Magnetic transcutaneous fixation: an experimental study in pigs.

BACKGROUND: Magnetic subdermal implants have never been studied in the context of magnetic fixation of an external device to the body's surface. Excessive attractive force between the implant and the external device may compromise local circulation due to mechanical compression, leading to necrosis. OBJECTIVE: To evaluate the feasibility of transcutaneous magnetic fixation and assess secondary skin changes when subjected to a continuous static magnetic field. METHODS: Using the pig as an animal model, 72 implants were introduced in 12 animals. After wound healing, ultrasonography was performed to measure implant depths. Computer simulations were applied to allow magnetic attachment between implants and external devices without impairing local blood flow. External devices of different magnetic strengths were applied over the skin for 7 days. Local skin was examined and collected for analysis. A senior dermatopathologist blindly examined skin specimens and controls for abnormal findings, measuring dermal and epidermal thickness. Statistical analysis (P <0.05) was performed over the data. RESULTS: Nineteen implants presented extrusion. The remaining 53 skin sites underwent magnetic compression, of which 43 (81%) evolved uneventfully. Implant depth varied between 4.6 mm and 8.3 mm (5.8 mm; ± 8.6 mm) with estimated pressure levels between 13.28 mmHg and 37.04 mmHg (27.6 mmHg; ±6.0 mmHg). Stronger magnets were associated with an increase in dermal thickness (P = 0.011) and neovascularization (P = 0.045). CONCLUSIONS: Transcutaneous magnetic fixation is compatible with skin viability in vivo, under experimental conditions. Skin interposition between two permanent magnets resulted in a continuous static magnetic field stimulation, which showed similar effects to pulsed electromagnetic fields reported on scientific literature.

Influence of acid treatment on surface properties and in vivo performance of Ti6Al4V alloy for biomedical applications.

The purpose of this work was to investigate the influence of acid treatment on the surface properties and in vivo performance of titanium grade 5 (Ti6Al4V) alloy. Mini-implants with surface treatment were inserted into New Zealand rabbit tibia for 1, 4 and 8 weeks. SEM analysis showed intercommunicated micropores in acid treated samples. AFM showed micron and sub-micron roughness. The thickness of the titanium oxide layer increased with surface treatment, with a significant reduction of Al and V concentration. Acid treated implant removal torque was larger than without treatment. The implants/bone interface of acid treated implants showed dense adhered Ca/P particles with spreading osteoblasts after 4 weeks and newly formed bone trabeculae after 8 weeks. Analysis of rabbit blood that received treated implant showed lower Al and V contents at all times. Acid treatment improved surface morphology and mechanical stability, which allowed initial events of osseointegration, while Al-V ion release was reduced. GRAPHICAL ABTSRACT.

Viability of randomized skin flaps-an experimental study in rats.

BACKGROUND: Randomized skin flaps are extensively used in plastic surgery, but the possibility of necrosis has challenged their use. Several studies have been conducted aiming to find ways to reduce the occurrence of necrosis. We evaluated the effects of pentoxifylline (PTX) and hyaluronidase (HLD), each alone or combined, on randomized rat skin flaps. MATERIALS AND METHODS: Fifty male Wistar rats were divided into five groups of 10 animals each: control I, control II, PTX, HLD, PTX-HLD. Substances were administered from the first to the 14th postoperative day. The necrotic area was measured on the seventh and 14th postoperative day; the animals were killed on the 14th day, when samples were collected for histologic and immunohistochemical examination. RESULTS: On the seventh day, percentage of the necrotic area was significantly reduced in PTX, HLD, and PTX-HLD animals compared with control groups. On 14th day, percentage of the necrotic area in PTX, HDL, and PTX-HLD groups was also significantly reduced compared with control groups. PTX and PTX-HLD showed a significant reduction in dermis cellularity, VV of macrophages, and myofibroblasts compared with control groups; PTX showed a significant enhancement of LV of blood vessels compared with all other groups. CONCLUSIONS: The use of each substance alone or combined increased flap viability compared with control groups. On the seventh day, PTX exhibited lower viability than HLD, whereas on the 14th day there was no difference between treated groups. PTX alone enhanced the LV of blood vessels, whereas PTX-HLD did not. However, PTX-HLD was more effective in decreasing the dermis cellularity and macrophage VV than HLD alone.

A new model for the standardization of experimental burn wounds.

