Renato Barros Eleotério

Comparison of in vivo properties of hydroxyapatite-polyhydroxybutyrate composites assessed for bone substitution.

This study compared 3 composites made of hydroxyapatite and polyhydroxybutyrate to determine their biocompatibility, osteointegration, and osteoconduction in rabbits bone defects. Hydroxyapatite-polyhydroxybutyrate was tested in a 10:90 vol/vol ratio for composite 1, 25:75 for composite 2, and 50:50 for composite 3, whereas defects in the control group remained unfilled. Limbs were clinically and radiographically evaluated, and samples were taken 8, 45, and 90 days after surgery for histologic and histomorphometrical analysis. No significant difference was found in the clinical parameters: pain, lameness, dehiscence, infection, and edema among the 4 groups. No signs of osteolysis or periosteal reaction were observed. Bone regeneration in groups 1, 2, and 3 occurred histomorphologically similar to the control group. No inflammatory infiltrate was present on any date of observation. More bone than connective tissue was significantly found in the defects of the 3 groups on all observation dates, and the percentage of bone tissue in the interface was similar for composites 2 and 3. Bone and connective tissue were observed in pores of composites 2 and 3. Osteoclasts were found in the bone-composite interface, and multinucleated giant cells were seen on the surface of composite fragments, found among mesenchymal tissue on the 45th and 90th days. No significant difference was observed in osteoclast number among the 4 groups. In summary, composites were considered biocompatible and able to integrate to bone. They also showed signs of biodegradability, and composites 2 and 3 were osteoconductive, the first displaying best characteristics for bone substitution.

Plasma rico em plaquetas associado ou não ao osso esponjoso autógeno no reparo de falhas ósseas experimentais

The present study evaluated autogenous platelet rich plasmas (PRP) influence on the reparation process of four bone defects made on rabbits skull, associated or not to autogenous bone graft (EOE). Defect I received PRP only; defect II received 3mg of EOE only; defect III received EOE associated to PRP; defect IV was left to heal naturally, serving as control. After each surgery the animals were randomly divided into three groups that were euthanized at 30, 60 and 90 days. In the mesoscopic evaluation bone ingrowth started from the defects borders to the center and from the bottom to the surface for all observation times on the control (VI) and PRP only (I) groups. In the groups treated with EOE only (II) and EOE associated to PRP (III) new bone was observed in the center of the defects. Radiographic analysis showed greater central radiopacity for groups treated with EOE only (II) and EOE associated to PRP (III) at all observation times. Microscopically in the group treated with EOE associated to PRP (III) at 30 days the graft was indistinguishable from new bone present on the border of the defect, associated to a moderate quantity of a very vascularized and cellular fibrous connective tissue. This tissue showed an extracelular eosinophilic amorphous foamy material, associated to an inflammatory process constituted by lymphocytes and in less number by macrophages and multinucleated giant cells that may have negatively influenced early bone formation. At 60 and 90 days occasional spots of lymphocytic inflammation were observed. Both treatments, PRP associated or not to EOE, were similar for the bone ingrowth at the final time of observation; the graft used alone determined early bone reparation and thromboplastine used for the platelet gel formation incited a foreign body-like reaction that acted negatively on the initial reparation.

Membrana amniótica canina utilizada como bandagem em úlcera superficial de córnea de coelhos - aspectos clínicos

Twenty-eight rabbits were submitted to superficial keratectomy. The treated group consisted of 14 animals received canine amniotic membrane as a bandage, sutured in a way that its epithelial surface was in contact with the corneal surface. The control group did not receive any treatment. The animals were submitted to clinical evaluations 24 hours after surgery, at each two-day interval during one week and at each four-day interval during 180 days. The amniotic membranes were evaluated as a bandage comparing the time needed for corneal epithelization in the treated and non-treated groups and determining the period necessary for the cornea to become completely transparent. The corneal opacity was present during the entire time of observation. The treated animals presented more opaque cornea in the early period of regeneration, with neovascularization and more pain and discomfort than the animals from control group, showing a delayed epithelization.

