Banu Coskun Yilmaz

Bacteriophage therapy in implant-related infections: an experimental study.

BACKGROUND Implant-related infections with bacteria resistant to multiple antibiotics represent one of the major problems in orthopaedic surgery. It was our hypothesis that local application of bacteriophages, which are bacteria-destroying viruses, would be effective against biofilm-forming bacteria. METHODS An implant-related infection model was created using methicillin-resistant Staphylococcus aureus (MRSA) in forty-eight rats and Pseudomonas aeruginosa in another forty-eight rats. Each group was divided into four subgroups; one subgroup received a bacterium-specific bacteriophage (Sb-1 in the MRSA group and PAT14 in the Pseudomonas aeruginosa group), one received antibiotic for fourteen days (20 mg/kg/day teicoplanin in the MRSA group, and 120 mg/kg/day imipenem + cilastatin and 25 mg/kg/day amikacin in the Pseudomonas group), one received antibiotic and bacteriophage, and one received no treatment. Animals receiving bacteriophage therapy were injected locally with 107 bacteriophages in a 0.1-mL suspension on three consecutive days. All animals were killed on the fifteenth day after initiation of treatment, and the tibia was excised. Results were assessed with use of microbiology, light microscopy, and electron microscopy. RESULTS In the MRSA group, the antibiotic administration significantly decreased the number of colony-forming units per subject in quantitative cultures (control subgroup, 50,586; bacteriophage, 30,788; antibiotic, 17,165; antibiotic + bacteriophage, 5000; p = 0.004 for the comparison of the latter group with the control). Biofilm was absent only in the antibiotic + bacteriophage subgroup. In the Pseudomonas group, the number of colony-forming units per subject in quantitative cultures was significantly lower in each treatment subgroup compared with the control subgroup (control subgroup, 14,749; bacteriophage, 6484 [p = 0.016]; antibiotic, 2619 [p = 0.01]; antibiotic + bacteriophage, 1705 [p < 0.001]). The value in the antibiotic + bacteriophage subgroup was also significantly lower than the values in the other subgroups (p = 0.006). Biofilm thickness did not differ significantly among the subgroups in the Pseudomonas group. CONCLUSIONS The addition of bacteriophage treatment to an appropriate antibiotic regimen helped to dissolve the biofilm of both types of bacteria studied. This effect on MRSA was more pronounced than that on Pseudomonas aeruginosa.

Pressure applied during surgery alters the biomechanical properties of human saphenous vein graft

Pressure applied during harvesting of the saphenous vein (SV) graft in coronary artery bypass surgery might change its mechanical properties and thereby decrease the patency. This study was performed to assess the mechanical properties of the SV graft distended manually with different levels of pressure and to determine the pressure level that induces changes in its structure and mechanics. Saphenous vein graft segments, collected from 36 patients undergoing coronary artery bypass surgery, were distended with pressures of either 50–60, 75–100, or 130–150 mmHg. Grafts were tested for the stress–strain relationship; the Young’s moduli at the low- and high-strain regions were calculated, and their structures were examined by light and electron microscopy. Pressures of 50–60 mmHg did not influence the mechanics of the vein graft, whereas pressures of 75–100 mmHg elevated the elastic modulus of the vein at the low-strain region while pressures above 130 mmHg increased the elastic moduli at both low- and high-strain regions. There was a prominent loss of microfibrils at all distending pressure levels. The mechanical results suggest that distending pressures above 75 mmHg might play a role in graft failure. Furthermore, the absence of microfibrils surrounding elastin suggests that application of distending pressures, even as low as 50 mmHg, can cause degeneration of the elastic fibers following implantation, increasing the stiffness of the graft and thus impairing the graft’s function under its new hemodynamic conditions.

Molecular mechanism of vasorelaxant and antiatherogenic effects of the statins in the human saphenous vein graft

In this study we aimed to investigate the vasorelaxant and antiatherogenic effects of the statins (fluvastatin and pravastatin) in the human saphenous vein grafts at the molecular level by using histopathologic, pharmacological and immunochemical techniques. The saphenous vein grafts evaluated histopathologically displayed a loss in their endothelium up to a ratio of 30% and set forth indications of functional deterioration. The pharmacological evaluations proved that the relaxation responses induced by fluvastatin and pravastatin were significantly inhibited by nitric oxide synthase inhibitor, N(G)-nitro-l-arginine, and cyclooxygenase inhibitor, indomethacin, while these responses were significantly increased by angiotensin converting enzyme inhibitors, captopril and enalapril, and rho kinase inhibitor, Y27632. The results of immunochemical studies are in accordance with the results of the pharmacological studies that the related statins increased the levels of nitric oxide, phospholipase A(2) and they decreased the levels of angiotensin II and active rho kinase. On the other hand mevalonolactone, a substrate of lipid metabolism, failed to change the effects of fluvastatin and pravastatin in the related tissue. The experimental results indicate that activation of nitric oxide synthase and phospholipase A(2)-cyclooxygenase pathway and inhibition of angiotensin converting enzyme and rho kinase may have a role on the effects of fluvastatin and pravastatin in the human saphenous vein grafts. It seems that the vasorelaxant and antiatherogenic effects of the related statins are independent of their lipid lowering mechanism.

