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At least 811 records · Page 45Linked to original sources
PubMed1993

Molybdenum-induced changes in the epiphyseal growth plate.

Molybdenum (Mo), at high concentrations, induces changes in the epiphyseal growth plate through its effects on copper (Cu) metabolism but it is unclear whether or not Mo can induce changes independent of its effects on copper status. To this end, the effect of Mo on longitudinal bone growth was examined in rats. Dietary Mo was given either as ammonium heptamolybdate or as ammonium tetrathiomolybdate, the latter producing a marked Cu deficiency. There was a significant reduction in longitudinal bone growth in both groups; however, growth plate width was increased only in the Cu-deficient animals due to an increase in the width of the zone of transitional/hypertrophic chondrocytes. Both glucose 6-phosphate dehydrogenase activity and cell proliferation (assessed by bromodeoxyuridine incorporation) were markedly decreased in the proliferating zone of the growth plate in both Mo-treated groups. These changes were not apparently related to changes in circulating vitamin D metabolites or insulin-like growth factor-1. The results indicate that excess Mo impairs cell proliferation within the growth plate, whereas the effects of copper deficiency are more related to chondrocyte differentiation. Thus, Mo can induce changes in longitudinal bone growth which are distinct from those resulting from Cu deficiency.

Alkaline Phosphatase↗
PubMed1987

Light and electron microscopical localization of concanavalin A lectin binding sites in rat epiphyseal chondrocytes.

Concanavalin A lectin binding sites have been detected within the cytoplasm of epiphyseal chondrocytes. Correlative light and electron microscopic results were obtained, indicating the presence of alpha-D-mannose and/or alpha-D-glucose residues detected by the lectin in the rough endoplasmic reticulum region. Quantitation of the electron microscopic cytochemical reaction also showed that the specific labelling was almost exclusively localized in the lumen of endoplasmic reticulum cisternae. No significant staining was found in other membrane compartments or extracellular matrix. This labelling pattern could be considered as the cytochemical evidence of N-glycosylation processes occurring during the biosynthesis of cartilage extracellular matrix components by chondrocytes.

Animals↗
PubMed1992

An autosomal recessive variant of spondylo-epiphyseal dysplasia in three sibs.

A report of one male and two female sibs with an unusual form of spondylo-epiphyseal dysplasia (SED) manifesting in late childhood. The anomalies are pronounced at the femoral head. There is platyspondyly with biconcave deformation and irregular vertebral end-plates. As the parents are healthy autosomal recessive inheritance is likely.

Adolescent↗
PubMed1978

Correlation of freeze-fracture and scanning electron microscopy of epiphyseal chondrocytes.

Chondrocytes in epiphyseal cartilage were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using freeze-fracture techniques. Freeze-fracture replicas showed large numbers of fingerlike, 0.11-0.15 micrometer diameter, projections from the chondrocyte surface, with numerous 95-180 A diameter intramembranous particles associated with both the cell membrane surface and these projections. With SEM, these cytoplasmic projections were also obvious, but appeared collapsed into clusters of globular-shaped projections on the surface of the chondrocytes. With freeze-fracture techniques, in which shrinkage artifacts were essentially eliminated, the cytoplasmic projections were often seen in intimate contact with the extracapsular matrix. However, with chondrocytes prepared by both SEM and conventional TEM, there was evidence of shrinkage, the cytoplasmic projections having little contact with the extracapsular matrix. These findings show that the cytoplasmic processes are not artifacts of tissue processing and provide morphological evidence in support of the hypothesis that matrix vesicles are of cellular origin.

Animals↗
PubMed1984

Stereological studies on the epiphyseal growth plate in low phosphate, vitamin D-deficiency rickets with special reference to the distribution of matrix vesicles.

In low phosphate, vitamin D-deficiency rickets normal mineralization is reversibly arrested, and rickets is thus a suitable model for studying factors influencing the mineralization process. Partly on the basis of their distribution within the growth cartilage, the so-called matrix vesicles are considered to play an important role in the process of mineralization and it has been claimed that the distribution pattern is the same in rickets as in normal animals. With the use of modern stereological techniques, our group recently demonstrated a matrix vesicle distribution between the zones of the epiphyseal growth plate in normal rats different from that described earlier. The same bimodal distribution pattern was observed in rachitic rats in the present study, the highest volume density being found in the resting and upper hypertrophic zones and the lowest in the proliferative zone. The volume density differences are explained by differences in the number of vesicles between zones, the variation in mean caliper diameter being small. Our findings are discussed in relation to the proposed theories on matrix vesicle origin. The results seem to support the dynamic cell debris theory for matrix vesicle origin presented earlier, but the existence of subpopulations of matrix vesicles with a specialized function and origin cannot be ruled out.

