Biomedical subjects

A M Gatti

Publications and source records attributed to A M Gatti.

At least 19 recordsLinked to original sources

PubMed2001

Is the tricuspid position suitable for testing replacement bioprosthetic valves in the sheep model?

BACKGROUND AND AIM OF THE STUDY: Glutaraldehyde may promote calcification in xenograft tissue by the action of toxic aldehyde group residues involved in the cross-link process. Post-fixation treatment with homocysteic acid (HA) neutralizes this toxicity by bonding aldehyde groups, and enhances biocompatibility on the basis of strongly electronegative sulfonic groups. Previous studies in a rat subcutaneous model showed significant long-term mitigation of mineralization of glutaraldehyde-fixed pericardium treated with HA. This study aimed to assess the anticalcific efficacy of HA in a valvular implant in growing sheep, and establish if the tricuspid position is suitable for testing replacement bioprosthetic valves. METHODS: Eleven stented 25 mm Pericarbon bioprostheses (seven HA-treated, four standard) were implanted in the tricuspid position of growing sheep. Infective endocarditis occurred in four prostheses. Among the remaining seven, three (two HA-treated, one standard) were explanted at 91 days (mid-term), and four (two HA-treated, two standard) at 140-141 days (long-term). All explants were studied by gross, X-ray, light, transmission and scanning electron microscopy, as well as by atomic absorption spectroscopy. RESULTS: No histological and ultrastructural difference in tissue preservation were observed between HA-treated and standard Pericarbon bioprostheses, either in the mid or long term. The mean calcium content of mid-term HA-treated explants was 9.55 mg/g compared with 16.26 mg/g in mid-term standard explants. Only one late standard explant failed as a result of severe stenosis caused by massive dystrophic calcification. Among four late explants, two showed significant increase in mineralization (HA-treated, 87.45 mg/g; standard, 181.20 mg/g), while two showed calcium contents similar to those in mid-term explants (HA-treated, 11.96 mg/g; standard, 17.32 mg/g). CONCLUSION: Post-fixation treatment with HA preserves structural properties after tricuspid implantation in growing sheep. The tricuspid implant in the sheep model failed to reproduce remarkable accelerated progressive calcification in all xenografts so as to demonstrate a significant difference between HA and standard explants. The tricuspid position for testing replacement bioprosthetic valves should be abandoned, and investigations repeated with the prosthesis in the mitral position.

Animals↗

PubMed1998

Detoxified glutaraldehyde cross-linked pericardium: tissue preservation and mineralization mitigation in a subcutaneous rat model.

BACKGROUND AND AIM OF THE STUDY: Glutaraldehyde is considered a promoter of calcification by the action of toxic aldehyde group residuals from cross-linking. Post-fixation treatment with homocysteic acid (HA), besides bonding aldehyde groups and neutralizing toxicity, should enhance biocompatibility due to the strongly electronegative sulfonic group. The aim of this investigation was to evaluate HA efficacy on tissue preservation and dystrophic calcification mitigation in glutaraldehyde cross-linked bovine pericardium (BP) using a subcutaneous rat model. METHODS: Four samples of BP, two with glutaraldehyde-HA and two with glutaraldehyde treatment, were implanted in each of 24 male Sprague-Dawley rats. Three rats were killed at 14 days, eight at 28 days, eight at 56 days and five at 84 days. Unimplanted glutaraldehyde-HA- and glutaraldehyde-treated samples served as controls. All samples were studied by gross examination, mammography, light transmission and scanning electron microscopy, and atomic absorption spectroscopy. The nature of mineralization was investigated by coupling techniques of scanning electron microscopy, electron microprobe analysis and X-ray powder diffraction. RESULTS: No histological and ultrastructural differences were found between glutaraldehyde-HA- and glutaraldehyde-treated BP, whether implanted or unimplanted. In both groups, calcification progressed with time, but significantly less after glutaraldehyde-HA treatment than after glutaraldehyde alone and at all time intervals (14.63 +/- 21.34 versus 43.17 +/- 15.99 at 28 days, p = 0.003; 56.42 +/- 40.20 versus 90.59 +/- 32.90 at 56 days, p = 0.008; 91.68 +/- 67.68 versus 156.23 +/- 17.85 at 84 days, p = 0.01). Differences were evident by mammography and histology (von Kossa stain). Electron microprobe analysis in both groups showed the composition of calcified nuclei to be calcium phosphate, stoichiometrically close to apatite (Ca5(PO4)3(OH)). The occurrence of crystallized apatite was supported by X-ray powder diffraction findings, the amount of crystallized apatite being higher in glutaraldehyde-treated samples. CONCLUSIONS: Post-fixation treatment with HA preserves BP structural properties and significantly mitigates mineralization of long-term subcutaneous implants.

