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Biomedical subjects

M Rocca

Publications and source records attributed to M Rocca.

At least 55 records · Page 3Linked to original sources
PubMed1997

Experimental evaluation of a resorbable intramedullary plug for cemented total hip replacement.

In order to evaluate degradation kinetics and biocompatibility of a resorbable poly(D,L-lactic acid) (PDLLA) plug for total cemented hip prostheses, an experimental in vitro and in vivo study was carried out. Degradation rate studies were performed in Ringer solution and after in vivo plug implantation in the femoral medullar cavity of rabbits. In vitro biocompatibility was evaluated in murine fibroblast cell cultures. PDLLA plugs showed faster degradation kinetics in vivo than in vitro. Histological evaluations showed that PDLLA completely disappeared in vivo 26 weeks after implantation. Fibrous tissue in the medullar cavity was observed at 13 weeks, but no histological changes were observed after 26 weeks. Also, the in vitro tests showed good biocompatibility of the biomaterial. Our results show the possibility of considering this resorbable plug for clinical situations instead of the traditionally used plugs [polyethylene, poly(methyl methacrylate) or cancellous bone] due to its biocompatibility, degradation properties and simplicity of use.

Animals↗
PubMed1997

Biomaterials for orthopedic surgery in osteoporotic bone: a comparative study in osteopenic rats.

UNLABELLED: To evaluate orthopedic devices in pathological bone, an experimental study was performed by implanting Titanium (Ti) and Hydroxyapatite (HA) rods in normal and osteopenic bone. Twenty-four rats were used: 12 were left intact ( CONTROL: C) while the other 12 were ovariectomized (OVX). After 4 months all the animals were submitted to the implant of Ti or HA in the left femoral condyle (Ti-C, HA-C, Ti-OVX, HA-OVX). Two months later the animals were sacrificed for histomorphometric, ultrastructural and microanalytic studies. Our results show a significant difference between the Affinity Index (A.I.) of HA-C and Ti-C (77.0 +/- 7.4 vs 61.2 +/- 9.7) (p < 0.05). No significant differences were observed between the osteointegration of Ti-C and Ti-OVX (61.2 +/- 9.7 vs 48.2 +/- 6.7). Significant differences also exist between the osteointegration of HA-C and HA-OVX (77.0 +/- 7.4 vs 57.6 +/- 11.5) (p < 0.01). Microanalysis shows some modifications in Sulphur (S) concentration at the bone/biomaterial interface of the Ti-OVX group. Therefore our results confirmed the importance of biomaterials characteristics and of bone quality in osteointegration processes.

Animals↗
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

Clinical evaluation of the therapeutic effectiveness of ethinyl oestradiol and oestrone sulphate on prolonged bleeding in women using depot medroxyprogesterone acetate for contraception. World Health Organization, Special Programme of Research, Development and Research Training in Human Reproduction, Task Force on Long-acting Systemic Agents for Fertility Regulation.

A placebo-controlled randomized clinical trial was conducted in six centres to compare the effects of a 14 day treatment with either 50 micrograms ethinyl oestradiol daily or 2.5 mg oestrone sulphate daily, on depot medroxyprogesterone acetate (DMPA)-induced prolonged bleeding. Out of 1035 women admitted to the study, 278 requested treatment and were given ethinyl oestradiol (n = 90), oestrone sulphate (n = 91) or placebo (n = 97). Ethinyl oestradiol was successful in stopping the bleeding episode in 93% of cases, compared with oestrone sulphate and placebo which had success rates of 76 and 74% respectively. However, the relative advantage of ethinyl oestradiol was marginal, with an average reduction of 1 bleeding day and 3 spotting days compared with the other two groups. Immediately after treatment, women given ethinyl oestradiol had less bleeding but a more unpredictable pattern than the other two groups. In the long term, there were no differences between the bleeding patterns or the discontinuation rates for any reason in the three groups, and the most important single reason for discontinuation in those groups remained 'menstrual problems'. In summary, the study showed that treatment of DMPA-induced prolonged bleeding with ethinyl oestradiol had a limited short-term effect but no beneficial effect on the acceptability of DMPA as a contraceptive method. Treatment with oestrone sulphate was no different from placebo.

Adolescent↗
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↗
PubMed1996

Pathophysiological and histomorphological evaluation of polyacryloylmorpholine vs polyethylene glycol modified superoxide dismutase in a rat model of ischaemia/reperfusion injury.

Twenty Wistar rats were divided into two groups. Both underwent acute ischaemia followed by reperfusion of the left hind limb. The first group was a control group while the second was treated with PAcM-SOD. The survival percentage of the limb after 10 days was 30% for the first group and 70% for the second. Neither linear regression nor correlation were found between groups as far as the survival percentage of the limb after 10 days and reperfusion pmO2 data were concerned. After ten days the histomorphological analysis was significant regarding the fibre diameter and the percentage of central located nuclei in the specimens of PAcM-SOD treated limbs compared to normal limbs, but not when compared to the muscular fibres of the control group. Comparing these results with others obtained with native SOD and monomethoxypoly(ethylene glycol) modified SOD (mPEG-SOD) used in the same experimental model, we can conclude that the clinical and morphological results were better using mPEG-SOD, and that PAcM-SOD does have a protective effect on ischaemic muscle damage, although it is not as effective as mPEG-SOD in preventing ischaemia/reperfusion injury.

Acrylic Resins↗
PubMed1995

Immunological reactivity in ranitidine factory workers.

The involvement of immunological reactivity to ranitidine base (R-b) and ranitidine hydrochloride (R-HCl) in the development of occupationally related symptomatology was analyzed in 40 subjects employed in a pharmaceutical plant producing ranitidine and in 33 nonexposed controls, using a specific dose-response lymphocyte proliferative test (lymphocyte transformation test: LTT). Of the 40 workers, 11 (28%) gave positive reactions to LTT: 3/11 to R-b, 4/11 to R-HCl, and 4/11 to both compounds. None of the controls gave positive reactions. Cutaneous, oculonasal, or respiratory work-related symptoms were cited by 23 of the 40 (58%) subjects; ten of these 23 subjects (43%) were LTT positive. One asymptomatic case was LTT positive. The present results indicate that specific immune reactivity to ranitidine, analyzed by LTT, is associated with the presence of occupational symptomatology; R-HCl and R-b seem to share some antigenic determinants, because of the partial cross-reactivity shown by the examined compounds. Nonimmunological, probably irritative, mechanisms are also present in some of the symptomatic subjects.

Eye Diseases↗
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↗