BACKGROUND: Burns are common and recurrent events treated by physicians on a daily basis at most emergency rooms around the world. There is a constant need to understand the physiopathology of burns, so as to minimize their devastating results. The objective of the present report is to describe a burn apparatus in association with an innovative method of animal fixation, as to produce burns of varying sizes and depths. METHODS: Rats were subjected to burns of 60 °C, 70 °C, and 80 °C for 10 s and after 3 days half of the rats in each group were killed and the resulting lesions were analyzed using histological techniques. In the other half of the rats the wound was measured weakly until complete re-epithelialization. RESULTS: All burns were easily visible and the histological feature for the 60 °C burn was a superficial second-degree burn (28% of the dermis), for 70 °C we observed a deep second-degree burn (72% of the dermis), and in the 80 °C group, a third degree-burn was present (100% of the dermis). CONCLUSIONS: This is a safe, reliable, easy to construct and use model that has the ability to produce a regular and uniform reproducible burn due to precise temperature control associated with standardized animal positioning.

Effects of TachoSil and 5-fluorouracil on colonic anastomotic healing.

BACKGROUND: The administration of intraperitoneal (IP) 5-fluorouracil (5-FU) during the early postoperative period after cytoreductive surgery can decrease local cancer recurrence but may also cause impairment of the anastomotic healing. This study examined the effects of the use of this therapy and of the anastomotic sealing with TachoSil, a fibrin-thrombin coated sealant (FTCS), on the healing of colon anastomoses. MATERIALS AND METHODS: Forty male rats were divided into four groups (1-4, 10 rats each) that underwent transection and anastomosis of the left colon. The anastomoses were covered with FTCS in groups 2 and 4. Saline solution (2 mL/d-groups 1 and 2) or 5-FU (20 mg/kg/d; groups 3 and 4) was administered IP once daily for 3 d. Bursting pressure (BP) was recorded, and the anastomoses were examined macroscopically and graded histologically. RESULTS: The relative weight loss was significantly higher in group 3 than in the other groups (P = 0.0004). Anastomotic dehiscence, postoperative adhesion formation, perianastomotic collections, and preanastomotic dilatation did not differ significantly among groups. BP was significantly lower in group 3 compared with all other groups (P = 0.001). Neoangiogenesis was significantly lower in group 3 compared with groups 1 and 2 (P = 0.05). Fibroblastic activity was significantly higher in group 1 compared with group 3 (P = 0.035). Inflammatory cell infiltration and collagen deposition did not differ significantly among groups. CONCLUSIONS: Our results shown that the early postoperative IP chemotherapy with 5-FU impaired the healing of colon anastomoses. However, anastomotic sealing with FTCS reversed some of the negative effects of this therapy.

Different from renal artery only clamping, artery and vein clamping causes a significant reduction in number of rat glomeruli during warm ischemia.

PURPOSE: To evaluate glomerular injury in the rat model during renal warm ischemia (WI), comparing artery and vein (AV) clamping with artery only (AO) clamping. MATERIALS AND METHODS: Twenty-four adult male rats underwent 60 minutes of renal WI in the left kidney. The animals were divided into three groups: AV clamping, AO clamping, and Sham surgery. After 30 days, the animals were euthanized, and both kidneys were processed for paraffin embedding and stained with hematoxylin and eosin. Glomerular volume density (Vv[glom]), mean glomerular volume (MGV), and number of glomeruli per mm(3) (Nv[glom]) were evaluated in the renal cortex. RESULTS: The Vv[glom] was reduced in the left kidney (ischemic) when compared with the right kidney in both AV and AO groups by 11.1% and 35.4%, respectively; however, the difference was significant only in the AV group. The Nv[glom] was reduced in the left kidney when compared with the right kidney in both AV and AO groups by 11.6% and 31.4%, respectively; nevertheless, the difference was significant only in the AV group. The MGV of left and right kidneys was the same in both Sham and AO groups and was diminished by 6.7% in the AV group-not significant. CONCLUSION: AV clamping causes a significant decrease in the number of glomeruli in the rat model, while AO clamping reduces the glomerular number, but not significantly. To minimize renal injury, AO clamping may be preferred over AV clamping when WI is necessary in patients with previously compromised renal function.

L-arginine and glycine supplementation in the repair of the irradiated colonic wall of rats.

