Biomedical subjects

S Stea

Publications and source records attributed to S Stea.

At least 55 records · Page 3Linked to original sources

PubMed1998

Growth hormone secretion and bone histomorphometric study in thalassaemic patients with acquired skeletal dysplasia secondary to desferrioxamine.

An auxological and endocrinological study was performed in 21 thalassaemic patients with growth retardation and skeletal dysplasia secondary to desferrioxamine. Bone metaphyseal proximal tibial or iliac crest biopsy was performed in six patients with severe genu valgum or non-traumatic vertebral compression. GH insufficiency/deficiency (GH deficiency: peak after stimulation test below 6 ng/ml) was found in 72% of our thalassaemic patients with skeletal dysplasia, but in only 41% of patients without skeletal dysplasia. Bone histology showed abnormal chondrocytes, alteration of staining pattern of cartilage, irregular columnar cartilage and lacunae in the cartilaginous tissue. The behaviour of bone tissue was unpredictable (presence of thick or thin osteoid layer). Bone microfractures were sometimes present. The bone microstructure showed scarce mineralization, which was evenly or irregularly distributed. The bone tissue apatitic phase was quantitatively reduced. The hardness of bone tissue was remarkably lower than that of normal bone in three out of six patients. In conclusion, iron chelation therapy in patients with acquired skeletal dysplasia seems to interfere with GH secretion. The early identification of clinical and radiological abnormalities of skeletal dysplasia is of paramount importance in preventing severe bone destruction.

Adolescent↗

PubMed1998

Comparison among three different biocoatings for orthopaedic prostheses. An experimental animal study.

One-hundred-eighty cylindrical monocortical titanium implants, 4mm diameter and 12mm long, with three different coatings: fluorohydroxyapatite (group A), hydroxyapatite (group B), and titanium oxide (group C), all applied by vacuum plasma spray were bilaterally, randomly implanted into the femurs and tibiae of twelve adult mongrel sheep. The sheep were divided into four groups (1, 2, 3 and 4) numbering three sheep each. Sheep of groups 1, 2, 3 and 4 were euthanized at two weeks, one month, three and nine months after implantation, respectively Biomechanical and histomorphological analysis were performed. Extraction torque increased over time in all groups until the nine months period. At all the studied periods, the bone-implant contact was higher in Groups A and B compared to Group C. However, only at nine months did this difference reach statistical significance (p<0.005 comparing Groups A and B to C). The results of this study show that all the three coatings could be recommended for clinical applications.

Animals↗

PubMed1997

High-performance liquid chromatography assay of N,N-dimethyl-p-toluidine released from bone cements: evidence for toxicity.

Five commercially available bone cements were analysed by high-performance liquid chromatography for detecting the residual content of an accelerator, the amine N,N-dimethyl-p-toluidine (DMPT), after curing. It was found that the concentration of DMPT in aqueous extracts decreases with time, being almost absent 7 days after curing. Differences were noticed among the cements; residual DMPT is higher in cements prepared with higher content of the amine. It is verified that DMPT's toxic effect on cell cultures is dose-related; a delay in the cell replication cycle is induced in vitro. Damage is reversible, thus justifying the low bone cement toxicity that is clinically ascertained.

Bone Cements↗

PubMed1997

In vitro complement activation after contact with pyrolytic carbon-coated and uncoated polyethylene terephthalate.

This study was undertaken to evaluate whether the pyrolytic carbon coating of polyethylene terephthalate induces complement activation. Complement activation induced by pyrolytic carbon-coated polyethylene terephthalate (PET+PC) in comparison with uncoated polyethylene terephthalate (PET) was assessed on whole blood collected with heparin. The activation of the classic pathway was evaluated by C4d fragment enzyme immunoassay. The activation of the alternative pathway was evaluated with Bb fragment enzyme immunoassay. The results show that uncoated PET activates the alternative pathway, but not the classic one. PET+PC does not induce complement activation, not even through the alternative pathway. Pyrolytic carbon coating therefore contributes to improving blood compatibility.

