Biomedical subjects

Necdet Demir

Publications and source records attributed to Necdet Demir.

11 recordsLinked to original sources

PubMed2006

A standardized method to create optic nerve crush: Yasargil aneurysm clip.

It is often difficult to compare results obtained by different investigators on nerve compression injuries, owing to differences in method of pressure application and noncomparable pressure levels. In the present study, we described a new method to crush the optic nerve by using a specially designed and commercially available device. We think that standardization of the compression methods is necessary to compare interlaboratory results.

Animals↗

PubMed2006

Transmission electron microscopy and autofluorescence findings in the cornea of diabetic rats treated with aminoguanidine.

BACKGROUND: The accumulation of advanced glycation end products (AGEs) has been implicated in the pathogenesis of diabetic keratopathy. The present study was aimed to understand if aminoguanidine (AG), an AGE inhibitor, was protective against the development of corneal complications in a diabetic rat model. METHODS: Wistar rats were divided into three experimental groups: control, diabetic, and AG-treated diabetic. Diabetes was induced in rats via a single intraperitoneal injection (60 mg/kg) of streptozocin (STZ) and AG was administered in drinking water at a dose of 1 g/L. All animals were sacrificed at the end of 10 weeks and corneas from diabetic and nondiabetic rats were analyzed via transmission electron microscopy (TEM). Corneal autofluorescence measurements were also performed in all experimental groups. RESULTS: Electron microscopic evaluation revealed that aminoguanidine treatment in diabetic rats prevented the formation of intracellular spaces between neighbouring cells in the superficial corneal epithelium. Hyperglycemia-induced degeneration of intracellular organelles and formation of cytoplasmic vacuoles in the corneal stroma was also prevented with the treatment of AG. Corneal autofluorescence detected in the diabetic group (5.98 +/- 2.17 Fi/mg protein) was found to be significantly greater than the control (3.92 +/- 0.56 Fi/mg protein) and the AG-treated diabetic group (4.18 +/- 0.59 Fi/mg protein) (p < 0.05). INTERPRETATION: The presented data provide evidence that AG is preventive against corneal alterations in experimental diabetes.

Animals↗

PubMed2005

PTEN-mediated Akt activation in human neocortex during prenatal development.

Akt is a crucial factor for cell survival and migration. Phosphatase and tensin (PTEN) negatively regulates cell growth and survival by inhibiting PI3K-dependent signaling. PTEN also blocks Akt phosphorylation, a main downstream molecule of PI3K cascade. So far, no studies have shown PTEN expression and Akt phosphorylation levels in the developing human neocortex. Our hypothesis is that spatial and temporal expression of PTEN is likely to modulate developing human brain cortical modeling by regulating Akt activation. Therefore, our aim is to analyze the expression pattern of PTEN and phospho-Akt levels using immunohistochemistry, Western blot, and semiquantitative analysis in the developing human neocortex (n=13 fetuses from first, second, and third trimesters). PTEN expression was decreased parallel to development, but some cells revealed strong nuclear immunoreactivity in the developing neocortex while the active Akt level was increased. Double immunohistochemistry was performed for proliferating cell nuclear antigen (PCNA)-Tuj1 (as neuronal marker) and PCNA-GFAP (Glial marker) to the subsequent sections of PTEN and Akt-stained slides. PCNA (+) cells were mostly positive for glial fibrillary acidic protein (GFAP) and correlated with active-Akt immunoreactivity. Our results suggest that Akt-mediated signaling plays an active role in cell migration, survival, and cerebral cortical modeling throughout prenatal life and that PTEN is the most likely protein to regulate this signaling.

Blotting, Western↗

PubMed2005

Minimally invasive method for murine brain fixation.

Complete brain fixation can be achieved with transthoracic cardiac infusion without thoracotomy. Light and electron microscopy tissue sections reveal preservation of cytoplasmic and nuclear structure at all magnification levels. Punched samples were obtained from the fixed tissue specimens in precisely localized areas for study using electron microscopy. This perfusion fixation technique provides both faster tissue harvesting capability and higher quality tissue preservation, without the artifacts of brain swelling and ventricular dilation observed in direct cardiac perfusion. Acute, discrete change in brain tissue can be studied.

Animals↗

PubMed2005

Physical training increases renal injury in rats with chronic NOS inhibition.

