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Biomedical subjects

M Akbulut

Publications and source records attributed to M Akbulut.

11 recordsLinked to original sources
PubMed2005

Wideband all-order polarization mode dispersion compensation via pulse shaping.

We demonstrate the application of ultrafast pulse-shaping techniques for experimental wideband all-order polarization mode dispersion (PMD) compensation, for the first time to our knowledge. PMD is treated as arbitrary variations of state of polarization and phase versus wavelength, in an all-order sense. Consequently, two pulse shapers are implemented in a serial manner to compensate for the polarization and the phase spectra independently. We report compensation of subpicosecond pulses (14 nm bandwidth around 1550 nm) that are anomalously spread to more than 2 ps as a result of PMD. This PMD compensation scheme can potentially be a powerful and cost-effective solution for fiber optic telecommunication networks.

Journal Article↗
PubMed2005

Melatonin inhibits neural apoptosis induced by homocysteine in hippocampus of rats via inhibition of cytochrome c translocation and caspase-3 activation and by regulating pro- and anti-apoptotic protein levels.

In the present study, we examined the molecular mechanism by which homocysteine causes neuronal cell apoptosis. We further investigated the mechanisms of melatonin's ability to reduce homocysteine-induced apoptosis. Consistent with its antioxidant properties, melatonin reduced homocysteine-induced lipid peroxidation and stimulated glutathione peroxidase enzyme activity in hippocampus of rats with hyperhomocysteinemia. Furthermore, melatonin treatment diminished cytochrome c release from mitochondria and reduced caspase 3 and caspase 9 activation induced by hyperhomocysteinemia. Chronic hyperhomocysteinemia also led to poly(ADP-ribose) polymerase cleavage and subsequently DNA fragmentation. Treatment with melatonin markedly inhibited poly(ADP-ribose) polymerase cleavage and reduced DNA damage. Hyperhomocysteinemia caused an elevation of pro-apoptotic Bax levels while reducing anti-apoptotic protein, Bcl-2, levels. Daily administration of melatonin up-regulated Bcl-2 and down-regulated Bax levels. We propose that, in addition to its antioxidant properties, melatonin has the ability to protect neuronal cells against apoptosis mediated homocysteine neurotoxicity by modulating apoptosis-regulatory proteins in the hippocampus of rats.

Animals↗
PubMed2004

Broadband polarization correction with programmable liquid-crystal modulator arrays.

We demonstrate a novel method of parallel, multiwavelength state-of-polarization (SOP) correction. Using a new liquid-crystal modulator array design, we are able to rotate the distorted input SOP spectrum to a fixed linear state on a wavelength-by-wavelength basis. We report experimental correction of up to 25.5-dB polarization-dependent loss over a 13-nm bandwidth around 1550 nm.

Journal Article↗
PubMed2002

Role of Ca2+ in drought stress signaling in wheat seedlings.

Plants use complex signal transduction pathways to perceive and react to various biotic and/or abiotic stresses. As a consequence of this signaling, plants can modify their metabolism to adapt themselves to new conditions. One such change is the accumulation of proline in response to drought and salinity stresses. We have studied drought and salinity induced proline accumulation and the roles of Ca2+ (10 mM) and indoleacetic acid (IAA, 0.3 mM) in this response. Subjecting seedlings to both drought (6% polyethylene glycol, PEG) and salinity (150 mM NaCl) stress resulted in a dramatic increase in proline accumulation (7-fold higher than control level). However, the application of Ca2+ along with these stress factors had different effects. Unlike the salinity stress, Ca2+ prevented the drought induced proline accumulation indicating that these stress factors use distinct signaling pathways to induce similar responses. Experiments with IAA and EGTA (10 mM) supported this interpretation and suggested that Ca2+ and auxin participate in signaling mechanisms of drought-induced proline accumulation. Drought and salt stress-induced proline accumulation was compared on salt resistant (cv. Gerek 79) and salt sensitive (cv. Bezostaya) wheat varieties. Although proline level of the first was twofold lower than that of the second in control, relative proline accumulation was dramatically higher in the case of the salt resistant wheat variety under stress conditions.

Calcium↗
PubMedDate not supplied

Infarction after fine needle aspiration biopsy of pleomorphic adenoma of the parotid gland.

BACKGROUND: Fine needle aspiration (FNA) is a well-established and safe method for the rapid diagnosis of pleomorphic adenoma. A few clinically important complications, including bleeding, infection and inflammatory reactions, result from FNA. In a small number of cases FNA has been followed by varying degrees of necrosis in some organs. In the literature there are a few reports associated with necrosis in a pleomorphic adenoma of the parotid gland following FNA. CASE: A 27-year-old female had a two-year history of a right parotid mass. FNA revealed pleomorphic adenoma. A histologic diagnosis of pleomorphic adenoma of the right parotid with infarction was made. CONCLUSION: Necrosis associated with infarction may cause diagnostic problems. It is not a sufficient sign of malignant transformation.

Adenoma, Pleomorphic↗
PubMedDate not supplied

Predictive value of C-reactive protein in patients with unstable angina pectoris undergoing coronary artery stent implantation.

In-stent restenosis is a major problem following coronary stent implantation, and inflammation plays an active role. We evaluated the effectiveness of the inflammatory marker C-reactive protein (CRP) as a predictor of in-stent restenosis after successful stent implantation, in 86 patients with unstable angina pectoris. Plasma CRP was measured in all patients before the procedure, and at 48 - 72 h and 1, 2 and 3 months post-procedure. An angiographic loss of 50% at follow-up was accepted as in-stent restenosis. We found negative and positive predictive values of the pre-procedural plasma CRP for determining 6-month in-stent restenosis of 34% and 61%, respectively. We also found a strong correlation between the 3-month post-procedural CRP value and 6-month in-stent restenosis; the negative and positive predictive values being 8% and 76%, respectively. In conclusion, we showed that a plasma CRP value > 3 mg/l in the third month after coronary stent implantation was a strong predictor of angiographic in-stent restenosis.

Aged↗