Biomedical subjects

M Fini

Publications and source records attributed to M Fini.

At least 163 records · Page 9Linked to original sources

PubMed1997

Influence of membrane oxygenators on the pulsatile flow in extracorporeal circuits: an experimental analysis.

An experimental analysis was carried out to evaluate the effects induced by two typical extracorporeal circuits on the pressure and flow generated by a roller pump with a pulsatile module. The hydraulic behaviour of the patient was simulated by means of a mechanical mock-up system consisting of a few lumped parameters reproducing the physiologic vascular impedance. Pressure and flow tracings were acquired at different locations along the circuit using an automatic data acquisition system. Nine lest conditions with different pulse frequency and systolic time values were examined using a mean volumetric flow rate of approximately 4 l/min. A complete analysis of the results obtained in terms of pressure drops and inflow-outflow differences across the components of the arterial line, as well as the calculation of the hydraulic pulsatile power along the circuit, allowed us to assess the influence of the various components upon the pulsatility. The results indicated that the membrane oxygenators tested slightly affect the pulsatility of the flow and the pressure; on the contrary the arterial pipe line is responsible for large damping and head losses. To optimize the use of pulsatile flow for cardiopulmonary bypass it is necessary to reduce the length of the arterial pipe lines thus integrating the circuit as much as possible.

Cardiopulmonary Bypass↗

PubMed1997

[Effects of synthetic salmon calcitonin and alendronate on bone quality in ovariectomized rats].

BACKGROUND: The aim of this study was to assess the effect of calcitonin (CCT) and alendronate (ALN) on bone quality through histomorphometric, histological, densitometric and crystallographic evaluations in an experimental model of osteoporosis obtained in ovariectomized rats. METHODS: The animals were randomly assigned to the treatment with CCT (2 IU/kg/day, N-12) or with ALN (6 micrograms/kg/day, N-12) given subcutaneously, starting three months after ovariectomy: treatment lasted 60 days. Six rats untreated after ovariectomy and other 6 non ovariectomized (intact) were taken as controls. At the end of treatment the animals were sacrificed and femurs explanted for laboratory examinations. Results were evaluated by an ANOVA followed by the Tukey's test when appropriate. RESULTS: The histomorphometric analysis showed a significant increase of the trabecular bone volume and of the cortical bone thickness either with CCT and ALN in comparison with the ovariectomized untreated controls. Optic and electronic microscopy examinations suggest a higher bone remodeling after ALN than after CCT, but accompanied by areas of imperfect mineralization, and more irregular osteon and collagen fibres disposition. The densitometry carried out at the femoral head and diaphysis showed a similar bone mass increase following either CCT and ALN, but significantly higher in comparison to the untreated controls. At the diaphysis level ALN was superior in increasing the bone mass also when compared to the intact rats. The mineralogic exams showed that CCT acted on the re-elaboration of the mineral phase approaching the molar ratio Ca/PO4 to the physiological values typical of senescence, and crystallography revealed that the formation of hydroxyapatite crystals follows a physiological mineral redeposition: those phenomena were not observed for ALN. CONCLUSIONS: In conclusion both CCT and ALN could reduce the bone loss due to osteoporosis, by increasing the bone mass and thickness. Nevertheless the submicroscopic and chemical bone structure are less similar to the physiologic ones after treatment with ALN.

Alendronate↗

PubMed1997

Bioabsorbable polyphosphazene matrices as systems for calcitonin controlled release.

To provide a suitable delivery system for the calcitonin controlled release 80 mg bioabsorbable polyphosphazene matrices were obtained with entrapped 50 or 250 micrograms calcitonin. The in vitro behaviour demonstrated a release burst for about 24 hours, followed by a period of slow release of the peptide lasting for weeks. Matrices containing 250 micrograms calcitonin were implanted under general anaesthesia in osteoporotic female rats, while a group of animals (control group) received unloaded matrices. After thirty days a second batch of matrices was implanted in both groups to prolong the period of treatment until two months. The explanted matrices were histologically evaluated together with the surrounding tissues, and the dosage of the residual calcitonin was also performed. Results demonstrated the good biocompatibility of the system and the complete release of the calcitonin from the matrices 30 days after implantation. The therapeutic effect, after sixty days of treatment was confirmed by the better densitometric values observed in the femoral bone of treated animals than in controls.

Animals↗

PubMed1996

Effectiveness of a bioabsorbable conduit in the repair of peripheral nerves.

