Biomedical subjects

J R Ralphs

Publications and source records attributed to J R Ralphs.

50 records · Page 3Linked to original sources

PubMed1992

Development of functionally distinct fibrocartilages at two sites in the quadriceps tendon of the rat: the suprapatella and the attachment to the patella.

This paper describes the post-natal development of two fibrocartilages in the quadriceps tendon of the rat. The compression-resisting fibrocartilage of the suprapatella was derived from a cell population present in neonates and positioned on the deep surface of the tendon of vastus intermedius. The cells secreted a metachromatic, coarsely fibrous extracellular matrix that was rich in chondroitin sulphate but lacked keratan sulphate or type II collagen. The cells themselves accumulated large quantities of vimentin. The adult form of the suprapatella was attained 8 weeks after birth. The fibrocartilage of the attachment zone of the quadriceps tendon to the patella was formed in a different manner. In animals up to 4 weeks of age, the quadriceps tendon inserted directly into the cartilage model of the patella. When later this was resorbed, and replaced by bone, the cartilage at the attachment zone remained, along with that of the articular surface of the patella. Attachment-zone fibrocartilage was therefore rich in type II collagen, unlike that of the suprapatella. Thus two functionally different fibrocartilages have been shown to have different origins, even when separated by only a short distance within the same tendon. The compositional differences between attachment-zone and compressive region fibrocartilages are also due to their different origins.

Animals↗

PubMed1992

Development and ageing of phenotypically distinct fibrocartilages associated with the rat Achilles tendon.

We describe by routine histology and by immunohistochemistry three phenotypically and developmentally distinct fibrocartilages associated with the Achilles tendon of the rat. All the fibrocartilages develop after birth and show significant age-related changes in the composition of their extracellular matrix. Attachment-zone fibrocartilage occurs at the insertion of the tendon on the calcaneus. It derives from the cartilage rudiment of the calcaneus and from the region where the tendon merges with the perichondrium. The extracellular matrix contain type II collagen and chondroitin sulphate. Compressive tendon fibrocartilage occurs in the deep part of the tendon where it presses against the calcaneus, and is derived by metaplasia of tendon cells. The cells label strongly for the intermediate filament vimentin, and the extracellular matrix contains chondroitin and keratan sulphates, but type II collagen only in very old animals (> 2 years). Calcaneal fibrocartilage covered the posterior surface of the calcaneus where it was in contact with the Achilles tendon. It labelled intensely for type II collagen and contained chondroitin and keratan sulphates. The cells were rich in vimentin. This fibrocartilage was derived from the calcaneal perichondrium.

Achilles Tendon↗

PubMed1992

Chondrogenesis and myogenesis in micromass cultures of mesenchyme from mouse facial primordia.

The face develops from small buds of tissue positioned around the primitive mouth. The chondrogenic and myogenic cell populations contained within these facial primordia in mouse embryos have been investigated in short-term micromass culture. Chondrogenesis occurred in frontonasal mass mesenchyme from E11-E13 embryos, in maxillary mesenchyme from E12.5 embryos and was absent in mandibular mesenchyme. Myogenesis was greatest in mandibular mesenchyme, moderate in maxillary mesenchyme and low in the frontonasal mass. When compared with chick embryos the mouse facial primordia have lower chondrogenic potential, which in the case of the frontonasal mass may be related to the relative outgrowth of the primordia in the two species. Chondrogenesis in the mouse mandibular mesenchyme may be affected by the presence of a large population of odontogenic mesenchyme. The behavior of myogenic cell populations is related to the pattern of the musculature of the face, as the mandible contains the most muscle, the maxilla some, and the frontonasal mass none. However, the presence of myoblasts in early mesenchyme of all primordia may indicate that, as with chick, facial primordia are initially seeded with muscle cells and that the size of the cell population is subsequently controlled according to the development of the musculature within the primordia.

Animals↗

PubMed1992

Cartilage and related tissues in the trunk and fins of teleosts.

