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At least 937 records · Page 52Linked to original sources
PubMed1996

Accessory ossification centres associated with osteochondral fragments in the extremities of horses.

Fifty-six tarsocrural joints and 94 metatarsophalangeal joints were examined, at necropsy, from horses aged < or = 2 years. Osteochondral fragments at the cranial aspect of the intermediate ridge of the distal part of the tibia were seen in six horses, and at the proximoplantar aspect of the proximal phalanx in seven horses. Defects in the proximoplantar aspect of the proximal phalanx without osteochondral fragments were seen in a further two horses. Inflammatory and degenerative changes were not observed in any of the joints examined. From the incidence and natural course of these fragments, and from the radiological and microscopical findings, accessory ossification centres would seem the most probable cause of the osteochondral fragments at the cranial aspect of the intermediate ridge of the distal part of the tibia and at the proximoplantar aspect of the proximal phalanx.

Animals↗
PubMed1999

Involvement of leukotriene B4 in arthritis models.

We investigated the role of leukotriene B4 (LTB4) in murine arthritis models using a leukotriene A4 (LTA4) hydrolase inhibitor, SA6541. SA6541 inhibited the severity of collagen-induced arthritis and muramyl dipeptide (MDP)-induced hyperproliferation of synovial cells in vivo. SA6541 also inhibited LTA4-induced hyperproliferation of synovial stromal cells in vitro. These results suggest that LTB4 may play an important role in arthritis models.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

Degenerative joint disease in poultry--differences in composition and morphology of articular cartilage are associated with strain susceptibility.

The morphology and basic biochemical composition of articular cartilage from two strains of fowl were examined. Broiler breeder fowl are considered susceptible to degenerative joint disease (DJD); histological examination of one-year-old broiler breeders showed in some samples, articular cartilage thinning, fibrillation and chondrocyte cluster formation, features considered typical of DJD. Examination of similar samples from laying strain fowl showed only minor age-related changes such as some slight cartilage thinning and very mild fibrillation. The articular cartilage from the broiler breeder birds was significantly more hydrated with a higher uronic acid content than that of the laying strain birds. In addition, unloaded articular surfaces such as the proximal humerus had significantly higher amounts of uronic acid than the loaded cartilage surfaces of the proximal tarsometatarsus and the distal tibiotarsus; this suggested that the joint loading may have a role in any biochemical differences found between joints and between strains of fowl. These findings concur with other reports in mammals that showed increased hydration and uronic acid in association with early DJD and in models of osteoarthritis (OA). Thus, despite some differences between avian and mammalian articular cartilage, studies on avian DJD may give insights into mammalian disease.

Animals↗
PubMedDate not supplied

Relationships between the bone pathologies, ash and mineral content of long bones in 35-day-old broiler chickens.

Histological examinations and estimations of the contents of ash, phosphorus and calcium were used to investigate the femora and tibiotarsi from lame and normal 35-day-old broilers from Holland, Northern Ireland and Scotland. The prevalence of different pathologies varied with the source of the broilers and there were correlations between histological and bone ash values. The most common condition causing lameness was bacterial infection within the physis and cartilaginous epiphysis (bacterial chondronecrosis) of the proximal tibiotarsus, and there was a possible link between rickets attributable to a relative phosphorus deficiency and this condition. There were wide variations between birds in the cortical bone quality as assessed histologically and by estimates of the bone ash content and phosphorus to calcium ratios. Theses variations may be related to different probabilities of bone fracture.

Animals↗
PubMed2002

Age-related changes in primary somatosensory cortex of rats: evidence for parallel degenerative and plastic-adaptive processes.

