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A Shteyer

Publications and source records attributed to A Shteyer.

At least 37 records · Page 2Linked to original sources
PubMed1987

Hormone-responsive cells derived from human dental papilla: characterization in vitro and in vivo in diffusion chambers.

Cells of the dental papilla are capable of odontoblastic, fibroblastic, and endothelial differentiation and formation of dentin and the dental pulp. In the present study dental papilla cells, obtained from human tooth buds (HDP cells), were cultured in vitro through 3 to 7 passages. After exposure to prostaglandin E2 there was a marked decrease in intracellular cyclic AMP (cAMP) levels as compared to hormone-free controls. Parathyroid hormone and calcitonin had stimulatory effects with 1 and 2 log increases in cAMP, respectively. The HDP cells showed moderate activity of alkaline phosphatase, 1 log higher than that of hamster kidney fibroblasts (BHK 13) and 1 log lower than that of osteoblastic osteosarcoma cells (ROS 17/2). When cultured for 4 or 8 wk in diffusion chambers (DC) implanted in athymic mice, many of the HDP cells underwent odontoblastic morphodifferentiation with very long, single processes extending into the matrix. This matrix contained banded and unbanded collagen fibers. Neither light nor electron microscopy of the DC content revealed mineral deposits. These results suggest that HDP cells have an intrinsic potential for partial odontoblastic differentiation; inductive signals like those originating from odontogenic epithelium are probably essential for the completion of hard tissue formation.

Alkaline Phosphatase↗
PubMed1987

Enhancement by extracts of mineralized tissues of protein production by human gingival fibroblasts in vitro.

Non-confluent cell cultures were exposed to both guanidine and guanidine-EDTA extracts of cementum, dentine and alveolar bone, at concentrations from 2 to 50 micrograms/ml for 48 h. The cells were radioactively labelled during the last 24 h. Total protein production was measured via incorporation of radioactive proline; collagen production was estimated by digestion of the radioactive protein mixture with bacterial collagenase. All guanidine-EDTA extracts elicited statistically-significant increases in total protein production when compared to controls. At 50 micrograms/ml of extract, the increase in protein production was 340, 143 and 338 per cent for bone, cementum and dentine, respectively. Similar results were obtained for collagen production. Guanidine-EDTA extracts also stimulated an increase in the production of specific proteins, as ascertained by gel electrophoresis. In contrast, the guanidine extracts had no effect on either protein or collagen production. Thus the functions of gingival fibroblasts can be altered by proteins from associated mineralized tissues. Identification of such proteins and their biological functions would enhance knowledge of the mechanisms that regulate connective-tissue regeneration.

Alveolar Process↗
PubMed1987

Characteristics of a neutral amino acid transport system (system A) in osteoblastic rat osteosarcoma cells.

Transport of alpha-aminoisobutyric acid (AIB) in the clonal, osteoblastic-like cell line, ROS 17/2, was characterized. AIB transport was time-, temperature- and Na+-dependent. Both ouabain and monensin inhibited AIB transport in these cells. AIB uptake followed Michaelis-Menten kinetics with an apparent Km = 0.57 mM and a Vmax = 4.07 nmol/30 min/plate. These characteristics are consistent with the presence of system A neutral amino acid transport in ROS 17/2 cells. Exposure of ROS 17/2 cells to either parathyroid hormone or dibutyryl cyclic AMP (db-cAMP), but not to dibutyryl cyclic GMP (db-cGMP), markedly stimulated AIB transport. This suggests that extracellular stimuli which enhance osteogenic responses in this cell type, coordinately upregulate system A transport.

Aminoisobutyric Acids↗
PubMed1987

Stimulation of mannose incorporation into rat osteoblastic osteosarcoma cells by parathyroid hormone.

