Protective effects of pentoxifylline and nimodipine on acoustic trauma in Guinea pig cochlea.

OBJECTIVE: To examine the protective effects of the vasodilator and hemorheologically active drug pentoxifylline and the calcium channel blocker nimodipine on the cochlea after acoustic overexposure in guinea pigs. METHODS: Eighteen guinea pigs were used. The animals were divided into 5 groups: 1) control, 2) acoustic trauma, 3) nimodipine plus acoustic trauma, 4) pentoxifylline plus acoustic trauma, and 5) pentoxifylline plus nimodipine plus acoustic trauma. Nimodipine was given to the guinea pigs 3 mg/kg intraperitoneally in a single dose; pentoxifylline was given 150 mg/kg in a single dose intraperitoneally. A gunnery range was used to create acoustic trauma. The auditory brainstem response of each guinea pig was determined first; then, the animals were killed, and their cochleas were examined under an electron microscope. RESULTS: In the acoustic trauma group, negative auditory brainstem response potentials were seen as was well-adjusted cellular damage to the organ of Corti. In the pentoxifylline group, near-normal auditory brainstem response recordings and organ of Corti histologic findings were found. Organ of Corti damage was seen in the pentoxifylline plus nimodipine plus acoustic trauma group. CONCLUSION: We determined that pentoxifylline was highly protective against noise, but nimodipine was not. Also, pentoxifylline and nimodipine, when used together, increased damage to the organ of Corti.

Effect of Er:YAG and CO2 lasers with and without sodium fluoride gel on dentinal tubules: a scanning electron microscope examination.

OBJECTIVE: The aim of this pilot study was to evaluate the occluding effect of erbium:yttrium-aluminum-garnet (Er:YAG) and carbon dioxide (CO2) lasers as monotherapy and in combination with topical fluoride gel on human dentinal tubules by scanning electron microscopic (SEM) examination. MATERIALS AND METHODS: Thirty-six dentine specimens with exposed dentinal tubule orifices were included in this study. The samples were divided into six groups. Group A served as controls, group B was treated with 2% sodium fluoride (NaF) gel alone, groups C and D were irradiated with Er:YAG (30 Hz, 60 mJ, for 10 sec) and CO2 (1 W, continuous-wave mode, for 10 sec) lasers, respectively, and groups E and F received NaF gel plus Er:YAG and CO2 laser irradiation, respectively. RESULTS: Under SEM analysis, numerous exposed, normally-structured dentinal tubule orifices were seen in the control group. Some narrowing of the exposed tubule orifices was seen in group B. A melted, irregular surface structure with small peaks was observed in group C. The surface of group D also had a melted appearance, but a fibrillar deformation of the surface structure was seen on the specimens. However, the surface morphologies seen were remarkably different in groups E and F. While the tubule orifices were obviously occluded but depressed into craters in group E, the surface structure of group F primarily showed a smooth appearance. In terms of numbers and diameters of open dentinal tubules, there was no significant difference between the laser-alone and combination groups, whereas the difference was found to be significant when the control and NaF groups were compared with each other and the remaining laser-alone or combination groups. CONCLUSION: The dentinal tubules in all laser groups were occluded after laser irradiation, but more marked occlusions were observed when laser and NaF gel were combined.

Effect of oral magnesium supplementation on cisplatin ototoxicity.

OBJECTIVE: The purpose of this study is to evaluate the effect of Mg supplementation on cisplatin ototoxicity in guinea pigs. METHODS: Twenty guinea pigs were divided into two groups and were fed different Mg-containing diets. Following 6 mg/kg of cisplatin injection, the animals were sacrificed and the extent of cochlear damage was assessed with the scanning electron microscope and compared with the control group. Additionally, intracardiac blood samples were taken to determine the plasma Mg levels of the subjects before and after cisplatin exposure. RESULTS: The outer hair cell damage owing to cisplatin was not statistically different in both groups (p > .05). Following cisplatin injection, the plasma Mg levels of both groups were found to be significantly lower than the plasma Mg levels before exposure, but the resulting values of the Mg-rich fed group was compatible with control group Mg levels. CONCLUSION: Our study showed that a Mg-rich diet can prevent the severe hypomagnesemia that cisplatin causes in guinea pigs, but this measure has not been enough to protect the inner ear against its ototoxic effect.

Release behaviour and biocompatibility of drug-loaded pH sensitive particles.

The purpose of this work was to investigate the physical properties of drug-loaded poly(methacrylic acid-g-ethylene glycol) {P(MAA-g-EG)} particles, their biocompatibility with the gastrointestinal tract of rats and also the effects of these particles on the tight junctions of the rat intestinal epithelium. Model drugs such as diltiazem HCl, diclofenac Na, ciprofloxacin HCl and isoniazid were used in this study. P(MAA-g-EG) particles were prepared by free radical solution polymerization of methacrylic acid (MAA) and poly(ethylene glycol) (PEG). The loading efficiency of the model drugs in the particles and in vitro release profiles were investigated in pH 7.4 phosphate buffer and in gradually pH changing buffers (pH 1.2, 5.8, 6.8 and 7.4). The stability of free particles and drug-loaded particles was established by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). In conclusion, P(MAA-g-EG) particles controlled the release rate of small molecular weight model drugs according to the pH of the medium. Stability of those particles loaded with drugs did not change in accelerated stability conditions. Histopathological results indicated that loading drugs to the particles prevented cell and tissue damage after 20 h. Free particles showed no change of tight junctions after 2 and 10 h. The results of TEM showed that increasing the amount of P(MAA-g-EG) particles from 100 to 385 mg clearly opened the tight junction, but with serious epithelial cell disruption.

Comparison of functional results of nerve graft, vein graft, and vein filled with muscle graft in end-to-side neurorrhaphy.

End-to-side neurorrhaphy is an alternative method in the situation where the proximal part of the nerve cannot be found. When the intact nerve is not close enough to perform end-to-side neurorrhaphy, it will be necessary to use a graft for transporting the regenerating axons. In this study, we tried to find out whether it is possible to use a graft in an end-to-side neurorrhaphy, and compared the nerve graft with possible alternative grafts, i.e., vein and muscle-filled vein grafts. Thirty male Sprague Dawley rats were used, with an average weight of 293 g (range, 250-350 g). All experiments were done on the right side. A 2-cm nerve graft, beginning 1 cm distal to the branching level, was sectioned from the peroneal nerve. A 1-mm epineural window was opened in the tibial nerve. In the first group, the proximal side of this graft was sutured to the tibial nerve side in an end-to-side fashion, and the distal side was sutured to the distal peroneal nerve stump in an end-to-end fashion. In the second group, the right 2-cm jugular vein was harvested, and was used to bridge the defect instead of the nerve graft used in the first group. In the third group, a 2-cm jugular vein filled with fresh skeletal muscle was used to bridge the defect. At 2, 4, 8, 12, 20, and 28 weeks, functional assessment of nerve regeneration was performed, using walking-track analysis. The numbers of myelinated fibers and fiber diameters were measured, and an electron microscopic evaluation was carried out. Based on walking-track analysis and fiber diameters, the differences of all three groups were statistically significant (P < 0.05). While the differences of myelinated fibers between the first and second groups were not significant, the differences between the rest (group 1-group 3 and group 2-group 3) were significant (P < 0.05). Our study showed that, in end-to-side neurorrhaphy, the use of a nerve graft is possible, and a vein graft is also a good alternative, but a muscle-filled vein graft is not.