Composites PVDF-TrFE/BT used as bioactive membranes for enhancing bone regeneration

In this paper a piezoelectric composite membranes were developed for charge generator to promoter bone regeneration on defects sites. Is known that the osteogenesis process is induced by interactions between biological mechanisms and electrical phenomena. The membranes were prepared by mixing Barium Titanate (BT) powders and PVDF-TrFE (PVDF:TrFE = 60:40 mol%) on dimethylformamide medium. This precursor solution was dried and crystallized at 100degreesC for 12 hours. Composites membranes were obtained by following methods: solvent casting (SC), spincoating (SP), solvent extraction by water addition (WS) and hot pressing (HP).The microstructural analysis performed by SEM showed connectivity type 3-0 and 3-1 with high homogeneity for samples of ceramic volume fraction major than 0.50. Powder agglomerates within the polymer matrix was evidenced were observed for composites with the BT volume fraction major than 40%. The composite of ceramic fraction of 0.55 presented the best values of remanent polarization (similar to33 muC/cm(2)), but the flexibility of these composites with the larger ceramic fraction was significantly affected.For in vivo evaluation PVDF-TrFE/BT 90/10 membranes with 3cm larger were longitudinally implanted under tibiae of male rabbit. After 21 days the animals were sacrificed. By histological analyses were observed neo formed bone with a high mitotic activity. In the interface bone-membrane was evidenced a pronounced callus formation. These results encourage further applications of these membranes in bone-repair process.

Physiology of temperature regulation: Comparative aspects

Few environmental factors have a larger influence on animal energetics than temperature, a fact that makes thermoregulation a very important process for survival. In general, endothermic species, i.e., mammals and birds, maintain a constant body temperature (Tb) in fluctuating environmental temperatures using autonomic and behavioural mechanisms. Most of the knowledge on thermoregulatory physiology has emerged from studies using mammalian species, particularly rats. However, studies with all vertebrate groups are essential for a more complete understanding of the mechanisms involved in the regulation of Tb. Ectothermic vertebrates-fish, amphibians and reptiles-thermoregulate essentially by behavioural mechanisms. With few exceptions, both endotherms and ectotherms develop fever (a regulated increase in Tb) in response to exogenous pyrogens, and regulated hypothermia (anapyrexia) in response to hypoxia. This review focuses on the mechanisms, particularly neuromediators and regions in the central nervous system, involved in thermoregulation in vertebrates, in conditions of euthermia, fever and anapyrexia. (c) 2006 Elsevier B.V. All rights reserved.

New attachment achieved by guided tissue regeneration using a bioresorbable polylactic acid membrane in dogs

Created periodontal defects in dogs were randomly assigned for experimental (Guidor bioresorbable membranes) or control (conventional therapy) treatment the results showed that the new connective issue attachment was significantly greater in test sites than in controls. This new attachment averaged 2.79 +/- 0.74 mm and 1.47 +/- 0.20 mm at test and control sites, respectively (P < 0.05). Epithelial downgrowth was also reduced in the test sites (P < 0.05). No differences in bone response were found. The bioresorbable barrier was effective in blocking gingival epithelial downgrowth and connective tissue proliferation, promoting new attachment according to the principles of guided tissue regeneration.

Regeneration of poly-L-lysine modified carbon electrodes in the accumulation and cathodic stripping voltammetric determination of the cromoglycate anion

Cromoglycate is accumulated on a poly-L-lysine (PLL) modified carbon electrode best from pH 4 solution, where it is anionic and the PLL is cationic, and at which pH the cromoglycate gives a good reduction peak at -0.82 V. The PLL film can be regenerated readily by washing the electrode with 3 M sodium hydroxide solution, in which the PLL is deprotonated. Regeneration of the film is not required as frequently when larger amounts of PLL are incorporated into it. This allows standard addition procedures to be carried out without regenerating the electrode. Linear calibration graphs have been obtained typically in the range 0.1 - 1.5 mug ml(-1). Detection limits have been calculated to be 10 ng ml(-1). The standard addition method has been applied satisfactorily to diluted urine solutions. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Treatment of ligature-induced peri-implantitis by lethal photosensitization and guided bone regeneration: A preliminary histologic study in dogs

