摘要:

AbstractIn vitro, cartilage proteoglycans (PGs) are effective inhibitors of hydroxyapatite formation and growth. Their inhibitory ability decreases with decreasing PG size and charge density. It has been suggested that the enzyme‐mediated alteration in the size and conformation of PGs in the growth plate may similarly facilitate the calcification process. In this study, a gelatin gel system was used to monitor hydroxyapatite formation and growth in the presence of proteoglycan aggregates, before and after enzyme treatment. To reproduce the physeal degradation cascade, an enzyme preparation was used that contained all of the growth plate enzymes. At a concentration of 500 μg/ml, the untreated proteoglycan aggregates reduced the amount of mineral formed by 30%. When the aggregates were treated with the heat‐inactivated enzyme, the same extent of inhibition was found. In contrast, treating the aggregates with the crude growth plate enzyme preparation removed all the inhibitory ability, such that 500 μg/ml of proteoglycan preparation yielded 10% more mineral than the controls. Treatment of the aggregates with chondroitinase ABC and trypsin, similarly removed all the inhibitory ability. These data, suggest that enzymatic degradation of proteoglycans may contribute to the regulation of growth plate calcific

ISSN:0736-0266    

DOI:10.1002/jor.1100100302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractChanges in plasminogen activator activity were studied during the sequential developmental stages of matrix‐induced cartilage, bone, and bone marrow development. The morphological transitions were correlated with biochemical parameters. Morphologic evidence of vascularization of calcified hypertrophic cartilage was accompanied by a concomitant rise in plasminogen activator activity. Thereafter, a steady decline during mineralization and deposition of new bone was observed. Maximal plasminogen activator activity occurs at approximately the same time as peak activity of alkaline and acid phosphatase. These results imply a role for plasminogen activator during angiogenesis, vascular invasion, and attendant bone differentiatio

ISSN:0736-0266    

DOI:10.1002/jor.1100100303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractWe studied the effect of prenatal alcohol exposure on growth in the proximal tibial growth plate in 0‐ and 15‐day‐old rats, using histomorphometric methods. Body weight and tibial length were reduced in all alcohol‐exposed rats. In 15‐day‐old rats, these parameters were lower than in the 15‐day‐old controls, thus showing a persistence of the effects of ethanol. The proximal tibial growth plate showed alterations, principally in 15‐day‐old rats. The most notable of these was a decrease in growth plate height produced by a significant reduction in hypertrophic zone height. Likewise, there were fewer cells in this zone in alcohol‐exposed rats than in controls. This work shows that prenatal ethanol exposure induces growth retardation which may be due to growth plate alterations that might reflect i

ISSN:0736-0266    

DOI:10.1002/jor.1100100304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn order to investigate the effects of short‐term ischemia on cortical bone microperfusion, an isolated porcine tibia diaphyseal preparation based on intact nutrient vessels was developed. Laser Doppler flowmetry (LDF) was utilized to assess continuously the cortical microcirculation and the response to short‐term ischemia. The femoral artery was isolated and clamped to develop the condition of bone ischemia. On release of the clamp, reactive hyperemia was documented in all animals. Using a roller pump connected to a segment of femoral artery, the same preparation was utilized to investigate the effect of a changing femoral artery flow on the cortical microcirculation. A positive correlation between LDF output and change in arterial inflow (r= 0.64) was defined. This model has the potential for studying the effect of ischemia on bone cell viabil

ISSN:0736-0266    

DOI:10.1002/jor.1100100305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThis in viro study investigates whether intraosseous endothelial cells can regulate long bone blood flow by secretion of vasodilator prostaglandin and EDRF (endothelium‐derived relaxing factor). Canine tibia were perfused through the nutrient artery at a constant flow rate, and the increases in perfusion pressure caused by standard doses of norepinephirine were recorded first under control conditions and then during acetylcholine infusion. Acetyl‐ choline attenuated the norepinephrine pressure responses (−62±3%). This attenuatintg effect of acetylcholine was partially abolished by inhibition of pros‐taglandin synthesis (−20±6%) and completely abolished by inhibition of EDRF synthesis (+73±43%) or combined inhibition of prostaglandin and EDRF synthesis (+134±30%). These results are statistically significant (p<0.0001) and suggest that both EDRF and vasodilator prostaglandin are synthesized by intraosseous endothelial cells, and can modify long bone vascular resistance. Thus, as in other organs, intraosseous endothelial cells may provide bone with an autoregulatory control mechanism and enable it to respond to a diverse group of vasodi

ISSN:0736-0266    

DOI:10.1002/jor.1100100306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe release rates of specific components of the proteoglycan aggregates (G1 domain, the chondroitin sulfate and keratan sulfate containing portion of the protein core, and link protein) of the articular cartilage of mature beagles were studied at early stages of canine experimental osteoarthritis (OA), generated by transection of the anterior cruciate ligament. Analysis of cartilage explants and synovial fluids indicates that at early stages of experimental OA, there is increased release of the proteoglycan aggregates of the articular cartilage. This involves a release from the tissue of the components of the proteoglycan that are specifically involved with aggregation together with the glycosaminoglycans of the proteoglycan. These components were detected at elevated levels in the media of explants of cartilage from the operated joint, and in the synovial fluids of the operated joints.