Nitric oxide (NO) is involved in regulation of vascular tone and renal hemodynamics. Inhibition of NO synthase (NOS) by Nomega-nitro-L-arginine methyl ester (L-NAME) promotes systemic hypertension and glomerular damage. Exercise is effective in reducing elevated blood pressure in hypertensive individuals and rats treated with L-NAME. We investigated the effects of regular aerobic exercise on renal injury in hypertensive rats with NOS inhibition. Adult Wistar rats were divided into four groups: sedentary or exercising, nonhypertensive (two groups) and hypertensive, sedentary or exercising (two groups). Treadmill running exercise was prolonged for 4 weeks (60 min.day(-1), 5 days/week, 20 m.min(-1), no incline), and hypertension was induced by L-NAME given orally to rats for 4 weeks (25 mg.kg(-1).day(-1) in drinking water). Blood pressure was monitored at baseline and then once a week throughout L-NAME administration. Kidney sections were examined for renal histopathology. Hypertensive animals exhibited elevated blood pressure, and exercise partly prevented this elevation. Renal injury observed as arteriolar wall thickening, focal tubular atrophy, and interstitial inflammatory infiltration was apparent in hypertensive animals, and exercise induced further renal damage in hypertensive animals. The present training protocol exacerbates renal insufficiency in NOS-blockage hypertension in rats.

Adaptation, Physiological↗

PubMed2004

Distribution of N-cadherin in human cerebral cortex during prenatal development.

An important subgroup of adhesion molecules is the superfamily of cadherins, which takes part in cell recognition and differentiation during development. To our knowledge only one study describing N-cadherin expression in developing human brain has been performed so far. Our aim is to identify N-cadherin expression to establish a relationship between its expression and function in human cerebral cortex during prenatal development. In the present study, localization and intensity of N-cadherin was investigated in developing cerebral cortex. Fetuses from spontaneous abortions (n=13) were obtained from first, second, and third trimesters. Western blot analysis revealed three bands and the third trimester samples showed the strongest bands for N-cadherin. Cell processes, axon bundles, and some of the developing neurons revealed immunoreactivity for N-cadherin throughout pregnancy. The immunoreactivity increased in the developing neocortex and expanded from the ventricular layer toward the marginal zone as development progressed. Moreover, the immunoreactivity was strong in vascular endothelium during all three trimesters. We conclude that N-cadherin is dynamically related to the organization of cerebral cortex layers during prenatal development. The dynamic expression pattern implicates N-cadherin as a potential regulator of cell migration, axon extension and fasciculation, the establishment of synaptic contacts, and neurovascular angiogenesis in the developing human cerebral cortex.

Abortion, Spontaneous↗

PubMed2004

Ultrastructural and immunohistochemical similarities of two distinct entities; multiple sclerosis and hereditary motor sensory neuropathy.

In the present study, we present the ultrastructural and immunohistochemical properties of the sural nerves of two patients, one of whom was diagnosed as having multiple sclerosis with involvement of the peripheral nervous system (PNS), and the other as having hereditary motor sensory neuropathy type-I with involvement of the central nervous system (CNS). Expression of several extracellular matrix (ECM) proteins (fibronectin, laminin, and collagen type-IV), intermediate filaments (vimentin) and S-100 protein (marker for the axon-Schwann cell interface) was investigated by means of immunohistochemical methods. In addition, the tissue samples were evaluated ultrastructurally. Immunohistochemical staining revealed increased expression of the ECM molecules mentioned above in relation with the sural nerves of the patients. We hypothesize that this enhanced expression is due to Schwann cell-axon interactions. Vimentin expression was different in Schwann cells and S-100 immunostaining was decreased near the Schwann cell-axon interface. Myelin fragmentation, axon vacuolization, onion bulbs, tomoculous formation, axonal degeneration were found to occur. These results suggest that there is active ECM reorganization in the sural nerve of these patients, and some ultrastructural changes are similar in the damaged axonal organization and in Schwann cells although the changes are not completely the same in the two patients. In conclusion, our study demonstrates that there is an association between the demyelinization process in the CNS and the PNS even though they are affected by different mechanisms.

Adult↗

PubMed2003

Fiber structure of optic nerve in cadmium-exposed diabetic rats: an ultrastructural study.