Animals↗
PubMed1996

Matrix vesicles and focal proteoglycan aggregates are the nucleation sites revealed by the lanthanum incubation method: a correlated study on the hypertrophic zone of the rat epiphyseal cartilage.

Correlated studies were performed with light and electron microscopy, and backscattered electron image in conjunction with X-ray microanalysis, of lanthanum-incubated epiphyseal cartilage of the young rat. The hall-mark of this procedure is the appearance of LaP electron-dense deposits (not present in control sections) in precise sites of the hypertrophic zone. The ultrastructural study revealed a dual nature of these sites: "dense matrix vesicles" and "focal filament aggregates". The dense matrix vesicles are a specific type of matrix vesicle with the intrinsic capacity of precipitating LaP mineral, as soon as they originate from the hypertrophic chondrocytes. Furthermore, the matrix vesicles were found to be heterogeneous because lanthanum-devoid, "light matrix vesicles" were also present. The focal filament aggregates, which were not recognized in unstained sections and in controls, are apparently focal concentrations of proteoglycans with high lanthanum binding capacity, although the presence in them of other components (e.g., type X collagen, C-propeptide of type II collagen) cannot be excluded. The were in close connection with the light matrix vesicles in the upper hypertrophic zone, and were loaded with a variable quantity of LaP irregular electron-dense deposits in the lower hypertrophic zone. These irregular deposits are similar to, but distinct from, calcification nodules. The lanthanum incubation method indirectly detects the matrix Ca-binding components (which bind La ions), and the calcification initiation sites (which precipitate a LaP-mineral phase). A sequence is proposed of successive steps of LaP nucleation within the focal filament aggregates, which possibly mimics calcium phosphate deposition. Such a sequence seems to require the participation not only of dense matrix vesicles, but also of the filamentous components of the focal aggregates, possibly together with the activity of alkaline phosphatase.

Animals↗
PubMed1988

Electron microscopic analysis of mineral deposits in the calcifying epiphyseal growth plate.

Early mineral deposits within calcifying rat epiphyseal growth plates were studied by bright field and selected-area dark field electron microscopy, and X-ray microanalysis. These mineral deposits were prepared in situ by high-pressure freezing, freeze substitution, and low-temperature embedding, and were examined in unstained, stained, and ethyleneglycol tetraacetic acid (EGTA)-treated stained thin sections. On unstained sections mineral rods occur within an amorphous density of calcium and phosphorus (CaP). X-ray microanalysis of stained sections reveals that the location of electron-dense deposits does not always correspond to that of the CaP mineral deposits identified in electron microscopic images. Such an analysis showed a depletion of both Ca and P in stained sections at sites corresponding to high levels of these elements in unstained sections. Staining thus demineralizes early deposition sites of CaP; at the same time lead (Pb) and uranium (U) bind to the organic components of the extracellular matrix formerly associated with Ca and P. This substitution phenomenon alters the overall fine structure of mineral sites by depleting the amorphous density of Ca and P, and by creating isolated rodlike structures that have formerly been interpreted as representing hydroxyapatite (HAP) crystals. Selected-area dark field imaging shows nascent sites of HAP crystals to be associated with the limiting membrane of matrix vesicles, but such crystals were undetectable at these sites with conventional bright field images. Dark field imaging also showed that the typical 30-80 nm crystal rods found in calcified cartilage consist of aggregates of HAP crystals.

Animals↗
PubMed1993

[Behavior of artificially-induced epiphyseal groove defects in rabbits. Part 2. Transplantation of autologous and homologous groove cartilage].

In this experimental study in rabbits we evaluated histologically the effect of reproducible drill holes through the distal femoral growth plate. We could demonstrate epi-metaphyseal bone-bridging as uniform reaction of the physeal cartilage in response to this traumatisation. The defects have been filled with autologous or homologous epiphyseal cartilage from distal ulnar growth plate. Autologous transplants fulfilled the demand avoiding partial bony closure of the growth plate. Homologous growth cartilage used for filling the defects underwent resorption and could not prevent the development of a bony bridge and growth disturbances.

Animals↗
PubMed1993

[Internal callus distraction in epiphyseal groove defect--a physiologic means of spontaneous correction. Results of a comparative histomorphologic study in a small and large animal experiment].

For this experimental study we removed with a trephine in small (rabbit) and larger (pigs) animals cylinders of 2 mm respectively 8 mm diameter from the central growth plate area of proximal tibia. The direction of burring is in the axial line of the femur proximo-distally; the insertion point of the trephine is chosen on the cheek of the medial femoral condyle. As common reaction to that kind of trauma the defects in growth plates of rabbits become filled with a bone bridge that joins the epiphyseal core to the metaphyseal trabeculae, leading to gross growth disturbances. In pigs a similar solid bridging as first reaction develops, interrupted later by a zone of longitudinal collagen fibre bundles within a non-mineralized matrix. The distending pressure of surrounding intact growth cartilage continuously brakes fracture callus formation and its calcification. Such so-called internal callus distraction leads to unaltered longitudinal bone growth.

