The effect of Bosentan on healing of colonic anastomosis

BACKGROUND: Ischemia is the most important factor compromises wound healing in colonic anastomosis. Mesenteric vessels are ligated at first while performing colonic resection and following anastomosis. Therefore blood supply of the related segments of colon temporarily interrupted and ischemia can easily occur. This study was carried out to explore whether Bosentan, an endothelin-receptor antagonist, can eliminate vasoconstruction, increase blood flow in the splanchnic area and anastomotic region and therefore possibly facilitate wound healing and prevent intra-abdominal adhesion formation. METODS: Study is conducted on 30 female Wistar-Albino rats weighing 180–240 gr. Rats were allocated into three groups. Group 1 (n = 10) recevied full-thickness resection of the left colon and end-to-end anastomosis. In Groups 2 (n = 10) and 3 (n = 10), vessels of 2–3 cm segment of the left colon were ligated, indications of necrosis of that segment were expected, followed by resection and end-to-end anastomosis. Two milliliter of saline and 5 mg/kg Bosentan was given intraperitoneally in Group 2 and 3, respectively. On postoperativ day 6, intra-abdominal adhesions were scored. Healing of anastomosis, anastomotic bursting pressures, tissue hydroxyproline levels and histopatologically healing scores were assessed. RESULTS: Macroscopic adhesion score in Group 3 was lower than the remained groups (p < 0.05). Tissue hydroxyproline levels were significantly higher in Group 3 compared to the Groups 1 and 2 (p < 0.001). Mean anastomotic bursting pressures were 200 mmHg, 164 mmHg and 240 mmHg in Groups 1, 2 an 3, respectively (p < 0.05 between Groups 1 and 3; p < 0.001 between Groups 2 and 3). Histopathologically, healing scores of Group 1 were significantly higher than the other groups (p < 0.05 group 1–3, group 2–3). CONCLUSION: Bosentan increases anastomotic healing of ischemic colonic anastomosis and decreases intra-abdominal adhesion formation

Toz metalurjisi yöntemiyle köpüksü saf titanyum ve Ti6AI4V alaşım üretimi ve karakterizasyonu

TÜBİTAK MAG Proje15.04.200

Gözenekli titanyum alaşımlarının üretimi ve karakterizasyonu.

In the present study, production of titanium and Ti6Al4V alloy foams has been investigated using powder metallurgical “space holder technique” in which magnesium powder were utilized to generate porosities in the range 30 to 90 vol. %. Also, sintering of titanium and Ti-6Al-4V alloy powders in loose and compacted condition at various temperatures (850-1250oC) and compaction pressures (120-1125 MPa), respectively, were investigated to elucidate the structure and mechanical properties of the porous cell walls present due to partial sintering of powders in the specimens prepared by space holder technique. In addition, microstructure and mechanical response of the porous alloys were compared with the furnace cooled bulk samples of Ti-6Al-4V-ELI alloy subsequent to betatizing. It has been observed that the magnesium also acts as a deoxidizer during foaming experiments, and its content and removal temperature is critical in determining the sample collapse. Stress-strain curves of the foams exhibited a linear elastic region; a long plateau stage; and a densification stage. Whereas, curves of loose powder sintered samples were similar to that of bulk alloy. Shearing failure in foam samples occurred as series of deformation bands formed in the direction normal to the applied load and cell collapsing occured in discrete bands. Average neck size of samples sintered in loose or compacted condition were found to be different even when they had the same porosity, and the strength was observed to change linearly with the square of neck size ratio. The relation between mechanical properties of the foam and its relative density, which is calculated considering the micro porous cell wall, was observed to obey power law. The proportionality constant and the exponent reflect the structure and properties of cell walls and edges and macro pore character.Ph.D. - Doctoral Progra

Characterization of Ti-6Al-4V alloy foams synthesized by space holder technique

Ti-6Al-4V foams, biomedical candidate materials, were synthesized by powder metallurgical space holder technique as a result of evaporation of magnesium to achieve desired porosity content. Final products contained porosities in the range similar to 43-64% with an average macropore size between 485 and 572 mu m and a lamellar type Widmanstatten microstructure composed of alpha-platelets and beta-laths. Unlike the case of bulk Ti-6Al-4V alloy tested under compression loading, compression stress-strain curves of manufactured Ti-6Al-4V foams were similar to those of elastic-plastic foams, which contain a linear elastic region; a plateau stage: and a densification stage. In the plateau region deformation bands perpendicular to the compression axis were developed and cell collapsing took place together with the buckling and fracture of some of the cell walls and edges in a ductile manner. Calculated elastic modulus and yield strength were in the range 1.42-14.7 GPa and 28.2-150 MPa, respectively, and the foam mechanical properties were found to be dependent on micro porous cell wall properties, which in turn depends on neck size between powder particles. Around 330 MPa yield strength value was calculated for porous cell walls by the use of Ti-6Al-4V alloy powder samples sintered in loose and compacted conditions, which were utilized to simulate the cell wall structure of foams. In addition, overall mechanical properties of foam s were investigated considering macro porosity fraction, p(macro), and the yield strength of foams exhibited a power law dependence, similar to commonly used minimum solid area models, in the form of A*(1 - p(marco))(n), where the proportionality constant "A" was found to be the yield strength of micro porous cell walls

Surface characteristics and in-vitro behavior of chemically treated bulk Ti6Al7Nb alloys

The effect of various treatments on surface chemical composition and structure, and bioactivity of Ti6Al7Nb bulk alloys has been investigated. The alloys were treated employing aqueous solutions of NaOH and CaCl2 separately, and also by subsequent CaCl2 treatment after NaOH treatment (NaOH-CaCl2 treatment) which were followed by heat treatment. NaOH treatment was observed to be effective in enrichment of surface layer with Na. On the other hand, Na+ ions were mostly replaced by Ca2+ ions as a result of NaOH-CaCl2 treatment, while single step CaCl2 treatment was less effective in Ca incorporation. Additionally, porous network surface structure seen in NaOH and NaOH-CaCl2 treated samples was completely different than globular morphology detected in CaCl2-treated samples in single step. Subsequent heat treatments caused coarsening of surface structure and loss of some Na+ and Ca2+ ions. NaOH and NaOH-heat treated samples did not exhibit apatite formation within 15 days immersion in simulated body fluid (SBF). On the other hand, NaOH-CaCl2 samples had the highest apatite formation; however, NaOH-CaCl2-heat treated samples did not display any mineralization. Conversely, CaCl2 treated samples allowed apatite formation after heat treatment