Animals↗

PubMed1997

Mobilization and transplantation of Philadelphia-negative peripheral-blood progenitor cells early in chronic myelogenous leukemia.

PURPOSE: Mobilization of Philadelphia (Ph) chromosome-negative progenitors is now possible in many Ph1-positive chronic myelogenous leukemia (CML) patients who had received interferon alfa (IFN-alpha) with no cytogenetic response. In this pilot study, we used this approach in patients without prior IFN-alpha therapy to determine if the number and quality of mobilized progenitors would be increased and to evaluate the potential effect of these cells as autografts. PATIENTS AND METHODS: Twenty-two untreated patients were mobilized within 12 months of diagnosis. The treatment regimen consisted of the mini-ICE protocol. Beginning on day +8, granulocyte colony-stimulating factor (G-CSF) was used in all patients. Leukophoresis was performed as the patients were recovering from aplasia, when WBC count exceeded 0.8 x 10(9)/L. RESULTS: In 14 patients, (63%) the leukophoresis product was entirely Ph1-negative and in four patients the Ph1-positive cell rate was < or = 7%. Significant numbers of long-term culture-initiating cells (LTC-IC) and CD34+ Thy1+Lin- cells were found in most of the Ph1-negative collections that were tested. Twelve patients underwent autografting with their mobilized peripheral-blood progenitor cells (PBPC) (Ph1-negative collections, 10 patients; major cytogenetic response, two patients). All patients engrafted and are alive; six have Ph1-negative marrow 7 to 15 months after autografting. Posttransplant treatment was IFN-alpha combined with interleukin (IL)-2 because of the recent demonstration of synergistic activity in augmenting cytolytic activity. CONCLUSION: Intensive chemotherapy given in early chronic phase of CML is well tolerated and results in high numbers of circulating Ph1-negative precursor cells.

Adult↗

PubMed1996

Importance of microanalysis in understanding mechanism of transformation in active glassy biomaterials.

This work deals with a method to study bioactive glassy materials used for repair of bone defects in order to understand the mechanism of the bioactivity and thus have its in vivo behavior optimized. The study of these materials takes into account their changes in morphology, by means of electron microscopy, after implantation in different animal models and evaluates the mechanism of the bioactivity through semi- and quantitative microanalytical evaluations in order to quantify the phenomenon of glass corrosion and the formation of a chemical bond with bone. Special preparations of glass granules before implantation were prepared to microanalytically study surfaces with different permeabilities.

Biocompatible Materials↗

PubMed1996

Twelve years experience with high-dose therapy and autologous stem cell transplantation for high-risk Hodgkin's disease patients in first remission after MOPP/ABVD chemotherapy.

High-dose therapy followed by autografting can cure patients with aggressive Hodgkin's disease (HD) refractory or with early relapse to first-line combination chemotherapy. On the other hand, the eradication of the disease is rarely achieved in heavily pretreated patients. It has been suggested that patients with HD with very high risk characteristics at diagnosis, often relapse despite appropriate therapy with 7-8 drugs combination. Thus it seems to us that such patients are potential candidates for early autografting during first remission. Twelve years ago, we initiated a pilot study to investigate whether patients with very high risk characteristics, would benefit from early autografting. The application of early autografting was compared with our historical group of patients in complete remission after receiving MOPP/ABVD, who had the same negative prognostic characteristics, refused autografting and who did not receive other treatment after achieving complete remission. Among the 22 consecutive patients entered into the pilot study and autografted, 18 are alive and 17 (77%) remain alive in unmaintained remission at a median of 86 months. One patient (4%) died of interstitial pneumonitis in the transplantation group. Only 8/24 (33%) patients, who did not receive an autograft, are currently alive and disease free at a median of 89 months. In conclusion, the early application of autografting appears to improve the outcome in patients with very high risk HD who achieved remission with MOPP/ABVD.

Adolescent↗

PubMed1996

High-dose chemo-radiotherapy followed by autologous Philadelphia chromosome-negative blood progenitor cell transplantation in patients with chronic myelogenous leukemia.