Background: the purpose of this pilot study was to evaluate the healing potential and reosseointegration in ligature-induced peri-implantitis defects adjacent to various dental implant surfaces following lethal photosensitization.Methods: A total of 36 dental implants with 4 different surface coatings (9 commercially pure titanium surface [CPTi]; 9 titanium plasma-sprayed [TPS]; 9 hydroxyapatite [HA]; and 9 acid-etched [AE]) were inserted in 6 male mongrel dogs 3 months after extraction of mandibular premolars. After a 2-month period of ligature-induced peri-implantitis and 12 months of natural peri-implantitis progression, only 19 dental implants remained. The dogs underwent surgical debridement of the remaining dental implant sites and lethal photosensitization by combination of toluidine blue O (100 mug/ml) and irradiation with diode laser. All exposed dental implant surfaces and bone craters were meticulously cleaned by mechanical means, submitted to photodynamic therapy, and guided bone regeneration (GBR) using expanded polytetrafluoroethylene (ePTFE) membranes. Five months later, biopsies of the implant sites were dissected and prepared for ground sectioning and analysis.Results: the percentage of bone fill was HA: 48.28 +/- 15.00; TPS: 39.54 +/- 12.34; AE: 26.88 +/- 22.16; and CPTi: 26.70 +/- 16.50. The percentage of reosseointegration was TPS: 25.25 +/- 11.96; CPTi: 24.91 +/- 17.78; AE: 17.30 +/- 15.41; and HA: 15.83 +/- 9.64.Conclusion: These data suggest that lethal photosensitization may have potential in the treatment of peri-implantitis.

Effect of calcitonin on bone regeneration in male rats: a histomorphometric analysis

The aim of this study was to evaluate the effectiveness of calcitonin in promoting bone growth in surgical bone defects in rat mandibles. Fifty male rats were divided into two groups: bone defect (control) and bone defect with calcitonin (experimental). A circular bone defect 4 mm in diameter was made in the mandibular bone of the rats in the angle region, and covered with a polytetrafluoroethylene barrier. The experimental group received 2 IU/kg of synthetic salmon calcitonin intramuscularly three times a week, with treatment starting immediately after surgery. The animals were killed 3, 7, 14, 21 and 28 days after the surgical procedure. The bone defects were examined histologically and by histomorphometric analysis. The Student t-test was applied to the histomorphometric data, with the level of significance set at 5%. The animals of the experimental group showed a lower level of bone formation at almost all time points than the control group, but no difference between groups was observed 28 days after surgery. The volume of newly formed bone matrix was significantly greater in the control than the experimental group at 7, 14 and 21 days, as determined by both morphologic and histomorphometric analysis. Bone repair in the calcitonin-treated animals was delayed in comparison to controls, indicating the need for further studies on male rats.

Comparative genomics of two Leptospira interrogans serovars reveals novel insights into physiology and pathogenesis

Leptospira species colonize a significant proportion of rodent populations worldwide and produce life-threatening infections in accidental hosts, including humans. Complete genome sequencing of Leptospira interrogans serovar Copenhageni and comparative analysis with the available Leptospira interrogans serovar Lai genome reveal that despite overall genetic similarity there are significant structural differences, including a large chromosomal inversion and extensive variation in the number and distribution of insertion sequence elements. Genome sequence analysis elucidates many of the novel aspects of leptospiral physiology relating to energy metabolism, oxygen tolerance, two-component signal transduction systems, and mechanisms of pathogenesis. A broad array of transcriptional regulation proteins and two new families of afimbrial adhesins which contribute to host tissue colonization in the early steps of infection were identified. Differences in genes involved in the biosynthesis of lipopolysaccharide 0 side chains between the Copenhageni and Lai serovars were identified, offering an important starting point for the elucidation of the organism's complex polysaccharide surface antigens. Differences in adhesins and in lipopolysaccharide might be associated with the adaptation of serovars Copenhageni and Lai to different animal hosts. Hundreds of genes encoding surface-exposed lipoproteins and transmembrane outer membrane proteins were identified as candidates for development of vaccines for the prevention of leptospirosis.