Electrophysiological, biochemical and ultrastructural effects of radiotherapy on normal rat sciatic nerve.

Abstract Purpose: The aim of the present study was to evaluate the electrophysiological, biochemical and ultrastructural changes on the rat sciatic nerve after radiotherapy. Material and Methods: Thirty male Wistar albino rats were divided into three groups as: Control group (n = 10), Group I: 3 months after radiotherapy (n = 10), and Group II: 6 months after radiotherapy (n = 10). Groups I and II were irradiated with a 60Co gamma source. A dose of 20 Gy in 10 fractions was applied to Groups I and II. Compound motor action potentials (CMAP) were recorded in all groups. Superoxide dismutase (SOD) and catalase (CAT) activities and malondialdehyde (MDA) levels were measured in the sciatic nerve of rats using the biochemical methods. Ultrastructural changes were determined by electron microscopy. Results: In Groups I and II, the amplitude of CMAP was significantly lower and the latency was significantly higher than that of the control group. There were no significant differences between Groups I and II regarding the CMAP amplitude and latency. The MDA levels were significantly increased, whereas the SOD and CAT activities were significantly decreased in experimental groups when compared with the control group. However, there were no significant changes in these parameters between Groups I and II. Degeneration in myelinated nerve fibers was observed ultrastructurally only in the experimental groups. Significant changes were observed between the control group and experimental groups in terms of ultrastructural myelin grading score and axonal damage score. No significant differences were found between Groups I and II. Conclusions: These findings indicated that the dose of 20 Gy in 10 fractions radiotherapy caused neuropathic damages in normal rat sciatic nerve 3 and 6 months after irradiation.

Optimal transport time and conditions for cartilage tissue samples and expanded chondrocyte suspensions.

For autologous chondrocyte implantation, the chondral tissue obtained is transferred from the operating room to the laboratory using specialized carrier systems within 24 hours. Similar expenses are used for the transport of cultured chondrocytes. The purpose of this study was to find the optimal temperature, size of tissue, and time that the chondrocytes can stand without losing viability and proliferative capacity. Fresh calf cartilage was harvested and divided into 24 groups. Half of the samples were diced into 1- to 2-mm(3) pieces. All 12 groups were kept at either 4 degrees C, 25 degrees C, or 37 degrees C for 1, 3, 5, or 7 days and were seeded for cell culture. Times to reach confluence values were compared. Produced cell suspensions were grouped similarly and tested similarly. Neither the temperature nor the waiting days caused any difference in the proliferative capacity of the cells. Diced tissues yielded a shorter time to reach confluence values. Chondral tissue obtained from the patient can be transferred to the laboratory at temperatures ranging from 4 degrees C to 37 degrees C in up to 7 days. These conditions did not affect the proliferative capacity or the viability of the chondrocytes. Dicing the tissue prior to transport will shorten total culturing time. The expanded cell suspensions should be transferred at temperatures from 4 degrees C to 25 degrees C within 3 days. Specialized carrier systems to get the chondral tissue from the operating room to the laboratory and to take the expanded chondrocytes back to the operating room within hours may not be necessary.