Journal Article↗

PubMed1997

Biomechanical, scanning electron microscopy, and microhardness analyses of the bone-pin interface in hydroxyapatite coated versus uncoated pins.

OBJECTIVE: To evaluate the bone-pin interface in hydroxyapatite coated versus uncoated pins. DESIGN: Eighty-four bicylindrical stainless steel external fixation pins were implanted in a test group of 14 sheep. One-half of the pins were coated with hydroxyapatite and the rest remained uncoated. INTERVENTION: Six coated pins were implanted in the left tibia of seven sheep, and six uncoated pins were implanted in the left tibia of the other seven sheep. In all sheep, the right tibia was left intact. During pin implantation, the final insertion torque was measured, and a linear external fixator was mounted on the pins. Then the medial tibial mid-diaphysis was exposed and a 5-mm resection osteotomy was performed. The sheep were killed six weeks after surgery. MAIN OUTCOME MEASURES: The extraction torque was measured on four pins removed from each sheep. Radiographic pin tract rarefaction was measured on all the pins. Two pins from each sheep were used for histologic, scanning electron microscopy (SEM), and microhardness analysis. Histomorphometric analysis was carried out on the SEM specimens at x 36 magnification. RESULTS: Radiographic pin tract rarefaction was significantly lower in the hydroxyapatite coated pins than in the uncoated pins (P < 0.001). Group average insertion torque was 960 +/- 959 N/mm in the hydroxyapatite coated pins, and 709 +/- 585 N/mm in the uncoated pins (p = not significant). Group average extraction torque was 1485 +/- 1308 N/mm and 298 +/- 373 N/mm, respectively (p = 0.0001). Histomorphometric analysis showed that the group average bone-pin contact was 50.7 +/- 16.9% in the hydroxyapatite coated pins and 27.6 +/- 7.1% in the uncoated pins (p < 0.01). Microhardness analysis showed that bone tissue close to the pins was softer than bone tissue far from them. CONCLUSION: Hydroxyapatite coating is an effective method of refining the bone-pin interface and may improve the clinical results of the external fixation technique.

Animals↗

PubMed1997

[Plasma protein adsorption on variously treated +polybutylene terephthalate].

BACKGROUND: The aim of the research was the evaluation of plasmatic protein adsorption on untreated polybutylene terephthalate, corona treated polybutylene terephthalate and polyvinylacetate coated corona treated polybutylene terephthalate. METHODS: Total proteins, albumin, immunoglobulins, fibrinogen, insulin and ostecalcin were determined on plasma after contact with these polymers. RESULTS: Unsignificant variations were observed for the assayed proteins. CONCLUSIONS: The conclusions are drawn that the tested materials do not adsorbe significantly the most important plasmatic proteins.

Adsorption↗

PubMed1996

Improvement of the bone-pin interface with hydroxyapatite coating: an in vivo long-term experimental study.

The present study was designed to comparatively evaluate the bone-pin interface in a long-term unloaded experimental study in two groups of pins, uncoated and coated with hydroxyapatite. Forty pins made of stainless steel were used. Half of the pins were plasma-sprayed with hydroxyapatite, and the other half remained uncoated. Four adult sheep were selected. Each sheep tibia was implanted with five pins. Two sheep were euthanized 4 months after surgery and the remaining two 12 months after surgery. Extraction torque was higher in the hydroxyapatite-coated pins compared with the uncoated ones at both 4 (p < or = 0.0005) and 12 months (p < or = 0.0005) after implantation. The histological patterns observed in the sheep euthanized 4 and 12 months after implantation were very similar. An extensive bony coverage of the hydroxyapatite-coated pins without any coating resorption and delamination from the metallic substrate was observed. Fibrous tissue encapsulation was found in the uncoated pins. These results demonstrate that the hydroxyapatite coating significantly improved the bone-pin interface. A similar improvement of bone-pin interface rigidity in many clinical situations is likewise possible.

