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J Sela

Publications and source records attributed to J Sela.

At least 37 records · Page 2Linked to original sources
PubMed1992

In vivo regulation of matrix vesicle concentration and enzyme activity during primary bone formation.

In vivo regulation of matrix vesicles (MV) during primary bone formation was examined using tibial marrow ablation in rats as the experimental model. The effects of bone-bonding and nonbonding implants on the number of MV/micron 2 of matrix and the alkaline phosphatase (ALPase) and phospholipase A2 (PA2) activities of MV-enriched microsomes (MVEM) isolated from the healing bone were studied. MV concentration, ALPase, and PA2 were increased by bone-bonding implants by day 3 post-surgery; a similar effect was seen in the contralateral limb, but at a lower magnitude. Nonbonding implants had no effect at day 3 and decreased MV concentration and PA2 activity at later time points; the same behavior was observed in the contralateral limb. These results demonstrate that MVs are influenced in a differential manner by implant materials, both locally and systemically, and can be regulated during primary mineralization.

Alkaline Phosphatase↗
PubMed1992

The effect of bone injury on extracellular matrix vesicle proliferation and mineral formation.

Removal of tibial bone marrow in rats is followed by primary bone formation, resorption and marrow restitution. The first week of healing is characterized by partially calcified trabeculae. After 2 weeks, a higher degree of calcification and partial resorption are observed. The third week is characterized by massive resorption of the trabeculae, which are replaced in the fourth week by new bone marrow tissue. This model was used to study primary calcification. Transmission electron micrographs of the young bone revealed osteoblasts, matrix vesicles and calcified fronts. The different vesicular types were defined as 'empty', 'amorphous', 'crystal', and 'rupture'. The vesicles were studied on days 3, 6, 8, 12, 14, 18, 21, 23 and 28 after injury. The mean diameters of most vesicles ranged between 100.3 and 121.9 nm, and their mean distance from the calcified front was less than 976.6 nm. Vesicular density, calculated as number per 10 m2, increased on the eighth day and decreased from the fourteenth day onwards. Highest diameter values were recorded on the sixth day, and decreased onward. Vesicular distance from the calcified front decreased continuously. Distribution of vesicle number, diameter, and distance in each class showed that numbers of empty and amorphous vesicles decreased and of crystal and rupture increased throughout the experiment. Distances from the calcified front and vesicular diameters varied as follows: 'rupture', 'crystal', amorphous', and 'empty', the 'rupture' type being the closest to the front and of the largest diameter. The results confirm the hypothesis that the cell is responsible for the secretion of electron lucent vesicles that accumulate Ca and Pi to form amorphous calcium phosphate complexes that convert to hydroxyapatite. Crystal growth is followed by membrane rupture.

Animals↗
PubMed1991

Effect of glass ceramic and titanium implants on primary calcification during rat tibial bone healing.

The effect of bone bonding (KG Cera, Mina 13, and titanium) and nonbone bonding (KGy-213, M 8/1) implants on primary calcification in endosteal bone was examined by comparing changes in the morphometry of matrix vesicles to those occurring during normal bone healing following ablation of rat tibial marrow. The concentration of matrix vesicles, their diameter, and their distance from the calcification front were determined using computerized cytomorphometry at the transmission electron microscopic level. The results demonstrated that bone bonding materials supported an increase in matrix vesicle concentration when compared with control bone at 6 and 14 days postimplantation. At 14 days, there were fewer matrix vesicles in the bone adjacent to the nonbonding implants. Though matrix vesicle diameter decreased in the control bone between 6 and 14 days, it increased in all of the experimental samples. Diameters were significantly greater in the bone bonding samples at 14 days and significantly lower in the nonbonding samples at 6 days. Distance from the calcification front decreased between 6 and 14 days in all groups except in bone adjacent to the KGy-213 implants. In bone adjacent to the bone bonding implants, distance from the calcification front was comparable to or further than that of control bone; in the nonbonding samples it was closer to the calcification front. These results demonstrate that production and maturation of matrix vesicles is influenced in a differential manner by the presence of implant materials.

Animals↗
PubMed1991

The early host and material response of bone-bonding and non-bonding glass-ceramic implants as revealed by scanning electron microscopy and histochemistry.

The interface of bone-bonding and non-bonding glass-ceramics in the femur of of rats with the concomitant material and host response has been investigated by scanning electron microscopy (SEM) and histochemistry after transverse fractures in the interface level. During wound healing around these implants, four overlapping phases could be distinguished: (1) blood clot formation, (2) formation of organization tissue, (3) formation of primary bone and calcification, and (4) remodelling which lasts from months to years. This sequence of healing was disturbed around metal ions containing non-bonding implants, as shown by a longer settlement of acid phosphatase positive macrophages and a disturbed calcification at the surface of the material. Only bone-bonding implants developed considerable changes in surface morphology due to leaching and corrosion phenomena. A preferential leaching of the glass moiety, starting at the phase transition between glass and ceramic, contributes to the production of surface elevations which provide adhesion points for fibres and fibrils. Subsequent mineralization of inserting fibres contributes to a tensile strength at the interface. These findings are essential for further understanding of bone-bonding mechanisms and for further development of surface-reactive materials.