Twenty-three patients with chronic myelogenous leukemia in early chronic phase (ECP) and not previously treated with alpha-interferon (IFN-alpha) (10 patients), in ECP but pretreated with IFN-alpha (<12 months) (seven patients) and in late chronic phase (LCP) pretreated with IFN-alpha (>12 months) (six patients) underwent autografting with Philadelphia (Ph) chromosome-negative blood progenitor cells (BPCs) (20 patients), or partially/totally Ph-positive BPCs (three patients), previously mobilized during the early phase of recovery after aplasia induced by intensive chemotherapy. The conditioning regimen consisted of high-dose chemotherapy alone or followed by total body irradiation (TBI). Recombinant G-CSF was given after BPCs infusion on day +8. All patients in ECP not pretreated with IFN-alpha are alive and five of them are Ph-negative in the marrow after autografting. Six of seven patients autografted with Ph-negative BPCs in the group of ECP pretreated with IFN-alpha (<12 months) are alive and two of them are still Ph-negative in the marrow. In the same group, the only patient transplanted with partially Ph-positive BPCs, died of blastic transformation 2 months after reinfusion. Three patients (two patients autografted with Ph-negative BPCs and one patient with Ph-positive BPC) in the group of LCP pretreated with IFN-alpha >12 months are alive but Ph-positive after autografting. The other three patients of the same group died of procedure-related toxicity (two patients) and blastic transformation (one patient). Seventeen patients (10/10 ECP not pretreated with IFN-alpha; 5/7 ECP pretreated with IFN-alpha and 2/6 LCP pretreated with IFN-alpha) of 23 autografted patients were treated with IFN-alpha +/- IL-2. Toxicities after autografting were mostly related to myelosuppression, particularly thrombocytopenia. All patients of the two groups pretreated with IFN-alpha developed febrile episodes during the aplastic phase following BPCs reinfusion. No patient autografted in ECP and those not pretreated with IFN-alpha developed febrile episodes. This is also probably due to the use of i.v. antibiotic and antimicotic prophylaxis when neutrophils were < or = 1 x 10(9)/l after autografting. Greater toxicity was observed in patients pretreated with IFN-alpha, being lethal in two cases in LCF. In conclusion, the "in vivo' manipulation approach employed in our institution is a safe procedure and it results in a high collection of Ph-negative cells in the blood if the cells are harvested: (1) in early chronic phase; (2) in early phase of recovery after chemotherapy-inducing aplasia; (3) in patients not extensively pretreated with IFN-alpha. The data presented here have shown encouraging trends in chronic phase of CML and offer new perspective for patients without an HLA-identical donor or for patients who do not respond to IFN-alpha.

Adult↗

PubMed1995

Physico-chemical observations on a failed Greenfield vena cava filter.

A Greenfield vena cava filter for the prevention of thromboembolism failed in vivo due to the displacement of 2 of the 6 legs and their subsequent break. The explanted stainless steel filter was analyzed with an electron microscope and energy dispersion system in order to assess the reason for the break. Fatigue and corrosion of the metal were responsible for the failure.

Corrosion↗

PubMed1994

Analysis of the in vivo reactions of a bioactive glass in soft and hard tissue.

A bioactive glass, S53P4, was implanted as granules subcutaneously in muscles and connective tissue of rabbits, as well as in the mandibular bone of a sheep. After the implantation period of 2-3 months, cross-sections were prepared and studied by scanning electron microscopy and energy dispersive X-ray analysis. The glass reacted essentially in the same way in all types of tissue. The granules consisted of an unreacted core and a reacted layer with a silica-rich and calcium phosphate-rich zone. Large hydroxyapatite crystals were occasionally found on top of the calcium phosphate surface of the granules implanted in soft tissue. On the basis of elemental analysis of the reaction layers it was found that the release of calcium from inside the glass is sufficient to account for the formation of the calcium phosphate surface layer, whereas the release of phosphate from the glass is not sufficient.

Animals↗

PubMed1993

In vivo behavior of a high performance duplex stainless steel.

An in vivo investigation of a new high molybdenum and nitrogen duplex stainless steel (25Cr--7Ni--4Mo--0.3N) has been performed. Cylindrical pins and specially developed devices, to test in static conditions the in vivo localized corrosion resistance, made of this new duplex steel and of a common austenitic stainless steel were implanted in rabbit's femurs for 6 and 12 months. After sacrifice, SEM observations and EDS microanalyses to detect metallic ion release were carried out on the femur sections surrounding the pins. Morphologic observations with stereoscope and SEM were performed on the metallic surfaces of the special devices in order to detect the presence of localized corrosion. Both ion release and localized corrosion were observed for the specimens made of austenitic stainless steel, but not for those made of 25Cr--7Ni--4Mo--0.3N duplex stainless steel.