ISSN:0736-0266    

DOI:10.1002/jor.1100100307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractLongitudinal lesions in the avascular part of the dog's meniscus were repaired by implantation of a porous polyurethane. Ingrowing repair tissue was characterized by biochemical and immunological analysis. Histologically, repair tissue initially was composed of fibrous tissue containing type I collagen. After 3 months, fibrocartilaginous tissue developed inside the implants, whereas control defects only showed fibrous repair tissue. Both type I and II collagen, the major collagen types of normal meniscal fibrocartilage, could be detected in this newly formed fibrocartilage. It is concluded that fibrocartilage resembling normal meniscal tissue is formed and that longitudinal lesions can be healed after mensical repair by implantation of a porous polymer.

ISSN:0736-0266    

DOI:10.1002/jor.1100100308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractDual‐photon absorptiometry characterized bone loss in males aged5 years after injury). Significant differences (p<0.0001) in bone mass mineral between groups at the arms, pelvis, legs, distal femur, and proximal tibia were found, with no differences for the head or trunk. Post hoc analyses indicated no differences between the acutely injured at 16 months and the chronically injured. Paraplegic and quadriplegic subjects were significantly different only at the arms and trunk, but were highly similar at the pelvis and below. In the acutely injured, a slight but statistically insignificant rebound was noted above the pelvis. Regression techniques demonstrated early, rapid, linear (p<0.0001) decline of bone below the pelvis. Bone mineral loss occurs throughout the entire skeleton, except the skull. Most bone loss occurs rapidly and below the pelvis. Homeostasis is reached by 16 months at two thirds of original bone mass, near fracture threshol

ISSN:0736-0266    

DOI:10.1002/jor.1100100309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe β‐adrenergic blocking agent propranolol was shown in previous studies to increase orthotopic bone formation in rats. To understand the cellular mechanisms underlying this observation, propranolol was tested for its effects on osteoblastic cells, which posses adenylate cyclase‐coupled β‐adrenergic receptors. The ability of propranolol to modulate parathyroid hormone (PTH) and isoproterenol effects on adenylate cyclase activity and on alkaline phosphatase expression was studied in the osteoblast‐like rat osteosarcoma cell line ROS 17/2.8. At concentrations between 0.1 and 10 μM, DL‐propranolol specifically inhibited adenylate cyclase stimulation by the β‐adrenergic agonist isoproterenol, but did not alter either basal or PTH‐stimulated activity. At these concentrations, propranolol also blunted the inhibition of alkaline phosphatase activity by isoproterenol but not PTH. Propranolol alone had minimal effects on ROS alkaline phosphatase activity at low concentrations (0.1–1 μM), but became inhibitory at high concentrations (10–100 μM). Thus, the direct effects of physiologically relevant propranolol concentrations on osteoblastic cells can be attributed principally to β‐adrenergic blockade. These findings further suggest that propranolol may enhance bone formation by preserving osteoblastic activity in the face of inhibitio

ISSN:0736-0266    

DOI:10.1002/jor.1100100310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIsolated newborn rat calvarial bone cells grown in monolayer on polyurethane membranes in specially constructed culture chambers and subjected to a cyclical biaxial mechanical strain of 0.17% at a frequency of 1 Hz for 30 min demonstrated a 16% increase in DNA synthesis during the subsequent 24 h. The metabolites of the inositol phosphate pathway, shown to be an important second messenger in many cell types, were shown to be elevated using high‐performance liquid chromatography to separate and quantitate the various inositol polyphosphates. Inositol 1,4,5‐trisphosphate, inositol 1,4‐bisphosphate, and inositol 1,3,4,5‐tetrakisphosphate reached peak accumulations after 20 s of mechanical strain. Inositol 1,3,4‐trisphosphate reached a peak accumulation after 2 min, and inositol 1,2,3,4,5,6 phosphate reached a peak accumulation after 60 min of mechanical strain. Neomycin, an inhibitor of phospholipase C, a membrane‐bound enzyme that hydrolyzes phosphatidyl inositol 4,5‐bisphosphate to start the inositol phosphate cascade, completely inhibited accumulation of the above inositol phosphates during mechanical straining of the bone cells. Neomycin also completely abolished the increase in DNA synthesis that was seen after a mechanical strain of 0.17%. It is concluded from this study that the inositol phosphate pathway is activated by mechanical strain in bone cells and that this pathway is an important and primary mediator in the transduction of mechanical strain into cellular proliferation i

ISSN:0736-0266    

DOI:10.1002/jor.1100100311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY