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Biomedical subjects

S Palazzini

Publications and source records attributed to S Palazzini.

11 recordsLinked to original sources
PubMed2000

[In vitro study of periodontal ligament cells].

BACKGROUND: The aim of this research is to outline a procedure able to promote specific cellular differentiation and proliferation with consequent periodontal regeneration. To achieve this goal, use was made of various compounds supposed to have the capacity of aiding periodontal regeneration. METHODS: The cells utilised for this study were obtained from explants of human periodontal ligaments. Their proliferation and differentiation capacity was examined in the presence of: coral granules (350, 500 mu), collagene type 1, growth factors (Platelet derived growth factor, PDGF and Transforming growth factor beta 1, TGF beta 1), both on their own and in different combination with one another. The differentiation activity was evaluated by ultrastructural morphological method (Transmission electron microscope-TEM) and by spectrophotometric investigation of the alkaline phosphatasis (ALP). RESULTS: The data show that the coral granules and among the growth factors used only TGF beta 1 stimulate the differentiation activity of the periodontal ligament cells valued on the basis of their capacity of producing ALP. These data are supported by the observation with TEM. CONCLUSIONS: From these results it is suggested that there may be therapeutic efficiency in the periodontal field of substances promoting cellular proliferation and differentiation.

Cell Culture Techniques↗
PubMed1998

Stromal cell structure and relationships in perimedullary spaces of chick embryo shaft bones.

Structure and relationships of stromal cells were studied by light (LM) and transmission electron microscopy (TEM) in the perimedullary spaces that form the growing cortex of the chick embryo tibia. Observation under LM showed that in all perimedullary spaces the interstices between the cells carpeting the bone surface and the endothelial lining contain stromal cells surrounded by an amorphous matrix. Two types of stromal cells were distinguished: stellate and spindle-shaped. All stromal cells are alkaline phosphatase-positive. TEM showed that both types of stromal cells have cytoplasmic processes of various length and calibre, coming into contact with each other as well as with endothelial cells and osteoblasts or bone lining cells. Capillaries were found to have a continuous endothelial lining; occasionally endothelial cells radiate cytoplasmic processes towards stromal cells. Along all the above-mentioned cellular contacts adherens and/or gap junctions were often observed. The results of the present study, together with our previous findings on osteoblast-osteocyte relationships, show that the cells of the osteogenic lineage form a continuous protoplasmic network that extends from the osteocytes to the vascular endothelium, passing through osteoblasts (or bone lining cells) and stromal cells. The occurrence of gap junctions among this cytoplasmic network, namely of junctions enabling metabolic and electric coupling, indicates that it forms a functional syncytium, suggesting the hypothesis that the activity of the cells pertaining to the osteogenic lineage might be regulated not only by diffusion (volume transmission) through the intercellular fluids of systemic (hormones) and local factors (cytokines, etc.) but also by signals issued through the cytoplasmic network of the osteogenic cells (wiring transmission).

Alkaline Phosphatase↗
PubMed1996

Intermittent compressive load stimulates osteogenesis and improves osteocyte viability in bones cultured "in vitro".

The effect of mechanical stresses on osteogenesis, the viability of osteocytes and their metabolic activity in organ culture of bones intermittently loaded "in vitro" are reported. Metatarsal bones, isolated from 12-day-old rats, were cultured in BGJb medium (with 10% foetal calf serum, 75 micrograms/ml of ascorbic acid, 100 U/ml of penicillin and 100 micrograms/ml of streptomycin), in humidified air enriched by 5% CO2 and 30% O2, and loaded in our original device for 1/2 an hour at 1 Hz. homotypic isolated and unloaded bones, cultured in the same medium, were taken as controls. The ALP (alkaline phophatase activity) increases in the media of loaded bones in comparison with the control bones. The percentage of viable osteocytes is significantly greater in loaded than in control bones. TEM observations demonstrate that in both loaded and control unloaded bones, osteocytes show well developed organelle machinery and several gap junctions with adjacent cellular processes. In the cells of loaded bones, however, a higher number of cytoplasmic organelles and gap junctions were found. In particular, RER increases twice, gap junctions three times. The induced osteogenesis and the TEM observations demonstrate the suitability of this experimental model and support the recent advanced hypothesis according to which the mechanical loading may exert a trophic function on osteocytes, stimulating both the proteic synthesis in the above-mentioned cells and the cell-to-cell communication. Furthermore, the loading is likely to exert a biological stimulus on osteoblasts via signalling molecules produced by osteocytes.

Alkaline Phosphatase↗
PubMed1995

Morphometric study of collagen maturation in chick compact bone.