Aged rats show a characteristic decline of the sensorimotor state, most strikingly expressed in an impairment of the hindlimbs leading to significantly reduced sensory stimulation on the hindpaw. We review recent studies using optical imaging and electrophysiological recordings to investigate the effects of aging on somatosensory cortex and to identify age-related changes in terms of degeneration or plastic adaptation. For the cortical hindpaw representation, reduction of map size, receptive field enlargement and reduced response strength were described. None of these changes were reported in the forepaw representation in the same individual, however, in both the fore-and hindpaw representations response latencies and cerebral blood flow were affected. Changes of latencies and blood flow are best explained by degeneration, but the regional and specific changes of maps, receptive fields and response strength by plastic phenomena arising from the reduced sensory inputs. While the degenerative changes are not modifiable by enriched environmental conditions or application of Ca(2+) blocker, the plastic changes were fully reversible under these conditions. We discuss the implications of these findings for cognitive functions at old age and possible treatments of age-related changes in human subjects.

Action Potentials↗
PubMed1997

Islet amyloid polypeptide and calcitonin gene-related peptide expression are upregulated in lumbar dorsal root ganglia after unilateral adjuvant-induced inflammation in the rat paw.

After unilateral adjuvant-induced inflammation, expression of neuropeptides believed to be involved in the inflammatory response, e.g. substance P and calcitonin gene-related peptide (CGRP), is upregulated in innervating sensory neurons. Islet amyloid polypeptide (IAPP) is structurally related to CGRP and constitutively expressed in sensory CGRP-containing neurons; the role of IAPP in sensory neurons is unknown. To examine whether IAPP could play a role in inflammation, IAPP expression in L5 dorsal root ganglion (DRG) and its distribution in the dorsal horn were investigated after unilateral adjuvant-induced inflammation in the rat paw and compared with CGRP, using in situ hybridization and immunocytochemistry. At 12 h and day 3, but not day 21, the percentage of nerve cell profiles expressing IAPP and CGRP mRNA was greater in the ipsilateral L5 DRG; these changes paralleled the occurrence of edema around the tarsotibial joint and a slight limp. IAPP expression in individual nerve cell profiles was higher in the ipsilateral L5 DRG at 12 h, but not at days 3 and 21; the corresponding CGRP mRNA level was higher at days 3 and 21. At day 3, the higher expression of IAPP and CGRP on the ipsilateral side was accompanied by increased numbers of immunoreactive DRG neurons and fibers in the spinal cord dorsal horn. Largely, expression of IAPP and CGRP seems to be co-ordinately regulated by localized inflammation, although the rapid, but transient, upregulation in DRG neurons of IAPP mRNA expression and the slower, but sustained, upregulation of CGRP mRNA expression may indicate dissociated regulation of the peptides. Thus, IAPP could play a role in the initial phase of localized inflammation.

Amyloid↗
PubMed1998

Diagnostic imaging of osteochondrosis.

This article includes imaging of the glenohumeral (shoulder), elbow, stifle, and tarsal joints. The imaging modalities discussed are survey radiography, contrast arthrography, linear tomography, ultrasound, computed tomography, scintigraphy and magnetic resonance. Survey radiography is the first choice imaging modality for diagnosing osteochondrosis dissecans in dogs. In cases where survey radiography fail to demonstrate a lesion other modalities such as scintigraphy, linear tomography, computed tomography, and magnetic resonance may be helpful. Survey radiography, contrast arthrography, computed tomography, and magnetic resonance may also provide additional information contributing to early diagnosis and treatment.

Animals↗
PubMed1998

Diagnostic and surgical arthroscopy in osteochondrosis lesions.

In the dog, as in man and the horse, arthroscopy has an important role in treatment of joint disease. In the shoulder, elbow, and stifle joints, surgical arthroscopy can and should replace the classical surgical methods of treating osteochondrosis lesions. In elbow and tarsocrural joint disorders, the diagnostic potentials of arthroscopy are evident. With the established techniques, not only can the lesions be diagnosed with accuracy, but they can also be treated within the same procedure, making arthroscopy the treatment of choice to deal with osteochondrosis lesions. Without a doubt, arthroscopy will play an important role in the understanding of the etiopathology of different joint diseases, especially within the elbow joint, where so many questions remain unresolved. The advantages of arthroscopy in the diagnosis and treatment of osteochondrosis have also encouraged other veterinary surgeons to adopt the technique. In the developmental stage of arthroscopy in the dog, a frequently expressed comment was that arthrotomy was as valuable and as easy (or easier) to perform as arthroscopy. Now that the advantages of arthroscopy have been demonstrated, the skepticism has changed into enthusiasm. The same evolution is noted with arthroscopy in both man and the horse.

