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Biomedical subjects

I Bab

Publications and source records attributed to I Bab.

67 records · Page 4Linked to original sources
PubMed1982

Patterns of matrix vesicle calcification in osteomalacia of Gyro mice.

Homozygous Gyro mice manifest widespread abnormalities in the inner ear and other parts of the skeleton. These disorders were attributed to a sex linked dominant gene. In the present study, tissue specimens were obtained from the inner ear and maxillary and tibial bones, and undecalcified samples were processed for light and transmission electron microscopy. Light microscopy revealed osseous changes consistent with osteomalacia. These alterations comprised broad bands of osteoid with partial or complete failure of calcification. Electron micrographs showed longitudinal calcifying fronts composed of hydroxyapatite crystals. Abundance of matrix vesicles could be demonstrated in the extracellular matrix. Many of the vesicles contained crystaline mineral. In addition, calcification alongside collagen fibers was recorded. Occasionally, apatite crystals were attached to plasma membranes. Female and hemizygous male mice showed normal patterns of calcification. The findings in the affected Gyro mice appear to be similar to previously reported changes in human osteomalacia. Further definition of the pathological process in this animal model may be valuable in defining mechanisms operative in the development of osteomalacia in man.

Animals↗
PubMed1982

Correlative clinico-pathological evaluation of oral premalignancy.

In 1972, the World Health Organization's "Meeting of Investigators on the Histological Definitions in Precancerous Lesions" defined a precancerous lesion as a "morphologically altered tissue in which cancer is more likely to occur than in its apparently normal counter part" (Pindborg 1980). There are two generally accepted precancerous lesions in the oral cavity, leukoplakia and erythroplakia (Pindborg 1980). Leukoplakia is currently defined as "a white patch or plaque that cannot be characterized clinically or pathologically as any other disease" (WHO 1978). This definition has no histological connotation and is used in a strictly clinical sense (Pindborg 1980, Banoczy 1977). Erythroplakia is defined as a "bright red velvety plaque which cannot be characterized clinically or pathologically as being due to any other condition" (Pindborg 1980).

Diagnosis, Differential↗
PubMed1982

Calcification patterns of rat condylar cartilage after induced unilateral malocclusion.

Occlusal interferences on right upper molars in rats produced ultrastructural changes in the calcification of ipsilateral condylar cartilage. This was characterized by premature appearance of apatite crystals within extracellular matrix vesicles present in the proliferative cell zone. The normal proliferative cell zone in the rat condyle manifested noncalcifying vesicles. The zone of calcification in rats with an occlusal splint revealed longitudinal calcifying fronts in the vicinity of the chondrocytes. These fronts were composed of haphazardly distributed apatite crystals. These ultrastructural alterations support the generally accepted view that mechanical stimuli induce changes in the process of primary mineralization.

Animals↗
PubMed1982

Primary mineralization of dentin in rats after pulp capping with calcium-hydroxide.

It has been previously reported that short term application of calcium-hydroxide to the dental pulp resulted in the formation of a dentin bridge with matrix vesicle calcification. The present study deals with the induction of reparative dentin in rat molar pulps by direct capping with calcium-hydroxide. The teeth were examined after 21 and 35 days. Transmission electron microscopy (TEM) revealed that the calcification process in the newly formed dentin was characterized by apatite deposition in matrix vesicles and the occurrence of calcifying nodules in the matrix. The persistence of these features of primary mineralization, during the experimental period, was associated with the continuous calcium hydroxide contact with pulp tissue, producing changes in its metabolic state.

Animals↗
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

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

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

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↗
PubMedDate not supplied

Biochemical characterization of matrix vesicles from bone and cartilage.

Extracellular matrix vesicles from bone and epiphyseal cartilage of femur and tibia of rats were isolated by collagenase digestion (crude vesicles) and further purified by sucrose gradient centrifugation. Fractions containing cells and membranes were also isolated from the two tissues. The alkaline and acid phosphatase and ATPase activities, as well as protein content of all fractions including crude and purified matrix vesicles, were assayed. The crude vesicles from both tissues demonstrated a high alkaline phosphatase specific activity (5-20 times higher than in the cell fraction). The total enzyme activities and protein content were significantly higher in all fractions from cartilage than those from bone. A major peak of alkaline phosphatase activity and protein content was obtained following the sucrose gradient centrifugation. The position of this peak was similar for both tissues. The specific activity of alkaline phosphatase of purified matrix vesicles was significantly higher in bone than in cartilage. The phosphatase activities from cartilage and bone showed a similar pH dependence and a similar response to metal ions. Of the metal ions tested (Na+, Mg2+, Zn2+, and Ca2+) only Zn2+ (at 5 mM concentration) inhibited significantly the alkaline phosphatase activity of purified matrix vesicles. The electrophoretic profile of purified matrix vesicles showed eight major protein bands common for both tissues. In addition, cartilage vesicles appeared to possess two peptides not found in bone.

Acid Phosphatase↗
PubMedDate not supplied

Ultrastructure of bone and cartilage formed in vivo in diffusion chambers.

Osteogenic tissue formed in vivo in diffusion chambers inoculated with a suspension of marrow cells contains both bone and cartilage. Observations by transmission electron microscopy on the transitional zone between these tissues showed a mixture of osseous and cartilaginous features in both matrix and cells. Two forms of collagen, morphologically consistent with Types I and II, are found in intimate association within the same intercellular septa. The results suggest the possibility that the different collagen types are synthesized by the same cells and that the variation in cellular morphology could be associated with the changes in the type of collagen synthesized. This unique characteristic of calcified tissues formed in diffusion chambers is probably the result of isolation from direct blood circulation, mechanical stress, and cellular mechanisms of tissue breakdown.

Animals↗