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Biomedical subjects

A Carano

Publications and source records attributed to A Carano.

At least 19 recordsLinked to original sources
PubMed1991

Eminence-posterior occlusal plane angle in patients with temporomandibular disorders.

The causes of temporomandibular disorder are not clearly understood. The controversy regarding the role of the features, either dental or skeletal, still exists after nearly a half century of debate. The present study demonstrates an interesting correlation, expressed as an angular value, between the posterior surface of the articular eminence and the posterior occlusal plane. The group with dysfunction had a mean value significantly lower (133 +/- 4) than the group without symptoms (144 +/- 5). In light of this data, it is suggested to interpret a small eminence-posterior occlusal plane as an anatomical predisposing pattern for dysfunction.

Adolescent↗
PubMed1991

Bone matrix constituents stimulate interleukin-1 release from human blood mononuclear cells.

To test the hypothesis that mononuclear cells are stimulated to release interleukin 1 (IL-1) by bone fragments released in the bone microenvironment during the remodeling cycle, we have investigated the effects of bone matrix and some of its constituents on IL-1 secretin from peripheral blood mononuclear cells (PBMC). Increases in IL-1 activity were observed when either PBMC or adherent monocytes, but not lymphocytes depleted of monocytes, were co-cultured with either human or rat bone particles but not with latex particles of similar size. Co-culture of PBMC with bone particles in a transwell system where the cells were physically separated from the bone particles, or with osteoblast- or osteoclast-covered bone particles, did not stimulate IL-1 release, indicating that a physical contact between PBMC and the bone surface is required for eliciting IL-1 release. This was confirmed by the finding of a lower stimulatory effect of bone particles pretreated with etidronate, a bisphosphonate which decreases the bone binding capacity of PBMC. Constituents of bone matrix, such as collagen fragments, hydroxyproline, and, to a lesser extent, transforming growth factor-beta, but not osteocalcin, alpha 2HS glycoprotein, fragments of either bone sialoprotein or osteopontin, and fibronectin, stimulated PBMC IL-1 release in a dose-dependent fashion. Collagen-stimulated IL-1 release was partially and specifically inhibited by a monoclonal antibody directed against the alpha 2 beta 1-integrin cell surface collagen receptor. These data demonstrate that products of bone resorption, known to be chemotactic for mononuclear cells, stimulate PBMC IL-1 activity. These findings may help explain previous documentation of increased IL-1 secretion by circulating monocytes obtained from patients with high turnover osteoporosis.

Animals↗
PubMed1990

Bisphosphonates directly inhibit the bone resorption activity of isolated avian osteoclasts in vitro.

Bisphosphonates are useful in treatment of disorders with increased osteoclastic activity, but the mechanism by which bisphosphonates act is unknown. We used cultures of chicken osteoclasts to address this issue, and found that 1-hydroxyethylidenediphosphonic acid (EHDP), dichloromethylidenediphosphonic acid (Cl2MDP), or 3-amino-1-hydroxypropylidene-1,1-diphosphonic acid (APD) all cause direct dose-dependent suppression of osteoclastic activity. Effects are mediated by bone-bound drugs, with 50% reduction of bone degradation occurring at 500 nM to 5 microM of the different agents. Osteoclastic bone-binding capacity decreased by 30-40% after 72 h of bisphosphonate treatment, despite maintenance of cell viability. Significant inhibition of bone resorption in each case is seen only after 24-72 h of treatment. Osteoclast activity depends on ATP-dependent proton transport. Using acridine orange as an indicator, we found that EHDP reduces proton accumulation by osteoclasts. However, inside-out plasma membrane vesicles from osteoclasts transport H+ normally in response to ATP in high concentrations of EHDP, Cl2MDP, or APD. This suggests that the bisphosphonates act as metabolic inhibitors. Bisphosphonates reduce osteoclastic protein synthesis, supporting this hypothesis. Furthermore, [3H]leucine incorporation by the fibroblast, which does not resorb bone, is also diminished by EHDP, Cl2MDP and APD except when co-cultured with bisphosphonate-binding bone particles. Thus, the resorption-antagonizing capacities of EHDP, Cl2MDP and APD reflect metabolic inhibition, with selectivity for the osteoclast resulting from high affinity binding to bone mineral.

Animals↗
PubMed1990

[Ultrasound in endodontics: S.E.M. verification].

