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Biomedical subjects

A Teti

Publications and source records attributed to A Teti.

120 records · Page 7Linked to original sources
PubMed1982

Tympanic membrane homografts. Histological findings in a human case.

The structure of a human tympanic membrane has been studied with the electron microscope 12 months after implantation. The lamina propria of the epidermis and the connective submucosal layer were thicker in the homograft than in the normal tympanic membrane. Creeping substitution in the fibers of the outer radial and inner circular layers was not observed but cannot be excluded. The protective role of the skin of the external meatus and of the epithelial cells of the mucosal layer has been noted.

Connective Tissue↗
PubMed1981

[Separation of osteoclasts from bird medullary bone by sedimentation at unit gravity].

A procedure for the isolation of osteoclasts from the heterogeneus population of medullary bone and marrow cells is presented. Cell suspensions were prepared from medullary bone of laying hens by mechanical dispersion. Following an osmotic shock and two 90 min unit gravity sedimentations, fractions highly enriched in osteoclasts were collected and subsequently cultivated in MEM with FCS. Ara C was added to the cultures for 48h to remove all the cells entering the mitotic cycle. The advantages and the possible applications of the method are discussed.

Animals↗
PubMed1981

[Variations in mineralization of cortical and medullary bone in laying hens during and after hypocalcemic diet].

Compact and medullary bone of femur, tibia and humerus during a period of calcium depletion and repletion have been studied by microradiographic and microdurimetric method. From our preliminary results it appears that the degree of mineralization varies only in medullary bone, where the existing trabeculaea are eroded and substituted by others that don't complete mineralization. The cortical bone is deeply eroded during the diet and slowly reconstructed during the period of calcium repletion.

Animals↗
PubMed1981

The osteoclasts of hen medullary bone under hypocalcaemic conditions.

Osteoclasts of medullary bone after several days of hypocalcaemic diet are substituted on the trabecular surface by active osteoblasts. The fate and the ultrastructure of the osteoclasts withdrawn from medullary bone surfaces in the course of a low calcium diet has been studied in serial semithin and ultrathin sections. The cytoplasmic surface of osteoclasts located in marrow compartments presents blebs and protrusions and the whole cell is often irregularly branched in several directions. A large amount of granular endoplasmic reticulum is accumulated at the cell periphery; often the cisternae are distended to form vesicles with an inner core of dense material. Osteoclasts seem to divide into mono or polynucleated smaller units.

Animals↗
PubMed1980

[Quantitative evaluation of experimentally induced osteocytic osteoplasia in hen's femur].

The extent of osteocytic osteoplasia has been studied in laying hens fed for seven days a hypocalcaemic diet and returned to the commercial laying ratio. The microscopic examination of the femur shows the presence of newly formed bone matrix on the wall of osteocytic lacunae, much more numerous in the experimental animals than in the controls. The physiological significance of the finding is briefly discussed.

Animals↗
PubMed1980

Influence of calcium depletion on medullary bone of laying hens.

Medullary bone of birds maintained on a low-calcium diet represents a good model to study modifications of matrix composition in calcified tissue undergoing intense formation and resorption. The composition of the bone matrix during the low-calcium diet has been analyzed by both chemical and histological techniques. Sixty White Leghorn pullets 1 year old were used for the experiment. Fifteen birds served as controls and were killed on day zero; the remaining birds were placed on a calcium-deficient diet (0.13% calcium) and sacrificed after 4, 7, and 12 days of treatment in groups of 15. Serum levels of calcium, PTH, and estrogens were also measured. Chemical analysis of the samples were made for total nitrogen, hydroxyproline, hexosamine, hexoses, calcium, and phosphorus. Collagen and proteoglycans of the matrix of medullary bone of the egg-laying hens were found to be affected by the low-calcium diet. They either increased or decreased during the experiment but never in parallel. The increment of serum PTH is considered responsible for the variations in the amount of collagen. The effects of this hormone are magnified by the fall of serum estrogens as shown also by variations in the amounts of noncollagenous protein. In the late phase of the diet the matrix is represented by poorly calcified osteoid tissue rich in noncollagenous protein, i.e., proteoglycans and glycoproteins.

Animals↗
PubMed1979

[Structural modifications of medullary bone osteoclasts during a hypocalcemic diet].

