Search

Objective: This is an experimental study with the objective of analyses the increase of rigidity in synthetic tibia bones with external fixators, with single and double connecting rods and with stable and unstable fracture patterns., Methods: The external fixators were used in the monoplanar, half pin configuration submitted to an axial compression load using the connecting bar in different patterns. Forty-eight similar models to the human tibia had been used. In all the models were left an interval of 0,5 cm between the fragments and were made cuts of 15 masculine and 45 masculine to simulate stable and unstable fracture patterns, respectively. The models had been divided in four groups in accordance with the cut (15 masculine and 45 masculine) and the number of metallic bars in assembly (1 and 2 bars). The study used the Instron testing machine which the models were submitted to the axial load until the fragments that were separated by a gap made full contact., Results: The instability forces in the assembly with a double bar had been sufficiently superior to the forces with only one bar. It was still observed that the group with unstable fracture pattern and with only one connecting rod had a lesser variability compared with the other groups and presented more homogeneous results, with a minor average., Conclusion: The assembly with a double longitudinal connecting rod in the studied models is more stable than the others to stand compression load.

Purpose: To evaluate the role of Losartan in skin healing repair., Methods: One hundred and eleven male Wistar rats were distributed into four groups, at random. Group I (n=31) underwent a laparotomy to induce hypertension by stenosis of the left renal artery, and 48 hours later it received Losartan (10 mg/Kg) daily. Group II (n=30) went through the same procedure and received isotonic saline solution. Group III (n=30) underwent a simulated laparotomy. Group IV (n=20) to confirm the induced hypertension method. Ketamine and Xylazin anesthesia was used in every painful/stressful procedure. After 15 days, skin healing repair was studied by a dorsal midline skin incision and second layer-skin incision in groups I, II and III, that was sutured in one layer with 4-0 nylon suture. Samples of the dorsal wall scar were taken 4, 7 and 14 days after the last procedure, and sent to strength and displacement analysis and histological preparation., Results: By the 4th and 7th days of the analysis, group II scars showed to be less resistant than group III scars (p<0,05). The total amount of collagen was higher in group III on the three studied periods. The percentage occupied by total collagen in the wound area, on the 14th day, was lower in group I, due to its lower percentage of type I collagen, Conclusion: Scars treated with Losartan were initially less resistant and had a lower collagen deposition.

Purpose: Some investigators have stated that collagen synthesis is slower in elderly individuals, others have reported a reduction of collagen I and III synthesis, and still others have reported normal synthesis. The objective of the present study was to determine the collagen deposition occurring through the pores of a propylene net implanted in the abdominal wall of young adult rats compared to old rats., Methods: Ten male rats aged 100 to 120 days and 10 rats aged 850 to 900 days were used. Under inhalatory anesthesia, a median incision was made in the ventral abdominal wall and a 4 cm2 gap was formed. The muscle-aponeurosis plane was removed and the peritoneal plane was maintained. The gap was corrected with a polypropylene mesh fixed with separate 5.0 polypropylene sutures and the skin margins were joined. The animals were sacrificed 30 days later and the ventral abdominal wall with the prosthesis was removed. The flap with the graft was divided into 2 parts, one for the traction assay and the other for histopathological study. The sections obtained were stained with hematoxylin-eosin and Sirius-red and examined under a polarized light microscope using the Image Plus software., Results: The traction assay did not demonstrate a significant difference in resistance between groups. An acute-chronic inflammatory reaction with large quantities of giant foreign body cells was present at similar intensity in both groups, the same being observed for total collagen concentration (p=0.1440) and type I collagen concentration (p=0.3981). In contrast, type III collagen concentration was higher in the sections from old animals (p=0.0364)., Conclusions: These results permit us to conclude that aging does not impair the resistance gain or collagen deposition, although a delayed tissue maturation occurs.

Purpose: The symptoms of the climacteric coincide with the marked appearance of signs of skin aging. Studies on animal models have shown that estrogen is a critical mediator in wound healing. The authors report a study of the influence of hormonal replacement therapy (HRT) on colon anastomoses performed in female rats., Methods: Three groups of Wistar rats were used: one submitted to oophorectomy and receiving HRT with 50 mg estrogen and 2 mg medroxyprogesterone acetate, one submitted to oophorectomy without HRT, and one of laparotomized but not oophorectomized rats. Hormonal condition was confirmed 28 days after oophorectomy and HRT or physiological saline was then administered daily. Left colotomy was performed after 2 months with end-to-end anastomosis, and resistance and collagen density were determined after 7 and 14 days., Results: the anastomoses of the colons of rats receiving no HRT were less resistant than those of the control group both on the 7th (p = 0.0488) and 14th (p = 0.0115) day. Collagen density was lower on the 7th day (p = 0.0210), with a lower presence of collagen I (p = 0.0023) and collagen III (p = 0.0470), and these differences continued to be significant on the 14th day. The colon anastomoses of rats receiving HRT did not differ significantly from control., Conclusion: The lack of ovarian hormones leads to a lower resistance and delays the maturation of colon anastomosis in rats and these deficiencies are compensated for by HRT.

