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Biomedical subjects

L B Jeffcott

Publications and source records attributed to L B Jeffcott.

At least 19 recordsLinked to original sources
PubMed2003

Differential distribution of cathepsins B and L in articular cartilage during skeletal development in the horse.

REASONS FOR PERFORMING STUDY: This study was designed to examine a new role for cysteine proteinases in the process of endochondral ossification. OBJECTIVES: The aim of the present study was to investigate the presence and distribution of cathepsin B and cathepsin L in equine articular cartilage during development. METHODS: Full-depth cartilage samples from a total of 40 horses (age range: 4 month fetuses to 2 years) were examined and enzymes detected by immunocytochemical localisation. RESULTS: Observations on the presence of cathepsins B and L revealed significant age-related differences, resulting in clear division of the animals into 2 age groups: i) fetuses and neonates; ii) young growing horses (age 4 weeks to 2 years). Cathepsin B was not detected in cartilage from the majority of fetuses and neonates but was located characteristically in chondrocytes at the articular surface and hypertrophic zone in all growing horses. In contrast, cathepsin L was predominantly present in fetal and neonatal cartilage, located primarily in proliferating chondrocytes. CONCLUSIONS: This study is the first to demonstrate differential and site-specific roles for cathepsin B and cathepsin L in skeletal development in the horse. POTENTIAL RELEVANCE: The demonstrated involvement of cathepsins B and L in endochondral ossification is of relevance to developmental orthopaedic diseases such as osteochondrosis in which there is a focal failure of bone formation.

Age Factors↗
PubMed2002

Localisation and activity of cathepsins K and B in equine osteoclasts.

Cathepsin K and cathepsin B were immunolocalised in equine osteoclasts (OC s) present in ex vivo cartilage/subchondral bone samples. Samples were obtained post mortem from the lateral trochlear ridge (LTR) of six horses and ponies aged between 303 days gestation to 8 months. Strong expression of cathepsin K was detected in OC s, particularly those located at the osteochondral junction, apparently involved in the resorption of calcified cartilage. Cathepsin K expression was also detected in hypertrophic chondrocytes and in the endothelial cells of some blood vessels penetrating the hypertrophic zone of cartilage. By contrast, cathepsin B was either absent or present at very low levels in OC s.Osteoclast-like cells (OCL s) were generated in vitro from bone marrow (BM), obtained from the femurs of one horse and two ponies. High levels of cathepsin K activity but only very low levels of cathepsin B activity were demonstrated in OCL s using fluorogenic substrates for these enzymes. The cathepsin K activity could be blocked by the general cysteine proteinase inhibitor, E-64, but not by the cathepsin B inhibitor, CA-074Me. The cathepsin B activity was completely blocked by both CA-074Me and E-64. Taken together, these results suggest that cathepsin K is more important than cathepsin B in the osteoclastic resorption of bone and calcified cartilage of developing equine long bones. Given the apparent importance of cathepsin K in equine endochondral ossification further investigation into the possibility that abnormal expression of this enzyme is involved in the pathogenesis of equine developmental orthopaedic disease is warranted.

Animals↗
PubMed2002

Generation and activity of equine osteoclasts in vitro: effects of the bisphosphonate pamidronate (APD).

Equine osteoclast-like cells (OCLs) were generated from the bone marrow (BM) of two ponies and one horse in the presence of RANKL, the receptor activator of NF kappa B ligand and macrophage colony-stimulating factor (M-CSF). The phenotype of these cells was confirmed by demonstration of characteristics typical of osteoclasts (OCs) including: the expression of tartrate-resistant acid phosphatase (TRAP), the vitronectin receptor (VNR) and the calcitonin receptor (CTR), the demonstration of responsiveness to calcitonin (CT) and the ability to form resorption lacunae on ivory slices and calcium phosphate films. The bisphosphonate pamidronate (APD) dose-dependently inhibited resorption of calcium phosphate films by equine OCLs with an IC(50) of 5.8 x 10(-7) M in one horse. APD also dose-dependently inhibited the number of OCLs present in BM cultures after 7 days. However, this effect is most likely attributable to increased OCL death rather than decreased OCL formation. Paradoxically, ADP appeared to cause an early, transient, increase in OCL formation in BM cultures, however, this effect was reversed after 7 days. These preliminary in vitro data support the potential use of APD in clinical conditions characterised by increased bone turnover such as osteomyelitis, osteitis, septic osteoarthritis, navicular disease, cystic bone lesions and immobilisation-induced osteoporosis and provide useful information for future pharmacokinetic studies and clinical trials in vivo.