PURPOSE: Radiotherapy is widely used for cancer treatment but has harmful effects. This study aimed to assess the effects of L-arginine and glycine supplementation on the colon wall of rats submitted to abdominal irradiation. METHODS: Forty male Wistar rats were randomly divided into four groups: I-healthy, II-irradiated with no amino acid supplementation, III-irradiated and supplemented with L-arginine, and IV-irradiated and supplemented with glycine. The animals received supplementation for 14 days, with irradiation being applied on the eighth day of the experiment. All animals underwent laparotomy on the 15th day for resection of a colonic segment for stereologic analysis. Parametric and nonparametric tests were used for statistical analysis, with the level of significance set at p ≤0.05. RESULTS: Stereologic analysis showed that irradiation induced a reduction of the total volume of the colon wall of group II and III animals compared to healthy controls, but not of group IV animals supplemented with glycine. The mucosal layer of the irradiated animals of all groups was reduced compared to healthy group I animals, but supplementation with L-arginine and glycine was effective in maintaining the epithelial surface of the mucosal layer. CONCLUSION: The present results suggest that glycine supplementation had a superior effect on the irradiated colon wall compared to L-arginine supplementation since it was able to maintain the thickness of the wall and the epithelial surface of the mucosa, whereas L-arginine maintained the partial volume of the epithelium and the epithelial surface, but not the total volume of the intestinal wall.

Role of L-glutamine and glycine supplementation on irradiated colonic wall.

BACKGROUND AND AIMS: Radiotherapy is frequently used for cancer treatment, but it may be associated with several complications. Thus, this study aimed to evaluate the role of L-glutamine and/or glycine supplementation on the colonic wall in rats submitted to abdominal radiation. MATERIALS AND METHODS: Sixty adult Wistar rats were randomly divided into six groups: I-healthy, II (control)-irradiated rats without amino acid supplementation, III-irradiated rats with glycine supplementation, IV-irradiated rats with L-glutamine supplementation, V-irradiated rats with glycine supplementation 7 days before irradiation and with L-glutamine supplementation 7 days after irradiation, and VI-irradiated rats with L-glutamine supplementation 7 days before irradiation and with glycine supplementation 7 days after irradiation. Abdominal irradiation was employed with a dose of 1,000 cGy on the eighth day of the experiment. All animals underwent laparotomy on the 15th day for resection of a colonic segment for stereologic analysis. Parametric and nonparametric tests were used for statistical analysis, with the level of significance set at p

C-peptide: much more than a byproduct of insulin biosynthesis.

OBJECTIVES: During the past decade, numerous studies in both humans and animals have demonstrated that C-peptide, although not influencing blood sugar control, might play a role in preventing and potentially reversing some of the chronic complications of type 1 diabetes. The aim of this paper is to present an up-to-date review of C-peptide, focusing on its role in insulin biosynthesis and in the classification of diabetes mellitus, as well as its potential clinical applications. METHODS AND RESULTS: The relevant literature cited in the MEDLINE database shows that the measurement of C-peptide production combined with screening for the presence of islet-cell and other autoantibodies seems to exert an important role in the accurate differentiation between patients with type 1 and type 2 diabetes. Also, both experimental and clinical data provide evidence suggesting that combined replacement of insulin and C-peptide has potential therapeutic value in patients with type 1 diabetes. CONCLUSIONS: Further study in this area is warranted, but the findings that pancreas transplants promote the reversal of diabetic neuropathy and stabilization of diabetic retinopathy and that both pancreas and islet transplants lead to the reversal of diabetic nephropathy lend credence to the concept that combined replacement of insulin and C-peptide may more effectively mitigate the inexorable progression of diabetes-related complications.

Long-term outcome of sirolimus rescue in kidney-pancreas transplantation.

Sirolimus (SRL) rescue in kidney-pancreas transplantation has not been well described. We reviewed 112 KPTxs performed at our institution between December 3, 1995 and June 27, 2002. All patients received antibody induction, tacrolimus (TAC), mycophenolate mofetil (MMF), and steroids. In 35 patients, SRL was substituted for MMF for the following reasons: acute rejection (AR) of kidney or pancreas despite adequate TAC levels, MMF intolerance, increasing creatinine levels, and TAC-induced hyperglycemia. Three-year kidney and pancreas graft survivals were 97% and 90%, respectively. Of 10 patients who were switched to SRL because of AR, one kidney failed because of antibody-resistant AR, and one kidney developed borderline AR; the other eight patients remain AR-free. AR developed in seven other patients despite therapeutic SRL levels; six had TAC levels less than 4.5 ng/mL. The mean creatinine levels overall and for the group with increasing creatinine remained stable. All patients who were switched to SRL for TAC-induced hyperglycemia or MMF intolerance improved. Kidney-pancreas transplant recipients can be safely switched to SRL with excellent graft and patient survival.