After giving a brief illustration of the complex morphology of the root canal system, the Authors discuss the use of ultrasound in Endodontics. Following a critical evaluation of the literature and of the mechanisms of ultrasonic instruments, they illustrate their experience through a wide selection of S.E.M. photographs of teeth treated in vitro with sodium hypochlorite at various concentrations and for different lengths of time. They demonstrate the synergistic action between ultrasound and irrigation solutions, and conclude that the best results are with 2.5% hypochlorite for 1 minute.

Dental Pulp Cavity↗
PubMed1989

Cytoplasmic pH is regulated in isolated avian osteoclasts by a Cl-/HCO3- exchanger.

Osteoclast resorb bone in an acid compartment formed by the bone-attachment site. The low pH of the resorption compartment provides a lysosome-like milieu suitable for acid proteases to degrade collagen. Solubilization of the hydroxyapatite that makes up bone mineral consumes about 2 moles of protons per moles of calcium dissolved, requiring a massive proton flux to maintain a low pH in the resorption compartment. In order to determine how the osteoclast maintains a physiological cytoplasmic pH while secreting massive amounts of acid, we studied the intracellular pH of osteoclasts using esterified fluorescein derivatives while controlling the electrolyte composition of the medium. The principal finding is that osteoclasts have a high capacity for chloride/bicarbonate exchange which enables them to maintain normal intracellular pH in the face of a large loading of base equivalents. Thus, the overall process of proton secretion during bone resorption is similar to the polarized acid elimination by renal epithelia, involving a proton pump on one surface of the cell, and a Cl-/HCO3- exchange to maintain cytoplasmic pH.

Acid-Base Equilibrium↗
PubMed1989

Immunolocalization of beta 3 subunit of integrins in osteoclast membrane.

Utilizing isolated and cultured osteoclasts it has been possible to establish that they adhere to the substrate through specialized close contact areas, the podosomes, that in fully spread osteoclasts in vitro or in vivo are located within the clear zone. The cytochemical organization of podosomes has further been investigated in order to elucidate their possible involvement in the control of substrate recognition, that precedes bone resorption. An immunofluorescence investigation, performed utilizing human osteoclasts, shows that the beta 2 integrin subunit that in human monocytes is expressed and located in podosomes is absent in human osteoclasts, while the beta 3 subunit of the vitronectin receptor is expressed by osteoclasts, but not by other monocyte-derived cells and colocalizes with vinculin around the actin core of the podosome. The beta 1 subunit of the fibronectin receptors is also found, but with a diffuse pattern, in the osteoclast membrane. These results indicate that podosomes, while present in different cell types, may have in the osteoclast an unique cytochemical organization related to the peculiar function of this cell.

Bone Resorption↗
PubMed1988

Effect of vitamin A on bone resorption: evidence for direct stimulation of isolated chicken osteoclasts by retinol and retinoic acid.

The effects of retinol (vitamin A) and retinoic acid on primary cultures of isolated chicken osteoclasts have been studied. The experiments were performed to establish the direct actions of these two agents on the organization of cytoskeletal structures, on the acid phosphatase contents, and on the bone resorption activities of these cells. The results showed that by treating the cultures with retinol or retinoic acid, from 10(-8) to 10(-5) M, there were dose-related responses of the osteoclasts. Adhesion to the substratum was stimulated by increasing the number of cells exhibiting the specialized dot-like adhesion structures, or podosomes, which represent the active part of the sealing zone. The treatments also induced rearrangement of the microtubular patterns with reversible depolymerization of microtubules. Acid phosphatase activity was significantly higher both in vitamin A-treated osteoclasts and in their media. When [3H]proline-labeled bone particles were added to the retinoid-treated osteoclasts, the release of [3H]proline was increased significantly compared to controls. These results suggest that the two vitamin A metabolites cause several modifications of the metabolic status of isolated osteoclasts that result in augmented rates of bone resorption.

Acid Phosphatase↗
PubMed1988

The distribution of podosomes in osteoclasts cultured on bone laminae: effect of retinol.

Osteoclasts, isolated and purified from the medullary bone of calcium-deficient egg-laying hens, adhere to glass coverslips in vitro by means of specialized protrusions of the ventral membrane, denoted podosomes. These structures represent dotlike close-contact adhesion sites in which most cytoskeletal proteins involved in linking the plasma membrane to microfilaments are organized according to a specific and previously described pattern also shared by many oncogene-transformed cells. We show now that podosomes are not only a feature of osteoclasts adhering to artificial glass surfaces but are also present in the ventral membrane of osteoclasts adhering to bone laminae. Moreover, the quantity and the topography of podosomes may be modulated by retinol, which increases bone-resorbing activity of osteoclasts both in vivo and in vitro. A comparative transmission electron microscopy study of osteoclasts adhering on bone laminae in vitro or in vivo indicates that podosomes with identical features are present in the clear zone of the osteoclasts in either condition. Since podosomes are the sealing structures of the clear zone, podosome formation may represent one of the modifications involved in the reorganization process of the osteoclast that precedes bone resorption.

