Abit Aktaş

Platelet gel does not improve peripheral nerve regeneration: an electrophysiological, stereological, and electron microscopic study.

Although use of platelet gel (PG) for promoting tissue regeneration is a popular approach because of its capacity to accelerate tissue regeneration, to our knowledge, its effects on peripheral nerve have still not been elucidated. Therefore, the aim of this study was to investigate effects of PG on sciatic nerve regeneration using electrophysiology, stereology, and electron microscopy. The study was performed using five groups of rats: sham operated (Sham), collagen tube conduit (CT), collagen tube conduit plus platelet gel (CT + PG), autogenous nerve graft (ANG), and primary repair (PR) groups. Gap length for CT and CT + PG groups is 1 cm. Electrophysiology showed that nerve conduction velocity was not different among experimental groups; the amplitude of compound action potential of PR group was significantly higher than other groups. Examination of the nerves showed that Sham group not only had a larger axon diameter but also a thicker myelin sheath. A higher number of myelinated axon was found in both ANG and PR groups in comparison to Sham, CT, and CT+PG groups. There is no significant difference between morphological quantities of CT+PG and CT group. It was expected that regeneration degree of the nerve fibers of CT+PG group would be better than CT group, which was the control group permitting to disclose the presence of a positive effect of PG on nerve regeneration, but this was not the case. Therefore, our results suggest that PG does not improve axon regeneration after microsurgical reconstruction of a nerve gap by collagen tubes.

The effect of melatonin and platelet gel on sciatic nerve repair: An electrophysiological and stereological study

Nerve regeneration after surgical reconstruction is far from optimal, and thus effective strategies for improving the outcome of nerve repair are being sought. In this experiment, we verified if postoperative intraperitoneal melatonin (MLT) administration after intraoperative platelet gel application improves peripheral nerve regeneration. In adult male rats, 1‐cm long sciatic nerve defects were repaired using four different strategies: autologous nerve graft repair followed by MLT (NM, n = 5), collagen conduit repair followed by MLT (CM, n = 5), platelet gel‐enriched collagen conduit repair followed by MLT (CGM, n = 6), and platelet gel‐enriched collagen conduit (CG, n = 5) repair followed by no substance administration. Sham operated animals were used as controls (Cont, n = 5). Ninety days after surgery, the nerve regeneration outcome was comparatively assessed by means of electrophysiological and stereological analysis. Electrophysiology revealed no significant differences between the experimental and the sham control groups. Stereological analysis showed no significant differences among the experimental groups regarding axon size and myelin thickness, but the axon number was significantly lower in the CM compared to Cont and NM group. Moreover, there was no significant difference between number of axons in CG and Cont groups, between CGM and CM, and between CM and NM. Although it was observed that platelet gel have a positive effect on nerve regeneration, but a combination of local platelet gel with MLT does not have the same effect on nerve repair.

Prenatal exposure to a non-steroidal anti-inflammatory drug or saline solution impairs sciatic nerve morphology: a stereological and histological study

The toxic effect of non‐steroidal anti‐inflammatory drugs (NSAIDs) during development has been widely investigated. While it has been shown that these drugs impair central nervous development and compromise the neural activity, the effects of these substances on the development of peripheral nerves are still not clarified. In the present study, sciatic nerves withdrawn from three experimental groups of 4‐week‐old rats, prenatally exposed to either saline solution, or diclofenac sodium, and controls not exposed to any substance, were evaluated in terms of axon number, cross‐sectional area of axon and myelin sheet thickness as well as of the ultrastructure of nerve fibers. Comparisons of stereological estimations among these three groups showed that axon number and mean axon cross‐sectional area, but not average myelin sheet thickness, were significantly decreased in rats that were exposed to both diclofenac sodium and also to the saline solution, in comparison of the control group. Electron microscope analysis revealed, in both treated groups, deterioration of myelin sheaths that was more pronounced in rats that were exposed to diclofenac sodium. Altogether, these findings show that the prenatal administration of both diclofenac sodium and saline solution impairs peripheral nervous system development, thus suggesting that this potential teratogenic effect should be also taken into consideration in the clinical use of these substances in pregnant patients.