Acid Phosphatase↗
PubMed2000

Equine osteoclast-like cells generated in vitro demonstrate similar characteristics to directly isolated mature osteoclasts.

We report on novel methods to isolate osteoclasts (OC s) and generate osteoclast-like cells (OCL s) from the bone and bone marrow of the equine femur. OC s were successfully isolated from bone scrapings taken from the endosteal surface of the femurs of three horses. OCL s were generated from bone marrow cells taken from the same animals. The validity of using the formation of OCL s as a method for studying OC differentiation and activity was confirmed by the similar characteristics of these two cells. In particular, they both were multinuclear, expressed the enzyme tartrate resistant acid phosphatase and the vitronectin receptor. Most importantly, both were able to resorb bone as demonstrated by the formation of extensive resorption pits when cultured on dentine slices. The generation of OCL s from bone marrow obtained from the equine femur can therefore be used to study equine OC differentiation and for studies requiring the generation of large numbers of these cells. OC s isolated directly from the same bones may be used to examine the effect of a variety of factors on bone resorption in vitro and to continually reaffirm the validity of using OCL s for large-scale studies on OC biology. Such research is essential for improved understanding of bone turnover and endochondral ossification in the horse.

Animals↗
PubMed1999

Back problems. Historical perspective and clinical indications.

This article is presented as an introduction to the complex subject of back pain and its management in horses. It considers some of the historical perspectives and deals with some of the limiting factors when attempting to evaluate back pain. The clinical indications of a back problem are considered, as is the important distinction of primary versus secondary back pain. Finally, a list of considerations capable of causing back pain and impaired performance is included.

Animals↗
PubMed1999

Back problems. Radiology and scintigraphy.

Radiology and, more recently, scintigraphy are important ancillary diagnostic aids in the diagnosis of a horse with suspected back pain. Although the image quality is restricted by the size of the patient, radiographs have been used for several decades. With the introduction of modern fast-screen film systems, the quality of the images has greatly improved. These imaging techniques allow assessment of the anatomy and physiology of structures in the spine that are difficult or impossible to palpate. This article reviews the techniques and limitations of imaging the equine back, in addition to correlation imaging results and clinical findings.

Animals↗
PubMed1999

Validity of saddle pressure measurements using force-sensing array technology--preliminary studies.

Back pain is a common and poorly understood clinical problem. An important factor in this regard is the induction or exacerbation of back pain from badly designed or poorly fitting saddles. This study used a pressure-sensing mat to investigate saddle fit. The aims of the study were to confirm the accuracy and reliability of the force-sensing array technology when used to measure pressure beneath the saddles of horses, and to collect some initial data from normal healthy horses with well-fitting saddles. Experiments were undertaken to establish that a linear relationship existed between the total force (weight) exerted and the pressure measured beneath the saddle, using both a wooden horse and a live horse in the standing position. Further studies were performed to demonstrate that characteristic changes of the centre of pressure occur while horses move at the walk, sitting trot, rising trot, and canter.

Animals↗
PubMed1999

Contributions of equine exercise physiology research to the success of the 1996 Equestrian Olympic Games: a review.

Following public concern about the weather conditions for the 1996 Olympic Games in Atlanta an international research programme was initiated. The primary objective of this effort was to identify strategies for ensuring welfare of horses competing in the heat. Field observations of horses during the endurance test of 3-day events in Europe, Canada, and the USA characterised the work effort of this form of competition; laboratory treadmill studies assessed limitations to performance of heat and humidity, explored the relationships of thermoregulatory demands to the phases of the competition and documented fluid and electrolyte losses. Estimates of energy expenditure and heat production during the endurance test were made. Strategies for facilitating heat dissipation were also studied in depth. Assessment of the effect of environmental conditions was based upon intensive climate monitoring using a modification of the Wet Bulb Globe Temperature index. Studies of heat acclimation provided a basis for recommendation of acclimatization times for horses before the Games. The results of all these studies guided the management of equine athletes at the 1996 Olympic Games and significantly advanced knowledge of thermoregulation in competitive horses.