Acid Phosphatase↗
PubMed1988

The effects of parathyroid hormone or 1,25-dihydroxyvitamin D3 on monocyte-osteoclast fusion.

3H-thymidine-labeled blood monocytes were cultured with osteoclasts in the presence or absence of parathyroid hormone or 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in order to evaluate (1) the percentage of monocytes capable of fusing with osteoclasts, (2) if parathyroid hormone or 1,25(OH)2D3 influences the contribution of blood monocytes to osteoclast nuclear turnover. We found that within 24 hours of culture, about 8% of blood monocytes fuse with osteoclasts regardless of the presence of parathyroid hormone (PTH) or 1,25(OH)2D3. On the other hand, formation of non-osteoclastic giant cells by fusion of monocytes is enhanced by 5 x 10(-9) M 1,25(OH)2D3 but only in the presence of the bone resorptive cells.

Acid Phosphatase↗
PubMedDate not supplied

[Use of the perpendicular vertical in cephalometric analysis].

Cephalometric analysis is a useful diagnostic tool in orthodontics. The intracranial planes, commonly used as reference lines for cephalometric measurements, are not constant in the population. The variation of these references could constitute source of diagnostic error. On the light of this potential errors, the use of the vertical to the ground (or of its perpendicular line, orizzontal to the ground) constitutes a better reference for cephalometric measurements. The advantage of the vertical as reference is represented by its consistency in the same individuals and between different subjects.

Adolescent↗
PubMedDate not supplied

[Distalization of molars with magnets: biomechanical considerations].

Repelling magnets have recently been proposed to move maxillary molars distally. Although the technique presents some clinical indications, the biomechanics of tooth movement with magnets has not been clearly investigated. The results of the Author's experience suggest that the repelling magnets mainly generate a tipping movement of the crowns on the sagittal plane. The distal-tipping of the molars represents almost 50% of the total effect, the mesial tipping of the bicuspids-cuspids-incisors constitutes the remaining 50%. Also, on the horizontal plane, the force generated by the magnets tends to rotate the crowns of the molars palatally.

Adolescent↗
PubMedDate not supplied

[Biomechanical view of the histology of the TMJ].

Several reasons could explain the confusion and controversy that reign over every aspect of temporomandibular joint dysfunction. The discord includes not only diagnosis and treatment of the dysfunction, but even involves the anatomy and the histology of the TMJ. Different data in the literature indicate the major role of the biomechanical influences on the histology of the temporomandibular joint and on the adaptability of its structures. On the basis of these concepts, the histology of the TMJ has been revisited and a new functional interpretation of the microscopic morphology of the condyle, disc and periarticular connective tissue has been described.

Biomechanical Phenomena↗
PubMedDate not supplied

[A new experimental approach to the study of mechanical force in orthodontics].

Orthodontics is based upon the cellular response to biomechanical forces. Unfortunately, however, little is known about the manner in which cells respond to such forces. We have, therefore, devised an experimental model to permit morphologic and metabolic characterization of human cells subjected to a range of cyclic or static mechanical stimuli similar to those which may prevail in orthodontic-orthopedic therapy. This system involves attachment of cells to silicon collagen coated membranes which are then subjected to continuous or cyclic stretching by a motor coupled to a movable supporting frame. Because collagenase is an enzyme likely to play an important role in the ultimate effect of orthodontic forces, we evaluated the impact of biomechanical forces on secretion of this protein in a new experimental model in vitro. We found that cyclic stretching of human fibroblasts over a four day period approximately doubles collagenase production as compared to the control. Continuous stretching, on the other hand, is only 50% as effective in enhancing the enzyme release. In contrast, secretion of the inhibitor of metalloproteinases (collagenase inhibitor) is uneffected by either form of mechanical forces. Thus, the mechanical forces applied upon fibroblasts in this system promote gene expression in favor of matrix degradation. This model, we believe, will offer major insights into the cellular basis of orthodontics.

Cells, Cultured↗