A new conduit made with a bioabsorbable copolymer, poly (L-lactide-co-6-caprolactone), was evaluated in an animal model as a guide for nerve regeneration. The conduit had an inner diameter of 1.3 mm and a wall thickness of 175 microns. Segments of length 1.2 cm were interposed between the proximal and distal stumps of transected ischiatic nerves in Wistar rats, bridging a nerve gap of 1 cm. All of the procedure was performed under general anaesthesia using microsurgical techniques. Controls were performed at 1, 3 and 6 months and it was demonstrated that the conduit was still undamaged after 30 d. Progressive signs of degradation appeared at 90 and 180 d. Nerve regeneration in the lumen was effective as confirmed by histological and electron microscopical investigations. These preliminary results emphasize the interesting properties of the conduit with regard to the achievement of a neural prosthesis.

Absorption↗

PubMed1996

Pericellular pO2 as an alternative method to test cytotoxicity.

Pericellular pO2 (ppcO2) was compared with the release of cytoplasmatic enzyme lactate dehydrogenase (LDH) and mitochondrial metabolic function (tetrazolium salt reduction, MTT) as an alternative method to evaluate cytotoxicity. L-929 cells were seeded and incubated with 3 different control materials to test their cytotoxicity effects by these methods. High density polyethylene and copper were respectively used as negative and positive controls, while a 0.9% NaCl solution was as reagent control and extraction vehicle. PpcO2 was measured by a rod polarographic Clark-type probe connected to Licox pO2 computer (GMS mbH, Kiel, Germany). One-way ANOVA test showed significant differences among groups regarding every methods (p < 0.0005). The comparison of the mean variation coefficients of three methods showed no significant differences. In addition, a significant correlation was found between ppcO2 and MTT (r = 0.621; p < 0.001) as well as ppcO2 and LDH data (r = 0.474; p < 0.001). In conclusion, ppcO2 may be considered a reliable, safely and alternative method to test cytotoxicity.

Animals↗

PubMed1996

[Experimental orthopedic surgery: the practical aspects and management].

The funds to grant for a scientific research project are more and more interesting public and private administrations. A quantitative analysis of experimental research prices in all its phases is mandatory for an optimization process. The aim of this paper is to define practical and economical aspects of the experimental 'in vivo' models designed for the validation of biomaterials, with particular respect to the managerial bookkeeping of consumer goods, based on the experience of our Institute. Some tables were realized in order to quantify the resources needed to perform experimental 'in vivo' models. These tables represent a reliable tool for a continuous monitoring of managerial costs for the current year and for an accurate budget planning for the future years considering the experimental projects in progress and the planned researches. A business organization of public research facilities may lead to an optimization of costs and an easier national and international funds achievement increasing, also, the partnership with private appointers.

Animals↗

PubMed1996

[The osseointegration process: a still open chapter in experimental and clinical research].

The osseointegration of biomaterials for dental and orthopaedic use is a still open topic in experimental and clinical research. Some aspects of this complex mechanism are not completely research. Some aspects of this complex mechanism are not completely explained yet. These reasons make the process of osseointegration a topical subject both in clinical and experimental view points. The authors describe how this complex event has not been studied with standard investigation and report also most of present research lines on the basis of their experience. A particular attention is paid to some factors related to both biomaterial and implant site, which can influence significantly the process of osseointegration.

Animals↗

PubMed1996

[Experimental osteoporosis caused by estrogen deficiency in rats. Role of a lactose, L-arginine and L-lysine combination in the prevention and therapy].

The role of a lactose, L-arginine and L-lysine association in the treatment of osteoporosis was evaluated in an in vivo model. Fifty Sprague Dawley female rats, 10 months age, were divided into 5 groups: 10 non-ovariectomized animals sacrificed at the beginning of the study (I group); 10 ovariectomized animals (OVX) without treatment and sacrificed at three months (II group); 10 OVX animals without treatment sacrificed at 6 months; 10 OVX animals treated starting from the I post-operative day with the association for three months (IV group, prevention) and 10 OVX animals treated like those of the IV group starting three months after surgery (V group, therapy). Animals were sacrificed in general anesthesia according to the scheduled times for radiologic, densitometric, histologic and mineralogic investigations. Preliminary results, which will need further researches, seem to show a progressive reduction of bone mass after ovariectomy in 10 months female rat and that the pharmacological association given as therapy (V group) may be able to lessen the reduction of bone mineral content.

Animals↗

PubMed1995

Comparison of hemodialysis versus hemoperfusion in the clearance of high-dose methotrexate in pigs.

