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Biomedical subjects

E Bonucci

Publications and source records attributed to E Bonucci.

At least 145 records · Page 8Linked to original sources
PubMed1977

Ultrastructural aspects of chondrodystrophia calcificans congenita (syndrome of Conradi-Hünermann).

An ultrastructural study of chondrodystrophia calcificans congenita is reported. Foci of initial calcification of cartilage are characterized by coexistence of three different types of crystals, probably due to abnormal proteoglycan composition of cartilage matrix. The calcification process in chondrodystrophia calcificans congenita is apparently not related to 'matrix vesicles' as it is in normal cartilage.

Calcinosis↗
PubMed1976

Bone changes in hemodialyzed uremic subjects. Comparative light and electron microscope investigations.

Needle biopsies from the iliac crest of 40 uremic patients treated with hemodialysis have been compared by light and electron microscopy. The most obvious bone changes were represented by an increased amount of osteoid tissue (osteomalacic changes) and by enhanced bone resorption. The osteomalacic changes were chiefly characterized by the presence of thick osteoid borders whose collagen fibrils were often completely uncalcified. In a few cases, small roundish aggregates of crystals were irregularly present through the osteoid matrix; some of them were closely related to roundish, electron-dense bodies surrounded by a membrane. The increased rate of bone resorption, which was often comparable to that which occurs in the most severe cases of primary hyperparathyroidism, was due to both osteoclastic activity and osteocytic osteolysis. Electron microscopy showed that the enlargement and irregularity of the osteocytic lacunae were not always due to osteocytic osteolysis; the same effect might be due to defective calcification of the lacunar wall. The advantages of comparing the same specimens under the light and electron microscopes are discussed.

Bone Resorption↗
PubMed1976

Matrix vesicles in aging cartilage.

The calcification process that occurs in aging has been studied with the electron microscope in costal and tracheal cartilage of rats and in human costal cartilage. In these tissues, the early stage of the calcification process is induced and regulated by matrix vesicles in the same way as it occurs in epiphyseal cartilage, bone, and dentine. However, the spreading of inorganic substance from vesicles into the surrounding matrix is frequently impaired in aged cartilage, either because of a too low concentration of calcium ions, or because the structure of the cartilage matrix is not suitable for inorganic substance deposition. This shows that matrix vesicles have a calcium affinity and calcium-binding potentiality greater than that of other components of the cartilage matrix. Most matrix vesicles are produced by "Verdämmerung der Zellen." This degenerative process of the chondrocytes leads also to the formation of pericellular halos consisting of aggregates of amorphous substance and thin filaments. Part of the material that forms these aggregates seems to be produced by disruption of matrix vesicles. Within this disruptive material, thick collagen fibrils can be formed. Moreover, this material seems capable of inducing calcification. These findings suggest that matrix vesicles, by releasing their content into the matrix, can be involved in some way in collagen formation, and that the released material maintains the calcium affinity and calcium-binding property it has within the vesicles.

Adolescent↗
PubMed1976

Histological and histochemical investigations of achondroplastic mice: a possible model of human achondroplasia.

Histological and histochemical investigations of tibial epiphyses, costo-chondral junctions and caudal vertebrae of achondroplastic (cn) mice have shown that, in spite of conspicuous reduction of bone length, endochondrial ossification occurs in much the same way as in controls. Moreover, the histological structure of seriated cartilage, and the distribution of proteoglycans in resting cartilage are the same in cn/cn mice and in controls. The only difference betweeen the two types of animals is represented by the occurence of early aging-like changes of chondrocytes and cartilage matrix in achondroplastic mice, leading to premature shortening of the cell columns and to early reduction of the proteoglycan concentration. The premature "aging" of the cartilage, the consequent inhibition of the calcification process and bone growth, and the normal rate of perichondral ossification give to long bones, vertebrae and ribs a typical achondroplastic appearance. The cn/cn mice seem to represent a useful model for studying the pathogenesis and therapy of human achondroplasia.

Achondroplasia↗
PubMed1975

Histochemical and electron microscopy investigations on medullary bone.