Animals↗

PubMed1996

Disposition and bioavailability of ceftazidime after intraperitoneal administration in patients receiving continuous ambulatory peritoneal dialysis.

This study investigated the disposition and bioavailability of ceftazidime when it was given intraperitoneally. Seven patients were given 1 gm of ceftazidime intravenously, and 1 wk later, the same dose was given intraperitoneally. After both intravenous and intraperitoneal dosing, serum and peritoneal dialysate samples were obtained at set time intervals over a 24-h period. High-performance liquid chromatography was used to determine the ceftazidime concentrations in the serum and dialysate samples. Inspection of the concentration versus time data after intraperitoneal dosing demonstrated that serum ceftazidime concentrations reached therapeutic (> 8 micrograms/mL) levels within 30 min and remained in the therapeutic range for the entire 24-h period. Simulation of a variety of ceftazidime dosing regimens using the mean pharmacokinetic parameters from this population of patients suggests that a regimen of 1.5 gm administered intraperitoneally every 24 h produces trough serum drug concentrations (approximately 40 micrograms/mL) similar to those achieved with a standard regimen of 1.0 gm given intravenously every 24 h in patients undergoing continuous ambulatory peritoneal dialysis. It was concluded that the intraperitoneal dosing of ceftazidime in these patients is an equally effective and a more convenient alternative to its administration.

Aged↗

PubMed1995

Silicone breast implants: the role of immune system on capsular contracture formation.

We evaluated the role of the immune system in the pathogenesis of the periprosthetic capsular contracture, the most frequently occurring complication following the implant of silicone prostheses. Peripheral blood samples from 22 patients with silicone-gel-filled implants were examined. In all cases a capsule was felt by palpation, and it was classified according to the Baker scale. Ten patients (group 1) had a Baker 2 contracture, and 12 (group 2) had severe contracture rated 3 and 4. The cells positive to antigens CD3, CD4, CD8, HLA-DR, CD19, CD25, CD57, CD16, and CD14, and the cytotoxic activity of the lymphocytes on target cells K562 were assessed by cytofluorimetric analysis. At time 0 there were no statistically significant differences between patients and normal subjects, nor between the two groups. At 48 h, the group 2 patients had a number/mm3 of cells CD57 + significantly higher than both group 1 and control group (P < .05). In group 1 patients, the cytotoxic activity was similar to that of normal subjects, whereas in group 2 it was significantly increased, in respect to both the controls (P < .05) and group 1 (P < .001). In all groups, the contact of the lymphocytes with the silicone extract did not modify either the antigen expression or the lymphocyte functional activity. On the basis of these results we hypothesize the involvement of the immune system in the formation of the capsular contracture around the prosthesis.

Adult↗

PubMed1995

Assessment of viability and proliferation of in vivo silicone-primed lymphocytes after in vitro re-exposure to silicone.

The functional response of peripheral blood lymphocytes isolated from 22 patients with silicone gel-filled breast implants was assessed after in vitro re-exposure to silicone. Using cell culture test methods to quantify proliferation and viability and/or activation of lymphocyte microcultures, i.e., the uptake of tritiated thymidine (3H-TdR uptake test) and the reduction of formazan salts (MTT assay), interesting data were obtained. Peripheral blood lymphocytes purified from patients wearing silicone gel-filled breast implants react in vitro to silicone showing a statistically significant increase of both proliferation and viability, while healthy subjects do not respond on in vitro exposure to silicone. Differences resulted even more statistically significant when patients were divided into two groups depending on the type of surgery they underwent: patients with breast augmentation for aesthetic reasons seem to have an increased responsiveness in vitro to silicone compared to patients who experienced a reconstructive surgery of the breast. Although they are still preliminary, being referred to a limited population, these results suggest that the lymphocytes of patients with silicone gel-filled breast implants could be sensitized in vivo toward silicone; the re-exposure of these cells to silicone leads to a higher functional response which could be looked for by using quantitative in vitro test methods.