Animals↗
PubMed1982

The adverse effects of HEPES, TES, and BES zwitterion buffers on the ultrastructure of cultured chick embryo epiphyseal chondrocytes.

Chick embryo epiphyseal chondrocytes cultured in media containing HEPES, TES, and BES zwitterion buffers, used in combination or independently, consistently developed cytoplasmic vacuoles. This cytoplasmic vacuolation was resolved when the zwitterion buffered media was replaced by media containing bicarbonate:CO2 enriched air buffer. Vacuoles were infrequent or absent in cultures grown in bicarbonate:CO2 enriched air. Chondrocytes with an established extracellular matrix showed less vacuolation than fibroblastlike and polygonal shaped cells that lacked such a matrix. The granular endoplasmic reticulum and Golgi dictyosomes of zwitterion buffered chondrocytes were distended and contained a flocculent amorphous material. Cytoplasmic vacuoles (0.5 to 3.0 micron diam) formed by the fusion and intracellular accumulation of Golgi vesicles and vacuoles also contained a flocculent material enhanced by ruthenium red. Membrane bound extracellular vacuoles containing ruthenium red stained proteoglycan aggregates were common in the extracellular matrix of zwitterion buffered cultures but were generally absent from bicarbonate treated cultures. Electron dense calcium deposits seemed much larger and more numerous in the presence of zwitterion buffers. It is suggested that HEPES, TES, and BES buffers, used alone or in combination, may adversely affect cell membrane systems, and thus the transport or secretory mechanisms operative in cultured chondrocytes, or both, resulting in vacuole formation and the intracellular accumulation of synthesized export material. Although the mechanism by which HEPES, TES, and BES induce these changes remains unclear, the use of zwitterion buffers in biological preparations should be treated with caution.

Alkanesulfonates↗
PubMed1984

Morphological studies of the epiphyseal growth zone in the brachymorphic (bm/bm) mouse.

Light microscopy, including immunohistochemical techniques, and electron microscopy were performed on epiphyseal growth cartilage from brachymorphic (bm/bm) mice and age-matched phenotypically normal siblings aged 5, 16 and 25 days. In the bm/bm mice light microscopy showed a disturbed columnar arrangement and numerous chondrocytes with pronounced regressive changes. The normal development of proliferative cells into hypertrophic cells was halted and thus only a rather small and ill-defined hypertrophic zone was seen. The calcifying zone was irregular and the normal lacunae were replaced by a densely staining matrix. Using immunofluorescence techniques, the presence of considerable amounts of both type II and type V collagen was demonstrated in the bm/bm mice, while the cartilage from controls contained only type II. Ultrastructurally the lacunar matrix contained bundles of fine fibrils without the typical collagen periodicity which might indicate synthesis of a defective procollagen. Our observations together with the previously demonstrated deficiency of 3'-phosphoadenosine 5'-phosphosulphate, illustrate the complexity of the growth cartilage disturbance in the bm/bm mouse. Most of our findings are at variance with those described in the literature and possible pathogenetic mechanisms for the observed alterations in the growth cartilage are discussed.

Animals↗
PubMed1984

Stereological analysis of the epiphyseal growth cartilage in the brachymorphic (bm/bm) mouse, with special reference to the distribution of matrix vesicles.

The brachymorphic (bm/bm) mutation in the mouse leads to disproportional dwarfism due to a disturbance of endochondral bone formation. The morphological characteristics of bm/bm epiphyseal growth cartilage are signs of cellular degeneration and disintegration and alteration of the composition of the extracellular matrix, with an abnormal mineralization pattern. The present stereological study of the bm/bm growth plate revealed a clearly altered distribution of matrix vesicles as compared with the controls. It was also demonstrated that the bm/bm matrix vesicles have an abnormal size distribution, with an increased mean caliper diameter. The biological significance of these findings is discussed in relation to the different hypotheses on the origin of matrix vesicles and their possible role in the mineralization process. The results support the opinion that extracellular matrix vesicles, at least partly, constitute cellular debris.

Animals↗
PubMed1999

Animal model of experimentally induced ectopic enchondral ossification in nude mice with xenograft of porcine epiphyseal cartilage.