Folliculin administration to pigeons stimulates the development of medullary bone in marrow spaces of the femora and other long bones. It is a specialized osseus tissue not devoted to mechanical functions and which is rapidly reabsorbed before egg-shell formation. Medullary bone is formed and reabsorbed in the same way as other types of bone. Consequently, because of its very rapid rate of formation and resorption, it represents an ideal tissue for studying osteoblastic, osteoclastic and osteocytic activity, and the calcification process. Medullary bone is deeply stained by PAS, Alcian blue and colloidal iron and is metachromatic after toluidine blue staining. This shows that its interfibrially ground substance contains relatively high amounts of glycoproteins and acid proteoglycans. Calcification initially occurs in maxtrix vesicles (or calcifying globules) which are very numerous between the collagen fibrils of the osteoid tissue, and successively spreads into the surrounding interfibrillar matrix. Here, the crystals are closely related to thin, filament-like organic structures which seem to be components of ground substance proteoglycans. These findings confirm that in medullary bone, as in other types of calcifying tissue, the inorganic substances is initially laid down within calcifying globules and is successively closely related to organic, non-collagenous, filamentous organic structures (crystal ghosts) which probably represent a framework for calcium salt deposition.

Animals↗
PubMed1975

Osteopetrosis fetalis. Report on a case, with special reference to ultrastructure.

The clinical and pathological findings concerning the skeletal abnormalities in a case of osteopetrosis fetalis have been reported. The principal data can be summarized as follows. The areas of endochondral ossification have a rickety appearance because of excessive number of hypertrophic and degenerate chondrocytes. These cells are highly vacuolated and the vacuoles, which are of mitochondrial origin, contain beaded filaments which are exocytosed and become part of the matrix. The calcification process is delayed, probably in consequence of a reduced number of matrix vesicles. Abnormal collagen fibrils are sometimes present in the cartilage. The osteoclasts have a very low reabsorbing activity and appear structurally abnormal. The combined effect of all these abnormalities leads to excessive development of osteocartilaginous trabeculae in marrow spaces. These trabeculae have a Ca/P ratio of 1.79 and their mineral substance appears qualitatively normal under the electron microscope.

Bone and Bones↗
PubMed1975

Filaments and granules in mitochondrial vacuoles in chondrocytes.

As chondrocytes degenerate mitochondria frequently become vacuolated. Vacuoles seem to form by an invagination of mitochondria into their own matrix followed by cytoplasmic invasion. The bounding membrane of vacuoles and the electron dense granules which are intermittently dispersed around its periphery are positive when stained with phosphotungstic acid and with silver nitrate methenamine after periodic acid oxidation, indicating the presence of glycoprotein; they are also positive after staining with colloidal iron and bismuth nitrate, indicating the presence of acid proteoglycans. Within vacuoles and apparently arising from their glycoprotein proteoglycan boundary are small filaments composed of granular and filamentous protions. Vacuoles and their contents are exocytosed thus accounting for the presence of granules and filaments in pericellular lacunae. In pericellular lacunae and in the extracellular matrix, filaments interconnect with granules or with collagen fibrils, or both. Filaments decrease in number as the distance from the cell increases, while granules decrease in size but remain numerous. Filaments and granules decrease in the extracellular matrix as collagen fibrils aggregate and as the matric calcifies. Thus, they may play a role in aggregation of collagen fibrils. Filaments and granules also decrease with increasing age. Filaments and granules do not seem to be derived from Golgi vacuoles. They are present in costal, tracheal, and epiphyseal cartilage in three different species of animals.

Aging↗
PubMed1975

Dihydrotachysterol-induced aortic calcification. A histochemical and ultrastructural investigation.

Early dihydrotachysterol-induced calcification of the rat aorta occurs in elastic lamellae. The first deposition of inorganic substance leads to the formation of very thin filament-like structures of low electron density. The characteristic shape of these structures suggests that they could correspond to calcified filamentous components of the elastic tissue. When calcification spreads from the calcified elastic lamellae into the adjacent tissue, the inorganic substance is initially collected in roundish structures, probably of cellular origin, and is successively laid down in the entire matrix of the aortic wall, including collagen fibrils. All the calcified areas contain glycoproteins and acid proteoglycans. A cartilage-like tissue often develops near calcified areas. Its fine structure is very similar to that of the normal hyaline cartilage. It can be calcified, but usually the inorganic substance is not crystalline as it is in normal cartilage. It seems to consist of very small, linearly aggregated inorganic granules which form irregular structures. These seem to develop in close relationship with the fibrillar, probably collagenic, network of the matrix. No ultrastructural findings have been obtained for explaining cartilage induction near calcified areas of the aortic wall. It is possible that cartilage differentiation is regulated by diffusible substances which cannot be recognized under the electron microscope.

Animals↗