Adult↗

PubMed1995

Microhardness of bone at the interface with ceramic-coated metal implants.

We evaluated bone microhardness at the interface with hydroxyapatite-coated stainless-steel pins used in an external fracture fixation system. Pins were transversally inserted into the diaphyses of sheep tibiae and were loaded in for 6 weeks. Uncoated pins were implanted as controls. Microhardness analysis, based on the measure of the resistance of the bone to the penetration of a small diamond pyramid, yielded an accurate and reproducible measure of the mineralization degree and of the orientation of collagen fibers. Bone tissue close to the pin is less hard than bone tissue far from it. Moreover, the presence of hydroxyapatite coating on the pins did not significantly affect bone hardness; actually, the mean hardness at the interface with the pins was 56.9 Vickers degrees, whereas at the interface with the uncoated pins it was 62.2. It can be concluded that, 6 weeks postsurgery, the bone growing into the threadings of a loaded screwed implant reached maturity at a degree lower than that of the host bone in both uncoated and coated implants.

Animals↗

PubMed1995

Microstructural investigation of bone-cement interface.

We evaluated the microstructural characteristics of newly formed bone tissue at the interface with cement. The bone-cement interfaces of the femoral components of nine hip prostheses retrieved after loosening were investigated by means of X-ray diffraction on microareas and microhardness. The bone far from the interface of two stable prostheses was used as a control. The newly formed bone adjacent to cement in the loosened prostheses showed a maturity degree lower than that of bone adjacent to cement in stable prostheses. The lattice parameters of bone apatite did not show significant variations as compared to the reference values. Bone trabeculae at the interface with loosened prostheses often showed an osteoid lining characterized by a strongly demineralized lamellar and haversian structure. Radioopaque cement particles are sometimes found in the trabecular bone tissue around the prosthesis.

Apatites↗

PubMed1995

In vitro effects of bone cements on the cell cycle of osteoblast-like cells.

The effects of orthopaedic cements on the proliferation and cell cycle of in vitro cultured MG63 osteoblast-like cells were examined. Five different cements were mixed and extracted at different time intervals (15 and 60 min, 6, 24 and 48 h). Cell proliferation inhibition (CPI) was evaluated after 72 h culture as the toxicity parameter. As for the toxicity degree, the extracts were considered to have 'high toxicity' (CPI > or = 50%), 'medium toxicity' (50% > CPI > 25%), 'low toxicity' (CPI < or = 25%) and 'no toxicity' (CPI = 0). Cell cycle phases of MG63 cells were evaluated at 24, 48 and 72 h by flow cytometry; the DNA content was assessed using the propidium iodide uptake and the percentage of cells in the S phase was determined using 5'-bromodeoxyuridine uptake. According to our results, the toxicity is inversely correlated with the time interval between polymerization and extract preparation, and is different according to the cement type. For some cements the effects are still observed 48 h after polymerization. The damaging effect is not linked to a specific phase of the cell cycle, nor does it hamper the restarting of cell proliferation at 72 h.

Bone Cements↗

PubMed1995

Platelet and coagulation factor variations induced in vitro by polyethylene terephthalate (Dacron) coated with pyrolytic carbon.

The haemocompatibility of polyethylene terephthalate (Dacron) coated with pyrolytic carbon was examined in vitro, evaluating its capability of inducing adhesion and platelet activation, and of modifying the intrinsic coagulation pathway. Platelet adhesion was evaluated by counting platelets before and after in vitro contact of human plasma with the material under examination. Platelet activation was evaluated by determining platelet factor 4 (PF4) and thromboxane B2. Intrinsic coagulation pathway alterations were studied by determining activated partial thromboplastin time (APTT) and the activity of single factors. The results obtained show that pyrolytic carbon-coated Dacron induces platelet adhesion, reduction in platelet volume and lower increase in thromboxane production than that obtained after contact with uncoated Dacron. Pyrolytic carbon-coated Dacron does not induce PF4 release, contrary to uncoated Dacron induces a significant release. Moreover, pyrolytic carbon-coated Dacron, induces a significant extension of APTT by reducing the activity of intrinsic pathway factors, particularly factor XI.