Animals↗
PubMed1990

The effect of glass-ceramic implants on matrix vesicle calcification after two weeks of rat tibial bone healing.

Type, size and distribution of extracellular matrix vesicles (MV), known mediators of primary calcification, were studied around bone-bonding and metal-oxide containing, nonbonding, glass-ceramic implants. This was performed in order to further understand the different effects of implants on bone healing. At 14 days after implantation in adult rat tibial bone the effects of different implants on MV were studied by transmission electron microscopy and computerized morphometry. A total number of 4607 MV in 245 electron micrographs were counted and grouped according to diameter, distance from the calcifying front, and classified as four types: "empty," "amorphous," "crystal," and "rupture." The sequence of types according to diameter and distance was recorded as follows around both implants tested: "rupture" MV were the closest to the front with the largest diameter, followed by "crystal," "amorphous," and "empty," MV with the largest distance from the front and the smallest diameter. Most vesicles were concentrated in a distance of less than 2.4 microns from the front and between diameters of 0.06 microns and 0.22 microns. The noncalcified extracellular matrix around bone-bonding implants contained more MV than the matrix around the nonbonding type (26.24 MV/10 microns2 and 18.76 MV/10 microns2). MV distribution according to types showed that around bonding implants there was a higher percentage of "crystal" and a lower percentage of "rupture" when compared to the nonbonding type. These results indicate that bonding implants affect osteoblastic function by increasing the vesicular number and retardation of intravesicular crystal formation. It might be suggested that bonding implants induce an increase in the process of primary calcification and a decreased rate of crystal formation resulting with the highest organization of the healing bone.

Animals↗
PubMed1990

The use of monoclonal anti-CEA antibody immunohistochemistry in detecting the origin of oral cavity metastasis.

A 75-year-old woman presented with a painless swelling in the right mandibular retromolar area and numbness of the left lower lip. Radiographic examination of the mandible demonstrated an osteolytic lesion of the ascending ramus. Biopsy revealed adenocarcinoma of obscure origin. Staining of the specimen with a monoclonal antibody specific to colon carcinoma revealed its origin. On subsequent examinations, a primary tumor in the rectosigmoid region with extensive lung, liver and skeletal metastases were diagnosed. This unusual case of colonorectal carcinoma, presenting as a metastatic lesion of the mandible, was readily diagnosed by a novel immunohistochemical technique that utilizes highly specific monoclonal antibodies.

Adenocarcinoma↗
PubMed1990

Correlations between uptake of technetium, calcium, phosphate, and mineralization in rat tibial bone repair.

Technetium-99m-(99mTc) phosphates are extensively used for detection of bone formation and resorption. The present is a study of 99mTc incorporation during bone remodeling. Uptake of 99mTc-labeled phosphate was studied in an animal model of primary osteogenesis following tibial marrow injury and incorporation was correlated to that of calcium-47 (47Ca), phosphorus-32 (32P), and with matrix vesicle calcification. Isotope uptake on Day 6 in the whole bone was increased compared to controls. On this day, an increase in vesicular diameter and distance from the calcified front was previously observed. Technetium-99m-labeled phosphates were detected only in the organic phase. Phosphorus-32 and 47Ca were detected in both organic and inorganic phases. It is suggested that 99mTc serves as a specific marker to the anabolic phase of remodeling. Increased incorporation of 99mTc during bone healing indicates enhanced organic matrix formation and not calcification.

Animals↗
PubMed1989

Effect of glass-ceramic implants on primary calcification in rat tibial bone after injury.

Using histomorphometry and transmission electron microscopy the distribution of extracellular matrix vesicles around bone-bonding and non-bonding glass-ceramic implants in tibial bone healing was studied. Grouping of vesicles was performed according to type, diameter and distance to the calcified front. Most vesicles were 0.06-0.22 microns in diameter in both implants tested. The mean vesicular distance of matrix vesicles to the calcified front was statistically significantly lower in non-bonding material compared with KG Cera. The sequence of vesicle arrangement according to diameter was: 'empty', 'amorphous', 'crystal', 'rupture'. Empty vesicles were the smallest and rupture vesicles the largest. Distances of vesicles to the calcified front showed the same sequence of arrangement, while the rupture type was located nearest to the front. The findings support the widely acknowledged hypothesis on the role of matrix vesicles in mineralization. It was shown that mineralizing tissue around bone-bonding glass-ceramics contains more matrix vesicles, which are distributed further from the front with a lower degree of calcification. The parameters studied could serve as standard criteria for the evaluation of implant materials.