Animals↗
PubMed2002

Interactions between cutaneous afferent inputs to a withdrawal reflex in the decerebrated rabbit and their control by descending and segmental systems.

Previous studies have suggested that activation of nociceptive afferents from the heel recruits a supraspinal mechanism, which is modulated by adrenergic descending inhibition, that augments withdrawal reflexes in medial gastrocnemius (MG) motoneurones. To test this idea, we have studied the temporal evolution of reflexes evoked in MG by electrical stimulation of sural nerve A(beta)-, A(delta)- and C-fibre axons at 1 Hz, in decerebrated rabbits. Reflexes were analysed in three time bands, estimated to accord to afferent drive from A(beta)- (phase 1), A(delta)- (phase 2) and C-fibre (phase 3) inputs. Stimulation of A(delta)- and C-fibres gave significant temporal summation of all reflexes. The alpha(2)-adrenoceptor antagonist RX 821002 ((2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)-4,5-dihydro-1-H-imidazole)-HCl) (100 microg intrathecal (i.t.)) potentiated, and the alpha(2)-agonist dexmedetomidine (1-30 microg i.t.) depressed all reflexes per se, but the effects of these drugs on temporal summation were secondary to changes in baseline excitability. When C-fibres were stimulated, the N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (1 mg i.t.) reduced temporal summation of phase 2 and 3 but not phase 1 reflexes. Spinalisation at L1 in the absence of drugs increased phase 2 and 3 reflexes but had no effect on phase 1, whereas spinalisation after RX 821002 resulted in decreased phase 1 responses with no significant change in later phases. Spinalisation in the presence of dizocilpine resulted in small reductions in phase 3 reflexes only. In all cases spinalisation virtually abolished temporal summation. In spinalised animals, dizocilpine selectively reduced late reflexes, and the opioid antagonist naloxone (100 microg i.t.) augmented all reflexes but gave rise to temporal subtraction of reflexes when C-fibres were stimulated.The present experiments have revealed a number of novel and important features of the sural-MG reflex pathway: (i) activity in fine afferent axons augments the reflexogenic potential of all subsequent afferent input, thereby allowing all afferent drive from the sural field to contribute to withdrawal of the heel; (ii) endogenous adrenergic control of this reflex pathway is completely non-selective; (iii) there is a non-adrenergic element of descending inhibition that is selective for the late components of MG reflex responses, and this element is directed particularly against transmission through NMDA receptors; (iv) temporal summation in this reflex is dependent on NMDA receptor-dependent and -independent mechanisms; and (v) this temporal summation is in some way dependent on the integrity of descending pathways.

Adrenergic alpha-Agonists↗
PubMed1992

Prevention of myonecrosis in mdx mice: effect of immobilization by the local tetanus method.

Sixteen mdx mice of three-week-old were injected with tetanus toxin into the right gastrocnemius muscle and then subjected to sustained dorsiflexion of the right ankle joint (local tetanus) for 2 to 56 days. Another 16 mdx mice of the same age were not injected with tetanus toxin, serving as controls. The incidence of centronucleated muscle fibers, which indicate preceding myodegeneration, was significantly reduced in the tetanus toxin injected soleus muscle (SOL) and extensor digitorum longus muscle (EDL), compared with that in the untreated control mdx mice. It seems that myonecrosis in the mdx mouse is facilitated by muscle movement itself and that immobilization of muscle prevents myonecrosis. This concept is helpful for understanding the mechanism underlying myonecrosis in patients with Duchenne muscular dystrophy, and for instruction concerning rehabilitation programs and activities in daily life.

Animals↗
PubMed2000

Asymmetric adaptive modeling of central tarsal bones in racing greyhounds.