Animals↗

PubMed1993

Subcutaneous recombinant human erythropoietin for the treatment of anemia in myelodysplastic syndromes.

Recombinant human erythropoietin (rhEPO) was administered subcutaneously to 13 anemic (Hb < 10 g/dl) patients with myelodysplasia (MDS). rhEPO was given 3 times a week at doses of 75-250 U/kg body weight, over a maximum period of 24 weeks. Five patients (38%) showed a response to rhEPO treatment. rhEPO was well tolerated and without relevant side effects throughout the study. All responding patients had low but detectable pretreatment circulating erythroid progenitor cells (BFU-E) and the response to rhEPO was associated with a significant increase in BFU-E (p < 0.01); concentrations of serum transferrin receptor (TfR) also consistently rose in all responding patients. Baseline erythropoietin (EPO) concentrations did not significantly differ between responders and nonresponders, although 4 out of the 5 responders had relatively low levels of EPO. In conclusion, subcutaneous rhEPO administration appears to be an effective treatment of anemia in a substantial subset of patients with MDS. Relatively low baseline EPO concentrations, detectable pretreatment circulating BFU-E and an early increase in the serum concentrations of TfR seem to be criteria for predicting response to rhEPO in patients with MDS.

Aged↗

PubMed1993

In vivo evaluation of an experimental dental HA-Ti implant.

A new design of Titanium dental implant, coated with Titanium oxide and with a Hydroxyapatite apex, was experimented in a Beagle dog's jaw for one year to evaluate the biocompatibility of the materials used and the biomechanical efficiency of the design. The explanted prosthesis and the surrounding bone were embedded in methylmethacrylate resin and the sections observed under Scanning Electron Microscopy (SEM), with an X-ray microprobe to check the interface with bone and the occurrence of ionic release. The results showed that the pin was well accepted by the bone. New bone grew on the metal surface developing a mechanical bond with the prosthesis. No ionic release of the metal was seen.

Animals↗

PubMed1991

Long-term behaviour of active glasses in sheep mandibular bone.

Granules of a glass (A) prepared according to Hench's formula and a new vitreous material for biological applications (AKRA 15) were used for repair of bone defects in the dental field. The behaviour of these materials implanted in holes drilled in sheep's mandibular bone was examined 4, 8, 12 month after implantation. Microradiographic analyses, optical and scanning electron microscopic observations, and X-ray microprobe evaluations were carried out using undecalcified, methacrylate-embedded sections of the jaw containing the granules. After one year the granules of A disappeared, but not important bone growth was observed also in the holes containing AKRA 15. SEM and microprobe showed: disappearance of Na and Si ions at different stages; increase of P and Ca up to 4 month and then decrease, but in different ways in the two glasses; unexpected appearance of K ions after 4 month only in AKRA 15.

Animals↗

PubMed1991

Short-term behaviour of two similar active glasses used as granules in the repair of bone defects.

The bioactivity of two similar vitreous materials used in the form of granules of 'critical' size was investigated in bone defects in jaws of two sheep. The granules consisted of Hench's Bioglass and another glass with the same chemical composition made in Italy. Two months after implantation, the sheep were killed and elemental analyses carried out on sections of the embedded jaws. The microanalyses for both the glasses showed a diffusion from the granules towards the surrounding tissue of silicon and sodium, and an inverse diffusion (from the surrounding tissue towards the granules) of calcium and phosphorus. The degradation for the Italian glass was slower than for the Bioglass. No significant osteoinduction was seen after that time at the interface of the glass granules or in the bone pocket.

Animals↗

PubMed1991

Physical characterization of acrylic bone cement cured with new accelerator systems.