An efficient stereological sampling approach for quantitative assessment of nerve regeneration

Aims: The aim of the present study was to find the most efficient sampling strategy for stereological analysis of peripheral nerve, including the number of myelinated nerve fibres, axon cross‐sectional area and myelin sheet thicknesses of nerve fibres. Methods: Two groups of rats underwent experimental resection of the tibial and peroneal nerves. The first group received tibial‐peroneal end to end autograft repair (n = 6). Tibial and peroneal nerves were isolated, transected, and separated 1 cm distal to the trifurcation, where they lay adjacent to each other by a 1‐cm gap, then repaired with an autologous nerve graft taken from the tibial nerve. The proximal stump of the tibial nerve and distal stump of the peroneal nerve were connected to each other by means of the nerve graft. The second group received tibial‐peroneal repair with a flexible collagen tube (n = 6). After 90 days of recovery, animals were sacrificed and nerve segments were removed and sectioned for microscopy. Three different sampling strategies, that is, small, medium and large step sizes were applied to obtain each quantitative parameter. Results: There are no significant differences between these sampling strategies with respect to total number of myelinated nerve fibres, axon cross‐sectional area and myelin sheet thicknesses of nerve fibres. Conclusion: Findings show that one can achieve the desired estimate precisely with a rather large and less time‐consuming sampling approach. In addition, it was observed that the size discrepancy of nerve regeneration can be improved by collagen tube conduit even with a 1‐cm gap.

Sertoli cell proliferation during the post hatching period in domestic fowl.

There has been no study aimed at directly determining of the periods of Sertoli cell proliferation in birds even domestic fowl. The aims of this study were to observe the cessation of post-hatching mitotic proliferation of Sertoli cells in domestic fowl, and to determine the volume density of Sertoli and germ cells during this period. A total of 50 Leghorn chicks were used in this study. The testes sections of the animals were immunostained with BrdU to observe the proliferation of cells from one to 10 weeks of age. The volume density of the Sertoli and germ cells were determined using the standard point counting method. The volume density of the germ cell nuclei was initially less than that of the Sertoli cells but the volume density converged by week 6, and remained relatively constant until the commencement of meiosis. Clear labeling of Sertoli and germ cells was observed from week 1 to week 7. The only those cells still labeled after 8 weeks were germ cells, indicating that Sertoli cell proliferation had ceased. Therefore, it is recommended that any research into the testes of domestic fowl should consider the cessation of Sertoli cell proliferation by approximately 8 weeks.

The role of oxidative stress and inflammatory response in high-fat diet induced peripheral neuropathy

OBJECTIVE Earlier studies suggest that high-calorie diet is an important risk factor for neuronal damage resulting from oxidative stress of lipid metabolism. In our experimental study of rats under high-fat diet, oxidative stress markers and axonal degeneration parameters were used to observe the sciatic nerve neuropathy. The aim of this study is to evaluate the pathophysiology of neuropathy induced by high-fat diet. METHODS A total of 14 male rats (Wistar albino) were randomly divided into two experimental groups as follows; control group (n=7) and the model group (n=7); while control group was fed with standard diet; where the model group was fed with a high-fat diet for 12 weeks. At the end of 12 weeks, the lipid profile and blood glucose levels, interleukin-1β (IL-1), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) levels were studied. Tissue malondialdehyde (MDA), nitric oxide (NO) levels and super-oxide dismutase (SOD), paraoxonase-1 (PON-1) and glutathione peroxidase (GPx) activities were studied. The distal blocks of the left sciatic nerves were evaluated for histomorphological analysis (including mean axon area, axon numbers, nerve fiber diameters, axon diameters, and thickness of myelin sheets). RESULTS Body weights, serum glucose and high-density lipoprotein (HDL) levels of rats were found not statistically significantly different compared between the model and the control groups (p>0.05). Serum cholesterol, triglyceride, TGF-β and TNF-α levels were significantly higher in the model group when compared with the control group (p<0.05). IL-1 and IL-6 levels were not statistically significantly different compared between the model group and the control group (p>0.05). The MDA and NO levels and the SOD and GPx activities of the sciatic nerves in model group were statistically significantly higher than the control group (p<0.05). In addition, the activities of PON-1 were statistically significantly lower in the model group when compared with the control group (p<0.05). The difference in the total number of myelinated axons between the control group and the model group was not statistically significant (p>0.05). The nerve fiber diameter and the thickness of the myelin sheet were statistically significantly lower in the model group when compared with the control group (p<0.05). The axon diameter and area were significantly decreased in the model group when compared with the control group (p<0.05). CONCLUSION Our results support that dyslipidemia is an independent risk factor for the development of neuropathy. In addition, we postulated that oxidative stress and inflammatory response may play an important role in the pathogenesis of high-fat diet induced neuropathy.