Animals↗
PubMed1998

Studies on growth cartilage in the horse and their application to aetiopathogenesis of dyschondroplasia (osteochondrosis)

The importance of osteochondrosis (dyschondroplasia) to the horse industry has been well documented since it was first recorded 50 years ago. The condition is known to be multifactorial in origin, arising from focal failure of endochondral ossification at predilection sites in articular/epiphyseal growth cartilage, but specific information on its aetiopathogenesis is sparse. This paper reviews the current knowledge of growth cartilage metabolism and the process of normal endochondral ossification in the horse. It highlights the localization of various protein products of chondrocytes and the differences in the zones of articular cartilage. In the early focal lesions (referred to as dyschondroplasia) there are alterations in the chondrocytes, extracellular matrix and some of the local protein products. The most obvious feature is an alteration in matrix metabolism which may be responsible for triggering a range of other factors leading to the development of a retained core of cartilage and a primary lesion of dyschondroplasia. Based on available evidence, a preliminary hypothesis for pathogenesis is presented. This suggests that there are a number of factors capable of initiating the condition. One of these involves high circulating insulin levels from high energy feeding which may affect chondrocyte maturation leading to altered matrix metabolism and faulty mineralization resulting in the formation of cartilage cores which characterize the condition. Further research to test this hypothesis is needed before there can be a rational basis for prophylaxis.

Animals↗
PubMed1998

Immunolocalization of cathepsin B in equine dyschondroplastic articular cartilage.

A polyclonal antiserum raised in sheep against human cathepsin B was tested for specificity and cross-reactivity with the horse homologue by SDS-PAGE and Western blotting, prior to being used for immunolocalization of the enzyme in equine articular cartilage. In Western blots, the antiserum recognized the 30 kDa single chain and 25 kDa heavy chain of the mature enzyme in purified bovine cathepsin B, and corresponding bands at 32 and 27 kDa in equine chondrocyte and fibroblast lysates. This antiserum was then used to compare the expression and distribution of cathepsin B in normal and dyschondroplastic cartilage of young horses. In normal articular cartilage (n = 6 animals), significant amounts of enzyme were detected only in hypertrophic chondrocytes in the deep zone. The enzyme was intracellular, located in the lysosomal granules. No extracellular matrix staining was observed. Levels of cathepsin B were increased slightly above normal in the deep zone in age-matched dyschondroplastic cartilage (n = 5 animals). The most striking finding, however, was the abundance of the enzyme in chondrocyte clonal clusters associated with the lesions. Cathepsin B levels were low in chondrocytes isolated from normal cartilage (n = 6), but increased progressively during serial subculture, reaching a maximum at passage 5-6. In contrast, primary cultures of dyschondroplastic chondrocytes (n = 3) expressed abundant cathepsin B.

Animals↗
PubMed1997

Equine dyschondroplasia (osteochondrosis)--histological findings and type VI collagen localization.

This study describes (1) the histological appearance of dyschondroplasia, the primary lesion of osteochondrosis, in articular cartilage of the horse and (2) the localization of type VI collagen which is an important constituent of the extracellular matrix (ECM). Dyschondroplastic cartilage was identified on the basis of the presence of cartilage cores (i.e., cartilage extending into the subchondral bone) and confirmed with subsequent histological examination. Full-thickness cartilage samples from 57 horses were collected and paraffin embedded. Histological examination was used to examine the normal architecture of equine growth cartilage and to determine the presence of various pathological changes in dyschondroplastic lesions. Immunolocalization was used to identify type VI collagen in normal and dyschondroplastic lesions. The abnormalities observed in the dyschondroplastic cartilage fell into two groups. In Group A (n = 18) the lesions were associated with a disruption in the normal sequential transition of the chondrocytes through proliferation and maturation resulting in an accumulation of large numbers of small, rounded chondrocytes. A decrease in type VI collagen immunoreactivity compared with normal animals was detected except around chondrocyte clusters. Group B lesions (n = 9) were characterized by an alteration in the staining pattern of the mineralized cartilage and underlying bone. In these lesions type VI collagen immunoreactivity was increased. In both groups the presence of retained blood vessels, chondrocyte clusters, chondronecrosis and fissure formation was detected. These two histologically-distinct groups suggest that equine dyschondroplasia may be comprised of different pathological entities and that it is associated with alterations in the pattern of distribution of an ECM protein.

Animals↗
PubMed1997

Cellular heterogeneity in cathepsin D distribution in equine articular cartilage.

The distribution of cathepsin D in normal equine growth cartilage has been examined immunocytochemically using an antiserum raised against human cathepsin D. The cross-reactivity and specificity of the antiserum for equine cathepsin D was confirmed, and its lysosomal localisation was demonstrated in horse skin fibroblasts by confocal scanning microscopy. Cultured horse chondrocytes were heterogenous in their expression of cathepsin D. Heterogeneity of distribution of the enzyme was also seen in chondrocytes in cartilage from different anatomical sites. A high level of cathepsin D was observed in the deep layer of cartilage from the lateral trochlear ridge of the distal femur. Cathepsin D was absent in the hypertrophic zone of the distal radial growth plate.

Animals↗