Biocompatible Materials↗

PubMed1995

Adhesive protein expression on endothelial cells after contact in vitro with polyethylene terephthalate coated with pyrolytic carbon.

This research aims at evaluating the expression of some adhesive proteins on endothelial cell surface with polyethylene terephthalate coated with pyrolytic carbon (PET + PC). Twenty-two different cultures of human umbilical vein endothelial cells (HUVECs) were put in contact with PET + PC. Both HUVECs grown without the biomaterial and HUVECs incubated with endotoxin were used as control. After 24 h, platelet endothelial cell adhesion molecule-1 (PECAM-1), endothelial leukocyte adhesion molecule-1 (ELAM-1), intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were evaluated on the cells by monoclonal antibodies and flow cytometry. In agreement with the literature, after 24 h the culture incubated with endotoxin determined a significant increase in the percentage of positive cells for ELAM-1, a significant increase in fluorescence intensity of ICAM-1, and a significant increase in the percentage of positive cells and fluorescence intensity for VCAM-1. After 24 h of culture with PET + PC, no significant variations in the antigens examined were observed. This demonstrates that such material does not activate in vitro the proteins involved in the adhesion between leucocytes and endothelium or in the adhesion between endothelial cells themselves.

Antigens, Differentiation, Myelomonocytic↗

PubMed1995

Endodontic cements induce alterations in the cell cycle of in vitro cultured osteoblasts.

The effects of endodontic cements on the cell cycle of MG63 osteoblasts cultured in vitro have been examined. Three groups of compounds were tested. Group I encompassed zinc oxide- and eugenol-based cements (Tubliseal, Argoseal, N2), group II consisted of cements with a phenol group other than eugenol (AH26, Forfenan, Methode R/R), and group III included CaOH-based cements (Biocalex, Endocalex). The cell cycle of MG63 cells was analyzed by flow cytometry; the DNA content was evaluated by means of the propidium iodide uptake method, whereas the proportion of cells in the S phase was defined by the incorporation of bromodeoxyuridine later revealed by a specific antibody. The results showed that some root canal sealers could hamper the periapex healing processes by inhibiting the cell proliferation through a selective action on different phases of the cell cycle.

Analysis of Variance↗

PubMed1995

[Evaluation of the biocompatibility of medical devices based on European standards].

Several issues concerning the biocompatibility) testing of medical devices as stated in European directive 90/385 and 93/42 are discussed. The authors describe the fundamental characteristics that biomaterials should have to be employed in the human body, the assays useful for testing different aspects of biocompatibility and the harmonized regulations already available or under development. The testing protocol applied by the a. in their Lab covering many issues of biocompatibility is presented: a body of experience was gained over the years and it has been revised under the new regulatory items. In conclusion, the biocompatibility of devices must be assessed following the European harmonized standards, the available. Where proper standards are still lacking, feasible testing methods, even if not officially adopted yet, have to be used.

Biocompatible Materials↗

PubMed1994

Mutagenic potential of root canal sealers: evaluation through Ames testing.

The mutagenic potential of 12 commercially available dental cements and of two 'pure substances' (zinc oxide and eugenol) used in root canal filling were examined. The cements were prepared according to the manufacturers' indications and set for defined times. Ames tests were performed in their extracts by using Salmonella typhimurium strains TA 98 and TA 100. The results showed that most cements present strong bactericidal activity that disappears or decreases remarkably in time. One of the tested cements showed mutagenicity with both Salmonella strains. Two cements yielded doubtful results. The remaining cements and the two 'pure substances' showed no mutagenic potential. The authors conclude that it is convenient to examine endodontic cements with the Ames test and to eliminate those that present mutagenicity in time.

Animals↗