Animals↗
PubMed1989

Changes in extracellular matrix vesicles during healing of rat tibial bone: a morphometric and biochemical study.

Primary mineral formation in woven bone has been associated with the production of extracellular matrix vesicles. Previous studies have demonstrated an increase in phospholipid: Ca:Pi complexes (CPLX) immediately prior to hydroxyapatite formation. Since matrix vesicles are enriched in phosphatidylserine and PS is the major phospholipid in CPLX, the present study examined whether the morphologic appearance of matrix vesicles and initial formation of crystals within them could be correlated to changes in their phospholipid composition and metabolism. Ablation of the tibial marrow in rats was used as the model since this procedure induces endosteal repair with primary mineralization. The morphologic appearance of the matrix vesicles was assessed by morphometric analysis at the electron microscopic level. Matrix vesicles were divided into 4 categories: empty, amorphic, crystal, and rupture. There was time dependent decrease in the number of empty and amorphic matrix vesicles which correlated with an increase in crystal and rupture type. Distance from the calcification front decreased as more rupture-type vesicles were noted. In a parallel set of experiments, matrix vesicle-enriched membranes (MVEM) were isolated from homogenates of endosteal tissue removed from the treated tibia as well as from the contralateral control. There was an increase at 6 days in MVEM alkaline phosphatase and phospholipase A2 specific activities in both limbs, the magnitude of response being significantly greater in the treated legs. The phospholipid composition of the MVEM changed with time. SPH was highest at day 3, PS was detectable only in day 6 and 14 samples, and PC exhibited a time dependent decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1989

Response of the dental pulp to capping with a composite resin-bonded ceramic and dental adhesive in rat molars.

An inflammatory response occurs in the pulp tissue following the application of dental materials due to their chemical properties and/or a secondary bacterial irritation. Recently, a new line of composite resin products with reported improved esthetic qualities was designed to allow an intimate adherence with the dentin. This intense bonding could prevent bacterial penetration and marginal discoloration of these restorations. In addition, this method allows prevention of excessive removal of hard tissue. The present study examines pulpal reaction to capping with P-10 composite resin (Dental Products, USA) in rats. Histological examination did not reveal any inflammatory reaction in the nonexposed pulps. Direct pulp capping with P-10 induced formation of reparative dentin bridges.

Animals↗
PubMed1989

Pulp capping with hydroxyapatite ceramic in rat molars.

Direct pulp capping with a hydroxyapatite ceramic in rat molars induced the formation of reparative dentin in the exposure sites after 2 weeks. In addition, foci of acute and chronic pulpitis were detected. After 6-8 weeks of application of the material partial or total necrosis occurred. The use of hydroxyapatite as a possible pulp capping material is discussed.

Animals↗
PubMed1989

Effect of verapamil on bone resorption and formation in uremic rats.

It has been shown in vitro that verapamil inhibits parathyroid hormone-induced bone resorption. To determine the effect of verapamil administration on bone histology in rats with chronic renal failure, male Wistar rats were divided into three groups: subtotally nephrectomized (SNX), SNX treated with verapamil, 8 mg/kg/day p.o. (SNX-V) and control (C). Thirteen weeks later, the mandibular condyle bone was studied by histomorphometry. When compared to C rats, SNX rats had active bone disease, with increased resorption parameters (resorption surface, active resorption surface, osteoclast number) and accelerated mineral appositional rate. These parameters improved with verapamil administration. When compared to C rats, SNX-V rats had decreased osteoid seam width and mineral appositional rate. Serum parathyroid hormone was similarly elevated in both uremic groups. These data suggest that verapamil administration improves active bone disease in rats with chronic renal failure and decreases bone formation.

Animals↗
PubMed1988

The distribution of extracellular matrix vesicles in healing of rat tibial bone three days after intramedullary injury.

The distribution of extracellular matrix vesicles on the third day of bone healing was studied by morphometric analysis of transmission electron micrographs. Detection and grouping of the vesicles was performed according to type, diameter, and distance from the calcified front. The different types were selected as follows: vesicles with electron-lucent contents ("empty"), vesicles with amorphous electron-opaque contents ("amorphic"), vesicles containing crystalline depositions ("crystal"), and vesicles containing crystalline structures with ruptured membranes ("rupture"). The majority of vesicles were between 0.07 micron and 0.12 micron in diameter and were located at less than 3 micron from the calcified front. The distribution of the "empty", "amorphic", "crystal", and "rupture" vesicles was 23.2%, 74%, 2.5%, and 0.3% respectively. Their sequence of arrangement according to diameter was as follows: "empty", "amorphic", "crystal", and "rupture", the empty vesicles constituting the smallest and the "rupture" the largest type. Distances from the calcified front were similar for the "empty", "amorphic", and "crystal" vesicles, while the "rupture" type was located nearest to the front. The present observations support the widely acknowledged hypothesis on the role of extracellular matrix vesicles in mineralization. It is thought that the secretion of "empty" vesicles from the cell is followed by intravascular accumulation of amorphous Ca and Pi to form a hydroxyapatite crystal that, in turn, ruptures the vesicle's membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Inhibition of the inductive activity of demineralized bone matrix by different percutaneous implants.