Fatigue fracture of the cuboidal bones of the foot, especially the navicular tarsal bone, is common in athletes and dancers. The racing greyhound is a naturally occurring animal model of this injury because both microcracking and complete fracture occur in the right central (navicular) tarsal bone (CTB). The right limb is on the outside when racing in a counter-clockwise direction on circular tracks, and is subjected to asymmetric cyclic compressive loading. We wished to study in more detail adaptive modeling in the right CTB in racing greyhounds. We hypothesized that cyclic asymmetric loading of a cuboidal bone induced by racing on a circular track would induce site-specific bone adaptation. We also hypothesized that such an adaptive response would be attenuated in greyhounds that were retired from racing and no longer subjected to cyclic asymmetric loading. Central tarsal bones from racing greyhounds (racing group, n = 6) and retired greyhounds being used for breeding (nonracing group, n = 4) were examined using quantitative computed tomography (CT). Bone mineral density (BMD) was determined in a 3-mm diameter region-of-interest (ROI) in six contiguous 1-mm-thick sagittal CT slices of each CTB. Bones were subsequently examined histomorphometrically and percentage bone area (B.Ar./T.Ar., %) was determined in 10 ROI from dorsal to plantar in a transverse plane, mid-way between the proximal and distal articular surfaces. The BMD of the right CTB was greater than the left in all greyhounds (p < 0. 001). In comparing ipsilateral limbs between groups, BMD of the racing group was greater than the nonracing group for each side (p < 0.005). In sagittal plane histologic sections, bone in the dorsal region of the right CTB had undergone adaptive modeling, through thickening and compaction of trabeculae. B.Ar./T.Ar., % in the right CTB of the racing group was greater than in the contralateral CTB (p < 0.001), and the ipsilateral CTB of the nonracing group (p < 0.001). In the nonracing group, B.Ar./T.Ar., % in the right CTB was not significantly different from left CTB (p > 0.8; power = 80% at Delta = 48%). It was concluded that greyhounds racing on circular tracks develop site-specific bone adaptation with compaction of trabecular bone and increase in BMD in the right CTB in particular, the most common site for fatigue fracture. Our data also suggested that partial reversal of this adaptive process occurred in retired, nonracing greyhounds, after cessation of asymmetric cyclic loading at racing speed. Racing greyhounds provide a model in which to study fatigue fracture and adaptation of cuboidal foot bones subjected to cyclic loading.

Animals↗
PubMed2000

Does the mechanical milieu associated with high-speed running lead to adaptive changes in diaphyseal growing bone?

Exercise during growth can be important for attaining optimal bone mass. High-intensity long-duration protocols, however, can have detrimental effects on immature bone morphology and mechanics. The underlying mechanisms are poorly understood. Here, we quantified the mechanical environment of the middiaphyseal rooster tarsometatarsus during high-speed running and examined whether short bouts of this exercise-related mechanical milieu can induce positive changes in cortical bone morphology, mechanics, and mineral ash content. At 9 weeks of age, roosters were assigned to controls (n = 9) and runners (n = 8). Treadmill running was applied in loading sessions of 5 min, three times per day (approximately 2600 cycles/day) for 8 weeks. Both controls and runners received double-fluorochrome labels during weeks 3 and 8 of the protocol. Middiaphyseal distributions of tarsometatarsal longitudinal normal strain, strain rate, and strain gradients engendered by walking and running were determined via in vivo strain gauges. Compared with walking, running elevated mean peak strain magnitude by 19%, peak strain rates by 136%, and peak strain gradients by approximately 18%. After 8 weeks of running, middiaphyseal areal and mechanical properties and normalized ash weight were no different between runners and controls. Transient and focal reductions in periosteal mineral apposition rates occurred during the exercise protocol. Our current data suggest that reducing the number of loading cycles can mitigate the adverse response previously observed in this model with long-duration running. This study also supports the tenet that the exercise-generated mechanical milieu must differ substantially from the habitual milieu to induce significant adaptations.

Adaptation, Physiological↗