Biomedical subjects

A Pizzoferrato

Publications and source records attributed to A Pizzoferrato.

At least 55 records · Page 3Linked to original sources

PubMed1994

[The capability of silicone prostheses to promote postoperative infections. An in-vitro study].

The authors have quantitatively evaluated and compared in vitro the Staphylococcus aureus and Staphylococcus epidermidis strain adhesiveness on various types of silicone used in surgery. The results show that there are some adhesiveness differences between the two assayed strains (S. epidermidis adhesiveness > S. aureus adhesiveness) and among silicone types (adhesiveness on soft silicones > adhesiveness on hard silicones). However all silicones are suitable substrata for in vitro bacterial adhesion.

Bacterial Adhesion↗

PubMed1994

Calcium regulating hormones in healthy elderly men: relation to intestinal calcium absorption.

Aged male subjects often have osteoporosis and it has been suggested that the cause is an age-related lack of vitamin D. We evaluated the calcium regulating endocrine mechanism in healthy aged males in order to verify this hypothesis. We studied serum levels of PTH and 1,25(OH)2D in relation to intestinal calcium absorption, radial bone mass density (BMD) and osteocalcin plasma levels in 30 healthy elderly men (61-88 yr.). 1,25(OH)2D levels and calcium absorption, assessed by oral strontium test, did not change with age with respect to a young control group. PTH was higher (p < 0.02) in the elderly than in the control group, and correlated positively with nephrogenous cAMP levels (p < 0.01; r = 0.65). Radial BMD (measured by single photon absorptiometry) was lower (p < 0.01) in elderly than in young subjects and negatively correlated with age (p < 0.01; r = -0.45). Osteocalcin levels, used as a mark of bone turnover, were unchanged. The data suggest that decreased 1,25(OH)2D levels are not a feature of normal male aging. Senile hyperparathyroidism could compensate for impairments in endogenous metabolism of vitamin D in elderly males and maintain calcium absorption at an efficient level, without increasing bone turnover.

Adult↗

PubMed1994

[Variations in the antibiotic sensitivity of bacterial strains after contact with the metals used for the construction of prosthetic implants].

The antibiotic sensitivity of 19 Gram-positive bacterial strains (11 Staphylococcus aureus and 8 Staphylococcus epidermidis) and 16 Gram-negative strains (8 Escherichia coli and 8 Proteus species) was evaluated after contact with stainless steel and with some metals compounding the alloys used for prosthetic devices. The hypothesis was that the resistance to antibiotic therapy of infections associated with prosthetic implants is also due to a modification in the sensitivity of microorganisms. The results, compared to those obtained from control tests, showed only slight variations in the antibiotic sensitivity of the strains put in contact with the metals. In Gram-positive strains, after contact with metals, the increase in sensitivity occurred more frequently than the reduction. In Gram-negative strains, the decrease in sensitivity was more frequent than the increase. Proteus strains showed sensitivity variations more frequently than Escherichia coli strains. Titanium and nickel induced the highest number of variations, both in Gram-positive and Gram-negative strains.

Anti-Bacterial Agents↗

PubMed1993

Production of prostacyclin and fibrinolysis modulators by endothelial cells cultured in the presence of polyethylene terephthalate.

The aim of this study was the evaluation of the in vitro production of prostacyclin, and of tissue plasminogen activator (tPA) and its inhibitor, PAI-1, by human endothelial cells cultured in the presence of polyethylene terephthalate (PET). After a 48 h contact between the cells and the polymer, the concentration of 6-keto-PGF1 alpha, a stable metabolite of prostacyclin, tPA, and PAI-1, was assayed on the supernatants. Contact of the endothelial cells with PET produced a highly significant reduction of 6-keto-PGF1 alpha with respect to control cultures. Tissue plasminogen activator concentration in the supernatants of the cultures in contact with the material was similar to that observed in the controls, while PAI-1 production was significantly reduced. It can be concluded that the contact between endothelial cells and PET determines a reduction in the platelet aggregability and an increase of the fibrinolytic activity due to a decrease in PAI-1, while tPA concentration remains unchanged.

6-Ketoprostaglandin F1 alpha↗

PubMed1993

In vitro evaluation of cell/biomaterial interaction by MTT assay.