The medullary bone of laying hens after seven days of hypocalcaemic diet has been investigated with the aim of analyzing the fate of osteoclasts, very numerous in the first days of the diet and after substituted on the trabecular surfaces by active osteoblasts. The first observations show that there is a marked change in the osteoclasts ultrastructure. Large amount of endoplasmic granular reticulum in regular rows are accumulated at the cell periphery. Cytoplasmatic blebs, microvilli and laminae ondulantes are visible on the cell surfaces. Mononuclear cells with variable amount of cytoplasm rich in organuli are detached from osteoclasts. The ultrastructure and the fate of this elements are discussed.

Animals↗
PubMedDate not supplied

Protein kinase C modulates estrogen receptors in differentiated osteoblastic cells in vitro.

Several reports have shown an interaction between the estrogen receptor (ER) and the protein kinase C (PKC) intracellular pathways. Data from our laboratory showed that PKC activation can modulate ER levels and responsiveness in estrogen target tissues such as uterus and bone. In particular, ROS.SMER #14 osteoblastic cells, stably transfected with the mouse ER, undergo specific morphological changes in vitro. ROS.SMER #14 cells at post-confluence express a differentiated phenotype and become unresponsive to estrogenic stimulation. Interestingly, ER mRNA and protein levels were not modified by post-confluence, but ER binding sites/cell (2500-3000/cell at subconfluence) were undetectable. Moreover, PKC activity was significantly increased in post-confluent cells. Inhibition of PKC by H7 or staurosporin (PKC inhibitors) or down-regulation by long-term treatment with 12-O-tetradecanoylphorbol-13-acetate enchanced ER binding capacity in a dose-dependent manner. Since the PKC family includes several different isoforms that play different roles in cell homeostasis, we evaluated whether specific isoenzymes were involved in this event. To address this question, Western blotting analysis was performed on both sub- and post-confluent ROS.SMER #14 cells using antibodies against different PKC isoforms. In conclusion, our preliminary data indicate that estrogen responsiveness of osteoblastic cells can be highly regulated by PKC. Finally, these data suggest that this intracellular interaction might play an important role in modulating hormonal and pharmacological responsiveness of bone tissue.

Animals↗
PubMedDate not supplied

A novel calcium sensor stimulating inositol phosphate formation and [Ca2+]i signaling expressed by GCT23 osteoclast-like cells.

Osteoclast activity is inhibited by elevated [Ca2+]o; however, the underlying molecular mechanism is unknown. We used the human osteoclast-like cells GCT23 to elucidate their cation-sensing properties. Cells responded to elevated [Ca2+]o with rapid concentration-dependent [Ca2+]i transients (EC50 = 7.8 mm, time to peak 44 +/- 4 sec) that were due to release from intracellular stores, followed by Ca2+ influx across the plasma membrane. Ca2+ store depletion by thapsigargin, endothelin-1, or bradykinin activated calcium entry pathways. Cells responded similarly to Ni2+ and Cd2+ with albeit slower kinetics (EC50 <10 microm and <100 microm, times to peak 140 +/- 25 sec and 150 +/- 24 sec, respectively). The three cations stimulated inositol phosphate production (two-fold, p <.02) similar to bradykinin (2.5-fold, p <. 002), which activates a phospholipase C (PLC)-coupled receptor in GCT23 cells. The cells did not respond to 0.1-1 mM Gd3+ or neomycin B, indicating that the parathyroid calcium receptor (PCaR) is not functionally expressed. In confirmation, PCaR could not be detected by reverse transcriptase polymerase chain reaction in GCT23 cells and in mouse osteoclasts, and the calcimimetic compound NPS R-568 failed to produce the left shift of the concentration-response curve characteristic for PCaR. Our data demonstrate for the first time that cation sensing by osteoclast-like GCT23 cells is mediated by a PLC-coupled receptor that is not identical to PCaR.

Animals↗
PubMedDate not supplied

Metaplasic bone tissue in tympanosclerosis.

Two different tissues have been observed in specimens of tympanosclerotic material studied under light and electron microscopy. The first, devoid of cells and blood vessels, is a dense fibrous tissue similar to that already described in fibrous tympanosclerosis. The second resembles a bone tissue, containing osteocytes and vascular channels; it is laid down by metaplasic fibroblasts following the invasion of the first tissue by osteoclasts and blood vessels after its calcification.

Ear, Middle↗