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Biomedical subjects

J Sela

Publications and source records attributed to J Sela.

At least 73 records · Page 4Linked to original sources
PubMed1982

Transplantation of free perichondrial grafts into rabbit articular cartilage is associated with matrix vesicle calcification.

Autogenous perichondrial grafts from rabbit ear were transplanted into articular cartilage defects in the knee joint. Electron micrographs performed after 2 months revealed calcifications associated with cartilaginous-forming cells and extracellular matrix vesicles. Many of these vesicles contained apatite crystals, particularly in areas adjacent to the calcifying fronts. In these areas the vesicular membrane was occasionally ruptured by the crystals. Many crystals in the calcifying front proper were organized alongside collagen fibers. Examination of sham-operated and normal controls revealed the occurrence of non-calcifying matrix vesicles. The results of the present and previous studies suggest that matrix vesicles occur in normal articular cartilage in a latent form, their calcification being associated with changes of the metabolic state of the tissue.

Animals↗
PubMed1981

Extracellular matrix vessels in human osteogenic neoplasms: an ultrastructural and enzymatic study.

The results of a study of the ultrastructural and enzymatic features of extracellular matrix vesicles in human osteogenic neoplasms are reported. Specimens from three osteosarcomas, a chondrosarcoma, and an osteoblastoma were processed for electron microscopic study and for preparation of vesicular, membrane, and cellular fractions. Electron micrographs of each lesion showed primary mineralization comprised of matrix vesicles and calcifying nodules. There was a distinct pattern of distribution of enzymatic activity among fractions from the osteosarcomas; namely that the highest values for specific activity of alkaline and pyrosphosphatases and adenosine triphosphases (ATPases) in the vesicle fractions and lowest in the cell fractions. This pattern was not consistent in fractions from the other neoplasms. The aforementioned enzymes are considered essential for the onset of mineralization. The data presented establish the role of matrix vesicles in neoplastic calcification and suggest the need for further studies into the diagnostic value of the vesicles.

Acid Phosphatase↗
PubMed1981

The ultrastructure of the interface between a glass ceramic and bone.

The interface of alkali-poor glass ceramic implanted in femora of male Sprague-Dawley rats shows soft tissue, chondroid, osteoid, and bone in connection with the implant. The ultrastructure of the interface with soft tissue mainly exhibits a corrosion process, during which the dissolution of the crystalline phase of the glass ceramic precedes the dissolution of the glassy phase. Macrophages are involved in this process phagocytosing debris of the glassy phase and removing as well as dissolving the remainders of the glass ceramic. Under circumstances not yet fully understood, the corrosion stops, and ground substance like material is deposited, which can be, at least partially, mineralized. After the disappearance of macrophages, chondroblasts, and/or osteoblasts lay down collagen fibrils and ground substance in which matrix vesicles are discernible, representing initial foci of mineralization. Areas with bone connection display collagen fibers and deposits of apatite crystals in close relationship to the bulk glass ceramic as well as small particles mainly derived from the glassy phase of the implant, providing the micromorphological substrate for the shearing and tensile strength of the interface between glass ceramic and bone.

Animals↗
PubMed1981

The occurrence of hydroxyapatite crystals in extracellular matrix vesicles after surgical manipulation of the rabbit knee joint.

Free autologous grafts of synovial tissue were transplanted into experimental defects produced in the articular cartilage of rabbit knee joints. The grafted tissue underwent transformation into fibrocartilage. Extracellular matrix vesicles associated with calcified areas were present at the grafted sites. Hydroxyapatite crystals were found within these vesicles and in their vicinity. No calcification occurred in articular cartilage from sham operated joints in which defects were produced but no grafts made and in normal controls. These tissues showed abundant matrix vesicles devoid of crystalline mineral. A careful study of normal synovial tissue did not reveal matrix vesicles and calcifications. The present observations suggest that matrix vesicles in normal articular cartilage exist in a latent form. Vesicle mineralization following surgical manipulations of the joint is probably a manifestation of the metabolic stage of the tissue.

Animals↗
PubMed1981

Primary mineralization and extracellular matrix vesicles in rat bone after administration of glass-ceramic implants.