Processo de reparação de lesões da córnea e a membrana amniótica na oftalmologia

The events included in the process of repair of corneal damage occur simultaneously and involve proliferation, migration, differentiation, cell apoptosis and intercellular communication. Several soluble factors, mesenchymal matrix proteins, proteoglycans, proteolytic enzymes and some cell types are covered in this review, which explains the processes of repair of corneal wounds, either superficial or penetrating. The amniotic membrane, used in ophthalmic surgery, was studied because of the contribution of its functions to the repair process. However, these functions may be lost when the amniotic membrane is subjected to conservation. Therefore, it is important to understand the repair process of lesions involving or not the entire thickness of the cornea, and choose the best use of the amniotic membrane, when it is indicated for the treatment of these lesions.

Compósito para fabricação de implantes reabsorvíveis para osteossíntese: avaliação da biocompatibilidade em coelhos

Biocompatibility, osseointegration, and resorption of a 10% hydroxyapatite (HAP-91®) - 90% polyhydroxybutyrate composite were analyzed after implantation in rabbits´ bone defects. Clinical, radiographic, histologic and histomorphometric data were collected on the 8th, 45th, and 90th days after surgery and the results were compared to those of unfilled defects. No significant differences between groups for the evaluated clinical parameters existed. Radiographs showed bone-composite direct contact. Bone tissue was formed normally in the defect and at the composite-tissue interface when compared to the control. No inflammatory infiltrated was observed. For each sampling day, the percentages of bone were greater than those of connective tissues (P=0.001 on the 8th and 45th days and 0.022 on the 90th day) inside the defect. Bone and connective tissues were seen at the interface with the composite, being the last one significantly greater than the first on the 90th day (P=0.004). Composites resorption signs were evident: giant cells on the surface of composite fragments separated from the original bloc. Data support that such composite is biocompatible in rabbits, resorbable and integrate to bone.

Osseointegração clínica-radiológica do compósito hidroxiapatita-lignina entre implante metálico e tecido ósseo em coelho

This study evaluated a sinthetic hydroxyapatite-lignin composite for osseoingration between metallic implant and bone tissue. Twenty New Zealand rabbits were used. A defect was made a the proximal region of lateral surfaces of both tibias. An intramedullary pin was inserted in the medullary cavity of the left tibia after filling the cavity with 1,000mg of the composite and covering the thread part of the pin with the composite. The same procedure was made in control tibias without the composite. Clinical evaluation was based on inflammatory reaction, dehiscence, lameness, pain, and tibial circumference. Radiographs were made immediately after surgery and then on days eight, 30, 60, 90, and 120. Most of the animals presented normal clinical progression. Radiographies of treated group showed decrease in the defect and medullary cavity radiopacity to the same pattern of the surrounding bone, while the contrary happened in control group; but, in this group, the medullary cavity remained radioluscent at the last observation date. It can be concluded that the hydroxyapatite-lignin composite did not show clinical signs of rejection and that radiopacity of the tissue in the bone defect and surrounding the pin was similar to bone radiopacity, suggesting that the material promoted osseointegration.

Tissue response to the composite 50% hydroxyapatite: 50% polyhydroxybutyrate for bone substitution in rabbits

Avaliaram-se a biocompatibilidade, a osseointegracao, a osseoconducao e a biodegradacao de compositos de 50% hidroxiapatita (HAP-91®) e 50% poli-hidroxibutirato. O composito foi implantado em defeitos osseos em 12 coelhos (grupo experimental), sendo comparado a defeitos nao preenchidos (grupo-controle, de igual numero). Os parâmetros clinicos dor, claudicacao, infeccao, deiscencia e edema foram avaliados nos primeiros oito dias apos a cirurgia e aos 45 e 90 dias. Radiografias foram realizadas aos oito, 45 e 90 dias apos a cirurgia em quatro animais por grupo que, em seguida, foram submetidos a eutanasia para coleta de amostras destinadas a analises histologica e histomorfometrica. Nao ocorreram diferencas entre os grupos para todos os parâmetros clinicos. Radiografias demonstraram um composito com radiopacidade semelhante a do osso vizinho e contato direto entre osso e composito aos 45 e 90 dias. Diferenca significativa foi observada entre a porcentagem dos tecidos osseo e conjuntivo dentro do defeito nos dias oito, 45 e 90, assim como na interface aos 45 e 90 dias. Foram observadas projecoes dos tecidos osseo e conjuntivo no interior do composito e sinais de biodegradacao na ausencia de infiltrado inflamatorio. Pode-se concluir que o composito e biocompativel, osseocondutor, biodegradavel e se integra ao tecido osseo.