To evaluate the different capabilities of hemo-perfusion (HP) and hemodialysis (HD) treatment in resolving the side effects during high-dose methotrexate (MTX) therapy, an experimental comparative study was done. Under general anesthesia, 12 female Large-White pigs, 35 +/- 5 kg body weight, underwent a bilateral renal vessel ligature to create an acute renal failure and avoid the physiologic elimination of MTX. An MTX i.v. infusion was performed using a dose of 12.5 g/m2 and for a specific time according to its pharmacokinetics. The animals were divided into 2 groups of 6 animals each and connected to the extracorporeal circuit; the first group was submitted to a 1-h HP with an anion exchange resin (Dow 1X-2, Dow Chemical) and the second group to 1-h HD with capillary polysulfone fibers (F6, Fresenius). Blood samples were taken at established intervals for hematological and biochemical evaluations. The results demonstrate a higher capability of HP treatment (P < 0.001) related to HD in MTX removal.

Animals↗

PubMed1995

In vitro evaluation of heparin adsorption during haemoperfusion with Dowex 1 x 2 anion exchange resin.

Haemoperfusion treatments have found clinical applications in various pathologies, even though problems due to the insufficient biocompatibility of sorbents have often limited its employment. Among these problems, there is that of heparin adsorption which can determine coagulation disorders or the necessity of a dosage correction during the extra corporeal circulation. The aim of the study was to test the influence of different methods of coating on heparin adsorption from an anion exchange resin coated with poly-hydroxyethyl-methacrylate. Eight haemoperfusion cartridges were prepared using 8 g of resin for each (4 cartridges contained resin coated by spray-coating technique and 4 coated by phase-separation one). Haemoperfusion was performed by using 600 IU of heparin (25,000 IU) corresponding to 0.12 ml in 500 ml of swine blood and a closed circuit. Blood flow rate was maintained at 15 ml/min and the circuit pressure was 70 torr during haemoperfusion. Blood samples were withdrawn at timed intervals before and after the column in order to evaluate blood heparin levels. The results demonstrated the superiority of the phase-separation technique that does not permit any interactions between adsorbent substance and drug. As a result of this, the adjustment of the dosage may not be necessary during further in vivo experiments.

Adsorption↗

PubMed1995

Biopolymeric modification of superoxide dismutase (mPEG-SOD) to prevent muscular ischemia-reperfusion damage.

The efficacy of preventing ischemia-reperfusion damage by employing native or modified (mPEG-SOD) superoxide dismutase in an experimental animal model of acute ischemia of the left hindlimb was tested. Four hours and thirty minutes complete warm ischemia was induced in the left hindlimb of 43 Wistar rats, by clamping the femoral artery and monitoring its efficacy with Laser Doppler flowmetry. After ten days, a significative difference (p = 0.004) of the survival leg rate was found in the group treated with mPEG-SOD (86.6%) compared with the control group (30%). Histomorphological and ultrastructural analysis were performed at different time intervals confirming what the clinical course had already pointed out. These results show that SOD in its modified form, despite the lower dosage, can provide good protection against ischemia/reperfusion injury of muscles.

Animals↗

PubMed1995

[In vivo experimental research in vascular surgery. Methodology and current Italian law].

Authors underscore the importance of research in vascular surgery progress and approach some basic aspects on the correct conduction of an experimental research in vascular surgery fields and in particular on synthetic prosthesis of different diameter. Some important aspects of the current Italian law on animal experimentation are shown because they could cause new changes either on methodology or animal selection. Finally some experimental models adopted in the department of experimental surgery of the Rizzoli Orthopaedic Institutes on vascular prosthesis are described.

Animal Welfare↗

PubMed1995

Biological and synthetic conduits in peripheral nerve repair: a comparative experimental study.

Two different types of conduits, one biological, obtained with homologous glutaraldehyde preserved vein segments and the other synthetic bioabsorbable, made with Poly [L-lactide-co-6-caprolactone], were evaluated as guides for nerve repair in alternative to autologous grafts in an experimental animal model. Under general anesthetic, the ischiatic nerve of a number Wistar rats was transected to create a 1 cm gap, which was then repaired by means of the conduits or autologous grafts. Controls were performed at 1, 3 and 6 months; nerve regeneration was effective with both conduits, but the count of myelinated axons showed a significant difference between the synthetic and biological tubes (p < 0.001). The Poly [L-lactide-co-6-caprolactone] guide was still intact 30 days after implant; progressive signs of degradation were present at 90 and 180 days. These results show that the synthetic conduits are better than those obtained with preserved vein segments and might be considered in alternative to autologous grafts in peripheral nerve reconstruction.

Animals↗

PubMed1995

Resorbable device for fracture fixation: in vivo degradation and mechanical behaviour.