The tetrazolium-based colorimetric assay (MTT test) measures only in vitro living cells and the results are directly related to the number of viable cultured cells. It has been adopted in immunological investigations, cancer research and, recently, biocompatibility evaluation. We used the MTT method with minor modifications to fit it to an in vitro study of biomaterial-cell interactions. The MTT assay was confirmed to be feasible, rapid and reproducible. Moreover, it showed a good correlation with other in vitro proliferation assays, such as the 3H-thymidine uptake assay. By using the MTT method and the ASTM procedure for extracting biomaterials, we quantified the in vitro cell compatibility of different metals and polymers.

Biocompatible Materials↗

PubMed1993

X-ray diffraction of newly formed bone close to alumina- or hydroxyapatite-coated femoral stem.

The study was focused on the bone tissue response to two types of ceramic coating [alumina and hydroxyapatite (HA)] obtained with a plasma-spray technique. The HA coating was performed on titanium stems, while the alumina coating was on chromium-cobalt-molybdenum stems. The investigation was carried out by means of micro-area X-ray diffractometric analyses and microdiffractometric analyses at the bone-implant interface. Moreover, the coating before and after implantation was analysed by means of the conventional powder X-ray diffractometric technique. This study demonstrated that 1 yr after implantation in animals the newly formed bone adjacent to the HA-coated hip prosthesis stems was mineralized as much as the pre-existing bone, while 24-64 months after surgery in humans the newly formed bone close to the alumina-coated hip prosthesis stems showed a lamellar and Haversian structure strongly demineralized, probably due to the release of aluminum ions from the alumina covering. The authors conclude that the X-ray diffraction allows the evaluation of the structural modifications of the ceramic coating, the bone formation rate close to the coating and the chemical nature of the particles released from the coating.

Aluminum Oxide↗

PubMed1993

Heparin surface treatment of poly(methylmethacrylate) alters adhesion of a Staphylococcus aureus strain: utility of bacterial fatty acid analysis.

Bacterial adhesion on biomaterials is an important cause of associated infection. Many authors have studied the adhesion mechanisms of bacteria on biomaterials. These studies were useful in making materials more and more refractory to bacterial adhesion. We analysed the gas chromatographic modifications of structural fatty acids of a Staphylococcus aureus strain after adhesion on two polymers, poly(methylmethacrylate) (PMMA), whose biological compatibility is known, and heparin-surface-modified PMMA (HSM-PMMA). We noted changes to the chromatographic peaks peculiar to the fatty acids of S. aureus for each tested material and particularly for HSM-PMMA.

Bacterial Adhesion↗

PubMed1993

Morphometric and microanalytical analyses of alumina wear particles in hip prostheses.

We analysed tissues harvested during 24 retrievals of hip joint prostheses, with one or both articular components made of alumina. We describe the morphology of wear particles, measure their size and analyse their chemical composition. We relate histopathological aspects to the parameters that characterize ceramic wear particles, and notice that tissue reaction relates to the physical aspect and amount of wear debris and does not necessarily depend on their chemical composition.

Aluminum Oxide↗

PubMed1993

Numerical and functional modifications in platelets induced by polyester coated by a hydrophilic polymer.

We evaluated the alterations in number, functionality and release reaction of the platelets contained in plasma, filtered through a polyester filter and coated with a hydrophilic polymer. The alterations in number were examined by counting before and after filtration. The morphological modifications were studied by determining the mean platelet volume. The functional alterations were analysed by a platelet aggregation test, induced by ADP and collagen. The presence of products from the release reaction in filtered plasma was studied using radioimmunoassays of beta-thromboglobulin, platelet factor 4 and thromboxane B2. The results obtained showed that the filtration of plasma through the material did not determine a significant platelet adhesion, did not alter the volume or the functionality of the platelets and induced no release reaction.

Biocompatible Materials↗

PubMed1993

[Assessment of the plasma phase of coagulation in platelet-rich plasma after passage through a special polyester filter].

The authors have examined the alterations in the coagulation pathway of plasma filtered through a polyester filter coated by a hydrophilic polymer. The activation of the coagulation pathway was evaluated by measuring prothrombin time, activated partial thromboplastin time, coagulation factors and fibrinopeptide A. The results obtained demonstrate that the examined filter does not induce significative activation of the coagulation pathway.

Blood Coagulation↗

PubMed1993

[The oral strontium load test in the assessment of intestinal calcium absorption].

A close correlation between calcium and strontium intestinal absorption has been described. In this study, a test using Stable Strontium has been assessed in women without abnormal calcium or bone metabolism, with no history of drugs which might affect calcium or bone metabolism. Decreasing values of Strontium intestinal absorption, according to the length of the postmenopausal period, have been observed. Besides, the Stable Strontium Test has been given in postmenopausal women with osteoporotic femur fractures. In comparison with age matched healthy women, this latter group showed a significantly lower Strontium intestinal absorption. Analogous behaviour has been reported for Calcium intestinal absorption.