An ultrastructural-morphometric study was carried out on the process of osteoid maturation in growing surfaces of parallel-fibered chick bone. The aim was to investigate the distribution, size and amount of collagen fibrils (CFs), as well as the proteoglycan (PG) content, throughout the osteoid seam and in the adjacent bone. The results show that the organic components secreted by osteoblasts undergo complete maturation inside the osteoid seam only. Proceeding from the secreting plasma membrane of osteoblasts (osteoidogenic surface) towards the mineralizing surface, we found that CFs gradually increase in diameter but not in number per surface unit. As a consequence, the proportion of osteoid seam occupied by CF increases too, at the expense of the interfibrillar substance. PG content also decreases inversely in this direction. In the adjacent bone, CF size and density do not change significantly with respect to the mature osteoid close to the mineralizing surface.

Animals↗
PubMed1992

A quantitative evaluation of osteoblast-osteocyte relationships on growing endosteal surface of rabbit tibiae.

Scanning electron microscopy (SEM) was used to quantify the intercellular relationships between osteoblasts and osteocytes on the growing endosteal surfaces of the medullary canal of the tibia in four rabbits of different ages. The area of each osteoblast was measured on the SEM micrographs by means of an Image Analyzer. The number of osteocyte cytoplasmic processes was indirectly evaluated by counting the canalicular openings present on the same microscopic fields after the removal of the osteoblasts. The metabolic activity of the osteoblasts was indirectly evaluated from their shape, and the structure was analyzed by transmission electron microscope (TEM) in sections taken from the samples studied by SEM. In all four animals, the surface area of the osteoblasts (OA) was found to vary a great deal, whereas the density of canalicular openings was fairly uniform. Moreover, although the OA mean value increases significantly with the age of the animals, the density of canalicular openings does not; it would therefore appear that the older the animal and the more flattened the osteoblasts, the greater the number of canaliculi beneath them. Since osteoblast activity has previously been shown to be inversely proportional to the area of the protoplasm in contact with the bone surface, it appears that the less active osteoblasts should contact a greater number of osteocyte cytoplasmic processes. These findings suggest that osteocytes might play an important role in modulating osteoblast activity and in recruiting osteoblasts that differentiate into osteocytes, possibly by means of inhibitory signals transmitted via gap junctions.

Animals↗
PubMed1990

Morphological study of intercellular junctions during osteocyte differentiation.

Ultrastructural studies were carried out on intercellular relationships during osteocyte differentiation in primary parallel-fibred bone of newborn rabbit. It was found that throughout the whole differentiative process preosteocytes are in close relationship with the neighboring cells (osteoblasts, osteocytes) by means of variously-shaped intercellular contacts (invaginated finger-like, side-to-side, and end-to-end) and two types of specialized junctions: gap and adherens. The pivotal role played by these contacts and junctions in osteocyte differentiation and activity is considered in the context of their particular functional significance.

Animals↗
PubMed1990

Osteocyte differentiation in the tibia of newborn rabbit: an ultrastructural study of the formation of cytoplasmic processes.

The morphological changes undergone by the osteoblast at the ultrastructural level, during its differentiation into osteocyte, were studied in the primary parallel-fibred bone of the newborn rabbit by means of incomplete three-dimensional reconstruction from partially serial-sectioned preosteocytes. The findings obtained suggest that the formation of osteocyte cytoplasmic processes is an asynchronous and asymmetrical phenomenon that seems to precede the mineralization of the organic matrix and to give rise to an asymmetrical mature osteocyte. The functions of cytoplasmic processes as regards bone formation, cell nutrition and osteoblast modulation are discussed. The mechanism by which the osteoblast 'enters' the bone matrix is hypothesized.

Animals↗
PubMed1982

Activity of osteoclasts and osteocytes in compact human bone at various ages, both with and without osteoporosis.

As part of a programme of research designed to assess the respective roles of osteoclasts and osteocytes in the processes of bone resorption, the metabolic activity of these cells was evaluated indirectly by a morphometric method in the compact bone of human tibias from subjects of various ages, both normal and those affected by osteoporosis. Statistical analysis of the quantitative data was in agreement with the microradiographic examination of the sections, and showed that whereas the intensity of osteoclastic resorption varied in the various subjects according to age, periosteocytic osteolysis--in the classical sense of a phenomenon involving widening of the lacunae detectable with the optical microscope--did not occur in compact bone whether it was normal or highly porotic.

Adult↗
PubMed1981

Morphometric analysis of osteoblast dynamics in the chick embryo tibia.

Structure and size of the osteoblasts have been analyzed during growth of the tibial diaphyses in chick embryos from 10 days incubation until hatching. Statistical analyses of the results indicate that both size and density of the osteoblasts gradually decrease from the subperiosteal towards the endosteal regions of the shaft; the osteoblast secretory territory, on the other hand increases. These structural changes of the osteoblasts, which appear to be related to differences of the appositional growth rate, seem to derive mainly from structural modifications of differentiated osteoblasts rather than from differentiation of new osteoblasts, of progressively smaller size, from osteoprogenitor cells. The data reported in this paper compared with those in previous investigations indicate that the size of the osteoblasts does not significantly differ in animals of different species.

Animals↗