Glass-ceramic implants were administered into cavities prepared in rat femoral shaft. Electron microscope examination revealed formation of collagenous rich matrix in the implant-bone interface. Features typical to primary mineralization as well as bone and implant resorption were present in the interface. Primary mineralization was characterized by the occurrence of active forming cells, extracellular matrix vesicles and calcifying calcospheritic structures. Intensive primary mineralization in association with the implants indicates that glass-ceramic may be stimulative to ossification, allowing favorable tissue-implant relationship.

Animals↗
PubMed1981

The occurrence of extracellular matrix vesicles in pulmonary alveolar microlithiasis.

Mineralization in pulmonary alveolar microlithiasis was studied by transmission electron microscopy. The disease is characterized by psammoma like calcifications composed of hydroxyapatite crystals. The calcifications were surrounded by typical forming cells and matrix composed of collagen fibers arranged in a longitudinal pattern. Abundant calcifying extracellular matrix vesicles were found between the cells and the calcified fronts. The type of calcification found in the present lesion is similar to ectopic primary mineralization in other diseases, embryonal ossification and bone wound healing.

Adult↗
PubMed1981

A comparative study on the occurrence and activity of extracellular matrix vesicles in young and adult rat maxillary bone.

The occurrence of matrix vesicles in the maxillary bone of normal young and adult rats was demonstrated by both ultrastructural and enzymatic studies. Transmission electron microscopy revealed that the vesicles are invested in trilaminar membranes. Occasionally, crystals were found both within the vesicles and in the surrounding matrix. Separated fractions of vesicles, membranes, and cells were studied biochemically. The amounts of vesicular protein and enzymatic activity per gram bone in the adult rats were significantly lower than in the young. This coincides with the higher number of vesicles observed in the TEM specimens of young rats when compared to that in the old ones. The specific activities of all enzymes examined in the three bone fractions obtained from both young and adult rats were similar. This indicates that no significant difference exists in the enzymatic characteristics of matrix vesicles from the maxillary bone of young and adult rats.

Acid Phosphatase↗
PubMed1981

Purification and further characterization of isolated matrix vesicles from rat alveolar bone.

Extracellular matrix vesicles from rat alveolar bone were isolated by collagenase digestion and differential centrifugation. Further purification was performed by discontinuous sucrose density gradient centrifugation. Control tissues, kidney and liver, were processed according to the same procedures. Sucrose density gradient centrifugation of bone matrix vesicles revealed two peaks of enzymatic activity: "light" and "heavy" vesicle-enriched fractions. Electron micrographs revealed a higher degree of purification of the "light" rather than the "heavy" vesicle-enriched fraction. This coincided with the high levels of enzymatic activity detected in this fraction. Preparations obtained from kidney and liver had significantly lower levels of activity of alkaline phosphatase and ATPase as compared to the bone matrix vesicle fractions. There were also differences in the positions of enzyme activity peaks in the sucrose gradient fractions from the three tissues studied. Electron microscopic examination of kidney and liver fractions revealed structures larger than the purified bone matrix vesicles. In addition no electron-dense material was found within organelles from kidney and liver and they were studded with numerous ribosomes. Our observations indicate that the present method of isolation and purification yields fractions of matrix vesicles which are specific to bone and are significantly different from those obtained from kidney and liver.

Acid Phosphatase↗
PubMed1981

Transmission electron microscopy of reparative dentin in rat molar pulps. Primary mineralization via extracellular matrix vesicles.

A reparative dentin bridge was induced in rat molar teeth by pulp exposure and capping with calcium hydroxide. Transmission electron-microscopic examination after 10 days revealed the presence of odontoblastic cells and collagenous matrix with focal calcifications. The calcifying fronts were composed of hydroxyapatite crystals. Numerous extracellular matrix vesicles were scattered between the forming cells and the calcifying fronts. Some of the vesicles contained electron-dense material and in others, apatite crystals were detected. Matrix vesicles could not be identified in normal, mature calcifying dentin matrix. In view of the present observations and studies on surgical manipulations in articular cartilage, it is concluded that matrix vesicle calcification may result from alterations in the metabolic state of mesenchymal tissues. These changes can be induced surgically or chemically.

Animals↗
PubMed1979

Ultrastructural and biochemical study of extracellular matrix vesicles in normal alveolar bone of rats.