Administration, Oral↗

PubMed1992

Microradiographic and histochemical evaluation of mineralization inhibition at the bone-alumina interface.

Microradiographic and histochemical tests were used to examine the behaviour of the bone tissue close to the alumina coating in cementless hip prostheses which were radiologically stable and explanted because of pain. The presence was detected of a decalcification stripe of the bone tissue with a thickness of about 300 microns, parallel to the prosthesis profile and in appearance not influenced by the roughness of the surface. This phenomenon was attributed to the presence of aluminium ions similarly to what happens in osteomalacic osteodystrophy in nephropathic dialysed patients. It was concluded that the phenomenon must be carefully considered because, in the long term, it could cause failure in the alumina coating.

Aluminum↗

PubMed1992

Metabolic changes in bone in old age.

The authors conducted a study on the effect of aging upon the factors which regulate calcium metabolism. Hormonal and biochemical tests were performed on samples from patients selected on the basis of sex, age, and other characteristics in order to determine the trend of these regulatory factors in middle and old age, with particular attention to osteoporosis in women. The authors propose several theories regarding the pathogenetic mechanisms of osteoporosis on the basis of this study as well as the literature.

Adult↗

PubMed1992

[In vitro and in vivo evaluation of the blood-biomaterial interaction].

The Authors, after a short description of the phenomena following the interaction between blood and biomaterials, take into consideration the different methods used in studying the in vitro, in vivo and ex vivo hemocompatibility, as well as the problems involved by each method and its contribution to the knowledge of hemocompatibility. The Authors report their experience on the in vitro study of the effects induced by some biomaterials on platelets and coagulation factors.

Animals↗

PubMed1992

In vitro methods to evaluate metal-cell interactions.

The aim of this study was to test different metals, widely employed in constructing prosthetic devices, by in vitro methods. Biological effects of such materials were analyzed through four different assays on human lymphocytes and granulocytes. The lymphocyte proliferation assay gave quantitative results, while the viability test showed the morphological appearance of the cells correlated well with previous results. NK cytotoxicity and granulocyte chemokinesis tests provided interesting data on leucocyte performance when challenged with metals. Therefore the present study adds new basic information on cell behaviour when metal products are present in the body, e.g. around devices implanted in human tissues.

Biocompatible Materials↗

PubMed1989

Comparative study of the thromboresistance of Dacron combined with various polyurethanes.

In vitro tests were carried out on Dacron samples differently knitted and on Dacron vascular prostheses coated with various urethanes. All the materials were put in contact with human platelet-rich plasma; the subsequent assay of three platelet released substances, i.e. beta-thromboglobulin, platelet factor 4 and thromboxane B2, as well as the quantification of platelet retention, were used to establish the degree of thrombogenicity of the material itself. In some cases Dacron-urethanes composites showed better thromboresistance than any other materials conventionally used in vascular surgery.

Biocompatible Materials↗

PubMed1988

Multilayered bead ceramic composite coating for hip prostheses: experimental studies and preliminary clinical results.

The clinical use of a new ceramic composite material made up of multilayered alumina beads and adhered to a ceramic surface with a high-temperature-melting bioglass is proposed. The result is a structure characterised by a 27% porosity and an average pore diameter of 400 microns. The actual structure of the parts as well as their interface interaction were determined by Raman laser. The mechanical resistance of the adherence of this coating for the ceramic substratum was good enough to resist the stress to which it was submitted when used for a new model of prosthetic acetabulum. Experiments with rabbits revealed the good biocompatibility of the composite. The osteoproductive activity of the tissue surrounding the implant led to the gradual filling of the porosity with trabecular structures. The preliminary results of the clinical experience which began in November 1985, confirm the good compatibility of the ceramic composite.

Aluminum Oxide↗

PubMed1988

Results of histological grading on 100 cases of hip prosthesis failure.

One hundred cases of hip prosthesis failure were classified on the basis of the different types of tissue reaction occurring around alloplastic material. The results revealed infectious phlogosis in 32% of the cases, phlogosis due to wear in 42%, phlogosis due to allergy in 1% and mixed phlogosis in 25%. The distribution of the type and degree of intensity of the phlogosis, in relation to the duration of the implant, is also highlighted. This new grading technique yields reproducible results.

Biocompatible Materials↗