Purpose: The aim of this study was to assess abdominal wall healing in old and young adult rats., Methods: On average, young animals were 110 days old and old animals were 762 days old. A 4.0 cm median laparotomy was performed under anesthesia, followed by laparorrhaphy on two synthesis planes, i.e. peritoneum-muscle-aponeurosis and skin, using continuous 5.0 nylon sutures. The animals were evaluated on the 3rd, 7th, 14th and 21st postoperative days. The resistance of the two planes was studied separately and a histopathologic analysis was performed on sections stained with hematoxylineosin and Sirius Red. Immunohistochemical analysis was also carried out using PCNA, LCA and CD34., Results: The skin scars gained resistance in a similar manner at the initial time points, but those of young rats were more resistant on the 21st day (p=0.0029). Total and type III collagen content was similar in the two groups and type I collagen content was higher in young animals on the 14th day. Inflammatory cell infiltration was more marked in the skin wounds of young animals on the 3rd day (p=0.0190). Reepithelialization was similar and angiogenesis was more intense in the skin wounds of young animals on the 14th day (p=0.0062). The peritoneum-muscle-aponeurosis wounds gained similar resistance during the early phases, but were more resistant on the 14th day (p=0.0005) and on the 21st day (p=0.0023) in old rats Collagen concentration was higher in the wounds of old animals on the 3rd day (p=0.0112) and in the wounds of young animals on the 21st day (p=0.0348). The inflammatory reaction was more intense in the wounds of old animals on the 3rd day (p=0.0060) and angiogenesis was more intense on the 14th day (0.0432)., Conclusion: Although there are some differences in the healing course between young and old animals, age, of itself, does not impair the healing of abdominal wall wounds in rats.

Purpose: Hypothyroidism is a common situation among the aged which affects protein synthesis. The objective of the present study was to determine the influence of hypothyroidism on the healing process in aged rats., Methods: 96 male Wistar rats were used, 48 of them with a mean age of 110 days and 48 with a mean age of 750 days. Half the young animals and half the old ones were euthyroid and half were hypothyroid. Hypothyroidism was obtained by total thyroidectomy. Thirty days after surgery the animals were submitted to median laparotomy followed by laparorrhaphy on 2 synthesis planes. Six animals from each group were submitted to euthanasia by drawing lots on the 3rd, 7th and 14th postoperative day and submitted to macroscopic, resistance, and histopathological analysis., Results: The resistance of the skin scars was lower in hypothyroid animals, both the young (p = 0.0145) and old (p = 0.0242) ones, with no significant relation with age being detected. The resistance of the scars on the peritoneum-muscle-aponeurosis plane was lower in old animals on the 24th day (p = 0.0014) and even lower in hypothyroid old animals (p = 0.0000). The histological evolution was similar, but differences in collagen presence were observed. On the 7th day the skin scars had a lower collagen content in young (p = 0.0201) and old (p = 0.0003). hypothyroid animals. On the 14th day the scars of old hypothyroid animals had less collagen than those of normal old animals (p = 0.0092) and those of young hypothyroid animals (p = 0.0283). On the 3rd day, the scars of hypothyroid animals on the peritoneum-muscle-aponeurosis plane presented less collagen than those of both young (p = 0.0089) and old (p = 0.0171) normal controls, but there was no relation with age. This association persisted on the 7th and 17th day, but age dependence was observed at these time points., Conclusion: Analysis of the results permits us to conclude that healing is impaired in the presence of hypothyroidism and worsens with aging.

The aim of this study was to present clear evidence of a stress concentration in bone as a two-phase composite of a collagen matrix reinforced by hydroxyapatite (HAP) mineral particles. X-ray diffractometry was performed on cortical bone from a bovine femur in order to measure strain in HAP along the c-axis as a response to a macroscopically applied force. From the obtained strain of HAP, the stress applied to HAP particles was determined by using Young's modulus value of HAP in the literature. Dividing the stress of HAP by that macroscopically applied to a bone specimen, the stress concentration coefficient, Chi H, was estimated. Using the Hirsch equation with the estimated Chi H, value, mineral content of bone was estimated, which accords with the mineral content values of bone in the literature.