Agents considered to alter cAMP accumulation in bone cells were evaluated for their effects on protein production and sugar incorporation by bone cells. Total protein production or mannose incorporation by cells and in media were measured by the amount of radioactivity incorporated into trichloroacetic-acid precipitable fractions. Incorporation of radioactive leucine into the cellular and secreted proteins was linear over 5 h; radioactive mannose incorporation was linear only up to 2 h. Cells were also incubated with selected agents and radioactive mannose or leucine for 2 h. Addition of parathyroid hormone (PTH), isoproterenol or dibutyryl cAMP to osteoblasts resulted in a significant increase in mannose incorporation; dibutyryl cGMP and butyric acid had no effect on mannose incorporation. None of the agents altered total protein production. Thus PTH stimulates mannose incorporation into osteoblasts and this effect is, at least in part, modulated by cAMP.

Animals↗
PubMed1986

Formation of calcifying matrix by osteosarcoma cells in diffusion chambers in vivo.

The potential of clonal rat osteosarcoma (ROS) cell lines to form mineralized matrices was assessed in diffusion chambers in vivo. Diffusion chambers were inoculated with osteoblastic (ROS 17/2 and its subclone ROS 17/2.8) and non-osteoblastic (ROS 24/1) clonal lines and implanted either intraperitoneally into athymic mice or subcutaneously into syngeneic ACI rats. Control chamber cultures of rabbit marrow or spleen cells were also incubated in athymic mice. Light and electron microscopy of chambers with ROS 17/2 and ROS 17/2.8 cells revealed production of mineralized matrices typical of osteosarcoma and characterized by abundance of collagen fibrils and associated mineralizing nodules. ROS 24/1 cells produced similar collagenous matrices, but these were devoid of mineral. The present experiments, carried out independently in two different laboratories, demonstrate the potential of ROS cells to produce a mineralized matrix. This corroborates previous studies on other osteoblastic features of these cell lines.

Animals↗
PubMed1986

Inflammatory cells and bacteria in pericoronal exudates from acute pericoronitis.

The present work is one in a series of studies carried out to verify the relationship between bacteria and gingival tissues in pericoronitis. Exudates from 6 cases of acute pericoronitis were examined by light and electron microscopy, including ultrathin sections and negative staining. While bacterial phagocytosis was prevalent in all the exudates studied, spirochetes, which were the predominant microorganisms, were not observed being phagocytized by PMNs or macrophages. The presence of spirochetes in pericoronitis as compared with acute necrotizing ulcerative gingivitis is discussed.

Acute Disease↗
PubMed1985

Pericoronitis: a reappraisal of its clinical and microbiologic aspects.

Pericoronitis is an infectious disease of the operculum overlying an erupting or semi-impacted tooth. It manifests itself mainly in late adolescence and young adulthood and nearly always occurs around the lower third molar. The distinctive location, age, clinical picture, and link with predisposing factors warranted a reappraisal of pericoronitis and its etiology. Spirochetes and fusobacteria proved prevalent at all stages of the disease. The presence of these microbacteria may provide a clue as to the late appearance, particular location, and singular clinical picture of pericoronitis. The fact that spirochetes and fusobacteria are also found in acute necrotizing ulcerative gingivitis, and have been associated with alveolar osteitis, indicates a possible relationship between these disorders and pericoronitis.

Adolescent↗
PubMed1981

Salivary calculi: ultrastructural morphology and bacterial etiology.

Ultrastructural morphology of 16 salivary calculi was studied by means of transmission and scanning electron microscopy. The external surface was mostly globular or coarse, and on high magnifications and features could be divided into four main groups: a) amorphic calcified deposits covering extensive areas, b) other areas covered with crystals in a variety of arrangements, c) heavy accumulations of calcified rod-like and filamentouslike microorganisms, and d) platelet crystals in juxtaposition to calcified microorganisms in several areas. In most calculi the split area was found to be laminated. It is suggested that microorganisms have an important role in the formation and growth of salivary calculi.

Bacteria↗
PubMed1979

Odontoma in the subcondylar region.

An instance of a compound odontoma in the condylar process in a 24-year-old female is described. Location of odontomas in the coronoid or condylar processes were not reported. A hypothesis of migration of the third molar bud into the condylar region, an interfering local factor such as trauma or infection are suggested as aetiologic factors to the tumour in this case. Pre-operative radiographic localisation of the mass, are essential for treatment planning. An intra-oral approach was the treatment of choice.

Adult↗