Inducing Ocular Allergy with β-Lactoglobulin: A New Experimental Model

Purpose: To develop a new experimental ocular allergy animal model induced by β-lactoglobulin (BLG), a major cow’s milk allergen, and to discuss the clinical, histopathological and immunohistochemical findings. Methods: Forty Balb/c mice were randomized and separated into groups of 10. Groups were determined according to the different concentrations of BLG drops used. Study groups were immunized with 2.5, 5 or 10 mg/ml topical BLG (groups 2, 3 and 4, respectively) following intraperitoneal injection for the systemic immunization. The control group (group 1) was immunized with aluminium hydroxide (alum) alone within the same intervals. After ocular challenge, all the animals were evaluated clinically, histopathologically (mast cell and eosinophil infiltration) and immunhistochemically in terms of both T helper type 1- (IFNγ, TNFα) and T helper type 2- (IL-3, IL-4, IL-5, IL-10) specific cytokines. Results: Both clinical and immunohistochemical findings showed that an allergic conjunctivitis was induced in all study groups, with an optimized dosage of topical 5 mg/ml BLG. The conjunctivitis was associated with both Th1 and Th2 response, with a slight predominance of Th1 reaction. Conclusion: We describe a new murine model of acute allergic conjunctivitis induced by BLG. We believe that this new preliminary model has the immune parameters of the late phase of acute allergic conjunctivitis and it provides an alternative means for studying the pathogenesis and future treatments of ocular allergy. Our results should be enhanced with more detailed cellular and humoral parameters.

Potential protective effects of naringenin against vancomycin-induced nephrotoxicity via reduction on apoptotic and oxidative stress markers in rats.

Abstract Vancomycin (VCM), a glycopeptide antibiotic, is a drug widely used in severe infections. However, VCM induce notable nephrotoxic side effects. Naringenin (NAR) is a natural of flavonoid and are known as strongly antioxidant, nefroprotective, antiapoptotic, and anti-inflammatory. The purpose of this study was to determine the potential protective effects of NAR against VCM-induced nephrotoxicity by measuring apoptotic and oxidative stress markers and evaluating histopathological alterations in rats. For this purpose, we used male Wistar albino rats that divided into seven groups: (i) Control [saline, intraperitoneally (i.p.)], (ii) carboxymethyl cellulose (0.5% CMC, orally), (iii) VCM (400 mg/kg, i.p.), (iv) NAR100 (100 mg/kg, orally), (v) VCM + NAR25 (25 mg/kg, orally), (vi) VCM + NAR50 (50 mg/kg, orally), and (vii) VCM + NAR100 (100 mg/kg, orally) groups. VCM administration was started one day after the first treatment of NAR and continued across 7-day. Caspase-3, -8, and-9 activities and malondialdehyde (MDA) and nitric oxide (NO) levels were measured by colorimetric methods in the kidney tissues, creatinine, and blood urea nitrogen (BUN) levels were analyzed based on ELISA in serum. Caspase-3 and -8 activities, NO levels, serum creatinine and BUN levels were significantly higher in VCM group in comparison with VCM + NAR (25, 50, and 100) groups (p < 0.05). Caspase-9 activity and MDA were significantly higher in VCM group compared to VCM + NAR (25 and 50) groups (p < 0.05). Histopathological alterations in VCM group were significantly diminished by administration of NAR, especially NAR 25. In conclusion, NAR 25 and 50 mg have more potent protective effects on VCM-induced nephrotoxicity compared to NAR 100 mg.

GDF9 and BMP15 Expressions and Fine Structure Changes during Folliculogenesis in Polycystic Ovary Syndrome.

Background: Polycystic ovary syndrome is the most frequently seen endocrine disorder in women of reproductive age with a prevalence of about 10%. Aims: To investigate the efficiency of growth differentiation factor 9 and bone morphogenetic protein 15 during folliculogenesis in a dehydroepiandrosterone-induced mouse Polycystic ovary syndrome model. Study Design: Animal experimentation. Methods: Mice were divided into 3 groups: control, vehicle and Polycystic ovary syndrome. Polycystic ovary syndrome model mice were developed by the injection of dehydroepiandrosterone dissolved in 0.1 mL of sesame oil. Ovarian tissues were examined for growth differentiation factor 9 and bone morphogenetic protein 15 using immunofluorescent labelling and electron microscopic examinations. Results: The immunoreactivity of growth differentiation factor 9 and bone morphogenetic protein 15 proteins decreased (p<0.05) in the Polycystic ovary syndrome group (27.73±8.43 and 24.85±7.03, respectively) compared with the control group (33.72±11.22 and 31.12±11.05, respectively) and vehicle group (33.95±10.75 and 29.99±10.72, respectively). Apoptotic changes were observed in granulosa cells, lipid vacuoles increased in Theca cells and thickening and irregularities were noted in the basal lamina of granulosa cells. An increased electron density in the zona pellucida in some of the multilaminar primary and secondary follicles in the Polycystic ovary syndrome model was also observed at the ultrastructural level. Conclusion: These results suggest that the decrease in the growth differentiation factor 9 and bone morphogenetic protein 15 expression initiated at the primary follicle stage effect the follicle development and zona pellucida structure and may cause subfertility or infertility in Polycystic ovary syndrome.