In the attempt to substitute dimethyl-p-toluidine (DMPT), a toxic tertiary aryl-amine accelerator, into the formulation of acrylic cements, less toxic accelerator systems are developed. These systems consist of benzoyl peroxide (BPO) and unsaturated tertiary-aryl-amines, such as acryloyl- (ANP) and methacryloyl-(MNP) N-phenylpiperazine, which can be chemically incorporated in the polymerizing resin or, at least, result in less leaching from cured materials. In this work compressive mechanical properties and ageing tests for colour stability of acrylic cement cured with BPO and ANP or MNP have been considered. For compressive tests, cylindrical specimens were cured with BPO and equivalent molecular amounts of DMPT, ANP and MNP. Compressive yield stress (sigma y), strain at yield (epsilon y, %) and elastic modulus (E) gave very similar results for samples cured with DMPT and ANP, and slightly lower results for samples cured with MNP. In colour stability tests, the samples (disks of 1.5 cm diameter) were exposed to UV light at different irradiation times (up to 42 h). The evaluation of the colour change was performed with a digital analyser for images, and observed under scanning electron microscopy. From the obtained results, ANP appeared to be the best candidate as accelerator in the preparation of biomedical acrylic resins and composites.

Acrylic Resins↗

PubMed1991

Calcification of chemically treated bovine pericardium.

One of the most important problems arising in cardiac bioprostheses made with bovine pericardium and, more generally, with biologically-derived tissues is tissue calcification. The present study assessed four chemical treatments on patches of bovine pericardium, intended to avoid or minimize calcification. Pericardium specimens were treated with: A) 0.5% glutaraldehyde; B) 0.5% glutaraldehyde + 4% formaldehyde; C) same as A, but with a further neutralization treatment; D) acylation of fresh bovine pericardium. Circular samples of 1 cm diameter were subcutaneously implanted in the abdominal region of three groups of six rats. The explants were retrieved after 2, 4 and 8 weeks. The calcium content and the histological results showed better behaviour for C and D samples than with the commonly used fixation methods (A and B). The lowest calcification was observed with treatment D, even though its morphological structures were somewhat modified with homogenation of collagen bundles. Among the glutaraldehyde-based treatments, treatment C appears to be the most promising because the pericardium shows slower calcium accumulation with a diffusive pattern.

Animals↗

PubMed1990

Behaviour of tricalcium phosphate and hydroxyapatite granules in sheep bone defects.

Granules of hydroxyapatite (HA) and tricalcium phosphate (TCP) were implanted in separate holes drilled in mandibular bone of sheep to check the bone growth and in vivo behaviour of the materials. The experiment was performed in three sheep, killed respectively at 4, 8, 12 month. Samples of bone with the materials were explanted, microradiographed and sectioned to evaluate the interface under optical and electron scanning electron microscope. The hole, left empty as a reference, showed no full repair; whereas 4 month after implantation the TCP granules induce total repair of the hole. HA granules crumbled and no new bone induction was seen even 12 month after implantation.

Animals↗

PubMed1990

Comparative analyses among interfaces of some ceramic materials and bone in sheep.

Aim of this work is the evaluation of "in situ" implants in an animal model to study the interfaces that some ceramic materials for dental bone defects develop with bone and to check which material is more osteoconductive. In a sheep's jaw, eight holes were drilled and filled with six ceramic materials in granular shape. Two bilateral holes were left empty as reference. The ceramic materials were: porous tricalcium phosphate (TCP), porous hydroxylapatite (HA) and four bioactive glasses. The glasses differ for doping agents that affect the velocity of biodegradation in the living body. Monthly radiographs were taken and the X-ray pictures analyzed by means of a Video Display Computer in order to quantify the optical density changes occurred in the holes. After 4 months implantation, the segments of the jaw containing the materials were fixed in paraformaldehyde, embedded in methylmethacrylate and sectioned. The results obtained under the microradiograph, the SEM and the X-ray microprobe showed a good bone repair only with TCP granules. A great degradation was seen in HA granules and particularly in glasses. The degradation modified the structure and the composition of the glass granules, but it was not followed by a consequent bone deposition.

Animals↗

PubMed1990

[Monocrystalline aluminum dental implants in animals: a study of the peri-implant tissue].

After the extraction of two molars in a dog's jaw, a single crystal alumina screw was implanted. Monthly radiographs were taken and analyzed by means of a video display computer (VDC) to obtain densitometric informations about the interface. After one year implantation, the bone segment containing the prosthesis was fixed in 4% paraformaldehyde, embedded in methacrylate and sectioned by a microtome saw. The results in light microscopy with ordinary and polarized light, in SEM and X-ray microanalysis, show the presence of a thick connective tissue layer interposed between the screw and the bone. The histological findings confirm the results obtained through the VDC analysis of the radiographic images.

Absorptiometry, Photon↗