In a specific animal model the induction of heterologous enchondral ossification was examined in long term follow-up. Physiologically normal and devitalized frozen porcine epiphyseal cartilage as a control group were transplanted as s.c. xenograft into athymic nude mice (nu/nu). 15 weeks after transplantation the porcine growth plate cartilage showed the development of viable cartilage tissue in the recipients, further differentiating to juvenile long bone with epiphysis, diaphysis and growth plate. Porcine growth plate cartilage increased s.c. in the recipient nude mice, showing enchondral ossification without any physiological load, and finally an unexpected development towards complete juvenile long bone.

Animals↗
PubMed2003

Medial meniscus interposition in proximal tibial epiphyseal fracture: a case report and review of the literature.

Proximal tibial fractures are rare in children, and most are treated conservatively. We report a case of a minimally displaced proximal tibial epiphyseal injury (Salter-Harris type III) in an 11-year-old child. We initially thought to treat this fracture conservatively, but the presence of massive haemarthrosis and considerable pain made us choose arthroscopy under general anaesthetic. During examination under anesthesia no instability could be detected, but the knee was locked in 5 degrees of flexion. On screening the fracture was not reducible anatomically. At arthroscopy the medial meniscus was not visualised as it was displaced into the fracture site. A small medial arthrotomy showed the meniscus trapped in the fracture site without any avulsion in the anterior or posterior horns. The fracture easily reduced once the meniscus was levered out. The importance of this injury is the fact that it could have been easily missed and would have led to serious functional deficit of the knee joint. We present radiographs and intra-operative pictures of this interesting injury.

Arthroscopy↗
PubMed2006

Evaluation of activity of epiphyseal plates in growing males and females.

To investigate the age-related activity of the epiphyseal plates, a retrospective study of (99m)Tc-methylene diphosphonate bone scans was undertaken. The study comprised 81 males and 46 females aged 2 weeks to 24 years. The total percentage (%) whole-body (ratio of total physis activity to whole-body activity) and the regional % whole-body (ratio of physis activity of one region to whole-body activity) were derived. The ratio of physis activity of one region to the total physis activity was defined as % physis. Before age 12, total physis activity was found to contribute about 10% to whole-body activity. All total and regional % whole-body activities followed sigmoid curves with age. The differences of the parameters (transition centers and widths) suggested that there might be a later and longer period for the disappearance of physis activity in males than in females. For all the regions, % physis changed little with age until after puberty. At age <1, the proportion of bone activity in the body was about 30-35% for skull, 20-25% for lower limbs, and 5-15% for the rest of the regions. The maximal changes during growth occurred in the skull and the lower limbs. The age-related changes of physis activity during growth reflect a combination of the potential of bone to grow and the processes of bone growth and bone turnover. Bone scintigraphy is useful in understanding the changes of physis activity during growth.

Adolescent↗
PubMed2000

Growth parameters in the epiphyseal cartilage of brachymorphic (bm/bm) mice.

We studied kinetics in the epiphyseal cartilage of the brachymorphic (bm/bm) mouse, combining morphometry and labeling with halogenated nucleotides. The defective synthesis of the sulfate donor PAPS in these homozygous mutants is evident in tissues with a large production of glycosaminoglycans; these compounds become undersulfated. Compared with their heterozygous siblings, the longitudinal growth of the mutant mice was reduced by two-thirds. This was mainly associated with (1) reduced height of the proliferating zone, (2) a substantial number of G0 cells in this zone, and (3) reduced hypertrophy which, in turn, may be related to premature mineralization and prevention of normal expansion of cells. No significant effects on cell-cycle parameters were detected, such as S-phase time or cell-cycle time, and the rate at which each cell increased the matrix volume seemed normal. An effect on matrix mineralization may be related to known changes in the structure of matrix PGs, whereas the effect on proliferation may be related to other factors. Candidates for such other effects of undersulfation are the cell surface PGs, which are important for binding of growth factors.

Animals↗
PubMed2004

MED, COMP, multilayered and NEIN: an overview of multiple epiphyseal dysplasia.

This overview covers the group of disorders that presents radiographically as multiple epiphyseal dysplasia (MED). The disorders include "classic MED" (Ribbing and Fairbank types): MED that is caused by mutations in the cartilage oligomeric matrix protein (COMP), type IX collagen, and matrilin 3 genes (MATN3); and MED with multilayered patella, brachydactyly, and clubbed feet resultant from mutations in gene defect diastrophic dysplasia (DTDST). The recently identified gene/molecular abnormalities in these disorders have made more exact identification possible in many cases, although clinical testing is not always available. However, there are specific radiographic findings that allow the accurate diagnosis to be made, thus potentially guiding which molecular defect(s) should be investigated. The modes of inheritance of these distinct MED conditions are not identical. When a specific diagnosis is made, proper genetic counseling as well as prognostication, management issues and complications can be delineated to the patient and family. This review will include the mechanics of diagnostic and molecular triage for these disorders.

Cartilage Oligomeric Matrix Protein↗