The effect of prenatal exposure of a non-steroidal anti-inflammatory drug on the optic nerve of female rats: a stereological, histological, and electron microscopic study

Abstract Objective: Non-steroidal anti-inflammatory drugs (NSAIDs) can have adverse effects for in both mother and fetus following administration during the prenatal period. If given during pregnancy, diclofenac sodium (DS), an NSAID, is given during the pregnancy, may also affect the development of the central nervous system (CNS) or related structures. Methods: Pregnant rats were separated into pure control (PG), saline (SG) and diclofenac groups (DG). A daily dose of 1 mg/kg of DS and 1 mL/kg saline was injected intraperitoneally to the DG and SG groups, respectively, from the 5th gestation day for a 15 day of period; the PG group received no treatment. After spontaneous delivery, female offspring were obtained from all groups. After the 20th week of postnatal life, the animals (n = 6 for each group) were perfused and the right optic nerves were resected. Sections were subjected to stereological and histological analysis. Results: There were no significant differences (p > 0.05) between PG, SG and DG groups with respect to myelin thickness, axonal cross-sectional area, axon numerical density, total section area of optic nerve and axon number. Conclusions: Histological and stereological results indicated that treatment with DS or saline produced undesirable effects on female rat optic nerve development and myelinization with respect to morphology.

Effects of prenatal exposure to diclofenac sodium and saline on the optic nerve of 4- and 20-week-old male rats: a stereological and histological study

Abstract We investigated the effects of diclofenac sodium (DS) on development of the optic nerve in utero. Pregnant female rats were separated into three groups: control, saline treated and DS treated. Offspring of these animals were divided into 4-week-old and 20-week-old groups. At the end of the 4th and 20th weeks of postnatal life, the animals were sacrificed, and right optic nerves were excised and sectioned for ultrastructural and stereological analyses. We demonstrated that both DS and saline produced structural and morphometric changes in the total axon number and density of axons, but decreased the myelin sheath thickness in male optic nerves. All ultrastructural and morphometric features were well developed in 20-week-old rats. We showed that development of the optic nerve continues during the early postnatal period and that some compensation for exposure to deleterious agents in utero may occur during early postnatal life.

Effects of prenatal diclofenac sodium exposure on newborn testis: a histomorphometric study.

Diclofenac sodium (DS) is used primarily to treat fever and to alleviate pain and inflammation. We investigated the effects of DS exposure during gestation on the testes of rat pups to investigate the safety of its use during the prenatal period. Pregnant rats were separated into control, saline, low dose, medium dose and high dose groups. DS was given between weeks 15 and 21 of gestation. Total numbers of spermatogonia and Sertoli cells were counted in the testes of 7-day-old male rats using the physical disector method. By the end of the study, the total number of Sertoli cells was decreased significantly in a dose dependent manner in the medium and high dose groups compared to controls. No significant differences were found in the total number of spermatogonia in the control, saline and low dose DS groups. Medium and high dose DS administration reduced the total number of spermatogonia compared to other groups. We suggest that prenatal administration of DS can cause deleterious effects on the testis development, especially in high doses.

Comparison between Flexible Collagen and Vein Conduits Used for Size-Discrepant Nerve Repair: An Experimental Study in Rats

Primary nerve repair is the gold standard in nerve reconstruction. When primary repair is not possible for injured nerves, conduit-assisted repair methods are frequently used. As conduits, autologous vein segments or allogenic biodegradable products can be used. However, their effectiveness when used in a nerve defect where a size discrepancy exists has not been compared. In this study, either a vein graft or a synthetic collagen conduit was used to bridge 10-mm defects between size-discrepant tibial and peroneal nerves in a rat model. After 90 days, nerve regeneration was evaluated using electrophysiological and histological methods. It can be concluded based on the results of this study that bridging a 10-mm nerve gap with synthetic collagen conduits and autologous vein grafts yielded similar results in small-to-large nerve coaptations, with the vein graft being slightly more effective.