The structure and distribution of cartilage and related tissues in the dorsal fin, caudal fin and vertebrae of teleosts were studied in 11 species. With the exception of Zellknorpel, all the tissues previously described in teleost heads were present in the trunk and fins, although they were found in smaller quantities. The distribution of the supporting tissues indicates that they serve different functions. Hyaline cartilage was restricted to vertebral and fin bones undergoing endochondral ossification, fibro/cell-rich cartilage acted as an articular tissue, and hyaline-cell cartilage and its subtypes formed flexible and resilient supports in the caudal fin. Mucous connective tissue was packed as a space-filler around neurovascular bundles in fin rays, and chondroid bone was found beneath articular surfaces. The differences between cranial, and trunk and fin supporting tissues may reflect developmental as well as functional differences between the cranial and postcranial skeleton.

Animals↗

PubMed1992

The structure of the insertions of the tendons of biceps brachii, triceps and brachialis in elderly dissecting room cadavers.

The terminal portions of the tendon of brachialis, and the distal tendons of biceps brachii and triceps, were compared by routine histology. All tendons came from elderly dissecting room cadavers. There were pronounced quantitative differences between the 3 tendons in (1) the thickness of the attachment-zone fibrocartilage, (2) the thickness of cortical calcified tissue, and (3) the percentage of bone to marrow. There was significantly more uncalcified fibrocartilage at the attachment of biceps than at the other sites, reflecting greater range of movement of the tendon at this site. The thickness of cortical calcified tissue and the percentage of bone to marrow were significantly greater at the attachment of brachialis than either biceps or triceps. The large quantities of bone at the attachment of brachialis may be related more to the importance of the coronoid process in buttressing the elbow joint than to any special requirement for large amounts of calcified tissue at the tendon attachment. Near its attachment zone, the biceps tendon splits into superficial and deep laminae that are distinct from the macroscopic subdivision of this tendon. It is suggested that the lamination may facilitate the movements of pronation and supination. In support of this, the deep portion of the superficial lamina contained fibrocartilage where it rubbed against the attachment-zone of the deep lamina. In one body, the fibrocartilage of the biceps attachment-zone was subject to degenerative changes, including cell clumping and matrix fissuring.

Aged↗

PubMed1991

Cell and matrix biology of the suprapatella in the rat: a structural and immunocytochemical study of fibrocartilage in a tendon subject to compression.

The structure, ultrastructure, histochemistry, and immunohistochemistry of the suprapatella have been described in the rat. The suprapatella is a fibrocartilaginous sesamoid within the tendon of quadriceps femoris that articulates with the femoral condyles during flexion of the knee joint and reduces the amount of bending required at the tendon-bone junction. The cells of the suprapatella were much larger and more numerous than those in the associated tendon and were packed with vimentin-containing, intermediate filaments. The tendon cells contained far fewer filaments. The cells of both regions contained actin and tubulin. Histochemical and immunohistochemical studies showed that the suprapatellar cells were embedded in a matrix that is rich in chondroitin sulphate, but does not contain keratan or heparan sulphate. The fibrocartilage of the adjacent attachment zone of the quadriceps tendon also contained chondroitin sulphate, but in addition was rich in type II collagen. The structure of the suprapatella was similar to that of the fibrocartilaginous regions of tendons that pass around bony pulleys. However, there were differences in matrix composition that could reflect functional differences between the fibrocartilages.

Actin Cytoskeleton↗

PubMed1991

Age-related changes in tendon fibrocartilage.

Age-related changes are reported in the rat suprapatella: a fibrocartilage that resists compression of the quadriceps tendon against the femur in the flexed knee. The suprapatella was studied by histology, immunohistochemistry and electron microscopy in rats aged 11-14 weeks, and 12, 15, 18 and 24 months. Type II collagen was absent in the matrix of animals 11-14 weeks old, but appeared by 12 months; immunolabelling increased further with age. Chondroitin sulphate was present in all animals, although immunolabelling decreased with age. Keratan sulphate appeared transiently at 12 months. The structure of the suprapatellar cells also changed with age. In some respects the suprapatellar cells of aged rats are similar to those of younger animals; they contain relatively few organelles and their cytoplasm is packed with intermediate filaments which contain vimentin. However, lipid droplets and glycogen are more prominent in older animals, and the nuclei become elaborately infolded and multilobed. Type II collagen was present in rats aged 11-14 weeks in fibrocartilage of the attachment of quadriceps femoris to the patella, but with increasing age it spread proximally, further into the tendon.