Teflon tubes with either Gore-Tex (PTFE) or Dacron felt sleeves were implanted percutaneously in rats, in conjunction with demineralized bone matrix. This resulted in different inflammatory reactions, as well as in chondrogenesis and osteogenesis in the subcutaneous tissues. Although induction of osteogenesis by the demineralized bone matrix in the vicinity of the foreign material was inhibited, circumferential bone formation was highly reproducible. The prospect of utilizing demineralized bone matrix in order to enhance acceptance of percutaneous tubes is discussed.

Animals↗
PubMed1988

99mTc-MDP uptake and histological changes during rat bone marrow regeneration.

An established experimental model of tibial bone regeneration in rats was used in order to try to provide further information on the binding site of 99mTc-MDP, which is still not clearly defined. Four groups of rats on which surgical tibial bone marrow evacuation was performed and two control groups (nonoperated animals and sham-operated animals) underwent bone scan during the different stages of marrow regeneration; they were killed immediately after, and histological examination carried out. The correlation between the scintigraphic and the histological findings suggests that 99mTc-MDP binds primarily to calcification sites in young bone trabecules.

Animals↗
PubMed1988

The relationship between extracellular matrix vesicles and the calcifying front on the 21st day after injury to rat tibial bone.

The relationship between extracellular matrix vesicles and the calcifying fronts was examined by studying vesicular diameters and types. Transmission electron microscopy combined with computerized morphometry three weeks after injury to the tibial bone in rats was used. The different vesicle types were defined as: (1) vesicles with electron lucent contents referred to as empty; (2) vesicles with amorphous electron opaque contents, called amorphic; (3) vesicles containing crystalline depositions, called crystalline; and (4) vesicles containing crystalline structures with ruptured membranes, referred to as ruptured. The diameters of most vesicles ranged between 0.07 and 0.17 micron. More than 95% of the vesicles were located less than 2 micron from the calcified front. The vesicles were distributed among the categories as follows: empty, 9.6%; amorphic, 19.3%; crystal, 39.2%; and ruptured, 31.9%, respectively. The diameters of the crystalline and ruptured vesicles were significantly larger than those of the empty and amorphic types. The ruptured type had the largest diameters. The sequence of distances from the calcified front was recorded as follows: ruptured, crystalline, amorphic, and empty, with the ruptured and crystalline types being the closest to the front. This study supports the accepted theory on matrix vesicle mineralization. The cell is responsible for secretion of empty vesicles that accumulate amorphous Ca and Pi to form a hydroxyapatite crystal. This is followed by rupture of the vesicular membrane. The propagation of the process is accompanied by an increase in the vesicular diameter and its approximation to the calcifying front.

Animals↗
PubMed1987

Changes in the distribution of extracellular matrix vesicles during healing of rat tibial bone (computerized morphometry and electron microscopy).

A study of the distribution of extracellular matrix vesicles during the first 3 weeks of healing of adult rat tibial bone was performed by transmission electron microscopy in combination with computerized morphometry. Bone injury comprised removal of the marrow followed by regeneration of the tissue via a phase of primary mineralization. A total number of 39,498 vesicles were traced on electron micrographs and sorted according to their diameters, distance from the calcified front and types. The different vesicular types were defined as follows: (a) vesicles with electron lucent contents, i.e. "empty", (b) vesicles with amorphous electron opaque contents, i.e. "amorphic", (c) vesicles containing crystalline depositions, i.e. "crystal", and (d) vesicles containing crystalline structures with ruptured membranes i.e. "rupture". The vesicles were studied on the days 3, 6, 14 and 21 after bone injury. Most of the vesicles were concentrated between diameters of 0.07 and 0.17 micron. Most of the vesicles were found in a distance less than 3 microns from the calcified front. The sequence of changes of distances from the calcified front and of the vesicular diameters were recorded as follows: "rupture", "crystal", "amorphic" and "empty", the "rupture" type being the closet to the front and of the largest diameter in each day. The results of the present study confirm the accepted hypothesis on calcification via extracellular matrix vesicles. It is thought that the cell secretes "empty" vesicles that accumulate Ca and Pi forming amorphous calcium phosphate that is then converted to hydroxyapatite. This is followed by rupture of the vesicular membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