma sodium were significantly higher in the pygmy mouse and plasma calcium was lower, as compared with the laboratory mouse. We believe these intramitochondrial inclusions to be lipid which accumulates divalent cations, particularly calcium, which acts as a sodium pump allowing the pygmy mouse to conserve water and adapt to its environment.