Aging↗

PubMed1991

Extracellular matrix of connective tissues in the heads of teleosts.

The distribution of extracellular matrix molecules (chondroitin and keratan sulphates, type II collagen) is described in cranial connective tissues of teleosts. Hyaline cartilage was similar to that in mammals and usually contained all 3 molecules. The more cellular cartilages that are not normally present in mammals were more variable in composition. Scleral cartilage closely resembled hyaline cartilage, Zellknorpel in the gill filaments resembled it in some species but not in others, and elastic/cell-rich and hyaline-cell cartilages were unlike hyaline cartilage. These variations may be related to functional or developmental differences between the tissues. Bone and chondroid bone also varied in composition between species. Whilst both tissues contained chondroitin sulphate, bone contained type II collagen in 5 of the 12 species examined. This suggests that cartilage components are more widespread in teleost bone than has previously been shown. Type II collagen also occurred in dense connective tissues of some species. Notably, where this molecule was present in one of these tissues, it was present in all.

Animals↗

PubMed1990

Distribution of insulin-like growth factor peptides in the developing chick embryo.

Growth factors are likely to be of major significance in developmental biology. Here, the distribution of insulin-like growth factor (IGF) peptides is described during development of the chick embryo. IGF was immunolocalised using a polyclonal antibody to human IGF I detected with a modified Vectastain ABC procedure. Under the conditions used, the antibody binds strongly to IGF I and weakly to IGF II; thus the distribution of IGF peptide, rather than the individual factors, is described. Muscle, peripheral nerve and the notochord were labelled whenever present. Muscle label was associated with the myotubes and neural labelling with neurons; Schwann cells were unlabelled. IGF distribution changed during differentiation of connective tissues. Regions of mesenchyme destined to form cartilage labelled weakly or not at all, and cartilage condensations were unlabelled. In the limb, chondrocytes became labelled once cartilage rudiments had formed; however, in later development, label was absent in zones of rounded and flattened chondrocytes and appeared strongly at the onset of hypertrophy. Early osteogenic mesenchyme was also unlabelled, although later bone cells were strongly stained. In the neural tube, label was associated with differentiating neuroblasts and cell bodies and with axons, especially in the developing dorsolateral tracts. These results show a possible correlation between IGF label and cell division in early mesenchyme; cartilage condensations, which have reduced mitotic indices, do not label. In other tissues, notably muscle and nerve but also later connective tissues, label is associated with differentiating, rather than dividing, cells.

Animals↗

PubMed1989

Ultrastructural features of the osteoid of patients with fibrogenesis imperfecta ossium.

The osteoid of a patient with Fibrogenesis Imperfecta Ossium is described. Three iliac crest biopsies were taken; firstly before treatment, secondly after calcitriol therapy and finally after successful treatment with melphalan and prednisolone. In the pretreatment biopsy the osteoid was greatly enlarged, showed complete absence of the birefringence characteristic of oriented collagen fibers, and at ultrastructural level was shown to be composed of abnormal collagen fibrils. The fibrils were often curved and were extremely variable in thickness. Calcification within the osteoid took the form of calcospherites and spread of calcification from these to collagen fibrils was greatly delayed. In the second biopsy two aspects of osteoid ultrastructure were noted; some samples resembled the first biopsy, but others had a different organization. The osteoid of these samples had two regions: an inner region containing abnormal collagen fibrils and an outer region composed of moderately electron-dense amorphous material. The osteoblasts associated with this region were clearly highly biosynthetically active. The third biopsy, after treatment with Melphalan and prednisolone, showed a reversion to more normal bone ultrastructure with uniform, oriented collagen fibrils and prompt mineralization resulting in narrow osteoid seams. Remnants of the original abnormal osteoid were present in the marrow space as calcified debris. Reasons for the success of this therapeutic regime are unclear; however, some speculation is made as to the possible roles of the cytotoxic drug and the glucocorticoid in the regression of this condition.