A new surgical technique to treat corneal perforations using amniotic membrane and surgical adhesive

The objectives of this study were to compare surgical techniques and the effects of using n-butyl 2-cyanoacrylate and bovine amniotic membrane to repair perforated lesions in corneas. Penetrating keratoplasty was performed in sixty New Zealand White rabbits under general anesthesia. Group 1 (G1) was treated with n-butyl 2-cyanoacrylate, group 2 (G2) received a fragment of amniotic membrane through the anterior chamber and application of n-butyl 2-cyanoacrylate over the lesion, group 3 (G3) was treated with the same technique as G2 with the addition of an amniotic membrane bandage covering the cornea and sutured in the limbus region, and group 4 (G4) was treated with an amniotic membrane sutured to the lesion and an amniotic membrane bandage sutured in the limbus region. Clinical, histological and histomorphometric examinations of the corneas were performed. The membrane acted as a barrier for aqueous humor in G2 and G3, thereby keeping the surface dry for adhesive application; it also prevented the adhesive from contacting intraocular structures. The groups treated with amniotic membrane and surgical adhesive showed better results than the groups treated with either material alone. Thus, the combination of the membrane with the adhesive is recommended for this type of lesion.

Glucosamine and chondroitin sulfate in the repair of osteochondral defects in dogs - clinical-radiographic analysis

Among the proposed treatments to repair lesions of degenerative joint disease (DJD), chondroprotective nutraceuticals composed by glucosamine and chondroitin sulfate are a non-invasive theraphy with properties that favors the health of the cartilage. Although used in human, it is also available for veterinary use with administration in the form of nutritional supplement independent of prescription, since they have registry only in the Inspection Service, which does not require safety and efficacy testing. The lack of such tests to prove efficacy and safety of veterinary medicines required by the Ministry of Agriculture and the lack of scientific studies proving its benefits raises doubts about the efficiency of the concentrations of such active substances. In this context, the objective of this study was to evaluate the efficacy of a veterinary chondroprotective nutraceutical based on chondroitin sulfate and glucosamine in the repair of osteochondral defects in lateral femoral condyle of 48 dogs, through clinical and radiographic analysis. The animals were divided into treatment group (TG) and control group (CG), so that only the TG received the nutraceutical every 24 hours at the rate recommended by the manufacturer. The results of the four treatment times (15, 30, 60 and 90 days) showed that the chondroprotective nutraceutical, in the rate, formulation and administration at the times used, did not improve clinical signs and radiologically did not influence in the repair process of the defects, since the treated and control groups showed similar radiographic findings at the end of the treatments.

A comparison of the effects of propofol and thiopental on tear production in dogs

The tear film plays an important role in maintaining the integrity of the ocular suface. During general anesthesia, tear production is considerably reduced, which requires care to prevent adverse effects that result in diseases of these structures. Studies comparing the effects of induction of anaesthesia with thiopental and propofol on tear production have not been carried out yet. Because these drugs are used in veterinary medicine, we decided to evaluate the tear production in 30 dogs undergoing experimental surgery as well as routine procedures at the veterinary hospital of Federal University of Vicosa. Patients were divided into two groups of equal number. All animals were sedated with clorpromazine and maintained with isoflurane in diluted oxygen. Group 1 was induced with thiopental whereas group 2 with propofol. Schirmer tear test 1 was performed before sedation (T0), 15 minutes after sedation (T1) and 10 minutes after induction of anesthesia (T2) with the drug chosen for one of the groups. There was a significant decrease in tear production for both drugs, but no significant statistical differences were found between them. Thus, considering the results and the way in which the study was conducted, we suggest protecting the cornea and conjunctiva of patients during anesthesia using any of the drugs here evaluated.