This study aimed to show ultrastructural effects of diabetes and cadmium on the optic nerve. We used 52 healthy Swiss albino male rats. They were divided into four groups: control (C), diabetic (D), cadmium, (Cd), and diabetic with cadmium (D + Cd). The diabetic condition was created by intravenous injection of 5 mg alloxan/100 g. Intraperitoneal CdCl2(2 mg kg/week) was given to Cd and D + Cd groups for two months. At the end of the experimental period, animals were sacrificed and the optic nerves were dissected at the front level of chiasma opticum. The tissue samples were investigated by using light and electron microscopic techniques. It was found that both diabetes and Cd intoxication cause myelin disorganization and organelle destruction in axoplasm and cytoplasm of glia. The results suggested that Cd increases the oxidative stress induced by diabetes, by disturbing some enzymatic mechanisms.

Animals↗

PubMed2002

Effect of exercise on blood pressure in rats with chronic NOS inhibition.

Regular training lowers blood pressure in hypertensive humans and other animals. We investigated the response to 4 weeks of treadmill exercise training in hypertensive male Wistar rats receiving the nitric oxide synthase inhibitor N(omega)-nitro- L-arginine methyl ester ( L-NAME). The rats were on either a short- (4 weeks) or long-term (10 weeks) L-NAME treatment protocol and were subjected to running exercise that started concomitantly in the short-term group and in the 6th week in the long-term group. Four weeks of exercise training induced a fall in mean arterial pressure in both the short- [mean (SEM) 137.6 (4.0) mmHg] and long-term hypertensive groups [161.4 (2.3) mmHg] compared to their sedentary hypertensive controls [160.4 (3.3) mmHg and 176.8 (8.9) mmHg, respectively]. Exercise also increased muscle nitric oxide synthase activity in both of the trained hypertensive groups. Muscle nitrite levels were higher in the exercising short-term hypertensive group compared to both the sedentary control and the sedentary hypertensive groups, and were not different between the sedentary and exercising long-term hypertensive groups. Increased wall thickness of the aortic and mesenteric vessels was observed in the hypertensive groups, but was prevented in the exercising long-term hypertensive group. In rat, exercise reduces the elevated blood pressure in L-NAME-induced hypertension via increasing nitric oxide synthase activity. Changes in vessel structure with exercise training may also be involved in the blood-pressure-lowering effects.

Adaptation, Physiological↗

PubMed2002

Effect of cadmium on sciatic nerve in diabetic rats: an ultrastructural study.

The present study demonstrated the ultrastructural effects of diabetes and cadmium on the peripheral nervous system. In this study we used 52 healthy Swiss male albino rats. They were divided into four groups: control (C), diabetic (D), cadmium (Cd), and diabetic and cadmium (D + Cd). The diabetic condition was induced by intravenous injection of 5 mg alloxan/100 g body weight, via the caudal vein. Cd and D + Cd groups were injected with CdCl2 intraperitoneally (2 mg/Kg/week) for two months. At the end of the experimental period, animals were sacrificed and their sciatic nerves were dissected. The tissue samples were investigated by using light and electron microscopic techniques. Upon investigation, it was seen that myelinated axons in sciatic nerve of diabetic and Cd treatment groups had onion-bulb type myelin destruction, melting, and protrusion. Basal lamina of capillary endothelia of D, Cd, and D + Cd groups were thickened and the endothelial apical membrane was rough. In conclusion, Cd toxicity exacerbated the destructive effect of diabetes on the peripheral nervous system.

Animals↗

PubMed2002

Maternal bilateral adrenalectomy alters nuclear composition in cerebral cortex of fetal rat.

The present study examined the effects of maternal bilateral adrenalectomy on cell nucleus composition of developing fetal rat cerebral cortex. Pregnant adult rats underwent adrenalectomy (ADX) on day 4 of gestation. Fetal brain tissues from sham and ADX groups were examined at each of 10 embryonal stages, E11-E20. From each fetus three slides of dorsal-central region of developing brain were taken and the diameter and long axis of nucleus of cells in these samples were measured. Maternal adrenalectomy generally produces increased nuclear diameter and number of ovoid nucleus in fetal cerebral cortex especially late prenatal stages. It is shown that ADX may change nuclear composition of developing cerebral cortex.

Adrenal Glands↗