Biopsy↗

PubMed1989

Differentiation of myogenic cells in micromass cultures of cells from chick facial primordia.

Antibodies to the myosin heavy chains of striated muscle were used to trace myogenic differentiation in the developing face and in cultures of cells from the facial primordia of chick embryos. In the intact face, myogenic cells differentiate first in the mandibular primordia and can be detected at stage 28. The early muscle blocks contain both fast and slow classes of myosin heavy chains. At stages 20 and 24, no myogenic cells are found in any of the facial primordia. However, when the cells are placed in micromass (high density) cultures, myogenic cells differentiate, revealing the presence of potentially myogenic cells in all the facial primordia. The number of myogenic cells bears no consistent relationship to the extent and pattern of chondrogenesis. Therefore the ability of the cell populations of the facial primordia to differentiate into cartilage when placed in culture is independent of the muscle cell lineage. The facial primordia represent a mixed cell population of neural crest and mesodermal cells from at least as early as stage 18.

Animals↗

PubMed1988

Separation of rabbit epiphyseal chondrocytes in various stages of differentiation.

Separation of fractions enriched in hypertrophic cells and proliferative cells has been achieved by density gradient centrifugation of cells from collagenase digests of rabbit epiphyseal cartilage. Concentrated suspensions of cells are centrifuged on a continuous Percoll density gradient. Hypertrophic cells remain in the upper part of the gradient and proliferative zone cells move to the lower regions. The resultant fractions show differences in mean cell diameter, alkaline phosphatase activity, morphology and synthetic activity in culture. Fractions rich in hypertrophic cells contain larger cells and more alkaline phosphatase activity than those enriched in proliferative cells. In culture the hypertrophic cells flatten as large irregular polygonal cells, whereas proliferative fractions form smaller spindle-shaped cells. In micromass culture hypertrophic fractions incorporate less 35S-sulphate and 14C-proline, and less tritiated thymidine than do proliferative fractions. These results suggest a general reduction in matrix and DNA synthesis with the attainment of the fully differentiated hypertrophic state, coincident with the expression of alkaline phosphatase activity and mineralisation of the cartilage matrix.

Animals↗

PubMed1988

Pattern formation in the facial primordia.

Pattern formation is the developmental process that leads to the spatial ordering of cell differentiation. We have explored the problem of pattern formation in the development of the face of chick embryos. At early stages, the developing face consists of a series of small buds of tissue, the facial primordia that encircle the primitive mouth. The concepts of positional information provide a framework for considering how the patterns of differentiated cells are generated in the face. We suggest that the cranial neural crest cells must first be informed to which facial primordium they belong and then of their position within that primordium. The cells of the early primordia appear indistinguishable. However, when the mesenchyme cells are placed in high-density culture, cartilage differentiates. The extent and pattern of cartilage differentiation is characteristic for the cell population of each facial primordium. Myogenic cells also differentiate in the cultures, but the proportion of myogenic cells is independent of the extent of chondrogenesis. Within the facial primordia, a set of epithelial-mesenchymal interactions appears to be required for outgrowth and pattern formation along the proximodistal axis of the chick beaks. In culture, face epithelium locally inhibits cartilage differentiation and suggests that another set of epithelial-mesenchymal interactions may be involved in cell patterning. The mechanisms involved in specifying the mediolateral axis of the face, for example, the midpoint of the upper beak, are not known. Vitamin A derivatives, collectively known as retinoids, affect the development of the face of chick embryos and lead to a specific facial defect. Upper beak development is inhibited but the lower beak develops normally. The response to retinoids could be related to the specification of cells to belong to the facial primordium that will form the upper beak. Alternatively, retinoids may interfere with positional cues that operate to inform cells of their position within that primordium.

Animals↗

PubMed1987

MZ15, a monoclonal antibody recognizing keratan sulphate, stains chick tendon.

Biochemical, morphometric and electron histochemical methods have failed to demonstrate the presence in tendon of keratan sulphate, a common component of connective tissue proteoglycans. Using a monoclonal antibody specific for keratan sulphate, a positive localization of this molecule was made in the gastrocnemius tendon of stage 44 chicken embryos both at the light and electron microscopical levels.

Animals↗