The occurrence of vesicles in the extracellular matrix of alveolar bone of normal young rats was demonstrated by both ultrastructural and enzymatic studies. Transmission electron microscopy revealed abundant vesicles in the matrix. The presence of hydroxyapatite crystals, both within the vesicles and in the matrix, was affiliated with rupture of the vesicular membrane. Calcifying nodules were scarce. High levels of both specific and total activities of alkaline- and pyrophosphatases were found in the fraction of isolated vesicles. This fraction also showed activities of different ATPases and acid phosphatase.

Acid Phosphatase↗
PubMed1979

The relationship between extracellular matrix vesicles and calcospherities in primary mineralization of neoplastic bone tissue. TEM and SEM studies on osteosarcoma.

Primary mineralization in neoplastic tissue was studied in osteosarcoma, correlating observations obtained by SEM to those found with TEM. The process is characterized by extracellular matrix vesicles, distributed in the matrix between the forming neoplastic cells and the calcifying fronts. The occurrence of osmiophilic material and solitary hydroxyapatite crystals within the vesicles is followed by accumulation of apatite crystals, disappearance of the vesicular membrane and formation of calcospherites and calcified fronts. The process described here in neoplastic tissue is essentially similar to primary calcification in normal calcified tissues.

Apatites↗
PubMed1979

Effect of irradiation-timing on the initial socket healing in rats.

The effect of a single dose of 1500 R on early postextraction socket healing was studied in jaws of rats. A severe delay in healing was found in animals irradiated 2 weeks prior to extraction. Retardation of healing to a lesser degree was demonstrated in sockets irradiated immediately after exodontia.

Alveolar Process↗
PubMed1979

Correlative transmission and scanning electron microscopy of the initial mineralization of healing alveolar bone in rats.

Primary mineralization in healing sockets after extraction of molar teeth was studied in rats. The observations obtained by scanning electron microscopy were correlated by transmission electron microscopy. The process is characterized by abundance of extracellular matrix vesicles distributed between the forming cells and the calcifying fronts. The occurrence of osmiophilic material and solitary hydroxyapatitte crystals within the vesicles was followed by accumulation of hydroxyapatite crystals, disappearance of the vesicular membrane and formation of calcospherites that conglomerate into calcified fronts. The process described here in bone healing is essentially similar to primary mineralization in other normal and pathological calcified tissues.

Alveolar Process↗
PubMed1977

Further observations on the relationship between the matrix and the calcifying fronts in osteosarcoma.

Human osteosarcoma biopsies were studied with the SEM using sequential etching with sodium hypochlorite solutions after removal of aluminium or gold coatings. Osteosarcomas differ from normal hard tissues in that the matrix never proceeds to complete mineralization, so that the specimens fragment on hypochlorite treatment. Details of the fibrillar pattern and calcospheritic type of mineralization pattern can be seen in hypochlorite etched, fractured surfaces and mineralizing fronts.

Bone Matrix↗
PubMed1977

Bone remodeling in pathologic conditions. A scanning electron microscopic study.

Bone remodeling in pathologic conditions was studied with the scanning electron microscope (SEM). Benign and malignant ossification were examined in cases of myositis ossificans, ossifying fibroma, osteoid osteoma, and osteosarcoma, Resorption of bone due to invasion by non-ossifying tumors was found in cases of squamous cell carcinoma, adenocarcinoma, ameloblastoma, and multiple myeloma. Bone formation due to excessive production of growth hormone was studied in a case of acromegaly. Resorption of bone due to pathologic processes resembled the pattern found in surfaces which were undergoing resorption by osteoclasts. Lamelar-cortical bone formation in acromegally was similar in nature to normal bone. The deformities were rleated to the excessive continuous osteogenesis that occurs in these instances. Neoplastic ossification was characterized by calcifying globules, the diameters of which ranged from 1 to 3 micron. The surfaces of these globules were constructed of minute calcospherites with diameters ranging from 0.1 to 0.3 micron. It is suggested that the pattern of globular calcification is similar to the type that was found with the SEM in fetal bone and cartilage, during healing of fractured bone, and also with the TEM in normal and pathologic calcification.

Acromegaly↗