The availability of a high molecular weight poly(L-lactide), with supposed good mechanical properties, encouraged us to carry out an in vivo experimental study to evaluate the degradation rate and accompanying loss of strength during interaction with bone. Small cylindrical PLLA rods were manufactured by compression moulding. Thirty-six male New Zealand rabbits (b.w. 3 kg), randomly divided into six groups of six animals each, were submitted to implantation of the rods under general anaesthesia (phi 3 x 7 mm rods in the lateral condylic region of the right femur and phi 3 x 50 mm rods in the intracondylic channel of the left femur). The animals were then sacrificed at the end of each experimental time (4, 8, 12, 24, 52, 64 weeks), hence the femurs were explanted. Histology showed no inflammatory cells with fragmentation or resorption of bone trabeculae. Mechanical studies showed a decrease in mechanical properties and flexional stiffness, and the absence of evident material resorption. Finally, the properties of this newly developed resorbable device, when confirmed, seem to justify future clinical introduction of this synthetic material.

Animals↗

PubMed1994

Preparation of a new nerve guide from a poly(L-lactide-co-6-caprolactone).

A copolymer of L-lactide and 6-caprolactone (50:50, w/w) was synthesized and characterized. The thermal behaviour of this material did not show any crystallinity for several months; only after more than 1 yr of aging at room temperature and, particularly, in the in vitro degradation tests did it partially crystallize. The values of tensile strength, percent elongation at break and elastic modulus were, respectively, 25 MPa, 490% and 3 MPa. Transparent, elastic nerve guides having inner diameter of 1.3 mm and wall thickness of 175 microns were prepared.

Animals↗

PubMed1994

Stimulatory effect on bone formation exerted by a modified chitosan.

A novel modified chitosan carrying covalently linked imidazole groups (average molecular weight 700,000, degree of substitution 0.28, degree of acetylation 0.08) was used to stimulate bone formation in an animal model. Lesions (7 mm diameter) were surgically made in the femoral condyle of sheep and treated with the modified chitosan. Within 40 d after surgery, the neoformed tissue occluded the surgical hole and assumed a trabecular structure in the peripheral area of the lesion, while looking like a mineralization nodule in the central part in association with a fibrous component. In the control, no sign of osteoinduction or reparative process was observed and bone marrow was rich in adipocytes.

Adipocytes↗

PubMed1994

A new material with theoretical osteoinductive properties: experimental evaluation.

An intensive research for bone substitutes has been in progress for several decades in order to find a new ideal material for bone replacement. In the present study the Authors report some data on a new developed material in comparison with synthetic hydroxyapatite. The new material was characterised by means of a crystallographic spectroscopic and chemical study. An in vitro test was also performed using murine fibroblasts. The results of this preliminary study showed that the sintered material has an and beta-tricalcium-phosphate (TCP) lattice depending on thermal treatment in accordance with literature data. Moreover, it showed a high level of biocompatibility. Though it is still in an investigation stage, perhaps this biomaterial is a highly reactive and unstable compound that could interact with CO2 and H2O.

Animals↗

PubMed1994

Long-term cryopreservation of autologous veins in rabbits.

This study was undertaken to determine the effect of long-term cryopreservation on graft ultrastructure and endothelial cell viability in an animal model. The jugular veins from 12 New Zealand White rabbits were excised with a 'no-touch' technique and divided into four groups: control group (fresh veins); group 1, veins cryopreserved for 1 month; group 2, veins cryopreserved for 2 months; and group 3, veins cryopreserved for 3 months. Cryopreservation was accomplished by rapid freezing (-5 degrees C s-1 to -196 degrees C) in a solution of 17.5% dimethylsulphoxide and 20% fetal bovine serum and by storage in liquid nitrogen. Veins were then implanted as a carotid autograft (three grafts/group). At the time of graft implantation a segment of the paired matched vein was perfusion-fixed and evaluated by scanning and transmission electron microscopy, whereas the remainder were subjected to endothelial cell culture techniques to determine cell viability. Autografts were removed 1 month after implantation and subjected to similar evaluations. Histological changes seen in cryopreserved veins were dependent on preservation time and included focal endothelial cell blebbing, cytoplasmic vacuolization and disruption of cell-to-cell contacts. Smooth muscle cells showed mitochondrial swelling. Patency was identical in all groups (66.6%). Explants at 1 month were similar in histological appearance to fresh veins with a smooth endothelial cell lining arranged longitudinally and intact cell junctions. Endothelial cells could be cultured from fresh veins and 1-month-old explants but not from the cryopreserved graft surface before implantation. the present technique of cryopreservation leads to some damage of graft architecture and loss of endothelial cell viability.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